WorldWideScience

Sample records for four-point density correlation

  1. Spatially heterogeneous dynamics investigated via a time-dependent four-point density correlation function

    DEFF Research Database (Denmark)

    Lacevic, N.; Starr, F. W.; Schrøder, Thomas

    2003-01-01

    two-point time-dependent density correlation functions, while providing information about the transient "caging" of particles on cooling, are unable to provide sufficiently detailed information about correlated motion and dynamical heterogeneity. Here, we study a four-point, time-dependent density...... simulations of a binary Lennard-Jones mixture approaching the mode coupling temperature from above. We find that the correlations between particles measured by g4(r,t) and S4(q,t) become increasingly pronounced on cooling. The corresponding dynamical correlation length xi4(t) extracted from the small......-q behavior of S4(q,t) provides an estimate of the range of correlated particle motion. We find that xi4(t) has a maximum as a function of time t, and that the value of the maximum of xi4(t) increases steadily from less than one particle diameter to a value exceeding nine particle diameters in the temperature...

  2. Four-point correlation function of stress-energy tensors in N=4 superconformal theories

    CERN Document Server

    Korchemsky, G P

    2015-01-01

    We derive the explicit expression for the four-point correlation function of stress-energy tensors in four-dimensional N=4 superconformal theory. We show that it has a remarkably simple and suggestive form allowing us to predict a large class of four-point correlation functions involving the stress-energy tensor and other conserved currents. We then apply the obtained results on the correlation functions to computing the energy-energy correlations, which measure the flow of energy in the final states created from the vacuum by a source. We demonstrate that they are given by a universal function independent of the choice of the source. Our analysis relies only on N=4 superconformal symmetry and does not use the dynamics of the theory.

  3. Four-point correlation functions in the AdS/CFT correspondence.

    Energy Technology Data Exchange (ETDEWEB)

    Chalmers, G.; Schalm, K.

    1999-02-09

    We examine correlation functions within the correspondence between gauged supergravity on anti-de Sitter space and N = 4 super Yang-Mills theory in Minkowski space. The imaginary parts of four-point functions in momentum space are computed, in addition to particular examples of three-point functions. Exchange diagrams for gravitons are included. The results indicate additional structure in N = 4 super Yang-Mills theory at strong 't Hooft coupling and in the large N limit.

  4. Primordial non-Gaussianity in noncanonical warm inflation: Three- and four-point correlations

    Science.gov (United States)

    Zhang, Xiao-Min; Ma, Hong-Yang; Chu, Peng-Cheng; Zhu, Jian-Yang

    2017-08-01

    Non-Gaussianity generated in inflation can be contributed by two parts. The first part, denoted by fNL δ N, is the contribution from the four-point correlation of the inflaton field which can be calculated using δ N formalism, and the second part, denoted by fNL int , is the contribution from the three-point correlation function of the inflaton field. We consider the two contributions to the non-Gaussianity in noncanonical warm inflation throughout (noncanonical warm inflation is a new inflationary model which is proposed in X. M. Zhang and J. Y. Zhu, Phys. Rev. D 90, 123519 (2014), 10.1103/PhysRevD.90.123519). We find the two contributions are complementary to each other. The four-point correlation contribution to the non-Gaussianity is overwhelmed by the three-point one in the strong noncanonical limit, while the conclusion is the opposite in the canonical case. We also discuss the influence of the field redefinition, thermal dissipative effect and noncanonical effect to the non-Gaussianity in noncanonical warm inflation.

  5. Relationship between bond-breakage correlations and four-point correlations in heterogeneous glassy dynamics: Configuration changes and vibration modes

    Science.gov (United States)

    Shiba, Hayato; Kawasaki, Takeshi; Onuki, Akira

    2012-10-01

    We investigate the dynamic heterogeneities of glassy particle systems in the theoretical schemes of bond breakage and four-point correlation functions. In the bond-breakage scheme, we introduce the structure factor Sb(q,t) and the susceptibility χb(t) to detect the spatial correlations of configuration changes. Here χb(t) attains a maximum at t=tbmax as a function of time t, where the fraction of the particles with broken bonds φb(t) is about 1/2. In the four-point scheme, treating the structure factor S4(q,t) and the susceptibility χ4(t), we detect superpositions of the heterogeneity of bond breakage and that of thermal low-frequency vibration modes. While the former grows slowly, the latter emerges quickly to exhibit complex space-time behavior. In two dimensions, the vibration modes extending over the system yield significant contributions to the four-point correlations, which depend on the system size logarithmically. A maximum of χ4(t) is attained at t=t4max, where these two contributions become of the same order. As a result, t4max is considerably shorter than tbmax.

  6. Four-point high time resolution information on electron densities by the electric field experiments (EFW on Cluster

    Directory of Open Access Journals (Sweden)

    A. Pedersen

    Full Text Available For accurate measurements of electric fields, spherical double probes are electronically controlled to be at a positive potential of approximately 1 V relative to the ambient magnetospheric plasma. The spacecraft will acquire a potential which balances the photoelectrons escaping to the plasma and the electron flux collected from the plasma. The probe-to-plasma potential difference can be measured with a time resolution of a fraction of a second, and provides information on the electron density over a wide range of electron densities from the lobes (~ 0.01 cm-3 to the magnetosheath (>10 cm-3 and the plasmasphere (>100 cm-3. This technique has been perfected and calibrated against other density measurements on GEOS, ISEE-1, CRRES, GEOTAIL and POLAR. The Cluster spacecraft potential measurements opens the way for new approaches, particularly near boundaries and gradients where four-point measurements will provide information never obtained before. Another interesting point is that onboard data storage of this simple parameter can be done for complete orbits and thereby will provide background information for the shorter full data collection periods on Cluster. Preliminary calibrations against other density measurements on Cluster will be reported.

    Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers Space plasma physics (spacecraft sheaths, wakes, charging; instruments and techniques

  7. The four-point correlator in multifield inflation, the operator product expansion and the symmetries of de Sitter

    Energy Technology Data Exchange (ETDEWEB)

    Kehagias, A., E-mail: kehagias@central.ntua.gr [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece); Riotto, A. [Department of Theoretical Physics and Center for Astroparticle Physics (CAP), 24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland)

    2013-03-21

    We study the multifield inflationary models where the cosmological perturbation is sourced by light scalar fields other than the inflaton. We exploit the operator product expansion and partly the symmetries present during the de Sitter epoch to characterize the non-Gaussian four-point correlator in the squeezed limit. We point out that the contribution to it from the intrinsic non-Gaussianity of the light fields at horizon crossing can be larger than the usually studied contribution arising on superhorizon scales and it comes with a different shape. Our findings indicate that particular attention needs to be taken when studying the effects of the primordial NG on real observables, such as the clustering of dark matter halos.

  8. All three-loop four-point correlators of half-BPS operators in planar $ \\mathcal{N} $ = 4 SYM

    CERN Document Server

    Chicherin, Dmitry; Heslop, Paul; Sokatchev, Emery

    2016-01-01

    We obtain the planar correlation function of four half-BPS operators of arbitrary weights, up to three loops. Our method exploits only elementary properties of the integrand of the planar correlator, such as its symmetries and singularity structure. This allows us to write down a general ansatz for the integrand. The coefficients in the ansatz are fixed by means of a powerful light-cone OPE relation between correlators with different weights. Our result is formulated in terms of a limited number of functions built from known one-, two- and three-loop conformal integrals. These results are useful for checking recent integrability predictions for the OPE structure constants.

  9. Exponential decay of equal-time four-point correlation functions in the Hubbard model on the copper-oxide lattice

    CERN Document Server

    Kashima, Yohei

    2012-01-01

    For the Hubbard model on the two-dimensional copper-oxide lattice, equal-time four-point correlation functions at positive temperature are proved to decay exponentially in the thermodynamic limit if the magnitude of the on-site interactions is smaller than some power of temperature. This result especially implies that the equal-time correlation functions for singlet Cooper pairs of various symmetries decay exponentially in the distance between the Cooper pairs in high temperatures or in low-temperature weak-coupling regimes. The proof is based on a multi-scale integration over the Matsubara frequency.

  10. Four-point correlation function of a passive scalar field in rapidly fluctuating turbulence: Numerical analysis of an exact closure equation.

    Science.gov (United States)

    Mizuno, Y; Ohi, K; Sogabe, T; Yamamoto, Y; Kaneda, Y

    2010-09-01

    A numerical analysis is made on the four-point correlation function in a similarity range of a model of two-dimensional passive scalar field ψ advected by a turbulent velocity field with infinitely small correlation time. The model yields an exact closure equation for the four-point correlation Ψ{4} of ψ, which may be casted into the form of an eigenvalue problem in the similarity range. The analysis of the eigenvalue problem gives not only the scale dependence of Ψ{4} , but also the dependence on the configuration of the four points. The numerical analysis gives S4(R)∝R{ζ{4}} in the similarity range in which S2(R)∝R{ζ{2}} , where S_{N} is the structure function defined by S{N}(R)≡⟨[ψ(x+R)-ψ(x)]{N} and ζ{4}≠2ζ{2} . The estimate of ζ_{4} by the numerical analysis of the eigenvalue problem is in good agreement with numerical simulations so far reported. The agreement supports the idea of universality of the exponent ζ{4} in the sense that ζ_{4} is insensitive to conditions of ψ outside the similarity range. The numerical analysis also shows that the correlation C(R,r)≡[ψ(x+R)-ψ(x)]{2}[ψ(x+r)-ψ(x)]{2}> is stronger than that given by the joint-normal approximation, and scales like C(R,r)∝(r/R){χ} for r/R<1 with R and r in the similarity range, where χ is a constant depending on the angle between R and r .

  11. Correlation of Nonexponentiality with Dynamic Heterogeneity from Four-Point Dynamic Susceptibility X4(t) and Its Approximation XT(t)

    Science.gov (United States)

    2010-01-01

    Theoretische Physik, Technische Universitat Wien, Wiedner Hauptstraße 8-10, A-1040 Wien, Austria 3Dipartimento di Fisica , Università di Pisa, Largo Pontecorvo 3...models of the glass transition generally posit a growing dynamic correlation length as causing the marked increase of in vitrifying liquids 15–19

  12. Junction leakage measurements with micro four-point probes

    DEFF Research Database (Denmark)

    Lin, Rong; Petersen, Dirch Hjorth; Wang, Fei

    2012-01-01

    We present a new, preparation-free method for measuring the leakage current density on ultra-shallow junctions. The junction leakage is found by making a series of four-point sheet resistance measurements on blanket wafers with variable electrode spacings. The leakage current density is calculate...

  13. Four-Point Wavelets and Their Applications

    Institute of Scientific and Technical Information of China (English)

    魏国富; 陈发来

    2002-01-01

    Multiresolution analysis (MRA) and wavelets provide useful and efficient tools for representing functions at multiple levels of details. Wavelet representations have been used in a broad range of applications, including image compression, physical simulation and numerical analysis. In this paper, the authors construct a new class of wavelets, called four-point wavelets,based on an interpolatory four-point subdivision scheme. They are of local support, symmetric and stable. The analysis and synthesis algorithms have linear time complexity. Depending on different weight parameters w, the scaling functions and wavelets generated by the four-point subdivision scheme are of different degrees of smoothness. Therefore the user can select better wavelets relevant to the practice among the classes of wavelets. The authors apply the fourpoint wavelets in signal compression. The results show that the four-point wavelets behave much better than B-spline wavelets in many situations.

  14. Junction leakage measurements with micro four-point probes

    DEFF Research Database (Denmark)

    Lin, Rong; Petersen, Dirch Hjorth; Wang, Fei;

    2012-01-01

    We present a new, preparation-free method for measuring the leakage current density on ultra-shallow junctions. The junction leakage is found by making a series of four-point sheet resistance measurements on blanket wafers with variable electrode spacings. The leakage current density is calculated...... using a fit of the measured four-point resistances to an analytical two-sheet model. The validity of the approximation involved in the two-sheet model is verified by a comparison to finite element model calculations....

  15. Scanning microscopic four-point conductivity probes

    DEFF Research Database (Denmark)

    Petersen, Christian Leth; Hansen, Torben Mikael; Bøggild, Peter

    2002-01-01

    A method for fabricating microscopic four-point probes is presented. The method uses silicon-based microfabrication technology involving only two patterning steps. The last step in the fabrication process is an unmasked deposition of the conducting probe material, and it is thus possible to select...... the conducting material either for a silicon wafer or a single probe unit. Using shadow masking photolithography an electrode spacing (pitch) down to 1.1 mum was obtained, with cantilever separation down to 200 run. Characterisation measurements have shown the microscopic probes to be mechanically very flexible...

  16. Fundamental size limitations of micro four-point probes

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Petersen, Dirch Hjorth; Hansen, Ole

    2009-01-01

    -scaled as well in order to correctly characterize the extremely thin films used. This presents a four-point probe design and fabrication challenge. We analyze the fundamental limitation on down-scaling of a generic micro four-point probe (M4PP) in a comprehensive study, where mechanical, thermal, and electrical...

  17. Locality of correlation in density functional theory.

    Science.gov (United States)

    Burke, Kieron; Cancio, Antonio; Gould, Tim; Pittalis, Stefano

    2016-08-07

    The Hohenberg-Kohn density functional was long ago shown to reduce to the Thomas-Fermi (TF) approximation in the non-relativistic semiclassical (or large-Z) limit for all matter, i.e., the kinetic energy becomes local. Exchange also becomes local in this limit. Numerical data on the correlation energy of atoms support the conjecture that this is also true for correlation, but much less relevant to atoms. We illustrate how expansions around a large particle number are equivalent to local density approximations and their strong relevance to density functional approximations. Analyzing highly accurate atomic correlation energies, we show that EC → -AC ZlnZ + BCZ as Z → ∞, where Z is the atomic number, AC is known, and we estimate BC to be about 37 mhartree. The local density approximation yields AC exactly, but a very incorrect value for BC, showing that the local approximation is less relevant for the correlation alone. This limit is a benchmark for the non-empirical construction of density functional approximations. We conjecture that, beyond atoms, the leading correction to the local density approximation in the large-Z limit generally takes this form, but with BC a functional of the TF density for the system. The implications for the construction of approximate density functionals are discussed.

  18. Four point bending setup for characterization of semiconductor piezoresistance

    DEFF Research Database (Denmark)

    Richter, Jacob; Arnoldus, Morten Berg; Hansen, Ole

    2008-01-01

    We present a four point bending setup suitable for high precision characterization of piezoresistance in semiconductors. The compact setup has a total size of 635 cm3. Thermal stability is ensured by an aluminum housing wherein the actual four point bending fixture is located. The four point...... bending fixture is manufactured in polyetheretherketon and a dedicated silicon chip with embedded piezoresistors fits in the fixture. The fixture is actuated by a microstepper actuator and a high sensitivity force sensor measures the applied force on the fixture and chip. The setup includes heaters...

  19. Electron correlation by polarization of interacting densities

    CERN Document Server

    Whitten, Jerry L

    2016-01-01

    Coulomb interactions that occur in electronic structure calculations are correlated by allowing basis function components of the interacting densities to polarize, 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 . A method of avoiding redundancy is described. Applications to atoms, negative ions and molecules representing different types of bonding and spin states are discussed.

  20. Tessellating cushions: four-point functions in N=4 SYM

    CERN Document Server

    Eden, Burkhard

    2016-01-01

    We consider a class of planar tree-level four-point functions in N=4 SYM in a special kinematic regime: one BMN operator with two scalar excitations and three half-BPS operators are put onto a line in configuration space; additionally, for the half-BPS operators a co-moving frame is chosen in flavour space. In configuration space, the four-punctured sphere is naturally triangulated by tree-level planar diagrams. We demonstrate on a number of examples that each tile can be associated with a modified hexagon form-factor in such a way as to efficiently reproduce the tree-level four-point function. Our tessellation is not of the OPE type, fostering the hope of finding an independent, integrability-based approach to the computation of planar four-point functions.

  1. A laboratory on the four-point probe technique

    Science.gov (United States)

    Schuetze, Andrew P.; Lewis, Wayne; Brown, Chris; Geerts, Wilhelmus J.

    2004-02-01

    We describe how a classic electrostatics experiment can be modified to be a four-point probe lab experiment. Students use the four-point probe technique to investigate how the measured resistance varies as a function of the position of the electrodes with respect to the edge of the sample. By using elementary electromagnetism concepts such as the superposition principle, the continuity equation, the relation between electric field and electric potential, and Ohm's law, a simple model is derived to describe the four-point probe technique. Although the lab introduces the students to the ideas behind the Laplace equation and the methods of images, advanced mathematics is avoided so that the experiment can be done in trigonometry and algebra based physics courses. In addition, the experiment introduces the students to a standard measurement technique that is widely used in industry and thus provides them with useful hands-on experience.

  2. Scaled density functional theory correlation functionals.

    Science.gov (United States)

    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.

  3. Four-point function in the IOP matrix model

    Science.gov (United States)

    Michel, Ben; Polchinski, Joseph; Rosenhaus, Vladimir; Suh, S. Josephine

    2016-05-01

    The IOP model is a quantum mechanical system of a large- N matrix oscillator and a fundamental oscillator, coupled through a quartic interaction. It was introduced previously as a toy model of the gauge dual of an AdS black hole, and captures a key property that at infinite N the two-point function decays to zero on long time scales. Motivated by recent work on quantum chaos, we sum all planar Feynman diagrams contributing to the four-point function. We find that the IOP model does not satisfy the more refined criteria of exponential growth of the out-of-time-order four-point function.

  4. Four-point function in the IOP matrix model

    CERN Document Server

    Michel, Ben; Rosenhaus, Vladimir; Suh, S Josephine

    2016-01-01

    The IOP model is a quantum mechanical system of a large-$N$ matrix oscillator and a fundamental oscillator, coupled through a quartic interaction. It was introduced previously as a toy model of the gauge dual of an AdS black hole, and captures a key property that at infinite $N$ the two-point function decays to zero on long time scales. Motivated by recent work on quantum chaos, we sum all planar Feynman diagrams contributing to the four-point function. We find that the IOP model does not satisfy the more refined criteria of exponential growth of the out-of-time-order four-point function.

  5. Developing Multidimensional Likert Scales Using Item Factor Analysis: The Case of Four-Point Items

    Science.gov (United States)

    Asún, Rodrigo A.; Rdz-Navarro, Karina; Alvarado, Jesús M.

    2016-01-01

    This study compares the performance of two approaches in analysing four-point Likert rating scales with a factorial model: the classical factor analysis (FA) and the item factor analysis (IFA). For FA, maximum likelihood and weighted least squares estimations using Pearson correlation matrices among items are compared. For IFA, diagonally weighted…

  6. Micro-four-point Probe Hall effect Measurement method

    DEFF Research Database (Denmark)

    Petersen, Dirch Hjorth; Hansen, Ole; Lin, Rong

    2008-01-01

    barriers and with a magnetic field applied normal to the plane of the sheet. Based on this potential, analytical expressions for the measured four-point resistance in presence of a magnetic field are derived for several simple sample geometries. We show how the sheet resistance and Hall effect......We report a new microscale Hall effect measurement method for characterization of semiconductor thin films without need for conventional Hall effect geometries and metal contact pads. We derive the electrostatic potential resulting from current flow in a conductive filamentary sheet with insulating...... contributions may be separated using dual configuration measurements. The method differs from conventional van der Pauw measurements since the probe pins are placed in the interior of the sample region, not just on the perimeter. We experimentally verify the method by micro-four-point probe measurements...

  7. Comparative study of size dependent four-point probe sheet resistance measurement on laser annealed ultra-shallow junctions

    DEFF Research Database (Denmark)

    Petersen, Dirch Hjorth; Lin, Rong; Hansen, Torben Mikael;

    2008-01-01

    In this comparative study, the authors demonstrate the relationship/correlation between macroscopic and microscopic four-point sheet resistance measurements on laser annealed ultra-shallow junctions (USJs). Microfabricated cantilever four-point probes with probe pitch ranging from 1.5 to 500 mu m...... have been used to characterize the sheet resistance uniformity of millisecond laser annealed USJs. They verify, both experimentally and theoretically, that the probe pitch of a four-point probe can strongly affect the measured sheet resistance. Such effect arises from the sensitivity (or "spot size......") of an in-line four-point probe. Their study shows the benefit of the spatial resolution of the micro four-point probe technique to characterize stitching effects resulting from the laser annealing process....

  8. Magic identities for conformal four-point integrals

    CERN Document Server

    Drummond, J M; Smirnov, V A; Sokatchev, E S

    2007-01-01

    We propose an iterative procedure for constructing classes of off-shell four-point conformal integrals which are identical. The proof of the identity is based on the conformal properties of a subintegral common for the whole class. The simplest example are the so-called `triple scalar box' and `tennis court' integrals. In this case we also give an independent proof using the method of Mellin--Barnes representation which can be applied in a similar way for general off-shell Feynman integrals.

  9. Accuracy of micro four-point probe measurements on inhomogeneous samples: A probe spacing dependence study

    OpenAIRE

    Wang, Fei; Petersen, Dirch Hjorth; Østerberg, Frederik Westergaard; Hansen, Ole

    2009-01-01

    In this paper, we discuss a probe spacing dependence study in order to estimate the accuracy of micro four-point probe measurements on inhomogeneous samples. Based on sensitivity calculations, both sheet resistance and Hall effect measurements are studied for samples (e.g. laser annealed samples) with periodic variations of sheet resistance, sheet carrier density, and carrier mobility. With a variation wavelength of ¿, probe spacings from 0.0012 to 1002 have been applied to characterize the ...

  10. Density fluctuations and correlations of confined fluids

    Science.gov (United States)

    Varea, C.; Robledo, A.

    The density fluctuations about the equilibrium structure of fluids confined by parallel planar walls are analyzed for the cases of identical and symmetrically opposed fields at the walls. We determine the stability matrix (of the second derivatives of the free energy functional with respect to the density) for conditions both above and below the wetting transition temperature Tw of the semi-infinite system and corroborate in all cases that the equilibrium configurations are stable. We identify the fluctuations close to the walls and in the middle of the slab and discuss their effect when the wall separation L diverges. For competing walls above Tw the localized fluctuation with lowest eigenvalue describes the displacements of the incipient wetting films that become unimpeded interfacial translations for L→∞. Below Tw the fluctuations with lowest eigenvalue correspond to stiffer deformations extended across the slab. For identical walls above Tw coexisting states display incipient prewetting films and the lowest eigenvalue describes the nature of their growth as L increases. We also calculate the pair correlation function for the inhomogeneous states and, for symmetrically opposed walls, we obtain standard Ornstein-Zernike (OZ) behavior at the walls, but find significant deviations from this law at the interface-like region in the middle of the slab. To model fluids with short-ranged forces we use a ferromagnetic Ising-type Hamiltonian in mean-field approximation.

  11. Open-Source Automated Mapping Four-Point Probe

    Directory of Open Access Journals (Sweden)

    Handy Chandra

    2017-01-01

    Full Text Available Scientists have begun using self-replicating rapid prototyper (RepRap 3-D printers to manufacture open source digital designs of scientific equipment. This approach is refined here to develop a novel instrument capable of performing automated large-area four-point probe measurements. The designs for conversion of a RepRap 3-D printer to a 2-D open source four-point probe (OS4PP measurement device are detailed for the mechanical and electrical systems. Free and open source software and firmware are developed to operate the tool. The OS4PP was validated against a wide range of discrete resistors and indium tin oxide (ITO samples of different thicknesses both pre- and post-annealing. The OS4PP was then compared to two commercial proprietary systems. Results of resistors from 10 to 1 MΩ show errors of less than 1% for the OS4PP. The 3-D mapping of sheet resistance of ITO samples successfully demonstrated the automated capability to measure non-uniformities in large-area samples. The results indicate that all measured values are within the same order of magnitude when compared to two proprietary measurement systems. In conclusion, the OS4PP system, which costs less than 70% of manual proprietary systems, is comparable electrically while offering automated 100 micron positional accuracy for measuring sheet resistance over larger areas.

  12. Open-Source Automated Mapping Four-Point Probe.

    Science.gov (United States)

    Chandra, Handy; Allen, Spencer W; Oberloier, Shane W; Bihari, Nupur; Gwamuri, Jephias; Pearce, Joshua M

    2017-01-26

    Scientists have begun using self-replicating rapid prototyper (RepRap) 3-D printers to manufacture open source digital designs of scientific equipment. This approach is refined here to develop a novel instrument capable of performing automated large-area four-point probe measurements. The designs for conversion of a RepRap 3-D printer to a 2-D open source four-point probe (OS4PP) measurement device are detailed for the mechanical and electrical systems. Free and open source software and firmware are developed to operate the tool. The OS4PP was validated against a wide range of discrete resistors and indium tin oxide (ITO) samples of different thicknesses both pre- and post-annealing. The OS4PP was then compared to two commercial proprietary systems. Results of resistors from 10 to 1 MΩ show errors of less than 1% for the OS4PP. The 3-D mapping of sheet resistance of ITO samples successfully demonstrated the automated capability to measure non-uniformities in large-area samples. The results indicate that all measured values are within the same order of magnitude when compared to two proprietary measurement systems. In conclusion, the OS4PP system, which costs less than 70% of manual proprietary systems, is comparable electrically while offering automated 100 micron positional accuracy for measuring sheet resistance over larger areas.

  13. Correlation energy, correlated electron density, and exchange-correlation potential in some spherically confined atoms.

    Science.gov (United States)

    Vyboishchikov, Sergei F

    2016-12-05

    We report correlation energies, electron densities, and exchange-correlation potentials obtained from configuration interaction and density functional calculations on spherically confined He, Be, Be(2+) , and Ne atoms. The variation of the correlation energy with the confinement radius Rc is relatively small for the He, Be(2+) , and Ne systems. Curiously, the Lee-Yang-Parr (LYP) functional works well for weak confinements but fails completely for small Rc . However, in the neutral beryllium atom the CI correlation energy increases markedly with decreasing Rc . This effect is less pronounced at the density-functional theory level. The LYP functional performs very well for the unconfined Be atom, but fails badly for small Rc . The standard exchange-correlation potentials exhibit significant deviation from the "exact" potential obtained by inversion of Kohn-Sham equation. The LYP correlation potential behaves erratically at strong confinements. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  14. Lengthscale dependence of dynamic four-point susceptibilities in glass formers

    OpenAIRE

    Chandler, David; Juan P Garrahan; Jack, Robert L.; Maibaum, Lutz; Pan, Albert C.

    2006-01-01

    Dynamical four-point susceptibilities measure the extent of spatial correlations in the dynamics of glass forming systems. We show how these susceptibilities depend on the length scales that necessarily form part of their definition. The behaviour of these susceptibilities is estimated by means of an analysis in terms of renewal processes within the context of dynamic facilitation. The analytic results are confirmed by numerical simulations of an atomistic model glass-former, and of two kinet...

  15. Face pose tracking using the four-point algorithm

    Science.gov (United States)

    Fung, Ho Yin; Wong, Kin Hong; Yu, Ying Kin; Tsui, Kwan Pang; Kam, Ho Chuen

    2017-06-01

    In this paper, we have developed an algorithm to track the pose of a human face robustly and efficiently. Face pose estimation is very useful in many applications such as building virtual reality systems and creating an alternative input method for the disabled. Firstly, we have modified a face detection toolbox called DLib for the detection of a face in front of a camera. The detected face features are passed to a pose estimation method, known as the four-point algorithm, for pose computation. The theory applied and the technical problems encountered during system development are discussed in the paper. It is demonstrated that the system is able to track the pose of a face in real time using a consumer grade laptop computer.

  16. Accuracy of micro four-point probe measurements on inhomogeneous samples: A probe spacing dependence study

    DEFF Research Database (Denmark)

    Wang, Fei; Petersen, Dirch Hjorth; Østerberg, Frederik Westergaard

    2009-01-01

    In this paper, we discuss a probe spacing dependence study in order to estimate the accuracy of micro four-point probe measurements on inhomogeneous samples. Based on sensitivity calculations, both sheet resistance and Hall effect measurements are studied for samples (e.g. laser annealed samples...... the probe spacing is smaller than 1/40 of the variation wavelength, micro four-point probes can provide an accurate record of local properties with less than 1% measurement error. All the calculations agree well with previous experimental results.......) with periodic variations of sheet resistance, sheet carrier density, and carrier mobility. With a variation wavelength of ¿, probe spacings from 0.0012 to 1002 have been applied to characterize the local variations. The calculations show that the measurement error is highly dependent on the probe spacing. When...

  17. Stiffness identification of four-point-elastic-support rigid plate

    Institute of Scientific and Technical Information of China (English)

    彭利平; 刘初升; 武继达; 王帅

    2015-01-01

    As the stiffness of the elastic support varies with the physical-chemical erosion and mechanical friction, model catastrophe of a single degree-of-freedom (DOF) isolation system may occur. A 3-DOF four-point-elastic-support rigid plate (FERP) structure is presented to describe the catastrophic isolation system. Based on the newly-established structure, theoretical derivation for stiffness matrix calculation by free response (SMCbyFR) and the method of stiffness identification by stiffness matrix disassembly (SIbySMD) are proposed. By integrating the SMCbyFR and the SIbySMD and defining the stiffness assurance criterion (SAC), the procedures for stiffness identification of a FERP structure (SIFERP) are summarized. Then, a numerical example is adopted for the SIFERP validation, in which the simulated tested free response data are generated by the numerical methods, and operation for filtering noise is conducted to imitate the practical application. Results in the numerical example demonstrate the feasibility and accuracy of the developed SIFERP for stiffness identification.

  18. Beyond van der Pauw: Novel methods for four-point magnetotransport characterization

    Science.gov (United States)

    Zhou, Wang

    In this thesis, the conventional four-point measurement technique and the van der Pauw (vdP) method are systematically investigated in the presence of non-ideal conditions, namely, non-uniform carrier density distribution and absence of ohmic contacts, which are nonetheless commonly encountered in semiconductor characterizations. Upon understanding the challenges in the conventional methods, novel characterization techniques are developed to address these challenges. A longitudinal magnetoresistance asymmetry method was developed to study the carrier density non-uniformity in two-dimensional samples. By analyzing the asymmetric longitudinal magnetoresistance under positive and negative B-fields, an analytical model based on a linear density gradient across the sample was deduced to quantitatively describe the asymmetry. Based on the theoretical model, a practical method was described which enabled one to experimentally measure the density gradient within a single sample. The method requires only measurements of longitudinal resistances R xx and Ryy under both positive and negative B-fields, and equations have been provided to extract both the angle and the magnitude of density gradients from the measured resistances. The method was demonstrated in a GaAs quantum well wafer at cryogenic temperatures and n-GaAs bulk-doped wafer at room temperature. In both systems, the density gradient vectors extracted with our method matched well with the interpolated density gradient vectors estimated from actual density distribution maps as a base comparison set, suggesting that our method can be a universal extension of the vdP method to extract density gradients in various systems. The method also allows one to uncover the true local longitudinal resistivity rhoxx at the center of the sample, which the conventional vdP method cannot describe in the presence of non-uniform densities. The ability to find rhoxx makes it possible to study interesting physics in semiconductors such

  19. Spatial correlation between weed species densities and soil properties

    DEFF Research Database (Denmark)

    Walter, Mette; Christensen, Svend; Simmelsgaard, Svend Erik

    2002-01-01

    -correlated with the phosphorus content in the soil in all years. The density of Veronica spp. and Poa annua L. was negatively cross-correlated with pH in all three years. Other spatial cross-correlations that were found in this study were inconsistent over time or field site. The densities of some of the weed species were......The spatial cross-correlation between weed species densities and six soil properties within fields was analysed using cross-semivariograms. The survey was carried out in three successive years in two fields. The most consistent relationship between weed species density (numbers m−2) and soil...... spatially cross-correlated with more than one soil property. The results showed that the range of spatial dependence varied not only between fields, but also between weed species and soil properties, as well as between years. This study indicates that the weed pattern is field-specific and that the spatial...

  20. Density-Matrix Propagation Driven by Semiclassical Correlation

    CERN Document Server

    Elliott, Peter

    2016-01-01

    Methods based on propagation of the one-body reduced density-matrix hold much promise for the simulation of correlated many-electron dynamics far from equilibrium, but difficulties with finding good approximations for the interaction term in its equation of motion have so far impeded their application. These difficulties include the violation of fundamental physical principles such as energy conservation, positivity conditions on the density, or unchanging natural orbital occupation numbers. We review some of the recent efforts to confront these problems, and explore a semiclassical approximation for electron correlation coupled to time-dependent Hartree-Fock propagation. We find that this approach captures changing occupation numbers, and excitations to doubly-excited states, improving over TDHF and adiabatic approximations in density-matrix propagation. However, it does not guarantee $N$-representability of the density-matrix, consequently resulting sometimes in violation of positivity conditions, even thou...

  1. Equilibrium time correlation functions in the low density limit

    NARCIS (Netherlands)

    Beijeren, H. van; Lanford, O.E.; Lebowitz, J.L.; Spohn, H.

    1980-01-01

    We consider a system of hard spheres in thermal equilibrium. Using Lanford's result about the convergence of the solutions of the BBGKY hierarchy to the solutions of the Boltzmann hierarchy, we show that in the low-density limit (Boltzmann-Grad limit): (i) the total time correlation function is

  2. Geological correlations with the interior density structure of Venus

    Science.gov (United States)

    Herrick, Robert R.; Phillips, Roger J.

    1992-01-01

    The paper develops a geophysical model for Venus that allows separation of topography supported by shallow density anomalies, e.g., crustal thickening, from that interpreted to be caused by mantle convection, and produces estimates of the planforms of lithospheric density anomalies and the mantle convection pattern. The topography caused by these two planforms is compared to several global data sets compiled from analysis of Magellan data. The mantle convection pattern agrees qualitatively with numerical simulations by Bercovici et al. (1989) and shows isolated upwellings amidst a network of downwellings. Crustal thickening does not exhibit a similar pattern. Impact crater density is nearly uniform and does not correlate with either crustal thickening or the mantle convection patterns. Large volcanic structures exhibit a good but imperfect correlation with mantle upwellings. Coronae locations are anticorrelated with large upwellings and large downwellings. A scenario is proposed for global tectonics on Venus and its relationship to mantle convection.

  3. Is the Accuracy of Density Functional Theory for Atomization Energies and Densities in Bonding Regions Correlated?

    Science.gov (United States)

    Brorsen, Kurt R; Yang, Yang; Pak, Michael V; Hammes-Schiffer, Sharon

    2017-05-04

    The development of approximate exchange-correlation functionals is critical for modern density functional theory. A recent analysis of atomic systems suggested that some modern functionals are straying from the path toward the exact functional because electron densities are becoming less accurate while energies are becoming more accurate since the year 2000. To investigate this trend for more chemically relevant systems, the electron densities in the bonding regions and the atomization energies are analyzed for a series of diatomic molecules with 90 different functionals. For hybrid generalized gradient approximation functionals developed since the year 2000, the errors in densities and atomization energies are decoupled; the accuracy of the energies remains relatively consistent while the accuracy of the densities varies significantly. Such decoupling is not observed for generalized gradient and meta-generalized gradient approximation functionals. Analysis of electron densities in bonding regions is found to be important for the evaluation of functionals for chemical systems.

  4. Cluster magnetic field observations in the magnetosheath: four-point measurements of mirror structures

    Directory of Open Access Journals (Sweden)

    E. A. Lucek

    Full Text Available The Cluster spacecraft have returned the first simultaneous four-point measurements of the magnetosheath. We present an analysis of data recorded on 10 November 2000, when the four spacecrafts observed an interval of strong mirrorlike activity. Correlation analysis between spacecraft pairs is used to examine the scale size of the mirror structures in three dimensions. Two examples are presented which suggest that the scale size of mirror structures is ~ 1500–3000 km along the flow direction, and shortest along the magnetopause normal (< 600 km, which, in this case, is approximately perpendicular to both the mean magnetic field and the magnetosheath flow vector. Variations on scales of ~ 750–1000 km are found along the maximum variance direction. The level of correlation in this direction, however, and the time lag observed, are found to be variable. These first results suggest that variations occur on scales of the order of the spacecraft separation ( ~ 1000 km in at least two directions, but analysis of further examples and a statistical survey of structures observed with different magnetic field orientations and tetrahedral configurations will enable us to describe more fully the size and orientation of mirror structures.

    Key words. Magnetosphenic physics (magnetosheath; plasma waves and instabilities

  5. Incidence of histological prostatitis and its correlation with PSA density

    Directory of Open Access Journals (Sweden)

    Affonso Celso Piovesan

    2009-11-01

    Full Text Available OBJECTIVE: The aim of this study was to determine the incidence of asymptomatic, histologically proven prostatitis in men with symptoms of benign prostate hyperplasia and to observe the correlation between asymptomatic prostatitis and prostate specific antigen (PSA density. INTRODUCTION: The incidence of type IV prostatitis is unknown. There is a tendency to correlate the presence of inflammatory prostatitis with an elevation of PSA. MATERIALS AND METHODS: From August 2000 to January 2006, 183 patients who underwent surgical treatment for benign prostate hyperplasia as a result of obstructive or irritative symptoms were prospectively studied. In accordance with the histology findings, these patients were divided into two groups: group I included patients with the presence of histological prostatitis and group II included patients with the absence of histological prostatitis. The mean PSA densities were compared. RESULTS: Histological evidence of prostatitis was observed in 145 patients. In this group, the mean PSA density was 0.136 ± 0.095. In 38 cases, there was no evidence of inflammation upon histological examination of the surgical samples. In these 38 cases, the mean PSA density was 0.126 ± 0.129. No statistically significant differences were detected between the two groups; the p-value is 0.124. CONCLUSION: Abnormal PSA density should not be attributed to the inflammatory prostatitis process.

  6. A simple local correlation energy functional for spherically confined atoms from ab initio correlation energy density.

    Science.gov (United States)

    Vyboishchikov, Sergei F

    2017-09-03

    We propose a simple method of calculating the electron correlation energy density e_c(r) and the correlation potential V_c(r) from second-order Møller-Plesset amplitudes and its generalization for the case of a Configuration Interaction wavefunction, based on Nesbet's theorem. The correlation energy density obtained by this method for free and spherically confined Be and He atoms was employed to fit a local analytical density functional based on Wigner's functional. The functional is capable to reproduce a strong increase of the correlation energy with decreasing the confined radius for the Be atom. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. A Tale of Two Electrons: Correlation at High Density

    CERN Document Server

    Loos, Pierre-François

    2010-01-01

    We review our recent progress in the determination of the high-density correlation energy $\\Ec$ in two-electron systems. Several two-electron systems are considered, such as the well known helium-like ions (helium), and the Hooke's law atom (hookium). We also present results regarding two electrons on the surface of a sphere (spherium), and two electrons trapped in a spherical box (ballium). We also show that, in the large-dimension limit, the high-density correlation energy of two opposite-spin electrons interacting {\\em via} a Coulomb potential is given by $\\Ec \\sim -1/(8D^2)$ for any radial external potential $V(r)$, where $D$ is the dimensionality of the space. This result explains the similarity of $\\Ec$ in the previous two-electron systems for $D=3$.

  8. Four point function of R-currents in N=4 SYM in the Regge limit at weak coupling

    Energy Technology Data Exchange (ETDEWEB)

    Bartels, J.; Mischler, A.M.; Salvadore, M. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik

    2008-04-15

    We compute, in N = 4 super Yang-Mills, the four point correlation function of R-currents in the Regge limit in the leading logarithmic approximation at weak coupling. Such a correlator is the closest analog to photon-photon scattering within QCD, and there is a well defined procedure to perform the analogous computation at strong coupling via AdS/CFT. The main result of this paper is, on the gauge theory side, the proof of Regge factorization and the explicit computation of the R-current impact factors. (orig.)

  9. EXISTENCE FOR SECOND-ORDER FOUR-POINT BOUNDARY VALUE PROBLEM AT RESONANCE

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper is concerned with the existence of solutions for a second-order four-point boundary value problem at resonance. The main methods depend on the technique of the upper and lower solutions and the coincidence degree theory.

  10. Resolution enhancement of scanning four-point-probe measurements on two-dimensional systems

    DEFF Research Database (Denmark)

    Hansen, Torben Mikael; Stokbro, Kurt; Hansen, Ole;

    2003-01-01

    A method to improve the resolution of four-point-probe measurements of two-dimensional (2D) and quasi-2D systems is presented. By mapping the conductance on a dense grid around a target area and postprocessing the data, the resolution can be improved by a factor of approximately 50 to better than 1....../15 of the four-point-probe electrode spacing. The real conductance sheet is simulated by a grid of discrete resistances, which is optimized by means of a standard optimization algorithm, until the simulated voltage-to-current ratios converges with the measurement. The method has been tested against simulated...... data as well as real measurements and is found to successfully deconvolute the four-point-probe measurements. In conjunction with a newly developed scanning four-point probe with electrode spacing of 1.1 µm, the method can resolve the conductivity with submicron resolution. ©2003 American Institute...

  11. Mesoscopic current transport in two-dimensional materials with grain boundaries: Four-point probe resistance and Hall effect

    Science.gov (United States)

    Lotz, Mikkel R.; Boll, Mads; Østerberg, Frederik W.; Hansen, Ole; Petersen, Dirch H.

    2016-10-01

    We have studied the behavior of micro four-point probe (M4PP) measurements on two-dimensional (2D) sheets composed of grains of varying size and grain boundary resistivity by Monte Carlo based finite element (FE) modelling. The 2D sheet of the FE model was constructed using Voronoi tessellation to emulate a polycrystalline sheet, and a square sample was cut from the tessellated surface. Four-point resistances and Hall effect signals were calculated for a probe placed in the center of the square sample as a function of grain density n and grain boundary resistivity ρ GB . We find that the dual configuration sheet resistance as well as the resistance measured between opposing edges of the square sample have a simple unique dependency on the dimension-less parameter √{ n } ρ GB G 0 , where G0 is the sheet conductance of a grain. The value of the ratio R A / R B between resistances measured in A- and B-configurations depends on the dimensionality of the current transport (i.e., one- or two-dimensional). At low grain density or low grain boundary resistivity, two-dimensional transport is observed. In contrast, at moderate grain density and high grain resistivity, one-dimensional transport is seen. Ultimately, this affects how measurements on defective systems should be interpreted in order to extract relevant sample parameters. The Hall effect response in all M4PP configurations was only significant for moderate grain densities and fairly large grain boundary resistivity.

  12. Is Abdominal Muscle Activity Different from Lumbar Muscle Activity during Four-Point Kneeling?

    OpenAIRE

    Soraya Pirouzi; Farahnaz Emami; Shohreh Taghizadeh; Ali Ghanbari

    2013-01-01

    Background: Stabilization exercises can improve the performance of trunk and back muscles, which are effective in the prevention and treatment of low back pain. The four-point kneeling exercise is one of the most common types of stabilization exercises. This quasi-experimental study aimed to evaluate and compare the level of activation between abdominal and lumbar muscles in the different stages of the four-point kneeling exercise. Methods: The present study was conducted on 30 healthy wom...

  13. Conductivity of individual particles measured by a microscopic four-point-probe method

    OpenAIRE

    Ling Sun; Jianjun Wang; Elmar Bonaccurso

    2013-01-01

    We introduce a technique for measuring the conductivity of individual hybrid metal, semiconducting core-shell and full-metal conducting particles by a microscopic four-point probe (μ-4PP) method. The four-point probe geometry allows for minimizing contact resistances between electrodes and particles. By using a focused ion beam we fabricate platinum nanoleads between four microelectrodes on a silicon chip and an individual particle, and determine the particle's conductivity via sensitive curr...

  14. Optimally focused cold atom systems obtained using density-density correlations.

    Science.gov (United States)

    Putra, Andika; Campbell, Daniel L; Price, Ryan M; De, Subhadeep; Spielman, I B

    2014-01-01

    Resonant absorption imaging is a common technique for detecting the two-dimensional column density of ultracold atom systems. In many cases, the system's thickness along the imaging direction greatly exceeds the imaging system's depth of field, making the identification of the optimally focused configuration difficult. Here we describe a systematic technique for bringing Bose-Einstein condensates (BEC) and other cold-atom systems into an optimal focus even when the ratio of the thickness to the depth of field is large: a factor of 8 in this demonstration with a BEC. This technique relies on defocus-induced artifacts in the Fourier-transformed density-density correlation function (the power spectral density, PSD). The spatial frequency at which these artifacts first appear in the PSD is maximized on focus; the focusing process therefore both identifies and maximizes the range of spatial frequencies over which the PSD is uncontaminated by finite-thickness effects.

  15. Some Correlations for Saturated-Liquid Density of Refrigerant Mixtures

    Science.gov (United States)

    Maezawa, Yukishige; Sato, Haruki; Watanabe, Koichi

    Three methods to correlate and estimate the saturated-1iquid density of refrigerant mixtures are compared and evaluated on the basis of the measurements for five bibary and one ternary mixtures performed by the present authors. The first of them is a method using Peng-Robinson equation (PR-method) proposed originally by Peneloux et al. Since this method dose not require any measurements of the saturated-liquid density of mixture, it is useful for the estimation. However, the applicability of this method to various substances may be restricted. The second is the modified Rackett equation proposed by Spencer and Dannar (mR-method). The temperature functional form of this equation is quite simple, so it is useful to use it as a functional form of the fitting. Unfortunately this method can not be used for strongly non-ideal mixtures. The last one is the Hankinson-Brobst-Thomson equation (HBT-method). This method can provide the most accurate density values among the three methods with two kinds of binary parameters where these binary parameters are introduced by the present authors. In the case that many experimental saturated liquid densities of mixtures are available in the wide range of temperatures, the HBT-method is recommended for the practical use.

  16. Covariance and correlation estimation in electron-density maps.

    Science.gov (United States)

    Altomare, Angela; Cuocci, Corrado; Giacovazzo, Carmelo; Moliterni, Anna; Rizzi, Rosanna

    2012-03-01

    Quite recently two papers have been published [Giacovazzo & Mazzone (2011). Acta Cryst. A67, 210-218; Giacovazzo et al. (2011). Acta Cryst. A67, 368-382] which calculate the variance in any point of an electron-density map at any stage of the phasing process. The main aim of the papers was to associate a standard deviation to each pixel of the map, in order to obtain a better estimate of the map reliability. This paper deals with the covariance estimate between points of an electron-density map in any space group, centrosymmetric or non-centrosymmetric, no matter the correlation between the model and target structures. The aim is as follows: to verify if the electron density in one point of the map is amplified or depressed as an effect of the electron density in one or more other points of the map. High values of the covariances are usually connected with undesired features of the map. The phases are the primitive random variables of our probabilistic model; the covariance changes with the quality of the model and therefore with the quality of the phases. The conclusive formulas show that the covariance is also influenced by the Patterson map. Uncertainty on measurements may influence the covariance, particularly in the final stages of the structure refinement; a general formula is obtained taking into account both phase and measurement uncertainty, valid at any stage of the crystal structure solution.

  17. Patching the Exchange-Correlation Potential in Density Functional Theory.

    Science.gov (United States)

    Huang, Chen

    2016-05-10

    A method for directly patching exchange-correlation (XC) potentials in materials is derived. The electron density of a system is partitioned into subsystem densities by dividing its Kohn-Sham (KS) potential among the subsystems. Inside each subsystem, its projected KS potential is required to become the total system's KS potential. This requirement, together with the nearsightedness principle of electronic matters, ensures that the electronic structures inside subsystems can be good approximations to the total system's electronic structure. The nearsightedness principle also ensures that subsystem densities could be well localized in their regions, making it possible to use high-level methods to invert the XC potentials for subsystem densities. Two XC patching methods are developed. In the local XC patching method, the total system's XC potential is improved in the cluster region. We show that the coupling between a cluster and its environment is important for achieving a fast convergence of the electronic structure in the cluster region. In the global XC patching method, we discuss how to patch the subsystem XC potentials to construct the XC potential in the total system, aiming to scale up high-level quantum mechanics simulations of materials. Proof-of-principle examples are given.

  18. Mesoscopic current transport in two-dimensional materials with grain boundaries: Four-point probe resistance and Hall effect

    DEFF Research Database (Denmark)

    Lotz, Mikkel Rønne; Boll, Mads; Østerberg, Frederik Westergaard

    2016-01-01

    We have studied the behavior of micro four-point probe (M4PP) measurements on two-dimensional (2D) sheets composed of grains of varying size and grain boundary resistivity by Monte Carlo based finite element (FE) modelling. The 2D sheet of the FE model was constructed using Voronoi tessellation......-configurations depends on the dimensionality of the current transport (i.e., one- or two-dimensional). At low grain density or low grain boundary resistivity, two-dimensional transport is observed. In contrast, at moderate grain density and high grain resistivity, one-dimensional transport is seen. Ultimately......, this affects how measurements on defective systems should be interpreted in order to extract relevant sample parameters. The Hall effect response in all M4PP configurations was only significant for moderate grain densities and fairly large grain boundary resistivity....

  19. Density-functional formula for strongly correlated systems

    Institute of Scientific and Technical Information of China (English)

    WANG Huaiyu; HAN Rushan; CHEN Nanxian

    2005-01-01

    Density functional method is applied for strongly correlated systems. Based on the assumption that the systems are composed of electrons in singly-occupied orbitals and those in doubly-occupied orbitals, a set of self-consistent equations are obtained by standard variation procedure. The equations consist of two parts. One part is to solve the wave functions of the electrons in singly-occupied orbitals and the other is to solve the wave functions of the electrons in doubly-occupied orbitals. The physical meanings of the terms appearing in the equations are discussed.

  20. Laplacian-level density functionals for the kinetic energy density and exchange-correlation energy

    Science.gov (United States)

    Perdew, John P.; Constantin, Lucian A.

    2007-04-01

    We construct a Laplacian-level meta-generalized-gradient-approximation (meta-GGA) for the noninteracting (Kohn-Sham orbital) positive kinetic energy density τ of an electronic ground state of density n . This meta-GGA is designed to recover the fourth-order gradient expansion τGE4 in the appropriate slowly varying limit and the von Weizsäcker expression τW=∣∇n∣2/(8n) in the rapidly varying limit. It is constrained to satisfy the rigorous lower bound τW(r)⩽τ(r) . Our meta-GGA is typically a strong improvement over the gradient expansion of τ for atoms, spherical jellium clusters, jellium surfaces, the Airy gas, Hooke’s atom, one-electron Gaussian density, quasi-two-dimensional electron gas, and nonuniformly scaled hydrogen atom. We also construct a Laplacian-level meta-GGA for exchange and correlation by employing our approximate τ in the Tao-Perdew-Staroverov-Scuseria (TPSS) meta-GGA density functional. The Laplacian-level TPSS gives almost the same exchange-correlation enhancement factors and energies as the full TPSS, suggesting that τ and ∇2n carry about the same information beyond that carried by n and ∇n . Our kinetic energy density integrates to an orbital-free kinetic energy functional that is about as accurate as the fourth-order gradient expansion for many real densities (with noticeable improvement in molecular atomization energies), but considerably more accurate for rapidly varying ones.

  1. Sensitivity study of micro four-point probe measurements on small samples

    DEFF Research Database (Denmark)

    Wang, Fei; Petersen, Dirch Hjorth; Hansen, Torben Mikael

    2010-01-01

    The authors calculate the sensitivities of micro four-point probe sheet resistance and Hall effect measurements to the local transport properties of nonuniform material samples. With in-line four-point probes, the measured dual configuration sheet resistance is more sensitive near the inner two...... probes than near the outer ones. The sensitive area is defined for infinite film, circular, square, and rectangular test pads, and convergent sensitivities are observed for small samples. The simulations show that the Hall sheet resistance RH in micro Hall measurements with position error suppression...

  2. Resolution enhancement of scanning four-point-probe measurements on two-dimensional systems.

    OpenAIRE

    Hansen, Torben Mikael; Stokbro, Kurt; Hansen, Ole; Hassenkam, T.; Shiraki, I.; Hasegawa, S.; Bøggild, Peter

    2003-01-01

    A method to improve the resolution of four-point-probe measurements of two-dimensional (2D) and quasi-2D systems is presented. By mapping the conductance on a dense grid around a target area and postprocessing the data, the resolution can be improved by a factor of approximately 50 to better than 1/15 of the four-point-probe electrode spacing. The real conductance sheet is simulated by a grid of discrete resistances, which is optimized by means of a standard optimization algorithm, until the ...

  3. Direct measurement of resistance of multiwalled carbon nanotubes using micro four-point probes

    DEFF Research Database (Denmark)

    Dohn, Søren; Mølhave, Kristian; Bøggild, Peter

    2005-01-01

    The electrical properties of multiwalled carbon nanotubes was investigated by micro four point probes, fabricated using conventional silicon microfabrication techniques. After positioning of chemical vapour deposition-grown multi-walled carbon nanotubes on a SiO2 substrate, the two- or four-point...... resistance at specific positions along the nanotubes, was measured by microprobes with different microelectrocle spacings. Individual nanotubes were investigated in more detail by measuring current as a function of bias voltage until the point of failure and the results are compared to previously reported...

  4. Functional relations for the density-functional exchange and correlation functionals connecting functionals at three densities

    Science.gov (United States)

    Joubert, Daniel P.

    2012-03-01

    It is shown that the density-functional-theory exchange and correlation functionals satisfy 0=γEhx[ρN]+2Ecγ[ρN]-γEhx[ρN-1γ]-2Ecγ[ρN-1γ]+2∫d3r'[ρN-10(r)-ρN-1γ(r)]v0([ρN];r)+∫d3r'[ρN-10(r)-ρN-1γ(r)]r·∇v0([ρN];r)+∫d3r'ρN(r)r·∇vcγ([ρN];r)-∫d3r'ρN-1γ(r)r·∇vcγ([ρN-1γ];r)-∫d3r'fγ(r)r·∇vhxcγ([ρN];r)-2∫d3r'fγ(r)vhxcγ([ρN];r). In the derivation of this equation the adiabatic connection formulation is used, where the ground-state density of an N-electron system ρN is kept constant independent of the electron-electron coupling strength γ. Here Ehx[ρ] is the Hartree plus exchange energy, Ecγ[ρ] is the correlation energy, vhxcγ[ρ] is the Hartree plus exchange-correlation potential, vc[ρ] is the correlation potential, and v0[ρ]is the Kohn-Sham potential. The charge densities ρN and ρN-1γ are the N- and (N-1)-electron ground-state densities of the same Hamiltonian at electron-electron coupling strength γ. fγ(r)=ρN(r)-ρN-1γ(r) is the Fukui function. This equation can be useful in testing the internal self-consistency of approximations to the exchange and correlation functionals. As an example the identity is tested on the analytical Hooke's atom charge density for some frequently used approximate functionals.

  5. Electrical conduction through surface superstructures measured by microscopic four-point probes

    DEFF Research Database (Denmark)

    Hasegawa, S.; Shiraki, I.; Tanabe, F.

    2003-01-01

    For in-situ measurements of the local electrical conductivity of well-defined crystal surfaces in ultra-high vacuum, we have developed two kinds of microscopic four-point probe methods. One involves a "four-tip STM prober," in which four independently driven tips of a scanning tunneling microscope...

  6. Direct measurement of surface-state conductance by microscopic four-point probe method

    DEFF Research Database (Denmark)

    Hasegawa, S.; Shiraki, I.; Tanikawa, T.

    2002-01-01

    For in situ measurements of local electrical conductivity of well defined crystal surfaces in ultrahigh vacuum, we have developed microscopic four-point probes with a probe spacing of several micrometres, installed in a scanning-electron - microscope/electron-diffraction chamber. The probe...

  7. Design of a miniature electrolyte conductivity probe using ISFETs in a four point configuration

    NARCIS (Netherlands)

    Volanschi, A.; Olthuis, W.; Bergveld, P.

    1994-01-01

    In this work the design, fabrication and testing of a four point electrode configuration based on ISFETs for the measurement of electrolytic conductivity are presented. The final design uses a distance between the ISFET gates of only 100 ¿m allowing a chip area in contact with the electrolyte of 2.2

  8. The conductivity of Bi(111) investigated with nanoscale four point probes

    DEFF Research Database (Denmark)

    Wells, J.W.; Handrup, K.; Kallehauge, J.F.;

    2008-01-01

    The room temperature conductance of Bi(111) was measured using microscopic four point probes with a contact spacing down to 500 nm. The conductance is remarkably similar to that of the bulk, indicating that surface scattering is not a major mechanism for restricting the mobility at this length...

  9. Degradation Assessment in IGBT Modules Using Four-Point Probing Approach

    DEFF Research Database (Denmark)

    Pedersen, Kristian Bonderup; Kristensen, Peter Kjær; Popok, Vladimir;

    2015-01-01

    Four-point probing of electrical parameters on various components of IGBT modules is suggested as an approach for the estimation of degradation in stressed devices. By comparison of these parameters for stressed and new components one can evaluate an overall degradation of the module and find out...

  10. Bubble shape and orientation determination with a four-point optical fibre probe

    NARCIS (Netherlands)

    Guet, S.; Luther, S.; Ooms, G.

    2003-01-01

    We propose a new method to estimate the aspect ratio and orientation of bubbles by using their time series obtained with a four-point optical-fibre probe. The feasibility and accuracy of the method was first analysed by using synthetic bubble–probe interaction data and single bubble experiments in p

  11. Symmetric point four-point functions at one loop in QCD

    Science.gov (United States)

    Gracey, J. A.

    2017-03-01

    We evaluate the quartic ghost and quark Green's functions as well as the gluon-ghost, gluon-quark and ghost-quark four-point functions of quantum chromodynamics at one loop at the fully symmetric point in a linear covariant gauge. Similar expressions for the analogous Green's functions in quantum electrodynamics are also provided.

  12. Review of electrical characterization of ultra-shallow junctions with micro four-point probes

    DEFF Research Database (Denmark)

    Petersen, Dirch Hjorth; Hansen, Ole; Hansen, Torben M.;

    2010-01-01

    techniques will become even more evident. In several recent studies micro four-point probe (M4PP) has been demonstrated as a reliable high precision metrology method for both sheet resistance and Hall effect measurements of ultra-shallow implants and has revealed a promising potential for carrier profiling....

  13. Existence of Solutions for Nonlinear Four-Point -Laplacian Boundary Value Problems on Time Scales

    Directory of Open Access Journals (Sweden)

    Topal SGulsan

    2009-01-01

    Full Text Available We are concerned with proving the existence of positive solutions of a nonlinear second-order four-point boundary value problem with a -Laplacian operator on time scales. The proofs are based on the fixed point theorems concerning cones in a Banach space. Existence result for -Laplacian boundary value problem is also given by the monotone method.

  14. Transport through correlated systems with density functional theory

    Science.gov (United States)

    Kurth, S.; Stefanucci, G.

    2017-10-01

    We present recent advances in density functional theory (DFT) for applications in the field of quantum transport, with particular emphasis on transport through strongly correlated systems. We review the foundations of the popular Landauer–Büttiker(LB)  +  DFT approach. This formalism, when using approximations to the exchange-correlation (xc) potential with steps at integer occupation, correctly captures the Kondo plateau in the zero bias conductance at zero temperature but completely fails to capture the transition to the Coulomb blockade (CB) regime as the temperature increases. To overcome the limitations of LB  +  DFT, the quantum transport problem is treated from a time-dependent (TD) perspective using TDDFT, an exact framework to deal with nonequilibrium situations. The steady-state limit of TDDFT shows that in addition to an xc potential in the junction, there also exists an xc correction to the applied bias. Open shell molecules in the CB regime provide the most striking examples of the importance of the xc bias correction. Using the Anderson model as guidance we estimate these corrections in the limit of zero bias. For the general case we put forward a steady-state DFT which is based on one-to-one correspondence between the pair of basic variables, steady density on and steady current across the junction and the pair local potential on and bias across the junction. Like TDDFT, this framework also leads to both an xc potential in the junction and an xc correction to the bias. Unlike TDDFT, these potentials are independent of history. We highlight the universal features of both xc potential and xc bias corrections for junctions in the CB regime and provide an accurate parametrization for the Anderson model at arbitrary temperatures and interaction strengths, thus providing a unified DFT description for both Kondo and CB regimes and the transition between them.

  15. Out-of-Time-Ordered Density Correlators in Luttinger Liquids

    Science.gov (United States)

    Dóra, Balázs; Moessner, Roderich

    2017-07-01

    Information scrambling and the butterfly effect in chaotic quantum systems can be diagnosed by out-of-time-ordered (OTO) commutators through an exponential growth and large late time value. We show that the latter feature shows up in a strongly correlated many-body system, a Luttinger liquid, whose density fluctuations we study at long and short wavelengths, both in equilibrium and after a quantum quench. We find rich behavior combining robustly universal and nonuniversal features. The OTO commutators display temperature- and initial-state-independent behavior and grow as t2 for short times. For the short-wavelength density operator, they reach a sizable value after the light cone only in an interacting Luttinger liquid, where the bare excitations break up into collective modes. This challenges the common interpretation of the OTO commutator in chaotic systems. We benchmark our findings numerically on an interacting spinless fermion model in 1D and find persistence of central features even in the nonintegrable case. As a nonuniversal feature, the short-time growth exhibits a distance-dependent power.

  16. Correlation of Density Pedestal Width and Neutral Penetration

    Science.gov (United States)

    Xu, X. Q.; Nevins, W. M.; Cohen, R. H.; Rognlien, T. D.; Umansky, M. V.

    2003-10-01

    Pedestal studies in DIII-D and C-Mod find a good correlation between the width of the H-mode density barrier and the neutral penetration length.[1][2] These results suggest that the width may be set by the combined effects of neutral and plasma transport. This paper is a report on fluid simulations of boundary plasma using BOUT code [3] with neutral source added. Thus both neutral and plasma physics are treated. The plasma transport is self-consistently driven by boundary turbulence due to the resistive X-point mode, while neutral is described by a simple fluid diffusive model. The plasma profiles are evolved on the same time scale as the turbulence for the given heat source from the core plasma and particle source from the neutrals. For prescribed neutral profiles, we find the formation of a density pedestal inside the separatrix in the L-mode even though the calculated plasma diffusion coefficients are almost radially constant and without the formation of a temperature pedestal. These results support the hypothesis that particle fueling can provide the dominant control for the size of the H-mode density barrier. The width of the density barrier, and its relationship to pedestal height and neutral penetration length at the midplane, will be given by using hyperbolic-tangent fit to the simulation data. [1] R.J.Groebner, M.A.Mahdavi, A.W.Leonard, 19th IAEA Fusion Energy Conference(Lyon, France, 14 to 19 October 2002), IAEA-CN-94/EX/C2-3. [2] D.Mossessian, J.W.Hughes, M.Greenwald, et al., ``Local dimensionless identity method as a tool for studying H-mode pedestal'', The 9th Joint US-European TTF workshop (Madison, Wisconsin, April 2nd - 5th, 2003). [3] X.Q.Xu, R.H.Cohen, T.D.Rognlien and J.R.Myra, Physics of Plasma, Vol. 7, 1951-1958 (2000).

  17. Molecular Kohn-Sham exchange-correlation potential from the correlated ab initio electron density

    Science.gov (United States)

    Gritsenko, Oleg V.; van Leeuwen, Robert; Baerends, Evert Jan

    1995-09-01

    The molecular Kohn-Sham (KS) exchange-correlation potential vxc has been constructed for LiH from the correlated ab initio density ρ by means of the simple iterative procedure developed by van Leeuwen and Baerends [Phys. Rev. A 49, 2421 (1994)]. The corresponding KS energy characteristics, such as the kinetic energy of noninteracting particles Ts, kinetic part of the exchange-correlation energy Tc, and energy of the highest occupied molecular orbital ɛN, have been obtained with reasonable accuracy. A relation between the form of vxc and the electronic structure of LiH has been discussed. Test calculations for the two-electron H2 molecule have shown the efficiency of the procedure.

  18. Ultrasound-guided bilateral dual transversus abdominis plane block: a new four-point approach

    DEFF Research Database (Denmark)

    Neimann, Jens Dupont Børglum; Maschmann, C; Belhage, B;

    2011-01-01

    Background: We describe a new ultrasound-guided bilateral dual transversus abdominis plane block. Our hypothesis was that we could anaesthetize both the upper (Th6–Th9) and the lower (Th10–Th12) abdominal wall bilaterally using a four-point single-shot technique to provide effective post-operativ......Background: We describe a new ultrasound-guided bilateral dual transversus abdominis plane block. Our hypothesis was that we could anaesthetize both the upper (Th6–Th9) and the lower (Th10–Th12) abdominal wall bilaterally using a four-point single-shot technique to provide effective post...... scale 0–10) from a mean of 8.2 to a mean of 2.2 10 min after block performance (P

  19. Experimental and Theoretical Deflections of Hybrid Composite Sandwich Panel under Four-point Bending Load

    Directory of Open Access Journals (Sweden)

    Jauhar Fajrin

    2017-03-01

    Full Text Available This paper presents a comparison of theoretical and experimental deflection of a hybrid sandwich panel under four-point bending load. The paper initially presents few basic equations developed under three-point load, followed by development of model under four-point bending load and a comparative analysis between theoretical and experimental results. It was found that the proposed model for predicting the deflection of hybrid sandwich panels provided fair agreement with the experimental values. Most of the sandwich panels showed theoretical deflection values higher than the experimental values, which is desirable in the design. It was also noticed that the introduction of intermediate layer does not contribute much to reduce the deflection of sandwich panel as the main contributor for the total deflection was the shear deformation of the core that mostly determined by the geometric of the samples and the thickness of the core.

  20. Conductivity of individual particles measured by a microscopic four-point-probe method.

    Science.gov (United States)

    Sun, Ling; Wang, Jianjun; Bonaccurso, Elmar

    2013-01-01

    We introduce a technique for measuring the conductivity of individual hybrid metal, semiconducting core-shell and full-metal conducting particles by a microscopic four-point probe (μ-4PP) method. The four-point probe geometry allows for minimizing contact resistances between electrodes and particles. By using a focused ion beam we fabricate platinum nanoleads between four microelectrodes on a silicon chip and an individual particle, and determine the particle's conductivity via sensitive current and voltage measurements. Up to sixteen particles can be taken up by each chip, which allows for multiple conductivity measurements by simply multiplexing the electric contacts connected to a multimeter. Although, for demonstration, we used full Au (conducting) and Ag-coated latex particles (semiconducting) of a few micrometers in diameter, the method can be applied to other types of conducting or semiconducting particles of different diameters.

  1. Four-point bending test of the Bauschinger effect in prestrained IF steel thin sheet

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Hiroyuki, E-mail: hkato@eng.hokudai.ac.jp [Mechanical and Space Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Sasaki, Kazuaki [Mechanical and Space Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Mori, T. [National Defense Academy, Yokosuka 239-0811 (Japan)

    2015-08-26

    The Bauschinger effect in a 1 mm thick sheet of interstitial free (IF) steel was examined by tensile testing (prestraining) and subsequent four-point bending. The effect was absent when the prestrain was below 4% and was present when the prestrain was above 4%. The Bauschinger effect parameter determined the elastic back stress which developed after prestraining. The occurrence of back stress coincided with the development of dislocation cell structures, observed with transmission electron microscopy.

  2. On the ABJM four-point amplitude at three loops and BDS exponentiation

    Science.gov (United States)

    Bianchi, Marco S.; Leoni, Matias

    2014-11-01

    We study the three-loop four-point amplitude in ABJM theory. We determine the dual conformal invariant integrals with highest number of propagators and fix their coefficients by two-particle cuts. Evaluating such a combination of integrals in dimensional regularization we provide evidence for exponentiation of the amplitude, including the finite terms. In addition we show that the three-loop amplitude can be expressed in terms of classical polylogarithms of uniform degree of transcendentality.

  3. On the ABJM four-point amplitude at three loops and BDS exponentiation

    CERN Document Server

    Bianchi, Marco S

    2014-01-01

    We study the three-loop four-point amplitude in ABJM theory. We determine the dual conformal invariant integrals with highest number of propagators and fix their coefficients by two-particle cuts. Evaluating such a combination of integrals in dimensional regularization we provide evidence for exponentiation of the amplitude, including the finite terms. In addition we show that the three-loop amplitude can be expressed in terms of classical polylogarithms of uniform degree of transcendentality.

  4. Fourth-Order Four-Point Boundary Value Problem: A Solutions Funnel Approach

    Directory of Open Access Journals (Sweden)

    Panos K. Palamides

    2012-01-01

    Full Text Available We investigate the existence of positive or a negative solution of several classes of four-point boundary-value problems for fourth-order ordinary differential equations. Although these problems do not always admit a (positive Green's function, the obtained solution is still of definite sign. Furthermore, we prove the existence of an entire continuum of solutions. Our technique relies on the continuum property (connectedness and compactness of the solutions funnel (Kneser's Theorem, combined with the corresponding vector field.

  5. Dynamic Carrying Capacity Analysis of Double-Row Four-Point Contact Ball Slewing Bearing

    OpenAIRE

    Yunfeng Li; Di Jiang

    2015-01-01

    Carrying capacity is the most important performance index for slewing bearings. Maximizing the carrying capacity of slewing bearing is one pursuing goal for the bearing designer; this is usually realized by optimizing the design parameters. A method of analyzing the carrying capacity of double-row four-point contact ball slewing bearing by using dynamic carrying capacity surfaces was proposed in this paper. Based on the dynamic load carrying capacity surface of the slewing bearing, the effect...

  6. Revenue Management Performance Drivers: An Empirical Analysis at Four Points by Sheraton

    OpenAIRE

    Shroff, Avinash

    2009-01-01

    The purpose of this management project is to analyse the current and future scenario of the revenue streams of the Four Points hotel Mumbai in India. Revenue Management (RM) is an important tool for matching supply and demand by segmenting customers into different segments based on their willingness-to-pay and allocating scarce capacity to the different segments in a way that maximizes firm revenues. The benefits of RM are well accepted in the hospitality industry, and the technical aspects o...

  7. Manifest Ultraviolet Behavior in the Three-Loop Four-Point Amplitude of N=8 Supergravity

    Energy Technology Data Exchange (ETDEWEB)

    Bern, Z.; Carrasco, J.J.M.; /UCLA; Dixon, L.J.; /SLAC; Johansson, H.; /UCLA; Roiban, R.; /Penn State U.

    2008-09-03

    Using the method of maximal cuts, we obtain a form of the three-loop four-point scattering amplitude of N = 8 supergravity in which all ultraviolet cancellations are made manifest. The Feynman loop integrals that appear have a graphical representation with only cubic vertices, and numerator factors that are quadratic in the loop momenta, rather than quartic as in the previous form. This quadratic behavior reflects cancellations beyond those required for finiteness, and matches the quadratic behavior of the three-loop four-point scattering amplitude in N = 4 super-Yang-Mills theory. By direct integration we confirm that no additional cancellations remain in the N = 8 supergravity amplitude, thus demonstrating that the critical dimension in which the first ultraviolet divergence occurs at three loops is D{sub c} = 6. We also give the values of the three-loop divergences in D = 7, 9, 11. In addition, we present the explicitly color-dressed three-loop four-point amplitude of N = 4 super-Yang-Mills theory.

