Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Coordinates

  • atomic coordinate
  • cartesian coordinate
  • cie coordinate
  • color coordinate
  • cylindrical coordinate
  • generalized coordinate
  • internal coordinate
  • intrinsic reaction coordinate
  • polar coordinate
  • principal coordinate
  • reaction coordinate
  • spatial coordinate
  • spherical coordinate
  • three-dimensional coordinate
  • vertical coordinate

  • Terms modified by Coordinates

  • coordinate analysis
  • coordinate data
  • coordinate system
  • coordinate transformation

  • Selected Abstracts

    Multidimensional Reaction Coordinate for the Excited-state H-atom Transfer in Perylene Quinones: Importance of the 7-Membered Ring in Hypocrellins A and B

    Anindya Datta
    ABSTRACT The excited-state intramolecular H-atom transfer reactions of hypocrellins B and A are compared by using time-resolved absorption and fluorescence upconversion techniques. The hypocrellin B photophysics are well described by a simple model involving one ground-state species and excited-state forward and reverse H-atom transfer with a nonfluorescent excited state. We suggest that excited-state conformational changes are coupled to the H-atom transfer in hypocrellin B just as gauche/anti changes are coupled to the H-atom transfer in hypocrellin A. [source]

    Transition-State Energy and Position along the Reaction Coordinate in an Extended Activation Strain Model,

    CHEMPHYSCHEM, Issue 8 2007
    G. Theodoor de Jong Dr.
    Abstract We investigate palladium-induced activation of the CH, CC, CF, and CCl bonds in methane, ethane, cyclopropane, fluoromethane, and chloromethane, using relativistic density functional theory (DFT) at ZORA-BLYP/TZ2P. Our purpose is to arrive at a qualitative understanding, based on accurate calculations, of the trends in activation barriers and transition state (TS) geometries (e.g. early or late along the reaction coordinate) in terms of the reactants' properties. To this end, we extend the activation strain model (in which the activation energy ,E, is decomposed into the activation strain ,E,strain of the reactants and the stabilizing TS interaction ,E,int between the reactants) from a single-point analysis of the TS to an analysis along the reaction coordinate ,, that is, ,E(,)=,Estrain(,)+,Eint(,). This extension enables us to understand qualitatively, trends in the position of the TS along , and, therefore, the values of the activation strain ,E,strain=,Estrain(,TS) and TS interaction ,E,int=,Eint(,TS) and trends therein. An interesting insight that emerges is that the much higher barrier of metal-mediated CC versus CH activation originates from steric shielding of the CC bond in ethane by CH bonds. Thus, before a favorable stabilizing interaction with the CC bond can occur, the CH bonds must be bent away, which causes the metal,substrate interaction ,Eint(,) in CC activation to lag behind. Such steric shielding is not present in the metal-mediated activation of the CH bond, which is always accessible from the hydrogen side. Other phenomena that are addressed are anion assistance, competition between direct oxidative insertion (OxIn) versus the alternative SN2 pathway, and the effect of ring strain. [source]

    Shock Coordinated with High Power of Morphology Electrogram Improves Defibrillation Success in Patients with Implantable Cardioverter Defibrillators

    BERKOWITSCH, A., et al.: Shock Coordinated with High Power of Morphology Electrogram Improves Defibrillation Success in Patients with Implantable Cardioverter Defibrillators. Animal studies have suggested that the success of defibrillation may depend on the properties of VF waveform obtained from the morphology electrogram (ME) at the time of the shock. The reliable identification of depolarization events in the fibrillatory signal can be achieved using adaptive estimation of the instantaneous signal power (P). The aim of this study was to investigate if a high P of the ME (PME) was related to ventricular DFT and if the upslope in ME can be associated with the depolarization event. A total of 575 VF (mean duration 10 s) episodes recorded and stored during ICD implantation in 77 patients with ventricular arrhythmias were used for analysis. The DFT was defined using a double step-down test. The values of PME immediately before pulse delivery (Pshock) and shock outcomes were registered. The differences between Pshock of successful and failed defibrillation were tested with the Mann-Whitney U test. The relationship between individual medians of Pshock (Pmed) and DFT was analyzed using the Kruskall-Wallis H-test. The coincidence between identified depolarization and upslope in ME was tested using the chi-square test. A P value of 0.05 was set for an error probability. The Pshock in case of failed defibrillation was significantly lower than Pshock in successful cases by the pulses of any strength (P < 0.001). The test revealed a significant inverse correlation between Pmed and DFT with P < 0.001. The depolarization corresponded to the upslope of ME in 85% of cases. This study demonstrated that a high value of instantaneous power of ME indicates the optimal time for shock delivery. The implementation of this algorithm in ICDs may improve the defibrillation efficacy. [source]

