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1

Effect of nozzle geometry and semi-confinement on the potential core of a turbulent axisymmetric free jet  

Microsoft Academic Search

The effects of nozzle geometry and confinement on the potential core and subsequent axial development of a turbulent axisymmetric air jet at a Reynolds number of 22 500 have been studied. Four jet exit conditions, namely, flat and fully developed velocity profiles for unconfined and semi-confined cases were investigated. Mean velocity and turbulence profiles were measured using laser-Doppler anemometry. Liquid

S. Ashforth-Frost; K. Jambunathan

1996-01-01

2

Effects of Confining Geometry on Ballistic Transport in Quantum Wires  

Microsoft Academic Search

The effects of confining geometry are investigated on ballistic transport in quasi-one-dimensional quantum wires. The coupled channel type method is used in order to calculate the conductance of the quantum wires as a function of the Fermi energy. It is shown that oscillations existing in the conductance of the wire with a confining potential of `step wise' type geometry disappear

Hideaki Kasai; Kunihiro Mitsutake; Ayao Okiji

1991-01-01

3

Polymer Statics and Dynamics in Confined Geometries  

NASA Astrophysics Data System (ADS)

Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. Little is known about the possibility of inducing a glass transition through pure dimensional confinement. We are concerned with whether or not there is a critical value of the confining length scale. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain by measuring quantities such as the magnitude end-to-end vector, the radius of gyration, and single monomer motion (JACS 124, 20 (2004)). A primary question is whether the self-avoidance constraint manifests itself in a manner similar to kinetically constrained models of the glass transition. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.

Kalb, Joshua; Chakraborty, Bulbul

2006-03-01

4

Plasma confinement. [Physics for magnetic geometries  

SciTech Connect

The physics of plasma confinement by a magnetic field is developed from the basic properties of plasmas through the theory of equilibrium, stability, and transport in toroidal and open-ended configurations. The close relationship between the theory of plasma confinement and Hamiltonian mechanics is emphasized, and the modern view of macroscopic instabilities as three-dimensional equilibria is given.

Boozer, A.H.

1985-03-01

5

Thermodynamic Properties of Alkanes in Confined Geometries  

NASA Astrophysics Data System (ADS)

Reported are the results of two related investigations. The first is a theoretical study of the thermal response of a model differential scanning calorimeter (DSC) yielding insights into proper techniques for sample preparation, instrument calibration, and interpretation of phase transition data. This is followed by a calorimetric study of the melting and freezing behavior of cyclohexane ( rm C_6H_{12}), cyclooctane (rm C_8H_{16}), and n-octane (rm C_8H_{18 }), confined within the pore spaces of a series of porous silica glasses with mean pore radii r between 4.1 +/- 0.3 and 64 +/- 5 nm. The melting and freezing temperatures and latent heats of the pore alkanes were found to be increasingly depressed from the bulk values with decreasing pore size r. Unlike previous studies of phase transitions of confined organic substances, we have observed melting temperature depressions which are stronger than r^{ -1}. These temperature depressions can be expressed by the empirical cluster equation rm T_{m} = T_{o} - A/(r - r_{rm o}). The latent heats were found to vary approximately linearly with the inverse pore radius. The transition data from incompletely filled pores indicate that the alkanes are not layering the pore walls evenly, but are gathering as plugs at the pore necks. Studies using glasses in which the silica surface was modified using a standard derivatization technique suggest that the replacement ligands are not forming a complete monolayer. We have also observed cyclooctane supercools by 10-15 K below the expected freezing point, both in bulk and confined within the porous glass.

Sheehan, Joseph F., III

6

Temperature-resonant cyclotron spectra in confined geometries  

NASA Astrophysics Data System (ADS)

We consider a two-dimensional gas of colliding charged particles confined to finite size containers of various geometries and subjected to a uniform orthogonal magnetic field. The gas spectral densities are characterized by a broad peak at the cyclotron frequency. Unlike for infinitely extended gases, where the amplitude of the cyclotron peak grows linearly with temperature, here confinement causes such a peak to go through a maximum for an optimal temperature. In view of the fluctuation-dissipation theorem, the reported resonance effect has a direct counterpart in the electric susceptibility of the confined magnetized gas.

Pototsky, A.; Hänggi, P.; Marchesoni, F.; Savel'Ev, S.

2011-07-01

7

Sedimentation dynamics of spherical particles in confined geometries  

NASA Astrophysics Data System (ADS)

We study the steady-state dynamics of sedimenting non-Brownian particles in confined geometries with full hydrodynamic interactions at small but finite Reynolds numbers. We employ extensive computer simulations using a method where a continuum liquid phase is coupled through Stokesian friction to a discrete particle phase. In particular, we consider a sedimentation box which is otherwise periodic except that it is confined by two parallel walls parallel to gravity with a spacing Lx . By systematically varying Lx we explore the change in dynamics from a quasi-two-dimensional (2D) case to a three-dimensional case. We find that in such confined geometries there is a depletion of particle number density at the walls for small volume fractions, while for large volume fractions there is an excess number of particles at the walls. For the average sedimentation velocity, we find that the Richardson-Zaki law is well obeyed but the decrease of the velocity for dilute systems is slower for smaller values of Lx . We study the anisotropy of the velocity fluctuations and find that in the direction of gravity there is excellent agreement with the predicted scaling with respect to Lx . We also find that the behavior of the corresponding diffusion coefficients as a function of Lx is qualitatively different in the direction parallel to gravity and perpendicular to it. In the quasi-2D limit where particles block each other, the velocity fluctuations behave differently from the other confined systems.

Kuusela, E.; Lahtinen, J. M.; Ala-Nissila, T.

2004-06-01

8

Superfluid Phases of 3He in a Periodic Confined Geometry  

NASA Astrophysics Data System (ADS)

Predictions and discoveries of new phases of superfluid 3He in confined geometries, as well as novel topological excitations confined to surfaces and edges of near a bounding surface of 3He, are driving the fields of superfluid 3He infused into porous media, as well as the fabrication of sub-micron to nano-scale devices for controlled studies of quantum fluids. In this report we consider superfluid 3He confined in a periodic geometry, specifically a two-dimensional lattice of square, sub-micron-scale boundaries ("posts") with translational invariance in the third dimension. The equilibrium phase(s) are inhomogeneous and depend on the microscopic boundary conditions imposed by a periodic array of posts. We present results for the order parameter and phase diagram based on strong pair breaking at the boundaries. The ordered phases are obtained by numerically minimizing the Ginzburg-Landau free energy functional. We report results for the weak-coupling limit, appropriate at ambient pressure, as a function of temperature T, lattice spacing L, and post edge dimension, d. For all d in which a superfluid transition occurs, we find a transition from the normal state to a periodic, inhomogeneous "polar" phase with T_{c1} < Tc for bulk superfluid 3He. For fixed lattice spacing, L, there is a critical post dimension, d c , above which only the periodic polar phase is stable. For d

Wiman, J. J.; Sauls, J. A.

2013-10-01

9

Critical comparison between magnetic and inertial confinement schemes and their geometries  

SciTech Connect

The interaction mechanism between the plasma and magnetic field in a tokamak does not provide complete magnetic confinement as is usually imagined. Also, the toroidal geometry itself is not particularly well suited for containing a hot plasma. Qualitative arguments reveal an intrinsic superiority of the inertial confinement spherical geometry over any geometry of magnetic confinement for fusion purposes. Moreover, from the point of view of applications, spherical devices such as the inertial electrostatic confinement device and the inertial confinement fusion-spherical pinch are giving immediate spin-offs of industrial interest. 12 refs., 1 fig.

Salingaros, N.A. [Univ. of Texas, San Antonio, TX (United States)

1995-05-01

10

Phase diagram of the topological superfluid 3He confined in a nanoscale slab geometry.  

PubMed

The superfluid phases of helium-3 ((3)He) are predicted to be strongly influenced by mesoscopic confinement. However, mapping out the phase diagram in a confined geometry has been experimentally challenging. We confined a sample of (3)He within a nanofluidic cavity of precisely defined geometry, cooled it, and fingerprinted the order parameter using a sensitive nuclear magnetic resonance spectrometer. The measured suppression of the p-wave order parameter arising from surface scattering was consistent with the predictions of quasi-classical theory. Controlled confinement of nanofluidic samples provides a new laboratory for the study of topological superfluids and their surface- and edge-bound excitations. PMID:23687043

Levitin, L V; Bennett, R G; Casey, A; Cowan, B; Saunders, J; Drung, D; Schurig, Th; Parpia, J M

2013-05-17

11

Confining Potential when a Biopolymer Filament Reptates  

NASA Astrophysics Data System (ADS)

Using single-molecule fluorescence imaging, we track Brownian motion perpendicular to the contour of tightly entangled F-actin filaments and extract the confining potential. The chain localization presents a small-displacement Hookean regime followed by a large amplitude regime where the effective restoring force is independent of displacement. The implied heterogeneity characterized by a distribution of tube width is modeled.

Wang, Bo; Guan, Juan; Anthony, Stephen M.; Bae, Sung Chul; Schweizer, Kenneth S.; Granick, Steve

2010-03-01

12

Electrolysis in nanochannels for in situ reagent generation in confined geometries.  

PubMed

In situ generation of reactive species within confined geometries, such as nanopores or nanochannels is of significant interest in overcoming mass transport limitations in chemical reactivity. Solvent electrolysis is a simple process that can readily be coupled to nanochannels for the electrochemical generation of reactive species, such as H(2). Here the production of hydrogen-rich liquid volumes within nanofluidic structures, without bubble nucleation or nanochannel occlusion, is explored both experimentally and by modeling. Devices comprised of multiple horizontal nanochannels intersecting planar working and quasi-reference electrodes were constructed and used to study the effects of confinement and reduced working volume on the electrochemical reduction of H(2)O to H(2) and OH(-). H(2) production in the nanochannel-embedded electrode reactor output was monitored by fluorescence emission of fluorescein, which exhibits a pH-dependent emission intensity. Initially, the fluorescein solution was buffered to pH 6.0 prior to stepping the potential cathodic of E(0)' for the generation of OH(-) and H(2). Because the electrochemical products are obtained in a 2:1 stoichiometry, local measurements of pH during and after the cathodic potential steps can be converted into H(2) production rates. Independent experimental estimates of the local H(2) concentration were then obtained from the spatiotemporal fluorescence behavior and current measurements, and these were compared with finite element simulations accounting for electrolysis and subsequent convection and diffusion within the confined geometry. Local dissolved H(2) concentrations were correlated to partial pressures through Henry's Law and values as large as 8.3 atm were obtained at the most negative potential steps. The downstream availability of electrolytically produced H(2) in nanochannels is evaluated in terms of its possible use as a downstream reducing reagent. The results obtained here indicate that H(2) can easily reach saturation concentrations at modest overpotentials. PMID:21912801

Contento, Nicholas M; Branagan, Sean P; Bohn, Paul W

2011-09-13

13

Langevin dynamics for the transport of flexible biological macromolecules in confined geometries.  

PubMed

The transport of flexible biological macromolecules in confined geometries is found in a variety of important biophysical systems including biomolecular movements through pores in cell walls, vesicle walls, and synthetic nanopores for sequencing methods. In this study, we extend our previous analysis of the Fokker-Planck and Langevin dynamics for describing the coupled translational and rotational motions of single structured macromolecules near structured external surfaces or walls [M. H. Peters, J. Chem. Phys. 110, 528 (1999); 112, 5488 (2000)] to the problem of many interacting macromolecules in the presence of structured external surfaces representing the confining geometry. Overall macromolecular flexibility is modeled through specified interaction potentials between the structured Brownian subunits (B-particles), as already demonstrated for protein and DNA molecules briefly reviewed here. We derive the Fokker-Planck equation using a formal multiple time scale perturbation expansion of the Liouville equation for the entire system, i.e., solvent, macromolecules, and external surface. A configurational-orientational Langevin displacement equation is also obtained for use in Brownian dynamics applications. We demonstrate important effects of the external surface on implicit solvent forces through formal descriptions of the grand friction tensor and equilibrium average force of the solvent on the B-particles. The formal analysis provides both transparency of all terms of the Langevin displacement equation as well as a prescription for their determination. As an example, application of the methods developed, the real-time movement of an ?-helix protein through a carbon nanotube is simulated. PMID:21241153

Peters, Michael H

2011-01-14

14

Langevin dynamics for the transport of flexible biological macromolecules in confined geometries  

NASA Astrophysics Data System (ADS)

The transport of flexible biological macromolecules in confined geometries is found in a variety of important biophysical systems including biomolecular movements through pores in cell walls, vesicle walls, and synthetic nanopores for sequencing methods. In this study, we extend our previous analysis of the Fokker-Planck and Langevin dynamics for describing the coupled translational and rotational motions of single structured macromolecules near structured external surfaces or walls [M. H. Peters, J. Chem. Phys. 110, 528 (1999); 112, 5488 (2000)] to the problem of many interacting macromolecules in the presence of structured external surfaces representing the confining geometry. Overall macromolecular flexibility is modeled through specified interaction potentials between the structured Brownian subunits (B-particles), as already demonstrated for protein and DNA molecules briefly reviewed here. We derive the Fokker-Planck equation using a formal multiple time scale perturbation expansion of the Liouville equation for the entire system, i.e., solvent, macromolecules, and external surface. A configurational-orientational Langevin displacement equation is also obtained for use in Brownian dynamics applications. We demonstrate important effects of the external surface on implicit solvent forces through formal descriptions of the grand friction tensor and equilibrium average force of the solvent on the B-particles. The formal analysis provides both transparency of all terms of the Langevin displacement equation as well as a prescription for their determination. As an example, application of the methods developed, the real-time movement of an ?-helix protein through a carbon nanotube is simulated.

Peters, Michael H.

2011-01-01

15

Dynamics of laser-blow-off induced Li plume in confined geometry  

NASA Astrophysics Data System (ADS)

Dynamics of Li plasma plume created by laser-blow-off technique in air ambient is reported. Plasma plume dynamics and its optical emission are investigated in planar and confined geometries using time resolved shadowgraph imaging and optical emission spectroscopy. Significant differences in the plasma characteristics in confined geometry are quantitatively investigated by comparing the plasma parameters (temperature and density) in free expansion and confined geometry configurations. Dynamics and physical parameters of the primary as well as the reflected shock waves (in confined geometry) and their interactions with expanding plasma are briefly addressed. A large enhancement in the emission intensities of Li I 610.3 nm (2p 2P1/2, 3/2 <-- 3d 2P3/2, 5/2) and 670.8 nm (2s 2S1/2 <-- 2p 2P1/2, 3/2) is correlated with the shock wave dynamics in the two geometries. Strong self reversal in the neutral emission infers an increase in the population density of neutrals within the confined plasma plume.

Kumar, Bhupesh; Singh, R. K.; Kumar, Ajai

2013-08-01

16

Beam-ion confinement for different injection geometries  

SciTech Connect

The DIII-D tokamak is equipped with neutral beam sources that inject in four different directions; in addition, the plasma can be moved up or down to compare off-axis with on-axis injection. Fast-ion data for eight different conditions have been obtained: co/counter, near-tangential/near-perpendicular and on-axis/off-axis. Neutron measurements during short beam pulses assess prompt and delayed losses under low-power conditions. As expected, co-injection has fewer losses than counter, tangential fewer than perpendicular and on-axis fewer than off-axis; the differences are greater at low current than at higher current. The helicity of the magnetic field has a weak effect on the overall confinement. Fast-ion D-alpha (FIDA) and neutron measurements diagnose the confinement at higher power. The basic trends are the same as in low-power plasmas but, even in plasmas without long wavelength Alfven modes or other MHD, discrepancies with theory are observed, especially in higher temperature plasmas. At modest temperature, two-dimensional images of the FIDA light are in good agreement with the simulations for both on-axis and off-axis injection. Discrepancies with theory are more pronounced at low fast-ion energy and at high plasma temperature, suggesting that fast-ion transport by microturbulence is responsible for the anomalies.

Heidbrink, W. W. [University of California, Irvine; Murakami, Masanori [ORNL; Park, Jin Myung [ORNL; Petty, C C. [General Atomics, San Diego; Van Zeeland, Michael [General Atomics; Yu, J.H. [University of California, San Diego; Mckee, G. R. [University of Wisconsin, Madison

2009-01-01

17

Deformable cells in confined geometries: From hemolysis to hydrodynamic interactions  

NASA Astrophysics Data System (ADS)

Recent developments in microfluidics allow a wide range of possibilities for studying cellular-scale hydrodynamics. Here we use microfluidic technology to address several open questions in the blood flow literature where cell deformation and hydrodynamic interactions are significant. In particular, we investigate the pressure-driven flow of a dilute suspension in a channel and characterize the transition from steady axisymmetric cell shapes (for which numerical calculations exist) to asymmetric, highly extended shapes, which are precursors to hemolysis (i.e. destruction of the cell). In addition, we examine the influence of geometry on hydrodynamic interactions of deformable cells by contrasting one-dimensional motion of a train of particles in a channel with two-dimensional motions in a Hele-Shaw cell. This study can help to understand flow of cells in microcirculation from the unidirectional flow in capillaries to the two-dimensional flow in the lung alveoli and provides the basic steps to understand certain aspects of microcirculatory deseases like sickle cell anemia for example.

Abkarian, Manouk; Faivre, Magalie; Stone, Howard A.

2004-11-01

18

Electrostatically Confined Plasma in Segmented Hollow Cathode Geometries for Surface Engineering  

Microsoft Academic Search

A segmented hollow cathode (SHC) geometry was used for electrostatic confinement of plasma, and surface engi- neering treatments were conducted in this arrangement. The as- sessed processes included plasma nitriding, reactive deposition of sputtered material, and deposition of carbonaceous films by plas- ma-enhanced chemical vapor deposition with a bipolar pulsed-dc power supply on steel substrates. The treated specimens exhibited uniform

Santiago Corujeira Gallo; Ângela E. Crespi; Felipe Cemin; Carlos A. Figueroa; Israel J. R. Baumvol

2011-01-01

19

Observations on the potential confinement of a light fermion  

SciTech Connect

We consider possible dynamical models for a light fermion confined by a potential field. With the Dirac equation only Lorentz scalar confinement yields normalizable wave functions, while with the ``no pair`` variant of the Dirac equation only Lorentz vector confinement has normal Regge behavior. A systematic investigation of Regge properties and phenomenological properties is carried out, including calculations of the Isgur-Wise (IW) function. We point out that the Isgur-Wise function provides a sensitive test of confinement models. In particular, the slope of the IW function at the zero recoil point is found to be {xi}{prime}(1){congruent}{minus}0.90 for the Dirac equation with scalar confinement and {xi}{prime}(1){congruent}{minus}1.20 for the no pair equation with vector confinement. Using heavy-light meson data alone we argue against scalar confinement.

Olsson, M.G.; Veseli, S. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Williams, K. [Continuous Electron Beam Accelerator Facility, Newport News, Virginia 29606 (United States)]|[Physics Department, Hampton University, Hampton, Virginia 29668 (United States)

1995-05-01

20

Effect of nozzle geometry on local convective heat transfer to a confined impinging air jet  

Microsoft Academic Search

This article reports results on the effects of hyperbolic nozzle geometry on the local heat-transfer coefficients for confined impinging air jets. A thermochromatic liquid-crystal technique is used to visualize and record isotherms on a uniformly heated impingement surface. Experiments are conducted at low nozzle-to-plate spacings (0.25 < HD < 6.0) and Reynolds numbers in the range of 10,000 to 50,000

D. W. Colucci; R. Viskanta

1996-01-01

21

The capillarity of nanometric water menisci confined inside closed-geometry viral cages  

PubMed Central

We present an investigation of water menisci confined in closed geometries by studying the structural effects of their capillary forces on viruses during the final stage of desiccation. We used individual particles of the bacteriophage ?29 and the minute virus of mice. In both cases the genomic DNA was ejected from the capsid. However, although the structural integrity of the minute virus of mice was essentially preserved, the ?29 capsid underwent a wall-to-wall collapse. We provide evidence that the capillary forces of water confined inside the viruses are mainly responsible for these effects. Moreover, by performing theoretical simulations with a lattice gas model, we found that some structural differences between these 2 viruses may be crucial to explain the different ways in which they are affected by water menisci forces confined at the nanoscale.

Carrasco, C.; Douas, M.; Miranda, R.; Castellanos, M.; Serena, P. A.; Carrascosa, J. L.; Mateu, M. G.; Marques, M. I.; de Pablo, P. J.

2009-01-01

22

Charged colloidal model systems under confinement in slit geometry: a new setup for optical microscopic studies.  

PubMed

A new experimental setup for optical microscopic studies of charged colloidal model systems under confinement between two flat walls is presented. The measurement cell consists of optically flat quartz substrates attached to piezo actuators. Those facilitate fast and flexible adjustment of the confining geometry. Optionally, the local cell height can be quantitatively controlled by in situ interferometric measurements. Proper choice of materials guarantees sufficient chemical inertia against contamination with salt ions. For efficient preparation of charged colloidal suspensions under strongly deionized conditions, the cell can be connected to a conventional pump circuit including a mixed bed ion exchanger column. The usefulness of this setup, in particular for investigating the equilibrium phase behavior of colloids at low background salt concentrations, is demonstrated recalling recent experiments. PMID:23822357

Reinmüller, A; Palberg, T; Schöpe, H J

2013-06-01

23

Charged colloidal model systems under confinement in slit geometry: A new setup for optical microscopic studies  

NASA Astrophysics Data System (ADS)

A new experimental setup for optical microscopic studies of charged colloidal model systems under confinement between two flat walls is presented. The measurement cell consists of optically flat quartz substrates attached to piezo actuators. Those facilitate fast and flexible adjustment of the confining geometry. Optionally, the local cell height can be quantitatively controlled by in situ interferometric measurements. Proper choice of materials guarantees sufficient chemical inertia against contamination with salt ions. For efficient preparation of charged colloidal suspensions under strongly deionized conditions, the cell can be connected to a conventional pump circuit including a mixed bed ion exchanger column. The usefulness of this setup, in particular for investigating the equilibrium phase behavior of colloids at low background salt concentrations, is demonstrated recalling recent experiments.

Reinmüller, A.; Palberg, T.; Schöpe, H. J.

2013-06-01

24

Lattice-Boltzmann simulations of the dynamics of polymer solutions in periodic and confined geometries.  

PubMed

A numerical method to simulate the dynamics of polymer solutions in confined geometries has been implemented and tested. The method combines a fluctuating lattice-Boltzmann model of the solvent [Ladd, Phys. Rev. Lett. 70, 1339 (1993)] with a point-particle model of the polymer chains. A friction term couples the monomers to the fluid [Ahlrichs and Dunweg, J. Chem. Phys. 111, 8225 (1999)], providing both the hydrodynamic interactions between the monomers and the correlated random forces. The coupled equations for particles and fluid are solved on an inertial time scale, which proves to be surprisingly simple and efficient, avoiding the costly linear algebra associated with Brownian dynamics. Complex confined geometries can be represented by a straightforward mapping of the boundary surfaces onto a regular three-dimensional grid. The hydrodynamic interactions between monomers are shown to compare well with solutions of the Stokes equations down to distances of the order of the grid spacing. Numerical results are presented for the radius of gyration, end-to-end distance, and diffusion coefficient of an isolated polymer chain, ranging from 16 to 1024 monomers in length. The simulations are in excellent agreement with renormalization group calculations for an excluded volume chain. We show that hydrodynamic interactions in large polymers can be systematically coarse-grained to substantially reduce the computational cost of the simulation. Finally, we examine the effects of confinement and flow on the polymer distribution and diffusion constant in a narrow channel. Our results support the qualitative conclusions of recent Brownian dynamics simulations of confined polymers [Jendrejack et al., J. Chem. Phys. 119, 1165 (2003) and Jendrejack et al., J. Chem. Phys. 120, 2513 (2004)]. PMID:15836176

Berk Usta, O; Ladd, Anthony J C; Butler, Jason E

2005-03-01

25

Thermal resistivity of He-4 in confined geometries near the superfluid transition  

NASA Astrophysics Data System (ADS)

Measurements of the thermal conductivity of liquid 4 He confined in cylindrical channels will be presented. At vapor pressure, cylinder radii L from 0.5 to 2.5 ?m have been used. Along various isobars between vapor pressure and 28 bars, measurements have been made for L = 1?m. Within their resolution, the data obey finite-size scaling as a function of L. As a function of pressure they are consistent with a universal scaling function. Future plans for measurements in rectangular geometries and for the microgravity experiment BEST (Boundary Effects on the Superfluid Transition) will be discussed.

Murphy, D.; Genio, E.; Aouaroun, T.; Liu, F.; Liu, Y.; Ahlers, G.

26

Transient and asymptotic dispersion in confined sphere packings with cylindrical and non-cylindrical conduit geometries.  

PubMed

We study the time and length scales of hydrodynamic dispersion in confined monodisperse sphere packings as a function of the conduit geometry. By a modified Jodrey-Tory algorithm, we generated packings at a bed porosity (interstitial void fraction) of ?=0.40 in conduits with circular, rectangular, or semicircular cross section of area 100?d(p)(2) (where d(p) is the sphere diameter) and dimensions of about 20d(p) (cylinder diameter) by 6553.6d(p) (length), 25d(p) by 12.5d(p) (rectangle sides) by 8192d(p) or 14.1d(p) (radius of semicircle) by 8192d(p), respectively. The fluid-flow velocity field in the generated packings was calculated by the lattice Boltzmann method for Péclet numbers of up to 500, and convective-diffusive mass transport of 4×10(6) inert tracers was modelled with a random-walk particle-tracking technique. We present lateral porosity and velocity distributions for all packings and monitor the time evolution of longitudinal dispersion up to the asymptotic (long-time) limit. The characteristic length scales for asymptotic behaviour are explained from the symmetry of each conduit's velocity field. Finally, we quantify the influence of the confinement and of a specific conduit geometry on the velocity dependence of the asymptotic dispersion coefficients. PMID:21576163

Khirevich, Siarhei; Höltzel, Alexandra; Tallarek, Ulrich

2011-06-28

27

Attractive potential between confined colloids at low ionic strength  

Microsoft Academic Search

Digital video microscopy is used to locate the positions of 1.27 mum diameter polystyrene spheres suspended in low ionic strength water and confined between two glass plates. A method is developed to obtain the pair potential of the colloidal particles from measurements of the pair-correlation function of both dilute and moderately concentrated dispersions. We find that the measured pair potential

Grace Martinelli Kepler; Seth Fraden

1994-01-01

28

Potential Well Structures in Spherical Inertial Electrostatic Confinement Devices  

Microsoft Academic Search

Inertial electrostatic confinement (IEC) devices are of interest as neutron generators for many applications. Experiments by Hirsch inspired further efforts to decipher the potential distribution within IEC devices. In this paper, previous analyzes of potential distributions in IEC devices are reviewed and extended. Three types of IEC systems are classified and analyzed according to the arrangement of electrodes and the

Ryan M. Meyer; Sudarshan K. Loyalka; Mark A. Prelas

2005-01-01

29

Modelling the role of surface stress on the kinetics of tissue growth in confined geometries.  

PubMed

In a previous paper we presented a theoretical framework to describe tissue growth in confined geometries based on the work of Ambrosi and Guillou [Ambrosi D, Guillou A. Growth and dissipation in biological tissues. Cont Mech Thermodyn 2007;19:245-51]. A thermodynamically consistent eigenstrain rate for growth was derived using the concept of configurational forces and used to investigate growth in holes of cylindrical geometries. Tissue growing from concave surfaces can be described by a model based on this theory. However, an apparently asymmetric behaviour between growth from convex and concave surfaces has been observed experimentally, but is not predicted by this model. This contradiction is likely to be due to the presence of contractile tensile stresses produced by cells near the tissue surface. In this contribution we extend the model in order to couple tissue growth to the presence of a surface stress. This refined growth model is solved for two geometries, within a cylindrical hole and on the outer surface of a cylinder, thus demonstrating how surface stress may indeed inhibit growth on convex substrates. PMID:23099300

Gamsjäger, E; Bidan, C M; Fischer, F D; Fratzl, P; Dunlop, J W C

2012-10-22

30

Ultracold dipolar collisions of KRb molecules in a 2D confined geometry  

NASA Astrophysics Data System (ADS)

Ultracold fermionic polar molecules of ^40K^87Rb in their absolute rovibronic and hyperfine ground state [1] have been recently created and pave the way to probe ultracold chemistry of polar molecules [2]. When an electric field is applied, KRb + KRb -> K2 + Rb2 chemical rates increase as the sixth power of the molecule induced dipole moment [3], due dominantly to head-to-tail collisions. As a consequence, chemical reactions are enhanced in an electric field and are unfavorable to long lifetimes of polar molecules. To prevent these collisions, an additional optical lattice can be used to confine the molecules in two dimensions. In this talk, we will present a theoretical investigation of ultracold dipolar collisions of indistinguishable KRb molecules in a presence of an electric field in a 2D confined geometry. We will present expected chemical rates as a function of the electric field and discuss if this will be favorable to achieve evaporative cooling of a dense sample of KRb molecules. [1] Ni et al., Science 322, 231 (2008) ; Ospelkaus et al., Phys. Rev. Lett. 104, 030402 (2010). [2] Ospelkaus et al., arXiv:0912.3854, Science, in press (2010). [3] Qu'em'ener et al., Phys. Rev. A, in press (2010) ; Ni et al., arXiv:1001.2809, submitted (2010).

Quemener, Goulven; Bohn, John

2010-03-01

31

Pressure Dependence of the Thermal Resistivity of Liquid ^4He in a Confined Geometry near T_?  

NASA Astrophysics Data System (ADS)

We present results of measurements of the thermal resistivity R(t,P) of liquid ^4He in a confined geometry near the superfluid transition as a function of the pressure P and reduced temperature t? T/T_?(P) - 1. The confining medium was a micro-channel plate with holes of a uniform radius L=1.0 ?m, and six pressures ranging from saturated vapor pressure (SVP) to 28 bar were used. Our data are consistent with a universal scaling relation between R and t close to T_?(P) which is valid for all pressures. In particular, plotting F=(L/?_0)^x/?( R/R_0) versus X= (L/?_0)^1/?t, where R0 and x are the pressure-dependent amplitude and effective exponent of the bulk resistivity, ?0 is the pressure-dependent bare correlation length, and ?=0.6705 is the pressure-independent exponent of the correlation length, causes the data to collapse onto a single curve, a result which is consistent with dynamic finite-size scaling. Other features of the data below T_?(P) will be discussed.

Murphy, Daniel; Genio, Edgar; Ahlers, Guenter; Liu, Feng-Chuan; Liu, Yuan-Ming

2002-03-01

32

Surface thermodynamic analysis of fluid confined in a cone and comparison with the sphere-plate and plate-plate geometries.  

PubMed

The behavior of pure fluid confined in a cone is investigated using thermodynamic stability analysis. Four situations are explained on the basis of the initial confined phase (liquid/vapor) and its pressure (above/below the saturation pressure). Thermodynamic stability analysis (a plot of the free energy of the system versus the size of the new potential phase) reveals whether the phase transition is possible and, if so, the number and type (unstable/metastable/stable) of equilibrium states in each of these situations. Moreover we investigated the effect of the equilibrium contact angle and the cone angle (equivalent to the confinement's surface separation distance) on the free energy (potential equilibrium states). The results are then compared to our previous study of pure fluid confined in the gap between a sphere and a flat plate and the gap between two flat plates.1 Confined fluid behavior of the four possible situations (for these three geometries) can be explained in a unified framework under two categories based on only the meniscus shape (concave/convex). For systems with bulk-phase pressure imposed by a reservoir, the stable coexistence of pure liquid and vapor is possible only when the meniscus is concave. PMID:24041429

Zargarzadeh, Leila; Elliott, Janet A W

2013-10-09

33

Mixtures of Bose Gases Confined in a Ring Potential  

SciTech Connect

The rotational properties of a mixture of two distinguishable Bose gases that are confined in a ring potential provide novel physical effects that we demonstrate in this study. Persistent currents are shown to be stable for a range of the population imbalance between the two components at low angular momentum. At higher values of the angular momentum, even small admixtures of a second species of atoms make the persistent currents highly fragile.

Smyrnakis, J.; Kavoulakis, G. M.; Magiropoulos, M. [Technological Education Institute of Crete, P.O. Box 1939, GR-71004, Heraklion (Greece); Bargi, S.; Kaerkkaeinen, K.; Reimann, S. M. [Mathematical Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund (Sweden)

2009-09-04

34

Potential for general relativity and its geometry  

NASA Astrophysics Data System (ADS)

The unique ghost-free mass and nonlinear potential terms for general relativity are presented in a diffeomorphism and local Lorentz invariant vierbein formalism. This construction requires an additional two-index Stückelberg field, beyond the four scalar fields used in the metric formulation, and unveils a new local SL(4) symmetry group of the mass and potential terms, not shared by the Einstein-Hilbert term. The new field is auxiliary but transforms as a vector under two different Lorentz groups, one of them the group of local Lorentz transformations, the other an additional global group. This formulation enables a geometric interpretation of the mass and potential terms for gravity in terms of certain volume forms. Furthermore, we find that the decoupling limit is much simpler to extract in this approach; in particular, we are able to derive expressions for the interactions of the vector modes. We also note that it is possible to extend the theory by promoting the two-index auxiliary field into a Nambu-Goldstone boson nonlinearly realizing a certain spacetime symmetry, and show how it is “eaten up” by the antisymmetric part of the vierbein.

Gabadadze, Gregory; Hinterbichler, Kurt; Pirtskhalava, David; Shang, Yanwen

2013-10-01

35

Nematic Ordering in Confined Geometry Applied to DNA Packaging in Viral Capsids  

NASA Astrophysics Data System (ADS)

We propose a density functional theory of conformation of a double stranded DNA inside a spherical viral capsid. For this purpose we apply the mathematical apparatus elaborated in the classic theories on nematic ordering to describe the arrangement principles of a long persistent polymeric chain in confined geometry. In this way, the local self-assembly of different segments of the chain can be considered as a nematic phase with a non-constant (distorted) director. Taking into account the only steric interactions in the second virial approximation is shown to be enough to demonstrate the principle possibility of the nematic ordering. As a result, the polymer density and orientational order distributions throughout the volume of the capsid were obtained. It is observed that a short and flexible polymeric chain is concentrated at the center of capsid being orientationally disordered, and behaving similar to a simple polymeric coil in the spherical cavity. In contrast, upon the increasing of the length and rigidity of the chain, it shifts towards the surface of the capsid locating predominantly at the equator, and undergoes the nematic transition.

Oskolkov, Nikolay; Linse, Per; Khokhlov, Alexei

2010-03-01

36

Potentials for Spatial Geometry Curriculum Development with Three-Dimensional Dynamic Geometry Software in Lower Secondary Mathematics  

ERIC Educational Resources Information Center

|Three-dimensional dynamic geometry software has the power to enhance students' learning of spatial geometry. The purpose of this research is to clarify what potential using three-dimensional dynamic geometry software can offer us in terms of how to develop the spatial geometry curriculum in lower secondary schools. By focusing on the impacts the…

Miyazaki, Mikio; Kimiho, Chino; Katoh, Ryuhei; Arai, Hitoshi; Ogihara, Fumihiro; Oguchi, Yuichi; Morozumi, Tatsuo; Kon, Mayuko; Komatsu, Kotaro

2012-01-01

37

Potentials for Spatial Geometry Curriculum Development with Three-Dimensional Dynamic Geometry Software in Lower Secondary Mathematics  

ERIC Educational Resources Information Center

Three-dimensional dynamic geometry software has the power to enhance students' learning of spatial geometry. The purpose of this research is to clarify what potential using three-dimensional dynamic geometry software can offer us in terms of how to develop the spatial geometry curriculum in lower secondary schools. By focusing on the impacts the…

Miyazaki, Mikio; Kimiho, Chino; Katoh, Ryuhei; Arai, Hitoshi; Ogihara, Fumihiro; Oguchi, Yuichi; Morozumi, Tatsuo; Kon, Mayuko; Komatsu, Kotaro

2012-01-01

38

Spin waves in the B-phase of superfluid 3He in confined cylindrical geometry  

NASA Astrophysics Data System (ADS)

We describe experiments on superfluid 3He in a cylinder of 1 mm in diameter. This geometry causes the preferred orientation of the n-vector in the superfluid B-phase to be locally different, resulting in a curved configuration across the sample. Exclusive to our experiment is the observation that we succeeded in obtaining a texture which is metastable and unchanged in our pressure and temperature ranges, most likely because the experiment is performed at low pressures and low magnetic fields. As this texture can be considered as a potential for spin waves, we had the unique opportunity to study spin waves for several pressures in exactly the same texture. Our geometry causes this texture potential to be nearly quadratic, allowing an analytic solution of the theory which can be compared to our experimental results. As predicted we find the intensities of all spin wave modes more or less equal. Increasing the pressure shows a gradual increase in the number of spin wave modes in our cell. Finally we were able to cause a transition from the metastable to the predicted stable texture, concluding unexpectedly that the metastable texture is realized if the growing (or cooling) speed is sufficiently slow.

Benningshof, O. W. B.; Jochemsen, R.

2013-09-01

39

Heavy quarks, gluons and the confinement potential in Coulomb gauge  

SciTech Connect

We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.

Popovici, Carina; Watson, Peter; Reinhardt, Hugo [Institut fuer Theoretische Physik, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2011-05-23

40

Gauss-Bonnet brane gravity with a confining potential  

SciTech Connect

A brane scenario is envisaged in which the m-dimensional bulk is endowed with a Gauss-Bonnet term and localization of matter on the brane is achieved by means of a confining potential. The resulting Friedmann equations on the brane are modified by various extra terms that may be interpreted as the X-matter, providing a possible phenomenological explanation for the accelerated expansion of the Universe. The age of the Universe in this scenario is studied and shown to be consistent with the present observational data.

Heydari-Fard, M.; Sepangi, H. R. [Department of Physics, Shahid Beheshti University, Evin Tehran 19839 (Iran, Islamic Republic of)

2007-03-15

41

Soliton dynamics in confining time-dependent potentials  

NASA Astrophysics Data System (ADS)

The dynamics of nonlinear solitary waves is studied in the framework of the nonlinear Schrodinger equation model with time-dependent confining harmonic oscillator potential. The model allows one to analyse on the general basis a variety of nonlinear phenomena appearing both in Bose-Einstein condensate, condensed matter physics and in nonlinear optics and biophysics. The nonlinear effect of the soliton parametric resonance is investigated by using two complementary methods: the adiabatic perturbation theory and direct numerical experiments. Conditions for reversible and irreversible denaturation of soliton bound states are also considered.

Belyaeva, T. L.; Serkin, V. N.; Hernandez-Tenorio, C.; Kovachev, L. M.

2008-12-01

42

A calorimetric study of liquid crystalline phase transitions in confined geometries  

NASA Astrophysics Data System (ADS)

The behavior of the mesophase to isotropic transitions of liquid crystals in confined geometries has been studied using differential scanning calorimetry in an effort to understand the effects of finite size on the transition temperature and the latent heat. Liquid crystals 4-5-alkyl-4sp'-cyanobiphenyl, 4-10-alkyl-4sp '-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl, and 4-10-alkoxy-4sp'-cyanobiphenyl were confined in a series of porous silica glasses with mean pore radii between 6.4 and 146 nm. For each liquid crystalline material and for each pore radius, one completely filled and two partially filled samples were prepared by varying the ratio of the volume of liquid crystals to the available pore volume. The first order nematic to isotropic phase transition was studied using 4-5-alkyl-4sp'-cyanobiphenyl and 4-5-alkoxy-4sp '-cyanobiphenyl while 4-10-alkyl-4sp'-cyanobiphenyl and 4-10-alkoxy-4sp'-cyanobiphenyl were used in studying the smectic A to isotropic transition. In completely filled pores, the transition temperatures and latent heats were found to be increasingly depressed from their corresponding bulk values with decreasing pore radii. In each of the liquid crystals studied, the reduction in the transition temperature and latent heat with pore radii showed stronger dependence than the expected inverse radii behavior. In partially filled pores, the transition temperatures showed a linear decrease with inverse liquid crystal layer thickness. The latent heat of the smectic A to isotropic transition showed similar behavior to that of the transition temperature. The latent heat of the nematic to isotropic transition was found to decrease with decreasing layer thickness and reach a plateau at smaller thicknesses. The data were fit to a modified version of a nucleation based model for first order phase transitions. Using the best fit parameters, a lower and an upper bound for the surface free energy of the nematic/isotropic and smectic A/isotropic interfaces was estimated. The estimated lower bounds for the interfacial free energy of 4-5-alkyl-4sp'-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl, 4-10-alkyl-4sp '-cyanobiphenyl and 4-10-alkoxy-4sp'-cyanobiphenyl were 0.06 ± 0.04, 0.04 ± 0.02, 0.307 ± 0.001, and 0.316 ± 0.001 mJ/msp2, respectively. The corresponding estimated upperbounds for 4-5-alkyl-4sp'-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl,4-10-alkyl-4sp '-cyanobiphenyl and 4-10-alkoxy-4sp '-cyanobiphenyl were 0.12 ± 0.08, 0.09 ± 0.04, 0.614 ± 0.002, and 0.632 ± 0.002 mJ/msp2, respectively. Finally the temperature dependence of the interfacial free energy was also estimated.

Weerasekera, Indira Amarangani

43

Light-Cone Kaluza-Klein Geometry: Confined Propagation as a Particle Model  

Microsoft Academic Search

A modified Kaluza-Klein theory is proposed in which propagation takes place only at the speed of light. The propagation can be confined to a small volume, forming a particle with rest mass. The usual four space-time coordinates locate the confinement volume, and Kaluza's fifth coordinate is replaced by an internal degree of freedom. Electromagnetism corresponds to a gauge field on

Donald E. Jennings

2000-01-01

44

Geometry of nuclear fusion diagnostic data on information manifolds with an application to fusion plasma confinement  

NASA Astrophysics Data System (ADS)

Pattern recognition is becoming an increasingly important tool for making inferences from the massive amounts of data produced in fusion experiments. The purpose is to contribute to physics studies and plasma control. In this work, we address the visualization of plasma confinement data and their dynamics, the identification of confinement regimes and the establishment of a scaling law for the energy confinement time. We take an intrinsically probabilistic approach, modeling data from the International Global H-mode Confinement Database with Gaussian distributions. We show that pattern recognition operations working in the associated probability space are considerably more powerful than their counterparts in a Euclidean data space. This opens up new possibilities for analyzing confinement data and for fusion data processing in general.

Verdoolaege, Geert; Karagounis, Giorgos; Van Oost, Guido

2013-08-01

45

Light-Cone Kaluza-Klein Geometry: Confined Propagation as a Particle Model  

Microsoft Academic Search

A modified Kaluza-Klein theory is proposed in which propagation takes place\\u000aonly at the speed of light. The propagation can be confined to a small volume,\\u000aforming a particle with rest mass. The usual four space-time coordinates locate\\u000athe confinement volume, and Kaluza's fifth coordinate is replaced by an\\u000ainternal degree of freedom. Electromagnetism corresponds to a gauge field on

Donald E. Jennings

2000-01-01

46

Protection from Potential Exposure for the Chernobyl New Safe Confinement  

SciTech Connect

The Bechtel/EDF/Battelle Consortium has recently completed developing the conceptual design for the Chernobyl New Safe Confinement (NSC). Battelle has the scope of work related to environment and safety of the design. As part of the safety analysis, an analysis was performed to determine the degree of protection to be provided during the construction and 100-year operation period for expected upsets and lower-probability events that would occur from errors, procedures, other human factors, and equipment failures, i.e., ''potential exposures'' other than normal operations. The analysis was based on results of the Preliminary Hazards Analysis. The potential exposure analysis was performed in accordance with existing Ukranian regulations and working processes and procedures in place at the Shelter Object. KSK (a Ukranian Consortium), a subcontractor to the Bechtel/EDF/Battelle Consortium, performed much of the dose analysis. The analysis concluded that potential exposures, outside of those expected during normal operations, would be acceptable and that design criteria and features, and preventative and mitigative measures currently in place at the Shelter would be sufficient to meet operating exposure limits.

Shipler, Dillard B.; Rudko, Vladimir; Batiy, Valeriy; Timmins, Douglas C.; Brothers, Alan J.; Schmidt, John P.; Swearingen, Gary L.; Schmieman, Eric A.

2004-03-24

47

Formation of discrete solitons as a function of waveguide array geometry under the well-confined mode condition  

NASA Astrophysics Data System (ADS)

Based on numerical techniques, in this paper, we study light propagation in two types of waveguide arrays. One array contains hexagonal cells, and the second contains honeycomb cells. The waveguides demonstrate the well-confined mode condition and possess Kerr nonlinearity. The mathematical model is based on the modified discrete nonlinear Schrödinger equation, which allows us to evaluate the influence of the array geometry on nonlinear light propagation, primarily the process of discrete soliton formation. The main conclusion involves the role of the coupling length; the greater the coupling length, the lower the power threshold required for discrete soliton formation.

Vergara-Betancourt, A.; Martí-Panameño, E.; Luis-Ramos, A.; Parada-Alfonso, R.

2013-10-01

48

A study of confined quantum systems using the Woods-Saxon potential  

NASA Astrophysics Data System (ADS)

We propose the Woods-Saxon (WS) potential to simulate spatial confinement. The great advantage of our methodology is that it enables the study of a wide range of systems and confinement regimes by varying two parameters in the model potential. To test the methodology we have studied the confined harmonic oscillator in two different regimes: when the confinement potential exhibits a sudden jump; and when the confinement is described by a smooth function. We have also applied the present procedure to a realistic problem, a confined quantum dot-atom. The numerical calculation is performed with the equally spaced discrete variable representation (DVR). Our results are in close agreement with those available in the literature, and we believe our method to be a good alternative for studying confined quantum systems.

Costa, L. S.; Prudente, F. V.; Acioli, P. H.; Soares Neto, J. J.; Vianna, J. D. M.

1999-05-01

49

Free energy and extension of a semiflexible polymer in cylindrical confining geometries  

NASA Astrophysics Data System (ADS)

We consider a long, semiflexible polymer with persistence length P and contour length L fluctuating in a narrow cylindrical channel of diameter D . In the regime D?P?L the free energy of confinement ?F and the length of the channel R? occupied by the polymer are given by Odijk’s relations ?F/R?=A?kBTP-1/3D-2/3 and R?=L[1-??(D/P)2/3] , where A? and ?? are dimensionless amplitudes. Using a simulation algorithm inspired by the pruned enriched Rosenbluth method, which yields results for very long polymers, we determine A? and ?? and the analogous amplitudes for a channel with a rectangular cross section. For a semiflexible polymer confined to the surface of a cylinder, the corresponding amplitudes are derived with an exact analytic approach. The results are relevant for interpreting experiments on biopolymers in microchannels or microfluidic devices.