  8. Development of a practical multicomponent density functional for electron-proton correlation to produce accurate proton densities

    Science.gov (United States)

    Yang, Yang; Brorsen, Kurt R.; Culpitt, Tanner; Pak, Michael V.; Hammes-Schiffer, Sharon

    2017-09-01

    Multicomponent density functional theory (DFT) enables the consistent quantum mechanical treatment of both electrons and protons. A major challenge has been the design of electron-proton correlation (epc) functionals that produce even qualitatively accurate proton densities. Herein an electron-proton correlation functional, epc17, is derived analogously to the Colle-Salvetti formalism for electron correlation and is implemented within the nuclear-electronic orbital (NEO) framework. The NEO-DFT/epc17 method produces accurate proton densities efficiently and is promising for diverse applications.

  9. Is Abdominal Muscle Activity Different from Lumbar Muscle Activity during Four-Point Kneeling?

    Directory of Open Access Journals (Sweden)

    Soraya Pirouzi

    2013-12-01

    Full Text Available Background: Stabilization exercises can improve the performance of trunk and back muscles, which are effective in the prevention and treatment of low back pain. The four-point kneeling exercise is one of the most common types of stabilization exercises. This quasi-experimental study aimed to evaluate and compare the level of activation between abdominal and lumbar muscles in the different stages of the four-point kneeling exercise. Methods: The present study was conducted on 30 healthy women between 20 and 30 years old. Muscle activity was recorded bilaterally from transversus abdominis, internal oblique, and multifidus muscles with an electromyography (EMG device during the different stages of the four-point kneeling exercise. All the collected EMG data were normalized to the percentage of maximum voluntary isometric contraction. The repeated measures ANOVA and paired t-test were used for the statistical analysis of the data. Results: A comparison between mean muscle activation in right arm extension and left leg extension showed that left internal oblique and left transverse abdominis muscles produced greater activation during left leg extension (P<0.05. The comparison of mean muscle activation between right arm extension and the bird-dog position showed that, except for the right internal oblique, all the muscles produced higher activation in the bird-dog stage (P<0.05. In comparison to the bird-dog stage, the left multifidus showed high activation during left leg extension (P<0.05. Conclusion: The results of this study showed that the activity of all the above-mentioned muscles during quadruped exercise can provide stability, coordination, and smoothness of movements.

  10. An all order identity between ABJM and N=4 SYM four-point amplitudes

    CERN Document Server

    Bianchi, Marco S; Penati, Silvia

    2011-01-01

    We derive an exact algebraic identity between the two-loop four-point amplitude in ABJM theory and the corresponding one-loop amplitude in N=4 SYM theory. This identity generalizes previous partial results to an exact relation valid at all orders in the IR regulator. Moreover, it allows to conjecture an exact iterative expression for the complete three dimensional amplitude in terms of the BDS ansatz for the four dimensional one, indicating that the strict relation between the two amplitudes experimented at two loops might propagate to all orders. In particular, an almost complete expression for the ABJM amplitude at four loops is derived.

  11. Automatized channel for resistivity measurements in layered materials by four-point probe technique

    Science.gov (United States)

    Gryaznov, A. O.; Savchenko, S. S.; Vokhmintsev, A. S.; Weinstein, I. A.

    2016-09-01

    An automatized channel for measuring the resistivity in materials by the four-point probe technique was developed. The installation was based on Cascade Microtech MPS150 microprobe station, National Instruments PXIe-4143 power supply unit and PXI-4072 digital multimeter. Registration modes of surface and bulk specific resistance for samples with positioning the probes in a line or at square vertices were implemented. Measurements under corresponding modes were carried out for metallic, semiconducting bulk samples and thin coatings. Conductive and optical properties of 10, 20 and 30 nm Au layers formed on quartz glass by magnetron sputtering were investigated.

  12. Electrically continuous graphene from single crystal copper verified by terahertz conductance spectroscopy and micro four-point probe.

    Science.gov (United States)

    Buron, Jonas D; Pizzocchero, Filippo; Jessen, Bjarke S; Booth, Timothy J; Nielsen, Peter F; Hansen, Ole; Hilke, Michael; Whiteway, Eric; Jepsen, Peter U; Bøggild, Peter; Petersen, Dirch H

    2014-11-12

    The electrical performance of graphene synthesized by chemical vapor deposition and transferred to insulating surfaces may be compromised by extended defects, including for instance grain boundaries, cracks, wrinkles, and tears. In this study, we experimentally investigate and compare the nano- and microscale electrical continuity of single layer graphene grown on centimeter-sized single crystal copper with that of previously studied graphene films, grown on commercially available copper foil, after transfer to SiO2 surfaces. The electrical continuity of the graphene films is analyzed using two noninvasive conductance characterization methods: ultrabroadband terahertz time-domain spectroscopy and micro four-point probe, which probe the electrical properties of the graphene film on different length scales, 100 nm and 10 μm, respectively. Ultrabroadband terahertz time-domain spectroscopy allows for measurement of the complex conductance response in the frequency range 1-15 terahertz, covering the entire intraband conductance spectrum, and reveals that the conductance response for the graphene grown on single crystalline copper intimately follows the Drude model for a barrier-free conductor. In contrast, the graphene grown on commercial copper foil shows a distinctly non-Drude conductance spectrum that is better described by the Drude-Smith model, which incorporates the effect of preferential carrier backscattering associated with extended, electronic barriers with a typical separation on the order of 100 nm. Micro four-point probe resistance values measured on graphene grown on single crystalline copper in two different voltage-current configurations show close agreement with the expected distributions for a continuous 2D conductor, in contrast with previous observations on graphene grown on commercial copper foil. The terahertz and micro four-point probe conductance values of the graphene grown on single crystalline copper shows a close to unity correlation, in

  13. Quantifying Correlations Between Isovector Observables and the Density Dependence of Nuclear Symmetry Energy away from Saturation Density

    CERN Document Server

    Fattoyev, F J; Li, Bao-An

    2014-01-01

    According to the Hugenholtz-Van Hove theorem, the nuclear symmetry energy $S(\\rho)$ and its slope $L(\\rho)$ at arbitrary densities can be decomposed in terms of the density and momentum dependence of the single-nucleon potentials in isospin-asymmetric nuclear matter which are potentially accessible to experiment. We quantify the correlations between several well-known isovector observables and $L(\\rho)$ to locate the density range in which each isovector observable is most sensitive to the density dependence of the $S(\\rho)$. We then study the correlation coefficients between those isovector observables and all the components of the $L(\\rho)$. The neutron skin thickness of $^{208}$Pb is found to be strongly correlated with the $L(\\rho)$ at a subsaturation density of $\\rho = 0.59 \\rho_0$ through the density dependence of the first-order symmetry potential. Neutron star radii are found to be strongly correlated with the $L(\\rho)$ over a wide range of supra-saturation densities mainly through both the density an...

  14. Superfluid LDA (SLDA): Local Density Approximation for Systems with Superfluid Correlations

    CERN Document Server

    Bulgac, A; Bulgac, Aurel; Yu, Yongle

    2004-01-01

    We present a concise account of our development of the first genuine Local Density Approximation (LDA) to the Energy Density Functional (EDF) for fermionic systems with superfluid correlations, with a particular emphasis to nuclear systems.

  15. Correlation of Critical Current Density with Cu3+ Concentration and Density in YBa2Cu3O7-x

    Science.gov (United States)

    Dou, S. X.; Liu, H. K.; Zhou, J. P.; Bourdillon, A. J.; Savvides, N.; Apperley, M.; Gouch, A.; Sorrell, C. C.

    Superconducting YBa2Cu3O7 wires and tapes were fabricated by cold drawing, rolling and extrusion processes. It was found that the critical current density, after O2 equilibration, correlates both with density and Cu3+ concentration. Full density was achieved by using a special heat treatment, but the critical current density was low owing to the low Cu3+ concentration present in this heavily twinned material. The best critical current density results were obtained for material with density of 92-95% of the theoretical value. The low critical current density of the porous specimens is attributed not only to a poor connectivity between grains but also to a low Cu3+ concentration due to the instability of Cu3+ at crystallite surfaces which increase in area with specimen porosity.

  16. Nonlocal Four-Point Boundary Value Problem for the Singularly Perturbed Semilinear Differential Equations

    Directory of Open Access Journals (Sweden)

    Vrabel Robert

    2011-01-01

    Full Text Available Abstract This paper deals with the existence and asymptotic behavior of the solutions to the singularly perturbed second-order nonlinear differential equations. For example, feedback control problems, such as the steady states of the thermostats, where the controllers add or remove heat, depending upon the temperature detected by the sensors in other places, can be interpreted with a second-order ordinary differential equation subject to a nonlocal four-point boundary condition. Singular perturbation problems arise in the heat transfer problems with large Peclet numbers. We show that the solutions of mathematical model, in general, start with fast transient which is the so-called boundary layer phenomenon, and after decay of this transient they remain close to the solution of reduced problem with an arising new fast transient at the end of considered interval. Our analysis relies on the method of lower and upper solutions.

  17. Electrical four-point probing of spherical metallic thin films coated onto micron sized polymer particles

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Sigurd R., E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no; Stokkeland, August Emil; Zhang, Zhiliang; He, Jianying, E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Kristiansen, Helge [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway); Njagi, John; Goia, Dan V. [Center for Advanced Materials Processing, Clarkson University, Potsdam, New York 13699-5814 (United States); Redford, Keith [Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway)

    2016-07-25

    Micron-sized metal-coated polymer spheres are frequently used as filler particles in conductive composites for electronic interconnects. However, the intrinsic electrical resistivity of the spherical thin films has not been attainable due to deficiency in methods that eliminate the effect of contact resistance. In this work, a four-point probing method using vacuum compatible piezo-actuated micro robots was developed to directly investigate the electric properties of individual silver-coated spheres under real-time observation in a scanning electron microscope. Poly(methyl methacrylate) spheres with a diameter of 30 μm and four different film thicknesses (270 nm, 150 nm, 100 nm, and 60 nm) were investigated. By multiplying the experimental results with geometrical correction factors obtained using finite element models, the resistivities of the thin films were estimated for the four thicknesses. These were higher than the resistivity of bulk silver.

  18. Advanced carrier depth profiling on Si and Ge with micro four-point probe

    DEFF Research Database (Denmark)

    Clarysse, Trudo; Eyben, Pierre; Parmentier, Brigitte

    2008-01-01

    In order to reach the ITRS goals for future complementary metal-oxide semiconductor technologies, there is a growing need for the accurate extraction of ultrashallow electrically active dopant (carrier) profiles. In this work, it will be illustrated that this need can be met by the micro four......-point probe (M4PP) tool. M4PP sheet resistance measurements taken along beveled Si and Ge blanket shallow structures will be investigated. From the differential sheet resistance changes, the underlying carrier profile can be reconstructed without the need to rely on a complicated contact modeling, i.e., M4PP...... carrier profiling is an absolute carrier depth profiling technique. On Si, it is found that the more sensitive a structure is to carrier spilling along the bevel, the better the M4PP system performs relative to conventional spreading resistance probe (SRP) due to its much lower probe pressure...

  19. Ultra-shallow junction (USJ) sheet resistance measurements with a non-penetrating four point probe

    Science.gov (United States)

    Benjamin, M. C.; Hillard, R. J.; Borland, J. O.

    2005-08-01

    An accurate method to measure the four point probe (4PP) sheet resistance (RS) of ultra shallow junction (USJ) Source-Drain Extension structures is described. The method utilizes Elastic Material probes (EM-probes) to form non-penetrating contacts to the silicon surface [R.J. Hillard, P.Y. Hung, William Chism, C. Win Ye, W.H. Howland, L.C. Tan, C.E. Kalnas, Characterization and Metrology for ULSI Technology, AIP Conference proceedings 683 (2003) 802.]. The probe design is kinematic and the force is controlled to ensure elastic deformation of the probe material. The probe material is such that large direct tunneling currents can flow through the native oxide thereby forming a low impedance contact. Sheet resistance measurements on USJ implanted P+/N structures with Secondary Ion Mass Spectroscopy (SIMS) junction depths less than 15 nm have been measured. The method is demonstrated on implanted USJ structures and found to be consistent with expectations.

  20. Dynamics of graphite fiber intercalation: In situ resistivity measurements with a four point probe

    Science.gov (United States)

    Jaworske, D. A.

    1984-01-01

    The dynamics of ferric chloride intercalation of single graphite fibers were studied, in situ, using a four point dc bridge. Measurements before, during and after the intercalation showed that the intercalation occurred within minutes at 200 C. Changes in fiber resistivity after exposure to air suggested hydration of the graphite intercalation compound. Deintercalation of the ferric chloride was initiated at temperatures in excess of 400 C. cycling the intercalant into and out of the graphite fiber gave no improvements in fiber resistivity. The activation energy of the ferric chloride intercalation reaction was found to be 17 + or - 4 kcal/mol 1 consistent with the concept of a preliminary nucleation step in the intercalation reaction.

  1. Fast and direct measurements of the electrical properties of graphene using micro four-point probes.

    Science.gov (United States)

    Klarskov, M B; Dam, H F; Petersen, D H; Hansen, T M; Löwenborg, A; Booth, T J; Schmidt, M S; Lin, R; Nielsen, P F; Bøggild, P

    2011-11-04

    We present measurements of the electronic properties of graphene using a repositionable micro four-point probe system, which we show here to have unique advantages over measurements made on lithographically defined devices; namely speed, simplicity and lack of a need to pattern graphene. Measurements are performed in ambient, vacuum and controlled environmental conditions using an environmental scanning electron microscope (SEM). The results are comparable to previous results for microcleaved graphene on silicon dioxide (SiO(2)). We observe a pronounced hysteresis of the charge neutrality point, dependent on the sweep rate of the gate voltage; and environmental measurements provide insight into the sensor application prospects of graphene. The method offers a fast, local and non-destructive technique for electronic measurements on graphene, which can be positioned freely on a graphene flake.

  2. Electronic transport at semiconductor surfaces - from point-contact transistor to micro-four-point probes

    DEFF Research Database (Denmark)

    Hasegawa, S.; Grey, Francois

    2002-01-01

    show that this type of conduction is measurable using new types of experimental probes, such as the multi-tip scanning tunnelling microscope and the micro-four-point probe. The resulting electronic transport properties are intriguing, and suggest that semiconductor surfaces should be considered......The electrical properties of semiconductor surfaces have played a decisive role in one of the most important discoveries of the last century, transistors. In the 1940s, the concept of surface states-new electron energy levels characteristic of the surface atoms-was instrumental in the fabrication...... of the first point-contact transistors, and led to the successful fabrication of field-effect transistors. However, to this day, one property of semiconductor surface states remains poorly understood, both theoretically and experimentally. That is the conduction of electrons or holes directly through...

  3. Dynamic Carrying Capacity Analysis of Double-Row Four-Point Contact Ball Slewing Bearing

    Directory of Open Access Journals (Sweden)

    Yunfeng Li

    2015-01-01

    Full Text Available Carrying capacity is the most important performance index for slewing bearings. Maximizing the carrying capacity of slewing bearing is one pursuing goal for the bearing designer; this is usually realized by optimizing the design parameters. A method of analyzing the carrying capacity of double-row four-point contact ball slewing bearing by using dynamic carrying capacity surfaces was proposed in this paper. Based on the dynamic load carrying capacity surface of the slewing bearing, the effect of changes of the bearing design parameters, such as axial clearance, raceway groove radius coefficient, and contact angle, on the dynamic carrying capacity of the slewing bearing was researched; the trend and the degree of the effect of the micro changes of the bearing design parameters on the dynamic load carrying capacity of the bearing were discussed, and the results provide the basis for optimizing the design parameter of this type of slewing bearing.

  4. Fast and direct measurements of the electrical properties of graphene using micro four-point probes

    DEFF Research Database (Denmark)

    Klarskov, Mikkel Buster; Dam, Henrik Friis; Petersen, Dirch Hjorth

    2011-01-01

    . Measurements are performed in ambient, vacuum and controlled environmental conditions using an environmental scanning electron microscope (SEM). The results are comparable to previous results for microcleaved graphene on silicon dioxide (SiO2). We observe a pronounced hysteresis of the charge neutrality point......We present measurements of the electronic properties of graphene using a repositionable micro four-point probe system, which we show here to have unique advantages over measurements made on lithographically defined devices; namely speed, simplicity and lack of a need to pattern graphene......, dependent on the sweep rate of the gate voltage; and environmental measurements provide insight into the sensor application prospects of graphene. The method offers a fast, local and non-destructive technique for electronic measurements on graphene, which can be positioned freely on a graphene flake....

  5. Four-point Bend Testing of Irradiated Monolithic U-10Mo Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Rabin, B. H. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lloyd, W. R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Schulthess, J. L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wright, J. K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lind, R. P. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Scott, L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wachs, K. M. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-03-01

    This paper presents results of recently completed studies aimed at characterizing the mechanical properties of irradiated U-10Mo fuel in support of monolithic base fuel qualification. Mechanical properties were evaluated in four-point bending. Specimens were taken from fuel plates irradiated in the RERTR-12 and AFIP-6 Mk. II irradiation campaigns, and tests were conducted in the Hot Fuel Examination Facility (HFEF) at Idaho National Laboratory (INL). The monolithic fuel plates consist of a U-10Mo fuel meat covered with a Zr diffusion barrier layer fabricated by co-rolling, clad in 6061 Al using a hot isostatic press (HIP) bonding process. Specimens exhibited nominal (fresh) fuel meat thickness ranging from 0.25 mm to 0.64 mm, and fuel plate average burnup ranged from approximately 0.4 x 1021 fissions/cm3 to 6.0 x 1021 fissions/cm3. After sectioning the fuel plates, the 6061 Al cladding was removed by dissolution in concentrated NaOH. Pre- and post-dissolution dimensional inspections were conducted on test specimens to facilitate accurate analysis of bend test results. Four-point bend testing was conducted on the HFEF Remote Load Frame at a crosshead speed of 0.1 mm/min using custom-designed test fixtures and calibrated load cells. All specimens exhibited substantially linear elastic behavior and failed in a brittle manner. The influence of burnup on the observed slope of the stress-strain curve and the calculated fracture strength is discussed.

  6. High Temperature, high pressure equation of state density correlations and viscosity correlations

    Energy Technology Data Exchange (ETDEWEB)

    Tapriyal, D.; Enick, R.; McHugh, M.; Gamwo, I.; Morreale, B.

    2012-07-31

    Global increase in oil demand and depleting reserves has derived a need to find new oil resources. To find these untapped reservoirs, oil companies are exploring various remote and harsh locations such as deep waters in Gulf of Mexico, remote arctic regions, unexplored deep deserts, etc. Further, the depth of new oil/gas wells being drilled has increased considerably to tap these new resources. With the increase in the well depth, the bottomhole temperature and pressure are also increasing to extreme values (i.e. up to 500 F and 35,000 psi). The density and viscosity of natural gas and crude oil at reservoir conditions are critical fundamental properties required for accurate assessment of the amount of recoverable petroleum within a reservoir and the modeling of the flow of these fluids within the porous media. These properties are also used to design appropriate drilling and production equipment such as blow out preventers, risers, etc. With the present state of art, there is no accurate database for these fluid properties at extreme conditions. As we have begun to expand this experimental database it has become apparent that there are neither equations of state for density or transport models for viscosity that can be used to predict these fundamental properties of multi-component hydrocarbon mixtures over a wide range of temperature and pressure. Presently, oil companies are using correlations based on lower temperature and pressure databases that exhibit an unsatisfactory predictive capability at extreme conditions (e.g. as great as {+-} 50%). From the perspective of these oil companies that are committed to safely producing these resources, accurately predicting flow rates, and assuring the integrity of the flow, the absence of an extensive experimental database at extreme conditions and models capable of predicting these properties over an extremely wide range of temperature and pressure (including extreme conditions) makes their task even more daunting.

  7. Scaling laws for density correlations and fluctuations in multiparticle dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, E.A. de [Universitaire Instelling Antwerpen, Wilrijk (Belgium). Dept. of Physics]|[Interuniversity Inst. for High Energies, Brussels (Belgium); Dremin, I.M. [Rossijskaya Akademiya Nauk, Moscow (Russian Federation). Fizicheskij Inst.; Kittel, W. [Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Nijmegen (Netherlands)

    1996-05-01

    Experimental data on particle correlations and fluctuations in various high-energy multiparticle collisions are presented, with special emphasis on evidence for scaling-law evolution in small phase-space domains. The notions of intermittency and fractality as related to the above findings are described. Phenomenological and theoretical work on the subject is reviewed. (orig.).

  8. Communication: Simple and accurate uniform electron gas correlation energy for the full range of densities

    Science.gov (United States)

    Chachiyo, Teepanis

    2016-07-01

    A simple correlation energy functional for the uniform electron gas is derived based on the second-order Moller-Plesset perturbation theory. It can reproduce the known correlation functional in the high-density limit, while in the mid-density range maintaining a good agreement with the near-exact correlation energy of the uniform electron gas to within 2 × 10-3 hartree. The correlation energy is a function of a density parameter rs and is of the form a * ln ( 1 + /b r s + /b rs 2 ) . The constants "a" and "b" are derived from the known correlation functional in the high-density limit. Comparisons to the Ceperley-Alder's near-exact Quantum Monte Carlo results and the Vosko-Wilk-Nusair correlation functional are also reported.

  9. The Complete Four-Loop Four-Point Amplitude in N

    Energy Technology Data Exchange (ETDEWEB)

    Bern, Z.; Carrasco, J.J.M.; /UCLA; Dixon, Lance J.; /SLAC /CERN; Johansson, H.; /Saclay, SPhT; Roiban, R.; /Penn State U.

    2010-08-25

    We present the complete four-loop four-point amplitude in N = 4 super-Yang-Mills theory, for a general gauge group and general D-dimensional covariant kinematics, and including all non-planar contributions. We use the method of maximal cuts - an efficient application of the unitarity method - to construct the result in terms of 50 four-loop integrals. We give graphical rules, valid in D-dimensions, for obtaining various non-planar contributions from previously-determined terms. We examine the ultraviolet behavior of the amplitude near D = 11/2. The non-planar terms are as well-behaved in the ultraviolet as the planar terms. However, in the color decomposition of the three- and four-loop amplitude for an SU(N{sub c}) gauge group, the coefficients of the double-trace terms are better behaved in the ultraviolet than are the single-trace terms. The results from this paper were an important step toward obtaining the corresponding amplitude in N = 8 supergravity, which confirmed the existence of cancellations beyond those needed for ultraviolet finiteness at four loops in four dimensions. Evaluation of the loop integrals near D = 4 would permit tests of recent conjectures and results concerning the infrared behavior of four-dimensional massless gauge theory.

  10. Comparison of Visual and Acoustic Emission Observations in a Four Point Bending Experiment on Barre Granite

    Science.gov (United States)

    Li, Bing Qiuyi; Einstein, Herbert H.

    2017-09-01

    We present an experimental study in which a pre-notched specimen of Barre Granite was subjected to four point bending under crack mouth opening displacement control. The experimental observations consisted of load-displacement measurements, acoustic emissions, and photography on a macroscopic ( cm) as well as microscopic ( μm) scale. These observations were compared and analysed to better understand process zone development and crack propagation. Load-displacement data showed that the load reaches its maximum at crack initiation, and the machine input work is constant while the crack propagates. AE moment magnitudes between Mw = -6 to -10 were observed, and focal mechanisms consisted of both shear and tensile components. During process zone development, AE formed a large cloud of events located near the notch tip and then tended to occur away from the notch tip as the crack propagated. Image analysis at the microscopic scale showed that microcracks formed and coalesced during process zone development; specifically, the microcracks initiated in tension and then propagated as a series of en-echelon cracks. In general, the synthesis of the three observations showed that a wider bulb of activity at lower energy tended to occur during process zone development, while crack propagation tended to be more spatially concentrated and contained higher energy.

  11. Development of four-point bending fatigue test method using continuously hydrogen-charging pipe specimen

    Science.gov (United States)

    Yoshimoto, T.; Matsuo, T.

    2017-05-01

    To evaluate hydrogen embrittlement, the following two types of testing method are available: (i) testing in high-pressure hydrogen gas environment and (ii) testing in ambient air using hydrogen precharged specimen. Testing in high-pressure hydrogen gas environment is technically difficult and expensive because high-pressure gas equipments, such as high-pressure vessel and pipe, have to be installed in the laboratory. On the other hand, in the case of precharging method, outgassing of hydrogen from the specimen occurs during the test. Therefore, hydrogen embrittlement can hardly be evaluated properly, especially, in long-term testing such as high cycle fatigue test at low frequency. In this study, to effectively evaluate the hydrogen embrittlement in fatigue, an experimental method, which was the four-point bending fatigue test system with a mechanism of internal circulation of hydrogen-charging solution in a pipe specimen, was developed. By using this method, the fatigue crack growth properties in the presence of hydrogen were investigated at frequencies of 0.05 Hz and 1 Hz.

  12. Cluster observes the Earth’s magnetopause: coordinated four-point magnetic field measurements

    Directory of Open Access Journals (Sweden)

    M. W. Dunlop

    Full Text Available The four-spacecraft Cluster mission has provided high-time resolution measurements of the magnetic field from closely maintained separation distances (200–600 km. Four-point coverage of the Earth’s magnetopause began on the 9 and 10 November 2000 when all spacecraft first exited the dusk-side magnetosphere at about 19:00 LT, providing extensive coverage of the near flank magnetosheath and magnetopause boundary layer on re-entry to the magnetosphere. The traversals on this occasion were caused by the arrival of an intense CME at the Earth, which produced a large compression of the magnetopause and high magnetic activity. The magnetopause traversals represent an unprecedented data set, allowing detailed analysis of the local magnetic structure (gradients and dynamics of the magnetopause boundary. By performing minimum variance analysis (MVA on the magnetic field data from all four spacecraft, we demonstrate that the magnetopause was planar on the scale of the spacecraft separation scales and that the transverse scale size of the magnetopause boundary layer was 1000–1100 km. We also show that the motion of the boundary (defined by the magnetic shear at the current layer, is changing over the sequence of spacecraft crossings so that acceleration of the magnetopause can be very high in this region of the magnetosphere. Indeed, the magnetopause speed reaches the order of 300 km/s in response to the arrival of the interplanetary shock. Using MVA coordinates, we have identified a number of magnetospheric and magnetosheath FTE signatures, which are sampled simultaneously by all spacecraft at different distances from and on either side of the magnetopause. The signatures show a variation of scale with distance from the boundary.

    Key words. Magnetospheric physics (magnetopause, cusp and boundary layers Space plasma physics (discontinuities; magnetic reconnection

  13. A Systems Engineering Analysis of Three-Point and Four-Point Wind Turbine Drivetrain Configurations

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yi; Parsons, Tyler; Dykes, Katherine; King, Ryan N.

    2017-03-01

    This study compares the impact of drivetrain configuration on the mass and capital cost of a series of wind turbines ranging from 1.5 MW to 5.0 MW power ratings for both land-based and offshore applications. The analysis is performed with a new physics-based drivetrain analysis and sizing tool, Drive Systems Engineering (DriveSE), which is part of the Wind-Plant Integrated System Design & Engineering Model. DriveSE uses physics-based relationships to size all major drivetrain components according to given rotor loads simulated based on International Electrotechnical Commission design load cases. The model's sensitivity to input loads that contain a high degree of variability was analyzed. Aeroelastic simulations are used to calculate the rotor forces and moments imposed on the drivetrain for each turbine design. DriveSE is then used to size all of the major drivetrain components for each turbine for both three-point and four-point configurations. The simulation results quantify the trade-offs in mass and component costs for the different configurations. On average, a 16.7% decrease in total nacelle mass can be achieved when using a three-point drivetrain configuration, resulting in a 3.5% reduction in turbine capital cost. This analysis is driven by extreme loads and does not consider fatigue. Thus, the effects of configuration choices on reliability and serviceability are not captured. However, a first order estimate of the sizing, dimensioning and costing of major drivetrain components are made which can be used in larger system studies which consider trade-offs between subsystems such as the rotor, drivetrain and tower.

  14. The correlations of ions density with geomagnetic activity and solar dynamic pressure in cusp region

    Institute of Scientific and Technical Information of China (English)

    GUO JianGuang; SHI JianKui; ZHANG TieLong; LIU ZhenXing; A. FAZAKERLEY; H. R(E)ME; Ⅰ. DANDOURAS; E. LUCEK

    2007-01-01

    A statistical study of the properties of ions (O+, He+ and H+) measured by the Cluster-Ⅱ in cusp region as a function of the solar wind dynamic pressure and geomagnetic index Kp respectively was made during the summer and fall of 2001 -2003. The main results are that: (1) O+ ion density responds in a significant way to geomagnetic index Kp, and He+ ion density is not correlated with geomagnetic index Kp,both of them have a significant positive correlation with solar wind dynamic pressure; (2) H+ ion density is also observed to increase with solar wind dynamic pressure, and not correlated with geomagnetic index Kp.

  15. Modification of the in vivo four-point loading model for studying mechanically induced bone adaptation.

    Science.gov (United States)

    Forwood, M R; Bennett, M B; Blowers, A R; Nadorfi, R L

    1998-09-01

    We modified the noninvasive, in vivo technique for strain application in the tibiae of rats (Turner et al., Bone 12:73-79, 1991). The original model applies four-point bending to right tibiae via an open-loop, stepper-motor-driven spring linkage. Depending on the magnitude of applied load, the model produces new bone formation at periosteal (Ps) or endocortical surfaces (Ec.S). Due to the spring linkage, however, the range of frequencies at which loads can be applied is limited. The modified system replaces this design with an electromagnetic vibrator. A load transducer in series with the loading points allows calibration, the loaders' position to be adjusted, and cyclic loading completed under load control as a closed servo-loop. Two experiments were conducted to validate the modified system: (1) a strain gauge was applied to the lateral surface of the right tibia of 5 adult female rats and strains measured at applied loads from 10 to 60 N; and (2) the bone formation response was determined in 28 adult female Sprague-Dawley rats. Loading was applied as a haversine wave with a frequency of 2 Hz for 18 sec, every second day for 10 days. Peak bending loads were applied at 33, 40, 52, and 64 N, and a sham-loading group was included at 64 N. Strains in the tibiae were linear between 10 and 60 N, and the average peak strain at the Ps.S at 60 N was 2664 +/- 250 microstrain, consistent with the results of Turner's group. Lamellar bone formation was stimulated at the Ec.S by applied bending, but not by sham loading. Bending strains above a loading threshold of 40 N increased Ec lamellar bone formation rate, bone forming surface, and mineral apposition rate with a dose response similar to that reported by Turner et al. (J Bone Miner Res 9:87-97, 1994). We conclude that the modified loading system offers precision for applied loads of between 0 and 70 N, versatility in the selection of loading rates up to 20 Hz, and a reproducible bone formation response in the rat tibia

  16. Density matrix renormalization group with efficient dynamical electron correlation through range separation

    Energy Technology Data Exchange (ETDEWEB)

    Hedegård, Erik Donovan, E-mail: erik.hedegard@phys.chem.ethz.ch; Knecht, Stefan; Reiher, Markus, E-mail: markus.reiher@phys.chem.ethz.ch [Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich (Switzerland); Kielberg, Jesper Skau; Jensen, Hans Jørgen Aagaard, E-mail: hjj@sdu.dk [Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, Odense (Denmark)

    2015-06-14

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electron-correlation effects in multiconfigurational electronic structure problems.

  17. Spectral density of the correlation matrix of factor models: a random matrix theory approach.

    Science.gov (United States)

    Lillo, F; Mantegna, R N

    2005-07-01

    We studied the eigenvalue spectral density of the correlation matrix of factor models of multivariate time series. By making use of the random matrix theory, we analytically quantified the effect of statistical uncertainty on the spectral density due to the finiteness of the sample. We considered a broad range of models, ranging from one-factor models to hierarchical multifactor models.

  18. Density Matrix Renormalization Group with Efficient Dynamical Electron Correlation Through Range Separation

    CERN Document Server

    Hedegård, Erik Donovan; Kielberg, Jesper Skau; Jensen, Hans Jørgen Aagaard; Reiher, Markus

    2015-01-01

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electron-correlation effects in multiconfigurational electronic structure problems.

  19. Correlation of densities with shear wave velocities and SPT N values

    Science.gov (United States)

    Anbazhagan, P.; Uday, Anjali; Moustafa, Sayed S. R.; Al-Arifi, Nassir S. N.

    2016-06-01

    Site effects primarily depend on the shear modulus of subsurface layers, and this is generally estimated from the measured shear wave velocity (V s) and assumed density. Very rarely, densities are measured for amplification estimation because drilling and sampling processes are time consuming and expensive. In this study, an attempt has been made to derive the correlation between the density (dry and wet density) and V s/SPT (standard penetration test) N values using measured data. A total of 354 measured V s and density data sets and 364 SPT N value and density data sets from 23 boreholes have been used in the study. Separate relations have been developed for all soil types as well as fine-grained and coarse-grained soil types. The correlations developed for bulk density were compared with the available data and it was found that the proposed relation matched well with the existing data. A graphical comparison and validation based on the consistency ratio and cumulative frequency curves was performed and the newly developed relations were found to demonstrate good prediction performance. An attempt has also been made to propose a relation between the bulk density and shear wave velocity applicable for a wide range of soil and rock by considering data from this study as well as that of previous studies. These correlations will be useful for predicting the density (bulk and dry) of sites having measured the shear wave velocity and SPT N values.

  20. A test of bosonization at the level of four-point functions in Chern-Simons vector models

    CERN Document Server

    Bedhotiya, Akshay

    2015-01-01

    We study four-point functions in Chern-Simons vector models in the large $N$ limit. We compute the four-point function of the scalar primary to all orders in the `t Hooft coupling $\\lambda=N/k$ in $U(N)_k$ Chern-Simons theory coupled to a fundamental fermion, in both the critical and non-critical theory, for a particular case of the external momenta. These theories cover the entire 3-parameter "quasi-boson" and 2-parameter "quasi-fermion" families of 3-dimensional quantum field theories with a slightly-broken higher spin symmetry. Our results are consistent with the celebrated bosonization duality, as we explicitly verify by calculating four-point functions in the free critical and non-critical bosonic theories.

  1. The role of exchange and correlation in time-dependent density-functional theory for photoionization

    Science.gov (United States)

    Stener, M.; Decleva, P.; Görling, A.

    2001-05-01

    Atomic photoionization cross sections are calculated by time-dependent density-functional (TDDF) methods using different exchange-correlation potentials including the exact one. The exchange-correlation kernel is treated in the adiabatic local density approximation (ALDA). Results for the exact full and the exact exchange-only Kohn-Sham (KS) potential are very similar, the calculated photo cross section agree very well with experimental data. Thus the exact correlation potential seems to have no influence on photoionization and the ALDA for the exchange-correlation kernel seems to be sufficient for most features of the cross sections. The TDDF method employing the exact exchange-only KS potential in combination with the ALDA exchange-correlation kernel therefore is a promising approach to describe photoionization. Deviations from experiment are observed for the widths and shape of the autoionization resonances and have to be attributed to deficiencies of the ALDA exchange-correlation kernel. The calculation of widths and shapes of autoionization resonances therefore may serve as a severe test for new approximate exchange-correlation density-functionals. The asymptotically exact exchange-correlation potential of van Leeuwen and Baerends also leads to quite good photo cross section, which, however, shows deficiencies close to the ionization threshold and in the energetic position of the autoionization resonances. Supplementation of the exact exchange potential with the LDA correlation potential leads to a worsening of the photo cross section because the LDA correlation potential is too attractive.

  2. Lack of correlation of glucose levels in filtered blood plasma to density and conductivity measurements.

    Science.gov (United States)

    Gordon, David M; Ash, Stephen R

    2009-01-01

    The purpose of this research project was to determine whether the glucose level of a blood plasma sample from a diabetic patient could be predicted by measuring the density and conductivity of ultrafiltrate of plasma created by a 30,000 m.w. cutoff membrane. Conductivity of the plasma filtrate measures electrolyte concentration and should correct density measurements for changes in electrolytes and water concentration. In vitro studies were performed measuring conductivity and density of solutions of varying glucose and sodium chloride concentrations. Plasma from seven hospitalized patients with diabetes was filtered across a 30,000 m.w. cutoff membrane. The filtrate density and conductivity were measured and correlated to glucose levels. In vitro studies confirmed the ability to predict glucose from density and conductivity measurements, in varying concentrations of glucose and saline. In plasma filtrate, the conductivity and density measurements of ultrafiltrate allowed estimation of glucose in some patients with diabetes but not others. The correlation coefficient for the combined patient data was 0.45 which was significant but only explained 20% of the variability in the glucose levels. Individually, the correlation was significant in only two of the seven patients with correlation coefficients of 0.79 and 0.88. The reasons for lack of correlation are not clear, and cannot be explained by generation of idiogenic osmoles, effects of alcohol dehydrogenase, water intake, etc. This combination of physical methods for glucose measurement is not a feasible approach to measuring glucose in plasma filtrate.

  3. Correlation between enhancement characteristics of MR mammography and capillary density of breast lesions

    Energy Technology Data Exchange (ETDEWEB)

    Poellinger, Alexander, E-mail: alexander.poellinger@charite.de [Charité, Universitätsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); El-Ghannam, Sahra; Diekmann, Susanne; Fischer, Thomas [Charité, Universitätsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Kristiansen, Glen [Universitätsklinikum Bonn, Department of Pathology, Sigmund-Freud-Str. 25, D-53127 Bonn (Germany); Fritzsche, Florian [Institut für Histologie und Zytologie, Bahnhofplatz 11, Postfach, 9101 Herisau (Switzerland); Fallenberg, Eva [Charité, Universitätsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Morawietz, Lars [Diagnostik Ernst von Bergmann GmbH, Charlottenstr. 72, 14467 Potsdam (Germany); Diekmann, Felix [Charité, Universitätsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany)

    2014-12-15

    Highlights: • We correlate capillary density of breast lesions with MRM. • Capillary density correlates with tumor enhancement for all lesions. • However no such correlation exists for the malignant or benign groups separately. • Mean vessel number of lymphatic vessels do not correlate with tumor enhancement.These results might be of help in the workup of MR-guided breast biopsies. • These results might be of help in the workup of MR-guided breast biopsies. - Abstract: Objective: To correlate capillary density of breast lesions using the markers D2-40, CD31, and CD34 with early and late enhancement of magnetic resonance mammography (MRM). Materials and methods: The local ethics committee approved this study, and informed consent was available from all patients. The study included 64 women with 66 histologically proven breast lesions (41 malignant, 25 benign). MR-enhancement 1 min after contrast medium administration was determined in the tumor (I{sub t1}/I{sub t0} ratio) and in comparison to the surrounding tissue (I{sub t1}/I{sub t1-fat} ratio). Capillary density was quantified based on immunohistological staining with D2-40, CD31, and CD34 in breast tumors and surrounding breast tissue. Mean capillary densities were correlated with contrast enhancement in the tumor and surrounding breast tissue. The Kruskal–Wallis test was used to test whether lesions with different MR enhancement patterns differed in terms of capillary density. Results: For CD34, there was statistically significant correlation between capillary density and tumor enhancement (r = 0.329, p = 0.012), however not for the malignant or benign groups separately. Mean vessel number identified by staining with D2-40 and CD31 did not correlate significantly with tumor enhancement (D2-40: r = −0.188, p = 0.130; CD31: r = 0.095, p = 0.448). There were no statistically significant differences in capillary density between breast lesions with delayed enhancement or a plateau and lesions showing

  4. Background {sup 18}F-FDG uptake in positron emission mammography (PEM): Correlation with mammographic density and background parenchymal enhancement in breast MRI

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Hye Ryoung, E-mail: huilings@hanmail.net [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Moon, Woo Kyung, E-mail: moonwk@snu.ac.kr [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Chun, In Kook, E-mail: inkook.chun@gmail.com [Department of Nuclear Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Eo, Jae Seon, E-mail: jaeseon76@gmail.com [Department of Nuclear Medicine, Korea University Guro Hospital, 148 Gurodongro, Guro-gu, Seoul 152-703 (Korea, Republic of); Jeyanth, Joseph Xavier, E-mail: jeyanth7@snu.ac.kr [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Chang, Jung Min, E-mail: imchangjm@gmail.com [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Cho, Nariya, E-mail: river7774@gmail.com [Department of Radiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of); Kang, Keon Wook, E-mail: kangkw@snu.ac.kr [Department of Nuclear Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744 (Korea, Republic of)

    2013-10-01

    We aimed to determine whether background {sup 18}F-FDG uptake in positron emission mammography (PEM) was related to mammographic density or background parenchymal enhancement in breast MRI. Methods: We studied a total of 52 patients (mean age, 50.9 years, 26 premenopausal, 26 postmenopausal) with newly diagnosed breast cancer who underwent {sup 18}F-FDG PEM (positron emission mammography), conventional mammography and breast MRI. The background mean {sup 18}F-FDG uptake value on PEM was obtained by drawing a user-defined region of interest (ROI) in a normal area of the contralateral breast. We reviewed the mammography retrospectively for overall breast density of contralateral breast according to the four-point scale (grade 1–4) of the Breast Imaging Reporting and Data System (BI-RADS) classification. The background parenchymal enhancement of breast MRI was classified as minimal, mild, moderate, or marked. All imaging findings were interpreted by two readers in consensus without knowledge of image findings of other modalities. Results: Multiple linear regression analysis revealed a significant correlation between background {sup 18}F-FDG uptake on PEM and mammographic density after adjustment for age and menopausal status (P < 0.01), but not between background {sup 18}F-FDG uptake on PEM and background parenchymal enhancement on MRI. Conclusion: Background {sup 18}F-FDG uptake on PEM significantly increases as mammographic density increases. Background parenchymal enhancement in breast MRI was not an independent predictor of the background {sup 18}F-FDG uptake on PEM unlike mammographic density.

  5. Density functional with full exact exchange, balanced nonlocality of correlations, and constraint satisfaction

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Jianmin [Los Alamos National Laboratory; Perdew, John P [TULANE UNIV; Staroverov, Viktor N [UNIV OF WESTERN ONTARIO; Scuseria, Gustavo E [RICE UNIV

    2008-01-01

    We construct a nonlocal density functional approximation with full exact exchange, while preserving the constraint-satisfaction approach and justified error cancellations of simpler semilocal functionals. This is achieved by interpolating between different approximations suitable for two extreme regions of the electron density. In a 'normal' region, the exact exchange-correlation hole density around an electron is semilocal because its spatial range is reduced by correlation and because it integrates over a narrow range to -1. These regions are well described by popular semilocal approximations (many of which have been constructed nonempirically), because of proper accuracy for a slowly-varying density or because of error cancellation between exchange and correlation. 'Abnormal' regions, where non locality is unveiled, include those in which exchange can dominate correlation (one-electron, nonuniform high-density, and rapidly-varying limits), and those open subsystems of fluctuating electron number over which the exact exchange-correlation hole integrates to a value greater than -1. Regions between these extremes are described by a hybrid functional mixing exact and semi local exchange energy densities locally (i.e., with a mixing fraction that is a function of position r and a functional of the density). Because our mixing fraction tends to 1 in the high-density limit, we employ full exact exchange according to the rigorous definition of the exchange component of any exchange-correlation energy functional. Use of full exact exchange permits the satisfaction of many exact constraints, but the nonlocality of exchange also requires balanced nonlocality of correlation. We find that this nonlocality can demand at least five empirical parameters (corresponding roughly to the four kinds of abnormal regions). Our local hybrid functional is perhaps the first accurate size-consistent density functional with full exact exchange. It satisfies other known

  6. Turbulence in nearly incompressible fluids: density spectrum, flows, correlations and implication to the interstellar medium

    Directory of Open Access Journals (Sweden)

    S. Dastgeer

    2005-01-01

    Full Text Available Interstellar scintillation and angular radio wave broadening measurements show that interstellar and solar wind (electron density fluctuations exhibit a Kolmogorov-like k-5/3 power spectrum extending over many decades in wavenumber space. The ubiquity of the Kolmogorov-like interstellar medium (ISM density spectrum led to an explanation based on coupling incompressible magnetohydrodynamic (MHD fluctuations to density fluctuations through a 'pseudosound' relation within the context of 'nearly incompressible' (NI hydrodynamics (HD and MHD models. The NI theory provides a fundamentally different explanation for the observed ISM density spectrum in that the density fluctuations can be a consequence of passive scalar convection due to background incompressible fluctuations. The theory further predicts generation of long-scale structures and various correlations between the density, temperature and the (magneto acoustic as well as convective pressure fluctuations in the compressible ISM fluids in different thermal regimes that are determined purely by the thermal fluctuation level. In this paper, we present the results of our two dimensional nonlinear fluid simulations, exploring various nonlinear aspects that lead to inertial range ISM turbulence within the context of a NI hydrodymanics model. In qualitative agreement with the NI predictions and the in-situ observations, we find that i the density fluctuations exhibit a Kolmogorov-like spectrum via a passive convection in the field of the background incompressible fluctuations, ii the compressible ISM fluctuations form long scale flows and structures, and iii the density and the temperature fluctuations are anti-correlated.

  7. Towards efficient orbital-dependent density functionals for weak and strong correlation

    CERN Document Server

    Zhang, Igor Ying; Perdew, John P; Scheffler, Matthias

    2016-01-01

    We present a new paradigm for the design of exchange-correlation functionals in density-functional theory. Electron pairs are correlated explicitly by means of the recently developed second order Bethe-Goldstone equation (BGE2) approach. Here we propose a screened BGE2 (sBGE2) variant that efficiently regulates the coupling of a given electron pair. sBGE2 correctly dissociates H$_2$ and H$_2^+$, a problem that has been regarded as a great challenge in density-functional theory for a long time. The sBGE2 functional is then taken as a building block for an orbital-dependent functional, termed ZRPS, which is a natural extension of the PBE0 hybrid functional. While worsening the good performance of sBGE2 in H$_2$ and H$_2^{+}$, ZRPS yields a remarkable and consistent improvement over other density functionals across various chemical environments from weak to strong correlation.

  8. Correlation of Lymph Node Density With Negative Outcome Predictors in Oral and Maxillofacial Squamous Cell Carcinoma.

    Science.gov (United States)

    Kim, Roderick Youngdo; Ward, Brent Benson; Brockhoff, Hans C; Helman, Joseph I; Braun, Thomas M; Skouteris, Christos A

    2016-10-01

    Lymph node density is defined as the number of positive lymph nodes per total number of excised lymph nodes. In oral and maxillofacial cancer, there are recent data showing that increased lymph node density leads to worse outcomes for patients. However, data correlating lymph node density with other known risk parameters are lacking. This study investigated whether a direct correlation exists among cervical lymph node density, depth of invasion, perineural invasion, and extracapsular tumor spread. A retrospective chart review was undertaken to include all patients who underwent neck dissection with resection of primary oral and maxillofacial squamous cell carcinoma from January 2009 through July 2014. After applying the exclusion criteria, 286 patients were identified. Primary tumor depth of invasion, perineural invasion, and lymph node status, including extracapsular spread, were obtained from the standard pathology report. Descriptive statistics were applied. The association between 2 continuous tumor characteristics was summarized with the Pearson correlation coefficient, and the association between a continuous and a binary tumor characteristic was summarized with 2-sample t test. Statistical significance for the study was set at a P value less than .05. Mean age at time of surgery was 63.9 ± 12.5 years. The final study included 169 men and 117 women (N = 286). The mean depth of invasion was 12.3 ± 11 mm (range, 1 to 69 mm). Mean lymph node density was 0.04 ± 0.1 (range, 0 to 0.81). There was a positive association between lymph node density and depth of tumor invasion (Pearson correlation coefficient, r = 0.21; P negative; P negative; P correlated with other known prognostic features that lead to poor outcomes. Lymph node density could be an important feature to capture in future prospective trials. Pathology standards would be crucial in this endeavor. Copyright © 2016 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc

  9. Mammographic density in asymptomatic menopausal women: correlation with clinical and sonographic findings

    Directory of Open Access Journals (Sweden)

    Beatriz Regina Alvares

    2012-06-01

    Full Text Available OBJECTIVE: To evaluate mammographic breast density in asymptomatic menopausal women in correlation with clinical and sonographic findings. MATERIALS AND METHODS: Mammograms and clinical and sonographic findings of 238 asymptomatic patients were retrospectively reviewed in the period from February/2022 to June/2006. The following variables were analyzed: mammographic density patterns, sonographic findings, patients' age, parity, body mass index and use of hormone replacement therapy. RESULTS: Age, parity and body mass index showed a negative correlation with breast density pattern, while use of hormone replacement therapy showed a positive correlation. Supplementary breast ultrasonography was performed in 103 (43.2% patients. Alterations which could not be visualized at mammography were found in 34 (33% of them, most frequently in women with breast density patterns 3 and 4. CONCLUSION: The authors concluded that breast density patterns were influenced by age, parity, body mass index and time of hormone replacement therapy. Despite not having found any malignant abnormality in the studied cases, the authors have observed a predominance of benign sonographic abnormalities in women with high breast density patterns and without mammographic abnormalities, proving the relevance of supplementary ultrasonography to identify breast lesions in such patients.

  10. Performance of a nonempirical exchange functional from the density matrix expansion: comparative study with different correlation

    CERN Document Server

    Mo, Yuxiang; Tao, Jianmin

    2016-01-01

    Recently, Tao and Mo proposed an accurate meta-generalized gradient approximation for the exchange-correlation energy. The exchange part is derived from the density matrix expansion, while the correlation part is obtained by improving the TPSS correlation in the low-density limit. To better understand this exchange functional, in this work, we combine the TM exchange with the original TPSS correlation, which we call TMTPSS, and make a systematic assessment on molecular properties. The test sets include the 223 G3/99 enthalpies of formation, 58 electron affinities, 8 proton affinities, 96 bond lengths, 82 harmonic frequencies, and 10 hydrogen-bonded molecular complexes. Our calculations show that the TMTPSS functional is competitive with or even more accurate than TM functional for some properties. In particular, it is the most accurate nonempirical semilocal DFT for the enthalpies of formation and harmonic vibrational frequencies, suggesting the robustness of TM exchange.

  11. Correlation between the Flux Density and Polarization for Flat Spectrum Radio Quasars

    Indian Academy of Sciences (India)

    Fei-Peng Pi; Yong-Xiang Wang; Jing Pan

    2011-03-01

    In this paper, using the preliminary database of the University of Michigan Radio Astronomy Observatory (UMRAO) at the radio frequencies, we calculated the weighted polarization at 8 GHz and investigated the correlation between the polarization and the flux density for 92 flat spectrum radio quasars (FSRQs). We found that the two observations are closely and positively correlated for FSRQs. This is perhaps from a relativistic beaming effect.

  12. The correlation function for density perturbations in an expanding universe. II - Nonlinear theory

    Science.gov (United States)

    Mcclelland, J.; Silk, J.

    1977-01-01

    A formalism is developed to find the two-point and higher-order correlation functions for a given distribution of sizes and shapes of perturbations which are randomly placed in three-dimensional space. The perturbations are described by two parameters such as central density and size, and the two-point correlation function is explicitly related to the luminosity function of groups and clusters of galaxies

  13. Four point measurements of electrons using PEACE in the high-altitude cusp

    Directory of Open Access Journals (Sweden)

    M. G. G. T. Taylor

    Full Text Available We present examples of electron measurements from the PEACE instruments on the Cluster spacecraft in the high-latitude, high-altitude region of the Earth’s magnetosphere. Using electron density and energy spectra measurements, we examine two cases where the orbit of the Cluster tetrahedron is outbound over the northern hemisphere, in the afternoon sector approaching the magnetopause. Data from the magnetometer is also used to pinpoint the position of the spacecraft with respect to magnetospheric boundaries. This preliminary work specifically highlights the benefit of the multipoint measurement capability of the Cluster mission. In the first case, we observe a small-scale spatial structure within the magnetopause boundary layer. The Cluster spacecraft initially straddle a boundary, characterised by a discontinuous change in the plasma population, with a pair of spacecraft on either side. This is followed by a complete crossing of the boundary by all four spacecraft. In the second case, Cluster encounters an isolated region of higher energy electrons within the cusp. The characteristics of this region are consistent with a trapped boundary layer plasma sheet population on closed magnetospheric field lines. However, a boundary motion study indicates that this region convects past Cluster, a characteristic more consistent with open field lines. An interpretation of this event in terms of the motion of the cusp boundary region is presented.

    Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; solar wind-magnetosphere interactions

  14. [Four points on the sociodemographic problematic of the city of Puebla].

    Science.gov (United States)

    Sanchez Avina, J G

    1991-12-01

    The city of Puebla has become an important pole of regional economic growth in Mexico as a result of sizeable investments in industry and services over the past 3 decades and because of its location on the route from the gulf of Mexico to Mexico City. The growth of the city and surrounding municipios has led to considerable expansion of the urbanized area. The city today contains 26% of the state population in less than 2% of its territory. The population density of 2012 per sq km is far above the state average of 121. Puebla's growth has resulted form in-migration from nearby settlements and of rural dwellers from farther afield hoping to escape rural hardships and from absorption of small surrounding settlements by the city, as well as from natural increase. The city suffers from a deficiency of equipment and services needed to satisfy the needs of its rapidly growing population. 4 serious problems in the city related to its rapid growth are the spread of marginal housing, impoverishment of the architectural landscape of the city. Disarticulation of the road system and anarchy in the public transportation system, and dangerous contamination of water. The majority of recent migrants to Puebla have not been rapidly and adequately absorbed into the urban population. Underemployment and marginalization have awaited many rural migrants, who have sought to establish themselves in impoverished zones of the city. Breakdowns in family relationships and other forms of social pathology are common in these zones. The uncontrolled population increase and urbanization of Puebla have transformed the city into a propitious area for social conflict.

  15. Electromyographic activity of trunk and hip muscles during stabilization exercises in four-point kneeling in healthy volunteers

    OpenAIRE

    Stevens, Veerle K.; Vleeming, Andry; Bouche, Katie G.; Mahieu, Nele N; Vanderstraeten, Guy G.; Danneels, Lieven A

    2006-01-01

    Stabilization exercises are intended to optimize function of the muscles that are believed to govern trunk stability. Debate exists whether certain muscles are more important than others in optimally performing these exercises. Thirty healthy volunteers were asked to perform three frequently prescribed stabilization exercises in four-point kneeling. The electromyographic activity of different trunk and hip muscles was evaluated. Average amplitudes obtained during the exercises were normalized...

  16. Nanobits, Nembranes and Micro Four-Point Probes: Customizable Tools for insitu Manipulation and Characterisation of Nanostructures

    DEFF Research Database (Denmark)

    Bøggild, Peter; Petersen, Dirch Hjorth; Sardan Sukas, Özlem;

    2010-01-01

    on a cantilever; (ii) scanning micro four point probes allow fast, non- destructive mapping of local electrical properties (sheet resistance and Hall mobility) and hysteresis effects of graphene sheets; (iii) sub 100 nm freestanding devices with wires, heaters, actuators, sensors, resonators and probes were...... defined in a 100 nm thin membrane with focused ion beam milling. By patterning generic membrane templates (Nembranes) the fabrication time of a TEM compatible NEMS device is effectively reduced to less around 20 minutes....

  17. Extending the random-phase approximation for electronic correlation energies: the renormalized adiabatic local density approximation

    DEFF Research Database (Denmark)

    Olsen, Thomas; Thygesen, Kristian S.

    2012-01-01

    while chemical bond strengths and absolute correlation energies are systematically underestimated. In this work we extend the RPA by including a parameter-free renormalized version of the adiabatic local-density (ALDA) exchange-correlation kernel. The renormalization consists of a (local) truncation...... of the ALDA kernel for wave vectors q > 2kF, which is found to yield excellent results for the homogeneous electron gas. In addition, the kernel significantly improves both the absolute correlation energies and atomization energies of small molecules over RPA and ALDA. The renormalization can...

  18. Density functionals for surface science: Exchange-correlation model development with Bayesian error estimation

    DEFF Research Database (Denmark)

    Wellendorff, Jess; Lundgård, Keld Troen; Møgelhøj, Andreas

    2012-01-01

    A methodology for semiempirical density functional optimization, using regularization and cross-validation methods from machine learning, is developed. We demonstrate that such methods enable well-behaved exchange-correlation approximations in very flexible model spaces, thus avoiding the overfit...

  19. Resonant soft x-ray scattering and charge density waves in correlated systems

    NARCIS (Netherlands)

    Rusydi, Andrivo

    2006-01-01

    Summary This work describes results obtained on the study of charge density waves (CDW) in strongly correlated systems with a new experimental method: resonant soft x-ray scattering (RSXS). The basic motivation is the 1986 discovery by Bednorz and Müler of a new type of superconductor, based on Cu a

  20. Description of correlated densities for few-electron atoms by simple functional forms

    Energy Technology Data Exchange (ETDEWEB)

    Porras, I.; Arias de Saavedra, F. [Univ. de Granada (Spain). Dept. de Fisica Moderna

    1999-02-20

    Simple analytical functional forms for the electron density of two- and three-electron atoms which reproduce fairly the correlated (exact) values are presented. The procedure is based on the fitting of an auxiliary f(r) function which has adequate properties for this purpose and can be extended to more complex atoms.

  1. Closed-Form Representations of the Density Function and Integer Moments of the Sample Correlation Coefficient

    Directory of Open Access Journals (Sweden)

    Serge B. Provost

    2015-07-01

    Full Text Available This paper provides a simplified representation of the exact density function of R, the sample correlation coefficient. The odd and even moments of R are also obtained in closed forms. Being expressed in terms of generalized hypergeometric functions, the resulting representations are readily computable. Some numerical examples corroborate the validity of the results derived herein.

  2. Density ripples in expanding low-dimensional gases as a probe of correlations

    DEFF Research Database (Denmark)

    Imambekov, A.; Mazets, I. E.; Petrov, D. S.

    2009-01-01

    fluctuations. For the case of free ballistic expansion relevant to current experiments, we present simple analytical relations between the spectrum of "density ripples" and the correlation functions of the original confined systems. We analyze several physical regimes, including weakly and strongly interacting...

  3. Resonant soft x-ray scattering and charge density waves in correlated systems

    NARCIS (Netherlands)

    Rusydi, Andrivo

    2006-01-01

    Summary This work describes results obtained on the study of charge density waves (CDW) in strongly correlated systems with a new experimental method: resonant soft x-ray scattering (RSXS). The basic motivation is the 1986 discovery by Bednorz and Müler of a new type of superconductor, based on Cu

  4. Absolute choline concentration measured by quantitative proton MR spectroscopy correlates with cell density in meningioma

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Qiang [University of Tsukuba, Department of Neurosurgery, Institute of Clinical Medicine, Tsukuba Science City, Ibaraki (Japan)]|[West China Hospital of Sichuan University, Huaxi MR Research Center, Department of Radiology, Chengdu (China); Shibata, Yasushi; Kawamura, Hiraku; Matsumura, Akira [University of Tsukuba, Department of Neurosurgery, Institute of Clinical Medicine, Tsukuba Science City, Ibaraki (Japan); Isobe, Tomonori [Kitasato University, Department of Medical Technology, School of Allied Health Sciences, Minato, Tokyo (Japan); Anno, Izumi [University of Tsukuba, Department of Radiology, Institute of Clinical Medicine, Tsukuba, Ibaraki (Japan); Gong, Qi-Yong [West China Hospital of Sichuan University, Huaxi MR Research Center, Department of Radiology, Chengdu (China)]|[University of Liverpool, Division of Medical Imaging, Faculty of Medicine, Liverpool (United Kingdom)

    2009-01-15

    This study was aimed to investigate the relationship between quantitative proton magnetic resonance spectroscopy (1H-MRS) and pathological changes in meningioma. Twenty-two meningioma cases underwent single voxel 1H-MRS (point-resolved spectroscopy sequence, repetition time/echo time = 2,000 ms/68, 136, 272 ms). Absolute choline (Cho) concentration was calculated using tissue water as the internal reference and corrected according to intra-voxel cystic/necrotic parts. Pathological specimens were stained with MIB-1 antibody to measure cell density and proliferation index. Correlation analysis was performed between absolute Cho concentration and cell density and MIB-1 labeled proliferation index. Average Cho concentration of all meningiomas before correction was 2.95 {+-} 0.86 mmol/kg wet weight. It was increased to 3.23 {+-} 1.15 mmol/kg wet weight after correction. Average cell density of all meningiomas was 333 {+-} 119 cells/HPF, and average proliferation index was 2.93 {+-} 5.72%. A linear, positive correlation between cell density and Cho concentration was observed (r = 0.650, P = 0.001). After correction of Cho concentration, the correlation became more significant (r = 0.737, P < 0.001). However, no significant correlation between Cho concentration and proliferation index was found. There seemed to be a positive correlation trend after correction of Cho concentration but did not reach significant level. Absolute Cho concentration, especially Cho concentration corrected according to intra-voxel cystic/necrotic parts, reflects cell density of meningioma. (orig.)

  5. Universal dynamics of density correlations at the transition to the many-body localized state

    Science.gov (United States)

    Mierzejewski, M.; Herbrych, J.; Prelovšek, P.

    2016-12-01

    Within one-dimensional disordered models of interacting fermions, we perform a numerical study of several dynamical density correlations, which can serve as hallmarks of the transition to the many-body localized state. The results confirm that density-wave correlations exhibit quite an abrupt change with increasing disorder, with a nonvanishing long-time value characteristic for the nonergodic phase. In addition, our results reveal a logarithmic variation of correlations in time in a wide time window, which we can bring in connection with the anomalous behavior of the dynamical conductivity near the transition. Our results support the view that the transition to many-body localization can be characterized by universal dynamical exponents.

  6. [Ultrasonographic density of amniotic fluid and its correlation with fetal pulmonary maturity].

    Science.gov (United States)

    Romero-Gutiérrez, G; Avelar-Jaime, R

    1996-07-01

    In order to determine if the amniotic fluid density is correlated with fetal lung maturity, we carried out a prospective study in the Hospital de Gineco-Obstetricia del Centro Médico León del Instituto Mexicano del Seguro Social. One hundred and forty one patients with pregnancies between 13 and 41 gestation weeks were included. The amniotic fluid density was calculated by counting the level of echoes (free-floating particles) in the amniotic fluid. We found a significant correlation (P < 0.05) between the level of echoes and the gestation age, nevertheless, the correlation coefficient was very low (R = 0.28), therefore we concluded that this procedure is not a reliable predictor of fetal lung maturity.

  7. Kinetic Field Theory: Effects of momentum correlations on the cosmic density-fluctuation power spectrum

    CERN Document Server

    Bartelmann, Matthias; Kozlikin, Elena; Lilow, Robert; Dombrowski, Johannes; Mildenberger, Julius

    2016-01-01

    In earlier work, we have developed a Kinetic Field Theory (KFT) for cosmological structure formation and showed that the non-linear density-fluctuation power spectrum known from numerical simulations can be reproduced quite well even if particle interactions are taken into account to first order only. Besides approximating gravitational interactions, we had to truncate the initial correlation hierarchy of particle momenta at the second order. Here, we substantially simplify KFT. We show that its central object, the free generating functional, can be factorized, taking the full hierarchy of momentum correlations into account. The factors appearing in the generating functional have a universal form and can thus be tabulated for fast access in perturbation schemes. Our results show that the complete hierarchy of initial momentum correlations is responsible for a characteristic deformation in the density-fluctuation power spectrum, caused by mode transport independent of the particle interaction. At the present e...

  8. Probing heterogeneous dynamics from spatial density correlation in glass-forming liquids

    Science.gov (United States)

    Li, Yan-Wei; Zhu, You-Liang; Sun, Zhao-Yan

    2016-12-01

    We numerically investigate the connection between spatial density correlation and dynamical heterogeneity in glass-forming liquids. We demonstrate that the cluster size defined by the spatial aggregation of densely packed particles (DPPs) can better capture the difference between the dynamics of the Lennard-Jones glass model and the Weeks-Chandler-Andersen truncation model than the commonly used pair correlation functions. More interestingly, we compare the mobility of DPPs and loosely packed particles, and we find that high local density correlates well with slow dynamics in systems with relatively hard repulsive interactions but links to mobile ones in the system with soft repulsive interactions at one relaxation time scale. Our results show clear evidence that the above model dependence behavior stems from the hopping motion of DPPs at the end of the caging stage due to the compressive nature of soft repulsive spheres, which activates the dynamics of DPPs in the α relaxation stage.

  9. Colorimetry of woods from Eucalyptus and Corymbia genus and its correlation with density

    Directory of Open Access Journals (Sweden)

    Rosilei Aparecida Garcia

    2014-12-01

    Full Text Available The objectives of this study were to characterize the wood color of Corymbia citriodora (Hook. K.D. Hill & L.A.S. Johnson, Eucalyptus pellita F. Muell, Eucalyptus paniculata Sm. and Eucalyptus grandis Hill ex Maiden; and to determine its correlationship with wood density in order to evaluate the potential of colorimetry as a tool for identification and qualification of wood. Color analysis were performed on the CIE L*a*b* system by using the CM 2600d spectrophotometer from Konica Minolta. Theresults indicated significant differences between wood densities of all species. Eucalyptus paniculata wood presented the highest density while Eucalyptus grandis wood presented the lowest density. Correlation analysis between color and density showed that the denser woods, considering the species from the Eucalyptus genus studied, are darker (lower L* and present redder (a* and more yellow (b* hues. However, the behavior was different for Corymbia citriodora, whose wood had high density, light color and little red hue, indicating that color variables and density combination has potential to segregate the Corymbia citriodora species from other Eucalyptus species studied. The denser woods of Eucalyptus pellita are darker in the radial section, while woods of Eucalyptus paniculata presented more yellow hue (b* in the tangential section. Each species presented a specific color, given by colorimetric variables, showing the potential of colorimetry for wood identification.

  10. Fragment-based treatment of delocalization and static correlation errors in density-functional theory.

    Science.gov (United States)

    Nafziger, Jonathan; Wasserman, Adam

    2015-12-21

    One of the most important open challenges in modern Kohn-Sham (KS) density-functional theory (DFT) is the correct treatment of systems involving fractional electron charges and spins. Approximate exchange-correlation functionals struggle with such systems, leading to pervasive delocalization and static correlation errors. We demonstrate how these errors, which plague density-functional calculations of bond-stretching processes, can be avoided by employing the alternative framework of partition density-functional theory (PDFT) even using the local density approximation for the fragments. Our method is illustrated with explicit calculations on simple systems exhibiting delocalization and static-correlation errors, stretched H2 (+), H2, He2 (+), Li2 (+), and Li2. In all these cases, our method leads to greatly improved dissociation-energy curves. The effective KS potential corresponding to our self-consistent solutions displays key features around the bond midpoint; these are known to be present in the exact KS potential, but are absent from most approximate KS potentials and are essential for the correct description of electron dynamics.

  11. Density-functional theory of strongly correlated Fermi gases in elongated harmonic traps

    Science.gov (United States)

    Xianlong, Gao; Polini, Marco; Asgari, Reza; Tosi, M. P.

    2006-03-01

    Two-component Fermi gases with tunable repulsive or attractive interactions inside quasi-one-dimensional (Q1D) harmonic wells may soon become the cleanest laboratory realizations of strongly correlated Luttiger and Luther-Emery liquids under confinement. We present a microscopic Kohn-Sham density-functional theory of these systems, with specific attention to a gas on the approach to a confinement-induced Feshbach resonance. The theory employs the one-dimensional Gaudin-Yang model as the reference system and transfers the appropriate Q1D ground-state correlations to the confined inhomogeneous gas via a suitable local-density approximation to the exchange and correlation energy functional. Quantitative understanding of the role of the interactions in the bulk shell structure of the axial density profile is thereby achieved. While repulsive intercomponent interactions depress the amplitude of the shell structure of the noninteracting gas, attractive interactions stabilize atomic-density waves through spin pairing. These should be clearly observable in atomic clouds containing of the order of up to 100 atoms.

  12. Nonlocal Wigner-like correlation energy density functional: parametrization and tests on two-electron systems.

    Science.gov (United States)

    Katriel, Jacob; Bauer, Michael; Springborg, Michael; McCarthy, Shane P; Thakkar, Ajit J

    2007-07-14

    Reparametrization of Wigner's correlation energy density functional yields a very close fit to the correlation energies of the helium isoelectronic sequence. However, a quite different reparametrization is required to obtain an equally close fit to the isoelectronic sequence of Hooke's atom. In an attempt to avoid having to reparametrize the functional for different choices of the one-body potential, we propose a parametrization that depends on global characteristics of the ground-state electron density as quantified by scale-invariant combinations of expectation values of local one-body operators. This should be viewed as an alternative to the density-gradient paradigm, allowing one to introduce the nonlocal dependence of the density functional on the density in a possibly more effective way. Encouraging results are obtained for two-electron systems with one-body potentials of the form r(zeta) with zeta=-12,+12,1, which span the range between the Coulomb potential (zeta=-1) and the Hooke potential (zeta=2).

  13. Communication: Near-locality of exchange and correlation density functionals for 1- and 2-electron systems

    Science.gov (United States)

    Sun, Jianwei; Perdew, John P.; Yang, Zenghui; Peng, Haowei

    2016-05-01

    The uniform electron gas and the hydrogen atom play fundamental roles in condensed matter physics and quantum chemistry. The former has an infinite number of electrons uniformly distributed over the neutralizing positively charged background, and the latter only one electron bound to the proton. The uniform electron gas was used to derive the local spin density approximation to the exchange-correlation functional that undergirds the development of the Kohn-Sham density functional theory. We show here that the ground-state exchange-correlation energies of the hydrogen atom and many other 1- and 2-electron systems are modeled surprisingly well by a different local spin density approximation (LSDA0). LSDA0 is constructed to satisfy exact constraints but agrees surprisingly well with the exact results for a uniform two-electron density in a finite, curved three-dimensional space. We also apply LSDA0 to excited or noded 1-electron densities, where it works less well. Furthermore, we show that the localization of the exact exchange hole for a 1- or 2-electron ground state can be measured by the ratio of the exact exchange energy to its optimal lower bound.

  14. Characterization of maximally random jammed sphere packings. II. Correlation functions and density fluctuations

    Science.gov (United States)

    Klatt, Michael A.; Torquato, Salvatore

    2016-08-01

    In the first paper of this series, we introduced Voronoi correlation functions to characterize the structure of maximally random jammed (MRJ) sphere packings across length scales. In the present paper, we determine a variety of different correlation functions that arise in rigorous expressions for the effective physical properties of MRJ sphere packings and compare them to the corresponding statistical descriptors for overlapping spheres and equilibrium hard-sphere systems. Such structural descriptors arise in rigorous bounds and formulas for effective transport properties, diffusion and reactions constants, elastic moduli, and electromagnetic characteristics. First, we calculate the two-point, surface-void, and surface-surface correlation functions, for which we derive explicit analytical formulas for finite hard-sphere packings. We show analytically how the contact Dirac delta function contribution to the pair correlation function g2(r ) for MRJ packings translates into distinct functional behaviors of these two-point correlation functions that do not arise in the other two models examined here. Then we show how the spectral density distinguishes the MRJ packings from the other disordered systems in that the spectral density vanishes in the limit of infinite wavelengths; i.e., these packings are hyperuniform, which means that density fluctuations on large length scales are anomalously suppressed. Moreover, for all model systems, we study and compute exclusion probabilities and pore size distributions, as well as local density fluctuations. We conjecture that for general disordered hard-sphere packings, a central limit theorem holds for the number of points within an spherical observation window. Our analysis links problems of interest in material science, chemistry, physics, and mathematics. In the third paper of this series, we will evaluate bounds and estimates of a host of different physical properties of the MRJ sphere packings that are based on the

  15. On the Alternatives for Bath Correlators and Spectral Densities from Mixed Quantum-Classical Simulations

    OpenAIRE

    2012-01-01

    We investigate on the procedure of extracting a "spectral density" from mixed QM/MM calculations and employing it in open quantum systems models. In particular, we study the connection between the energy gap correlation function extracted from ground state QM/MM and the bath spectral density used as input in open quantum system approaches. We introduce a simple model which can give intuition on when the ground state QM/MM propagation will give the correct energy gap. We also discuss the role ...

