Sample records for confinement potential geometry

  1. Freezing in confined geometries

    NASA Technical Reports Server (NTRS)

    Sokol, P. E.; Ma, W. J.; Herwig, K. W.; Snow, W. M.; Wang, Y.; Koplik, Joel; Banavar, Jayanth R.

    1992-01-01

    Results of detailed structural studies, using elastic neutron scattering, of the freezing of liquid O2 and D2 in porous vycor glass, are presented. The experimental studies have been complemented by computer simulations of the dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls. Results point to a new simple physical interpretation of freezing in confined geometries.

  2. Diffusion in confined geometries.

    PubMed

    Burada, P Sekhar; Hänggi, Peter; Marchesoni, Fabio; Schmid, Gerhard; Talkner, Peter

    2009-01-12

    Diffusive transport of particles or, more generally, small objects, is a ubiquitous feature of physical and chemical reaction systems. In configurations containing confining walls or constrictions, transport is controlled both by the fluctuation statistics of the jittering objects and the phase space available to their dynamics. Consequently, the study of transport at the macro- and nanoscales must address both Brownian motion and entropic effects. Herein we report on recent advances in the theoretical and numerical investigation of stochastic transport occurring either in microsized geometries of varying cross sections or in narrow channels wherein the diffusing particles are hindered from passing each other (single-file diffusion). For particles undergoing biased diffusion in static suspension media enclosed by confining geometries, transport exhibits intriguing features such as 1) a decrease in nonlinear mobility with increasing temperature or also 2) a broad excess peak of the effective diffusion above the free diffusion limit. These paradoxical aspects can be understood in terms of entropic contributions resulting from the restricted dynamics in phase space. If, in addition, the suspension medium is subjected to external, time-dependent forcing, rectification or segregation of the diffusing Brownian particles becomes possible. Likewise, the diffusion in very narrow, spatially modulated channels is modified via contact particle-particle interactions, which induce anomalous sub-diffusion. The effective sub-diffusion constant for a driven single file also develops a resonance-like structure as a function of the confining coupling constant. PMID:19025741

  3. Reactive collisions in confined geometries

    E-print Network

    Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne

    2015-02-06

    We consider low energy threshold reactive collisions of particles interacting via a van der Waals potential at long range in the presence of external confinement and give analytic formulas for the confinement modified scattering in such circumstances. The reaction process is described in terms of the short range reaction probability. Quantum defect theory is used to express elastic and inelastic or reaction collision rates analytically in terms of two dimensionless parameters representing phase and reactivity. We discuss the modifications to Wigner threshold laws for quasi-one-dimensional and quasi-two-dimensional geometries. Confinement-induced resonances are suppressed due to reactions and are completely absent in the universal limit where the short-range loss probability approaches unity.

  4. Reactive collisions in confined geometries

    NASA Astrophysics Data System (ADS)

    Idziaszek, Zbigniew; Jachymski, Krzysztof; Julienne, Paul S.

    2015-03-01

    We consider low energy threshold reactive collisions of particles interacting via a van der Waals potential at long range in the presence of external confinement and give analytic formulas for the confinement modified scattering in such circumstances. The reaction process is described in terms of the short range reaction probability. Quantum defect theory is used to express elastic and inelastic or reaction collision rates analytically in terms of two dimensionless parameters representing phase and reactivity. We discuss the modifications to Wigner threshold laws for quasi-one-dimensional and quasi-two-dimensional geometries. Confinement-induced resonances are suppressed due to reactions and are completely absent in the universal limit where the short-range loss probability approaches unity.

  5. PREFACE: Water in confined geometries

    NASA Astrophysics Data System (ADS)

    Rovere, Mauro

    2004-11-01

    The study of water confined in complex systems in solid or gel phases and/or in contact with macromolecules is relevant to many important processes ranging from industrial applications such as catalysis and soil chemistry, to biological processes such as protein folding or ionic transport in membranes. Thermodynamics, phase behaviour and the molecular mobility of water have been observed to change upon confinement depending on the properties of the substrate. In particular, polar substrates perturb the hydrogen bond network of water, inducing large changes in the properties upon freezing. Understanding how the connected random hydrogen bond network of bulk water is modified when water is confined in small cavities inside a substrate material is very important for studies of stability and the enzymatic activity of proteins, oil recovery or heterogeneous catalysis, where water-substrate interactions play a fundamental role. The modifications of the short-range order in the liquid depend on the nature of the water-substrate interaction, hydrophilic or hydrophobic, as well as on its spatial range and on the geometry of the substrate. Despite extensive study, both experimentally and by computer simulation, there remain a number of open problems. In the many experimental studies of confined water, those performed on water in Vycor are of particular interest for computer simulation and theoretical studies since Vycor is a porous silica glass characterized by a quite sharp distribution of pore sizes and a strong capability to absorb water. It can be considered as a good candidate for studying the general behaviour of water in hydrophilic nanopores. But there there have been a number of studies of water confined in more complex substrates, where the interpretation of experiments and computer simulation is more difficult, such as in zeolites or in aerogels or in contact with membranes. Of the many problems to consider we can mention the study of supercooled water. It is particularly important to understand whether the glass transition temperature could be experimentally accessible for confined water. In this respect the modifications induced by the confinement on the dynamics of water on supercooling are of extreme interest and a number of experimental and computer simulation studies have been devoted in recent years to this topic. This special section contains papers from different groups which have contributed with various experimental and computer simulation techniques to the progress made in the study of water in confined geometry. I thank all of the authors for their stimulating contributions. I am very pleased in particular that Sow-Hsin Chen agreed to contribute since he has done pioneering experimental work on the dynamical properties of confined water upon supercooling, and he is still very active in the field. The work presented by the group of J Swenson concerns also the glass transition of confined water. The Messina group (Crupi et al) is very active in the study of dynamical properties of confined water and they present their results on water in zeolites. From the experimental side there is also a contribution from J Dore's group, one of the first to perform neutron scattering studies on confined water. The work of J Klein looks at the mobility of water molecules confined in subnanometre films. Important contributions on the computer simulation side come from the Geiger group (Brovchenko et al). They performed very accurate simulations of water in nanopores, exploring a large portion of the phase space. Puibasset et al were able to build a very realistic model to simulate water inside Vycor. Zangi et al review the extensive work performed on confined water. Jedlovszky is an expert on the model potential for water and studied how the hydrogen bond network of water can be modified by the presence of an interface. The special issue is intended to stimulate interest and future work on this important subject.

  6. Amoeboid motion in confined geometry

    E-print Network

    Wu, Hao; Hu, Wei-Fan; Farutin, Alexander; Rafaï, Salima; Lai, Ming-Chih; Peyla, Philippe; Misbah, Chaouqi

    2015-01-01

    Cells of the immune system, as well as cancer cells, migrating in confined environment of tissues undergo frequent shape changes (described as amoeboid motion) that enable them to move forward through these porous media without the assistance of adhesion sites. In other words, they perform amoeboid swimming (AS) while using extracellular matrices and cells of tissues as support. We introduce a simple model of AS in a confined geometry solved by means of 2D numerical simulations. We find that confinement promotes AS, unless being so strong that it restricts shape change amplitude. A straight AS trajectory in the channel is found to be unstable, and ample lateral excursions of the swimmer prevail. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. This is a spontaneous symmetry-breaking bifurcation. We find that there exists an optimal confinement for migration. We provide numerical results as...

  7. Amoeboid motion in confined geometry

    E-print Network

    Hao Wu; Marine Thiébaut; Wei-Fan Hu; Alexander Farutin; Salima Rafaï; Ming-Chih Lai; Philippe Peyla; Chaouqi Misbah

    2015-02-13

    Cells of the immune system, as well as cancer cells, migrating in confined environment of tissues undergo frequent shape changes (described as amoeboid motion) that enable them to move forward through these porous media without the assistance of adhesion sites. In other words, they perform amoeboid swimming (AS) while using extracellular matrices and cells of tissues as support. We introduce a simple model of AS in a confined geometry solved by means of 2D numerical simulations. We find that confinement promotes AS, unless being so strong that it restricts shape change amplitude. A straight AS trajectory in the channel is found to be unstable, and ample lateral excursions of the swimmer prevail. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. This is a spontaneous symmetry-breaking bifurcation. We find that there exists an optimal confinement for migration. We provide numerical results as well as scaling laws. This study raises the question of the relevance of these scenarios to complex situations encountered in vivo.

  8. Vortex physics in confined geometries

    NASA Astrophysics Data System (ADS)

    Marchetti, M. Cristina; Nelson, David R.

    2000-03-01

    Patterned irradiation of cuprate superconductors with columnar defects allows a new generation of experiments which can probe the properties of vortex liquids by forcing them to flow in confined geometries. Such experiments can be used to distinguish experimentally between continuous disorder-driven glass transitions of vortex matter, such as the vortex glass or the Bose glass transition, and non-equilibrium polymer-like glass transitions driven by interaction and entanglement. For continuous glass transitions, an analysis of such experiments that combines an inhomogeneous scaling theory with the hydrodynamic description of viscous flow of vortex liquids can be used to infer the critical behavior. After generalizing vortex hydrodynamics to incorporate currents and field gradients both longitudinal and transverse to the applied field, the critical exponents for all six vortex liquid viscosities are obtained. In particular, the shear viscosity is predicted to diverge as | T- TBG| - ?z at the Bose glass transition, with ??1 and z?4.6 the dynamical critical exponent. The scaling behavior of the AC resistivity is also derived. As concrete examples of flux flow in confined geometries, flow in a channel and in the Corbino disk geometry are discussed in detail. Finally, the implications of scaling for the hydrodynamic description of transport in the DC flux transformer geometry are discussed.

  9. Glass Transition in Confined Geometry

    E-print Network

    Simon Lang; Vitalie Botan; Martin Oettel; David Hajnal; Thomas Franosch; Rolf Schilling

    2010-08-23

    Extending mode-coupling theory, we elaborate a microscopic theory for the glass transition of liquids confined between two parallel flat hard walls. The theory contains the standard MCT equations in bulk and in two dimensions as limiting cases and requires as input solely the equilibrium density profile and the structure factors of the fluid in confinement. We evaluate the phase diagram as a function of the distance of the plates for the case of a hard sphere fluid and obtain an oscillatory behavior of the glass transtion line as a result of the structural changes related to layering.

  10. Confinement of color and geometry

    E-print Network

    A. Di Giacomo

    2009-10-27

    A natural explanation of confinement can be given in terms of symmetry. Since color symmetry is exact, the candidate symmetry is dual and related to homotopy,i.e., in (3+1)d, to magnetic charge conservation. A set of r abelian 'tHooft-like tensors (r = rank of the gauge group) can be defined and the dual charge is a violation of the corresponding Bianchi identities. It is shown that this is equivalently described by non-abelian Bianchi identities.

  11. Planar geometry inertial electrostatic confinement fusion device

    NASA Astrophysics Data System (ADS)

    Knapp, Daniel R.

    2015-03-01

    In the classic gridded inertial electrostatic confinement (IEC) fusion reactor, ion bombardment of the grid leads to heating, thermionic electron emission, significant power loss, and ultimately melting of the grid. Gridless IEC devices have sought to overcome these limitations. Klein reported a gridless device in which ions are circulated as a linear beam in an electrostatic analogue of an optical resonator. To overcome limits of stored ions due to space charge effects at the turning regions, the device employed multiple overlapping traps. The work reported here seeks to further increase the turning region space in a gridless trap by employing a planar geometry. Ion trapping in the planar device was examined by simulating trajectories of 2H+ ions with SIMION 8.1 software. Simulations were carried out using multiple potentials as in Klein's device and for a single potential trap as a planar analogue of the anharmonic ion trap. Scattering by background gas was simulated using a hard sphere collision model, and the results suggested the device will require operation at low pressure with a separate ion source.

  12. Effective confining potentials for QCD

    NASA Astrophysics Data System (ADS)

    Trawi?ski, Arkadiusz P.; G?azek, Stanis?aw D.; Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter

    2014-10-01

    We observe that the linear potential used as a leading approximation for describing color confinement in the instant form of dynamics corresponds to a quadratic confining potential in the front form of dynamics. In particular, the instant-form potentials obtained from lattice gauge theory and string models of hadrons agree with the potentials determined from models using front-form dynamics and light-front holography, not only in their shape, but also in their numerical strength.

  13. Dirac equations with confining potentials

    NASA Astrophysics Data System (ADS)

    Noble, J. H.; Jentschura, U. D.

    2015-01-01

    This paper is devoted to a study of relativistic eigenstates of Dirac particles which are simultaneously bound by a static Coulomb potential and added linear confining potentials. Under certain conditions, despite the addition of radially symmetric, linear confining potentials, specific bound-state energies surprisingly preserve their exact Dirac-Coulomb values. The generality of the "preservation mechanism" is investigated. To this end, a Foldy-Wouthuysen transformation is used to calculate the corrections to the spin-orbit coupling induced by the linear confining potentials. We find that the matrix elements of the effective operators obtained from the scalar, and time-like confining potentials mutually cancel for specific ratios of the prefactors of the effective operators, which must be tailored to the preservation mechanism. The result of the Foldy-Wouthuysen transformation is used to verify that the preservation is restricted (for a given Hamiltonian) to only one reference state, rather than traceable to a more general relationship among the obtained effective low-energy operators. The results derived from the nonrelativistic effective operators are compared to the fully relativistic radial Dirac equations. Furthermore, we show that the preservation mechanism does not affect antiparticle (negative-energy) states.

  14. Classical Coulomb fluids in a confined geometry

    Microsoft Academic Search

    B. Jancovici; G. Manificat

    1992-01-01

    It has already been argued that a classical (three-dimensional) Coulomb fluid confined between two parallel walls exhibits ideal gas features when the distance between the walls becomes small; this is confirmed in the present paper. Two-dimensional models of Coulomb fluids (with a logarithmic interaction), confined in a strip, are also studied. These models do not become ideal gases in the

  15. Layer-by-layer assembly in confined geometries

    E-print Network

    DeRocher, Jonathan P

    2011-01-01

    The fundamental nature of layer-by-layer (LbL) assembly in confined geometries was investigated for a number of different chemical systems. The first part of this thesis concerns the modification of microfluidic and ...

  16. Asymmetrical microbubble streaming in a confined geometry

    NASA Astrophysics Data System (ADS)

    Tsai, J.-C.; Hansen, David; Hilgenfeldt, Sascha

    2007-11-01

    Ultrasound-driven oscillating microbubbles situated on a substrate induce steady streaming flows that show great potential in cellular-scale force actuation for bioengineering or in microfluidic applications [1-3]. We have demonstrated for a streaming flow of azimuthal symmetry around a single bubble that the presence of a second wall opposite to the substrate does not compromise the flow speed but instead enhances the circulation efficiency. Additionally, we show here that a continuous spectrum of flow patterns ranging from localized vortex circulations to transport-dominated directional flows can be created by breaking the symmetry either passively (by changing the subtrate topology) or actively (by imposing a large-scale flow field). The spatial confinement provides a dominant lengthscale that simplifies the flow patterns and enhances the transport efficiency. Asymmetrical microbubble streaming, with its capability to fine-tune the relative strength between the circulation and forward transport, offers a continuously adjustable tool for microfluidic applications that demand the simultaneous optimization of mixing rate and transport efficiency. Ref: [1] P. Marmottant and S. Hilgenfeldt, Nature 423, 153 (2003). [2] P. Marmottant and S. Hilgenfeldt, Proc. Natl. Acad. Science USA, 101, 9523 (2004). [3] P. Marmottant, J.-P. Raven, H. Gardeniers, J. G. Bomer, and S. Hilgenfeldt, J. Fluid Mech., vol.568, 109 (2006).

  17. Hertz Potentials and Differential Geometry

    E-print Network

    Bouas, Jeffrey David

    2011-08-08

    . . . . . . . . . . . . . . . . . . . . . . . 34 C. Non-Trivial Topology . . . . . . . . . . . . . . . . . . . . . 35 V HERTZ POTENTIALS AND DIFFERENTIAL GEOMETRY : 36 A. Hertz Potential 2-Forms . . . . . . . . . . . . . . . . . . . 36 B. Gauge Invariance... . . . . . . . . . . . . . . . . . . . . . . . 37 C. Scalar Hertz Potentials . . . . . . . . . . . . . . . . . . . . 39 D. Higher-Order Gauge Transformations . . . . . . . . . . . . 47 E. Non-Trivial Topology . . . . . . . . . . . . . . . . . . . . . 49 v CHAPTER Page VI APPLICATIONS...

  18. Temperature-resonant cyclotron spectra in confined geometries

    E-print Network

    Andrey Pototsky; Peter Hänggi; Fabio Marchesoni; Sergey Savel'ev

    2011-05-22

    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.

  19. Self-assembled morphologies of diblock copolymers confined in nanochannels: effects of confinement geometry.

    PubMed

    Yu, Bin; Sun, Pingchuan; Chen, Tiehong; Jin, Qinghua; Ding, Datong; Li, Baohui; Shi, An-Chang

    2007-05-28

    The self-assembly of diblock copolymers confined in channels of various shaped cross sections is studied using a simulated annealing technique with the "single-site bond fluctuation" model. In the bulk, the asymmetric diblock copolymers used in this study form hexagonally packed cylinders with period L0. The cross sections of the confining channels are of different shapes including regular triangles, rectangles, squares, regular hexagons, regular octagons, and ellipses. For a given geometry, the channel size (characterized by one or two lengths) is varied from very small to several times of L0. It is found that the geometry and size of the confining channels have a large effect on the structure and symmetry of the self-assembled morphologies. Multiple packed cylinders with the symmetry of the confining channels are the major morphologies for low-symmetry cross sections such as triangle, rectangle, and square. More complex structures such as helices or stacked toroids spontaneously form when the confining channels are shaped such as a regular hexagon, a regular octagon, or an ellipse. The domain spacing of the self-assembled structures can be altered by the shape and size of the confining channels. Our results are consistent with available experiments. These results indicate that the self-assembled structures of block copolymers can be manipulated by the shape of the confining channels. PMID:17552796

  20. Confinement-dependent localization of diffusing aggregates in cellular geometries

    NASA Astrophysics Data System (ADS)

    Keramati, Mahdi Rezaei; Wasnik, Vaihbav; Ping, Liyan; Das, Dibyendu; Emberly, Eldon

    2015-01-01

    Confinement has a strong influence on diffusing nano-sized clusters. In particular, biomolecular aggregates within the shell-like confining space of a bacterial cell have been shown to display a variety of localization patterns, from being midcell to the poles. How does the confining space determine where the aggregate will localize? Here, using Monte Carlo simulations we have calculated the equilibrium spatial distribution of fixed-sized clusters diffusing in spherocylindrical shells. We find that localization to the poles depends strongly on shell thickness and the size of the cluster. Compared to being at midcell, polar clusters can be more bent and hence have higher energy, but they also can have a greater number of defects and hence have more entropy. Under certain conditions this can lead to polar clusters having a lower free energy than at midcell, favoring localization to the poles. Our findings suggest possible localization selection mechanisms within shell-like geometries that can arise purely from cluster confinement.

  1. Binding of two helium atoms in confined geometries

    SciTech Connect

    Kilic, S. [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik] [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik; [Univ. of Split (Croatia). Faculty of Natural Sciences; Krotscheck, E.; Zillich, R. [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik] [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik

    1999-08-01

    The authors carry out a comprehensive study of the binding of two helium atoms in unrestricted and, in particular, in restricted geometries in both two and three dimensions. Besides the well known binding of the {sup 4}He dimer in unrestricted geometry in two and three dimensions, the authors also find weakly bound states of the {sup 3}He-{sup 4}He molecule and the {sup 3}He dimer in 2 dimensions. Furthermore, any combination of two {sup 4}He or {sup 3}He atoms can form a molecule if their motion is sufficiently confined. The calculations are carried out by numerically solving the Schroedinger equation as well as by constructing a suitable variational wave function.

  2. Statistical geometry of cavities in a metastable confined fluid

    SciTech Connect

    Vishnyakov, Aleksey [TRI/Princeton, 601 Prospect Avenue, Princeton, New Jersey 08540 (United States)] [TRI/Princeton, 601 Prospect Avenue, Princeton, New Jersey 08540 (United States); Debenedetti, Pablo G. [Chemical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States)] [Chemical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States); Neimark, Alexander V. [TRI/Princeton, 601 Prospect Avenue, Princeton, New Jersey 08540 (United States)] [TRI/Princeton, 601 Prospect Avenue, Princeton, New Jersey 08540 (United States)

    2000-07-01

    The statistical geometry of cavities in a confined Lennard-Jones (LJ) fluid is investigated with the focus on metastable states in the vicinity of the stability limit of the liquidlike state. For a given configuration of molecules, a cavity is defined as a connected region where there is sufficient space to accommodate an additional molecule. By means of grand canonical Monte Carlo simulations, we generated a series of equilibrium stable and metastable states along the adsorption-desorption isotherm of the LJ fluid in a slit-shaped pore of ten molecular diameters in width. The geometrical parameters of the cavity distributions were studied by Voronoi-Delaunay tessellation. We show that the cavity size distribution in liquidlike states, characterized by different densities, can be approximated by a universal log-normal distribution function. The mean void volume increases as the chemical potential {mu} and, correspondingly, the density decreases. The surface-to-volume relation for individual cavities fulfills the three-dimensional scaling S{sub cav}=gV{sub cav}{sup 2/3} with the cavity shape factor g=8.32-9.55. The self-similarity of cavities is observed over six orders of magnitude of the cavity volumes. In the very vicinity of the stability limit, {mu}{yields}{mu}{sub sl}, large cavities are formed. These large cavities are ramified with a fractal-like surface-to-volume relation, S{sub cav}{proportional_to}V{sub cav}. Better statistics are needed to check if these ramified cavities are similar to fragments of a spanning percolation cluster. At the limit of stability, the cavity volume fluctuations are found to diverge as (-{sup 2}){proportional_to}[({mu}-{mu}{sub sl})/kT]{sup -{gamma}{sub c}} with the exponent {gamma}{sub c}{approx_equal}0.93. This exponent can be referred to as the cavity pseudocritical exponent, in analogy with the other pseudocritical exponents characterizing the divergence of thermodynamic quantities at the spinodal point. (c) 2000 The American Physical Society.

  3. Critical comparison between magnetic and inertial confinement schemes and their geometries

    SciTech Connect

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

    1995-05-01

    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.

  4. Yukawa particles in a confining potential

    SciTech Connect

    Girotto, Matheus, E-mail: matheus.girotto@ufrgs.br; Levin, Yan, E-mail: levin@if.ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil); Santos, Alexandre P. dos, E-mail: alexandreps@ufcspa.edu.br [Departamento de Educação e Informação em Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre, 90050-170, Porto Alegre, RS (Brazil); Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina (Brazil); Colla, Thiago, E-mail: thiago.colla@ufrgs.br [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria)

    2014-07-07

    We study the density distribution of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show that the mean-field theory is able to accurately account for the particle distribution. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. For strongly correlated systems, we construct a density functional theory which provides an excellent description of the particle distribution, without any adjustable parameters.

  5. Collisional aspects of bosonic and fermionic dipoles in quasi-two-dimensional confining geometries

    SciTech Connect

    D'Incao, Jose P.; Greene, Chris H. [Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)

    2011-03-15

    Fundamental aspects of ultracold collisions between identical bosonic or fermionic dipoles are studied under quasi-two-dimensional (Q2D) confinement. In the strongly dipolar regime, bosonic and fermion species are found to share important collisional properties as a result of the confining geometry, which suppresses the inelastic rates irrespective of the quantum statistics obeyed. A potential negative is that the confinement causes dipole-dipole resonances to be extremely narrow, which could make it difficult to explore Q2D dipolar gases with tunable interactions. Such properties are shown to be universal, and a simple WKB model reproduces most of our numerical results. In order to shed light on the many-body behavior of dipolar gases in Q2D we have analyzed the scattering amplitude and developed an energy-analytic form of the pseudopotentials for dipoles.

  6. Clustering of branching Brownian motions in confined geometries.

    PubMed

    Zoia, A; Dumonteil, E; Mazzolo, A; de Mulatier, C; Rosso, A

    2014-10-01

    We study the evolution of a collection of individuals subject to Brownian diffusion, reproduction, and disappearance. In particular, we focus on the case where the individuals are initially prepared at equilibrium within a confined geometry. Such systems are widespread in physics and biology and apply for instance to the study of neutron populations in nuclear reactors and the dynamics of bacterial colonies, only to name a few. The fluctuations affecting the number of individuals in space and time may lead to a strong patchiness, with particles clustered together. We show that the analysis of this peculiar behavior can be rather easily carried out by resorting to a backward formalism based on the Green's function, which allows the key physical observables, namely, the particle concentration and the pair correlation function, to be explicitly derived. PMID:25375449

  7. Clustering of branching Brownian motions in confined geometries

    NASA Astrophysics Data System (ADS)

    Zoia, A.; Dumonteil, E.; Mazzolo, A.; de Mulatier, C.; Rosso, A.

    2014-10-01

    We study the evolution of a collection of individuals subject to Brownian diffusion, reproduction, and disappearance. In particular, we focus on the case where the individuals are initially prepared at equilibrium within a confined geometry. Such systems are widespread in physics and biology and apply for instance to the study of neutron populations in nuclear reactors and the dynamics of bacterial colonies, only to name a few. The fluctuations affecting the number of individuals in space and time may lead to a strong patchiness, with particles clustered together. We show that the analysis of this peculiar behavior can be rather easily carried out by resorting to a backward formalism based on the Green's function, which allows the key physical observables, namely, the particle concentration and the pair correlation function, to be explicitly derived.

  8. Universal properties of branching random walks in confined geometries

    NASA Astrophysics Data System (ADS)

    de Mulatier, C.; Mazzolo, A.; Zoia, A.

    2014-08-01

    Characterizing the occupation statistics of random walks through confined geometries amounts to assessing the distribution of the travelled length ? and the number of collisions n performed by the stochastic process in a given region, for which remarkably simple Cauchy-like formulas were established in the case of branching Pearson random walks with exponentially distributed jumps. In this letter, we derive two key results: first, we show that such formulas strikingly carry over to the much broader class of branching processes with arbitrary jumps, and have thus a universal character; second, we obtain a stronger version of these formulas relating the travelled length density and the collision density at any point of the phase space. Our results are key to such technological issues as the analysis of radiation flow for nuclear reactor design and medical diagnosis and apply more broadly to physical and biological systems with diffusion, reproduction and death.

  9. Polymer escape from a confining potential

    E-print Network

    Harri Mökkönen; Timo Ikonen; Tapio Ala-Nissila; Hannes Jónsson

    2015-03-26

    The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.

  10. Electrophoretic mobility of deformable elastic particles in confined geometries

    NASA Astrophysics Data System (ADS)

    Gao, Tong; Hu, Howard

    2010-11-01

    Electrophoretic motion of a dielectric neo-Hookean elastic particle in a confined microchannel is simulated by an Arbitrary Lagrangian-Eulerian moving mesh technique. The particle with a fixed zeta potential is initially elliptical and aligned perpendicular to the direction of the applied electric field. The size of the electrical double layer is assumed to be negligible compared with the particle size and the classical Helmholtz-Smoluchowski slip boundary conditions are applied on the particle surface. When the Reynolds number is low, the elastic deformation is purely induced by the viscous shear force distribution along the body. In the unbounded domain, it is known that the particle will move with a constant Helmholtz-Smoluchowski velocity which is independent of the particle deformation. However, in the confined channel, the rigid walls not only alter the particle-electrical field interaction but also tend to slow the particle motion. To explore the wall effect on the electrophoretic mobility of the particle, the migration velocity is examined by systematically changing both the channel size and the material properties. Also the particle motion in non- Newtonian fluids are simulated and compared with Newtonian cases.