Yang, Yingzi; Burkhardt, Theodore W.; Gompper, Gerhard

2007-07-01

50

Confined geometry effects on reorientational dynamics of molecular liquids in porous silica glasses  

Microsoft Academic Search

This work investigates the relative role of the pure geometrical confinement and the strength of the surface effect on the dynamics of liquids in porous silica glasses prepared by the sol-gel process. The deuteron NMR spin-lattice relaxation times T1 of several molecular liquids in porous silica glasses are reported as function of pore size in the range from 18 to

G. Liu; Y. Li; J. Jonas

1991-01-01

51

DNA electrophoresis in confined, periodic geometries: a new lakes-straits model.  

PubMed

We present a method to study the dynamics of long DNA molecules inside a cubic array of confining spheres, connected through narrow openings. Our method is based on the coarse-grained, lakes-straits model of Zimm and is therefore much faster than Brownian dynamics simulations. In contrast to Zimm's approach, our method uses a standard stochastic kinetic simulation to account for the mass transfer through the narrow straits and the formation of new lakes. The different rates, or propensities, of the reactions are obtained using first-passage time statistics and a Monte Carlo sampling to compute the total free energy of the chain. The total free energy takes into account the self-avoiding nature of the chain as well as confinement effects from the impenetrable spheres. The mobilities of various chains agree with biased reptation theory at low and high fields. At moderate fields, confinement effects lead to a new regime of reptation where the mobility is a linear function of molecular weight and the dispersion is minimal. PMID:21186855

Laachi, Nabil; Dorfman, Kevin D

2010-12-21

52

A Potential Flow Model for Fiber Geometry in Wood  

NASA Astrophysics Data System (ADS)

A three-dimensional potential flow model for fibers in wood is introduced. The local geometry in the vicinity of a knot is of basic interest. The flow is generated by dipole distributions. Streamlines are produced by numerical integration. Annual rings are represented by flow sheets. Annual ring patterns in a plank appear as the intersection curves of these sheets with a plane. The flow is approximated by slender body theory, which is standard in aerodynamics and ship hydrodynamics. A knot in the wood is modelled by a cone with apex in the centre of the trunk.

Tyvand, Peder A.

1991-01-01

53

Finite difference solution of the 2-dimensional Poisson–Boltzmann equation for spheres in confined geometries  

Microsoft Academic Search

Published experimental data has shown a long-range attractive interaction between identical colloidal particles close to a charged surface. However, previous numerical calculations for a capillary geometry, which indicated that such attractions could arise from solution of the non-linear Poisson–Boltzmann equation (PBE) have been shown to be both qualitatively and quantitatively in error. The present paper uses a finite difference method

W. Richard Bowen; Paul M. Williams

2002-01-01

54

Propulsion of targets with different confinement geometries in water by Nd: YAG laser at 1064nm  

NASA Astrophysics Data System (ADS)

Laser propulsion in air or vacuum has been developed as a thruster technology for the attitude control of micro class satellites. Laser propulsion in water can be used as a technology for propelling underwater platform or controlling microfluid device. Laser propulsion effects in water are much better in air due to the force from laser-induced bubble in water. The target geometries will influence the propulsion effects in air. In order to investigate the influence of target geometries on laser propulsion in water, targets with/without conical cavity and hemispherical cavity are designed in this paper. The momentum IT gained by targets and the momentum coupling coefficient Cm are investigated experimentally by high-speed photography method. It shows that the propulsion effects are better if there is a cavity on the laser irradiated surface of the target, and a hemispherical cavity works better than a conical cavity. In addition, IT increases with the laser energy, but the increasing trend slows gradually, and Cm increases with the laser energy first, and then levels off for all four targets. These results are both due to the laser plasma shielding. In conclusion, we need design suitable target geometries and use optimal laser energy to get the best propulsion effect for controlling microfluid device or micro class satellites.

Chen, Jun; Li, Bei-Bei; Zhang, Hong-Chao; Han, Bing; Shen, Zhong-Hua; Ni, Xiao-Wu

2013-02-01

55

Geometry  

NSDL National Science Digital Library

Geometry is the branch of mathematics which investigates the relations, properties, and measurement of solids, surfaces, lines, and angles. It is the science of the relations of space. Sourse: Webster's Dictionary

K-12 Outreach,

56

Adaptive generalized periodic boundary conditions for lattice Boltzmann simulations of pressure-driven flows through confined repetitive geometries  

NASA Astrophysics Data System (ADS)

An algorithm for an adaptive boundary condition for the simulation of fully developed, pressure driven flows using the lattice-Boltzmann method is introduced. The method simulates the effect of the solid walls confining a structure with dual periodicity, such as used in microfluidic devices. We combine a recently introduced boundary condition by Kim and Pitsch [Phys. Fluids 19, 108101 (2007)]10.1063/1.2780194 for the treatment of pressure driven flows in periodic structures with a controller loop that adjusts a perpendicular pressure gradient to suppress any net momentum perpendicular to the outer walls. The method’s accuracy in asymmetric geometries is tested against a periodic array structure that uses regularized zero-velocity boundary conditions as outer walls.

Gräser, Oliver; Grimm, Andrej

2010-07-01

57

THE POTENTIAL OF AUGMENTED REALITY IN DYNAMIC GEOMETRY EDUCATION  

Microsoft Academic Search

This paper summarizes work done within the previous 6 years to integrate and implement Virtual and Augmented Reality (VR\\/AR) technologies in geometry education. A VR\\/AR application supporting dynamic 3D geometry is presented, intended for real use in high school and university geometry education. Related areas such as dynamic three-dimensional geometry, usability and user interface design, spatial abilities, pedagogy and low-cost

Hannes KAUFMANN

2006-01-01

58

Solution of Two-Body Bound State Problems with Confining Potentials  

SciTech Connect

The homogeneous Lippmann-Schwinger integral equation is solved in momentum space by using confining potentials. Since the confining potentials are unbounded at large distances, they lead to a singularity at small momentum. In order to remove the singularity of the kernel of the integral equation, a regularized form of the potentials is used. As an application of the method, the mass spectra of heavy quarkonia, mesons consisting from heavy quark and antiquark ({Upsilon}(bb-bar), {psi}(cc-bar)), are calculated for linear and quadratic confining potentials. The results are in good agreement with configuration space and experimental results.

Hadizadeh, M. R. [Instituto de Fisica Teorica (IFT), Universidade Estadual Paulista (UNESP), Barra Funda, 01140-070, Sao Paulo (Brazil); Tomio, Lauro [Instituto de Fisica Teorica (IFT), Universidade Estadual Paulista (UNESP), Barra Funda, 01140-070, Sao Paulo (Brazil); Instituto de Fisica, Universidade Federal Fluminense, 24210-346, Niteroi, RJ (Brazil)

2010-11-12

59

Measurements of heat transfer to helium II at atmospheric pressure in a confined geometry  

SciTech Connect

Recently the enhanced heat removal capability of unsaturated superfluid helium II has been exploited in fusion and accelerator dipole magnets. In superfluid the internal convection mechanism dominates the heat removal process and orientation with respect to gravity becomes of secondary importance. Heat transfer, however, can be influenced by the thermodynamic state of the liquid, especially with regard to possible phase transformations. The transformation from non-saturated He II must involve an He I state before the film boiling transition is experienced. Some steady state measurements of heat transfer to non-saturated He II have been previously reported. In typical magnet designs, cooling passages between turns result from gaps between the electrical insulation, and are typically on the order of a fraction of a millimeter. The purpose of the work reported here is to measure the attenuation of the heat transfer within such a restrictive geometry.

Warren, R.P.; Caspi, S.

1981-08-01

60

Two and three dimensional study of the hydrogen molecular ion H2+ confined between double boxes of spheroidal and spherical geometries.  

NASA Astrophysics Data System (ADS)

Considering first a two-dimensional system, we study the hydrogen molecular ion confined in the space between two ellipses, and then we consider its confinement in the space between two prolate spheroids. In the Born -- Oppenheimer approximation, we solve numerically the Schrodinger's equation for the above mentioned cases, using an algorithm that allows us to calculate the energies for different given values of the confinement parameters. We also consider the confinement in the region limited by two concentric circumferences and in the three-dimensional case, in the region between two concentric spherical shells. In the last two cases we use the variational method in order to estimate the energy of the ground state. Some properties of the system as the pressure exerted by the confinement, the polarizability in the approximations of Kirkwood and Buckingham and the energies of the vibrational states are calculated. The behavior of the internuclear separation is analyzed for all the geometries considered.

Molinar, Martin; Campoy, German

2009-03-01

61

A numerical study on the thermal initiation of a confined explosive in 2-D geometry.  

PubMed

Insensitive munitions design against thermal stimuli like slow or fast cook-off has become a significant requirement for today's munitions. In order to achieve insensitive munitions characteristics, the response of the energetic material needs to be predicted against heating stimuli. In this study, a 2D numerical code was developed to simulate the slow and fast cook-off heating conditions of confined munitions and to obtain the response of the energetic materials. Computations were performed in order to predict the transient temperature distribution, the ignition time, and the location of ignition in the munitions. These predictions enable the designers to have an idea of when and at which location the energetic material ignites under certain adverse surrounding conditions. In the paper, the development of the code is explained and the numerical results are compared with available experimental and numerical data in the literature. Additionally, a parametric study was performed showing the effect of dimensional scaling of munitions and the heating rate on the ignition characteristics. PMID:21130568

Aydemir, Erdo?an; Ulas, Abdullah

2010-11-12

62

Space potential profiles in relativistic spherical inertial electrostatic confinement (SIEC) devices  

Microsoft Academic Search

Summary form only given. Spherical inertial electrostatic confinement (SIEC) devices could potentially be used as neutron generators for a number of applications. Since Hirsch put forward the hypothesis that a number of alternating virtual electrodes at the center of these devices could be acting as a confinement mechanism, a modest amount of research has been dedicated to verify the existence

Ryan M. Meyer; Sudarshan K. Loyalka; Mark A. Prelas

2006-01-01

63

Geometry  

NSDL National Science Digital Library

Shapes, lines, and more! Here are some fun games to practice geometry and not get bored! Here\\'s a review to help you through the fun... Identify Geometric Shapes and then you will be on your way! After you have reviewed...show me all you know with this Shape Quiz and then all the fun begins!!! Is it a polygon or not? You tell me. Drag them into the bins and we will see! ...

Walker, Ms.

2008-03-31

64

Communication: impact of inertia on biased Brownian transport in confined geometries.  

PubMed

We consider the impact of inertia on biased Brownian motion of point-size particles in a two-dimensional channel with sinusoidally varying width. If the time scales of the problem separate, the adiabatic elimination of the transverse degrees of freedom leads to an effective description for the motion along the channel given by the potential of mean force. The possibility of such description is intimately connected with equipartition. Numerical simulations show that in the presence of external bias the equipartition may break down leading to non-monotonic dependence of mobility on external force and several other interesting effects. PMID:22443741

Martens, S; Sokolov, I M; Schimansky-Geier, L

2012-03-21

65

Confined quantum time of arrival for the vanishing potential  

SciTech Connect

We give full account of our recent report in E. A. Galapon, R. Caballar, and R. Bahague, Phys. Rev. Lett. 93, 180406 (2004), where it is shown that formulating the free quantum time of arrival problem in a segment of the real line suggests rephrasing the quantum time of arrival problem to finding a complete set of states that evolve to unitarily arrive at a given point at a definite time. For a spatially confined particle, here it is shown explicitly that the problem admits a solution in the form of an eigenvalue problem of a class of compact and self-adjoint time of arrival operators derived by a quantization of the classical time of arrival. The eigenfunctions of these operators are numerically demonstrated to unitarily arrive at the origin at their respective eigenvalues.

Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines); Theoretical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Chemical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Caballar, Roland F.; Bahague, Ricardo [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines)

2005-12-15

66

Nonlinear Poisson-Nernst-Planck equations for ion flux through confined geometries  

NASA Astrophysics Data System (ADS)

The mathematical modelling and simulation of ion transport through biological and synthetic channels (nanopores) is a challenging problem, with direct application in biophysics, physiology and chemistry. At least two major effects have to be taken into account when creating such models: the electrostatic interaction of ions and the effects due to size exclusion in narrow regions. While mathematical models and methods for electrostatic interactions are well-developed and can be transferred from other flow problems with charged particles, e.g. semiconductor devices, less is known about the appropriate macroscopic modelling of size exclusion effects. Recently several papers proposed simple or sophisticated approaches for including size exclusion effects into entropies, in equilibrium as well as off equilibrium. The aim of this paper is to investigate a second potentially important modification due to size exclusion, which often seems to be ignored and is not implemented in currently used models, namely the modification of mobilities due to size exclusion effects. We discuss a simple model derived from a self-consisted random walk and investigate the stationary solutions as well as the computation of conductance. The need of incorporating nonlinear mobilities in high density situations is demonstrated in an investigation of conductance as a function of bath concentrations, which does not lead to obvious saturation effects in the case of linear mobility.

Burger, M.; Schlake, B.; Wolfram, M.-T.

2012-04-01

67

Effect of confining wall potential on charged collimated dust beam in low-pressure plasma  

NASA Astrophysics Data System (ADS)

The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10-4 millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (~pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

Kausik, S. S.; Kakati, B.; Saikia, B. K.

2013-05-01

68

The hydrogen atom confined in both Debye screening potential and impenetrable spherical box  

NASA Astrophysics Data System (ADS)

The ground state energy, some low-lying excited state energies and oscillator strengths for a hydrogen atom confined in both a Debye screening potential and finite impenetrable spherical box have been calculated. These have been calculated using a linear variational method based on B-spline basis functions. The results have been compared with those of other authors. The evaluated energies and oscillator strengths with respect to different plasma screening parameters with a certain confinement radii are discussed.

Kang, Shuai; Yang, You-Chang; He, Juan; Xiong, Fei-Qiao; Xu, Ning

2013-05-01

69

Confinement, the gluon propagator and the interquark potential for heavy mesons  

NASA Astrophysics Data System (ADS)

The interquark static potential for heavy mesons described by a massive one-gluon exchange interaction obtained from the propagator of the truncated Dyson-Schwinger equations does not reproduced the expected Cornell potential. I show that no formulation based on a finite propagator will lead to confinement of quenched QCD. I propose a mechanism based on a singular nonperturbative coupling constant which has the virtue of giving rise to a finite gluon propagator and (almost) linear confinement. The mechanism can be slightly modified to produce the screened potentials of unquenched QCD.

Vento, V.

2013-06-01

70

Reconstruction of confining or attractive potentials of one-dimensional Schrodinger equation  

Microsoft Academic Search

This paper investigates the dependence of confining or attractive potentials on the characteristics of the discrete spectrum of the one-dimensional Schrodinger equation. Asymptotic expressions are obtained for the regular solutions and the corrections to the potential in different cases of variation of the spectral characteristics. The connection between oneparameter transformations of the normalization constants and the nonlinear evolution equations for

U. B. Gostev; A. R. Frenkin

1985-01-01

71

Effect of large ion angular momentum spread and high current on inertial electrostatic confinement potential structures  

Microsoft Academic Search

Prior inertial electrostatic confinement (IEC) studies have assumed that very low angular momentum (zero in the ideal case) is necessary to achieve a potential well structure capable of trapping energetic ions in the center of a spherical device. However, the present study shows that high-current ion beams having large-angular-momentum spread can also form deep potential well traps

Ivon V. Tzonev; John M. DeMora; George H. Miley

1995-01-01

72

Correlation between potential well structure and neutron production in inertial electrostatic confinement fusion  

Microsoft Academic Search

The electrostatic potential well in inertial electrostatic confinement (IEC) is studied using two approaches. First, the equilibrium potential profile is obtained by solving the charge neutrality condition, i.e. ni=ne, assuming the appropriate distribution functions for the ions and the electrons. The formation of a double well structure is demonstrated, with a depth depending upon the ratio between the focus radii

M. Ohnishi; K. H. Sato; Y. Yamamoto; K. Yoshikawa

1997-01-01

73

Ways towards pure deuterium inertial confinement fusion through the attainment of gigavolt potentials  

Microsoft Academic Search

The attainment of ultrahigh electric potentials by suppressing the stepped leader breakdown of a highly charged conductor levitated in a spiraling Taylor flow opens up the possibility of order of magnitude larger driver energies for the ignition of thermonuclear reactions by inertial confinement. In reaching gigavolt potentials, intense 1016 Watt, GeV ion beams become possible. Together with their large self-magnetic

Friedwardt Winterberg

2008-01-01

74

The effective potential of the confinement order parameter in the Hamiltonian approach  

NASA Astrophysics Data System (ADS)

The effective potential of the order parameter for confinement is calculated within the Hamiltonian approach by compactifying one spatial dimension and using a background gauge fixing. Neglecting the ghost and using the perturbative gluon energy one recovers the Weiss potential. From the full non-perturbative potential calculated within a variational approach a critical temperature of the deconfinement phase transition of 269 MeV is found for the gauge group SU(2).

Reinhardt, Hugo; Heffner, Jan

2012-12-01

75

Coarse-grained potential models for structural prediction of carbon dioxide (CO2) in confined environments.  

PubMed

In this paper, we propose coarse-grained single-site (CGSS), wall-CO(2), and CO(2)-CO(2) interaction potential models to study the structure of carbon dioxide under confinement. The CGSS potentials are used in an empirical potential based quasi-continuum theory, EQT, to compute the center-of-mass density and potential profiles of CO(2) confined inside different size graphite slit pores. Results obtained from EQT are compared with those obtained from all-atom molecular dynamics (AA-MD) simulations, and are found to be in good agreement with each other. Though these CGSS interaction potentials are primarily developed and parameterized for EQT, they are also used to perform coarse-grained molecular dynamics (CG-MD) simulations. The results obtained from CG-MD simulations are also found to be in reasonable agreement with AA-MD simulation results. PMID:22260559

Sanghi, T; Aluru, N R

2012-01-14

76

On PT-Symmetric Periodic Potential, Quark Confinement, and Other Impossible Pursuits  

Microsoft Academic Search

As we know, it has been quite common nowadays for particle physicists to think of six impossible things before breakfast, just like what their cosmology fellows used to do. In the present paper, we discuss a number of those impossible things, including PT-symmetric periodic potential, its link with condensed matter nuclear science, and possible neat link with Quark confinement theory.

Vic Christianto; Florentin Smarandache

2009-01-01

77

Microtubule Organization in Three-Dimensional Confined Geometries: Evaluating the Role of Elasticity Through a Combined In Vitro and Modeling Approach  

PubMed Central

Microtubules or microtubule bundles in cells often grow longer than the size of the cell, which causes their shape and organization to adapt to constraints imposed by the cell geometry. We test the reciprocal role of elasticity and confinement in the organization of growing microtubules in a confining box-like geometry, in the absence of other (active) microtubule organizing processes. This is inspired, for example, by the cortical microtubule array of elongating plant cells, where microtubules are typically organized in an aligned array transverse to the cell elongation axis. The method we adopt is a combination of analytical calculations, in which the polymers are modeled as inextensible filaments with bending elasticity confined to a two-dimensional surface that defines the limits of a three-dimensional space, and in vitro experiments, in which microtubules are polymerized from nucleation seeds in microfabricated chambers. We show that these features are sufficient to organize the polymers in aligned, coiling configurations as for example observed in plant cells. Though elasticity can account for the regularity of these arrays, it cannot account for a transverse orientation of microtubules to the cell's long axis. We therefore conclude that an additional active, force-generating process is necessary to create a coiling configuration perpendicular to the long axis of the cell.

Lagomarsino, Marco Cosentino; Tanase, Catalin; Vos, Jan W.; Emons, Anne Mie C.; Mulder, Bela M.; Dogterom, Marileen

2007-01-01

78

Streaming potentials during the confined compression creep test of normal and proteoglycan-depleted cartilage  

Microsoft Academic Search

The streaming potential response of cartilage in the confined compression creep configuration was assessed theoretically and\\u000a measured experimentally in normal and proteoglycan-depleted tissue. The analytical solution, using the linear biphasic continuum\\u000a model including electrokinetics and assuming homogeneous material properties, predicted that: (i) the peak streaming potentials\\u000a is ?V=ke·??, where ke is the electrokinetic coefficient and ?? is the change in

Albert C. Chen; Tara T. Nguyen; Robert L. Sah

1997-01-01

79

Persistent currents in dipolar Bose-Einstein condensates confined in annular potentials  

SciTech Connect

We consider a dipolar Bose-Einstein condensate confined in an annular potential, with all the dipoles being aligned along some arbitrary direction. In addition to the dipole-dipole interaction, we also assume a zero-range hard-core potential. We investigate the stability of the system against collapse, as well as the stability of persistent currents as a function of the orientation of the dipoles and of the strength of the hard-core interaction.

Malet, F.; Reimann, S. M. [Mathematical Physics, Lund University, LTH, P.O. Box 118, SE-22100 Lund (Sweden); Kavoulakis, G. M. [Technological Educational Institute of Crete, P.O. Box 1939, GR-71004, Heraklion (Greece)

2011-10-15

80

Flow characteristics and heat transfer performances of a semi-confined impinging array of jets: effect of nozzle geometry  

Microsoft Academic Search

The flow and heat transfer characteristics of confined jet array impingement with crossflow is investigated. Discrete impingement pressure measurements are used to obtain the jet orifice discharge flow coefficient. Digital particle image velocimetry (DPIV) and flow visualization are used to determine the flow characteristics. Two thermal boundary conditions at the impinging surface are presented: an isothermal surface, and a uniform

Bertrand P. E. Dano; James A. Liburdy; Koonlaya Kanokjaruvijit

2005-01-01

81

Relativistic versus nonrelativistic solution of the N-fermion problem in a hyperradius-confining potential  

NASA Astrophysics Data System (ADS)

We investigate the quantum system of N identical fermions in the relativistic limit. In this article the considered potential is a combination of Coulombic, linear confining and harmonic oscillator terms. By using Jacobi coordinates and introducing the hyperradius quantity we obtain the wave functions of the system as well as the corresponding energy eigenvalues. Assuming that all particles are confined within a hypersphere we calculate the corresponding x bag . In particular we consider the case N = 3 which corresponds to baryonic systems. By using the experimental values of the charge radius of each baryon we calculate the potential coefficients. Within our treatment the results of the MIT bag model are recovered for N = 1. Finally we compare the results obtained by the Dirac equation with the corresponding results of the Schrödinger equation and we find that the energy spectra obtained by the former are much closer to experimental values.

Hassanabadi, H.; Rajabi, A. A.

2007-12-01

82

The Use of Quantum Potentials for Confinement and Tunnelling in Semiconductor Devices  

Microsoft Academic Search

As MOSFETs are scaled to sub 100 nm dimensions, quantum mechanical confinement in the direction normal to the silicon dioxide interface and tunnelling (through the gate oxide, band-to-band and from source- to-drain) start to strongly affect their characteristics. Recently it has been demonstrated that first order quantum corrections can be successfully introduced in self-consistent drift diffusion-type models using Quantum Potentials.

A. ASENOV; J. R. WATLING; A. R. BROWN; D. K. FERRY

2002-01-01

83

A 1D-3D mixed method for the numerical simulation of blast waves in confined geometries  

NASA Astrophysics Data System (ADS)

Blast wave generated by a high detonating spherical charge and propagating in confined domains is modeled using the Euler equations. The problem is split into two parts. The first calculation part relies on spherical isotropy to solve the problem in the radial component. Overpressure distribution is presented and shows a very good agreement with experimental and numerical data. The one-dimensional data need to be made three-dimensional mesh-compatible thanks to an appropriate remapping technique. To this end, a remapping technique is presented and its effectiveness, accuracy and efficiency are demonstrated. The second calculation part consists of a three-dimensional computation fed with the remapped data. The effectiveness of this mixed approach is demonstrated through three-dimensional applications in confined domains.

Benselama, Adel M.; William-Louis, Mame J.-P.; Monnoyer, François

2009-10-01

84

Fluids in extreme confinement.  

PubMed

For extremely confined fluids with a two-dimensional density n in slit geometry of an accessible width L, we prove that in the limit L ? 0, the lateral and transversal degrees of freedom decouple, and the latter become ideal-gas-like. For a small wall separation, the transverse degrees of freedom can be integrated out and renormalize the interaction potential. We identify nL(2) as the hidden smallness parameter of the confinement problem and evaluate the effective two-body potential analytically, which allows calculating the leading correction to the free energy exactly. Explicitly, we map a fluid of hard spheres in extreme confinement onto a 2D fluid of disks with an effective hard-core diameter and a soft boundary layer. Two-dimensional phase transitions are robust and the transition point experiences a shift O(nL(2)). PMID:23368297

Franosch, Thomas; Lang, Simon; Schilling, Rolf

2012-12-11

85

Spin and pseudospin symmetries of the Dirac equation with confining central potentials  

NASA Astrophysics Data System (ADS)

We derive the node structure of the radial functions which are solutions of the Dirac equation with scalar S and vector V confining central potentials, in the conditions of exact spin or pseudospin symmetry, i.e., when one has V=±S+C, where C is a constant. We show that the node structure for exact spin symmetry is the same as the one for central potentials which go to zero at infinity but for exact pseudospin symmetry the structure is reversed. We obtain the important result that it is possible to have positive energy bound solutions in exact pseudospin symmetry conditions for confining potentials of any shape, including naturally those used in hadron physics, from nuclear to quark models. Since this does not occur for potentials going to zero at large distances, which are used in nuclear relativistic mean-field potentials or in the atomic nucleus, this shows the decisive importance of the asymptotic behavior of the scalar and vector central potentials on the onset of pseudospin symmetry and on the node structure of the radial functions. Finally, we show that these results are still valid for negative energy bound solutions for antifermions.

Alberto, P.; de Castro, A. S.; Malheiro, M.

2013-03-01

86

Low-Lying Excited States of the Hydrogen Molecule in Cylindrical Harmonic Confinement  

NASA Astrophysics Data System (ADS)

The low-lying excited states of the hydrogen molecule confined in the harmonic potential were studied using the configuration interaction method and large basis sets. Axially symmetric harmonic oscillator potentials were used. The effect of the confinement on the geometry and spectroscopic constants was analyzed. Detailed analysis of the effect of confinement on the composition of the wavefunction was performed.

Lo, John M. H.; Klobukowski, Mariusz; Diercksen, Geerd H. F.

87

Structural features of the liquid/plastic crystal phase transition for cyclohexane in bulk and confined geometry  

NASA Astrophysics Data System (ADS)

Neutron diffraction measurements have been made for cyclohexane, C6D12 as a function of temperature for bulk samples and also in porous silica with characteristic pore dimensions of ~90Å. The results show that the simplifying assumption of cyclohexane as an unhindered rotator are not valid and that complex spatial correlations exist in all phases. The nucleation of the plastic crystal phase is displaced to low temperature for the confined material and the diffraction pattern of the plastic crystal phase is found to depend on thermal history as well as temperature. The results may be interpreted in terms of defect properties which influence the orientational correlations between neighbouring molecules.

Farman, H.; Coveney, F. M.; Dore, J. C.

1992-06-01

88

Potential profile measurements using a collimated proton detector in spherical inertial-electrostatic plasma confinement  

SciTech Connect

A collimated proton detector has been developed for spatial resolved proton measurements in inertial-electrostatic plasma confinement (IEC) fusion experiments. These are the first proton measurements used to infer potential well profiles on an IEC device. This paper describes a new technique for investigating the existence of multiple potential wells inside IEC devices. Analysis of the observed proton energy and source profile indicates that (for a 12-mA cathode current, a 30-kV cathode voltage in a 4-mTorr D{sub 2} background) predominantly beam-background fusion occurs. Computer simulation suggests that a positive space charge potential approximately half that of the applied voltage is formed inside the cathode. These results establish the first measurement of a positive potential well structure inside an ion-injected IEC device.

Nadler, J.H. (U.S. Department of Energy, Field Office, Idaho, Idaho Falls, Idaho 83401 (United States)); Gu, Y.B.; Miley, G.H. (Fusion Studies Laboratory, University of Illinois, Urbana, Illinois 61801 (United States))

1992-10-01

89

Holonomy potential and confinement from a simple model of the gauge topology  

NASA Astrophysics Data System (ADS)

We discuss an ensemble of topological solitons—instanton-dyons and antidyons—in SU(2) pure gauge theory at finite temperatures above and below the deconfinement phase transition temperature. The main focus is on the combined effect of this ensemble on the so called effective holonomy potential, which drives the confinement/deconfinement phase transition. Using a simple model with excluded volume and lattice data on caloron density we find that repulsive part of the potential is robust enough to induce the phase transition at the right temperature. Model's predictions—the holonomy potential, electric and magnetic screening masses as a function of T—are in qualitative agreement with the available lattice data. Further predictions are densities of various dyon types as a function of temperature: while some lattice measurements of them had been made, much more accurate data are needed to test these predictions.

Shuryak, E.; Sulejmanpasic, T.

2013-10-01

90

On PT-Symmetric Periodic Potential, Quark Confinement, and Other Impossible Pursuits  

NASA Astrophysics Data System (ADS)

As we know, it has been quite common nowadays for particle physicists to think of six impossible things before breakfast, just like what their cosmology fellows used to do. In the present paper, we discuss a number of those impossible things, including PT-symmetric periodic potential, its link with condensed matter nuclear science, and possible neat link with Quark confinement theory. In recent years, the PT-symmetry and its related periodic potential have gained considerable interests among physicists. We begin with a review of some results from a preceding paper discussing derivation of PT-symmetric periodic potential from biquaternion Klein-Gordon equation and proceed further with the remaining issues. Further observation is of course recommended in order to refute or verify this proposition.

Christianto, V.; Smarandache, Florentin

2009-04-01

91

Foraging on the potential energy surface: a swarm intelligence-based optimizer for molecular geometry.  

PubMed

We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials. PMID:23181297

Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D; Sebastiani, Daniel

2012-11-21

92

Microscopic theory of the tube confinement potential and relaxation of entangled needle liquids under stress  

NASA Astrophysics Data System (ADS)

We have developed a first-principles theory of the transverse confinement potential in an entangled needle fluid based on exactly enforcing uncrossability at the two-rod level while self-consistently renormalizing many-particle effects [Sussman & Schweizer PRL 107, 078102 (2011); J. Chem. Phys. 135, 131104 (2011)]. The predicted tube radius and long-time diffusion constant are consistent with the asymptotic reptation scaling laws under quiescent conditions, but in contrast with the usual tube model strong anharmonicities soften the confinement potential in a manner that quantitatively agrees with experiments on heavily entangled F-actin solutions. This weakening of entanglement constraints has multiple dramatic consequences under applied deformation: tube dilation, accelerated reptation, reduction of the transverse entropic barrier, and a critical stress or strain beyond which tube localization is destroyed. The degree-of-entanglement-dependent competition between reptative and transverse-hopping relaxation is established as a function of stress and strain. A mapping between rigid rods and flexible chain systems is also proposed, allowing predictions to be made for the tube diameter, entanglement onset, and transport properties of chain polymer liquids.

Sussman, Daniel; Schweizer, Ken

2012-02-01

93

Interplay of optical potential and condensate properties for bosons in different optical lattice geometries  

NASA Astrophysics Data System (ADS)

Motivated by the availability of optical lattices with tunable geometries in experiments, we compute different physical properties such as condensate fraction, fluctuation and depletion of the condensate density and quasi-particle velocity as a function of the interparticle interaction strength for bosons in different 2D optical potentials that correspond to square, triangular and honeycomb geometries. Our results demonstrate an interplay of these features with that of the coordination number and underlying lattice geometries. A triangular lattice, which has a coordination number z = 6, shows larger condensate fraction and fluctuation of the condensate density, along with a low depletion of the ground state occupancy. The other candidates, namely the square lattice (z = 4) and honeycomb lattice (z = 3) occupy second and third places, respectively, with regard to these properties. The quasi-particle velocities for these geometries follow a similar pattern as that of the condensate fraction data. The observations are explained by the behaviour of the low-energy quasi-particle density of states. Finally, to make the role of lattice geometry obvious, we include a discussion on a kagome lattice, which in spite of having the same coordination number as that of a square lattice, i.e. z = 4, yields a significantly low condensate fraction than that of the square lattice for all values of the interacting strength.

Barman, Apurba; Basu, Saurabh

2012-05-01

94

Architectural variability of confined turbidite sheet-sands: facies, geometry and infill of associated elementary channels. Examples from the Trois Evêchés Basin, Annot Sandstone Formation, SE France  

NASA Astrophysics Data System (ADS)

The worldwide known Annot Sandstone Formation has been considered as a reference of confined siliciclastic turbidite system. This formation crops out in SE France and represents the Upper Eocene to Lower Oligocene gravitary infill of complex foreland basins, developed in front of the Alpine thrusts. This system can be assimilated as a sand-rich turbidite ramp, sourced by multiple fan deltas leading to topographically complex sub-basins. Highly bypassing channelized systems dominate in the most proximal and most confined areas. They distally evolve to relatively less confined areas, in which sedimentary bodies appear to be more continuous and homogenous on a regional scale. These last architectural elements, defined as sheet-sands or depositional lobes, have been the focus of this study in poorly documented areas. From an important dataset made of very high resolution outcrop correlations (gathered mainly in the Trois Evêchés and Lauzanier sub-basins), we have quantified the complex distribution of sedimentary facies and structures, grain-size and key surfaces in sand-rich sheets. This was done to understand their variability from depositional event to architectural element scales and to better characterize dimensions and characteristics of their components. Six main types of architectural elements were defined, composed of both channelized and unchannelized elements. Channelized units show a high variability in terms of facies, geometry and patterns of infill that are related to multiple erosional and depositional processes, which will be discussed. We notably relate some evidences of sinuous channels, represented by lateral accretion deposits in the channel complex axis and by low angle cross-bedded facies. We interpret this particular facies as the result of flow deconfinement and overbanks above channel margins. The stratigraphic analysis of elementary objects allows us to propose a genetic model and a spatial distribution model of sheet-sand architectural elements. The latter provides their longitudinal repartition, from proximal vertically stacked internal channels to distal compensating sheets. Those features have not been accurately described in relatively distal sand-rich turbidite deposits so far and this high internal variability necessarily implies heterogeneities both in terms of petrophysical characteristics and reservoir connection. Besides, it also implies reconsidering sedimentary processes involved in these environments. Key Words: Annot Sandstones, Confined Systems, Reservoir Heterogeneities, Turbidite Sheet-sands.

Etienne, S.; Mulder, T.; Pace, A.; Bez, M.; Desaubliaux, G.

2012-04-01

95

Mode-coupling glass transition in a fluid confined by a periodic potential  

NASA Astrophysics Data System (ADS)

We show that a fluid under strong spatially periodic confinement displays a glass transition within mode-coupling theory at a much lower density than the corresponding bulk system. We use fluctuating hydrodynamics, with confinement imposed through a periodic potential whose wavelength plays an important role in our treatment. To make the calculation tractable we implement a detailed calculation in one dimension. Although we do not expect simple 1d fluids to show a glass transition, our results are indicative of the behavior expected in higher dimensions. In a certain region of parameter space we observe a three-step relaxation reported recently in computer simulations [S. H. Krishnan, Ph.D. thesis, Indian Institute of Science (2005); Kim , Eur. Phys. J. Special TopicsPRLTAO1951-635510.1140/epjst/e2010-01315-y 189, 135 (2010)] and a glass-glass transition. We compare our results to those of Krakoviack [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.75.031503 75, 031503 (2007)] and Lang [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.125701 105, 125701 (2010)].

Nandi, Saroj Kumar; Bhattacharyya, Sarika Maitra; Ramaswamy, Sriram

2011-12-01

96

Selective manipulation of InAs quantum dot electronic states using a lateral potential confinement layer  

NASA Astrophysics Data System (ADS)

To further the objective of controlled manipulation of the electronic states in epitaxial island quantum dots (QDs), we introduce the notion of a lateral potential confinement layer (LPCL) whose judicious placement during island capping allows selective impact on ground and excited electron and hole states. The energy states of InAs/In0.15Ga0.85As QDs are manipulated using 10-monolayer-thick In0.15Al0.25Ga0.60As LPCLs positioned at the bottom, upper, and top region of the QDs. The changes in the photoluminescence (PL) and PL excitation spectra reveal the nature of the electronic transitions impacted selectively through the spatial charge distributions of the states involved.

Kim, Eui-Tae; Chen, Zhonghui; Madhukar, Anupam

2002-10-01

97

Effective potential of the confinement order parameter in the Hamiltonian approach  

NASA Astrophysics Data System (ADS)

The effective potential of the order parameter for confinement is calculated for SU(N) Yang-Mills theory in the Hamiltonian approach. Compactifying one spatial dimension and using a background gauge fixing, this potential is obtained within a variational approach by minimizing the energy density for given background field. In this formulation the inverse length of the compactified dimension represents the temperature. Using Gaussian trial wave functionals we establish an analytic relation between the propagators in the background gauge at finite temperature and the corresponding zero-temperature propagators in Coulomb gauge. In the simplest truncation, neglecting the ghost and using the ultraviolet form of the gluon energy, we recover the Weiss potential. Neglecting the ghost and using for the gluon energy ?(p) the approximate Gribov formula ?(p)?p+M2/p one finds a critical temperature of 3M/?. We explicitly show that the omission of the ghost drastically increases the transition temperature. From the full nonperturbative potential (with the ghost included) we extract a critical temperature of the deconfinement phase transition of 269 MeV for the gauge group SU(2) and 283 MeV for SU(3).

Reinhardt, Hugo; Heffner, Jan

2013-08-01

98

Effective potential for quantum scalar fields in a de Sitter geometry.  

PubMed

We study the quantum theory of an O(N) scalar field on de Sitter geometry at leading order in a nonperturbative 1/N expansion. This resums the infinite series of so-called superdaisy loop diagrams. We obtain the de Sitter symmetric solutions of the corresponding, properly renormalized, dynamical field equations and compute the complete effective potential. Because of its self-interactions, the field acquires a strictly positive square mass which screens potential infrared divergences. Moreover, strongly enhanced ultralong-wavelength fluctuations prevent the existence of a spontaneously broken symmetry state in any dimension. PMID:22181592

Serreau, Julien

2011-11-03

99

Effective Potential for Quantum Scalar Fields in a de Sitter Geometry  

NASA Astrophysics Data System (ADS)

We study the quantum theory of an O(N) scalar field on de Sitter geometry at leading order in a nonperturbative 1/N expansion. This resums the infinite series of so-called superdaisy loop diagrams. We obtain the de Sitter symmetric solutions of the corresponding, properly renormalized, dynamical field equations and compute the complete effective potential. Because of its self-interactions, the field acquires a strictly positive square mass which screens potential infrared divergences. Moreover, strongly enhanced ultralong-wavelength fluctuations prevent the existence of a spontaneously broken symmetry state in any dimension.

Serreau, Julien

2011-11-01

100

The potential impact of flooding on confined animal feeding operations in eastern North Carolina.  

PubMed Central

Thousands of confined animal feeding operations (CAFOs) have been constructed in eastern North Carolina. The fecal waste pit and spray field waste management systems used by these operations are susceptible to flooding in this low-lying region. To investigate the potential that flood events can lead to environmental dispersion of animal wastes containing numerous biologic and chemical hazards, we compared the geographic coordinates of 2,287 CAFOs permitted by the North Carolina Division of Water Quality (DWQ) with estimates of flooding derived from digital satellite images of eastern North Carolina taken approximately 1 week after Hurricane Floyd dropped as much as 15-20 inches of rain in September 1999. Three cattle, one poultry, and 237 swine operations had geographic coordinates within the satellite-based flooded area. DWQ confirmed 46 operations with breached or flooded fecal waste pits in the same area. Only 20 of these 46 CAFOs were within the satellite-based estimate of the inundated area. CAFOs within the satellite-based flood area were located in 132 census block groups with a population of 171,498 persons in the 2000 census. African Americans were more likely than whites to live in areas with flooded CAFOs according to satellite estimates, but not according to DWQ reports. These areas have high poverty rates and dependence on wells for drinking water. Our analysis suggests that flood events have a significant potential to degrade environmental health because of dispersion of wastes from industrial animal operations in areas with vulnerable populations.

Wing, Steve; Freedman, Stephanie; Band, Lawrence

2002-01-01

101

The potential impact of flooding on confined animal feeding operations in eastern North Carolina.  

PubMed

Thousands of confined animal feeding operations (CAFOs) have been constructed in eastern North Carolina. The fecal waste pit and spray field waste management systems used by these operations are susceptible to flooding in this low-lying region. To investigate the potential that flood events can lead to environmental dispersion of animal wastes containing numerous biologic and chemical hazards, we compared the geographic coordinates of 2,287 CAFOs permitted by the North Carolina Division of Water Quality (DWQ) with estimates of flooding derived from digital satellite images of eastern North Carolina taken approximately 1 week after Hurricane Floyd dropped as much as 15-20 inches of rain in September 1999. Three cattle, one poultry, and 237 swine operations had geographic coordinates within the satellite-based flooded area. DWQ confirmed 46 operations with breached or flooded fecal waste pits in the same area. Only 20 of these 46 CAFOs were within the satellite-based estimate of the inundated area. CAFOs within the satellite-based flood area were located in 132 census block groups with a population of 171,498 persons in the 2000 census. African Americans were more likely than whites to live in areas with flooded CAFOs according to satellite estimates, but not according to DWQ reports. These areas have high poverty rates and dependence on wells for drinking water. Our analysis suggests that flood events have a significant potential to degrade environmental health because of dispersion of wastes from industrial animal operations in areas with vulnerable populations. PMID:11940456

Wing, Steve; Freedman, Stephanie; Band, Lawrence

2002-04-01

102

Process controls on the development of stratigraphic trap potential on the margins of confined turbidite systems and aids to reservoir evaluation  

Microsoft Academic Search

Stratigraphic trapping at pinch-out margins is a key feature of many turbidite-hosted hydrocarbon reservoirs. In systems confined by lat- eral or oblique frontal slopes, outcrop studies show that there is a continuum between two geometries of pinch-out configuration. In type A, turbidites thin onto the confining surface—although the final sandstone pinch-out is commonly abrupt—and individual beds tend not to erode

William McCaffrey; Benjamin Kneller

103

Optical studies of quantum confined nanostructures  

Microsoft Academic Search

Recent advances in material growth techniques have led to the laboratory realization of quantum confined nanostructures. By engineering the geometry of these systems it is possible to tailor their optical, electrical and vibrational properties. We now envision integrated electronic and optical devices potentially harnessing quantum mechanical properties of photons, electrons or even phonons. The realization of these next generation devices

Anthony Nickolas Vamivakas

2008-01-01

104

QCD string tension curve, the ferromagnetic magnetization, and the quark-antiquark confining potential at finite temperature  

SciTech Connect

We study the string tension as a function of temperature, fitting the SU(3) lattice QCD finite temperature free energy potentials computed by the Bielefeld group. We compare the string tension points with order parameter curves of ferromagnets, superconductors, or string models, all related to confinement. We also compare the SU(3) string tension with the one of SU(2) lattice QCD. With the curve providing the best fit to the finite temperature string tensions, the spontaneous magnetization curve, we then show how to include finite temperature, in the state of the art confining and chiral invariant quark models.

Bicudo, P. [CFTP, Departamento de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

2010-08-01

105

Crossover in domain wall potential polarity as a function of anti-notch geometry  

NASA Astrophysics Data System (ADS)

We have carried out a systematic study on domain wall (DW) pinning at an anti-notch in a Ni80Fe20 nanowire. Micromagnetic studies reveal that the potential polarity experienced by the DW at the anti-notch is a function of both DW chirality and anti-notch geometry. A transition in the potential disruption experienced by the DW is observed when the anti-notch height-to-width ratio (HAN/WAN) is 2. This transition is due to the relative orientation of the spins in the anti-notch with respect to the transverse component of the DW. When the anti-notch acts as a potential barrier, the DW undergoes damped oscillations prior to coming to an equilibrium position. The equilibrium position is a strong function of the anti-notch dimensions when the HAN/WAN ratio <2 and is constant for HAN/WAN >= 2. The effect of the relative orientation between the spins in the anti-notch and the transverse component of the DW on the shape of the potential is discussed.

Sekhar, M. Chandra; Goolaup, S.; Purnama, I.; Lew, W. S.

2011-06-01

106

Two and three dimensional study of the hydrogen molecular ion H2+ confined between double boxes of spheroidal and spherical geometries  

Microsoft Academic Search

Considering first a two-dimensional system, we study the hydrogen molecular ion confined in the space between two ellipses, and then we consider its confinement in the space between two prolate spheroids. In the Born -- Oppenheimer approximation, we solve numerically the Schrodinger's equation for the above mentioned cases, using an algorithm that allows us to calculate the energies for different

Martin Molinar; German Campoy

2009-01-01

107

Exploiting individual primary visual cortex geometry to boost steady state visual evoked potentials  

NASA Astrophysics Data System (ADS)

Objective. The steady-state visual evoked potential (SSVEP) is an electroencephalographic response to flickering stimuli generated partly in primary visual area V1. The typical ‘cruciform’ geometry and retinotopic organization of V1 is such that certain neighboring visual regions project to neighboring cortical regions of opposite orientation. Here, we explored ways to exploit this organization in order to boost scalp SSVEP amplitude via oscillatory summation. Approach. We manipulated flicker-phase offsets among angular segments of a large annular stimulus in three ways, and compared the resultant SSVEP power to a conventional condition with no temporal phase offsets. (1) We divided the annulus into standard octants for all subjects, and flickered upper horizontal octants with opposite temporal phase to the lower horizontal ones, and left vertical octants opposite to the right vertical ones; (2) we individually adjusted the boundaries between the eight contiguous segments of the standard octants condition to coincide with cruciform-consistent, early-latency topographical shifts in pattern-pulse multifocal visual-evoked potentials (PPMVEP) derived for each of 32 equal-sized segments; (3) we assigned phase offsets to stimulus segments following an automatic algorithm based on the relative amplitudes of vertically- and horizontally-oriented PPMVEP components. Main results. The three flicker-phase manipulations resulted in a significant enhancement of normalized SSVEP power of (1) 202%, (2) 383%, and (3) 300%, respectively. Significance. We have thus demonstrated a means to obtain more reliable measures of visual evoked activity purely through consideration of cortical geometry. This principle stands to impact both basic and clinical research using SSVEPs.

Vanegas, M. Isabel; Blangero, Annabelle; Kelly, Simon P.

2013-06-01

108

Multi-potential well formation and neutron production in inertial-electrostatic confinement fusion by numerical simulations  

Microsoft Academic Search

The electrostatic potential well in an inertial-electrostatic confinement (IEC) is calculated by performing the numerical simulations based on the particle-in-cell method. The single, double and triple wells, depending on the amount of the injected ion current, are observed to be formed for the ions with a mono-energetic distribution. The well in the center of the multi-well structure is unstable and

M. Ohnishi; Y. Yamamoto; K. Yoshikawa; K. Sato

1995-01-01

109

POTENTIAL PARTICULATE EMISSIONS BY WIND EROSION FROM THE INDIANA HARBOR CONFINED DISPOSAL FACILITY  

Technology Transfer Automated Retrieval System (TEKTRAN)

An Indiana Harbor Confined Disposal Facility (CDF) located in East Chicago, Indiana with a total area of about 140 acres is being designed by the U.S. Army Corp of Engineers. The CDF will contain contaminated sediments dredged from Indiana harbor ship canal. As part of the design process, analyses...