    Barycentric Coordinates on Surfaces

    Raif M. Rustamov
    This paper introduces a method for defining and efficiently computing barycentric coordinates with respect to polygons on general surfaces. Our construction is geared towards injective polygons (polygons that can be enclosed in a metric ball of an appropriate size) and is based on replacing the linear precision property of planar coordinates by a requirement in terms of center of mass, and generalizing this requirement to the surface setting. We show that the resulting surface barycentric coordinates can be computed using planar barycentric coordinates with respect to a polygon in the tangent plane. We prove theoretically that the surface coordinates properly generalize the planar coordinates and carry some of their useful properties such as unique reconstruction of a point given its coordinates, uniqueness for triangles, edge linearity, similarity invariance, and smoothness; in addition, these coordinates are insensitive to isometric deformations and can be used to reconstruct isometries. We show empirically that surface coordinates are shape-aware with consistent gross behavior across different surfaces, are well-behaved for different polygon types/locations on variety of surface forms, and that they are fast to compute. Finally, we demonstrate effectiveness of surface coordinates for interpolation, decal mapping, and correspondence refinement. [source]

    Moving Least Squares Coordinates

    Josiah Manson
    Abstract We propose a new family of barycentric coordinates that have closed-forms for arbitrary 2D polygons. These coordinates are easy to compute and have linear precision even for open polygons. Not only do these coordinates have linear precision, but we can create coordinates that reproduce polynomials of a set degree m as long as degree m polynomials are specified along the boundary of the polygon. We also show how to extend these coordinates to interpolate derivatives specified on the boundary. [source]

    Visual Clustering in Parallel Coordinates

    Hong Zhou
    Abstract Parallel coordinates have been widely applied to visualize high-dimensional and multivariate data, discerning patterns within the data through visual clustering. However, the effectiveness of this technique on large data is reduced by edge clutter. In this paper, we present a novel framework to reduce edge clutter, consequently improving the effectiveness of visual clustering. We exploit curved edges and optimize the arrangement of these curved edges by minimizing their curvature and maximizing the parallelism of adjacent edges. The overall visual clustering is improved by adjusting the shape of the edges while keeping their relative order. The experiments on several representative datasets demonstrate the effectiveness of our approach. [source]

    Differential localization of carbachol- and bicuculline-sensitive pontine sites for eliciting REM sleep-like effects in anesthetized rats

    Summary Carbachol, a cholinergic agonist, and GABAA receptor antagonists injected into the pontine dorsomedial reticular formation can trigger rapid eye movement (REM) sleep-like state. Data suggest that GABAergic and cholinergic effects interact to produce this effect but the sites where this occurs have not been delineated. In urethane-anesthetized rats, in which carbachol effectively elicits REM sleep-like episodes (REMSLE), we tested the ability of 10 nL microinjections of carbachol (10 mm) and bicuculline (0.5 or 2 mm) to elicit REMSLE at 47 sites located within the dorsal pontine reticular formation at the levels -8.00 to -10.80 from bregma (B) (Paxinos and Watson, The Rat Brain in Stereotaxic Coordinates, Academic Press, San Diego, 1997). At rostral levels, most carbachol and some bicuculline injections elicited REMSLE with latencies that gradually decreased from 242 to 12 s for carbachol and from 908 to 38 s for bicuculline for more caudal injection sites. As the latencies decreased, the durations of bicuculline-elicited REMSLE increased from 104 s to over 38 min, and the effect was dose dependent, whereas the duration of carbachol-elicited REMSLE changed little (104,354 s). Plots of REMSLE latency versus the antero-posterior coordinates revealed that both drugs were maximally effective near B-8.80. At levels caudal to B-8.80, carbachol was effective at few sites, whereas bicuculline-elicited REMSLE to at least B-9.30 level. Thus, the bicuculline-sensitive sites extended further caudally than those for carbachol and antagonism of GABAA receptors both triggered REMSLE and controlled their duration, whereas carbachol effects on REMSLE duration were small or limited by its concurrent REMSLE-opposing actions. [source]

    Brownian Dynamics Simulations of Rotational Diffusion Using the Cartesian Components of the Rotation Vector as Generalized Coordinates