  16. Alternative separation of exchange and correlation energies in range-separated density-functional perturbation theory

    OpenAIRE

    Cornaton, Yann; Stoyanova, Alexandrina; Jensen, Hans Jørgen Aa.; Fromager, Emmanuel

    2013-01-01

    An alternative separation of short-range exchange and correlation energies is used in the framework of second-order range-separated density-functional perturbation theory. This alternative separation was initially proposed by Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] and relies on a long-range interacting wavefunction instead of the non-interacting Kohn-Sham one. When second-order corrections to the density are neglected, the energy expression reduces to a range-separated double-hyb...

  17. Tailoring correlations of the local density of states in disordered photonic materials

    CERN Document Server

    Riboli, F; Monaco, G; Caselli, N; Intonti, F; Gurioli, M; Skipetrov, S E

    2016-01-01

    We present experimental evidence for the different mechanisms driving the fluctuations of the local density of states (LDOS) in disordered photonic systems. We establish a clear link between the microscopic structure of the material and the frequency correlation function of LDOS accessed by a near-field hyperspectral imaging technique. We show, in particular, that short- and long-range frequency correlations of LDOS are controlled by different physical processes (multiple or single scattering processes, respectively) that can be---to some extent---manipulated independently. We also demonstrate that the single scattering contribution to the LDOS fluctuations is sensitive to subwavelength features of the material and, in particular, to the correlation length of its dielectric function. Our work paves the way towards a complete control of statistical properties of disordered photonic systems, allowing for designing materials with predefined LDOS correlations.

  18. Quantum and classical correlations for a two-qubit X structure density matrix

    Institute of Scientific and Technical Information of China (English)

    Ding Bang-Fu; Wang Xiao-Yun; Zhao He-Ping

    2011-01-01

    We derive explicit expressions for quantum discord and classical correlation for an X structure density matrix.Based on the characteristics of the expressions,the quantum discord and the classical correlation are easily obtained and compared under different initial conditions using a novel analytical method.We explain the relationships among quantum discord,classical correlation,and entanglement,and further find that the quantum discord is not always larger than the entanglement measured by concurrence in a general two-qubit X state.The new method,which is different from previous approaches,has certain guiding significance for analysing quantum discord and classical correlation of a two-qubit X state,such as a mixed state.

  19. Common pediatric cerebellar tumors: correlation between cell densities and apparent diffusion coefficient metrics.

    Science.gov (United States)

    Koral, Korgün; Mathis, Derek; Gimi, Barjor; Gargan, Lynn; Weprin, Bradley; Bowers, Daniel C; Margraf, Linda

    2013-08-01

    To test whether there is correlation between cell densities and apparent diffusion coefficient (ADC) metrics of common pediatric cerebellar tumors. This study was reviewed for issues of patient safety and confidentiality and was approved by the Institutional Review Board of the University of Texas Southwestern Medical Center and was compliant with HIPAA. The need for informed consent was waived. Ninety-five patients who had preoperative magnetic resonance imaging and surgical pathologic findings available between January 2003 and June 2011 were included. There were 37 pilocytic astrocytomas, 34 medulloblastomas (23 classic, eight desmoplastic-nodular, two large cell, one anaplastic), 17 ependymomas (13 World Health Organization [WHO] grade II, four WHO grade III), and seven atypical teratoid rhabdoid tumors. ADCs of solid tumor components and normal cerebellum were measured. Tumor-to-normal brain ADC ratios (hereafter, ADC ratio) were calculated. The medulloblastomas and ependymomas were subcategorized according to the latest WHO classification, and tumor cellularity was calculated. Correlation was sought between cell densities and mean tumor ADCs, minimum tumor ADCs, and ADC ratio. When all tumors were considered together, negative correlation was found between cellularity and mean tumor ADCs (ρ = -0.737, P correlation between cellularity and ADC ratio. Negative correlation was found between cellularity and minimum tumor ADC in atypical teratoid rhabdoid tumors (ρ = -0.786, P correlation was found between cellularity and mean tumor ADC and ADC ratio. There was no correlation between the ADC metrics and cellularity of the pilocytic astrocytomas, medulloblastomas, and ependymomas. Negative correlation was found between cellularity and ADC metrics of common pediatric cerebellar tumors. Although ADC metrics are useful in the preoperative diagnosis of common pediatric cerebellar tumors and this utility is generally attributed to differences in cellularity of tumors

  20. Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation

    Science.gov (United States)

    Roberts, D. A.

    1990-01-01

    The Helios, IMP 8, ISEE 3, ad Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. Previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here it is shown that this evolution is not a solar cycle effect, and that the correlations become even more strongly negative at heliocentric distance larger than 9.5 AU. There is considerable variability in the distributions of the correlations at a given heliocentric distance, but this is not simply related to the solar cycle. Examination of the evolution of correlations between density and speed suggest that most of the structures responsible for evolution in the anticorrelation between n and B are not slow-mode waves, but rather pressure balance structures. The latter consist of both coherent structures such as tangential discontinuities and the more generally pervasive 'pseudosound' which may include the coherent structures as a subset.

  1. Spectral density analysis of time correlation functions in lattice QCD using the maximum entropy method

    CERN Document Server

    Fiebig, H R

    2002-01-01

    We study various aspects of extracting spectral information from time correlation functions of lattice QCD by means of Bayesian inference with an entropic prior, the maximum entropy method (MEM). Correlator functions of a heavy-light meson-meson system serve as a repository for lattice data with diverse statistical quality. Attention is given to spectral mass density functions, inferred from the data, and their dependence on the parameters of the MEM. We propose to employ simulated annealing, or cooling, to solve the Bayesian inference problem, and discuss practical issues of the approach.

  2. Correlations of the density and of the current in non-equilibrium diffusive systems

    Science.gov (United States)

    Sadhu, Tridib; Derrida, Bernard

    2016-11-01

    We use fluctuating hydrodynamics to analyze the dynamical properties in the non-equilibrium steady state of a diffusive system coupled with reservoirs. We derive the two-time correlations of the density and of the current in the hydrodynamic limit in terms of the diffusivity and the mobility. Within this hydrodynamic framework we discuss a generalization of the fluctuation dissipation relation in a non-equilibrium steady state where the response function is expressed in terms of the two-time correlations. We compare our results to an exact solution of the symmetric exclusion process. This exact solution also allows one to directly verify the fluctuating hydrodynamics equation.

  3. Alternative separation of exchange and correlation energies in range-separated density-functional perturbation theory

    DEFF Research Database (Denmark)

    Cornaton, Y.; Stoyanova, A.; Jensen, Hans Jørgen Aagaard;

    2013-01-01

    An alternative separation of short-range exchange and correlation energies is used in the framework of second-order range-separated density-functional perturbation theory. This alternative separation was initially proposed by Toulouse and relies on a long-range-interacting wave function instead...... expression when expanded in perturbation theory. In contrast to the usual RSDH functionals, RSDHf describes the coupling between long- and short-range correlations as an orbital-dependent contribution. Calculations on the first four noble-gas dimers show that this coupling has a significant effect...

  4. Novel four-point-probe design and nanorobotic dual endeffector strategy for electrical characterization of as-grown SWCNT bundles

    DEFF Research Database (Denmark)

    Eichhorn, V; Fatikow, S; Sardan Sukas, Özlem

    2010-01-01

    In this paper, a novel nanorobotic strategy for non-destructive and direct electrical characterization of as-grown bundles of single-walled carbon nanotubes (SWCNTs) is presented. For this purpose, test patterns of SWCNT bundles having different diameters are grown on a silicon substrate...... by chemical vapor deposition. A new design of microstructured four-point-probes is proposed and fabricated allowing for direct contacting of vertically aligned bundles of SWCNTs. A nanorobotic setup is upgraded into a dual endeffector system to achieve good electrical contact between four...

  5. Micro-four-point probes in a UHV scanning electron microscope for in-situ surface-conductivity measurements

    DEFF Research Database (Denmark)

    Shiraki, I.; Nagao, T.; Hasegawa, S.;

    2000-01-01

    For in-situ measurements of surface conductivity in ultrahigh vacuum (UHV), we have installed micro-four-point probes (probe spacings down to 4 mum) in a UHV scanning electron microscope (SEM) combined with scanning reflection-high-energy electron diffraction (RHEED). With the aid of piezoactuators...... for precise positioning of the probes, local conductivity of selected surface domains of well-defined superstructures could be measured during SEM and RHEED observations. It was found that the surface sensitivity of the conductivity measurements was enhanced by reducing the probe spacing, enabling...

  6. Electronic properties and momentum densities of tin chalcogenides: Validation of PBEsol exchange-correlation potential

    Energy Technology Data Exchange (ETDEWEB)

    Ahuja, B.L., E-mail: blahuja@yahoo.ik [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Raykar, Veera; Joshi, Ritu [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Tiwari, Shailja [Department of Physics, Govt. Women Engineering College, Ajmer 305001, Rajasthan (India); Talreja, Sonal [Department of Computer Science, M.L. Sukhadia University, Udaipur 313001 (India); Choudhary, Gopal [Department of Physics, Techno India NJR Institute of Technology, Udaipur 313001, Rajasthan (India)

    2015-05-15

    We report Compton profiles of SnS and SnTe at a momentum resolution of 0.34 a.u. using a 20 Ci {sup 137}Cs Compton spectrometer. To compare our experimental data, we have also computed the theoretical Compton profiles using density functional theory within linear combination of atomic orbitals (LCAO) method. To interpret the relative nature of bonding in these compounds, we have scaled the experimental and theoretical Compton profiles on equal-valence-electron-density (EVED). On the basis of EVED profiles, it is seen that SnTe shows more covalent character than SnS. To rectify the substantial disagreement between experimental and theoretical band gaps, we have also presented the energy bands and density of states of both the compounds using full-potential linearized augmented plane wave method (FP-LAPW) including spin–orbit interaction within the PBEsol exchange-correlation potential.

  7. Velocity statistics from spectral line data effects of density-velocity correlations, magnetic field, and shear

    CERN Document Server

    Esquivel, A; Pogosyan, D; Cho, J; Esquivel, Alejandro; Cho, Jungyeon

    2003-01-01

    In a previous work Lazarian and Pogosyan suggested a technique to extract velocity and density statistics, of interstellar turbulence, by means of analysing statistics of spectral line data cubes. In this paper we test that technique, by studying the effect of correlation between velocity and density fields, providing a systematic analysis of the noise, and exploring the effect of a linear shear. We make use of both compressible MHD simulations and synthetic data to emulate spectroscopic observations. With such synthetic spectroscopic data, we studied anisotropies of the two point statistics and related those anisotropies with the magnetic field direction. This presents a new technique for magnetic field studies. The results show that the velocity and density spectral indices measured are consistent with the analytical predictions. We identified the dominant source of error with the limited number of data points along a given line of sight. We argue that in real observations the number of emmiting elements is...

  8. Pure density functional for strong correlation and the thermodynamic limit from machine learning

    Science.gov (United States)

    Li, Li; Baker, Thomas E.; White, Steven R.; Burke, Kieron

    2016-12-01

    We use the density-matrix renormalization group, applied to a one-dimensional model of continuum Hamiltonians, to accurately solve chains of hydrogen atoms of various separations and numbers of atoms. We train and test a machine-learned approximation to F [n ] , the universal part of the electronic density functional, to within quantum chemical accuracy. We also develop a data-driven, atom-centered basis set for densities which greatly reduces the computational cost and accurately represents the physical information in the machine-learning calculation. Our calculation (a) bypasses the standard Kohn-Sham approach, avoiding the need to find orbitals, (b) includes the strong correlation of highly stretched bonds without any specific difficulty (unlike all standard DFT approximations), and (c) is so accurate that it can be used to find the energy in the thermodynamic limit to quantum chemical accuracy.

  9. Correlation of different bone markers with bone density in patients with rheumatic diseases on glucocorticoid therapy.

    Science.gov (United States)

    Loddenkemper, Konstanze; Bohl, Nicole; Perka, Carsten; Burmester, Gerd-Rüdiger; Buttgereit, Frank

    2006-02-01

    Osteoporosis is a common concomitant disease in patients with rheumatic diseases on glucocorticoid (GC) therapy. Bone status is usually evaluated by determination of bone density in combination with clinical examinations and laboratory tests. However, the strength of individual biochemical bone makers in GC-induced osteoporosis has yet to be fully clarified. For this reason, different bone markers were investigated in correlation with bone density in patients with rheumatic diseases. Approximately 238 patients (212 women, 26 men) with a rheumatic disease and under GC therapy were examined consecutively for the first time with regard to bone density (BMD) and bone markers [osteocalcin, bone-specific alkaline phosphatase (precipitation method/tandem-MP ostase), crosslinks [pyridinoline (PYD), deoxypyridinoline (DPX), N-terminal telopeptide (NTX)

  10. A new access density definition and its correlation with crash rates by microscopic traffic simulation method.

    Science.gov (United States)

    Huang, Bing; Zhang, Yu; Lu, Linjun; Lu, Jian John

    2014-03-01

    Better access management can improve highway safety by reducing potential crashes and conflicts. To make adequate access management decisions, it is essential to understand the impact of different access types on roadway safety, usually represented by the crash rate of a roadway segment. The objective of this paper is to propose a new access density definition reflecting the impact of traffic speed variation of different access types. The traffic speed variation was obtained from a microscopic traffic simulation software package TSIS-CORSIM. A sample roadway Temple Terrace Highway was selected to perform traffic simulation. Access Weight was obtained from traffic speed variation, and access density was obtained from access weight. The proposed access density was then compared with the existing definition by analyzing their correlations with crash rates on one suburban street in Temple Terrace, Florida. The comparison demonstrates that crash rates are more highly correlated with the proposed access density than that in the previous study, which is helpful for Federal Highway Administration (FHWA), United States Department of Transportation (USDOT), and transportation consulting companies to regulate the construction, management and design of roadway segments.

  11. Molecular aspects of osteopathy in type 1 Gaucher disease: correlation between genetics and bone density.

    Science.gov (United States)

    Arnheim, Efrat; Chicco, Gaya; Phillips, Mici; Lebel, Ehud; Foldes, A Joseph; Itzchaki, Menachem; Elstein, Deborah; Zimran, Ari; Altarescu, Gheona

    2008-07-01

    Bone-related complications in Gaucher disease are considered to be poorly responsive to specific enzyme replacement therapy. Polymorphisms of candidate genes associated with low bone density were investigated to see whether they are correlated with bone mineral density (BMD) and bone involvement in Gaucher disease. Genotyping for polymorphisms in candidate genes (interleukins 1alpha and 1beta, interleukin-1 receptor antagonist; cytochrome P450; collagen 1A1; low-density Lipoprotein Receptor; bone morphogenic protein 4; vitamin D receptor; and estrogen receptor 2beta) were performed using standard methodologies. BMD was measured by dual energy X-ray absorptiometry (DXA). One hundred and ninety-four patients and 100 controls were genotyped for the above polymorphisms. Thirteen haplotypes were obtained, with several correlations with BMD in patients; also, a haplotype (T889-T3954-C511-240VNTR of IL1) was significantly correlated with T-scores and Z-score for femur neck and lumbar spine (p = 0.01) in patients. Haplotypes of bone-specific candidate genes associated with BMD may predict severity of these features in Gaucher disease.

  12. Flexural and bond strengths of relined denture polymers assessed by four-point bending tests and Weibull analysis.

    Science.gov (United States)

    Polyzois, Gregory L; Lagouvardos, Panagiotis E; Frangou, Maria J

    2012-06-01

    The aim of this study was to (1) investigate the flexural strengths of three denture resins i.e. heat, photopolymerised and microwaved and how it was affected by relining with auto- and visible light-polymerised hard reliners, (2) investigate the bond strengths between denture resins and hard reliners and (3) interpret the results of both tests by utilising Weibull analysis. Specimens (65 × 10 × 2.5 mm) from denture resins, relined and bonded combinations were tested using a four-point bending test in a universal testing machine and a crosshead speed of 5 mm/min. Ten specimens for each bulk resin and denture resin-reliner combination for a total of 150 were tested. Statistical analysis indicated significant differences between bulk materials (p < 0.001) and between reliners (p < 0.001) for flexural and bond strength tests. was concluded that (1) the four-point flexural strength was different between the denture base materials, (2) flexure strength between bulk and relined or between relined with autopolymerised and photopolymerised bases was different, (3) flexural strength among relined denture bases was different and (4) bond strengths among relined denture bases were different. © 2011 The Gerodontology Society and John Wiley & Sons A/S.

  13. On the HI column density - radio source size anti-correlation in compact radio sources

    CERN Document Server

    Curran, S J; Glowacki, M; Whiting, M T; Sadler, E M

    2013-01-01

    Existing studies of the atomic hydrogen gas content in distant galaxies, through the absorption of the 21-cm line, often infer that the total column density is anti-correlated with the linear extent of the background radio source. We investigate this interpretation, by dissecting the various parameters from which the column density is derived, and find that the relationship is driven primarily by the observed optical depth, which, for a given absorber size, is anti-correlated with the linear size. Therefore, the inferred anti-correlation is merely the consequence of geometry, in conjunction with the assumption of a common spin temperature/covering factor ratio for each member of the sample, an assumption for which there is scant observational justification. While geometry can explain the observed correlation, many radio sources comprise two radio lobes and so we model the projected area of a two component emitter intercepted by a foreground absorber. From this, the observed optical depth/linear size relations...

  14. Correlation of seismic wave velocities with fracture densities: Implications for the critical zone in mountain watersheds

    Science.gov (United States)

    Peters, M. P.; Holbrook, W. S.; Flinchum, B. A.; Pasquet, S.

    2016-12-01

    Despite increasing scientific interest in the critical zone, the accurate determination of fracture density in the subsurface remains difficult as access and costs can prohibit ground-truthing through drilling. A more precise characterization of the fracturing process provides critical insight in to subsurface structures. This is particularly important in determining the point at which protolithic rock becomes fractured bedrock and then degrades to soil through the process of weathering. We studied outcrops in the Laramie Range of southeastern Wyoming were studied and fracture densities were correlated with seismic pressure (P) wave velocities. We used the Differential Effective Medium (DEM) rock physics model to validate our findings and provide a more robust characterization of the role of P-wave velocities acquired on outcrops play in critical zone science. This approach marks a significant departure from previous research, which has not applied P-wave fracture relationships in outcrops onto the critical zone for subsurface characterization. We compared our results with borehole data to establish a relationship between surface outcrops and subsurface rock structures. We found a clear, inverse relationship between a decrease in P-wave velocity and an increase in fracture density consistent with borehole data in the studied area. Our findings suggest that outcrops can be used to determine fracture density in the critical zone. We show that the use of seismic refraction surveys on outcrops provides a non-invasive, highly transferrable method through which we can predict fracturing densities in the subsurface.

  15. Velocity-density correlations from the cosmicflows-3 distance catalogue and the 2MASS Redshift Survey

    Science.gov (United States)

    Nusser, Adi

    2017-09-01

    The peculiar velocity of a mass tracer is on average aligned with the dipole modulation of the surrounding mass density field. We present a first measurement of the correlation between radial peculiar velocities of objects in the cosmicflows-3 catalogue and the dipole moment of the 2MRS galaxy distribution in concentric spherical shells centred on these objects. Limiting the analysis to cosmicflows-3 objects with distances of 100h-1 Mpc, the correlation function is detected at a confidence level of ≳ 4σ. The measurement is found consistent with the standard ΛCDM model at the ≲ 1.7σ level. We formally derive the constraints 0.32 confidence level) or equivalently 0.34 type of correlations.

  16. The density matrix functional approach to electron correlation: Dynamic and nondynamic correlation along the full dissociation coordinate

    Energy Technology Data Exchange (ETDEWEB)

    Mentel, Ł. M.; Meer, R. van; Gritsenko, O. V. [Section Theoretical Chemistry, VU University, Amsterdam (Netherlands); Pohang University of Science and Technology, Pohang (Korea, Republic of); Baerends, E. J. [Section Theoretical Chemistry, VU University, Amsterdam (Netherlands); Pohang University of Science and Technology, Pohang (Korea, Republic of); Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2014-06-07

    For chemistry an accurate description of bond weakening and breaking is vital. The great advantage of density matrix functionals, as opposed to density functionals, is their ability to describe such processes since they naturally cover both nondynamical and dynamical correlation. This is obvious in the Löwdin-Shull functional, the exact natural orbital functional for two-electron systems. We present in this paper extensions of this functional for the breaking of a single electron pair bond in N-electron molecules, using LiH, BeH{sup +}, and Li{sub 2} molecules as prototypes. Attention is given to the proper formulation of the functional in terms of not just J and K integrals but also the two-electron L integrals (K integrals with a different distribution of the complex conjugation of the orbitals), which is crucial for the calculation of response functions. Accurate energy curves are obtained with extended Löwdin-Shull functionals along the complete dissociation coordinate using full CI calculations as benchmark.

  17. BREAST CANCER RISK EVALUATION - A CORRELATION BETWEEN MAMMOGRAPHIC DENSITY AND THE GAIL MODEL

    Directory of Open Access Journals (Sweden)

    George Baytchev

    2015-05-01

    Full Text Available The Gail model is a statistical tool, which assesses breast cancer probability, based on nonmodifiable risk factors. In contrast, the evaluation of mammographic breast density is an independent and dynamic risk factor influenced by interventions modifying breast cancer risk incidence. The aim of the present study is to compare the possibilities for risk factor integration and analysis and to search for a correlation between mammographic density and the Gail model for breast cancer risk evaluation. The subject of this prospective study is a cohort of 107 women at ages from 37 to 71 years, who have had benign breast diseases, digital mammograms, and Gail model risk evaluation. Mammographic density is evaluated in craniocaudal projection subjectively visually and objectively using the computer imaging software. (Image J software The Gail risk evaluation is completed using the standardized NCI questionnaire (Breast Cancer Risk Assessment Tool. In concordance with the Breast Imaging Reporting and Data System (BI-RAD by ACR, mammographic density is evaluated using a four-grade scale. Low density D1 (less than 25% was determined in 24 cases, D2 (25-50% in 36 cases, D3 (51-75% in 31 cases and high density D4 (greater than 75% in 16 cases. According to the Gail model, 80 (74,8% of the examined patients did not have an increased risk (less than 1,67% for a five-year period, whereas the remaining 27 (25,2% had a statistically significant increase in risk (greater than 1,67% for a five-year period. Women with increased risk more often present with denser breast (34% with D3, D4 versus 18,3% for D1, D2. The Gail model does not adequately explain the correlation between breast density and statistically calculated risk. The development of more detailed tools, which take into consideration breast density, as well as other risk factors, may be helpful for a more accurate evaluation of the individual risk for breast cancer.

  18. Carotenoid-chlorophyll coupling and fluorescence quenching correlate with protein packing density in grana-thylakoids.

    Science.gov (United States)

    Holleboom, Christoph-Peter; Yoo, Sunny; Liao, Pen-Nan; Compton, Ian; Haase, Winfried; Kirchhoff, Helmut; Walla, Peter Jomo

    2013-09-26

    The regulation of light-harvesting in photosynthesis under conditions of varying solar light irradiation is essential for the survival and fitness of plants and algae. It has been proposed that rearrangements of protein distribution in the stacked grana region of thylakoid membranes connected to changes in the electronic pigment-interaction play a key role for this regulation. In particular, carotenoid-chlorophyll interactions seem to be crucial for the down-regulation of photosynthetic light-harvesting. So far, it has been difficult to determine the influence of the dense protein packing found in native photosynthetic membrane on these interactions. We investigated the changes of the electronic couplings between carotenoids and chlorophylls and the quenching in grana thylakoids of varying protein packing density by two-photon spectroscopy, conventional chlorophyll fluorometry, low-temperature fluorescence spectroscopy, and electron micrographs of freeze-fracture membranes. We observed an increasing carotenoid-chlorophyll coupling and fluorescence quenching with increasing packing density. Simultaneously, the antennas size and excitonic connectivity of Photosystem II increased with increasing quenching and carotenoid-chlorophyll coupling whereas isolated, decoupled LHCII trimers decreased. Two distinct quenching data regimes could be identified that show up at different protein packing densities. In the regime corresponding to higher protein packing densities, quenching is strongly correlated to carotenoid-chlorophyll interactions whereas in the second regime, a weak correlation is apparent with low protein packing densities. Native membranes are in the strong-coupling data regime. Consequently, PSII and LHCII in grana membranes of plants are already quenched by protein crowding. We concluded that this ensures efficient electronic connection of all pigment-protein complexes for intermolecular energy transfer to the reaction centers and allows simultaneously

  19. Capillary waves and the decay of density correlations at liquid surfaces

    Science.gov (United States)

    Hernández-Muñoz, Jose; Chacón, Enrique; Tarazona, Pedro

    2016-12-01

    Wertheim predicted strong density-density correlations at free liquid surfaces, produced by capillary wave fluctuations of the interface [M. S. Wertheim, J. Chem. Phys. 65, 2377 (1976), 10.1063/1.433352]. That prediction has been used to search for a link between capillary wave (CW) theory and density functional (DF) formalism for classical fluids. In particular, Parry et al. have recently analyzed the decaying tails of these CW effects moving away from the interface as a clue for the extended CW theory [A. O. Parry et al., J. Phys.: Condens. Matter 28, 244013 (2016), 10.1088/0953-8984/28/24/244013], beyond the strict long-wavelength limit studied by Wertheim. Some apparently fundamental inconsistencies between the CW and the DF theoretical views of the fluid interfaces arose from the asymptotic analysis of the CW signal. In this paper we revisit the problem of the CW asymptotic decay with a separation of local non-CW surface correlation effects from those that are a truly nonlocal propagation of the CW fluctuations from the surface towards the liquid bulk.

  20. The correlation function for density perturbations in an expanding universe. I - Linear theory

    Science.gov (United States)

    Mcclelland, J.; Silk, J.

    1977-01-01

    The evolution of the two-point correlation function for adiabatic density perturbations in the early universe is studied. Analytical solutions are obtained for the evolution of linearized spherically symmetric adiabatic density perturbations and the two-point correlation function for these perturbations in the radiation-dominated portion of the early universe. The results are then extended to the regime after decoupling. It is found that: (1) adiabatic spherically symmetric perturbations comparable in scale with the maximum Jeans length would survive the radiation-dominated regime; (2) irregular fluctuations are smoothed out up to the scale of the maximum Jeans length in the radiation era, but regular fluctuations might survive on smaller scales; (3) in general, the only surviving structures for irregularly shaped adiabatic density perturbations of arbitrary but finite scale in the radiation regime are the size of or larger than the maximum Jeans length in that regime; (4) infinite plane waves with a wavelength smaller than the maximum Jeans length but larger than the critical dissipative damping scale could survive the radiation regime; and (5) black holes would also survive the radiation regime and might accrete sufficient mass after decoupling to nucleate the formation of galaxies.

  1. Correlation between the extent of catalytic activity and charge density of montmorillonites.

    Science.gov (United States)

    Ertem, Gözen; Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

    2010-09-01

    The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH₃-(CH₂)(n)-NH₃](+), where n = 3-16 and 18, and then measuring d(₀₀₁), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed.

  2. Correlation between the High Density Lipoprotein and its Subtypes in Coronary Heart Disease

    Directory of Open Access Journals (Sweden)

    Fen Gao

    2016-05-01

    Full Text Available Background/Aims: To detect the changes of high density lipoprotein (HDL and its subtypes in serum of patients with coronary heart disease (CHD. Methods: 337 hospitalized patients were selected from our hospital during August, 2014 - January, 2015, and divided into CHD group (n = 190 and control group (n = 127. Lipoprint lipoprotein analyzer was used to classify low density lipoprotein (LDL particle size and its sub-components, as well as HDL particle size and its sub-components. The changes of the subtypes in patients with CHD were statistically analyzed. The possible mechanism was explored. Results: (1 Compared with the control group, the concentration of HDL in CHD patients reduced, HDLL significantly decreased (P S increased (P L had the most significant decreased; (3 HDL and all HDL subtypes were positively correlated with apolipoprotein A-I (apoA-I, of which, HDLL had the biggest correlation with apoA-I (P M had a maximum correlation with HDL (P Conclusion: HDL maturation disorders existed in the serum of CHD patients, HDLL may be protected factor for CHD, whose decrease was closely related wit the risk increase of CHD. The cardiovascular protection function of HDLL may be related with apoA-I content.

  3. Tetrahedral shape and surface density wave of $^{16}$O caused by $\\alpha$-cluster correlations

    CERN Document Server

    Kanada-En'yo, Yoshiko

    2016-01-01

    $\\alpha$-cluster correlations in the $0^+_1$ and $3^-_1$ states of $^{12}$C and $^{16}$O are studied using the method of antisymmetrized molecular dynamics, with which nuclear structures are described from nucleon degrees of freedom without assuming existence of clusters. The intrinsic states of $^{12}$C and $^{16}$O have triangle and tetrahedral shapes, respectively, because of the $\\alpha$-cluster correlations. These shapes can be understood as spontaneous symmetry breaking of rotational invariance, and the resultant surface density oscillation is associated with density wave (DW) caused by the instability of Fermi surface with respect to particle-hole correlations with the wave number $\\lambda=3$. $^{16}$O($0^+_1$) and $^{16}$O($3^-_1$) are regarded as a set of parity partners constructed from the rigid tetrahedral intrinsic state, whereas $^{12}$C($0^+_1$) and $^{12}$C($3^-_1$) are not good parity partners as they have triangle intrinsic states of different sizes with significant shape fluctuation because...

  4. Pairing in high-density neutron matter including short- and long-range correlations

    CERN Document Server

    Ding, D; Dickhoff, W H; Dussan, H; Polls, A; Witte, S J

    2015-01-01

    The influence of short-range correlations (SRC) on the spectral distribution of neutrons is incorporated in the solution of the gap equation for the ${}^3P_2-{}^3F_2$ coupled channel in pure neutron matter at high density. This effect is studied for three different realistic interactions. The gap in this channel is strongly suppressed by these correlations but does not vanish. For a consistent treatment we also include for the first time the effect of long-range correlations (LRC) by incorporating polarization terms in addition to the bare interaction. This allows the neutrons to exchange density and spin fluctuations governed by the strength of Landau parameters with values that are consistent with the available literature. While these LRC have an antiscreening tendency, they only slightly increase the gap in the ${}^3P_2-{}^3F_2$ coupled channel for all three realistic interactions as long as SRC are included. All three interactions generate maximum gaps around 0.1 to 0.2 MeV at most with a small dependence...

  5. Improved correlation between CT emphysema quantification and pulmonary function test by density correction of volumetric CT data based on air and aortic density

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Song Soo [Department of Radiology, Chungnam National University Hospital, Chungnam National University School of Medicine (Korea, Republic of); Seo, Joon Beom, E-mail: seojb@amc.seoul.kr [Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center (Korea, Republic of); Kim, Namkug; Chae, Eun Jin [Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center (Korea, Republic of); Lee, Young Kyung [Department of Radiology, Kyung Hee University Hospital at Gangdong (Korea, Republic of); Oh, Yeon Mok; Lee, Sang Do [Division of Pulmonology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center (Korea, Republic of)

    2014-01-15

    Objectives: To determine the improvement of emphysema quantification with density correction and to determine the optimal site to use for air density correction on volumetric computed tomography (CT). Methods: Seventy-eight CT scans of COPD patients (GOLD II–IV, smoking history 39.2 ± 25.3 pack-years) were obtained from several single-vendor 16-MDCT scanners. After density measurement of aorta, tracheal- and external air, volumetric CT density correction was conducted (two reference values: air, −1000 HU/blood, +50 HU). Using in-house software, emphysema index (EI) and mean lung density (MLD) were calculated. Differences in air densities, MLD and EI prior to and after density correction were evaluated (paired t-test). Correlation between those parameters and FEV{sub 1} and FEV{sub 1}/FVC were compared (age- and sex adjusted partial correlation analysis). Results: Measured densities (HU) of tracheal- and external air differed significantly (−990 ± 14, −1016 ± 9, P < 0.001). MLD and EI on original CT data, after density correction using tracheal- and external air also differed significantly (MLD: −874.9 ± 27.6 vs. −882.3 ± 24.9 vs. −860.5 ± 26.6; EI: 16.8 ± 13.4 vs. 21.1 ± 14.5 vs. 9.7 ± 10.5, respectively, P < 0.001). The correlation coefficients between CT quantification indices and FEV{sub 1}, and FEV{sub 1}/FVC increased after density correction. The tracheal air correction showed better results than the external air correction. Conclusion: Density correction of volumetric CT data can improve correlations of emphysema quantification and PFT.

  6. Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua, E-mail: canhualiu@sjtu.edu.cn, E-mail: jfjia@sjtu.edu.cn; Jia, Jin-Feng, E-mail: canhualiu@sjtu.edu.cn, E-mail: jfjia@sjtu.edu.cn [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

    2015-05-15

    Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO{sub 3} surface.

  7. Effect of recovery from muscle strength imbalance in lower limb using four point weight bearing reduction system.

    Science.gov (United States)

    Yu, Chang Ho; Kang, Seung Rok; Jeong, Ho Choon; Kim, Kyung; Kwon, Tae Kyu

    2014-01-01

    This study was performed to assess the improvement of muscle strength imbalance in the lower limbs using a four point weight bearing reduction system with a two-belt treadmill. Participants, each having differences in muscle function of the left and right legs of over 20%, were divided into two groups of ten. The participants were involved in experiments progressing 40 minutes per day, 3 days per week, during a period of 4 weeks. The maximal peak torque and average power were measured for testing joint torque in the hip, knee and ankle. The results showed the improvement of muscle imbalance as assessed by the maximal muscle strength was the most effective in the hip joint, while the improvement of muscular reaction was the most effective in the knee joint. We suggest that the method of weight bearing reduction could be sufficient to reduce muscle imbalance in the lower limbs.

  8. Characterization of positional errors and their influence on micro four-point probe measurements on a 100 nm Ru film

    DEFF Research Database (Denmark)

    Kjær, Daniel; Hansen, Ole; Østerberg, Frederik Westergaard;

    2015-01-01

    Thin-film sheet resistance measurements at high spatial resolution and on small pads are important and can be realized with micrometer-scale four-point probes. As a result of the small scale the measurements are affected by electrode position errors. We have characterized the electrode position...... errors in measurements on Ru thin film using an Au-coated 12-point probe. We show that the standard deviation of the static electrode position error is on the order of 5 nm, which significantly affects the results of single configuration measurements. Position-error-corrected dual......-configuration measurements, however, are shown to eliminate the effect of position errors to a level limited either by electrical measurement noise or dynamic position errors. We show that the probe contact points remain almost static on the surface during the measurements (measured on an atomic scale) with a standard...

  9. Note: a simple approach to fabricate a microscopic four-point probe for conductivity measurements in ultrahigh vacuum.

    Science.gov (United States)

    Pang, Fei; Liang, Xuejin; Chen, Dongmin

    2013-07-01

    We present a simple method to fabricate microscopic four-point probe (M4PP) with spacing of 70-100 μm for conductivity measurements in ultrahigh vacuum. The probe includes four gold wires with 30 μm diameter and a 0.5 mm thickness sapphire slice as cantilever. One of the dual scanning tunneling microscope (DSTM) is replaced by M4PP. As a result, in situ transport measurement could be performed by M4PP and investigation of surface morphology by STM. Finally, we measure conductivity of 14 monolayer Bi(111) epitaxial film on n type Si which is 1.6 × 10(-3) Ω(-1)∕[larger open square].

  10. Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement.

    Science.gov (United States)

    Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua; Jia, Jin-Feng

    2015-05-01

    Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO3 surface.

  11. Pure density functional for strong correlations and the thermodynamic limit from machine learning

    CERN Document Server

    Li, Li; White, Steven R; Burke, Kieron

    2016-01-01

    We use density-matrix renormalization group, applied to a one-dimensional model of continuum Hamiltonians, to accurately solve chains of hydrogen atoms of various separations and numbers of atoms. We train and test a machine-learned approximation to $F[n]$, the universal part of the electronic density functional, to within quantum chemical accuracy. Our calculation (a) bypasses the standard Kohn-Sham approach, avoiding the need to find orbitals, (b) includes the strong correlation of highly-stretched bonds without any specific difficulty (unlike all standard DFT approximations) and (c) is so accurate that it can be used to find the energy in the thermodynamic limit to quantum chemical accuracy.

  12. Analytic representations of bath correlation functions for ohmic and superohmic spectral densities using simple poles

    Science.gov (United States)

    Ritschel, Gerhard; Eisfeld, Alexander

    2014-09-01

    We present a scheme to express a bath correlation function (BCF) corresponding to a given spectral density (SD) as a sum of damped harmonic oscillations. Such a representation is needed, for example, in many open quantum system approaches. To this end we introduce a class of fit functions that enables us to model ohmic as well as superohmic behavior. We show that these functions allow for an analytic calculation of the BCF using pole expansions of the temperature dependent hyperbolic cotangent. We demonstrate how to use these functions to fit spectral densities exemplarily for cases encountered in the description of photosynthetic light harvesting complexes. Finally, we compare absorption spectra obtained for different fits with exact spectra and show that it is crucial to take properly into account the behavior at small frequencies when fitting a given SD.

  13. A density matrix functional with occupation number driven treatment of dynamical and nondynamical correlation.

    Science.gov (United States)

    Rohr, Daniel R; Pernal, Katarzyna; Gritsenko, Oleg V; Baerends, Evert Jan

    2008-10-28

    A recently proposed series of corrections to the earliest JK-only functionals has considerably improved the prospects of density matrix functional theory (DMFT). Still, the most advanced of these functionals (correction C3) requires a preselection of the terms in the pair density Gamma(r(1),r(2)) involving the bonding and antibonding natural orbitals (NOs) belonging to an electron pair bond. Ideally, a DMFT functional should only depend on the NOs and their occupation numbers, and we propose a functional with an occupation number driven weighing of terms in the pair density. These are formulated as "damping" for certain ranges of occupation numbers of the two-electron cumulant that arises in the expansion of the two-particle density matrix of the paradigmatic two-electron system. This automatic version of C3, which we denote AC3, provides the correct dissociation limit for electron pair bonds and it excellently reproduces the potential energy curves of the multireference configuration interaction (MRCI) method for the dissociation of the electron pair bond in the series of the ten-electron hydrides CH(4), NH(3), H(2)O, and HF. AC3 reproduces closely the experimental equilibrium distances and at R(e) it yields correlation energies of the ten-electron systems with an average error in the absolute values of only 3.3% compared to the MRCI values. We stress the importance of treatment of strong correlation cases (NO occupation numbers differing significantly from 2.0 and 0.0) by appropriate terms in the cumulant.

  14. Correlated electron dynamics and memory in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Thiele, Mark

    2009-07-28

    Time-dependent density functional theory (TDDFT) is an exact reformulation of the time-dependent many-electron Schroedinger equation, where the problem of many interacting electrons is mapped onto the Kohn-Sham system of noninteracting particles which reproduces the exact electronic density. In the Kohn-Sham system all non-classical many-body effects are incorporated in the exchange-correlation potential which is in general unknown and needs to be approximated. It is the goal of this thesis to investigate the connection between memory effects and correlated electron dynamics in strong and weak fields. To this end one-dimensional two-electron singlet systems are studied. At the same time these systems include the onedimensional helium atom model, which is an established system to investigate the crucial effects of correlated electron dynamics in external fields. The studies presented in this thesis show that memory effects are negligible for typical strong field processes. Here the approximation of the spatial nonlocality is of primary importance. For the photoabsorption spectra on the other hand the neglect of memory effects leads to qualitative and quantitative errors, which are shown to be connected to transitions of double excitation character. To develop a better understanding of the conditions under which memory effects become important quantum fluid dynamics has been found to be especially suitable. It represents a further exact reformulation of the quantum mechanic many-body problem which is based on hydrodynamic quantities such as density and velocity. Memory effects are shown to be important whenever the velocity field develops strong gradients and dissipative effects contribute. (orig.)

  15. Multiconfiguration Pair-Density Functional Theory: A New Way To Treat Strongly Correlated Systems.

    Science.gov (United States)

    Gagliardi, Laura; Truhlar, Donald G; Li Manni, Giovanni; Carlson, Rebecca K; Hoyer, Chad E; Bao, Junwei Lucas

    2017-01-17

    The electronic energy of a system provides the Born-Oppenheimer potential energy for internuclear motion and thus determines molecular structure and spectra, bond energies, conformational energies, reaction barrier heights, and vibrational frequencies. The development of more efficient and more accurate ways to calculate the electronic energy of systems with inherently multiconfigurational electronic structure is essential for many applications, including transition metal and actinide chemistry, systems with partially broken bonds, many transition states, and most electronically excited states. Inherently multiconfigurational systems are called strongly correlated systems or multireference systems, where the latter name refers to the need for using more than one ("multiple") configuration state function to provide a good zero-order reference wave function. This Account describes multiconfiguration pair-density functional theory (MC-PDFT), which was developed as a way to combine the advantages of wave function theory (WFT) and density functional theory (DFT) to provide a better treatment of strongly correlated systems. First we review background material: the widely used Kohn-Sham DFT (which uses only a single Slater determinant as reference wave function), multiconfiguration WFT methods that treat inherently multiconfigurational systems based on an active space, and previous attempts to combine multiconfiguration WFT with DFT. Then we review the formulation of MC-PDFT. It is a generalization of Kohn-Sham DFT in that the electron kinetic energy and classical electrostatic energy are calculated from a reference wave function, while the rest of the energy is obtained from a density functional. However, there are two main differences with respent to Kohn-Sham DFT: (i) The reference wave function is multiconfigurational rather than being a single Slater determinant. (ii) The density functional is a function of the total density and the on-top pair density rather than

  16. Current Issues in Finite-T Density-Functional Theory and Warm-Correlated Matter †

    Directory of Open Access Journals (Sweden)

    M. W. C. Dharma-wardana

    2016-03-01

    Full Text Available Finite-temperature density functional theory (DFT has become of topical interest, partly due to the increasing ability to create novel states of warm-correlated matter (WCM.Warm-dense matter (WDM, ultra-fast matter (UFM, and high-energy density matter (HEDM may all be regarded as subclasses of WCM. Strong electron-electron, ion-ion and electron-ion correlation effects and partial degeneracies are found in these systems where the electron temperature Te is comparable to the electron Fermi energy EF. Thus, many electrons are in continuum states which are partially occupied. The ion subsystem may be solid, liquid or plasma, with many states of ionization with ionic charge Zj. Quasi-equilibria with the ion temperature Ti ≠ Te are common. The ion subsystem in WCM can no longer be treated as a passive “external potential”, as is customary in T = 0 DFT dominated by solid-state theory or quantum chemistry. Many basic questions arise in trying to implement DFT for WCM. Hohenberg-Kohn-Mermin theory can be adapted for treating these systems if suitable finite-T exchange-correlation (XC functionals can be constructed. They are functionals of both the one-body electron density ne and the one-body ion densities ρj. Here, j counts many species of nuclei or charge states. A method of approximately but accurately mapping the quantum electrons to a classical Coulomb gas enables one to treat electron-ion systems entirely classically at any temperature and arbitrary spin polarization, using exchange-correlation effects calculated in situ, directly from the pair-distribution functions. This eliminates the need for any XC-functionals. This classical map has been used to calculate the equation of state of WDM systems, and construct a finite-T XC functional that is found to be in close agreement with recent quantum path-integral simulation data. In this review, current developments and concerns in finite-T DFT, especially in the context of non-relativistic warm

  17. High-energy spin-density-wave correlated fluctuations in paramagnetic Cr + 5 at. % V

    Energy Technology Data Exchange (ETDEWEB)

    Werner, S.A. (Missouri Univ., Columbia, MO (United States). Dept. of Physics); Fawcett, E. (Toronto Univ., ON (Canada). Dept. of Physics); Elmiger, M.W.; Shirane, G. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    Measurements of the magnetic fluctuations, termed spin-density-wave (SDW) paramagnons, in the nearly antiferromagnetic alloy Cr + 5 at.%V are extended up in energy to about 80 MeV. These fluctuating spin-spin correlations occur at incommensurate positions, corresponding to the SDW wavevector Q. Their characteristic energy is at least an order of magnitude larger than that of the magnetic fluctuations seen in the paramagnetic phase of pure Cr, but their intensity is more than two orders of magnitude smaller. We find that the dynamic susceptibility decreases by about 50% between temperature T = 10K and 300K.

  18. High-energy spin-density-wave correlated fluctuations in paramagnetic Cr + 5 at. % V

    Energy Technology Data Exchange (ETDEWEB)

    Werner, S.A. [Missouri Univ., Columbia, MO (United States). Dept. of Physics; Fawcett, E. [Toronto Univ., ON (Canada). Dept. of Physics; Elmiger, M.W.; Shirane, G. [Brookhaven National Lab., Upton, NY (United States)

    1992-11-01

    Measurements of the magnetic fluctuations, termed spin-density-wave (SDW) paramagnons, in the nearly antiferromagnetic alloy Cr + 5 at.%V are extended up in energy to about 80 MeV. These fluctuating spin-spin correlations occur at incommensurate positions, corresponding to the SDW wavevector Q. Their characteristic energy is at least an order of magnitude larger than that of the magnetic fluctuations seen in the paramagnetic phase of pure Cr, but their intensity is more than two orders of magnitude smaller. We find that the dynamic susceptibility decreases by about 50% between temperature T = 10K and 300K.

  19. Depletion of density of states near Fermi energy induced by disorder and electron correlation in alloys

    Science.gov (United States)

    Noh, Han-Jin; Nahm, Tschang-Uh; Kim, Jae-Young; Park, W.-G.; Oh, S.-J.; Hong, J.-P.; Kim, C.-O.

    2000-03-01

    We have performed high resolution photoemission study of substitutionally disordered alloys Cu-Pt, Cu-Pd, Cu-Ni, and Pd-Pt. The ratios between alloy spectra and pure metal spectra are found to have dips at the Fermi level when the residual resistivity is high and when rather strong repulsive electron-electron interaction is expected. This is in accordance with Altshuler and Aronov's model which predicts depletion of density of states at the Fermi level when both disorder and electron correlation are present.

  20. Multiflavor Correlation Functions in non-Abelian Gauge Theories at Finite Density in two dimensions

    CERN Document Server

    Christiansen, H R; Christiansen, Hugo R.; Schaposnik, Fidel A.

    1996-01-01

    We compute vacuum expectation values of products of fermion bilinears for two-dimensional Quantum Chromodynamics at finite flavored fermion densities. We introduce the chemical potential as an external charge distribution within the path-integral approach and carefully analyse the contribution of different topological sectors to fermion correlators. We show the existence of chiral condensates exhibiting an oscillatory inhomogeneous behavior as a function of a chemical potential matrix. This result is exact and goes in the same direction as the behavior found in QCD$_4$ within the large $N$ approximation.

  1. Inverse correlation between fibrinogen and bone mineral density in women: Preliminary findings.

    Science.gov (United States)

    Chen, Jui-Tung; Kotani, Kazuhiko

    2016-01-01

    Hemostatic factors may be involved in bone health. The present preliminary study investigated the association between plasma fibrinogen and bone mineral density (BMD) in perimenopausal women. A significant inverse correlation between fibrinogen and BMD was observed (correlation coefficient = -0.42, p high level of high-sensitivity C-reactive protein than in that with a low level of high-sensitivity C-reactive protein, and in the subgroup with a high level of diacron reactive oxygen metabolites (an oxidative stress marker) than in that with a low level of diacron reactive oxygen metabolites. Thus, fibrinogen may be a possible marker of BMD in this population. More studies on the associations among hemostasis, inflammation, oxidative stress, and bone metabolism are warranted in the clinical setting.

  2. Angiogenesis in Paget's Disease of the Vulva and the Breast: Correlation with Microvessel Density

    Directory of Open Access Journals (Sweden)

    Patricia E. Ellis

    2012-01-01

    Full Text Available Our understanding of the pathogenesis of Paget's disease of the vulva and the breast remains limited. Current evidence supports the fact that angiogenesis plays an important role in the pathogenesis of several diseases. Therefore, we sought to define its role, as correlated with microvessel density, in Paget's disease of the vulva and the breast. Microvessels were analysed using anti-von Willebrand factor antibody in 105 cases of Paget's disease of the vulva and the breast comprising 71 cases of Paget's disease of the vulva, including 8 cases with invasive disease, and 34 cases of Paget's disease of the breast. The latter included 12 cases with DCIS, 5 cases with both DCIS and invasive carcinoma, and 6 with carcinoma alone. Eleven cases had no underlying tumour identified. Increased microvessel density was demonstrated in Paget's disease of the breast with DCIS and with carcinoma alone compared to Paget's disease of the breast alone, <0.08 and <0.013, respectively. There were no significant differences in microvessel density in the vulval cases. Neovascularisation is an important process in the development of Paget's disease of the breast. Other biological and molecular processes are more involved in the pathogenesis of Paget's disease of the vulva.

  3. Correlation of vitamin D, bone mineral density and parathyroid hormone levels in adults with low bone density

    Directory of Open Access Journals (Sweden)

    Sunil Kota

    2013-01-01

    Full Text Available Background: Bone mineral densiy (BMD is known to be affected by serum 25-hydroxyvitamin D (25(OH D levels, intact parathyroid hormone (iPTH levels. Indian data pertinent to above observation is scant. Our study aimed to investigate the relationships between serum 25-hydroxyvitamin D (25(OH D levels, intact parathyroid hormone (iPTH levels and bone mineral density (BMD in a cohort of Indian patients. Materials and Methods: Adults with or without fragility fractures with low BMD at the hip or lumbar spine were evaluated clinically along with laboratory investigations. T-scores of the hip and spine were derived from BMD-DEXA (dual-energy X-ray absorptiometry. Multivariate regression models were used to investigate the relationships between serum 25(OH D, iPTH and BMD. Results: Total of 102 patients (male:female = 38:64 with a mean age of 62.5 ± 6.4 years were included in the study. Forty-four patients had osteopenia. Osteoporosis was present in 58 patients. The mean values for serum 25(OH D and iPTH levels were 21.3 ± 0.5 ng/ml and 53.1 ± 22.3 pg/ml, respectively. In 84.3% of patients, serum 25(OH D levels were below 30 ng/ml (Normal = 30-74 ng/ml, confirming vitamin D deficiency. There was no association between 25(OH D levels and BMD at the hip or lumbar spine (P = 0.473 and 0.353, respectively. Both at the hip and lumbar spine; iPTH levels, male gender, body mass index (BMI and age were found to be significant predictors of BMD. Patients with higher BMI had significantly lower BMD and T-score. At levels <30 ng/ml, 25(OH D was negatively associated with iPTH (P = 0.041. Conclusion: Among our cohort of patients with low BMD, no direct relationship between serum 25(OH D levels and BMD was observed. However, a negative correlation between iPTH and 25(OH D at serum 25(OH D concentrations <30 ng/ml. Serum iPTH levels showed a significant negative association with BMD at the hip and lumbar spine. Our findings underscore the critical role of

  4. Exchange-Correlation Effects for Noncovalent Interactions in Density Functional Theory.

    Science.gov (United States)

    Otero-de-la-Roza, A; DiLabio, Gino A; Johnson, Erin R

    2016-07-12

    In this article, we develop an understanding of how errors from exchange-correlation functionals affect the modeling of noncovalent interactions in dispersion-corrected density-functional theory. Computed CCSD(T) reference binding energies for a collection of small-molecule clusters are decomposed via a molecular many-body expansion and are used to benchmark density-functional approximations, including the effect of semilocal approximation, exact-exchange admixture, and range separation. Three sources of error are identified. Repulsion error arises from the choice of semilocal functional approximation. This error affects intermolecular repulsions and is present in all n-body exchange-repulsion energies with a sign that alternates with the order n of the interaction. Delocalization error is independent of the choice of semilocal functional but does depend on the exact exchange fraction. Delocalization error misrepresents the induction energies, leading to overbinding in all induction n-body terms, and underestimates the electrostatic contribution to the 2-body energies. Deformation error affects only monomer relaxation (deformation) energies and behaves similarly to bond-dissociation energy errors. Delocalization and deformation errors affect systems with significant intermolecular orbital interactions (e.g., hydrogen- and halogen-bonded systems), whereas repulsion error is ubiquitous. Many-body errors from the underlying exchange-correlation functional greatly exceed in general the magnitude of the many-body dispersion energy term. A functional built to accurately model noncovalent interactions must contain a dispersion correction, semilocal exchange, and correlation components that minimize the repulsion error independently and must also incorporate exact exchange in such a way that delocalization error is absent.

  5. Modeling of delamination in carbon/epoxy composite laminates under four point bending for damage detection and sensor placement optimization

    Science.gov (United States)

    Adu, Stephen Aboagye

    Laminated carbon fiber-reinforced polymer composites (CFRPs) possess very high specific strength and stiffness and this has accounted for their wide use in structural applications, most especially in the aerospace industry, where the trade-off between weight and strength is critical. Even though they possess much larger strength ratio as compared to metals like aluminum and lithium, damage in the metals mentioned is rather localized. However, CFRPs generate complex damage zones at stress concentration, with damage progression in the form of matrix cracking, delamination and fiber fracture or fiber/matrix de-bonding. This thesis is aimed at performing; stiffness degradation analysis on composite coupons, containing embedded delamination using the Four-Point Bend Test. The Lamb wave-based approach as a structural health monitoring (SHM) technique is used for damage detection in the composite coupons. Tests were carried-out on unidirectional composite coupons, obtained from panels manufactured with pre-existing defect in the form of embedded delamination in a laminate of stacking sequence [06/904/0 6]T. Composite coupons were obtained from panels, fabricated using vacuum assisted resin transfer molding (VARTM), a liquid composite molding (LCM) process. The discontinuity in the laminate structure due to the de-bonding of the middle plies caused by the insertion of a 0.3 mm thick wax, in-between the middle four (4) ninety degree (90°) plies, is detected using lamb waves generated by surface mounted piezoelectric (PZT) actuators. From the surface mounted piezoelectric sensors, response for both undamaged (coupon with no defect) and damaged (delaminated coupon) is obtained. A numerical study of the embedded crack propagation in the composite coupon under four-point and three-point bending was carried out using FEM. Model validation was then carried out comparing the numerical results with the experimental. Here, surface-to-surface contact property was used to model the

  6. The Role of Home Bleaching Agent on the Fracture Toughness of Resin Composites Using Four-Point Bending Test

    Directory of Open Access Journals (Sweden)

    Ghazvini Ferooz M

    2014-09-01

    Full Text Available Statement of Problem: Resin composites are a common type of tooth coloured restorative materials. These materials are brittle and their major shortcomings are sensitivity to flaws and defects, low tensile strength, and susceptibility to catastrophic failure.The role of home bleaching agents on the fracture toughness of resin composites using four-point bending test is scanty. Objectives: To compare the fracture toughness (KIc of resin composites on a fourpoint bending test and to assess the effect of distilled water and a home bleaching agent on the resistance of the materials to fracture. Materials and Methods: seventy-two bar-shaped specimens were prepared from three materials: Rok (SDI, Estelite (Tokuyama, and Vit-l-escence (Ultradent and divided into three groups. Two groups were assigned as “control” and conditioned in distilled water at 37oC for 24 hours or 21 days, respectively. The specimens in the third group (treatment were stored in distilled water for 21 days and bleached using Polanight (SDI for 2 hours daily. For each material, a total of 24 disc-shaped specimens were prepared and after each time interval loaded in a four-point bending test using a universal testing machine with a crosshead speed of 0.5 mm/m. The maximum load to specimen failure was recorded and the KIc was calculated. Results: Statistical analysis using two-way ANOVA showed a significant relationship between materials and treatment (P<0.05. Tukey’s test showed that after 24 hours of immersion in distilled water, KIc was not significantly different between materials; Rok revealed the highest value followed by Estelite and Vit-l-escence. The bleaching agent significantly decreased the KIc values of Estelite and Rok while it did not affect that of Vita-l-escence. Immersion in distilled water for all resin composites caused a significant decrease in KIc. Conclusion: The fracture toughness of the resin composites was affected by the bleaching agent and 21day

  7. Density functional for short-range correlation: Is the random phase approximation accurate for iso-electronic energy changes?

    Science.gov (United States)

    Yan, Zidan; Perdew, John P.; Kurth, Stefan

    2000-03-01

    Within a density functional context, the random phase approximation (RPA) for the correlation emergy makes a short-range error which is well-suited for correction by a local spin density or generalized gradient approximation (GGA). Here we construct a GGA for the short-range correction, following the same reliable procedure used earlier to construct the GGA for the whole exchange-correlation energy: real-space cutoff of the spurious long-range contribution to the gradient expansion of the hole around an electron. The resulting density functional is nearly local, and predicts a substantial correction to the RPA correlation energy of an atom but \\underlinevery small corrections to the RPA atomization energy of a molecule, which may by itself come close to "chemical accuracy", and to the RPA surface energy of a metal. A by-product of this work is a density functional for the system-averaged correlation hole within RPA.

  8. A self-adjustable four-point probing system using polymeric three dimensional coils and non-toxic liquid metal

    Energy Technology Data Exchange (ETDEWEB)

    Oyunbaatar, Nomin-Erdene; Choi, Young Soo; Lee, Dong-Weon, E-mail: mems@jnu.ac.kr [MEMS and Nanotechnology Laboratory, School of Mechanical Engineering, Chonnam National University, Gwangju 500757 (Korea, Republic of)

    2015-12-15

    This paper describes a self-adjustable four-point probe (S4PP) system with a square configuration. The S4PP system consists of 3D polymer coil springs for the independent operation of each tungsten (W) probe, microfluidic channels filled with a nontoxic liquid metal, and a LabView-based control system. The 3D coil springs made by PMMA are fabricated with a 3D printer and are positioned in a small container filled with the non-toxic liquid metal. This unique configuration allows independent self-adjustment of the probe heights for precise measurements of the electrical properties of both flexible and large-step-height microsamples. The feasibility of the fabricated S4PP system is evaluated by measuring the specific resistance of Cr and Au thin films deposited on silicon wafers. The system is then employed to evaluate the electrical properties of a Au thin film deposited onto a flexible and easily breakable silicon diaphragm (spring constant: ∼3.6 × 10{sup −5} N/m). The resistance of the Cr thin films (thickness: 450 nm) with step heights of 60 and 90 μm is also successfully characterized. These experimental results indicate that the proposed S4PP system can be applied to common metals and semiconductors as well as flexible and large-step-height samples.

  9. A self-adjustable four-point probing system using polymeric three dimensional coils and non-toxic liquid metal.

    Science.gov (United States)

    Oyunbaatar, Nomin-Erdene; Choi, Young Soo; Choi, Yong Soo; Lee, Dong-Weon

    2015-12-01

    This paper describes a self-adjustable four-point probe (S4PP) system with a square configuration. The S4PP system consists of 3D polymer coil springs for the independent operation of each tungsten (W) probe, microfluidic channels filled with a nontoxic liquid metal, and a LabView-based control system. The 3D coil springs made by PMMA are fabricated with a 3D printer and are positioned in a small container filled with the non-toxic liquid metal. This unique configuration allows independent self-adjustment of the probe heights for precise measurements of the electrical properties of both flexible and large-step-height microsamples. The feasibility of the fabricated S4PP system is evaluated by measuring the specific resistance of Cr and Au thin films deposited on silicon wafers. The system is then employed to evaluate the electrical properties of a Au thin film deposited onto a flexible and easily breakable silicon diaphragm (spring constant: ∼3.6 × 10(-5) N/m). The resistance of the Cr thin films (thickness: 450 nm) with step heights of 60 and 90 μm is also successfully characterized. These experimental results indicate that the proposed S4PP system can be applied to common metals and semiconductors as well as flexible and large-step-height samples.

  10. Temperature-dependent thermal conductivities of 1D semiconducting nanowires via four-point-probe 3-ω method.

    Science.gov (United States)

    Lee, Seung-Yong; Lee, Mi-Ri; Park, No-Won; Kim, Gil-Sung; Choi, Heon-Jin; Choi, Tae-Youl; Lee, Sang-Kwon

    2013-12-13

    We report on a systematic study of the thermal transport characteristics of both as-grown zinc oxide and gallium nitride nanowires (NWs) via the four-point-probe 3-ω method in the temperature range 130-300 K. Both as-grown NWs were synthesized by a vapor-liquid-solid growth mechanism, and show clear n-type semiconducting behavior without any defects, which enables both the NWs to be promising candidates for thermoelectric materials. To measure the thermal conductivities of both NWs with lower heat loss and measurement errors, the suspended structures were formed by a combination of an e-beam lithography process and a random dispersion method. The measured thermal conductivities of both NWs are greatly reduced compared to their bulk materials due to the enhanced phonon scattering via the size effect and dopants (impurities). Furthermore, we observed that the Umklapp peaks of both NWs are shifted to a higher temperature than those of their bulk counterparts, indicating that phonon-boundary scattering dominates over other phonon scattering due to the size effect.

  11. Density functional theory and dynamical mean-field theory. A way to model strongly correlated systems

    Energy Technology Data Exchange (ETDEWEB)

    Backes, Steffen

    2017-04-15

    The study of the electronic properties of correlated systems is a very diverse field and has lead to valuable insight into the physics of real materials. In these systems, the decisive factor that governs the physical properties is the ratio between the electronic kinetic energy, which promotes delocalization over the lattice, and the Coulomb interaction, which instead favours localized electronic states. Due to this competition, correlated electronic systems can show unique and interesting properties like the Metal-Insulator transition, diverse phase diagrams, strong temperature dependence and in general a high sensitivity to the environmental conditions. A theoretical description of these systems is not an easy task, since perturbative approaches that do not preserve the competition between the kinetic and interaction terms can only be applied in special limiting cases. One of the most famous approaches to obtain the electronic properties of a real material is the ab initio density functional theory (DFT) method. It allows one to obtain the ground state density of the system under investigation by mapping onto an effective non-interacting system that has to be found self-consistently. While being an exact theory, in practical implementations certain approximations have to be made to the exchange-correlation potential. The local density approximation (LDA), which approximates the exchange-correlation contribution to the total energy by that of a homogeneous electron gas with the corresponding density, has proven quite successful in many cases. Though, this approximation in general leads to an underestimation of electronic correlations and is not able to describe a metal-insulator transition due to electronic localization in the presence of strong Coulomb interaction. A different approach to the interacting electronic problem is the dynamical mean-field theory (DMFT), which is non-perturbative in the kinetic and interaction term but neglects all non

  12. Performance monitoring of large-scale autonomously healed concrete beams under four-point bending through multiple non-destructive testing methods

    Science.gov (United States)

    Karaiskos, G.; Tsangouri, E.; Aggelis, D. G.; Van Tittelboom, K.; De Belie, N.; Van Hemelrijck, D.

    2016-05-01

    Concrete is still the leading structural material due to its low production cost and great structural design flexibility. Although it is distinguished by such a high durability and compressive strength, it is vulnerable in a series of ambient and operational degradation factors which all too frequently result in crack formation that can adversely affect its mechanical performance. The autonomous healing system, using encapsulated polyurethane-based, expansive, healing agent embedded in concrete, is triggered by the crack formation and propagation and promises material repair and operational service life extension. As shown in our previous studies, the formed cracks on small-scale concrete beams are sealed and repaired by filling them with the healing agent. In the present study, the crack formation and propagation in autonomously healed, large-scale concrete beams are thoroughly monitored through a combination of non-destructive testing (NDT) methods. The ultrasonic pulse velocity (UPV), using embedded low-cost and aggregate-size piezoelectric transducers, the acoustic emission (AE) and the digital image correlation (DIC) are the NDT methods which are comprehensively used. The integrated ultrasonic, acoustic and optical monitoring system introduces an experimental configuration that detects and locates the four-point bending mode fracture on large-scale concrete beams, detects the healing activation process and evaluates the subsequent concrete repair.

  13. $\\eta^\\prime$ meson mass from topological charge density correlator in QCD

    CERN Document Server

    Fukaya, H; Cossu, G; Hashimoto, S; Kaneko, T; Noaki, J

    2015-01-01

    The flavor-singlet component of the eta prime meson is related to the topological structure of the SU(3) gauge field through the chiral anomaly. We perform a 2+1-flavor lattice QCD calculation and demonstrate that the two-point function of a gluonically defined topological charge density after a short Yang-Mills gradient flow contains the propagation of the eta prime meson, by showing that its mass in the chiral and continuum limit is consistent with the experimental value. The gluonic correlator does not suffer from the contamination of the pion contribution, and the clean signal is obtained at significantly lower numerical cost compared to the conventional method with the quark bilinear operators.

  14. ESTIMATION OF THE NUMBER OF CORRELATED SOURCES WITH COMMON FREQUENCIES BASED ON POWER SPECTRAL DENSITY

    Institute of Scientific and Technical Information of China (English)

    LI Ning; SHI Tielin

    2007-01-01

    Blind source Separation and estimation of the number of sources usually demand that the number of sensors should be greater than or equal to that of the sources, which, however, is very difficult to satisfy for the complex Systems. A new estimating method based on power spectral density (PSD) is presented. When the relation between the number of sensors and that of sources is unknown, the PSD matrix is first obtained by the ratio of PSD of the observation signals, and then the bound of the number of correlated sources with common frequencies can be estimated by comparing every column vector of PSD matrix. The effectiveness of the proposed method is verified by theoretical analysis and experiments, and the influence of noise on the estimation of number of source is simulated.

  15. Towards a Density Functional Theory Exchange-Correlation Functional able to describe localization/delocalization

    Science.gov (United States)

    Mattsson, Ann E.; Wills, John M.

    2013-03-01

    The inability to computationally describe the physics governing the properties of actinides and their alloys is the poster child of failure of existing Density Functional Theory exchange-correlation functionals. The intricate competition between localization and delocalization of the electrons, present in these materials, exposes the limitations of functionals only designed to properly describe one or the other situation. We will discuss the manifestation of this competition in real materials and propositions on how to construct a functional able to accurately describe properties of these materials. I addition we will discuss both the importance of using the Dirac equation to describe the relativistic effects in these materials, and the connection to the physics of transition metal oxides. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  16. Self-consistent implementation of ensemble density functional theory method for multiple strongly correlated electron pairs

    Science.gov (United States)

    Filatov, Michael; Liu, Fang; Kim, Kwang S.; Martínez, Todd J.

    2016-12-01

    The spin-restricted ensemble-referenced Kohn-Sham (REKS) method is based on an ensemble representation of the density and is capable of correctly describing the non-dynamic electron correlation stemming from (near-)degeneracy of several electronic configurations. The existing REKS methodology describes systems with two electrons in two fractionally occupied orbitals. In this work, the REKS methodology is extended to treat systems with four fractionally occupied orbitals accommodating four electrons and self-consistent implementation of the REKS(4,4) method with simultaneous optimization of the orbitals and their fractional occupation numbers is reported. The new method is applied to a number of molecular systems where simultaneous dissociation of several chemical bonds takes place, as well as to the singlet ground states of organic tetraradicals 2,4-didehydrometaxylylene and 1,4,6,9-spiro[4.4]nonatetrayl.

  17. Coral reef degradation is not correlated with local human population density

    Science.gov (United States)

    Bruno, John F.; Valdivia, Abel

    2016-07-01

    The global decline of reef-building corals is understood to be due to a combination of local and global stressors. However, many reef scientists assume that local factors predominate and that isolated reefs, far from human activities, are generally healthier and more resilient. Here we show that coral reef degradation is not correlated with human population density. This suggests that local factors such as fishing and pollution are having minimal effects or that their impacts are masked by global drivers such as ocean warming. Our results also suggest that the effects of local and global stressors are antagonistic, rather than synergistic as widely assumed. These findings indicate that local management alone cannot restore coral populations or increase the resilience of reefs to large-scale impacts. They also highlight the truly global reach of anthropogenic warming and the immediate need for drastic and sustained cuts in carbon emissions.

  18. Expression of Thrombospondin-1 is Correlated with Microvessel Density in Prostate Cancer

    Institute of Scientific and Technical Information of China (English)

    Hui Zhang; Jiaju Lu; Ying Liu; Qiang Fu

    2006-01-01

    OBJECTIVE To observe the expression of thrombospondin-1 (TSP-1) in prostate cancer, and examine its expression in relation to angiogenesis.METHODS The expression of TSP-1 and microvessel density (MVD) were studied in 22 prostate cancer patients by using immunohistochemistry.RESULTS Positive expression of the TSP-1 protein was detected in 16(72.7%)of the 22 cases. Most of the positive staining for TSP-1 was seen in the cytoplasm of the cancer cells, but some was in the extracellular matrix. The mean MVD in the 22 prostate cancer cases was 71.21±31.14vessels per 100 high field of vision. Tumors with an elevated expression of TSP-1 showed a high MVD resulting in a correlation between TSP-1immunopositivity and microvessel density that was highly significant (r=0.54, P=0.009).CONCLUSION TSP-1 is strongly expressed in most prostate cancers and is associated with neovascularization. Therefore TSP-1 is a likely contributor to the extensive neovascularization in prostate cancer and increased TSP-1 expression might participate in an angiogenic phenotype.

  19. The impact of degenerative spinal changes on the correlation of peripheral and axial bone density

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, P. (Klinik und Poliklinik fuer Nuklearmedizin, Wuerzburg Univ. (Germany)); Boerner, W. (Klinik und Poliklinik fuer Nuklearmedizin, Wuerzburg Univ. (Germany))

    1994-08-01

    Results of bone density measurements by quantitative computed tomography of the peripheral skeleton (pQCT) were compared with those of measurements at the axial skeleton with a view to study the effects of degenerative spinal changes on the validity of bone densitometry of the lumbar spine. 556 consecutive patients were examined by dual-energy X-ray absorptiometry (DXA) of the spine and by peripheral quantitative computed tomography (pQCT) of the distal radius. There were significant differences between the bone mineral values at the distal radius and those at the spine, depending on the degree of spinal degeneration. As expected, spinal degenerations showed a highly significant age dependence. With increasing degeneration the correlations between the radius total bone mineral concentration and the bone density of the lumbar spine decreased from r=0.45 to 0.23 in women and from r=0.64 to 0.28 in men. We conclude that the value of spinal DXA is reduced in patients with degenerative spinal disease, compared to the pQCT at the peripheral skeleton. (orig.)

  20. Bacterial spore heat resistance correlated with water content, wet density, and protoplast/sporoplast volume ratio.

    Science.gov (United States)

    Beaman, T C; Greenamyre, J T; Corner, T R; Pankratz, H S; Gerhardt, P

    1982-05-01

    Five types of dormant Bacillus spores, between and within species, were selected representing a 600-fold range in moist-heat resistance determined as a D100 value. The wet and dry density and the solids and water content of the entire spore and isolated integument of each type were determined directly from gram masses of material, with correction for interstitial water. The ratio between the volume occupied by the protoplast (the structures bounded by the inner pericytoplasm membrane) and the volume occupied by the sporoplast (the structures bounded by the outer pericortex membrane) was calculated from measurements made on electron micrographs of medially thin-sectioned spores. Among the various spore types, an exponential increase in the heat resistance correlated directly with the wet density and inversely with the water content and with the protoplast/sporoplast volume ratio. Altogether with results supported a hypothesis that the extent of heat resistance is based in whole or in part on the extent of dehydration and diminution of the protoplast in the dormant spore, without implications about physiological mechanisms for attaining this state.