110

The Potential Profile and its Influence on the Neutron Yield of Inertial Electrostatic Confinement Fusion Device  

Microsoft Academic Search

We have simulated an IECF (inertial electrostatic confinement fusion) device by developing and using a particle code. Because a virtual anode is built up at large current region, which decelerates ions and reduces neutron yield, suppression of this virtual anode by supply of electrons from an additional electrode inside the cathode has been tried in the simulations. The simulation results

K. Noborio; Y. Yamamoto; Y. Ueno; S. Konishi

2005-01-01

111

Electron relaxation times due to the deformation-potential interaction of electrons with confined acoustic phonons in a free-standing quantum well  

Microsoft Academic Search

The confined acoustic phonons in free-standing quantum wells are considered in detail. The Hamiltonian describing interactions of the confined acoustic phonons with electrons in the approximation of the deformation potential and the corresponding electron transition probability density are derived. They are used to analyze the electron scattering times (inverse scattering rate, momentum relaxation time, and the energy relaxation time) in

N. Bannov; V. Aristov; V. Mitin; M. A. Stroscio

1995-01-01

112

Making Conjectures in Dynamic Geometry: The Potential of a Particular Way of Dragging  

ERIC Educational Resources Information Center

When analyzing what has changed in the geometry scenario with the advent of dynamic geometry systems (DGS), one can notice a transition from the traditional graphic environment made of paper-and-pencil, and the classical construction tools like the ruler and compass, to a virtual graphic space, made of a computer screen, graphical tools that are…

Mariotti, Maria Alessandra; Baccaglini-Frank, Anna

2011-01-01

113

An ab Initio Study on Solar Geometry and Potential for N-E India  

NASA Astrophysics Data System (ADS)

In north-east (N-E) India, there is severe power shortage and associated power quality problems; the quality of grid supply in most of the places is characterized by large voltage and frequency fluctuations, scheduled and unscheduled power cuts and load restrictions. Load shedding due to power shortage and faults in many cities in N-E India is a major problem for which there is no immediate remedy in near future since the gap between power demand and supply is increasing every year. But this region being rich in sun shine, solar energy is available all over the year at free of cost. In order to harness solar energy, it is important to know the amount of solar radiation available at a given location at a given time. Knowledge of solar radiation requires information about many parameters. This paper tries to analyze the solar geometry and potential of the region and presents various parameters for evaluation of solar resource as a promising option for power generation in N-E India.

Bhattacharjee, S.

2012-09-01

114

Inversion of self-potential anomalies caused by simple-geometry bodies using global optimization algorithms  

NASA Astrophysics Data System (ADS)

Three naturally inspired meta-heuristic algorithms—the genetic algorithm (GA), simulated annealing (SA) and particle swarm optimization (PSO)—were used to invert some of the self-potential (SP) anomalies originated by some polarized bodies with simple geometries. Both synthetic and field data sets were considered. The tests with the synthetic data comprised of the solutions with both noise-free and noisy data; in the tests with the field data some SP anomalies observed over a copper belt (India), graphite deposits (Germany) and metallic sulfide (Turkey) were inverted. The model parameters included the electric dipole moment, polarization angle, depth, shape factor and origin of the anomaly. The estimated parameters were compared with those from previous studies using various optimization algorithms, mainly least-squares approaches, on the same data sets. During the test studies the solutions by GA, PSO and SA were characterized as being consistent with each other; a good starting model was not a requirement to reach the global minimum. It can be concluded that the global optimization algorithms considered in this study were able to yield compatible solutions with those from widely used local optimization algorithms.

Göktürkler, G.; Balkaya, Ç.

2012-10-01

115

Influence of petroleum deposit geometry on local gradient of electron acceptors and microbial catabolic potential.  

PubMed

A field survey was conducted following the Deepwater Horizon blowout and it was noted that resulting coastal petroleum deposits possessed distinct geometries, ranging from small tar balls to expansive horizontal oil sheets. A subsequent laboratory study evaluated the effect of oil deposit geometry on localized gradients of electron acceptors and microbial community composition, factors that are critical to accurately estimating biodegradation rates. One-dimensional top-flow sand columns with 12-h simulated tidal cycles compared two contrasting geometries (isolated tar "balls" versus horizontal "sheets") relative to an oil-free control. Significant differences in the effluent dissolved oxygen and sulfate concentrations were noted among the columns, indicating presence of anaerobic zones in the oiled columns, particularly in the sheet condition. Furthermore, quantification of genetic markers of terminal electron acceptor and catabolic processes via quantitative polymerase chain reaction of dsrA (sulfate-reduction), mcrA (methanogenesis), and cat23 (oxygenation of aromatics) genes in column cores suggested more extensive anaerobic conditions induced by the sheet relative to the ball geometry. Denaturing gradient gel electrophoresis similarly revealed that distinct gradients of bacterial communities established in response to the different geometries. Thus, petroleum deposit geometry impacts local dominant electron acceptor conditions and may be a key factor for advancing attenuation models and prioritizing cleanup. PMID:22574781

Singh, Gargi; Pruden, Amy; Widdowson, Mark A

2012-05-17

116

A Fortran 90 program to solve the Hartree Fock equations for interacting spin-12 fermions confined in harmonic potentials  

NASA Astrophysics Data System (ADS)

A set of weakly interacting spin-12 Fermions, confined by a harmonic oscillator potential, and interacting with each other via a contact potential, is a model system which closely represents the physics of a dilute gas of two-component fermionic atoms confined in a magneto-optic trap. In the present work, our aim is to present a Fortran 90 computer program which, using a basis set expansion technique, solves the Hartree Fock (HF) equations for spin-12 Fermions confined by a three-dimensional harmonic oscillator potential, and interacting with each other via pair-wise delta-function potentials. Additionally, the program can also account for those anharmonic potentials which can be expressed as a polynomial in the position operators x, y, and z. Both the restricted-HF (RHF), and the unrestricted-HF (UHF) equations can be solved for a given number of Fermions, with either repulsive or attractive interactions among them. The option of UHF solutions for such systems also allows us to study possible magnetic properties of the physics of two-component confined atomic Fermi gases, with imbalanced populations. Using our code we also demonstrate that such a system exhibits shell structure, and follows Hund's rule. Catalogue identifier: AEBB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 17?750 No. of bytes in distributed program, including test data, etc.: 205?138 Distribution format: tar.gz Programming language: mostly Fortran 90 Computer: PCs—SUN, HP Alpha, IBM Operating system: Linux, Solaris, Tru64, AIX Classification: 7.7 Nature of problem: The simplest description of a spin 12; trapped system at the mean field level is given by the Hartree Fock method. This program presents an efficient approach to solving these equations. Additionally, this program can solve for time-independent Gross Pitaevskii and Hartree Fock equations for bosonic atoms confined in a harmonic trap. Thus the combined program can handle mean-field equations for both the Fermi and the Bose particles. Solution method: The solutions of the Hartree Fock equation corresponding to the Fermi systems in atomic traps are expanded as linear combinations of simple-harmonic oscillator eigenfunctions. Thus, the Hartree Fock equations which comprise a set of nonlinear integro-differential equations, are transformed into a matrix eigenvalue problem. Thereby, solutions are obtained in a self-consistent manner, using methods of computational linear algebra. Running time: The run times of example jobs are from a few seconds to a few minutes. For jobs involving very large basis sets, the run time can extend into hours.

Pal, Hridis Kumar; Shukla, Alok

2008-08-01

117

Within-compound associations explain potentiation and failure to overshadow learning based on geometry by discrete landmarks.  

PubMed

In three experiments, rats were trained to locate a submerged platform in one of the base corners of a triangular arena above each of which was suspended one of two distinctive landmarks. In Experiment 1, it was established that these landmarks differed in their salience by the differential control they gained over behavior after training in compound with geometric cues. In Experiment 2, it was shown that locating the platform beneath the less salient landmark potentiated learning based on geometry compared with control rats for which landmarks provided ambiguous information about the location of the platform. The presence of the more salient landmark above the platform for another group of animals appeared to have no effect on learning based on geometry. Experiment 3 established that these landmark and geometry cues entered into within-compound associations during compound training. We argue that these within-compound associations can account for the potentiation seen in Experiment 2, as well as previous failures to demonstrate overshadowing of geometric cues. We also suggest that these within-compound associations need not be of different magnitudes, despite the different effects of each of the landmarks on learning based on geometry seen in Experiment 2. Instead, within-compound associations appear to mitigate the overshadowing effects that traditional theories of associative learning would predict. PMID:23627798

Austen, Joe M; Kosaki, Yutaka; McGregor, Anthony

2013-04-29

118

Numerical Solution of the Boundary Problem for 2D Laplace Equation for Electrostatic Potential in Given Geometry  

NASA Astrophysics Data System (ADS)

This work has been performed as a student project for the upper division Electricity & Magnetism course. The objective was to numerically model the potential grid and the electric field of 2-dimensional capacitors of various geometries and compare them to the experimental data. This has been accomplished by the implementation of finite difference Gauss-Seidel iteration method through the use of the C programming language. Numeric results were then compared to experimental data. The expectations for this project were to successfully simulate the mapping of the experimental potential grid and electric field through the program code. The final results were satisfying since they closely resemble measured potentials.

Land, Jared; Land, Jeremy; Khan, Sheharyar

2012-03-01

119

Relating Epicardial to Body Surface Potential Distributions by Means of Transfer Coefficients Based on Geometry Measurements  

Microsoft Academic Search

Although it has been known throughout this century that a complex sequence of electrical events is produced on the body surface by the electrophysiological properties of the heart, the question of how well these body surface events can be explained mathematically on the basis of experimental measurements of cardiac geometry and electrical activity remains unanswered. Recent advances in experimental capabilities

Roger C. Barr; Maynard Ramsey; Madison S. Spach

1977-01-01

120

A continuous cable method for determining the transient potential in passive dendritic trees of known geometry  

Microsoft Academic Search

Models using cable equations are increasingly employed in neurophysiological analyses, but the amount of computer time and memory required for their implementation are prohibitively large for many purposes and many laboratories. A mathematical procedure for determining the transient voltage response to injected current or synaptic input in a passive dendritic tree of known geometry is presented that is simple to

W. R. Holmes

1986-01-01

121

The potential role of electric fields and plasma barodiffusion on the inertial confinement fusion database  

NASA Astrophysics Data System (ADS)

The generation of strong, self-generated electric fields (GV/m) in direct-drive, inertial-confinement-fusion (ICF) capsules has been reported [Rygg et al., Science 319, 1223 (2008); Li et al., Phys. Rev. Lett. 100, 225001 (2008)]. A candidate explanation for the origin of these fields based on charge separation across a plasma shock front was recently proposed [Amendt et al., Plasma Phys. Controlled Fusion 51 124048 (2009)]. The question arises whether such electric fields in imploding capsules can have observable consequences on target performance. Two well-known anomalies come to mind: (1) an observed ~2× greater-than-expected deficit of neutrons in an equimolar D3He fuel mixture compared with hydrodynamically equivalent D [Rygg et al., Phys. Plasmas 13, 052702 (2006)] and DT [Herrmann et al., Phys. Plasmas 16, 056312 (2009)] fuels, and (2) a similar shortfall of neutrons when trace amounts of argon are mixed with D in indirect-drive implosions [Lindl et al., Phys. Plasmas 11, 339 (2004)]. A new mechanism based on barodiffusion (or pressure gradient-driven diffusion) in a plasma is proposed that incorporates the presence of shock-generated electric fields to explain the reported anomalies. For implosions performed at the Omega laser facility [Boehly et al., Opt. Commun. 133, 495 (1997)], the (low Mach number) return shock has an appreciable scale length over which the lighter D ions can diffuse away from fuel center. The depletion of D fuel is estimated and found to lead to a corresponding reduction in neutrons, consistent with the anomalies observed in experiments for both argon-doped D fuels and D3He equimolar mixtures. The reverse diffusional flux of the heavier ions toward fuel center also increases the pressure from a concomitant increase in electron number density, resulting in lower stagnation pressures and larger imploded cores in agreement with gated, self-emission, x-ray imaging data.

Amendt, Peter; Wilks, S. C.; Bellei, C.; Li, C. K.; Petrasso, R. D.

2011-05-01

122

The potential role of electric fields and plasma barodiffusion on the inertial confinement fusion database  

SciTech Connect

The generation of strong, self-generated electric fields (GV/m) in direct-drive, inertial-confinement-fusion (ICF) capsules has been reported [Rygg et al., Science 319, 1223 (2008); Li et al., Phys. Rev. Lett. 100, 225001 (2008)]. A candidate explanation for the origin of these fields based on charge separation across a plasma shock front was recently proposed [Amendt et al., Plasma Phys. Controlled Fusion 51 124048 (2009)]. The question arises whether such electric fields in imploding capsules can have observable consequences on target performance. Two well-known anomalies come to mind: (1) an observed {approx_equal}2x greater-than-expected deficit of neutrons in an equimolar D{sup 3}He fuel mixture compared with hydrodynamically equivalent D [Rygg et al., Phys. Plasmas 13, 052702 (2006)] and DT [Herrmann et al., Phys. Plasmas 16, 056312 (2009)] fuels, and (2) a similar shortfall of neutrons when trace amounts of argon are mixed with D in indirect-drive implosions [Lindl et al., Phys. Plasmas 11, 339 (2004)]. A new mechanism based on barodiffusion (or pressure gradient-driven diffusion) in a plasma is proposed that incorporates the presence of shock-generated electric fields to explain the reported anomalies. For implosions performed at the Omega laser facility [Boehly et al., Opt. Commun. 133, 495 (1997)], the (low Mach number) return shock has an appreciable scale length over which the lighter D ions can diffuse away from fuel center. The depletion of D fuel is estimated and found to lead to a corresponding reduction in neutrons, consistent with the anomalies observed in experiments for both argon-doped D fuels and D{sup 3}He equimolar mixtures. The reverse diffusional flux of the heavier ions toward fuel center also increases the pressure from a concomitant increase in electron number density, resulting in lower stagnation pressures and larger imploded cores in agreement with gated, self-emission, x-ray imaging data.

Amendt, Peter; Wilks, S. C.; Bellei, C. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Li, C. K.; Petrasso, R. D. [Plasma Science and Fusion Center, MIT, Cambridge, Massachusetts 02139 (United States)

2011-05-15

123

Oscillatory and fluctuating terms in energies of assemblies of equicharged particles subject to spherically symmetric power-law confining potentials  

NASA Astrophysics Data System (ADS)

Energies E(N) of assemblies of equicharged particles subject to spherically symmetric power-law confining potentials vary in a convoluted fashion with the particle totalities N. Accurate rigorous upper bounds to these energies, which are amenable to detailed mathematical analysis, are found to comprise terms with smooth, oscillatory, and fluctuating dependences on N. The smooth energy component is obtained as a power series in N-2/3 with the first two terms corresponding to the bulk and Madelung energies. The oscillatory component possesses the large-N asymptotics given by a product of N1/(? + 1), where ? is the power-law exponent, and a function periodic in N1/3. The amplitude of the fluctuating component, which originates mostly from the irregular dependence of the Thomson energy ETh(n) on n, also scales like N1/(? + 1).

Cioslowski, Jerzy; Albin, Joanna

2013-09-01

124

Minimizing manganin/system noise for potential use in small geometry experiments  

SciTech Connect

Manganin gauges are piezo resistive devices often used for pressure measurements on larger, planer impact experiments. These gauges function in this capacity as a result of their ability to change resistance in a consistent fashion relative to the pressure exerted against them. Pressures to 400 kbar have been reliably recorded (H.C. Vantine et al.[1]). Because the mini-manganin is significantly physically smaller than other types, there has been interest in the ability to place these gauges on small geometry (detonator) type experiments. Of primary concern is that the detonator shock front has significant curvature associated with it--especially at small geometries--and that this curvature will cause unknown distortion (stretching) of the manganin gauge and therefore may indicate erroneous data. A problem encountered while configuring this experiment was noise as a result of the proximity and high current levels of the fireset to the manganin gauge. Initial results indicate noise on the order of 130 mV peak-to-peak (p-p) and running as long as the CVR signal from the ringdown charge voltage of 775 V. These noise problems significantly worsened while discharging the full charge voltage of 1500 V on the fireset through the chip slapper.

Phillips, D; May, C; Vandersall, K; Garcia, F

2008-10-02

125

Influence of the muscle fibre end geometry on the extracellular potentials  

Microsoft Academic Search

Intra- and extracellular action potentials of isolated frog muscle fibres were recorded at different distances to the end of the fibre. The first and second time derivatives of the intracellular action potentials were also recorded. The intracellular action potentials and their first and second time derivatives were almost the same regardless of the place of recording. With the decrease in

A. Gydikov; L. Gerilovsky; N. Radicheva; N. Trayanova

1986-01-01

126

Influence of the radial profile of the electric potential on the confinement of a high-{beta} two-component plasma in a gas-dynamic trap  

SciTech Connect

One of the most important problems to be studied in the gas-dynamic trap (GDT) facility is the investigation of MHD stability and cross-field transport in a plasma with a relatively high value of {beta} = {pi}p/B{sup 2}. Recent experiments demonstrated that the radial electric field produced in the plasma by using radial limiters and coaxial end plasma collectors improves plasma stability in axisymmetric magnetic mirror systems without applying special MHD stabilizers. The experimental data presented in this work show that stable plasma confinement can be achieved by producing a radial potential drop across a narrow region near the plasma boundary. Creating radial electric fields of strength 15-40 V/cm causes a shear plasma flow, thereby substantially increasing the plasma confinement time. When all the radial electrodes were grounded, the confinement was unstable and the plasma confinement time was much shorter than the characteristic time of plasma outflow through the magnetic mirrors. Measurements of cross-field plasma fluxes with the use of a specially designed combined probe show that, in confinement modes with differential plasma rotation, transverse particle losses are negligibly small as compared to longitudinal ones and thus can be ignored. It is also shown that, when the GDT plasma is in electric contact with the radial limiters and end collectors, the growth rate of interchange instability decreases considerably; such a contact, however, does not ensure complete MHD stability when the electrodes are at the same potential.

Soldatkina, E. I.; Bagryansky, P. A.; Solomakhin, A. L. [Russian Academy of Sciences, Budker Institute of Nuclear Physics, Siberian Branch (Russian Federation)

2008-04-15

127

SUPPLEMENTAL RISK ANALYSIS FOR POTENTIAL AIR EMISSIONS FROM THE PROPOSED CONFINED DISPOSAL FACILITY FOR THE INDIANA HARBOR AND SHIPPING CANAL SEDIMENT DREDGING AND DISPOSAL PROJECT  

EPA Science Inventory

In 1995, EPA completed a risk assessment for potential air emissions from the operation of a proposed confined disposal facility (CDF) to be constructed and operated by the U.S. Army Corps of Engineers for dredged sediments from the Indiana Harbor and Shipping Canal in East Chica...

128

Electrostatic-Inertial Plasma Confinement.  

National Technical Information Service (NTIS)

The work was directed towards an answer to the question: 'How dense a plasma can be confined by electrostatic-inertial means.' Electrostatic-inertial plasma confinement consists of trapping charged particles in potential wells (of the electric field), whi...

T. J. Dolan J. T. Verdeyen B. E. Cherrington D. J. Meeker

1970-01-01

129

Computation of action potential propagation and presynaptic bouton activation in terminal arborizations of different geometries.  

PubMed Central

Action potential propagation in axons with bifurcations involving short collaterals with synaptic boutons has been simulated using SPICE, a general purpose electrical circuit simulation program. The large electrical load of the boutons may lead to propagation failure at otherwise uncritical geometric ratios. Because the action potential gradually fails while approaching the branch point, the electrotonic spread of the failing action potential cannot depolarize the terminal boutons above an assumed threshold of 20 mV (Vrest = 0 mV) for the presynaptic calcium inflow, and therefore fails to evoke transmitter release even for boutons attached at short collaterals. For even shorter collaterals the terminal boutons can again be activated by the spread of passive current reflected at the sealed end of the bouton which increases the membrane potential above firing threshold. The action potential is then propagated in anterograde fashion into the main axon and may activate the terminal bouton on the other collateral. Differential activation of the synaptic boutons can be observed without repetitive activation of the main axon and with the assumption of uniform membrane properties. Axon enlargements above a critical size at branch points can increase the safety factor for propagation significantly and may serve a double function: they can act both as presynaptic boutons and as boosters, facilitating invasion of the action potential into the terminal arborizations. The architecture of the terminal arborizations has a profound effect on the activation pattern of synapses, suggesting that terminal arborizations not only distribute neural information to postsynaptic cells but may also be able to process neural information presynaptically.

Luscher, H R; Shiner, J S

1990-01-01

130

Electronic structure of the reduced blue copper active site. Contributions to reduction potentials and geometry  

SciTech Connect

A detailed electronic structure description of the reduced blue copper active site has now been developed. Photoelectron spectroscopy (PES) of imidazole, dimethyl sulfide, and methanethiolate bound to Cu(I) sites at single crystal surfaces has been used to define normal Cu(I) bonding to ligands relevant to the blue copper site. Variable photon energy PES has been used to assign valence band spectra, assess metal-ligand covalency, and probe specific orbital contributions to Cu(I) bonding. Self Consistent Field-X{alpha}-Scattered Wave (SCF-X{alpha}-SW) molecular orbital calculations calibrated to the photoelectron spectra have been performed to quantitatively complement the experimental bonding descriptions. These calculations have been extended to the reduced blue copper active site in plastocyanin, the prototypical blue copper protein, to detail the electronic structure changes that occur relative to normal Cu(I) bonding and upon oxidation. Ionization energies have been used to estimate the electronic structure contributions to the reduction potential. The long Cu-thioether axial bond present at the active site destabilizes the oxidized state and is therefore a key determining factor in the high reduction potentials generally observed for blue copper proteins. Linear coupling terms have been evaluated for the distortions of a blue copper site unconstrained by the protein backbone. 99 refs., 22 figs., 12 tabs.

Guckert, J.A.; Lowery, M.D.; Solomon, E.I. [Stanford Univ., CA (United States)

1995-03-15

131

Geometry-controlled kinetics  

Microsoft Academic Search

It has long been appreciated that the transport properties of molecules can control reaction kinetics. This effect can be characterized by the time it takes a diffusing molecule to reach a target-the first-passage time (FPT). Determining the FPT distribution in realistic confined geometries has until now, however, seemed intractable. Here, we calculate this FPT distribution analytically and show that transport

O. Bénichou; C. Chevalier; J. Klafter; B. Meyer; R. Voituriez

2010-01-01

132

Working safely in confined spaces  

Microsoft Academic Search

Working in confined spaces is a delicate balance of the correct equipment, hazard knowledge, proper training, and common sense. Anything less has potentially deadly consequences. The dangerous atmospheric and physical hazards often encountered in confined spaces must be recognized and accounted for. In addition, procedures and practices must conform to Occupational Safety and health Administration (OSHA) confined space regulations. Last

C. Bush; J. Versweyveld

1992-01-01

133

Generating end plug potentials in tandem mirror plasma confinement by heating thermal particles so as to escape low density end stoppering plasmas  

DOEpatents

The invention provides a method and apparatus for raising the potential of a magnetic mirror cell by pumping charged particles of the opposite sign of the potential desired out of the mirror cell through excitation, with the pumping being done by an externally imposed field at the bounce frequency of the above charged particles. These pumped simple mirror cells then provide end stoppering for a center mirror cell for the tandem mirror plasma confinement apparatus. For the substantially complete pumping case, the end plugs of a tandem mirror can be up to two orders of magnitude lower in density for confining a given center mirror cell plasma than in the case of end plugs without pumping. As a result the decrease in recirculating power required to keep the system going, the technological state of the art required, and the capital cost are all greatly lowered.

Baldwin, David E. (Danville, CA); Logan, B. Grant (Danville, CA)

1981-01-01

134

Preliminary identification of potentially disruptive scenarios at the Greater Confinement Disposal Facility, Area 5 of the Nevada Test Site  

Microsoft Academic Search

The Greater Confinement Disposal location is being evaluated to determine whether defense-generated transuranic waste buried at this location complies with the Containment Requirements established by the US Environmental Protection Agency. One step in determining compliance is to identify those combinations of events and processes (scenarios) that define possible future states of the disposal system for which performance assessments must be

R. V. Guzowski; G. Newman

1993-01-01

135

A numerical study of geometry dependent errors in velocity, temperature, and density measurements from single grid planar retarding potential analyzers  

SciTech Connect

Planar retarding potential analyzers (RPAs) have been utilized numerous times on high profile missions such as the Communications/Navigation Outage Forecast System and the Defense Meteorological Satellite Program to measure plasma composition, temperature, density, and the velocity component perpendicular to the plane of the instrument aperture. These instruments use biased grids to approximate ideal biased planes. These grids introduce perturbations in the electric potential distribution inside the instrument and when unaccounted for cause errors in the measured plasma parameters. Traditionally, the grids utilized in RPAs have been made of fine wires woven into a mesh. Previous studies on the errors caused by grids in RPAs have approximated woven grids with a truly flat grid. Using a commercial ion optics software package, errors in inferred parameters caused by both woven and flat grids are examined. A flat grid geometry shows the smallest temperature and density errors, while the double thick flat grid displays minimal errors for velocities over the temperature and velocity range used. Wire thickness along the dominant flow direction is found to be a critical design parameter in regard to errors in all three inferred plasma parameters. The results shown for each case provide valuable design guidelines for future RPA development.

Davidson, R. L.; Earle, G. D.; Heelis, R. A. [William B. Hanson Center for Space Sciences, University of Texas at Dallas, 800 W. Campbell Road, WT15, Richardson, Texas 75080 (United States); Klenzing, J. H. [Space Weather Laboratory/Code 674, Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2010-08-15

136

Confinement of nonneutral plasma in unconventional geometries  

Microsoft Academic Search

Interest in efficient storage of cold, nonneutral plasma has been motivated by the elegant studies on cryogenic nonneutral electron plasmas at UCSD and by the remarkable results obtained from the laser-cooled ion plasmas at the NIST, Boulder, Colorado. Also motivating the study is the perceived need to develop the most expedient means of storing antimatter, whether it be antiprotons for

Leaf Turner

1990-01-01

137

Spiral Evolution in a Confined Geometry  

NASA Astrophysics Data System (ADS)

Supported nanoscale lead crystallites with a step emerging from a noncentered screw dislocation on the circular top facet were prepared by rapid cooling from just above the melting temperature. STM observations of the top facet show a nonuniform rotation rate and shape of the spiral step as the crystallite relaxes. These features can be accurately modeled using curvature driven dynamics, as in classical models of spiral growth, with boundary conditions fixing the dislocation core and regions of the step lying along the outer facet edge.

Ranganathan, Madhav; Dougherty, D. B.; Cullen, W. G.; Zhao, Tong; Weeks, John D.; Williams, E. D.

2005-11-01

138

Hydrodynamics of confined membranes  

NASA Astrophysics Data System (ADS)

We calculate the hydrodynamic interaction ?(k) (Oseen interaction kernel) and relaxation frequency ?(k) for the fluctuations of a membrane that is harmonically bounded to a permeable or impermeable wall. We show that due to the confining wall there is an increase in the effective viscosity of the fluid surrounding the membrane. This has been observed in experiments on confined membranes, such as lamellar phases and the red-blood cell membrane. Our results allow a quantitative analysis of these experiments, in terms of the strength of the membrane confining potential and dislocations.

Gov, N.; Zilman, A. G.; Safran, S.

2004-07-01

139

System of fermions confined in a harmonic potential and subject to a magnetic field or a rotational motion  

SciTech Connect

Making use of the Bloch density matrix technique, we derive exact analytical expressions for the density profile in Fourier space, for the current density and the so-called integrated current for fermionic systems confined by a two-dimensional harmonic oscillator, in the presence of a magnetic field or in a rotating trap of arbitrary strength. We present numerical, illustrative examples with or without magnetic field (with or without rotation).

Naiedja, H.; Quentin, P. [Centre d'Etudes Nucleaires de Bordeaux-Gradignan, Universite Bordeaux-I and CNRS/IN2P3, B.P. 120, F-33175 Gradignan (France); Bencheikh, K. [Departement de Physique, Laboratoire de Physique Quantique et Systemes Dynamiques, Universite de Setif, Setif 19000 (Algeria); Bartel, J. [Institut Pluridisciplinaire Hubert Curien, Universite de Strasbourg and CNRS/IN2P3, B.P. 28, F-67037 Strasbourg (France)

2011-05-15

140

System of fermions confined in a harmonic potential and subject to a magnetic field or a rotational motion  

NASA Astrophysics Data System (ADS)

Making use of the Bloch density matrix technique, we derive exact analytical expressions for the density profile in Fourier space, for the current density and the so-called integrated current for fermionic systems confined by a two-dimensional harmonic oscillator, in the presence of a magnetic field or in a rotating trap of arbitrary strength. We present numerical, illustrative examples with or without magnetic field (with or without rotation).

Naïdja, H.; Bencheikh, K.; Bartel, J.; Quentin, P.

2011-05-01

141

The Effects of Quantum Confinement on the Binding Energy of Hydrogenic Impurities in a Spherical Quantum Dot  

NASA Astrophysics Data System (ADS)

The binding energy of a shallow hydrogenic impurity of a spherical quantum dot confined by harmonic oscillator-like and by rectangular well-like potentials, using a variational procedure within the effective mass approximation, has been determined. The calculations of the binding energy of the donor impurity as a function of the system geometry, and the donor impurity position have been investigated. The binding energy of shallow donor impurity depends not only on the quantum confinements but also on the impurity position. Our results reveal that (i) the donor binding energy decreases as the dot size increases irrespective of the impurity position, and (ii) the binding energy values of rectangular confinement are larger than the values of parabolic confinement and (iii) the rectangular confinement is better than the parabolic confinement in a spherical quantum dot.

Peter, A. John

142

SELF-ADJOINTNESS OF SCHR¨ ODINGER-TYPE OPERATORS WITH SINGULAR POTENTIALS ON MANIFOLDS OF BOUNDED GEOMETRY  

Microsoft Academic Search

We consider the Schrodinger type dierential expression HV = r r + V, where r is a C1-bounded Hermitian connection on a Hermitian vector bundle E of bounded geometry over a manifold of bounded geometry (M,g) with metric g and positive C1-bounded measure dµ, and V = V1 + V2, where 0 V1 2 L1 loc(EndE) and 0 V2 2

OGNJEN MILATOVIC

2003-01-01

143

Study of QCD Confinement  

NASA Astrophysics Data System (ADS)

Substantial numerical studies on pure lattice gauge theory have shown that the non-Abelian gauge theory is permanently confined at zero temperature and undergoes a deconfining phase transition at very high temperature. This thesis, however, is dedicated to the analytical study of the pure lattice gauge theory. Our focus is also on the confinement property of the gauge fields. This study is motivated by the effective spin model approach developed by Svetitsky and Yaffe. By using a variational principle, we have derived exactly the d dimensional effective spin model from the d + 1 dimensional SU(N) gauge theory for both zero and finite temperature cases. For both cases, the dynamics is rather simple: only nearest neighbor coupling exists. Therefore our effective spin model provides a competitive model for the study of the QCD vacuum properties. Based on our zero temperature effective spin model, our analysis shows that if the gauge field is confined, the quark anti-quark potential must be linear, which confirms the string picture of confinement. The 1 + 1 dimensional SU(2) gauge field theory has been solved exactly and its confinement is trivially confirmed. In particular, we have shown that in this case the Polyakov quark potential is equivalent to the Wilson potential. This strongly supports the conjecture that the definitions of the quark potential by Wilson and Polyakov are equivalent. We have also shown that our approach has the (tantalizing) potential to solve the confinement problem for 3 + 1 dimensional non-Abelian gauge fields. Finally, the 3 dimensional finite temperature effective spin model has also been investigated. We showed explicitly that the SU(2) gauge field undergoes second and SU(N) (N > 3) first order deconfining phase transitions. The deconfining phase transition temperature has also been studied for SU(2) gauge field by using the variational cumulant expansion method. The results are rather satisfactory.

Zhu, Zheng-Kun

1995-01-01

144

A combined effective fragment potential-fragment molecular orbital method. II. Analytic gradient and application to the geometry optimization of solvated tetraglycine and chignolin  

NASA Astrophysics Data System (ADS)

The gradient for the fragment molecular orbital (FMO) method interfaced with effective fragment potentials (EFP), denoted by FMO/EFP, was developed and applied to polypeptides solvated in water. The structures of neutral and zwitterionic tetraglycine immersed in water layers of 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5 A? are investigated by performing FMO/EFP geometry optimizations at the RHF/cc-pVDZ level of theory for the solutes. The geometries optimized with FMO-RHF/EFP are compared to those from the conventional RHF/EFP and are found to be in very close agreement. Using the optimized geometries, the stability of the hydrated zwitterionic and neutral structures is discussed structurally and in terms of energetics at the second-order Møller-Plesset theory (MP2)/cc-pVDZ level. To demonstrate the potential of the method for proteins, the geometry of hydrated chignolin (protein data bank ID: 1UAO) was optimized, and the importance of the inclusion of water was examined by comparing the solvated and gas phase structures of chignolin with the experimental NMR structure.

Nagata, Takeshi; Fedorov, Dmitri G.; Sawada, Toshihiko; Kitaura, Kazuo; Gordon, Mark S.

2011-01-01

145

Cataloguing the geometry of the human coronary arteries: a potential tool for predicting risk of coronary artery disease  

PubMed Central

Background The nonuniform distribution of atherosclerosis in the human vasculature suggests that local fluid dynamics or wall mechanics may be involved in atherogenesis. Thus certain aspects of vascular geometry, which mediates both fluid dynamics and wall mechanics, might be risk factors for coronary atherosclerosis. Cataloguing the geometry of normal human coronary arteries and its variability is a first step toward identifying specific geometric features that increase vascular susceptibility to the disease. Methods Images of angiographically normal coronary arteries, including 32 left anterior descending (LAD) and 35 right coronary arteries (RCA), were acquired by clinical biplane cineangiography from 52 patients. The vessel axes in end diastole were reconstructed and geometric parameters that included measures of curvature, torsion and tortuosity were quantified for the proximal, middle and distal segments of the arteries. Results Statistical analysis shows that (1) in the LAD, curvature, torsion and tortuosity are generally highest in the distal portion, (2) in the RCA, these parameters are smallest in the middle segment, (3) the LAD exhibits significant higher torsion than the RCA (P<0.005), and (4) >80% of the variability of coronary arterial geometry can be expressed in terms of two factors, one dominated by the curvature measures and tortuosity, and the other emphasizing the torsion parameters. Conclusions This study has comprehensively documented the normal arterial geometry of the LAD and RCA in end diastole. This information may be used to guide the identification of geometric features that might be atherogenic risk factors.

Zhu, Hui; Ding, Zhaohua; Piana, Robert N.; Gehrig, Thomas R.; Friedman, Morton H.

2009-01-01

146

Decreasing operating potential for water electrolysis to hydrogen via local confinement of iron-based soft coordination suprapolymers.  

PubMed

Currently there is intense interest in decreasing the operating potential for hydrogen evolution in water electrolysis to considerably decrease the energy cost. In this work we report a significant decrease of the operating potential for hydrogen evolution from neutral water mediated by an iron based soft coordination polymer (Fe(III)-SCSP). The creation of a local acidic environment with a thickness in the range of ?40 nm on the surface of a glassy carbon electrode allows enrichment of H(+) on the GCE, so that the operating potentials were effectively decreased. This strategy thus generates a new paradigm for lowering the operating potential of hydrogen generation from neutral water without the use of additional acids and organic cosolvents. PMID:23949627

Liang, Yawei; Xu, Limin; Zhou, Yinglin; Zhang, Xinxiang; Huang, Jianbin; Yan, Yun

2013-08-15

147

Confinement of quarks  

NASA Astrophysics Data System (ADS)

A general introduction to the topological mechanism responsible for the absolute confinement of quarks inside hadronic bound states is given, including the effects of a finite instanton angle. We then propose a calculational technique for computing these states and their properties, where instead of topology we rely on a perturbative mechanism. It assumes that already before the topological mechanism can come into effect there is already a strong inclination of quarks to be confined. In particular the planar limit of large N QCD should exhibit this mechanism. By renormalizing the infrared divergence of one-loop diagrams, one may already realize a confining potential. In practice, our procedure will require gauge-fixing in advance, but it would be more elegant if, at an intermediate level, the theory with infrared counter terms included could be written as a gauge-invariant effective model. Models of the desired kind are described. They are not renormalizable, but they are local, gauge- and lorentz invariant.

't Hooft, Gerard

2003-06-01

148

Electrohydrodynamics of DNA in confinement  

NASA Astrophysics Data System (ADS)

New methods of DNA sequencing aim to exploit the direct reading of individual DNA molecules. Such methods require one be able to elongate DNA molecules so that individual base-pairs may be accessed. In turn, this requires a detailed understanding of the mechanical and thermodynamic behavior of DNA, so that external manipulation and confinement successfully stretch the molecule. We aim to study the interplay between electrostatic and hydrodynamic interactions on the conformations of coarse-grained DNA through use of computer simulations with the general geometry Ewald-like method (GGEM), both in bulk and under geometric confinement.

Whitmer, Jonathan K.; Hernandez-Ortiz, Juan P.; de Pablo, Juan J.

2012-02-01

149

Hybrid model in general geometry  

Microsoft Academic Search

We propose hybrid model equations in toroidal (or more general) geometry for magnetically confined plasmas. This is suitable for low frequency toroidal modes, for example, the trapped electron and current diffusive ballooning instabilities. This model consists of fluid ions and drift kinetic electrons. We discuss the numerical algorithm of these model equations. The linear dispersion relation of this model equations

M. Yagi; T. Tajima; M. J. Lebrun

1994-01-01

150

Diffusing Polymers in Confined Microdomains and Estimation of Chromosomal Territory Sizes from Chromosome Capture Data  

NASA Astrophysics Data System (ADS)

Is it possible to extract the size and structure of chromosomal territories (confined domain) from the encounter frequencies of chromosomal loci? To answer this question, we estimate the mean time for two monomers located on the same polymer to encounter, which we call the mean first encounter time in a confined microdomain (MFETC). We approximate the confined domain geometry by a harmonic potential well and obtain an asymptotic expression that agrees with Brownian simulations for the MFETC as a function of the polymer length, the radius of the confined domain, and the activation distance radius ? at which the two searching monomers meet. We illustrate the present approach using chromosome capture data for the encounter rate distribution of two loci depending on their distances along the DNA. We estimate the domain size that restricts the motion of one of these loci for chromosome II in yeast.

Amitai, A.; Holcman, D.

2013-06-01

151

Subwavelength metallic waveguides as a tool for extreme confinement of THz surface waves.  

PubMed

Research on surface waves supported by metals at THz frequencies is experiencing a tremendous growth due to their potential for imaging, biological sensing and high-speed electronic circuits. Harnessing their properties is, however, challenging because these waves are typically poorly confined and weakly bound to the metal surface. Many design strategies have been introduced to overcome these limitations and achieve increased modal confinement, including patterned surfaces, coated waveguides and a variety of sub-wavelength geometries. Here we provide evidence, using a combination of numerical simulations and time-resolved experiments, that shrinking the transverse size of a generic metallic structure always leads to solutions with extreme field confinement. The existence of such a general behavior offers a new perspective on energy confinement and should benefit future developments in THz science and technology. PMID:23463351

Gacemi, D; Mangeney, J; Colombelli, R; Degiron, A

2013-01-01

152

Geometry Information  

NSDL National Science Digital Library

This article from New Zealand maths contains justifications for teaching geometry in the elementary grades and thoughts on how children learn geometry, including ideas from Piaget and the van Hieles. The article concludes with an example of how adults in a non-school setting would apply the van Hiele stages in an unfamiliar space.

2010-01-01

153

Elmo bumpy square plasma confinement device  

DOEpatents

The invention is an Elmo bumpy type plasma confinement device having a polygonal configuration of closed magnet field lines for improved plasma confinement. In the preferred embodiment, the device is of a square configuration which is referred to as an Elmo bumpy square (EBS). The EBS is formed by four linear magnetic mirror sections each comprising a plurality of axisymmetric assemblies connected in series and linked by 90/sup 0/ sections of a high magnetic field toroidal solenoid type field generating coils. These coils provide corner confinement with a minimum of radial dispersion of the confined plasma to minimize the detrimental effects of the toroidal curvature of the magnetic field. Each corner is formed by a plurality of circular or elliptical coils aligned about the corner radius to provide maximum continuity in the closing of the magnetic field lines about the square configuration confining the plasma within a vacuum vessel located within the various coils forming the square configuration confinement geometry.

Owen, L.W.

1985-01-01

154

Ground-state energy shift of He close to a surface and its relation with the scattering potential: A confinement model  

NASA Astrophysics Data System (ADS)

The relation between scattering potential and ground-state energy shift of a helium atom (ion) close to a surface is investigated through use of a model of spatial limitation whereby the surface is represented by an infinitely rigid planar boundary. The model of an atom confined in a semi-infinite space with a plane boundary allows the variational evaluation of the ground-state energies and wave functions for He and He+ at different positions from the surface. The respective Born-Oppenheimer energy curves serve to model the ground-state energy shift for the elastic scattering channel in atom (ion) surface interactions. Independent calculations for the He-graphite and He-Al (111), (110), and (100) continuous planar potentials are carried out using high-quality ab initio calculations reported in the literature for the lowest He-C and He-Al binary interaction potentials. It is shown in this case that the He ground-state energy shift obtained within this model corresponds to an upper limit to the usual continuous planar potential. A discussion on the physical origin of this agreement is presented in terms of the static nature for the surface considered in both the hard-wall model and the atomic binary interactions used to construct the planar potentials, i.e., no account of the dynamic surface response is allowed as the projectile approaches. This is done by taking a reference pilot calculations based on electron nuclear dynamics for 100eV He (He+) -benzene (C6H6) interactions by considering the benzene molecule as a rough approximation to a local graphitic surface sector. It is found that the static planar potential provides a reasonable average representation of the interaction for neutral He, and supporting evidence for the use of the static O’Connor-Biersack potential is given. Finally, the effective scattering potential for He/He+-Al (111) is constructed through the use of the static planar potential for He-Al (111) considering the energy shift due to the classical image interaction for He+ approaching a perfectly Al (111) conducting plane before charge neutralization takes place. It is concluded that this scattering potential is directly related with the ground-state energy shift of the emerging already neutralized He atoms in He/He+-Al(111) grazing scattering experiments.

Cruz, S. A.; Ley-Koo, E.; Cabrera-Trujillo, R.

2008-09-01

155

Effects of confinement on the thermodynamics of supercooled water  

NASA Astrophysics Data System (ADS)

The main focus of this thesis is to understand how confinement alters the phase diagram of supercooled liquid water by employing methods of statistical mechanics and numerical simulations. Water is very complex and anomalous when compared to simple liquids. For example, experimental data for liquid water reveals the presence of a temperature of maximum density (TMD) below which the density decreases under isobaric cooling. Another anomaly is the hypothesized liquid--liquid phase transition (LLPT) between two types of liquid water with different densities. In this thesis we study how confinement affects such anomalies as TMD and LLPT in supercooled liquid water. This thesis is separated into three parts: (i) Monte Carlo simulations of a 2D coarse-grained model of a water layer confined in a fixed disordered matrix of hydrophobic nanoparticles, (ii) molecular dynamics simulations of a Jagla ramp model of liquid confined in fixed ordered and disordered matrices of hydrophobic nanoparticles, and (iii) all-atom simulations of trehalose and maltose in aqueous solution of lysozyme. In Part (i), we perform Monte Carlo simulations and find that a nanoparticle concentration as small as 2.4% is enough to destroy the LLPT for pressure P > 0.14 GPa. Moreover, we find a substantial (more than 90%) decrease of compressibility, thermal expansion coefficient and specific heat at high P and low temperature T upon increase of nanoparticle concentration from 0% to 25%. In Part (ii), we ask how, for single component systems interacting via a soft-core isotropic potential with two characteristic length scales, the geometry of hydrophobic confinement affects the phase diagram. We use molecular dynamics simulations to study particles interacting through a ramp potential and a shoulder potential, each confined in a fixed matrix of nanoscopic particles with a fixed volume fraction. We find a substantial weakening of the LLPT and the disappearance of TMD upon the increase of disorder in the confining geometry. In Part (iii), we study aqueous systems with all-atom simulations. We are currently investigating the mechanism of water-trehalose-protein and water-maltose-protein interaction upon supercooling for its relevance to bioprotection.

Strekalova, Elena G.

156

Projective Geometry  

NSDL National Science Digital Library

This site departs from the common themes taught in general geometry classes and introduces projective geometry, which has to do with special properties resulting from the intersection of lines, planes, and points. The coincidence of such elements is what is referred to as an incidence, and this is the basis of the topic. The site makes extensive use of animated figures to demonstrate principles involved in projective geometry, such as path curves, pivot transforms, and the curious concept of counter space. The author does a good job of explaining what is depicted in the figures as well as the underlying theory.

157

Geometry Sender  

NSDL National Science Digital Library

The Geometry Sender at Keio University includes many 3D object data, including WebOOGL, off, rwx format, tutorial on data formats, and information about external viewers for 3D object on Web are available.

158

Working safely in confined spaces  

SciTech Connect

Working in confined spaces is a delicate balance of the correct equipment, hazard knowledge, proper training, and common sense. Anything less has potentially deadly consequences. The dangerous atmospheric and physical hazards often encountered in confined spaces must be recognized and accounted for. In addition, procedures and practices must conform to Occupational Safety and health Administration (OSHA) confined space regulations. Last year, three men were asphyxiated while surveying beneath a manhole in Boulder, CO. An area newspaper called the deaths the result of a freak accident. Whatever the cause, entering a manhole without first monitoring the air and posting an outside attendant is both extremely dangerous and a violation of safe entry procedures. The National Institute for Health and Occupational Safety (NIOSH) estimates that millions of workers from a wide range of occupations and industries are exposed to confined space hazards every year. Although confined space deaths are not a new phenomenon, only recently has the problem received serious study. Government regulatory agencies are becoming more involved OSHA recently proposed ruling 1910.146, Permit Required Confined Spaces, to mandate safe entry practices and procedures. The ruling requires all employers to develop a specific action plan for confined space entry, including entry procedures, worker training, safety equipment, and emergency action. This first article defines a confined space and examines some common hazards, including toxic, combustible, and oxygen-deficient atmospheres and combustible dusts. A subsequent article will review the use of test instruments, personal protective equipment, worker training, and emergency response.

Bush, C.; Versweyveld, J. (Lab Safety Supply, Janesville, WI (United States))

1992-08-13

159

Semiempirical quantum mechanical method PM6-DH2X describes the geometry and energetics of CK2-inhibitor complexes involving halogen bonds well, while the empirical potential fails.  