  11. Structure of charged polymer chains in confined geometry.

    SciTech Connect

    Gilbert, E. P.; Auvray, L.; Lal, J.

    2000-12-15

    The intra- and interchain structure of sodium poly(styrenesulphonate) when free and when confined in contrast matched porous Vycor has been investigated by SANS. When confined, a peak is observed whose intensity increases with molecular weight and the 1/q scattering region is extended compared to the bulk. We infer that the chains are sufficiently extended, under the influence of confinement, to highlight the large scale disordered structure of Vycor. The asymptotic behavior of the observed interchain structure factor is = 1/q{sup 2} and = 1/q for free and confined chains respectively.

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

    NASA Astrophysics Data System (ADS)

    Peters, Michael H.

    2011-01-01

    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.

  13. Thermal-mechanical fluctuations of fluid membranes in confined geometries: The case of soft confinement

    Microsoft Academic Search

    Rudi Podgornik; V. Adrian Parsegian

    1992-01-01

    By definition, membrane or macromolecular assembly is an event of molecular confinement against the configurational entropy of a disordered state. Bilayer membranes under progressive confinement experience a continual damping of undulatory fluctuations, first interpreted as a steric force (Helfrich. Z. Naturforsch. 1978). This paper uses a new, diffusion-equation formalism based on the Feynman-type variational principle to describe how direct interbilayer

  14. tt* Geometry and Closed String Tachyon Potential

    Microsoft Academic Search

    Atish Dabholkar; Cumrun Vafa

    2002-01-01

    We propose a closed string tachyon action including kinetic and potential terms for non-supersymmetric orbifolds. The action is given in terms of solutions to tt* equations which captures the geometry of vacua of the corresponding N = 2 worldsheet theory. In certain cases the solutions are well studied. In case of tachyons of Bbb C\\/Bbb Zn, solutions to affine toda

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

    SciTech Connect

    Kumar, Bhupesh; Singh, R K; Kumar, Ajai [Institute for Plasma Research, Bhat, Gandhinagar-382 428 (India)] [Institute for Plasma Research, Bhat, Gandhinagar-382 428 (India)

    2013-08-15

    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 {sup 2}P{sub 1/2,3/2}? 3d {sup 2}P{sub 3/2,5/2}) and 670.8 nm (2s {sup 2}S{sub 1/2}? 2p {sup 2}P{sub 1/2,3/2}) 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.

  16. Spin probe dynamics of n-hexadecane in confined geometry

    NASA Astrophysics Data System (ADS)

    Lukešová, Miroslava; Švajdlenková, Helena; Sippel, Pit; Macová, Eva; Berek, Dušan; Loidl, Alois; Bartoš, Josef

    2015-02-01

    A combined study of the rotational dynamics of the stable free radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and the phase behavior of n-hexadecane (n-HXD) in the bulk and the confined states in a series of silica gels (SG) by means of ESR and DSC is presented. A slow to fast motion transition of the spin probe TEMPO in the bulk n-HXD occurs at T50 G,bulk ? Tm,bulk, i.e., well below the melting temperature due to its trapping and localized mobility in the interlamellar gap of the crystallites [J. Bartoš, H. Švajdlenková, M. Zaleski, M. Edelmann, M. Lukešová, Physica B 430, 99 (2013)]. On the other hand, the dynamics of the TEMPO in the confined systems is strongly slowing down with T50 G (Dpore) >Tm(Dpore) and slightly increases with the pore size Dpore = 60, 100 and 300 Å of the SG's. At the same time, both the corresponding melting temperature, Tm (Dpore), and melting enthalpy, ?Hm (Dpore), decrease with Dpore together with the mutual anti-correlation between T50 G and Tm as a function of the inverse of pore diameter, 1/Dpore. Moreover, the dynamic heterogeneity of the TEMPO in the confined state below T50 G (Dpore) is closely related to the phase transformation. The strong slowing down of the spin probe motion likely results from its preferential localization at the interface layer of the matrix pore due to specific interaction of TEMPO molecules with the polar silanol groups of the SG matrix. This is supported by special study on a series of the variously filled n-HXD/SG systems, other similar experimental findings as well as by theoretical spectral argument.

  17. DNA confined in a two-dimensional strip geometry

    E-print Network

    Aiqun Huang; Aniket Bhattacharya

    2014-03-25

    Semiflexible polymers characterized by the contour length $L$ and persistent length $\\ell_p$ confined in a spatial region $D$ have been described as a series of ``{\\em spherical blobs}'' and ``{\\em deflecting lines}'' by de Gennes and Odjik for $\\ell_p BD) simulation which also reveals that the prefactor $A$ used to describe the chain extension in the Odjik limit is independent of physical dimension $d$ and is the same as previously found by Yang {\\em et al.}[Y. Yang, T. W. Burkhardt, G. Gompper, Phys. Rev. E {\\bf 76}, 011804 (2007)]. Our studies are relevant for optical maps of DNA stretched inside a nano-strip.

  18. DNA confined in a two-dimensional strip geometry

    E-print Network

    Huang, Aiqun

    2013-01-01

    Semiflexible polymers characterized by the contour length $L$ and persistent length $\\ell_p$ confined in a spatial region $D$ have been described as a series of ``{\\em spherical blobs}'' and ``{\\em deflecting lines}'' by de Gennes and Odjik for $\\ell_p < D$ and $\\ell_p \\gg D$ respectively. Recently new intermediate regimes ({\\em extended de Gennes} and {\\em Gauss-de Gennes}) have been investigated by Tree {\\em et al.} [Phys. Rev. Lett. {\\bf 110}, 208103 (2013)]. In this letter we derive scaling relations to characterize these transitions in terms of universal scaled fluctuations in $d$-dimension as a function of $L,\\ell_p$, and $D$, and show that the Gauss-de Gennes regime is absent and extended de Gennes regime is vanishingly small for polymers confined in a 2D strip. We validate our claim by extensive Brownian dynamics (BD) simulation which also reveals that the prefactor $A$ used to describe the chain extension in the Odjik limit is independent of physical dimension $d$ and is the same as previously fou...

  19. Effects of confinement for single-well potentials

    E-print Network

    Oran Gannot

    2014-09-30

    We study bound states generated by a unique potential minimum, in particular the situation where the system is confined to a bounded region containing the minimum. In the latter case, the eigenvalues of the confined system depart from those of the unconfined system by an exponentially small quantity in the semiclassical limit. An asymptotic expansion for this shift is established. The formulas are evaluated explicitly for the harmonic oscillator, and an application to the Coulomb potential at a fixed angular momentum is given.

  20. Study of the nonlinear instability of confined geometries

    NASA Astrophysics Data System (ADS)

    Okawa, Hirotada; Cardoso, Vitor; Pani, Paolo

    2014-11-01

    The discovery of a "weakly turbulent" instability of anti-de Sitter spacetime supports the idea that confined fluctuations eventually collapse to black holes and suggests that similar phenomena might be possible in asymptotically flat spacetime, for example in the context of spherically symmetric oscillations of stars or nonradial pulsations of ultracompact objects. Here we present a detailed study of the evolution of the Einstein-Klein-Gordon system in a cavity, with different types of deformations of the spectrum, including a mass term for the scalar and Neumann conditions at the boundary. We provide numerical evidence that gravitational collapse always occurs, at least for amplitudes that are three orders of magnitude smaller than Choptuik's critical value and corresponding to more than 105 reflections before collapse. The collapse time scales as the inverse square of the initial amplitude in the small-amplitude limit. In addition, we find that fields with nonresonant spectrum collapse earlier than in the fully resonant case, a result that is at odds with the current understanding of the process. Energy is transferred through a direct cascade to high frequencies when the spectrum is resonant, but we observe both direct- and inverse-cascade effects for nonresonant spectra. Our results indicate that a fully resonant spectrum might not be a crucial ingredient of the conjectured turbulent instability and that other mechanisms might be relevant. We discuss how a definitive answer to this problem is essentially impossible within the present framework.

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

    Microsoft Academic Search

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

    2009-01-01

    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 varphi29 and the minute virus of mice. In both cases the genomic DNA was ejected from the capsid. However, although the structural integrity of the

  2. X-ray and dielectric measurements of the smectic- A hexatic- B transitionin bulk and confined geometries

    Microsoft Academic Search

    Chethan V. Lobo; S. Krishna Prasad; D. S. Shankar Rao

    2004-01-01

    We report x-ray and dielectric measurements on a liquid crystal exhibiting a smectic- A hexatic- B (Sm- A Hex- B ) transition in bulk and confined geometries. The confined geometry experiments have been performed by filling the compound, n -butyl 4' - n -hexyloxybiphenyl-4-carboxylate, into Anopore membranes with 20 nm pore size. The surprising result seen in the x-ray studies

  3. Deformable cells in confined geometries: From hemolysis to hydrodynamic interactions

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

    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.

  4. Potential Well Structures in Spherical Inertial Electrostatic Confinement Devices

    Microsoft Academic Search

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

    2005-01-01

    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

  5. Preparation of nanocrystals and nanocomposites of nanocrystal-conjugated polymer, and their photophysical properties in confined geometries

    NASA Astrophysics Data System (ADS)

    Xu, Jun

    Semiconductors nanocrystals (NCs), also called quantum dots (QDs), have attracted tremendous interest over the past decade in the fields of physics, chemistry, and engineering. Due to the quantum-confined nature of QDs, the variation of particle size provides continuous and predictable changes in fluorescence emission. On the other hand, conjugated polymers (CPs) have been extensively studied for two decades due to their semiconductor-like optical and electronic properties. The electron and energy transfer between NCs and CPs occur in solar cells and light emitting diodes (LEDs), respectively. Placing CPs in direct contact with a NC (i.e., preparing NC-CP nanocomposites) carries advantage over cases where NC aggregation dominates. Such NC-CP nanocomposites possess a well-defined interface that significantly promotes the charge or energy transfer between these two components. However, very few studies have centered on such direct integration. We prepared NCs and NC-CP nanocomposites based on heck coupling and investigated the energy and charge transfer between semiconductor NCs (i.e., CdSe QDs), CPs (i.e., poly(3-hexyl thiophene) (P3HT)) in the nanocomposites in confined geometries. Two novel strategies were used to confine NC and/or NC-CP nanocomposites: (a) directly immobilizing nanohybrids, QDs and nanorods in nanoscopic porous alumina membrane (PAM), and (b) confining the QDs and CPs in sphere-on-flat geometry to induce self-assembly. While investigating the confinement effect, gradient concentric ring patterns of high regularity form spontaneously simply by allowing a droplet of solution containing either conjugated polymer or semiconductor nanocrystal in a consecutive stick-slip motion in a confined geometry. Such constrained evaporation can be utilized as a simple, cheap, and robust strategy for self-assembling various materials with easily tailored optical and electronic properties into spatially ordered, two-dimensional patterns. These self-organized patterns of functional nanoscale materials over large areas offer a tremendous potential for applications in optoelectronic devices, LEDs, solar cells, and biosensors. Meanwhile, spherical nanocrystals (i.e. CdSe/ZnS core/shell QDs) were placed in a hexagonal array of highly ordered cylindrical nanopores of PAMs by a simple dip-coating method and vacuum suction process, respectively. The fluorescence of CdSe/ZnS QD was retained after being filled inside PAMs and the filling contents were obtained via transmission UV-vis measurements.

  6. Heavy quarks, gluons and the confinement potential in Coulomb gauge

    SciTech Connect

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

    2011-05-23

    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.

  7. Inversion structures: Geometry and petroleum potential

    SciTech Connect

    Chermette, J.C. (TOTAL, Paris La Defense (France)); Letouzey, J.; Colletta, B. (Institut Francaise du Petrole, Rueil-Malmaison (France))

    1993-09-01

    Inversion tectonics (or more generally reactivation of older structural elements) is a widespread structural phenomenon. From a petroleum exploration veiwpoint, it plays an important but very ambiguous part, since it may either create the favorable conditions for structural trapping or, on the contrary, destroy previous hydrocarbon accumulations. Therefore, it is important to analyze the mechanisms and geometry of such deformations. An extensive analog modeling program was designed for this purpose and implemented by sandbox experiments. Deformation was analyzed in real time by x-ray tomography. A special emphasis was put on studying the effects of strike-slip components of the displacement along the reactivated feature. Analog models with know experimental conditions were then compared with field and seismic examples. Once inversion geometries have been recognized, it becomes important to reconstruct the burial history of the postulated source-rock horizons, which are often located in the invented trough. In this case, the timing of maturation vs. structuration becomes a critical factor. This can be implemented through three-dimensional decompaction softwares. This paper is based on joint research projects by TOTAL, ELF, IEF, and AGIP.

  8. Confinement

    SciTech Connect

    Goldston, R.J.; Stotler, D.P.; Bateman, G. (PPPL (United States)); Waltz, R.E. (GA (United States)); Singer, C.E.; Kinsey, J. (Univ. of Illinois (United States))

    1992-05-01

    The problem of projecting the energy confinement properties of future devices is a lonf standing one in toroidal confinement research. While substantial progress has been made in characterizing the transport properties of tokamaks and stellarators, no definitive understanding of the mechanism(s) of cross-field transport has been achieved. The BPX physics groups, in collaboration with the Transport Task Force and the Doublet III-D (DIII-D) and the Tokamak Fusion Test Reactor (TFTR) experimental teams, has recently begun to explore another avenue of approach, in which dimensionally scaled confinement (eg. confinement time normalized by gyrofrequency [omega][sub c][tau][sub E]) is expressed in terms of key dimensionless variables such a [beta], collisionality [nu], and gyroradius divided by plasma half width [rho]/a. This paper presents the full range of different approaches to projecting the confinement performance of BPX.

  9. Diffusion-Limited Reactions and Mortal Random Walkers in Confined Geometries

    NASA Astrophysics Data System (ADS)

    Lohmar, Ingo; Krug, Joachim

    2009-01-01

    Motivated by the diffusion-reaction kinetics on interstellar dust grains, we study a first-passage problem of mortal random walkers in a confined two-dimensional geometry. We provide an exact expression for the encounter probability of two walkers, which is evaluated in limiting cases and checked against extensive kinetic Monte Carlo simulations. We analyze the continuum limit which is approached very slowly, with corrections that vanish logarithmically with the lattice size. We then examine the influence of the shape of the lattice on the first-passage probability, where we focus on the aspect ratio dependence: Distorting the lattice always reduces the encounter probability of two walkers and can exhibit a crossover to the behavior of a genuinely one-dimensional random walk. The nature of this transition is also explained qualitatively.

  10. Protection from Potential Exposure for the Chernobyl New Safe Confinement

    SciTech Connect

    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

    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.

  11. Potential for general relativity and its geometry

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  12. Effects of self-heating and phase change on the thermal profile of hydrogen isotopes in confined geometries

    SciTech Connect

    Baxamusa, S., E-mail: baxamusa1@llnl.gov; Field, J.; Dylla-Spears, R.; Kozioziemski, B.; Suratwala, T.; Sater, J. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)

    2014-03-28

    Growth of high-quality single-crystal hydrogen in confined geometries relies on the in situ formation of seed crystals. Generation of deuterium-tritium seed crystals in a confined geometry is governed by three effects: self-heating due to tritium decay, external thermal environment, and latent heat of phase change at the boundary between hydrogen liquid and vapor. A detailed computation of the temperature profile for liquid hydrogen inside a hollow shell, as is found in inertial confinement fusion research, shows that seeds are likely to form at the equatorial plane of the shell. Radioactive decay of tritium to helium slowly alters the composition of the hydrogen vapor, resulting in a modified temperature profile that encourages seed formation at the top of the shell. We show that the computed temperature profile is consistent with a variety of experimental observations.

  13. Magnetic properties of electrons confined in an anisotropic cylindrical potential

    NASA Astrophysics Data System (ADS)

    Nedelkoski, Zlatko; Petreska, Irina

    2014-11-01

    In the present paper a theoretical model, describing the effects of external electric and magnetic fields on an electron confined in an anisotropic parabolic potential, is considered. The exact wave functions are used to calculate electron current and orbital magnetic dipole momentum for the single electron. Exact expressions, giving the force and energy of the dipole-dipole interaction, are also determined. Further, the system is coupled to a heat bath, and mean values and fluctuations of the magnetic dipole momentum, utilizing the canonical ensemble are calculated. Influences of the temperature, as well as the external magnetic field, expressed via the Larmor frequency are analyzed. We also include the dependencies of the magnetic dipole momentum and its fluctuations on the effective mass of the electron, considering some experimental values for low-dimensional systems, that are extensively studied for various applications in electronics. Our results suggest that the average momentum or its fluctuations are strongly related to the effective mass of the electron. Having on mind that parabolically shaped potentials have very wide area of application in the low-dimensional systems, such as quantum dots and rings, carbon nanotubes, we believe that the proposed model and the consequent analysis is of general importance, since it offers exact analytical approach.

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

    ERIC Educational Resources Information Center

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

    2012-01-01

    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…

  15. Stability of a jet in confined pressure-driven biphasic flows at low Reynolds number in various geometries.

    PubMed

    Guillot, Pierre; Colin, Annie; Ajdari, Armand

    2008-07-01

    We adress the question of the stability of a confined coflowing jet at low Reynolds number in various geometries. Our study is motivated by recent experiments in microfluidic devices. When immiscible fluids flow in microchannels, either monodisperse droplets or parallel flows are obtained depending upon the flow rate of the aqueous phase and the oil phase. In these experiments, the confining and the shape of the geometry play a fundamental role. In a previous paper [Guillot, Phys. Rev. Lett 99, 104502 (2007)], we analyzed the stability of the jet in the framework of the lubrication approximation at low Reynolds number in a cylindrical geometry, and we related the transition between the droplets regime and the jet regime to the absolute-convective transition of the Rayleigh plateau instability. In this work, the effect of the channel geometry and the jet position within the microfluidic device are discussed. New flow patterns are pointed out. Bidimensional jets are encountered in square and rectangular geometry. Contrary to jets occuring in circular geometry, these two-dimensional jets are absolutely stable. Focusing on situations where the inner fluid is more viscous than the outer one, we evidence a range of parameters where droplets are produced through a blocking and pinching mechanism. In this particular case, the flow is unstable, the growing perturbations are convected upstream. This induces the clogging of the channel by the internal phase and its pinching by the external one. In a future presentation we will give a comparison between this model and experimental data. PMID:18764050

  16. Macromolecular crowding and confinement: biochemical, biophysical, and potential physiological consequences*

    PubMed Central

    Zhou, Huan-Xiang; Rivas, Germán; Minton, Allen P.

    2009-01-01

    Expected and observed effects of volume exclusion on the free energy of rigid and flexible macromolecules in crowded and confined systems, and consequent effects of crowding and confinement on macromolecular reaction rates and equilibria are summarized. Findings from relevant theoretical/simulation and experimental literature published from 2004 onward are reviewed. Additional complexity arising from the heterogeneity of local environments in biological media, and the presence of nonspecific interactions between macromolecules over and above steric repulsion are discussed. Theoretical and experimental approaches to the characterization of crowding- and confinement-induced effects in systems approaching the complexity of living organisms are suggested. PMID:18573087

  17. Long Time Motion of NLS Solitary Waves in a Confining Potential

    E-print Network

    Long Time Motion of NLS Solitary Waves in a Confining Potential B. L. G. Jonsson1,2, , J. Fr. March 7, 2005 Abstract We study the motion of solitary-wave solutions of a family of focusing gener- alized nonlinear Schr¨odinger equations with a confining, slowly varying external potential, V (x

  18. Influence of Particle Shape on Bending Rigidity of Colloidal Monolayer Membranes and Particle Deposition during Droplet Evaporation in Confined Geometries

    NASA Astrophysics Data System (ADS)

    Yunker, Peter J.; Gratale, Matthew; Lohr, Matthew A.; Still, Tim; Lubensky, T. C.; Yodh, A. G.

    2012-06-01

    We investigate the influence of particle shape on the bending rigidity of colloidal monolayer membranes (CMMs) and on evaporative processes associated with these membranes. Aqueous suspensions of colloidal particles are confined between glass plates and allowed to evaporate. Confinement creates ribbonlike air-water interfaces and facilitates measurement and characterization of CMM geometry during drying. Interestingly, interfacial buckling events occur during evaporation. Extension of the description of buckled elastic membranes to our quasi-2D geometry enables the determination of the ratio of CMM bending rigidity to its Young’s modulus. Bending rigidity increases with increasing particle anisotropy, and particle deposition during evaporation is strongly affected by membrane elastic properties. During drying, spheres are deposited heterogeneously, but ellipsoids are not. Apparently, increased bending rigidity reduces contact line bending and pinning and induces uniform deposition of ellipsoids. Surprisingly, suspensions of spheres doped with a small number of ellipsoids are also deposited uniformly.

  19. Computer simulations of structure, dynamics, and phase behavior of colloidal fluids in confined geometry and under shear

    NASA Astrophysics Data System (ADS)

    Winkler, A.; Winter, D.; Chaudhuri, P.; Statt, A.; Virnau, P.; Horbach, J.; Binder, K.

    2013-11-01

    Using computer simulations, colloidal systems in different external fields are investigated. Colloid-polymer mixtures, described in terms of the Asakura-Oosawa (AO) model, are considered under strong confinement. Both in cylindrical and spherical confinement, the demixing transition of the three-dimensional AO model is rounded and, using Monte Carlo simulations, we analyze in detail the consequences of this rounding (occurrence of multi-domain states in cylindrical geometry, non-equivalence of conjugate ensembles due to different finite-size corrections in spherical geometry etc.). For the case of the AO model confined between two parallel walls, spinodal decomposition is studied using a combination of molecular dynamics simulation and the multiparticle collision dynamics method. This allows us to investigate the influence of hydrodynamic interactions on the domain growth during spinodal decomposition. For a binary glass-forming Yukawa mixture, non-linear active micro-rheology is considered, i.e. a single particle is pulled through a deeply supercooled liquid. The diffusion dynamics of the pulled particle is analyzed in terms of the van Hove correlation function. Finally, the Yukawa mixture in the glass state, confined between walls, is studied under the imposition of a uniform shear stress. Below and around the yield stress, persistent creep in the form of shear-banded structures is observed.

  20. Dynamics of a ±1/2 defect pair in a confined geometry: A thin hybrid aligned nematic cell

    NASA Astrophysics Data System (ADS)

    Lu, Li-Xia; Zhang, Zhi-Dong

    2015-02-01

    Confined geometry can change the defect structure and its properties. In this paper, we investigate numerically the dynamics of a dipole of ±1/2 parallel wedge disclination lines in a confined geometry: a thin hybrid aligned nematic (HAN) cell, based on the Landau–de Gennes theory. When the cell gap d is larger than a critical value of 12? (where ? is the characteristic length for order-parameter change), the pair annihilates. A pure HAN configuration without defect is formed in an equilibrium state. In the confined geometry of d ? 12?, the diffusion process is discovered for the first time and an eigenvalue exchange configuration is formed in an equilibrium state. The eigenvalue exchange configuration is induced by different essential reasons. When 10? < d ? 12?, the two defects coalesce and annihilate. The biaxial wall is created by the inhomogeneous distortion of the director, which results in the eigenvalue exchange configuration. When d ? 10?, the defects do not collide and the eigenvalue exchange configuration originates from the biaxial seeds concentrated at the defects. Project supported by the National Natural Science Foundation of China (Grant No. 11374087) and the Key Subject Construction Project of Hebei Province University.

  1. Manifold configurations of the director field formed by topological defects in free and confined geometry in smectic films

    NASA Astrophysics Data System (ADS)

    Dolganov, P. V.; Cluzeau, P.

    2014-12-01

    We study the topology of the c -director field near topological defects with point core and with a droplet in the core of the defect in nonpolar smectic-C and ferroelectric smectic-C * freestanding films using polarized optical microscopy. Free and confined geometry of topological defects and droplets with strong outer boundary condition are compared. The c -director field can be remarkably different around a point defect and a droplet with the same topological charge S =+1 . In ferroelectric films, splay deformation of the c -director transforms into bend deformation after droplet nucleation. Heating a ferroelectric film with an S =+1 droplet leads to a dramatic change of the c -director topology from bend to splay. In confined geometry we found spiral structures in which the c -director has opposite direction of rotation along the inner and outer boundaries of the island. Our observations are discussed on the basis of theories taking into account both the influence of polarity and of confined geometry on elasticity and topology of the c -director field.

  2. Solution of Two-Body Bound State Problems with Confining Potentials

    SciTech Connect

    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

    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.

  3. Adapting SAFT-? perturbation theory to site-based molecular dynamics simulation. III. Molecules with partial charges at bulk phases, confined geometries and interfaces

    NASA Astrophysics Data System (ADS)

    Ghobadi, Ahmadreza F.; Elliott, J. Richard

    2014-09-01

    In Paper I [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 139(23), 234104 (2013)], we showed that how a third-order Weeks-Chandler-Anderson (WCA) Thermodynamic Perturbation Theory and molecular simulation can be integrated to characterize the repulsive and dispersive contributions to the Helmholtz free energy for realistic molecular conformations. To this end, we focused on n-alkanes to develop a theory for fused and soft chains. In Paper II [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 141(2), 024708 (2014)], we adapted the classical Density Functional Theory and studied the microstructure of the realistic molecular fluids in confined geometries and vapor-liquid interfaces. We demonstrated that a detailed consistency between molecular simulation and theory can be achieved for both bulk and inhomogeneous phases. In this paper, we extend the methodology to molecules with partial charges such as carbon dioxide, water, 1-alkanols, nitriles, and ethers. We show that the electrostatic interactions can be captured via an effective association potential in the framework of Statistical Associating Fluid Theory (SAFT). Implementation of the resulting association contribution in assessing the properties of these molecules at confined geometries and interfaces presents satisfactory agreement with molecular simulation and experimental data. For example, the predicted surface tension deviates less than 4% comparing to full potential simulations. Also, the theory, referred to as SAFT-? WCA, is able to reproduce the specific orientation of hydrophilic head and hydrophobic tail of 1-alkanols at the vapor-liquid interface of water.