  1. Correlation of structural order, anomalous density, and hydrogen bonding network of liquid water.

    Science.gov (United States)

    Bandyopadhyay, Dibyendu; Mohan, S; Ghosh, S K; Choudhury, Niharendu

    2013-07-25

    We use extensive molecular dynamics simulations employing different state-of-the-art force fields to find a common framework for comparing structural orders and density anomalies as obtained from different water models. It is found that the average number of hydrogen bonds correlates well with various order parameters as well as the temperature of maximum densities across the different models, unifying apparently disparate results from different models and emphasizing the importance of hydrogen bonding in determining anomalous properties and the structure of water. A deeper insight into the hydrogen bond network of water reveals that the solvation shell of a water molecule can be defined by considering only those neighbors that are hydrogen-bonded to it. On the basis of this view, the origin of the appearance of a non-tetrahedral peak at a higher temperature in the distribution of tetrahedral order parameters has been explained. It is found that a neighbor that is hydrogen-bonded to the central molecule is tetrahedrally coordinated even at higher temperatures. The non-tetrahedral peak at a higher temperature arises due to the strained orientation of the neighbors that are non-hydrogen-bonded to the central molecule. With the new definition of the solvation shell, liquid water can be viewed as an instantaneously changing random hydrogen-bonded network consisting of differently coordinated hydrogen-bonded molecules with their distinct solvation shells. The variation of the composition of these hydrogen-bonded molecules against temperature accounts for the density anomaly without introducing the concept of large-scale structural polyamorphism in water.

  2. Plasma miRNA levels correlate with sensitivity to bone mineral density in postmenopausal osteoporosis patients.

    Science.gov (United States)

    Li, Hongqiu; Wang, Zhe; Fu, Qin; Zhang, Jing

    2014-11-01

    In our study, we detect the levels of three micro-RNAs (miRNAs; miR-21, miR-133a and miR-146a) in the plasma of 120 Chinese postmenopausal women who were divided into three groups (normal, osteopenia and osteoporosis) according to the T-scores. Downregulation of miR-21, as well as upregulation of miR-133a, was validated in the plasma of osteoporosis and osteopenia patients versus the normal group. The difference in expression regarding the miR-146a level in plasma among the three groups was not significant (p > 0.01). The circulating miRNA expression levels and bone mineral density (BMD) were examined during a multiple correlation analysis as a dependent variable after adjusting for age, weight and height. We have demonstrated that specific miRNAs species are significantly changed in the plasma of osteoporosis and osteopenia patients and correlated with the BMD. Our study suggested a potential use of miR-21 and miR-133a as sensitive and plasma biomarkers for postmenopausal osteoporosis.

  3. Crack initiation at high loading rates applying the four-point bending split Hopkinson pressure bar technique

    Directory of Open Access Journals (Sweden)

    Henschel Sebastian

    2015-01-01

    Full Text Available Dynamic crack initiation with crack-tip loading rates of K̇ ≈ 2.106MPa√ms-1 in a high strength G42CrMoS4 steel was investigated. To this end, a previously developed split Hopkinson pressure bar with four-point bending was utilised. V-notched and pre-cracked Charpy specimens were tested. The detection of dynamic crack initiation was performed by analysing the dynamic force equilibrium between the incident and the transmission bar. Additionally, the signal of a near-field strain gauge and high-speed photography were used to determine the instant of crack initiation. To account for vibrations of the sample, a dynamic analysis of the stress intensity factor was performed. The dynamic and static analyses of the tests produced nearly the same results when a force equilibrium was achieved. Fracture-surface analysis revealed that elongated MnS inclusions strongly affected both the dynamic crack initiation and growth. Blunting of the precrack did not take place when a group of MnS inclusions was located directly at the precrack tip. Due to the direction of the elongated MnS inclusions perpendicular to the direction of crack growth, the crack could be deflected. The comparison with a 42CrMo4 steel without elongated MnS inclusions revealed the detrimental effect in terms of resistance to crack initiation. Taking the loading-rate dependency into consideration, it was shown that there was no pronounced embrittlement due to the high loading rates.

  4. Bone Mineral Density in Patients with Ankylosing Spondylitis: Incidence and Correlation with Demographic and Clinical Variables

    Directory of Open Access Journals (Sweden)

    Laura MUNTEAN

    2009-12-01

    Full Text Available Objective: To evaluate bone mineral density (BMD in patients with ankylosing spondylitis (AS and determine its correlation with the demographic and clinical characteristics of AS. Patients and Methods: Demographic, clinical and osteodensitometric data were evaluated in a cross-sectional study that included 136 patients with AS. Spine and hip BMD were measured by means of dual energy X-ray absorptiometry (DXA. Using the modified Schober’s test we assessed spine mobility. We examined the sacroiliac, anteroposterior and lateral dorso-lumbar spine radiographs in order to grade sacroiliitis and assess syndesmophytes. Disease activity was evaluated using C-reactive protein (CRP levels and erythrocyte sedimentation rate (ESR. Demographic data and BMD measurements were compared with those of 167 age- and sex-matched healthy controls. Results: Patients with AS had a significantly lower BMD at the spine, femoral neck, trochanter and total hip as compared to age-matched controls (all p<0.01. According to the WHO classification, osteoporosis was present in 20.6% of the AS patients at the lumbar spine and in 14.6% at the femoral neck. There were no significant differences in BMD when comparing men and women with AS, except for trochanter BMD that was lower in female patients. No correlations were found between disease activity markers (ESR, CRP and BMD. Femoral neck BMD was correlated with disease duration, Schober’s test and sacroiliitis grade. Conclusion: Patients with AS have a lower spine and hip BMD as compared to age- and sex-matched controls. Bone loss at the femoral neck is associated with disease duration and more severe AS.

  5. Spin-density correlations in the dynamic spin-fluctuation theory: Comparison with polarized neutron scattering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, N.B., E-mail: melnikov@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Reser, B.I., E-mail: reser@imp.uran.ru [Miheev Institute of Metal Physics, Ural Branch of Russian Academy of Sciences, Ekaterinburg 620990 (Russian Federation); Paradezhenko, G.V., E-mail: gparadezhenko@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

    2016-08-01

    To study the spin-density correlations in the ferromagnetic metals above the Curie temperature, we relate the spin correlator and neutron scattering cross-section. In the dynamic spin-fluctuation theory, we obtain explicit expressions for the effective and local magnetic moments and spatial spin-density correlator. Our theoretical results are demonstrated by the example of bcc Fe. The effective and local moments are found in good agreement with results of polarized neutron scattering experiment over a wide temperature range. The calculated short-range order is small (up to 4 Å) and slowly decreases with temperature.

  6. Correlation between CT perfusion parameters and microvessel density and vascular endothelial growth factor in adrenal tumors.

    Directory of Open Access Journals (Sweden)

    Hai-yan Qin

    Full Text Available We evaluated the correlation between computed tomography (CT perfusion parameters and markers of angiogenesis in adrenal adenomas and non-adenomas to determine if perfusion CT can be used to distinguish between them. Thirty-four patients with pathologically-confirmed adrenal tumors (17 adenomas, 17 non-adenomas received CT perfusion imaging before surgery. CT perfusion parameters (blood flow [BF], blood volume [BV], mean transit time [MTT], and permeability surface area product [PS] were calculated. Tumor tissue sections were examined with immunohistochemical methods for vascular endothelial growth factor (VEGF expression and microvessel density (MVD. The mean age of the 34 patients was 43 years. The median BV was significantly higher in adenomas than in non-adenomas [12.3 ml/100 g, inter-quartile range (IQR: 10.4 to 16.5 ml/100 g vs. 8.8 ml/100 g, IQR: 3.3 to 9.4 ml/100 g, p=0.001]. Differences in BF, MTT, and PS parameter values between adenomas and non-adenomas were not significant (p>0.05. The mean MVD was significantly higher in adenomas compared to non-adenomas (98.5 ± 28.5 vs. 53.5 ± 27.0, p<0.0001. Adenomas also expressed significantly higher median VEGF than non-adenomas (65%, IQR: 50 to 79% vs. 45%, IQR: 35 to 67%, p=0.02. A moderately strong correlation between BF and VEGF (r=0.53, p=0.03 and between BV and MVD among adenomas (r=0.57, p=0.02 exist. Morphology, MVD, and VEGF expression in adenomas differ significantly from non-adenomas. Of the CT perfusion parameters examined, both BF and BV correlate with MVD, but only BF correlates with VEGF, and only in adenomas. The significant difference in BV suggests that BV may be used to differentiate adenomas from non-adenomas. However, the small difference in BV shows that it may only be possible to use BV to identify adenomas vs. non-adenomas at extreme BV values.

  7. Calculation of spin-densities within the context of density functional theory. The crucial role of the correlation functional

    NARCIS (Netherlands)

    Filatov, M; Cremer, D

    2005-01-01

    It is demonstrated that the LYP correlation functional is not suited to be used for the calculation of electron spin resonance hyperfine structure (HFS) constants, nuclear magnetic resonance spin-spin coupling constants, magnetic, shieldings and other properties that require a balanced account of

  8. Correlations between acoustic properties and bone density in bovine cancellous bone from 0.5 to 2 MHz

    Science.gov (United States)

    Lee, Kang Il; Roh, Heui-Seol; Yoon, Suk Wang

    2003-05-01

    Correlations between acoustic properties and bone density were investigated in the 12 defatted bovine cancellous bone specimens in vitro. Speed of sound (SOS) and broadband ultrasonic attenuation (BUA) were measured in three different frequency bandwidths from 0.5 to 2 MHz using three matched pairs of transducers with the center frequencies of 1, 2.25, and 3.5 MHz. The relative orientation between ultrasonic beam and bone specimen was the mediolateral (ML) direction of the bovine tibia. SOS shows significant linear positive correlation with apparent density for all three pairs of transducers. However, BUA shows relatively weak correlation with apparent density. SOS and BUA are only weakly correlated with each other. The linear combination of SOS and BUA in a multiple regression model leads to a significant improvement in predicting apparent density. The correlations among SOS, BUA, and bone density can be effectively and clearly represented in the three-dimensional space by the multiple regression model. These results suggest that the frequency range up to 1.5 MHz and the multiple regression model in the three-dimensional space can be useful in the osteoporosis diagnosis.

  9. VOLUME STUDY WITH HIGH DENSITY OF PARTICLES BASED ON CONTOUR AND CORRELATION IMAGE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Tatyana Yu. Nikolaeva

    2014-11-01

    Full Text Available The subject of study is the techniques of particle statistics evaluation, in particular, processing methods of particle images obtained by coherent illumination. This paper considers the problem of recognition and statistical accounting for individual images of small scattering particles in an arbitrary section of the volume in case of high concentrations. For automatic recognition of focused particles images, a special algorithm for statistical analysis based on contouring and thresholding was used. By means of the mathematical formalism of the scalar diffraction theory, coherent images of the particles formed by the optical system with high numerical aperture were simulated. Numerical testing of the method proposed for the cases of different concentrations and distributions of particles in the volume was performed. As a result, distributions of density and mass fraction of the particles were obtained, and the efficiency of the method in case of different concentrations of particles was evaluated. At high concentrations, the effect of coherent superposition of the particles from the adjacent planes strengthens, which makes it difficult to recognize images of particles using the algorithm considered in the paper. In this case, we propose to supplement the method with calculating the cross-correlation function of particle images from adjacent segments of the volume, and evaluating the ratio between the height of the correlation peak and the height of the function pedestal in the case of different distribution characters. The method of statistical accounting of particles considered in this paper is of practical importance in the study of volume with particles of different nature, for example, in problems of biology and oceanography. Effective work in the regime of high concentrations expands the limits of applicability of these methods for practically important cases and helps to optimize determination time of the distribution character and

  10. Distribution and correlates of non-high-density lipoprotein cholesterol and triglycerides in Lebanese school children.

    Science.gov (United States)

    Gannagé-Yared, Marie-Hélène; Farah, Vanessa; Chahine, Elise; Balech, Nicole; Ibrahim, Toni; Asmar, Nadia; Barakett-Hamadé, Vanda; Jambart, Selim

    2016-01-01

    The prevalence of dyslipidelmia in pediatric Middle-Eastern populations is unknown. Our study aims to investigate the distribution and correlates of non-high-density lipoprotein cholesterol (non-HDL-C) and triglycerides among Lebanese school children. A total of 969 subjects aged 8-18 years were included in the study (505 boys and 464 girls). Recruitment was done from 10 schools located in the Great Beirut and Mount-Lebanon areas. Non-fasting total cholesterol, triglycerides, and HDL-cholesterol (HDL-C) were measured. Non-HDL-C was calculated. Schools were categorized into 3 socioeconomic statuses (SESs; low, middle, and high). In the overall population, the prevalence of high non-HDL-C (>3.8 mmol/L), very high non-HDL-C (>4.9 mmol/L), and high triglycerides (>1.5 mmol/l) are respectively 9.2%, 1.24%, and 26.6%. There is no significant gender difference for non-HDL-C or triglycerides. Non-HDL-C and triglycerides are inversely correlated with age in girls (P triglycerides are higher in children from lower SES schools. After adjustment for age and body mass index (BMI), testosterone is inversely associated with triglycerides in boys (P triglycerides are independently associated with BMI and schools' SES in both girls and boys. This study confirms, in our population, the association between obesity and both high non-HDL-C and triglycerides, and between high triglycerides and low SES. Copyright © 2016 National Lipid Association. Published by Elsevier Inc. All rights reserved.

  11. Exact thermal density functional theory for a model system: Correlation components and accuracy of the zero-temperature exchange-correlation approximation

    Science.gov (United States)

    Smith, J. C.; Pribram-Jones, A.; Burke, K.

    2016-06-01

    Thermal density functional theory calculations often use the Mermin-Kohn-Sham scheme, but employ ground-state approximations to the exchange-correlation (XC) free energy. In the simplest solvable nontrivial model, an asymmetric Hubbard dimer, we calculate the exact many-body energies and the exact Mermin-Kohn-Sham functionals for this system and extract the exact XC free energy. For moderate temperatures and weak correlation, we find this approximation to be excellent. We extract various exact free-energy correlation components and the exact adiabatic connection formula.

  12. Correlation between peak energy and Fourier power density spectrum slope in gamma-ray bursts

    CERN Document Server

    Dichiara, S; Amati, L; Frontera, F; Margutti, R

    2016-01-01

    The origin of the gamma-ray burst (GRB) prompt emission still defies explanation, in spite of recent progress made, for example, on the occasional presence of a thermal component in the spectrum along with the ubiquitous non-thermal component that is modelled with a Band function. The combination of finite duration and aperiodic modulations make GRBs hard to characterise temporally. Although correlations between GRB luminosity and spectral hardness on one side and time variability on the other side have long been known, the loose and often arbitrary definition of the latter makes the interpretation uncertain. We characterise the temporal variability in an objective way and search for a connection with rest-frame spectral properties for a number of well-observed GRBs. We studied the individual power density spectra (PDS) of 123 long gamma-ray bursts with measured redshift, rest-frame peak energy Ep,i of the time-averaged nuFnu spectrum, and well-constrained PDS slope alpha detected with Swift, Fermi and past s...

  13. Magneto-structural correlations in trinuclear Cu(II) complexes: a density functional study

    CERN Document Server

    Rodríguez-Forteá, A; Alvarez, S; Centre-De Recera-En-Quimica-Teorica; Alemany, P A; Centre-De Recera-En-Quimica-Teorica

    2003-01-01

    Density functional theoretical methods have been used to study magneto-structural correlations for linear trinuclear hydroxo-bridged copper(II) complexes. The nearest-neighbor exchange coupling constant shows very similar trends to those found earlier for dinuclear compounds for which the Cu-O-Cu angle and the out of plane displacement of the hydrogen atoms at the bridge are the two key structural factors that determine the nature of their magnetic behavior. Changes in these two parameters can induce variations of over 1000 cm sup - sup 1 in the value of the nearest-neighbor coupling constant. On the contrary, coupling between next-nearest neighbors is found to be practically independent of structural changes with a value for the coupling constant of about -60 cm sup - sup 1. The magnitude calculated for this coupling constant indicates that considering its value to be negligible, as usually done in experimental studies, can lead to considerable errors, especially for compounds in which the nearest-neighbor c...

  14. Correlation between bone mineral density and oxidative stress in postmenopausal women

    Directory of Open Access Journals (Sweden)

    Tripti Sharma

    2015-01-01

    Full Text Available Background: Postmenopausal osteoporosis affects large fraction of elderly women. Oxidative stress (OS appears to be involved in its pathogenesis. The scarcity of human studies focusing on the correlation between bone mineral density (BMD and OS in postmenopausal women has prompted us to study on this issue. Materials and Methods: We conducted a cross sectional study in 95 subjects, between 21-65 years of age, including postmenopausal osteoporotic females (n = 35, healthy postmenopausal females (n = 30 and healthy females in reproductive age group (n = 30. We measured serum antioxidant activity of superoxide dismutase (SOD, catalase, glutathione peroxidase (GPx, and total antioxidant power (TAP. BMD was obtained at lumbar spine and femur neck by dual-energy X-ray absorptiometry scan. Osteoporosis was considered when subjects had a BMD of 2.5 standard deviations or more below the mean value for young adults. Results: Serum GPx, SOD, catalase and TAP level were found significantly lower in osteoporotic postmenopausal group as compared to healthy postmenopausal women and women in healthy reproductive age group healthy reproductive women (P 0.005. Conclusion: These findings support that oxidative stress plays an important role in pathogenesis of postmenopausal osteoporosis. We did not find any significant association between BMD and serum level of antioxidants (P > 0.05. The failure to detect this association does not preclude the role of OS in osteoporosis because OS is complex and dynamic process.

  15. Exact ensemble density functional theory for excited states in a model system: Investigating the weight dependence of the correlation energy

    Science.gov (United States)

    Deur, Killian; Mazouin, Laurent; Fromager, Emmanuel

    2017-01-01

    Ensemble density functional theory (eDFT) is an exact time-independent alternative to time-dependent DFT (TD-DFT) for the calculation of excitation energies. Despite its formal simplicity and advantages in contrast to TD-DFT (multiple excitations, for example, can be easily taken into account in an ensemble), eDFT is not standard, which is essentially due to the lack of reliable approximate exchange-correlation (x c ) functionals for ensembles. Following Smith et al. [Phys. Rev. B 93, 245131 (2016), 10.1103/PhysRevB.93.245131], we propose in this work to construct an exact eDFT for the nontrivial asymmetric Hubbard dimer, thus providing more insight into the weight dependence of the ensemble x c energy in various correlation regimes. For that purpose, an exact analytical expression for the weight-dependent ensemble exchange energy has been derived. The complementary exact ensemble correlation energy has been computed by means of Legendre-Fenchel transforms. Interesting features like discontinuities in the ensemble x c potential in the strongly correlated limit have been rationalized by means of a generalized adiabatic connection formalism. Finally, functional-driven errors induced by ground-state density-functional approximations have been studied. In the strictly symmetric case or in the weakly correlated regime, combining ensemble exact exchange with ground-state correlation functionals gives better ensemble energies than when calculated with the ground-state exchange-correlation functional. However, when approaching the asymmetric equiensemble in the strongly correlated regime, the former approximation leads to highly curved ensemble energies with negative slope which is unphysical. Using both ground-state exchange and correlation functionals gives much better results in that case. In fact, exact ensemble energies are almost recovered in some density domains. The analysis of density-driven errors is left for future work.

  16. Mesoscopic current transport in two-dimensional materials with grain boundaries: Four-point probe resistance and Hall effect

    DEFF Research Database (Denmark)

    Lotz, Mikkel Rønne; Boll, Mads; Østerberg, Frederik Westergaard;

    2016-01-01

    configuration sheet resistance as well as the resistance measured between opposing edges of the square sample have a simple unique dependency on the dimension-less parameter √nρGBG0, where G0 is the sheet conductance of a grain. The value of the ratio RA/RB between resistances measured in A- and B......-configurations depends on the dimensionality of the current transport (i.e., one- or two-dimensional). At low grain density or low grain boundary resistivity, two-dimensional transport is observed. In contrast, at moderate grain density and high grain resistivity, one-dimensional transport is seen. Ultimately...

  17. Correlation of Friedewald's calculated low-density lipoprotein cholesterol levels with direct low-density lipoprotein cholesterol levels in a tertiary care hospital.

    Science.gov (United States)

    Nanda, Sunil Kumar; Bharathy, M; Dinakaran, Asha; Ray, Lopamudra; Ravichandran, K

    2017-01-01

    One of the risk factors for the development of coronary heart disease is high low-density lipoprotein (LDL) cholesterol levels. National Cholesterol Education Program ATP III guidelines suggest drug therapy to be considered at LDL-cholesterol levels >130 mg/dl. This makes accurate reporting of LDL cholesterol crucial in the management of Coronary heart disease. Estimation of LDL cholesterol by direct LDL method is accurate, but it is expensive. Hence, We compared Friedewald's calculated LDL values with direct LDL values. To evaluate the correlation of Friedewalds calculated LDL with direct LDL method. We compared LDL cholesterol measured by Friedewald's formula with direct LDL method in 248 samples between the age group of 20-70 years. Paired t-test was used to test the difference in LDL concentration obtained by a direct method and Friedewald's formula. The level of significance was taken as P correlation formula was used to test the correlation between direct LDL values with Friedewald's formula. There was no significant difference between the direct LDL values when compared to calculated LDL by Friedewalds formula (P = 0.140). Pearson correlation showed there exists good correlation between direct LDL versus Friedewalds formula (correlation coefficient = 0.98). The correlation between direct LDL versus Friedewalds calculated LDL was best at triglycerides values between 101 and 200 mg/dl. This study indicates calculated LDL by Friedewalds equation can be used instead of direct LDL in patients who cannot afford direct LDL method.

  18. The large-scale correlations of multi-cell densities and profiles, implications for cosmic variance estimates

    CERN Document Server

    Codis, Sandrine; Pichon, Christophe

    2016-01-01

    In order to quantify the error budget in the measured probability distribution functions of cell densities, the two-point statistics of cosmic densities in concentric spheres is investigated. Bias functions are introduced as the ratio of their two-point correlation function to the two-point correlation of the underlying dark matter distribution. They describe how cell densities are spatially correlated. They are computed here via the so-called large deviation principle in the quasi-linear regime. Their large-separation limit is presented and successfully compared to simulations for density and density slopes: this regime is shown to be rapidly reached allowing to get sub-percent precision for a wide range of densities and variances. The corresponding asymptotic limit provides an estimate of the cosmic variance of standard concentric cell statistics applied to finite surveys. More generally, no assumption on the separation is required for some specific moments of the two-point statistics, for instance when pre...

  19. Prediction of the derivative discontinuity in density functional theory from an electrostatic description of the exchange and correlation potential

    CERN Document Server

    Andrade, Xavier

    2011-01-01

    We propose a new approach to approximate the exchange and correlation (XC) functional in density functional theory. The XC potential is considered as an electrostatic potential, generated by a fictitious XC density, which is in turn a functional of the electronic density. We apply the approach to develop a correction scheme that fixes the asymptotic behavior of any approximated XC potential for finite systems. Additionally, the correction procedure gives the value of the derivative discontinuity; therefore it can directly predict the fundamental gap as a ground-state property.

  20. The density matrix renormalization group for strongly correlated electron systems: A generic implementation

    Science.gov (United States)

    Alvarez, G.

    2009-09-01

    The purpose of this paper is (i) to present a generic and fully functional implementation of the density-matrix renormalization group (DMRG) algorithm, and (ii) to describe how to write additional strongly-correlated electron models and geometries by using templated classes. Besides considering general models and geometries, the code implements Hamiltonian symmetries in a generic way and parallelization over symmetry-related matrix blocks. Program summaryProgram title: DMRG++ Catalogue identifier: AEDJ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDJ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: See file LICENSE No. of lines in distributed program, including test data, etc.: 15 795 No. of bytes in distributed program, including test data, etc.: 83 454 Distribution format: tar.gz Programming language: C++, MPI Computer: PC, HP cluster Operating system: Any, tested on Linux Has the code been vectorized or parallelized?: Yes RAM: 1 GB (256 MB is enough to run included test) Classification: 23 External routines: BLAS and LAPACK Nature of problem: Strongly correlated electrons systems, display a broad range of important phenomena, and their study is a major area of research in condensed matter physics. In this context, model Hamiltonians are used to simulate the relevant interactions of a given compound, and the relevant degrees of freedom. These studies rely on the use of tight-binding lattice models that consider electron localization, where states on one site can be labeled by spin and orbital degrees of freedom. The calculation of properties from these Hamiltonians is a computational intensive problem, since the Hilbert space over which these Hamiltonians act grows exponentially with the number of sites on the lattice. Solution method: The DMRG is a numerical variational technique to study quantum many body Hamiltonians. For one-dimensional and quasi one-dimensional systems, the

  1. Effects of water salinity on the correlation scale of Root density and Evapotranspiration fluxes

    Science.gov (United States)

    Ajeel, Ali; Saeed, Ali; Dragonetti, Giovanna; Comegna, Alessandro; Lamaddalena, Nicola; Coppola, Antonio

    2015-04-01

    Spatial pattern and the correlation of different soil and plant parameters were examined in a green bean field experiment carried out at the Mediterranean Agronomic Institute of Bari, Italy. The experiment aimed to evaluate the role of local processes of salt accumulation and transport which mainly influences the evapotranspiration (and thus the root uptake) processes under different water salinity levels. The experiment consisted of three transects of 30m length and 4.2 m width, irrigated with three different salinity levels (1dSm-1, 3dSm-1, 6dSm-1). Soil measurements (electrical conductivity and soil water content) were monitored along transects in 24 sites, 1 m apart by using TDR probes and Diviner 2000. Water storage measured by TDR and Diviner sensor were coupled for calculating directly the evapotranspiration fluxes along the whole soil profile under the different salinity levels imposed during the experiment. In the same sites, crop monitoring involved measurements of Leaf Area Index (LAI), Osmotic Potential (OP), Leaf Water Potential (LWP), and Root length Density (RlD). Soil and plant properties were analyzed by classical statistics, geostatistics methods and spectral analysis. Results indicated moderate to large spatial variability across the field for soil and plant parameters under all salinity treatments. Furthermore, cross-semivariograms exhibited a strong positive spatial interdependence between electrical conductivity of soil solution ECw with ET and RlD in transect treated with 3dSm-1 as well as with LAI in transect treated with 6dSm-1 at all 24 monitoring sites. Spectral analysis enabled to identify the observation window to sample the soil salinity information responsible for a given plant response (ET, OP, RlD). It is also allowed a clear identification of the spatial scale at which the soil water salinity level and distribution and the crop response in terms of actual evapotranspiration ET, RlD and OP, are actually correlated. Additionally

  2. The flexible nature of exchange, correlation, and Hartree physics: Resolving ``delocalization'' errors in a ``correlation free'' density functional

    Science.gov (United States)

    Gould, Tim; Dobson, John F.

    2013-01-01

    By exploiting freedoms in the definitions of "correlation," "exchange," and "Hartree" physics in ensemble systems, we better generalise the notion of "exact exchange" (EXX) to systems with fractional occupations of the frontier orbitals, arising in the dissociation limit of some molecules. We introduce the linear EXX ("LEXX") theory whose pair distribution and energy are explicitly piecewise linear in the occupations f^{σ }i. We provide explicit expressions for these functions for frontier s and p shells. Used in an optimised effective potential (OEP) approach the LEXX yields energies bounded by the piecewise linear "ensemble EXX" (EEXX) energy and standard fractional optimised EXX energy: EEEXX ⩽ ELEXX ⩽ EEXX. Analysis of the LEXX explains the success of standard OEP methods for diatoms at large spacing, and why they can fail when both spins are allowed to be non-integer so that "ghost" Hartree interactions appear between opposite spin electrons in the usual formula. The energy ELEXX contains a cancellation term for the spin ghost case. It is evaluated for H, Li, and Na fractional ions with clear derivative discontinuities for all cases. The p-shell form reproduces accurate correlation-free energies of B-F and Al-Cl. We further test LEXX plus correlation energy calculations on fractional ions of C and F and again we find both derivative discontinuities and good agreement with exact results.

  3. The flexible nature of exchange, correlation, and Hartree physics: resolving "delocalization" errors in a "correlation free" density functional.

    Science.gov (United States)

    Gould, Tim; Dobson, John F

    2013-01-07

    By exploiting freedoms in the definitions of "correlation," "exchange," and "Hartree" physics in ensemble systems, we better generalise the notion of "exact exchange" (EXX) to systems with fractional occupations of the frontier orbitals, arising in the dissociation limit of some molecules. We introduce the linear EXX ("LEXX") theory whose pair distribution and energy are explicitly piecewise linear in the occupations f(i)(σ). We provide explicit expressions for these functions for frontier s and p shells. Used in an optimised effective potential (OEP) approach the LEXX yields energies bounded by the piecewise linear "ensemble EXX" (EEXX) energy and standard fractional optimised EXX energy: E(EEXX) ≤ E(LEXX) ≤ E(EXX). Analysis of the LEXX explains the success of standard OEP methods for diatoms at large spacing, and why they can fail when both spins are allowed to be non-integer so that "ghost" Hartree interactions appear between opposite spin electrons in the usual formula. The energy E(LEXX) contains a cancellation term for the spin ghost case. It is evaluated for H, Li, and Na fractional ions with clear derivative discontinuities for all cases. The p-shell form reproduces accurate correlation-free energies of B-F and Al-Cl. We further test LEXX plus correlation energy calculations on fractional ions of C and F and again we find both derivative discontinuities and good agreement with exact results.

  4. Correlation between density fluctuations and plasma gradients at the edge of the TORE SUPRA tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Devynck, P.; Garbet, X.; Laviron, C.; Payan, J.; Haas, J. de; Clairet, F.; Talvard, M. [Association Euratom-CEA, Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Gervais, F.; Gresillon, D.; Hennequin, P.; Quemeneur, A.; Truc, A. [Ecole Polytechnique, 91 - Palaiseau (France). Lab. de Physique des Milieux Ionises

    1993-12-31

    The ALTAIR diagnostic uses scattering on the plasma electrons with the help of an IR laser beam to obtain information on the density fluctuations. This diagnostic can simultaneously record fluctuations from two independent wave numbers. Two experiments are carried out: study of the density fluctuations during strong plasma heating that combined both low hybrid waves and ion cyclotron heating; density fluctuations associated to the tokamak gas-feed modulation. 6 figs., 5 refs.

  5. Correlations between the peak flux density and the position angle of inner-jet in three blazars

    CERN Document Server

    Liu, X; Liu, B -R; Li, Q -W

    2012-01-01

    We aim to investigate the relation between the long-term flux density and the position angle (PA) evolution of inner-jet in blazars. We have carried out the elliptic Gaussian model-fit to the `core' of 50 blazars from 15 GHz VLBA data, and analyzed the variability properties of three blazars from the model-fit results. Diverse correlations between the long-term peak flux density and the PA evolution of the major axis of the `core' have been found in $\\sim$ 20% of the 50 sources. Of them, three typical blazars have been analyzed, which also show quasi-periodic flux variations of a few years (T). The correlation between the peak flux density and the PA of inner-jet is positive for S5~0716+714, and negative for S4~1807+698. The two sources cannot be explained with the ballistic jet models, the non-ballistic models have been analyzed to explain the two sub-luminal blazars. A correlation between the peak flux density and the PA (with a T/4 time lag) of inner-jet is found in [HB89]~1823+568, this correlation can be...

  6. Density structure of the cratonic mantle in Southern Africa. 2. Correlations with kimberlite distribution, seismic velocities, and Moho sharpness

    DEFF Research Database (Denmark)

    Artemieva, Irina; Vinnik, Lev

    2016-01-01

    across) lowdensity (down to 3.34 g/cm3) and high-density (up to 3.41 g/cm3) anomalies. High (3.40–3.42 g/cm3) mantle densities beneath the Eastern Cape Fold belt require the presence of a significant amount of eclogite in the mantle, such as associated with subducted oceanic slabs. We find a strong...... the composition and rheology of the lithospheric mantle to make it unfavorable for consequent kimberlite eruptions. (5) Density anomalies in the lithospheric mantle show inverse correlation with seismic Vp, Vs velocities at 100–150 km depth. However, this correlation is weaker than reported in experimental...

  7. Differential virial theorem in relation to a sum rule for the exchange-correlation force in density-functional theory.

    Science.gov (United States)

    Holas, A; March, N H; Rubio, Angel

    2005-11-15

    Holas and March [Phys. Rev. A. 51, 2040 (1995)] gave a formally exact theory for the exchange-correlation (xc) force F(xc)(r)= -inverted Deltaupsilon(xc)(r) associated with the xc potential upsilon(xc)(r) of the density-functional theory in terms of low-order density matrices. This is shown in the present study to lead, rather directly, to the determination of a sum rule nF(xc)=0 relating the xc force with the ground-state density n(r). Some connection is also made with an earlier result relating to the external potential by Levy and Perdew [Phys. Rev. A. 32, 2010 (1985)] and with the quite recent study of Joubert [J. Chem. Phys. 119, 1916 (2003)] relating to the separation of the exchange and correlation contributions.

  8. Density matrix renormalization group with efficient dynamical electron correlation through range separation

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Knecht, Stefan; Kielberg, Jesper Skau

    2015-01-01

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electroncorrelation...

  9. Self-consistent local-density approximation with model Coulomb pair-correlation functions for electronic systems

    Science.gov (United States)

    Gritsenko, O. V.; Rubio, A.; Balbás, L. C.; Alonso, J. A.

    1993-03-01

    The model Coulomb pair-correlation functions proposed several years ago by Gritsenko, Bagaturyants, Kazansky, and Zhidomirov are incorporated into the self-consistent local-density approximation (LDA) scheme for electronic systems. Different correlation functions satisfying well-established local boundary conditions and integral conditions have been tested by performing LDA calculations for closed-shell atoms. Those correlation functions contain a single parameter which can be optimized by fitting the atomic correlation energies to empirical data. In this way, a single (universal) value of the parameter is found to give a very good fit for all the atoms studied. The results provide a substantial improvement of calculated correlation energies as compared to the usual LDA functionals and the scheme should be useful for molecular and cluster calculations.

  10. Correlation of Friedewald's calculated low-density lipoprotein cholesterol levels with direct low-density lipoprotein cholesterol levels in a tertiary care hospital

    Science.gov (United States)

    Nanda, Sunil Kumar; Bharathy, M; Dinakaran, Asha; Ray, Lopamudra; Ravichandran, K

    2017-01-01

    Background: One of the risk factors for the development of coronary heart disease is high low-density lipoprotein (LDL) cholesterol levels. National Cholesterol Education Program ATP III guidelines suggest drug therapy to be considered at LDL-cholesterol levels >130 mg/dl. This makes accurate reporting of LDL cholesterol crucial in the management of Coronary heart disease. Estimation of LDL cholesterol by direct LDL method is accurate, but it is expensive. Hence, We compared Friedewald's calculated LDL values with direct LDL values. Aim: To evaluate the correlation of Friedewalds calculated LDL with direct LDL method. Materials and Methods: We compared LDL cholesterol measured by Friedewald's formula with direct LDL method in 248 samples between the age group of 20–70 years. Paired t-test was used to test the difference in LDL concentration obtained by a direct method and Friedewald's formula. The level of significance was taken as P values with Friedewald's formula. Results: There was no significant difference between the direct LDL values when compared to calculated LDL by Friedewalds formula (P = 0.140). Pearson correlation showed there exists good correlation between direct LDL versus Friedewalds formula (correlation coefficient = 0.98). The correlation between direct LDL versus Friedewalds calculated LDL was best at triglycerides values between 101 and 200 mg/dl. Conclusion: This study indicates calculated LDL by Friedewalds equation can be used instead of direct LDL in patients who cannot afford direct LDL method.

  11. The flexible nature of exchange, correlation and Hartree physics: resolving "delocalization" errors in a 'correlation free' density functional

    CERN Document Server

    Gould, Tim

    2013-01-01

    By considering the physics of non-interacting ensembles we better generalise the notion of `exact exchange' (EXX) to systems with fractional occupations in the frontier orbitals (called LEXX), in part by exploiting ambiguities in the definitions of `correlation', `exchange' and `Hartree' physics in ensemble systems. The LEXX is employed in an optimised effective potential (OEP) approach (OLEXX) to approximate groundstate energies, where it is bounded by the `ensemble EXX' (EEXX) energy and standard fractional OEXX energy via $E^{\\EEXX}\\leq E^{\\OLEXX} \\leq E^{\\OEXX}$. Analysis of the OLEXX explains the success of standard OEP methods for diatoms at large spacing, and why they can fail when both spins are allowed to be non-integer. The OLEXX is demonstrated on H, Li and Na with fractional electron number with improvements over OEXX for all cases.

  12. Correlation between radiographic analysis of alveolar bone density around dental implant and resonance frequency of dental implant

    Science.gov (United States)

    Prawoko, S. S.; Nelwan, L. C.; Odang, R. W.; Kusdhany, L. S.

    2017-08-01

    The histomorphometric test is the gold standard for dental implant stability quantification; however, it is invasive, and therefore, it is inapplicable to clinical patients. Consequently, accurate and objective alternative methods are required. Resonance frequency analysis (RFA) and digital radiographic analysis are noninvasive methods with excellent objectivity and reproducibility. To analyze the correlation between the radiographic analysis of alveolar bone density around a dental implant and the resonance frequency of the dental implant. Digital radiographic images for 35 samples were obtained, and the resonance frequency of the dental implant was acquired using Osstell ISQ immediately after dental implant placement and on third-month follow-up. The alveolar bone density around the dental implant was subsequently analyzed using SIDEXIS-XG software. No significant correlation was reported between the alveolar bone density around the dental implant and the resonance frequency of the dental implant (r = -0.102 at baseline, r = 0.146 at follow-up, p > 0.05). However, the alveolar bone density and resonance frequency showed a significant difference throughout the healing period (p = 0.005 and p = 0.000, respectively). Conclusion: Digital dental radiographs and Osstell ISQ showed excellent objectivity and reproducibility in quantifying dental implant stability. Nonetheless, no significant correlation was observed between the results obtained using these two methods.

  13. Time-dependent reduced density matrix functional theory applied to laser-driven, correlated two-electron dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brics, Martins; Kapoor, Varun; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)

    2013-07-01

    Time-dependent density functional theory (TDDFT) with known and practicable exchange-correlation potentials does not capture highly correlated electron dynamics such as single-photon double ionization, autoionization, or nonsequential ionization. Time-dependent reduced density matrix functional theory (TDRDMFT) may remedy these problems. The key ingredients in TDRDMFT are the natural orbitals (NOs), i.e., the eigenfunctions of the one-body reduced density matrix (1-RDM), and the occupation numbers (OCs), i.e., the respective eigenvalues. The two-body reduced density matrix (2-RDM) is then expanded in NOs, and equations of motion for the NOs can be derived. If the expansion coefficients of the 2-RDM were known exactly, the problem at hand would be solved. In practice, approximations have to be made. We study the prospects of TDRDMFT following a top-down approach. We solve the exact two-electron time-dependent Schroedinger equation for a model Helium atom in intense laser fields in order to study highly correlated phenomena such as the population of autoionizing states or single-photon double ionization. From the exact wave function we calculate the exact NOs, OCs, the exact expansion coefficients of the 2-RDM, and the exact potentials in the equations of motion. In that way we can identify how many NOs and which level of approximations are necessary to capture such phenomena.

  14. Correlations between insulin sensitivity and bone mineral density in non-diabetic men

    DEFF Research Database (Denmark)

    Abrahamsen, B.; Rohold, A.; Henriksen, Jan Erik

    2000-01-01

    AIMS: To investigate relationships between bone mineral density (BMD), insulin secretion and insulin sensitivity, controlling for body composition, in view of data suggesting that hyperglycaemia [corrected] leads to decreased osteoblast proliferation and a negative calcium balance and that insulin...

  15. Density changes in shear bands of a metallic glass determined by correlative analytical transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rösner, Harald, E-mail: rosner@uni-muenster.de [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Peterlechner, Martin [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Kübel, Christian [Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology (INT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Schmidt, Vitalij [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Wilde, Gerhard [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China)

    2014-07-01

    Density changes between sheared zones and their surrounding amorphous matrix as a result of plastic deformation in a cold-rolled metallic glass (melt-spun Al{sub 88}Y{sub 7}Fe{sub 5}) were determined using high-angle annular dark-field (HAADF) detector intensities supplemented by electron-energy loss spectroscopy (EELS), energy-dispersive X-ray (EDX) and nano-beam diffraction analyses. Sheared zones or shear bands were observed as regions of bright or dark contrast arising from a higher or lower density relative to the matrix. Moreover, abrupt contrast changes from bright to dark and vice versa were found within individual shear bands. We associate the decrease in density mainly with an enhanced free volume in the shear bands and the increase in density with concomitant changes of the mass. This interpretation is further supported by changes in the zero loss and Plasmon signal originating from such sites. The limits of this new approach are discussed. - Highlights: • We describe a novel approach for measuring densities in shear bands of metallic glasses. • The linear relation of the dark-field intensity I/I{sub 0} and the mass thickness ρt was used. • Individual shear bands showed abrupt contrast changes from bright to dark and vice versa. • Density changes ranging from about −10% to +6% were found for such shear bands. • Mixtures of amorphous/medium range ordered domains were found within the shear bands.

  16. Correlation analysis between bone mineral density and serum element contents of postmenopausal women in Xi'an urban area.

    Science.gov (United States)

    Liu, Shun-Zhi; Yan, Hong; Xu, Peng; Li, Jian-Ping; Zhuang, Gui-Hua; Zhu, Bo-Feng; Lu, She-Min

    2009-12-01

    The objective of this paper is to investigate the correlation between serum macro-element and trace element contents and bone mineral density (BMD) as well as the occurrence of osteoporosis. After the epidemiological investigation of 290 postmenopausal women from ages 45 to 65 in the Xi'an urban area, their blood was collected and serum concentrations of macro-elements, calcium, phosphonium, potassium, sodium, magnesium, and trace elements, zinc, iron, copper, and selenium were determined using atomic absorption spectrometry. Their BMD was measured by QDR-2000 dual-energy X-ray absorptiometry (DEXA). The correlation analysis between BMD and serum element contents was done with the software of SPSS 13.0. The correlation analysis of serum elements of postmenopausal women showed that there was a significant correlation between serum calcium and the other elements, and also a significant correlation between serum phosphonium and the others except serum potassium. The serum potassium content had a significant correlation with serum calcium, sodium and iron, but sodium content showed a significant correlation with the others except iron and selenium. In addition, copper had a significant correlation with the others except potassium and selenium. In correlation analysis between BMD and the elements contents, only did the potassium content show a significant positive correlation with BMD of lumbar vertebra and proximal femora. The comparison results between osteoporosis group, osteopenia group, and healthy group showed that there was no significant difference in the element contents between the groups, but there existed a tendency that potassium content increased with the rise of BMD. There exist significant correlations between the contents of serum elements such as calcium, phosphonium, sodium, potassium, magnesium, zinc, iron, copper, and selenium, but no significant differences in these elements contents between the osteoporosis group, osteopenia group, and healthy

  17. Effective homogeneity of the exchange-correlation and non-interacting kinetic energy functionals under density scaling.

    Science.gov (United States)

    Borgoo, Alex; Teale, Andrew M; Tozer, David J

    2012-01-21

    Correlated electron densities, experimental ionisation potentials, and experimental electron affinities are used to investigate the homogeneity of the exchange-correlation and non-interacting kinetic energy functionals of Kohn-Sham density functional theory under density scaling. Results are presented for atoms and small molecules, paying attention to the influence of the integer discontinuity and the choice of the electron affinity. For the exchange-correlation functional, effective homogeneities are highly system-dependent on either side of the integer discontinuity. By contrast, the average homogeneity-associated with the potential that averages over the discontinuity-is generally close to 4/3 when the discontinuity is computed using positive affinities for systems that do bind an excess electron and negative affinities for those that do not. The proximity to 4/3 becomes increasingly pronounced with increasing atomic number. Evaluating the discontinuity using a zero affinity in systems that do not bind an excess electron instead leads to effective homogeneities on the electron abundant side that are close to 4/3. For the non-interacting kinetic energy functional, the effective homogeneities are less system-dependent and the effect of the integer discontinuity is less pronounced. Average values are uniformly below 5/3. The study provides information that may aid the development of improved exchange-correlation and non-interacting kinetic energy functionals. © 2012 American Institute of Physics

  18. Testing for the Gaussian nature of cosmological density perturbations through the three-point temperature correlation function

    Science.gov (United States)

    Luo, Xiaochun; Schramm, David N.

    1993-01-01

    One of the crucial aspects of density perturbations that are produced by the standard inflation scenario is that they are Gaussian where seeds produced by topological defects tend to be non-Gaussian. The three-point correlation function of the temperature anisotropy of the cosmic microwave background radiation (CBR) provides a sensitive test of this aspect of the primordial density field. In this paper, this function is calculated in the general context of various allowed non-Gaussian models. It is shown that the Cosmic Background Explorer and the forthcoming South Pole and balloon CBR anisotropy data may be able to provide a crucial test of the Gaussian nature of the perturbations.

  19. Generalized-active-space pair-density functional theory: an efficient method to study large, strongly correlated, conjugated systems.

    Science.gov (United States)

    Ghosh, Soumen; Cramer, Christopher J; Truhlar, Donald G; Gagliardi, Laura

    2017-04-01

    Predicting ground- and excited-state properties of open-shell organic molecules by electronic structure theory can be challenging because an accurate treatment has to correctly describe both static and dynamic electron correlation. Strongly correlated systems, i.e., systems with near-degeneracy correlation effects, are particularly troublesome. Multiconfigurational wave function methods based on an active space are adequate in principle, but it is impractical to capture most of the dynamic correlation in these methods for systems characterized by many active electrons. We recently developed a new method called multiconfiguration pair-density functional theory (MC-PDFT), that combines the advantages of wave function theory and density functional theory to provide a more practical treatment of strongly correlated systems. Here we present calculations of the singlet-triplet gaps in oligoacenes ranging from naphthalene to dodecacene. Calculations were performed for unprecedently large orbitally optimized active spaces of 50 electrons in 50 orbitals, and we test a range of active spaces and active space partitions, including four kinds of frontier orbital partitions. We show that MC-PDFT can predict the singlet-triplet splittings for oligoacenes consistent with the best available and much more expensive methods, and indeed MC-PDFT may constitute the benchmark against which those other models should be compared, given the absence of experimental data.

  20. Comparison of selective electromyographic activity of the superficial lumbar multifidus between prone trunk extension and four-point kneeling arm and leg lift exercises

    OpenAIRE

    Kim, Jun-Seok; Kang, Min-Hyeok; Jang, Jun-Hyeok; Oh, Jae-Seop

    2015-01-01

    [Purpose] This study examined the selective electromyographic activity of the lumbar paraspinal muscles in healthy male and female subjects in the prone trunk extension (PTE) and four-point kneeling arm and leg lift (FPKAL) exercises to determine the most beneficial exercise for selective activation of the lumbar multifidus (LM). [Subjects and Methods] Twenty healthy male and female subjects participated in this study. Surface electromyographic data were collected from the left-side lumbar er...

  1. Miniaturized volume holographic optical data storage and correlation system with a storage density of 10 Gb/cm3

    Institute of Scientific and Technical Information of China (English)

    CAO Liangcai; HE Qingsheng; WEI Haoyun; LIU Guodong; OUYANG Chuan; ZHAO Jian; WU Minxian; JIN Guofan

    2004-01-01

    The general idea of holographic optical data storage (HODS) is briefly introduced. Based on the recent advances of HODS, the key techniques and the challenges of HODS are discussed. Some new techniques are proposed to improve the system. A miniaturized volume holographic data storage and correlation system is presented. It can achieve a density of 10 Gb/cm3 and a fast correlation recognition rate of more than 2000 images per second. It shows the attracting potential advantages over other conventional storage methods in the information storage as well as information processing.

  2. Analysis of correlation between initial alveolar bone density and apical root resorption after 12 months of orthodontic treatment without extraction

    Directory of Open Access Journals (Sweden)

    Paula Cabrini Scheibel

    2014-10-01

    Full Text Available OBJECTIVE: The aim of the present study was to investigate the correlation between initial alveolar bone density of upper central incisors (ABD-UI and external apical root resorption (EARR after 12 months of orthodontic movement in cases without extraction. METHODS: A total of 47 orthodontic patients 11 years old or older were submitted to periapical radiography of upper incisors prior to treatment (T1 and after 12 months of treatment (T2. ABD-UI and EARR were measured by means of densitometry. RESULTS: No statistically significant correlation was found between initial ABD-UI and EARR at T2 (r = 0.149; p = 0.157. CONCLUSION: Based on the present findings, alveolar density assessed through periapical radiography is not predictive of root resorption after 12 months of orthodontic treatment in cases without extraction.

  3. Neutron diffraction study of quantum effects on the pair correlation function of low-density {sup 4}He

    Energy Technology Data Exchange (ETDEWEB)

    Guarini, E. [Istituto Nazionale per la Fisica della Materia, Unita di Ricerca di Firenze, Polo Scientifico Universita di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Barocchi, F. [Istituto Nazionale per la Fisica della Materia, Unita di Ricerca di Firenze, Polo Scientifico Universita di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Dipartimento di Fisica, Polo Scientifico Universita di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Celli, M.; Zoppi, M. [Istituto Nazionale per la Fisica della Materia, Unita di Ricerca di Firenze, Polo Scientifico Universita di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Istituto di Fisica Applicata ' ' Nello Carrara' ' , Consiglio Nazionale delle Ricerche, via Panciatichi 56/30, 50127 Firenze (Italy); Fischer, H.E. [Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9 (France); Magli, R. [Istituto Nazionale per la Fisica della Materia, Unita di Ricerca di Firenze, Polo Scientifico Universita di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Dipartimento di Chimica e Biochimica Medica, Universita di Milano, LITA, via F. lli Cervi 93, 20090 Segrate Milano (Italy)

    2002-07-01

    An extensive neutron diffraction investigation on low-density (n<4.35 nm{sup -3}) states of helium gas along the 6-K isotherm has been performed by means of both wide- and small-angle experiments, allowing for the extraction of the zero- and first-order density coefficients of c(k), the Fourier transform of the direct correlation function, in a very wide wavevector region extending from k=1 nm{sup -1} to k=160 nm{sup -1}. The two independent measurements provide quantitatively consistent results, and the experimental quantities show a good agreement with the thermodynamic (i.e. k=0) data. The comparison of the experimental pure two-body correlation with the corresponding result of a classical calculation clearly indicates the need of a quantum-mechanical approach. (orig.)

  4. The role of magnetic islands in modifying long range temporal correlations of density fluctuations and local heat transport

    CERN Document Server

    van Milligen, B Ph; Garcia, L; Bruna, D Lopez; Carreras, B A; Xu, Y; Ochando, M; Hidalgo, C; Reynolds-Barredo, J M; Fraguas, A Lopez

    2016-01-01

    This work explores the relation between magnetic islands, long range temporal correlations and heat transport. A low order rational surface ($\\iota/2\\pi = 3/2$) was purposely scanned outward through an Electron Cyclotron Resonance Heated (ECRH) plasma in the TJ-II stellarator. Density turbulence and the poloidal flow velocity (or radial electric field) were characterized using a two channel Doppler Reflectometer. Simultaneously, the ECRH power was modulated to characterize heat transport, using measurements from a 12 channel Electron Cyclotron Emission diagnostic. A systematic variation of the poloidal velocity was found to be associated with the stationary $\\iota/2\\pi = 3/2$ magnetic island. Inside from the rational surface, the Hurst coefficient, quantifying the nature of long-range correlations, was found to be significantly enhanced. Simultaneously, heat transport was enhanced as well, establishing a clear link between density fluctuations and anomalous heat transport. The variation of the Hurst coefficie...

  5. Isothermal density derivative of S(k) and the triplet correlation function: an experimental study in liquid Kr

    Science.gov (United States)

    Fontana, Raffaella; Magli, Renato

    1993-08-01

    Recent accurate measurements performed on liquid Kr have been used to test some of the models proposed in the literature for the triplet correlation function g 3( r, s). It turns out that neither the superposition approximation suggested by Kirkwood (J.P. Hansen and I.R. McDonald, Theory of simple liquids, Academic Press, London, 1986), nor a modification of it which partially takes into account linear density effects (H. Fredrikze, Ph.D. Thesis, Delft, 1985) are able to satisfactorily reproduce the experimental isothermal derivatives of the structure factor. Also the uniform fluid model (P.A. Egelstaff, D.I. Page and C.R.T. Heard, J. Phys. C, 4 (1971) 1453), gives a poor representation especially at lower densities. It is concluded that, in order to correctly describe triplet correlation effects, a full account of the irreducible contributions to g 3( r, s) is necessary.

  6. Current Density Functional Theory Using Meta-Generalized Gradient Exchange-Correlation Functionals.

    Science.gov (United States)

    Furness, James W; Verbeke, Joachim; Tellgren, Erik I; Stopkowicz, Stella; Ekström, Ulf; Helgaker, Trygve; Teale, Andrew M

    2015-09-08

    We present the self-consistent implementation of current-dependent (hybrid) meta-generalized gradient approximation (mGGA) density functionals using London atomic orbitals. A previously proposed generalized kinetic energy density is utilized to implement mGGAs in the framework of Kohn-Sham current density functional theory (KS-CDFT). A unique feature of the nonperturbative implementation of these functionals is the ability to seamlessly explore a wide range of magnetic fields up to 1 au (∼235 kT) in strength. CDFT functionals based on the TPSS and B98 forms are investigated, and their performance is assessed by comparison with accurate coupled-cluster singles, doubles, and perturbative triples (CCSD(T)) data. In the weak field regime, magnetic properties such as magnetizabilities and nuclear magnetic resonance shielding constants show modest but systematic improvements over generalized gradient approximations (GGA). However, in the strong field regime, the mGGA-based forms lead to a significantly improved description of the recently proposed perpendicular paramagnetic bonding mechanism, comparing well with CCSD(T) data. In contrast to functionals based on the vorticity, these forms are found to be numerically stable, and their accuracy at high field suggests that the extension of mGGAs to CDFT via the generalized kinetic energy density should provide a useful starting point for further development of CDFT approximations.

  7. A continuing discussion about the correlation of tidal gravity anomalies and heat flow densities

    Science.gov (United States)

    Melchior, P.

    1995-04-01

    On the basis of several objections, Rydelek et al. (Phys. Earth Planet. Inter., 68: 215-219, 1991) (hereafter noted RZH) denied the existence of a correlation between residuals of tidal gravity ( R) and heat flow ( H) suggested by other workers. To re-examine the whole matter on safe grounds, we previously revised and reanalysed all the original tidal data from 300 stations, taking care of the RZH objections by eliminating what they considered as the important sources of errors in the data, essentially calibration errors of the instruments in amplitude and phase. Using this new data base, we meet here, one by one, the other criticisms not related to the original tidal measurements and show that most of them are not valid, in particular those concerning oceanic load and attraction corrections. The findings are as follows: (1) no correlation between diurnal tide and semi-diurnal tide residuals is normal; (2) distance from the sea is not a valid criterion for elimination of several excellent stations; (3) unexpected residues at the South Pole are not due to imperfections of the cotidal Schwiderski maps but to ice-shelf tides not considered by RZH; (4) the correlation of the tidal gravity residues with the age of tectonic provinces is proposed as an alternative to the correlation with heat flow. The data used in 1991 having been corrected are recalculated for comparison with 1986-1991 statistics: the correlation is confirmed with the same degree of probability. Also, new tidal gravity data obtained since 1990 with 'nullified' instruments, as recommended by RZH, in Africa (31 stations) and Latin America (34 stations), are included in new statistics which also confirm the correlation. The global result, obtained from 174 revised and new stations on all continents, gives a correlation coefficient k = 0.691 with a linear regression R = 0.0201( H - 57) - 0.063 ± 0.0013 (where R is in microgals, and H is in mW m -2). As there is at present no practical or theoretical means

  8. Eigenvalue density of cross-correlations in Sri Lankan financial market

    Science.gov (United States)

    Nilantha, K. G. D. R.; Ranasinghe; Malmini, P. K. C.

    2007-05-01

    We apply the universal properties with Gaussian orthogonal ensemble (GOE) of random matrices namely spectral properties, distribution of eigenvalues, eigenvalue spacing predicted by random matrix theory (RMT) to compare cross-correlation matrix estimators from emerging market data. The daily stock prices of the Sri Lankan All share price index and Milanka price index from August 2004 to March 2005 were analyzed. Most eigenvalues in the spectrum of the cross-correlation matrix of stock price changes agree with the universal predictions of RMT. We find that the cross-correlation matrix satisfies the universal properties of the GOE of real symmetric random matrices. The eigen distribution follows the RMT predictions in the bulk but there are some deviations at the large eigenvalues. The nearest-neighbor spacing and the next nearest-neighbor spacing of the eigenvalues were examined and found that they follow the universality of GOE. RMT with deterministic correlations found that each eigenvalue from deterministic correlations is observed at values, which are repelled from the bulk distribution.

  9. Correlation Matrix Renormalization Theory: Improving Accuracy with Two-Electron Density-Matrix Sum Rules.

    Science.gov (United States)

    Liu, C; Liu, J; Yao, Y X; Wu, P; Wang, C Z; Ho, K M

    2016-10-11

    We recently proposed the correlation matrix renormalization (CMR) theory to treat the electronic correlation effects [Phys. Rev. B 2014, 89, 045131 and Sci. Rep. 2015, 5, 13478] in ground state total energy calculations of molecular systems using the Gutzwiller variational wave function (GWF). By adopting a number of approximations, the computational effort of the CMR can be reduced to a level similar to Hartree-Fock calculations. This paper reports our recent progress in minimizing the error originating from some of these approximations. We introduce a novel sum-rule correction to obtain a more accurate description of the intersite electron correlation effects in total energy calculations. Benchmark calculations are performed on a set of molecules to show the reasonable accuracy of the method.

  10. Correlation of Serum Leptin Level with Bone Mineral Density and Bone Turnover Markers in Chinese Adolescent Dancers

    Institute of Scientific and Technical Information of China (English)

    LI-CHEN YANG; YAN LAN; JING HU; YAN-HUA YANG; QIAN ZHANG; JIAN-HUA PIAO

    2009-01-01

    Objective To investigate plasma leptin concentrations in adolescent female dancers and to determine whether leptin has some effects on their bone mineral density (BMD) and bone turnover markers. Methods Sixty dancers aged 15-17 years and 77 healthy controls were enrolled in the study. Bone mineral density (BMD) and body composition were detected by dual energy X-ray absorptiometry. Serum leptin concentrations were measured by radioimmunoassay (RIA). Two bone turnover markers, bone-specific alkaline phosphatase (BAP) and tartrate-resistant acid phosphatase(TRACP), were determined by ELISA. Results The dancers had a lower fat mass and a lower leptin level than the controls, while they had a relatively higher BMD of the total body and legs after adjustment for BMI and age. The levels of bone resorption and formation of markers were higher in the dancers than in the controls. Leptin was positively correlated with BMI, body weight, fat mass, and percentage of body fat. In dancers, Leptin was positively correlated with the BMD of the total body and the left leg. However, after adjustment for BMI, no correlation of serum leptin concentrations with BMD values was found in either dancers or controls. Nor correlation was found between leptin and bone turnover markers after adjustment for BMI. Conclusion The leptin profile is different between the controls and the dancers with a lower BMI and a lower fat mass. Circulating plasma leptin level depends on BMI and is not a direct determinant of BMD in Chinese adolescent dancers.

  11. The Correlation between Dispersion Measure and X-ray Column Density from Radio Pulsars

    CERN Document Server

    He, C; Kaspi, V M

    2013-01-01

    Pulsars are remarkable objects that emit across the entire electromagnetic spectrum, providing a powerful probe of the interstellar medium. In this study, we investigate the relation between dispersion measure (DM) and X-ray absorption column density NH using 68 radio pulsars detected at X-ray energies with the Chandra X-ray Observatory or XMM-Newton. We find a best-fit empirical linear relation of NH (10^20 cm^-2)= 0.30+0.13-0.09 DM (pc cm^-3), which corresponds to an average ionization of 10+4-3%, confirming the ratio of one free electron per ten neutral hydrogen atoms commonly assumed in the literature. We also compare different NH estimates and note that some NH values obtained from X-ray observations are higher than the total Galactic HI column density along the same line of sight, while the optical extinction generally gives the best NH predictions.

  12. [gamma]-ray CT examination of density gradients in slip ceramics: correlation with stress distribution

    Energy Technology Data Exchange (ETDEWEB)

    Sawicka, B.D. (AECL Research, Chalk River Labs., Ontario (Canada)); Murphy, J.G.; Taheri, F.; Kanary, L.E. (Advanced Materials Engineering Centre, Halifax, Nova Scotia (Canada))

    1992-06-01

    Residual stresses caused by processing techniques reduce the safe allowable design life of components. This is especially critical for brittle materials, like ceramics, which do not exhibit plastic deformation. During development of the manufacturing process for an experimental high-precision ceramic component, a characteristic cracking pattern occurred in a series of prototypes, which suggested development of stresses during densification, either during drying or sintering. To examine parameters which may influence the development of these residual stresses, a series of simple geometry specimens were prepared and characterized for density gradients using computed tomography (CT). Using the measured values of density gradients, a model of the sintering process was made and the resultant stress distribution in the parts calculated. Results indicate that the use of nonlinear finite element analysis in conjunction with hypoelastic materials modeling qualitatively represents the sintering stresses.

  13. γ-ray CT examination of density gradients in slip cast ceramics: correlation with stress distribution

    Science.gov (United States)

    Sawicka, B. D.; Murphy, J. G.; Taheri, F.; Kanary, L. E.

    1992-06-01

    Residual stresses caused by processing techniques reduce the safe allowable design life of components. This is especially critical for brittle materials, like ceramics, which do not exhibit plastic deformation. During development of the manufacturing process for an experimental high-precision ceramic component, a characteristic cracking pattern occurred in a series of prototypes, which suggested development of stresses during densification, either during drying or sintering. To examine parameters which may influence the development of these residual stresses, a series of simple geometry specimens were prepared and characterized for density gradients using computed tomography (CT). Using the measured values of density gradients, a model of the sintering process was made and the resultant stress distribution in the parts calculated. Results indicate that the use of nonlinear finite element analysis in conjunction with hypoelastic materials modelling qualitatively represents the sintering stresses.

  14. Correlates of Bone Mineral Density and Sagittal Spinal Balance in the Aged

    OpenAIRE

    2015-01-01

    Objective To investigate the relationship between bone mineral density (BMD) and sagittal spinal balance in the Korean elderly population. Methods The retrospective study included subjects aged 60 years and above, who had whole-spine lateral radiography and dual-energy X-ray absorptiometry (DEXA) within a year's gap between each other. Sagittal vertical axis (SVA) for evaluation of sagittal spinal balance and five spinopelvic parameters were measured through radiography. The presence of compr...

  15. Negative electron affinities from DFT: influence of asymptotic exchange-correlation potential and effective homogeneity under density scaling.

    Science.gov (United States)

    Borgoo, Alex; Tozer, David J

    2012-06-07

    The influence of the asymptotic exchange-correlation potential and density-scaling homogeneity on negative electron affinities determined using the approach of Tozer and De Proft [J. Phys. Chem. A2005, 109, 8923] is investigated. Application of an asymptotic correction to the potential improves the accuracy for several of the systems with the most negative affinities, reflecting their diffuse lowest unoccupied orbitals. For systems with modest affinities, it reduces the accuracy marginally. Enforcing a near-exact effective homogeneity through a simple shift in the potential leads to improved correlation with experimental values but significantly overestimated affinities. Optimal effective homogeneities are therefore determined, and a simple scheme is proposed for enforcing an average optimal value. Application of the scheme to a series of organic molecules maintains the excellent correlation with the experimental values while significantly reducing the absolute errors.

  16. Current Density-Functional Theory using meta-Generalized Gradient Exchange--Correlation Functionals

    CERN Document Server

    Furness, James W; Tellgren, Erik I; Stopkowicz, Stella; Ekström, Ulf; Helgaker, Trygve; Teale, Andrew M

    2015-01-01

    We present the self-consistent implementation of current-dependent (hybrid) meta generalized gradient approximation (mGGA) density functionals using London atomic orbitals. A previously proposed generalized kinetic energy density is utilized to implement mGGAs in the framework of Kohn--Sham current density-functional theory (KS-CDFT). A unique feature of the non-perturbative implementation of these functionals is the ability to seamlessly explore a wide range of magnetic fields up to 1 a.u. ($\\sim 235000$T) in strength. CDFT functionals based on the TPSS and B98 forms are investigated and their performance is assessed by comparison with accurate CCSD(T) data. In the weak field regime magnetic properties such as magnetizabilities and NMR shielding constants show modest but systematic improvements over GGA functionals. However, in strong field regime the mGGA based forms lead to a significantly improved description of the recently proposed perpendicular paramagnetic bonding mechanism, comparing well with CCSD(T...

  17. The correlation analysis of the expression of VEGF and the DCs’ infiltration density of gastric cancer tissues

    Institute of Scientific and Technical Information of China (English)

    Feng Yang; Ai-Mei Li; De-Huai Jing

    2016-01-01

    Objective:To investigate the correlation of the expression of vascular endothecial growth factor (VEGF) and the dendritic cells (DCs) infiltration density of tumor tissues in patients with gastric cancer and the correlation of the frequency of DCs of VEGF in gastric cancer tissues and the clinic stages; and to analyze the expressions of HLA-DR and CD86 on peripheral blood monocyte-derived DCs.Methods:Immuno fluorescence method was applied to test the expressions of CD11c and VEGF in gastric cancer tissues and para-carcinoma tissues and enzyme-linked immune sorbent assay was used to detect the concentration of serum VEGF. Peripheral blood mononuclear cells of the gastric cancer patients and healthy people were separated and induced DCs by GM-CSF and IL-4in vitro. Then, the expressions of HLA-DR and CD86 on DCs were tested by flow cytometry. Finally, the recombinant VEGF protein was added into DCs cultures to explore how VEGF affected the expression of CD86. Results: There was a negative correlation between the expression intensity of VEGF on gastric cancer cells and the tumor-infiltrating density of DCs; while there was a certain positive correlation between the frequency of DCs of VEGF and the development of the disease. The concentration of serum VEGF had no association with the density of tumor-infiltrating DCs. As for peripheral blood mononuclear cell, it had a certain induced effect on the decrease of DCs, the expressions of HLA-DR and CD86 and the expression of CD86 on DCs’ cell surface by VEGF.Conclusions:The activities of DCs were inhibited by VEGF secretion of gastric cancer tissues so as to mediate immune escape of the cancer cells. In addition, DCs infiltrated in gastric cancer tissues may secrete VEGF to participate the development of the disease.

  18. Housefly population density correlates with shigellosis among children in Mirzapur, Bangladesh: a time series analysis.

    Directory of Open Access Journals (Sweden)

    Tamer H Farag

    Full Text Available BACKGROUND: Shigella infections are a public health problem in developing and transitional countries because of high transmissibility, severity of clinical disease, widespread antibiotic resistance and lack of a licensed vaccine. Whereas Shigellae are known to be transmitted primarily by direct fecal-oral contact and less commonly by contaminated food and water, the role of the housefly Musca domestica as a mechanical vector of transmission is less appreciated. We sought to assess the contribution of houseflies to Shigella-associated moderate-to-severe diarrhea (MSD among children less than five years old in Mirzapur, Bangladesh, a site where shigellosis is hyperendemic, and to model the potential impact of a housefly control intervention. METHODS: Stool samples from 843 children presenting to Kumudini Hospital during 2009-2010 with new episodes of MSD (diarrhea accompanied by dehydration, dysentery or hospitalization were analyzed. Housefly density was measured twice weekly in six randomly selected sentinel households. Poisson time series regression was performed and autoregression-adjusted attributable fractions (AFs were calculated using the Bruzzi method, with standard errors via jackknife procedure. FINDINGS: Dramatic springtime peaks in housefly density in 2009 and 2010 were followed one to two months later by peaks of Shigella-associated MSD among toddlers and pre-school children. Poisson time series regression showed that housefly density was associated with Shigella cases at three lags (six weeks (Incidence Rate Ratio = 1.39 [95% CI: 1.23 to 1.58] for each log increase in fly count, an association that was not confounded by ambient air temperature. Autocorrelation-adjusted AF calculations showed that a housefly control intervention could have prevented approximately 37% of the Shigella cases over the study period. INTERPRETATION: Houseflies may play an important role in the seasonal transmission of Shigella in some developing

  19. Evidence that platelet buoyant density, but not size, correlates with platelet age in man.

    Science.gov (United States)

    Mezzano, D; Hwang, K; Catalano, P; Aster, R H

    1981-01-01

    Following infusion of 51Cr-labeled autologous platelets into normal subjects, high-density (HD) and low-density (LD) platelet cohorts were isolated by prolonged centrifugation in isosmotic arabino-galactan (Stractan). Specific radio-activity of LD platelets declined rapidly post-infusion (T1/2 = 1.5 days), but specific radioactivity of HD platelets remained constant or increased over a 3--4-day period and gradually declined for 6--7 days thereafter. These differences were exaggerated when platelet cohorts enriched in LD or HD cells by slow centrifugation in high-density albumin were labeled and transfused. Mean survival of a platelet cohort enriched with HD cells was significantly (P less than 0.02) shorter (7.73 days) than that of a cohort enriched with LD cells (9.33) days). In normal subjects treated with aspirin, capacity for thromboxane synthesis was regained more rapidly (P less than 0.05) in LD than in HD platelets. HD and LD platelets differed only slightly in mean volume (HD platelets = 7.57 mu3, LD platelets = 6.87 mu3, 0.05 less than P less than 0.01). We believe the most logical interpretation of these findings is that under normal conditions in man, newly formed platelets are less dense on the average than total platelets and become more dense as they age in the circulation. Thus, specific radioactivity of LD platelets declines rapidly as these platelets move into a more dense compartment and are replaced by newly formed, unlabelled cells; specific radioactivity of HD platelets remains constant or increases as labelled platelets enter this compartment in numbers equal to or greater than the number leaving it at the end of their life span. The similarity in mean volumes of LD and HD platelets suggests that platelet size is unrelated to platelet age under normal conditions.

  20. Evidence that platelet buoyant density, but not size, correlates with platelet age in man

    Energy Technology Data Exchange (ETDEWEB)

    Mezzano, D.; Hwang, K.; Catalano, P.; Aster, R.H.