    Tom Richard Evensen
    Abstract Here, we report on the first Brownian dynamics (BD) simulations of rotational diffusion using the Cartesian components of the rotation vector as the generalized coordinates. The model system employed in this study consists of freely rotating and non-interacting rigid particles with arbitrary surface topography. The numerical BD algorithm contains no singularities and yields numerical results that are in full agreement with known theoretical results. Because of the absence of singularities, this new algorithm is several orders of magnitude more efficient than a simple BD algorithm employing the Euler angles as the generalized coordinates. The general theory for using generalized coordinates in studies of more complex systems involving both translation, rotation, and fluid dynamic interactions is well known. Consequently, the benefits reported here can readily be extended to such systems. Important examples are segmented polymer chains, with and without holonomic constraints, and liquid crystals. [source]

    Shape difference visualization for ancient bronze mirrors through 3D range images

    Tomohito Masuda
    Abstract Japanese archaeologists have paid special attention to ancient Chinese bronze mirrors because the mirrors may provide a key for the exact location of Yamatai State, which is one of the major archaeological controversies. Currently, archaeologists visually analyse ancient Chinese bronze mirrors for their shape difference. The practice requires a huge amount of time and effort. In this paper, we propose an automatic method for detecting the shape difference between a pair of ancient mirrors. The 3D data of the mirrors are obtained using a laser range scanner. Our algorithm then aligns them into the same coordinate and visualizes their shape differences. Our proposed algorithm provides fast and non-damaging analysis for shape difference. Further analysis can be evaluated on our data instead of the actual mirror, so it can be performed by more than one group of archaeologists. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    General Gyrokinetic Equations for Edge Plasmas

    H. Qin
    Abstract During the pedestal cycle of H-mode edge plasmas in tokamak experiments, large-amplitude pedestal build-up and destruction coexist with small-amplitude drift wave turbulence. The pedestal dynamics simultaneously includes fast time-scale electromagnetic instabilities, long time-scale turbulence-induced transport processes, and more interestingly the interaction between them. To numerically simulate the pedestal dynamics from first principles, it is desirable to develop an effective algorithm based on the gyrokinetic theory. However, existing gyrokinetic theories cannot treat fully nonlinear electromagnetic perturbations with multi-scale-length structures in spacetime, and therefore do not apply to edge plasmas. A set of generalized gyrokinetic equations valid for the edge plasmas has been derived. This formalism allows large-amplitude, time-dependent background electromagnetic fields to be developed fully nonlinearly in addition to small-amplitude, short-wavelength electromagnetic perturbations. It turns out that the most general gyrokinetic theory can be geometrically formulated. The Poincaré-Cartan-Einstein 1-form on the 7D phase space determines particles' worldlines in the phase space, and realizes the momentum integrals in kinetic theory as fiber integrals. The infinitesimal generator of the gyro-symmetry is then asymptotically constructed as the base for the gyrophase coordinate of the gyrocenter coordinate system. This is accomplished by applying the Lie coordinate perturbation method to the Poincaré-Cartan-Einstein 1-form. General gyrokinetic Vlasov-Maxwell equations are then developed as the Vlasov-Maxwell equations in the gyrocenter coordinate system, rather than a set of new equations. Because the general gyrokinetic system developed is geometrically the same as the Vlasov-Maxwell equations, all the coordinate-independent properties of the Vlasov-Maxwell equations, such as energy conservation, momentum conservation, and phase space volume conservation, are automatically carried over to the general gyrokinetic system. The pullback transformation associated with the coordinate transformation is shown to be an indispensable part of the general gyrokinetic Vlasov-Maxwell equations. As an example, the pullback transformation in the gyrokinetic Poisson equation is explicitly expressed in terms of moments of the gyrocenter distribution function, with the important gyro-orbit squeezing effect due to the large electric field shearing in the edge and the full finite Larmour radius effect for short wavelength fluctuations. The familiar "polarization drift density" in the gyrocenter Poisson equation is replaced by a more general expression. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Extensions of the 3-Dimensional Plasma Transport Code E3D

    A. Runov
    Abstract One important aspect of modern fusion research is plasma edge physics. Fluid transport codes extending beyond the standard 2-D code packages like B2-Eirene or UEDGE are under development. A 3-dimensional plasma fluid code, E3D, based upon the Multiple Coordinate System Approach and a Monte Carlo integration procedure has been developed for general magnetic configurations including ergodic regions. These local magnetic coordinates lead to a full metric tensor which accurately accounts for all transport terms in the equations. Here, we discuss new computational aspects of the realization of the algorithm. The main limitation to the Monte Carlo code efficiency comes from the restriction on the parallel jump of advancing test particles which must be small compared to the gradient length of the diffusion coefficient. In our problems, the parallel diffusion coefficient depends on both plasma and magnetic field parameters. Usually, the second dependence is much more critical. In order to allow long parallel jumps, this dependence can be eliminated in two steps: first, the longitudinal coordinate x3 of local magnetic coordinates is modified in such a way that in the new coordinate system the metric determinant and contra-variant components of the magnetic field scale along the magnetic field with powers of the magnetic field module (like in Boozer flux coordinates). Second, specific weights of the test particles are introduced. As a result of increased parallel jump length, the efficiency of the code is about two orders of magnitude better. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Migration of mesenchymal cell fated to blastema is necessary for fish fin regeneration