  4. Resonant tunneling of 1-dimensional electrons across an array of 3-dimensionally confined potential wells

    Microsoft Academic Search

    D. R. Allee; S. Y. Chou; J. S. Harris; R. F. W. Pease

    1990-01-01

    A lateral resonant tunneling field effect transistor has been fabricated with a gate electrode in the form of a railway such that the two rails form a lateral double barrier potential at the GaAs\\/AlGaAs interface. The ties confine the electrons in the third dimension forming an array of potential boxes or three dimensionally confined potential wells. The width of the

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

    E-print Network

    The potential role of electric fields and plasma barodiffusion on the inertial confinement fusion. Related Articles Investigating inertial confinement fusion target fuel conditions through x-ray spectroscopy Phys. Plasmas 19, 056312 (2012) Analytic criteria for shock ignition of fusion reactions

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

    Microsoft Academic Search

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

    2006-01-01

    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

  7. Directed self-assembly of field-responsive fluids in confined geometries Ramin Haghgooie*a

    E-print Network

    Doyle, Patrick S.

    principles associated with the self-assembly of magnetorheological (MR) fluids in the microfluidic setting-assembly of magnetorheological (MR) fluids in microfluidic confinement and the important role of channel topology. We will focus

  8. Unusual large-pitch banding in poly(L-lactic acid): Effects of composition and geometry confinement

    SciTech Connect

    Woo, Eamor M.; Lugito, Graecia; Hsieh, Ya-Ting [Department of Chemical Engineering, National Cheng Kung University, Tainan, 701-01, Taiwan (China); Nurkhamidah, Siti [Department of Chemical Engineering, Faculty of Industrial Technology, Sepuluh Nopember Institute of Technology Kampus ITS Sukolilo, Surabaya 60111 (Indonesia)

    2014-02-24

    Lamellar patterns and orientations in blends of two crystalline polymers: poly(ethylene oxide) (PEO) and low-molecular-weight poly(L-lactic acid) (PLLA) were investigated using polarizing light optical microscopy (POM), and atomic and scanning electron microscopy (AFM, SEM). Specific etching off of PEO was used to reveal the complex earlier-grown PLLA lamellae patterns with various PEO content in blends. Banding of extremely long pitch (50 ?m) in crystallized PLLA spherulites was induced by two kinetic factors: geometry confinement by top cover and introduction of diluent such as PEO. The mechanisms and correlation among the lamellar assembly, ring bands, and cracks are exemplified. Lamellar patterns and ring-band types in blends were found to vary with respect to not only blend compositions, but also confinement of top-cover.

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

    SciTech Connect

    Kausik, S. S.; Kakati, B.; Saikia, B. K. [Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402 (India)] [Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402 (India)

    2013-05-15

    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{sup ?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.

  10. Confined quantum time of arrival for the vanishing potential

    SciTech Connect

    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

    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.

  11. An x-ray setup to investigate the atomic order of confined liquids in slit geometry

    SciTech Connect

    Lippmann, M.; Ehnes, A.; Seeck, O. H. [Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg (Germany)] [Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg (Germany)

    2014-01-15

    A setup has been designed to investigate thin films of confined liquids with the use of X-ray scattering methods. The confinement is realized between the flat culets of a pair of diamonds by positioning and orienting the lower diamond with nanometer and micro radian accuracy. We routinely achieve gaps between 5 and 50 nm at culet diameters of 200 ?m. With this setup and a micro focused X-ray beam we have investigated the in-plane and the out-off-plane atomic order of benzene with atomic resolution.

  12. Dynamics and statistics of wave-particle interactions in a confined geometry.

    PubMed

    Gilet, Tristan

    2014-11-01

    A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors. PMID:25493868

  13. Dynamics and statistics of wave-particle interactions in a confined geometry

    NASA Astrophysics Data System (ADS)

    Gilet, Tristan

    2014-11-01

    A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors.

  14. An x-ray setup to investigate the atomic order of confined liquids in slit geometry.

    PubMed

    Lippmann, M; Ehnes, A; Seeck, O H

    2014-01-01

    A setup has been designed to investigate thin films of confined liquids with the use of X-ray scattering methods. The confinement is realized between the flat culets of a pair of diamonds by positioning and orienting the lower diamond with nanometer and micro radian accuracy. We routinely achieve gaps between 5 and 50 nm at culet diameters of 200 ?m. With this setup and a micro focused X-ray beam we have investigated the in-plane and the out-off-plane atomic order of benzene with atomic resolution. PMID:24517811

  15. Phase separation in confined geometries: Solving the Cahn–Hilliard equation with generic boundary conditions

    Microsoft Academic Search

    R. Kenzler; F. Eurich; P. Maass; B. Rinn; J. Schropp; E. Bohl; W. Dieterich

    2001-01-01

    We apply implicit numerical methods to solve the Cahn–Hilliard equation for confined systems. Generic boundary conditions for hard walls are considered, as they are derived from physical principles. Based on a detailed stability analysis an automatic time step control could be implemented, which makes it possible to explore the demixing kinetics of two thermodynamically stable phases over many orders in

  16. Microscopic Theory of the Tube Confinement Potential for Liquids of Topologically Entangled Rigid Macromolecules

    NASA Astrophysics Data System (ADS)

    Sussman, Daniel M.; Schweizer, Kenneth S.

    2011-08-01

    We formulate and apply a microscopic self-consistent theory for the dynamic transverse confinement field in solutions of zero-excluded-volume rods based solely on topological entanglements. In agreement with the phenomenological tube model, an infinitely deep potential is predicted. However, strong anharmonicities are found to qualitatively soften localization, in quantitative agreement with experiments on heavily entangled biopolymer solutions. Predictions are also made for the effect of rod alignment on the transverse diffusion constant, tube diameter, and confinement force.

  17. Adapting SAFT-? perturbation theory to site-based molecular dynamics simulation. III. Molecules with partial charges at bulk phases, confined geometries and interfaces.

    PubMed

    Ghobadi, Ahmadreza F; Elliott, J Richard

    2014-09-01

    In Paper I [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 139(23), 234104 (2013)], we showed that how a third-order Weeks-Chandler-Anderson (WCA) Thermodynamic Perturbation Theory and molecular simulation can be integrated to characterize the repulsive and dispersive contributions to the Helmholtz free energy for realistic molecular conformations. To this end, we focused on n-alkanes to develop a theory for fused and soft chains. In Paper II [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 141(2), 024708 (2014)], we adapted the classical Density Functional Theory and studied the microstructure of the realistic molecular fluids in confined geometries and vapor-liquid interfaces. We demonstrated that a detailed consistency between molecular simulation and theory can be achieved for both bulk and inhomogeneous phases. In this paper, we extend the methodology to molecules with partial charges such as carbon dioxide, water, 1-alkanols, nitriles, and ethers. We show that the electrostatic interactions can be captured via an effective association potential in the framework of Statistical Associating Fluid Theory (SAFT). Implementation of the resulting association contribution in assessing the properties of these molecules at confined geometries and interfaces presents satisfactory agreement with molecular simulation and experimental data. For example, the predicted surface tension deviates less than 4% comparing to full potential simulations. Also, the theory, referred to as SAFT-? WCA, is able to reproduce the specific orientation of hydrophilic head and hydrophobic tail of 1-alkanols at the vapor-liquid interface of water. PMID:25194387

  18. FREE ENERGY AND SOLUTIONS OF THE VLASOV-POISSON-FOKKER-PLANCK SYSTEM : EXTERNAL POTENTIAL AND CONFINEMENT

    E-print Network

    Dolbeault, Jean

    FREE ENERGY AND SOLUTIONS OF THE VLASOV-POISSON-FOKKER-PLANCK SYSTEM : EXTERNAL POTENTIAL 1. Large time behavior in a confining potential 2. Vanishing when there is an external but non-Poisson-Fokker-Planck system is nonlin- ear since E(t, x) depends on f through equation (P). In the following, we shall assume

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

    Microsoft Academic Search

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

    1997-01-01

    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

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

    SciTech Connect

    Tzonev, I.V.; DeMora, J.M.; Miley, G.H. [Univ. of Illinois, Urbana, IL (United States)

    1995-12-31

    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.

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

    Microsoft Academic Search

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

    1995-01-01

    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

  2. Geometry

    NSDL National Science Digital Library

    Rusin, Dave

    A short article designed to provide an introduction to geometry, including classical Euclidean geometry and synthetic (non-Euclidean) geometries; analytic geometry; incidence geometries (including projective planes); metric properties (lengths and angles); and combinatorial geometries such as those arising in finite group theory. Many results in this area are basic in either the sense of simple, or useful, or both. History; applications and related fields and subfields; textbooks, reference works, and tutorials; software and tables; other web sites with this focus.

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

    NASA Astrophysics Data System (ADS)

    Laachi, Nabil; Dorfman, Kevin D.

    2010-12-01

    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.

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

    PubMed

    Laachi, Nabil; Dorfman, Kevin D

    2010-12-21

    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

  5. Reply to "Comment on 'Vortex distribution in a confining potential' ".

    PubMed

    Girotto, Matheus; dos Santos, Alexandre P; Pakter, Renato; Levin, Yan

    2014-08-01

    We argue that contrary to recent suggestions, nonextensive statistical mechanics has no relevance for inhomogeneous systems of particles interacting by short-range potentials. We show that these systems are perfectly well described by the usual Boltzmann-Gibbs statistical mechanics. PMID:25215853

  6. Potential energy profile of colloidal nanoparticles in optical confinement.

    PubMed

    Fu, Jinxin; Zhan, Qiwen; Lim, Min Yao; Li, Zhiyuan; Ou-Yang, H Daniel

    2013-10-15

    An optical bottle method is developed to determine the potential-energy profile of colloidal Rayleigh nanoparticles in an optical trap. The three-dimensional distribution of fluorescent particles in the trap is measured by laser scanning confocal fluorescence microscopy. At sufficiently low concentrations at which interactions between the particles are negligible, the single-particle trapping potential-energy profile is determined from the equilibrium number-density profile by use of the Boltzmann distribution. Fluorescence imaging as well as calculations based on a discrete dipole approximation show that effects due to scattering forces are negligible for polystyrene particles of size less than 10% of the wavelength of the trapping laser, thus justifying the assumption of conservative forces in the equilibrium potential-energy determinations. The new optical bottle method measures the entire two-dimensional trapping-potential profile for an individual nanoparticle without the restriction that only one particle be contained in the trap, thus obviating the need for high laser power. PMID:24321903

  7. A numerical approach to study the Kramers equation for finite geometries: boundary conditions and potential fields

    NASA Astrophysics Data System (ADS)

    Araújo, Adérito; Das, Amal K.; Sousa, Ercília

    2015-01-01

    The Kramers equation for the phase-space function, which models the dynamics of an underdamped Brownian particle, is the subject of our study. Numerical solutions of this equation for natural boundaries (unconfined geometries) have been well reported in the literature. But not much has been done on the Kramers equation for finite (confining) geometries which require a set of additional constraints imposed on the phase-space function at physical boundaries. In this paper we present numerical solutions for the Kramers equation with a variety of potential fields—namely constant, linear, harmonic and periodic—in the presence of fully absorbing and fully reflecting boundary conditions (BCs). The choice of the numerical method and its implementation take into consideration the type of BCs, in order to avoid the use of ghost points or artificial conditions. We study and assess the conditions under which the numerical method converges. Various aspects of the solutions for the phase-space function are presented with figures and discussed in detail.

  8. Quasilinear theory of collisionless Fermi acceleration in a multicusp magnetic confinement geometry

    NASA Astrophysics Data System (ADS)

    Dewar, R. L.; Ciubotariu, C. I.

    1999-12-01

    Particle motion in a cylindrical multiple-cusp magnetic field configuration is shown to be highly (though not completely) chaotic, as expected by analogy with the Sinai billiard. This provides a collisionless, linear mechanism for phase randomization during monochromatic wave heating. A general quasilinear theory of collisionless energy diffusion is developed for particles with a Hamiltonian of the form H0+H1, motion in the unperturbed Hamiltonian H0 being assumed chaotic, while the perturbation H1 can be coherent (i.e., not stochastic). For the multicusp geometry, two heating mechanisms are identified-cyclotron resonance heating of particles temporarily mirrortrapped in the cusps, and nonresonant heating of nonadiabatically reflected particles (the majority). An analytically solvable model leads to an expression for a transit-time correction factor, exponentially decreasing with increasing frequency. The theory is illustrated using the geometry of a typical laboratory experiment.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

  10. Planar ion trap geometry for microfabrication

    Microsoft Academic Search

    M. J. Madsen; W. K. Hensinger; D. Stick; J. A. Rabchuk; C. Monroe

    2004-01-01

    We describe a novel high aspect ratio radiofrequency linear ion trap geometry that is amenable to modern microfabrication techniques. The ion trap electrode structure consists of a pair of stacked conducting cantilevers resulting in confining fields that take the form of fringe fields from parallel plate capacitors. The confining potentials are modeled both analytically and numerically. This ion trap geometry

  11. Magnetoconductance oscillations and hall current for a two-dimensional electron gas with harmonic confining potential

    Microsoft Academic Search

    G. Kliros; A. Jannussis

    1988-01-01

    Summary  In the present paper we calculate exactly the density of states of an ideal 2DEG in uniform magnetic and electric fields with parabolic confining potential. From the density of states, we obtain the magnetoconductance oscillations. Consequently, we get the Hall current by means of the Feynman-Hellman theorem and study its quantization.

  12. Potential regime for heavy quarks dynamics and Lorentz nature of confinement

    NASA Astrophysics Data System (ADS)

    Kalashnikova, Yu. S.; Nefediev, A. V.

    1997-11-01

    Propagation of the heavy quark in the field of a static antiquark source is studied in the framework of effective Dirac equation. The model of QCD vacuum is described by bilocal gluonic correlators. In the heavy quark limit the effective interaction is reduced to the potential one with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement, while spin-orbit term is in agreement with Eichten-Feinberg-Gromes results. New spin-independent corrections to the leading confining regime are identified, which arise due to the nonlocality of the interaction in time direction and quark Zitterbewegung.

  13. Communication: Effects of stress on the tube confinement potential and dynamics of topologically entangled rod fluids

    NASA Astrophysics Data System (ADS)

    Sussman, Daniel M.; Schweizer, Kenneth S.

    2011-10-01

    A microscopic theory for the effect of applied stress on the transverse topological confinement potential and slow dynamics of heavily entangled rigid rods is presented. The confining entanglement force localizing a polymer in a tube is predicted to have a finite strength. As a consequence, three regimes of terminal relaxation behavior are predicted with increasing stress: accelerated reptation due to tube widening (dilation), relaxation via deformation-assisted activated transverse barrier hopping, and complete destruction of the lateral tube constraints corresponding to microscopic yielding or a disentanglement transition.

  14. Communication: effects of stress on the tube confinement potential and dynamics of topologically entangled rod fluids.

    PubMed

    Sussman, Daniel M; Schweizer, Kenneth S

    2011-10-01

    A microscopic theory for the effect of applied stress on the transverse topological confinement potential and slow dynamics of heavily entangled rigid rods is presented. The confining entanglement force localizing a polymer in a tube is predicted to have a finite strength. As a consequence, three regimes of terminal relaxation behavior are predicted with increasing stress: accelerated reptation due to tube widening (dilation), relaxation via deformation-assisted activated transverse barrier hopping, and complete destruction of the lateral tube constraints corresponding to microscopic yielding or a disentanglement transition. PMID:21992275

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

    SciTech Connect

    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

    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.

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

    SciTech Connect

    Warren, R.P.; Caspi, S.

    1981-08-01

    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.

  17. [Structure and dynamics of microemulsions in bulk, at interfaces, and in confined geometries]. Progress report

    SciTech Connect

    Not Available

    1993-12-31

    The authors have been constructing a special purpose small angle neutron scattering spectrometer (SAND) in collaboration with IPNS of Argonne National Laboratory and Texaco Research Laboratories in Beacon, New York. The spectrometer, having a moderate neutron flux, will be uniquely suited for detailed studies of complex fluids in their various phases. This spectrometer will be fully available to general users of the small angle scattering community after a year of testing and upon installation of the auxiliary equipment. The general research objective of the MIT group is to continue studies of the microstructural relationship to phase-behavior in three-component microemulsion systems. Specifically, they shall study the (1) variation of bulk structures when a microemulsion undergoes a non-wetting to wetting transition, (2) correlating interfacial reflectivity measurements of these wetting transitions to the SANS results, (3) use the contrast variation technique they recently developed for measuring the mean and Gaussian curvatures of the surfactant sheet to study the structural inversion of water-in-oil to oil-in-water microemulsions and the transition of disordered bicontinuous microemulsion to ordered lamellar phases, (4) investigation of the effects of spatial confinement on the phase behavior and structure of bicontinuous microemulsions, and finally (5) they shall continue the study of the recently discovered non-exponential relaxation of droplet density fluctuations near the critical and percolation points in water-in-oil droplet microemulsions.

  18. A Bayesian Inference Scheme to Extract Diffusivity and Potential Fields from Confined Single-Molecule Trajectories

    PubMed Central

    Türkcan, Silvan; Alexandrou, Antigoni; Masson, Jean-Baptiste

    2012-01-01

    Currently used techniques for the analysis of single-molecule trajectories only exploit a small part of the available information stored in the data. Here, we apply a Bayesian inference scheme to trajectories of confined receptors that are targeted by pore-forming toxins to extract the two-dimensional confining potential that restricts the motion of the receptor. The receptor motion is modeled by the overdamped Langevin equation of motion. The method uses most of the information stored in the trajectory and converges quickly onto inferred values, while providing the uncertainty on the determined values. The inference is performed on the polynomial development of the potential and on the diffusivities that have been discretized on a mesh. Numerical simulations are used to test the scheme and quantify the convergence toward the input values for forces, potential, and diffusivity. Furthermore, we show that the technique outperforms the classical mean-square-displacement technique when forces act on confined molecules because the typical mean-square-displacement analysis does not account for them. We also show that the inferred potential better represents input potentials than the potential extracted from the position distribution based on Boltzmann statistics that assumes statistical equilibrium. PMID:22677382

  19. A Bayesian inference scheme to extract diffusivity and potential fields from confined single-molecule trajectories.

    PubMed

    Türkcan, Silvan; Alexandrou, Antigoni; Masson, Jean-Baptiste

    2012-05-16

    Currently used techniques for the analysis of single-molecule trajectories only exploit a small part of the available information stored in the data. Here, we apply a Bayesian inference scheme to trajectories of confined receptors that are targeted by pore-forming toxins to extract the two-dimensional confining potential that restricts the motion of the receptor. The receptor motion is modeled by the overdamped Langevin equation of motion. The method uses most of the information stored in the trajectory and converges quickly onto inferred values, while providing the uncertainty on the determined values. The inference is performed on the polynomial development of the potential and on the diffusivities that have been discretized on a mesh. Numerical simulations are used to test the scheme and quantify the convergence toward the input values for forces, potential, and diffusivity. Furthermore, we show that the technique outperforms the classical mean-square-displacement technique when forces act on confined molecules because the typical mean-square-displacement analysis does not account for them. We also show that the inferred potential better represents input potentials than the potential extracted from the position distribution based on Boltzmann statistics that assumes statistical equilibrium. PMID:22677382

  20. Dielectric constant of liquids confined in the extended nanospace measured by a streaming potential method.

    PubMed

    Morikawa, Kyojiro; Kazoe, Yutaka; Mawatari, Kazuma; Tsukahara, Takehiko; Kitamori, Takehiko

    2015-02-01

    Understanding liquid structure and the electrical properties of liquids confined in extended nanospaces (10-1000 nm) is important for nanofluidics and nanochemistry. To understand these liquid properties requires determination of the dielectric constant of liquids confined in extended nanospaces. A novel dielectric constant measurement method has thus been developed for extended nanospaces using a streaming potential method. We focused on the nonsteady-state streaming potential in extended nanospaces and successfully measured the dielectric constant of liquids within them without the use of probe molecules. The dielectric constant of water was determined to be significantly reduced by about 3 times compared to that of the bulk. This result contributes key information toward further understanding of the chemistry and fluidics in extended nanospaces. PMID:25569302

  1. Structural orderings of anisotropically confined colloids interacting via a quasi-square-well potential

    NASA Astrophysics Data System (ADS)

    Campos, L. Q. Costa; Apolinario, S. W. S.

    2015-01-01

    We implement Brownian dynamics to investigate the static properties of colloidal particles confined anisotropically and interacting via a potential which can be tailored in a repulsive-attractive-respulsive fashion as the interparticle distance increases. A diverse number of structural phases are self-assembled, which were classified according to two aspects, that is, their macroscopic and microscopic patterns. Concerning the microscopic phases we found the quasicrystalline, triangular, square, and mixed orderings, where this latter is a combination of square and triangular cells in a 3 ×2 proportion, i.e., the so-called (33,42) Archimedian lattice. On the macroscopic level the system could self-organize in a compact or perforated single cluster surrounded or not by fringes. All the structural phases are summarized in detailed phases diagrams, which clearly show that the different phases are extended as the confinement potential becomes more anisotropic.

  2. Long Time Motion of NLS Solitary Waves in a Confining Potential

    Microsoft Academic Search

    B. Lars G. Jonsson; Jürg Fröhlich; Stephen Gustafson; Israel Michael Sigal

    2006-01-01

    We study the motion of solitary-wave solutions of a family of focusing generalized nonlinear Schroedinger equations with a confining, slowly varying external potential, $V(x)$. A Lyapunov-Schmidt decomposition of the solution combined with energy estimates allows us to control the motion of the solitary wave over a long, but finite, time interval. We show that the center of mass of the

  3. Plasma physics simulations of double potential wells in an inertial electrostatic confinement (IEC) device

    Microsoft Academic Search

    I. V. Tzonev; G. H. Miley; R. A. Nebel

    1995-01-01

    Summary form only given. The formation and behavior of double potential wells in an IEC fusion device was investigated using IXL-a one-dimensional code that solves the Poisson-Vlasov equations for a collisionless spherical plasma. IXL results represent an important limiting case where space charge effects dominate. The formation of a deep and stable double well is essential for good ion confinement,

  4. A study of two confined electrons using the Woods-Saxon potential

    NASA Astrophysics Data System (ADS)

    Xie, Wenfang

    2009-03-01

    In this paper, we studied two electrons confined in a quantum dot with the Woods-Saxon potential by using the method of numerical diagonalization of the Hamiltonian matrix within the effective-mass approximation. The great advantage of our methodology is that it enables confinement regimes by varying two parameters in the model potential. A ground-state behavior (singlet \\rightarrow triplet state transitions) as a function of the strength of a magnetic field has been investigated. We found that the confinement barrier size and the barrier inclination of a Woods-Saxon potential are important for the singlet-triplet oscillation of a two-electron quantum dot. Based on the computed energies and wavefunctions, the linear and nonlinear optical absorption coefficients have been examined between the 1S state (L = 0) and the 1P state (L = 1). The results are presented as a function of the incident photon energy for the different values of the barrier size and height. It is found that the optical properties of the two-electron system in a quantum dot are strongly affected by the barrier height and size.

  5. Effect of channel geometry on the electrostatic potential in acetylcholine channels.

    PubMed

    Aidoo, Anthony Y

    2003-12-01

    We study the effect of channel geometry on the potential barrier encountered by ions as they permeate the acetylcholine receptor channel. Among the various channel geometries which have been used to represent the acetylcholine receptor channel include the cylinder and the toroidal catenary. The main reasons for those choices appear to be the facilitation of separation of the Poisson equation, rather than biological considerations. We consider a novel and realistic acetylcholine channel geometry, and calculate the electrostatic potential profiles within it, and compare our results with results from other channel geometries. PMID:14583171

  6. Geometry

    NSDL National Science Digital Library

    2014-09-18

    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

  7. Deep sub-nanosecond reversal of vortex cores confined in a spin-wave potential well

    SciTech Connect

    Dong, Xinwei; Wang, Zhenyu; Wang, Ruifang, E-mail: wangrf@xmu.edu.cn [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China)

    2014-03-17

    A spin-wave potential well is created in a permalloy nanodisk by setting up a cylindrical cavity in the center of the sample. We then apply a single-harmonic external magnetic field perpendicular to the disk plane to switch the vortex polarity of the sample. Our micromagnetic numerical studies establish that the effective spin-wave confinement by the potential well leads to much stronger magnetization oscillation in the sample. Therefore, the vortex core can be reversed well below 200 ps and over a wide range of field frequency. Our findings present an additional efficient means for ultrafast switching of magnetic vortices.

  8. Long time motion of NLS solitary waves in a confining potential

    E-print Network

    B. L. G. Jonsson; J. Froehlich; S. Gustafson; I. M. Sigal

    2005-03-07

    We study the motion of solitary-wave solutions of a family of focusing generalized nonlinear Schroedinger equations with a confining, slowly varying external potential, $V(x)$. A Lyapunov-Schmidt decomposition of the solution combined with energy estimates allows us to control the motion of the solitary wave over a long, but finite, time interval. We show that the center of mass of the solitary wave follows a trajectory close to that of a Newtonian point particle in the external potential $V(x)$ over a long time interval.

  9. Measurements of localized potential profiles by LIF polarization spectroscopy in an inertial-electrostatic confinement discharge

    NASA Astrophysics Data System (ADS)

    Motoyasu, Tatsunori; Namba, Shinichi; Takiyama, Ken

    2014-10-01

    Spatial distributions of the electric field were measured in inertial-electrostatic confinement plasmas generated in a glided cylindrical hollow cathode in He gas as a function of the applied voltage using laser-induced fluorescence polarization spectroscopy to obtain profiles of the potential and the charge density. With increasing applied voltage, the potential difference between the center of the plasma and the cathode decreased, while a virtual anode due to converging positive ions was clearly appeared at the center of the cathode. These are probably caused by the increase in the number of electrons emitted from the cathode surface due to the increasing ion bombardment with increasing applied voltage.

  10. Core/shell/shell spherical quantum dot with Kratzer confining potential: Impurity states and electrostatic multipoles

    NASA Astrophysics Data System (ADS)

    Hayrapetyan, D. B.; Kazaryan, E. M.; Petrosyan, L. S.; Sarkisyan, H. A.

    2015-02-01

    An exactly solvable problem of impurity states is considered in core/shell/shell spherical quantum dot. Kratzer molecular potential is taken for confinement potential. The analytical expressions are obtained for the energy spectrum and wave functions of the impurity electron. The dependencies of the total energy and the binding energy of the impurity on the parameters of the confining potential are investigated. The possibility of the impurity electron leakage is shown in the external environment, due to the specific form of the Kratzer potential. The character of the electrostatic field created by the impurity and the electron is observed on the basis of obtained results. The multipole corrections caused by the dipole and quadrupole moments of the electron are calculated. It is shown that the dipole moment is absent, and the problem reduces to the calculation of only z component for the average values of the diagonal elements of the quadrupole moment tensor. The dependencies of the average values of the quadrupole moment on the Kratzer potential parameters are studied.

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

    SciTech Connect

    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

    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.

  12. Geometry

    NSDL National Science Digital Library

    Weisstein, Eric W.

    Basic geometry resources are always in demand, and educators and students alike will breathe an easy sigh of relief as they are introduced to this set of resources dedicated to this ancient branch of mathematics. Provided by Eric Weisstein at Wolfram Research, the site is simple to navigate and is divided into subtopics that include coordinate geometry, dissection, distance, line geometry, and several dozen other fields of interest. Within each of these subtopics, each topic is addressed in a language that is accessible, accompanied by graphs, charts, and other visual aids that complement the written explanations. Visitors are welcome to leave their own comments on each explanation, and hypertext links lead to other appropriate resources and definitions.

  13. Geometry and earthquake potential of the shoreline fault, central California

    USGS Publications Warehouse

    Hardebeck, Jeanne L.