PubMed

In the present study, we have investigated complexes of CK2 protein kinase with halogenated inhibitors by means of the advanced semiempirical quantum mechanical (SQM) PM6 method (called PM6-DH2X), which describes various types of noncovalent interactions including halogen bonding well. The PM6-DH2X method provides reliable geometries of those CK2 protein kinase-inhibitor complexes involving halogen bonds that agree well with the X-ray crystal structures. When the Amber empirical potential is applied, this agreement becomes considerably worse. Similarly, the binding free energies determined by the PM6-DH2X SQM method are much closer to the experimental inhibition constants than those based on the Amber empirical potential. PMID:21648479

Dobes, Petr; Rezác, Jan; Fanfrlík, Jindrich; Otyepka, Michal; Hobza, Pavel

2011-06-16

160

Some physics considerations of magnetic inertial-electrostatic confinement: A new concept for spherical converging-flow fusion. (Reannouncement with new availability information)  

SciTech Connect

A new method of energizing and confining charged particles has been devised that offers promise for efficient small-scale control of their motion in spherically converging recirculating flow and for the generation of fusion reactions among them. This method uses special magnetohydrodynamically (MHD) stable magnetic field configuration to confine energetic electrons that are injected to form a negative potential well that is within the volume bounded by the magnetic fields. These fields consist of point cusps arranged in an alternating pattern in a generally spherical geometry around the confinement region, such that they occupy the faces of polyhedra with an even number of faces around each vortex.

Bussard, R.W.

1991-03-01

161

Geometry and architectural associations of co-genetic debrite–turbidite beds in basin-margin strata, Carboniferous Ross Sandstone (Ireland): Applications to reservoirs located on the margins of structurally confined submarine fans  

Microsoft Academic Search

Co-genetic debrite–turbidite beds are most commonly found in distal basin-plain settings and basin margins. This study documents the geometry, architectural association and paleogeographic occurrence of co-genetic debrite–turbidite beds in the Carboniferous Ross Sandstone with the goal of reducing uncertainty in the interpretation of subsurface data in similarly shaped basins where oil and gas is produced.The Ross Sandstone of western Ireland

David R. Pyles; D. C. Jennette

2009-01-01

162

Fault geometry, rupture dynamics and ground motion from potential earthquakes on the North Anatolian Fault under the Sea of Marmara  

NASA Astrophysics Data System (ADS)

Using the 3-D finite-element method, we develop dynamic spontaneous rupture models of earthquakes on the North Anatolian Fault system in the Sea of Marmara, Turkey, considering the geometrical complexity of the fault system in this region. We find that the earthquake size, rupture propagation pattern and ground motion all strongly depend on the interplay between the initial (static) regional pre-stress field and the dynamic stress field radiated by the propagating rupture. By testing several nucleation locations, we observe that those far from an oblique normal fault stepover segment (near Istanbul) lead to large through-going rupture on the entire fault system, whereas nucleation locations closer to the stepover segment tend to produce ruptures that die out in the stepover. However, this pattern can change drastically with only a 10° rotation of the regional stress field. Our simulations also reveal that while dynamic unclamping near fault bends can produce a new mode of supershear rupture propagation, this unclamping has a much smaller effect on the speed of the peak in slip velocity along the fault. Finally, we find that the complex fault geometry leads to a very complex and asymmetric pattern of near-fault ground motion, including greatly amplified ground motion on the insides of fault bends. The ground-motion pattern can change significantly with different hypocentres, even beyond the typical effects of directivity. The results of this study may have implications for seismic hazard in this region, for the dynamics and ground motion of geometrically complex faults, and for the interpretation of kinematic inverse rupture models.

Oglesby, David D.; Mai, P. Martin

2012-03-01

163

A Review of Quantum Confinement  

NASA Astrophysics Data System (ADS)

A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker [1]-henceforth cited as SW-in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell. The conclusions are shown to be relevant to a proposed `quantum computer'. The description of the actual geometry of C60, as opposed to a purely spherical approximation, leads to some qualification of the computed results.

Connerade, Jean-Patrick

2009-12-01

164

Sacred Geometry  

NSDL National Science Digital Library

The material on this website is used for a course taught at Dartmouth University called, Geometry in Art and Architecture. The website presents several images of "polygons, tilings & sacred geometry" along with descriptions of the geometric patterns. Although the text is obviously written for students who follow a particular course and hasn't been updated since 2002, the author provides some interesting examples of how the fields of art and mathematics overlap. Information on the author's book on the subject and bibliographical references are also posted for anyone wanting to explore this topic further.

165

Algebraic Geometry  

NSDL National Science Digital Library

A short article designed to provide an introduction to algebraic geometry, which combines the algebraic with the geometric for the benefit of both. Thus the recent proof of "Fermat's Last Theorem" - ostensibly a statement in number theory - was proved with geometric tools. Conversely, the geometry of sets defined by equations is studied using quite sophisticated algebraic machinery. This is an enticing area but the important topics are quite deep. This area includes elliptic curves. Applications and related fields and subfields; textbooks, reference works, and tutorials; software and tables; other web sites with this focus.

Rusin, David J., 1957-

2007-12-18

166

Isomers and Conformers of H(NH?BH?)(n)H Oligomers: Understanding the Geometries and Electronic Structure of Boron-Nitrogen-Hydrogen Compounds as Potential Hydrogen Storage Materials  

SciTech Connect

Boron-nitrogen-hydrogen (BNHx) materials are polar analogs of hydrocarbons with potential applications as media for hydrogen storage. As H(NH?BH?)nH oligomers result from dehydrogenation of NH?BH? and NH?BH? materials, understanding the geometries, stabilities, and electronic structure of these oligomers is essential for developing chemical methods of hydrogen release and regeneration of the BNHx-based hydrogen storage materials. In this work we have performed computational modeling on the H(NH?BH?)nH (n = 1 – 6) oligomers using density functional theory (DFT). We have investigated linear chain structures and the stabilizing effects of coiling, biradicalization, and branching through Car-Parrinello molecular dynamics simulations and geometry optimizations. We find that the zig-zag linear oligomers are unstable with respect to the coiled, square-wave chain, and branched structures, with the coiled structures being the most stable. Dihydrogen bonding in oligomers, where protic H??(N) hydrogens interact with hydridic H??(B) hydrogens, plays a crucial role in stabilizing different isomers and conformers. The results are consistent with structures of products that are seen in experimental NMR studies of dehydrogenated ammonia borane.

Li, Jun; Kathmann, Shawn M.; Schenter, Gregory K.; Gutowski, Maciej S.

2007-02-07

167

Holographic Schwinger effect in confining phase  

NASA Astrophysics Data System (ADS)

We consider the Schwinger effect in confining phase by using a holographic setup. The potential analysis is performed for the confining D3-brane and D4-brane back-grounds. We find the critical electric field above which there is no potential barrier and the system becomes unstable catastrophically. An intriguing point is that no Schwinger effect occurs when the electric field is smaller than the confining string tension.

Sato, Yoshiki; Yoshida, Kentaroh

2013-09-01

168

Spectra of confined two-electron atoms  

NASA Astrophysics Data System (ADS)

Spectra of two electrons confined in a spherically symmetric potential of mixed Coulomb and harmonic form are studied using the Hartree-Fock and configuration interaction methods. The model studied corresponds to a two-electron atom confined in a harmonic oscillator potential. The spectral consequences of the interplay between the effects of the confinement due to the Hooke's law and due to the nuclear attraction force are investigated in detail.

Bielinska-Waz, D.; Karwowski, J.; Diercksen, G. H. F.

2001-05-01

169

Development of empirical potential functions for the study of molecular geometry, and applications to chlorophyll a dimers. [Dissertation  

SciTech Connect

A purpose of the present studies is twofold: (1) development of an empirical potential function (EPF) and (2) application of it to the studies of photoreaction center chlorophyll a dimer. The reliable estimate of geometric structures and energies of large molecules by quantum mechanical methods is not possible at the present time. An alternative method is, therefore, needed for the studies of large molecular systems, and Chapter I is dedicated to the development of this tool, i.e., an empirical potential function, which could suffice this purpose. Because of a large number of variable chemical compositions and functional groups characteristically present in a large molecule, it is important to include a large number of structurally diverse molecules in the development of the EPF. In Chapter II, the EPF is applied to study the geometrical structure of a chlorophyll a (Chl a) dimer, which is believed to exist at the photoreaction center of green plants and is known to play an essential role in photosynthetic energy conversion. Although various models have been proposed for this dimer structure, there is still a great need for information concerning the detailed geometric structure of this dimer. Therefore, in this chapter the structural stabilities of various dimer models are examined by the EPF, and detailed and quantitative information on the structure and stability of these models is provided.

Oie, T.

1980-01-01

170

Development of empirical potential functions for the study of molecular geometry and applications to chlorophyll A dimers  

NASA Astrophysics Data System (ADS)

The reliable estimate of geometric structures and energies of large molecules by quantum mechanical methods is not possible at the present time. For the studies of large molecular systems, an empirical potential function (EPF) which could suffice this purpose, is proposed. Because of a large number of variable chemical compositions and functional groups characteristically present in a large molecule, it is important to include a large number of structurally diverse molecules in the development of the EPF. The EPF is applied to study the geometrical structure of a chlorophyll, a (Chl a) dimer, which is believed to exist at the photoreaction center of green plants and is known to play an essential role in photosynthetic energy conversion. The structural stabilities of various dimer models are examined by the EPF and quantitative information on the structure and stability of these models is provided.

Oie, T.

1980-03-01

171

Self-consistent Thomas-Fermi calculation of potential and current distributions in a two-dimensional Hall bar geometry  

NASA Astrophysics Data System (ADS)

The electrostatics of a two-dimensional, in-plane-gate-defined Hall bar is investigated by imposing the electrochemical equilibrium within the Thomas-Fermi approximation. We calculate the electrostatic potential self-consistently with the electron distribution and examine associated magnetic-field-induced compressible and incompressible regions as a function of temperature, bare screening length, and gate voltage with and without nondissipative currents. We find that the widths of the incompressible and compressible regions depend strongly on temperature and bare screening length. At very low temperature and small screening length, our results agree with an analytical work by Chklovskii, Matveev, and Shklovskii. For a small current applied on the Hall bar, the electron distribution is found to be slightly deformed while the width of the incompressible regions is not changed. Neglecting diamagnetic currents, we find that the current densities are distributed over the whole region occupied by electrons.

Oh, J. H.; Gerhardts, Rolf R.

1997-11-01

172

Spectra of Confined Atoms and Molecules  

NASA Astrophysics Data System (ADS)

The properties of spectra of atoms and molecules confined by an external potential are analyzed. The effects of spatial confinement are studied using quantum-chemical models. The confinement of the system is described by an external one-particle potential. Two-electron atoms confined in a spherically symmetric harmonic oscillator potential are investigated in detail [1]. In this case the interplay between the effects of the confinement due to the Hooke's law and due to the nuclear attraction forces are studied. The existence of a special case when the harmonic oscillator frequency ? and the nuclear charge Z are changed simultaneously so that the structure of the confined atom remains unchanged up to the second order of the perturbation theory, is demonstrated. Moreover, the structure and the spectral properties of the hydrogen molecule confined in a harmonic oscillator potential are studied [2]. The bond length and the vibronic transitions (the intensities and the number of lines) depend in a specific way on the strength of the confining potential. In particular, due to the confinement, the absorption and the emission vibronic bands are blue shifted.

Bieli?ska-Waz, D.

2003-04-01

173

Current-induced skyrmion dynamics in constricted geometries.  

PubMed

Magnetic skyrmions-vortex-like swirling spin structures with a quantized topological number that are observed in chiral magnets-are appealing for potential applications in spintronics because it is possible to control their motion with ultralow current density. To realize skyrmion-based spintronic devices, it is essential to understand skyrmion motions in confined geometries. Here we show by micromagnetic simulations that the current-induced motion of skyrmions in the presence of geometrical boundaries is very different from that in an infinite plane. In a channel of finite width, transverse confinement results in steady-state characteristics of the skyrmion velocity as a function of current that are similar to those of domain walls in ferromagnets, whereas the transient behaviour depends on the initial distance of the skyrmion from the boundary. Furthermore, we show that a single skyrmion can be created by an electric current in a simple constricted geometry comprising a plate-shaped specimen of suitable size and geometry. These findings could guide the design of skyrmion-based devices in which skyrmions are used as information carriers. PMID:24013132

Iwasaki, Junichi; Mochizuki, Masahito; Nagaosa, Naoto

2013-09-08

174

Current-induced skyrmion dynamics in constricted geometries  

NASA Astrophysics Data System (ADS)

Magnetic skyrmions--vortex-like swirling spin structures with a quantized topological number that are observed in chiral magnets--are appealing for potential applications in spintronics because it is possible to control their motion with ultralow current density. To realize skyrmion-based spintronic devices, it is essential to understand skyrmion motions in confined geometries. Here we show by micromagnetic simulations that the current-induced motion of skyrmions in the presence of geometrical boundaries is very different from that in an infinite plane. In a channel of finite width, transverse confinement results in steady-state characteristics of the skyrmion velocity as a function of current that are similar to those of domain walls in ferromagnets, whereas the transient behaviour depends on the initial distance of the skyrmion from the boundary. Furthermore, we show that a single skyrmion can be created by an electric current in a simple constricted geometry comprising a plate-shaped specimen of suitable size and geometry. These findings could guide the design of skyrmion-based devices in which skyrmions are used as information carriers.

Iwasaki, Junichi; Mochizuki, Masahito; Nagaosa, Naoto

2013-10-01

175

Fractal Geometry  

NSDL National Science Digital Library

This is a web site to support a first course in fractal geometry for students without a strong mathematical background. It covers a wide range of topics in fractals, modern dynamics, and chaos. Each of the topics contains examples of fractals in the arts, humanities, or social sciences. The site also contains lesson plans and software that can be used for a broad range of classes.

Frame, Michael; Mandelbrot, Benoit

2004-11-30

176

Confined drying of copolymer solutions  

NASA Astrophysics Data System (ADS)

We developed a simple tool for the rapid screening of phase diagrams of polymer and surfactant solutions. Our technique is based on the controlled drying of a droplet solution in a confined geometry. A ?L-sized droplet of an aqueous solution is confined between two wafers (diameter 3 cm), separated by a controlled thickness ( 150 ?m). The confinement casts a well-defined timescale to the drying kinetics, mainly governed by the wafer area. Indeed, water removal only occurs through a diffusive process from the edge of droplet to the edge of the wafer. Confinement also permits a simple 2D description, and allows simple observations of the drying. We studied the drying of an aqueous solution of a tribloc copolymer (Pluronics, P104) thanks to three different techniques: polarized microscopy, fluorescent microscopy, and Raman imaging. With our tool and techniques, we not only build an accurate phase diagram of the solution (with one microliter only) but also measure both the mutual diffusion coefficient and the activity of the solution as a function of its concentration, including the Flory-Huggins parameter.

Laure, Daubersies; Jacques, Leng; Jean-Baptiste, Salmon

2012-02-01

177

Facilitated diffusion on confined DNA  

NASA Astrophysics Data System (ADS)

In living cells, proteins combine three-dimensional bulk diffusion and one-dimensional sliding along the DNA to reach a target faster. This process is known as facilitated diffusion and we investigate its dynamics in the physiologically relevant case of confined DNA. The confining geometry and DNA elasticity are key parameters: We find that facilitated diffusion is most efficient inside an isotropic volume and on a flexible polymer. By considering the typical copy numbers of proteins in vivo, we show that the speedup due to sliding becomes insensitive to fine tuning of parameters, rendering facilitated diffusion a robust mechanism to speed up intracellular diffusion-limited reactions. The parameter range we focus on is relevant for in vitro systems and for facilitated diffusion on yeast chromatin.

Foffano, G.; Marenduzzo, D.; Orlandini, E.

2012-02-01

178

Noncommutative geometry and reality  

Microsoft Academic Search

We introduce the notion of realstructure in our spectral geometry. This notion is motivated by Atiyah’s KR-theory and by Tomita’s involution J. It allows us to remove two unpleasant features of the ‘‘Connes–Lott’’ description of the standard model, namely, the use of bivector potentials and the asymmetry in the Poincare´ duality and in the unimodularity condition.

Alain Connes

1995-01-01

179

Fractal Geometry  

NSDL National Science Digital Library

This is one of the best online resources about fractals, and is "meant to support a first course in fractal geometry for students without especially strong mathematical preparation." The site is incredibly deep, providing everything from the most basic definitions and non-technical discussions to involved mathematical formulations. Interactive Java applets, downloadable software for the PC and Macintosh, and laboratory activities are also presented. A particularly interesting section of the site explores about 100 places in nature and society where fractals are found.

Frame, Michael; Mandelbrot, Benoit; Neger, Nial

180

The Role of Confinement on Biologically Derived Liquid Crystals  

NASA Astrophysics Data System (ADS)

Suspensions of stabilized, dilute microtubules provide a versatile model system for understanding the structure of confined liquid crystals. Microtubule solutions are easily transported as a simple monomeric fluid that can easily be polymerized into rod-like macromolecules after they are confined within quasi-2D geometries (microfluidics). Using polarization and confocal microscopy, we analyze the structure of liquid crystals in a variety of geometries. We will present results on the role of confinement, boundary conditions and concentration, specifically discussing how each variable alters nematic ordering.

Brown, Marguerite; Blair, Daniel

2013-03-01

181

Confinement from correlation functions  

NASA Astrophysics Data System (ADS)

We compute the Polyakov loop potential in Yang-Mills theory from the fully dressed primitively divergent correlation functions only. This is done in a variety of functional approaches ranging from functional renormalization group equations over Dyson-Schwinger equations to two-particle irreducible functionals. We present a confinement criterion that links the infrared behavior of propagators and vertices to the Polyakov loop expectation value. The present work extends the works of [J. Braun , Phys. Lett. B 684, 262 (2010)PYLBAJ0370-2693; F. Marhauser and J. M. Pawlowski, arXiv:0812.1144; J. Braun , Eur. Phys. J. C 70, 689 (2010)EPCFFB1434-6044] to general functional methods and sharpens the confinement criterion presented there. The computations are based on the thermal correlation functions in the Landau gauge calculated in [L. Fister and J. M. Pawlowski, arXiv:1112.5440; L. Fister and J. M. Pawlowski, arXiv:1112.5429; L. Fister, Ph.D. thesis, Heidelberg University, 2012].

Fister, Leonard; Pawlowski, Jan M.

2013-08-01

182

QUIESCENT H-MODE, AN ELM-FREE HIGH-CONFINEMENT MODE ON DIII-D WITH POTENTIAL FOR STATIONARY STATE OPERATION  

SciTech Connect

OAK-B135 The quiescent H-mode (QH-mode) is an ELM-free and stationary state mode of operation discovered on DIII-D. This mode achieves H-mode levels of confinement and pedestal pressure while maintaining constant density and radiated power. The elimination of edge localized modes (ELMs) and their large divertor loads while maintaining good confinement and good density control is of interest to next generation tokamaks. This paper reports on the correlations found between selected parameters in a QH-mode database developed from several hundred DIII-D counter injected discharges. Time traces of key plasma parameters from a QH-mode discharge are shown. On DIII-D the negative going plasma current (a) indicates that the beam injection direction is counter to the plasma current direction, a common feature of all QH-modes. The D{sub {alpha}} time behavior (c) shows that soon after high powered beam heating (b) is applied, the discharge makes a transition to ELMing H-mode, then the ELMs disappear, indicating the start of the QH period that lasts for the remainder of the high power beam heating (3.5 s). Previously published work showing density and temperature profiles indicates that long-pulse, high-triangularity QH discharges develop an internal transport barrier in combination with the QH edge barrier. These discharges are known as quiescent, double-barrier discharges (QDB). The H-factor (d) and stored energy (c) rise then saturate at a constant level and the measured axial and minimum safety factors remain above 1.0 for the entire QH duration. During QDB operation the performance of the plasma can be very good, with {beta}{sub N}*H{sub 89L} product reaching 7 for > 10 energy confinement times. These discharges show promise that a stationary state can be achieved.

WEST,WP; BURRELL,KH; deGRASSIE,JS; DOYLE,EJ; GREENFIELD,CM; LASNIER,CJ; SNYDER,PB; ZENG,L

2003-08-01

183

Note: Light output enhanced fast response and low afterglow {sup 6}Li glass scintillator as potential down-scattered neutron diagnostics for inertial confinement fusion  

SciTech Connect

The characteristics of an APLF80+3Ce scintillator are presented. Its sufficiently fast decay profile, low afterglow, and an improved light output compared to the recently developed APLF80+3Pr, were experimentally demonstrated. This scintillator material holds promise for applications in neutron imaging diagnostics at the energy regions of 0.27 MeV of DD fusion down-scattered neutron peak at the world's largest inertial confinement fusion facilities such as the National Ignition Facility and the Laser Megajoule.

Arikawa, Yasunobu; Yamanoi, Kohei; Nagai, Takahiro; Watanabe, Kozue; Kouno, Masahiro; Sakai, Kohei; Nakazato, Tomoharu; Shimizu, Toshihiko; Cadatal, Marilou Raduban; Estacio, Elmer Surat; Sarukura, Nobuhiko; Nakai, Mitsuo; Norimatsu, Takayoshi; Azechi, Hiroshi [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Murata, Takahiro [Kumamoto University, 2-40-1 Kurokami, Kumamoto 860-8555 (Japan); Fujino, Shigeru [Kyushu University, 744, Kishiku, Motooka, Fukuoka 819-0395 (Japan); Yoshida, Hideki [Ceramic Research Center of Nagasaki, 605-2, Hiekoba Hasami Higashisonogi, Nagasaki 859-3726 (Japan); Izumi, Nobuhiko [Lawerence Livermore National Laboratory, Livermore, California 94550 (United States); Satoh, Nakahiro; Kan, Hirofumi [Hamamatsu Photonics k.k., 1-8-3, Shinmiyakoda Kitaku, Hamamatsu 431-2103 (Japan)

2010-10-15

184

Note: Light output enhanced fast response and low afterglow 6Li glass scintillator as potential down-scattered neutron diagnostics for inertial confinement fusion.  

PubMed

The characteristics of an APLF80+3Ce scintillator are presented. Its sufficiently fast decay profile, low afterglow, and an improved light output compared to the recently developed APLF80+3Pr, were experimentally demonstrated. This scintillator material holds promise for applications in neutron imaging diagnostics at the energy regions of 0.27 MeV of DD fusion down-scattered neutron peak at the world's largest inertial confinement fusion facilities such as the National Ignition Facility and the Laser Me?gajoule. PMID:21034133

Arikawa, Yasunobu; Yamanoi, Kohei; Nagai, Takahiro; Watanabe, Kozue; Kouno, Masahiro; Sakai, Kohei; Nakazato, Tomoharu; Shimizu, Toshihiko; Cadatal, Marilou Raduban; Estacio, Elmer Surat; Sarukura, Nobuhiko; Nakai, Mitsuo; Norimatsu, Takayoshi; Azechi, Hiroshi; Murata, Takahiro; Fujino, Shigeru; Yoshida, Hideki; Izumi, Nobuhiko; Satoh, Nakahiro; Kan, Hirofumi

2010-10-01

185

Bifurcated equilibria in centrifugally confined plasma  

SciTech Connect

A bifurcation theory and associated computational model are developed to account for abrupt transitions observed recently on the Maryland Centrifugal eXperiment (MCX) [R. F. Ellis et al. Phys. Plasmas 8, 2057 (2001)], a supersonically rotating magnetized plasma that relies on centrifugal forces to prevent thermal expansion of plasma along the magnetic field. The observed transitions are from a well-confined, high-rotation state (HR-mode) to a lower-rotation, lesser-confined state (O-mode). A two-dimensional time-dependent magnetohydrodynamics code is used to simulate the dynamical equilibrium states of the MCX configuration. In addition to the expected viscous drag on the core plasma rotation, a momentum loss term is added that models the friction of plasma on the enhanced level of neutrals expected in the vicinity of the insulators at the throats of the magnetic mirror geometry. At small values of the external rotation drive, the plasma is not well-centrifugally confined and hence experiences the drag from near the insulators. Beyond a critical value of the external drive, the system makes an abrupt transition to a well-centrifugally confined state in which the plasma has pulled away from the end insulator plates; more effective centrifugal confinement lowers the plasma mass near the insulators allowing runaway increases in the rotation speed. The well-confined steady state is reached when the external drive is balanced by only the viscosity of the core plasma. A clear hysteresis phenomenon is shown.

Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

2008-12-15

186

Extreme Lagrangian acceleration in confined turbulent flow.  

PubMed

A Lagrangian study of two-dimensional turbulence for two different geometries, a periodic and a confined circular geometry, is presented to investigate the influence of solid boundaries on the Lagrangian dynamics. It is found that the Lagrangian acceleration is even more intermittent in the confined domain than in the periodic domain. The flatness of the Lagrangian acceleration as a function of the radius shows that the influence of the wall on the Lagrangian dynamics becomes negligible in the center of the domain, and it also reveals that the wall is responsible for the increased intermittency. The transition in the Lagrangian statistics between this region, not directly influenced by the walls, and a critical radius which defines a Lagrangian boundary layer is shown to be very sharp with a sudden increase of the acceleration flatness from about 5 to about 20. PMID:18518379

Kadoch, Benjamin; Bos, Wouter J T; Schneider, Kai

2008-05-08

187

Industrial Applications to the Inertial Electrostatic Confinement Configuration  

Microsoft Academic Search

Since Fransworth's observation of inertial electrostatic confinement in the 1930's several applications have been proposed and studied with fusion being the main focus. Inertial electrostatic confinement is a scheme in which ions are focused and confined by means of either an electrostatic field or a combination of electrostatic and magnetic fields to produce an effective spherical potential well. Due to

Elijah Martin; Steve Shannon; Mohamed Bourham

2009-01-01

188

Flux confinement for a class of effective Lagrangians  

NASA Astrophysics Data System (ADS)

Confinement properties recently proved in the leading logarithm model are shown to be generally truc for a wide class of effective Lagrangians. These include nonexistence of isolated quarks, confining static potential betweenqbar q pair and flux confinement within a characteristic acting as a free boundary. A new variational principle is formulated.

Yong-Shi, Wu; Zee, A.

1983-06-01

189

Geometry of thermodynamic control.  

PubMed

A deeper understanding of nonequilibrium phenomena is needed to reveal the principles governing natural and synthetic molecular machines. Recent work has shown that when a thermodynamic system is driven from equilibrium then, in the linear response regime, the space of controllable parameters has a Riemannian geometry induced by a generalized friction tensor. We exploit this geometric insight to construct closed-form expressions for minimal-dissipation protocols for a particle diffusing in a one-dimensional harmonic potential, where the spring constant, inverse temperature, and trap location are adjusted simultaneously. These optimal protocols are geodesics on the Riemannian manifold and reveal that this simple model has a surprisingly rich geometry. We test these optimal protocols via a numerical implementation of the Fokker-Planck equation and demonstrate that the friction tensor arises naturally from a first-order expansion in temporal derivatives of the control parameters, without appealing directly to linear response theory. PMID:23214570

Zulkowski, Patrick R; Sivak, David A; Crooks, Gavin E; DeWeese, Michael R

2012-10-26

190

Geometry of thermodynamic control  

NASA Astrophysics Data System (ADS)

A fundamental problem in modern thermodynamics is how a molecular-scale machine performs useful work, while operating away from thermal equilibrium without excessive dissipation. We show that when a thermodynamic system is driven from equilibrium, in the linear response regime, the space of controllable parameters has a Riemannian geometry induced by a generalized friction tensor. This metric structure controls the dissipation of finite-time transformations, and bestows optimal protocols (geodesics on the Riemannian manifold) with many useful properties. We exploit this geometric insight to construct closed-form expressions for minimal-dissipation protocols for a model system of a particle diffusing in a one-dimensional harmonic potential, where the spring constant, inverse temperature, and trap location are adjusted simultaneously. This simple model has a surprisingly rich geometry, which we test via a numerical implementation of the Fokker-Planck equation.

Sivak, David; Zulkowski, Patrick; Deweese, Michael; Crooks, Gavin

2013-03-01

191

Geometry of thermodynamic control  

NASA Astrophysics Data System (ADS)

A deeper understanding of nonequilibrium phenomena is needed to reveal the principles governing natural and synthetic molecular machines. Recent work has shown that when a thermodynamic system is driven from equilibrium then, in the linear response regime, the space of controllable parameters has a Riemannian geometry induced by a generalized friction tensor. We exploit this geometric insight to construct closed-form expressions for minimal-dissipation protocols for a particle diffusing in a one-dimensional harmonic potential, where the spring constant, inverse temperature, and trap location are adjusted simultaneously. These optimal protocols are geodesics on the Riemannian manifold and reveal that this simple model has a surprisingly rich geometry. We test these optimal protocols via a numerical implementation of the Fokker-Planck equation and demonstrate that the friction tensor arises naturally from a first-order expansion in temporal derivatives of the control parameters, without appealing directly to linear response theory.

Zulkowski, Patrick R.; Sivak, David A.; Crooks, Gavin E.; DeWeese, Michael R.

2012-10-01

192

Capillary condensation in a square geometry with surface fields  

NASA Astrophysics Data System (ADS)

We study the influence of wetting on capillary condensation for a simple fluid in a square geometry with surface fields, where the reference system is an infinitely long slit. The corner transfer matrix renormalization group method has been extended to study a two-dimensional Ising model confined in an L×L geometry with equal surface fields. Our results have confirmed that in both geometries the coexistence line shift is governed by the same scaling powers, but their prefactors are different.

Zubaszewska, M.; Gendiar, A.; Drzewi?ski, A.

2012-12-01

193

Progress in toroidal confinement and fusion research  

SciTech Connect

During the past 30 years, the characteristic T/sub i/n tau/sub E/-value of toroidal-confinement experiments has advanced by more than seven orders of magnitude. Part of this advance has been due to an increase of gross machine parameters. Most of this advance has been due to an increase of gross machine parameters. Most of the advance is associated with improvements in the ''quality of plasma confinement.'' The combined evidence of spherator and tokamak research clarifies the role of magnetic-field geometry in determining confinement and points to the importance of shielding out plasma edge effects. A true physical understanding of anomalous transport remains to be achieved. 39 refs., 11 figs., 1 tab.

Furth, H.P.

1987-10-01

194

Hydrodynamic Fluctuations in Confined Particle-Laden Fluids  

NASA Astrophysics Data System (ADS)

We address the collective dynamics of non-Brownian particles cruising in a confined microfluidic geometry and provide a comprehensive characterization of their spatiotemporal density fluctuations. We show that density excitations freely propagate at all scales, and in all directions even though the particles are neither affected by potential forces nor by inertia. We introduce a kinetic theory which quantitatively accounts for our experimental findings, demonstrating that the fluctuation spectrum of this nonequilibrium system is shaped by the combination of truly long-range hydrodynamic interactions and local collisions. We also demonstrate that the free propagation of density waves is a generic phenomenon which should be observed in a much broader range of hydrodynamic systems.

Desreumaux, Nicolas; Caussin, Jean-Baptiste; Jeanneret, Raphael; Lauga, Eric; Bartolo, Denis

2013-09-01

195

Wetting and domain-growth kinetics in confined geometries  

NASA Astrophysics Data System (ADS)

In this paper, we review the theoretical and experimental progress in understanding the controversial phase behavior of binary liquids in dense porous media. Experimental observation of metastability and hysteresis in the phase-separation behavior has led to two widely different theoretical interpretations: the random-field Ising picture and the single-pore picture. We argue that the random-field model is inapplicable to binary liquids in low-porosity media such as Vycor, and discuss the available experimental evidence on such systems. Next, we present Monte Carlo studies of phase-separation kinetics of an Ising model in a pore. We find that the domain-growth kinetics slow down dramatically once the domain size becomes comparable to the pore size, as predicted by the single-pore model. In addition, we examine the influence of temperature and interfacial phase transitions on the kinetics, and show that the domain-growth rate slows down as the temperature moves further into the two-phase region. Finally, our results for small pores, only 20 spins across, suggest that macroscopic descriptions are surprisingly successful, even at short length scales.

Monette, Liza; Liu, Andrea J.; Grest, Gary S.

1992-12-01

196

Enhancement of confinement in tokamaks  

SciTech Connect

A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime.

Furth, H.P.

1986-05-01

197

Molecular Simulations of Polymer Crystallization under Nano-Confinement  

NASA Astrophysics Data System (ADS)

Crystallization offers polymers under nano-scale-space confinement not only the stability of sizes and properties, but also the anisotropy of electrical conductivity, mechanical strength, and optical dichroism, etc. We make an overview on recent dynamic Monte Carlo simulations of lattice polymers performing crystallization under nano-confinement. The confined geometries include ultrathin films, nano-pores and nano- droplets of homopolymers, as well as lamellar,cylindrical and spherical self-assembled microdomains of diblock copolymers. The effects of nano-confinement on polymer crystallization can be summarized into three categories, i.e. the interface (both on enthalpy and entropy), the anisotropy of geometries and the block junction (both in its restriction and orientation). Such knowledge will facilitate our better understanding on the fabrication of nano-crystals of polymers.

Hu, Wenbing

2010-03-01

198

Confinement Aquaculture. Final Report.  

ERIC Educational Resources Information Center

|The Delaplaine Agriculture Department Confinement Project, begun in June 1988, conducted a confinement aquaculture program by comparing the growth of channel catfish raised in cages in a pond to channel catfish raised in cages in the Black River, Arkansas. The study developed technology that would decrease costs in the domestication of fish,…

Delaplaine School District, AR.

199

Advantages of studying the fractional quantum Hall effect in a cylindrical geometry  

NASA Astrophysics Data System (ADS)

We report results of numerical studies of the fractional quantum Hall effect in the cylindrical geometry using exact diagonalization as well as density-matrix renormalization group techniques. We provide convergence benchmarks that illustrate the advantage of the cylinder over the sphere, based on the number of sweeps and basis elements that need to be kept in order to achieve the desired accuracy for the ground state at ?=5/2 filling [1]. Further, we address several issues of interest that can be studied more directly using the cylindrical geometry. These include (i) transitions between the hierarchy of fractional quantum Hall states as a function of the confining potential; (ii) quasiparticle tunneling between the two edges of the cylinder; and (iii) generalized off-diagonal long-range order as a probe of the local geometry fluctuations in fractional quantum Hall liquids due to confinement potential or mass anisotropy.[4pt] [1] Zi-Xiang Hu, Z. Papic, S. Johri, R. N. Bhatt, Peter Schmitteckert, Phys. Lett. A 376, 2157 (2012)

Johri, Sonika; Papic, Z.; Hu, Zi-Xiang; Bhatt, R. N.; Schmitteckert, Peter

2013-03-01

200

Spectral Properties of Confined Atoms  

Microsoft Academic Search

The changes in energy and photoionization spectra of atoms upon confinement by a spherical environment are explored theoretically. Two kinds of confinement are considered: an endohedral confinement, such as inside the bucky-ball C60, and an impenetrable spherical confinement of adjustable radius. We demonstrate modifications in the energy spectrum and electron correlation effects in confined atoms, the appearance, nature and origin

V. K. Dolmatov; J. P. Connerade; A. P. Lakshmi; S. T. Manson

2002-01-01

201

Geometry in Medias Res  

ERIC Educational Resources Information Center

Geometry provides a natural window into what it is like to do mathematics. In the world of geometry, playful experimentation is often more fruitful than following a procedure, and logic plus a few axioms can open new worlds. Nonetheless, teaching a geometry course in a way that combines both rigor and play can be difficult. Many geometry courses…

Cukier, Mimi; Asdourian, Tony; Thakker, Anand

2012-01-01

202

Dynamic Geometry on WWW.  

ERIC Educational Resources Information Center

The first section of this paper on World Wide Web applications related to dynamic geometry addresses dynamic geometry and teaching, including the relationship between dynamic geometry and direct manipulation, key features of dynamic geometry environments, the importance of direct engagement of the learner using construction software for…

Kuntz, Gilles

203

Confinement and Light-Front QCD  

Microsoft Academic Search

Numerical results for the (rest-frame) $Q\\\\bar{Q}$ potential in light-front quantized $QCD_{2+1}$ on a $\\\\perp$ lattice are presented. Both in the longitudinal as well as the $\\\\perp$ spatial directions one obtains linear confinement. The confinement mechanism in light-front QCD depends on the orientation of the external charges: for longitudinally (with respect to the boost direction in the infinite momentum frame) separated

Matthias Burkardt

1996-01-01

204

Nonlinear Spectral Singularities for Confined Nonlinearities  

NASA Astrophysics Data System (ADS)

We introduce a notion of spectral singularity that applies for a general class of nonlinear Schrödinger operators involving a confined nonlinearity. The presence of the nonlinearity does not break the parity-reflection symmetry of spectral singularities but makes them amplitude dependent. Nonlinear spectral singularities are, therefore, associated with a resonance effect that produces amplified waves with a specific amplitude-wavelength profile. We explore the consequences of this phenomenon for a complex ?-function potential that is subject to a general confined nonlinearity.

Mostafazadeh, Ali

2013-06-01

205

Single string based global optimizer for geometry optimization in strongly coupled finite clusters: An adaptive mutation-driven strategy  

NASA Astrophysics Data System (ADS)

We propose and implement a simple adaptive heuristic to optimize the geometries of clusters of point charges or ions with the ability to find the global minimum energy configurations. The approach uses random mutations of a single string encoding the geometry and accepts moves that decrease the energy. Mutation probability and mutation intensity are allowed to evolve adaptively on the basis of continuous evaluation of past explorations. The resulting algorithm has been called Completely Adaptive Random Mutation Hill Climbing method. We have implemented this method to search through the complex potential energy landscapes of parabolically confined 3D classical Coulomb clusters of hundreds or thousands of charges--usually found in high frequency discharge plasmas. The energy per particle (EN/N) and its first and second differences, structural features, distribution of the oscillation frequencies of normal modes, etc., are analyzed as functions of confinement strength and the number of charges in the system. Certain magic numbers are identified. In order to test the feasibility of the algorithm in cluster geometry optimization on more complex energy landscapes, we have applied the algorithm for optimizing the geometries of MgO clusters, described by Coulomb-Born-Mayer potential and finding global minimum of some Lennard-Jones clusters. The convergence behavior of the algorithm compares favorably with those of other existing global optimizers.

Sarkar, Kanchan; Bhattacharyya, S. P.

2013-08-01

206

On confinement index  

NASA Astrophysics Data System (ADS)

The smallest integer t for which the Wilson loop Wt fails to exhibit area law is known as the confinement index of a given field theory. The confinement index provides us with subtle information on the vacuum properties of the system. We study the behavior of the Wilson and 't Hooft loops and compute the confinement index in a wide class of N=1 supersymmetric gauge theories. All possible electric and magnetic screenings are taken into account. The results found are consistent with the ? periodicity, and whenever such a check is available, with the factorization property of Seiberg-Witten curves.

Konishi, Kenichi; Ookouchi, Yutaka

2010-03-01

207

Hot electron confinement in a microwave heated spindle cusp  

SciTech Connect

The Plasma Research Laboratory at the University of Missouri-Columbia was established with awards from the McDonnel Douglas Foundation, ARMCO, Union Electric, Black and Vetch, Kansas City Power and Light, the National Science Foundation, and DOE. The Plasma Research Lab's major effort is the Missouri Magnetic Mirror (MMM or M{sup 3}) Project. The technical goals of MMM have been (1) Diagnostic Development, (2) Plasma Physics in the Cusp geometry, (3) plasma-wall interactions, (4) impurity effects in a steady-state plasma, and (5) Development of Diagnostics for use in harsh plasma processing environments. The other major goal of MMM has remained providing a facility for hands-on training in experimental plasma physics. The major experimental facility of MMM is the MMM Modified Experiment (M4X). Other research efforts in the Plasma Research Laboratory include small efforts in cold fusion, toroidal magnetic confinement, and inertial confinement and a potentially major effort in direct conversion of nuclear energy.

Prelas, M.A.

1991-08-01

208

Hot electron confinement in a microwave heated spindle cusp  

NASA Astrophysics Data System (ADS)

The Plasma Research Laboratory at the University of Missouri-Columbia was established with awards from the McDonnell Douglas Foundation, ARMCO, Union Electric, Black and Vetch, Kansas City Power and Light, the National Science Foundation, and DOE. The Plasma Research Lab's major effort is the Missouri Magnetic Mirror (MMM or M(exp 3)) Project. The technical goals of MMM have been (1) Diagnostic Development, (2) Plasma Physics in the Cusp geometry, (3) plasma-wall interactions, (4) impurity effects in a steady-state plasma, and (5) Development of Diagnostics for use in harsh plasma processing environments. The other major goal of MMM has remained providing a facility for hands-on training in experimental plasma physics. The major experimental facility of MMM is the MMM Modified Experiment (M4X). Other research efforts in the Plasma Research Laboratory include small efforts in cold fusion, toroidal magnetic confinement, and inertial confinement and a potentially major effort in direct conversion of nuclear energy.

Prelas, M. A.

1991-08-01

209

Single polymer systems under geometric confinement  

NASA Astrophysics Data System (ADS)

Confining a single polymer system leads to a competition between internal cooperativity length scales and external length scales arising from the confining geometry. This competition is relevant in the realm of polymer glasses and in the crowded environment inside cells. In this thesis, I present two different types of single polymer confinement, a single polymer confined to a tube and to a box. Both geometries lead to nontrivial changes in the static and dynamic properties of the polymer as is shown using Monte Carlo simulations. The simulations show confined polymers exhibit regimes of relaxation in their dynamics including non-monotonic time scales for dynamics in a box. In addition, equilibrium monomer-monomer correlations inside the box differ from that of the unconfined polymer. To understand the origin of these simulation results, a theory is developed using a set of Langevin equations. In general, this set of equations has no simple solution, but by assuming that non-interacting normal modes solve these equations, their Fourier transformed equivalents become linearized equations and I solve them self-consistently. The dynamical theory makes use of the equilibrium behavior of the polymer, specifically its monomer-monomer correlations functions which I extracted from blob picture arguments. I then compare the predictions of this linearized Rouse theory to the simulations results. I am not only able to extract the scaling relations, but also able to make predictions on the functional form of the dynamics and crossover time scales. The linearized Rouse theory agrees very well with the simulations of the polymer in a tube. For the polymer in a box, the theory makes good predictions for low volume fractions, but fails at high volume fractions. One approach introduced to solve this problem involves a renormalization of the friction coefficient.

Kalb, Joshua

210

Confined pyrolysis of Tertiary lacustrine source rocks in the Western Qaidam Basin, Northwest China: Implications for generative potential and oil maturity evaluation  

Microsoft Academic Search

The parameter S1+S2 (genetic potential) of Rock-Eval analysis is widely used as an evaluation of the genetic potential for the source rocks. Oligocene–Miocene saline lacustrine source rocks in the western Qaidam basin have low total organic C contents (TOC), most around 0.5% with a few exceptions >1.0%. Mineral matrix effects are substantial for source rocks with low TOC, resulting in

Changchun Pan; Min Zhang; Dehua Peng; Linping Yu; Jinzhong Liu; Guoying Sheng; Jiamo Fu

2010-01-01

211

Influence of confinement on dynamical heterogeneities in dense colloidal samples.  

PubMed

We study a dense colloidal suspension confined between two quasiparallel glass plates as a model system for a supercooled liquid in confined geometries. We directly observe the three-dimensional Brownian motion of the colloidal particles using laser scanning confocal microscopy. The particles form dense layers along the walls, but crystallization is avoided as we use a mixture of two particle sizes. A normally liquidlike sample, when confined, exhibits slower diffusive motion. Particle rearrangements are spatially heterogeneous, and the shapes of the rearranging regions are strongly influenced by the layering. These rearranging regions become more planar upon confinement. The wall-induced layers and changing character of the spatially heterogeneous dynamics appear strongly connected to the confinement-induced glassiness. PMID:22680469

Edmond, Kazem V; Nugent, Carolyn R; Weeks, Eric R

2012-04-11

212

Colloidal Interactions in a Two-Dimensional Geometry  

NASA Astrophysics Data System (ADS)

This thesis presents experimental work with two -dimensional (2D) colloidal dispersions of polystyrene spheres in water. The spheres, which are negatively charged, are confined, in a single layer, between negatively charged glass plates. This geometry is typical of 2D melting experiments. Using video microscopy techniques, we have measured the 2D radial distribution function, g(r), of the spheres as they move in the plane parallel to the plates. From measurements of g(r) for dilute dispersions, we obtain the pair potential for the spheres at different ionic concentrations. The experimentally obtained potentials show an attraction, between spheres in a 2D system, which persists even for low ionic strength dispersions. This attractive potential is longer-ranged than would be expected from the DLVO potential with the accepted values of the Hamaker constant. We also present measurements of g(r), for fixed ionic strength, as the density is varied. The pair potential is obtained from the dilute data and used in Brownian dynamics simulations. The results show that, the form of g(r), from the simulations, roughly follows the experimental data, but the details of the structure (lattice constants) do not match. The disagreement is probably due to inaccuracies in the hard repulsive part of the potential. This portion of the pair potential is difficult to obtain from the g(r) data due to the small number of counts in this region. In addition, we have used a new video microscopy technique to explore the interactions between the spheres and the confining plates. By calibrating sphere intensity to vertical motion, we are able to obtain histograms of sphere displacement perpendicular to the plates, for five different plate spacings. As expected, the results show a broadening of the distributions as the gap is increased. A comparison is made with the theoretical results of an oscillator undergoing Brownian motion.

Kepler, Grace Martinelli

213

Atomic scale mixing for inertial confinement fusion associated hydro instabilities  

NASA Astrophysics Data System (ADS)

Hydro instabilities have been identified as a potential cause of performance degradation in inertial confinement fusion (ICF) experiments. We study instabilities associated with a single Richtmyer-Meshkov (RM) interface in a circular geometry, idealized from an ICF geometry. In an ICF application, atomic level mix, as an input to nuclear burn, is an important, but difficult to compute, variable. We find numerical convergence for this important quantity, in a purely hydro study, with only a mild dependence on the Reynolds number of the flow, in the high Reynolds number limit. We also find that mixing properties show a strong sensitivity to turbulent transport parameters; this sensitivity translates into an algorithmic dependence and a nonuniqueness of solutions for nominally converged solutions. It is thus a complication to any verification and validation program. To resolve the nonuniqueness of the solution, we propose a validation program with an extrapolation component, linking turbulent transport quantities in experimental regimes to mildly perturbed turbulent transport values in ICF Reynolds number regimes. In view of the observed solution nonuniqueness, the validation program and its justification from the results presented here, has a fundamental significance.

Melvin, J.; Rao, P.; Kaufman, R.; Lim, H.; Yu, Y.; Glimm, J.; Sharp, D. H.