    1981-01-01

    Following infusion of 51Cr-labeled autologous platelets into normal subjects, high-density (HD) and low-density (LD) platelet cohorts were isolated by prolonged centrifugation in isosmotic arabino-galactan (Stractan). Specific radio-activity of LD platelets declined rapidly post-infusion (T1/2 . 1.5 days), but specific radioactivity of HD platelets remained constant or increased over a 3--4-day period and gradually declined for 6--7 days thereafter. These differences were exaggerated when platelet cohorts enriched in LD or HD cells by slow centrifugation in high-density albumin were labeled and transfused. Mean survival of a platelet cohort enriched with HD cells was significantly (P less than 0.02) shorter (7.73 days) than that of a cohort enriched with LD cells (9.33) days). In normal subjects treated with aspirin, capacity for thromboxane synthesis was regained more rapidly (P less than 0.05) in LD than in HD platelets. HD and LD platelets differed only slightly in mean volume (HD platelets . 7.57 mu3, LD platelets . 6.87 mu3, 0.05 less than P less than 0.01). We believe the most logical interpretation of these findings is that under normal conditions in man, newly formed platelets are less dense on the average than total platelets and become more dense as they age in the circulation. Thus, specific radioactivity of LD platelets declines rapidly as these platelets move into a more dense compartment and are replaced by newly formed, unlabelled cells; specific radioactivity of HD platelets remains constant or increases as labelled platelets enter this compartment in numbers equal to or greater than the number leaving it at the end of their life span. The similarity in mean volumes of LD and HD platelets suggests that platelet size is unrelated to platelet age under normal conditions.

  1. Nutritional Correlates of Koala Persistence in a Low-Density Population

    Science.gov (United States)

    Stalenberg, Eleanor; Wallis, Ian R.; Cunningham, Ross B.; Allen, Chris; Foley, William J.

    2014-01-01

    It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus) populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts) compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence. PMID:25470599

  2. Nutritional correlates of koala persistence in a low-density population.

    Directory of Open Access Journals (Sweden)

    Eleanor Stalenberg

    Full Text Available It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.

  3. Cell density-correlated induction of pyruvate decarboxylase under aerobic conditions in the yeast Pichia stipitis.

    Science.gov (United States)

    Mergler, M; Klinner, U

    2001-01-01

    During the aerobic batch cultivation of P. stipitis CBS 5776 with glucose, pyruvate decarboxylase was activated in a cell number-correlated manner. Activation started when a cell number between 7 x 10(7) and x 10(8) cells ml(-1) was reached and the enzyme activity increased during further cultivation. This induction might have been triggered either by an unknown quorum sensing system or by a shortage of cytoplasmic acetyl-CoA.

  4. Universal bulk charge-density-wave (CDW) correlations in the cuprate superconductors

    Science.gov (United States)

    Tabis, Wojciech

    2014-03-01

    The recent observation of bulk CDW order in YBa2Cu3O8+δ(YBCO) in competition with superconductivity is a significant development. Using Cu L-edge resonant X-ray scattering, we also observe bulk CDW order in HgBa2CuO4+δ(Hg1201 Tc = 72K). The correlations appear below TCDW ~ 200K, well below the pseudogap temperature T* ~ 320K associated with unusual magnetism, but coincident with the onset of Fermi-liquid-like charge transport. In contrast to YBCO, we observe no decrease of the CDW amplitude below Tc, and the correlation length is short and temperature independent. CDW correlations therefore are a universal property of underdoped cuprates, enhanced by low structural symmetry and a magnetic field, but fundamentally not in significant competition with superconductivity. We also discuss the relationship between the CDW modulation wave vector and the Fermi surface area extracted from QO experiments. Work supported by DOE-BES. In collaboration with Y. Li, M. Le Tacon, L. Braicovich, A. Kreyssig, M. Minola, G. Dellea, E. Weschke, M. Veit, A. Goldman, T. Schmitt, G. Ghiringhelli, N. Barisic, M.K. Chan, C. Dorow, G. Yu, X. Zhao, B. Keimer, M. Greven.

  5. Density-scaling exponents and virial potential-energy correlation coefficients for the (2n, n) Lennard-Jones system

    Indian Academy of Sciences (India)

    IDA M FRIISBERG; LORENZO COSTIGLIOLA; JEPPE C DYRE

    2017-07-01

    This paper investigates the relation between the density-scaling exponent γ and the virial potential energy correlation coefficient R at several thermodynamic state points in three dimensions for the generalized (2n, n) Lennard-Jones (LJ) system for n = 4, 9, 12, 18, as well as for the standard n = 6 LJ system in two,three, and four dimensions. The state points studied include many low-density states at which the virial potential energy correlations are not strong. For these state points we find the roughly linear relation γ∼=3n R/d in d dimensions. This result is discussed in light of the approximate “extended inverse power law” description of generalized LJ potentials (Bailey N P et al. 2008 J. Chem. Phys. 129 184508). In the plot of γ versus R there is in all cases a transition around R ≈ 0.9, above which γ starts to decrease as R approaches unity. This is consistent with the fact that γ → 2n/d for R → 1, a limit that is approached at high densities and/or high temperatures at which the repulsive r−2n term dominates the physics.

  6. Dynamic structure factor of a strongly correlated Fermi superfluid within a density functional theory approach

    Science.gov (United States)

    Zou, Peng; Dalfovo, Franco; Sharma, Rishi; Liu, Xia-Ji; Hu, Hui

    2016-11-01

    We theoretically investigate the dynamic structure factor of a strongly interacting Fermi gas at the crossover from Bardeen-Cooper-Schrieffer superfluids to Bose-Einstein condensates, by developing an improved random phase approximation within the framework of a density functional theory (DFT)—the so-called superfluid local density approximation. Compared with the previous random-phase-approximation studies based on the standard Bogoliubov-de Gennes equations, the use of the DFT greatly improves the accuracy of the equation of state at the crossover, and leads to a better description of both collective Bogoliubov-Anderson-Goldstone phonon mode and single-particle fermionic excitations at small transferred momentum. Near unitarity, where the s-wave scattering length diverges, we show that the single-particle excitations start to significantly contribute to the spectrum of dynamic structure factor once the frequency is above a threshold of the energy gap at 2{{Δ }}. The sharp rise in the spectrum at this threshold can be utilized to measure the pairing gap Δ. Together with the sound velocity determined from the phonon branch, the dynamic structure factor provides us some key information of the crossover Fermi superfluid. Our predictions could be examined in experiments with 6Li or 40K atoms using Bragg spectroscopy.

  7. The FACT-Melanoma quality-of-life instrument: comparison of a five-point and four-point response scale using the Rasch measurement model.

    Science.gov (United States)

    Winstanley, Julie B; Saw, Robyn; Boyle, Frances; Thompson, John

    2013-02-01

    The FACT-Melanoma (FACT-M) is one of only two validated quality-of-life instruments designed specifically for use in patients with melanoma. The instrument incorporates FACT-G, followed by a set of questionnaire items that are specific to melanoma; all items are scored on a five-point response scale. The primary aim of this study was to evaluate the five-point response format of the FACT-M for goodness of fit to the Rasch measurement model, and to investigate whether rescoring the instrument using a four-point response format improved the psychometric properties. Two data sets of similar patient sample sizes (n=127 and 123) were used to test the reliability and validity of the generic instrument (FACT-G) to measure quality of life for patients with melanoma. The Additional Concerns and Melanoma Surgery subscales were subjected to a more detailed analysis using a combination of confirmatory factor analysis and Rasch analysis techniques. The Rasch model fit of the FACT-M was improved by the use of a four-point response format, together with the deletion of three items. Principal components analysis suggested that two melanoma-specific subscales existed within the Additional Concerns subscale and each could be reduced to seven items, respectively, with improved goodness of fit to the Rasch model. The FACT-M instrument showed improved fit to the Rasch model specifications when the items adopted a four-point response format. These results point to possible improvements in the content and structure of the FACT-M for use in future melanoma clinical trials. However, further study should be conducted with larger samples, selected by disease and treatment status.

  8. A computer program to calculate the resistivity of a thin film deposited on a conductive substrate from four-point probe measurements

    Science.gov (United States)

    Oberle, L. G.; Fralick, G. C.

    1986-01-01

    A series of FORTRAN-77 programs is described which correct for the effect of a conducting substrate when a linear four-point probe is used to measure the resistivity of a thin film. The resistivity of the film is given in terms of the thicknesses of the film and substrate, the known resistivity of the substrate, and the measured delta V/I. A full development is given as well as a complete description of the operation of the programs. The programs themselves can be obtained through COSMIC, and are identified as LEW No. 14381.

  9. Precise determination of full matrix of piezo-optic coefficients with a four-point bending technique: the example of lithium niobate crystals.

    Science.gov (United States)

    Krupych, Oleg; Savaryn, Viktoriya; Vlokh, Rostyslav

    2014-04-01

    A recently proposed technique representing a combination of digital imaging laser interferometry with a classical four-point bending method is applied to a canonical nonlinear optical crystal, LiNbO₃, to precisely determine a full matrix of its piezo-optic coefficients (POCs). The contribution of a secondary piezo-optic effect to the POCs is investigated experimentally and analyzed theoretically. Based on the POCs thus obtained, a full matrix of strain-optic coefficients (SOCs) is calculated and the appropriate errors are estimated. A comparison of our experimental errors for the POCs and SOCs with the known reference data allows us to claim the present technique as the most precise.

  10. Coulomb correlation effects and density dependence of radiative recombination rates in polar AlGaN quantum wells

    Science.gov (United States)

    Rupper, Greg; Rudin, Sergey; Bertazzi, Francesco; Garrett, Gregory; Wraback, Michael

    2013-03-01

    AlGaN narrow quantum wells are important elements of deep-ultraviolet light emitting devices. The electron-hole radiative recombination rates are important characteristics of these nanostructures. In this work we evaluated their dependence on carrier density and lattice temperature and compared our theoretical results with the experimentally determined radiative lifetimes in the c-plane grown AlGaN quantum wells. The bands were determined in the k .p approximation for a strained c-plane wurtzite quantum well and polarization fields were included in the model. In order to account for Coulomb correlations at relatively high densities of photo-excited electron-hole plasma and arbitrary temperature, we employed real-time Green's function formalism with self-energies evaluated in the self-consistent T-matrix approximation. The luminescence spectrum was obtained from the susceptibility by summing over scattering in-plane directions and polarization states. The recombination coefficient was obtained from the integrated photo-luminescence. The density dependence of the radiative recombination rate shows effects of strong screening of the polarization electric field at high photo-excitation density.

  11. Correlation between Density and Resorption of Fresh-Frozen and Autogenous Bone Grafts

    Directory of Open Access Journals (Sweden)

    Simone Lumetti

    2014-01-01

    Full Text Available Trial Design. This analysis compared the outcome of fresh-frozen versus autologous bone block grafts for horizontal ridge augmentation in patients with Cawood and Howell class IV atrophies. Methods. Seventeen patients received autologous grafts and 21 patients received fresh-frozen bone grafts. Patients underwent CT scans 1 week and 6 months after surgery for graft volume and density analysis. Results. Two autologous and 3 fresh-frozen grafts failed. Autologous and fresh-frozen grafts lost, respectively, 28% and 46% of their initial volume (P=0.028. It is noteworthy that less dense fresh-frozen blocks lost more volume than denser grafts (61% versus 16%. Conclusions. According to these 6-month results, only denser fresh-frozen bone graft may be an acceptable alternative to autologous bone for horizontal ridge augmentation. Further studies are needed to investigate its behaviour at longer time points.

  12. Kinetic theory of correlated fluids: from dynamic density functional to Lattice Boltzmann methods.

    Science.gov (United States)

    Marconi, Umberto Marini Bettolo; Melchionna, Simone

    2009-07-07

    Using methods of kinetic theory and liquid state theory we propose a description of the nonequilibrium behavior of molecular fluids, which takes into account their microscopic structure and thermodynamic properties. The present work represents an alternative to the recent dynamic density functional theory, which can only deal with colloidal fluids and is not apt to describe the hydrodynamic behavior of a molecular fluid. The method is based on a suitable modification of the Boltzmann transport equation for the phase space distribution and provides a detailed description of the local structure of the fluid and its transport coefficients. Finally, we propose a practical scheme to solve numerically and efficiently the resulting kinetic equation by employing a discretization procedure analogous to the one used in the Lattice Boltzmann method.

  13. SUSY-QCD corrections for direct detection of neutralino dark matter and correlations with relic density

    Science.gov (United States)

    Klasen, M.; Kovařík, K.; Steppeler, P.

    2016-11-01

    In this paper, we perform a full next-to-leading order (NLO) QCD calculation of neutralino scattering on protons or neutrons in the minimal supersymmetric standard model. We match the results of the NLO QCD calculation to the scalar and axial-vector operators in the effective field theory approach. These govern the spin-independent and spin-dependent detection rates, respectively. The calculations have been performed for general bino, wino and higgsino decompositions of neutralino dark matter and required a novel tensor reduction method of loop integrals with vanishing relative velocities and Gram determinants. Numerically, the NLO QCD effects are shown to be of at least of similar size and sometimes larger than the currently estimated nuclear uncertainties. We also demonstrate the interplay of the direct detection rate with the relic density when consistently analyzed with the program dm@nlo.

  14. Thermodynamics of lithium intercalation into graphite studied using density functional theory calculations incorporating van der Waals correlation and uncertainty estimation

    CERN Document Server

    Pande, Vikram

    2016-01-01

    Graphite is the most widely used and among the most widely-studied anode materials for lithium-ion batteries. Lithium intercalation into graphite has been extensively studied theoretically using density functional theory (DFT) calculations, complemented by experimental studies through X-ray diffraction, spectroscopy, optical imaging and other techniques. However, previous theoretical studies have not directly included van der Waals (vdW) interactions in their density functional theory calculations and vdW interactions play a crucial role in determining the stable phases. In this work, we present a first principles based model using DFT calculations, employing Bayesian Error Estimation Functional with van der Waals (BEEF-vdW) as the exchange correlation functional, and statistical thermodynamics to determine the phase transformations and subsequently, the thermodynamic intercalation potential diagram. We explore the entire configurational phase space by determining the important interactions and applying clust...

  15. Correlative investigation of copper/low-density polyethylene nanocomposite on the endometrial angiogenesis in rats

    Institute of Scientific and Technical Information of China (English)

    LI Jianxiong; LIU Zilong; LI Shuang; XIE Changsheng; DUAN Yonggang; YU Jing; ZHU Changhong

    2007-01-01

    The purpose of this study was to investigate the effects of copper/low-density polyethylene nanocomposite (nano-Cu/LDPE)on the endometrial angiogenesis in rats,and 100 sexual mature female SD rats were randomly divided into five groups:sham-operation groups(SO group,n=20),bulk copper groups(Cu group,n=20),LDPE groups(n=20),nano-Cu/LDPE groups I(n=20)and II(n=20).The levels of angiopoietin-2(Ang-2),its receptor(Tie-2)and CD34 of the rats' endometria in each group were examined by using the S-P method of the immunohistochemistry 30 and 180 days after insertion,respectively.Compared with those in the SO group,the expression of Ang-2 and Tie-2 in all the experimental groups was obviously increased 30 days after insertion,and these parameters in nano-Cu/LDPE groups,except for Ang-2 level in nano-Cu/LDPE group II,were significantly lower in comparison with those in Cu group (P<0.05).On the 180th day after insertion,Ang-2 and Tie-2 levels were still higher in Cu group and LDPE group,but there was no difference of Ang-2 and Tie-2 levels between nano-Cu/LDPE groups and the SO group(P>0.05).Compared with those in the SO group,the significant increases in microvessel density(MVD)were observed on the 30th and the 180th day after the insertion of the bulk copper(P<0.05).There was no significant difference in MVD counts before and after the insertion of nano-Cu/LDPE(P>0.05).The results show that Nano-Cu/LDPE have slighter influence on the endometrial angiogenesis than bulk copper.

  16. Correlation of the Vesicular Acetylcholine Transporter Densities in the Striata to the Clinical Abilities of Women with Rett Syndrome (RTT)

    Science.gov (United States)

    BRAŠIĆ, JAMES ROBERT; BIBAT, GENILA; KUMAR, ANIL; ZHOU, YUN; HILTON, JOHN; YABLONSKI, MARYBETH E.; DOGAN, AHMET SEMIH; GUEVARA, MARIA RITA; STEPHANE, MASSOUD; JOHNSTON, MICHAEL; WONG, DEAN FOSTER; NAIDU, SAKKUBAI

    2012-01-01

    Rett syndrome (RTT) is a neurodevelopmental disability characterized by mutations in the X-linked methyl-CpG-binding protein 2 (MeCP2) located at the Xq28 region. The severity is modified in part by X chromosomal inactivation resulting in wide clinical variability. We hypothesized that the ability to perform the activities of daily living (ADL) is correlated with the density of vesicular acetylcholine transporters in the striata of women with RTT. The density of the vesicular acetylcholine transporters in the living human brain can be estimated by single-photon emission-computed tomography (SPECT) after the administration of (−)-5-[123I]iodobenzovesamicol ([123I]IBVM). Twenty-four (24) hours following the intravenous injection of approximately 333 MBq (9 mCi) [123I]IBVM, four women with RTT and nine healthy adult volunteer control participants underwent SPECT brain scans for sixty (60) minutes. The Vesicular Acetylcholine Transporter Binding Site Index (VATBSI) (Kuhl et al., 1994), a measurement of the density of vesicular acetylcholine transporters, was estimated in the striatum and the reference structure, the cerebellum. The women with RTT were assessed for certain activities of daily living (ADL). Although striatal VATSBI was not significantly lower in RTT (5.2 ± 0.9) than in healthy adults (5.7 ± 1.6), RTT striatal VATSBI and ADL scores were linearly associated (ADL = 0.89*VATSBI + 4.5; R2=0.93; p<0.01), suggesting a correlation between the ability to perform ADL and the density of vesicular acetylcholine transporters in the striata of women with RTT. [123I]IBVM is a promising tool to characterize the pathophysiological mechanisms of RTT and other neurodevelopmental disabilities. PMID:22223404

  17. Higher-spin correlators

    CERN Document Server

    Alday, Luis F

    2013-01-01

    We analyze the properly normalized three-point correlator of two protected scalar operators and one higher spin twist-two operator in N=4 super Yang-Mills, in the limit of large spin j. The relevant structure constant can be extracted from the OPE of the four-point correlator of protected scalar operators. We show that crossing symmetry of the four point correlator plus a judicious guess for the perturbative structure of the three-point correlator, allow to make a prediction for the structure constant at all loops in perturbation theory, up to terms that remain finite as the spin becomes large. Furthermore, the expression for the structure constant allows to propose an expression for the all loops four-point correlator G(u,v), in the limit u,v -> 0. Our predictions are in perfect agreement with the large j expansion of results available in the literature.

  18. Depletion of the density of states near the Fermi energy induced by disorder and electron correlation in alloys

    Science.gov (United States)

    Noh, H.-J.; Nahm, T.-U.; Kim, J.-Y.; Park, W.-G.; Oh, S.-J.; Hong, J.-P.; Kim, C.-O.

    2000-09-01

    We have performed high-resolution photoemission study of substitutionally disordered alloys Cu-Pt, Cu-Ni, and Pd-Pt. The ratios between alloy spectra and pure metal spectra are found to have dips at the Fermi level when the residual resistivity is high and when strong repulsive electron-electron interaction is expected. This is in accordance with Altshuler and Aronov's model which predicts a depletion of the density of states at the Fermi level when both disorder and electron correlation are present.

  19. Constraints on rapidity-dependent initial conditions from charged particle pseudorapidity densities and two-particle correlations

    CERN Document Server

    Ke, Weiyao; Bernhard, Jonah E; Bass, Steffen A

    2016-01-01

    We study the initial three-dimensional spatial configuration of the quark-gluon plasma produced in relativistic heavy-ion collisions using centrality and rapidity-dependent measurements of charged particle pseudorapidity densities and two-particle correlations. A cumulant-generating function is used to parametrize the rapidity dependence of local entropy deposition and extend arbitrary boost-invariant initial conditions to nonzero beam rapidities. The model is compared to p+Pb and Pb+Pb single-particle distributions and systematically optimized using Bayesian parameter estimation to extract high-probability initial condition parameters. The optimized initial conditions are then compared to a number of experimental observables including two-particle rapidity correlations, the rapidity dependence of anisotropic flow, and event-plane decorrelations.

  20. Correlation between Cohesive Energy Density, Fractional Free Volume, and Gas Transport Properties of Poly(ethylene-co-vinyl acetate Materials

    Directory of Open Access Journals (Sweden)

    Piotr Kubica

    2015-01-01

    Full Text Available The transport properties of the poly(ethylene-co-vinyl acetate (EVA materials to He, N2, O2, and CO2 are correlated with two polymer molecular structure parameters, that is, cohesive energy density (CED and fractional free volume (FFV, determined by the group contribution method. In our preceding paper, the attempt was made to approximate EVA permeability using a linear function of 1/FFV as predicted by the free volume theory. However, the deviations from this relationship appeared to be significant. In this paper, it is shown that permeation of gas molecules is controlled not only by free volume but also by the polymer cohesive energy. Moreover, the behavior of CO2 was found to differ significantly from that of other gases. In this instance, the correlation is much better when diffusivity instead of permeability is taken into account in a modified transport model.

  1. Search for the ground-state electronic configurations of correlated organometallic metallocenes from constraint density functional theory

    Science.gov (United States)

    Nawa, Kenji; Kitaoka, Yukie; Nakamura, Kohji; Imamura, Hiroshi; Akiyama, Toru; Ito, Tomonori; Weinert, M.

    2016-07-01

    The ground-state electronic configurations of the correlated organometallic metallocenes, M Cp2,M =V , Cr, Mn, Fe, Co, and Ni, are investigated using constraint density functional theory combined with nonempirical Ueff parameters determined from linear-response theory. The relative stability of the various d -orbital electronic configurations of these organometallic molecules is found to be sensitive to the amount of correlation. Using nonempirical values of Ueff, the calculated electronic configurations are in agreement with the experiments: 4A2 g ,3E2 g ,6A1 g ,1A1 g ,2E1 g , and 3A2 g for the VCp2,CrCp2,MnCp2,FeCp2,CoCp2 , and NiCp2, respectively.

  2. Development of an exchange-correlation functional with uncertainty quantification capabilities for density functional theory

    Science.gov (United States)

    Aldegunde, Manuel; Kermode, James R.; Zabaras, Nicholas

    2016-04-01

    This paper presents the development of a new exchange-correlation functional from the point of view of machine learning. Using atomization energies of solids and small molecules, we train a linear model for the exchange enhancement factor using a Bayesian approach which allows for the quantification of uncertainties in the predictions. A relevance vector machine is used to automatically select the most relevant terms of the model. We then test this model on atomization energies and also on bulk properties. The average model provides a mean absolute error of only 0.116 eV for the test points of the G2/97 set but a larger 0.314 eV for the test solids. In terms of bulk properties, the prediction for transition metals and monovalent semiconductors has a very low test error. However, as expected, predictions for types of materials not represented in the training set such as ionic solids show much larger errors.

  3. 四探针测半导体材料杂质分布%THE MEASUREMENT OF IMPURITY DISTRIBUTION IN SEMICODUCTOR MATERIAL WITH FOUR POINT PROBE METHOD

    Institute of Scientific and Technical Information of China (English)

    高玮; 谢宜臣

    2001-01-01

    设计一个新的近代物理实验题目.利用阳极氧化法对半导体材料逐次去层,采用四探针法测量其每层的电阻率及相应杂质浓度,可得出半导体材料的杂质分布N(x).实验设备简单,测量方便,结果准确.并提供了自制四探针测量仪的方法.%A new topic in modern physics experiment is designed. Semiconductor material is removed layer by layer with anode oxidation method. Resistivity and relevant impurity concentration in every layer is measured with four point probe method. The impurity distribution of semiconductor material N(x)is obtained. The experiment equipment is simple, measurement is convenient, and result is accurate. The method to make four point probe instrument is provided.

  4. Mammographic density is the main correlate of tumors detected on ultrasound but not on mammography.

    Science.gov (United States)

    Häberle, Lothar; Fasching, Peter A; Brehm, Barbara; Heusinger, Katharina; Jud, Sebastian M; Loehberg, Christian R; Hack, Carolin C; Preuss, Caroline; Lux, Michael P; Hartmann, Arndt; Vachon, Celine M; Meier-Meitinger, Martina; Uder, Michael; Beckmann, Matthias W; Schulz-Wendtland, Rüdiger

    2016-11-01

    Although mammography screening programs do not include ultrasound examinations, some diagnostic units do provide women with both mammography and ultrasonography. This article is concerned with estimating the risk of a breast cancer patient diagnosed in a hospital-based mammography unit having a tumor that is visible on ultrasound but not on mammography. A total of 1,399 women with invasive breast cancer from a hospital-based diagnostic mammography unit were included in this retrospective study. For inclusion, mammograms from the time of the primary diagnosis had to be available for computer-assisted assessment of percentage mammographic density (PMD), as well as Breast Imaging Reporting and Data System (BIRADS) assessment of mammography. In addition, ultrasound findings were available for the complete cohort as part of routine diagnostic procedures, regardless of any patient or imaging characteristics. Logistic regression analyses were conducted to identify predictors of mammography failure, defined as BIRADS assessment 1 or 2. The probability that the visibility of a tumor might be masked at diagnosis was estimated using a regression model with the identified predictors. Tumors were only visible on ultrasound in 107 cases (7.6%). PMD was the strongest predictor for mammography failure, but age, body mass index and previous breast surgery also influenced the risk, independently of the PMD. Risk probabilities ranged from 1% for a defined low-risk group up to 40% for a high-risk group. These findings might help identify women who should be offered ultrasound examinations in addition to mammography.

  5. Linear response theory for the density matrix renormalization group: efficient algorithms for strongly correlated excited states.

    Science.gov (United States)

    Nakatani, Naoki; Wouters, Sebastian; Van Neck, Dimitri; Chan, Garnet Kin-Lic

    2014-01-14

    Linear response theory for the density matrix renormalization group (DMRG-LRT) was first presented in terms of the DMRG renormalization projectors [J. J. Dorando, J. Hachmann, and G. K.-L. Chan, J. Chem. Phys. 130, 184111 (2009)]. Later, with an understanding of the manifold structure of the matrix product state (MPS) ansatz, which lies at the basis of the DMRG algorithm, a way was found to construct the linear response space for general choices of the MPS gauge in terms of the tangent space vectors [J. Haegeman, J. I. Cirac, T. J. Osborne, I. Pižorn, H. Verschelde, and F. Verstraete, Phys. Rev. Lett. 107, 070601 (2011)]. These two developments led to the formulation of the Tamm-Dancoff and random phase approximations (TDA and RPA) for MPS. This work describes how these LRTs may be efficiently implemented through minor modifications of the DMRG sweep algorithm, at a computational cost which scales the same as the ground-state DMRG algorithm. In fact, the mixed canonical MPS form implicit to the DMRG sweep is essential for efficient implementation of the RPA, due to the structure of the second-order tangent space. We present ab initio DMRG-TDA results for excited states of polyenes, the water molecule, and a [2Fe-2S] iron-sulfur cluster.

  6. Linear response theory for the density matrix renormalization group: Efficient algorithms for strongly correlated excited states

    Science.gov (United States)

    Nakatani, Naoki; Wouters, Sebastian; Van Neck, Dimitri; Chan, Garnet Kin-Lic

    2014-01-01

    Linear response theory for the density matrix renormalization group (DMRG-LRT) was first presented in terms of the DMRG renormalization projectors [J. J. Dorando, J. Hachmann, and G. K.-L. Chan, J. Chem. Phys. 130, 184111 (2009)]. Later, with an understanding of the manifold structure of the matrix product state (MPS) ansatz, which lies at the basis of the DMRG algorithm, a way was found to construct the linear response space for general choices of the MPS gauge in terms of the tangent space vectors [J. Haegeman, J. I. Cirac, T. J. Osborne, I. Pižorn, H. Verschelde, and F. Verstraete, Phys. Rev. Lett. 107, 070601 (2011)]. These two developments led to the formulation of the Tamm-Dancoff and random phase approximations (TDA and RPA) for MPS. This work describes how these LRTs may be efficiently implemented through minor modifications of the DMRG sweep algorithm, at a computational cost which scales the same as the ground-state DMRG algorithm. In fact, the mixed canonical MPS form implicit to the DMRG sweep is essential for efficient implementation of the RPA, due to the structure of the second-order tangent space. We present ab initio DMRG-TDA results for excited states of polyenes, the water molecule, and a [2Fe-2S] iron-sulfur cluster.

  7. Correlation of mammographic density and serum calcium levels in patients with primary breast cancer.

    Science.gov (United States)

    Hack, Carolin C; Stoll, Martin J; Jud, Sebastian M; Heusinger, Katharina; Adler, Werner; Haeberle, Lothar; Ganslandt, Thomas; Heindl, Felix; Schulz-Wendtland, Rüdiger; Cavallaro, Alexander; Uder, Michael; Beckmann, Matthias W; Fasching, Peter A; Bayer, Christian M

    2017-06-01

    Percentage mammographic breast density (PMD) is one of the most important risk factors for breast cancer (BC). Calcium, vitamin D, bisphosphonates, and denosumab have been considered and partly confirmed as factors potentially influencing the risk of BC. This retrospective observational study investigated the association between serum calcium level and PMD. A total of 982 BC patients identified in the research database at the University Breast Center for Franconia with unilateral BC, calcium and albumin values, and mammogram at the time of first diagnosis were included. PMD was assessed, using a semiautomated method by two readers. Linear regression analyses were conducted to investigate the impact on PMD of the parameters of serum calcium level adjusted for albumin level, and well-known clinical predictors such as age, body mass index (BMI), menopausal status and confounder for serum calcium like season in which the BC was diagnosed. Increased calcium levels were associated with reduced PMD (P = 0.024). Furthermore, PMD was inversely associated with BMI (P < 0.001) and age (P < 0.001). There was also an association between PMD and menopausal status (P < 0.001). The goodness-of-fit of the regression model was moderate. This is the first study assessing the association between serum calcium level and PMD. An inverse association with adjusted serum calcium levels was observed. These findings add to previously published data relating to vitamin D, bisphosphonates, denosumab, and the RANK/RANKL signaling pathway in breast cancer risk and prevention. © 2017 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

  8. Expression of inducible nitric oxide synthase and cyclooxygenase-2 in pancreatic adenocarcinoma:Correlation with microvessel density

    Institute of Scientific and Technical Information of China (English)

    Hans U. Kasper; Hella Wolf; Uta Drebber; Helmut K. Wolf; Michael A. Kern

    2004-01-01

    AIM: Cyclooxygenases (COX) are key enzymes for conversion of arachidonic acid to prostaglandins. Nitric oxide synthase (NOS) is the enzyme responsible for formation of nitric oxide.Both have constitutive and inducible isoforms. The inducible isoforms (iNOS and COX-2) are of great interest as regulators of tumor angiogenesis, tumorigenesis and inflammatory processes. This study was to clarify their role in pancreatic adenocarcinomas.METHODS: We investigated the immunohistochemical iNOS and COX-2 expression in 40 pancreatic ducal adenocarcinomas of different grade and stage. The results were compared with microvessel density and clinicopathological data.RESULTS: Twenty-one (52.5%) of the cases showed iNOS expression, 15 (37.5%) of the cases were positive for COX-2.The immunoreaction was heterogeneously distributed within the tumors. Staining intensity was different between the tumors. No correlation between iNOS and COX-2 expression was seen. There was no relationship with microvessel density.However, iNOS positive tumors developed more often distant metastases and the more malignant tumors showed a higher COX-2 expression. There was no correlation with other clinicopathological data.CONCLUSION: Approximately half of the cases expressed iNOS and COX-2. These two enzymes do not seem to be the key step in angiogenesis or carcinogenesis of pancreatic adenocarcinomas. Due to a low prevalence of COX-2expression, chemoprevention of pancreatic carcinomas by COX-2 inhibitors can only achieve a limited success.

  9. Quantifying the importance of orbital over spin correlations in delta-Pu within density-functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Soderlind, P; Wolfer, W

    2007-07-27

    Spin and orbital and electron correlations are known to be important when treating the high-temperature {delta} phase of plutonium within the framework of density-functional theory (DFT). One of the more successful attempts to model {delta}-Pu within this approach has included condensed-matter generalizations of Hund's three rules for atoms, i.e., spin polarization, orbital polarization, and spin-orbit coupling. Here they perform a quantitative analysis of these interactions relative rank for the bonding and electronic structure in {delta}-Pu within the DFT model. The result is somewhat surprising in that spin-orbit coupling and orbital polarization are far more important than spin polarization for a realistic description of {delta}-Pu. They show that these orbital correlations on their own, without any formation of magnetic spin moments, can account for the low atomic density of the {delta} phase with a reasonable equation-of-state. In addition, this unambiguously non-magnetic (NM) treatment produces a one-electron spectra with resonances close to the Fermi level consistent with experimental valence band photoemission spectra.

  10. Gauge-invariant two-point correlator of energy density in deconfining SU(2) Yang-Mills thermodynamics

    CERN Document Server

    Keller, Jochen

    2008-01-01

    The thesis is considering aspects of SU(2) Yang-Mills thermodynamics in its deconfining high-temperature phase. We calculate the two-point correlation function of the energy density of the photon in a thermalized gas, at first in the conventional U(1) gauge theory, followed by a calculation, where the photon is identified with the massless gauge mode in deconfining SU(2) Yang-Mills thermodynamics. Apart from the fact, that this calculation is interesting from a technical point of view, we can consider several aspects of phenomenological relevance. Since we interpret the two-point correlator of energy density as a measure for the energy transfer, and thus for the electromagnetic interaction of microscopic objects, such as atoms immersed into a photon gas, we are able to give an explanation for the unexpected stability of cold, innergalactic clouds consisting of atomic hydrogen. Subsequently, we evaluate the spatial string tension in deconfining SU(2) Yang-Mills thermodynamics, which can be regarded as measure ...

  11. Effects of exchange-correlation potentials in density functional descriptions of ground-state and photoionization of fullerenes

    Science.gov (United States)

    Choi, Jinwoo; Chang, Eonho; Anstine, Dylan M.; Chakraborty, Himadri

    2016-05-01

    We study the ground state properties of C60 and C240 molecules in a spherical frame of local density approximation (LDA). Within this mean-field theory, two different approximations to the exchange-correlation (xc) functional are used: (i) The Gunnerson-Lundqvist parametrization augmented by a treatment to correct for the electron self-interaction and (ii) the van Leeuwen and Baerends (LB94) model potential that inclusively restores electron's asymptotic properties. Results show differences in the ground-state potential, level energies and electron densities between the two xc choices. We then use the ground structure to find the excited and ionized states of the systems and calculate dipole single-photoionization cross sections in a time-dependent LDA method that incorporates linear-response dynamical correlations. Comparative effects of the choices of xc on collective plasmon and single-excitation Auger resonances as well as on geometry driven cavity oscillations are found significant. The work is supported by the NSF, USA.

  12. Height and weight are correlated with lumbar spinal bone mineral contents and densities in Chinese adolescents with early ankylosing spondylitis

    Institute of Scientific and Technical Information of China (English)

    MA Xing; HU Yun-yu; MA Xiang-dong; WANG Quan-ping; LI Xiao-juan; LU Rong; WANG Jun; XU Xin-zhi

    2004-01-01

    Objective: To explore the possible factors influencing lumbar spinal bone mineral contents and bone mineral densities in Chinese adolescents with early ankylosing spondylitis(AS). Methods: Thirty-one male Chinese adolescent outpatients with early AS were included and compared with 31 age-matched male controls. Age (year), height (cm), total body weight (kg) together with body mass index (BMI, kg/m2 ) of all subjects and disease duration (month), BASMI,BASFI, BASDAI, SASSS as well as ESR (mm/h) of AS patients were obtained. Lumbar2-4 bone mineral content (L2-4BMC, g) and lumbar2-4 areal bone mineral density (L2-4 BMD, g/cm2 ) were evaluated using dual-energy X-ray absorptiometry (DEXA) with Lunar DPX-IQ device and lumbar2-4 volumetric bone mineral apparent density (L2-4 BMAD, g/cm3 )was subsequently calculated. Correlation and multiple regression analyses were performed. Results: Compared with 31 agematched male controls, AS patients had significantly lower L2-4 BMD [ (0. 984 ± 0.142) g/cm2 vs ( 1.055 ± 0. 137) g/cm2,P = 0.049 ] and L2- 4 BMAD [ (0. 1527 ± 0. 0173) g/cm3 vs (0. 1630 ± 0. 0195) g/cm3, P = 0. 032 ]. In AS patients,multiple regression analysis identified that only the factor of height was significantly correlated with L2- 4 BMC ( R = 0. 673,P = 0.000) and the factor of weight had predominant influences on L2-4 BMD ( R = 0. 620, P = 0. 000) as well as L2-4BMAD (R=0.510, P = 0.003). Conclusion: The young patients with early AS had marked reduction in lumbar spine bone mineral densities, which indicated an important primary event leading to osteoporosis. Positive effects of height and weight on lumbar spine bone mass and densities could expectantly make favorable contributions to early prevention of AS associated bone loss and subsequent osteoporosis.

  13. Neurophysiologic Correlates of Ketamine Sedation and Anesthesia: A High-density Electroencephalography Study in Healthy Volunteers.

    Science.gov (United States)

    Vlisides, Phillip E; Bel-Bahar, Tarik; Lee, UnCheol; Li, Duan; Kim, Hyoungkyu; Janke, Ellen; Tarnal, Vijay; Pichurko, Adrian B; McKinney, Amy M; Kunkler, Bryan S; Picton, Paul; Mashour, George A

    2017-07-01

    Previous studies have demonstrated inconsistent neurophysiologic effects of ketamine, although discrepant findings might relate to differences in doses studied, brain regions analyzed, coadministration of other anesthetic medications, and resolution of the electroencephalograph. The objective of this study was to characterize the dose-dependent effects of ketamine on cortical oscillations and functional connectivity. Ten healthy human volunteers were recruited for study participation. The data were recorded using a 128-channel electroencephalograph during baseline consciousness, subanesthetic dosing (0.5 mg/kg over 40 min), anesthetic dosing (1.5 mg/kg bolus), and recovery. No other sedative or anesthetic medications were administered. Spectrograms, topomaps, and functional connectivity (weighted and directed phase lag index) were computed and analyzed. Frontal theta bandwidth power increased most dramatically during ketamine anesthesia (mean power ± SD, 4.25 ± 1.90 dB) compared to the baseline (0.64 ± 0.28 dB), subanesthetic (0.60 ± 0.30 dB), and recovery (0.68 ± 0.41 dB) states; P ketamine anesthesia. Weighted phase lag index demonstrated theta phase locking within anterior regions (0.2349 ± 0.1170, P ketamine anesthesia. Alpha power gradually decreased with subanesthetic ketamine, and anterior-to-posterior directed connectivity was maximally reduced (0.0282 ± 0.0772) during ketamine anesthesia compared to all other states (P Ketamine anesthesia correlates most clearly with distinct changes in the theta bandwidth, including increased power and functional connectivity. Anterior-to-posterior connectivity in the alpha bandwidth becomes maximally depressed with anesthetic ketamine administration, suggesting a dose-dependent effect.

  14. Quantitative Analysis of Lens Nuclear Density Using Optical Coherence Tomography (OCT with a Liquid Optics Interface: Correlation between OCT Images and LOCS III Grading

    Directory of Open Access Journals (Sweden)

    You Na Kim

    2016-01-01

    Full Text Available Purpose. To quantify whole lens and nuclear lens densities using anterior-segment optical coherence tomography (OCT with a liquid optics interface and evaluate their correlation with Lens Opacities Classification System III (LOCS III lens grading and corrected distance visual acuity (BCVA. Methods. OCT images of the whole lens and lens nucleus of eyes with age-related nuclear cataract were analyzed using ImageJ software. The lens grade and nuclear density were represented in pixel intensity units (PIU and correlations between PIU, BCVA, and LOCS III were assessed. Results. Forty-seven eyes were analyzed. The mean whole lens and lens nuclear densities were 26.99 ± 5.23 and 19.43 ± 6.15 PIU, respectively. A positive linear correlation was observed between lens opacities (R2 = 0.187, p<0.01 and nuclear density (R2 = 0.316, p<0.01 obtained from OCT images and LOCS III. Preoperative BCVA and LOCS III were also positively correlated (R2 = 0.454, p<0.01. Conclusions. Whole lens and lens nuclear densities obtained from OCT correlated with LOCS III. Nuclear density showed a higher positive correlation with LOCS III than whole lens density. OCT with a liquid optics interface is a potential quantitative method for lens grading and can aid in monitoring and managing age-related cataracts.

  15. Contrast-enhanced ultrasonography for the detection and characterization of prostate cancer: Correlation with microvessel density and Gleason score

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J. [Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai 200092 (China); Chen, Y., E-mail: joychen_1266@163.com [Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai 200092 (China); Zhu, Y.; Yao, X.; Qi, J. [Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai 200092 (China)

    2011-08-15

    Aim: To determine whether there is a correlation between the peak intensity of the lesion at contrast-enhanced ultrasonography and the microvessel density (MVD) and Gleason score in biopsy specimens of prostate cancer. Materials and methods: Contrast-enhanced ultrasonography using cadence-contrast pulse sequence (CPS) technology was performed in 147 patients with suspected prostate cancer before biopsy. An auto-tracking contrast quantification (ACQ) software was used to analyse the peak intensity (PI) of the lesion. The Gleason score and MVD immunoreactivity were determined in the prostate biopsy specimens. Ultrasound findings were correlated with biopsy findings. Results: Prostate cancer was detected in 73 of 147 patients. The PI values of prostate cancer patients were significantly higher than those of non-malignant patients [9.81 (4.23) versus 5.69 (3.19) dB; p < 0.01]. The mean (SD) PIs of prostate cancer lesions with a Gleason score of 6-9 were 7.08 (3.80), 8.65 (4.08), 9.76 (3.75), and 9.85 (4.13) dB, respectively. The PI value increased significantly with a higher Gleason score (p < 0.01). The mean (SD) MVDs observed in prostate cancer lesions with a Gleason score of 6-9 were 52.50 (10.54), 56.85 (10.31), 59.91 (9.29), and 66.04 (11.82), respectively. There was a positive correlation between PI and MVD in prostate cancer, with a correlation coefficient of 0.617. No correlation was found between PI value and age, prostate specific antigen (PSA) or prostate specific antigen density (PSAD) level (p > 0.05). Conclusion: The PI obtained by CPS harmonic ultrasonography appears to be of value as an indicator of MVD and increases with a higher Gleason score. CPS harmonic ultrasonography could be promising as a useful imaging technique in the detection and characterization of prostate cancer.

  16. Strong correlation between D 2 density and electron temperature at the target of divertors found in SOLPS analysis

    Science.gov (United States)

    Stangeby, P. C.; Sang, Chaofeng

    2017-05-01

    A companion paper (Sang et al 2016 Nucl. Fusion (https://doi.org/10.1088/1741-4326/aa6548)) reports an assessment, using the SOLPS5.0 (B2-EIRENE) code, of the relative importance of two key aspects of divertor-baffle geometry: (i) divertor closure, and (ii) field-target angle. A wide range of the degree of divertor closure and field-target angle were modeled. An unexpectedly strong and simple correlation has been discovered in these data (and is reported here) between the electron temperature, T et, and the D 2 density, n{{D2}t}{} at the target, for T et  <  10 eV and extending over two orders of magnitude for each correlate: {{T}\\text{et}}   =  ~6.14× {{10}13}n{{D2}t}-0.68 with R 2 = 0.98. The values of T et, and n{{D2}t}{} are for each individual flux tube of the computational grid spanning two power decay widths outward from the separatrix. This may imply that achievement of low T et reduces, essentially, to identifying the divertor-baffle geometry which achieves the highest gas density near the target. To try to identify the controlling physics involved, two-point model formatting (2PMF) has been applied to the code output; it finds an equally strong and simple correlation between the 2PMF volumetric power-loss factor, {{f}\\text{vol-\\text{pwr}-\\text{loss}}} , and n{{D2}t}{} for each flux tube: {{f}\\text{vol-\\text{pwr}-\\text{loss}}}=1.2× {{10}29}n{{D2}t}-1.54~ with R 2 = 0.93. While these trends are broadly as would be expected, the simplicity, tightness and span of the correlations are not understood at present. Additionally, since more of the volumetric power loss is due to impurities than to deuterium, and as the impurities do not radiate just at the target, it is not evident why {{f}\\text{vol-\\text{pwr}-\\text{loss}}} is so strongly correlated with n{{D2}t}{} . To address these questions, in future work 2PMF analysis will be extended to compute the individual contributions to {{f}\\text{vol-\\text{pwr}-\\text{loss}}} .

  17. Exact ensemble density functional theory for excited states in a model system: investigating the weight dependence of the correlation energy

    CERN Document Server

    Deur, Killian; Fromager, Emmanuel

    2016-01-01

    Ensemble density functional theory (eDFT) is an exact time-independent alternative to time-dependent DFT (TD-DFT) for the calculation of excitation energies. Despite its formal simplicity and advantages in contrast to TD-DFT (multiple excitations, for example, can be easily taken into account in an ensemble), eDFT is not standard which is essentially due to the lack of reliable approximate exchange-correlation (xc) functionals for ensembles. Following Burke and coworkers [Phys. Rev. B 93, 245131 (2016)], we propose in this work to construct an exact eDFT for the nontrivial asymmetric Hubbard dimer, thus providing more insight into the weight dependence of the ensemble xc energy in various correlation regimes. For that purpose, an exact analytical expression for the weight-dependent ensemble exchange energy has been derived. The complementary exact ensemble correlation energy has been computed by means of Legendre-Fenchel transforms. Interesting features like discontinuities in the ensemble xc potential in the...

  18. Type ⅡB human skeletal muscle fibers positively correlate with bone mineral density irrespective to age

    Institute of Scientific and Technical Information of China (English)

    Wing-Hoi Cheung; Wing-Sze Lee; Ling Qin; Ning Tang; Vivian Wing-Yin Hung; Kwok-Sui Leung

    2010-01-01

    Background Age-associated decrease in type ⅡA/B human skeletal muscle fibers was detected in human biopsies in our previous study. The relationship between change in muscle fiber typing and bone mineral density (BMD) is, however,unknown either cross-sectionally or longitudinally. We therefore conducted a cross-sectional study to investigate their correlation using human muscle biopsies.Methods Forty human subjects aged (53.4±20.2) years were recruited. Histomorphometric parameters of their muscle biopsies were measured by ATPase staining and image analysis, including average area percentage, fiber number percentage, mean fiber area, and area percentage of connective tissues. Hip and spine BMD was measured by dual-energy X-ray absorptiometry. Partial correlation with adjusting age was performed.Results Type ⅡB muscle fiber was found positively correlated with hip BMD irrespective to age and demonstrated significantly stronger relationship with BMD among all fiber types, in terms of its cross-sectional area (r=0.380, P=0.029)and size (r=0.389, P=0.025). Type ⅡA muscle fibers associated with hip BMD in mean fiber area only (r=0.420, P=0.015).Conclusions Type ⅡB muscle fiber may play an important role in maintaining bone quality. This may also be a relatively more sensitive fiber type of sarcopenia and osteoporosis. These findings further consolidate the muscle-bone relationship.

  19. Perfusion imaging of brain gliomas using arterial spin labeling: correlation with histopathological vascular density in MRI-guided biopsies

    Energy Technology Data Exchange (ETDEWEB)

    Di, Ningning; Pang, Haopeng; Ren, Yan; Yao, Zhenwei; Feng, Xiaoyuan [Huashan Hospital Fudan University, Department of Radiology, Shanghai (China); Dang, Xuefei [Shang Hai Gamma Knife Hospital, Shanghai (China); Cheng, Wenna [Binzhou Medical University Affiliated Hospital, Department of Pharmacy, Binzhou (China); Wu, Jingsong; Yao, Chengjun [Huashan Hospital Fudan University, Department of Neurosurgery, Shanghai (China)

    2017-01-15

    This study was designed to determine if cerebral blood flow (CBF) derived from arterial spin labeling (ASL) perfusion imaging could be used to quantitatively evaluate the microvascular density (MVD) of brain gliomas on a ''point-to-point'' basis by matching CBF areas and surgical biopsy sites as accurate as possible. The study enrolled 47 patients with treatment-naive brain gliomas who underwent preoperative ASL, 3D T1-weighted imaging with gadolinium contrast enhancement (3D T1C+), and T2 fluid acquisition of inversion recovery (T2FLAIR) sequences before stereotactic surgery. We histologically quantified MVD from CD34-stained sections of stereotactic biopsies and co-registered biopsy locations with localized CBF measurements. The correlation between CBF and MVD was determined using Spearman's correlation coefficient. P ≤.05 was considered statistically significant. Of the 47 patients enrolled in the study, 6 were excluded from the analysis because of brain shift or poor co-registration and localization of the biopsy site during surgery. Finally, 84 biopsies from 41 subjects were included in the analysis. CBF showed a statistically significant positive correlation with MVD (ρ = 0.567; P =.029). ASL can be a useful noninvasive perfusion MR method for quantitative evaluation of the MVD of brain gliomas. (orig.)

  20. Comparison of selective electromyographic activity of the superficial lumbar multifidus between prone trunk extension and four-point kneeling arm and leg lift exercises.

    Science.gov (United States)

    Kim, Jun-Seok; Kang, Min-Hyeok; Jang, Jun-Hyeok; Oh, Jae-Seop

    2015-04-01

    [Purpose] This study examined the selective electromyographic activity of the lumbar paraspinal muscles in healthy male and female subjects in the prone trunk extension (PTE) and four-point kneeling arm and leg lift (FPKAL) exercises to determine the most beneficial exercise for selective activation of the lumbar multifidus (LM). [Subjects and Methods] Twenty healthy male and female subjects participated in this study. Surface electromyographic data were collected from the left-side lumbar erector spinae (LES) and LM muscles during PTE and FPKAL exercises. [Results] The LM/LES ratio related to selective activation of the lumbar paraspinal muscles during the FPKAL exercise was higher than that during PTE. [Conclusion] FPKAL exercise is safe and effective for the selective activation of the LM muscle.

  1. Anisotropy in conductance of a quasi-one-dimensional metallic surface state measured by a square micro-four-point probe method.

    Science.gov (United States)

    Kanagawa, Taizo; Hobara, Rei; Matsuda, Iwao; Tanikawa, Takehiro; Natori, Akiko; Hasegawa, Shuji

    2003-07-18

    We have devised a "square micro-four-point probe method" using an independently driven ultrahigh-vacuum four-tip scanning tunneling microscope, and succeeded for the first time to directly measure anisotropic electrical conductance of a single-atomic layer on a solid surface. A quasi-one-dimensional metal of a single-domain Si(111)4 x 1-In had a surface-state conductance along the metallic atom chains (sigma(axially)) to be 7.2(+/-0.6) x 10(-4) S/square at room temperature, which was larger than that in the perpendicular direction (sigma(radially)) by approximately 60 times. The sigma(axially) was consistently interpreted by a Boltzmann equation with the anisotropic surface-state band dispersion, while the sigma(radially) was dominated by a surface-space-charge-layer conductance.

  2. Thermal conductivity measurements of single-crystalline bismuth nanowires by the four-point-probe 3-ω technique at low temperatures.

    Science.gov (United States)

    Lee, Seung-Yong; Kim, Gil-Sung; Lee, Mi-Ri; Lim, Hyuneui; Kim, Wan-Doo; Lee, Sang-Kwon

    2013-05-10

    We have successfully investigated the thermal conductivity (κ) of single-crystalline bismuth nanowires (BiNWs) with [110] growth direction, via a straightforward and powerful four-point-probe 3-ω technique in the temperature range 10-280 K. The BiNWs, which are well known as the most effective material for thermoelectric (TE) device applications, were synthesized by compressive thermal stress on a SiO2/Si substrate at 250-270 °C for 10 h. To understand the thermal transport mechanism of BiNWs, we present three kinds of experimental technique as follows, (i) a manipulation of a single BiNW by an Omni-probe in a focused ion beam (FIB), (ii) a suspended bridge structure integrating a four-point-probe chip by micro-fabrication to minimize the thermal loss to the substrate, and (iii) a simple 3-ω technique system setup. We found that the thermal transport of BiNWs is highly affected by boundary scattering of both phonons and electrons as the dominant heat carriers. The thermal conductivity of a single BiNW (d ~ 123 nm) was estimated to be ~2.9 W m(-1) K(-1) at 280 K, implying lower values compared to the thermal conductivity of the bulk (~11 W m(-1) K(-1) at 280 K). It was noted that this reduction in the thermal conductivity of the BiNWs could be due to strongly enhanced phonon-boundary scattering at the surface of the BiNWs. Furthermore, we present temperature-dependent (10-280 K) thermal conductivity of the BiNWs using the 3-ω technique.

  3. The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems.

    Science.gov (United States)

    Miccoli, I; Edler, F; Pfnür, H; Tegenkamp, C

    2015-06-10

    The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.

  4. The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems

    Science.gov (United States)

    Miccoli, I.; Edler, F.; Pfnür, H.; Tegenkamp, C.

    2015-06-01

    The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.

  5. Low density lipoprotein cholesterol level inversely correlated with coronary flow velocity reserve in patients with Type 2 diabetes

    Institute of Scientific and Technical Information of China (English)

    Jie Yu; Jiang-Li Han; Li-Yun He; Xin-Heng Feng; Wei-Hong Li; Jie-Ming Mao; Wei Gao; Guang Wang

    2013-01-01

    Objectives To evaluate the association of coronary artery endothelial function and plasma levels of low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) in patients with Type 2 Diabetes Mellitus (DM). Methods We investigated 90 participants from our institution between October 2007 to March 2010: non-DM (n = 60) and DM (n = 30). As an indicator of coronary endothelial dysfunction, we used non-invasive Doppler echocardiography to quantify coronary flow velocity reserve (CFVR) in the distal part of the left descending artery after rest and after intravenous adenosine administration. Results Plasma level of LDL-C was significantly higher in patients with DM than in non-DM (3.21 0.64 vs. 2.86 0.72 mmo/L, P < 0.05), but HDL-C level did not differ between the groups (1.01 0.17 vs. 1.05 0.19 mmo/L). Furthermore, the CFVR value was lower in DM patients than non-diabetics (2.45±0.62 vs. 2.98±0.68, P < 0.001). Plasma levels of LDL-C were negatively correlated with CFVR in all subjects (r = 0.35, P < 0.001; 95% confidence interval (CI): 0.52 -C0.15) and in the non-DM (r = 0.29, P < 0.05; 95% CI: 0.51–0.05), with an even stronger negative correlation in the DM group (r = 0.42, P < 0.05; 95% CI: 0.68 –0.06). Age (β = 0.019, s = 0.007, sβ = 0.435, 95% CI: 0.033 –0.005, P = 0.008), LDL-C (β = 0.217, s = 0.105, sβ = 0.282, 95% CI: 0.428 –0.005, P = 0.045) remained independently correlated with CFVR in the DM group. However, we found no correlation between HDL-C level and CFVR in any group. Conclusions Diabetes may contribute to coronary artery disease (CAD) by inducing dysfunction of the coronary artery endothelium. Increased LDL-C level may adversely impair coronary endothelial function in DM. HDL-C may lose its endothelial-protective effects, in part as a result of pathological conditions, especially under abnormal glucose metabolism.

  6. Density functional study of photoabsorption in metallic clusters using an exchange-correlation potential with correct long-range behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Torres, M.B. [Dpto. de Matematicas y Computacion, Universidad de Burgos, Burgos (Spain); Balbas, L.C. [Dpto. de Fisica Teorica, Universidad de Valladolid, Valladolid (Spain)

    2002-06-17

    The atomic exchange-correlation (xc) potential with the correct -1/r asymptotic behaviour constructed by Parr and Ghosh (Parr R G and Ghosh S K 1995 Phys. Rev. A 51 3564) is adapted here to study, within time density functional theory, the linear response to external fields of (i) neutral and charged sodium clusters, and (ii) doped clusters of the type Na{sub n}Pb (n=4, 6, 16). The resulting photoabsorption cross sections are compared to experimental results, when available, and to results from previous calculations using local and non-local xc functionals. The calculated static polarizabilities and plasmon frequencies are closer to the experimental values than previous results. (author)

  7. Correlation between traffic density and particle size distribution in a street canyon and the dependence on wind direction

    Directory of Open Access Journals (Sweden)

    J. Voigtländer

    2006-05-01

    Full Text Available Combustion of fossil fuel in gasoline and diesel powered vehicles is a major source of aerosol particles in a city. In a street canyon, the number concentration of particles smaller than 300 nm in diameter, which can be inhaled and cause serious health effects, is dominated by particles originating from this source.

    In this study we measured both, particle number size distribution and traffic density continuously in a characteristic street canyon in Germany for a time period of 6 months. The street canyon with multistory buildings and 4 traffic lanes is very typical for larger cities. Thus, the measurements are also representative for many other street canyons. In contrast to previous studies, we measured and analyzed the particle number size distribution with high size resolution using a Twin Differential Mobility Analyzer (TDMPS. The measured size range was from 3 to 800 nm, separated into 40 size channels.

    Correlation coefficients between particle number concentration for integrated size ranges and traffic up to 0.5 counts were determined. Correlations were also calculated for each of the 40 size channels of the DMPS system, respectively. We found two maxima of the correlation coefficient for particles about 10 nm and in the size range 60–80 nm in diameter.

    Furthermore, correlations between traffic and particles in dependence of meteorological data were calculated. Relevant parameters were identified by a multiple regression method. In our experiment only wind parameters have influenced the particle number concentration significantly. Very high correlation coefficients (up to 0.85 could be observed in the lee side of the street canyon as well as particles in the range between 60 and 80 nm in diameter. These values are significantly higher than correlation coefficients for other wind directions and other particle sizes. A minimum was found in the luff side of the street. These findings are in good agreement

  8. Correlation of liver density by magnetic resonance imaging and hepatic iron levels. A noninvasive means to exclude homozygous hemochromatosis.

    Science.gov (United States)

    Lawrence, S P; Caminer, S J; Yavorski, R T; Borosky, B D; Rak, K M; Merenich, J A; McDermott, M T; McNally, P R

    1996-09-01

    The diagnosis of hemochromatosis requires liver biopsy and the quantification of hepatic iron. Magnetic resonance imaging (MRI) of the liver shows a characteristic decrease in tissue signal intensity in iron overload states, but its role in the diagnosis of hemochromatosis has not been fully delineated. Forty-three patients (31 men and 12 women) were referred for the evaluation of hemochromatosis based upon a fasting transferrin saturation > 55% and/or a serum ferritin > 400 ng/ml in males or > 300 ng/ml in females. Each patient prospectively underwent MRI of the liver prior to percutaneous liver biopsy and quantitative hepatic iron determination. Homozygous hemochromatosis was diagnosed in 10 patients based upon an hepatic iron/age index > or = 2. MRI was performed with a 1.5 Tesla system using standard spin-echo sequences (T1; TR = 300-500 ms, TE = 13-17 ms, PD; TR = 2,000-2,600 ms, TE = 30 ms). Signal intensity values were blindly determined for regions of interest in liver and skeletal muscle at T1 and proton density. Ratios of liver to muscle (LM) for T1 and proton density (PD) calculated from these values showed a significant correlation with quantitative iron by multiple regression analysis. The LMPD ratio provided the best correlation with hepatic iron (r = -0.6946; p 0.5 had hepatic iron/age indices of < 2.0, thereby excluding homozygous hemochromatosis. These results suggest that LMPD ratios derived from MRI of the liver can accurately predict hepatic iron content. These ratios can be clinically useful in the evaluation of hemochromatosis among patients who either refuse or have contraindications to liver biopsy.

  9. Increasing Public Awareness of Direct-to-Consumer Genetic Tests: Health Care Access, Internet Use, and Population Density Correlates

    Directory of Open Access Journals (Sweden)

    Lila J. Finney Rutten

    2012-01-01

    Full Text Available Uncertainty around the value of and appropriate regulatory models for direct-to-consumer (DTC genetic testing underscores the importance of tracking public awareness of these services. We analyzed nationally representative, cross-sectional data from the Health Information National Trends Survey in 2008 (n=7,674 and 2011 (n=3,959 to assess population-level changes in awareness of DTC genetic testing in the U.S. and to explore sociodemographic, health care, Internet use, and population density correlates. Overall, awareness increased significantly from 29% in 2008 to 37% in 2011. The observed increase in awareness from 2008 to 2011 remained significant (OR=1.39 even when adjusted for sociodemographic variables, health care access, Internet use, and population density. Independent of survey year, the odds of awareness of DTC genetic tests were significantly higher for those aged 50–64 (OR=1.64, and 65–74 (OR=1.60; college graduates (OR=2.02; those with a regular source of health care (OR=1.27; those with a prior cancer diagnosis (OR=1.24; those who use the Internet (OR=1.27; and those living in urban areas (OR=1.25. Surveillance of awareness—along with empirical data on use of and response to genetic risk information—can inform public health and policy efforts to maximize benefits and minimize risks of DTC genetic testing.

  10. Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

    Science.gov (United States)

    Provine, J.; Schindler, Peter; Kim, Yongmin; Walch, Steve P.; Kim, Hyo Jin; Kim, Ki-Hyun; Prinz, Fritz B.

    2016-06-01

    The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiNx), particularly for use a low k dielectric spacer. One of the key material properties needed for SiNx films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiNx and evaluate the film's WER in 100:1 dilutions of HF in H2O. The remote plasma capability available in PEALD, enabled controlling the density of the SiNx film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiNx of 6.1 Å/min, which is similar to WER of SiNx from LPCVD reactions at 850 °C.

  11. Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Provine, J., E-mail: jprovine@stanford.edu; Schindler, Peter; Kim, Yongmin; Walch, Steve P.; Kim, Hyo Jin [Department of Mechanical Engineering, Stanford University, Stanford, California 94305 (United States); Kim, Ki-Hyun [Manufacturing Technology Center, Samsung Electronics, Suwon, Gyeonggi-Do (Korea, Republic of); Prinz, Fritz B. [Department of Mechanical Engineering, Stanford University, Stanford, California 94305 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)

    2016-06-15

    The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiN{sub x}), particularly for use a low k dielectric spacer. One of the key material properties needed for SiN{sub x} films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiN{sub x} and evaluate the film’s WER in 100:1 dilutions of HF in H{sub 2}O. The remote plasma capability available in PEALD, enabled controlling the density of the SiN{sub x} film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiN{sub x} of 6.1 Å/min, which is similar to WER of SiN{sub x} from LPCVD reactions at 850 °C.

  12. Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

    Directory of Open Access Journals (Sweden)

    J. Provine

    2016-06-01

    Full Text Available The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD of silicon nitride (SiNx, particularly for use a low k dielectric spacer. One of the key material properties needed for SiNx films is a low wet etch rate (WER in hydrofluoric (HF acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD of SiNx and evaluate the film’s WER in 100:1 dilutions of HF in H2O. The remote plasma capability available in PEALD, enabled controlling the density of the SiNx film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiNx of 6.1 Å/min, which is similar to WER of SiNx from LPCVD reactions at 850 °C.

  13. Effects of exchange-correlation potentials on the density-functional description of C60 versus C240 photoionization

    Science.gov (United States)

    Choi, Jinwoo; Chang, EonHo; Anstine, Dylan M.; Madjet, Mohamed El-Amine; Chakraborty, Himadri S.

    2017-02-01

    We study the photoionization properties of the C60 versus C240 molecule in a spherical jellium frame of the density-functional method. Two prototypical approximations of the exchange-correlation (xc) functional are used: (i) the Gunnarsson-Lundqvist parametrization [Gunnarsson and Lundqvist, Phys. Rev. B 13, 4274 (1976), 10.1103/PhysRevB.13.4274] with a correction for the electron self-interaction (SIC) introduced artificially from the outset and (ii) a gradient-dependent augmentation of approximation (i) using the van Leeuwen and Baerends model potential [van Leeuwen and Baerends, Phys. Rev. A 49, 2421 (1994), 10.1103/PhysRevA.49.2421], in lieu of SIC, that restores electrons' asymptotic properties intrinsically within the formalism. Ground-state results from the two schemes for both molecules show differences in the shapes of mean-field potentials and bound-level properties. The choice of an xc scheme also significantly alters the dipole single-photoionization cross sections obtained by an ab initio method that incorporates linear-response dynamical correlations. Differences in the structures and ionization responses between C60 and C240 uncover the effect of molecular size on the underlying physics. Analysis indicates that the collective plasmon resonances with the gradient-based xc option produce results noticeably closer to the experimental data available for C60.

  14. Effects of exchange-correlation potentials on the density functional description of C_60 versus C_240 photoionization

    CERN Document Server

    Choi, Jinwoo; Anstine, Dylan M; Madjet, Mohamed El-Amine; Chakraborty, Himadri S

    2016-01-01

    We study the photoionization properties of the C_60 versus C_240 molecule in a spherical jellium frame of density functional method. Two different approximations to the exchange-correlation (xc) functional are used: (i) The Gunnerson-Lundqvist parametrization [Phys. Rev. B 13, 4274 (1976)] with an explicit correction for the electron self-interaction (SIC) and (ii) a gradient-dependent augmentation of (i) by using the van Leeuwen and Baerends model potential [Phys. Rev. A 49, 2421 (1994)], in lieu of SIC, to implicitly restore electrons' asymptotic properties. Ground state results from the two schemes for both molecules show differences in the shapes of mean-field potentials and bound-level properties. The choice of a xc scheme also significantly alters the dipole single-photoionization cross sections obtained by an abinitio method that incorporates linear-response dynamical correlations. Differences in the structures and ionization responses between C_60 and C_240 uncover the effect of molecular size on the ...

  15. Microscopic Effects of Shock Metamorphism in Crystalline Rocks Correlated With Shock Induced Changes in Density, Haughton Impact Structure

    Science.gov (United States)

    Singleton, A. C.; Osinski, G.; Moser, D.

    2009-05-01

    from a representative selection of shocked and unshocked Precambrian gneiss from the Haughton impact structure were investigated in transmitted light with a petrographic microscope and each sample was assigned a shock level based on the identification of shock features. Features identified include kink banding in mica, planar deformation features in quarts and feldspar, and partial or complete melting of various minerals. The density of each sample was also measured. Preliminary results suggest a correlation between decreasing density and increasing shock level. These results may be important not only for understanding shock metamorphism, but also for astrobiology. Impact- induced density decreases in crystalline rocks present opportunities for microbial colonization that would not exist otherwise [4]. The colonization of the shocked material in craters represents a potential mechanism for pioneer organisms to invade an impact structure in the earliest stages of post-impact primary succession. This is a possible mechanism by which microbes may gain a foothold on planetary surfaces that do not have other hospitable habitats. This may be of particular relevance to Mars [4]. [1] Langenhorst, F., Bulletin of the Czech Geo. Survey, 2002. 77, (4): p. 265-282. [2] Therriault, A.M. et al. Bul- letin of the Czech Geo. Survey, 2002. 77, (4): p. 253-263. [3] Stöffler, D. (1971) Journal of Geo-physical Research, 79, (23) [4] Cockell, C.S. et al. Met. & Pl. Sci., 2002. 37, p. 1287-1298.

  16. Correlation between the expression of estrogen receptor beta 1 and microvessel density in human thyroid tumor and its clinical significance

    Directory of Open Access Journals (Sweden)

    Dong-ling JIN

    2011-06-01

    Full Text Available Objective To explore the difference in expression of estrogen receptor beta 1(ERβ1 in different histological types of thyroid carcinoma,and to investigate the correlation between the ERβ1 expression and microvessel density(MVD in human thyroid carcinoma tissue.Methods Among 163 paraffin-embedded samples,collected from Jan.2004 to Dec.2009,107 were follicular differentiated thyroid carcinoma [59 cases of papillary thyroid carcinoma(PTC and 48 cases of follicular thyroid carcinoma(FTC],and 56 were thyroid adenoma.Another 10 cases of normal thyroid tissue,pathologically testified,were enrolled as control.Immunohistochemistry was used to evaluate the expressions of ERβ1 and CD31,and the positive results of CD31 were used to calculate MVD of tissues.The expression status and localization of ERβ1 and CD31 in the thyroid tissue were observed,the expression levels of ERβ1 in different histological types of thyroid carcinoma were compared.The correlation between cervical lymph node metastasis of cancer cells and ERβ1 expression and MVD was analyzed,and the correlation between ERβ1 and MVD was also observed.Results CD31 was mainly expressed in vascular endothelial cells in each type of thyroid tissues,while ERβ1 in both follicular epithelial cells and vascular endothelial cells.In different types such as normal thyroid tissue,thyroid adenoma tissue and thyroid carcinoma tissue,the positive expression rate of ERβ1 was 80%,48.2% and 29.8%,respectively(P < 0.05,with mean value of gray level of 116.22±14.23,130.08±17.51,146.26±18.13,respectively(P < 0.05.The expression level of ERβ1 was significantly lower in the cancer cells with higher metastasis and strong infiltration than in those with lower metastasis and weaker infiltration(P < 0.05,and MVD was significant higher in thyroid carcinoma with lymph node metastasis than in those without lymph node metastasis.MVD was notablely lower in thyroid carcinoma tissue with ERβ1 expression than in those

  17. The effect of contact stresses in four-point bend testing of graphite/epoxy and graphite/PMR-15 composite beams

    Science.gov (United States)

    Binienda, Wieslaw K.; Roberts, Gary D.; Papadopoulos, Demetrios S.

    1992-01-01

    The results of in-plane four-point bend experiments on unidirectionally reinforced composite beams are presented for graphite/epoxy (T300/934) and graphite/polyimide (G30-500/PMR-15) composites. The maximum load and the location of cracks formed during failure were measured for testpieces with fibers oriented at various angles to the beam axis. Since most of the beams failed near one or more of the load points, the strength of the beams was evaluated in terms of a proposed model, for the local stress distribution. In this model, an exact solution to the problem of a localized contact force acting on a unidirectionally reinforced half plane is used to describe the local stress field. The stress singularity at the load points is treated in a manner similar to the stress singularity at a crack tip in fracture mechanisms problems. Using this approach, the effect of fiber angle and elastic material properties on the strength of the beam is described in terms of a load intensity factor. For fiber angles less than 45 deg from the beam axis, a single crack is initiated near one of the load points at a critical value of the load intensity factor. The critical load intensity factor decreases with the increasing fiber angle. For larger fiber angles, multiple cracks occur at locations both near and away from the load points, and the load intensity factor at failure increases sharply with increasing fiber angle.

  18. Effect of contact stresses in four-point bend testing of graphite/epoxy and graphite/PMR-15 composite beams

    Science.gov (United States)

    Binienda, W. K.; Roberts, G. D.; Papadopoulos, D. S.

    1992-01-01

    The results of in-plane four-point bend experiments on unidirectionally reinforced composite beams are presented for graphite/epoxy (T300/934) and graphite/polyimide (G30-500/PMR-15) composites. The maximum load and the location of cracks formed during failure were measured for testpieces with fibers oriented at various angles to the beam axis. Since most of the beams failed near one or more of the load points, the strength of the beams was evaluated in terms of a proposed model for the local stress distribution. In this model, an exact solution to the problem of a localized contact force acting on a unidirectionally reinforced half plane is used to describe the local stress field. The stress singularity at the load points is treated in a manner similar to the stress singularity at a crack tip in fracture mechanisms problems. Using this approach, the effect of fiber angle and elastic material properties on the strength of the beam is described in terms of a load intensity factor. For fiber angles less than 45 deg from the beam axis, a single crack is initiated near one of the load points at a critical value of the load intensity factor. The critical load intensity factor decreases with increasing fiber angle. For larger fiber angles, multiple cracks occur at locations both near and away from the load points, and the load intensity factor at failure increases sharply with increasing fiber angle.