    2013-01-01

    The Shoreline fault is a vertical strike?slip fault running along the coastline near San Luis Obispo, California. Much is unknown about the Shoreline fault, including its slip rate and the details of its geometry. Here, I study the geometry of the Shoreline fault at seismogenic depth, as well as the adjacent section of the offshore Hosgri fault, using seismicity relocations and earthquake focal mechanisms. The Optimal Anisotropic Dynamic Clustering (OADC) algorithm (Ouillon et al., 2008) is used to objectively identify the simplest planar fault geometry that fits all of the earthquakes to within their location uncertainty. The OADC results show that the Shoreline fault is a single continuous structure that connects to the Hosgri fault. Discontinuities smaller than about 1 km may be undetected, but would be too small to be barriers to earthquake rupture. The Hosgri fault dips steeply to the east, while the Shoreline fault is essentially vertical, so the Hosgri fault dips towards and under the Shoreline fault as the two faults approach their intersection. The focal mechanisms generally agree with pure right?lateral strike?slip on the OADC planes, but suggest a non?planar Hosgri fault or another structure underlying the northern Shoreline fault. The Shoreline fault most likely transfers strike?slip motion between the Hosgri fault and other faults of the Pacific–North America plate boundary system to the east. A hypothetical earthquake rupturing the entire known length of the Shoreline fault would have a moment magnitude of 6.4–6.8. A hypothetical earthquake rupturing the Shoreline fault and the section of the Hosgri fault north of the Hosgri–Shoreline junction would have a moment magnitude of 7.2–7.5.

  14. Deriving geological contact geometry from potential field data

    NASA Astrophysics Data System (ADS)

    Ugalde, Hernan; Morris, William A.

    2010-02-01

    The building process of any geological map involves linking sparse lithological outcrop information with equally sparse geometrical measurements, all in a single entity which is the preferred interpretation of the field geologist. The actual veracity of this interpretative map is partially dependent upon the frequency and distribution of geological outcrops compounded by the complexity of the local geology. Geophysics is commonly used as a tool to augment the distribution of data points, however it normally does not have sufficient geometrical constraints due to: a) all geophysical inversion models being inherently non-unique; and b) the lack of knowledge of the physical property contrasts associated with specific lithologies. This contribution proposes the combined use of geophysical edge detection routines and `threepoint' solutions from topographic data as a possible approach to obtaining geological contact geometry information (strike and dip), which can be used in the construction of a preliminary geological model. This derived geological information should first be assessed for its compatibility with the scale of the problem, and any directly observed geological data. Once verified it can be used to help constrain the preferred geological map interpretation being developed by the field geologist. The method models the contacts as planar surfaces. Therefore, it must be ensured that this assumption fits the scale and geometry of the problem. Two examples are shown from folded sequences at the Bathurst Mining Camp, New Brunswick, Canada.

  15. Finite-geometry models of electric field noise from patch potentials in ion traps

    E-print Network

    Low, Guang Hao

    We model electric field noise from fluctuating patch potentials on conducting surfaces by taking into account the finite geometry of the ion trap electrodes to gain insight into the origin of anomalous heating in ion traps. ...

  16. Ultracold atoms confined in rf-induced two-dimensional trapping potentials

    E-print Network

    Yves Colombe; Elena Knyazchyan; Olivier Morizot; Brigitte Mercier; Vincent Lorent; Helene Perrin

    2004-02-29

    We present the experimental implementation of a new trap for cold atoms proposed by O. Zobay and B. M. Garraway. It relies on adiabatic potentials for atoms dressed by a rf field in an inhomogeneous magnetic field. This trap is well suited to confine atoms tightly along one direction to produce a two-dimensional atomic gas. We transferred ultracold atoms into this trap, starting either from thermal samples or Bose--Einstein condensates. In the latter case, technical noise during the loading stage caused heating and prevented us from observing 2D BECs.

  17. Long Time Motion of NLS Solitary Waves in a Confining Potential

    Microsoft Academic Search

    B. Lars G. Jonsson; Jürg Fröhlich; Stephen Gustafson; Israel Michael Sigal

    2006-01-01

    .  We study the motion of solitary-wave solutions of a family of focusing generalized nonlinear Schrdinger equations with a\\u000a confining, slowly varying external potential, V(x).\\u000a \\u000a A Lyapunov-Schmidt decomposition of the solution combined with energy estimates allows us to control the motion of the solitary\\u000a wave over a long, but finite, time interval.\\u000a \\u000a \\u000a \\u000a We show that the center of mass of the

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

    NASA Astrophysics Data System (ADS)

    Christianto, V.; Smarandache, Florentin

    2009-04-01

    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.

  19. On the electrostatic potential in the scrape-off layer of magnetic confinement devices

    NASA Astrophysics Data System (ADS)

    Loizu, J.; Ricci, P.; Halpern, F. D.; Jolliet, S.; Mosetto, A.

    2013-12-01

    The mechanism regulating the equilibrium electrostatic potential in the scrape-off layer (SOL) of magnetic confinement devices is elucidated. Based on a generalized Ohm's law and the boundary conditions at the magnetic presheath entrance, an analytical expression for the equilibrium electrostatic potential is derived. Results imply that the relative importance of the plasma dynamics at the sheath and far away from the wall in setting the value of the electrostatic potential depends on the density and temperature drops that are established between the two regions. Global, three-dimensional fluid simulations of tokamak SOL turbulence in a simple configuration are performed, confirming the validity of our predictions. The results presented here are general and can be applied to other open-field-line configurations, including linear devices and simple magnetized toroidal devices.

  20. Geometry

    NSDL National Science Digital Library

    Ms. Jackson

    2008-03-24

    We are going to review and sharpen our geometry skills with these fun activities and websites! This game is similar to memory. Practice making making matches with this fun memory game. Match the shape to its definition! Think back to what we have learned and practice identifying geometric shapes and lines by the clues given. This game is timed! Re-arrange the colored pieces given to fit them into the square in ...

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

    NASA Astrophysics Data System (ADS)

    Sussman, Daniel; Schweizer, Ken

    2012-02-01

    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.

  2. Spectral geometry of power-law potentials in quantum mechanics

    NASA Astrophysics Data System (ADS)

    Hall, Richard L.

    1989-06-01

    It is supposed that a single particle moves in openR3 in an attractive central power-law potential V(q)(r)=sgn(q)rq, q>-2, and obeys nonrelativistic quantum mechanics. This paper is concerned with the question: How do the discrete eigenvalues Enl(q) of the Hamiltonian H=-?+V(q) depend on the power parameter q\\? Pure power-law potentials have the elementary property that, for ppotentials'' to construct a global geometrical theory for the spectrum of H and also for more general operators of the form H'=-?+, A(q)?openR. This geometrical approach greatly simplifies the description of the spectra and also facilitates the construction of some general eigenvalue bounds and approximation formulas.

  3. Prediction of potential well structure formed in spherical inertial electrostatic confinement fusion devices with various parameters

    NASA Astrophysics Data System (ADS)

    Ghasemi, M.; Habibi, M.; Amrollahi, R.; Amrollahi

    2013-06-01

    In this paper, the theoretical analysis regarding potential structure on the inertial electrostatic confinement fusion devices has been carried out. Negatively biased grid as cathode placed at the center of the device surrounded by anode is assumed. The device is an ion-injection system and electrons may be emitted from the surface of the cathode. So the existence of both ion and electron currents inside the cathode is considered. Dependence of radial potential well structure on some important parameters as the spreads in the normalized total and angular electron and ion energies, the ratio of ion circulating current to electron circulating current, ion perveance, and grid transparency are investigated by solving Poisson equation.

  4. Monte Carlo study of one-dimensional confined fluids with Gay-Berne intermolecular potential

    NASA Astrophysics Data System (ADS)

    Moradi, M.; Hashemi, S.

    2011-11-01

    The thermodynamic quantities of a one dimensional system of particles with Gay-Berne model potential confined between walls have been obtained by means of Monte Carlo computer simulations. For a number of temperatures, the systems were considered and their density profiles, order parameter, pressure, configurational temperature and average potential energy per particle are reported. The results show that by decreasing the temperature, the soft particles become more ordered and they align to the walls and also they don't show any tendency to be near the walls at very low temperatures. We have also changed the structure of the walls by embedding soft ellipses in them, this change increases the total density near the wall whereas, increasing or decreasing the order parameter depend on the angle of embedded ellipses.

  5. Implementation of the electron propagator to second order on GPUs to estimate the ionization potentials of confined atoms

    NASA Astrophysics Data System (ADS)

    García-Hernández, Erwin; Díaz-García, Cecilia; Vargas, Rubicelia; Garza, Jorge

    2014-09-01

    The best way to estimate ionization potentials (I) for confined atoms is by using the same Hamiltonian for the neutral and the corresponding hypothetical ionized atom. For this purpose, we have implemented the electron propagator to second order (EP2) by using parallel programming techniques on graphic processing units (GPUs). These programming techniques exploit the GPUs for the evaluation of two-electron integrals, which is required for a self- consistent process and because of the reduction involved in the four-index integral transformation. As an example, we present results for confined helium, beryllium and neon atoms, and these are contrasted with previously reported results. Although Koopmans’ theorem (KT) provides good estimates for ionization potentials, it is evident that EP2 corrects these estimates. Unfortunately, the correction made by EP2 does not reveal a trend for confined atoms because in the case of certain confinement regions KT overestimates, whereas for other regions, KT underestimates the ionization potential. The orbital crossing between unoccupied orbitals is responsible for this behavior. In particular, if the lowest unoccupied atomic orbital (LUMO) crosses a virtual orbital, the difference {{I}_{EP2}}-{{I}_{KT}} will change its sign. Thus, EP2 approximation is required when the ionization potential is estimated for confined atoms.

  6. Description of an aeronautical geometry conversion package: Wave-drag to Langley Wireframe Geometry Standard (LaWGS) to Supersonic Implicit Marching Potential (SIMP)

    NASA Technical Reports Server (NTRS)

    Wiese, Michael R.

    1987-01-01

    Documented is an aeronautical geometry conversion package which translates wave-drag geometry into the Langley Wireframe Geometry Standard (LaWGS) format and then into a format which is used by the Supersonic Implicit Marching Potential (SIMP) program. The programs described were developed by Computer Sciences Corporation for the Advanced Vehicles Division/Advanced Concepts Branch at NASA Langley Research Center. Included also are the input and output from a benchmark test case.

  7. Finite geometry models of electric field noise from patch potentials in ion traps

    E-print Network

    Guang Hao Low; Peter F. Herskind; Isaac L. Chuang

    2011-09-14

    We model electric field noise from fluctuating patch potentials on conducting surfaces by taking into account the finite geometry of the ion trap electrodes to gain insight into the origin of anomalous heating in ion traps. The scaling of anomalous heating rates with surface distance, $d$, is obtained for several generic geometries of relevance to current ion trap designs, ranging from planar to spheroidal electrodes. The influence of patch size is studied both by solving Laplace's equation in terms of the appropriate Green's function as well as through an eigenfunction expansion. Scaling with surface distance is found to be highly dependent on the choice of geometry and the relative scale between the spatial extent of the electrode, the ion-electrode distance, and the patch size. Our model generally supports the $d^{-4}$ dependence currently found by most experiments and models, but also predicts geometry-driven deviations from this trend.

  8. Finite-geometry models of electric field noise from patch potentials in ion traps

    SciTech Connect

    Low, Guang Hao [MIT-Harvard Center for Ultracold Atoms, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Physics, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge, CB3 0HE (United Kingdom); Herskind, Peter F.; Chuang, Isaac L. [MIT-Harvard Center for Ultracold Atoms, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2011-11-15

    We model electric field noise from fluctuating patch potentials on conducting surfaces by taking into account the finite geometry of the ion trap electrodes to gain insight into the origin of anomalous heating in ion traps. The scaling of anomalous heating rates with surface distance d is obtained for several generic geometries of relevance to current ion trap designs, ranging from planar to spheroidal electrodes. The influence of patch size is studied both by solving Laplace's equation in terms of the appropriate Green's function as well as through an eigenfunction expansion. Scaling with surface distance is found to be highly dependent on the choice of geometry and the relative scale between the spatial extent of the electrode, the ion-electrode distance, and the patch size. Our model generally supports the d{sup -4} dependence currently found by most experiments and models, but also predicts geometry-driven deviations from this trend.

  9. Thermal stress and plastic deformation of Al fine line structures: Effects of oxide confinement and line geometry

    Microsoft Academic Search

    P. S. Ho; I.-S. Yeo; S. G. H. Anderson; C. K. Hu

    1994-01-01

    The effects of oxide confinement on the thermal stress and yield behavior of Al(Cu) line structures have been studied as a function of linewidth to submicron dimensions. Measurements have been carried out on unpassivated and passivated lines during thermal cycling using a bending-beam technique. By measuring periodic line structures with lines oriented parallel and perpendicular to the beam direction, the

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

    PubMed Central

    Wing, Steve; Freedman, Stephanie; Band, Lawrence

    2002-01-01

    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

  11. X-ray and Dielectric Measurements of Smectic A-Hexatic B Transition in Bulk and Confined Geometries

    Microsoft Academic Search

    Chethan V. Lobo; S. Krishna Prasad; D. S. Shankar Rao

    2005-01-01

    Calorimetric, X-ray and dielectric measurements on a liquid crystal exhibiting a smectic A-Hexatic B (Sm A-Hex B) transition in bulk and upon confinement in Anopore matrix are reported. In the calorimetric experiments the sample in the Anopore matrix shows a much stronger rate-dependent shift in the transition temperature than in the bulk. X-ray studies on both the bulk and the

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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.

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

    PubMed

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

    2012-11-21

    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

  14. Particles of Spin Zero and 1/2 in Electromagnetic Field with Confining Scalar Potential in Modified Heisenberg Algebra

    NASA Astrophysics Data System (ADS)

    Tilbi, A.; Merad, M.; Boudjedaa, T.

    2015-03-01

    In this paper, we propose to solve the relativistic Klein Gordon and Dirac equations subjected to the action of a uniform electomagnetic field confining scalar potential yin the presence of a minimal length in the momentum space. In both cases, the energy eigenvalues and their corresponding eigenfunctions are obtained. The limiting cases is then deduced for a small parameter of deformation.

  15. Particles of Spin Zero and 1/2 in Electromagnetic Field with Confining Scalar Potential in Modified Heisenberg Algebra

    NASA Astrophysics Data System (ADS)

    Tilbi, A.; Merad, M.; Boudjedaa, T.

    2015-02-01

    In this paper, we propose to solve the relativistic Klein Gordon and Dirac equations subjected to the action of a uniform electomagnetic field confining scalar potential yin the presence of a minimal length in the momentum space. In both cases, the energy eigenvalues and their corresponding eigenfunctions are obtained. The limiting cases is then deduced for a small parameter of deformation.

  16. The QCD string tension curve, the ferromagnetic magnetization, and the quark-antiquark confining potential at finite Temperature

    E-print Network

    P. Bicudo

    2010-03-04

    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.

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

    SciTech Connect

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

    2010-08-01

    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.

  18. Structural transitions and long-time self-diffusion of interacting colloids confined by a parabolic potential.

    PubMed

    Euán-Díaz, Edith C; Herrera-Velarde, Salvador; Misko, Vyacheslav R; Peeters, François M; Castañeda-Priego, Ramón

    2015-01-14

    We report on the ordering and dynamics of interacting colloidal particles confined by a parabolic potential. By means of Brownian dynamics simulations, we find that by varying the magnitude of the trap stiffness, it is possible to control the dimension of the system and, thus, explore both the structural transitions and the long-time self-diffusion coefficient as a function of the degree of confinement. We particularly study the structural ordering in the directions perpendicular and parallel to the confinement. Further analysis of the local distribution of the first-neighbors layer allows us to identify the different structural phases induced by the parabolic potential. These results are summarized in a structural state diagram that describes the way in which the colloidal suspension undergoes a structural re-ordering while increasing the confinement. To fully understand the particle dynamics, we take into account hydrodynamic interactions between colloids; the parabolic potential constricts the available space for the colloids, but it does not act on the solvent. Our findings show a non-linear behavior of the long-time self-diffusion coefficient that is associated to the structural transitions induced by the external field. PMID:25591382

  19. Magnetocapacitance of quantum wires: Effect of confining potential on one-dimensional subbands and suppression of exchange enhanced g factor

    NASA Astrophysics Data System (ADS)

    Pallecchi, I.; Heyn, Ch.; Lohse, J.; Kramer, B.; Hansen, W.

    2002-03-01

    By means of magnetocapacitance measurements, we study subband filling in field effect induced arrays of quantum wires in GaAs/AlGaAs heterostructures. The confining potential is defined by fork-shaped interdigitated metallic gates with lithographic width of ~150 nm, realized by e-beam lithography. The capacitance allows us to investigate the density of states. Evolution of one-dimensional subband spacing and filling as a function of confinement, gate voltage and magnetic field is analyzed and quantitatively explained. Also the development of a structure related to spin splitting is studied as a function of both magnetic field and confinement. In different regimes, we find for the g factor either an enhancement up to a factor of almost 50 with respect to the ``bare'' value or a suppression, accounting for exchange interactions and kinetic energy of edge electrons, respectively, in agreement with theoretical models.

  20. Bent waveguides for matter-waves: supersymmetric potentials and reflectionless geometries.

    PubMed

    del Campo, Adolfo; Boshier, Malcolm G; Saxena, Avadh

    2014-01-01

    Non-zero curvature in a waveguide leads to the appearance of an attractive quantum potential which crucially affects the dynamics in matter-wave circuits. Using methods of supersymmetric quantum mechanics, pairs of bent waveguides are found whose geometry-induced potentials share the same scattering properties. As a result, reflectionless waveguides, dual to the straight waveguide, are identified. Strictly isospectral waveguides are also found by modulating the depth of the trapping potential. Numerical simulations are used to demonstrate the efficiency of these approaches in tailoring and controlling curvature-induced quantum-mechanical effects. PMID:24919423

  1. Bent waveguides for matter-waves: supersymmetric potentials and reflectionless geometries

    PubMed Central

    Campo, Adolfo del; Boshier, Malcolm G.; Saxena, Avadh

    2014-01-01

    Non-zero curvature in a waveguide leads to the appearance of an attractive quantum potential which crucially affects the dynamics in matter-wave circuits. Using methods of supersymmetric quantum mechanics, pairs of bent waveguides are found whose geometry-induced potentials share the same scattering properties. As a result, reflectionless waveguides, dual to the straight waveguide, are identified. Strictly isospectral waveguides are also found by modulating the depth of the trapping potential. Numerical simulations are used to demonstrate the efficiency of these approaches in tailoring and controlling curvature-induced quantum-mechanical effects. PMID:24919423

  2. Numerical simulation of a laterally confined double dot with tunable interaction potential

    E-print Network

    Finck, Aaron David Kiyoshi

    2005-01-01

    Recent technological advances have allowed for the construction of small (on the order of 100-1000 nm) systems of confined electrons called quantum dots. Often kept within semiconductor heterostructures, these systems are ...

  3. H2: entanglement, probability density function, confined Kratzer oscillator, universal potential and (Mexican hat- or bell-type) potential energy curves

    E-print Network

    G. Van Hooydonk

    2011-04-29

    We review harmonic oscillator theory for closed, stable quantum systems. The H2 potential energy curve (PEC) of Mexican hat-type, calculated with a confined Kratzer oscillator, is better than the Rydberg-Klein-Rees (RKR) H2 PEC. Compared with QM, the theory of chemical bonding is simplified, since a confined Kratzer oscillator gives the long sought for universal function, once called the Holy Grail of Molecular Spectroscopy. This is validated with HF, I2, N2 and O2 PECs. We quantify the entanglement of spatially separated H2 quantum states, which gives a braid view. The equal probability for H2, originating either from HA+HB or HB+HA, is quantified with a Gauss probability density function. At the Bohr scale, confined harmonic oscillators behave properly at all extremes of bound two-nucleon quantum systems and are likely to be useful also at the nuclear scale.

  4. Geometry induced potential on a 2D-section of a wormhole: catenoid

    E-print Network

    Rossen Dandoloff; Avadh Saxena; Bjorn Jensen

    2009-12-11

    We show that a two dimensional wormhole geometry is equivalent to a catenoid, a minimal surface. We then obtain the curvature induced geometric potential and show that the ground state with zero energy corresponds to a reflectionless potential. By introducing an appropriate coordinate system we also obtain bound states for different angular momentum channels. Our findings can be realized in suitably bent bilayer graphene sheets with a neck or in a honeycomb lattice with an array of dislocations or in nanoscale waveguides in the shape of a catenoid.

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

    Microsoft Academic Search

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

    1995-01-01

    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

  6. Patterned time-orbiting potentials for the confinement and assembly of magnetic dipoles

    PubMed Central

    Chen, A.; Sooryakumar, R.

    2013-01-01

    We present an all-magnetic scheme for the assembly and study of magnetic dipoles within designed confinement profiles that are activated on micro-patterned permalloy films through a precessing magnetic field. Independent control over the confinement and dipolar interactions is achieved by tuning the strength and orientation of the revolving field. The technique is demonstrated with superparamagnetic microspheres field-driven to assemble into closely packed lattice sheets, quasi-1D and other planar structures expandable into dipolar arrays that mirror the patterned surface motifs. PMID:24185093

  7. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2014-12-01

    Semiconducting quantum dots - more fancifully dubbed artificial atoms - are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement - or the lack of any degree of freedom for the electrons (and/or holes) - in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines' random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level transitions are seen to be forbidden. The spherical quantum dots have an edge over the strictly two-dimensional quantum dots in that the additional (magnetic) quantum number makes the physics richer (but complex). A deeper grasp of the Coulomb blockade, quantum coherence, and entanglement can lead to a better insight into promising applications involving lasers, detectors, storage devices, and quantum computing.

  8. Evolution of a Bose-condensed gas under variations of the confining potential

    Microsoft Academic Search

    Yu. Kagan; E. L. Surkov; G. V. Shlyapnikov

    1996-01-01

    We discuss the dynamic properties of a trapped Bose-condensed gas under variations of the confining field and find analytical scaling solutions for the evolving coherent state (condensate). We further discuss the characteristic features and the depletion of this coherent state.

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

    Microsoft Academic Search

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

    2005-01-01

    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

  10. Observing the confinement potential of bacterial pore-forming toxin receptors inside rafts with nonblinking Eu(3+)-doped oxide nanoparticles.

    PubMed

    Türkcan, Silvan; Masson, Jean-Baptiste; Casanova, Didier; Mialon, Geneviève; Gacoin, Thierry; Boilot, Jean-Pierre; Popoff, Michel R; Alexandrou, Antigoni

    2012-05-16

    We track single toxin receptors on the apical cell membrane of MDCK cells with Eu-doped oxide nanoparticles coupled to two toxins of the pore-forming toxin family: ?-toxin of Clostridium septicum and ?-toxin of Clostridium perfringens. These nonblinking and photostable labels do not perturb the motion of the toxin receptors and yield long uninterrupted trajectories with mean localization precision of 30 nm for acquisition times of 51.3 ms. We were thus able to study the toxin-cell interaction at the single-molecule level. Toxins bind to receptors that are confined within zones of mean area 0.40 ± 0.05 ?m(2). Assuming that the receptors move according to the Langevin equation of motion and using Bayesian inference, we determined mean diffusion coefficients of 0.16 ± 0.01 ?m(2)/s for both toxin receptors. Moreover, application of this approach revealed a force field within the domain generated by a springlike confining potential. Both toxin receptors were found to experience forces characterized by a mean spring constant of 0.30 ± 0.03 pN/?m at 37°C. Furthermore, both toxin receptors showed similar distributions of diffusion coefficient, domain area, and spring constant. Control experiments before and after incubation with cholesterol oxidase and sphingomyelinase show that these two enzymes disrupt the confinement domains and lead to quasi-free motion of the toxin receptors. Our control data showing cholesterol and sphingomyelin dependence as well as independence of actin depolymerization and microtubule disruption lead us to attribute the confinement of both receptors to lipid rafts. These toxins require oligomerization to develop their toxic activity. The confined nature of the toxin receptors leads to a local enhancement of the toxin monomer concentration and may thus explain the virulence of this toxin family. PMID:22677383

  11. Host-guest interactions in the confined geometries formed from molecular aggregates of push-pull molecules.

    PubMed

    K, Rohini; Swathi, R S

    2013-07-18

    We have considered push-pull molecules, aminonitroacetylene and aminonitrodiacetylene (O2N-(C?C)n-NH2; n = 1 and 2) as the basic units to design a series of molecular aggregates containing favorable hydrogen bonding interactions. Linear, closed, and stacked geometries of dimers, trimers, tetramers, and pentamers formed from these molecules are found to have very good stabilization energies due to the strong hydrogen bonding abilities of the terminal -NO2 and -NH2 groups. The closed hydrogen-bonded assemblies can act as supramolecular hosts for accommodating some molecules and ions as guests. We have been able to find substantial host-guest interaction energies for the complexes of the hydrogen-bonded closed assemblies with some highly reactive molecules like hexahydro-1,3,5-trinitro-s-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), pentafluoroethane (R-125), and difluoromethane (R-32). Further investigations on the interaction of the ions Li(+), Na(+), K(+), Mg(2+), Ca(2+), Al(3+), F(-), Cl(-), and Br(-) with the monomers as well as the oligomers reveal the formation of strong ion-? complexes, unlike the conventional weak ion-? complexes found in similar acetylenic systems without the end groups. This opens up the possibility of tuning the nature of ionic interactions in ?-systems by varying the terminal groups. PMID:23772692

  12. Pseudo-Newtonian Potential for Charged Particle in Kerr-Newman Geometry

    E-print Network

    Rossen I. Ivanov; Emil M. Prodanov

    2005-04-06

    We consider the equatorial circular motion of a test particle of specific charge q/m Newman geometry of a rotating charged black hole. We find the particle's conserved energy and conserved projection of the angular momentum on the black hole's axis of rotation as corrections, in leading order of q/m, to the corresponding energy and angular momentum of a neutral particle. We determine the centripetal force acting on the test particle and, consequently, we find a classical pseudo-Newtonian potential with which one can mimic this general relativistic problem.

  13. Confinement, the Abelian Decomposition, and the Contribution of Topology to the Static Quark Potential

    E-print Network

    Nigel Cundy; Yongmin Cho; Weonjong Lee

    2014-11-04

    In the past few years, we have presented a new way of considering quark confinement. Through a careful choice of a Cho-Duan-Ge Abelian Decomposition, we can construct the QCD Wilson Loop in terms of an Abelian restricted field. The relationship between the QCD and restricted string tensions is exact; and we do not need to gauge fix, apply any path ordering of gauge links, or additional path integrals. This hints at why mesons are colour neutral. Furthermore, the Abelian restricted field contains two parts: a Maxwell term, and a topological term. The topological term can describe magnetic monopoles and other topological objects, which can be studied both numerically and theoretically. By examining the topological part of the restricted field strength we have found evidence suggesting that these objects, which will contribute to confinement if present, are indeed there. Previous studies have used simplifications, breaking the exact relationship between the restricted and QCD string tensions, but it was found that the topological term dominated the restricted string tension. Here we remove those simplifications, and show that the Abelian restricted field does indeed fully explain confinement. However, our results for how much of the restricted string tension arises from the topological objects show strong dependence on the lattice spacing and level of smearing, so we are not yet able to draw a definitive conclusion.

  14. Consistent prediction of streaming potential in non-Newtonian fluids: the effect of solvent rheology and confinement on ionic conductivity.