2013-06-01

214

Negative ions in inertial electrostatic confinement devices  

Microsoft Academic Search

The UW-Inertial Electrostatic Confinement (IEC) device is comprised of concentric, nearly transparent, spherical metallic grids within a cylindrical vacuum vessel. The central grid, which can be held at high negative potentials (~ -100 to -200 kV) is the device cathode, while the outer grid, held at ground potential, is the device anode. This configuration accelerates ions, created near the anode,

D. R. Boris; J. F. Santarius; G. L. Kulcinski

2009-01-01

215

Simulations of Knotting in Confined Circular DNA  

PubMed Central

The packing of DNA inside bacteriophages arguably yields the simplest example of genome organization in living organisms. As an assay of packing geometry, the DNA knot spectrum produced upon release of viral DNA from the P4 phage capsid has been analyzed, and compared to results of simulation of knots in confined volumes. We present new results from extensive stochastic sampling of confined self-avoiding and semiflexible circular chains with volume exclusion. The physical parameters of the chains (contour length, cross section, and bending rigidity) have been set to match those of P4 bacteriophage DNA. By using advanced sampling techniques, involving multiple Markov chain pressure-driven confinement combined with a thermodynamic reweighting technique, we establish the knot spectrum of the circular chains for increasing confinement up to the highest densities for which available algorithms can exactly classify the knots. Compactified configurations have an enclosing hull diameter ?2.5 times larger than the P4 caliper size. The results are discussed in relation to the recent experiments on DNA knotting inside the capsid of a P4 tailless mutant. Our investigation indicates that confinement favors chiral knots over achiral ones, as found in the experiments. However, no significant bias of torus over twist knots is found, contrary to the P4 results. The result poses a crucial question for future studies of DNA packaging in P4: is the discrepancy due to the insufficient confinement of the equilibrium simulation or does it indicate that out-of-equilibrium mechanisms (such as rotation by packaging motors) affect the genome organization, hence its knot spectrum in P4?

Micheletti, C.; Marenduzzo, D.; Orlandini, E.; Sumners, D. W.

2008-01-01

216

Potential function of simplified protein models for discriminating native proteins from decoys: combining contact interaction and local sequence-dependent geometry  

Microsoft Academic Search

An effective potential function is critical for protein structure prediction and folding simulation. For simplified models of proteins where coordinates of only Ca atoms need to be specified, an accurate potential function is important. Such a simplified model is essential for efficient search of conformational space. In this work, we present a formulation of potential function for simplified representations of

Jinfeng Zhang; Rong Chen; Jie Liang

2004-01-01

217

Polymer Statics and Dynamics Under Box Confinement  

NASA Astrophysics Data System (ADS)

Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. We are concerned with whether or not there is a critical length scale for a confined polymer system. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain confined to a box by measuring dynamical quantities such as the end-to-end vector and single monomer positions (JACS 124, 20 (2004)). A primary question is how spatial correlations between monomers, `blob's, influence the dynamics. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.

Kalb, Joshua; Chakraborty, Bulbul

2007-03-01

218

Compact inertial confinement multireactor concepts  

SciTech Connect

Inertial confinement fusion (ICF) commercial-applications plant-optimum driver pulse repetition rates may exceed reactor pulse-repetition-rate capabilities. Thus, more than one reactor may be required for low-cost production of electric power, process heat, fissionable fuels, etc., in ICF plants. Substantial savings in expensive reactor containment cells and blankets can be realized by placing more than one reactor in a cell and by surrounding more than one reactor cavity with a single blanket system. There are also some potential disadvantages associated with close coupling in compact multicavity blankets and multireactor cells. Tradeoffs associated with several scenarios have been studied.

Pendergrass, J.H.

1985-01-01

219

Critical dynamics in confined systems with quenched random impurities  

Microsoft Academic Search

We study the critical dynamics of a system confined to a hypercubic geometry with periodic boundary conditions in the presence of quenched short-range correlated impurities. By using the random Tc model with purely relaxational dynamics (model A) and the renormalization group method in the vicinity of the upper critical dimension du=4 , we derive to first order in gamma=4-d the

H. Chamati; E. Korutcheva

2008-01-01

220

Geometry Formulas and Facts  

NSDL National Science Digital Library

Rewritten and updated excerpts from the 30th Edition of the CRC Standard Mathematical Tables and Formulas. Covers all of geometry, minus differential geometry. Very complete collection of definitions, formulas, tables and diagrams, divided into two- and three- dimensional geometry, and further into 16 subdivisions such as transformations, polygons, coordinate systems, isometries, polyhedra and spheres.

Levy, Silvio

2007-12-07

221

Formation of DNA toroids inside confined droplets adsorbed on mica surfaces  

Microsoft Academic Search

We report observations of in vitro DNA compaction into toroids in the absence of any condensing agent. The DNA toroid formation is induced by geometry confinement from microdroplets on mica surfaces. With AFM imaging we show that the confined DNA molecules may take the form of random coils or semiordered folded loops with large microdroplets, while they readily take the

Xi-Miao Hou; Wei Li; Shuo-Xing Dou; Ling-Yun Zhang; Ping Xie; Wei-Chi Wang; Peng-Ye Wang

2009-01-01

222

Experimental study on hydraulic fracturing of soft rocks: Influence of fluid rheology and confining stress  

Microsoft Academic Search

This paper presents an experimental study on hydraulic fracturing of unconsolidated rocks focusing on mechanisms of fracture initiation and propagation using different injection fluids at various confining stresses. Thus, a serial of parameter study including confining stress, type of injection fluid and geometry of injection section was carried out to explore the dependency of fracturing on these variables. Results showed

B. Bohloli; C. J. de Pater

2006-01-01

223

Microscopic mechanisms of confinement-induced slow solvation.  

PubMed

Several studies show that the dynamics of solvent molecules around a solute slows down in a nanoscale confined geometry compared to the bulk condition. Here we perform numerical simulations to investigate the microscopic mechanisms of such slowing down. We show a substantial slowing down of solvation dynamics around a solute in strong solvophilic confinements due to suppression of fluid diffusion in the presence of solvophilic walls, along with restricted solvent dynamics due to geometrical constraints. The solvation in strong solvophobic confinements becomes slower than the same in the bulk as well, but not as significantly as in the solvophilic case. This is due to the competition between restriction in solvent dynamics and faster in-plane solvent diffusion. We place our findings in perspective of various solvation dominated chemical processes in nanoconfined geometry. PMID:24053723

Das, Amit; Chakrabarti, J

2013-10-03

224

Lattice QCD Study for Confinement in Hadrons  

SciTech Connect

We study three subjects on quark confinement in hadrons in SU(3)c lattice QCD. From the accurate lattice calculation for more than 300 different patterns of three-quark (3Q) systems, we find that the static 3Q potential is well described by Y-Ansatz, i.e., the Coulomb plus Y-type linear potential. We also study the multi-quark (4Q, 5Q) potentials in lattice QCD, and find that they are well described by the one-gluon-exchange (OGE) Coulomb plus string-theoretical linear potential, which supports the infrared string picture even for the multi-quarks. The second subject is a lattice-QCD determination of the relevant gluonic momentum component for confinement. The string tension (confining force) is found to be almost unchanged even after cutting off the high-momentum gluon component above 1.5GeV in the Landau gauge. In fact, quark confinement originates from the low-momentum gluon below about 1.5GeV. Finally, we consider a possible gauge of QCD for the quark potential model, by investigating 'instantaneous inter-quark potential' in generalized Landau gauge, which describes a continuous change from the Landau gauge to the Coulomb gauge.

Suganuma, H.; Iritani, T.; Yamamoto, A. [Department of Physics, Kyoto University, Kitashirakawaoiwake, Sakyo, Kyoto 606-8502 (Japan); Okiharu, F. [Faculty of Education, Niigata University, Ikarashi 2-8050, Niigata 950-2181 (Japan); Takahashi, T. T. [Gunma National College of Technology, Maebashi, Gunma 371-8530 (Japan)

2011-10-21

225

Lattice QCD Study for Confinement in Hadrons  

NASA Astrophysics Data System (ADS)

We study three subjects on quark confinement in hadrons in SU(3)c lattice QCD. From the accurate lattice calculation for more than 300 different patterns of three-quark (3Q) systems, we find that the static 3Q potential is well described by Y-Ansatz, i.e., the Coulomb plus Y-type linear potential. We also study the multi-quark (4Q, 5Q) potentials in lattice QCD, and find that they are well described by the one-gluon-exchange (OGE) Coulomb plus string-theoretical linear potential, which supports the infrared string picture even for the multi-quarks. The second subject is a lattice-QCD determination of the relevant gluonic momentum component for confinement. The string tension (confining force) is found to be almost unchanged even after cutting off the high-momentum gluon component above 1.5GeV in the Landau gauge. In fact, quark confinement originates from the low-momentum gluon below about 1.5GeV. Finally, we consider a possible gauge of QCD for the quark potential model, by investigating ``instantaneous inter-quark potential'' in generalized Landau gauge, which describes a continuous change from the Landau gauge to the Coulomb gauge.

Suganuma, H.; Iritani, T.; Okiharu, F.; Takahashi, T. T.; Yamamoto, A.

2011-10-01

226

Anomalous diffusion in confined turbulent convection.  

PubMed

Turbulent convection in quasi-one-dimensional geometry is studied by means of high-resolution direct numerical simulations within the framework of Rayleigh-Taylor turbulence. Geometrical confinement has dramatic effects on the dynamics of the turbulent flow, inducing a transition from superdiffusive to subdiffusive evolution of the mixing layer and arresting the growth of kinetic energy. A nonlinear diffusion model is shown to reproduce accurately the above phenomenology. The model is used to predict, without free parameters, the spatiotemporal evolution of the heat flux profile and the dependence of the Nusselt number on the Rayleigh number. PMID:23005221

Boffetta, G; De Lillo, F; Musacchio, S

2012-06-27

227

Non-extremal geometries and holographic phase transitions  

NASA Astrophysics Data System (ADS)

Using the low energy limit of type IIB superstring theory, we obtain the non-extremal limit of deformed conifold geometry which is dual to the IR limit of large N thermal QCD. At low temperatures, the extremal geometry without black hole is favored while at high temperatures, the field theory is described by non-extremal black hole geometry. We compute the ten dimensional on shell action for extremal and non-extremal geometries and demonstrate that at a critical temperature T c there is a first order confinement to deconfinement phase transition. We compute T c as a function of 'tHooft coupling and study the thermodynamics of the dual gauge theory by evaluating the free energy and entropy of the ten dimensional geometry. We find agreement with the conformal limit while thermodynamics of non-conformal strongly coupled gauge theories is explored using the black hole geometries in non-AdS space.

Mia, Mohammed; Chen, Fang

2013-01-01

228

The entropic cost of polymer confinement.  

PubMed

The confinement of a polymer into a small space is thermodynamically unfavorable because of the reduction in the number of conformational states. The entropic penalty affects a variety of biological processes, and it plays an important role in polymer transport properties and in microfluidic devices. We determine the entropic penalty for the confinement of elastic polymer of persistence length P in the long-chain limit. We examine three geometries: (1) parallel planes separated by a distance d (a slit); (2) a circular tube of diameter d; and (3) a sphere of diameter d. We first consider infinitely thin (ideal) chains. As d/P drops from 100 to 0.01, T?S rises from ?5 × 10(-4) kT to ?30 kT per persistence length for cases (1) and (2), with the entropic penalty for case (2) being consistently about twice that for case (1). T?S is ?5 kT per persistence length for confinement to a sphere when d = P, about twice the value predicted by mean field theory. For all three geometries, in the limit d/P ? 1, the asymptotic behavior of ?S vs d is consistent with the d(-2) behavior predicted by theory. In the limit d/P ? 1, the scaling of ?S for slits and tubes is also consistent with earlier predictions (d(-2/3)). Finally, we treat volume exclusion effects, examining chains of diameter D > 0. Confinement to a narrow slit or tube (d/P ? 1) has the same entropic penalty as that for an ideal chain in a slit or tube with d' = d - D; in the weak confinement regime (d/P ? 1), the entropic penalties are significantly larger than those for infinitely thin chains. When a chain of finite diameter is forced into a sphere or other closed cavity, the entropic confinement penalty rises without limit because there are no configurations available to the chain once its volume exceeds that of the cavity. PMID:22905742

Smyda, Mark R; Harvey, Stephen C

2012-08-27

229

Studies in confined biopolymers  

Microsoft Academic Search

In this work we analyze the theoretical aspects of a single polymer confined inside a cavity. The problem is of biological relevance since it is known, for instance, that molecules like proteins need an isolated environment in order to quickly and correctly reach their folded native state. The polymer is considered in the Grand Canonical ensemble of its monomeric units,

Samuela Pasquali

2005-01-01

230

Totally Confined Explosive Welding.  

National Technical Information Service (NTIS)

A method and associated apparatus for confining the undesirable by-products and limiting noise of explosive welding are discussed. The apparatus consists fo a simple enclosure into which the explosive is placed and within which the explosion occurs. The s...

L. J. Bement

1974-01-01

231

Large eddy simulations of confined turbulent wake flows  

NASA Astrophysics Data System (ADS)

The influence of confinement on turbulent obstacle-free wake is numerically investigated by means of large eddy simulations (LES). The numerical solver makes use of a multi-domain Fourier-Chebyshev spectral method and the LES capability is implemented through a spectral vanishing viscosity technique. The geometry is channel like and the transverse direction is homogeneous. A top hat like velocity profile is assumed at the inlet and no slip conditions are considered at the confining walls. Prescribing the velocity ratio, defined as the ratio of the velocity gap to the mean velocity, we study the influence of confinement on such flows at the Reynolds number Re = 5000. Several quantities are analyzed, as one-dimensional velocity spectra, third-order structure function, turbulent kinetic energy and its dissipation rate. It turns out that for obstacle-free wakes confinement increases the intensity of turbulence and its three-dimensional feature.

Biancofiore, Luca; Gallaire, François; Pasquetti, Richard

2011-12-01

232

Electrofreezing of confined water.  

PubMed

We report results from molecular dynamics simulations of the freezing transition of TIP5P water molecules confined between two parallel plates under the influence of a homogeneous external electric field, with magnitude of 5 V/nm, along the lateral direction. For water confined to a thickness of a trilayer we find two different phases of ice at a temperature of T=280 K. The transformation between the two, proton-ordered, ice phases is found to be a strong first-order transition. The low-density ice phase is built from hexagonal rings parallel to the confining walls and corresponds to the structure of cubic ice. The high-density ice phase has an in-plane rhombic symmetry of the oxygen atoms and larger distortion of hydrogen bond angles. The short-range order of the two ice phases is the same as the local structure of the two bilayer phases of liquid water found recently in the absence of an electric field [J. Chem. Phys. 119, 1694 (2003)]. These high- and low-density phases of water differ in local ordering at the level of the second shell of nearest neighbors. The results reported in this paper, show a close similarity between the local structure of the liquid phase and the short-range order of the corresponding solid phase. This similarity might be enhanced in water due to the deep attractive well characterizing hydrogen bond interactions. We also investigate the low-density ice phase confined to a thickness of 4, 5, and 8 molecular layers under the influence of an electric field at T=300 K. In general, we find that the degree of ordering decreases as the distance between the two confining walls increases. PMID:15267616

Zangi, Ronen; Mark, Alan E

2004-04-15

233

Spectral Properties of Confined Atoms  

NASA Astrophysics Data System (ADS)

The changes in energy and photoionization spectra of atoms upon confinement by a spherical environment are explored theoretically. Two kinds of confinement are considered: an endohedral confinement, such as inside the bucky-ball C60, and an impenetrable spherical confinement of adjustable radius. We demonstrate modifications in the energy spectrum and electron correlation effects in confined atoms, the appearance, nature and origin of ``confinement'' resonances in photoionization spectra of such atoms, as well as new regularities in the periodic table for ``compressed'' atoms. These findings are of importance for basic and applied physics and chemistry of atoms, molecules, surfaces, etc.

Dolmatov, V. K.; Connerade, J. P.; Lakshmi, A. P.; Manson, S. T.

234

Z-Pinch Generated X-Rays in Static-Wall Hohlraum Geometry Demonstrate Potential for Indirect-Drive ICF Studies  

SciTech Connect

Hohlraums of full ignition scale (6-mm diameter by 7-mm length) have been heated by x-rays from a z-pinch target on Z to a variety of temperatures and pulse shapes which can be used to simulate the early phases of the National Ignition Facility (NIF) temperature drive. The pulse shape is varied by changing the on-axis target of the z pinch in a static-wall-hohlraum geometry. A 2-{micro}m-thick walled Cu cylindrical target of 8-mm diameter filled with 10 mg/cm{sup 3} CH, for example, produces foot-pulse conditions of {minus}85 eV for a duration of {approximately} 10 ns, while a solid cylindrical target of 5-mm diameter and 14-mg/cm{sup 3} CH generates first-step-pulse conditions of {approximately} 122 eV for a duration of a few ns. Alternatively, reducing the hohlraum size (to 4-mm diameter by 4-mm length) with the latter target has increased the peak temperature to {approximately} 150 eV, which is characteristic of a second-step-pulse temperature. In general, the temperature T of these x-ray driven hohlraums is in agreement with the Planckian relation (T-(P/A){sup 1/4}). P is the measured x-ray input power and A is the surface area of the hohlraum. Fully-integrated 2-D radiation-hydrodynamic simulations of the z pinch and subsequent hohlraum heating show plasma densities within the useful volume of the hohlraums to be on the order of air or less.

Sandord, T.W.L.; Olson, R.E.; Chandler, G.A.; Hebron, D.E.; Mock, R.C.; Leeper, R.J.; Nash, T.J.; Ruggles, L.E.; Simpson, W.W.; Struve, K.W.; Vesey, R.A.; Bowers, R.L.; Matuska, W.; Peterson, D.L.; Peterson, R.R.

1999-08-25

235

Z-Pinch Generated X-Rays in Static-Wall Hohlraum Geometry Demonstrate Potential for Indirect-Drive ICF Studies  

SciTech Connect

Hohlraums of full ignition scale (6-mm diameter by 7-mm length) have been heated by x-rays from a z-pinch magnet on Z to a variety of temperatures and pulse shapes which can be used to simulate the early phases of the National Ignition Facility (NIF) temperature drive. The pulse shape is varied by changing the on-axis target of the z pinch in a static-wall-hohlraum geometry. A 2-{micro}m-thick walled Cu cylindrical target of 8-mm diameter filled with 10 mg/cm{sup 3} CH, for example, produces foot-pulse conditions of {approx}85 eV for a duration of {approx}10 ns, while a solid cylindrical target of 5-mm diameter and 14-mg/cm{sup 3} CH generates first-step-pulse conditions of {approx}122 eV for a duration of a few ns. Alternatively, reducing the hohlraum size (to 4-mm diameter by 4-mm length) with the latter target has increased the peak temperature to {approx}150 eV, which is characteristic of a second-step-pulse temperature. In general, the temperature T of these x-ray driven hohlraums is in agreement with the Planckian relation T{approx}(P/A){sup 1/4}. P is the measured x-ray input power and A is the surface area of the hohlraum. Fully-integrated 2-D radiation-hydrodynamic simulations of the z pinch and subsequent hohlraum heating show plasma densities within the useful volume of the hohlraums to be on the order of air or less.

BOWERS,RICHARD; CHANDLER,GORDON A.; HEBRON,DAVID E.; LEEPER,RAMON J.; MATUSLKA,WALTER; MOCK,RAYMOND CECIL; NASH,THOMAS J.; OLSON,CRAIG L.; PETERSON,BOB; PETERSON,DARRELL; RUGGLES,LAURENCE E.; SANFORD,THOMAS W. L.; SIMPSON,WALTER W.; STRUVE,KENNETH W.; VESEY,ROGER A.

1999-11-01

236

Beam optics in inertial electrostatic confinement fusion  

Microsoft Academic Search

We study the transport of ions and electrons near the cathode of the inertial electrostatic confinement fusion that is expected to be a portable neutron source. We carry out a PIC particle simulation in order to obtain the self-consistent electrostatic potential and the transparency of the cathode for the accelerated ions. The transparency is shown to be much less than

Masami Ohnishi; Chikara Hoshino; Kiyoshi Yoshikawa; Kai Masuda; Yasushi Yamamoto

2000-01-01

237

Symmetries in confined classical Coulomb systems  

NASA Astrophysics Data System (ADS)

The properties of charged particles confined in a harmonic oscillator potential have become of increased interest lately in view of the development of techniques in ion traps and storage rings. The symmetries in such systems intrigued the imagination of Ted Hecht in connection with the storage ring at Heidelberg, and so perhaps it is an appropriate subject for this symposium.

Schiffer, J. P.

238

Symmetries in confined classical Coulomb systems  

SciTech Connect

The properties of charged particles confined in a harmonic oscillator potential have become of increased interest lately in view of the development of techniques in ion traps and storage rings. The symmetries in such systems intrigued the imagination of Ted Hecht in connection with the storage ring at Heidelberg, and so perhaps it is an appropriate subject for this symposium.

Schiffer, J.P.

1991-01-01

239

Confined Crystals on Substrates: Order and Fluctuations in Between One and Two Dimensions  

NASA Astrophysics Data System (ADS)

The effect of lateral confinement on a crystal of point particles in d = 2 dimensions in a strip geometry is studied by Monte Carlo simulations and using phenomenological theoretical concepts. Physically, such systems confined in long strips of width D can be realized via colloidal particles at the air-water interface, or by adsorbed monolayers at suitably nanopatterned substrates, etc. As a generic model, we choose a repulsive interparticle potential decaying with the twelfth inverse power of distance. This system has been well studied in the bulk as a model for two-dimensional melting. The state of the system is found to depend very sensitively on the boundary conditions providing the confinement. For corrugated boundaries commensurate with the order of the bulk (i.e., a triangular crystalline lattice structure), both orientational and positional orders are enhanced, and near the boundaries surface-induced order persists also at temperatures where the system is fluid in the bulk. For incommensurate corrugated boundaries, however, soliton staircases near the boundaries form, causing a pattern of standing strain waves in the strip. However, smooth unstructured repulsive boundaries enhance orientational order only, positional long-range order is destroyed. The strip then exhibits a vanishing shear modulus. A comparison with surface effects on phase transitions in simple Ising and XY-models is also made. Finally, possible applications are discussed.

Binder, K.; Chui, Y. H.; Nielaba, P.; Ricci, A.; Sengupta, S.

240

Effect of confinement on reaction rates within polymer nanotemplates  

NASA Astrophysics Data System (ADS)

The most efficient catalysts have been developed and optimized by living systems. Indeed, in vivo enzyme-catalyzed reactions are several orders of magnitude more efficient than platinum based catalyzed reactions. However, the rate of reaction and equilibrium interactions are considerably reduced when the biological systems are studied in vitro. This phenomenon is largely attributed to the effect of confinement or macromolecular crowding present in the cell. Confinement can also be observed in an aqueous solution containing surfactants (amphiphilic copolymers). For example, copolymers can self-assemble into well defined ordered structures such as micelles, nanotubes, vesicles; and the geometries and shapes of a given copolymer can be controlled by their solvent affinity. The hollow nanoarchitectures obtained by self-assembly can be used as a model template to study confinement within a soft shell system to mimic biosystems. These systems provide a very controlled environment for the study of confinement. In this paper we will present the effect of confinement on polymerisation reactions combining both simulation and experimental characterisation for a comprehensive study of the effect of confinement on the interactions among confined molecules.

Malardier-Jugroot, Cecile; Li, Xia

2012-02-01

241

Influence of short range potential on field induced chain aggregation in low density dipolar particles  

NASA Astrophysics Data System (ADS)

We investigate, by Monte Carlo simulation, the effect of the steepness of the short range repulsive potential on mesostructure formation in dipolar particles submitted to a strong external field. Columnar clusters made of several dipolar chains are only observed when the short-range potential is sufficiently steep. The confinement of the dipolar liquid in a slit geometry instead of bulk conditions suppresses the formation of columns.

Richardi, J.; Weis, J.-J.

2013-06-01

242

Phenomenology and Theory of Confinement.  

National Technical Information Service (NTIS)

Phenomenological and theoretical arguments of the separation of the hadronization dynamics from confinement and the idea of the ''kinematic'' confinement are discussed. The recent theory contains results which point out that the Wilson criterion and the c...

V. N. Pervushin

1987-01-01

243

Inertial Electrostatic Confinement (IEC) devices.  

National Technical Information Service (NTIS)

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination...

R. A. Nebel L. Turner T. N. Tiouririne D. C. Barnes W. D. Nystrom

1994-01-01

244

Topology and Geometry Software  

NSDL National Science Digital Library

The Topology and Geometry Software site provides downloads for games and interactive simulations. These help the user to understand finitely infinite systems. Many are available in multiple languages.

Weeks, Jeff

2009-06-15

245

Molecular reactivity dynamics in a confined environment.  

PubMed

Time evolution of various reactivity parameters viz. hardness, electrophilicity, chemical potential, polarizability, etc. in a confined environment has been studied through quantum fluid density functional theory formalism during time dependent processes such as proton-molecule collisions and molecule-field interaction. A Dirichlet type boundary condition has been incorporated to confine the systems. Responses in the reactivity parameters of the diatomic molecules, in the dynamical context, in ground state as well as in excited state, have been reported. Harmonic spectra are generated in the cases of the external laser field interacting with H2 and N2 molecules. PMID:23471169

Khatua, Munmun; Chattaraj, Pratim Kumar

2013-04-21

246

Electrokinetic confinement of axonal growth for dynamically configurable neural networks.  

PubMed

Axons in the developing nervous system are directed via guidance cues, whose expression varies both spatially and temporally, to create functional neural circuits. Existing methods to create patterns of neural connectivity in vitro use only static geometries, and are unable to dynamically alter the guidance cues imparted on the cells. We introduce the use of AC electrokinetics to dynamically control axonal growth in cultured rat hippocampal neurons. We find that the application of modest voltages at frequencies on the order of 10(5) Hz can cause developing axons to be stopped adjacent to the electrodes while axons away from the electric fields exhibit uninhibited growth. By switching electrodes on or off, we can reversibly inhibit or permit axon passage across the electrodes. Our models suggest that dielectrophoresis is the causative AC electrokinetic effect. We make use of our dynamic control over axon elongation to create an axon-diode via an axon-lock system that consists of a pair of electrode 'gates' that either permit or prevent axons from passing through. Finally, we developed a neural circuit consisting of three populations of neurons, separated by three axon-locks to demonstrate the assembly of a functional, engineered neural network. Action potential recordings demonstrate that the AC electrokinetic effect does not harm axons, and Ca(2+) imaging demonstrated the unidirectional nature of the synaptic connections. AC electrokinetic confinement of axonal growth has potential for creating configurable, directional neural networks. PMID:23314575

Honegger, Thibault; Scott, Mark A; Yanik, Mehmet F; Voldman, Joel

2013-02-21

247

Confined Vortex Scrubber  

SciTech Connect

The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards. This is to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber. This is the first quarterly technical progress report under this contract. Accordingly, a summary of the cleanup concept and the structure of the program is given here.

Not Available

1990-02-01

248

Topological confinement and superconductivity  

SciTech Connect

We derive a Kondo Lattice model with a correlated conduction band from a two-band Hubbard Hamiltonian. This mapping allows us to describe the emergence of a robust pairing mechanism in a model that only contains repulsive interactions. The mechanism is due to topological confinement and results from the interplay between antiferromagnetism and delocalization. By using Density-Matrix-Renormalization-Group (DMRG) we demonstrate that this mechanism leads to dominant superconducting correlations in aID-system.

Al-hassanieh, Dhaled A [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory

2008-01-01

249

Innovative confinement concepts workshop  

SciTech Connect

The Innovative Confinement Concepts Workshop occurred in California during the week preceding the Second Symposium on Current Trends in International Fusion Research. An informal report was made to the Second Symposium. A summary of the Workshop concluded that some very promising ideas were presented, that innovative concept development is a central element of the restructured US DOE. Fusion Energy Sciences program, and that the Workshop should promote real scientific progress in fusion.

Kirkpatrick, R.C.

1998-06-01

250

Interactive Geometry Dictionary: Areas in Geometry  

NSDL National Science Digital Library

The applets in this Interactive Geometry Dictionary (IGD) will allow students an opportunity to explore finding the area of some common shapes. The applets demonstrate how to find the area of a triangle using the area of a parallelogram, which in turn can be found using the area of a rectangle. This tool also supports the lesson "What's My Area" cataloged separately.

2011-01-01

251

Geometry Here, Geometry There, Geomerty is EVERYWHERE!  

NSDL National Science Digital Library

See if you know your geometry by using coordinate planes! GAME 1 Space Boy To The Rescue! See if you can fly through space using coordinate pairs if you dare! Directions: Double click on the space astronaut on the right hand side of the screen. Your astronaut should ...

Tiller, Miss

2012-02-05

252

Confined vortex scrubber  

SciTech Connect

The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards. This is to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber (CVS). The CVS consists of a cylindrical vortex chamber with tangential flue gas inlets. The clean gas exit is via tangent slots in a central tube. Liquid is introduced into the chamber and is confined with the vortex chamber by the centrifugal force generated by the gas flow itself. This confined liquid forms a layer through which the flue gas is then forced to bubble, producing a strong gas/liquid interaction, high inertial separation forces and efficient particulate cleanup. In effect, each of the sub-millimeter diameter gas bubbles in the liquid layer acts as a micro-cyclone, inertially separating particles into the surrounding liquid. The CVS thus obtains efficient particle removal by forcing intimate and vigorous interaction between the particle laden flue gas and the liquid scrubbing medium.

Not Available

1990-05-01

253

Simulating tumor growth in confined heterogeneous environments  

NASA Astrophysics Data System (ADS)

The holy grail of computational tumor modeling is to develop a simulation tool that can be utilized in the clinic to predict neoplastic progression and propose individualized optimal treatment strategies. In order to develop such a predictive model, one must account for many of the complex processes involved in tumor growth. One interaction that has not been incorporated into computational models of neoplastic progression is the impact that organ-imposed physical confinement and heterogeneity have on tumor growth. For this reason, we have taken a cellular automaton algorithm that was originally designed to simulate spherically symmetric tumor growth and generalized the algorithm to incorporate the effects of tissue shape and structure. We show that models that do not account for organ/tissue geometry and topology lead to false conclusions about tumor spread, shape and size. The impact that confinement has on tumor growth is more pronounced when a neoplasm is growing close to, versus far from, the confining boundary. Thus, any clinical simulation tool of cancer progression must not only consider the shape and structure of the organ in which a tumor is growing, but must also consider the location of the tumor within the organ if it is to accurately predict neoplastic growth dynamics.

Gevertz, Jana L.; Gillies, George T.; Torquato, Salvatore

2008-09-01

254

The Properties of Confined Water and Fluid Flow at the Nanoscale  

SciTech Connect

This project has been focused on the development of accurate computational tools to study fluids in confined, nanoscale geometries, and the application of these techniques to probe the structural and electronic properties of water confined between hydrophilic and hydrophobic substrates, including the presence of simple ions at the interfaces. In particular, we have used a series of ab-initio molecular dynamics simulations and quantum Monte Carlo calculations to build an understanding of how hydrogen bonding and solvation are modified at the nanoscale. The properties of confined water affect a wide range of scientific and technological problems - including protein folding, cell-membrane flow, materials properties in confined media and nanofluidic devices.

Schwegler, E; Reed, J; Lau, E; Prendergast, D; Galli, G; Grossman, J C; Cicero, G

2009-03-09

255

Three-dimensional subwavelength confinement of terahertz electromagnetic surface modes in a coupled slit structure.  

PubMed

We report on the three-dimensional subwavelength confinement of the electromagnetic waves at a coupled metallic slit structure beyond diffraction limit in terahertz region. Lateral confinement behavior, leading to the three-dimensional confinement, is caused by a strong funneling effect of the light which occurs at the intersection of slits with a sharp metal geometry. Tunability of the resonant frequency and the position of the light confinement is achieved by controlling the slit length and the position of the intersection of slits, respectively. PMID:21997030

Yang, Jin-Kyu; Kee, Chul-Sik; Lee, Joong Wook

2011-10-10

256

The virtual geometry model  

Microsoft Academic Search

The Virtual Geometry Model (VGM) was introduced at CHEP in 2004 [1], where its concept, based on the abstract interfaces to geometry objects, has been presented. Since then, it has undergone a design evolution to pure abstract interfaces, it has been consolidated and completed with more advanced features. Currently it is used in Geant4 VMC for the support of TGeo

I. Hrivnácová; B. Viren

2008-01-01

257

Introduction to combinatorial geometry  

Microsoft Academic Search

The combinatorial geometry package as used in many three-dimensional multimedia Monte Carlo radiation transport codes, such as HETC, MORSE, and EGS, is becoming the preferred way to describe simple and complicated systems. Just about any system can be modeled using the package with relatively few input statements. This can be contrasted against the older style geometry packages in which the

T. A. Gabriel; M. B. Emmett

1985-01-01

258

Geometry + Technology = Proof  

ERIC Educational Resources Information Center

|Several interactive geometry software packages are available today to secondary school teachers. An example is The Geometer's Sketchpad[R] (GSP), also known as Dynamic Geometry[R] software, developed by Key Curriculum Press. This numeric based technology has been widely adopted in the last twenty years, and a vast amount of creativity has been…

Lyublinskaya, Irina; Funsch, Dan

2012-01-01

259

Geometry + Technology = Proof  

ERIC Educational Resources Information Center

Several interactive geometry software packages are available today to secondary school teachers. An example is The Geometer's Sketchpad[R] (GSP), also known as Dynamic Geometry[R] software, developed by Key Curriculum Press. This numeric based technology has been widely adopted in the last twenty years, and a vast amount of creativity has been…

Lyublinskaya, Irina; Funsch, Dan

2012-01-01

260

Geometry of multihadron production  

SciTech Connect

This summary talk only reviews a small sample of topics featured at this symposium: Introduction; The Geometry and Geography of Phase space; Space-Time Geometry and HBT; Multiplicities, Intermittency, Correlations; Disoriented Chiral Condensate; Deep Inelastic Scattering at HERA; and Other Contributions.

Bjorken, J.D.

1994-10-01

261

Euclidean Geometry via Programming.  

ERIC Educational Resources Information Center

Describes the Plane Geometry System computer software developed at the Educational Computer Systems laboratory in Sofia, Bulgaria. The system enables students to use the concept of "algorithm" to correspond to the process of "deductive proof" in the development of plane geometry. Provides an example of the software's capability and compares it to…

Filimonov, Rossen; Kreith, Kurt

1992-01-01

262

Confinement Induced Splay-to-Bend Transition of Colloidal Rods  

NASA Astrophysics Data System (ADS)

We study the nematic phase of rodlike fd-virus particles confined to channels with wedge-structured walls. Using laser scanning confocal microscopy we observe a splay-to-bend transition at the single particle level as a function of the wedge opening angle. Lattice Boltzmann simulations reveal the underlying origin of the transition and its dependence on nematic elasticity and wedge geometry. Our combined work provides a simple method to estimate the splay-to-bend elasticity ratios of the virus and offers a way to control the position of defects through the confining boundary conditions.

Dammone, Oliver J.; Zacharoudiou, Ioannis; Dullens, Roel P. A.; Yeomans, Julia M.; Lettinga, M. P.; Aarts, Dirk G. A. L.

2012-09-01

263

Radial distribution function for semiflexible polymers confined in microchannels  

NASA Astrophysics Data System (ADS)

An analytic expression is derived for the distribution G(vec R) of the end-to-end distance vec R of semiflexible polymers in external potentials to elucidate the effect of confinement on the mechanical and statistical properties of biomolecules. For parabolic confinement the result is exact, whereas for realistic potentials a self-consistent ansatz is applied, so that G(vec R) is given explicitly even for hard-wall confinement. The theoretical result is in good quantitative agreement with fluorescence microscopy data for actin filaments confined in rectangularly shaped microchannels. This allows an unambiguous determination of persistence length LP and the dependence of statistical properties such as Odijk's deflection length ? on the channel width D. It is shown that neglecting the effect of confinement leads to a significant overestimation of bending rigidities for filaments.

Levi, P.; Mecke, K.

2007-05-01

264

Self-organization of particles and nanofluids under confinements: Applications to spreading, wetting and soil removal  

NASA Astrophysics Data System (ADS)

We studied the self-organization of different-sized particles in different confined geometries. The structure formations of millimeter-sized granules confined to a solid substrate, micrometer-sized colloidal particles confined to a fluid-liquid interface, and nanometer-sized particles confined in the wedge film are discussed. We spread the steel particles (diameter: 1.59mm) on a silicon wafer and a polystyrene surface to form a two-dimensional (2D) hard-sphere system and a 2D charged-sphere system, respectively. The 2D granular structures versus the particle area fraction were monitored and analyzed through the radial distribution function, potential of the mean force, structure factor, and bond orientation order parameter or correlation functions. We observed the particle structural transition from liquid-like to triangular-lattice crystal-like with increasing particle coverage (A = 0.70--0.82) in the 2D hard-sphere system. In a 2D charged system, a 'fluid-like' structure was observed in the particle area fraction range of A = 0.01 to 0.18. We 'investigated' the structuring of micrometer-sized particles confined in a fluid-liquid interface through Monte Carlo simulations using the asymptotic pair potential proposed by Hurd (1985) which includes both the screened Coulomb contribution and the dipole-dipole interactions. The effects of the multi-particle effective interactions and of the particle charge on the 2D particle structuring were elucidated by the radial distribution function. The technological concept of the nanoparticle structuring in the wedge film was explored with regards to its application to the spreading, wetting, and soil removal phenomena. The experimental and theoretical investigations on the cleansing of canola oil from a glass substrate using commercially available nanofluids were pursued. The positive contributions of the nanoparticles to the soil cleaning performance were rationalized in terms of the decrease in the contact angle and the interfacial tension, positive second virial coefficient, and high osmotic pressure of the nanofluid. These results confirm the novel mechanism of detergency using nanofluids based on the normal force (i.e., disjoining pressure) arising from the ordered nanoparticle structure formation in the confined space between the soil and the solid substrate (i.e., the wedge film).

Wu, Stanley

265

Dirac confinement of a heavy quark-light quark system (Q,q-bar) in high orbital angular momentum states  

SciTech Connect

The Regge behaviour of the solutions of a Dirac hamiltonian describing a heavy quark-light quark system in high orbital angular momentum states is analyzed. It is found that the solutions of a scalar confining potential are physically admissible while those of a vector confining potential are not. It is concluded that with a Dirac hamiltonian a scalar confining potential is preferred over a vector confining potential for any value of the orbital angular momentum.

Avila, M. A. [Departamento de Fisica, Facultad de Ciencias, UAEM, Cuernavaca 62210, Morelos (Mexico)

1998-10-05

266

Review of Inertial Confinement Fusion  

NASA Astrophysics Data System (ADS)

The physics of inertial confinement fusion is reviewed. The trend to short-wavelength lasers is argued, and the distinction between direct and indirect (soft X-ray) drive is made. Key present issues include the non-linear growth of Rayleigh-Taylor (R-T) instabilities, the seeding of this instability by the initial laser imprint, the relevance of self-generated magnetic fields, and the importance of parametric instabilities (stimulated Brillouin and Raman scattering) in gas-filled hohlraums. Experiments are reviewed which explore the R-T instability in both planar and converging geometry. The employment of various optical smoothing techniques is contrasted with the overcoating of the capsule by gold coated plastic foams to reduce considerably the imprint problem. The role of spontaneously generated magnetic fields in non-symmetric plasmas is discussed. Recent hohlraum compression results are presented together with gas bag targets which replicate the long-scale-length low density plasmas expected in NIF gas filled hohlraums. The onset of first Brillouin and then Raman scattering is observed. The fast ignitor scheme is a proposal to use an intense short pulse laser to drill a hole through the coronal plasma and then, with laser excited fast electrons, create a propagating thermonuclear spark in a dense, relatively cold laser-compressed target. Some preliminary results of laser hole drilling and 2-D and 3-D PIC simulations of this and the > 10^8 Gauss self-generated magnetic fields are presented. The proposed National Ignition Facility (NIF) is described.

Haines, M. G.

267

Confinement studies in TFTR  

SciTech Connect

The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B/sub T/ increased to 4.0 T, I/sub p/ to 2.0 MA, injection power (P/sub b/) to 5 MW with H/sup 0/ or D/sup 0/ beams anti n/sub e/ to 5 x 10/sup 19/ m/sup -3/, and Z/sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (tau/sub E/ = anti n/sub e/q) has been confirmed at higher I/sub p/ and B/sub T/, and the maximum tau/sub E/ of 0.4 sec has been achieved. With NBI at P/sub b/ substantially (by factor >2) higher than P/sub OH/, excellent power and particle accountability have been established. This suggests that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. tau/sub E/ is observed to scale approximately as I/sub p/ P/sub b//sup -0.5/ (independent of anti n/sub e/), consistent with previous L-mode scalings. With NBI we have achieved the maximum tau/sub E/ of 0.2 sec and the maximum T/sub i/(o) of 4.4 keV in the normal operating regime, and even higher T/sub i/(o) in the energetic-ion regime with low-n/sub e/ and low-I/sub p/ operation.

Murakami, M.; Arunasalam, V.; Bell, J.D.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Boody, F.; Boyd, D.; Bretz, N.; Bush, C.E.

1985-06-01

268

Confinement Vessel Dynamic Analysis  

SciTech Connect

A series of hydrodynamic and structural analyses of a spherical confinement vessel has been performed. The analyses used a hydrodynamic code to estimate the dynamic blast pressures at the vessel's internal surfaces caused by the detonation of a mass of high explosive, then used those blast pressures as applied loads in an explicit finite element model to simulate the vessel's structural response. Numerous load cases were considered. Particular attention was paid to the bolted port connections and the O-ring pressure seals. The analysis methods and results are discussed, and comparisons to experimental results are made.

R. Robert Stevens; Stephen P. Rojas

1999-08-01

269

Confinement Contains Condensates  

SciTech Connect

Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass-scales that fill all spacetime, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence, and incidentally expose misconceptions in a recent Comment.

Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

2012-03-12

270

Understanding Confinement From Deconfinement  

NASA Astrophysics Data System (ADS)

We show that a dual SU(N) effective theory of the confined phase of SU(N) Yang-Mills theory can be used in the temperature interval Tc < T < 4Tc to calculate non-perturbative magnetic properties of the deconfined phase, including the magnetic screening mass and the spatial string tension. We suggest that evidence for the quanta of the effective theory should be sought in analyses of both lattice simulations of Yang-Mills theory and experiments on heavy ion collisions.

Baker, M.

2007-02-01

271

Confinement contains condensates  

NASA Astrophysics Data System (ADS)

Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass scales that fill all space-time, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence and incidentally expose misconceptions in a recent Comment.

Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

2012-06-01

272

Packing of charged chains on toroidal geometries  

NASA Astrophysics Data System (ADS)

We study a strongly adsorbed flexible polyelectrolyte chain on tori. In this generalized Thomson problem, the patterns of the adsorbed chain are analyzed in the space of the toroidal coordinates and in terms of the orientation of each chain segment. Various patterns are found, including double spirals, disclination-like structures, Janus tori, and uniform wrappings, arising from the long-range electrostatic interaction and the toroidal geometry. Their broken mirror symmetry is quantitatively characterized by introducing an order parameter, an integral of the torsion. The uniform packing, which breaks the mirror symmetry the least, has the lowest value of the order parameter. In addition, it is found that the electrostatic energy of confined chains on tori conforms to a power law regardless of the screening effect in some typical cases studied. Furthermore, we study random walks on tori that generate chain configurations in the large screening limit or at large thermal fluctuation; some features associated with the toroidal geometry are discussed.

Yao, Zhenwei; de la Cruz, Monica Olvera

2013-01-01

273

Chirally symmetric but confining dense, cold matter  

SciTech Connect

The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at T=0 and finite chemical potential {mu} and obtain a clear chiral restoration phase transition at the critical value {mu}{sub cr}. Below this value the spectrum is similar to the previously obtained one at {mu}=0. At {mu}>{mu}{sub cr} the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.

Glozman, L. Ya.; Wagenbrunn, R. F. [Institute for Physics, Theoretical Physics Branch, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria)

2008-03-01

274

Inertial Electrostatic Confinement as a Power Source for Electric Propulsion.  

National Technical Information Service (NTIS)

The potential use of an INERTIAL ELECTROSTATIC CONFINEMENT (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engi...

G. H. Miley R. Burton J. Javedani Y. Yamamoto A Satsangi

1993-01-01

275

Inertial Electrostatic Confinement as a Power Source for Electric Propulsion.  

National Technical Information Service (NTIS)

The potential use of an Inertial Electrostatic Confinement (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engi...

G. H. Miley R. Burton J. Javedani Y. Yamamoto A. Satsangi

1993-01-01

276

Expansion, geometry, and gravity  

NASA Astrophysics Data System (ADS)

In general-relativistic cosmological models, the expansion history, matter content, and geometry are closely intertwined. In this brief paper, we clarify the distinction between the effects of geometry and expansion history on the luminosity distance. We show that the cubic correction to the Hubble law, measured recently with high-redshift supernovae, is the first cosmological measurement, apart from the cosmic microwave background, that probes directly the effects of spatial curvature. We illustrate the distinction between geometry and expansion with a toy model for which the supernova results already indicate a curvature radius larger than the Hubble distance.

Caldwell, Robert R.; Kamionkowski, Marc

2004-09-01

277

Native American Geometry  

NSDL National Science Digital Library

A physical, proportional geometry that originates from the simple circle. A growing body of architectural and iconographic evidence suggests this geometry was a relatively common tradition and has been practiced for at least 2000 years. The site is divided into four areas: Foundations, Anthropology, Designs, and Education; it introduces this two-dimensional non-random geometry in a connect-the-point format, exploring the intellectual and cultural implications of pre-Columbian geometric traditions in the New World. It also provides a list of European mathematical ramifications of the designs.

Forum, Math; Hardaker, Chris

2000-01-01

278

Confinement of Toroidal Non-neutral Plasma in Proto-RT  

SciTech Connect

In contrast to linear configurations for non-neutral plasmas, toroidal devices allow us to trap charged particles without the use of a plugging electric field. Thus it has a potential ability to confine high-energy particles or to simultaneously trap multiple particles with different charges. In spite of the relatively long history of the study in pure toroidal magnetic field devices, toroidal non-neutral plasmas are attracting renewed interest with the use of magnetic surface configurations. Possible applications of toroidal traps for non-neutral plasmas are formation of matter-antimatter plasmas, investigation on the fundamental properties of exotic plasmas including pair (equal mass) plasmas, and experimental test on the equilibrium and stability of flowing plasmas. As an initial test on non-neutral plasmas in the toroidal magnetic-surface geometry, formation and confinement properties of pure electron plasma have been investigated at Prototype-Ring Trap (Proto-RT) device with a dipole magnetic field. Electrons can be injected by using chaotic orbit near a magnetic null line generated by the combination of dipole and vertical magnetic fields. The confinement time of electrons is limited due to the effects of collisions with remaining neutral gas, and electrons of {approx} 1012 are trapped for {approx} 0.5 s in the typical magnetic field strength of 100 G and back pressure of 4 x 10-7 Torr in Proto-RT. Although the present experiment was carried out on the single-component plasma, the result shows that a stable confinement configuration has been realized for toroidal non-neutral plasmas by using the magnetic surface configuration. Together with the experiment on the toroidal pure electron plasma in Proto-RT, preliminary prospects for the injection and trap of anti-protons and positrons in the toroidal magnetic surface configuration, and creation of multi-component plasmas will be described.