    Yuki Nakatani
    Urodeles and fish have higher regeneration ability in a variety of tissues and organs than do other vertebrate species including mammals. Though many studies have aimed at identifying the cellular and molecular basis for regeneration, relatively little is known about the detailed cellular behaviors and involved molecular basis. In the present study, a small molecule inhibitor was used to analyzed the role of phosphoinositide 3-kinase (PI3K) signaling during regeneration. We showed that the inhibitor disrupted the formation of blastema including the expression of characteristic genes. The failure of blastema formation was due to the impaired migration of mesenchymal cells to the distal prospective blastema region, although it had a little affect on cell cycle activation in mesenchymal cells. Moreover, we found that the epidermal remodeling including cell proliferation, distal cell migration and Akt phosphorylation was also affected by the inhibitor, implying a possible involvement of epidermis for proper formation of blastema. From these data, we propose a model in which distinct signals that direct the cell cycle activation, mesenchymal cell migration and epidermal remodeling coordinate together to accomplish the correct blastema formation and regeneration. [source]

    Syntheses, Characterization, and Luminescent Properties of Monoethylzinc Complexes with Anilido,Imine Ligands

    Qing Su
    Abstract The syntheses of three anilido,imine ligands of the general formula ortho -C6H4(NHAr,)(CH=NAr, [Ar, = 7-(2,4-Me2)C9H4N, Ar, = 2,6-Me2C6H3 (2a); Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6-Et2C6H3 (2b); Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6- iPr2C6H3 (2c)] and four zinc(II) complexes of the general formula [ortho -C6H4(NHAr,)(CH=NAr,)]ZnEt [Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6-Me2C6H3 (3a); Ar, = 7-(2,4-Me2)C9H4N, Ar,= 2,6-Et2C6H3 (3b); Ar, = 7-(2,4-Me2)C9H4N, Ar, = 2,6- iPr2C6H3 (3c); Ar, = 2,6-Me2C6H3, Ar, = 2,6- iPr2C6H3 (3d)] are described. The complexes were synthesized from the reaction of ZnEt2 with corresponding ligands 2 by alkane elimination. All compounds were characterized by elemental analysis and 1H and 13C NMR spectroscopy. The molecular structures of compounds 2a, 2b, 3b, and 3c were determined by single-crystal X-ray crystallography. The X-ray analysis reveals that complexes 3b and 3c exist in the dimeric form with the N atom in the quinolyl ring coordinating to the other Zn atom to make the Zn atoms four coordinate. Luminescent properties of ligands 2a,2d and complexes 3a,3d in both solution and the solid state were studied. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Diastereopure Cationic NCN-Pincer Palladium Complexes with Square Planar ,4 - N,C,N,O Coordination

    Silvia Gosiewska
    Abstract Neutral NCN-pincer palladium bromide complex 2 containing the monoanionic, enantiopure pincer ligand 2,6-bis{[(S)-2-hydroxymethyl-1-pyrrolidinyl]methyl}phenyl bromide (1) with bis- ortho -(S)-prolinol substituents was synthesized and isolated as a mixture of three stereoisomers [(SN,SN,SC,SC), (RN,SN,SC,SC), and (RN,RN,SC,SC)] in a 1:1:1 ratio. Upon abstraction of the bromide ion from the unresolved mixture of 2, single diastereoisomers of the cationic complexes [3]BF4 and [3]PF6, respectively, were formed with a unique,4 - N,C,N,O coordination mode of ligand 1. X-ray crystal structure determination established the intramolecular,4 - N,C,N,O coordination of 1 to palladium where the typical mer -,3 - N,C,N pincer coordination is accompanied by coordination of one of the hydroxy groups of the (S)-prolinol moieties. The water molecule that was cocrystallized in the crystal structure of [3]PF6 does not coordinate to palladium, but instead is involved in a hydrogen bonding network. The catalytic potential of both cationic complexes, [3]BF4 and [3]PF6, was tested in an aldol reaction of aldehydes with methyl isocyanoacetate to yield the oxazoline products as racemic mixtures.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Synthesis and Characterisation of Coordination Polymers of CuII and ZnII with 1,3-Bis(1,2,3,4-tetrazol-2-yl)propane , Rotational Freedom of the Donor Group Favours Structural Diversification