    PubMed

    Bandopadhyay, Aditya; Chakraborty, Suman

    2015-03-01

    By considering an ion moving inside an imaginary sphere filled with a power-law fluid, we bring out the implications of the fluid rheology and the influence of the proximity of the other ions towards evaluating the conduction current in an ionic solution. We show that the variation of the conductivity as a function of the ionic concentration is both qualitatively and quantitatively similar to that predicted by the Kohlrausch law. We then utilize this consideration for estimating streaming potentials developed across narrow fluidic confinements as a consequence of the transport of ions in a convective medium constituting a power-law fluid. These estimates turn out to be in sharp contrast to the classical estimates of streaming potential for non-Newtonian fluids, in which the effect of rheology of the solvent is merely considered to affect the advection current, disregarding its contributions to the conduction current. Our results have potential implications of devising a new paradigm of consistent estimation of streaming potentials for non-Newtonian fluids, with combined considerations of the confinement effect and fluid rheology in the theoretical calculations. PMID:25693753

  15. Breaking the acoustic diffraction limit via nonlinear effect and thermal confinement for potential deep-tissue high-resolution imaging

    PubMed Central

    Yuan, Baohong; Pei, Yanbo; Kandukuri, Jayanth

    2013-01-01

    Our recently developed ultrasound-switchable fluorescence (USF) imaging technique showed that it was feasible to conduct high-resolution fluorescence imaging in a centimeter-deep turbid medium. Because the spatial resolution of this technique highly depends on the ultrasound-induced temperature focal size (UTFS), minimization of UTFS becomes important for further improving the spatial resolution USF technique. In this study, we found that UTFS can be significantly reduced below the diffraction-limited acoustic intensity focal size via nonlinear acoustic effects and thermal confinement by appropriately controlling ultrasound power and exposure time, which can be potentially used for deep-tissue high-resolution imaging. PMID:23479498

  16. Navigability Potential of Washington Rivers and Streams Determined with Hydraulic Geometry and a Geographic Information System

    USGS Publications Warehouse

    Magirl, Christopher S.; Olsen, Theresa D.

    2009-01-01

    Using discharge and channel geometry measurements from U.S. Geological Survey streamflow-gaging stations and data from a geographic information system, regression relations were derived to predict river depth, top width, and bottom width as a function of mean annual discharge for rivers in the State of Washington. A new technique also was proposed to determine bottom width in channels, a parameter that has received relatively little attention in the geomorphology literature. These regression equations, when combined with estimates of mean annual discharge available in the National Hydrography Dataset, enabled the prediction of hydraulic geometry for any stream or river in the State of Washington. Predictions of hydraulic geometry can then be compared to thresholds established by the Washington State Department of Natural Resources to determine navigability potential of rivers. Rivers with a mean annual discharge of 1,660 cubic feet per second or greater are 'probably navigable' and rivers with a mean annual discharge of 360 cubic feet per second or less are 'probably not navigable'. Variance in the dataset, however, leads to a relatively wide range of prediction intervals. For example, although the predicted hydraulic depth at a mean annual discharge of 1,660 cubic feet per second is 3.5 feet, 90-percent prediction intervals indicate that the actual hydraulic depth may range from 1.8 to 7.0 feet. This methodology does not determine navigability - a legal concept determined by federal common law - instead, this methodology is a tool for predicting channel depth, top width, and bottom width for rivers and streams in Washington.

  17. Diffuse versus square-well confining potentials in modelling A@C60 atoms

    NASA Astrophysics Data System (ADS)

    Dolmatov, V. K.; King, J. L.; Oglesby, J. C.

    2012-05-01

    A perceived advantage for the replacement of a discontinuous square-well pseudo-potential, which is often used by various researchers as an approximation to the actual C60 cage potential in calculations of endohedral atoms A@C60, by a more realistic diffuse potential is explored. The photoionization of endohedral H@C60 and Xe@C60 is chosen as the case study. The diffuse potential is modelled by a combination of two Woods–Saxon potentials. It is demonstrated that photoionization spectra of A@C60 atoms are largely insensitive to the degree ? of diffuseness of the potential borders, in a reasonably broad range of ?s. These spectra are found to be insensitive to discontinuity of the square-well potential as well. Both potentials result in practically identical calculated spectra. New numerical values for the set of square-well parameters, which lead to a better agreement between experimental and theoretical data for A@C60 spectra, are recommended for future studies.

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

    NASA Astrophysics Data System (ADS)

    Cioslowski, Jerzy; Albin, Joanna

    2013-09-01

    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).

  19. INFLUENCE OF END POTENTIAL PLATES ON PLASMA HEATING AND CONFINEMENT Sergey Yu. Taskaev

    E-print Network

    Taskaev, Sergey Yur'evich

    electron temperature of 50 eV that is of the most importance. It is just the high value of electron of freedom [5]. , V r, cm Fig. 2. Radial profile of plasma potential in the transport region (z = -243cm

  20. Hysteresis and metastability of Bose-Einstein-condensed clouds of atoms confined in ring potentials

    NASA Astrophysics Data System (ADS)

    Roussou, A.; Tsibidis, G. D.; Smyrnakis, J.; Magiropoulos, M.; Efremidis, Nikolaos K.; Jackson, A. D.; Kavoulakis, G. M.

    2015-02-01

    We consider a Bose-Einstein-condensed cloud of atoms which rotate in a toroidal or annular potential. Assuming one-dimensional motion, we evaluate the critical frequencies associated with the effect of hysteresis and the critical coupling for stability of the persistent currents. We perform these calculations using both the mean-field approximation and the method of numerical diagonalization of the many-body Hamiltonian which includes corrections due to the finiteness of the atom number.

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

    NASA Astrophysics Data System (ADS)

    Göktürkler, G.; Balkaya, Ç.

    2012-10-01

    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.

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

    ERIC Educational Resources Information Center

    Mariotti, Maria Alessandra; Baccaglini-Frank, Anna

    2011-01-01

    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…

  3. Exciton states and interband absorption of cylindrical quantum dot with Morse confining potential

    NASA Astrophysics Data System (ADS)

    Hayrapetyan, D. B.; Kazaryan, E. M.; Kotanjyan, T. V.; Tevosyan, H. Kh.

    2015-02-01

    In this paper the exciton and electron sates in cylindrical quantum dot with Morse potential made of GaAs are studied. For the regime of strong size quantization, energy spectrum with the parabolic approximation case are compared. For strong and weak size quantization regimes analytic expressions for the particle energy spectrum, absorption coefficient and dependencies of effective threshold frequencies of absorption on the geometrical parameters quantum dot are obtained. For the intermediate size quantization regime the problem solved in the framework of variation method. The selection rules corresponding to different transitions between quantum levels are found. The size dispersion distribution of growing quantum dots by the radius and height by two experimentally realizing distribution functions have been taken into account. Distribution functions of Gauss, Lifshits-Slezov have been considered.

  4. Mapping of diffusion in confined systems (beyond the concept of entropic potential)

    NASA Astrophysics Data System (ADS)

    Kalinay, Pavol

    2010-12-01

    Typical biological structures, like pores or fibers, are quasi one-dimensional (1D). We have to solve 3+1 dimensional differential equations to describe correctly transport through them or along them, but only the transport in the longitudinal direction is interesting in general. The question is to get rid of the transverse degrees of freedom in a mathematically correct way and to arrive at a pure 1D description of the system. We study this mathematical problem in the case of diffusion in a channel of varying cross section. We start with the simplest concept of entropic potential, logarithm of the number of states at some longitudinal position x, leading to the Fick-Jacobs equation. We present a rigorous mapping technique generating systematically corrections to the spatial operator of this equation in a small parameter ?, representing the ratio of the typical transverse and longitudinal lengths of the channel. Based on the result of this mapping, we discuss a hierarchy of various approximations, which can be applied to describe diffusion in the channel as purely one-dimensional. Finally, we give an outlook of possible extension of this mapping.

  5. A geometry package for generation of input data for a three-dimensional potential-flow program

    NASA Technical Reports Server (NTRS)

    Halsey, N. D.; Hess, J. L.

    1978-01-01

    The preparation of geometric data for input to three-dimensional potential flow programs was automated and simplified by a geometry package incorporated into the NASA Langley version of the 3-D lifting potential flow program. Input to the computer program for the geometry package consists of a very sparse set of coordinate data, often with an order of magnitude of fewer points than required for the actual potential flow calculations. Isolated components, such as wings, fuselages, etc. are paneled automatically, using one of several possible element distribution algorithms. Curves of intersection between components are calculated, using a hybrid curve-fit/surface-fit approach. Intersecting components are repaneled so that adjacent elements on either side of the intersection curves line up in a satisfactory manner for the potential-flow calculations. Many cases may be run completely (from input, through the geometry package, and through the flow calculations) without interruption. Use of the package significantly reduces the time and expense involved in making three-dimensional potential flow calculations.

  6. 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...

  7. Exploring Reaction Pathways of Single-Molecule Interactions through the Manipulation and Tracking of a Potential-Confined Microsphere in Three Dimensions

    E-print Network

    Heinrich, Volkmar

    of a Potential-Confined Microsphere in Three Dimensions Wesley P. Wong1,3 , Volkmar Heinrich1 , and Evan Evans1 of weak chemical transitions by analyzing the 3D Brownian fluctuations of a functionalized microsphere fluctuation regimes in the 3D motion of a test microsphere, and by quantifying the rates of transition between

  8. Multi-potential well formation and neutron production in inertial-electrostatic confinement fusion by numerical simulation

    SciTech Connect

    Ohnishi, Masami; Yamamoto, Yasushi; Yoshikawa, Kiyoshi [Kyoto Univ., Uji, Kyoto (Japan). Inst. of Atomic Energy; Sato, Kunihiro [Himeji Inst. of Tech., Himeji, Hyogo (Japan)

    1995-12-31

    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 oscillates at the period much longer than the ion plasma frequency. A double well structure can be formed even for the ions with a spread energy distribution when the ion current is larger than the threshold value. The time-averaged neutron production in D-D fusion events is found to be proportional to the third power of the ion current where the double well structure is formed. The numerical simulation reveals that an IEC possesses the favorable dependence of fusion reactions on the injected ion current for the application to a neutron source or a fusion reactor.

  9. Quasi-exactly-solvable confining solutions for spin-1 and spin-0 bosons in (1 + 1) -dimensions with a scalar linear potential

    NASA Astrophysics Data System (ADS)

    Castro, Luis B.; de Castro, Antonio S.

    2014-12-01

    We point out a misleading treatment in the recent literature regarding confining solutions for a scalar potential in the context of the Duffin-Kemmer-Petiau theory. We further present the proper bound-state solutions in terms of the generalized Laguerre polynomials and show that the eigenvalues and eigenfunctions depend on the solutions of algebraic equations involving the potential parameter and the quantum number.

  10. Relativistically corrected geometries obtained with analytical gradients: normalized elimination of the small component using an effective potential

    Microsoft Academic Search

    Michael Filatov; Dieter Cremer

    2003-01-01

    For the quasi-relativistic normalized elimination of small component using an effective potential (NESC-EP) method, analytical energy gradients were developed, programmed, and implemented in a standard quantum chemical program package. NESC-EP with analytical gradients was applied to determine geometry, vibrational frequencies, and dissociation enthalpies of ferrocene, tungsten hexafluoride, and tungsten hexacarbonyle. Contrary to non-relativistic calculations and calculations carried out with RECPs

  11. Are scaling laws of sub-optical wavelength electric field confinement in arrays of metal nanoparticles related to plasmonics or to geometry?

    PubMed

    Mezeme, M Essone; Brosseau, C

    2012-07-30

    In this work, we describe finite element simulations of the plasmonic resonance (PLR) properties of a self-similar chain of plasmonic nanostructures. Using a broad range of conditions, we find strong numerical evidence that the electric field confinement behaves as (?/?)(PLR)[proporationality] EFE(-?), where EFE is the electric field enhancement, ?is the linear size of the focusing length, and ? is the wavelength of the resonant excitation. We find that the exponent ? is close to 1, i.e. significantly lower than the 1.5 found for two-dimensional nanodisks. This scaling law provides support for the hypothesis of a universal regime in which the sub-optical wavelength electric field confinement is controlled by the Euclidean dimensionality and is independent of nanoparticle size, metal nature, or embedding medium permittivity. PMID:23038312

  12. Potential Distribution and Electrostatic Forces in Wedge-Shaped Geometries: Analytical and Numerical Results

    Microsoft Academic Search

    M. A. “Curt” Koenders; Steffen Reymann

    2000-01-01

    The interparticle force due to electrostatic\\/ionic origin in thermal equilibrium is modeled for two particles in close contact in an ion-laden fluid. The space between the particles presents approximately a wedge-shaped geometry. Two methods are used to ascertain the value of the interparticle force: an analytical approximation (equivalent to the traditional Debye–Hückel (DH) method) and a simulation of the ionic

  13. Preliminary potential-field constraints on the geometry of the San Fernando basin, Southern California

    USGS Publications Warehouse

    Langenheim, Victoria E.; Griscom, Andrew; Jachens, R.C.; Hildenbrand, T.G.

    2000-01-01

    Gravity and magnetic data provide new insights on the structural underpinnings of the San Fernando Basin region, which may be important to ground motion models. Gravity data indicate that a deep basin (>5 km) underlies the northern part of the San Fernando Valley; this deep basin is required to explain the lowest gravity values over the Mission Hills thrust fault. Gravity modeling, constrained by well data and density information, shows that the basin may reach a thickness of 8 km, coinciding with the upper termination of the 1994 Northridge earthquake mainshock rupture. The basin is deeper than previous estimates by 2 to 4 km; this estimate is the result of high densities for the gravels of the Pliocene-Pleisocene Saugus Formation. The geometry of the southern margin of the deep basin is not well-constrained by the gravity data, but may dip to the south. Recently acquired seismic data along the LARSE (Los Angeles Regional Seismic Experiment) II profile may provide constraints to determine the location and attitude of the basin edge. Gravity and aeromagnetic models across the eastern margin of the San Fernando Valley indicate that the Verdugo fault may dip to the southwest along its southern extent and therefore have a normal fault geometry whereas it clearly has a thrust fault geometry along its northern strand.

  14. Symplectic Geometry Metric geometry

    E-print Network

    Wolpert, Scott A.

    surfaces, metric space geometry, as well as the analytic/algebraic geometry of curvature, characteristicBasics Symplectic Geometry Curvature Metric geometry Random geodesics Weil-Petersson sampler;Basics Symplectic Geometry Curvature Metric geometry Random geodesics Table of contents 1 Introduction

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

    DOEpatents

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

    1981-01-01

    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.

  16. MHD Stability of Centrifugally Confined Plasmas

    Microsoft Academic Search

    Yi-Min Huang

    2003-01-01

    Centrifugally confined plasmas utilize centrifugal forces from plasma rotation to augment magnetic confinement, as an alternative approach to fusion. One magnetic geometry is mirror-type, with rotation about the axis induced from a central, biased core conductor. The outward centrifugal forces from the rotation have a component along the field lines, thus confining ions to the center. The immediate concern, of

  17. Deforming baryons into confining strings

    SciTech Connect

    Hartnoll, Sean A. [DAMTP, Centre for Mathematical Sciences, Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom); Portugues, Ruben [Centro de Estudios Cientificos (CECS), Avenida Arturo Prat 514, Casilla 1469, Valdivia (Chile)

    2004-09-15

    We find explicit probe D3-brane solutions in the infrared of the Maldacena-Nunez background. The solutions describe deformed baryon vertices: q external quarks are separated in spacetime from the remaining N-q. As the separation is taken to infinity we recover known solutions describing infinite confining strings in N=1 gauge theory. We present results for the mass of finite confining strings as a function of length. We also find probe D2-brane solutions in a confining type IIA geometry, the reduction of a G{sub 2} holonomy M theory background. The relation between these deformed baryons and confining strings is not as straightforward.

  18. A Barotropic Model of the Angular Momentum–Conserving Potential Vorticity Staircase in Spherical Geometry

    Microsoft Academic Search

    Timothy J. Dunkerton; Richard K. Scott

    2008-01-01

    An idealized analytical model of the barotropic potential vorticity (PV) staircase is constructed, con- strained by global conservation of absolute angular momentum, perfect homogenization of PV in mixing zones between (prograde) westerly jets, and the requirement of barotropic stability. An imposed functional relationship is also assumed between jet speed and latitudinal separation using a multiple of the \\

  19. Diffusion Geometry Diffusion Geometry

    E-print Network

    Hirn, Matthew

    Diffusion Geometry Diffusion Geometry for High Dimensional Data Matthew J. Hirn July 3, 2013 #12;Diffusion Geometry Introduction Embedding of closed curve Figure: Left: A closed, non-self-intersecting curve in 3 dimensions. Right: Its embedding as a circle. #12;Diffusion Geometry Introduction Cartoon

  20. X-ray studies of various shapes of electron-velocity distribution functions and of electron confinement affected by kilovolt-range electrostatic potentials

    NASA Astrophysics Data System (ADS)

    Cho, T.; Hirata, M.; Takahashi, E.; Ogura, K.; Masai, K.; Yamaguchi, N.; Kondoh, T.; Matsuda, K.; Hojo, H.; Inutake, M.; Ishii, K.; Kiwamoto, Y.; Mase, A.; Saito, T.; Yatsu, K.; Miyoshi, S.

    1992-02-01

    Several types of x-ray diagnostics, such as x-ray energy spectrum analyses, x-ray absorption methods, and x-ray tomographic reconstructions using various types of x-ray detectors (i.e., a Si(Li), a pure Ge, a NaI(Tl), Si surface-barrier detectors, as well as microchannel plates) have been employed for obtaining various shapes of electron-velocity distribution functions as well as their spatial profiles: (i) a plateau-shaped electron-velocity distribution function in the plug region, supporting a scaling theory between thermal-barrier potentials and ion-confining potentials (Cohen's strong electron-cyclotron heating theory); (ii) mirror-trapped 60-keV relativistic Maxwellian electrons in the thermal-barrier region; and (iii) two-component Maxwellian electrons in the central cell have been observed in the tandem-mirror GAMMA 10. During experiments with thermal barriers, it has been observed that the bulk-electron temperature and its evolution with time in the central cell are quite different from the electron energy and its temporal evolution in the plug region. These differences as well as the different shape of the electron-velocity distribution function in each region have clearly demonstrated the existence of a thermal-isolation effect due to the thermal barriers between the central cell and the plug region. X-ray tomography data in these three regions have shown good axisymmetric radial profiles peaked on the magnetic axis; this axisymmetric shape is useful for reducing nonambipolar radial particle losses. Furthermore, the validity of the Pastukhov theory for electron-energy confinement that is enhanced due to the formation of thermal-barrier potentials has been demonstrated using the electron-energy balance analyses. These data have represented a good electron-energy confinement capability due to the formation of thermal barriers.

  1. Solitary Confinement

    Microsoft Academic Search

    Robert Rogers

    1993-01-01

    If short-term solitary confinement were reintroduced on a large scale, it is suggested that the possible victimization and corruption of inexperienced inmates by career criminals might be partially eliminated. Moreover, it has the possibility of saving taxpayers' money. Currently staff salaries account for about three-fourths of all prison expenditures. A solitary confinement system would initially have construction costs. This would

  2. Ab initio calculations on accurate dissociation energy, equilibrium geometry, and analytic potential energy function for the b3? state of 7LiH molecule

    Microsoft Academic Search

    Deheng Shi; Yufang Liu; Jinfeng Sun; Zunlue Zhu; Xiangdong Yang

    2005-01-01

    The accurate dissociation energy and equilibrium geometry of the b3? state of 7LiH molecule is calculated using a symmetry-adapted-cluster configuration-interaction method in full active space. And the calculated results are 0.2580 eV and 0.1958 nm for the dissociation energy and equilibrium geometry, respectively. The whole potential energy curve for the b3? state is also calculated over the internuclear separation range

  3. Hydrodynamic description of the long-time tails of the linear and rotational velocity autocorrelation functions of a particle in a confined geometry.

    PubMed

    Frydel, Derek; Rice, Stuart A

    2007-12-01

    We report a hydrodynamic analysis of the long-time behavior of the linear and angular velocity autocorrelation functions of an isolated colloid particle constrained to have quasi-two-dimensional motion, and compare the predicted behavior with the results of lattice-Boltzmann simulations. Our analysis uses the singularity method to characterize unsteady linear motion of an incompressible fluid. For bounded fluids we construct an image system with a discrete set of fundamental solutions of the Stokes equation from which we extract the long-time decay of the velocity. For the case that there are free slip boundary conditions at walls separated by H particle diameters, the time evolution of the parallel linear velocity and the perpendicular rotational velocity following impulsive excitation both correspond to the time evolution of a two-dimensional (2D) fluid with effective density rho_(2D)=rhoH. For the case that there are no slip boundary conditions at the walls, the same types of motion correspond to 2D fluid motions with a coefficient of friction xi=pi(2)nu/H(2) modulo a prefactor of order 1, with nu the kinematic viscosity. The linear particle motion perpendicular to the walls also experiences an effective frictional force, but the time dependence is proportional to t(-2) , which cannot be related to either pure 3D or pure 2D fluid motion. Our incompressible fluid model predicts correct self-diffusion constants but it does not capture all of the effects of the fluid confinement on the particle motion. In particular, the linear motion of a particle perpendicular to the walls is influenced by coupling between the density flux and the velocity field, which leads to damped velocity oscillations whose frequency is proportional to c_(s)/H , with c_(s) the velocity of sound. For particle motion parallel to no slip walls there is a slowing down of a density flux that spreads diffusively, which generates a long-time decay proportional to t(-1) . PMID:18233847

  4. Seismic-Reflection Technology Defines Potential Vertical Bypass in Hydrogeologic Confinement within Tertiary Carbonates of the Southeastern Florida Platform

    NASA Astrophysics Data System (ADS)

    Cunningham, K. J.; Walker, C.; Westcott, R. L.

    2011-12-01

    Continuous improvements in shallow-focused, high-resolution, marine seismic-reflection technology has provided the opportunity to evaluate geologic structures that breach confining units of the Floridan aquifer system within the southeastern Florida Platform. The Floridan aquifer system is comprised mostly of Tertiary platform carbonates. In southeastern Florida, hydrogeologic confinement is important to sustainable use of the Floridan aquifer system, where the saline lower part is used for injection of wastewater and the brackish upper part is an alternative source of drinking water. Between 2007 and 2011, approximately 275 km of 24- and 48-channel seismic-reflection profiles were acquired in canals of peninsular southeastern Florida, Biscayne Bay, present-day Florida shelf margin, and the deeply submerged Miami Terrace. Vertical to steeply dipping offsets in seismic reflections indicate faults, which range from Eocene to possible early Pliocene age. Most faults are associated with karst collapse structures; however, a few tectonic faults of early Miocene to early Pliocene age are present. The faults may serve as a pathway for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability in the Floridan aquifer system. The faults may collectively produce a regional confinement bypass system. In early 2011, twenty seismic-reflection profiles were acquired near the Key Biscayne submarine sinkhole located on the seafloor of the Miami Terrace. Here the water depth is about 365 m. A steeply dipping (eastward) zone of mostly deteriorated quality of seismic-reflection data underlies the sinkhole. Correlation of coherent seismic reflections within and adjacent to the disturbed zone indicates a series of faults occur within the zone. It is hypothesized that upward movement of groundwater within the zone contributed to development of a hypogenic karst system and the resultant overlying sinkhole. Study of this modern seafloor sinkhole may provide clues to the genesis of the more deeply buried Tertiary karst collapse structures. Three-dimensional geomodeling of the seismic-reflection data from the Key Biscayne sinkhole further aids visualization of the seismic stratigraphy and structural system that underlies the sinkhole.

  5. A Fortran 90 program to solve the Hartree-Fock equations for interacting spin- 1/2 > fermions confined in harmonic potentials

    NASA Astrophysics Data System (ADS)

    Pal, Hridis Kumar; Shukla, Alok

    2008-08-01

    A set of weakly interacting spin- 1/2 > 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- 1/2 > 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. Program summaryProgram title: trap.x 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 1/2 >; 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.

  6. Alterations in streaming potential in presence of time periodic pressure-driven flow of a power law fluid in narrow confinements with nonelectrostatic ion-ion interactions.

    PubMed

    Dhar, Jayabrata; Ghosh, Uddipta; Chakraborty, Suman

    2014-03-01

    We study the coupled effect of electrokinetic phenomena and fluid rheology in altering the induced streaming potential in narrow fluidic confinements, which is manifested by establishing a time periodic pressure-driven flow in presence of electrical double layer phenomenon. However, in sharp contrast with reported literature, we take into account nonelectrostatic ion-ion interactions toward estimating the same in addition to electrostatic interactions and steric effects. We employ power law based rheological model for estimating the induced streaming potential. We bring out an intricate interaction between nonelectrostatic interactions and fluid rheology on the concerned electrokinetic phenomena, bearing immense consequences toward designing of integrated lab-on-a-chip-based microdevices and nanodevices. PMID:24132646

  7. Analytic gradients, geometry optimization and excited state potential energy surfaces from the particle-particle random phase approximation.

    PubMed

    Zhang, Du; Peng, Degao; Zhang, Peng; Yang, Weitao

    2015-01-14

    The energy gradient for electronic excited states is of immense interest not only for spectroscopy but also for the theoretical study of photochemical reactions. We present the analytic excited state energy gradient of the particle-particle random phase approximation (pp-RPA). The analytic gradient formula is developed from an approach similar to that of time-dependent density-functional theory (TDDFT). The formula is verified for both the Hartree-Fock and (Generalized) Kohn-Sham reference states via comparison with finite difference results. The excited state potential energy surfaces and optimized geometries of some small molecules are investigated, yielding results of similar or better quality compared to adiabatic TDDFT. The singlet-to-triplet instability in TDDFT resulting in underestimated energies of the lowest triplet states is eliminated by pp-RPA. Charge transfer excitations and double excitations, which are challenging for most adiabatic TDDFT methods, can be reasonably well captured by pp-RPA. Within this framework, ground state potential energy surfaces of stretched single bonds can also be described well. PMID:25410624

  8. Covariant isolation from an Abelian gauge field of its nondynamical potential, which, when fed back, can transform into a "confining Yukawa"

    E-print Network

    Steven Kenneth Kauffmann

    2010-05-06

    For Abelian gauge theory a properly relativistic gauge is developed by supplementing the Lorentz condition with causal determination of the time component of the four-vector potential by retarded Coulomb transformation of the charge density. This causal Lorentz gauge agrees with the Coulomb gauge for static charge densities, but allows the four-vector potential to have a longitudinal component that is determined by the time derivative of the four-vector potential's time component. Just as in Coulomb gauge, the two transverse components of the four-vector potential are its sole dynamical part. The four-vector potential in this gauge covariantly separates into a dynamical transverse four-vector potential and a nondynamical timelike/longitudinal four-vector potential, where each of these two satisfies the Lorentz condition. In fact, analogous partition of the conserved four-current shows each to satisfy a Lorentz-condition Maxwell equation system with its own conserved four-current. Because of this complete separation, either of these four-vector potentials can be tinkered with without affecting its counterpart. Since it satisfies the Lorentz condition, the nondynamical four-vector potential times a constant with dimension of inverse length squared is itself a conserved four-current, and so can be fed back into its own source current, which transforms its time component into an extended Yukawa, with both exponentially decaying and exponentially growing components. The latter might be the mechanism of quark-gluon confinement: in non-Abelian color gauge theory the Yukawa mixture ratio ought to be tied to color, with palpable consequences for "colorful" hot quark-gluon plasmas.