Saitoh, H.; Yoshida, Z.; Watanabe, S. [Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan)

2005-10-19

279

Integrating Transformation Geometry into Traditional High School Geometry.  

ERIC Educational Resources Information Center

Describes a geometry course that integrates transformation geometry into traditional high school geometry. Discussion of the scope and sequence of the course includes the topics of proof, congruence, translations, rotations, reflections, dilations, quadrilaterals, parallel lines, and similarity. (MDH)

Okolica, Steve; Macrina, Georgette

1992-01-01

280

Evaluation of several two-step scoring functions based on linear interaction energy, effective ligand size, and empirical pair potentials for prediction of protein-ligand binding geometry and free energy.  

PubMed

The performances of several two-step scoring approaches for molecular docking were assessed for their ability to predict binding geometries and free energies. Two new scoring functions designed for "step 2 discrimination" were proposed and compared to our CHARMM implementation of the linear interaction energy (LIE) approach using the Generalized-Born with Molecular Volume (GBMV) implicit solvation model. A scoring function S1 was proposed by considering only "interacting" ligand atoms as the "effective size" of the ligand and extended to an empirical regression-based pair potential S2. The S1 and S2 scoring schemes were trained and 5-fold cross-validated on a diverse set of 259 protein-ligand complexes from the Ligand Protein Database (LPDB). The regression-based parameters for S1 and S2 also demonstrated reasonable transferability in the CSARdock 2010 benchmark using a new data set (NRC HiQ) of diverse protein-ligand complexes. The ability of the scoring functions to accurately predict ligand geometry was evaluated by calculating the discriminative power (DP) of the scoring functions to identify native poses. The parameters for the LIE scoring function with the optimal discriminative power (DP) for geometry (step 1 discrimination) were found to be very similar to the best-fit parameters for binding free energy over a large number of protein-ligand complexes (step 2 discrimination). Reasonable performance of the scoring functions in enrichment of active compounds in four different protein target classes established that the parameters for S1 and S2 provided reasonable accuracy and transferability. Additional analysis was performed to definitively separate scoring function performance from molecular weight effects. This analysis included the prediction of ligand binding efficiencies for a subset of the CSARdock NRC HiQ data set where the number of ligand heavy atoms ranged from 17 to 35. This range of ligand heavy atoms is where improved accuracy of predicted ligand efficiencies is most relevant to real-world drug design efforts. PMID:21644546

Rahaman, Obaidur; Estrada, Trilce P; Doren, Douglas J; Taufer, Michela; Brooks, Charles L; Armen, Roger S

2011-06-06

281

Proof in Transformation Geometry  

ERIC Educational Resources Information Center

|The first of three articles showing how inductively-obtained results in transformation geometry may be organized into a deductive system. This article discusses two approaches to enlargement (dilatation), one using coordinates and the other using synthetic methods. (MM)|

Bell, A. W.

1971-01-01

282

Science U: Geometry Center  

NSDL National Science Digital Library

Science UTM offers online articles and activities for people who like science. Science U and the web-design and development company that owns and operates the website, Geometry Technologies, were formed as a result of the closure of The Geometry Center at the University of Minnesota. One of the conditions of that grant, which funded The Geometry Center and ended in 1998, was that the Center would find a way to keep their materials available to the public. In anticipation of the day when the Geometry Center goes offline, they are slowly migrating materials to this website. The Geometry Center section at Science U offers lessons on solids using interactive models, geometry tiling activities, an interactive fractal generator, and many other puzzles, articles and activities. Visitors can search their resources using an online query form or by browsing the topic index, subject listing or content listing. The content listing gives you an idea of the different types of resources available, such as articles, facts and figures, classroom materials, online simulations, hands-on-projects, or software. The Science U also offers other sections on astronomy, graphic arts, and a library with various online and print resources on science.

2007-12-12

283

An electrostatically and a magnetically confined electron gun lens system  

Microsoft Academic Search

Focal properties, electron trajectory calculations, and geometries are given for two electron 'gun' lens systems that have a variety of applications in, for example, electron-neutral and electron-ion scattering experiments. One nine-lens system utilizes only electrostatic confinement and is capable of focusing electrons onto a fixed target with extremely small divergence angles, over a range of final energies 1-790 eV. The

Mark T. Bernius; Kin F. Man; Ara Chutjian

1988-01-01

284

An electrostatically and a magnetically confined electron gun lens system  

Microsoft Academic Search

Focal properties, electron trajectory calculations, and geometries are given for two electron ‘‘gun’’ lens systems that have a variety of applications in, for example, electron-neutral and electron-ion scattering experiments. One nine-lens system utilizes only electrostatic confinement and is capable of focusing electrons onto a fixed target with extremely small divergence angles, over a range of final energies 1–790 eV. The

Mark T. Bernius; Kin F. Man; Ara Chutjian

1988-01-01

285

Inertial Electrostatic Confinement Modeling and Comparison to Experiments  

Microsoft Academic Search

In inertial-electrostatic confinement (IEC), a high voltage accelerates ions between concentric, nearly transparent grids, usually in spherical geometry. For typical parameters (˜0.3 Pa 2 mTorr, ˜100 kV, ˜30 mA, ˜0.5 m anode diameter), atomic and molecular processes dominate operation. A numerically solved integral equation[1,2] approach to modeling D^+, D2^+, D3^+, and D^- ions passing through D2 background gas will be

Gilbert Emmert; John Santarius; Eric Alderson; David Donovan

2010-01-01

286

Chiral Confinement in Quasirelativistic Bose-Einstein Condensates  

SciTech Connect

In the presence of a laser-induced spin-orbit coupling an interacting ultracold spinor Bose-Einstein condensate may acquire a quasirelativistic character described by a nonlinear Dirac-like equation. We show that as a result of the spin-orbit coupling and the nonlinearity the condensate may become self-trapped, resembling the so-called chiral confinement, previously studied in the context of the massive Thirring model. We first consider 1D geometries where the self-confined condensates present an intriguing sinusoidal dependence on the interparticle interactions. We further show that multidimensional chiral confinement is also possible under appropriate feasible laser arrangements, and discuss the properties of 2D and 3D condensates, which differ significantly from the 1D case.

Merkl, M.; Zimmer, F. E.; Oehberg, P. [SUPA, Department of Physics, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom); Jacob, A.; Santos, L. [Institute for Theoretical Physics, Appelstrasse 2, Leibniz University, Hannover (Germany)

2010-02-19

287

Modeling non-confined coronal flares: Dynamics and X-ray diagnostics  

NASA Astrophysics Data System (ADS)

Long-lasting, intense, stellar X-ray flares may approach conditions of breaking magnetic confinement and evolving in open space. In the perspective of searching for possible tracers of non-confinement, we explore this hypothesis with hydrodynamic simulations of flares occurring in a non-confined corona: model flares are triggered by a transient impulsive heating injected in a plane-parallel stratified corona. The plasma evolution is described by means of a numerical 2-D model in cylindrical geometry R,Z. We explore the space of fundamental parameters. As a reference model, we consider a flare triggered by a heating pulse of 10 erg cm-3 s-1 lasting 150 s and released in a region ~ 109 cm wide and at a height ~ 2 x 109 cm from the base of the stellar surface. The pressure at the base of the corona of the unperturbed atmosphere is 0.1 dyne cm-2. The heating would cause a 20 MK flare if delivered in a 40 000 km long closed loop. The modeled plasma evolution in the heating phase involves the propagation of a 10 MK conduction front and the evaporation of a shocked bow density front upwards from the chromosphere. As the heating is switched off, the temperature drops in few seconds while the density front still propagates, expanding, and gradually weakening. This kind of evolution is shared by other simulations with different coronal initial pressure, and location, duration and intensity of the heating. The X-ray emission, spectra and light curves at the ASCA/SIS focal plan, and in two intense X-ray lines (Mg XI at 9.169 Åand Fe XXI at 128.752 Å), have been synthesized from the models. The results are discussed and compared to features of confined events, and scaling laws are derived. The light curves invariably show a very rapid rise, a constant phase as long as the constant heating is on, and then a very fast decay, on time scales of few seconds, followed by a more gradual one (few minutes). We show that this evolution of the emission, and especially the fast decay, together with other potentially observable effects, are intrinsic to the assumption of non-confinement. Their lack indicates that observed long-lasting stellar X-ray flares should involve plasma strongly confined by magnetic fields.

Reale, F.; Bocchino, F.; Peres, G.

2002-03-01

288

Home versus hospital confinement  

PubMed Central

The case for hospital rather than home delivery has been powerfully argued, especially in and since the Report of the Peel Committee. Nevertheless, evidence of comparison with other countries, notably the Netherlands, suggests the choice is not necessarily simple. Some general practitioner units are now reporting perinatal mortality rates which are consistently lower than those of specialist units, and recent statistical analyses suggest that the presence of more high risk cases in consultant units does not explain this. The only big controlled home-versus-hospital trial did not lead to a significantly lower perinatal mortality rate in the hospital group. The onus of proof now seems to lie with those who advocate 100 per cent hospital confinement.

Barry, C. N.

1980-01-01

289

Inertial electrostatic confinement (IEC) neutron sources  

SciTech Connect

Inertial electrostatic confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2 x 10(exp 10) neutrons/sec in steady state. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. This paper discusses the IEC concept and how it can be adapted to a steady-state assaying source and an intense pulsed neutron source. Theoretical modeling and experimental results are presented.

Barnes, D.C.; Caramana, E.J.; Janssen, R.D.; Nystrom, W.D.; Tiouririne, T.N.; Trent, B.C.; Miley, G.H.; Javedani, J.

1995-01-01

290

Perlite for permanent confinement of cesium  

Microsoft Academic Search

We present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300K followed by densification by sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, upon careful heat

J. Balencie; D. Burger; J.-L. Rehspringer; C. Estournès; S. Vilminot; M. Richard-Plouet; A. Boos

2006-01-01

291

Geometry of Quantum Statistical Inference  

NASA Astrophysics Data System (ADS)

An efficient geometric formulation of the problem of parameter estimation is developed, based on Hilbert space geometry. This theory, which allows for a transparent transition between classical and quantum statistical inference, is then applied to the analysis of exponential families of distributions (of relevance to statistical mechanics) and quantum mechanical evolutions. The extension to quantum theory is achieved by the introduction of a complex structure on the given real Hilbert space. We find a set of higher order corrections to the parameter estimation variance lower bound, which are potentially important in quantum mechanics, where these corrections appear as modifications to Heisenberg uncertainty relations for the determination of the parameter.

Brody, Dorje C.; Hughston, Lane P.

1996-09-01

292

Students Discovering Spherical Geometry Using Dynamic Geometry Software  

ERIC Educational Resources Information Center

|Dynamic geometry software (DGS) such as Cabri and Geometers' Sketchpad has been regularly used worldwide for teaching and learning Euclidean geometry for a long time. The DGS with its inductive nature allows students to learn Euclidean geometry via explorations. However, with respect to non-Euclidean geometries, do we need to introduce them to…

Guven, Bulent; Karatas, Ilhan

2009-01-01

293

Students discovering spherical geometry using dynamic geometry software  

Microsoft Academic Search

Dynamic geometry software (DGS) such as Cabri and Geometers’ Sketchpad has been regularly used worldwide for teaching and learning Euclidean geometry for a long time. The DGS with its inductive nature allows students to learn Euclidean geometry via explorations. However, with respect to non-Euclidean geometries, do we need to introduce them to students in a deductive manner? Do students have

Bulent Guven; Ilhan Karatas

2009-01-01

294

QUANTUM CONFINEMENT IN NANOCRYSTALLINE SILICON  

Microsoft Academic Search

Quantum confinement effects in different kinds of nanocrystalline silicon systems are experimentally and theoretically investigated. Porous silicon structured as a nanowire network and silicon nanodots embedded in amorphous silicon dioxide are studied. The main quantum confinement effect in both cases is represented by the appearance of new energy levels in the silicon band gap. The corresponding energies can be experimentally

M. L. Ciurea

295

Inertial Electrostatic Confinement (IEC) devices  

Microsoft Academic Search

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950's. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated

R. A. Nebel; L. Turner; T. N. Tiouririne; D. C. Barnes; W. D. Nystrom; R. W. Bussard; G. H. Miley; J. Javedani; Y. Yamamoto

1994-01-01

296

Density of States Simulations of Confined Glasses  

NASA Astrophysics Data System (ADS)

Glassy systems under confinement have been studied with great enthusiasm and effort for the last decades. They are relevant both fundamentally and technically because there is still debate about the nature of glass transition in small geometries which is important for lithographic processes in the semiconductor and other industries. In this work we are using the Wang-Landau approach also known as Density of States Monte Carlo to study glassy systems in bulk and under confinement. We apply the technique to a model binary Lennard Jones glass as well as the small organic glass former Ortho-terphenyl (OTP). For Lennard Jones glasses we use a well tested model. For OTP we start from a united atom model and then derive systematically a coarse grained representation by replacing each phenyl ring with a bead and using the Iterative Boltzmann Inversion. The properties of bulk Lennard Jones model show very good agreement with literature values. The atomistic and coarse grained representations of ortho-terphenyl in the bulk are in good agreement with experiments. Unsupported freestanding films show a lower glass transition than the bulk value.

Faller, Roland; Ghosh, Jayeeta

2008-03-01

297

Quantum Geometry and Interferometry  

NASA Astrophysics Data System (ADS)

All existing experimental results are currently interpreted using classical geometry. However, there are theoretical reasons to suspect that at a deeper level, geometry emerges as an approximate macroscopic behavior of a quantum system at the Planck scale. If directions in emergent quantum geometry do not commute, new quantum-geometrical degrees of freedom can produce detectable macroscopic deviations from classicality: spatially coherent, transverse position indeterminacy between any pair of world lines, with a displacement amplitude much larger than the Planck length. Positions of separate bodies are entangled with each other, and undergo quantum-geometrical fluctuations that are not describable as metric fluctuations or gravitational waves. These fluctuations can either be cleanly identified or ruled out using interferometers. A Planck-precision test of the classical coherence of space-time on a laboratory scale is now underway at Fermilab.

Hogan, C.

2013-01-01

298

Geometry and Cloaking Devices  

NASA Astrophysics Data System (ADS)

Recently, the application of geometry and conformal mappings to artificial materials (metamaterials) has attracted the attention in various research communities. These materials, characterized by a unique man-made structure, have unusual optical properties, which materials found in nature do not exhibit. By applying the geometry and conformal mappings theory to metamaterial science, it may be possible to realize so-called ``Harry Potter cloaking device''. Although such a device is still in the science fiction realm, several works have shown that by using such metamaterials it may be possible to control the direction of the electromagnetic field at will. We could then make an object hidden inside of a cloaking device. Here, we will explain how to design invisibility device using differential geometry and conformal mappings.

Ochiai, T.; Nacher, J. C.

2011-09-01

299

Universality of geometry  

NASA Astrophysics Data System (ADS)

In models of emergent gravity the metric arises as the expectation value of some collective field. Usually, many different collective fields with appropriate tensor properties are candidates for a metric. Which collective field describes the "physical geometry"? We resolve this "metric ambiguity" by an investigation of the most general form of the quantum effective action for several metrics. In the long-distance limit the physical metric is universal and accounts for a massless graviton. Other degrees of freedom contained in the various metric candidates describe very massive scalars and symmetric second rank tensors. They only play a role at microscopic distances, typically around the Planck length. The universality of geometry at long distances extends to the vierbein and the connection. On the other hand, for distances and time intervals of Planck size geometry looses its universal meaning. Time is born with the big bang.

Wetterich, C.

2012-05-01

300

Ambipolar potential formation in TMX  

SciTech Connect

TMX experimental data on ambipolar potential control and on the accompanying electrostatic confinement are reported. New results on the radial dependence of the central-cell confining potential are given. Radial and axial particle losses as well as scaling of the central-cell axial confinement are discussed.

Correll, D.L.; Allen, S.L.; Casper, T.A.

1981-05-05

301

Dynamical properties of confined superfluids near the lambda point  

NASA Astrophysics Data System (ADS)

In the present paper, we report on our progress towards a long term goal to develop a scheme to calculate dynamical and transport properties of helium near the superfluid transition using large-scale numerical techniques. We wish to study the influence of the boundary conditions and the confinement on these properties near the transition temperature where the coherence length can become of the size of the confining length. We intend to study the behavior of thermal conductivity and dynamic structure functions as the system undergoes a crossover from one to three dimensional. We use a bar-like geometry, i.e. a H×H×L lattice with L>>H, where we have applied open boundary conditions on the bar sides and periodic along the long direction. This geometry is chosen in order to mimic the pore geometry used in experimental studies and in particular the experimental study of Boundary Effects on Superfluid Transition (BEST). In this paper we present results for the thermal conductivity and dynamic correlation functions obtained for one dimensional (H=1 and L>>1) superfluids. We use the planar magnet model (which is in the same universality class as model-E) and we use a combination of Monte-Carlo simulation and a recently developed technique to solve the dynamical equations of motion. We also present our preliminary results for bar-like geometry and compare our findings with the present ground-based experimental studies and we hope to make predictions for BEST. .

Nho, Kwangsik; Manousakis, Efstratios

2000-01-01

302

Designing Phoxonic Metamaterials with Fractal Geometry  

NASA Astrophysics Data System (ADS)

Recently, the concepts of fractal geometry have been introduced into electromagnetic and plasmonic metamaterials. With their self-similarity, structures based on fractal geometry should exhibit multi-band character with high Q factors due to the scaling law. However, there exist few studies of phononic metamaterials based on fractal geometry. We use COMSOL to investigate the wave propagation in two dimensional systems possessing fractal geometries. The simulations of these systems, guided by our recently developed general design framework, help to understand the role of design in determining the phononic properties of the structures. Proposed structures are being fabricated via standard lithographic or 3D printing techniques. The wave behavior of the structures can be characterized using Brillouin Light Scattering, Scanning Acoustic Microscope and Near-field Scanning Optical Microscopy. Due to their sparse spatial distribution, fractal phononic structures show potential fir ``smart skin'', where multifunctional components can be fabricated on the same platform.

Ni, Sisi; Koh, Cheong Yang; Kooi, Steve; Thomas, Edwin

2012-02-01

303

Correlation Effects in the Photoionization of Confined Calcium and Zinc  

NASA Astrophysics Data System (ADS)

Studies of atoms confined in an endohedral environment have aroused significant recent interest [1]. In this work, the photoionization @Ca and @Zn have been studied using the Relativistic-Random-Phase Approximation, modified to include the confinement potential. Photoionization of the 4s and 3p subshells of free and confined atomic calcium, along with the 4s, 3d, 3p and 3s subshells of free and confined atomic zinc, have been studied. The photoionization parameters of confined atoms differ significantly from those of their ``free'' counterparts. The dipole cross sections and angular distribution asymmetry parameters exhibit oscillations with energy arising from the back scattering of the escaping electron by the confining potential, i.e., ``confinement resonances'' [2]. These oscillations persist when nondipole matrix elements are also included as is reflected in the nondipole cross section and angular distribution asymmetry parameters [3]; the relative strengths of the oscillations due to back-scattering in the E1 and E2 photoionization parameters have qualitatively different profiles as a function of photon energy. [1] V. K. Dolmatov, A. S. Baltenkov, J.-P. Connerade and S. T. Manson, Radiation Phys. Chem. 70, 417 (2004). [2] M. Ya. Amusia, A. S. Baltenkov, V. K. Dolmatov, S. T. Manson and A. Z. Msezane, Phys. Rev. A 70, 023201 (2004). [3] P.C. Deshmukh, Tanima Banerjee, K. P. Sunanda and R. Hari Varma, Radiation Phys. and Chem (submitted).

Varma, R. Hari; Manson, S. T.

2005-05-01

304

Ground state geometry of binary condensates in axisymmetric traps  

NASA Astrophysics Data System (ADS)

We show that the ground state interface geometry of binary condensates in the phase-separated regime undergoes a smooth transition from planar to ellipsoidal to cylindrical geometry. This occurs for the condensates with repulsive interactions as the trapping potential is changed from prolate to oblate. The correct ground state geometry emerges when the interface energy is included in the energy minimization, whereas energy minimization based on the Thomas-Fermi approximation gives incorrect geometry. The planar and cylindrical interface geometries have less interface area and minimize the interface energy. These are the preferred ground states in the cigar- and pan-cake-shaped trap configurations.

Gautam, S.; Angom, D.

2010-05-01

305

Aspects of global Riemannian geometry  

Microsoft Academic Search

In this article we survey some of the developments in Riemann- ian geometry. We place special emphasis on explaining the relationship be- tween curvature and topology for Riemannian manifolds with lower curvature bounds. We shall in this survey explain the development of the branch of Riemannian geometry called global Riemannian geometry. The main goal of this particular type of geometry

Peter Petersen

1999-01-01

306

Cooperative Length Scale and Fragility of Polystyrene under Confinement  

NASA Astrophysics Data System (ADS)

While thin films are an attractive model system to investigate the impact of confinement on glassy behavior, extending studies beyond thin films to geometries of higher dimensionalities is vital from both scientific and technological viewpoints. In this talk, we present the impact of confinement on the characteristic length at the glass transition as well as the fragility for confined polystyrene (PS) nanoparticles under isochoric conditions. We measure the glass transition temperature (Tg), fictive temperature (Tf) and isochoric heat capacity of silica-capped PS nanoparticles as a function of diameter via differential scanning calorimetry. From the measurement of Tf, we obtain the isochoric fragility, and via the fluctuation formula, the characteristic length at the glass transition. We illustrate that confinement under isochoric conditions for PS nanoparticles leads to a significant increase in the isochoric fragility while the characteristic length is reduced with size. At the minimum the results demonstrate a relationship between fragility and the characteristics length of isochorically-confined polymer that is not intuitive from the Adam-Gibbs theory.

Zhang, Chuan; Guo, Yunlong; Priestley, Rodney

2012-02-01

307

Gate-defined Quantum Confinement in Suspended Bilayer Graphene  

NASA Astrophysics Data System (ADS)

Quantum confined devices in carbon-based materials offer unique possibilities for applications ranging from quantum computation to sensing. In particular, nanostructured carbon is a promising candidate for spin-based quantum computation due to the ability to suppress hyperfine coupling to nuclear spins, a dominant source of spin decoherence. Yet graphene lacks an intrinsic bandgap, which poses a serious challenge for the creation of such devices. We present a novel approach to quantum confinement utilizing tunnel barriers defined by local electric fields that break sublattice symmetry in suspended bilayer graphene. This technique electrostatically confines charges via band structure control, thereby eliminating the edge and substrate disorder that hinders on-chip etched nanostructures to date. We report clean single electron tunneling through gate-defined quantum dots in two regimes: at zero magnetic field using the energy gap induced by a perpendicular electric field and at finite magnetic fields using Landau level confinement. The observed Coulomb blockade periodicity agrees with electrostatic simulations based on local top-gate geometry, a direct demonstration of local control over the band structure of graphene. This technology integrates quantum confinement with pristine device quality and access to vibrational modes, enabling wide applications from electromechanical sensors to quantum bits. More broadly, the ability to externally tailor the graphene bandgap over nanometer scales opens a new unexplored avenue for creating quantum devices.

Allen, Monica

2013-03-01

308

Pure Mott phases in confined ultracold atomic systems.  

PubMed

We propose a novel scheme for confining atoms to optical lattices by engineering a spatially inhomogeneous hopping matrix element in the Hubbard-model (HM) description, a situation we term off-diagonal confinement (ODC). We show, via an exact numerical solution of the boson HM with ODC, that this scheme possesses distinct advantages over the conventional method of confining atoms using an additional trapping potential, including incompressible Mott phases at commensurate filling and a phase diagram that is similar to the uniform HM. The experimental implementation of ODC will thus allow a more faithful realization of correlated phases in cold-atom experiments. PMID:20482076

Rousseau, V G; Batrouni, G G; Sheehy, D E; Moreno, J; Jarrell, M

2010-04-19

309

Experimental study on confined two-phase jets  

SciTech Connect

The basic mixing phenomena in confined, coaxial, particle-laden turbulent flows are studied within the scope of ram combustor research activities. Cold-flow experiments in a relatively simple configuration of confined, coaxial two-phase jets provided both qualitative and quantitative insight on the multiphase mixing process. Pressure, tracer gas concentration, and two-phase velocity measurements revealed that unacceptably long ram combustors are needed for complete confined jet mixing. Comparison of the experimental results with a previous numerical simulation displayed a very good agreement, indicating the potential of the experimental facility for validation of computational parametric studies. 38 refs.

Levy, Y.; Albagli, D. (Technion - Israel Institute of Technology, Haifa (Israel))

1991-09-01

310

Mixed Confined-unconfined Flow In A Confined Aquifer  

NASA Astrophysics Data System (ADS)

Mixed confined and unconfined groundwater flow occurs in a bounded initially dry aquifer when the hydraulic head at the side boundary suddenly rises above the elevation of the aquifer's top boundary. The flow problem is modelled by the Boussinesq equation and involves two moving boundaries. Here, we present an approximate analytical solution for this flow problem. The approach is based on the transformed equation (a similarity transformation was used). This simple approximate analytical solution is compared with an "exact" numerical solution and is found to be a very accurate description of the mixed confined and unconfined flow in the confined aquifer.

Li, L.; Lockington, D. A.; Barry, D. A.; Parlange, J.-Y.

311

Inertial confinement fusion  

SciTech Connect

This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1--2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver, and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.

Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P.W. (eds.)

1992-01-01

312

Confinement of semiflexible polymers.  

PubMed

A variational framework is developed to examine the equilibrium states of a semiflexible polymer that is constrained to lie on a fixed surface. As an application the confinement of a closed polymer loop of fixed length 2? R within a spherical cavity of smaller radius, R(0), is considered. It is shown that an infinite number of distinct periodic completely attached equilibrium states exist, labeled by two integers: n = 2,3,4,... and p = 1,2,3,..., the number of periods of the polar and azimuthal angles, respectively. Small loops oscillate about a geodesic circle: n = 2, p = 1 is the stable ground state; states with higher n exhibit instabilities. If R ? 2R(0) new states appear as oscillations about a doubly covered geodesic circle; the state n = 3,p = 2 replaces the twofold as the ground state in a finite band of values of R. With increasing R, loop states make a transition from oscillatory and orbital behavior on crossing the poles, returning to oscillation upon collapse to a multiple cover of a geodesic circle (signaled, respectively, by an increase in p and an increase in n). The force transmitted to the surface does not increase monotonically with loop size, but does asymptotically. It behaves discontinuously where n changes. The contribution to energy from geodesic curvature is bounded. In large loops, the energy becomes dominated by a state independent contribution proportional to the loop size; the energy gap between the ground state and excited states disappears. PMID:22463345

Guven, Jemal; Vázquez-Montejo, Pablo

2012-02-16

313

Inertial Confinement Fusion  

NASA Astrophysics Data System (ADS)

This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1-2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; and the Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.

Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P. W.

314

Parallel Computational Geometry  

Microsoft Academic Search

We present efficient parallel algorithms for several basic problems in computational geometry: convex hulls, Voronoi diagrams,\\u000a detecting line segment intersections, triangulating simple polygons, minimizing a circumscribing triangle, and recursive data-structures\\u000a for three-dimensional queries.

Alok Aggarwal; Bernard Chazelle; Leonidas J. Guibas; Colm Ó'dúnlaing; Chee-keng Yap

1988-01-01

315

Geometry of Thermodynamic States  

Microsoft Academic Search

the canonical distribution of classical statistical mechanics. In this scheme thermodynamic states, or equivalently, statistical mechanical states, can be characterised concisely in terms of the geometry of a submanifold M of the unit sphere S in a real Hilbert space H. The measurement of a thermodynamic variable then corresponds to the reduction of a state vector in H to an

Dorje C. Brodyand

316

Geoff Giles and Geometry  

ERIC Educational Resources Information Center

Geoff Giles died suddenly in 2005. He was a highly original thinker in the field of geometry teaching. As early as 1964, when teaching at Strathallen School in Perth, he was writing in "MT27" about constructing tessellations by modifying the sides of triangles and (irregular) quadrilaterals to produce what he called "trisides" and "quadrisides".…

Fielker, David

2007-01-01

317

Geometry Scavenger Hunt  

NSDL National Science Digital Library

This activity allows learners to practice observation skills and to realize examples of geometric shapes are everywhere. This geometry scavenger hunt (PDF) contains a set of directions and a recording sheet to complete. Included also is a list of materials and extension ideas.

2010-01-01

318

The Geometry Tutor  

Microsoft Academic Search

The tutor for doing proofs in high school geometry consists of a cot of ideal and buggy rules (IRR), a tutor, and an interface. The IBR is responsible for ehiuertly computing matcher, to all the correct and incorrect rules The interface is responsible for interacting with the student and graphically representing the proof. The tutor is responsible for directing the

John R. Anderson; C. Franklin Boyle; Gregg Yost

1985-01-01

319

Geometry in 3-D  

NSDL National Science Digital Library

This resource guide from the Middle School Portal 2 project, written specifically for teachers, provides links to exemplary resources including background information, lessons, career information, and related national science education standards. The online resources featured in Geometry in 3-D actively engage students in exploring a variety of geometric shapes, at times through lessons that involve building models or creating paper nets that fold into three-dimensional shapes; at other times, through technology that allows students to rotate and zoom in on figures, noting their attributes and complexity. Other lessons offer problems on surface area and volume, a part of every middle school curriculum. The problems, each with a different twist on the subject, challenge students to reconsider their understanding of how to measure solids. Activities for developing spatial sense, another primary objective in teaching geometry, are also featured. Finally, there are online galleries of geometric solids, included for the rare opportunity they offer to show your students the beauty in mathematics. In Background Information, you will find workshop sessions developed for teachers and other materials that may interest you as a professional. Each resource deals specifically with three-dimensional geometry topics that align with the geometry and measurement standards recommended by NCTM.

Herrera, Terese

2006-09-01

320

Foundations of basic geometry  

Microsoft Academic Search

The basic notions of length, area and volume were not alien to the prehistoric civilizations. The pyramids, palaces and great\\u000a baths built more than 4000 years ago provide ample evidence. We begin our investigation of geometry with a discussion of areas\\u000a of simple geometric objects.

Jasbir S. Chahal

2006-01-01

321

Gravity is Geometry.  

ERIC Educational Resources Information Center

|Clarifies two concepts of gravity--those of a fictitious force and those of how space and time may have geometry. Reviews the position of Newton's theory of gravity in the context of special relativity and considers why gravity (as distinct from electromagnetics) lends itself to Einstein's revolutionary interpretation. (JN)|

MacKeown, P. K.

1984-01-01

322

Geometry in Engineering Education.  

ERIC Educational Resources Information Center

|Discusses the importance of mathematical geometric education for engineers. Describes geometry as the basic platform to get involved with the creation of models in the forms of images which can offer an unprecedented basis for logical reasoning supported by practical applications. (Author/YDS)|

Velichova, Daniela

2002-01-01

323

The Geometry of Terrorism  

Microsoft Academic Search

Terrorism in its purest form is self-help by organized civilians who covertly inflict mass violence on other civilians. Pure sociology explains terrorism with its social geometry—its multidimensional location and direction in social space. Here Ibuild on the work of Senechal de la Roche (1996) and propose the following geometrical model: Pure terrorism arises intercollectively and upwardly across long distances in

Donald Black

2004-01-01

324

Algebraic Geometry and Physics  

Microsoft Academic Search

This article is an interdisciplinary review and an on-going progress report over the last few years made by myself and collaborators in certain fundamental subjects on two major theoretic branches in mathematics and theoretical physics: algebraic geometry and quantum physics. I shall take a practical approach, concentrating more on explicit examples rather than formal developments. Topics covered are divided in

Shi-shyr Roan

2000-01-01

325

Remarks on Euclidean Geometry  

Microsoft Academic Search

\\u000a You have studied geometry in high school, a version of what was assembled from knowledge of the ancient Greeks (around 300\\u000a BCE) by the Greek-speaking textbook writer Euclid, who lived in Alexandria, Egypt.

Matthias Beck; Ross Geoghegan

326

Geometry of Dupin Cyclides.  

National Technical Information Service (NTIS)

In the 19th century, the French geometer Charles Pierre Dupin discovered a nonspherical surface with circular lines of curvature. He called it cyclide in his book, Applications de Geometrie published in 1822. Recently, cyclides have been revived for use a...

V. Chandru D. Dutta C. M. Hoffmann

1989-01-01

327

Central cell confinement in MFTF-B  

NASA Astrophysics Data System (ADS)

The point model code TANDEM was used to survey the range of plasma parameters which can be attained in MFTF-B. The code solves for the electron and ion densities and temperatures in the central cell, yin-yang, barrier, and A-cell regions as well as the plasma potential in each region. In these studies, the A-cell sloshing ion beams were fixed while the neutral beams in the yin-yang and central cell, the gas feed in the central cell, and the applied ECRH power in the barrier region were varied. The variations of the central cell beta, central cell ion density and temperature, and the confining potential are discussed. The calculations indicate that large changes in the central cell beta cannot be achieved by varying the central cell gas or neutral beams or the yin-yang beams. Changes in these beam and gas feeds have the greatest effect on the central cell ion temperature and generally degrade the central cell confinement. Increasing the ECRH power applied to the barrier region causes an improvement in the central cell confinement and a linear increase (with applied power) of the central cell beta.

Jong, R. A.

1981-09-01

328

Stable configurations of confined cold ionic systems.  

PubMed

The simple structures formed by charged particles confined in a harmonic potential have been investigated and the configurations of minimum potential energy were identified. For fewer than 12 particles these form polyhedrons centered on the origin. For structures with 13-22 particles one sits in the middle, for 23-26 particles two are in the interior, etc., until a third shell starts forming at 60. When the isotropy of the trap is changed, distortions and discrete phase changes are seen. These structures should correspond to ones formed in ion traps at very low temperatures PMID:11607146

Rafac, R; Schiffer, J P; Hangst, J S; Dubin, D H; Wales, D J

1991-01-15

329

Performance of Polywell inertial-electrostatic confinement for applications  

Microsoft Academic Search

Summary form only given, as follows. Recent ideas have motivated a fresh look at fusion based on inertial-electrostatic confinement (IEC). Inertial-electrostatic-confinement devices electrostatically focus ions into a dense core. The electrostatic potential is generated by either grids or magnetically trapped electrons (the polywell concept). Work will be reported on modeling Polywell particle and power balance, with an emphasis on moderate-Q

J. F. Santarius; K. H. Simmons

1995-01-01

330

Confinement of Fractional Quantum Hall States  

NASA Astrophysics Data System (ADS)

Confinement of small-gapped fractional quantum Hall states facilitates quasiparticle manipulation and is an important step towards quasiparticle interference measurements. Demonstrated here is conduction through top gate defined, narrow channels in high density, ultra-high mobility heterostructures. Transport evidence for the persistence of a correlated state at filling fraction 5/3 is shown in channels of 2?m length but gated to near 0.3?m in width. The methods employed to achieve this confinement hold promise for interference devices proposed for studying potential non-Abelian statistics at filling fraction 5/2. R.L. Willett, M.J. Manfra, L.N. Pfeiffer, K.W. West, Appl. Phys. Lett. 91, 052105 (2007).

Willett, Robert; Manfra, Michael; West, Ken; Pfeiffer, Loren

2008-03-01

331

Confinement effect on semiconductor nanowires properties  

NASA Astrophysics Data System (ADS)

We study the effect of confinement on various properties of semiconductor nanowires. First, we study the size and direction dependence of the band gap of germanium nanowires. We use the density functional theory in the local density approximation. Results shows that the band gap decreases with the diameter. The susceptibility of these nanowires is also computed. Second, we look at the confinement effect on the piezoelectric coefficients of ZnO and MN nanowires. The Berry phase method is used. It is found that depending on passivation, the piezoelectric effect can decrease or increase. Finally, we study the size and direction dependence of the melting temperature of silicon nanowires. We use the molecular dynamics with the Stillinger Weber potential. Results indicate that the melting temperature increases with the nanowire diameter and that it is direction dependent.

Nduwimana, Alexis

332

Interelectron magnetic coupling in electrides with one-dimensional cavity-channel geometry.  

PubMed

Dye and coworkers [J. L. Dye, Acc. Chem. Res., 2009, 42, 1564] established experimentally that the strength of interelectron coupling in electrides with open intercavity channels critically depends on the channel diameter but is less sensitive to the channel length. We explain these observations by theoretical analysis of model electrides with a simple geometry. Our model consists of two electrons confined in a dogbone-shaped cavity--two spherical cages connected by a cylindrical channel. The coupling constant J is obtained from the calculated singlet-triplet gap of this system. By approximating the confining potential of the dogbone-shaped cavity with a one-dimensional double-well potential we show that ln(-J/k(B)), where k(B) is the Boltzmann constant, is a near-linear function of ?((1/s) - (1/S)), where s and S are the cross-sectional areas of the channel and the cages, respectively. This prediction is in excellent agreement with the experiment for real electrides that have essentially one-dimensional cavity-channel networks. PMID:22068221

Ryabinkin, Ilya G; Staroverov, Viktor N

2011-11-09

333

Collective motion of squirmers in a quasi-2D geometry  

NASA Astrophysics Data System (ADS)

Microorganisms like bacteria, algae or spermatozoa typically move in an aqueous environment where they interact via hydrodynamic flow fields. Recent experiments studied the collective motion of dense suspensions of bacteria where swarming and large-scale turbulence emerged. Moreover, spherical artificial microswimmers, so-called squirmers, have been constructed and studied in a quasi-2D geometry. Here we present a numerical study of the collective dynamics of squirmers confined in quasi-2D between two parallel walls. Because of their spherical shape the reorientation of squirmers is solely due to noise and hydrodynamic interactions via induced flow fields. This is in contrast to elongated swimmers like bacteria which locally align due to steric interactions. We study the collective motion of pushers, pullers and potential swimmers at different densities. At small densities the squirmers are oriented parallel to the walls and pairwise collisions determine the reorientation rate. In dense suspensions rotational diffusion is greatly enhanced and pushers, in particular, tend to orient perpendicular to the walls. This effects the dynamics of the emerging clusters. In very dense suspensions we observe active jamming and long-lived crystalline structures.

ZöTtl, Andreas; Stark, Holger

2013-03-01

334

Alpha particle confinement in tokamaks  

SciTech Connect

An assessment of diffusive tokamak transport mechanisms of concern for alpha particles indicates that the ''stochastic regime'' is the only one which appears to pose a real danger for adequate alpha confinement. This fact, in conjunction with the threshold character of that mechanism, allows one to decide whether an alpha born at a given location will be lost or confined, according to a very simple criterion. Implementing this criterion numerically results in a new code for the assessment of alpha confinement, which is orders of magnitude faster than earlier codes used for this purpose. 13 refs., 3 figs., 1 tab.

White, R.B.; Mynick, H.E.

1988-11-01

335

Landscape as a Model: The Importance of Geometry  

PubMed Central

In all models, but especially in those used to predict uncertain processes (e.g., climate change and nonnative species establishment), it is important to identify and remove any sources of bias that may confound results. This is critical in models designed to help support decisionmaking. The geometry used to represent virtual landscapes in spatially explicit models is a potential source of bias. The majority of spatial models use regular square geometry, although regular hexagonal landscapes have also been used. However, there are other ways in which space can be represented in spatially explicit models. For the first time, we explicitly compare the range of alternative geometries available to the modeller, and present a mechanism by which uncertainty in the representation of landscapes can be incorporated. We test how geometry can affect cell-to-cell movement across homogeneous virtual landscapes and compare regular geometries with a suite of irregular mosaics. We show that regular geometries have the potential to systematically bias the direction and distance of movement, whereas even individual instances of landscapes with irregular geometry do not. We also examine how geometry can affect the gross representation of real-world landscapes, and again show that individual instances of regular geometries will always create qualitative and quantitative errors. These can be reduced by the use of multiple randomized instances, though this still creates scale-dependent biases. In contrast, virtual landscapes formed using irregular geometries can represent complex real-world landscapes without error. We found that the potential for bias caused by regular geometries can be effectively eliminated by subdividing virtual landscapes using irregular geometry. The use of irregular geometry appears to offer spatial modellers other potential advantages, which are as yet underdeveloped. We recommend their use in all spatially explicit models, but especially for predictive models that are used in decisionmaking.

Holland, E. Penelope; Aegerter, James N; Dytham, Calvin; Smith, Graham C

2007-01-01

336

Nozzle-geometry effects in liquid jet impingement heat transfer  

Microsoft Academic Search

Experiments were conducted to determine the effect of nozzle geometry (diameter and aspect ratio) on the local heat transfer coefficients from a small heat source to a normally impinging, axisymmetric, submerged and confined liquid jet of FC-77. A single jet with nozzle diameters in the range of 0.79–6.35 mm and up to seven different nozzle aspect ratios in the range

Suresh V. Garimella; Boris Nenaydykh

1996-01-01

337

Magnetic freezing of confined water  

NASA Astrophysics Data System (ADS)

We report results from molecular dynamic simulations of the freezing transition of liquid water in the nanoscale hydrophobic confinement under the influence of a homogeneous external magnetic field of 10 T along the direction perpendicular to the parallel plates. A new phase of bilayer crystalline ice is obtained at an anomalously high freezing temperature of 340 K. The water-to-ice translation is found to be first order. The bilayer ice is built from alternating rows of hexagonal rings and rhombic rings parallel to the confining plates, with a large distortion of the hydrogen bonds. We also investigate the temperature shifts of the freezing transition due to the magnetic field. The freezing temperature, below which the freezing of confined water occurs, shifts to a higher value as the magnetic field enhances. Furthermore, the temperature of the freezing transition of confined water is proportional to the denary logarithm of the external magnetic field.

Zhang, Guangyu; Zhang, Weiwei; Dong, Huijuan

2010-10-01

338

Magnetic freezing of confined water.  

PubMed

We report results from molecular dynamic simulations of the freezing transition of liquid water in the nanoscale hydrophobic confinement under the influence of a homogeneous external magnetic field of 10 T along the direction perpendicular to the parallel plates. A new phase of bilayer crystalline ice is obtained at an anomalously high freezing temperature of 340 K. The water-to-ice translation is found to be first order. The bilayer ice is built from alternating rows of hexagonal rings and rhombic rings parallel to the confining plates, with a large distortion of the hydrogen bonds. We also investigate the temperature shifts of the freezing transition due to the magnetic field. The freezing temperature, below which the freezing of confined water occurs, shifts to a higher value as the magnetic field enhances. Furthermore, the temperature of the freezing transition of confined water is proportional to the denary logarithm of the external magnetic field. PMID:20942551

Zhang, Guangyu; Zhang, Weiwei; Dong, Huijuan

2010-10-01

339

Solvent cavitation under solvophobic confinement.  

PubMed

The stability of liquids under solvophobic confinement can tip in favor of the vapor phase, nucleating a liquid-to-vapor phase transition that induces attractive forces between confining surfaces. In the case of water adjacent to hydrophobic surfaces, experimental and theoretical evidence support confinement-mediated evaporation stabilization of biomolecular and colloidal assemblies. The macroscopic thermodynamic theory of cavitation under confinement establishes the connection between the size of the confining surfaces, interfacial free energies, and bulk solvent pressure with the critical evaporation separation and interfacial forces. While molecular simulations have confirmed the broad theoretical trends, a quantitative comparison based on independent measurements of the interfacial free energies and liquid-vapor coexistence properties has, to the best of our knowledge, not yet been performed. To overcome the challenges of simulating a large number of systems to validate scaling predictions for a three-dimensional fluid, we simulate both the forces and liquid-vapor coexistence properties of a two-dimensional Lennard-Jones fluid confined between solvophobic plates over a range of plate sizes and reservoir pressures. Our simulations quantitatively agree with theoretical predictions for solvent-mediated forces and critical evaporation separations once the length dependence of the solvation free energy of an individual confining plate is taken into account. The effective solid-liquid line tension length dependence results from molecular scale correlations for solvating microscopic plates and asymptotically decays to the macroscopic value for plates longer than 150 solvent diameters. The success of the macroscopic thermodynamic theory at describing two-dimensional liquids suggests application to surfactant monolayers to experimentally confirm confinement-mediated cavitation. PMID:23947875

Ashbaugh, Henry S

2013-08-14

340

Hydration of ions under confinement  

Microsoft Academic Search

Molecular dynamics simulations are used to examine the changes in water density and hydration characteristics of NaCl solutions confined in slit-shaped graphitic pores. Using a structural signature, we define the hydration limit as the salt concentration at which a sharp drop in the hydration number is observed. At small pores (H = 8.0–10 Å), confined water does not possess bulk-like features and remains

Ateeque Malani; Sohail Murad; K. G. Ayappa

2010-01-01

341

Inflation in warped geometries  

NASA Astrophysics Data System (ADS)

We argue that brane anti-brane inflation in string theory de-Sitter vacua of Kachru-Kallosh-Linde-Trivedi (KKLT) is captured by the dynamics of a D3-brane probe in the local KKLT model constructed in hep-th/0203041. This provides a framework to study in a controllable way corrections to the inflationary slow roll parameter ? due to conformal symmetry breaking in a warped geometry throat. We compute the leading correction to ? for the inflation in the Klebanov-Tseytlin throat geometry. We find that in certain regime this correction tends to decrease ?. Computations in a different regime suggest however that it is unlikely that ?<<1 can be achieved with the D3-brane throat inflation.

Buchel, Alex; Roiban, Radu

2004-06-01

342

State Sums and Geometry  

NASA Astrophysics Data System (ADS)

In this thesis I review the definition of topological quantum field theories through state sums on triangulated manifolds. I describe the construction of state sum invariants of 3-manifolds from a graphical calculus and show how to evaluate the invariants as boundary amplitudes. I review how to define such a graphical calculus through SU(2) representation theory. I then review various geometricity results for the representation theory of SU(2), Spin(4) and SL(2,C), and define coherent boundary manifolds for state sums based on these representations. I derive the asymptotic geometry of the SU(2) based Ponzano-Regge invariant in three dimensions, and the SU(2) based Ooguri models amplitude in four dimensions. As a corollary to the latter results I derive the asymptotic behaviour of various recently proposed spin foam models motivated from the Plebanski formulation of general relativity. Finally the asymptotic geometry of the SL(2,C) based model is derived.

Hellmann, Frank

2011-02-01

343

Brane Universe: Global Geometry  

SciTech Connect

The global geometries of bulk vacuum space-times in the brane-universe models are investigated and classified in terms of geometrical invariants. The corresponding Carter-Penrose diagrams and embedding diagrams are constructed. It is shown that for a given energy-momentum induced on the brane there can be different types of global geometries depending on the signs of a bulk cosmological term and surface energy density of the brane (the sign of the latter does not influence the internal cosmological evolution). It is shown that in the Randall-Sundrum scenario it is possible to have an asymmetric hierarchy splitting even with a Z{sub 2}-symmetric matching of 'our' brane to the bulk.