    Robert Bronisz
    Abstract The novel bidentate ligand 1,3-bis(1,2,3,4-tetrazol-2-yl)propane (pbtz), which possesses a flexible spacer, was synthesised in order to investigate the influence of the flexibility of ligand molecules on the architecture of coordination polymers. For that purpose the reactions between pbtz and M(ClO4)2·6H2O salts (M = CuII and ZnII) were performed. The complexes [{Cu(pbtz)3}(ClO4)2], and [{Zn(pbtz)3}(ClO4)2·2EtOH], were characterised by IR and UV/Vis spectroscopy and their crystal structures were determined by single-crystal X-ray diffraction measurements. In both compounds the pbtz ligand molecules act as N4,N4, connectors bridging the central atoms, and the 2-substituted tetrazole rings coordinate in a monodentate fashion to the central atoms forming M(tetrazole)6 cores. [{Cu(pbtz)3}(ClO4)2], was isolated as a 1D coordination polymer. The copper(II) ions are triply bridged by ligand molecules, leading to the formation of infinite 1D chains. A highly unusual manner of bridging, with the tethering of two neighbouring central atoms by the same kind of ligand molecules, although possessing different conformations, is observed. In [{Zn(pbtz)3}(ClO4)2·2EtOH], the six-coordinate zinc(II) ions, which are bridged by single ligand molecules, serve as topological nodes, leading to the formation of a 3D ,-polonium-type network. The crystal structure of the ZnII complex contains only one such net solvated by ethanol molecules. A conformational analysis of the ligand molecules in both compounds demonstrates that the flexibility of the pbtz and the ability of the tetrazole rings in particular to adopt various, relative orientations is responsible for the diversity of the architectures of the obtained complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Adducts of Schiff Bases with Tris(,-diketonato)lanthanide(III) Complexes: Structure and Liquid-Crystalline Behaviour

    Koen Binnemans
    Abstract Adducts of the Schiff base 2-hydroxy- N -octadecyloxy-4-tetradecyloxybenzaldimine with tris(,-dibenzoylmethanato)lanthanide(III) complexes are described. The stoichiometry of the complexes is [Ln(dbm)3Lx], where Ln is a trivalent lanthanide ion (all lanthanides except Ce and Pm), Hdbm is dibenzoylmethane and L is the Schiff base; x = 2 for Ln = La,Er and x = 1 for Ln = Tm,Lu. The Schiff-base ligands are in a zwitterionic form and coordinate through the phenolic oxygen only. The X-ray single-crystal structure of [La(dbm)3L,2] with L, = N -butyl-2-hydroxy-4-methoxybenzaldimine is described. The solution structure of lanthanum(III) complexes has been investigated by 1D and 2D 1H NMR techniques. Although the long-chain Schiff-base ligand and the tris(,-dibenzoylmethanato)lanthanide(III) complexes are non-mesomorphic, some of the adducts exhibit a monotropic smectic A phase. The mesomorphic behaviour depends on the lanthanide ion, in the sense that only a mesophase is observed for the series Ln = La,Eu, not for the heavier lanthanides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    On the Structure of Cross-Conjugated 2,3-Diphenylbutadiene

    Cornelis A. van Walree
    Abstract The structure of the cross-conjugated compound 2,3-diphenylbutadiene was investigated by single-crystal X-ray diffraction and computational methods. In the crystal structure the central butadiene fragment adopts an s-gauche geometry [,55.6(2)° torsion angle , around the essential single bond], whereas the styrene moieties are close to planarity. MP2/6-311G* calculations show that the s-gauche conformation represents the global minimum along the , coordinate, but also revealed the existence of an s-trans local minimum. While the crystal structure seems to reflect dominance of styrene-like conjugation, the MP2/6-311G* calculations indicate that conjugation in both the styrene and butadiene ,-systems is important. An NBO orbital deletion study shows that the structure is primarily determined by (hyper)conjugation and that steric effects play a minor role. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Three-dimensional trajectories of 60Co-labelled earthworms in artificial cores of soil