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

    SciTech Connect

    Guzowski, R.V. [Science Applications International Corp., Albuquerque, NM (United States); Newman, G. [GRAM, Inc., Albuquerque, NM (United States)

    1993-12-01

    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 performed. An established scenario-development procedure was used to identify a comprehensive set of mutually exclusive scenarios. To assure completeness, 761 features, events, processes, and other listings (FEPS) were compiled from 11 references. This number was reduced to 205 primarily through the elimination of duplications. The 205 FEPs were screened based on site-specific, goal-specific, and regulatory criteria. Four events survived screening and were used in preliminary scenario development: (1) exploratory drilling penetrates a GCD borehole, (2) drilling of a withdrawal/injection well penetrates a GCD borehole, (3) subsidence occurs at the RWMS, and (4) irrigation occurs at the RWMS. A logic diagram was used to develop 16 scenarios from the four events. No screening of these scenarios was attempted at this time. Additional screening of the currently retained events and processes will be based on additional data and information from site-characterization activities. When screening of the events and processes is completed, a final set of scenarios will be developed and screened based on consequence and probability of occurrence.

  10. Spinning geometry = Twisted geometry

    NASA Astrophysics Data System (ADS)

    Freidel, Laurent; Ziprick, Jonathan

    2014-02-01

    It is well known that the SU(2)-gauge invariant phase space of loop gravity can be represented in terms of twisted geometries. These are piecewise-linear-flat geometries obtained by gluing together polyhedra, but the resulting geometries are not continuous across the faces. Here we show that this phase space can also be represented by continuous, piecewise-flat three-geometries called spinning geometries. These are composed of metric-flat three-cells glued together consistently. The geometry of each cell and the manner in which they are glued is compatible with the choice of fluxes and holonomies. We first remark that the fluxes provide each edge with an angular momentum. By studying the piecewise-flat geometries which minimize edge lengths, we show that these angular momenta can be literally interpreted as the spin of the edges: the geometries of all edges are necessarily helices. We also show that the compatibility of the gluing maps with the holonomy data results in the same conclusion. This shows that a spinning geometry represents a way to glue together the three-cells of a twisted geometry to form a continuous geometry which represents a point in the loop gravity phase space.

  11. Analytic eigenenergies of the Dirac equation with finite degrees of freedom under a confining linear potential using basis functions localized in spacetime

    E-print Network

    Kimichika Fukushima; Hikaru Sato

    2015-04-07

    Considering the propagation of fields in the spacetime continuum and the well-defined features of fields with finite degrees of freedom, the wave function is expanded in terms of a finite set of basis functions localized in spacetime. This paper presents the analytic eigenenergies derived for a confined fundamental fermion-antifermion pair under a linear potential obtained from the Wilson loop for the non-Abelian Yang-Mills field. The Hamiltonian matrix of the Dirac equation is analytically diagonalized using basis functions localized in spacetime. The squared system eigenenergies are proportional to the string tension and the absolute value of the Dirac's relativistic quantum number related to the total angular momentum, consistent with the expectation.

  12. Tropical geometric interpretation of ultradiscrete singularity confinement

    NASA Astrophysics Data System (ADS)

    Ormerod, Christopher M.

    2013-08-01

    Using the interpretation of the ultradiscretization procedure as a non-Archimedean valuation, we use results of tropical geometry to show how roots and poles manifest themselves in piece-wise linear systems as points of non-differentiability. This will allow us to demonstrate a correspondence between singularity confinement for discrete integrable systems and ultradiscrete singularity confinement for ultradiscrete integrable systems.

  13. Thermal noise in confined fluids

    NASA Astrophysics Data System (ADS)

    Sanghi, T.; Aluru, N. R.

    2014-11-01

    In this work, we discuss a combined memory function equation (MFE) and generalized Langevin equation (GLE) approach (referred to as MFE/GLE formulation) to characterize thermal noise in confined fluids. Our study reveals that for fluids confined inside nanoscale geometries, the correlation time and the time decay of the autocorrelation function of the thermal noise are not significantly different across the confinement. We show that it is the strong cross-correlation of the mean force with the molecular velocity that gives rise to the spatial anisotropy in the velocity-autocorrelation function of the confined fluids. Further, we use the MFE/GLE formulation to extract the thermal force a fluid molecule experiences in a MD simulation. Noise extraction from MD simulation suggests that the frequency distribution of the thermal force is non-Gaussian. Also, the frequency distribution of the thermal force near the confining surface is found to be different in the direction parallel and perpendicular to the confinement. We also use the formulation to compute the noise correlation time of water confined inside a (6,6) carbon-nanotube (CNT). It is observed that inside the (6,6) CNT, in which water arranges itself in a highly concerted single-file arrangement, the correlation time of thermal noise is about an order of magnitude higher than that of bulk water.

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

    NASA Astrophysics Data System (ADS)

    Amitai, A.; Holcman, D.

    2013-06-01

    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.

  15. Heavy Quark Potential at Finite Temperature in a Dual Gravity Closer to Large N QCD

    E-print Network

    Binoy Krishna Patra; Himanshu Khanchandani

    2015-04-01

    In gauge-gravity duality, the heavy quark potential at finite temperature is usually calculated with the pure AdS background, which does not capture the renormalization group (RG) running in the gauge theory part. In addition, the potential does not contain any confining term in the deconfined phase. Following the Klebanov-Strassler geometry, we employ a geometry, which captures the RG flow similar to QCD, to obtain the heavy quark potential by analytically continuing the string configurations into the complex plane. In addition to the attractive terms, the obtained potential has confining terms both at $T = 0$ and $T \

  16. Electrostatic Interactions between Nanoparticles in Confined Spaces: Influence of Confining Wall Roughness

    Microsoft Academic Search

    Prodip K. Das; Subir Bhattacharjee

    2003-01-01

    Nanoparticles confined in capillaries is a commonly encountered system in a variety of micro and nano electromechanical devices. In this paper we study the influence of the confining geometry on the electrostatic-interaction forces between two nanoparticles. Predictions of electrostatic double layer interaction forces between two similarly charged smooth spherical colloidal particles inside a long \\

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

    PubMed Central

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

    2009-01-01

    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. PMID:18597872

  18. Elmo bumpy square plasma confinement device

    DOEpatents

    Owen, L.W.

    1985-01-01

    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.

  19. Self-organization of supercooled liquids confined inside nano-porous materials

    E-print Network

    Victor Teboul

    2007-02-23

    Large scale molecular dynamics simulations are used to investigate the structural and dynamical modifications of supercooled water when confined inside an hydrophilic nanopore. We then investigate the evolution of the auto-organization of the most and the least mobile molecules (dynamical heterogeneity and string-like cooperative motions) when supercooled water is confined. Our calculations use the recent TIP5P intermolecular potential for water. We observe a strong slowing down of the dynamical properties when the liquid is confined, although the liquid structure is found to remain unchanged when corrected from the pore geometry. We then study cooperative motions inside supercooled confined water in comparison with bulk water. We observe strong modifications of the cooperative motions when the liquid is confined. We observe that dynamical heterogeneities and the associated correlation lengths are strongly increased as well as string-like motions in the confined liquid. This result, which is in opposition with the expected limitation of the correlation length by the confinement procedure, may explain (or be explained by) the slowing down of the dynamics. However the comparison of the dynamical heterogeneities at constant diffusion coefficient shows that the slowing down of the dynamics is not sufficient to explain the increase of the correlation lengths.

  20. Potentialities of a new bimodal Xray/fluorescence tomograph within a cylindrical geometry for pre-clinical studies

    NASA Astrophysics Data System (ADS)

    Koenig, Anne; Planat-Chrétien, Anne; Coutard, Jean-Guillaume; Hervé, Lionel; Brambilla, Marco; Josserand, Véronique; Coll, Jean-Luc; Dinten, Jean-Marc

    2011-03-01

    An instrument dedicated to the co-registration of optical and X-ray measurements is presented: specific acquisition protocol and reconstruction software have been developed for carrying out fluorescence diffuse optical tomography in a cylindrical geometry consistent with XCT. Actual animal geometry provided by the X-ray tomography is used to give animal boundaries to the diffuse optical tomography reconstruction algorithm. To evaluate performances of this new optical imaging system, experiments have been conducted on phantoms, mice with fluorescent capillaries, and finally on mice bearing tumors. The fluorescence reconstructions are shown to be geometrically consistent with X-ray ones. We determined that the sensibility limit of the system to detect fluorescence signal over intrinsic ones is 2 pmol for lungs area and 5 pmol for the abdomen area.

  1. CCSD(T) calculations of stabilities and properties of confined systems

    NASA Astrophysics Data System (ADS)

    Holka, F.; Urban, M.; Melicher?ík, M.; Neogrády, P.; Paldus, J.

    2015-01-01

    We analyze energies, electron affinities and polarizabilities of small anions exposed to an external confinement. The second electron in free O2- and S2- anions is unbound. We investigate the stabilizing effect of the spherical harmonic-oscillator confining potential ?. on these anions employing the Hartree-Fock stability analysis as introduced by ?ížek and Paldus. With increasing strength of the external harmonic-oscillator confinement potential ? the broken symmetry (BS) solutions are systematically eliminated. For ? larger than 0.1 all BS solutions for O2- disappear. For ? larger than 0.13 the CCSD(T) energy of O2- becomes more negative than the energy of the singly charged O- anion. We relate the harmonic-oscillator confining potential to a crystalline environment in which the O2- and S2- anions are stable. We also present a model allowing calculations of the in-crystal polarizabilities of anions. The model is based on CCSD(T) calculations of static polarizabilities of selected anions exposed to the spherical harmonic-oscillator confining potential ? This artificial confinement potential ? is then related to the ionic radii of the cation in representative crystal lattices. We investigate the polarizability of O2- and S2- anions in MgO, MgS, CaO, CaS, SrO, SrS, BaO and BaS crystals. We compare our results with alternative models for in-crystal polarizabilities. External confinement also stabilizes the uracil anion U-, as is shown by calculations with a stepwise micro-hydration of U-. Upon hydration is the CCSD(T) adiabatic electron affinity (AEA) of uracil enhanced by about 250 up to 570 meV in comparison with AEA of the isolated molecule, depending on the geometry of the hydrated uracil anion complex. We tried to find an analogy of the stabilization effect of the external confinement on the otherwise unstable anions. In uracil and its anion is the external confinement represented by the polarized continuum solvation model with dielectric constant as a variational parameter. The physical behavior of ions exposed to an artificial external, spherical harmonic-oscillator confining potential ?, the environment represented by a crystal structure and the confinement represented by the solvent, all have considerable stabilizing effect on the otherwise unstable free anion.

  2. Alternative approaches to plasma confinement

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1977-01-01

    The potential applications of fusion reactors, the desirable properties of reactors intended for various applications, and the limitations of the Tokamak concept are discussed. The principles and characteristics of 20 distinct alternative confinement concepts are described, each of which may be an alternative to the Tokamak. The devices are classed as Tokamak-like, stellarator-like, mirror machines, bumpy tori, electrostatically assisted, migma concept, and wall-confined plasma.

  3. Confined structures: basic crystallographic aspects.

    PubMed

    De Caro, Liberato; Giacovazzo, Carmelo; Siliqi, Dritan

    2002-09-01

    The concept of a confined structure is introduced. The statistical properties of the structure factors for such structures are derived and the main features of the Patterson function are described. It is shown that the structure-factor distributions for the confined structures coincide with those derived for the rational index reflections of ordinary structures. Algorithms potentially useful for protein crystal structure solution are identified and checked via experimental applications. PMID:12192112

  4. Semiflexible chains in confined spaces

    NASA Astrophysics Data System (ADS)

    Morrison, Greg; Thirumalai, D.

    2009-01-01

    We develop an analytical method for studying the properties of a noninteracting wormlike chain (WLC) in confined geometries. The mean-field-like theory replaces the rigid constraints of confinement with average constraints, thus allowing us to develop a tractable method for treating a WLC wrapped on the surface of a sphere, and fully encapsulated within it. The efficacy of the theory is established by reproducing the exact correlation functions for a WLC confined to the surface of a sphere. In addition, the coefficients in the free energy are exactly calculated. We also describe the behavior of a surface-confined chain under external tension that is relevant for single molecule experiments on histone-DNA complexes. The force-extension curves display spatial oscillations, and the extension of the chain, whose maximum value is bounded by the sphere diameter, scales as f-1 at large forces, in contrast to the unconfined chain that approaches the contour length as f-1/2 . A WLC encapsulated in a sphere, that is relevant for the study of the viral encapsulation of DNA, can also be treated using the mean-field approach. The predictions of the theory for various correlation functions are in excellent agreement with Langevin simulations. We find that strongly confined chains are highly structured by examining the correlations using a local winding axis. The predicted pressure of the system is in excellent agreement with simulations but, as is known, is significantly lower than the pressures seen for DNA packaged in viral capsids.

  5. The Geometry Algebraicizing

    E-print Network

    Goldman, William

    The Geometry of 2 Ã? 2 Matrices William M. Goldman Algebraicizing geometry Euclidean geometry William M. Goldman Algebraicizing geometry Euclidean geometry Spherical geometry Triangle tilings geometry Euclidean geometry Spherical geometry Triangle tilings Stereographic projection Hyperbolic

  6. A Review of Quantum Confinement

    SciTech Connect

    Connerade, Jean-Patrick [Quantum Optics and Laser Science Group, Physics Department, Imperial College, London (United Kingdom)

    2009-12-03

    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 - 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 C{sub 60}, as opposed to a purely spherical approximation, leads to some qualification of the computed results.

  7. Confinement induced instability of thin elastic film

    E-print Network

    Animangsu Ghatak

    2005-05-02

    A confined incompressible elastic film does not deform uniformly when subjected to adhesive interfacial stresses but with undulations which have a characteristic wavelength scaling linearly with the thickness of the film. In the classical peel geometry, undulations appear along the contact line below a critical film thickness or below a critical curvature of the plate. Perturbation analysis of the stress equilibrium equations shows that for a critically confined film the total excess energy indeed attains a minima for a finite amplitude of the perturbations which grow with further increase in the confinement.

  8. Advanced Review Geometry optimization

    E-print Network

    Schlegel, H. Bernhard

    , line searches, trust radius, and rational function optimization techniques. Single-ended and double electronic structure packages have a selection of geometry op- timization algorithms. By discussing cases for optimizing equilibrium geometries38 and TSs.39 POTENTIAL ENERGY SURFACES The structure

  9. Developments in special geometry

    E-print Network

    Mohaupt, Thomas

    2011-01-01

    We review the special geometry of N = 2 supersymmetric vector and hypermultiplets with emphasis on recent developments and applications. A new formulation of the local c-map based on the Hesse potential and special real coordinates is presented. Other recent developments include the Euclidean version of special geometry, and generalizations of special geometry to non-supersymmetric theories. As applications we disucss the proof that the local r-map and c-map preserve geodesic completeness, and the construction of four- and five-dimensional static solutions through dimensional reduction over time. The shared features of the real, complex and quaternionic version of special geometry are stressed throughout.

  10. Developments in special geometry

    E-print Network

    Thomas Mohaupt; Owen Vaughan

    2012-01-19

    We review the special geometry of N = 2 supersymmetric vector and hypermultiplets with emphasis on recent developments and applications. A new formulation of the local c-map based on the Hesse potential and special real coordinates is presented. Other recent developments include the Euclidean version of special geometry, and generalizations of special geometry to non-supersymmetric theories. As applications we disucss the proof that the local r-map and c-map preserve geodesic completeness, and the construction of four- and five-dimensional static solutions through dimensional reduction over time. The shared features of the real, complex and quaternionic version of special geometry are stressed throughout.

  11. Developments in special geometry

    NASA Astrophysics Data System (ADS)

    Mohaupt, Thomas; Vaughan, Owen

    2012-02-01

    We review the special geometry of Script N = 2 supersymmetric vector and hypermultiplets with emphasis on recent developments and applications. A new formulation of the local c-map based on the Hesse potential and special real coordinates is presented. Other recent developments include the Euclidean version of special geometry, and generalizations of special geometry to non-supersymmetric theories. As applications we disucss the proof that the local r-map and c-map preserve geodesic completeness, and the construction of four- and five-dimensional static solutions through dimensional reduction over time. The shared features of the real, complex and quaternionic version of special geometry are stressed throughout.

  12. A potentially pure test of cosmic geometry: galaxy clusters and the real space Alcock-Paczynski test

    E-print Network

    Young-Rae Kim; Rupert Croft

    2006-10-10

    We investigate the possibility of probing dark energy by measuring the isotropy of the galaxy cluster autocorrelation function (an Alcock-Paczynski test). The correlation function is distorted in redshift space because of the cluster peculiar velocities, but if these are known and can be subtracted, the correlation function measurement becomes in principle a pure test of cosmic geometry. Galaxy cluster peculiar velocities can be measured using the kinetic Sunyaev Zel'dovich (kSZ) effect. Upcoming CMB surveys, e.g., ACT, SPT, Planck, are expected to do this with varying levels of accuracy, dependent on systematic errors due to cluster temperature measurements, radio point sources, and the primary CMB anisotropy. We use the Hubble volume N-body simulation and the hydrodynamic simulation results of Nagai et. al (2003) to simulate various kSZ surveys. We find by model fitting that a measurement of the correlation function distortion can be used to recover the cosmological parameters that have been used to generate the simulation. However, the low space density of galaxy clusters requires larger surveys than are taking place at present to place tight constraints on cosmology. For example, with the SPT and ACT surveys, Omega_Lambda could be measured to within 0.1 and 0.2 respectively at one sigma, but only upper limits on the equation of state parameter w will be possible. Nevertheless, with accurate measurements of the kSZ effect, this test can eventually be used to probe the dark energy equation of state and its evolution with redshift, with different systematic errors than other methods.

  13. Hyperbolic Geometry

    Microsoft Academic Search

    JAMES W. CANNON; WILLIAM J. FLOYD; RICHARD KENYON; WALTER R. PARRY

    Non-Euclidean, or hyperbolic, geometry was created in the first half of the nine- teenth century in the midst of attempts to understand Euclid's axiomatic basis for geometry. Einstein and Minkowski found in non-Euclidean geometry a geometric basis for the understanding of physical time and space. In the early part of the twentieth century every serious student of mathematics and physics

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

    SciTech Connect

    Oie, Tetsuro

    1980-01-01

    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.

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

    SciTech Connect

    Oie, Tetsuro

    1980-07-28

    A purpose of the present studies is twofold: (1) development of an empirical potential function (EDF) 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 (Ch1 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.

  16. 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

    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

    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.

  17. Longitudinal response of confined semiflexible polymers

    NASA Astrophysics Data System (ADS)

    Thüroff, Florian; Obermayer, Benedikt; Frey, Erwin

    2011-02-01

    The longitudinal response of single semiflexible polymers to sudden changes in externally applied forces is known to be controlled by the propagation and relaxation of backbone tension. Under many experimental circumstances, realized, for example, in nanofluidic devices or in polymeric networks or solutions, these polymers are effectively confined in a channel- or tubelike geometry. By means of heuristic scaling laws and rigorous analytical theory, we analyze the tension dynamics of confined semiflexible polymers for various generic experimental setups. It turns out that in contrast to the well-known linear response, the influence of confinement on the nonlinear dynamics can largely be described as that of an effective prestress. We also study the free relaxation of an initially confined chain, finding a surprising superlinear ~t9/8 growth law for the change in end-to-end distance at short times.

  18. Longitudinal Response of Confined Semiflexible Polymers

    E-print Network

    Florian Thüroff; Benedikt Obermayer; Erwin Frey

    2010-09-12

    The longitudinal response of single semiflexible polymers to sudden changes in externally applied forces is known to be controlled by the propagation and relaxation of backbone tension. Under many experimental circumstances, realized, e.g., in nano-fluidic devices or in polymeric networks or solutions, these polymers are effectively confined in a channel- or tube-like geometry. By means of heuristic scaling laws and rigorous analytical theory, we analyze the tension dynamics of confined semiflexible polymers for various generic experimental setups. It turns out that in contrast to the well-known linear response, the influence of confinement on the non-linear dynamics can largely be described as that of an effective prestress. We also study the free relaxation of an initially confined chain, finding a surprising superlinear t^(9/8) growth law for the change in end-to-end distance at short times.

  19. Confinement-guided shaping of semiconductor nanowires and nanoribbons: "writing with nanowires".

    PubMed

    Pevzner, Alexander; Engel, Yoni; Elnathan, Roey; Tsukernik, Alexander; Barkay, Zahava; Patolsky, Fernando

    2012-01-11

    To fully exploit their full potential, new semiconductor nanowire building blocks with ab initio controlled shapes are desired. However, and despite the great synthetic advances achieved, the ability to control nanowire's geometry has been significantly limited. Here, we demonstrate a simple confinement-guided nanowire growth method that enables to predesign not only the chemical and physical attributes of the synthesized nanowires but also allows a perfect and unlimited control over their geometry. Our method allows the synthesis of semiconductor nanowires in a wide variety of two-dimensional shapes such as any kinked (different turning angles), sinusoidal, linear, and spiral shapes, so that practically any desired geometry can be defined. The shape-controlled nanowires can be grown on almost any substrate such as silicon wafer, quartz and glass slides, and even on plastic substrates (e.g., Kapton HN). PMID:22142384

  20. Quantum Confinement in Hydrogen Bond

    E-print Network

    Carlos da Silva dos Santos; Elso Drigo Filho; Regina Maria Ricotta

    2015-02-09

    In this work, the quantum confinement effect is proposed as the cause of the displacement of the vibrational spectrum of molecular groups that involve hydrogen bonds. In this approach the hydrogen bond imposes a space barrier to hydrogen and constrains its oscillatory motion. We studied the vibrational transitions through the Morse potential, for the NH and OH molecular groups inside macromolecules in situation of confinement (when hydrogen bonding is formed) and non-confinement (when there is no hydrogen bonding). The energies were obtained through the variational method with the trial wave functions obtained from Supersymmetric Quantum Mechanics (SQM) formalism. The results indicate that it is possible to distinguish the emission peaks related to the existence of the hydrogen bonds. These analytical results were satisfactorily compared with experimental results obtained from infrared spectroscopy.

  1. Confinement from correlation functions

    NASA Astrophysics Data System (ADS)

    Fister, Leonard; Pawlowski, Jan M.

    2013-08-01

    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].

  2. Sequence specificity, statistical potentials, and three-dimensional structure prediction with self-correcting distance geometry calculations of beta-sheet formation in proteins.

    PubMed Central

    Zhu, H.; Braun, W.

    1999-01-01

    A statistical analysis of a representative data set of 169 known protein structures was used to analyze the specificity of residue interactions between spatial neighboring strands in beta-sheets. Pairwise potentials were derived from the frequency of residue pairs in nearest contact, second nearest and third nearest contacts across neighboring beta-strands compared to the expected frequency of residue pairs in a random model. A pseudo-energy function based on these statistical pairwise potentials recognized native beta-sheets among possible alternative pairings. The native pairing was found within the three lowest energies in 73% of the cases in the training data set and in 63% of beta-sheets in a test data set of 67 proteins, which were not part of the training set. The energy function was also used to detect tripeptides, which occur frequently in beta-sheets of native proteins. The majority of native partners of tripeptides were distributed in a low energy range. Self-correcting distance geometry (SECODG) calculations using distance constraints sets derived from possible low energy pairing of beta-strands uniquely identified the native pairing of the beta-sheet in pancreatic trypsin inhibitor (BPTI). These results will be useful for predicting the structure of proteins from their amino acid sequence as well as for the design of proteins containing beta-sheets. PMID:10048326

  3. Efimov Trimers under Strong Confinement

    NASA Astrophysics Data System (ADS)

    Levinsen, Jesper; Massignan, Pietro; Parish, Meera M.

    2014-07-01

    The dimensionality of a system can fundamentally impact the behavior of interacting quantum particles. Classic examples range from the fractional quantum Hall effect to high-temperature superconductivity. As a general rule, one expects confinement to favor the binding of particles. However, attractively interacting bosons apparently defy this expectation: While three identical bosons in three dimensions can support an infinite tower of Efimov trimers, only two universal trimers exist in the two-dimensional case. Here, we reveal how these two limits are connected by investigating the problem of three identical bosons confined by a harmonic potential along one direction. We show that the confinement breaks the discrete Efimov scaling symmetry and successively destroys the weakest bound trimers. However, the deepest bound trimers persist even under strong confinement. In particular, the ground-state Efimov trimer hybridizes with the two-dimensional trimers, yielding a superposition of trimer configurations that effectively involves tunneling through a short-range repulsive barrier. Our results suggest a way to use strong confinement to engineer more stable Efimov-like trimers, which have so far proved elusive.

  4. Geometry Information

    NSDL National Science Digital Library

    2010-01-01

    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.

  5. Geometry compression

    Microsoft Academic Search

    Michael Deering

    1995-01-01

    This paper introduces the concept of Geometry Compression, al- lowing 3D triangle data to be represented with a factor of 6 to 10 times fewer bits than conventional techniques, with only slight loss- es in object quality. The technique is amenable to rapid decompres- sion in both software and hardware implementations; if 3D render- ing hardware contains a geometry decompression

  6. Current-induced skyrmion dynamics in constricted geometries.

    PubMed

    Iwasaki, Junichi; Mochizuki, Masahito; Nagaosa, Naoto

    2013-10-01

    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

  7. Current-induced skyrmion dynamics in constricted geometries

    NASA Astrophysics Data System (ADS)

    Iwasaki, Junichi; Mochizuki, Masahito; Nagaosa, Naoto

    2013-10-01

    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.

  8. Son of IXION: A Steady State Centrifugally Confined Plasma for Fusion

    Microsoft Academic Search

    Adil Hassam

    1996-01-01

    A magnetic confinement scheme in which the inertial, u.grad(u), forces effect parallel confinement is proposed. The basic geometry is mirror-like as far as the poloidal field goes or, more simply, multipole (FM-1) type. The rotation is toroidal in this geometry. A supersonic rotation can effect complete parallel confinement, with the usual magnetic mirror force rendered irrelevant. The rotation shear, in

  9. Industrial Applications to the Inertial Electrostatic Confinement Configuration

    Microsoft Academic Search

    Elijah Martin; Steve Shannon; Mohamed Bourham

    2009-01-01

    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

  10. 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.

  11. Differential geometry

    Microsoft Academic Search

    Lajos Tamássy

    \\u000a In the thirties of the 19th century János Bolyai and Nikolai Ivanovi? Lobacevskii created the hyperbolic geometry. Thus they proved that not only the\\u000a Euclidean but also other geometries may exist. Concerning its geometrical importance, this discovery can be compared to the\\u000a change which replaced the Ptolemaic geocentric concept of astronomy by the heliocentric point of view of Copernicus. Hyperbolic

  12. Confinement and screening in tachyonic matter

    E-print Network

    F. A. Brito; M. L. F. Freire; W. Serafim

    2014-11-20

    In this paper we consider confinement and screening of the electric field. We study the behavior of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the phenomenon of `anti-screening' in a medium with exotic dielectric. We show that tachyon matter behaves like an exotic way whose associated dielectric function modifies the Maxwell's equations and affects the fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that the confining regime coincides with the tachyon condensation, which resembles the effect of confinement due to condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance which is associated with {a screening phase

  13. Confinement and screening in tachyonic matter

    NASA Astrophysics Data System (ADS)

    Brito, F. A.; Freire, M. L. F.; Serafim, W.