Berezin, Victor [Institute for Nuclear Research, Russian Academy of Sciences, 60th October Anniversary Prospect, 7a, 117312, Moscow (Russian Federation)

2010-06-23

344

Multilevel geometry optimization  

SciTech Connect

Geometry optimization has been carried out for three test molecules using six multilevel electronic structure methods, in particular Gaussian-2, Gaussian-3, multicoefficient G2, multicoefficient G3, and two multicoefficient correlation methods based on correlation-consistent basis sets. In the Gaussian-2 and Gaussian-3 methods, various levels are added and subtracted with unit coefficients, whereas the multicoefficient Gaussian-x methods involve noninteger parameters as coefficients. The multilevel optimizations drop the average error in the geometry (averaged over the 18 cases) by a factor of about two when compared to the single most expensive component of a given multilevel calculation, and in all 18 cases the accuracy of the atomization energy for the three test molecules improves; with an average improvement of 16.7 kcal/mol. (c) 2000 American Institute of Physics.

Rodgers, Jocelyn M. [Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431 (United States); Fast, Patton L. [Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431 (United States); Truhlar, Donald G. [Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431 (United States)

2000-02-15

345

Codes on finite geometries  

Microsoft Academic Search

New algebraic methods for constructing codes based on hyperplanes of two different dimensions in finite geometries are presented. The new construction methods result in a class of multistep majority-logic decodable codes and three classes of low-density parity-check (LDPC) codes. Decoding methods for the class of majority-logic decodable codes, and a class of codes that perform well with iterative decoding in

Heng Tang; Jun Xu; Shu Lin; Khaled A. S. Abdel-ghaffar

2005-01-01

346

Geometry Constructions Language  

Microsoft Academic Search

Geometry Constructions Language (gcl) is a language for explicit descriptions of constructions in Euclidean plane and of their properties. Other mathematical\\u000a objects can also be described in the language. The language gcl is intuitive and simple, yet it supports arrays, flow control structures, user-defined procedures, etc. The processors for\\u000a the gcl language—applications gclc and Wingclc—enable visualization of described objects and

Predrag Janicic

2010-01-01

347

Confinement of atoms under general boundary conditions  

NASA Astrophysics Data System (ADS)

The energy spectrum of a nonrelativistic quantum particle and hydrogen-like atom is considered under the most general conditions of confinement in a spatial box (vacuum cavity). It is shown that the rearrangement of the lowest energy levels occurring in this case turns out to be considerably more significant when compared with the case of confinement achieved by the impenetrable potential barrier. The role in the rearrangement of this level, played by the von Neumann-Wigner level repulsion effect, is emphasized. For an atom confined in a spherical cavity of radius R, it is also shown that, when the role of the cavity boundary is played by the surface layer of nonzero depth d, the atomic ground state possesses a deep and pronounced minimum for the physically reasonable width and depth of that surface layer, in which the binding energy turns out to be an order of magnitude larger than that of the lowest 1 s-level of a free atom E 1 s . Also, it becomes possible to achieve a mode when the binding energy of an atom is noticeably higher than E 1 s at R on the order of 10-100 nm.

Sveshnikov, K. A.; Roenko, A. A.

2013-09-01

348

Quantum Confined Silicon Clathrate Quantum Dots  

NASA Astrophysics Data System (ADS)

Silicon (Si) allotropes can be synthesized in such a way that tetrahedrally bonded atoms form cage-like structures with bulk mechanical and opto-electronic properties distinct from those of diamond silicon (dSi). We use DFT, supplemented with many-body Green function analysis, to explore the structural stability of clathrate Si quantum dots (QDs) and to characterize their confinement as a function of crystal symmetry and size. Our results show that that there is a simple relationship between the confinement character of the QDs and the effective mass of the associated bulk crystals. Clathrate QDs and dSiQDs of the same size can exhibit differences of gap energies by as much as 2 eV. This offers the potential of synthesizing Si dots on the order of 1 nm that have optical gaps in the visible range but that do not rely on high-pressure routes such as those explored for the metastable BC8 and R8 phases. These results prompt the question as to how minimal quantum confinement can be in dots composed of Si. More broadly, clathrate QDs can in principle be synthesized for a wide range of semiconductors, and the design space can be further enriched via doping.

Lusk, Mark; Brawand, Nicholas

2013-03-01

349

Grade 2 Practice Problems: Geometry  

NSDL National Science Digital Library

This page contains 20 problems in geometry from the Port Angeles School District in Washington state. Links to state GLEs and revised standards are provided. Topics covered include shape in plane and solid geometry, bilateral symmetry, and logic.

2011-01-01

350

Circumference of Taxicab Geometry Circles.  

ERIC Educational Resources Information Center

Presented is an activity in which students apply familiar concepts of geometry to novel settings. Using square dot paper and isometric dot paper, students trace routes and determine the geometry of each circle. (KR)

Litwiller, Bonnie H.; Duncan, David R.

1991-01-01

351

Graphical debugging of combinational geometry.  

National Technical Information Service (NTIS)

A graphical debugger for combinatorial geometry being developed at Oak Ridge National Laboratory is described. The prototype debugger consists of two parts: a FORTRAN-based ''view'' generator and a Microsoft Windows application for displaying the geometry...

T. J. Burns M. S. Smith

1992-01-01

352

Geometry Is More Than Proof.  

ERIC Educational Resources Information Center

|Five basic skill areas needing more attention in standard high school geometry are discussed. Levels of student mental development in geometry and a need for less emphasis on formal proofs are reviewed. (MP)|

Hoffer, Alan

1981-01-01

353

Quantum-Confined Impurities as Single-Electron Quantum Dots: Application in Tereherz Emitters  

Microsoft Academic Search

This work will demonstrate that impurities within semiconductor crystals can be thought of as the ultimate in quantum dots, with the three-dimensional confining potential being provided by individual atoms which are each capable of localising single electrons or holes. A heterostruc- ture confining potential provides a means to tune the energy levels of the impurities. Just as im- portantly, quantum

P. Harrison; M. P. Halsall; W.-M. Zheng

2002-01-01

354

Gas solubility in hydrophobic confinement.  

PubMed

Measured forces between apolar surfaces in water have often been found to be sensitive to exposure to atmospheric gases despite low gas solubilities in bulk water. This raises questions as to how significant gas adsorption is in hydrophobic confinement, whether it is conducive to water depletion at such surfaces, and ultimately if it can facilitate the liquid-to-gas phase transition in the confinement. Open Ensemble molecular simulations have been used here to determine saturated concentrations of atmospheric gases in water-filled apolar confinements as a function of pore width at varied gas fugacities. For paraffin-like confinements of widths barely exceeding the mechanical instability threshold (spinodal) of the liquid-to-vapor transition of confined water (aqueous film thickness between three and four molecular diameters), mean gas concentrations in the pore were found to exceed the bulk values by a factor of approximately 30 or approximately 15 in cases of N2 and CO2, respectively. At ambient conditions, this does not result in visible changes in the water density profile next to the surfaces. Whereas the barrier to capillary evaporation has been found to decrease in the presence of dissolved gas (Leung, K.; Luzar, A.; and Bratko, D. Phys. Rev. Lett. 2003, 90, 065502), gas concentrations much higher than those observed at normal atmospheric conditions would be needed to produce noticeable changes in the kinetics of capillary evaporation. In simulations, dissolved gas concentrations corresponding to fugacities above approximately 40 bar for N2, or approximately 2 bar for CO2, were required to trigger expulsion of water from a hydrocarbon slit as narrow as 1.4 nm. For nanosized pore widths corresponding to the mechanical instability threshold or above, no significant coupling between adsorption layers at opposing confinement walls was observed. This finding explains the approximately linear increase in gas solubility with inverse confinement width and the apparent validity of Henry's law in the pores over a broad fugacity range. PMID:16853936

Luzar, Alenka; Bratko, Dusan

2005-12-01

355

RATIONAL CURVES AND PARABOLIC GEOMETRIES  

Microsoft Academic Search

The twistor transform of a parabolic geometry has two steps: lift up to a geometry of higher dimension, and then drop to a geometry of lower dimension. The rst step is a functor, but the second requires some compati- bility conditions. Local necessary conditions were uncovered by Andreas Cap (14). I prove necessary and sucient global conditions for complex parabolic

BENJAMIN MCKAY

356

Vortex lattices and crystalline geometries  

NASA Astrophysics Data System (ADS)

We consider AdS2×R2 solutions supported by a magnetic field, such as those which arise in the near-horizon limit of magnetically charged AdS4 Reissner-Nordstrom black branes. In the presence of an electrically charged scalar field, such magnetic solutions can be unstable to spontaneous formation of a vortex lattice. We solve the coupled partial differential equations that govern the charged scalar, gauge field, and metric degrees of freedom to lowest nontrivial order in an expansion around the critical point and discuss the corrections to the free energy and thermodynamic functions arising from the formation of the lattice. We describe how such solutions can also be interpreted, via S-duality, as characterizing infrared crystalline phases of conformal field theories doped by a chemical potential, but in zero magnetic field; the doped conformal field theories are dual to geometries that exhibit dynamical scaling and hyperscaling violation.

Bao, Ning; Harrison, Sarah; Kachru, Shamit; Sachdev, Subir

2013-07-01

357

Distance geometry based comparative modelling.  

PubMed

A distance geometry based protein modelling algorithm is presented which relies on the projection of simple model chain coordinates into Euclidean spaces with gradually decreasing dimensionality. Fast embedding was achieved by performing separate distance matrix projections on subsets of the model points. Structural equivalences between the unknown target and related proteins with known structures were deduced either from a mixed sequence/structure multiple alignment or from the output of various fold recognition (threading) approaches. These equivalences were mapped onto the model as structure-specific conserved C alpha atom distances and secondary structure assignments. Additional nonspecific distance restraints derived from general stereochemical properties of folded protein chains were used to guide the modelling process. The method quickly constructed a large number of low-resolution models which could then serve as starting conformations for full-atom refinement. Structure predictions for some targets in the 'Asilomar Challenge' (CASP2) are presented to illustrate potential applications of the approach. PMID:9218958

Aszódi, A; Munro, R E; Taylor, W R

1997-01-01

358

Confinement free energy of semiflexible polymers  

NASA Astrophysics Data System (ADS)

Using a novel scheme to compute the chemical potential of semiflexible polymers, we have measured the confinement free energy of a wormlike chain in a tube. We compare our result for the dependence of the free energy on the chain length, the persistence length and the diameter of the cylinder with the corresponding theoretical predictions based on the scaling theory of Odijk and the fluctuation theory of Helfrich. Our simulation data agree well with the exponents of the theoretically predicted power laws. We find evidence that, for long wavelengths, the mode damping assumption underlying Helfrich's theory is valid.

Dijkstra, Marjolein; Frenkel, Daan; Lekkerkerker, Henk N. W.

1993-04-01

359

Perlite for permanent confinement of cesium  

NASA Astrophysics Data System (ADS)

We present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300 K followed by densification by sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, upon careful heat treatment is demonstrated by X-ray diffraction. Leaching tests on the resulting glass-ceramics reveal a very low Cs departure of 0.5 mg m-2 d-1.

Balencie, J.; Burger, D.; Rehspringer, J.-L.; Estournès, C.; Vilminot, S.; Richard-Plouet, M.; Boos, A.

2006-06-01

360

Polymer translocation out of planar confinements  

NASA Astrophysics Data System (ADS)

Polymer translocation in three dimensions out of planar confinements is studied in this paper. Three membranes are located at z = -h, z = 0 and z = h1. These membranes are impenetrable, except for the middle one at z = 0, which has a narrow pore. A polymer with length N is initially sandwiched between the membranes placed at z = -h and z = 0 and translocates through this pore. We consider strong confinement (small h), where the polymer is essentially reduced to a two-dimensional polymer, with a radius of gyration scaling as Rg(2D)~N?2D here, ?2D = 0.75 is the Flory exponent in two dimensions. The polymer performs Rouse dynamics. On the basis of theoretical analysis and high-precision simulation data, we show that in the unbiased case h = h1, the dwell time ?d scales as N2+?2D, in perfect agreement with our previously published theoretical framework. For h_1=\\infty , the situation is equivalent to field-driven translocation in two dimensions. We show that in this case ?d scales as N2?2D, in agreement with several existing numerical results in the literature. This result violates the earlier reported lower bound N1+? for ?d for field-driven translocation. We argue, on the basis of energy conservation, that the actual lower bound for ?d is N2? and not N1+?. Polymer translocation in such theoretically motivated geometries thus resolves some of the most fundamental issues that have been the subject of much heated debate in recent times.

Panja, Debabrata; Barkema, Gerard T.; Ball, Robin C.

2008-02-01

361

Pulsed electric system for production and confinement of plasma in ETE (Spherical tokamak experiment)  

Microsoft Academic Search

Summary form only given. In this paper we present project and results of the Pulsed Electric System of the ETE tokamak. Tokamaks are experimental devices based on a vacuum chamber with toroidal geometry, inside of which plasmas of high temperature are generated and magnetically confined. For that, tokamaks possess a system of coils that generate the necessary magnetic and electric

L. F. W. Barbosa; J. G. Ferreira; G. O. Ludwig; E. D. Bosco; J. O. Rossi

2001-01-01

362

Confining the scalar field of the Kaluza-Klein wormhole soliton  

SciTech Connect

The Maison five-to-three dimensional reduction, generalized to the case of five-dimensional general relativity with sources, is applied to the problem of confining the scalar field of the Kaluza-Klein wormhole soliton by a very weak perfect fluid source, without affecting the spatial geometry of this localized solution.

Clement, G. (Universite de Nice (France))

1989-08-01

363

Theory of Weakly Collisional Modes in Magnetically Confined High Temperature Plasmas  

Microsoft Academic Search

We have investigated several aspects of the semi -collisional modes in magnetically confined high temperature plasmas. Kinetic effects associated with finite ion Larmor radius (FLR), which can significantly modify the conventional resistive magnetohydrodynamic (MHD) results are studied analytically. First, in a sheared slab geometry, the effects of transition from the unmagnetized ion response in the resistive region to the magnetized

Taik Soo Hahm

1984-01-01

364

Differential geometry based multiscale models.  

PubMed

Large chemical and biological systems such as fuel cells, ion channels, molecular motors, and viruses are of great importance to the scientific community and public health. Typically, these complex systems in conjunction with their aquatic environment pose a fabulous challenge to theoretical description, simulation, and prediction. In this work, we propose a differential geometry based multiscale paradigm to model complex macromolecular systems, and to put macroscopic and microscopic descriptions on an equal footing. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum mechanical description of the aquatic environment with the microscopic discrete atomistic description of the macromolecule. Multiscale free energy functionals, or multiscale action functionals are constructed as a unified framework to derive the governing equations for the dynamics of different scales and different descriptions. Two types of aqueous macromolecular complexes, ones that are near equilibrium and others that are far from equilibrium, are considered in our formulations. We show that generalized Navier-Stokes equations for the fluid dynamics, generalized Poisson equations or generalized Poisson-Boltzmann equations for electrostatic interactions, and Newton's equation for the molecular dynamics can be derived by the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows. Comparison is given to classical descriptions of the fluid and electrostatic interactions without geometric flow based micro-macro interfaces. The detailed balance of forces is emphasized in the present work. We further extend the proposed multiscale paradigm to micro-macro analysis of electrohydrodynamics, electrophoresis, fuel cells, and ion channels. We derive generalized Poisson-Nernst-Planck equations that are coupled to generalized Navier-Stokes equations for fluid dynamics, Newton's equation for molecular dynamics, and potential and surface driving geometric flows for the micro-macro interface. For excessively large aqueous macromolecular complexes in chemistry and biology, we further develop differential geometry based multiscale fluid-electro-elastic models to replace the expensive molecular dynamics description with an alternative elasticity formulation. PMID:20169418

Wei, Guo-Wei

2010-02-19

365

Open confinement systems and the D- sup 3 He reaction  

SciTech Connect

In this paper, the special synergisms between open-ended magnetic confinement systems and the D-{sup 3}He fuel cycle are discussed, both in general terms and through examples. Properties of open systems that make them especially suited for this fuel cycle include their ability to stably confine high-beta plasmas, their compatibility with electrostatic direct converters, and their linear geometry, which can greatly simplify the practical attainment of high magnetic fields. The example systems given include a linear collider and thermal barrier tandem mirror systems for both terrestrial and space travel applications. It is concluded that satisfying the demanding physics requirements posed by the D-{sup 3}He fuel cycle may be more readily possible through the use of open-ended magnetic systems than it will be through the use of closed systems of the tokamak genre.

Post, R.F. (Lawrence Livermore National Lab., CA (United States)); Santarius, J.F. (Wisconsin Univ., Madison, WI (United States). Food Research Inst.)

1992-08-01

366

Confinement induces actin flow in a meiotic cytoplasm  

PubMed Central

In vivo, F-actin flows are observed at different cell life stages and participate in various developmental processes during asymmetric divisions in vertebrate oocytes, cell migration, or wound healing. Here, we show that confinement has a dramatic effect on F-actin spatiotemporal organization. We reconstitute in vitro the spontaneous generation of F-actin flow using Xenopus meiotic extracts artificially confined within a geometry mimicking the cell boundary. Perturbations of actin polymerization kinetics or F-actin nucleation sites strongly modify the network flow dynamics. A combination of quantitative image analysis and biochemical perturbations shows that both spatial localization of F-actin nucleators and actin turnover play a decisive role in generating flow. Interestingly, our in vitro assay recapitulates several symmetry-breaking processes observed in oocytes and early embryonic cells.

Pinot, Mathieu; Steiner, Villier; Dehapiot, Benoit; Yoo, Byung-Kuk; Chesnel, Franck; Blanchoin, Laurent; Kervrann, Charles; Gueroui, Zoher

2012-01-01

367

Simulation study of charged nanoparticles confined in a rectangular tube with discrete wall charges.  

PubMed

The development of novel nanomaterials has been a subject of intense interest in recent years. An interesting structure among these materials is the so-called "pea pods" (i.e., nanoparticles confined in nanotubes). To facilitate the development and commercialization of these materials, it is important that we have an in-depth understanding of their behavior. The study of confined charged particles is particularly challenging because of the long-ranged nature of electrostatic interaction, and both interparticle and particle-confinement interactions are likely to play a role in determining the system behavior. The primary objective of this study is to develop a better understanding of the behavior of charged nanoparticles in a charged tubular confinement using Monte Carlo simulation, with particular focus on the effect of electrostatic interactions on the structure of the particles. Simulation results have shown that (i) the structuring of confined particles is associated with the asymmetry of the long-ranged interaction and (ii) factors such as confinement geometry and particle charge and size asymmetry can be manipulated to produce different particle structures. The present study represents the first step in an attempt to gain further insight into the behavior of confined nanosystems, with the ultimate objective of exploiting these characteristics, particularly the interactions between the confined particles and their external environment, in developing novel nanomaterials. PMID:16548546

Yuet, Pak K

2006-03-28

368

First-order Dyson coordinates and geometry.  

PubMed

The mathematical constructs of the Dyson coordinates and geometry are introduced. The former are a unitary transformation of the normal coordinates and the anharmonic vibrational counterpart of the Dyson orbitals in electronic structure theory. The first-order Dyson coordinates bring the sums of the harmonic force constants and their first-order diagrammatic perturbation corrections (the first-order Dyson self-energy) to a diagonal form. The first-order Dyson geometry has no counterpart in electronic structure theory. It is the point on the potential energy surface at which the sums of the energy gradients and their first-order diagrammatic perturbation corrections vanish. It agrees with the vibrationally averaged geometry of vibrational self-consistent field (VSCF) theory in the bulk limit. These constructs provide a unified view of the relationship of VSCF and its diagrammatically size-consistent modifications as well as the self-consistent phonon method widely used in solid-state physics. PMID:23577671

Hermes, Matthew R; Hirata, So

2013-05-01

369

Weyl Geometries, Fisher Information and Quantum Entropy in Quantum Mechanics  

NASA Astrophysics Data System (ADS)

It is known that quantum mechanics can be interpreted as a non-Euclidean deformation of the space-time geometries by means Weyl geometries. We propose here a dynamical explanation of such approach by deriving Bohm potential from minimum condition of Fisher information connected to the entropy of a quantum system.

Fiscaletti, Davide; Licata, Ignazio

2012-11-01

370

a Quark-Independent Description of Confinement  

NASA Astrophysics Data System (ADS)

Currently the quantitative description of confinement inside nuclear matter is exclusively limited to computer experiments, mainly on lattices, and concentrating upon calculating the static potential. There is no independent reference for comparison and support of the results, especially when it comes to the quark potential in the continuum limit. Yet, we are entitled to be optimistic, for the basic results of these calculations seem to be correct from an entirely different point of view, suggested by Manton's geometrization of Skyrme theory. The present work shows the reasons of this point of view, and offers a static potential that might serve as independent reference for comparison and endorsement of any lattice calculations, and in fact of any structural hypotheses of nuclear matter. A historical review of the pertinent key moments in the history of modeling of nuclear matter, as well as an outlook anticipating the necessary future work, close the argument.

Mazilu, Nicolae; Ioannou, Pavlos D.; Diakonos, Fotios K.; Maintas, Xantis N.; Agop, Maricel

2013-09-01

371

Proterozoic Geomagnetic Field Geometry  

NASA Astrophysics Data System (ADS)

Pre-Mesozoic continental reconstructions and paleoclimatic inferences from paleomagnetism rely critically upon the assumption of a time-averaged geocentric axial dipole (GAD) magnetic field. We have been testing the GAD assumption and localized non-dipole components in a different manner, by observing directional variations within the Matachewan, Mackenzie and Franklin dyke swarms. Large dyke swarms, commonly emplaced within a few million years, provide the necessary broad areal coverage to perform a test of global geomagnetic field geometry. Our analysis varies the quadrupole and octupole values of the generalized paleolatitude equation to determine a minimal angular dispersion and maximum precision of paleopoles from each dyke swarm. As a control, paleomagnetic data from the central Atlantic magmatic province (CAMP) show the sensitivities of our method to non-GAD contributions to the ancient geomagnetic field. Within the uncertainties, CAMP data are consistent with independent estimates of non-GAD contributions derived from global tectonic reconstructions (Torsvik & Van der Voo, 2002). Current results from the three Proterozoic dyke swarms all have best fits that are non-dipolar, but they differ in their optimal quadrupole/ octupole components. Treated together under the hypothesis of a static Proterozoic field geometry, the data allow a pure GAD geodynamo within the uncertainty of the method. Current results were performed using Fisherian statistics, but Bingham statistics will be included to account for the ellipticity of data.

Panzik, J. E.; Evans, D. A.

2011-12-01

372

CORRELATIONS IN CONFINED QUANTUM PLASMAS  

SciTech Connect

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

DUFTY J W

2012-01-11

373

Fluctuations and confinement in ATF  

SciTech Connect

In the period immediately prior to the suspension of ATF operation in November, 1991, a great deal of emphasis was palced on investigations of the fundamental mechanisms controlling confinement in this device. At that time, measurements of the density fluctuations throughout the plasma volume indicated the existence of theoretically predicted dissipative trapped electron and resistive interchange instabilities. These identifications were supported by results of dynamic configuration scans of the magnetic fields during which the extent of the magnetic well, shear, and fraction of confined trapped particles were changed continuously. Interpretation of the data from these experiments has been an ongoing exercise. Most recently, analysis of discharges employing strong gas puffing to change density gradients and fluctuation levels have strengthened the view that dissipative trapped electron modes may be present but do not play a significant direct role in energy transport. The present paper summarizes the current understanding concerning the identification of instabilities and their relationship to confinement in ATF.

Isler, R.C.; Harris, J.H.; Murakami, M.

1993-10-01

374

Hydrodynamics of Confined Active Fluids  

NASA Astrophysics Data System (ADS)

We theoretically describe the dynamics of swimmer populations in rigidly confined thin liquid films. We first demonstrate that hydrodynamic interactions between confined swimmers depend solely on their shape and are independent of their specific swimming mechanism. We also show that, due to friction with the nearby rigid walls, confined swimmers do not just reorient in flow gradients but also in uniform flows. We then quantify the consequences of these microscopic interaction rules on the large-scale hydrodynamics of isotropic populations. We investigate in detail their stability and the resulting phase behavior, highlighting the differences with conventional active, three-dimensional suspensions. Two classes of polar swimmers are distinguished depending on their geometrical polarity. The first class gives rise to coherent directed motion at all scales, whereas for the second class we predict the spontaneous formation of coherent clusters (swarms).

Brotto, Tommaso; Caussin, Jean-Baptiste; Lauga, Eric; Bartolo, Denis

2013-01-01

375

Symplectic geometry and physics: three introductory lectures.  

NASA Astrophysics Data System (ADS)

Contents: Lecture I: geometry and physics. Lecture II: the occurrence of symplectic geometry in optics and mechanics. Lecture III: three applications of symplectic geometry. Epilog: the cat's paradigm.

Provost, J.-P.

376

On the geometry of stiff knots  

NASA Astrophysics Data System (ADS)

We report on the geometry and mechanics of knotted strings. We focus on the situation where the string is stiff (it has a large bending rigidity), and thin (its width is much smaller than its length). We find that: (i) the equilibrium energy depends on the type of knot as the square of the bridge number; (ii) braid localization is a general feature of stiff strings entanglements; (iii) there is an upper bound for the multiplicity of the braids and contact points in the ground state. (iv) Finally, a general confinement inequality is used to derive an upper bound on the knot gyration radius. We shall also discuss the asymptotic behavior of the knot when the filament width is small, both in the presence and in the absence of torsion (twist) energy. We conjecture a universal ground state geometry for thin strings with torsion rigidity in the presence of a large twists. Ref: R. Gallotti, O. Pierre-Louis, Phys. Rev. E 75, 031801 (2007).

Pierre-Louis, Olivier

2009-03-01

377

Probing quantum confinement within single core-multishell nanowires.  

PubMed

Theoretically core-multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our experiment narrows the gap between optical microscopy and high-resolution X-ray imaging and calls for further studies on the underlying mechanisms of optoelectronic nanodevices. PMID:23030721

Martínez-Criado, Gema; Homs, Alejandro; Alén, Benito; Sans, Juan A; Segura-Ruiz, Jaime; Molina-Sánchez, Alejandro; Susini, Jean; Yoo, Jinkyoung; Yi, Gyu-Chul

2012-10-05

378

Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles  

SciTech Connect

A magnetospheric configuration gives rise to various peculiar plasma phenomena that pose conundrums to astrophysical studies; at the same time, innovative technologies may draw on the rich physics of magnetospheric plasmas. We have created a ''laboratory magnetosphere'' with a levitating superconducting ring magnet. Here we show that charged particles (electrons) self-organize a stable vortex, in which particles diffuse inward to steepen the density gradient. The rotating electron cloud is sustained for more than 300 s. Because of its simple geometry and self-organization, this system will have wide applications in confining single- and multispecies charged particles.

Yoshida, Z.; Saitoh, H.; Morikawa, J.; Yano, Y.; Watanabe, S.; Ogawa, Y. [Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8561 (Japan)

2010-06-11

379

Topological superconductivity, topological confinement, and the vortex quantum Hall effect  

SciTech Connect

Topological matter is characterized by the presence of a topological BF term in its long-distance effective action. Topological defects due to the compactness of the U(1) gauge fields induce quantum phase transitions between topological insulators, topological superconductors, and topological confinement. In conventional superconductivity, because of spontaneous symmetry breaking, the photon acquires a mass due to the Anderson-Higgs mechanism. In this paper we derive the corresponding effective actions for the electromagnetic field in topological superconductors and topological confinement phases. In topological superconductors magnetic flux is confined and the photon acquires a topological mass through the BF mechanism: no symmetry breaking is involved, the ground state has topological order, and the transition is induced by quantum fluctuations. In topological confinement, instead, electric charge is linearly confined and the photon becomes a massive antisymmetric tensor via the Stueckelberg mechanism. Oblique confinement phases arise when the string condensate carries both magnetic and electric flux (dyonic strings). Such phases are characterized by a vortex quantum Hall effect potentially relevant for the dissipationless transport of information stored on vortices.

Diamantini, M. Cristina; Trugenberger, Carlo A. [INFN and Dipartimento di Fisica, University of Perugia, via A. Pascoli, I-06100 Perugia (Italy); SwissScientific, chemin Diodati 10, CH-1223 Cologny (Switzerland)

2011-09-01

380

Self-confinement of finite dust clusters in isotropic plasmas.  

PubMed

Finite two-dimensional dust clusters are systems of a small number of charged grains. The self-confinement of dust clusters in isotropic plasmas is studied using the particle-in-cell method. The energetically favorable configurations of grains in plasma are found that are due to the kinetic effects of plasma ions and electrons. The self-confinement phenomenon is attributed to the change in the plasma composition within a dust cluster resulting in grain attraction mediated by plasma ions. This is a self-consistent state of a dust cluster in which grain's repulsion is compensated by the reduced charge and floating potential on grains, overlapped ion clouds, and depleted electrons within a cluster. The common potential well is formed trapping dust clusters in the confined state. These results provide both valuable insights and a different perspective to the classical view on the formation of boundary-free dust clusters in isotropic plasmas. PMID:23004877

Miloshevsky, G V; Hassanein, A

2012-05-15

381

Abelian Lagrangian algebraic geometry  

NASA Astrophysics Data System (ADS)

This paper begins a detailed exposition of a geometric approach to quantization, which is presented in a series of preprints ([23], [24], ...) and which combines the methods of algebraic and Lagrangian geometry. Given a prequantization U (1)-bundle L on a symplectic manifold M, we introduce an infinite-dimensional Kähler manifold \\mathscr P^{\\mathrm{hw}} of half-weighted Planck cycles. With every Kähler polarization on M we canonically associate a map \\mathscr P^{\\mathrm{hw}}\\overset{\\gamma}{\\to}H^{0}(M,L) to the space of holomorphic sections of the prequantization bundle. We show that this map has a constant Kähler angle and its "twisting" to a holomorphic map is the Borthwick-Paul-Uribe map. The simplest non-trivial illustration of all these constructions is provided by the theory of Legendrian knots in S^3.

Gorodentsev, A. L.; Tyurin, A. N.

2001-06-01

382

Geometry from Gauge Theory  

SciTech Connect

We discuss how geometrical and topological aspects of certain (1/2)-BPS type IIB geometries are captured by their dual operators in N = 4 Super Yang-Mills theory. The type IIB solutions are characterized by arbitrary droplet pictures in a plane and we consider, in particular, axially symmetric droplets. The 1-loop anomalous dimension of the dual gauge theory operators probed with single traces is described by some bosonic lattice Hamiltonians. These Hamiltonians are shown to encode the topology of the droplets. In appropriate BMN limits, the Hamiltonians spectrum reproduces the spectrum of near-BPS string excitations propagating along each of the individual edges of the droplet. We also study semiclassical regimes for the Hamiltonians. For droplets having disconnected constituents, the Hamiltonian admits different complimentary semiclassical descriptions, each one replicating the semiclassical description for closed strings extending in each of the constituents.

Correa, Diego H. [DAMTP, Centre for Mathematical Sciences, University of Cambridge Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Silva, Guillermo A. [IFLP-CCT-La Plata, CONICET and Departamento de Fisica, Universidad Nacional de La Plata CC 67, (1900) La Plata (Argentina)

2008-07-28

383

Symplectic Geometry of Entanglement  

NASA Astrophysics Data System (ADS)

We present a description of entanglement in composite quantum systems in terms of symplectic geometry. We provide a symplectic characterization of sets of equally entangled states as orbits of group actions in the space of states. In particular, using the Kostant-Sternberg theorem, we show that separable states form a unique symplectic orbit, whereas orbits of entangled states are characterized by different degrees of degeneracy of the canonical symplectic form on the complex projective space. The degree of degeneracy may be thus used as a new geometric measure of entanglement. The above statements remain true for systems with an arbitrary number of components, moreover the presented method is general and can be applied also under different additional symmetry conditions stemming, e.g., from the indistinguishability of particles. We show how to calculate the degeneracy for various multiparticle systems providing also simple criteria of separability.

Sawicki, Adam; Huckleberry, Alan; Ku?, Marek

2011-07-01

384

Studies in quantum geometry  

NASA Astrophysics Data System (ADS)

The geometric defects associated with open strings have become a mainstay in the arsenal of the string theorist. These objects are intimately tied to the properties of spacetime. D-branes have been well studied in the nineties and orientifolds are only now been thoroughly investigated. This thesis is built on two different studies. The first, done with Koenraad Schalm and Chuck Doran attempts to analyze the possible Orientifolds and their moduli, starting from Gepner models of the spacetime. The main focus was on elliptical compactifications, as this could be used as building block for more complex geometries. It is noteworthy that the orientifolds place constraints on the possible spacetime geometries, whilst also being characterized by the geometrical nature of the involutions defining them. The second study of this thesis, which was done with Frederik Denef, is on the low energy manifestations of D-branes as supergravity attractor solutions. Four dimensional N = 2 supergravity has regular, stationary, asymptotically flat BPS solutions with intrinsic angular momentum, describing bound states of separate extremal black holes with mutually nonlocal charges. Though the existence and some properties of these solutions were established some time ago, fully explicit analytic solutions were lacking thus far. In this study this gap is filled. We found that in general explicit solutions can be constructed whenever an explicit formula is known in the theory at hand for the Bekenstein-Hawking entropy of a single black hole as a function of its charges, and illustrated this with some simple examples. We also found an example of moduli-dependent black hole entropy.

Bates, Brandon D.

385

Inertial confinement fusion (ICF) review  

SciTech Connect

During its 1996 winter study JASON reviewed the DOE Inertial Confinement Fusion (ICF) program. This included the National Ignition Facility (NIF) and proposed studies. The result of the review was to comment on the role of the ICF program in support of the DOE Science Based Stockpile Stewardship program.

Hammer, D.; Dyson, F.; Fortson, N.; Novick, B.; Panofsky, W.; Rosenbluth, M.; Treiman, S.; York, H.

1996-03-01

386

Biased Diffusion in Confined Media  

Microsoft Academic Search

We study biased, diffusive transport of Brownian particles through narrow, spatially periodic structures in which the motion is constrained in lateral directions. The problem is analyzed using the Fick-Jacobs equation in which the effect of the lateral confinement is replaced by an entropic barrier. The validity of this approximation, being based on the assumption of an instantaneous equilibration of the

P. S. Burada; G. Schmid; D. Reguera; J. M. Rubi´

2007-01-01

387

Prospects of inertial confinement fusion  

Microsoft Academic Search

The present status of inertial confinement fusion (ICF) is briefly reviewed, emphasizing the National Ignition Facility (NIF) project in the US and the Megajoule project in France. Critical aspects of target performance such as symmetry and stability of capsule implosions and interaction physics in hohlraum targets are discussed. The advantages of heavy-ion beam drivers and corresponding research programs are pointed

J. Meyer-ter-Vehn

1997-01-01

388

Momentum Confinement at Low Torque  

SciTech Connect

Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.

Solomon, W M; Burrell, K H; deGrassie, J S; Budny, R; Groebner, R J; Heidbrink, W W; Kinsey, J E; Kramer, G J; Makowski, M A; Mikkelsen, D; Nazikian, R; Petty, C C; Politzer, P A; Scott, S D; Van Zeeland, M A; Zarnstorff, M C

2007-06-26

389

Droplet microfluidics driven by gradients of confinement  

PubMed Central

The miniaturization of droplet manipulation methods has led to drops being proposed as microreactors in many applications of biology and chemistry. In parallel, microfluidic methods have been applied to generate monodisperse emulsions for applications in the pharmaceuticals, cosmetics, and food industries. To date, microfluidic droplet production has been dominated by a few designs that use hydrodynamic forces, resulting from the flowing fluids, to break drops at a junction. Here we present a platform for droplet generation and manipulation that does not depend on the fluid flows. Instead, we use devices that incorporate height variations to subject the immiscible interfaces to gradients of confinement. The resulting curvature imbalance along the interface causes the detachment of monodisperse droplets, without the need for a flow of the external phase. Once detached, the drops are self-propelled due to the gradient of surface energy. We show that the size of the drops is determined by the device geometry; it is insensitive to the physical fluid properties and depends very weakly on the flow rate of the dispersed phase. This allows us to propose a geometric theoretical model that predicts the dependence of droplet size on the geometric parameters, which is in agreement with experimental measurements. The approach presented here can be applied in a wide range of standard applications, while simplifying the device operations. We demonstrate examples for single-droplet operations and high-throughput generation of emulsions, all of which are performed in simple and inexpensive devices.

Dangla, Remi; Kayi, S. Cagri; Baroud, Charles N.

2013-01-01

390

Droplet microfluidics driven by gradients of confinement.  

PubMed

The miniaturization of droplet manipulation methods has led to drops being proposed as microreactors in many applications of biology and chemistry. In parallel, microfluidic methods have been applied to generate monodisperse emulsions for applications in the pharmaceuticals, cosmetics, and food industries. To date, microfluidic droplet production has been dominated by a few designs that use hydrodynamic forces, resulting from the flowing fluids, to break drops at a junction. Here we present a platform for droplet generation and manipulation that does not depend on the fluid flows. Instead, we use devices that incorporate height variations to subject the immiscible interfaces to gradients of confinement. The resulting curvature imbalance along the interface causes the detachment of monodisperse droplets, without the need for a flow of the external phase. Once detached, the drops are self-propelled due to the gradient of surface energy. We show that the size of the drops is determined by the device geometry; it is insensitive to the physical fluid properties and depends very weakly on the flow rate of the dispersed phase. This allows us to propose a geometric theoretical model that predicts the dependence of droplet size on the geometric parameters, which is in agreement with experimental measurements. The approach presented here can be applied in a wide range of standard applications, while simplifying the device operations. We demonstrate examples for single-droplet operations and high-throughput generation of emulsions, all of which are performed in simple and inexpensive devices. PMID:23284169

Dangla, Rémi; Kayi, S Cagri; Baroud, Charles N

2013-01-02

391

Motion, relaxation dynamics, and diffusion processes in two-dimensional colloidal crystals confined between walls  

NASA Astrophysics Data System (ADS)

The dynamical behavior of single-component two-dimensional colloidal crystals confined in a slit geometry is studied by Langevin dynamics simulation of a simple model. The colloids are modeled as pointlike particles, interacting with the repulsive part of the Lennard-Jones potential, and the fluid molecules in the colloidal suspension are not explicitly considered. Considering a crystalline strip of triangular lattice structure with n=30 rows, the (one-dimensional) walls confining the strip are chosen as two rigidly fixed crystalline rows at each side, commensurate with the lattice structure and, thus, stabilizing long-range order. The case when the spacing between the walls is incommensurate with the ideal triangular lattice is also studied, where (due to a transition in the number of rows, n?n-1) the confined crystal is incommensurate with the confining boundaries, and a soliton staircase forms along the walls. It is shown that mean-square displacements (MSDs) of particles as a function of time show an overshoot and then saturate at a horizontal plateau in the commensurate case, the value of the plateau being largest in the center of the strip. Conversely, when solitons are present, MSDs are largest in the rows containing the solitons, and all MSDs do not settle down at well-defined plateaus in the direction parallel to the boundaries, due to the lack of positional long-range order in ideal two-dimensional crystals. The MSDs of the solitons (which can be treated like quasiparticles at very low temperature) have also been studied and their dynamics are found to be about an order of magnitude slower than that of the colloidal particles themselves. Finally, transport of individual colloidal particles by diffusion processes is studied: both standard vacancy-interstitial pair formation and cooperative ring rotation processes are identified. These processes require thermal activation, with activation energies of the order of 10Tm (Tm being the melting temperature of the crystal), while the motions due to long-wavelength phonons decrease only linearly in temperature.

Wilms, Dorothea; Virnau, Peter; Snook, Ian K.; Binder, Kurt

2012-11-01

392

Anomalous suppression of superfluidity in ^4He confined in a nano-porous glass  

NASA Astrophysics Data System (ADS)

When ^4He is confined in porous medium such as Vycor glass, the superfluidity is suppressed. This superfluid suppression may be enhanced as the pore size approaches the superfluid coherence length. Here we report a torsional oscillator measurement for ^4He confined in a porous Gelsil glass which has nanopores of 2.5 nm in diameter, at pressures up to 5 MPa[1]. At SVP the superfluid transition is observed at 1.4 K, which is much lower than the bulk lambda point 2.17 K. With increasing pressure, the superfluidity is drastically suppressed, and the transition temperature approaches 0 K at Pc = 3.5 MPa. The features are quite unprecedented for ^4He in any other confined geometries, and strongly suggest that the confined ^4He undergoes a quantum phase transition from superfluid to nonsuperfluid at 0 K, and at P_c. [1] K. Yamamoto et al., cond-mat/0310375.

Shirahama, Keiya; Yamamoto, Keiichi; Nakashima, Haruki; Shibayama, Yoshiyuki

2004-03-01

393

Towards assessing the violence of reaction during cookoff of confined energetic materials  

SciTech Connect

An analysis of post-ignition events in a variable confinement cookoff test (VCCT) geometry is presented aimed toward predicting the level of violence during cookoff of confined thermally-degraded energetic materials. This study focuses on the dynamic events following thermal initiation whereby accelerated combustion interacts with confinement. Numerical simulations, based on a model of reactive multiphase mixtures, indicate that the response of energetic material is highly dependent upon thermal/mechanical damage states prior to ignition. These damaged states affect the rate of pressurization, dynamic compaction behavior and subsequent growth to detonation. Variations of the specific surface area and porosity produced by decomposition of the energetic material causes different responses ranging from pressure burst to detonation. Calculated stress histories are used in estimating breakup of the VCCT confinement based on Grady-Kipp fragmentation theory.

Baer, M.R.; Kipp, M.E.; Schmitt, R.G.; Hobbs, M.L.

1996-11-01

394

Layering, freezing, and re-entrant melting of hard spheres in soft confinement  

NASA Astrophysics Data System (ADS)

Confinement can have a dramatic effect on the behavior of all sorts of particulate systems, and it therefore is an important phenomenon in many different areas of physics and technology. Here, we investigate the role played by the softness of the confining potential. Using grand canonical Monte Carlo simulations, we determine the phase diagram of three-dimensional hard spheres that in one dimension are constrained to a plane by a harmonic potential. The phase behavior depends strongly on the density and on the stiffness of the harmonic confinement. While we find the familiar sequence of confined hexagonal and square-symmetric packings, we do not observe any of the usual intervening ordered phases. Instead, the system phase separates under strong confinement, or forms a layered re-entrant liquid phase under weaker confinement. It is plausible that this behavior is due to the larger positional freedom in a soft confining potential and to the contribution that the confinement energy makes to the total free energy. The fact that specific structures can be induced or suppressed by simply changing the confinement conditions (e.g., in a dielectrophoretic trap) is important for applications that involve self-assembled structures of colloidal particles.

Curk, Tine; de Hoogh, Anouk; Martinez-Veracoechea, Francisco J.; Eiser, Erika; Frenkel, Daan; Dobnikar, Jure; Leunissen, Mirjam E.

2012-02-01

395

Layering, freezing, and re-entrant melting of hard spheres in soft confinement.  

PubMed

Confinement can have a dramatic effect on the behavior of all sorts of particulate systems, and it therefore is an important phenomenon in many different areas of physics and technology. Here, we investigate the role played by the softness of the confining potential. Using grand canonical Monte Carlo simulations, we determine the phase diagram of three-dimensional hard spheres that in one dimension are constrained to a plane by a harmonic potential. The phase behavior depends strongly on the density and on the stiffness of the harmonic confinement. While we find the familiar sequence of confined hexagonal and square-symmetric packings, we do not observe any of the usual intervening ordered phases. Instead, the system phase separates under strong confinement, or forms a layered re-entrant liquid phase under weaker confinement. It is plausible that this behavior is due to the larger positional freedom in a soft confining potential and to the contribution that the confinement energy makes to the total free energy. The fact that specific structures can be induced or suppressed by simply changing the confinement conditions (e.g., in a dielectrophoretic trap) is important for applications that involve self-assembled structures of colloidal particles. PMID:22463214

Curk, Tine; de Hoogh, Anouk; Martinez-Veracoechea, Francisco J; Eiser, Erika; Frenkel, Daan; Dobnikar, Jure; Leunissen, Mirjam E

2012-02-21

396

New confining N=1 supersymmetric gauge theories  

SciTech Connect

We examine N=1 supersymmetric gauge theories which confine in the presence of a tree-level superpotential. We show the confining spectra which satisfy the 't Hooft anomaly matching conditions and give a simple method to find the confining superpotential. Using this method we fix the confining superpotentials in the simplest cases, and show how these superpotentials are generated by multi-instanton effects in the dual theory. These new type of confining theories may be useful for model building, since the size of the matter content is not restricted by an index constraint. Therefore, one expects that a large variety of new confining spectra can be obtained using such models.

Csaki, C.; Murayama, H.

1998-10-01

397

Learning Geometry in Georgian England  

NSDL National Science Digital Library

How did people learn geometry in Georgian England? It was different than in our own time, to be sure. This feature from Loci, the online publication of the MAA Mathematical Sciences Digital Library offers a bit of detail on the matter, courtesy of the geometry copybook of a boy named Thomas Porcher. This particular feature was written by Benjamin Wardhaugh from the University of Oxford. In the six-part feature, Wardhaugh looks into why such a boy would learn geometry and also what the existing texts were at the time. The article contains sections like "Geometry and Measuring" and "Geometry and Practical Geometry." It's a fascinating study, and one that will be intriguing to those with a penchant for the history of mathematics and pedagogy.

Wardhaugh, Benjamin, 1979-; Porcher, Thomas

2012-09-21

398

Orbit averaged radial buildup code for tandem mirror geometry  

Microsoft Academic Search

The radial Fokker-Planck (RFP) model of A. Futch was modified to treat plasma buildup in the tandem mirror plug and center cell with a self-consistent model (TOARBUC). Two major changes have been made to the original version of this code. First, the center cell is treated as having separate electron and ion confining potentials with the ion potential having the

M. Campbell; A. H. Futch

1981-01-01

399

Inertial electrostatic confinement as a power source for electric propulsion  

Microsoft Academic Search

The potential use of an INERTIAL ELECTROSTATIC CONFINEMENT (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engine (QED) concept proposed by Bussard, in which the IEC is used to generate an electron beam which vaporizes liquid hydrogen for use as a propellant.