  19. Effect of contact stresses in four-point bend testing of graphite/epoxy and graphite/PMR-15 composite beams

    Science.gov (United States)

    Binienda, W. K.; Roberts, G. D.; Papadopoulos, D. S.

    1992-01-01

    The results of in-plane four-point bend experiments on unidirectionally reinforced composite beams are presented for graphite/epoxy (T300/934) and graphite/polyimide (G30-500/PMR-15) composites. The maximum load and the location of cracks formed during failure were measured for testpieces with fibers oriented at various angles to the beam axis. Since most of the beams failed near one or more of the load points, the strength of the beams was evaluated in terms of a proposed model for the local stress distribution. In this model, an exact solution to the problem of a localized contact force acting on a unidirectionally reinforced half plane is used to describe the local stress field. The stress singularity at the load points is treated in a manner similar to the stress singularity at a crack tip in fracture mechanisms problems. Using this approach, the effect of fiber angle and elastic material properties on the strength of the beam is described in terms of a load intensity factor. For fiber angles less than 45 deg from the beam axis, a single crack is initiated near one of the load points at a critical value of the load intensity factor. The critical load intensity factor decreases with increasing fiber angle. For larger fiber angles, multiple cracks occur at locations both near and away from the load points, and the load intensity factor at failure increases sharply with increasing fiber angle.

  20. Cardiopulmonary fitness correlates with regional cerebral grey matter perfusion and density in men with coronary artery disease.

    Directory of Open Access Journals (Sweden)

    Bradley J MacIntosh

    Full Text Available PURPOSE: Physical activity is associated with positive effects on the brain but there is a paucity of clinical neuroimaging data in patients with coronary artery disease (CAD, a cardiovascular condition associated with grey matter loss. The purpose of this study was to determine which brain regions are impacted by cardiopulmonary fitness and with the change in fitness after 6 months of exercise-based cardiac rehabilitation. METHODS: CAD patients underwent magnetic resonance imaging at baseline, and peak volume of oxygen uptake during exercise testing (VO2Peak was measured at baseline and after 6 months of training. T1-weighted structural images were used to perform grey matter (GM voxel-based morphometry (VBM. Pseudo-continuous arterial spin labeling (pcASL was used to produce cerebral blood flow (CBF images. VBM and CBF data were tested voxel-wise using VO2Peak and age as explanatory variables. RESULTS: In 30 men with CAD (mean age 65±7 years, VBM and CBF identified 7 and 5 respective regions positively associated with baseline VO2Peak. These included the pre- and post-central, paracingulate, caudate, hippocampal regions and converging findings in the putamen. VO2Peak increased by 20% at follow-up in 29 patients (t = 9.6, df = 28, p<0.0001. Baseline CBF in the left post-central gyrus and baseline GM density in the right putamen predicted greater change in VO2Peak. CONCLUSION: Perfusion and GM density were associated with fitness at baseline and with greater fitness gains with exercise. This study identifies new neurobiological correlates of fitness and demonstrates the utility of multi-modal MRI to evaluate the effects of exercise in CAD patients.

  1. Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, David E.; Sheldon, Erin S.; Wechsler, Risa H.; Rozo, Eduardo; Koester, Benjamin P.; Frieman, Joshua A.; McKay, Timothy A.; Evrard, August E.; Becker, Matthew; Annis, James

    2007-09-28

    We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. (2007). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. Since the mean cluster density profile is proportional to the cluster-mass correlation function, the mean profile is spherically symmetric by the assumptions of large-scale homogeneity and isotropy. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of {approx} 13% including both statistical and systematic errors. We also constrain the halo concentration parameter and halo bias as a function of cluster mass; both are in good agreement with predictions from N-body simulations of LCDM models. The methods employed here will be applicable to deeper, wide-area optical surveys that aim to constrain the nature of the dark energy, such as the Dark Energy Survey, the Large Synoptic Survey Telescope and space-based surveys.

  2. Macrophage Densities Correlated with CXC Chemokine Receptor 4 Expression and Related with Poor Survival in Anaplastic Thyroid Cancer

    Directory of Open Access Journals (Sweden)

    Dae In Kim

    2016-09-01

    Full Text Available BackgroundTumor associated macrophages (TAMs and CXC chemokine receptor 4 (CXCR4 have emerged as potential biomarkers in various human cancers. The aims of this study were to investigate the clinical characteristics of anaplastic thyroid cancer (ATC patients according to the TAM numbers in the tumor tissue, and to evaluate the associations between CXCR4 expressions and macrophage densities in ATC tumor microenvironment.MethodsTotal 14 ATC samples from thyroid tissue microarray were used. Immunohistochemical staining was performed using anti-CD163 and anti-CXCR4 antibodies. According to the immunoreactivity of CD163, all subjects were divided into two groups: low-CD163 (n=8 and high-CD163 (n=6 groups.ResultsThe mean diagnostic age was 65±7 years and the median tumor size was 4.3 cm, ranging 2.5 to 15 cm. Clinicopathological characteristics were not significantly different between low-CD163 and high-CD163 groups, while age of diagnosis was younger in high-CD163 group than that of low-CD163 group with marginal significance (56.9±5.5 years vs. 67.5±6.8 years, P=0.09. However, overall survival was significantly reduced in high-CD163 group (5.5 months [range, 1 to 10] compared with low-CD163 groups (8.8 months [range, 6 to 121; log-rank test, P=0.0443. Moreover, high-CD163 group showed strong CXCR4 expressions in both cancer and stromal compartments, while low-CD163 group showed relatively weak, stromal-dominant CXCR4 expressions. Additionally, CD163 and CXCR4 expressions showed a strong positive correlation (γ2=0.432, P=0.013.ConclusionIncreased number of TAMs showed poor overall survival in ATC, suggesting TAMs are potentially a prognostic biomarker for ATC. CXCR4 expression was significantly correlated with CD163-positive TAM densities, which suggest the possible role of CXCR4 in TAM recruitments.

  3. Correlation between Change Rates of GRACE-derived Density and Ground-measured Temperature in Tibetan Plateau, 2004-2008

    Science.gov (United States)

    Zhang, K.; Ma, J.

    2011-12-01

    The amount of mountain glaciers on the Tibetan plateau accounts for 81.6% of the total glacial volume in China, and thus they become origination of Asia's seven major rivers including the Yangtze River, Yellow River, Ganges River, Indus River, Yarlung Zangbo River, and Nujiang River. Unfortunately, with the climate warming since the 20th century, most glaciers are retreating at a rate of 7.0 percent annually. The fast rate of glacier melt has meant more water runoff from the plateau which might exacerbate soil erosion, trigger drought and lead to sandstorms and desertification in the downstream regions. Thus, quantitive estimation and understanding of these glaciers' mass balance will be helpful to long-term sustainability of agriculture and hazard mitigation and give insights into climate change. As the primary factor for the glacier ice melting, the rising temperature should be correlated with the losing ice mass in the Tibetan plateau. However, quantification of glacier mass losses has been challenged, limited by temporarily and spatially sparse measurements using conventional data types and also due to the significant variations in glaciers' melting rates from region to region, and among glaciers in the same region. Nevertheless, the particular sensitivity of mountain glaciers to climate change makes it possible to estimate their mass change rates using GRACE even though the limited resolution. GRACE observations in southeastern Alaska, Patagonia and Tibet provided independent supports for the ability of glaciers' ice loss rates there (e.g., Matsuo and Heki, 2010). Here we expected to examine the correlation between Temperature Change Rates (TCRs) and Mass Change Rates (MCRs) and thus we computed the monthly density change and obtained the yearly Density Change Rates (DCRs) in Tibetan plateau of latitudes from 27N to 38N and longitudes ranging from 75E to 103E, and compared TCRs of ground-measured temperatures at 52 stations higher than 3000m with GRACE

  4. Orbital-dependent exchange-correlation functionals in density-functional theory realized by the FLAPW method

    Energy Technology Data Exchange (ETDEWEB)

    Betzinger, Markus

    2011-12-14

    In this thesis, we extended the applicability of the full-potential linearized augmented-plane-wave (FLAPW) method, one of the most precise, versatile and generally applicable electronic structure methods for solids working within the framework of density-functional theory (DFT), to orbital-dependent functionals for the exchange-correlation (xc) energy. Two different schemes that deal with orbital-dependent functionals, the Kohn-Sham (KS) and the generalized Kohn-Sham (gKS) formalism, have been realized. Hybrid functionals, combining some amount of the orbital-dependent exact exchange energy with local or semi-local functionals of the density, are implemented within the gKS scheme. We work in particular with the PBE0 hybrid of Perdew, Burke, and Ernzerhof. Our implementation relies on a representation of the non-local exact exchange potential - its calculation constitutes the most time consuming step in a practical calculation - by an auxiliary mixed product basis (MPB). In this way, the matrix elements of the Hamiltonian corresponding to the non-local potential become a Brillouin-zone (BZ) sum over vector-matrix-vector products. Several techniques are developed and explored to further accelerate our numerical scheme. We show PBE0 results for a variety of semiconductors and insulators. In comparison with experiment, the PBE0 functional leads to improved band gaps and an improved description of localized states. Even for the ferromagnetic semiconductor EuO with localized 4f electrons, the electronic and magnetic properties are correctly described by the PBE0 functional. Subsequently, we discuss the construction of the local, multiplicative exact exchange (EXX) potential from the non-local, orbital-dependent exact exchange energy. For this purpose we employ the optimized effective potential (OEP) method. Central ingredients of the OEP equation are the KS wave-function response and the single-particle density response function. We show that a balance between the LAPW

  5. Density functional theory embedding for correlated wavefunctions: improved methods for open-shell systems and transition metal complexes.

    Science.gov (United States)

    Goodpaster, Jason D; Barnes, Taylor A; Manby, Frederick R; Miller, Thomas F

    2012-12-14

    Density functional theory (DFT) embedding provides a formally exact framework for interfacing correlated wave-function theory (WFT) methods with lower-level descriptions of electronic structure. Here, we report techniques to improve the accuracy and stability of WFT-in-DFT embedding calculations. In particular, we develop spin-dependent embedding potentials in both restricted and unrestricted orbital formulations to enable WFT-in-DFT embedding for open-shell systems, and develop an orbital-occupation-freezing technique to improve the convergence of optimized effective potential calculations that arise in the evaluation of the embedding potential. The new techniques are demonstrated in applications to the van-der-Waals-bound ethylene-propylene dimer and to the hexa-aquairon(II) transition-metal cation. Calculation of the dissociation curve for the ethylene-propylene dimer reveals that WFT-in-DFT embedding reproduces full CCSD(T) energies to within 0.1 kcal/mol at all distances, eliminating errors in the dispersion interactions due to conventional exchange-correlation (XC) functionals while simultaneously avoiding errors due to subsystem partitioning across covalent bonds. Application of WFT-in-DFT embedding to the calculation of the low-spin/high-spin splitting energy in the hexaaquairon(II) cation reveals that the majority of the dependence on the DFT XC functional can be eliminated by treating only the single transition-metal atom at the WFT level; furthermore, these calculations demonstrate the substantial effects of open-shell contributions to the embedding potential, and they suggest that restricted open-shell WFT-in-DFT embedding provides better accuracy than unrestricted open-shell WFT-in-DFT embedding due to the removal of spin contamination.

  6. Road density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  7. Global study of beyond-mean-field correlation energies in covariant energy density functional theory using a collective Hamiltonian method

    CERN Document Server

    Lu, K Q; Li, Z P; Yao, J M; Meng, J

    2015-01-01

    We report the first global study of dynamic correlation energies (DCEs) associated with rotational motion and quadrupole shape vibrational motion in a covariant energy density functional (CEDF) for 575 even-even nuclei with proton numbers ranging from $Z=8$ to $Z=108$ by solving a five-dimensional collective Hamiltonian, the collective parameters of which are determined from triaxial relativistic mean-field plus BCS calculation using the PC-PK1 force. After taking into account these beyond mean-field DCEs, the root-mean-square (rms) deviation with respect to nuclear masses is reduced significantly down to 1.14 MeV, which is smaller than those of other successful CEDFs: NL3* (2.96 MeV), DD-ME2 (2.39 MeV), DD-ME$\\delta$ (2.29 MeV) and DD-PC1 (2.01 MeV). Moreover, the rms deviation for two-nucleon separation energies is reduced by $\\sim34\\%$ in comparison with cranking prescription.

  8. Density functional theory embedding for correlated wavefunctions: Improved methods for open-shell systems and transition metal complexes

    CERN Document Server

    Goodpaster, Jason D; Manby, Frederick R; Miller, Thomas F

    2012-01-01

    Density functional theory (DFT) embedding provides a formally exact framework for interfacing correlated wave-function theory (WFT) methods with lower-level descriptions of electronic structure. Here, we report techniques to improve the accuracy and stability of WFT-in-DFT embedding calculations. In particular, we develop spin-dependent embedding potentials in both restricted and unrestricted orbital formulations to enable WFT-in-DFT embedding for open-shell systems, and we develop an orbital-occupation-freezing technique to improve the convergence of optimized effective potential (OEP) calculations that arise in the evaluation of the embedding potential. The new techniques are demonstrated in applications to the van-der-Waals-bound ethylene-propylene dimer and to the hexaaquairon(II) transition-metal cation. Calculation of the dissociation curve for the ethylene-propylene dimer reveals that WFT-in-DFT embedding reproduces full CCSD(T) energies to within 0.1 kcal/mol at all distances, eliminating errors in th...

  9. Long-range correlations of density fluctuations in the Kerner-Klenov-Wolf cellular automata three-phase traffic flow model.

    Science.gov (United States)

    Wu, J J; Sun, H J; Gao, Z Y

    2008-09-01

    Detrended fluctuation analysis (DFA) is a useful tool to measure the long-range power-law correlations in 1f noise. In this paper, we investigate the power-law dynamics behavior of the density fluctuation time series generated by the famous Kerner-Klenov-Wolf cellular automata model in road traffic. Then the complexities of spatiotemporal, average speed, and the average density have been analyzed in detail. By introducing the DFA method, our main observation is that the free flow and wide moving jam phases correspond to the long-range anticorrelations. On the contrary, at the synchronized flow phase, the long-range correlated property is observed.

  10. Nucleon-nucleon momentum-correlation function as a probe of the density distribution of valence neutrons in neutron-rich nuclei

    Science.gov (United States)

    Cao, X. G.; Cai, X. Z.; Ma, Y. G.; Fang, D. Q.; Zhang, G. Q.; Guo, W.; Chen, J. G.; Wang, J. S.

    2012-10-01

    Proton-neutron, neutron-neutron, and proton-proton momentum-correlation functions (Cpn,Cnn, and Cpp) are systematically investigated for 15C and other C-isotope-induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum-molecular-dynamics model complemented by the correlation after burner (crab) computation code. 15C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron-shell nucleus 14C. To study density dependence of the correlation function by removing the isospin effect, the initialized 15C projectiles are sampled from two kinds of density distribution from the relativistic mean-field (RMF) model in which the valence neutron of 15C is populated in both 1d5/2 and 2s1/2 states, respectively. The results show that the density distributions of the valence neutron significantly influence the nucleon-nucleon momentum-correlation function at large impact parameters and high incident energies. The extended density distribution of the valence neutron largely weakens the strength of the correlation function. The size of the emission source is extracted by fitting the correlation function by using the Gaussian source method. The emission source size as well as the size of the final-state phase space are larger for projectile samplings from more extended density distributions of the valence neutron, which corresponds to the 2s1/2 state in the RMF model. Therefore, the nucleon-nucleon momentum-correlation function can be considered as a potentially valuable tool to diagnose exotic nuclear structures, such as the skin and halo.

  11. Correlation between Onset Oxidation Temperature (OOT and Fourier Transform Infrared Spectroscopy (FTIR for monitoring the restabilization of Recycled Low-density Polyethylene (LDPE

    Directory of Open Access Journals (Sweden)

    Adhemar Ruvolo-Filho

    2013-01-01

    Full Text Available In this work a new method was developed for monitoring the oxidative stability of restabilized and non-restabilized low-density polyethylene (LDPE during multiple extrusion cycles. The method is based on correlations between Fourier Transform Infrared spectroscopy (FTIR and Onset Oxidation Temperature (OOT. Non-linear calibration curves correlating the concentration of primary or secondary antioxidants and the OOT values were obtained.

  12. Correlation between Onset Oxidation Temperature (OOT) and Fourier Transform Infrared Spectroscopy (FTIR) for monitoring the restabilization of Recycled Low-density Polyethylene (LDPE)

    Energy Technology Data Exchange (ETDEWEB)

    Ruvolo-Filho, Adhemar; Pelozzi, Tadeu Luiz Alonso, E-mail: adhemar@power.ufscar.br [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Quimica

    2013-07-01

    In this work a new method was developed for monitoring the oxidative stability of restabilized and non-restabilized low-density polyethylene (LDPE) during multiple extrusion cycles. The method is based on correlations between Fourier Transform Infrared Spectroscopy (FTIR) and Onset Oxidation Temperature (OOT). Non-linear calibration curves correlating the concentration of primary or secondary antioxidants and the OOT values were obtained. (author)

  13. Evaluation of exchange-correlation functionals for time-dependent density functional theory calculations on metal complexes.

    Science.gov (United States)

    Holland, Jason P; Green, Jennifer C

    2010-04-15

    The electronic absorption spectra of a range of copper and zinc complexes have been simulated by using time-dependent density functional theory (TD-DFT) calculations implemented in Gaussian03. In total, 41 exchange-correlation (XC) functionals including first-, second-, and third-generation (meta-generalized gradient approximation) DFT methods were compared in their ability to predict the experimental electronic absorption spectra. Both pure and hybrid DFT methods were tested and differences between restricted and unrestricted calculations were also investigated by comparison of analogous neutral zinc(II) and copper(II) complexes. TD-DFT calculated spectra were optimized with respect to the experimental electronic absorption spectra by use of a Matlab script. Direct comparison of the performance of each XC functional was achieved both qualitatively and quantitatively by comparison of optimized half-band widths, root-mean-squared errors (RMSE), energy scaling factors (epsilon(SF)), and overall quality-of-fit (Q(F)) parameters. Hybrid DFT methods were found to outperform all pure DFT functionals with B1LYP, B97-2, B97-1, X3LYP, and B98 functionals providing the highest quantitative and qualitative accuracy in both restricted and unrestricted systems. Of the functionals tested, B1LYP gave the most accurate results with both average RMSE and overall Q(F) unity (>0.990) for the copper complexes. The XC functional performance in spin-restricted TD-DFT calculations on the zinc complexes was found to be slightly worse. PBE1PBE, mPW1PW91 and B1LYP gave the most accurate results with typical RMSE and Q(F) values between 5.3 and 7.3%, and epsilon(SF) around 0.930. These studies illustrate the power of modern TD-DFT calculations for exploring excited state transitions of metal complexes.

  14. Correlating the Local Defect-Level Density with the Macroscopic Composition and Energetics of Chalcopyrite Thin-Film Surfaces.

    Science.gov (United States)

    Bröker, Sebastian; Kück, Dennis; Timmer, Alexander; Lauermann, Iver; Ümsür, Bünyamin; Greiner, Dieter; Kaufmann, Christian A; Mönig, Harry

    2015-06-17

    The unusual defect chemistry of polycrystalline Cu(In,Ga)Se2 (CIGSe) thin films is a main issue for a profound understanding of recombination losses in chalcopyrite thin-film solar cells. Especially, impurity-driven passivation of electronic levels due to point defects segregating at the surface and at grain boundaries is extensively debated. By combining current imaging tunneling spectroscopy with photoelectron spectroscopy, the local defect-level density and unusual optoelectronic grain-boundary properties of this material are correlated with the macroscopic energy levels and surface composition. Vacuum annealing of different CIGSe materials provides evidence that Na diffusion from the glass substrate does not affect the surface defect passivation or grain-boundary properties of standard Cu-poor materials. Furthermore, we find no major impact on the observed thermally activated dipole compensation or the accompanying change in surface band bending (up to 0.6 eV) due to Na. In contrast, Cu-rich CIGSe shows an opposing surface defect chemistry with only minor heat-induced band bending. Our results lead to a comprehensive picture, where the highly desirable type inversion at the p/n interface in standard chalcopyrite thin-film solar cells is dominated by band bending within the CIGSe absorber rather than the result of Na impurities or an n-type defect phase segregating at the interface. This is in accordance with recent studies suggesting a surface reconstruction as the origin for Cu depletion and band-gap widening at the surface of chalcopyrite thin films.

  15. Correlation of estrogen receptor alpha gene polymorphisms and bone mineral density in Chinese women with chronic periodontitis

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xuan; DAI Juan; LONG Yin; WU Hao; LI Xiao-juan; DING Yin

    2010-01-01

    Background Periodontitis and osteoporosis aro one of the frequently encountered diseases in post-menopausal women. Estrogen receptors (ERs) regulated bone metabolism. To investigate the possible effect of ER-alpha (α) gene polymorphisms on bone mineral density (BMD) in pre- and post-menopausal Chinese women with chronic periodontitis (CP), we provided sufficient quantitative information concerning the correlation between ER gene polymorphisms and BMD in periodontitis.Methods Sixty-five post-menopausal and eighty pro-menopausal CP women, and sixty post-menopausal healthy individuals were recruited in this study. Genomic DNA was extracted from oral mucosa swab sample of each subject by the Chelex-100 method. Determination of the ER-α polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique with Xbal and Pvull enzyme. The index for periodontal examination includes clinical attachment loss (CAL) and probing pocket depth (PPD). BMD was measured by dual-energy X-ray absorptiometry (DEXA).Results There were no significant differences between the ER-(α genotypes of Pvull and Xbal and BMD in post-menopausal and pro-menopausal CP patients, respectively (P >0.05). However, there was association between preand post-menopausal CP patients at BMD of lumbar spine L2-L4 (P=0.027) and Ward's BMD (P=0.004). Furthermore, the post-menopausal CP women who carried Pvull ∏ genotype presented significantly lower Ward's BMD than the pre-menopausal CP women (P=0.007), meanwhile, the post-menopausal CP women who carried Xbal AA genotype presented significantly lower spine L2-L4 BMD than the pre-menopausal CP women (P=0.003).Conclusions ER-(α gene polymorphisms may be a susceptible indicator for BMD variation of lumbar spine L2-L4 and Ward in Chinese pre- and post-menopausal women patients with CP.

  16. Calibrating Reaction Enthalpies: Use of Density Functional Theory and the Correlation Consistent Composite Approach in the Design of Photochromic Materials.

    Science.gov (United States)

    Letterman, Roger G; DeYonker, Nathan J; Burkey, Theodore J; Webster, Charles Edwin

    2016-12-22

    Acquisition of highly accurate energetic data for chromium-containing molecules and various chromium carbonyl complexes is a major step toward calibrating bond energies and thermal isomerization energies from mechanisms for Cr-centered photochromic materials being developed in our laboratories. The performance of six density functionals in conjunction with seven basis sets, utilizing Gaussian-type orbitals, has been evaluated for the calculation of gas-phase enthalpies of formation and enthalpies of reaction at 298.15 K on various chromium-containing systems. Nineteen molecules were examined: Cr(CO)6, Cr(CO)5, Cr(CO)5(C2H4), Cr(CO)5(C2ClH3), Cr(CO)5(cis-(C2Cl2H2)), Cr(CO)5(gem-(C2Cl2H2)), Cr(CO)5(trans-(C2Cl2H2)), Cr(CO)5(C2Cl3H), Cr(CO)5(C2Cl4), CrO2, CrF2, CrCl2, CrCl4, CrBr2, CrBr4, CrOCl2, CrO2Cl2, CrOF2, and CrO2F2. The performance of 69 density functionals in conjunction with a single basis set utilizing Slater-type orbitals (STO) and a zeroth-order relativistic approximation was also evaluated for the same test set. Values derived from density functional theory were compared to experimental values where available, or values derived from the correlation consistent composite approach (ccCA). When all reactions were considered, the functionals that exhibited the smallest mean absolute deviations (MADs, in kcal mol(-1)) from ccCA-derived values were B97-1 (6.9), VS98 (9.0), and KCIS (9.4) in conjunction with quadruple-ζ STO basis sets and B97-1 (9.3) in conjunction with cc-pVTZ basis sets. When considering only the set of gas-phase reaction enthalpies (ΔrH°gas), the functional that exhibited the smallest MADs from ccCA-derived values were B97-1 in conjunction with cc-pVTZ basis sets (9.1) and PBEPBE in conjunction with polarized valence triple-ζ basis set/effective core potential combination for Cr and augmented and multiple polarized triple-ζ Pople style basis sets (9.5). Also of interest, certainly because of known cancellation of errors, PBEPBE with the

  17. Pair correlation functions and the wavevector-dependent surface tension in a simple density functional treatment of the liquid-vapour interface

    Science.gov (United States)

    Parry, A. O.; Rascón, C.; Willis, G.; Evans, R.

    2014-09-01

    We study the density-density correlation function G(r, r‧) in the interfacial region of a fluid (or Ising-like magnet) with short-ranged interactions using square gradient density functional theory. Adopting a simple double parabola approximation for the bulk free-energy density, we first show that the parallel Fourier transform G(z, z‧ q) and local structure factor S(z q) separate into bulk and excess contributions. We attempt to account for both contributions by deriving an interfacial Hamiltonian, characterised by a wavevector dependent surface tension σ(q), and then reconstructing density correlations from correlations in the interface position. We show that the standard crossing criterion identification of the interface, as a surface of fixed density (or magnetization), does not explain the separation of G(z, z‧ q) and the form of the excess contribution. We propose an alternative definition of the interface position based on the properties of correlations between points that ‘float’ with the surface and show that this describes the full q and z dependence of the excess contributions to both G and S. However, neither the ‘crossing-criterion’ nor the new ‘floating interface’ definition of σ(q) are quantities directly measurable from the total structure factor Stot(q) which contains additional q dependence arising from the non-local relation between fluctuations in the interfacial position and local density. Since it is the total structure factor that is measured experimentally or in simulations, our results have repercussions for earlier attempts to extract and interpret σ(q).

  18. Comparison of three and four point bending evaluation of two adhesive bonding systems for glass-ceramic zirconia bi-layered ceramics.

    Science.gov (United States)

    Gee, C; Weddell, J N; Swain, M V

    2017-09-01

    To quantify the adhesion of two bonding approaches of zirconia to more aesthetic glass-ceramic materials using the Schwickerath (ISO 9693-2:2016) three point bend (3PB) [1] test to determine the fracture initiation strength and strain energy release rate associated with stable crack extension with this test and the Charalamabides et al. (1989) [2] four point bend (4PB) test. Two glass-ceramic materials (VITABLOCS Triluxe forte, Vita Zahnfabrik, Germany and IPS.emax CAD, Ivoclar Vivadent, Liechtenstein) were bonded to sintered zirconia (VITA InCeram YZ). The former was resin bonded using a dual-cure composite resin (Panavia F 2.0, Kuraray Medical Inc., Osaka, Japan) following etching and silane conditioning, while the IPS.emax CAD was glass bonded (IPS e.max CAD Crystall/Connect) during crystallization of the IPS.emax CAD. Specimens (30) of the appropriate dimensions were fabricated for the Schwickerath 3PB and 4PB tests. Strength values were determined from crack initiation while strain energy release rate values were determined from the minima in the force-displacement curves with the 3PB test (Schneider and Swain, 2015) [3] and for 4PB test from the plateau region of stable crack extension. Strength values for the resin and glass bonded glass ceramics to zirconia were 22.20±6.72MPa and 27.02±3.49MPa respectively. The strain energy release rates for the two methods used were very similar and for the glass bonding, (4PB) 15.14±5.06N/m (or J/m(2)) and (3PB) 16.83±3.91N/m and resin bonding (4PB) 8.34±1.93N/m and (3PB) 8.44±2.81N/m respectively. The differences in strength and strain energy release rate for the two bonding approaches were statistically significant (pceramics to zirconia. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  19. Does the epidermal nerve fibre density measured by skin biopsy in patients with peripheral neuropathies correlate with neuropathic pain?

    Science.gov (United States)

    Truini, A; Biasiotta, A; Di Stefano, G; Leone, C; La Cesa, S; Galosi, E; Piroso, S; Pepe, A; Giordano, C; Cruccu, G

    2014-04-01

    The different neuropathic pain types (e.g., ongoing burning pain and allodynia) are frequent and disabling complaints in patients with peripheral neuropathies. Although the reference standard technique for diagnosing painful small-fibre neuropathies is nerve fibre density assessment by skin biopsy, the relationship between the epidermal nerve fibre (ENF) density and neuropathic pain is still unclear. In a clinical and skin biopsy study designed to investigate whether changes in ENF density are directly related to pain, we enrolled 139 consecutive patients with distal symmetric peripheral neuropathy. All patients underwent clinical examination. The Neuropathic Pain Symptom Inventory was used to distinguish the different neuropathic pain types. A skin biopsy was conducted, and ENFs were immunostained with the antiprotein gene product 9.5, and their linear density was quantified with bright-field microscopy. No difference was found in ENF density between patients with and without neuropathic pain, nor between patients with and without ongoing burning pain. Conversely, ENF density was higher in patients with provoked pains (including mechanical dynamic allodynia) than in those without. The variable association between ENF density and symptoms of neuropathic pain supports the idea that neuropathic pain symptoms arise through distinct underlying mechanisms. The lack of relationship between ongoing burning pain and ENF density suggests that this type of pain reflects factors other than loss of nociceptive afferents. The association between ENF density and provoked pain (including mechanical dynamic allodynia) suggests that this type of pain might be mediated by spared and sensitised nociceptive afferents.

  20. A statistical model for estimation of fish density including correlation in size, space, time and between species from research survey data

    DEFF Research Database (Denmark)

    Nielsen, J. Rasmus; Kristensen, Kasper; Lewy, Peter

    2014-01-01

    Trawl survey data with high spatial and seasonal coverage were analysed using a variant of the Log Gaussian Cox Process (LGCP) statistical model to estimate unbiased relative fish densities. The model estimates correlations between observations according to time, space, and fish size and includes...

  1. The Correlation between the Triglyceride to High Density Lipoprotein Cholesterol Ratio and Computed Tomography-Measured Visceral Fat and Cardiovascular Disease Risk Factors in Local Adult Male Subjects.

    Science.gov (United States)

    Park, Hye-Rin; Shin, Sae-Ron; Han, A Lum; Jeong, Yong Joon

    2015-11-01

    We studied the association between the triglyceride to high-density lipoprotein cholesterol ratio and computed tomography-measured visceral fat as well as cardiovascular risk factors among Korean male adults. We measured triglycerides, high density lipoprotein cholesterol, body mass, waist circumference, fasting plasma glucose, hemoglobin A1c, systolic blood pressure, diastolic blood pressure, visceral fat, and subcutaneous fat among 372 Korean men. The visceral fat and subcutaneous fat areas were measured by computed tomography using a single computed tomography slice at the L4-5 lumbar level. We analyzed the association between the triglyceride to high density lipoprotein cholesterol ratio and visceral fat as well as cardiovascular risk factors. A positive correlation was found between the triglyceride to high density lipoprotein cholesterol ratio and variables such as body mass index, waist circumference, fasting plasma glucose, hemoglobin A1c, visceral fat, and the visceral-subcutaneous fat ratio. However, there was no significant correlation between the triglyceride to high density lipoprotein cholesterol ratio and subcutaneous fat or blood pressure. Multiple logistic regression analyses revealed significant associations between a triglyceride to high density lipoprotein cholesterol ratio ≥3 and diabetes, a body mass index ≥25 kg/m(2), a waist circumference ≥90 cm, and a visceral fat area ≥100 cm(2). The triglyceride to high density lipoprotein cholesterol ratio was not significantly associated with hypertension. There were significant associations between the triglyceride to high density lipoprotein cholesterol ratio and body mass, waist circumference, diabetes, and visceral fat among a clinical sample of Korean men. In the clinical setting, the triglyceride to high density lipoprotein cholesterol ratio may be a simple and useful indicator for visceral obesity and cardiovascular disease.

  2. A statistical model for estimation of fish density including correlation in size, space, time and between species from research survey data.

    Directory of Open Access Journals (Sweden)

    J Rasmus Nielsen

    Full Text Available Trawl survey data with high spatial and seasonal coverage were analysed using a variant of the Log Gaussian Cox Process (LGCP statistical model to estimate unbiased relative fish densities. The model estimates correlations between observations according to time, space, and fish size and includes zero observations and over-dispersion. The model utilises the fact the correlation between numbers of fish caught increases when the distance in space and time between the fish decreases, and the correlation between size groups in a haul increases when the difference in size decreases. Here the model is extended in two ways. Instead of assuming a natural scale size correlation, the model is further developed to allow for a transformed length scale. Furthermore, in the present application, the spatial- and size-dependent correlation between species was included. For cod (Gadus morhua and whiting (Merlangius merlangus, a common structured size correlation was fitted, and a separable structure between the time and space-size correlation was found for each species, whereas more complex structures were required to describe the correlation between species (and space-size. The within-species time correlation is strong, whereas the correlations between the species are weaker over time but strong within the year.

  3. Collapse-type shrinkage characteristics in plantation-grown eucalypts: I . Correlations of basic density and some structural indices with shrinkage and collapse properties

    Institute of Scientific and Technical Information of China (English)

    WUYi-qiang; HAYASHIKazuo; LIUYuan; CAIYing-chun; SUGIMORIMasatoshi; LUOJian-ju

    2005-01-01

    Collapse-type shrinkage is one of highly refractory drying defects in low-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD), microfibril angle (MFA), double fibre cell wall thickness (DWT), proportion of ray parenchyma (RP), unit cell wall shrinkage, total shrinkage and residual collapse, which are associated with collapse-type shrinkage characteristics, were investigated by using simple regression method for three species of collapse-susceptible Eucalyptus urophyll, E. grandis and E.urophyllaxE.grandis, planted at Dong-Men Forest Farm in Guangxi autonomous region, China. The results indicated that : unit cell wall shrinkage had a extremely strong positive correlation with BD, moderately strong positive correlation with DWT, and a weakly or moderately negative correlation with RP and MFA; total shrinkage was positively correlated with BD, DWT and RP and negatively related to MFA, but not able to be predicted ideally by any examined factors alone owing to lower R2 value (R2≤0.5712); residual collapse was negatively correlated with BD and DWT, linearly positively correlated with MFA, and had strongly positive linear correlation with RP. It is concluded that BD can be used as single factor (R2≥0.9412) to predicate unit cell wall shrinkage and RP is the relatively sound indicator for predicting residual collapse

  4. Detection of large scale intrinsic ellipticity-density correlation from the Sloan Digital Sky Survey and implications for weak lensing surveys

    CERN Document Server

    Mandelbaum, R; Ishak, M; Seljak, U; Brinkmann, J; Mandelbaum, Rachel; Hirata, Christopher M.; Ishak, Mustapha; Seljak, Uros; Brinkmann, Jonathan

    2006-01-01

    The power spectrum of weak lensing shear caused by large-scale structure is an emerging tool for precision cosmology, in particular for measuring the effects of dark energy on the growth of structure at low redshift. One potential source of systematic error is intrinsic alignments of ellipticities of neighbouring galaxies (II correlation) that could mimic the correlations due to lensing. A related possibility pointed out by Hirata and Seljak (2004) is correlation between the intrinsic ellipticities of galaxies and the density field responsible for gravitational lensing shear (GI correlation). We present constraints on both the II and GI correlations using 265 908 spectroscopic galaxies from the SDSS, and using galaxies as tracers of the mass in the case of the GI analysis. The availability of redshifts in the SDSS allows us to select galaxies at small radial separations, which both reduces noise in the intrinsic alignment measurement and suppresses galaxy- galaxy lensing (which otherwise swamps the GI correla...

  5. Ab initio-driven nuclear energy density functional method. A proposal for safe/correlated/improvable parametrizations of the off-diagonal EDF kernels

    Energy Technology Data Exchange (ETDEWEB)

    Duguet, T. [IRFU/Service de Physique Nucleaire, CEA, Centre de Saclay, Gif-sur-Yvette (France); Instituut voor Kern- en Stralingsfysica, KU Leuven, Leuven (Belgium); Michigan State University, National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, East Lansing, MI (United States); Bender, M. [Centre d' Etudes Nucleaires de Bordeaux Gradignan, Universite Bordeaux, UMR5797, Gradignan (France); Centre d' Etudes Nucleaires de Bordeaux Gradignan, CNRS/IN2P3, UMR5797, Gradignan (France); Ebran, J.P. [CEA, DAM, DIF, Arpajon (France); Lesinski, T.; Soma, V. [IRFU/Service de Physique Nucleaire, CEA, Centre de Saclay, Gif-sur-Yvette (France)

    2015-12-15

    This programmatic paper lays down the possibility to reconcile the necessity to resum many-body correlations into the energy kernel with the fact that safe multi-reference energy density functional (EDF) calculations cannot be achieved whenever the Pauli principle is not enforced, as is for example the case when many-body correlations are parametrized under the form of empirical density dependencies. Our proposal is to exploit a newly developed ab initio many-body formalism to guide the construction of safe, explicitly correlated and systematically improvable parametrizations of the off-diagonal energy and norm kernels that lie at the heart of the nuclear EDF method. The many-body formalism of interest relies on the concepts of symmetry breaking and restoration that have made the fortune of the nuclear EDF method and is, as such, amenable to this guidance. After elaborating on our proposal, we briefly outline the project we plan to execute in the years to come. (orig.)

  6. Auxiliary basis sets for density fitting second-order Møller-Plesset perturbation theory: correlation consistent basis sets for the 5d elements Hf-Pt.

    Science.gov (United States)

    Hill, J Grant

    2011-07-28

    Auxiliary basis sets specifically matched to the correlation consistent cc-pVnZ-PP, cc-pwCVnZ-PP, aug-cc-pVnZ-PP, and aug-cc-pwCVnZ-PP orbital basis sets (used in conjunction with pseudopotentials) for the 5d transition metal elements Hf-Pt have been optimized for use in density fitting second-order Møller-Plesset perturbation theory and other correlated ab initio methods. Calculations of the second-order Møller-Plesset perturbation theory correlation energy, for a test set of small to medium sized molecules, indicate that the density fitting error when utilizing these sets is negligible at three to four orders of magnitude smaller than the orbital basis set incompleteness error.

  7. Cohesive properties of (Cu,Ni)-(In,Sn) intermetallics: Database, electron-density correlations and interpretation of bonding trends

    Science.gov (United States)

    Ramos, S. B.; González Lemus, N. V.; Cabeza, G. F.; Fernández Guillermet, A.

    2016-06-01

    This paper presents a systematic and comparative study of the composition and volume dependence of the cohesive properties for a large group of Me-X intermetallic phases (IPs) with Me=Cu,Ni and X=In,Sn, which are of interest in relation with the design of lead-free soldering (LFS) alloys. The work relies upon a database with total-energy versus volume information developed by using projected augmented waves (PAW) calculations. In previous papers by the current authors it was shown that these results account satisfactorily for the direct and indirect experimental data available. In the present work, the database is further expanded to investigate the composition dependence of the volume (V0), and the composition and volume dependence of the bulk modulus (B0) and cohesive energy (Ecoh). On these bases, an analysis is performed of the systematic effects of replacing Cu by Ni in several Me-X phases (Me=Cu,Ni and X=In,Sn) reported as stable and metastable, as well as various hypothetical compounds involved in the thermodynamic modeling of IPs using the Compound-Energy Formalism. Moreover, it is shown that the cohesion-related quantities (B0/V0)½ and (Ecoh½/V0) can be correlated with a parameter expressing the number of valence electrons per unit volume. These findings are compared in detail with related relations involving the Miedema empirical electron density at the boundary of the Wigner-Seitz cell. In view of the co-variation of the cohesive properties, Ecoh is selected as a key property and its composition and structure dependence is examined in terms of a theoretical view of the bonding which involves the hybridization of the d-states of Cu or Ni with the s and p-states of In or Sn, for this class of compounds. In particular, a comparative analysis is performed of the DOS of various representative, iso-structural Me-X compounds. Various effects of relevance to understand the consequences of replacing Cu by Ni in LFS alloys are highlighted and explained

  8. Performance of density functional theory for 3d transition metal-containing complexes: utilization of the correlation consistent basis sets.

    Science.gov (United States)

    Tekarli, Sammer M; Drummond, Michael L; Williams, T Gavin; Cundari, Thomas R; Wilson, Angela K

    2009-07-30

    The performance of 44 density functionals used in conjunction with the correlation consistent basis sets (cc-pVnZ where n = T and Q) has been assessed for the gas-phase enthalpies of formation at 298.15 K of 3d transition metal (TM) containing systems. Nineteen molecules were examined: ScS, VO, VO(2), Cr(CO)(6), MnS, MnCl(2), Mn(CO)(5)Cl, FeCl(3), Fe(CO)(5), CoH(CO)(4), NiCl(2), Ni(CO)(4), CuH, CuF, CuCl, ZnH, ZnO, ZnCl, and Zn(CH(3))(2). Of the functionals examined, the functionals that resulted in the smallest mean absolute deviation (MAD, in parentheses, kcal mol(-1)) from experiment were B97-1 (6.9), PBE1KCIS (8.1), TPSS1KCIS (9.6), B97-2 (9.7), and B98 (10.7). All five of these functionals include some degree of Hartree-Fock (HF) exchange. The impact of increasing the basis set from cc-pVTZ to cc-pVQZ was found to be slight for the generalized gradient approximation (GGA) and meta-GGA (MGGA) functionals studied, indicating basis set saturation at the triple-zeta level. By contrast, for most of the generalized gradient exchange (GGE), hybrid GGA (HGGA), and hybrid meta-GGA (HMGGA) functionals considered, improvements in the average MAD of 2-3 kcal mol(-1) were seen upon progressing to a quadruple-zeta level basis set. Overall, it was found that the functionals that include Hartree-Fock exchange performed best overall, but those with greater than 40% HF exchange exhibit significantly poor performance for the prediction of enthalpies of formation for 3d TM complexes. Carbonyl-containing complexes, a mainstay in organometallic TM chemistry, are demonstrated to be exceedingly difficult to describe accurately with all but 2 of the 44 functionals considered. The most accurate functional, for both CO-containing and CO-free compounds, is B97-1/cc-pVQZ, which is shown to be capable of yielding results within 1 kcal mol(-1) of high-level ab initio composite methodologies.

  9. Astrocytosis measured by {sup 11}C-deprenyl PET correlates with decrease in gray matter density in the parahippocampus of prodromal Alzheimer's patients

    Energy Technology Data Exchange (ETDEWEB)

    Choo, IL Han [Karolinska Institutet, Department NVS, Center for Alzheimer Research, Translational Alzheimer Neurobiology, Stockholm (Sweden); Chosun University, Department of Neuropsychiatry, School of Medicine, Gwangju (Korea, Republic of); Carter, Stephen F. [Karolinska Institutet, Department NVS, Center for Alzheimer Research, Translational Alzheimer Neurobiology, Stockholm (Sweden); Manchester University, Wolfson Imaging Center, Manchester (United Kingdom); Schoell, Michael L. [Karolinska Institutet, Department NVS, Center for Alzheimer Research, Translational Alzheimer Neurobiology, Stockholm (Sweden); Gothenburg University, Med Tech West, Department of Neuroscience and Rehabilitation, Gothenburg (Sweden); Nordberg, Agneta [Karolinska Institutet, Department NVS, Center for Alzheimer Research, Translational Alzheimer Neurobiology, Stockholm (Sweden); Karolinska University Hospital Huddinge, Department of Geriatric Medicine, Stockholm (Sweden); Karolinska Institutet, Department NVS, Center for Alzheimer Research, Translational Alzheimer Neurobiology, Huddinge (Sweden)

    2014-11-15

    The Alzheimer's disease (AD) pathology is characterized by fibrillar amyloid deposits and neurofibrillary tangles, as well as the activation of astrocytosis, microglia activation, atrophy, dysfunctional synapse, and cognitive impairments. The aim of this study was to test the hypothesis that astrocytosis is correlated with reduced gray matter density in prodromal AD. Twenty patients with AD or mild cognitive impairment (MCI) underwent multi-tracer positron emission tomography (PET) studies with {sup 11}C-Pittsburgh compound B ({sup 11}C-PIB), {sup 18}F-Fluorodeoxyglucose ({sup 18}F-FDG), and {sup 11}C-deuterium-L-deprenyl ({sup 11}C-DED) PET imaging, as well as magnetic resonance imaging (MRI) scanning, cerebrospinal fluid (CSF) biomarker analysis, and neuropsychological assessments. The parahippocampus was selected as a region of interest, and each value was calculated for four different imaging modalities. Correlation analysis was applied between DED slope values and gray matter (GM) densities by MRI. To further explore possible relationships, correlation analyses were performed between the different variables, including the CSF biomarker. A significant negative correlation was obtained between DED slope values and GM density in the parahippocampus in PIB-positive (PIB + ve) MCI patients (p = 0.025) (prodromal AD). Furthermore, in exploratory analyses, a positive correlation was observed between PIB-PET retention and DED binding in AD patients (p = 0.014), and a negative correlation was observed between PIB retention and CSF Aβ42 levels in MCI patients (p = 0.021), while the GM density and CSF total tau levels were negatively correlated in both PIB + ve MCI (p = 0.002) and MCI patients (p = 0.001). No significant correlation was observed with FDG-PET and with any of the other PET, MRI, or CSF biomarkers. High astrocytosis levels in the parahippocampus of PIB + ve MCI (prodromal AD) patients suggest an early preclinical influence on cellular tissue loss. The

  10. Linear and curvilinear correlations of brain gray matter volume and density with age using voxel-based morphometry with the Akaike information criterion in 291 healthy children.

    Science.gov (United States)

    Taki, Yasuyuki; Hashizume, Hiroshi; Thyreau, Benjamin; Sassa, Yuko; Takeuchi, Hikaru; Wu, Kai; Kotozaki, Yuka; Nouchi, Rui; Asano, Michiko; Asano, Kohei; Fukuda, Hiroshi; Kawashima, Ryuta

    2013-08-01

    We examined linear and curvilinear correlations of gray matter volume and density in cortical and subcortical gray matter with age using magnetic resonance images (MRI) in a large number of healthy children. We applied voxel-based morphometry (VBM) and region-of-interest (ROI) analyses with the Akaike information criterion (AIC), which was used to determine the best-fit model by selecting which predictor terms should be included. We collected data on brain structural MRI in 291 healthy children aged 5-18 years. Structural MRI data were segmented and normalized using a custom template by applying the diffeomorphic anatomical registration using exponentiated lie algebra (DARTEL) procedure. Next, we analyzed the correlations of gray matter volume and density with age in VBM with AIC by estimating linear, quadratic, and cubic polynomial functions. Several regions such as the prefrontal cortex, the precentral gyrus, and cerebellum showed significant linear or curvilinear correlations between gray matter volume and age on an increasing trajectory, and between gray matter density and age on a decreasing trajectory in VBM and ROI analyses with AIC. Because the trajectory of gray matter volume and density with age suggests the progress of brain maturation, our results may contribute to clarifying brain maturation in healthy children from the viewpoint of brain structure.

  11. A modified method for accurate correlation between the craze density and the optomechanical properties of fibers using Pluta microscope.

    Science.gov (United States)

    Sokkar, T Z N; El-Farahaty, K A; El-Bakary, M A; Omar, E Z; Hamza, A A

    2016-05-01

    A modified method was suggested to improve the performance of the Pluta microscope in its nonduplicated mode in the calculation of the areal craze density especially, for relatively low draw ratio (low areal craze density). This method decreases the error that is resulted from the similarity between the formed crazes and the dark fringes of the interference pattern. Furthermore, an accurate method to calculate the birefringence and the orientation function of the drawn fibers via nonduplicated Pluta polarizing interference microscope for high areal craze density (high draw ratio) was suggested. The advantage of the suggested method is to relate the optomechanical properties of the tested fiber with the areal craze density, for the same region of the fiber material.

  12. Both electrical stimulation thresholds and SMI-32-immunoreactive retinal ganglion cell density correlate with age in S334ter line 3 rat retina.

    Science.gov (United States)

    Chan, Leanne L H; Lee, Eun-Jin; Humayun, Mark S; Weiland, James D

    2011-06-01

    Electrical stimulation threshold and retinal ganglion cell density were measured in a rat model of retinal degeneration. We performed in vivo electrophysiology and morphometric analysis on normal and S334ter line 3 (RD) rats (ages 84-782 days). We stimulated the retina in anesthetized animals and recorded evoked responses in the superior colliculus. Current pulses were delivered with a platinum-iridium (Pt-Ir) electrode of 75-μm diameter positioned on the epiretinal surface. In the same animals used for electrophysiology, SMI-32 immunolabeling of the retina enabled ganglion cell counting. An increase in threshold currents positively correlated with age of RD rats. SMI-32-labeled retinal ganglion cell density negatively correlated with age of RD rats. ANOVA shows that RD postnatal day (P)100 and P300 rats have threshold and density similar to normal rats, but RD P500 and P700 rats have threshold and density statistically different from normal rats (P < 0.05). Threshold charge densities were within the safety limits of Pt for all groups and pulse configurations, except at RD P600 and RD P700, where pulses were only safe up to 1- and 0.2-ms duration, respectively. Preservation of ganglion cells may enhance the efficiency and safety of electronic retinal implants.

  13. Correlation for the estimation of the density of fatty acid esters fuels and its implications. A proposed Biodiesel Cetane Index.

    Science.gov (United States)

    Lapuerta, Magín; Rodríguez-Fernández, José; Armas, Octavio

    2010-09-01

    Biodiesel fuels (methyl or ethyl esters derived from vegetables oils and animal fats) are currently being used as a means to diminish the crude oil dependency and to limit the greenhouse gas emissions of the transportation sector. However, their physical properties are different from traditional fossil fuels, this making uncertain their effect on new, electronically controlled vehicles. Density is one of those properties, and its implications go even further. First, because governments are expected to boost the use of high-biodiesel content blends, but biodiesel fuels are denser than fossil ones. In consequence, their blending proportion is indirectly restricted in order not to exceed the maximum density limit established in fuel quality standards. Second, because an accurate knowledge of biodiesel density permits the estimation of other properties such as the Cetane Number, whose direct measurement is complex and presents low repeatability and low reproducibility. In this study we compile densities of methyl and ethyl esters published in literature, and proposed equations to convert them to 15 degrees C and to predict the biodiesel density based on its chain length and unsaturation degree. Both expressions were validated for a wide range of commercial biodiesel fuels. Using the latter, we define a term called Biodiesel Cetane Index, which predicts with high accuracy the Biodiesel Cetane Number. Finally, simple calculations prove that the introduction of high-biodiesel content blends in the fuel market would force the refineries to reduce the density of their fossil fuels.

  14. Nucleon-nucleon momentum correlation function as a probe of the density distribution of valence neutron in neutron-rich nucleus

    CERN Document Server

    Cao, X G; Ma, Y G; Fang, D Q; Zhang, G Q; Guo, W; Chen, J G; Wang, J S; 10.1103/PhysRevC.86.044620

    2012-01-01

    Proton-neutron, neutron-neutron and proton-proton momentum correlation functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for $^{15}$C and other C isotopes induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum molecular dynamics (IDQMD) model complemented by the CRAB (correlation after burner) computation code. $^{15}$C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron shell nucleus $^{14}$C. In order to study density dependence of correlation function by removing the isospin effect, the initialized $^{15}$C projectiles are sampled from two kinds of density distribution from RMF model, in which the valence neutron of $^{15}$C is populated on both 1$d$5/2 and 2$s$1/2 states, respectively. The results show that the density distributions of valence neutron significantly influence nucleon-nucleon momentum correlation function at large impact parameter and high incident energy. T...

  15. Density-functional theory (hyper)polarizabilities of push-pull pi-conjugated systems: treatment of exact exchange and role of correlation.

    Science.gov (United States)

    Bulat, Felipe A; Toro-Labbé, Alejandro; Champagne, Benoît; Kirtman, Bernard; Yang, Weitao

    2005-07-01

    The performance of the optimized effective potential procedure for exact exchange in calculating static electric-field response properties of push-pull pi-conjugated systems has been studied, with an emphasis on NO2-(CH=CH)n-NH2 chains. Good agreement with Hartree-Fock dipole moments and (hyper)polarizabilities is obtained; particularly noteworthy is the chain length dependence for beta/n. Thus, the problem that conventional density-functional theory functionals dramatically overestimate these properties is largely solved, although there remains a significant correlation contribution that cannot be accounted for with current correlation functionals.

  16. Range-separated time-dependent density-functional theory with a frequency-dependent second-order Bethe-Salpeter correlation kernel

    CERN Document Server

    Rebolini, Elisa

    2015-01-01

    We present a range-separated linear-response time-dependent density-functional theory (TDDFT) which combines a density-functional approximation for the short-range response kernel and a frequency-dependent second-order Bethe-Salpeter approximation for the long-range response kernel. This approach goes beyond the adiabatic approximation usually used in linear-response TDDFT and aims at improving the accuracy of calculations of electronic excitation energies of molecular systems. A detailed derivation of the frequency-dependent second-order Bethe-Salpeter correlation kernel is given using many-body Green-function theory. Preliminary tests of this range-separated TDDFT method are presented for the calculation of excitation energies of four small molecules: N2, CO2, H2CO, and C2H4. The results suggest that the addition of the long-range second-order Bethe-Salpeter correlation kernel overall slightly improves the excitation energies.

  17. Densities and Viscosities of 1-butyl-3-methylimidazolium Hexafluorophosphate [bmim][PF6]+CO2 Binary System:Determination and Correlation

    Institute of Scientific and Technical Information of China (English)

    乔燕; 闫方友; 夏淑倩; 马沛生

    2013-01-01

    A gas-dissolving device was designed and connected to the falling-body viscometer, which was used to determine the viscosities of liquids in our lab before. The equipment can be used to determine the gas composition, the densities and viscosities of the solution at the same time. The densities and viscosities of [bmim][PF6]+CO2 binary system were determined in the temperature range of 313.2 to 413.2 K and pressure range of 5.0 to 25.0 MPa by the equipment. Then the viscosities of [bmim][PF6]+CO2 binary system at constant temperature, constant pres-sure, and different temperature and pressure were correlated, respectively. For the correlation at different tempera-ture and different pressure for different concentration mixtures the average relative deviation ARD is 0.037.

  18. Assessing Hubbard-corrected AM05+U and PBEsol+U density functionals for strongly correlated oxides CeO2 and Ce2O3.

    Science.gov (United States)

    Weck, Philippe F; Kim, Eunja

    2016-09-29

    The structure-property relationships of bulk CeO2 and Ce2O3 have been investigated using AM05 and PBEsol exchange-correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U) and density functional perturbation theory (DFPT+U). Compared with conventional PBE+U, RPBE+U, PW91+U and LDA+U functionals, AM05+U and PBEsol+U describe experimental crystalline parameters and properties of CeO2 and Ce2O3 with superior accuracy, especially when +U is chosen close to its value derived by the linear-response approach. The present findings call for a reexamination of some of the problematic oxide materials featuring strong f- and d-electron correlation using AM05+U and PBEsol+U.

  19. Plasticity in maximum stomatal conductance constrained by negative correlation between stomatal size and density: an analysis using Eucalyptus globulus

    National Research Council Canada - National Science Library

    Franks, Peter J; Drake, Paul L; Beerling, David J

    2009-01-01

    .... However, using basic equations for gas diffusion through stomata of different sizes, we show that a negative correlation between S and D offers several advantages, including plasticity in gwmax...

  20. Evaluation of serum undercarboxylated osteocalcin in premenopausal rheumatoid arthritis patients: its correlation with disease activity and bone mineral density

    Directory of Open Access Journals (Sweden)

    Heba A Esaily

    2016-01-01

    Conclusion Serum level of ucOC (which is a mirror of vitamin K deficiency was found to be higher in premenopausal RA patients than controls and correlated positively with disease activity and inversely with BMD measurement.

  1. Correlation of the indices of susceptibility weighted imaging and perfusion imaging with the expression of microvessel density and vascular endothelial growth factor in astrocytic tumor

    Institute of Scientific and Technical Information of China (English)

    韩彤

    2014-01-01

    Objective To detect the correlation of the expression of microvessel density(MVD)and vascular endothelial growth factor(VEGF)with the semi-quantivative indices of susceptibility weighted imaging(SWI)and perfusion imaging(PI)in astrocytic tumor.Methods SWI and PI were performed in 98 patients with varing grades of astrocytic tumors.According to the World Health Organization(WHO)classification of central nervous system tumors and grading criteria:8 cases of pilocytic astrocytoma(gradeⅠ,1

  2. Reporting Recommended Patch Density from Vehicle Panel Vibration Convergence Studies using both DAF and TBL Fits of the Spatial Correlation Function

    Science.gov (United States)

    Smith, Andrew M.; Davis, Robert Ben; LaVerde, Bruce T.; Jones, Douglas C.; Band, Jonathon L.

    2012-01-01

    Using the patch method to represent the continuous spatial correlation function of a phased pressure field over a structural surface is an approximation. The approximation approaches the continuous function as patches become smaller. Plotting comparisons of the approximation vs the continuous function may provide insight revealing: (1) For what patch size/density should the approximation be very good? (2) What the approximation looks like when it begins to break down? (3) What the approximation looks like when the patch size is grossly too large. Following these observations with a convergence study using one FEM may allow us to see the importance of patch density. We may develop insights that help us to predict sufficient patch density to provide adequate convergence for the intended purpose frequency range of interest

  3. Correlations Between the Density of Tryptase Positive Mast Cells (DMCT and that of New Blood Vessels (CD105+ in Patients with Gastric Cancer

    Directory of Open Access Journals (Sweden)

    Micu Gianina Viorica

    2016-06-01

    Full Text Available Mast cells proteases, tryptase and chymase are directly involved in the growth and progression of solid tumors due to their important role in tumor angiogenesis. We examined the density of tryptase positive mast cells and the mean density of new blood vessels in gastric malignant tumors of patients with and without Helicobacter pylori infection, using immunohistochemical staining for tryptase (for mast cells and CD 105 (for new vessels. Tryptase and CD 105 expression was detected in gastrectomy specimens. In this study, mast cell density correlates with angiogenesis and the growth and progression of gastric cancer. It also shows that the participation of Helicobacter pylori infection in the growth and progress of gastric neoplasia is due to an increase of peritumoral angiogenesis, with subsequent local and distant tumor spread and perivascular growth, but without perineural and nodal involvement.

  4. Charged plate in asymmetric electrolytes: One-loop renormalization of surface charge density and Debye length due to ionic correlations

    Science.gov (United States)

    Ding, Mingnan; Lu, Bing-Sui; Xing, Xiangjun

    2016-10-01

    Self-consistent field theory (SCFT) is used to study the mean potential near a charged plate inside a m :-n electrolyte. A perturbation series is developed in terms of g =4 π κ b , where b a n d 1 /κ are Bjerrum length and bare Debye length, respectively. To the zeroth order, we obtain the nonlinear Poisson-Boltzmann theory. For asymmetric electrolytes (m ≠n ), the first order (one-loop) correction to mean potential contains a secular term, which indicates the breakdown of the regular perturbation method. Using a renormalizaton group transformation, we remove the secular term and obtain a globally well-behaved one-loop approximation with a renormalized Debye length and a renormalized surface charge density. Furthermore, we find that if the counterions are multivalent, the surface charge density is renormalized substantially downwards and may undergo a change of sign, if the bare surface charge density is sufficiently large. Our results agrees with large MC simulation even when the density of electrolytes is relatively high.

  5. Gray Matter Density Negatively Correlates with Duration of Heroin Use in Young Lifetime Heroin-Dependent Individuals

    Science.gov (United States)

    Yuan, Yi; Zhu, Zude; Shi, Jinfu; Zou, Zhiling; Yuan, Fei; Liu, Yijun; Lee, Tatia M. C.; Weng, Xuchu

    2009-01-01

    Numerous studies have documented cognitive impairments and hypoactivity in the prefrontal and anterior cingulate cortices in drug users. However, the relationships between opiate dependence and brain structure changes in heroin users are largely unknown. In the present study, we measured the density of gray matter (DGM) with voxel-based…

  6. Multispin correlations and pseudo-thermalization of the transient density matrix in solid-state NMR: free induction decay and magic echo

    Science.gov (United States)

    Morgan, Steven W.; Oganesyan, Vadim; Boutis, Gregory S.

    2013-01-01

    Quantum unitary evolution typically leads to thermalization of generic interacting many-body systems. There are very few known general methods for reversing this process, and we focus on the magic echo, a radio-frequency pulse sequence known to approximately “rewind” the time evolution of dipolar coupled homonuclear spin systems in a large magnetic field. By combining analytic, numerical, and experimental results we systematically investigate factors leading to the degradation of magic echoes, as observed in reduced revival of mean transverse magnetization. Going beyond the conventional analysis based on mean magnetization we use a phase encoding technique to measure the growth of spin correlations in the density matrix at different points in time following magic echoes of varied durations and compare the results to those obtained during a free induction decay (FID). While considerable differences are documented at short times, the long-time behavior of the density matrix appears to be remarkably universal among the types of initial states considered – simple low order multispin correlations are observed to decay exponentially at the same rate, seeding the onset of increasingly complex high order correlations. This manifestly athermal process is constrained by conservation of the second moment of the spectrum of the density matrix and proceeds indefinitely, assuming unitary dynamics. PMID:23710125

  7. Correlation of fluid properties and geochemical parameters with heavy oil viscosity and density on trans-regional scale

    Energy Technology Data Exchange (ETDEWEB)

    Lehne, E.; Rojas, K.; McCarthy, K.; Taylor, S.D. [Schlumberger (Canada)

    2011-07-01

    Heavy oils around the world are characterized by high specific gravity and high contents of heavy components but their viscosity differs from one reservoir to another. This research aimed at finding correlations of geochemical characteristics with oil viscosity for heavy oil from different basins. This study was conducted on 15 heavy oil samples from northern and southern America and from Asia; the samples were characterized using gas chromatography, capillarity viscometer, data from stable carbon isotopes, SARA analysis, GC-FID and freezing point depression. Results showed that the degradation-viscosity correlation observed on a regional scale cannot be applied to the worldwide scale, and determined that, at that scale, oil viscosity depends on the original oil maturity and organofacies characteristics. In addition, biomarkers were found to help limit potential oil viscosity although they did not show a direct correlation. This study showed that original oil maturity and organofacies characteristics have to be taken into account in predictive models of oil viscosity.

  8. Microstructural and crystallographic imperfections of MgB2 superconducting wire and their correlation with the critical current density

    Directory of Open Access Journals (Sweden)

    Mohammed Shahabuddin

    2014-01-01

    Full Text Available A comprehensive study of the effects of structural imperfections in MgB2 superconducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB2 material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the π and σ bands of MgB2, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB2, however, even at low sintering temperature, and thus block current transport paths.

  9. Mast Cells Density Positive to Tryptase Correlate with Microvascular Density in both Primary Gastric Cancer Tissue and Loco-Regional Lymph Node Metastases from Patients That Have Undergone Radical Surgery.

    Science.gov (United States)

    Ammendola, Michele; Sacco, Rosario; Zuccalà, Valeria; Luposella, Maria; Patruno, Rosa; Gadaleta, Pietro; Zizzo, Nicola; Gadaleta, Cosmo Damiano; De Sarro, Giovambattista; Sammarco, Giuseppe; Oltean, Mihai; Ranieri, Girolamo

    2016-11-15

    Mast Cells (MCs) play a role in immune responses and more recently MCs have been involved in tumoral angiogenesis. In particular MCs can release tryptase, a potent in vivo and in vitro pro-angiogenic factor via proteinase-activated receptor-2 (PAR-2) activation and mitogen-activated protein kinase (MAPK) phosphorylation. MCs can release tryptase following c-Kit receptor activation. Nevertheless, no data are available concerning the relationship among MCs Density Positive to Tryptase (MCDPT) and Microvascular Density (MVD) in both primary gastric cancer tissue and loco-regional lymph node metastases. A series of 75 GC patients with stage T2-3N2-3M₀ (by AJCC for Gastric Cancer Seventh Edition) undergone to radical surgery were selected for the study. MCDPT and MVD were evaluated by immunohistochemistry and by image analysis system and results were correlated each to other in primary tumor tissue and in metastatic lymph nodes harvested. Furthermore, tissue parameters were correlated with important clinico-pathological features. A significant correlation between MCDPT and MVD was found in primary gastric cancer tissue and lymph node metastases. Pearson t-test analysis (r ranged from 0.74 to 0.79; p-value ranged from 0.001 to 0.003). These preliminary data suggest that MCDPT play a role in angiogenesis in both primary tumor and in lymph node metastases from GC. We suggest that MCs and tryptase could be further evaluated as novel targets for anti-angiogenic therapies.

  10. Correlations Between the Gradient of Contrast Density, Evaluated by Cardio CT, and Functional Significance of Coronary Artery Stenosis

    Directory of Open Access Journals (Sweden)

    Orzan Marius

    2016-06-01

    Full Text Available Background: Assessment of the hemodynamic significance of a coronary artery stenosis is a challenging task, being extremely important for the establishment of indication for revascularization in atherosclerotic coronary artery stenosis. The aim of this study was to evaluate the role of a new marker reflecting the functional significance of a coronary artery stenosis, represented by the attenuation degree of contrast density along the stenosis by Coronary CT.

  11. Correlations among densities of stream fishes in the upper Neosho River, with focus on the federally threatened Neosho madtom Noturus placidus

    Science.gov (United States)

    Tiemann, Jeremy S.; Gillette, David P.; Wildhaber, Mark L.; Edds, David R.

    2004-01-01

    We sampled fishes monthly from November 2000 to October 2001 at four gravel bar sites along a 34-km stretch of the upper Neosho River in Lyon County, Kansas. We assessed the potential for interspecific competition among stream fishes, with focus on the federally threatened Neosho madtom, Noturus placidus, by using Pearson's correlation analysis with sequential Bonferroni correction of alpha to examine relationships among fish densities. Of the 19 fish species analyzed, there were six significant positive and no significant negative correlations. Abundance of N. placidusdid not vary significantly with total abundance of fishes or with abundance of any of these potential competitors. The lack of significant negative correlations at these sites at this time might reflect an assemblage in equilibrium or one controlled abiotically rather than by ongoing active competition.

  12. The use of CT density changes at internal tissue interfaces to correlate internal organ motion with an external surrogate

    Energy Technology Data Exchange (ETDEWEB)

    Gaede, Stewart; Yu, Edward; Van Dyk, Jake; Battista, Jerry [Radiation Oncology Program, London Regional Cancer Program, London, Ontario (Canada); Carnes, Gregory; Lee, Ting-Yim [Department of Medical Biophysics, University of Western Ontario, London, Ontario (Canada)

    2009-01-21

    The purpose of this paper is to describe a non-invasive method to monitor the motion of internal organs affected by respiration without using external markers or spirometry, to test the correlation with external markers, and to calculate any time shift between the datasets. Ten lung cancer patients were CT scanned with a GE LightSpeed Plus 4-Slice CT scanner operating in a cine mode. We retrospectively reconstructed the raw CT data to obtain consecutive 0.5 s reconstructions at 0.1 s intervals to increase image sampling. We defined regions of interest containing tissue interfaces, including tumour/lung interfaces that move due to breathing on multiple axial slices and measured the mean CT number versus respiratory phase. Tumour motion was directly correlated with external marker motion, acquired simultaneously, using the sample coefficient of determination, r{sup 2}. Only three of the ten patients showed correlation higher than r{sup 2} = 0.80 between tumour motion and external marker position. However, after taking into account time shifts (ranging between 0 s and 0.4 s) between the two data sets, all ten patients showed correlation better than r{sup 2} = 0.8. This non-invasive method for monitoring the motion of internal organs is an effective tool that can assess the use of external markers for 4D-CT imaging and respiratory-gated radiotherapy on a patient-specific basis.

  13. 半导体表面电学特性微观四点探针测试技术研究进展%Latest development of electrical characterization of semicondutor surface by microscopic four-point probe technique

    Institute of Scientific and Technical Information of China (English)

    李建昌; 王永; 简晓慧; 巴德纯

    2011-01-01

    四探针法是材料学及半导体行业电学表征的常用方法.随着微电子器件尺度持续减小,新型纳米材料研究不断深入,须将探针间距控制到亚微米及其以下范畴才能获得更高的空间分辨率和表面灵敏度.近年来研究人员借助显微技术开发出两类微观四点探针测试系统,即整体式微观四点探针和独立四点扫描隧道显微镜探针系统,随着现代微加工技术的发展,当前探针间距已缩小到几十纳米范围.本文综述了微观四点探针技术近年来的研究进展,主要包括测试理论、系统结构与探针制备.其中,特别详述了涉及探针制备的方法、技术及所面临问题,并展望了微观四点探针研究的发展方向,并给出了一些具体建议.%Four-point probe characterization is a usual method for studying the electrical properties of solids and thin films. The distance between tip and sample in four-point probe technique has to be reduced to sub-micro scale at least in order to obtain expected surface sensitivity and spatial resolution. Therefore, microscopic four-point probes (M4PPs) need to be combined with some microscopy techniques. Two types of M4PPs have been developed in the past few years, which are monolithic micro-four-point probes and four-point scanning tunneling microscopy probes. In this paper, we review the latest development of M4PPs from aspects of system construction, probe structure and test theories. The approaches of probe preparation are discussed in detail. Probe life and sample surface damage are another two big challenges for the microscopic four-point probe technique. To deal with such problems, flexible cantilevers can be used as the probe by keeping a certain angle to the sample surface.

  14. A quantitative correlation of the effect of density distributions in roller-compacted ribbons on the mechanical properties of tablets using ultrasonics and X-ray tomography.

    Science.gov (United States)

    Akseli, Ilgaz; Iyer, Srinivas; Lee, Hwahsiung P; Cuitiño, Alberto M

    2011-09-01

    Enabling the paradigm of quality by design requires the ability to quantitatively correlate material properties and process variables to measureable product performance attributes. In this study, we show how heterogeneities in compacted ribbon densities quantitatively correlate to tablet mechanical properties. These density variations, which have been purposely modulated by internal and external lubrications, are characterized longitudinally and transversally by nondestructive ultrasonic and X-ray micro-computed tomography measurements. Subsequently, different transversal regions of the compacted ribbon are milled under the same conditions, and granules with nominally the same particle size distribution are utilized to manufacture cylindrical tablets, whose mechanical properties are further analyzed by ultrasonic measurements. We consider three different ribbon conditions: no lubrication (case 1); lubricated powder (case 2); and lubricated tooling (hopper, side sealing plates, feed screws, and rolls) (case 3). This study quantitatively reveals that variation in local densities in ribbons (for case 1) and process conditions (i.e., internal case 2 and external lubrication case 3) during roller compaction significantly affect the mechanical properties of tablets even for granules with the same particle size distribution. For case 1, the mechanical properties of tablets depend on the spatial location where granules are produced. For cases 2 and 3, the ribbon density homogeneity was improved by the use of a lubricant. It is demonstrated that the mechanical performances of tablets are decreased due to applied lubricant and work-hardening phenomenon. Moreover, we extended our study to correlate the speed of sound to the tensile strength of the tablet. It is found that the speed of sound increases with the tensile strength for the tested tablets.