    Y. Capowiez
    Summary Information on earthworm burrowing behaviour is scarce and therefore the evolution of the macroporosity related to earthworm activities is still poorly known. We have designed a new apparatus, ,Colonne Gamma', to follow the three-dimensional trajectories of radio-labelled earthworms in artificial cores of soil. Earthworms are radio-labelled by injecting into their coelomic cavity a small source of 60Co (volume 0.1 mm3, intensity 13.5 ,Ci). The emission of gamma rays is recorded by three detectors carried by a disc that oscillates vertically around the soil core where the earthworm is introduced. We have also developed a deterministic model to estimate the positions of the 60Co source from the number of gamma rays received by each detector during an oscillation. Numerical experiments showed that the uncertainties of estimates were less than 3 mm for each coordinate. To validate the results, we tracked the trajectory (one position every 4 minutes) of a radio-labelled earthworm for 1 week and compared it with the skeleton of the macroporosity obtained by computer assisted tomography of the same soil core. There was a general qualitative agreement between the trajectory and the skeleton. Moreover, based on the precise study of the successive positions of the earthworm we could distinguish two different kinds of activities in the trajectory: displacement and digging events. The ,Colonne Gamma' apparatus therefore has great potential for studies of the ecology and the behaviour of earthworms. [source]

    Magnetic forces and moving body induced voltages: applications to velocity sensing and DC,AC conversion

    J. A. Brandão Faria
    Abstract This research and tutorial paper illustrates two interlinked phenomena of the greatest importance for power and energy systems engineers, i.e., magnetic forces and moving body induced voltages. A two-solenoid system with driving and sensing parts is analyzed taking into account that a moving ferromagnetic core can freely move along the system axial coordinate. At first-order approximation the frequency of the oscillating core movement is shown to be linearly controllable by the direct-current intensity injected in the driving solenoid. On the other hand the induced voltage on the sensing solenoid is shown to be a sinusoidal voltage with a frequency twice the one of the moving core. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Quantum phenomena via complex measure: Holomorphic extension

    Article first published online: 11 MAY 200, S.K. Srinivasan
    The complex measure theoretic approach proposed earlier is reviewed and a general version of density matrix as well as conditional density matrix is introduced. The holomorphic extension of the complex measure density (CMD) is identified to be the Wigner distribution function of the conventional quantum mechanical theory. A variety of situations in quantum optical phenomena are discussed within such a holomorphic complex measure theoretic framework. A model of a quantum oscillator in interaction with a bath is analyzed and explicit solution for the CMD of the coordinate as well as the Wigner distribution function is obtained. A brief discussion on the assignment of probability to path history of the test oscillator is provided. [source]

    The effect of the electrical anisotropy on the response of helicopter-borne frequency-domain electromagnetic systems

    Changchun Yin
    ABSTRACT Helicopter electromagnetic (HEM) systems are commonly used for conductivity mapping and the data are often interpreted using an isotropic horizontally layered earth model. However, in regions with distinct dipping stratification, it is useful to extend the model to a layered earth with general anisotropy by assigning each layer a symmetrical 3 × 3 resistivity tensor. The electromagnetic (EM) field is represented by two scalar potentials, which describe the poloidal and toroidal parts of the magnetic field. Via a 2D Fourier transform, we obtain two coupled ordinary differential equations in the vertical coordinate. To stabilize the numerical calculation, the wavenumber domain is divided into two parts associated with small and large wavenumbers. The EM field for small wavenumbers is continued from layer to layer with the continuity conditions. For large wavenumbers, the EM field behaves like a DC field and therefore cannot be sensed by airborne EM systems. Thus, the contribution from the large wavenumbers is simply ignored. The magnetic fields are calculated for the vertical coaxial (VCX), horizontal coplanar (HCP) and vertical coplanar (VCP) coil configurations for a helicopter EM system. The apparent resistivities defined from the VCX, VCP and HCP coil responses, when plotted in polar coordinates, clearly identify the principal anisotropic axes of an anisotropic earth. The field example from the Edwards Aquifer recharge area in Texas confirms that the polar plots of the apparent resistivities identify the principal anisotropic axes that coincide well with the direction of the underground structures. [source]

    On the Enantioselectivity of Transition Metal-Catalyzed 1,3-Cycloadditions of 2-Diazocyclohexane-1,3-diones