G. H. Miley; R. Burton; J. Javedani; Y. Yamamoto; A. Satsangi; Y. Gu; P. Heck; R. Nebel; N. Schulze; J. Christensen

1993-01-01

400

Investigation of contaminant transport from the saginaw confined disposal facility  

Microsoft Academic Search

Pilot biomonitoring and modeling studies were conducted at the Saginaw Confined Disposal Facility (CDF), Saginaw Bay, Lake Huron, during 1987 to develop methods to assess the potential for or magnitude of (1) contaminant transport from the dike interior to the outside environment, (2) impacts of CDF disposal on the water column and sediments, and (3) impacts of CDF disposal on

Mark L. Velleux; Joseph E. Rathbun; Russell G. Kreis Jr; James L. Martin; Michael J. Mac; Marc L. Tuchman

1993-01-01

401

Improved virtual cathode formation in Inertial Electrostatic Confinement  

Microsoft Academic Search

Summary form only given. Continued experimentation on the inertial electrostatic confinement (IEC) of ions in a virtual cathode potential well at Los Alamos National Laboratory (LANL) is presented. The IEC virtual cathode is formed by focusing six diametrically opposed electron beams to the center of a spherical vacuum chamber. The electrons are accelerated using two highly transparent, concentric spherical grids

A. M. McEvoy; Y. H. Kim; H. W. Herrmann

2009-01-01

402

Inertial-electrostatic confinement (IEC) fusion for space power  

Microsoft Academic Search

Fusion offers the potential for a very high specific power, providing a large specific impulse that can be traded-off with thrust for mission optimization. Thus fusion is a leading candidate for missions beyond the moon. Here we discuss a new approach for space fusion power, namely Inertial-Electrostatic Confinement (IEC). This method offers a high power density in a relatively small,

George H. Miley; Jonathon H. Nadler; Timothy K. Hochberg; Olivier Barnouin; Yibin Gu

1991-01-01

403

Conceptual Design of the Chornobyl New Safe Confinement - an Overview  

Microsoft Academic Search

The Object Shelter, constructed over the Chornobyl nuclear power plant that was destroyed by a 1986 accident, is at risk of collapse. The Consortium of Bechtel, Electricité De France, and Battelle, in cooperation with subcontractor ÐСÐ, recently completed the conceptual design for a New Safe Confinement (NSC) building to reduce Shelter corrosion, to mitigate the consequences of potential collapse, and

Valery N. Kulishenko; Charles Hogg; Eric A. Schmieman; Matthew W. Wrona; Philippe Convert; Yuriy I. Nemchinov; Victor Shenderovich; Vladimir Shcherbin; Pascal Belicard; Bruce M. Durst

2006-01-01

404

Behavior of Plastic Sand Confinement Grids.  

National Technical Information Service (NTIS)

The concept of improving the load carrying ability of unbound aggregates, particularly sand, by lateral confinement has been investigated for some time. Extensive full-scale testing of the trafficability of confined beach sand pavement layers has been car...

1986-01-01

405

Analytic Coleman-de Luccia Geometries  

SciTech Connect

We present the necessary and sufficient conditions for a Euclidean scale factor to be a solution of the Coleman-de Luccia equations for some analytic potential V ({psi}), with a Lorentzian continuation describing the growth of a bubble of lower-energy vacuum surrounded by higher-energy vacuum. We then give a set of explicit examples that satisfy the conditions and thus are closed-form analytic examples of Coleman-de Luccia geometries.

Dong, Xi; /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC; Harlow, Daniel; /Stanford U., ITP /Stanford U., Phys. Dept.

2012-02-16

406

Whole-volume integrated gyrokinetic simulation of plasma turbulence in realistic diverted-tokamak geometry  

SciTech Connect

Performance prediction for ITER is based upon the ubiquitous experimental observation that the plasma energy confinement in the device core is strongly coupled to the edge confinement for an unknown reason. The coupling time-scale is much shorter than the plasma transport time-scale. In order to understand this critical observation, a multi-scale turbulence-neoclassical simulation of integrated edge-core plasma in a realistic diverted geometry is a necessity, but has been a formidable task. Thanks to the recent development in high performance computing, we have succeeded in the integrated multiscale gyrokinetic simulation of the ion-temperature-gradient driven turbulence in realistic diverted tokamak geometry for the first time. It is found that modification of the self-organized criticality in the core plasma by nonlocal core-edge coupling of ITG turbulence can be responsible for the core-edge confinement coupling.

Chang, C S [New York University; Ku, Seung-Hoe [New York University; Diamond, P. H. [University of California, San Diego; Adams, Mark [Columbia University; Tchoua, Roselyne B [ORNL; Chen, Yang [University of Colorado, Boulder; Cummings, J. [California Institute of Technology, University of California, Davis; D'Azevedo, Ed F [ORNL; Dif-Pradalier, Guilhem [University of California, San Diego; Ethier, Stephane [Princeton Plasma Physics Laboratory (PPPL); Greengard, Leslie [New York University; Hahm, Taik Soo [Princeton Plasma Physics Laboratory (PPPL); Hinton, Fred [University of California, San Diego; Keyes, David E [Columbia University; Klasky, Scott A [ORNL; Lin, Z. [University of California, Irvine; Lofstead, J. [Georgia Institute of Technology; Park, G. [New York University; Podhorszki, Norbert [ORNL; Schwan, Karsten [Georgia Institute of Technology; Shoshani, A. [Lawrence Berkeley National Laboratory (LBNL); Silver, D. [Rutgers University; Wolf, M. [Georgia Institute of Technology; Worley, Patrick H [ORNL; Zorin, Denis [New York University

2009-01-01

407

Whole-volume integrated gyrokinetc simulation of plasma turbulence in realistic diverted-tokamak geometry  

SciTech Connect

Performance prediction for ITER is based upon the ubiquitous experimental observation that the plasma energy confinement in the device core is strongly coupled to the edge confinement for an unknown reason. The coupling time-scale is much shorter than the plasma transport time-scale. In order to understand this critical observation, a multi-scale turbulence-neoclassical simulation of integrated edge-core plasma in a realistic diverted geometry is a necessity, but has been a formidable task. Thanks to the recent development in high performance computing, we have succeeded in the integrated multiscale gyrokinetic simulation of the ion-temperature-gradient driven turbulence in realistic diverted tokamak geometry for the first time. It is found that modification of the self-organized criticality in the core plasma by nonlocal core-edge coupling of ITG turbulence can be responsible for the core-edge confinement coupling.

Chang, C S [New York University; Ku, Seung-Hoe [New York University; Diamond, Patrick [Columbia University; Adams, Mark [Columbia University; Tchoua, Roselyne B [ORNL; Chen, Yang [University of Colorado, Boulder; Cummings, Julian [California Institute of Technology, Pasadena; D'Azevedo, Eduardo [ORNL; Dif-Pradalier, Guilhem [University of California, San Diego; Ethier, Stephane [Princeton Plasma Physics Laboratory (PPPL); Greengard, Leslie [New York University; Hahm, Taik Soo [Princeton Plasma Physics Laboratory (PPPL); Hinton, Fred [University of California, San Diego; Keyes, David E [Columbia University; Klasky, Scott A [ORNL; Lin, Zhihong [University of California, Irvine; Lofstead, J. [Georgia Institute of Technology; Park, G. [New York University; Parker, Scott [University of Colorado, Boulder; Podhorszki, Norbert [ORNL; Schwan, Karsten [Georgia Institute of Technology; Shoshani, A. [Lawrence Berkeley National Laboratory (LBNL); Silver, D. [Rutgers University; Weitzner, Harold [New York University; Wolf, M. [Georgia Institute of Technology; Worley, Patrick H [ORNL; Yoon, E. [Princeton Plasma Physics Laboratory (PPPL); Zorin, Denis [New York University

2009-01-01

408

Hierarchical models with inverse-square interaction in harmonic confinement  

NASA Astrophysics Data System (ADS)

A hierarchy of quantum models with inverse-square pairwise interaction is studied for the system with a confining harmonic potential. An approach based on renormalized harmonic oscillators is used to construct the energy spectrum, which naturally results in the renormalized Hartree-Fock description of the interaction. In the limit of weak confinement, the model may serve as a canonical model for multiple chiral Tomonaga-Luttinger liquids for the edge states of the fractional quantum Hall effect. For the SU(?) symmetric case, we find that the excitation spectrum is classified in terms of the simple roots and the weights of SU(?) Lie algebra.

Kawakami, Norio; Kuramoto, Yoshio

1994-08-01

409

Influence of confinement on thermodiffusion  

NASA Astrophysics Data System (ADS)

This work focuses on a possible influence of a nanoporous medium on the thermodiffusion of a fluid ``isotopic'' mixture. To do so, we performed molecular dynamics simulations of confined Lennard-Jones binary equimolar mixtures using grand-canonical like and non-equilibrium approaches in sub- and super-critical conditions. The study was conducted in atomistic slit pore of three adsorbent natures for various widths (from 5 to 35 times the size of a molecule). The simulation results indicate that for all thermodynamic conditions and whatever the pore characteristics, the confinement has a negligible effect on the thermal diffusion factor/Soret coefficient. However, when considered separately, the mass diffusion and thermodiffusion coefficients have been found to be largely influenced by the pore characteristics. These two coefficients decrease noticeably when adsorption is stronger and pore width smaller, a behavior that is consistent with a simple hydrodynamic explanation.

Hannaoui, Rachid; Galliero, Guillaume; Hoang, Hai; Boned, Christian

2013-09-01

410

Influence of confinement on thermodiffusion.  

PubMed

This work focuses on a possible influence of a nanoporous medium on the thermodiffusion of a fluid "isotopic" mixture. To do so, we performed molecular dynamics simulations of confined Lennard-Jones binary equimolar mixtures using grand-canonical like and non-equilibrium approaches in sub- and super-critical conditions. The study was conducted in atomistic slit pore of three adsorbent natures for various widths (from 5 to 35 times the size of a molecule). The simulation results indicate that for all thermodynamic conditions and whatever the pore characteristics, the confinement has a negligible effect on the thermal diffusion factor?Soret coefficient. However, when considered separately, the mass diffusion and thermodiffusion coefficients have been found to be largely influenced by the pore characteristics. These two coefficients decrease noticeably when adsorption is stronger and pore width smaller, a behavior that is consistent with a simple hydrodynamic explanation. PMID:24070302

Hannaoui, Rachid; Galliero, Guillaume; Hoang, Hai; Boned, Christian

2013-09-21

411

Quantum chromodynamics near the confinement limit  

SciTech Connect

These nine lectures deal at an elementary level with the strong interaction between quarks and its implications for the structure of hadrons. Quarkonium systems are studied as a means for measuring the interquark interaction. This is presumably (part of) the answer a solution to QCD must yield, if it is indeed the correct theory of the strong interactions. Some elements of QCD are reviewed, and metaphors for QCD as a confining theory are introduced. The 1/N expansion is summarized as a way of guessing the consequences of QCD for hadron physics. Lattice gauge theory is developed as a means for going beyond perturbation theory in the solution of QCD. The correspondence between statistical mechanics, quantum mechanics, and field theory is made, and simple spin systems are formulated on the lattice. The lattice analog of local gauge invariance is developed, and analytic methods for solving lattice gauge theory are considered. The strong-coupling expansion indicates the existence of a confining phase, and the renormalization group provides a means for recovering the consequences of continuum field theory. Finally, Monte Carlo simulations of lattice theories give evidence for the phase structure of gauge theories, yield an estimate for the string tension characterizing the interquark force, and provide an approximate description of the quarkonium potential in encouraging good agreement with what is known from experiment.

Quigg, C.

1985-09-01

412

Deuterium anions in inertial electrostatic confinement devices  

NASA Astrophysics Data System (ADS)

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5?A/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7cm2 . Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2- , and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device.

Boris, D. R.; Alderson, E.; Becerra, G.; Donovan, D. C.; Egle, B.; Emmert, G. A.; Garrison, L.; Kulcinski, G. L.; Santarius, J. F.; Schuff, C.; Zenobia, S. J.

2009-09-01

413

Deuterium anions in inertial electrostatic confinement devices.  

PubMed

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5 microA/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7 cm2. Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2(-), and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device. PMID:19905231

Boris, D R; Alderson, E; Becerra, G; Donovan, D C; Egle, B; Emmert, G A; Garrison, L; Kulcinski, G L; Santarius, J F; Schuff, C; Zenobia, S J

2009-09-30

414

Alternative approaches to plasma confinement  

Microsoft Academic Search

The paper discusses 20 plasma confinement schemes each representing an alternative to the tokamak fusion reactor. Attention is given to: (1) tokamak-like devices (TORMAC, Topolotron, and the Extrap concept), (2) stellarator-like devices (Torsatron and twisted-coil stellarators), (3) mirror machines (Astron and reversed-field devices, the 2XII B experiment, laser-heated solenoids, the LITE experiment, the Kaktus-Surmac concept), (4) bumpy tori (hot electron

J. R. Roth

1978-01-01

415

Plasma confinement studies in LHD  

Microsoft Academic Search

The initial experiments on the Large Helical Device (LHD) have extended confinement studies on currentless plasmas to a large scale (R = 3.9 m, a = 0.6 m). Heating by NBI of 3 MW produced plasmas with a fusion triple product of 8 × 1018m-3·keV·s at a magnetic field strength of 1.5 T. An electron temperature of 1.5 keV and

M. Fujiwara; H. Yamada; A. Ejiri; M. Emoto; H. Funaba; M. Goto; K. Ida; H. Idei; S. Inagaki; S. Kado; O. Kaneko; K. Kawahata; T. Kobuchi; A. Komori; S. Kubo; R. Kumazawa; S. Masuzaki; T. Minami; J. Miyazawa; T. Morisaki; S. MURAKAMI; S. Murakami; S. Muto; T. Mutoh; Y. Nagayama; Y. Nakamura; H. Nakanishi; K. Narihara; K. Nishimura; N. Noda; S. Ohdachi; N. Ohyabu; Y. Oka; M. Osakabe; T. Ozaki; B. J. Peterson; A. Sagara; S. Sakakibara; R. Sakamoto; H. Sasao; M. Sasao; K. Sato; M. Sato; T. Seki; T. Shimozuma; M. Shoji; H. Suzuki; Y. Takeiri; K. Tanaka; K. Toi; T. Tokuzawa; K. Tsumori; K. Tsuzuki; K. Y. Watanabe; T. Watari; I. Yamada; S. Yamaguchi; M. Yokoyama; R. Akiyama; H. Chikaraishi; K. Haba; S. Hamaguchi; M. Iima; S. Imagawa; N. Inoue; K. Iwamoto; S. Kitagawa; J. Kodaira; Y. Kubota; R. Maekawa; T. Mito; T. Nagasaka; A. Nishimura; C. Takahashi; K. Takahata; Y. Takita; H. Tamura; T. Tsuzuki; S. Yamada; K. Yamauchi; N. Yanagi; H. Yonezu; Y. Hamada; K. Matsuoka; K. Murai; K. Ohkubo; I. Ohtake; M. Okamoto; S. Satoh; T. Satow; S. Sudo; S. Tanahashi; K. Yamazaki; O. Motojima; A. Iiyoshi

1999-01-01

416

Plasma confinement studies in LHD  

NASA Astrophysics Data System (ADS)

The initial experiments on the Large Helical Device (LHD) have extended confinement studies on currentless plasmas to a large scale (R = 3.9 m, a = 0.6 m). Heating by NBI of 3 MW produced plasmas with a fusion triple product of 8 × 1018m-3·keV·s at a magnetic field strength of 1.5 T. An electron temperature of 1.5 keV and an ion temperature of 1.1 keV were achieved simultaneously at a line averaged electron density of 1.5 × 1019 m-3. The maximum stored energy reached 0.22 MJ with neither unexpected confinement deterioration nor visible MHD instabilities, which corresponds to langle?rangle = 0.7%. Energy confinement times reached a maximum of 0.17 s. A favourable dependence of energy confinement time on density remains in the present power density (~40 kW/m3) and electron density (3 × 1019 m-3) regimes, unlike the L mode in tokamaks. Although power degradation and significant density dependence are similar to the conditions on existing medium sized helical devices, the absolute value is enhanced by up to about 50% from the International Stellarator Scaling 95. Temperatures of both electrons and ions as high as 200 eV were observed at the outermost flux surface, which indicates a qualitative jump in performance compared with that of helical devices to date. Spontaneously generated toroidal currents indicate agreement with the physical picture of neoclassical bootstrap currents. Change of magnetic configuration due to the finite ? effect was well described by 3-D MHD equilibrium analysis. A density pump-out phenomenon was observed in hydrogen discharges, which was mitigated in helium discharges with high recycling.

Fujiwara, M.; Yamada, H.; Ejiri, A.; Emoto, M.; Funaba, H.; Goto, M.; Ida, K.; Idei, H.; Inagaki, S.; Kado, S.; Kaneko, O.; Kawahata, K.; Kobuchi, T.; Komori, A.; Kubo, S.; Kumazawa, R.; Masuzaki, S.; Minami, T.; Miyazawa, J.; Morisaki, T.; Morita, S.; Murakami, S.; Muto, S.; Mutoh, T.; Nagayama, Y.; Nakamura, Y.; Nakanishi, H.; Narihara, K.; Nishimura, K.; Noda, N.; Ohdachi, S.; Ohyabu, N.; Oka, Y.; Osakabe, M.; Ozaki, T.; Peterson, B. J.; Sagara, A.; Sakakibara, S.; Sakamoto, R.; Sasao, H.; Sasao, M.; Sato, K.; Sato, M.; Seki, T.; Shimozuma, T.; Shoji, M.; Suzuki, H.; Takeiri, Y.; Tanaka, K.; Toi, K.; Tokuzawa, T.; Tsumori, K.; Tsuzuki, K.; Watanabe, K. Y.; Watari, T.; Yamada, I.; Yamaguchi, S.; Yokoyama, M.; Akiyama, R.; Chikaraishi, H.; Haba, K.; Hamaguchi, S.; Iima, M.; Imagawa, S.; Inoue, N.; Iwamoto, K.; Kitagawa, S.; Kodaira, J.; Kubota, Y.; Maekawa, R.; Mito, T.; Nagasaka, T.; Nishimura, A.; Takahashi, C.; Takahata, K.; Takita, Y.; Tamura, H.; Tsuzuki, T.; Yamada, S.; Yamauchi, K.; Yanagi, N.; Yonezu, H.; Hamada, Y.; Matsuoka, K.; Murai, K.; Ohkubo, K.; Ohtake, I.; Okamoto, M.; Satoh, S.; Satow, T.; Sudo, S.; Tanahashi, S.; Yamazaki, K.; Motojima, O.; Iiyoshi, A.

1999-11-01

417

Limits on rock strength under high confinement  

Microsoft Academic Search

Understanding of deep earthquake source mechanisms requires knowledge of failure processes active under high confinement. Under low confinement the compressive strength of rock is well known to be limited by frictional sliding along stress-concentrating flaws. Under higher confinement strength is usually assumed limited by power-law creep associated with the movement of dislocations. In a review of existing experimental data, we

Carl E. Renshaw; Erland M. Schulson

2007-01-01

418

DEEP SEARCH IN LINGUISTIC GEOMETRY  

Microsoft Academic Search

This paper is a new step in the development and application of the Linguistic Geometry. We investigate heuristics extracted in the form of hierarchical networks of planning paths of autonomous agents. Employing Linguistic Geometry tools the dynamic hierarchy of networks is represented as a hierarchy of formal attribute languages. The main ideas of this methodology are shown in this paper

Boris Stilman

419

GPS: Geometry, Probability, and Statistics  

ERIC Educational Resources Information Center

|It might be said that for most occupations there is now less of a need for mathematics than there was say fifty years ago. But, the author argues, geometry, probability, and statistics constitute essential knowledge for everyone. Maybe not the geometry of Euclid, but certainly geometrical ways of thinking that might enable us to describe the…

Field, Mike

2012-01-01

420

PROP Profile of Poisson Geometry  

NASA Astrophysics Data System (ADS)

It is shown that some classical local geometries are of infinity origin, i.e. their smooth formal germs are (homotopy) representations of cofibrant (di) operads in spaces concentrated in degree zero. In particular, they admit natural infinity generalizations when one considers homotopy representations of the (di) operads in generic differential graded spaces. Poisson geometry provides us with a simplest manifestation of this phenomenon.

Merkulov, S. A.

2006-02-01

421

Hamiltonian Gravity and Noncommutative Geometry  

NASA Astrophysics Data System (ADS)

A version of foliated spacetime is constructed in which the spatial geometry is described as a time-dependent noncommutative geometry. The ADM version of the gravitational action is expressed in terms of these variables. It is shown that the vector constraint is obtained without the need for an extraneous shift vector in the action.

Hawkins, Eli

422

Achievement in Writing Geometry Proofs.  

ERIC Educational Resources Information Center

|In 1981 a nationwide assessment of achievement in writing geometry proofs was conducted by the Cognitive Development and Achievement in Secondary School Geometry project. Over 1,500 students in 11 schools in 5 states participated. This paper describes the sample, instruments, grading procedures, and selected results. Results include: (1) at the…

Senk, Sharon L.

423

New perspectives on FRC confinement  

NASA Astrophysics Data System (ADS)

Four factors relevant to FRC's motivate a rethinking the nature of confinement in FRCs. (1) Particle loss at the separatrix is regulated by drift turbulence with an oblique wave vector and perpendicular component comparable to the inverse of the ion gyroradius. The resulting transport scaling is better than gyroBohm, This mechanism gives a reasonable prediction of the particle confinement observed in FRC experiments. (2) The scrape-off layer can be modeled as a quasi-steady balance between radial particle diffusion and streaming endloss to the divertor region. (3) ``Tearing relaxation,'' i.e. tearing that maintains the internal profile at the marginal stability condition appears to explain the anomalous flux loss rate in FRCs. Application of the so-called nearby-equilibrium analysis led to this implication. If so, then the ``apparent'' resistivity at the O-point is only the manifestation of a completely different flux annihilation mechanism, namely tearing. (4) The transport of energy is convective, i.e. proportional to the particle diffusivity. Past extrapolations of FRC confinement were based on empirical scalings; these new advances allow, for the first time, a physics-based model of transport. This should foster more convincing extrapolations to next-generation experiments.

Steinhauer, Loren

2008-11-01

424

Simulations of plasma confinement in an antihydrogen trap  

SciTech Connect

The three-dimensional particle-in-cell (3-D PIC) simulation code WARP is used to study positron confinement in antihydrogen traps. The magnetic geometry is close to that of a UC Berkeley experiment conducted, with electrons, as part of the ALPHA collaboration (W. Bertsche et al., AIP Conf. Proc. 796, 301 (2005)). In order to trap antihydrogen atoms, multipole magnetic fields are added to a conventional Malmberg-Penning trap. These multipole fields must be strong enough to confine the antihydrogen, leading to multipole field strengths at the trap wall comparable to those of the axial magnetic field. Numerical simulations reported here confirm recent experimental measurements of reduced particle confinement when a quadrupole field is added to a Malmberg-Penning trap. It is shown that, for parameters relevant to various antihydrogen experiments, the use of an octupole field significantly reducesthe positron losses seen with a quadrupole field. A unique method for obtaining a 3-D equilibrium of the positrons in the trap with a collisionless PIC code was developed especially for the study of the antihydrogen trap; however, it is of practical use for other traps as well.

Gomberoff, K.; Fajans, J.; Friedman, A.; Grote, D.; Vay, J.-L.; Wurtele, J.S.

2007-10-15

425

Nonlocal effects in a hybrid plasmonic waveguide for nanoscale confinement.  

PubMed

The effect of nonlocal optical response is studied for a novel silicon hybrid plasmonic waveguide (HPW). Finite element method is used to implement the hydrodynamic model and the propagation mode is analyzed for a hybrid plasmonic waveguide of arbitrary cross section. The waveguide has an inverted metal nano-rib over a silicon-on-insulator (SOI) structure. An extremely small mode area of~10???² is achieved together with several microns long propagation distance at the telecom wavelength of 1.55 ?m. The figure of merit (FoM) is also improved in the same time, compared to the pervious hybrid plasmonic waveguide. We demonstrate the validity of our method by comparing our simulating results with some analytical results for a metal cylindrical waveguide and a metal slab waveguide in a wide wavelength range. For the HPW, we find that the nonlocal effects can give less loss and better confinement. In particular, we explore the influence of the radius of the rib's tip on the loss and the confinement. We show that the nonlocal effects give some new fundamental limitation on the confinement, leaving the mode area finite even for geometries with infinitely sharp tips. PMID:23389124

Huang, Qiangsheng; Bao, Fanglin; He, Sailing

2013-01-28

426

Autoionization resonance states of two-electron atomic systems with finite spherical confinement  

SciTech Connect

We investigate the lowest-lying S-wave resonant states of two-electron atoms confined by a spherical quantum cavity under the framework of the stabilization method. Hylleraas-type wave functions (basis length N = 444) taking the correlation effects between all the charged particles into account are used in the present paper. The finite oscillator potential is used to represent the confinement potential. We present the resonant parameters (energies and widths) of the quantum-confined two-electron atoms with different depths and various ranges of the potentials.

Chakraborty, Sumana [Department of Physics, NSHM Faculty of Engineering and Technology, NSHM Knowledge Campus, Arrah, Shibtala, Durgapur-713212 (India); Ho, Y. K. [Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei, Taiwan 106 (China)

2011-09-15

427

Competition between confinement potential fluctuations and band-gap renormalization effects in In0.53Ga0.47As\\/In0.525Ga0.235Al0.25As single and double quantum wells  

Microsoft Academic Search

We present the results of our studies on the emission properties of In0.53Ga0.47As\\/In0.525Ga0.235Al0.25As single and coupled double quantum wells (CDQWs) with different degrees of potential fluctuation. We have verified that the curve of the temperature (T) dependence of the emission peak energy (EPL) is significantly influenced by the potential fluctuations (which are magnified by the presence of the internal barrier

José Leonil Duarte; Luiz Carlos Poças; Edson Laureto; Ivan Frederico Lupiano Dias; Élder Mantovani Lopes; Sidney Alves Lourenço; J. C. Harmand

2008-01-01

428

Confined mixing of coaxial flows  

Microsoft Academic Search

An empirical approach is used to correlate the mixing of isothermal incompressible coaxial air flows in straight pipes of constant circular cross-section. An assumed decay function for kinetic momentum is correlated in terms of initial geometry and initial velocities of the mixing streams. The method allows the rapid estimation of quantities of engineering interest including the axial distribution of both

R. A. Tyler; R. G. Williamson

1980-01-01

429

Life-testing oxide confined VCSELs: Too good to last?  

SciTech Connect

The use of native oxides (selective oxidation) in vertical cavity surface emitting lasers has produced dramatic improvements in these laser diodes but has also been suspected of causing poor reliability because of incidental reports of short lifetimes and physical considerations. Here we discuss the results of thousands of hours life-tests for oxide confined and implant confined devices at current densities from 1 to 12 kA/cm{sup 2}. There was a single infant mortality failure from a sample of 14 oxide confined lasers with the remainder showing relatively stable operation. The failed device is analyzed in terms of light current characteristics and near-field electroluminescence images, and potential screening criteria are proposed.

Lear, K.L.; Kilcoyne, S.P.; Schneider, R.P. Jr.; Nevers, J.A.

1996-03-01

430

Confinement of electron plasma by levitating dipole magnet  

SciTech Connect

A recent experiment on the Ring Trap 1 device has demonstrated long-term (exceeding 300 s) confinement of non-neutral (pure electron) plasma in a dipole magnetic field; particles diffuse inward, steepening the density gradient and self-organizing into a stable vortex structure [Z. Yoshida et al., Phys. Rev. Lett. 104, 235004 (2010)]. In this study, the internal structures of the plasma are experimentally investigated, and it is shown that the observations are consistent with rigidly rotating charged particle clump. The radial profiles of electrostatic potential and electron density consistently show that the drift velocity has homogeneous angular frequency in the confinement region. The electrostatic fluctuations also rotate rigidly with a phase velocity that agrees with the drift velocity. The magnetospheric system should have a wide application in confining single-species and even multiple-species charged particles.

Saitoh, H.; Yoshida, Z.; Morikawa, J.; Yano, Y.; Hayashi, H.; Mizushima, T.; Kawai, Y.; Kobayashi, M.; Mikami, H. [Department of Advanced Energy, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)

2010-11-15

431

Shape and Current Profile Effects on Runaway Electron Confinement  

NASA Astrophysics Data System (ADS)

The potential for several MA of current carried by multi-MeV runaway electrons (REs) during ITER disruptions has motivated a variety of experiments in present-day tokamaks studying RE generation, confinement, and control. In both DIII-D and Alcator C Mod, different RE behavior is seen in limited vs. diverted plasmas, suggesting better RE confinement for limited shapes. NIMROD simulations of rapid shutdowns in both devices support this finding, and show reduced stochasticity in limited plasma shapes. Integration of RE drift-orbits also shows differences in RE strike-points that are consistent with experimental observations. In DIII-D a wide variation in RE confinement results for diverted discharges may also point to current density profile effects on RE confinement. Several DIII-D diverted discharges are modeled with NIMROD. Confined RE fractions found in NIMROD are mostly consistent with observed RE currents in DIII-D, although other effects, such as seed generation and avalanching may contribute to the experimental variation.

Izzo, V. A.; James, A. N.; Humphreys, D. A.; Granetz, R. S.; Whyte, D. G.; Olynyk, G. M.

2011-11-01

432

Phase transitions and phase equilibria in spherical confinement  

NASA Astrophysics Data System (ADS)

Phase transitions in finite systems are rounded and shifted and affected by boundary effects due to the surface of the system. This interplay of finite size and surface effects for fluids confined inside of a sphere of radius R is studied by a phenomenological theory and Monte Carlo simulations of a model for colloid-polymer mixtures. For this system the phase separation in a colloid-rich phase and a polymer-rich phase has been previously studied extensively in the bulk. It is shown that spherical confinement can strongly enhance the miscibility of the mixture. Depending on the wall potentials at the confining surface, the wetting properties of the wall can be controlled, and this interplay between preferential adsorption of one species to the confining surface and bulk unmixing leads to very special shapes of the loops observed for the chemical potential of the colloids as a function of their packing fraction. We also discuss the extent to which concepts used for phase transitions in macroscopic systems, such as critical exponents of the order parameter distinguishing the phases, or the Kelvin equation describing the shift of the chemical potential at phase coexistence with the radius R, are applicable.

Winkler, Alexander; Statt, Antonia; Virnau, Peter; Binder, Kurt

2013-03-01

433

Hermitesche Relativitätstheorie, Chromodynamik und Confinement  

NASA Astrophysics Data System (ADS)

Die Ausdehnung der Riemannschen Metrik der Allgemeinen Relativitätstheorie ins Komplexe bedeutet die Ersetzung der Symmetrie-Bedingungenfür den metrischen Tensor, Affinität und Ricci-Tensor durch die Hermiteschen BedingungenMit diesen Bedingungen führt das Einstein-Hilbert-Hamilton-Prinzipzu einer erweiterten Gravitationstheorie (Einstein), die im Sinne der EIH-Approximation neben der Newton-Einsteinschen Gravodynamik, auch die Chromodynamik der Elementarteilchenphysik enthält.Die von den Einstein-Schrödingerschen Feldgleichungen der Hermiteschen Relativitätstheorie implizierte Wechselwirkung zwischen Gravo- und Chromodynamik erzwingt das Confinement. Ohne dieses Confinement würde das Gravitationspotential divergieren, d.h., es könnte keine - nach Maßgabe der Einstein-Schrödingerschen Feldgleichungen - Riemannsche Raum-Zeit-Metrik gik = aik geben.Translated AbstractHermitian Relativity, Chromodynamics and ConfinementThe extension of the Riemannian metrics of General Relativity to the complex domain, i.e. the substitution of the symmetry conditions for the fundamental tensor gik, the affinity lik and the Ricci curvature Rik by the conditions of Hermiticity gives a Generalized Theory of Gravity (Einstein) which describes the Newton-Einstein gravodynamics combined with the chromodynamics of quarks.The Hermitian Theory of Relativity starts form the Einstein Lagrangian with and the Einstein-Schrödinger field equations result: > In the Einstein-Infeld-Hoffmann approximation (EIH) of General Relativity between point-like particles forces > are given by the conditions of integrability (generalized Bianchi-identics).Furthermore, solutions for the symmetrical part >

of the equations exist only if there is confinement for the charges QA = 0. Then the field masses MA are given by
>

with the distance L between the charges QA.The equations of motions with distance-independent forces QAQB and the confinement QA = 0 are a consequence of the Einstein-Schrödinger equations for Hermitian Relativity. The forte Einstein-Straus equations (with Rik = 0) do not give charges QA and therefore the Newtonian forces only.>

Treder, H.-J.

434

Influence of confinement by smooth and rough walls on particle dynamics in dense hard-sphere suspensions  

NASA Astrophysics Data System (ADS)

We used video microscopy and particle tracking to study the dynamics of confined hard-sphere suspensions. Our fluids consisted of 1.1-?m-diameter silica spheres suspended at volume fractions of 0.33--0.42 in water-dimethyl sulfoxide. Suspensions were confined in a quasiparallel geometry between two glass surfaces. First, as the separation distance (H) is decreased from 18 to 1 particle diameter, a transition takes place from a subdiffusive behavior (as in bulk) at large H, to completely caged particle dynamics at small H. These changes are accompanied by a strong decrease in the amplitude of the mean-square displacement (MSD) in the horizontal plane parallel to the confining surfaces. In contrast, the global volume fraction essentially remains constant when H is decreased. Second, measuring the MSD as a function of distance from the confining walls, we found that the MSD is not spatially uniform but smaller close to the walls.. Although confinement also induces local variations in volume fraction, the spatial variations in MSD can be attributed only partially to this effect. The changes in MSD are predominantly a direct effect of the confining surfaces. Hence, both the wall roughness and the separation distance (H) influence the dynamics in confined geometries.

Eral, Burak; van den Ende, Dirk; Duits, Michel; Mugele, Frieder

2011-11-01

435

Exciton Confinement in Traps Formed by a Laterally Modulated Gate Voltage  

NASA Astrophysics Data System (ADS)

In semiconductor materials, cold gases of bosons can be realized in the system of indirect excitons in coupled quantum well structures. Boson confinement in potential traps improves the critical temperature for Bose-Einstein condensation and allows manipulation of the bosons by varying the trap potential [1,2]. Here, we present in-plane potential traps for indirect excitons, where the traps are formed by a laterally modulated gate voltage. The calculated trap design allows effective exciton confinement as well as in situ manipulation of excitons by the gate electrodes that control the confining potential. The design also ensures that the electric fields caused by the confining potential are well below the threshold for the exciton dissociation. Experiments with indirect excitons in the traps are presented as well. 1. E.A. Cornell, C.E. Wieman, Rev. Mod. Phys. 74, 875 (2002). 2. W. Ketterle, Rev. Mod. Phys. 74, 1131 (2002).

Hammack, A. T.; Hanson, M.

2005-03-01

436

Fractal forest: Fractal geometry and applications in forest science. Forest Service general technical report  

SciTech Connect

Fractal geometry is a tool for describing and analyzing irregularity. Because most of what we measure in the forest is discontinuous, jagged, and fragmented, fractal geometry has potential for improving the precision of measurement and description. The study reviews the literature on fractal geometry and its applications to forest measurements.

Lorimer, N.D.; Haight, R.G.; Leary, R.A.

1994-07-20

437

Photonic bandgap confinement in an all-solid tellurite-glass photonic crystal fiber.  

PubMed

We report on the fabrication and optical assessment of an all-solid tellurite-glass photonic bandgap fiber. The manufacturing process via a preform drawing approach and the fiber characterization procedures are described and discussed. The fiber exhibits some minor morphological deformations that do not prevent the observation of optical confinement within the fiber by bandgap effects. The experimental fiber attenuation spectrum displays clear bandgap confinement regions whose positions are confirmed by modeling the guiding properties of the ideal geometry using a plane-wave expansion method. The model identifies the bound modes of the structure and provides confirmation of experimentally observed mode field profiles. PMID:23202091

Lousteau, Joris; Scarpignato, Gerardo; Athanasiou, Giorgos S; Mura, Emanuele; Boetti, Nadia; Olivero, Massimo; Benson, Trevor; Sewell, Phillip; Abrate, Silvio; Milanese, Daniel

2012-12-01

438

Hierarchical self-assembly of actin in micro-confinements using microfluidics  

PubMed Central

We present a straightforward microfluidics system to achieve step-by-step reaction sequences in a diffusion-controlled manner in quasi two-dimensional micro-confinements. We demonstrate the hierarchical self-organization of actin (actin monomers—entangled networks of filaments—networks of bundles) in a reversible fashion by tuning the Mg2+ ion concentration in the system. We show that actin can form networks of bundles in the presence of Mg2+ without any cross-linking proteins. The properties of these networks are influenced by the confinement geometry. In square microchambers we predominantly find rectangular networks, whereas triangular meshes are predominantly found in circular chambers.

Deshpande, Siddharth; Pfohl, Thomas

2012-01-01

439

Proton radiography of PBX 9502 detonation shock dynamics confinement sandwich test  

SciTech Connect

Recent results utilizing proton radiography (P-Rad) during the detonation of the high explosive PBX 9502 are presented. Specifically, the effects of confinement of the detonation are examined in the LANL detonation confinement sandwich geometry. The resulting detonation velocity and detonation shock shape are measured. In addition, proton radiography allows one to image the reflected shocks through the detonation products. Comparisons are made with detonation shock dynamics (DSD) and reactive flow models for the lead detonation shock and detonation velocity. In addition, predictions of reflected shocks are made with the reactive flow models.

Aslam, Tariq D [Los Alamos National Laboratory; Jackson, Scott I [Los Alamos National Laboratory; Morris, John S [Los Alamos National Laboratory

2009-01-01

440

Interim report on the injected internal target technique, (IT)/sup 2/, for measuring the geometry of EBT rings  

SciTech Connect

It was found that a diagnostic Hg beam can be used to determine the geometry and parameters of an essential element of the EBT concept, the ELMO rings. Consequently, an (IT)/sup 2/ diagnostic system would be of immense help in the EBT development program, particularly in assessing the impact of ring properties and power requirements on the overall economic feasibility of EBT reactors. The results of this study indicate strongly that an (IT)/sup 2/ system can not only measure the changes in ring geometry as the experimental parameters are varied, but also detailed spatial distributions of the temperature and density of the hot ring electrons. The (IT)/sup 2/ diagnostic system is the only method to date which appears to have the potential to perform directly these detailed measurements of the ring profiles. Furthermore, the Hg beam itself may find useful application as a heavy ion beam probe for measurements of the space potential of the confined plasma in EBT and as a tool to determine the magnetic field configuration within the ring.

Moses, K.; Quon, B.; Sperling, J.

1982-11-30

441

Order in very cold confined plasmas  

SciTech Connect

The study of the structure and dynamic properties of classical systems of charged particles confined by external forces, and cooled to very low internal energies, is the subject of this talk. An infinite system of identical charged particles has been known for some time to form a body-centered cubic lattice and is a simple classical prototype for condensed matter. Recent technical developments in storage rings, ion traps, and laser cooling of ions, have made it possible to produce such systems in the laboratory, though somewhat modified because of their finite size. I would like to discuss what one may expect in such systems and also show some examples of experiments. If we approximate the potential of an ion trap with an isotropic harmonic force F = {minus}Kr then the Hamiltonian for this collection of ions is the same as that for J. J. Thomson`s ``plum pudding`` model of the atom, where electrons were thought of as discrete negative charges imbedded in a larger, positive, uniformly charged sphere. The harmonic force macroscopically is canceled by the average space-charge forces of the plasma-, and this fixes the overall radius of the distribution. What remains, are the residual two-body Coulomb interactions that keep the particles within the volume as nearly equidistant as possible in order to minimize the potential energy. The configurations obtained for the minimum energy of small ionic systems [2] in isotropic confinement are shown in figure 1. Indeed this is an `Exotic Atom` and fits well into the subject of this symposium honoring the 60th birthday of Professor Toshi Yamazaki.

Schiffer, J.P. [Argonne National Lab., IL (United States)]|[Univ. of Chicago, Chicago, IL (United States)

1995-12-31

442

Thomson scattering from inertial confinement fusion plasmas  

SciTech Connect

Thomson scattering has been developed at the Nova laser facility as a direct and accurate diagnostic to characterize inertial confinement fusion plasmas. Flat disks coated with thin multilayers of gold and beryllium were with one laser beam to produce a two ion species plasma with a controlled amount of both species. Thomson scattering spectra from these plasmas showed two ion acoustic waves belonging to gold and beryllium. The phase velocities of the ion acoustic waves are shown to be a sensitive function of the relative concentrations of the two ion species and are in good agreement with theoretical calculations. These open geometry experiments further show that an accurate measurement of the ion temperature can be derived from the relative damping of the two ion acoustic waves. Subsequent Thomson scattering measurements from methane-filled, ignition-relevant hohlraums apply the theory for two ion species plasmas to obtain the electron and ion temperatures with high accuracy. The experimental data provide a benchmark for two-dimensional hydrodynamic simulations using LASNEX, which is presently in use to predict the performance of future megajoule laser driven hohlraums of the National Ignition Facility (NIF). The data are consistent with modeling using significantly inhibited heat transport at the peak of the drive. Applied to NIF targets, this flux limitation has little effect on x- ray production. The spatial distribution of x-rays is slightly modified but optimal symmetry can be re-established by small changes in power balance or pointing. Furthermore, we find that stagnating plasma regions on the hohlraum axis are well described by the calculations. This result implies that stagnation in gas-filled hohlraums occurs too late to directly affect the capsule implosion in ignition experiments.

Glenzer, S.H.; Back, C.A.; Suter, L.J. [and others

1997-07-08

443

Vortex confinement by magnetic domains in superconductor-ferromagnet bilayers  

NASA Astrophysics Data System (ADS)

We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in between to avoid proximity effect. The magnetic domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the decreasing temperature the magnetic pinning increases but this increase is substantially weaker than that of the intrinsic pinning. The analysis of the initial flux penetration suggests that vortices may form various vortex structures, including disordered Abrikosov lattice or single and double vortex chains, in which minimal vortex-vortex distance is comparable to the magnetic penetration depth.

Cieplak, Marta Z.; Adamus, Z.; Konczykowski, M.; Zhu, L. Y.; Chien, C. L.; Cheng, X. M.

2013-03-01

444

Structural Dynamics of a Confined Rectangular Jet in Crossflow  

NASA Astrophysics Data System (ADS)

(Supported by Procter & Gamble) The applications for jets in crossflow are extraordinarily varied, resulting in a wide range of flow parameters and geometries. The interaction among various parameters and the details of the resulting flow structures must be better understood to enable advances in predictive and design capabilities. This study involves an unusual geometry with a confined rectangular jet in crossflow. The parameters studied include six injection angles (18, 24, 30, 48, 60, 90 degrees), three velocity ratios (0.5, 1.0, 1.5) and five downstream distances corresponding to (3, 6, 9, 12, 15) jet diameters. A 2-D planar Mie scattering technique was used to evaluate the relative mixing effectiveness of the various configurations. In addition, a laser Doppler velocimeter (LDV) was used to map velocity fields corresponding to the scalar concentration data for several conditions. Large-scale secondary flow patterns and asymmetries in the scalar concentration are the signatures of prominent vortic! al! flow structures. These results are compared to others from a wide variety of different geometries to characterize the critical structural features in this flow which control its behavior.

Cusano, D. M.; Plesniak, M. W.

1997-11-01

445

Rheology of confined granular flows  

SciTech Connect

The properties of confined granular flows on a heap are studied through numerical simulations and experiments. We address how such system can be simulated with period boundaries in the flow direction. The packing fraction and velocity profiles are found to be described by one length scale. The dependence of the kinematic properties on the number of grains and on micromechanical parameters (coefficient of restitution and coefficient of friction) is described. Our results show that the friction at the sidewalls gradually decreases and that this decrease can be explained by the intermittent motion of the grains in the quasistatic part of the flow.

Richard, Patrick; Valance, Alexandre; Metayer, Jean-Francois; Crassous, Jerome; Delannay, Renaud [Universite Rennes 1, Institut de Physique de Rennes, UMR CNRS 6251, 263 av. General Leclerc, 35042 Rennes cedex FRANCE (France); Louge, Michel [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 (United States)

2010-05-05

446

String tension scaling in models of the confined phase  

NASA Astrophysics Data System (ADS)

We introduce a D-dimensional Hamiltonian formalism for the study of Polyakov loop models of finite temperature gauge theories in D+1 dimensions. Polyakov loop string tensions are obtained from energy eigenstates of the Hamiltonian. For D=1, the gauge theory reduces to quantum mechanics on the gauge group; for D>1, the Hamiltonian includes hopping terms that link sites on the transverse lattice. The deconfined phase is associated with a ground state which breaks Z(N) symmetry, and Svetitsky-Yaffe critical universality emerges naturally for D>1. A minimal model is proposed which naturally reproduces approximate Casimir scaling for a range of couplings. Different classes of potentials lead to different pictures of how confinement is realized. Such potential energy terms also modify string tension scaling laws, as we demonstrate using two potentials: one representing the perturbative thermal contributions from gluons, and the other arising from magnetic monopoles in certain confining supersymmetric theories.

Ogilvie, Michael

2006-12-01

447

Geometry simulation and physics with the CMS forward pixel detector  

NASA Astrophysics Data System (ADS)

The Forward Pixel Detector of CMS is an integral part of the Tracking system, which will play a key role in addressing the full physics potential of the collected data. It has a very complex geometry that encompasses multilayer structure of its detector modules. This presentation describes the development of geometry simulation for the Forward Pixel Detector. A new geometry package has been developed, which uses the detector description database (DDD) interface for the XML (eXtensive Markup Language) to GEANT simulation. This is necessary for digitization and GEANT4 reconstruction software for tracking. The expected physics performance is also discussed.

Parashar, N.

2008-06-01

448

Grade 1 Practice Problems: Geometry  

NSDL National Science Digital Library

This page contains 12 problems in geometry from the Port Angeles School District in Washington state. Links to state GLEs and revised standards are provided. Topics covered include position and shape.

2011-01-01

449

The Dilemma of Descriptive Geometry  

ERIC Educational Resources Information Center

Proposes that engineering students undergo a preparatory summer school training program in fundamentals of engineering drawing, descriptive geometry, and mathematics prior to being admitted to regular engineering studies. (SL)

Boleslavski, Moshe

1977-01-01

450

Lorentzian approach to noncommutative geometry  

NASA Astrophysics Data System (ADS)

This thesis concerns the research on a Lorentzian generalization of Alain Connes' noncommutative geometry. In the first chapter, we present an introduction to noncommutative geometry within the context of unification theories. The second chapter is dedicated to the basic elements of noncommutative geometry as the noncommutative integral, the Riemannian distance function and spectral triples. In the last chapter, we investigate the problem of the generalization to Lorentzian manifolds. We present a first step of generalization of the distance function with the use of a global timelike eikonal condition. Then we set the first axioms of a temporal Lorentzian spectral triple as a generalization of a pseudo-Riemannian spectral triple together with a notion of global time in noncommutative geometry.

Franco, Nicolas

2011-08-01

451

Emergent geometry from quantized spacetime  

SciTech Connect

We examine the picture of emergent geometry arising from a mass-deformed matrix model. Because of the mass deformation, a vacuum geometry turns out