  15. On the possible correlation of Galactic VHE source locations and enhancements of the surface density in the Galactic plane

    CERN Document Server

    Pedaletti, G; Torres, D F

    2014-01-01

    The association of very-high energy sources with regions of the sky rich in dust and gas has been noticed in the study of individual VHE sources. However, the statistical significance of such correlation for the whole population of TeV detections has not been assessed yet. Here we present a study of the association of VHE sources in the central Galactic region with positions of enhanced material content. We obtain estimates of the material content through two classical tracers: dust emission and intensity of the $^\\textrm{12}$CO(1$\\rightarrow$0) line. We make use of the recently released all-sky maps of astrophysical foregrounds of the Planck Collaboration and of the extensive existing CO mapping of the Galactic sky. In order to test the correlation, we construct randomized samples of VHE source positions starting from the inner Galactic plane survey sources detected by the H.E.S.S. array. We find hints of a positive correlation between positions of VHE sources and regions rich in molecular material, which in...

  16. Density cumulant functional theory from a unitary transformation: N-representability, three-particle correlation effects, and application to O{sub 4}{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, Alexander Yu., E-mail: asokolov@uga.edu; Schaefer, Henry F. [Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States); Kutzelnigg, Werner [Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

    2014-08-21

    A new approach to density cumulant functional theory is developed that derives density cumulant N-representability conditions from an approximate Fock space unitary transformation. We present explicit equations for the third- and fourth-order two-particle cumulant N-representability, as well as the second-order contributions that depend on the connected three-particle density cumulant. These conditions are used to formulate the ODC-13 method and the non-iterative (λ{sub 3}) correction that employ an incomplete description of the fourth-order two-particle cumulant N-representability and the second-order three-particle correlation effects, respectively. We perform an analysis of the ODC-13 N-representability description for the dissociation of H{sub 2} and apply the ODC-13 method and the (λ{sub 3}) correction to diatomic molecules with multiple bond character and the symmetry-breaking tetraoxygen cation (O{sub 4}{sup +}). For the O{sub 4}{sup +} molecule, the vibrational frequencies of the ODC-13(λ{sub 3}) method do not exhibit spatial symmetry breaking and are in a good agreement with the recent infrared photodissociation experiment. We report the O{sub 4}{sup +} equilibrium structure, harmonic frequencies, and dissociation energy computed using ODC-13(λ{sub 3}) with a diffuse, core-correlated aug-cc-pCVTZ basis set.

  17. Gas-phase formaldehyde adsorption isotherm studies on activated carbon: correlations of adsorption capacity to surface functional group density.

    Science.gov (United States)

    Carter, Ellison M; Katz, Lynn E; Speitel, Gerald E; Ramirez, David

    2011-08-01

    Formaldehyde (HCHO) adsorption isotherms were developed for the first time on three activated carbons representing one activated carbon fiber (ACF) cloth, one all-purpose granular activated carbon (GAC), and one GAC commercially promoted for gas-phase HCHO removal. The three activated carbons were evaluated for HCHO removal in the low-ppm(v) range and for water vapor adsorption from relative pressures of 0.1-0.9 at 26 °C where, according to the IUPAC isotherm classification system, the adsorption isotherms observed exhibited Type V behavior. A Type V adsorption isotherm model recently proposed by Qi and LeVan (Q-L) was selected to model the observed adsorption behavior because it reduces to a finite, nonzero limit at low partial pressures and it describes the entire range of adsorption considered in this study. The Q-L model was applied to a polar organic adsorbate to fit HCHO adsorption isotherms for the three activated carbons. The physical and chemical characteristics of the activated carbon surfaces were characterized using nitrogen adsorption isotherms, X-ray photoelectron spectroscopy (XPS), and Boehm titrations. At low concentrations, HCHO adsorption capacity was most strongly related to the density of basic surface functional groups (SFGs), while water vapor adsorption was most strongly influenced by the density of acidic SFGs.

  18. Is hand bone mineral density a marker for hand function in patients with established rheumatoid arthritis? The correlation among bone mineral density of the hand, radiological findings and hand function.

    Science.gov (United States)

    Dogu, Beril; Kuran, Banu; Yilmaz, Figen; Usen, Ahmet; Sirzai, Hulya

    2013-08-01

    The objective of this study is to assess the role of hand bone mineral density (BMD) as a prospective marker for hand function and the correlation of hand BMD with X-ray findings and hand functioning in patients with established rheumatoid arthritis (RA). Eighty-three female patients diagnosed with RA were enrolled. All BMD measurements were performed on both hands. The radiological evaluation was conducted according to the van der Heijde modification of the Sharp method (Sharp/van der Heijde). Duruöz Hand Index (DHI) was used to establish the disability in the hands. Furthermore, handgrip strength (HGS), pinch strength (PS), lateral pinch (LP), tip-to-tip pinch (TTP) and three-fingered pinch (TFP) on both the dominant and the non-dominant hands was measured. A significant positive correlation between hand BMD and HGS as well as all PSs with p DHI (p > 0.05). The hand BMD and the Sharp/van der Heijde scores were significantly in reverse correlation (p DHI-related variants, HGS and PS and the total DHI scores were reversely correlated, while there was a positive significant association with radiological scores (p DHI, HGS, LP, TTP, TFP and radiographic total scores. Our study demonstrated that a one-off hand BMD measurement failed to adequately indicate a loss in hand function as measured by DHI. Ultimately, HGS and TTP were shown to be the most effective indicators for measuring hand functions.

  19. Whole tumour quantitative measurement of first-pass perfusion of oesophageal squamous cell carcinoma using 64-row multidetector computed tomography: Correlation with microvessel density

    Energy Technology Data Exchange (ETDEWEB)

    Chen Tianwu, E-mail: twchenscu@yahoo.com.cn [Department of Radiology, West China Hospital of Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan 610041 (China); Sichuan Province Key Laboratory of Medical Imaging, and Department of Radiology, Affiliated Hospital of North Sichuan Medical College, 63 Wen Hua Lu, Nanchong, Sichuan 637007 (China); Yang Zhigang, E-mail: yangzg6666@yahoo.com.cn [Department of Radiology, West China Hospital of Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan 610041 (China); State Key Laboratory of Biotherapy, West China Hospital of Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan 610041 (China); Wang Qiling, E-mail: xiaohongmao99@126.com [Department of Radiology, West China Hospital of Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan 610041 (China); Li Yuan, E-mail: dr.liyuan@163.com [Department of Radiology, West China Hospital of Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan 610041 (China); Qian Lingling, E-mail: moneylinglingch1999@126.com [Department of Radiology, West China Hospital of Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan 610041 (China); Chen Huijiao, E-mail: joan-ch@sohu.com [Department of Pathology, West China Hospital of Sichuan University, 37 Guo Xue Xiang, Chengdu, Sichuan 610041 (China)

    2011-08-15

    Purpose: To assess correlations between whole tumour first-pass perfusion parameters obtained with 64-row multidetector computed tomography (MDCT), and microvessel density (MVD) in oesophageal squamous cell carcinoma. Materials and Methods: Thirty-one consecutive patients with surgically confirmed oesophageal squamous cell carcinomas were enrolled into our study. All the patients underwent whole tumour first-pass perfusion scan with 64-row MDCT. Perfusion parameters, including perfusion (PF), peak enhanced density (PED), blood volume (BV), and time to peak (TTP) were measured using Philips perfusion software. Postoperative tumour specimens were assessed for MVD. Pearson correlation coefficient tests were performed to determine correlations between each perfusion parameter and MVD. Results: Mean values for PF, PED, BV and TTP of the whole tumour were 28.85 {+-} 20.29 ml/min/ml, 23.16 {+-} 8.09 HU, 12.13 {+-} 5.21 ml/100 g, and 35.05 {+-} 13.85 s, respectively. Mean MVD in whole tumour at magnification (x200) was 15.75 {+-} 4.34 microvessel/tumour sample (vessels/0.723 mm{sup 2}). PED and BV were correlated with MVD (r = 0.651 and r = 0.977, respectively, all p < 0.05). However, PF and TTP were not correlated with MVD (r = 0.070 and r = 0.100, respectively, all p > 0.05). Conclusion: The BV value of first-pass perfusion CT could reflect MVD in oesophageal squamous cell carcinoma, and can be an indicator for evaluating the tumour angiogenesis.

  20. Correlation between expressions of hypoxia -inducible factor (HIF-1α, blood vessels density, cell proliferation, and apoptosis intensity in canine fibromas and fibrosarcomas

    Directory of Open Access Journals (Sweden)

    Madej Janusz A.

    2014-03-01

    Full Text Available The study aimed to demonstrate the expression of hypoxia-inducible factor (HIF-1α in soft tissue mesenchymal tumours (fibroma and fibrosarcoma in dogs. An attempt was made to correlate the obtained results with density of blood vessels (expression of von Willebrand Factor, vWF, expression of Ki-67 proliferation antigen, and with intensity of apoptosis in studied tumours. The study was performed on paraffin sections of 15 fibromas and 40 fibrosarcomas sampled from 55 female dogs aged 6 to 16 years. Immunohistochemical staining against HIF-1α, vWF, and Ki-67 was performed. Apoptosis was detected with the use of TUNEL reaction. A significantly higher HIF-1α expression was noted in fibrosarcomas in comparison to fibromas (P < 0.0001. HIF-1α expression in fibromas manifested strong positive correlation with tumour vascularity (r = 0.67, P = 0.007. Moreover, HIF-1α expression in fibrosarcomas manifested a moderate positive correlation with tumour malignancy grade (r = 0.44, P = 0.004, tumour vascularity (r = 0.52, P < 0.001, Ki-67 antigen expression (r = 0.42; P = 0.007, and TUNELpositive cells (r = 0.37, P = 0.017. Expression of HIF-1α was detected in 86.7% of fibroma type tumours and in 100% of fibrosarcomas. In all studied tumours expression of HIF-1α manifested positive correlation with the density of blood vessels, and in fibrosarcomas it correlated also with malignancy grade, intensity of Ki-67 expression, and with intensity of apoptosis in tumour cells.

  1. Combinations of coupled cluster, density functionals, and the random phase approximation for describing static and dynamic correlation, and van der Waals interactions

    CERN Document Server

    Garza, Alejandro J; Alencar, Ana G Sousa; Sun, Jianwei; Perdew, John P; Scuseria, Gustavo E

    2015-01-01

    Contrary to standard coupled cluster doubles (CCD) and Brueckner doubles (BD), singlet-paired analogues of CCD and BD (denoted here as CCD0 and BD0) do not break down when static correlation is present, but neglect substantial amounts of dynamic correlation. In fact, CCD0 and BD0 do not account for any contributions from multielectron excitations involving only same-spin electrons at all. We exploit this feature to add---without introducing double counting, self-interaction, or increase in cost---the missing correlation to these methods via meta-GGA density functionals (TPSS and SCAN). Furthermore, we improve upon these CCD0+DFT blends by invoking range separation: the short- and long-range correlations absent in CCD0/BD0 are evaluated with DFT and the direct random phase approximation (dRPA), respectively. This corrects the description of long-range van der Waals forces. Comprehensive benchmarking shows that the combinations presented here are very accurate for weakly correlated systems, while also providing...

  2. Ab initio-driven nuclear energy density functional method. A proposal for safe/correlated/improvable parametrizations of the off-diagonal EDF kernels

    CERN Document Server

    Duguet, T; Ebran, J -P; Lesinski, T; Somà, V

    2015-01-01

    This programmatic paper lays down the possibility to reconcile the necessity to resum many-body correlations into the energy kernel with the fact that safe multi-reference energy density functional (EDF) calculations cannot be achieved whenever the Pauli principle is not strictly enforced, as is for example the case when many-body correlations are parametrized under the form of empirical density dependencies. Our proposal is to exploit a newly developed ab initio many-body formalism to guide the construction of safe, explicitly correlated and systematically improvable parametrizations of the {\\it off-diagonal} energy and norm kernels that lie at the heart of the nuclear EDF method. The many-body formalism of interest relies on the concepts of symmetry breaking {\\it and} restoration that have made the fortune of the nuclear EDF method and is, as such, amenable to this guidance. After elaborating on our proposal, we briefly outline the project we plan to execute in the years to come.

  3. Sentinel lymph node identification in breast cancer using periareolar and subdermal injection of the radiopharmaceutical in four points; Identificacao do linfonodo sentinela no cancer de mama com injecao subdermica periareolar em quatro pontos do radiofarmaco

    Energy Technology Data Exchange (ETDEWEB)

    Coelho-Oliveira, Afranio; Rocha, Augusto Cesar Peixoto [Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, RJ (Brazil). Servico de Ginecologia]. E-mail: afranioliveira@hotmail.com; Gutfilen, Bianca; Pessoa, Maria Carolina Pinheiro; Fonseca, Lea Mirian Barbosa da [Universidade Federal, Rio de Janeiro, RJ (Brazil). Faculdade de Medicina. Dept. de Radiologia e Medicina Nuclear

    2004-08-01

    The aim of this study was to identify the sentinel node by periareolar injection of the radiopharmaceutical in four points, regardless of tumor topography. The sentinel node biopsy reduces morbidity in axillary staging. Fifty-seven sentinel node biopsies were prospectively performed in two groups: group A (25 patients) and group B (32 patients). The peritumoral injection technique was used in group A and the new injection technique in four points was used in group B. The sentinel node biopsies were studied by imprint cytology and hematoxylin and eosin staining followed by axillary lymph node dissection in all patients of group A and only in the positive cases of group B. In group A, 88% (22/25) of the sentinel nodes were identified. There was no false negative case; the sensibility and specificity were of 100%. In group B, 96% (31/32) of sentinel nodes were identified and the status of the axillary lymph nodes showed a predictive positive value of 100%. The number of sentinel nodes varied from 1 to 7, mode of 1 and median of 2.7. The hotspot area was 10 to 100 times the background radiation. The periareolar injection in four points seems to be a good lymphatic mapping method for identification of the sentinel node. We suggest the standardization of this site for injections to identify the sentinel node, although further studies to confirm these findings are necessary. (author)

  4. ωB97M-V: A combinatorially optimized, range-separated hybrid, meta-GGA density functional with VV10 nonlocal correlation

    Science.gov (United States)

    Mardirossian, Narbe; Head-Gordon, Martin

    2016-06-01

    A combinatorially optimized, range-separated hybrid, meta-GGA density functional with VV10 nonlocal correlation is presented. The final 12-parameter functional form is selected from approximately 10 × 109 candidate fits that are trained on a training set of 870 data points and tested on a primary test set of 2964 data points. The resulting density functional, ωB97M-V, is further tested for transferability on a secondary test set of 1152 data points. For comparison, ωB97M-V is benchmarked against 11 leading density functionals including M06-2X, ωB97X-D, M08-HX, M11, ωM05-D, ωB97X-V, and MN15. Encouragingly, the overall performance of ωB97M-V on nearly 5000 data points clearly surpasses that of all of the tested density functionals. In order to facilitate the use of ωB97M-V, its basis set dependence and integration grid sensitivity are thoroughly assessed, and recommendations that take into account both efficiency and accuracy are provided.

  5. Ensemble v-representable ab-initio density functional calculation of energy and spin in atoms: atest of exchange-correlation approximations

    CERN Document Server

    Kraisler, Eli; Kelson, Itzhak

    2010-01-01

    The total energies and the spin states for atoms and their first ions with Z = 1-86 are calculated within the the local spin-density approximation (LSDA) and the generalized-gradient approximation (GGA) to the exchange-correlation (xc) energy in density-functional theory. Atoms and ions for which the ground-state density is not pure-state v-representable, are treated as ensemble v- representable with fractional occupations of the Kohn-Sham system. A newly developed algorithm which searches over ensemble v-representable densities [E. Kraisler et al., Phys. Rev. A 80, 032115 (2009)] is employed in calculations. It is found that for many atoms the ionization energies obtained with the GGA are only modestly improved with respect to experimental data, as compared to the LSDA. However, even in those groups of atoms where the improvement is systematic, there remains a non-negligible difference with respect to the experiment. The ab-initio electronic configuration in the Kohn-Sham reference system does not always equ...

  6. CORRELATION BETWEEN SERUM PARAOXONASE ACTIVITY AND HIGH DENSITY LIPOPROTEIN LEVELS IN TYPE2 DIABETES PREDISPOSING TO ATEROSCLEROSIS

    Directory of Open Access Journals (Sweden)

    SK.Deepthi

    2014-11-01

    Full Text Available Human serum paraoxonase is physically associated with HDL and has been implicated in the detoxification of organophosphates and possibly in the prevention of LDL lipid peroxidation and therefore retards atherosclerosis. HDL levels are inversely related to the risk of developing atherosclerosis. We investigated the serum activity and concentration of paraoxonase and HDL levels in 104 subjects (42 diabetic patients without complications, 42 controls, 20 diabetic patients with complications.. Paraoxonase activity was found to be lower in diabetic patients than in controls. Similarly there was reduction in HDL levels in cases suggesting a positive correlation between HDL and paraoxonase levels.

  7. SUSY-QCD corrections for the direct detection of neutralino dark matter and correlations with the relic density

    CERN Document Server

    Klasen, Michael; Steppeler, Patrick

    2016-01-01

    In this paper, we perform a full next-to-leading order (NLO) QCD calculation of neutralino scattering on protons or neutrons in the MSSM. We match the results of the NLO QCD calculation to the scalar and axial-vector operators in the effective field theory approach. These govern the spin-independent and spin-dependent detection rates, respectively. The calculations have been performed for general bino, wino and higgsino decompositions of neutralino dark matter and required a novel tensor reduction method of loop integrals with vanishing relative velocities and Gram determinants. Numerically, the NLO QCD effects are shown to be of at least of similar size and sometimes larger than the currently estimated nuclear uncertainties. We also demonstrate the interplay of the direct detection rate with the relic density when consistently analyzed with the program \\texttt{DMNLO}.

  8. Non-acid-fastness in Mycobacterium tuberculosis ΔkasB mutant correlates with the cell envelope electron density.

    Science.gov (United States)

    Yamada, Hiroyuki; Bhatt, Apoorva; Danev, Radostin; Fujiwara, Nagatoshi; Maeda, Shinji; Mitarai, Satoshi; Chikamatsu, Kinuyo; Aono, Akio; Nitta, Koji; Jacobs, William R; Nagayama, Kuniaki

    2012-07-01

    The acid-fastness is the most important and the most specific characteristics in mycobacteria, the mechanism of which is not clear but may be attributed to the lipid rich cell wall of this bacterium. While the exact component(s) responsible for this staining method remained unidentified, a Mycobacterium tuberculosis mutant, attenuated strain that produced shorter mycolic acids with defects in trans-cyclopropanation was shown to be acid fast negative. In this study, we examined the ultrastructure of the cell envelope (CE) of the mutant strain ΔkasB (missing a beta-ketoacyl-ACP synthase involved in mycolic acid biosynthesis), the parental CDC1551 (wild type strain) and kasB complemented strain, and compared ultrastructural differences among them with conventional transmission electron microscopy (TEM) and cryo-transmission electron microscopy (CEM). Conventional TEM revealed that there were no detectable differences in the thickness of the cell envelope among three strains (wild-type: 43.35 ± 6.13 nm; ΔkasB: 45.98 ± 11.32 nm; complement: 40.71 ± 6.3 nm). However, CEM data demonstrated that the region between the inner and outer membranes of the mutant strain, which is composed mainly of cell wall anchored mycolic acids (MA), showed a significant decrease in electron density as compared to the wild type and kasB complement strain (567.1 ± 372.7 vs. 301.4 ± 262.1, or vs. 235.2 ± 174.9, p tuberculosis cell envelope, resulting in a reduced electron density of this layer as seen by CEM and loss of acid-fastness in light microscopical observation, and we propose a novel model of the cell envelope structure in tubercle bacilli.

  9. In-situ strain localization analysis in low density transformation-twinning induced plasticity steel using digital image correlation

    Science.gov (United States)

    Eskandari, M.; Yadegari-Dehnavi, M. R.; Zarei-Hanzaki, A.; Mohtadi-Bonab, M. A.; Basu, R.; Szpunar, J. A.

    2015-04-01

    The effect of deformation temperature on the strain localization has been evaluated by an adapted digital image correlation (DIC) technique during tensile deformation. The progress of strain localization was traced by the corresponding strain maps. The electron backscatter diffraction analysis and tint etching technique were utilized to determine the impact of martensitic transformation and deformation twinning on the strain localization in both elastic and plastic regimes. In elastic regime the narrow strain bands which are aligned perpendicular to the tension direction were observed in temperature range of 25 to 180 °C due to the stress-assisted epsilon martensite. The strain bands were disappeared by increasing the temperature to 300 °C and reappeared at 400 °C due to the stress-assisted deformation twinning. In plastic regime strain localization continued at 25 °C and 180 °C due to the strain-induced alfa-martensite and deformation twinning, respectively. The intensity of plastic strain localization was increased by increasing the strain due to the enhancement of martensite and twin volume fraction. The plastic strain showed more homogeneity at 300 °C due to the lack of both strain-induced martensite and deformation twinning. Effect of deformation mechanism by changing temperature on strain localization is investigated by digital image correlation. EBSD technique is served to validate deformation mechanism as well as microstructural evolution. Strain induced martensite as well as deformation twinning is activated in the present steel affecting strain localization.

  10. Density functional theory and the correlation consistent basis sets: the tight d effect on HSO and HOS.

    Science.gov (United States)

    Wang, Nick X; Wilson, Angela K

    2005-08-18

    The HSO and HOS isomers have been revisited using the DFT functionals, B3LYP, B3PW91, and PBE, in combination with tight d-augmented correlation consistent basis sets, cc-pV(x+d)Z and aug-cc-pV(x+d)Z for second-row atoms. Structures, vibrationally averaged structures, relative energies, harmonic and anharmonic frequencies, enthalpies of formation of HSO and HOS, and the barrier for the HSO/HOS isomerization have been determined. These results were compared with results from previous DFT and ab initio studies in which the standard correlation consistent basis sets were used. The relative energies of the two isomers converge more rapidly and smoothly with respect to increasing basis set size for the tight d-augmented sets than for the standard basis sets. Our best calculations, B3PW91/aug-cc-pV(5+d)Z, for the relative energy of the isomers are in excellent agreement with previous CCSD(T) results given by Wilson and Dunning.

  11. Anisotropic pair correlations in binary and multicomponent hard-sphere mixtures in the vicinity of a hard wall: A combined density functional theory and simulation study

    Science.gov (United States)

    Härtel, Andreas; Kohl, Matthias; Schmiedeberg, Michael

    2015-10-01

    The fundamental measure approach to classical density functional theory has been shown to be a powerful tool to predict various thermodynamic properties of hard-sphere systems. We employ this approach to determine not only one-particle densities but also two-particle correlations in binary and six-component mixtures of hard spheres in the vicinity of a hard wall. The broken isotropy enables us to carefully test a large variety of theoretically predicted two-particle features by quantitatively comparing them to the results of Brownian dynamics simulations. Specifically, we determine and compare the one-particle density, the total correlation functions, their contact values, and the force distributions acting on a particle. For this purpose, we follow the compressibility route and theoretically calculate the direct correlation functions by taking functional derivatives. We usually observe an excellent agreement between theory and simulations, except for small deviations in cases where local crystal-like order sets in. Our results set the course for further investigations on the consistency of functionals as well as for structural analysis on, e.g., the primitive model. In addition, we demonstrate that due to the suppression of local crystallization, the predictions of six-component mixtures are better than those in bidisperse or monodisperse systems. Finally, we are confident that our results of the structural modulations induced by the wall lead to a deeper understanding of ordering in anisotropic systems in general, the onset of heterogeneous crystallization, caging effects, and glassy dynamics close to a wall, as well as structural properties in systems with confinement.

  12. Efficacy, but not antibody titer or affinity, of a heroin hapten conjugate vaccine correlates with increasing hapten densities on tetanus toxoid, but not on CRM197 carriers.

    Science.gov (United States)

    Jalah, Rashmi; Torres, Oscar B; Mayorov, Alexander V; Li, Fuying; Antoline, Joshua F G; Jacobson, Arthur E; Rice, Kenner C; Deschamps, Jeffrey R; Beck, Zoltan; Alving, Carl R; Matyas, Gary R

    2015-06-17

    Vaccines against drugs of abuse have induced antibodies in animals that blocked the biological effects of the drug by sequestering the drug in the blood and preventing it from crossing the blood-brain barrier. Drugs of abuse are too small to induce antibodies and, therefore, require conjugation of drug hapten analogs to a carrier protein. The efficacy of these conjugate vaccines depends on several factors including hapten design, coupling strategy, hapten density, carrier protein selection, and vaccine adjuvant. Previously, we have shown that 1 (MorHap), a heroin/morphine hapten, conjugated to tetanus toxoid (TT) and mixed with liposomes containing monophosphoryl lipid A [L(MPLA)] as adjuvant, partially blocked the antinociceptive effects of heroin in mice. Herein, we extended those findings, demonstrating greatly improved vaccine induced antinociceptive effects up to 3% mean maximal potential effect (%MPE). This was obtained by evaluating the effects of vaccine efficacy of hapten 1 vaccine conjugates with varying hapten densities using two different commonly used carrier proteins, TT and cross-reactive material 197 (CRM197). Immunization of mice with these conjugates mixed with L(MPLA) induced very high anti-1 IgG peak levels of 400-1500 μg/mL that bound to both heroin and its metabolites, 6-acetylmorphine and morphine. Except for the lowest hapten density for each carrier, the antibody titers and affinity were independent of hapten density. The TT carrier based vaccines induced long-lived inhibition of heroin-induced antinociception that correlated with increasing hapten density. The best formulation contained TT with the highest hapten density of ≥30 haptens/TT molecule and induced %MPE of approximately 3% after heroin challenge. In contrast, the best formulation using CRM197 was with intermediate 1 densities (10-15 haptens/CRM197 molecule), but the %MPE was approximately 13%. In addition, the chemical synthesis of 1, the optimization of the conjugation

  13. Comment on "On the unphysical solutions of the Kadanoff-Baym equations in linear response: Correlation-induced homogeneous density-distribution and attractors"

    Science.gov (United States)

    Schlünzen, N.; Joost, J.-P.; Bonitz, M.

    2017-09-01

    In a recent Rapid Communication [A. Stan, Phys. Rev. B 93, 041103(R) (2016), 10.1103/PhysRevB.93.041103], the reliability of the Keldysh-Kadanoff-Baym equations (KBE) using correlated self-energy approximations applied to linear and nonlinear response has been questioned. In particular, the existence of a universal attractor has been predicted that would drive the dynamics of any correlated system towards an unphysical homogeneous density distribution regardless of the system type, the interaction, and the many-body approximation. Moreover, it was conjectured that even the mean-field dynamics would be damped. Here, by performing accurate solutions of the KBE for situations studied in that paper, we prove these claims wrong, being caused by numerical inaccuracies.

  14. Improving the correlation of structural FEA models by the application of automated high density robotized laser Doppler vibrometry

    Science.gov (United States)

    Chowanietz, Maximilian; Bhangaonkar, Avinash; Semken, Michael; Cockrill, Martin

    2016-06-01

    Sound has had an intricate relation with the wellbeing of humans since time immemorial. It has the ability to enhance the quality of life immensely when present as music; at the same time, it can degrade its quality when manifested as noise. Hence, understanding its sources and the processes by which it is produced gains acute significance. Although various theories exist with respect to evolution of bells, it is indisputable that they carry millennia of cultural significance, and at least a few centuries of perfection with respect to design, casting and tuning. Despite the science behind its design, the nuances pertaining to founding and tuning have largely been empirical, and conveyed from one generation to the next. Post-production assessment for bells remains largely person-centric and traditional. However, progressive bell manufacturers have started adopting methods such as finite element analysis (FEA) for informing and optimising their future model designs. To establish confidence in the FEA process it is necessary to correlate the virtual model against a physical example. This is achieved by performing an experimental modal analysis (EMA) and comparing the results with those from FEA. Typically to collect the data for an EMA, the vibratory response of the structure is measured with the application of accelerometers. This technique has limitations; principally these are the observer effect and limited geometric resolution. In this paper, 3-dimensional laser Doppler vibrometry (LDV) has been used to measure the vibratory response with no observer effect due to the non-contact nature of the technique; resulting in higher accuracy measurements as the input to the correlation process. The laser heads were mounted on an industrial robot that enables large objects to be measured and extensive data sets to be captured quickly through an automated process. This approach gives previously unobtainable geometric resolution resulting in a higher confidence EMA. This is

  15. Development of gradient-corrected exchange-correlation functionals in the density functional theory; Developpement de fonctionnelles corrigees du gradient en theorie de la fonctionnelle de la densite

    Energy Technology Data Exchange (ETDEWEB)

    Lembarki, A.

    1994-12-01

    In this work, we have developed some gradient-corrected exchange-correlation functionals. This study is in keeping with the density functional theory (DFT) formalism. In the first part of this memory, a description of Hartree-Fock (HF), post-HF and density functional theories is given. The second part is devoted the study the different approximations of DFT exchange-correlation functionals which have been proposed in the last years. In particular, we have underlined the approximations used for the construction of these functionals. The third part of this memory consists in the development of new gradient-corrected functionals. In this study, we have established a new relation between exchange energy, correlation energy and kinetic energy. We have deduced two new possible forms of exchange or correlation functionals, respectively. In the fourth part, we have studied the exchange potential, for which the actual formulation does not satisfy some theoretical conditions, such as the asymptotic behavior -1/r. Our contribution lies in the development of an exchange potential with a correct asymptotic -1/r behavior for large values of r. In this chapter, we have proposed a model which permits the obtention of the exchange energy from the exchange potential, using the virial theorem. The fifth part of this memory is devoted the application of these different functionals to simple systems (H{sub 2}O, CO, N{sub 2}O, H{sub 3}{sup +} and H{sub 5}{sup +}) in order to characterize the performance of DFT calculations in regards to those obtained with post-HF methods. (author). 215 refs., 8 figs., 28 tabs.

  16. Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

    CERN Document Server

    Johnston, David E; Wechsler, Risa H; Rozo, Eduardo; Koester, Benjamin P; Frieman, Joshua A; McKay, Timothy A; Evrard, August E; Becker, Matthew R; Annis, James

    2007-01-01

    We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. 2007 (Paper I). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of 13% including both statistical and systematic errors. We also constrain the halo concentration para...

  17. Longitudinal relaxation in dipole-coupled homonuclear three-spin systems: Distinct correlations and odd spectral densities

    Science.gov (United States)

    Chang, Zhiwei; Halle, Bertil

    2015-12-01

    A system of three dipole-coupled spins exhibits a surprisingly intricate relaxation behavior. Following Hubbard's pioneering 1958 study, many authors have investigated different aspects of this problem. Nevertheless, on revisiting this classic relaxation problem, we obtain several new results, some of which are at variance with conventional wisdom. Most notably from a fundamental point of view, we find that the odd-valued spectral density function influences longitudinal relaxation. We also show that the effective longitudinal relaxation rate for a non-isochronous three-spin system can exhibit an unusual inverted dispersion step. To clarify these and other issues, we present a comprehensive theoretical treatment of longitudinal relaxation in a three-spin system of arbitrary geometry and with arbitrary rotational dynamics. By using the Liouville-space formulation of Bloch-Wangsness-Redfield theory and a basis of irreducible spherical tensor operators, we show that the number of relaxation components in the different cases can be deduced from symmetry arguments. For the isochronous case, we present the relaxation matrix in analytical form, whereas, for the non-isochronous case, we employ a computationally efficient approach based on the stochastic Liouville equation.

  18. Longitudinal relaxation in dipole-coupled homonuclear three-spin systems: Distinct correlations and odd spectral densities

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Zhiwei; Halle, Bertil, E-mail: bertil.halle@bpc.lu.se [Department of Chemistry, Division of Biophysical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund (Sweden)

    2015-12-21

    A system of three dipole-coupled spins exhibits a surprisingly intricate relaxation behavior. Following Hubbard’s pioneering 1958 study, many authors have investigated different aspects of this problem. Nevertheless, on revisiting this classic relaxation problem, we obtain several new results, some of which are at variance with conventional wisdom. Most notably from a fundamental point of view, we find that the odd-valued spectral density function influences longitudinal relaxation. We also show that the effective longitudinal relaxation rate for a non-isochronous three-spin system can exhibit an unusual inverted dispersion step. To clarify these and other issues, we present a comprehensive theoretical treatment of longitudinal relaxation in a three-spin system of arbitrary geometry and with arbitrary rotational dynamics. By using the Liouville-space formulation of Bloch-Wangsness-Redfield theory and a basis of irreducible spherical tensor operators, we show that the number of relaxation components in the different cases can be deduced from symmetry arguments. For the isochronous case, we present the relaxation matrix in analytical form, whereas, for the non-isochronous case, we employ a computationally efficient approach based on the stochastic Liouville equation.

  19. Decay of correlations in fluids: The one-component plasma from Debye-Hückel to the asymptotic-high-density limit

    Science.gov (United States)

    Leote de Carvalho, R. J. F.; Evans, R.; Rosenfeld, Y.

    1999-02-01

    The decay of structural correlations in the classical one-component plasma is analyzed by calculating the poles of the Fourier transform of the total (pairwise) correlation function h(r) for two integral equation theories, the soft mean spherical approximation and the hypernetted chain (HNC). We show that for all except the largest values of the plasma coupling constant Γ, the leading-order pole contribution provides an accurate description of h(r) at intermediate range, as well as the ultimate asymptotic decay. The crossover from monotonic decay at weak coupling to exponentially damped oscillatory decay at strong coupling is shown to arise from the same mechanism as that which occurs for charge correlations in binary ionic fluids. We calculate the values of Γ at which the crossover occurs in the two theories. The role of higher-order poles and (within the HNC) other singularities in determining the intermediate range behavior of h(r) for strong coupling is discussed. We investigate the properties of the solutions of the integral equations in the strong coupling, Γ-->∞, asymptotic high-density limit (AHDL). Padé approximants are employed in order to test the validity of the scaling laws proposed for the potential energy, direct correlation function, and for the poles and their contributions to h(r) in the AHDL. Our numerical results provide strong support for the validity of the theoretical predictions concerning the AHDL.

  20. Perfusion parameters of dynamic contrast-enhanced magnetic resonance imaging in patients with rectal cancer: Correlation with microvascular density and vascular endothelial growth factor expression

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeo Eun [Dept. of Radiology, Seoul Medical Center, Seoul (Korea, Republic of); Lim, Joon Seok; Kim, Myeong Jin; Kim, Ki Whang; Choi, Jun Jeong [Yonsei University Health System, Seoul (Korea, Republic of); Kim, Dae Hong [Molecular Imaging and Therapy Branch, National Cancer Center, Goyang (Korea, Republic of); Myoung, Sung Min [Dept. of Medical Information, Jungwon University, Goesan (Korea, Republic of)

    2013-12-15

    To determine whether quantitative perfusion parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) correlate with immunohistochemical markers of angiogenesis in rectal cancer. Preoperative DCE-MRI was performed in 63 patients with rectal adenocarcinoma. Transendothelial volume transfer (K{sup trans}) and fractional volume of the extravascular-extracellular space (Ve) were measured by Interactive Data Language software in rectal cancer. After surgery, microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression scores were determined using immunohistochemical staining of rectal cancer specimens. Perfusion parameters (K{sup trans}, Ve) of DCE-MRI in rectal cancer were found to be correlated with MVD and VEGF expression scores by Spearman's rank coefficient analysis. T stage and N stage (negative or positive) were correlated with perfusion parameters and MVD. Significant correlation was not found between any DCE-MRI perfusion parameters and MVD (rs = -0.056 and p 0.662 for K{sup trans}; rs = -0.103 and p = 0.416 for Ve), or between any DCE-MRI perfusion parameters and the VEGF expression score (rs = -0.042, p 0.741 for K{sup trans}; r = 0.086, p = 0.497 for Ve) in rectal cancer. TN stage showed no significant correlation with perfusion parameters or MVD (p > 0.05 for all). DCE-MRI perfusion parameters, K{sup trans} and Ve, correlated poorly with MVD and VEGF expression scores in rectal cancer, suggesting that these parameters do not simply denote static histological vascular properties.

  1. The use of current source density as electrophysiological correlates in neuropsychiatric disorders: A review of human studies.

    Science.gov (United States)

    Kamarajan, Chella; Pandey, Ashwini K; Chorlian, David B; Porjesz, Bernice

    2015-09-01

    The use of current source density (CSD), the Laplacian of the scalp surface voltage, to map the electrical activity of the brain is a powerful method in studies of cognitive and affective phenomena. During the last few decades, mapping of CSD has been successfully applied to characterize several neuropsychiatric conditions such as alcoholism, schizophrenia, depression, anxiety disorders, childhood/developmental disorders, and neurological conditions (i.e., epilepsy and brain lesions) using electrophysiological data from resting state and during cognitive performance. The use of CSD and Laplacian measures has proven effective in elucidating topographic and activation differences between groups: i) patients with a specific diagnosis vs. healthy controls, ii) subjects at high risk for a specific diagnosis vs. low risk or normal controls, and iii) patients with specific symptom(s) vs. patients without these symptom(s). The present review outlines and summarizes the studies that have employed CSD measures in investigating several neuropsychiatric conditions. The advantages and potential of CSD-based methods in clinical and research applications along with some of the limitations inherent in the CSD-based methods are discussed in the review, as well as future directions to expand the implementation of CSD to other potential clinical applications. As CSD methods have proved to be more advantageous than using scalp potential data to understand topographic and source activations, its clinical applications offer promising potential, not only for a better understanding of a range of psychiatric conditions, but also for a variety of focal neurological disorders, including epilepsy and other conditions involving brain lesions and surgical interventions.

  2. The density of macrophages in the invasive front is inversely correlated to liver metastasis in colon cancer

    Directory of Open Access Journals (Sweden)

    Ding Ya

    2010-02-01

    Full Text Available Abstract Background Although an abundance of evidence has indicated that tumor-associated macrophages (TAMs are associated with a favorable prognosis in patients with colon cancer, it is still unknown how TAMs exert a protective effect. This study examined whether TAMs are involved in hepatic metastasis of colon cancer. Materials and methods One hundred and sixty cases of pathologically-confirmed specimens were obtained from colon carcinoma patients with TNM stage IIIB and IV between January 1997 and July 2004 at the Cancer Center of Sun Yat-Sen University. The density of macrophages in the invasive front (CD68TFHotspot was scored with an immunohistochemical assay. The relationship between the CD68TFHotspot and the clinicopathologic parameters, the potential of hepatic metastasis, and the 5-year survival rate were analyzed. Results TAMs were associated with the incidence of hepatic metastasis and the 5-year survival rate in patients with colon cancers. Both univariate and multivariate analyses revealed that the CD68TFHotspot was independently prognostic of survival. A higher 5-year survival rate among patients with stage IIIB after radical resection occurred in patients with a higher macrophage infiltration in the invasive front (81.0% than in those with a lower macrophage infiltration (48.6%. Most importantly, the CD68TFHotspot was associated with both the potential of hepatic metastasis and the interval between colon resection and the occurrence of hepatic metastasis. Conclusion This study showed evidence that TAMs infiltrated in the invasive front are associated with improvement in both hepatic metastasis and overall survival in colon cancer, implying that TAMs have protective potential in colon cancers and might serve as a novel therapeutic target.

  3. "Cuts in Action": A High-Density EEG Study Investigating the Neural Correlates of Different Editing Techniques in Film.

    Science.gov (United States)

    Heimann, Katrin S; Uithol, Sebo; Calbi, Marta; Umiltà, Maria A; Guerra, Michele; Gallese, Vittorio

    2016-11-24

    In spite of their striking differences with real-life perception, films are perceived and understood without effort. Cognitive film theory attributes this to the system of continuity editing, a system of editing guidelines outlining the effect of different cuts and edits on spectators. A major principle in this framework is the 180° rule, a rule recommendation that, to avoid spectators' attention to the editing, two edited shots of the same event or action should not be filmed from angles differing in a way that expectations of spatial continuity are strongly violated. In the present study, we used high-density EEG to explore the neural underpinnings of this rule. In particular, our analysis shows that cuts and edits in general elicit early ERP component indicating the registration of syntactic violations as known from language, music, and action processing. However, continuity edits and cuts-across the line differ from each other regarding later components likely to be indicating the differences in spatial remapping as well as in the degree of conscious awareness of one's own perception. Interestingly, a time-frequency analysis of the occipital alpha rhythm did not support the hypothesis that such differences in processing routes are mainly linked to visual attention. On the contrary, our study found specific modulations of the central mu rhythm ERD as an indicator of sensorimotor activity, suggesting that sensorimotor networks might play an important role. We think that these findings shed new light on current discussions about the role of attention and embodied perception in film perception and should be considered when explaining spectators' different experience of different kinds of cuts.

  4. Quantification of Valleys of Randomly Textured Substrates as a Function of Opening Angle: Correlation to the Defect Density in Intrinsic nc-Si:H.

    Science.gov (United States)

    Kim, Do Yun; Hänni, Simon; Schüttauf, Jan-Willem; van Swaaij, René A C M M; Zeman, Miro

    2016-08-17

    Optical and electrical properties of hydrogenated nanocrystalline silicon (nc-Si:H) solar cells are strongly influenced by the morphology of underlying substrates. By texturing the substrates, the photogenerated current of nc-Si:H solar cells can increase due to enhanced light scattering. These textured substrates are, however, often incompatible with defect-less nc-Si:H growth resulting in lower Voc and FF. In this study we investigate the correlation between the substrate morphology, the nc-Si:H solar-cell performance, and the defect density in the intrinsic layer of the solar cells (i-nc-Si:H). Statistical surface parameters representing the substrate morphology do not show a strong correlation with the solar-cell parameters. Thus, we first quantify the line density of potentially defective valleys of randomly textured ZnO substrates where the opening angle is smaller than 130° (ρSi:H (ρdefect), which is obtained by fitting external photovoltaic parameters from experimental results and simulations. We confirm that when ρ<130 increases the Voc and FF significantly drops. It is also observed that ρdefect increases following a power law dependence of ρ<130. This result is attributed to more frequently formed defective regions for substrates having higher ρ<130.

  5. Intense focused ultrasound can reliably induce sensations in human test subjects in a manner correlated with the density of their mechanoreceptors.

    Science.gov (United States)

    Dickey, Trevor C; Tych, Rowen; Kliot, Michel; Loeser, John D; Pederson, Kristin; Mourad, Pierre D

    2012-01-01

    Sensations generated by intense focused ultrasound (iFU) can occur cutaneously and/or at depth, in contrast to other forms of stimulation (e.g., heat, electricity), whose action usually occurs only at the skin surface, or mechanical stimulation (e.g., von Frey hairs, calibrated forceps, tourniquets) that compress and thus stimulate all tissue. Previous work on iFU stimulation has led to the hypothesis that the tactile basis of iFU stimulation should correlate with the density of mechanoreceptors at the site of iFU stimulation. Here we tested that hypothesis, correlating a "two-point" neurological examination-a standard measure of superficial mechanoreceptor density-with the intensity of superficially applied iFU necessary to generate sensations with high sensitivity and specificity. We applied iFU at 1.1 MHz for 0.1 s to the fingertip pads of 17 test subjects in a blinded fashion and escalated intensities until they consistently observed iFU-induced sensations. Most test subjects achieved high values of sensitivity and specificity, doing so at values of spatially and temporally averaged intensity measuring mechanoreceptors as determined by a standard two-point discrimination neurological examination, consistent with earlier hypotheses.

  6. Highly correlating distance/connectivity-based topological indices 5. Accurate prediction of liquid density of organic molecules using PCR and PC-ANN.

    Science.gov (United States)

    Shamsipur, Mojtaba; Ghavami, Raouf; Sharghi, Hashem; Hemmateenejad, Bahram

    2008-11-01

    The primary goal of a quantitative structure-property relationship (QSPR) is to identify a set of structurally based numerical descriptors that can be mathematically linked to a property of interest. Recently, we proposed some new topological indices (Sh indices) based on the distance sum and connectivity of a molecular graph that derived directly from two-dimensional molecular topology for use in QSAR/QSPR studies. In this study, the ability of these indices to predict the liquid densities (rho) of a large and diverse set of organic liquid compounds (521 compounds) has been examined. Ten different Sh indices were calculated for each molecule. Both linear and non-linear modeling methods were implemented using principal component regression (PCR) and principal component-artificial neural network (PC-ANN) with back-propagation learning algorithm, respectively. Correlation ranking procedure was used to rank the principal components and entered them into the models. PCR analysis of the data showed that the proposed Sh indices could explain about 91.82% of variations in the density data, while the variations explained by the ANN modeling were more than 97.93%. The predictive ability of the models was evaluated using external test set molecules and root mean square errors of prediction of 0.0308 g ml(-1) and 0.0248 g ml(-1) were obtained for liquid densities of external compounds by linear and non-linear models, respectively.

  7. Power spectral density function and spatial autocorrelation of the ambient vibration full-wavefield generated by a distribution of spatially correlated surface sources

    Science.gov (United States)

    Lunedei, Enrico; Albarello, Dario

    2016-03-01

    Synthetic dispersion curves are here computed in the frame of an ambient-vibration full-wavefield model, which relies on the description of both ambient-vibration ground displacement and its sources as stochastic fields defined on the Earth's surface, stationary in time and homogeneous in space. In this model, previously developed for computing synthetic Horizontal-to-Vertical Spectral Ratio curves, the power spectral density function and the spatial autocorrelation of the displacement are naturally described as functions of the power spectral density function of the generating forces and of the subsoil properties (via the relevant Green's function), by also accounting for spatial correlation of these forces. Dispersion curves are computed from the displacement power spectral density function and from the spatial autocorrelation according with the well-known f-k and SPAC techniques, respectively. Two examples illustrate the way this new ambient-vibration model works, showing its possible use in better understanding the role of the surface waves in forming the dispersion curves, as well as its capability to capture some remarkable experimental findings.

  8. Evaluation of Seismicity Using Density Analysis of 2000-2015 Earthquakes in The West Coastal Zone of Anatolia (Turkey) And Its Correlation with Geothermal Areas

    Science.gov (United States)

    Bakak, Özde

    2016-10-01

    The purpose of the study is to evaluate the seismic activity using the density analysis methods (point density and Kernel density analysis) for 2000-2015 earthquake catalogue belonging to the study area surrounded by Qanakkale to the north, Fethiye to the south and Denizli (Buharkent) to the east, and also to apply its correlation with geothermal regions. The earthquake data, in total 6.675 earthquakes with M>3 magnitudes were obtained from DDA Catalogue of Prime Ministry Disaster & Emergency Management Authority (AFAD) official website. In this survey, data analysis and maps were prepared using ArcGIS (version_10.1) program. The analysis maps present (1) the intensity clustered earthquakes dominant in Sigacik and Gokova Gulfs, (2) regions which have high seismic risk were determined according to Buffer analysis for 2 km distance, (3) geothermal areas (21.4-153°C) in the west coastal zone of Anatolia were mapped, (4) regions the most affected by seismic activity for the last 15 years were detected from 2015 population data, and as latest (5) Seferihisar, Urla, Gulbahge, Demircili, Bodrum, and Datga provinces are identified as areas having high seismic activity for the last 15 years. Consequently, all analysis results were compared with the geothermal areas, and the review made that earthquake catalogue has not the relationship with hot regions and also these shocks triggered by active faults in this region using ArcGIS program. the author recommends that these regions should be investigated the earthquake sensitivity analysis in the near future.

  9. Lung density

    DEFF Research Database (Denmark)

    Garnett, E S; Webber, C E; Coates, G

    1977-01-01

    The density of a defined volume of the human lung can be measured in vivo by a new noninvasive technique. A beam of gamma-rays is directed at the lung and, by measuring the scattered gamma-rays, lung density is calculated. The density in the lower lobe of the right lung in normal man during quiet...... breathing in the sitting position ranged from 0.25 to 0.37 g.cm-3. Subnormal values were found in patients with emphsema. In patients with pulmonary congestion and edema, lung density values ranged from 0.33 to 0.93 g.cm-3. The lung density measurement correlated well with the findings in chest radiographs...... but the lung density values were more sensitive indices. This was particularly evident in serial observations of individual patients....

  10. MN15-L: A New Local Exchange-Correlation Functional for Kohn-Sham Density Functional Theory with Broad Accuracy for Atoms, Molecules, and Solids.

    Science.gov (United States)

    Yu, Haoyu S; He, Xiao; Truhlar, Donald G

    2016-03-08

    Kohn-Sham density functional theory is widely used for applications of electronic structure theory in chemistry, materials science, and condensed-matter physics, but the accuracy depends on the quality of the exchange-correlation functional. Here, we present a new local exchange-correlation functional called MN15-L that predicts accurate results for a broad range of molecular and solid-state properties including main-group bond energies, transition metal bond energies, reaction barrier heights, noncovalent interactions, atomic excitation energies, ionization potentials, electron affinities, total atomic energies, hydrocarbon thermochemistry, and lattice constants of solids. The MN15-L functional has the same mathematical form as a previous meta-nonseparable gradient approximation exchange-correlation functional, MN12-L, but it is improved because we optimized it against a larger database, designated 2015A, and included smoothness restraints; the optimization has a much better representation of transition metals. The mean unsigned error on 422 chemical energies is 2.32 kcal/mol, which is the best among all tested functionals, with or without nonlocal exchange. The MN15-L functional also provides good results for test sets that are outside the training set. A key issue is that the functional is local (no nonlocal exchange or nonlocal correlation), which makes it relatively economical for treating large and complex systems and solids. Another key advantage is that medium-range correlation energy is built in so that one does not need to add damped dispersion by molecular mechanics in order to predict accurate noncovalent binding energies. We believe that the MN15-L functional should be useful for a wide variety of applications in chemistry, physics, materials science, and molecular biology.

  11. Quantitative dual-energy CT for phantomless evaluation of cancellous bone mineral density of the vertebral pedicle: correlation with pedicle screw pull-out strength

    Energy Technology Data Exchange (ETDEWEB)

    Wichmann, Julian L.; Booz, Christian; Bauer, Ralf W.; Kerl, J.M.; Fischer, Sebastian; Lehnert, Thomas; Vogl, Thomas J.; Khan, M.F. [University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt am Main (Germany); Wesarg, Stefan [Fraunhofer IGD, Cognitive Computing and Medical Imaging, Darmstadt (Germany); Kafchitsas, Konstantinos [Spine Center, Asklepios Klinik Lindenlohe, Schwandorf (Germany)

    2015-06-01

    To evaluate quantitative dual-energy computed tomography (DECT) for phantomless analysis of cancellous bone mineral density (BMD) of vertebral pedicles and to assess the correlation with pedicle screw pull-out strength. Twenty-nine thoracic and lumbar vertebrae from cadaver specimens were examined with DECT. Using dedicated post-processing software, a pedicle screw vector was mapped (R1, intrapedicular segment of the pedicle vector; R2, intermediate segment; R3, intracorporal segment; global, all segments) and BMD was calculated. To invasively evaluate pedicle stability, pedicle screws were drilled through both pedicles and left pedicle screw pull-out strength was measured. Resulting values were correlated using the paired t test and Pearson's linear correlation. Average pedicle screw vector BMD (R1, 0.232 g/cm{sup 3}; R2, 0.166 g/cm{sup 3}; R3, 0.173 g/cm{sup 3}; global, 0.236 g/cm{sup 3}) showed significant differences between R1-R2 (P < 0.002) and R1-R3 (P < 0.034) segments while comparison of R2-R3 did not reach significance (P > 0.668). Average screw pull-out strength (639.2 N) showed a far stronger correlation with R1 (r = 0.80; P < 0.0001) than global BMD (r = 0.42; P = 0.025), R2 (r = 0.37; P = 0.048) and R3 (r = -0.33; P = 0.078) segments. Quantitative DECT allows for phantomless BMD assessment of the vertebral pedicle. BMD of the intrapedicular segment shows a significantly stronger correlation with pedicle screw pull-out strength than other segments. (orig.)

  12. Electronically Excited States of Vitamin B12: Benchmark Calculations Including Time-Dependent Density Functional Theory and Correlated Ab Initio Methods

    CERN Document Server

    Kornobis, Karina; Wong, Bryan M; Lodowski, Piotr; Jaworska, Maria; Andruniów, Tadeusz; Rudd, Kenneth; Kozlowski, Pawel M; 10.1021/jp110914y

    2011-01-01

    Time-dependent density functional theory (TD-DFT) and correlated ab initio methods have been applied to the electronically excited states of vitamin B12 (cyanocobalamin or CNCbl). Different experimental techniques have been used to probe the excited states of CNCbl, revealing many issues that remain poorly understood from an electronic structure point of view. Due to its efficient scaling with size, TD-DFT emerges as one of the most practical tools that can be used to predict the electronic properties of these fairly complex molecules. However, the description of excited states is strongly dependent on the type of functional used in the calculations. In the present contribution, the choice of a proper functional for vitamin B12 was evaluated in terms of its agreement with both experimental results and correlated ab initio calculations. Three different functionals, i.e. B3LYP, BP86, and LC-BLYP, were tested. In addition, the effect of relative contributions of DFT and HF to the exchange-correlation functional ...

  13. Bond breaking and bond formation: how electron correlation is captured in many-body perturbation theory and density-functional theory

    CERN Document Server

    Caruso, Fabio; Hellgren, Maria; Ren, Xinguo; Rinke, Patrick; Rubio, Angel; Scheffler, Matthias

    2012-01-01

    For the paradigmatic case of H2-dissociation we compare state-of-the-art many-body perturbation theory (MBPT) in the GW approximation and density-functional theory (DFT) in the exact-exchange plus random-phase approximation for the correlation energy (EX+cRPA). For an unbiased comparison and to prevent spurious starting point effects both approaches are iterated to full self-consistency (i.e. sc-RPA and sc-GW). The exchange-correlation diagrams in both approaches are topologically identical, but in sc-RPA they are evaluated with non-interacting and in sc-GW with interacting Green functions. This has a profound consequence for the dissociation region, where sc-RPA is superior to sc-GW. We argue that for a given diagrammatic expansion, the DFT framework outperforms the many-body framework when it comes to bond-breaking. We attribute this to the difference in the correlation energy rather than the treatment of the kinetic energy.

  14. Application of Density Functional Theoretic Descriptors to Quantitative Structure-Activity Relationships with Temperature Constrained Cascade Correlation Network Models of Nitrobenzene Derivatives

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A temperature-constrained cascade correlation network(TCCCN), a back-propagation neural network(BP), and multiple linear regression(MLR) models were applied to quantitative structure-activity relationship(QSAR) modeling, on the basis of a set of 35 nitrobenzene derivatives and their acute toxicities. These structural quantum-chemical descriptors were obtained from the density functional theory(DFT). Stepwise multiple regression analysis was performed and the model was obtained. The value of the calibration correlation coefficient R is 0.925, and the value of cross-validation correlation coefficient R is 0.87. The standard error S=0.308 and the cross-validated(leave-one-out) standard error Scv=0.381. Principal component analysis(PCA) was carried out for parameter selection. RMS errors for training set via TCCCN and BP are 0.067 and 0.095, respectively, and RMS errors for testing set via TCCCN and BP are 0.090 and 0.111, respectively. The results show that TCCCN performs better than BP and MLR.

  15. The Correlation Research of Bone Density on Women with Premature Ovarian Failure%卵巢早衰患者骨量变化的相关研究

    Institute of Scientific and Technical Information of China (English)

    林琳; 齐铮琴; 金海红; 王智文; 岳天孚

    2011-01-01

    Abstract Objective To evaluate the change of bone density and its associated factors in women with premature ovarian failure (POF). Methods 42 patients with POF undergoing bone mineral density (BMD) were selected, compared to 60 women paired by age whose menstrual cycles were regular. The associated factors with BMD of POF patients were analyzed. Results In women with POF,the mean bone mineral density was 0.92 g/cm2 at the lumbar spine and 0.87 g/cm2 at the neck of femur,both of which were significantly lower than the control group (P<0.05). The BMD at lumbar spine and neck of femur of POF patients presented highly positive correlation with age and body mass index (BMI), and negative correlation with duration of estrogen deficiency and serum follicle-stimulating hormone (FSH) level. There was no significant correlation with age of menarche and serum luteinizing hormone (LH) level. Serum estradiol (E2) presented positive correlation with BMD of lumbar spine and no significant correlation with BMD of neck of femur. Conclusion Women with POF have a decrease in lumbar spine and femoral bone density. Age,BMI,duration of estrogen deficiency and FSH were associated with BMD. Early comprehensive therapy will be beneficial to prevent bone loss in POF patients.%目的 探讨特发性卵巢早衰(POF)患者的骨量变化及其影响因素.方法选择特发性POF患者42例,对照组健康女性60例,测定2组的体质量指数、血清雌二醇(E2)等性激素水平及腰椎、股骨颈骨密度,比较2组骨密度值,并对影响POF患者骨量变化的相关因素进行分析.结果POF患者的腰椎骨密度为0.92 g/cm2,股骨颈骨密度为0.87 g/cm2,显著低于对照组(P<0.05).POF患者的腰椎及股骨颈骨密度与年龄、体质量指数呈显著正相关(P<0.05),与雌激素缺乏时间及血清促卵泡素(FSH)水平呈显著负相关(P<0.05),与初潮年龄及血清黄体生成素(LH)水平无显著相关性.E2水平与腰椎骨密度呈显著正相

  16. Correlations of 3T DCE-MRI Quantitative Parameters with Microvessel Density in a Human-Colorectal-Cancer Xenograft Mouse Model

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Sung Jun; An, Chan Sik; Koom, Woong Sub; Song, Ho Taek; Suh, Jin Suck [Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2011-11-15

    To investigate the correlation between quantitative dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) parameters and microvascular density (MVD) in a human-colon-cancer xenograft mouse model using 3 Tesla MRI. A human-colon-cancer xenograft model was produced by subcutaneously inoculating 1 X 106 DLD-1 human-colon-cancer cells into the right hind limbs of 10 mice. The tumors were allowed to grow for two weeks and then assessed using MRI. DCE-MRI was performed by tail vein injection of 0.3 mmol/kg of gadolinium. A region of interest (ROI) was drawn at the midpoints along the z-axes of the tumors, and a Tofts model analysis was performed. The quantitative parameters (Ktrans, Kep and Ve) from the whole transverse ROI and the hotspot ROI of the tumor were calculated. Immunohistochemical microvessel staining was performed and analyzed according to Weidner's criteria at the corresponding MRI sections. Additional Hematoxylin and Eosin staining was performed to evaluate tumor necrosis. The Mann-Whitney test and Spearman's rho correlation analysis were performed to prove the existence of a correlation between the quantitative parameters, necrosis, and MVD. Whole transverse ROI of the tumor showed no significant relationship between the MVD values and quantitative DCE-MRI parameters. In the hotspot ROI, there was a difference in MVD between low and high group of Ktrans and Kep that had marginally statistical significance (ps = 0.06 and 0.07, respectively). Also, Ktrans and Kep were found to have an inverse relationship with MVD (r -0.61, p = 0.06 in Ktrans; r = -0.60, p = 0.07 in Kep). Quantitative analysis of T1-weighted DCE-MRI using hotspot ROI may provide a better histologic match than whole transverse section ROI. Within the hotspots, Ktrans and Kep tend to have a reverse correlation with MVD in this colon cancer mouse model.

  17. Influence of Exchange-Correlation Functional in the Calculations of Vertical Excitation Energies of Halogenated Copper Phthalocyanines using Time-Dependent Density Functional Theory (TD-DFT)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Uck [Univ. of Ulsan, Ulsan (Korea, Republic of)

    2013-08-15

    The accurate prediction of vertical excitation energies is very important for the development of new materials in the dye and pigment industry. A time-dependent density functional theory (TD-DFT) approach coupled with 22 different exchange-correlation functionals was used for the prediction of vertical excitation energies in the halogenated copper phthalocyanine molecules in order to find the most appropriate functional and to determine the accuracy of the prediction of the absorption wavelength and observed spectral shifts. Among the tested functional, B3LYP functional provides much more accurate vertical excitation energies and UV-vis spectra. Our results clearly provide a benchmark calibration of the TD-DFT method for phthalocyanine based dyes and pigments used in industry.

  18. Quantitative ultrasound of the calcaneus with parametric imaging: correlation with bone mineral density at different sites and with anthropometric data in menopausal women

    Energy Technology Data Exchange (ETDEWEB)

    Louis, O.; Kaufman, L.; Osteaux, M

    2000-07-01

    Objective: To prospectively study the relationship of quantitative ultrasound of the calcaneus with anthromopometric variables and with bone mineral density (BMD) assessed at the level of the calcaneus as well as at other sites. Method: Osteosonography of the non-dominant calcaneus was performed in 135 menopausal women, using a DTU-one device with parametric imaging. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were assessed. BMD of the calcaneus (BMDcal) was measured using dual energy X-ray absorptiometry (DXA), in a subregion matched with the region of interest for osteosonography. BMD of the lumbar trabecular bone was measured using quantitative computed tomography (BMD QCT) while the non-dominant hip was studied using DXA, which provided the total bone mineral density (BMDhip) and that of the Ward triangle (BMDWard). Results: The Pearson correlation coefficients between BUA, SOS and the various measurements of BMD ranged from 0.305 (SOS versus BMDhip) to 0.717 (BUA versus BMDcal). BMD QCT and BMDWard were found to depend on age, but not on weight or height, while BUA, SOS, BMDcal, BMDhip were unrelated to age, but correlated with weight (SOS, BMDhip) or with weight and height (BUA, BMDcal). In a multiple stepwise regression analysis, age was a significant predictor for BMD QCT, BMD hip and BMDWard; BMD QCT, BMDWard and BMDhip admitted BUA as sole predictor, while BMDcal was significantly related to both BUA and SOS. Conclusion: BUA and SOS of the calcaneus, assessed in 135 menopausal women using a parametric imaging device, reflected BMDcal, measured with DXA at a matched region of interest, and did not decline significantly with age.

  19. A Bone Sample Containing a Bone Graft Substitute Analyzed by Correlating Density Information Obtained by X-ray Micro Tomography with Compositional Information Obtained by Raman Microscopy

    Directory of Open Access Journals (Sweden)

    Johann Charwat-Pessler

    2015-06-01

    Full Text Available The ability of bone graft substitutes to promote new bone formation has been increasingly used in the medical field to repair skeletal defects or to replace missing bone in a broad range of applications in dentistry and orthopedics. A common way to assess such materials is via micro computed tomography (µ-CT, through the density information content provided by the absorption of X-rays. Information on the chemical composition of a material can be obtained via Raman spectroscopy. By investigating a bone sample from miniature pigs containing the bone graft substitute Bio Oss®, we pursued the target of assessing to what extent the density information gained by µ-CT imaging matches the chemical information content provided by Raman spectroscopic imaging. Raman images and Raman correlation maps of the investigated sample were used in order to generate a Raman based segmented image by means of an agglomerative, hierarchical cluster analysis. The resulting segments, showing chemically related areas, were subsequently compared with the µ-CT image by means of a one-way ANOVA. We found out that to a certain extent typical gray-level values (and the related histograms in the µ-CT image can be reliably related to specific segments within the image resulting from the cluster analysis.

  20. Chiral Spin-Density Wave, Spin-Charge-Chern Liquid, and d+id Superconductivity in 1/4-Doped Correlated Electronic Systems on the Honeycomb Lattice

    Directory of Open Access Journals (Sweden)

    Shenghan Jiang

    2014-09-01

    Full Text Available Recently, two interesting candidate quantum phases—the chiral spin-density wave state featuring anomalous quantum Hall effect and the d+id superconductor—were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping. Using a combination of exact diagonalization, density matrix renormalization group, the variational Monte Carlo method, and quantum field theories, we study the quantum phase diagrams of both the Hubbard model and the t-J model on the honeycomb lattice at 1/4 doping. The main advantage of our approach is the use of symmetry quantum numbers of ground-state wave functions on finite-size systems (up to 32 sites to sharply distinguish different quantum phases. Our results show that for 1≲U/t<40 in the Hubbard model and for 0.1density wave state or a spin-charge-Chern liquid, but not a d+id superconductor. However, in the t-J model, upon increasing J, the system goes through a first-order phase transition at J/t=0.80(2 into the d+id superconductor. Here, the spin-charge-Chern liquid state is a new type of topologically ordered quantum phase with Abelian anyons and fractionalized excitations. Experimental signatures of these quantum phases, such as tunneling conductance, are calculated. These results are discussed in the context of 1/4-doped graphene systems and other correlated electronic materials on the honeycomb lattice.

  1. Preliminary study report: topological texture features extracted from standard radiographs of the heel bone are correlated with femoral bone mineral density

    Science.gov (United States)

    Boehm, H. F.; Lutz, J.; Koerner, M.; Notohamiprodjo, M.; Reiser, M.

    2009-02-01

    With the growing number of eldery patients in industrialized nations the incidence of geriatric, i.e. osteoporotic fractures is steadily on the rise. It is of great importance to understand the characteristics of hip fractures and to provide diagnostic tests for the assessment of an individual's fracture-risk that allow to take preventive action and give therapeutic advice. At present, bone-mineral-density (BMD) obtained from DXA (dual-energy x-ray-absorptiometry) is the clinical standard of reference for diagnosis and follow-up of osteoporosis. Since availability of DXA - other than that of clinical X-ray imaging - is usually restricted to specialized medical centers it is worth trying to implement alternative methods to estimate an individual's BMD. Radiographs of the peripheral skeleton, e.g. the ankle, range among the most ordered diagnostic procedures in surgery for exclusion or confirmation of fracture. It would be highly beneficial if - as a by-product of conventional imaging - one could obtain a quantitative parameter that is closely correlated with femoral BMD in addition to the original diagnostic information, e.g. fracture status at the peripheral site. Previous studies could demonstrate a correlation between calcaneal BMD and osteoporosis. The objective of our study was to test the hypothesis that topological analysis of calcaneal bone texture depicted by a lateral x-ray projection of the ankle allows to estimate femoral BMD. Our analysis on 34 post-menopausal patients indicate that texture properties based on graylevel topology in calcaneal x-ray-films are closely correlated with BMD at the hip and may qualify as a substitute indicator of femoral fracture risk.

  2. Focused ion beam-assisted manipulation of single and double beta-SiC nanowires and their thermal conductivity measurements by the four-point-probe 3-omega method.

    Science.gov (United States)

    Lee, K M; Choi, T Y; Lee, S K; Poulikakos, D

    2010-03-26

    Control of one-dimensional (1D) nanostructures is demonstrated in this paper by selectively placing and aligning silicon carbide (beta-SiC) nanowires (NWs). We developed a reliable and highly reproducible way of placing a single or double SiC NW on pre-patterned electrodes by using a focused ion beam and a nanomanipulator. 3-omega signals obtained by the four-point-probe method were used in measuring the thermal conductivity of the NWs. The thermal conductivities of the placed single and double beta-SiC NWs were obtained at 82 +/- 6 W mK( - 1) and 73 +/- 5 W mK( - 1), respectively. The proposed technique offers new possibilities for manipulating and evaluating 1D nanoscale materials.

  3. Correlating Petrophysical Well Logs Using Fractal-based Analysis to Identify Changes in the Signal Complexity Across Neutron, Density, Dipole Sonic, and Gamma Ray Tool Types

    Science.gov (United States)

    Matthews, L.; Gurrola, H.

    2015-12-01

    Typical petrophysical well log correlation is accomplished by manual pattern recognition leading to subjective correlations. The change in character in a well log is dependent upon the change in the response of the tool to lithology. The petrophysical interpreter looks for a change in one log type that would correspond to the way a different tool responds to the same lithology. To develop an objective way to pick changes in well log characteristics, we adapt a method of first arrival picking used in seismic data to analyze changes in the character of well logs. We chose to use the fractal method developed by Boschetti et al[1] (1996). This method worked better than we expected and we found similar changes in the fractal dimension across very different tool types (sonic vs density vs gamma ray). We reason the fractal response of the log is not dependent on the physics of the tool response but rather the change in the complexity of the log data. When a formation changes physical character in time or space the recorded magnitude in tool data changes complexity at the same time even if the original tool response is very different. The relative complexity of the data regardless of the tool used is dependent upon the complexity of the medium relative to tool measurement. The relative complexity of the recorded magnitude data changes as a tool transitions from one character type to another. The character we are measuring is the roughness or complexity of the petrophysical curve. Our method provides a way to directly compare different log types based on a quantitative change in signal complexity. For example, using changes in data complexity allow us to correlate gamma ray suites with sonic logs within a well and then across to an adjacent well with similar signatures. Our method creates reliable and automatic correlations to be made in data sets beyond the reasonable cognitive limits of geoscientists in both speed and consistent pattern recognition. [1] Fabio Boschetti

  4. Comprehensive evaluation of medium and long range correlated density functionals in TD-DFT investigation of DNA bases and base pairs: gas phase and water solution study

    Science.gov (United States)

    Shukla, Manoj K.; Leszczynski, Jerzy

    2010-11-01

    A comprehensive analysis of the performance of the TD-DFT method using different density functionals including recently developed medium and long-range correlation corrected density functionals have been carried out for lower-lying electronic singlet valence transitions of nucleic acid bases and the Watson-Crick base pairs in the gas phase and in the water solution. The standard 6-311++G(d,p) basis set was used. Ground state geometries of bases and base pairs were optimized at the M05-2X/6-311++G(d,p) level. The nature of potential energy surfaces (PES) was ascertained through the harmonic vibrational frequency analysis; all geometries were found to be minima at the respective PES. Electronic singlet vertical transition energies were also computed at the CC2/def2-TZVP level in the gas phase. The effect of state-specific water solvation on TD-DFT computed transition energies was considered using the PCM model. For the isolated bases the performance of the B3LYP functional was generally found to be superior among all functionals, but it measurably fails for charge-transfer states in the base pairs. The CC2/def2-TZVP computed transition energies were also revealed to be inferior compared with B3LYP results for the isolated bases. The performance of the ωB97XD, CAM-B3LYP and BMK functionals were found to be similar and comparable with the CC2 results for the isolated bases. However, for the Watson-Crick adenine-thymine and guanine-cytosine base pairs the performance of the ωB97XD functional was found to be the best among all the studied functionals in the present work in predicting the locally excited transitions as well as charge transfer states.

  5. Asymptotic correction of the exchange-correlation kernel of time-dependent density functional theory for long-range charge-transfer excitations.