    Paul Müller
    The formal 1,3-cycloaddition of 2-diazocyclohexane-1,3-diones 1a,1d to acyclic and cyclic enol ethers in the presence of RhII -catalysts to afford dihydrofurans has been investigated. Reaction with a cis/trans mixture of 1-ethoxyprop-1-ene (13a) yielded the dihydrofuran 14a with a cis/trans ratio of 85,:,15, while that with (Z)-1-ethoxy-3,3,3-trifluoroprop-1-ene (13b) gave the cis -product 14b exclusively. The stereochemical outcome of the reaction is consistent with a concerted rather than stepwise mechanism for cycloaddition. The asymmetric cycloaddition of 2-diazocyclohexane-1,3-dione (1a) or 2-diazodimedone (=2-diazo-5,5-dimethylcyclohexane-1,3-dione; 1b) to furan and dihydrofuran was investigated with a representative selection of chiral, nonracemic RhII catalysts, but no significant enantioselectivity was observed, and the reported enantioselective cycloadditions of these diazo compounds could not be reproduced. The absence of enantioselectivity in the cycloadditions of 2-diazocyclohexane-1,3-diones is tentatively explained in terms of the Hammond postulate. The transition state for the cycloaddition occurs early on the reaction coordinate owing to the high reactivity of the intermediate metallocarbene. An early transition state is associated with low selectivity. In contrast, the transition state for transfer of stabilized metallocarbenes occurs later, and the reactions exhibit higher selectivity. [source]

    A systematic review and quantitative appraisal of fMRI studies of verbal fluency: Role of the left inferior frontal gyrus

    HUMAN BRAIN MAPPING, Issue 10 2006
    Sergi G. Costafreda
    Abstract The left inferior frontal gyrus (LIFG) has consistently been associated with both phonologic and semantic operations in functional neuroimaging studies. Two main theories have proposed a different functional organization in the LIFG for these processes. One theory suggests an anatomic parcellation of phonologic and semantic operations within the LIFG. An alternative theory proposes that both processes are encompassed within a supramodal executive function in a single region in the LIFG. To test these theories, we carried out a systematic review of functional magnetic resonance imaging studies employing phonologic and semantic verbal fluency tasks. Seventeen articles meeting our pre-established criteria were found, consisting of 22 relevant experiments with 197 healthy subjects and a total of 41 peak activations in the LIFG. We determined 95% confidence intervals of the mean location (x, y, and z coordinates) of peaks of blood oxygenation level-dependent (BOLD) responses from published phonologic and semantic verbal fluency studies using the nonparametric technique of bootstrap analysis. Significant differences were revealed in dorsal,ventral (z -coordinate) localizations of the peak BOLD response: phonologic verbal fluency peak BOLD response was significantly more dorsal to the peak associated with semantic verbal fluency (confidence interval of difference: 1.9,17.4 mm). No significant differences were evident in antero,posterior (x -coordinate) or medial,lateral (y -coordinate) positions. The results support distinct dorsal,ventral locations for phonologic and semantic processes within the LIFG. Current limitations to meta-analytic integration of published functional neuroimaging studies are discussed. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source]

    The making of twenty-first-century HR: An analysis of the convergence of HRM, HRD, and OD

    Wendy E. A. Ruona
    Twenty-first-century HR is emerging to uniquely combine activities and processes of human resource management (HRM), human resource development (HRD), and organization development (OD),three fields that "grew up" distinct from each other. Contributing strategically to organizations demands that HRM, HRD, and OD coordinate, partner, and think innovatively about how they relate and how what they do impacts people and organizations. An analysis of the evolutions of these fields helps to explain why the distinctions between them continue to blur and how the similarities among them provide the necessary synergy for HR to be a truly valued organizational partner. © 2004 Wiley Periodicals, Inc. [source]

    Localization of root canal orifices in mandibular second molars in relation to occlusal dimension

    O. Gorduysus
    Abstract Aim, To evaluate the localization and distribution of canal orifices of mandibular second molar teeth in relation to the mesio-distal and bucco-lingual dimensions of coronal tissue. Methodology, Fifty extracted mandibular second molar teeth were embedded into plaster blocks with their vertical axes aligned perpendicular to the horizontal plane. The teeth were photographed digitally from the occlusal aspect under 12 × magnification. Thereafter, the occlusal halves of crowns were sectioned off to expose the root canal orifices. The teeth were than photographed under the same magnification, after which the pre- and post-sectioning images of each specimen were stacked into a single file. To plot the coordinate of each canal orifice, a 0.5-mm grid analytical plane was mounted digitally on the stack so that the x - and y -axes of the plane were superimposed on the mesiodistal and buccolingual axes (bisectors) of the tooth crowns. Localization and distribution of the coordinates of the canal orifices were evaluated using the chi-square test (P = 0.05). Results, Only one tooth displayed a single root canal orifice, located in the mesiobuccal-distolingual ,centre' of the occlusal surface. The majority of mandibular second molars had three orifices (72%), followed by those with two (16%) and four (10%). The distal canal was located lingual to the centre of the occlusal plane. Conclusion, The distal canal was located lingual to the centre of the occlusal plane of mandibular second molars. The possibility of observing more divergent localizations and orifice numbers should not be overlooked in clinical practice. [source]