    2014-12-01

    In this paper we consider confinement and screening of the electric field. We study the behavior of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the phenomenon of `anti-screening' in a medium with exotic dielectric. We show that tachyon matter behaves like in an exotic way whose associated dielectric function modifies the Maxwell equations and affects the fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that the confining regime coincides with the tachyon condensation, which resembles the effect of confinement due to the condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance, which is associated with a screening phase.

  14. Algebra = Geometry Sandor Kovacs

    E-print Network

    Kovács, Sándor

    Algebra = Geometry S´andor Kov´acs University of Washington #12;Motto "To me, algebraic geometry is algebra with a kick" ­Solomon Lefschetz #12;Geometry Geometry = Space + Functions #12;Geometry Geometry = Space + Functions Type of function Type of Geometry #12;Geometry Geometry = Space + Functions Type

  15. New developments in special geometry

    E-print Network

    Thomas Mohaupt

    2006-02-17

    We review recent developments in special geometry, emphasizing the role of real coordinates. In the first part we discuss the para-complex geometry of vector and hypermultiplets in rigid Euclidean N=2 supersymmetry. In the second part we study the variational principle governing the near horizon limit of BPS black holes in matter-coupled N=2 supergravity and observe that the black hole entropy is the Legendre transform of the Hesse potential encoding the geometry of the scalar fields.

  16. Nano Shapes: Tiny Geometry

    NSDL National Science Digital Library

    Amy R. Taylor

    2007-01-01

    Advances in nanotechnology are due in part to the unique structure and properties of carbon nanotubes and buckyballs. These unusual structures are being studied for their potential use as vehicles for drug delivery, to strengthen materials, and as miniature circuits. Through an examination of the geometry of nanoscale materials, students explore the possibilities of nanoscale technologies.

  17. Algebraic Geometry

    NSDL National Science Digital Library

    Rusin, David J., 1957-

    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.

  18. 'Screening' of universal van der Waals Casimir terms by Coulomb gases in a fully finite two-dimensional geometry

    NASA Astrophysics Data System (ADS)

    Jancovici, B.; Samaj, L.

    2005-05-01

    This paper is a continuation of a previous one (Jancovici and Samaj, 2004 J. Stat. Mech. P08006) dealing with classical Casimir phenomena in semi-infinite wall geometries. In that paper, using microscopic Coulomb systems, the long-ranged Casimir force due to thermal fluctuations in conducting walls was shown to be screened by the presence of an electrolyte between the walls into some residual short-ranged force. Here, we aim to extend the study of the screening (cancellation) phenomena to universal Casimir terms appearing in the large-size expansions of the grand potentials for microscopic Coulomb systems confined in fully finite 2D geometries, in particular the disc geometry. Two cases are solved exactly: the high-temperature (Debye-Hückel) limit and the Thirring free-fermion point. Similarities and fundamental differences between fully finite and semi-finite geometries are pointed out.

  19. Programmed environment management of confined microsocieties

    NASA Technical Reports Server (NTRS)

    Emurian, Henry H.

    1988-01-01

    A programmed environment is described that assists the implementation and management of schedules governing access to all resources and information potentially available to members of a confined microsociety. Living and work schedules are presented that were designed to build individual and group performance repertoires in support of study objectives and sustained adaptation by participants. A variety of measurement requirements can be programmed and standardized to assure continuous assessment of the status and health of a confined microsociety.

  20. 1 Introduction Geometries

    E-print Network

    Choi, Suhyoung

    ­ Projective geometry ­ Conformal geometry: Poincare extensions ­ Hyperbolic geometry Lorentz group Geometry.4 Projective geometry Projective geometry · Projective geometry was first considered from fine art. · Desargues: http://www.math.poly.edu/courses/ projective_geometry/ · and http

  1. Confinement Aquaculture. Final Report.

    ERIC Educational Resources Information Center

    Delaplaine School District, AR.

    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, using…

  2. Frustrated order on extrinsic geometries

    E-print Network

    Badel L. Mbanga; Gregory M. Grason; Christian D. Santangelo

    2011-08-07

    We study, analytically and theoretically, defects in a nematically-ordered surface that couple to the extrinsic geometry of a surface. Though the intrinsic geometry tends to confine topological defects to regions of large Gaussian curvature, extrinsic couplings tend to orient the nematic in the local direction of maximum or minimum bending. This additional frustration is unavoidable and most important on surfaces of negative Gaussian curvature, where it leads to a complex ground state thermodynamics. We show, in contradistinction to the well-known effects of intrinsic geometry, that extrinsic curvature expels disclinations from the region of maximum curvature above a critical coupling threshold. On catenoids lacking an "inside-outside" symmetry, defects are expelled altogether.

  3. Field reversal experiments (FRX). [Equilibrium, confinement, and stability

    Microsoft Academic Search

    R. K. Linford; W. T. Armstrong; D. A. Platts; E. G. Sherwood

    1978-01-01

    The equilibrium, confinement, and stability properties of the reversed-field configuration (RFC) are being studied in two theta-pinch facilities. The RFC is an elongated toroidal plasma confined in a purely poloidal field geometry. The open field lines of the linear theta pinch support the closed-field RFC much like the vertical field centers the toroidal plasma in a tokamak. Depending on stability

  4. Transversally confined, noncausal gluons

    NASA Astrophysics Data System (ADS)

    Fried, H. M.

    1992-12-01

    A nonperturbative approach to the gluonic sector of four-dimensional QCD is defined, in which a gap equation is used to generate a mass scale M via dimensional transmutation in an arbitrary axial gauge, using a modification of Halpern's method of replacing conventional functional integration over gauge potentials by integration over equivalent field strengths. A consistency condition is used to show that, without further radiative corrections, the gluonic QCD system is apparently diaelectromagnetic against the insertion of color-electromagnetic fields when the spatial shape of the nonperturbative vacuum state is associated with tubes of color-electric or -magnetic flux. A final Gaussian approximation to the relevant functional integral over field strength leads to an extremely simple result of ``effective gluons'' propagating as ``free particles'' with a matrix-valued mass term, by means of a noncausal ``propagator'' that is effectively confined to the interior of a spatial tube, and that falls off with a large momentum k as [k2]-2. A non-Gaussian extension of this result for the effective gluon propagator (EGP) can be guessed. Either form of EGP may be used to compute a finite, gauge-invariant condensate which corresponds to color-electric flux inside and color-magnetic flux outside the tube, or vice versa. The introduction of quarks leads to a ``modified QED'' in an external, tadpole-generated field, where the EGP replaces the bare photon propagator.

  5. Transversally confined, noncausal gluons

    SciTech Connect

    Fried, H.M. (Physique Theorique, Institut Nonlineaire de Nice, Universite de Nice, 06108 Nice CEDEX 2 (France))

    1992-12-15

    A nonperturbative approach to the gluonic sector of four-dimensional QCD is defined, in which a gap equation is used to generate a mass scale [ital M] [ital via] dimensional transmutation in an arbitrary axial gauge, using a modification of Halpern's method of replacing conventional functional integration over gauge potentials by integration over equivalent field strengths. A consistency condition is used to show that, without further radiative corrections, the gluonic QCD system is apparently diaelectromagnetic against the insertion of color-electromagnetic fields when the spatial shape of the nonperturbative vacuum state is associated with tubes of color-electric or -magnetic flux. A final Gaussian approximation to the relevant functional integral over field strength leads to an extremely simple result of effective gluons'' propagating as free particles'' with a matrix-valued mass term, by means of a noncausal propagator'' that is effectively confined to the interior of a spatial tube, and that falls off with a large momentum [ital k] as [[ital k][sup 2

  6. Negative ions in inertial electrostatic confinement devices

    Microsoft Academic Search

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

    2009-01-01

    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,

  7. The form factor of the K meson and the meson radii in a quark-confining two-step potential model

    NASA Astrophysics Data System (ADS)

    Kulshreshtha, D. S.; Kaushal, R. S.

    1981-06-01

    Previous two-step potential model calculations for the pion form factor in the space-like region are now extended to include the form factor of the K meson, in an anticipation that the experimentalists will shortly be able to measure it for q2 up to, say, 2.0 GeV 2 also, as Dally et al. have already measured it for q2 up to 0.2 GeV 2. Although the curve does not fit well the present experimental data ( q2 up to 0.2 GeV 2), it is, however, anticipated that the model will probably fit the experimental data fairly well for slightly higher values of q2, say, up to 2.0 GeV 2, when measured, as it does very successfully in the case of the pion over a wide range of momentum transfer q2.

  8. Quantum confinement in self-assembled two-dimensional nanoporous honeycomb networks at close-packed metal surfaces

    NASA Astrophysics Data System (ADS)

    Kep?ija, N.; Huang, T.-J.; Klappenberger, F.; Barth, J. V.

    2015-03-01

    Quantum confinement of a two-dimensional electron gas by supramolecular nanoporous networks is investigated using the boundary elements method based on Green's functions for finite geometries and electron plane wave expansion for periodic systems. The "particle in a box" picture was analyzed for cases with selected symmetries that model previously reported architectures constructed from organic and metal-organic scattering centers confining surface state electrons of Ag(111) and Cu(111). First, by analyzing a series of cases with systematically defined parameters (scattering geometry, potentials, and effective broadening), we demonstrate how the scattering processes affect the properties of the confined electrons. For the features of the local density of states reported by scanning tunneling spectroscopy (STS), we disentangle the contributions of lifetime broadening and splitting of quantum well states due to coupling of neighboring quantum dots. For each system, we analyze the local electron density distribution and relate it to the corresponding band structure as calculated within the plane-wave expansion framework. Then, we address two experimental investigations, where in one case only STS data and in the other case mainly angle-resolved photoemission spectroscopy (ARPES) data were reported. In both cases, the experimental findings can be successfully simulated. Furthermore, the missing information can be complemented because our approach allows to correlate the information obtained by STS with that of ARPES. The combined analysis of several observations suggests that the scattering potentials created by the network originate primarily from the adsorbate-induced changes of the local surface dipole barrier.

  9. Quantum confinement in self-assembled two-dimensional nanoporous honeycomb networks at close-packed metal surfaces.

    PubMed

    Kep?ija, N; Huang, T-J; Klappenberger, F; Barth, J V

    2015-03-14

    Quantum confinement of a two-dimensional electron gas by supramolecular nanoporous networks is investigated using the boundary elements method based on Green's functions for finite geometries and electron plane wave expansion for periodic systems. The "particle in a box" picture was analyzed for cases with selected symmetries that model previously reported architectures constructed from organic and metal-organic scattering centers confining surface state electrons of Ag(111) and Cu(111). First, by analyzing a series of cases with systematically defined parameters (scattering geometry, potentials, and effective broadening), we demonstrate how the scattering processes affect the properties of the confined electrons. For the features of the local density of states reported by scanning tunneling spectroscopy (STS), we disentangle the contributions of lifetime broadening and splitting of quantum well states due to coupling of neighboring quantum dots. For each system, we analyze the local electron density distribution and relate it to the corresponding band structure as calculated within the plane-wave expansion framework. Then, we address two experimental investigations, where in one case only STS data and in the other case mainly angle-resolved photoemission spectroscopy (ARPES) data were reported. In both cases, the experimental findings can be successfully simulated. Furthermore, the missing information can be complemented because our approach allows to correlate the information obtained by STS with that of ARPES. The combined analysis of several observations suggests that the scattering potentials created by the network originate primarily from the adsorbate-induced changes of the local surface dipole barrier. PMID:25770520

  10. Structural and electronic properties of sodium clusters under confinement

    NASA Astrophysics Data System (ADS)

    Nagare, Balasaheb J.; Kanhere, Dilip G.; Chacko, Sajeev

    2015-02-01

    Using real-space density functional theory, electronic structure and equilibrium geometries of sodium clusters in the size range of 2-20 atoms have been calculated as a function of confinement. We have examined the evolution of the five lowest isomers as a function of volume for six different compressions. The minimum volume considered is about 1 /15 to 1 /10 of the free-space box volume. We observe a strong tendency for isomeric transitions in many cases, with the higher isomers evolving into the ground state under confinement. In general the clusters tend to become more spherical. The changes in the total energies and the geometries are not significant until the volume gets reduced beyond the 1/3 of the original volume. In this sense, the clusters are not easy to compress. Once the critical volume is reached, the changes in the total energies and geometries are rapid. It turns out that the increase in the total energy is mainly due to the ion-ion and Hartree energies of electrons. We also address how anisotropic confinement affects the geometry of clusters. We further show that geometries obtained with anisotropic confinement are strongly supported by the simulation of clusters inside a carbon nanotube using a hybrid quantum-mechanical and molecular-mechanics approach.

  11. Genuine Geometry!

    NSDL National Science Digital Library

    Ms. Yost

    2009-10-26

    Let's practice some geometry skills. First, try to feed Billy Bug all the grubs in Billy Bug: Quadrant I. Just click on "Start," move Billy Bug with the arrow keys on the screen, and click "Feed" when you're at the coordinate where the grub is located. If you're up for a challenge, try Billy Bug: All Quadrants! Then, in Robo Packer, you will ...

  12. Heavy Quark Potential at Finite Temperature in a Dual Gravity Closer to Large N QCD

    E-print Network

    Binoy Krishna Patra; Himanshu Khanchandani

    2014-12-16

    In gauge-gravity duality, heavy quark potential at finite temperature is usually calculated with the pure AdS background, which does not capture the renormalisation group (RG) running in the gauge theory part and the potential also does not contain any confining term in the deconfined phase. Following the developments in \\cite{KS}, a geometry was contructed recently in \\cite{ Mia:NPB2010, Mia:PRD2010}, which captures the RG flow similar to QCD and we employ their geometry to obtain the heavy quark potential by analytically continuing the string configurations into the complex plane. In addition to the attractive terms, the obtained potential has confining terms both at $T=0$ and $T \

  13. Environmental effects of dredging. Role of contaminant uptake in the potential use of phragmites australis (cav.) trin. On confined disposal facilities. Technical notes

    SciTech Connect

    Folsom, B.L.; VanDerWerff, M.

    1988-12-01

    PURPOSE: Phragmites australis (Cav.) Trin., common reed, is a plant species that is common to fresh- and brackish-water marshes of the world. P. australis has been recommended as one plant species that could survive and grow after being completely buried during dredged material disposal (Lee et al. 1976). P. australis can also serve as a physical barrier, because of its strong stems, to dredged material flow during hydraulic disposal. Decreasing dredged material flow helps to increase consolidation of hydraulically dredged material (Lee et al. 1976). P. australis is a plant species recommended for habitat development on dredged material disposal sites (Hunt et al. 1978). Plant establishment on marsh creation projects using uncontaminated dredged material poses little threat of increasing environmental cycling of contaminants. However, plant establishment or natural invasion of plants on contaminated dredged material has the potential for increased environmental cycling (mobility) of contaminants. Therefore, a literature review was conducted to determine contaminant uptake by P. australis since many dredged material disposal sites support lush stands of P. australis and contaminant uptake by this species was unknown.

  14. Elementary framework for cold field emission: Incorporation of quantum-confinement effects

    SciTech Connect

    Patterson, A. A., E-mail: apatters@mit.edu; Akinwande, A. I. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2013-12-21

    Although the Fowler-Nordheim (FN) equation serves as the foundation of cold field emission theory, it may not be suitable for predicting the emitted current density (ECD) from emitters with a quantum-confined electron supply. This work presents an analytical framework for treating cold field emission from metals that includes the effects of a quantum-confined electron supply. Within the framework, quantum confinement in emitters is classified into transverse and normal quantum confinement based on the orientation of the confinement relative to the emission direction. The framework is used to generate equations predicting the ECD from rectangular and cylindrical emitter geometries comprised of electron supplies of reduced dimensionality. Transverse quantum confinement of the electron supply leads to a reduction in the total ECD as transverse emitter dimensions decrease and normal quantum confinement results in an oscillatory ECD as a function of the normal quantum well width. Incorporating a geometry-dependent field enhancement factor into the model reveals an optimal transverse well width for which quantum confinement of the electron supply and field enhancement equally affect the ECD and a maximum total ECD for the emitter geometry at a given applied field is obtained. As a result, the FN equation over-predicts the ECD from emitters with transverse dimensions under approximately 5?nm, and in those cases, geometry-specific ECD equations incorporating quantum-confinement effects should be employed instead.

  15. Is sarcomere lattice geometry optimal? Analysis of several potential virtual polygon cross-sectional patterns for actin and myosin myofilaments in muscle.

    PubMed

    Kepner, Gordon R

    2014-09-01

    The hexagonal arrangement of actin filaments in skeletal muscle is not the fundamental geometrical or functioning myofilament unit. This analysis of several possible sarcomere lattice geometries for the arrangement of the actin and myosin filaments identifies several geometrical constraints that can be compared for their effect on muscle sarcomere functioning and efficiency. Three distinct virtual polygons, with myosins at their vertices and that tessellate the plane, are compared for both centered actin and perimeter actin arrangements. The analysis evaluates the optimal ratio of myosin to actin filaments, the packing density, and the effect on new myofilament formation in muscle hypertrophy for the various lattice geometries. The results support the view that no single measure of geometrical effectiveness can evaluate definitively the efficiency of any particular arrangement of the myofilaments. The analysis provides quantitative measures of several parameters that, taken overall, support the effectiveness of the myofilament arrangement in Nature. It provides a new definition of the fundamental myofilament unit (FMU). It is possible to calculate the number of actin and myosin myofilaments that need to be added to each polygon arrangement of the myofilaments to create a new FMU for that specific geometry. This leads to useful conclusions about the biochemical efficiency involved in where such units arise in the course of muscle hypertrophy. It supports the idea that the evolutionary endpoint for optimizing muscle's force-generating function can be better understood via the concepts of a FMU and the polygon arrangement of the sarcomere lattice geometry. PMID:25125188

  16. Precision platform for convex lens-induced confinement microscopy

    NASA Astrophysics Data System (ADS)

    Berard, Daniel; McFaul, Christopher M. J.; Leith, Jason S.; Arsenault, Adriel K. J.; Michaud, François; Leslie, Sabrina R.

    2013-10-01

    We present the conception, fabrication, and demonstration of a versatile, computer-controlled microscopy device which transforms a standard inverted fluorescence microscope into a precision single-molecule imaging station. The device uses the principle of convex lens-induced confinement [S. R. Leslie, A. P. Fields, and A. E. Cohen, Anal. Chem. 82, 6224 (2010)], which employs a tunable imaging chamber to enhance background rejection and extend diffusion-limited observation periods. Using nanopositioning stages, this device achieves repeatable and dynamic control over the geometry of the sample chamber on scales as small as the size of individual molecules, enabling regulation of their configurations and dynamics. Using microfluidics, this device enables serial insertion as well as sample recovery, facilitating temporally controlled, high-throughput measurements of multiple reagents. We report on the simulation and experimental characterization of this tunable chamber geometry, and its influence upon the diffusion and conformations of DNA molecules over extended observation periods. This new microscopy platform has the potential to capture, probe, and influence the configurations of single molecules, with dramatically improved imaging conditions in comparison to existing technologies. These capabilities are of immediate interest to a wide range of research and industry sectors in biotechnology, biophysics, materials, and chemistry.

  17. Bacteria in Confined Spaces

    NASA Astrophysics Data System (ADS)

    Wilking, Connie; Weitz, David

    2010-03-01

    Bacterial cells can display differentiation between several developmental pathways, from planktonic to matrix-producing, depending upon the colony conditions. We study the confinement of bacteria in hydrogels as well as in liquid-liquid double emulsion droplets and observe the growth and morphology of these colonies as a function of time and environment. Our results can give insight into the behavior of bacterial colonies in confined spaces that can have applications in the areas of food science, cosmetics, and medicine.

  18. Imaging quantum-dot-confined electron density in transition to fractional quantum Hall regime

    NASA Astrophysics Data System (ADS)

    Wach, E.; ?ebrowski, D. P.; Szafran, B.

    2015-01-01

    We consider mapping the charge density confined in quantum dots by the Coulomb blockade microscopy (CBM) at the transition to the fractional quantum Hall regime. We apply an exact diagonalization method to determine the exact charge density and its reaction to the scanning probe as well as to calculate the energy maps as functions of the position of the probe. From the energy maps—which are the only experimentally accessible quantity in CBM—we evaluate an apparent charge density solving an inverse integral problem given by the perturbation theory. We discuss the exact and apparent charge densities derived from the energy maps. We find that for magnetic fields corresponding to the integer fillings of the lowest Landau level, when the electron system exhibits a liquid-like reaction to the potential of the probe, the confined charge density can be quite accurately mapped by the CBM. For fractional fillings of the lowest Landau level the probe induces nucleation of single-electron islands which in circular quantum dots evade imaging by CBM. We demonstrate that mapping the molecular charge densities is possible for confinement potentials of lower symmetry that is consistent with the geometry of the single-electron islands distribution.

  19. Fusion, magnetic confinement

    SciTech Connect

    Berk, H.L.

    1992-08-06

    An overview is presented of the principles of magnetic confinement of plasmas for the purpose of achieving controlled fusion conditions. Sec. 1 discusses the different nuclear fusion reactions which can be exploited in prospective fusion reactors and explains why special technologies need to be developed for the supply of tritium or {sup 3}He, the probable fuels. In Sec. 2 the Lawson condition, a criterion that is a measure of the quality of confinement relative to achieving fusion conditions, is explained. In Sec. 3 fluid equations are used to describe plasma confinement. Specific confinement configurations are considered. In Sec. 4 the orbits of particle sin magneti and electric fields are discussed. In Sec. 5 stability considerations are discussed. It is noted that confinement systems usually need to satisfy stability constraints imposed by ideal magnetohydrodynamic (MHD) theory. The paper culminates with a summary of experimental progress in magnetic confinement. Present experiments in tokamaks have reached the point that the conditions necessary to achieve fusion are being satisfied.

  20. Mean field and the confined single homopolymer

    NASA Astrophysics Data System (ADS)

    Pasquali, S.; Percus, J. K.

    2009-10-01

    We develop a statistical model for a confined chain molecule based on a monomer grand canonical ensemble. The molecule is subject to an external chemical potential, a backbone interaction, and an attractive interaction between all monomers. Using a Gaussian variable formalism and a mean field approximation, we analytically derive a minimum principle from which we can obtain relevant physical quantities, such as the monomer density, and we explore the limit in which the chain is subject to a tight confinement. Through a numerical implementation of the minimization process we show how we can obtain density profiles in three dimensions for arbitraty potentials, and we test the limits of validity of the theory.

  1. Dynamics and energetics of hydrophobically confined water

    NASA Astrophysics Data System (ADS)

    Bauer, Brad A.; Ou, Shuching; Patel, Sandeep; Siva, Karthik

    2012-05-01

    The effects of water confined in regions between self-assembling entities is relevant to numerous contexts such as macromolecular association, protein folding, protein-ligand association, and nanomaterials self-assembly. Thus assessing the impact of confined water, and the ability of current modeling techniques to capture the salient features of confined water is important and timely. We present molecular dynamics simulation results investigating the effect of confined water on qualitative features of potentials of mean force describing the free energetics of self-assembly of large planar hydrophobic plates. We consider several common explicit water models including the TIP3P, TIP4P, SPC/E, TIP4P-FQ, and SWM4-NDP, the latter two being polarizable models. Examination of the free energies for filling and unfilling the volume confined between the two plates (both in the context of average number of confined water molecules and “depth” of occupancy) suggests TIP4P-FQ water molecules generally occupy the confined volume at separation distances larger than observed for other models under the same conditions. The connection between this tendency of TIP4P-FQ water and the lack of a pronounced barrier in the potential of mean force for plate-plate association in TIP4P-FQ water is explored by artificially, but systematically, populating the confined volume with TIP4P-FQ water at low plate-plate separation distances. When the critical separation distance [denoting the crossover from an unoccupied (dry) confined interior to a filled (wet) interior] for TIP4P-FQ is reduced by 0.5 Å using this approach, a barrier is observed; we rationalize this effect based on increased resistant forces introduced by confined water molecules at these low separations. We also consider the dynamics of water molecules in the confined region between the hydrophobes. We find that the TIP4P-FQ water model exhibits nonbulklike dynamics, with enhanced lateral diffusion relative to bulk. This is consistent with the reduced intermolecular water-water interaction indicated by a decreased molecular dipole moment in the interplate region. Analysis of velocity autocorrelation functions and associated power spectra indicate that the interplate region for TIP4P-FQ at a plate separation of 14.4 Å approaches characteristics of the pure water liquid-vapor interface. This is in stark contrast to the other water models (including the polarizable SWM4-NDP model).

  2. Dynamics and energetics of hydrophobically confined water.

    PubMed

    Bauer, Brad A; Ou, Shuching; Patel, Sandeep; Siva, Karthik

    2012-05-01

    The effects of water confined in regions between self-assembling entities is relevant to numerous contexts such as macromolecular association, protein folding, protein-ligand association, and nanomaterials self-assembly. Thus assessing the impact of confined water, and the ability of current modeling techniques to capture the salient features of confined water is important and timely. We present molecular dynamics simulation results investigating the effect of confined water on qualitative features of potentials of mean force describing the free energetics of self-assembly of large planar hydrophobic plates. We consider several common explicit water models including the TIP3P, TIP4P, SPC/E, TIP4P-FQ, and SWM4-NDP, the latter two being polarizable models. Examination of the free energies for filling and unfilling the volume confined between the two plates (both in the context of average number of confined water molecules and "depth" of occupancy) suggests TIP4P-FQ water molecules generally occupy the confined volume at separation distances larger than observed for other models under the same conditions. The connection between this tendency of TIP4P-FQ water and the lack of a pronounced barrier in the potential of mean force for plate-plate association in TIP4P-FQ water is explored by artificially, but systematically, populating the confined volume with TIP4P-FQ water at low plate-plate separation distances. When the critical separation distance [denoting the crossover from an unoccupied (dry) confined interior to a filled (wet) interior] for TIP4P-FQ is reduced by 0.5 Å using this approach, a barrier is observed; we rationalize this effect based on increased resistant forces introduced by confined water molecules at these low separations. We also consider the dynamics of water molecules in the confined region between the hydrophobes. We find that the TIP4P-FQ water model exhibits nonbulklike dynamics, with enhanced lateral diffusion relative to bulk. This is consistent with the reduced intermolecular water-water interaction indicated by a decreased molecular dipole moment in the interplate region. Analysis of velocity autocorrelation functions and associated power spectra indicate that the interplate region for TIP4P-FQ at a plate separation of 14.4 Å approaches characteristics of the pure water liquid-vapor interface. This is in stark contrast to the other water models (including the polarizable SWM4-NDP model). PMID:23004766

  3. Noncommutative geometry

    Microsoft Academic Search

    Alain Connes

    1994-01-01

    Through algebraic geometry we became familiar with the correspondence between geometrical spaces and commutative algebra.\\u000a The aim of this talk is to show an analogous correspondence, in the domain of real analysis, between geometrical spaces and\\u000a algebras of functional analysis, going beyond the commutative case. This theory is based on three essential points:\\u000a \\u000a \\u000a 1. \\u000a \\u000a The existence of many examples of

  4. Engaging All Students with "Impossible Geometry"

    ERIC Educational Resources Information Center

    Wiest, Lynda R.; Ayebo, Abraham; Dornoo, Michael D.