    Science.gov (United States)

    Gritsenko, Oleg; Baerends, Evert Jan

    2004-07-08

    Time-dependent density functional theory (TDDFT) calculations of charge-transfer excitation energies omegaCT are significantly in error when the adiabatic local density approximation (ALDA) is employed for the exchange-correlation kernel fxc. We relate the error to the physical meaning of the orbital energy of the Kohn-Sham lowest unoccupied molecular orbital (LUMO). The LUMO orbital energy in Kohn-Sham DFT--in contrast to the Hartree-Fock model--approximates an excited electron, which is correct for excitations in compact molecules. In CT transitions the energy of the LUMO of the acceptor molecule should instead describe an added electron, i.e., approximate the electron affinity. To obtain a contribution that compensates for the difference, a specific divergence of fxc is required in rigorous TDDFT, and a suitable asymptotically correct form of the kernel fxc(asymp) is proposed. The importance of the asymptotic correction of fxc is demonstrated with the calculation of omegaCT(R) for the prototype diatomic system HeBe at various separations R(He-Be). The TDDFT-ALDA curve omegaCT(R) roughly resembles the benchmark ab initio curve omegaCT CISD(R) of a configuration interaction calculation with single and double excitations in the region R=1-1.5 A, where a sizable He-Be interaction exists, but exhibits the wrong behavior omegaCT(R)

  6. Correlação entre a densidade óssea mandibular, femural, lombar e cervical Correlation among mandibular, femoral, lumbar and cervical bone density

    Directory of Open Access Journals (Sweden)

    Paula Cabrini Scheibel

    2009-08-01

    movimentação ortodôntica.INTRODUCTION: Due to the rise in frequency of adult patients who currently are submitted to orthodontic treatment, general health conditions of this age have been a reason of inquiries correlated to events related to bone metabolism, as dental movements are dependent on the process of bone remodeling, even though in a local level. Different standards of bone density can give different answers to the orthodontic movement. AIM: The present study evaluated the correlation of the general bone mineral density (BMD to the mandibular region. METHODS: Therefore, 22 healthy women aged between 30 and 45 years old were selected for bone densitometry examinations of lumbar, cervical, femoral, as well as mandibular alveolar region. The correlations to these readings were tested as well as values of reference were established for cervical and mandibular areas. RESULTS: The results did not demonstrate significant correlation among the mandibular density to the others studied areas. There was only significant correlation between cervical and femural region. Normal BMD average value for mandibular region was 0.983g/cm² (SD = 0.334, whereas for cervical region was 0.768g/cm² (SD = 0.102, and the average values for lumbar and femoral regions were respectively 1.127g/cm² (SD = 0.067 and 0.925g/cm² (SD = 0.078, these last ones were similar to the reference values of World Health Organization (WHO. CONCLUSIONS: It is suggested that the examination of the femoral area can comprehend the expected value to cervical area, however particular densitometry examination for the mandibular area is needed, and the exploration of the traditional values (lumbar and femoral is not appropriate to the estimative of this area. Additional studies are necessary to evaluate local density variations and its influence on orthodontic movement.

  7. Correlation of Computerized Tomography density patterns of lymph nodes with treatment results and outcome in head and neck cancer patients treated by 2 different chemoradiotherapy schedules

    Directory of Open Access Journals (Sweden)

    Sweta Jaju

    2014-01-01

    Full Text Available Aims/Background: Tumor necrosis is visualized on CT scan as non enhancing hypodense area. Necrotic areas contain less oxygen and results in poor response of chemo-radiotherapy. Literature review (1 has shown that for hypodense lesions in head and neck cancer the complete response rate is lower than the isodense lesions. Locally advanced head and neck cancer require the addition of surgery but after a radical dose of radiation that is, 7000 cGy, surgery become difficult but there is no tool initially that can be used for selection of patients after delivery of 4500 cGy, that is the dose after which surgery can be performed without much difficulty. The hypothesis is that, hypodense lymph nodes even when they are small will show less response to various schedules of chemoradiotherapy so hypodensity of lymph nodes can be used as a tool to select patient, who will go for surgery after initial 4500 cGy of radiotherapy. Surgery is usually performed 2 to 3 weeks after radiotherapy, so primary can be treated to full dose while the skin in region of lymph nodes radiation field will recover from acute radiation reaction. Correlation of C T density patterns of lymph nodes in head and neck cancer patients with treatment results when two different chemoradiotherapy schedules are used is studied. Materials and Methods: Eighty three patients with locally advanced head and neck cancer were treated with two schedules of concurrent chemoradiotherapy prospectively from August 2010 to July 2011. CT Scans of the entire neck region including primary were performed. An iodine based contrast material (150 ml was injected intravenously starting with a bolus of 50ml (3ml/s, followed by a slow (1ml/s infusion of the remaining dose. The total tumor volume of the primary and involved neck nodes was calculated as a cuboid volume using maximum dimension in each plane: Vc= (a x b x c. Nodal density was graded. Results and Conclusion: No statistically significant association

  8. Bone mineral density measurements of the proximal femur from routine contrast-enhanced MDCT data sets correlate with dual-energy X-ray absorptiometry

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, M. [Medical University of Vienna, Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Vienna (Austria); Bauer, J.S.; Dobritz, M.; Woertler, K.; Rummeny, E.J.; Baum, T. [Technische Universitaet Muenchen, Department of Radiology, Klinikum rechts der Isar, Munich (Germany); Beer, A.J. [Technische Universitaet Muenchen, Department of Nuclear Medicine, Munich (Germany); Wolf, P. [Technische Universitaet Muenchen, Institute for Medical Statistics and Epidemiology, Munich (Germany)

    2013-02-15

    To evaluate the utility of femoral bone mineral density (BMD) measurements in routine contrast-enhanced multi-detector computed tomography (ceMDCT) using dual-energy X-ray absorptiometry (DXA) as the reference standard. Forty-one patients (33 women, 8 men) underwent DXA measurement of the proximal femur. Subsequently, transverse sections of routine ceMDCT of these patients were used to measure BMD of the femoral head and femoral neck. The MDCT-to-DXA conversion equations for BMD and T-score were calculated using linear regression analysis. The conversion equations were applied to the MDCT data sets of 382 patients (120 women, 262 men) of whom 74 had osteoporotic fractures. A correlation coefficient of r = 0.84 (P < 0.05) was calculated for BMD{sub MDCT} values of the femoral head and DXA T-scores of the total proximal femur using the conversion equation T-score = 0.021 x BMD{sub MDCT} - 5.90. The correlation coefficient for the femoral neck was r = 0.79 (P < 0.05) with the conversion equation T-score = 0.016 x BMD{sub MDCT} - 4.28. Accordingly, converted T-scores for the femoral neck in patients with versus those without osteoporotic fractures were significantly different (female, -1.83 versus -1.47; male, -1.86 versus -1.47; P < 0.05). BMD measurements of the proximal femur were computed in routine contrast-enhanced MDCT and converted to DXA T-scores, which adequately differentiated patients with and without osteoporotic fractures. (orig.)

  9. How universal are hydrogen bond correlations? A density functional study of intramolecular hydrogen bonding in low-energy conformers of α-amino acids

    Science.gov (United States)

    Ramaniah, Lavanya M.; Kamal, C.; Kshirsagar, Rohidas J.; Chakrabarti, Aparna; Banerjee, Arup

    2013-10-01

    Hydrogen bonding is one of the most important and ubiquitous interactions present in Nature. Several studies have attempted to characterise and understand the nature of this very basic interaction. These include both experimental and theoretical investigations of different types of chemical compounds, as well as systems subjected to high pressure. The O-H..O bond is of course the best studied hydrogen bond, and most studies have concentrated on intermolecular hydrogen bonding in solids and liquids. In this paper, we analyse and characterise normal hydrogen bonding of the general type, D-H...A, in intramolecular hydrogen bonding interactions. Using a first-principles density functional theory approach, we investigate low energy conformers of the twenty α-amino acids. Within these conformers, several different types of intramolecular hydrogen bonds are identified. The hydrogen bond within a given conformer occurs between two molecular groups, either both within the backbone itself, or one in the backbone and one in the side chain. In a few conformers, more than one (type of) hydrogen bond is seen to occur. Interestingly, the strength of the hydrogen bonds in the amino acids spans quite a large range, from weak to strong. The signature of hydrogen bonding in these molecules, as reflected in their theoretical vibrational spectra, is analysed. With the new first-principles data from 51 hydrogen bonds, various parameters relating to the hydrogen bond, such as hydrogen bond length, hydrogen bond angle, bond length and vibrational frequencies are studied. Interestingly, the correlation between these parameters in these bonds is found to be in consonance with those obtained in earlier experimental studies of normal hydrogen bonds on vastly different systems. Our study provides some of the most detailed first-principles support, and the first involving vibrational frequencies, for the universality of hydrogen bond correlations in materials.

  10. Density-functional and electron correlated study of five linear birefringences--Kerr, Cotton-Mouton, Buckingham, Jones, and magnetoelectric--in gaseous benzene.

    Science.gov (United States)

    Rizzo, Antonio; Cappelli, Chiara; Jansík, Branislav; Jonsson, Dan; Sałek, Paweł; Coriani, Sonia; Agren, Hans

    2004-11-08

    We present the results of an extended study of five birefringences--Kerr, Cotton-Mouton, Buckingham, Jones, and Magnetoelectric--on benzene in the gas phase. The relevant molecular quantities--first-order properties, linear, quadratic, and cubic response functions--are computed employing the density-functional theory (DFT) response theory, with a choice of functionals. In some cases, different functionals are employed for the wave-function computational step and for the subsequent analytical response calculation to determine the combination yielding at the same time the optimal energy and energy derivative results. Augmented correlation consistent basis sets of double and triple zeta quality are used. The DFT results are compared to those obtained at the Hartree-Fock level and in some cases within a coupled cluster singles and doubles electronic structure model. The study tries to assess the ability of the DFT response theory to describe a wide range of properties in a system of rather large size and high complexity. The relative strength of the five birefringences for plausible experimental conditions is determined and, when possible, comparison is made with the results of the measurements.

  11. Bone marrow mast cell density correlates with serum levels of VEGF and CXC chemokines ENA-78 and GRO-α in multiple myeloma.

    Science.gov (United States)

    Pappa, C A; Tsirakis, G; Devetzoglou, M; Zafeiri, M; Vyzoukaki, R; Androvitsanea, A; Xekalou, A; Sfiridaki, K; Alexandrakis, M G

    2014-06-01

    Angiogenesis is a crucial process in growth and progression of multiple myeloma (MM). Mast cells (MCs) play an important role in MM angiogenesis. Various angiogenic mediators secreted by MCs regulate endothelial cell proliferation and function. Among them, ELR(+) CXC chemokines, such as growth-related oncogen-alpha (GRO-α) and epithelial neutrophil activating protein-78 (ENA-78), have been described as potential mediators in regulation of angiogenesis. The purpose of the study was to quantify MCs in bone marrow (BM) biopsies of MM patients, expressed as MC density (MCD), and correlate it with serum concentrations of vascular endothelial factor (VEGF), GRO-α, ENA-78. Fifty-four newly diagnosed MM patients and 22 healthy controls were studied. Tryptase was used for the immunohistochemical stain of MCs. VEGF, GRO-α, and ENA-78 were measured in sera by ELISA. MCD and serum levels of GRO-α, ENA-78, and VEGF were significantly higher in MM patients compared to controls (pENA-78. These findings support that MCs participate in the pathophysiology of MM and is implicated in the angiogenic process and disease progression.

  12. Correlation of local structure peculiarities and critical current density of 2G MOCVD YBCO tapes with BaZrO3 nanoinclusions

    Science.gov (United States)

    Menushenkov, A. P.; Ivanov, V. G.; Chepikov, V. N.; Nygaard, R. R.; Soldatenko, A. V.; Rudnev, I. A.; Osipov, M. A.; Mineev, N. A.; Kaul, A. R.; Mathon, O.; Monteseguro, V.

    2017-04-01

    We have studied the influence of BaZrO3 nanoinclusions on the local structure and critical current density of second-generation high temperature superconducting tapes based on YBa2Cu3O7-δ (YBCO) films. The films were made by metal-organic chemical vapor deposition (MOCVD). The crystal and local structure of the materials under study were analysed by x-ray diffraction and x-ray absorption spectroscopy (EXAFS + XANES). We have found that, being added at MOCVD process, Zr forms BaZrO3 nanoinclusions in YBCO matrix. The distance between Zr and the neighboring atoms is shorter than that one in a bulk crystalline BaZrO3, so we conclude that the nanoinclusions are in compressed state. The incorporation of 5 mol% BaZrO3 minimizes the static disorder of Cu-O bonds and maximizes their stiffness in YBCO. We show that the local structure peculiarities correlate well with the observed critical current behavior and consider this to be additional evidence in favor of small amounts of BaZrO3 nanoinclusions as efficient pinning centers.

  13. On the accuracy of van der Waals inclusive density-functional theory exchange-correlation functionals for ice at ambient and high pressures

    Science.gov (United States)

    Santra, Biswajit; Klimeš, Jiří; Tkatchenko, Alexandre; Alfè, Dario; Slater, Ben; Michaelides, Angelos; Car, Roberto; Scheffler, Matthias

    2013-10-01

    Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [B. Santra, J. Klimeš, D. Alfè, A. Tkatchenko, B. Slater, A. Michaelides, R. Car, and M. Scheffler, Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water.

  14. Electron-boson spectral density function of correlated multiband systems obtained from optical data: Ba0.6K0.4Fe2As2 and LiFeAs.

    Science.gov (United States)

    Hwang, Jungseek

    2016-03-31

    We introduce an approximate method which can be used to simulate the optical conductivity data of correlated multiband systems for normal and superconducting cases by taking advantage of a reversed process in comparison to a usual optical data analysis, which has been used to extract the electron-boson spectral density function from measured optical spectra of single-band systems, like cuprates. We applied this method to optical conductivity data of two multiband pnictide systems (Ba0.6K0.4Fe2As2 and LiFeAs) and obtained the electron-boson spectral density functions. The obtained electron-boson spectral density consists of a sharp mode and a broad background. The obtained spectral density functions of the multiband systems show similar properties as those of cuprates in several aspects. We expect that our method helps to reveal the nature of strong correlations in the multiband pnictide superconductors.

  15. Future Road Density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  16. Methodology for Measurement of Submicron Metallic Wire's Local Electrical Conductivity by Applying Four-points AFM Probe Technique%金属薄膜导线的亚微米局域电导率精确测量技术

    Institute of Scientific and Technical Information of China (English)

    吴蕾; 葛耀峥; 居冰峰

    2011-01-01

    作为薄膜器件最重要物理量之一的局域电导率的定量测定,能在保证性能、提高成品率、完善制作工艺等方面起关键作用.利用基于原子力显微镜(Atomic force microscope,AFM)的4电极微探针局域电导率测量技术,精确测量厚度为350nm、宽度分别为50.0 μm、25.0μm、5.0 μm、2.0μm及600 nm、纯度为99.999%的铝薄膜导线的电导率.由于被测试件宽度和厚度方向的尺寸明显缩小且十分接近电极的最小间距,综合考虑电极尺寸、不同批次电极的加工精度和加工参数、4个电极间的位置误差等几个影响测量精度的因素,修正电导率的计算模型并将传统4电极电导率测量法的应用领域拓展到亚微米级微观尺度.试验结果证明基于AFM的4电极微探针技术在亚微米级局域电导率测量方面的能力.%The quantitative measurement of electrical conductivity plays a key role in ensuring material performance, improving yield and fabrication process. The four-points AFM probe technique is applied for the purpose of quantitatively measuring local conductivities of the 99.999% aluminum wires and 350 nm thickness and different widths of 600 mn, 2.0 μm, 5.0 μm, 25.0 βm and 50.0 βm. As position the width and thickness of the specimen is very close to the minimum distance of the electrodes, we consider the factors that affect the measurement accuracy, such as size, diversity of parameter and precision in processing and position error of the four-points AFM probe, modify the calculation model of conductivity and extend the traditional four-electrode conductivity measurements to the sub-micron level. The repeatability of conductivity measurements indicates that this four-point AFM probe technique could be used for fast in situ characterization of local electrical properties of nanocircuits and nanodevices.

  17. Asymptotic correction approach to improving approximate exchange-correlation potentials: Time-dependent density-functional theory calculations of molecular excitation spectra

    Science.gov (United States)

    Casida, Mark E.; Salahub, Dennis R.

    2000-11-01

    The time-dependent density functional theory (TD-DFT) calculation of excitation spectra places certain demands on the DFT exchange-correlation potential, vxc, that are not met by the functionals normally used in molecular calculations. In particular, for high-lying excitations, it is crucial that the asymptotic behavior of vxc be correct. In a previous paper, we introduced a novel asymptotic-correction approach which we used with the local density approximation (LDA) to yield an asymptotically corrected LDA (AC-LDA) potential [Casida, Casida, and Salahub, Int. J. Quantum Chem. 70, 933 (1998)]. The present paper details the theory underlying this asymptotic correction approach, which involves a constant shift to incorporate the effect of the derivative discontinuity (DD) in the bulk region of finite systems, and a spliced asymptotic correction in the large r region. This is done without introducing any adjustable parameters. We emphasize that correcting the asymptotic behavior of vxc is not by itself sufficient to improve the overall form of the potential unless the effect of the derivative discontinuity is taken into account. The approach could be used to correct vxc from any of the commonly used gradient-corrected functionals. It is here applied to the LDA, using the asymptotically correct potential of van Leeuwen and Baerends (LB94) in the large r region. The performance of our AC-LDA vxc is assessed for the calculation of TD-DFT excitation energies for a large number of excitations, including both valence and Rydberg states, for each of four small molecules: N2, CO, CH2O, and C2H4. The results show a significant improvement over those from either the LB94 or the LDA functionals. This confirms that the DD is indeed an important element in the design of functionals. The quality of TDLDA/LB94 and TDLDA/AC-LDA oscillator strengths were also assessed in what we believe to be the first rigorous assessment of TD-DFT molecular oscillator strengths in comparison with

  18. Four-point bending JCOC process:A new technology for forming longitudinally submerged arc welding pipe%大型直缝焊管四点弯曲JCOC成形新工艺

    Institute of Scientific and Technical Information of China (English)

    赵军; 孙红磊; 宋晓抗; 马瑞

    2012-01-01

    在分析大型直缝焊管四点弯曲JCO成形力学原理的基础上,对缩径矫圆的理论和实验进行研究,提出了四点弯曲JCOC成形新工艺.该工艺具有成形道次少、生产效率高、无需预弯边、残余应力小、柔性程度高、成形质量好和防止缺陷扩大等成形特点和优势.按照相似性原理,采用JCOC成形新工艺,以X80钢级φ1219mm×22mm钢管为原型,同比例缩小模具和管件尺寸,制成缩径矫圆后φ260.4mm× 4.7mm管坯.该批管坯的椭圆度最大值≤0.5%,满足生产技术要求.JCOC成形新工艺具有良好的市场推广和工程应用价值.%Based on the analysis of the mechanical principles of the "four-point bending JCO (J-Forming C-Forming O-Forming)" process for LSAW (longitudinal submerged ard welding) pipe as well as theoretical and experimental researches on "compression to make round", this paper presented a new technology called the "four-point bending JCOC (J-Forming C-Forming O-Forming and Compression to make round) process". The advantages of the new technology included fewer steps of formation, higher pro-ductivity, the dispensing with crimping process, less residual stress, higher flexibility, better forming quality and preventing the expansion of flaws. Scaling down the mold and pipe dimensions in accordance with the principle of similarity, this experiment used the new technology to make φ260. 4mm× 4. 7mm pipe samples from φ1219mm× 22mm of X80 steel pipe. The samples made by the new process met production requirements with the ovality up to 0. 5%. This indicated that the new technology had good marketing and engineering applications.

  19. Comparison of Correlates of Bone Mineral Density in Individuals Adhering to Lacto-Ovo, Vegan, or Omnivore Diets: A Cross-Sectional Investigation

    Directory of Open Access Journals (Sweden)

    Jessica R. Knurick

    2015-05-01

    Full Text Available Vegetarian diets are associated with factors that may not support bone health, such as low body mass and low intakes of protein; yet, these diets are alkaline, a factor that favors bone mineral density (BMD. This study compared the correlates of BMD in young, non-obese adults consuming meat-based (n = 27, lacto-ovo vegetarian (n = 27, or vegan (n = 28 diets for ≥1 year. A 24 h diet recall, whole body DXA scan, 24 h urine specimen, and fasting blood sample were collected from participants. BMD did not differ significantly between groups. Protein intake was reduced ~30% in individuals consuming lacto-ovo and vegan diets as compared to those consuming meat-based diets (68 ± 24, 69 ± 29, and 97 ± 47 g/day respectively, p = 0.006; yet dietary protein was only associated with BMD for those following vegan diets. Urinary pH was more alkaline in the lacto-ovo and vegan groups versus omnivores (6.5 ± 0.4, 6.7 ± 0.4, and 6.2 ± 0.4 respectively, p = 0.003; yet urinary pH was associated with BMD in omnivores only. These data suggest that plant-based diets are not detrimental to bone in young adults. Moreover, diet prescriptions for bone health may vary among diet groups: increased fruit and vegetable intake for individuals with high meat intakes and increased plant protein intake for individuals who follow a vegetarian diet plan.

  20. Maize varieties released in different eras have similar root length density distributions in the soil, which are negatively correlated with local concentrations of soil mineral nitrogen.

    Directory of Open Access Journals (Sweden)

    Peng Ning

    Full Text Available Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N, phosphorus (P and potassium (K, two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 0-60 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 30-60 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD, especially in the 0-20 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize.

  1. Comparison of correlates of bone mineral density in individuals adhering to lacto-ovo, vegan, or omnivore diets: a cross-sectional investigation.

    Science.gov (United States)

    Knurick, Jessica R; Johnston, Carol S; Wherry, Sarah J; Aguayo, Izayadeth

    2015-05-11

    Vegetarian diets are associated with factors that may not support bone health, such as low body mass and low intakes of protein; yet, these diets are alkaline, a factor that favors bone mineral density (BMD). This study compared the correlates of BMD in young, non-obese adults consuming meat-based (n = 27), lacto-ovo vegetarian (n = 27), or vegan (n = 28) diets for ≥1 year. A 24 h diet recall, whole body DXA scan, 24 h urine specimen, and fasting blood sample were collected from participants. BMD did not differ significantly between groups. Protein intake was reduced ~30% in individuals consuming lacto-ovo and vegan diets as compared to those consuming meat-based diets (68 ± 24, 69 ± 29, and 97 ± 47 g/day respectively, p = 0.006); yet dietary protein was only associated with BMD for those following vegan diets. Urinary pH was more alkaline in the lacto-ovo and vegan groups versus omnivores (6.5 ± 0.4, 6.7 ± 0.4, and 6.2 ± 0.4 respectively, p = 0.003); yet urinary pH was associated with BMD in omnivores only. These data suggest that plant-based diets are not detrimental to bone in young adults. Moreover, diet prescriptions for bone health may vary among diet groups: increased fruit and vegetable intake for individuals with high meat intakes and increased plant protein intake for individuals who follow a vegetarian diet plan.

  2. Mandibulo-osseous predictors of osteoporosis: A double-blind study on the correlation and comparison of mental index with bone mineral density in post-menopausal women

    Directory of Open Access Journals (Sweden)

    Shefali Waghray

    2015-01-01

    Full Text Available Introduction: Osteoporosis is a metabolic bone disease characterized by microarchitectural deterioration in bone tissue leading to fractures, and is essentially a preventable disease when detected in the early stages. Novel methods for early identification of osteoporosis can have a great impact in combating this otherwise progressive disease. Aims: The present study was conducted with the objectives of evaluating the precision of a radiomorphometric index [mental index (MI] measured on a panoramic radiograph in early diagnosis of osteoporosis and finding its correlation with bone mineral density (BMD measured by digital X-ray radiogrammetry method. Materials and Methods: The study consisted of 71 women who were in natural menopause. The MI was calculated by two investigators, with each investigator recording two sets of measurements. The BMD was assessed and the T-score was obtained by digital X-ray radiogrammetry method. Based on the T-score obtained, the patients were divided into three study groups of normal (n = 24, osteopenic (n = 30, and osteoporotic (n = 17. The values obtained were tabulated for statistical analysis. Results: In the present study, it was found that there was a statistically significant difference in the mean scores of MI among normal, osteopenic, and osteoporotic subjects. Normal subjects had significantly higher MI (P < 0.001 than the osteopenic subjects and, similarly, the osteopenic subjects had significantly higher MI (P < 0.001 than the osteoporotic subjects. The inter- and intra-investigator variability was found to be low. Conclusion: Based on the results of the present study, it was concluded that a simple radiomorphometric index (MI which is relatively easier to measure on a panoramic radiograph can be an indicator of osteoporosis and may aid in early detection and treatment planning of one of the most prevalent metabolic bone diseases.

  3. Evaluation of group electronegativities and hardness (softness) of group 14 elements and containing functional groups through density functional theory and correlation with NMR spectra data

    Energy Technology Data Exchange (ETDEWEB)

    Vivas-Reyes, R.; Aria, A. [Universidad de Cartagena, Cartagena (Colombia). Facultad de Ciencias Naturales y Exactas. Grupo de Quimica Cuantica y Computacional]. E-mail: rvivasr@unicartagena.edu.co

    2008-07-01

    Quantum Chemical calculations for group 14 elements of Periodic Table (C, Si, Ge, Sn, Pb) and their functional groups have been carried out using Density Functional Theory (DFT) based reactivity descriptors such as group electronegativities, hardness and softness. DFT calculations were performed for a large series of tetra coordinated Sn compounds of the CH{sub 3}SnRR'X type, where X is a halogen and R and R' are alkyl, halogenated alkyl, alkoxy, or alkyl thio groups. The results were interpreted in terms of calculated electronegativity and hardness of the SnRR'X groups, applying a methodology previously developed by Geerlings and coworkers (J. Phys. Chem. 1993, 97, 1826). These calculations allowed to see the regularities concerning the influence of the nature of organic groups RR' and inorganic group X on electronegativities and hardness of the SnRR'X groups; in this case, it was found a very good correlation between the electronegativity of the fragment and experimental {sup 119}Sn chemical shifts, a property that sensitively reflects the change in the valence electronic structure of molecules. This work was complemented with the study of some compounds of the EX and ER types, where E= C, Si, Ge, Sn and R= CH{sub 3}, H, which was performed to study the influence that the central atom has on the electronegativity and hardness of molecules, or whether these properties are mainly affected for the type of ligand bound to the central atom. All these calculations were performed using the B3PW91 functional together with the 6-3 1 1 + + G basis set level for H, C, Si, Ge, F, Cl and Br atoms and the 3-21G for Sn and I atoms. (author)

  4. Elevated levels of oxidized low-density lipoprotein correlate positively with C-reactive protein in patients with acute coronary syndrome.

    Science.gov (United States)

    Zhang, Ya-chen; Wei, Jing-jing; Wang, Fei; Chen, Man-tian; Zhang, Mao-zhen

    2012-03-01

    The relationship between oxidized low-density lipoprotein (Ox-LDL) and C-reactive protein (CRP) in patients with acute coronary syndrome (ACS) is unknown. We, therefore, measured serum levels of Ox-LDL and high-sensitivity (hs)-CRP in 90 ACS patients, 45 stable angina pectoris (SAP) patients, and 66 healthy controls using sandwich ELISA. ACS patients were subdivided into: (1) acute myocardial infarction (AMI; n = 45); (2) unstable angina pectoris (UAP; n = 45) groups. In AMI patients, Ox-LDL (177.5 mmol/l) and hs-CRP (25.40 mg/l) levels were significantly higher (P LDL:107.5 mmol/l, hs-CRP:10.7 mg/l) and SAP (Ox-LDL:82.3 mmol/l, hs-CRP:2.10 mg/l) patients as well as controls (Ox-LDL:41.4 mmol/l, hs-CRP:1.76 mg/l). Ox-LDL/hs-CRP levels in UAP patients were significantly higher (P LDL and CRP (r = 0.622; P HDL, and LDL cholesterol did not differ among these patient groups. In conclusion, our data show that Ox-LDL and hs-CRP levels correlate positively in ACS patients, supporting the hypothesis that Ox-LDL and CRP may play a direct role in promoting the inflammatory component of atherosclerosis in these individuals. We suggest that Ox-LDL/CRP elevated levels may serve as markers of the severity of the disease in evaluation and management of ACS patients.

  5. Maize varieties released in different eras have similar root length density distributions in the soil, which are negatively correlated with local concentrations of soil mineral nitrogen.

    Science.gov (United States)

    Ning, Peng; Li, Sa; White, Philip J; Li, Chunjian

    2015-01-01

    Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N), phosphorus (P) and potassium (K), two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 0-60 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 30-60 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin) in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD), especially in the 0-20 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize.

  6. Correlations between critical current density, j{sub c}, critical temperature, T{sub c}, and structural quality of Y{sub 1}B{sub 2}Cu{sub 3}O{sub 7-x} thin superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Chrzanowski, J.; Xing, W.B.; Atlan, D. [Simon Fraser Univ., British Columbia (Canada)] [and others

    1994-12-31

    Correlations between critical current density (j{sub c}) critical temperature (T{sub c}) and the density of edge dislocations and nonuniform strain have been observed in YBCO thin films deposited by pulsed laser ablation on (001) LaAlO{sub 3} single crystals. Distinct maxima in j{sub c} as a function of the linewidths of the (00{ell}) Bragg reflections and as a function of the mosaic spread have been found in the epitaxial films. These maxima in j{sub c} indicate that the magnetic flux lines, in films of structural quality approaching that of single crystals, are insufficiently pinned which results in a decreased critical current density. T{sub c} increased monotonically with improving crystalline quality and approached a value characteristic of a pure single crystal. A strong correlation between j{sub c} and the density of edge dislocations N{sub D} was found. At the maximum of the critical current density the density of edge dislocations was estimated to be N{sub D}{approximately}1-2 x 10{sup 9}/cm{sup 2}.

  7. Analysis of bone mineral density of human bones for strength evaluation

    Indian Academy of Sciences (India)

    S N Khan; R M Warkhedkar; A K Shyam

    2015-08-01

    The bone density (BMD) is a medical term normally referring to the amount of mineral matter per square centimetre of bones. Twenty-five patients (18 female and 7 male patients with a mean age of 71.3 years) undergoing both lumbar spine DXA scans and computed tomography imaging were evaluated to determine if HU correlates with BMD and T-scores. BMD is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk. This medical bone density is not the true physical ``density'' of the bone, which would be computed as mass per volume. Dual-energy X-ray absorptiometry (DXA, previously DEXA), a means of measuring BMD, is the most widely used and most thoroughly studied bone density measurement technologies. Different types of bone strength are required for various applications, but this strength calculation requires different machines for each strength property or it is done by different software like X-ray, CT scan, DEXA and BIA. The paper includes the design of an experimental setup which performs different types of test like tension, compression, three point bending, four point bending and torsion. The modified correlation between BMD and HU for various strength calculations is found out and validated with the experimental results.

  8. LOCAL-DENSITY FUNCTIONAL AND ON-SITE CORRELATIONS - THE ELECTRONIC-STRUCTURE OF LA2CUO4 AND LACUO3

    NARCIS (Netherlands)

    CZYZYK, MT; SAWATZKY, GA

    1994-01-01

    State-of-the-art electronic-structure calculations based on the local-density approximation (LDA) to the density functional fail to reproduce the insulating antiferromagnetic ground state in the parent compounds of the high-temperature oxide superconductors. Similar problems have been observed earli

  9. Formation of stacking faults and their correlation with flux-pinning and critical current density for Sm-doped YBa2Cu3O7- films

    Energy Technology Data Exchange (ETDEWEB)

    Wee, Sung Hun [ORNL; Specht, Eliot D [ORNL; Cantoni, Claudia [ORNL; Zuev, Yuri L [ORNL; Maroni, V. A. [Argonne National Laboratory (ANL); Wong-Ng, W. [National Institute of Standards and Technology (NIST); Liu, G. [National Institute of Standards and Technology (NIST); Haugan, T. J. [Air Force Research Laboratory; Goyal, Amit [ORNL

    2011-01-01

    A correlation between flux-pinning characteristics and stacking faults (SFs) formed by Sm substitution on Y and Ba sites was found in Sm-doped YBa2Cu3O7- (YBCO) films. It was confirmed that 223 type SFs, Y2Ba2Cu3Ox, composed of extra Y and O planes aligned parallel to the ab-planes formed via Sm substitution on the Y site and increased in number with increasing Sm doping on the Ba site. The number density of 223 SFs is correlated strongly with the enhancement in ab-plane correlated flux-pinning, resulting in a sharpening of the H ab peak in the plot of critical current density versus magnetic field orientation.

  10. 维生素D受体及骨密度的研究进展%Research Progress on the Correlation between Vitamin D Receptor and Bone Mineral Density

    Institute of Scientific and Technical Information of China (English)

    陈露(综述); 赵琳(审校)

    2014-01-01

    维生素D是具有广泛生理作用的类固醇衍生物,它在人体内的作用是通过维生素 D 受体(VDR)介导的。而它的作用是通过维生素 D 受体(VDR)介导的。体内大多数组织和细胞都有VDR。随着科技基因技术的发展,发现其基因上存在多个多态性位点,且其各个位点的含量与许多疾病发生有关,在儿童时期参与佝偻病的发生,随着年龄的增长,又介导人体骨质疏松发生。该文主要介绍VDR的结构、分布、基因多态性的遗传易患性及与骨密度的相关性,为临床早期诊断以及治疗佝偻病和骨质疏松提供合适的理论依据。%Vitamin D is a steroid derivatives with a broad range of physiological functions .It mainly mediates cell function of vitamin D in the body,which is through vitamin D receptor(VDR).There are VDRs in most tissues and cells in the body .With the development of science and gene technology ,it has been found that there are multiple SNPs in VDR gene ,and the content of each SNP is associated with many diseases ,for instance,some SNPs participate in the occurrence of rickets during childhood,and some SNPs mediate the incidence of osteoporosis during adulthood.Here is to make a review of the VDR system structure,distribution and genetic susceptibility of VDR gene polymorphismand its correlation with bone mineral density ,so as to provide theoretical basis for early diagnosis and treatment for rickets and osteoporosis .

  11. Correlation functions in conformal Toda field theory II

    CERN Document Server

    Fateev, V A

    2009-01-01

    This is the second part of the paper 0709.3806v2. Here we show that three-point correlation function with one semi-degenerate field in Toda field theory as well as four-point correlation function with one completely degenerate and one semi-degenerate field can be represented by the finite dimensional integrals.

  12. CORRELATION OF PHYSICAL ACTIVITY LEVEL WITH BONE MINERAL DENSITY, CARDIO-RESPIRATORY FITNESS AND BODY COMPOSITION IN POST-MENOPAUSAL WOMEN

    Directory of Open Access Journals (Sweden)

    Niyati N Khona

    2017-09-01

    Full Text Available Background: Due to the hormonal changes in postmenopausal women they are prone for many complications like increased CVD risk factors, osteoporosis, obesity, mood swings and urinary incontinence. Physical inactivity in postmenopausal women leads to higher risk of developing CVD and osteoporosis. The objective was to find out the correlation of physical activity level with BMD, cardio-respiratory fitness and body composition in post-menopausal women Methods: 42 postmenopausal women were included. A detailed clinical evaluation with physical activity level (IPAQ-METS-mins/week, , BMD ( T-Scores, body composition (BMI, waist circumference, BIA & Skin fold calliper for fat %, cardio-respiratory fitness was measured by Balke protocol and VO2peak (ml/kg/min is estimated. Correlation of physical activity level with BMD, cardio-respiratory fitness and body composition were analysed using “Pearson’s product moment correlation co-efficient and Spearman’s rho.” Results: Spearman’s rank correlation rho for IPAQ with VO2 peak was 0.420,BMI was -0.388 and visceral fat was -0.384 indicating moderate positive correlation between IPAQ and cardio-respiratory fitness and weak negative correlation between IPAQ and BMI and visceral fat. Pearson’s product moment correlation coefficient of IPAQ with BMD was 0.147, body fat was -0.234 and waist circumference was -0.256 indicating no correlation. P value was significant for correlation of IPAQ with CRF (0.006, BMI (0.011 and Visceral fat (0.012. Conclusion: There is moderate positive correlation between IPAQ and cardio-respiratory fitness, weak negative correlation between IPAQ and BMI and visceral fat and no correlation between IPAQ and BMD, body fat and waist circumference

  13. Spontaneous magnetization in high-density quark matter

    DEFF Research Database (Denmark)

    Tsue, Yasuhiko; da Providência, João; Providência, Constanca;

    2015-01-01

    It is shown that spontaneous magnetization occurs due to the anomalous magnetic moments of quarks in high-density quark matter under the tensor-type four-point interaction. The spin polarized condensate for each flavor of quark appears at high baryon density, which leads to the spontaneous...... magnetization due to the anomalous magnetic moments of quarks. The implications for the strong magnetic field in compact stars is discussed....

  14. Performance of GaN-on-Si-based vertical light-emitting diodes using silicon nitride electrodes with conducting filaments: correlation between filament density and device reliability.

    Science.gov (United States)

    Kim, Kyeong Heon; Kim, Su Jin; Lee, Tae Ho; Lee, Byeong Ryong; Kim, Tae Geun

    2016-08-08

    Transparent conductive electrodes with good conductivity and optical transmittance are an essential element for highly efficient light-emitting diodes. However, conventional indium tin oxide and its alternative transparent conductive electrodes have some trouble with a trade-off between electrical conductivity and optical transmittance, thus limiting their practical applications. Here, we present silicon nitride transparent conductive electrodes with conducting filaments embedded using the electrical breakdown process and investigate the dependence of the conducting filament density formed in the transparent conductive electrode on the device performance of gallium nitride-based vertical light-emitting diodes. Three gallium nitride-on-silicon-based vertical light-emitting diodes using silicon nitride transparent conductive electrodes with high, medium, and low conducting filament densities were prepared with a reference vertical light-emitting diode using metal electrodes. This was carried to determine the optimal density of the conducting filaments in the proposed silicon nitride transparent conductive electrodes. In comparison, the vertical light-emitting diodes with a medium conducting filament density exhibited the lowest optical loss, direct ohmic behavior, and the best current injection and distribution over the entire n-type gallium nitride surface, leading to highly reliable light-emitting diode performance.

  15. Analysis of bone mellow density in adults of domestic local area using multi-detector computed tomography: Focus on correlation about eating habits, lifestyle, physical features and social characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tae Hui [Wonju Medical Center, Wonju (Korea, Republic of); Kim, Tae Hyung; So, Woon Young; Lim, Hei Gyeom [Kangwon National University Graduate School, Wonju (Korea, Republic of); Lim, Cheong Hwan [Hanseo University, Seosan (Korea, Republic of); Park, Myeong Hwan [Daegu Health College, Daegu (Korea, Republic of); Cheon, Myung Ki [Soongsil University, Seoul (Korea, Republic of)

    2016-12-15

    This study analyzed the correlation between BMD (bone mineral density) value calculated in the MDCT(multidetector computed tomography) and lifestyle, physical features and social characteristics. From July 15 2015 to June 6 2016, we converted from HU (hounsfield unit) value measured by using MDCT to T-score for BMD of 141 patients (male: 63, female: 78) in W medical center. We measured the 2nd, 3rd and 4th lumbar spine and analyzed the correlation between gender differences in BMD and lifestyle, physical features and social characteristics. Statistical significance was validated using independent sample T test with one way Anova. Gender BMD was confirmed that a statistically significant difference (p<0.05). BMD values decreased with increasing age but for the statistically men, there was no significant difference from 20s to 50s, it only showed a significant difference in 20s and 60s (p<0.001). For the statistically women, there was no significant difference from 20s to 40s. but since 50s BMD was decreased rapidly, which showed a significant difference(p<0.001). women showed significant differences for the menstruation and menopause, childbirth, alcohol, cereals and greasy food in bone mineral density (p<0.05) but there were no significant differences in men. The bone mineral density values calculated by the MDCT and lifestyle, physical features and social characteristics correlation analysis method is considered to be used as a basis for estimating the state in BMD and osteoporosis management.

  16. Non-contact measurement of the electrical conductivity and coverage density of silver nanowires for transparent electrodes using Terahertz spectroscopy

    Science.gov (United States)

    Park, Sung-Hyeon; Chung, Wan-Ho; Kim, Hak-Sung

    2017-02-01

    In this work, a terahertz time-domain spectroscopy (THz-TDS) imaging technique was used for non-contact measurement of the conductivity and coverage density (D C) of silver nanowires (SNWs) as transparent electrodes. The reflection mode of THz-TDS with an incident angle of 30° was used, and the sheet resistance (R sh) of SNW films was measured using the four-point probe method. The correlations between the THz reflection ratio and R sh were studied by comparing the results of the four-point probe method and the measured THz reflection ratios. Also, the D C of SNWs was evaluated using THz waveforms with a general refractivity formula. This result matched well with a conventional approximation method using a scanning electron microscope image. Furthermore, defects in the SNWs could be easily detected using the THz-TDS imaging technique. The non-contact THz-TDS measurement method that we developed is expected to be a promising technique for non-contact measurement of the R sh and D C for transparent conductive electrodes.

  17. 气象因素对农田鼠类数量影响的典型相关分析%Canonical correlation analysis of climate factors and farmland rodent density

    Institute of Scientific and Technical Information of China (English)

    刘自远

    2011-01-01

    Objective To study the impact of farmland climate factors on the rodent community. Methods From 1978 to 1993, canonical correlation analysis of the farmland rodent density and climate factors in Kaijiang county, Sichuan province was conducted. Results In the period, the overall farmland rodent density was 5.58%-26.57% ; Apodemus agrarius density 1.91%-18.41%, Rattus norvegicus density 0.68%-10.86%, and Anourosorex squamipes density 0.47%-9.50%. Among the canonical correlation coefficients between 12 climate factors including temperature, humidity, rainfall and sunshine, and four variables (overall rodent density, Ap. Agrarius density, R. Norvegicu density, An. Squamipes density), the first couple (correlation coefficient r-1.0000) was statistically significant (χ2=248.7032, P<0.01). The largest coefficient of the rodent density was noted in the overall rodent density (4.7748), and the largest coefficient of the climate factors was the average sunshine from July to August (-3.1532), followed by average humidity from July to August (-1.6177) and then average rainfall from July to August (-1.4652). All were negatively correlated. Conclusion Farmland rodent quantity was mainly affected by average sunshine, humidity and rainfall from July to August.%目的 探讨气象因素对农田鼠类数量的影响.方法 采用典型相关分析对开江县1978-1993年农田鼠密度与气象因素进行统计分析.结果 1978-1993年开江县农田总鼠密度为5.58%~26.57%,黑线姬鼠、褐家鼠、四川短尾鼩密度分别为1.91%~18.41%、0.68%~10.86%、0.47%~9.50%.气温、湿度、降雨量、日照数等12种气象因素与总鼠密度,黑线姬鼠、褐家鼠、四川短尾鼩密度4个因变量的典型相关系数中,第1对(r=1.0000)有统计学意义(x2=248.7032,P<0.01),鼠类数量以总鼠密度标准系数最大(4.7748),气象因素标准系数最大的依次为7-8月平均日照数(-3.1532)、7-8月平均湿度(-1.6177)和7-8

  18. Accumulation of low density lipoprotein associated cholesterol in calcifying vesicle fractions correlates with intimal thickening in thoracic aortas of juvenile rabbits fed a supplemental cholesterol diet

    Directory of Open Access Journals (Sweden)

    Culley Nathan C

    2006-10-01

    Full Text Available Abstract Background It has been shown that calcifying vesicles play an important role in aortic calcification and that cholesterol content in the isolated vesicle fraction is increased when rabbits are fed supplemental cholesterol diets. Whether lipoprotein-associated cholesterols and other lipids are also increased in the vesicle fraction and whether the increase correlates with atherosclerosis remain unknown. Results Fourteen juvenile male rabbits fed an atherogenic diet containing 0.5% cholesterol and 2% peanut oil for 3 months developed varying degrees of hypercholesterolemia and intimal thickening in the ascending thoracic aorta. The correlation between these two parameters was insignificant, and likely attributable to the use of small numbers of rabbits in this study. Despite this lack of correlation, we demonstrate that the accumulation of cholesterol in calcifying vesicle fractions obtained from the collagenase-digested aorta fragments correlates well with intimal thickening (r2 = 0.98, p Conclusion When limited numbers of rabbits are used, LDL-C accumulation in calcifying vesicle fractions is a better biomarker for atherosclerosis than LDL-C levels in the serum. The close association of LDL-C with calcifying vesicles may play an important role in atherosclerosis and calcification.

  19. Comparison of Anger camera and BGO mosaic position-sensitive detectors for `Super ACAR`. Precision electron momentum densities via angular correlation of annihilation radiation

    Energy Technology Data Exchange (ETDEWEB)

    Mills, A.P. Jr. [Bell Labs. Murray Hill, NJ (United States); West, R.N.; Hyodo, Toshio

    1997-03-01

    We discuss the relative merits of Anger cameras and Bismuth Germanate mosaic counters for measuring the angular correlation of positron annihilation radiation at a facility such as the proposed Positron Factory at Takasaki. The two possibilities appear equally cost effective at this time. (author)

  20. High-density lipoprotein cholesterol is a favorable prognostic factor and negatively correlated with C-reactive protein level in non-small cell lung carcinoma.

    Directory of Open Access Journals (Sweden)

    Pei-Dong Chi

    Full Text Available Although the alterations of lipid profile in lung cancer have been documented, the prognostic value of serum HDL-C level and its correlation with inflammation in NSCLC remain unknown.Levels of preoperative serum lipid concentrations (including HDL-C, LDL-C, TC, and TG and the inflammatory biomarker C-reactive protein level (CRP were retrospectively analyzed in 228 patients with NSCLC and in 300 healthy controls. The serum lipid levels in these two populations were compared. Univariate and multivariate cox hazards analyses were performed to investigate the prognostic value of serum lipid levels in NSCLC. The correlation between CRP and lipid profile were also analyzed.Compared with those in normal controls, the serum HDL-C, LDL-C, and TC levels were statistically decreased and the TG levels were significantly increased in 228 NSCLC patients. The patients with decreased levels of HDL-C had significantly lower 5-year survival rates than those with normal HDL-C, not only in the whole NSCLC cohort but also in the subgroups stratified according to the disease T, N classifications, and metastasis, whereas the other lipid components were not independent prognostic factors for NSCLC. Of the lipid components, a lower HDL-C level was observed more often in patients with a high CRP level than in those with a normal CRP level. Spearman's rank correlation analysis revealed that the HDL-C level presented a negative correlation with the CRP level (r = -0.360, p<0.001.A decreased level of preoperative HDL-C was found to be associated with poor survival in patients with NSCLC. Serum HDL-C level may be a clinical prognosis factor for NSCLC patients. In addition, a negative correlation was present between the levels of HDL-C and CRP, the well-known inflammation biomarker.

  1. Universal correlation between critical current density and normal-state resistivity in porous YBa{sub 2}Cu{sub 3}O{sub 7-x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bartolome, E [Instituto de Ciencia de Materiales de Barcelona-CSIC, Campus UAB, 08193-Bellaterra (Spain); Goemory, F [Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravska Cesta 9, 84239 Bratislava (Slovakia); Granados, X [Instituto de Ciencia de Materiales de Barcelona-CSIC, Campus UAB, 08193-Bellaterra (Spain); Puig, T [Instituto de Ciencia de Materiales de Barcelona-CSIC, Campus UAB, 08193-Bellaterra (Spain); Obradors, X [Instituto de Ciencia de Materiales de Barcelona-CSIC, Campus UAB, 08193-Bellaterra (Spain)

    2007-10-15

    We have simulated the inductive critical currents and transport currents in the dissipative state of superconducting thin films with an increasing amount of porosity by using a Bean model-based programme (Trazacorrientes{sup (registered))) and finite-element software. Simulations allowed us to find a quantitative, quasi-universal relationship between the overall critical current density and the normal-state resistivity via the sample porosity. This theoretical curve served to fit the experimental data found for a large number ({approx}150) of epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-x} thin films grown by the trifluoracetate route.

  2. Negative correlation between bone mineral density and TSH receptor antibodies in long-term euthyroid postmenopausal women with treated Graves’ disease

    DEFF Research Database (Denmark)

    Ercolano, Monica A; Drnovsek, Monica L; Croome, Maria C

    2013-01-01

    Thyrotoxicosis is a cause of secondary osteoporosis. High concentrations of triiodotironine (T3) in Graves' disease stimulate bone turnover, but it is unclear if euthyroidism will always normalize bone metabolism. Thyrotropin (TSH) is known to affect directly the bone metabolism through the TSH...... receptor and TSH receptor antibodies (TRAb) may have an important role in bone turn-over.The aim of our study was to determine, in pre and postmenopausal euthyroidism patients with previous overt hyperthyroidism due to Graves' disease the bone mineral density (BMD) as well as factors that could affect BMD...

  3. Correlation between bone mineral density with chronic periodontitis in middle-aged and elderly people%中老年人骨密度与慢性牙周炎的相关性研究

    Institute of Scientific and Technical Information of China (English)

    王景洁; 付婕; 王行; 谢昊; 郭小斌

    2016-01-01

    目的:研究中老年人骨密度降低及骨质疏松与牙周炎之间的关系。方法:选取122名进行体格检查的中老年人,女104名,男18名,进行骨密度测定及口腔检查。根据骨密度值(T值)分为观察组(T<-1.0)与对照组(T>-1.0)。根据附着丧失(CAL)、余留牙数目分为轻、中、重度牙周炎。运用统计学软件进行骨密度与慢性牙周炎分级间的χ2检验,并与牙周附着丧失进行相关性分析。结果:观察组较对照组,中、重度牙周炎的患病率显著增高(χ2=4.41, P<0.05)。中老年人群的骨密度值与CAL值显著负相关(tr=-3.88,P<0.001),即随着骨密度降低,CAL呈增加趋势。结论:中老年人群中,骨量减少及骨质疏松与慢性牙周炎的严重程度相关;骨密度降低可能是中老年人中、重度慢性牙周炎进展的促进因素。%Objective:To study the correlation between osteoporosis and chronic periodontitis in middle-aged and elderly people. Method: The oral condition of 122 individuals who had bone mineral density examination was examined. They were divided into observation group and control group according to the bone density. T score of the observation group was less than -1.0, the control group was more than -1.0. The severity of periodontitis was divided into mild, moderate and advanced according to clinical attachment loss and number of remaining teeth. The chi-square test was made between bone density and severity of periodontitis. Correlation analysis was made between bone density and clinical attachment loss. Result:In observation group, the rate of moderate and advanced chronic periodontitis was significantly higher than that in control group. (χ2=4.41, P<0.05). There was significant correlation between bone density and severity of periodontitis (χ2=4.41, P<0.05). There was negative correlation between bone density and clinical attachment loss (tr=-3.88, P<0.001). As the

  4. Correlation of expression pattern of aquaporin-1 in primary central nervous system tumors with tumor type, grade, proliferation, microvessel density, contrast-enhancement and perilesional edema

    Directory of Open Access Journals (Sweden)

    Prabal Deb

    2012-01-01

    Conclusions: AQP1-immunoexpression had a good correlation with high-grade tumors. AQP-upregulation in perilesional areas of high-grade tumors suggests its role in vasogenic edema. Further studies involving other AQP molecules, vascular endothelial growth factor (VEGF and hypoxia inducible factor-1 α (HIF-1α should be undertaken to evaluate its possible role as a potential surrogate marker of high-grade tumors heralding poor outcome, inhibition of which may serve as the basis for future targeted therapy.

  5. Density, viscosity, surface tension, and molar volume of propylene glycol + water mixtures from 293 to 323 K and correlations by the Jouyban–Acree model

    Directory of Open Access Journals (Sweden)

    Ibrahim S. Khattab

    2017-02-01

    Full Text Available Density, viscosity, surface tension and molar volume of propylene glycol + water mixtures at 293, 298, 303, 308, 313, 318, and 323 K are reported, compared with the available literature data and the Jouyban–Acree model was used for mathematical correlation of the data. The mean relative deviation (MRD was used as an error criterion and the MRD values for data correlation of density, viscosity, surface tension and molar volume at different investigated temperatures are 0.1 ± 0.1%, 7.6 ± 6.4%, 3.4 ± 3.7%, and 0.4 ± 0.4%, respectively. The corresponding MRDs for the predicted properties after training the model using the experimental data at 298 K are 0.1 ± 0.2%, 12.8 ± 9.3%, 4.7 ± 4.1% and 0.6 ± 0.5%, respectively for density, viscosity, surface tension, and molar volume data.

  6. Densidade básica do colmo e sua correlação com os valores de brix e pol em cana-de-açúcar Correlation between brix and pol values of sugarcane and culm basic density

    Directory of Open Access Journals (Sweden)

    Anisio Azzini

    1986-01-01

    Full Text Available Neste estudo procurou-se estabelecer as correlações entre a densidade básica do colmo e os valores de Brix e Pol em diversas variedades e "seedlings" de cana-de-açucar, visando ao estabelecimento de um método expedito e semiquantitativo de análise. Os resultados obtidos mostraram correlações significativas (p > 99% entre a densidade básica do colmo e os valores obtidos para Brix e Pol, principalmente para a região mediana do colmo. Desse modo, a densidade básica do colmo pode ser utilizada como um método expedito de análise para avaliar a concentração de sacarose em cana-de-açúcar.The correlation between the refractometric (Brix and polarimetric (Pol determinations and the culm basic density was determined. The objective was to establish a fast and semiquantitative method for sugarcane analysis, regarding sucrose determination in the culm. The results showed a significant correlation (p > 0.99 between the basic density and each of the values of Brix and Pol, mainly for the median portion of the culm. It was concluded that the culm basic density can be utilized as a speedy method to estimate the sucrose concentration of sugarcane culms.

  7. Serum anti-Helicobacter pylori immunoglobulin G titer correlates with grade of histological gastritis, mucosal bacterial density, and levels of serum biomarkers.

    Science.gov (United States)

    Tu, Huakang; Sun, Liping; Dong, Xiao; Gong, Yuehua; Xu, Qian; Jing, Jingjing; Yuan, Yuan

    2014-03-01

    OBJECTIVE. Clinical implications of serum anti-Helicobacter pylori immunoglobulin G (IgG) titer were unclear. This study investigated the associations of serum anti-H. pylori IgG titer with grade of histological gastritis, mucosal bacterial density and levels of serum biomarkers, including pepsinogen (PG) I, PGII, PGI/II ratio and gastrin-17. MATERIAL AND METHODS. Study participants were from a screening program in northern China. Serum anti-H. pylori IgG measurements were available for 5922 patients with superficial gastritis. Serum anti-H. pylori IgG titer and serum biomarkers were measured using ELISA, and gastric biopsies were evaluated using standardized criteria. RESULTS. In patients with mild, moderate or severe superficial gastritis, the mean serum anti-H. pylori IgG titers were 17.3, 33.4 and 54.4 EIU (p for trend gastritis, mucosal bacterial density and concentrations of serum PGI, PGII and gastrin-17, and negatively with PGI/II ratio.

  8. Density functional theory analysis of the structural and electronic properties of TiO2 rutile and anatase polytypes: performances of different exchange-correlation functionals.

    Science.gov (United States)

    Labat, Frédéric; Baranek, Philippe; Domain, Christophe; Minot, Christian; Adamo, Carlo

    2007-04-21

    The two polymorphs of TiO2, rutile and anatase, have been investigated at the ab initio level using different Hamiltonians with all-electron Gaussian and projector augmented plane wave basis sets. Their equilibrium lattice parameters, relative stabilities, binding energies, and band structures have been evaluated. The calculations have been performed at the Hartree-Fock, density functional theory (DFT), and hybrid (B3LYP and PBE0) levels. As regards DFT, the local density and generalized gradient (PBE) approximations have been used. Our results show an excellent agreement with the experimental band structures and binding energies for the B3LYP and PBE0 functionals, while the best structural descriptions are obtained at the PBE0 level. However, no matter which Hamiltonian and method are used, anatase is found more stable than rutile, in contrast with recent experimental reports, although the relative stabilities of the two phases are very close to each other. Nevertheless, based on the overall results, the hybrid PBE0 functional appears as a good compromise to obtain an accurate description of both structural and electronic properties of solids.

  9. 黑龙江地区女性乳腺密度与乳腺癌的风险因素相关性研究%Correlation between breast density and breast cancer risk factors in Hei-longjiang area

    Institute of Scientific and Technical Information of China (English)

    陈颖; 史春颖; 杨予川; 李睿; 刘源; 崔春玲

    2015-01-01

    Objective To explore the correlation between breast cancer and breast density in Heilongjiang region .Methods X-ray data and epidemiological data of 487 women from June 2010 to November 2010 in the First Affiliated Hospital of Harbin Medical University were col-lected, including 105 cases of breast cancer and 382 cases of healthy controls ( breast benign disease ) .Breast imaging reporting and data system recommended by americaradiology doctors was the standard for evaluation of breast density , breast density percentage was used to analyze the relationship between different levels of mammary gland photography density and breast canc -er risk factors .Results Based on 487 cases of mammary X-ray data , breast density was statis-tically different between breast cancer groups and healthy controls in Heilongjiang area , the oc-currence of breast cancer was associated with a high breast density , menopausal status did not affect breast density;breast density was associated with menarche age and history of lactation . Conclusion Breast X-ray photography density is associated with breast cancer risk factors .%目的:探讨黑龙江地区乳腺癌与其乳腺密度是否存在相关性。方法收集2010年6月至2010年11月哈尔滨医科大学附属第一医院就诊的487例黑龙江地区女性的乳腺钼靶X线检查资料及流行病学资料,其中105例为乳腺癌,382例为健康对照组,以美国放射医师学会推荐的乳腺影像报告和数据系统( breast imaging reporting and data system ,BI-RADS)作为评估乳腺密度的标准,以乳腺密度百分比分析不同等级乳腺摄影密度和乳腺癌危险因素的关系。结果乳腺癌组与健康对照组乳腺密度有统计学差异。绝经状态未对乳腺密度产生影响;乳腺密度与初潮年龄、哺乳史相关。结论乳腺X线摄影密度与乳腺癌危险因素均相关联。

  10. Auxiliary basis sets for density-fitting second-order Møller-Plesset perturbation theory: weighted core-valence correlation consistent basis sets for the 4d elements Y-Pd.

    Science.gov (United States)

    Hill, J Grant

    2013-09-30

    Auxiliary basis sets (ABS) specifically matched to the cc-pwCVnZ-PP and aug-cc-pwCVnZ-PP orbital basis sets (OBS) have been developed and optimized for the 4d elements Y-Pd at the second-order Møller-Plesset perturbation theory level. Calculation of the core-valence electron correlation energies for small to medium sized transition metal complexes demonstrates that the error due to the use of these new sets in density fitting is three to four orders of magnitude smaller than that due to the OBS incompleteness, and hence is considered negligible. Utilizing the ABSs in the resolution-of-the-identity component of explicitly correlated calculations is also investigated, where it is shown that i-type functions are important to produce well-controlled errors in both integrals and correlation energy. Benchmarking at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations level indicates impressive convergence with respect to basis set size for the spectroscopic constants of 4d monofluorides; explicitly correlated double-ζ calculations produce results close to conventional quadruple-ζ, and triple-ζ is within chemical accuracy of the complete basis set limit.

  11. Analysis on correlation between the density of dengue fever vector and climatic factors at Jieyang port%揭阳口岸登革热媒介密度及与气候因素相关分析

    Institute of Scientific and Technical Information of China (English)

    林燕如; 林志雄; 陈锐强; 方其丰

    2012-01-01

    目的 了解揭阳口岸登革热媒介伊蚊密度与季节消长及其与气候变化的关系,为防控提供科学依据.方法 采用人工小时法和集卵器法调查蚊虫密度,应用SPSS分析季节和气候变化与蚊虫密度的关系.结果 2008 - 2010年每年5- 10月份白纹伊蚊月平均密度为2~29.8只/人工小时;诱卵阳性指数为13.3~86.7;伊蚊密度与诱蚊指数存在正线性相关关系,伊蚊密度与月平均气温及前2个月降雨量呈正线性相关.结论 揭阳口岸白纹伊蚊密度较高,与月平均气温有正线性相关,月降雨量对蚊虫密度有滞后正效性关系.%Objective To survey the density of dengue fever vector and its seasonal fluctuation, and analyze the correlation between mosquito density and climatic factors so as to provide scientific evidence for monitoring and preventing dengue fever at Jieyang port. Methods The human baited captured and ovitrap methods for mosquitoes density survey, and the relationship between mosquito surveillance data and climate variables from 2008 to 2010 were analyzed by SPSS 13.0. Results The mean densities of Aedes albopictus were from 2 to 29.8 pieces per hour during May to October in 2008 -2010, and the ovitrap index were from 13. 3 to 86. 7. There was a positive correlation between the mean densities of Aedes albopictus adult and ovitrap index ( P = 0. 041 ) , and between the densities of mosquito and the monthly mean temperature, and pre-2-month precipitation. Conclusion The density of Aedes albopictus is at a high level at Jieyang port, and is affected by temperature and pre-2-month precipitation.

  12. Comment on "Communication: Simple and accurate uniform electron gas correlation energy for the full range of densities" [J. Chem. Phys. 145, 021101 (2016)

    CERN Document Server

    Karasiev, Valentin V

    2016-01-01

    A simple expression for the uniform electron gas (UEG) correlation energy, recently presented in Ref. [J. Chem. Phys. 145, 021101 (2016)], deviates from the reference quantum Monte-Carlo (QMC) data at large r_s. We propose to define one of the parameters from a requirement to match the large-rs QMC data. Functional with the new parameter provides much better agreement with the QMC data at large r_s without deterioration of the functional quality at small and intermediate r_s.

  13. Effects of Side-Chain and Electron Exchange Correlation on the Band Structure of Perylene Diimide Liquid Crystals: A Density Functional Study

    Energy Technology Data Exchange (ETDEWEB)

    Arantes, J. T.; Lima, M. P.; Fazzio, A.; Xiang, H.; Wei, S. H.; Dalpian, G. M.

    2009-04-01

    The structural and electronic properties of perylene diimide liquid crystal PPEEB are studied using ab initio methods based on the density functional theory (DFT). Using available experimental crystallographic data as a guide, we propose a detailed structural model for the packing of solid PPEEB. We find that due to the localized nature of the band edge wave function, theoretical approaches beyond the standard method, such as hybrid functional (PBE0), are required to correctly characterize the band structure of this material. Moreover, unlike previous assumptions, we observe the formation of hydrogen bonds between the side chains of different molecules, which leads to a dispersion of the energy levels. This result indicates that the side chains of the molecular crystal not only are responsible for its structural conformation but also can be used for tuning the electronic and optical properties of these materials.

  14. Correlation between superfluid density and T(C) of underdoped YBa2Cu3O6+x near the superconductor-insulator transition.

    Science.gov (United States)

    Zuev, Yuri; Kim, Mun Seog; Lemberger, Thomas R

    2005-09-23

    We report measurements of the ab-plane superfluid density n(s) (magnetic penetration depth lambda) of heavily underdoped films of YBa2Cu3O6+x, with T(C)'s from 6 to 50 K. We find the characteristic length for vortex unbinding transition equal to the film thickness, suggesting strongly coupled CuO2 layers. At the lowest dopings, T(C) is as much as 5 times larger than the upper limit set by the 2D Kosterlitz-Thouless-Berezinskii transition temperature calculated for individual CuO2 bilayers. Our main finding is that T(C) is not proportional to n(s)(0); instead, we find T(C) proportional to ns(1/2.3+/-0.4). This conflicts with a popular point of view that quasi-2D thermal phase fluctuations determine the transition temperature.

  15. Usefulness of measurement of circulation time using MgSO{sub 4} : correlation with time-density curve using electron beam computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung Ki; Lee, Hui Joong; Lee, Jong Min; Kim, Yong Joo; Kang, Duck Sik [Kyungpook National Univ., Kyungpook National Univ. Hospital, College of Medicine, Taegu (Korea, Republic of)

    1999-12-01

    To determine the usefulness of MgSO{sub 4} for measuring the systemic circulation time. Systemic circulation time, defined as elapsed time from the injection of MgSO{sub 4} solution to the point of pharyngeal burning sensation, was measured in 63 volunteers. MgSO{sub 4} was injected into a superficial vein of an upper extremity. Using dynamic electron beam computed tomography at the level of the abdominal aorta and celiac axis, a time-intensity curve was plotted, and for these two locations, maximal enhancement time was compared. For 60 of the 63 subjects, both systemic circulation time and maximal enhancement time were determined. Average systemic circulation time was 17.4 (SD:3.6) secs. and average maximal enhancement times at the level of the abdominal aorta and celiac axis were 17.5 (SD:3.0) secs. and 18.5 (SD:3.2) secs., respectively. Correlation coefficients between systemic circulation time and maximal enhancement time for the abdominal aorta and celiac axis were 0.73 (p<0.01) and 0.73 (p<0.05) respectively. The systemic circulation time demonstrated by MgSO{sub 4} injection and maximal enhancement time for the abdominal aorta showed significant correlation. Thus, to determine the appropriate scanning time in contrast-enhanced radiological studies, MgSO{sub 4} can be used instead of a test bolus study.

  16. Activation of Carbon-Hydrogen and Hydrogen-Hydrogen Bonds by Copper-Nitrenes: A Comparison of Density Functional Theory with Single- and Multireference Correlation Consistent Composite Approaches.

    Science.gov (United States)

    Tekarli, Sammer M; Williams, T Gavin; Cundari, Thomas R

    2009-11-10

    The kinetics and thermodynamics of copper-mediated nitrene insertion into C-H and H-H bonds (the former of methane) have been studied using several levels of theory: B3LYP/6-311++G(d,p), B97-1/cc-pVTZ, PBE1KCIS/cc-pVTZ, and ccCA (correlation consistent Composite Approach). The results show no significant difference among the DFT methods. All three DFT methods predict the ground state of the copper-nitrene model complex, L'Cu(NH), to be a triplet, while single reference ccCA predicts the singlet to be the ground state. The contributions to the total ccCA energy indicate that the singlet state is favored at the MP2/CBS level of theory, while electron correlation beyond this level (CCSD(T)) favors a triplet state, resulting in a close energetic balance between the two states. A multireference ccCA method is applied to the nitrene active species and supports the assignment of a singlet ground state. In general, the largest difference in the model reaction cycles between DFT and ccCA methods is for processes involving radicals and bond dissociation.

  17. Correlation between Clindamycin Use Density and Drug Resistance of Main Target Bacteria%克林霉素使用强度与其主要目标菌耐药相关性分析

    Institute of Scientific and Technical Information of China (English)

    蒋林; 张奇兵; 刘航

    2015-01-01

    目的:分析医院克林霉素使用强度与金黄色葡萄球菌(简称金葡菌)、表皮葡萄球菌(简称表葡菌)耐药性之间的相关性。方法统计医院2011年4季度至2014年2季度克林霉素使用强度和金葡菌和表葡菌敏感率,分析二者之间的相关性。结果克林霉素的使用强度与金葡菌对其敏感率呈显著负相关( P<0.05);克林霉素的使用强度与表葡菌对其敏感率呈显著负相关( P<0.05)。结论金葡菌和表葡菌对克林霉素的耐药性与克林霉素的使用强度有关,促进临床合理使用克林霉素,可延缓耐药菌出现。%Objective To analyze the correlation between the clindamycin use density and the drug resistance of staphylococcus aureus and staphylococcus epidermidis in our hospital. Methods The clindamycin use density and the sensitive rate of staphylococcus aureus and staphylococcus epidermidis in our hospital from the fourth quarter of 2011 to the second quarter of 2014 were performed the statistics and their correlation was analyzed. Results The clindamycin use density was significantly negatively correlated with the sensi-tive rate of staphylococcus aureus( P < 0. 05)and staphylococcus epidermidis ( P < 0. 05 ) . Conclusion The resistance of staphylococcus aureus and staphylococcus epidermidis to clindamycin is correlated with the clindamycin use density. Rational use of clindamycin can effectively delay the emergence of the drug-resistant strains.

  18. Inter-observer variability within BI-RADS and RANZCR mammographic density assessment schemes

    Science.gov (United States)

    Damases, Christine N.; Mello-Thoms, Claudia; McEntee, Mark F.

    2016-03-01

    This study compares variability associated with two visual mammographic density (MD) assessment methods using two separate samples of radiologists. The image test-set comprised of images obtained from 20 women (age 42-89 years). The images were assessed for their MD by twenty American Board of Radiology (ABR) examiners and twenty-six radiologists registered with the Royal Australian and New Zealand College of Radiologists (RANZCR). Images were assessed using the same technology and conditions, however the ABR radiologists used the BI-RADS and the RANZCR radiologists used the RANZCR breast density synoptic. Both scales use a 4-point assessment. The images were then grouped as low- and high-density; low including BIRADS 1 and 2 or RANZCR 1 and 2 and high including BI-RADS 3 and 4 or RANZCR 3 and 4. Four-point BI-RADS and RANZCR showed no or negligible correlation (ρ=-0.029 p<0.859). The average inter-observer agreement on the BI-RADS scale had a Kappa of 0.565; [95% CI = 0.519 - 0.610], and ranged between 0.328-0.669 while the inter-observer agreement using the RANZCR scale had a Kappa of 0.360; [95% CI = 0.308 - 0.412] and a range of 0.078-0.499. Our findings show a wider range of inter-observer variability among RANZCR registered radiologists than the ABR examiners.

  19. A METHOD TO SEARCH FOR CORRELATIONS OF ULTRA-HIGH ENERGY COSMIC-RAY MASSES WITH THE LARGE-SCALE STRUCTURES IN THE LOCAL GALAXY DENSITY FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, A. A., E-mail: ivanov@ikfia.ysn.ru [Shafer Institute for Cosmophysical Research and Aeronomy, 31 Lenin Avenue, Yakutsk 677980 (Russian Federation)

    2013-02-15

    One of the main goals of investigations using present and future giant extensive air shower (EAS) arrays is the mass composition of ultra-high energy cosmic rays (UHECRs). A new approach to the problem is presented, combining the analysis of arrival directions with the statistical test of the paired EAS samples. One of the ideas of the method is to search for possible correlations between UHECR masses and their separate sources; for instance, if there are two sources in different areas of the celestial sphere injecting different nuclei, but the fluxes are comparable so that arrival directions are isotropic, then the aim is to reveal a difference in the mass composition of cosmic-ray fluxes. The method is based on a non-parametric statistical test-the Wilcoxon signed-rank routine-which does not depend on the populations fitting any parameterized distributions. Two particular algorithms are proposed: first, using measurements of the depth of the EAS maximum position in the atmosphere; and second, relying on the age variance of air showers initiated by different primary particles. The formulated method is applied to the Yakutsk array data, in order to demonstrate the possibility of searching for a difference in average mass composition between the two UHECR sets, arriving particularly from the supergalactic plane and a complementary region.

  20. Improving constraints on the growth rate of structure by modelling the density-velocity cross-correlation in the 6dF Galaxy Survey

    Science.gov (United States)

    Adams, Caitlin; Blake, Chris

    2017-10-01

    We present the first simultaneous analysis of the galaxy overdensity and peculiar velocity fields by modelling their cross-covariance. We apply our new maximum-likelihood approach to data from the 6-degree Field Galaxy Survey (6dFGS), which has the largest single collection of peculiar velocities to date. We present a full derivation of the analytic expression for the cross-covariance between the galaxy overdensity and peculiar velocity fields and find direct evidence for a non-zero correlation between the fields on scales up to ∼50 h-1 Mpc. When utilizing the cross-covariance, our measurement of the normalized growth rate of structure is fσ _8(z=0) = 0.424^{+0.067}_{-0.064} (15 per cent precision), and our measurement of the redshift-space distortion parameter is β =0.341^{+0.062}_{-0.058} (18 per cent precision). Both measurements improve by ∼20 per cent compared to only using the autocovariance information. This is consistent with the literature on multiple-tracer approaches, as well as Fisher matrix forecasts and previous analyses of 6dFGS. Our measurement of fσ8 is consistent with the standard cosmological model, and we discuss how our approach can be extended to test alternative models of gravity.