    Finite element analyses of layered visco-elastic system under vertical circular loading

    Q. Xu
    Abstract Analyses for the response of a linear visco-elastic system subjected to axi-symmetric vertical circular loading are presented. Hankel transforms with respect to the radial spatial coordinate are used to reduce the three-dimensional problem to that involving only a single spatial dimension, which is then discretized using the finite element method. Three techniques are employed to handle the time factor in the visco-elastic material: (i) direct time integration; (ii) Fourier transforms; and (iii) Laplace transforms. These methods are compared and evaluated through their numerical results. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Analysis of singular stress fields at multi-material corners under thermal loading

    Chongmin SongArticle first published online: 7 SEP 200
    Abstract The scaled boundary finite-element method is extended to the modelling of thermal stresses. The particular solution for the non-homogeneous term caused by thermal loading is expressed as integrals in the radial direction, which are evaluated analytically for temperature changes varying as power functions of the radial coordinate. When applied to model a multi-material corner, only the boundary of the problem domain is discretized. The boundary conditions on the straight material interfaces and the side-faces forming the corner are satisfied analytically without discretization. The stress field is expressed semi-analytically as a series solution. The stress distribution along the radial direction, including both the real and complex power singularity and the power-logarithmic singularity, is represented analytically. The stress intensity factors are determined directly from their definitions in stresses. No knowledge on asymptotic expansions is required. Numerical examples are calculated to evaluate the accuracy of the scaled boundary finite-element method. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    A numerical scheme for strong blast wave driven by explosion

    Kaori Kato
    Abstract After the detonation of a solid high explosive, the material has extremely high pressure keeping the solid density and expands rapidly driving strong shock wave. In order to simulate this blast wave, a stable and accurate numerical scheme is required due to large density and pressure changes in time and space. The compressible fluid equations are solved by a fractional step procedure which consists of the advection phase and non-advection phase. The former employs the Rational function CIP scheme in order to preserve monotone signals, and the latter is solved by interpolated differential operator scheme for achieving the accurate calculation. The procedure is categorized into the fractionally stepped semi-Lagrangian. The accuracy of our scheme is confirmed by checking the one-dimensional plane shock tube problem with 103 times initial density and pressure jump in comparison with the analytic solution. The Sedov,Taylor blast wave problem is also examined in the two-dimensional cylindrical coordinate in order to check the spherical symmetry and the convergence rates. Two- and three-dimensional simulations for the blast waves from the explosion in the underground magazine are carried out. It is found that the numerical results show quantitatively good agreement with the experimental data. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    A ,-coordinate three-dimensional numerical model for surface wave propagation

    Pengzhi Lin
    Abstract A three-dimensional numerical model based on the full Navier,Stokes equations (NSE) in , -coordinate is developed in this study. The , -coordinate transformation is first introduced to map the irregular physical domain with the wavy free surface and uneven bottom to the regular computational domain with the shape of a rectangular prism. Using the chain rule of partial differentiation, a new set of governing equations is derived in the , -coordinate from the original NSE defined in the Cartesian coordinate. The operator splitting method (Li and Yu, Int. J. Num. Meth. Fluids 1996; 23: 485,501), which splits the solution procedure into the advection, diffusion, and propagation steps, is used to solve the modified NSE. The model is first tested for mass and energy conservation as well as mesh convergence by using an example of water sloshing in a confined tank. Excellent agreements between numerical results and analytical solutions are obtained. The model is then used to simulate two- and three-dimensional solitary waves propagating in constant depth. Very good agreements between numerical results and analytical solutions are obtained for both free surface displacements and velocities. Finally, a more realistic case of periodic wave train passing through a submerged breakwater is simulated. Comparisons between numerical results and experimental data are promising. The model is proven to be an accurate tool for consequent studies of wave-structure interaction. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    A linear three-center four electron bonding identity nucleophilic substitution at carbon, boron, and phosphorus.

    A theoretical study in combination with van't Hoff modeling
    Abstract We studied various identity nucleophilic substitution reactions based on an SN2 reaction profile. With calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff 's tetrahedron by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical and the corresponding tetrahedral bond distance is then 1.333. This value has been used in general as a calibration point for the understanding of the (in)stabilities of the complex formation on the SN2 reaction coordinate. The relevance of this approach has been also proved for enzymatic reactions focused on carbon and phosphorus substrates. Furthermore, it could be established that identity proton-in-line displacements are fully comparable with the relocation of carbon in a nucleophilic substitution reaction as Cl, + CH3Cl. The significance of this information will afford new insight in the dynamics of a linear three-center four-electron complex. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]