    2010-01-01

    Geometry is an area in which Australian students performed particularly poorly on the 2007 Trends in International Mathematics and Science Study (TIMSS). One innovative area of recreational geometry that has rich potential to engage and challenge a wide variety of students is "impossible geometry." An impossible geometric object is a…

  5. The Cascade inertial confinement fusion reactor concept

    NASA Astrophysics Data System (ADS)

    Pitts, J. H.; Hogan, W. J.; Tobin, M. T.; Bourque, R. F.; Meier, W. R.

    1990-12-01

    The Cascade reactor concept has the potential of converting inertial confinement fusion (ICF) energy into electrical power safely, efficiently, and with low activation. Its flexibility permits a number of options for materials, blankets, fuel-pellet designs and drivers. This report documents a theoretical and experimental study culminating in a reference Cascade conceptual design that produces 890 MW of electrical power with a net plant efficiency of 47 percent if a heavy-ion driver if used. The reactor is double-cone shaped and rotates at 50 rpm. A ceramic-granule blanket flows through the reactor held against the reactor wall by the rotation. The blanket serves several functions: it absorbs energy from fusion reactions that occur at 5 Hz in the center of the reactor, thereby protecting the reactor wall and extending its lifetime to that of power plant; it acts as a heat-exchange medium to transfer fusion energy to high-pressure helium gas used in power conversion; and it produces tritium to replace that burned in the fusion process. Cascade's illumination geometry is restricted, so that good energy coupling to presently-envisioned fuel pellets is practical only with heavy-ion drivers. Laser drivers would require the use of fuel pellets with advanced design features. We discuss the reactor concept, heat exchanger, balance of plant, other systems that would be necessary for a full-scale production of electrical power, and experiments that prove the feasibility of a flowing granular blanket. A cost study predicts that Cascade, using a heavy-ion driver, could produce electricity for between 5.5 and 6.8 cents/kWh-comparable to the cost of power using modular high-temperature gas-cooled reactors, pressurized-water reactors, or coal-fired power plants. Finally, we include an annotated bibliography of the over 50 reports which have been written about Cascade.

  6. Spinor geometry

    E-print Network

    A. Nicolaidis; V. Kiosses

    2012-01-03

    It has been proposed that quantum mechanics and string theory share a common inner syntax, the relational logic of C. S. Peirce. Along this line of thought we consider the relations represented by spinors. Spinor composition leads to the emergence of Minkowski spacetime. Inversely the Minkowski spacetime is istantiated by the Weyl spinors, while the merge of two Weyl spinors gives rise to a Dirac spinor. Our analysis is applied also to the string geometry. The string constraints are represented by real spinors, which create a parametrization of the string worldsheet identical to the Enneper-Weierstass representation of minimal surfaces. Further, a spinorial study of the AdS3 spacetime reveals a Hopf fibration AdS3 \\rightarrow AdS2. The conformal symmetry inherent in AdS3 is pointed out. Our work indicates the hidden ties between logic-quantum mechanics-string theory-geometry and vindicates the Wheeler's proposal of pregeometry as a large network of logical propositions.

  7. Projective Geometry Introduction

    E-print Network

    Giger, Christine

    Projective Geometry #12;Introduction · What is projective geometry? · an alternative algebraic is it good for? · projective geometry more convenient than Euclidean geometry to describe central projection progress #12;Introduction · Historical development · ca. 340: first mention of projective relations

  8. Geometry: Which Way?

    ERIC Educational Resources Information Center

    Scott, P. R.

    1977-01-01

    The good and bad points of Euclidean geometry and transformation geometry are briefly surveyed with emphasis on the teachability of Euclidean geometry and the mathematics of transformation geometry. (MN)

  9. Behavior of the potential antitumor V(IV)O complexes formed by flavonoid ligands. 1. Coordination modes and geometry in solution and at the physiological pH.

    PubMed

    Sanna, Daniele; Ugone, Valeria; Lubinu, Giuseppe; Micera, Giovanni; Garribba, Eugenio

    2014-11-01

    The coordination modes and geometry assumed in solution by the potent antitumor oxidovanadium(IV) complexes formed by different flavonoids were studied by spectroscopic (Electron Paramagnetic Resonance, EPR) and computational (Density Functional Theory, DFT) methods. A series of bidentate flavonoid ligands (L) with increasing structural complexity was examined, which can involve (CO, O(-)) donors and formation of five- and six-membered chelate rings, or (O(-), O(-)) donors and five-membered chelate rings. The geometry corresponding to these coordination modes can be penta-coordinated, [VOL2], or cis-octahedral, cis-[VOL2(H2O)]. The results show that, at physiological pH, ligands provided with (CO, O(-)) donor set yield cis-octahedral species with "maltol-like" coordination when five-membered chelate rings are formed (as with 3-hydroxyflavone), while penta-coordinated structures with "acetylacetone-like" coordination are preferred when the chelate rings are six-membered (as with chrysin). When both the binding modes are possible, as with morin, the "acetylacetone-like" coordination is observed. For the ligands containing a catecholic donor set, such as 7,8-dihydroxyflavone, baicalein, fisetin, quercetin and rutin, the formation of square pyramidal complexes with (O(-), O(-)) "catechol-like" coordination and five-membered chelate rings is preferred at physiological pH. The determination of the different coordination modes and geometry is important to define the biotransformation in the blood and the interaction of these complexes with the biological membranes. PMID:25127230

  10. Transport and boundary scattering in confined geometries: Analytical results

    Microsoft Academic Search

    R. A. Richardson; Franco Nori

    1993-01-01

    We utilize a geometric argument to determine the effects of boundary scattering on the carrier mean free path in samples of various cross sections. Analytic expressions for samples with rectangular and circular cross sections are obtained. We also outline a method for incorporating these results into calculations of the thermal conductivity.

  11. Acoustical Properties of Superfluid Helium in Confined Geometry

    E-print Network

    Sh. E. Kekutia; N. D. Chkhaidze

    2006-04-07

    The problem studied in this paper is to obtain the equations describing sound propagation in a consolidated porous medium filled with superfluid, determine the elastic coefficients, appearing in the equations, in terms of physically measurable quantities, and calculate the propagation velocities of transverse and longitudinal waves at high and low oscillating frequencies. In general, the obtained equations describe all volume modes that can propagate in a porous medium saturated with superfluid for any values of the porosity and frequencies. The derived equations are applied to the most important particular case when the normal component of superfluid helium is locked inside a highly porous media (aerogel, Im-helium sample) by viscous forces. For this case the velocities of two longitudinal sound modes and transverse mode are calculated from the derived equations. There are established the coupling between temperature and pressure oscillations in these fast and slow modes.

  12. Charge Transport through Organized Organic Assemblies in Confined Geometries

    E-print Network

    Schuckman, Amanda Eileen

    2012-07-16

    ................................................................................. 1 1.2 Background ............................................................................. 3 1.3 Measurement of Charge Transport in Molecular Assemblies . 17 1.4 Porphyrinoids on Surfaces... for charge transport measurements of molecular configurations on metal and semiconductor surfaces using Scanning Tunneling Microscopy (STM) or Conducting Probe Atomic Force Microscopy (CP-AFM) as well as in junctions such as nanogap electrodes, break...

  13. Numerical study of water-confinement geometries for laser propulsion

    Microsoft Academic Search

    Bing Han; Zhong-Hua Shen; Jian Lu; Xiao-Wu Ni

    2010-01-01

    The processes of laser propulsion in a water environment are investigated numerically in this paper. Four kinds of propelled surfaces are discussed: a plane, a hemispherical shell, a 90°-conical shell and a 30°-conical shell. The bubble radius and the velocity of the bubble surface varying with time during the first-expansion of the bubble are investigated. The evolution of the shock

  14. The instability of monodisperse bubbles passing through a confined geometry

    NASA Astrophysics Data System (ADS)

    Li, Yuting; Wu, Ping; Zhang, Haifeng; Luo, Zhaofeng; Wang, Yong; Cheng, Zhengdong; He, Liqun

    2014-11-01

    The dispersed bubble experiences an impact of flow-focusing from the outer viscous liquid, and may break into satellite bubbles after flowing through the narrower section. We show that the number of satellite bubbles can be characterized by a phase diagram that depends on the capillary number and the Weber number. The number of satellite bubbles can be estimated through the Tgrow (the growth time of the daughter bubble), Tpinch (the pinch-off time of the daughter bubble), and Tpass (the time the initial microbubble need to pass the pore). We defined N = Tpass/(Tpinch + Tgrow) as the dimensionless time and the critical condition: N ˜ 1 to evaluate the bubble breakup. Our work shows that the breakup of the microbubble or droplet through a sudden narrowing joint is predictable and controllable.

  15. Entropy, confinement, and chiral symmetry breaking

    NASA Astrophysics Data System (ADS)

    Cornwall, John M.

    2011-04-01

    This paper studies the way in which confinement leads to chiral symmetry breaking (CSB) through a gap equation. We argue that a combination of entropic effects, related to fluctuations of Wilson loops with massless constituents, and an Abelian gauge invariance of the confinement action as expressed in terms of the usual confining effective propagator 8?KF???/k4, in effect removes infrared singularities coming from use of this propagator in a standard gap equation (KF is the string tension). Beginning from an Abelian gauge-invariant description of CSB that differs from this standard gap equation, we show how to extract a corresponding gap equation that incorporates both entropic effects and Abelian gauge invariance by replacement of the confining propagator with 8?KF???/(k2+m2)2. Here the finite mass m turns out to be ?M(0) [M(p2) is the running quark mass], based on an extension of an old calculation of the author. This massive propagator gives semiquantitatively two critical properties of confinement: (1) a negative contribution to the confining potential coming from entropy; (2) an infrared cutoff required by Abelian gauge invariance. Entropic effects lead to a q¯q condensate and contribute a negative term ˜-KF/M(0), essential for a massless pion, to the pion Hamiltonian. The resulting gap equation leads to M2(0)?KF/?. We argue that one-gluon exchange is not strong enough in the IR to drive quark CSB, but in any case is necessary to get the correct renormalization-group ultraviolet behavior. We find the standard renormalization-group result with the improvement that the prefactor (related to ?q¯q?) can be calculated from the confining solution. Finally, we briefly point out the Minkowski-space virtues of using a principal-part propagator to describe confinement.

  16. Connectivity in Dense Networks Confined within Right Prisms

    E-print Network

    Dettmann, Carl

    Connectivity in Dense Networks Confined within Right Prisms Justin P. Coon1 , Orestis Georgiou2 the connectivity probability when the network resides within a convex right prism, a polyhedron that accurately within a convex right prism1 is connected. Right prism bounding geometries are interesting and useful

  17. Magnetohydrodynamic equilibrium and stability of centrifugally confined plasmas

    Microsoft Academic Search

    Yi-Min Huang

    2004-01-01

    Centrifugal confinement is an alternative approach to magnetic fusion, employing a magnetic field with an open field line configuration. In this scheme, a plasma with magnetic mirror geometry is made to rotate azimuthally at supersonic speeds. The resulting centrifugal forces, given the field line curvature, prevent the plasma from escaping along the field lines. This dissertation addresses the equilibrium and

  18. Micelle fragmentation and wetting in confined flow

    E-print Network

    Mona Habibi; Colin Denniston; Mikko Karttunen

    2014-09-30

    We use coarse-grained molecular-dynamics (MD) simulations to investigate the structural and dynamical properties of micelles under non-equilibrium Poiseuille flow in a nano-confined geometry. The effects of flow, confinement, and the wetting properties of die-channel walls on spherical sodium dodecyl sulfate (SDS) micelles are explored when the micelle is forced through a die-channel slightly smaller than its equilibrium size. Inside the channel, the micelle may fragment into smaller micelles. In addition to the flow rate, the wettability of the channel surfaces dictates whether the micelle fragments and determines the size of the daughter micelles: The overall behavior is determined by the subtle balance between hydrodynamic forces, micelle-wall interactions and self-assembly forces.

  19. Semiflexible Polymer Confined to a Spherical Surface Andrew J. Spakowitz and Zhen-Gang Wang

    E-print Network

    Straight, Aaron

    Semiflexible Polymer Confined to a Spherical Surface Andrew J. Spakowitz and Zhen-Gang Wang, persistence length lp, and sphere radius R.We predict two qualitatively different behaviors for a long polymerRevLett.91.166102 PACS numbers: 68.47.Pe, 05.20.­y, 36.20.Ey A polymer in a confined geometry

  20. Geometries for CAGD Helmut Pottmanna

    E-print Network

    Nawratil, Georg

    modeling and addresses Euclidean, affine and projective geometry, as well as differential geometry widely known. These are projective differential geometric methods, sphere geometries, line geometry areas such as projective geometry, differential geometry and algebraic geometry. 1. Curves and Surfaces

  1. Geometry in the Computer Age.

    ERIC Educational Resources Information Center

    Scott, Paul

    1988-01-01

    Discusses the use of computer graphics in the teaching of geometry. Describes five types of geometry: Euclidean geometry, transformation geometry, coordinate geometry, three-dimensional geometry, and geometry of convex sets. (YP)

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

    Microsoft Academic Search

    Jinfeng Zhang; Rong Chen; Jie Liang

    2004-01-01

    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

  3. CONFINED SPACE ENTRY Table Of Contents

    E-print Network

    US Army Corps of Engineers

    are not required to be labeled. c. If activities, such as welding, in a NPRCS create or has a potential to create all CSs and determine any specific installation requirements for entry. 33.A.05 Confined Space Entry (CSE) Procedures. a. PRCS Entry Procedures. Entry into PRCSs shall comply with the requirements of 29

  4. Beam optics in inertial electrostatic confinement fusion

    Microsoft Academic Search

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

    2000-01-01

    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

  5. Fusion plasma confinement research at the gas dynamic trap

    Microsoft Academic Search

    M. S. Korzhavina; V. V. Prikhodko; E. I. Soldatkina; A. L. Solomakhin; E. I. Pinzhenin; A. V. Lvovsky; A. N. Pushkareva; K. V. Zaytsev

    2011-01-01

    A so called vortex confinement of plasma in axially symmetric mirror device was studied. This recently developed approach enables to significantly reduce transverse particle and heat losses typically caused by MHD instabilities which can be excited in this case. Vortex confinement regime was established by application of different potentials to the radial plasma limiters and end-plates. As a result, the

  6. Ambipolar potential formation in TMX

    SciTech Connect

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

    1981-05-05

    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.

  7. Spectroscopic investigation of the binding interactions of a membrane potential molecule in various supramolecular confined environments: contrasting behavior of surfactant molecules in relocation or release of the probe between nanocarriers and DNA surface.

    PubMed

    Ghosh, Surajit; Banik, Debasis; Roy, Arpita; Kundu, Niloy; Kuchlyan, Jagannath; Sarkar, Nilmoni

    2014-12-01

    The fluorescence and optical properties of membrane potential probes are widely used to measure cellular transmembrane potentials. Hemicyanine dyes are also able to bind to membranes. The spectral properties of these molecules depend upon the charge shift from the donor moiety to the acceptor moiety. Changes in their spectral properties, i.e. absorption and emission maxima or intensities, are helpful in characterizing model membranes, microheterogeneous media, etc. In this article, we have demonstrated the binding interaction of a membrane potential probe, 1-ethyl-2-(4-(p-dimethylaminophenyl)-1,3-butadienyl)-pyridinium perchlorate (LDS 698), with various supramolecular confined environments. The larger dipole moment in the ground state compared to the excited state is a unique feature of hemicyanine dyes. Due to this unique feature, red shifts in the absorption maxima are observed in hydrophobic environments, compared with bulk solvent. On addition of surfactants and CT DNA to an aqueous solution containing LDS 698, significant increase in the emission intensity along with the quantum yield and lifetime indicate partition of the probe molecules into organized assemblies. In the case of the sodium dodecyl sulfate (SDS)-water system, due to interactions between the cationic LDS 698 and the anionic dodecyl sulfate moiety, the fluorescence intensity at ?666 nm decreases and an additional peak at ?590 nm appears at premicellar concentration (?0.20 mM-4.50 mM). But at ?5.50 mM SDS concentration, the absorbance in the higher wavelength region increases again, indicating encapsulation of the probe in micellar aggregates. This observation indicates that the premicellar aggregation behavior of SDS can also be judged by observing the changes in the UV-vis and fluorescence spectral patterns. The temperature dependent study also indicates that non-radiative deactivation of the dye molecules is highly restricted in the DNA micro-environment, compared with micelles. Besides, we have also investigated the specific interaction of surfactant micelles with DNA. Our observations reveal that, in the presence of CT DNA, LDS 698 interacts exclusively with SDS micelles, but that it preferentially releases from micelles and relocates to DNA surfaces in solutions containing TX-100 micelles. PMID:25327647

  8. Inverted critical adsorption of polyelectrolytes in confinement

    E-print Network

    de Carvalho, Sidney J; Cherstvy, Andrey G

    2015-01-01

    What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer-surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density $\\sigma_c$-defining the adsorption-desorption transition-are in excellent agreement with our analytical calculations based on the ground-state...

  9. Perspectives on water science: transport and application of confined water

    NASA Astrophysics Data System (ADS)

    Zeng, XiPing; Wu, JinBo; Li, ShunBo; Chau, YeungYeung; He, GuangHong; Wen, WeiJia; Yang, GuoZhen

    2014-05-01

    The confinements of water can be divided into two main categories, namely, the confinements on surface or interface and the confinements in bulk water. By adding ions or applying electric field, the intensity and distribution of the hydrogen bonds can be greatly affected. These are collectively known as confinement on water surface or interface, which has potential applications in life science and industries involving evaporation control. Confined bulk water could be found everywhere in nature, such as in granular and porous materials, macromolecules and gels, etc. The investigation of the physical properties and the transports of the confined bulk water will contribute to understanding certain types of life activities such as the water transport in plant and in new application of extracting the shale oil and water.

  10. Confinement Vessel Dynamic Analysis

    Microsoft Academic Search

    R. Robert Stevens; Stephen P. Rojas

    1999-01-01

    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

  11. Dirac confinement of a heavy quark-light quark system $(Q,\\bar{q})$ in high orbital angular momentum states

    E-print Network

    M. Avila

    1998-01-04

    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 argued that with a Dirac hamiltonian a scalar confining potential is preferred over a vector confining potential for any value of the orbital angular momentum.

  12. Tension of confining strings at low temperature

    NASA Astrophysics Data System (ADS)

    Giataganas, Dimitrios; Goldstein, Kevin

    2015-02-01

    In the low temperature confining phase of QCD or QCD-like theories it is challenging to capture the temperature dependence of observables through AdS/CFT. Using the blackfold approach we compute the quark-anti-quark linear static potential in the low temperature confining phase, taking into account the thermal excitations of the string. We find the explicit temperature dependence of the string tension and notice that, as naturally expected, tension decreases as temperature increases. We have also generalized the blackfold approach for the computation of the Wilson loops, making it directly applicable to a large class of backgrounds.

  13. Modeling UW Gridded Inertial-Electrostatic Confinement Fusion Experiments

    NASA Astrophysics Data System (ADS)

    Santarius, John F.

    2002-11-01

    Gridded inertial-electrostatic confinement (IEC) devices accelerate and focus ions using voltage differences between nearly transparent concentric grids in spherical or cylindrical geometry. High voltages can be produced relatively easily between the grids, giving the accelerated ions energies (>50 keV) suitable for producing fusion of advanced fuels, such as D-3He. The resulting fusion products potentially can produce radioisotopes useful for positron emission tomography and other applications. Research will be reported on the modeling effort for the UW gridded IEC device and diagnostics, including comparison to experiments. The following physics effects will be discussed: charge exchange, ionization, and dissociation cross-sections and reaction rates for hydrogen and helium isotopes; spherical Child-Langmuir radial electrostatic potential profile; attenuation by the cathode grid; multiple-pass ion and electron production due to charge exchange and ionization of the initial current; subsequent iterations of the resulting currents of particles; electron currents due to ionization, thermionic emission, and secondary electron emission; and fusion reactions due to several phenomena in the plasma.

  14. Tomographic imaging of sub-basalt Mesozoic sediments and shallow basement geometry for hydrocarbon potential below the Deccan Volcanic Province (DVP) of India

    NASA Astrophysics Data System (ADS)

    Behera, Laxmidhar; Sen, Mrinal K.

    2014-10-01

    We have derived a shallow subsurface 2-D tomographic P-wave velocity image of the Deccan Volcanic Province (DVP) of India using first-arrival traveltime data along a 90-km-long N-S trending seismic profile in the Deccan Syneclise region. The tomographic image depicts smooth velocity variations of Quaternary and Tertiary (2.0-3.0 km s-1) sediments, basalts/traps (5.0-5.5 km s-1), sub-trappean Mesozoic sediments (4.3-4.5 km s-1) as well as the basement (5.9-6.1 km s-1) geometry down to a maximum depth of 5.0 km. Due to Late Cretaceous volcanism and outpouring of basaltic lava flows, this region is affected by numerous dyke intrusions and thick basaltic trap (2-3 km) exposed on the surface and surrounded by graben structures due to deep basinal faults forming a large igneous province. Although sub-basalt imaging is a major challenge for the oil industry, with the help of tomographic imaging technique of first-arrival seismic refraction data, we were able to image sub-trappean Mesozoic sediments (<0.75 km) deposited below the two sequences of thick basaltic flows above the basement. The imaged Mesozoic sediments are expected to contain hydrocarbon because of their wide extension in this sedimentary basin with suitable trapping mechanism due to basalts. The robustness of the velocity image is assessed through numerous tests like velocity perturbations, ?2 estimates, rms residuals of traveltime fit, uncertainty estimates through computation of ray-density or hits and series of checkerboard resolution tests with velocity anomalies having different cell size. The thickness of the basalt and the sub-trappean Mesozoic sediments along with the basement geometry obtained from tomography are constrained through ray-trace modelling and pre-stack depth migration (PSDM) of the wide-angle reflection phases for different shot gathers along the profile.

  15. Effect of confinement on reaction rates within polymer nanotemplates

    NASA Astrophysics Data System (ADS)

    Malardier-Jugroot, Cecile; Li, Xia

    2012-02-01

    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.

  16. Plasma confinement with an RF trap

    SciTech Connect

    Nebel, R.A.; Finn, J.M.; Glasser, A.H. [Los Alamos National Lab., NM (United States)

    1996-12-31

    A fusion device based on an RF trap is described. An RF trap combines the axial field of a Penning Trap with the pondermotive confinement of a Paul Trap. The pondermotive confinement is provided by standing electromagnetic waves in a resonant cavity, although driven electrostatic fields may also be employed if one wishes to operate at lower frequencies. The major advantage of this device is that the electrostatic breakdown problem for high energy Penning traps can be alleviated allowing one to utilize larger sizes and potentially higher fusion power densities than a standard Penning Trap. Also, multiple species can be confined and focused in this device permitting the utilization of advanced fuels in pure ion plasmas. The major disadvantage is that the device requires large standing wave energies which may lead to unacceptable wall dissipation. The equations describing the trap, spatial and temporal focusing criteria, and reactor embodiments of the device will be presented.

  17. The physics of spherical confinement systems

    NASA Astrophysics Data System (ADS)

    Robinson, D. C.

    1999-03-01

    Spherical torus magnetic confinement systems, covering spheromaks and spherical tokamaks (STs), are reviewed. As well as being potentially very important for fusion, spherical tori research is enhancing our understanding of magnetic confinement systems with wider applications than fusion research. The studies contribute to the conventional tokamak, for example, ITER via a range of scalings, as well as to our understanding of `quiescent' plasmas and those subject to `turbulent magnetohydrodynamic (MHD) relaxation'. The theoretical and experimental properties are described, showing how these vary with configuration and contrasting them with the conventional aspect ratio tokamak. Topics covered include equilibrium, refuelling, helicity injection, influence of trapped particle fraction, plasma heating, confinement, stability (including pressure limits and energetic particle instabilities) and disruption resilience.

  18. Geometry and Picturing the

    E-print Network

    Gideon, Rudy A.

    Projective Geometry and Pappus' Theorem Kelly McKinnie History Pappus' Theorem Geometries Picturing the projective plane Lines in projective geometry Back to Pappus' Theorem Proof of Pappus' Theorem Projective Geometry and Pappus' Theorem Kelly McKinnie March 23, 2010 #12;Projective Geometry and Pappus' Theorem

  19. Algebraic geometry versus Kahler geometry Claire Voisin

    E-print Network

    Voisin, Claire

    Algebraic geometry versus K¨ahler geometry Claire Voisin CNRS, Institut de math´ematiques de THEORY AND GEOMETRY" organized by the Riemann International School of Mathematics in Verbania. The first, but topologi- cally non K¨ahler. More precisely, the projective manifolds will have a Hodge structure

  20. Confinement of Equilibrium Polymers

    NASA Astrophysics Data System (ADS)

    Feng, Edward

    2005-03-01

    We consider supramolecular polymer systems in which reversible intermolecular bonding affects the thermodynamics of the system. While we have formulated models for a number of such systems, this presentation focuses on equilibrium polymers in which monomers can reversibly link together to form linear polymers. This serves as a model for giant micelles of surfactant molecules that can break and recombine at any point along the cylindrical micelle. While equilibrium polymers in bulk environments have been studied, we investigate their behavior in confined environments such as between two parallel plates. Our model features a continuous distribution of polymer lengths and assumes a favorable energy decrease when two monomers form a bond. We are interested in how confinement affects the density profile and the polymer length distribution, and we calculate these properties analytically using the ground state dominance approximation and computationally employing self-consistent field theory.

  1. Totally confined explosive welding

    NASA Technical Reports Server (NTRS)

    Bement, L. J. (inventor)

    1978-01-01

    The undesirable by-products of explosive welding are confined and the association noise is reduced by the use of a simple enclosure into which the explosive is placed and in which the explosion occurs. An infrangible enclosure is removably attached to one of the members to be bonded at the point directly opposite the bond area. An explosive is completely confined within the enclosure at a point in close proximity to the member to be bonded and a detonating means is attached to the explosive. The balance of the enclosure, not occupied by explosive, is filled with a shaped material which directs the explosive pressure toward the bond area. A detonator adaptor controls the expansion of the enclosure by the explosive force so that the enclosure at no point experiences a discontinuity in expansion which causes rupture. The use of the technique is practical in the restricted area of a space station.

  2. The Shape of Geometry.

    ERIC Educational Resources Information Center

    Burn, Bob

    1990-01-01

    Compared is the use of Euclidean and synthetic geometry in American and European schools. Included is the history of the major developments in the teaching of geometry. Discussed is the demise of formal geometry since World War II. (KR)

  3. Energy confinement in tokamaks

    SciTech Connect

    Sugihara, M.; Singer, C.

    1986-08-01

    A straightforward generalization is made of the ohmic heating energy confinement scalings of Pfeiffer and Waltz and Blackwell et. al. The resulting model is systematically calibrated to published data from limiter tokamaks with ohmic, electron cyclotron, and neutral beam heating. With considerably fewer explicitly adjustable free parameters, this model appears to give a better fit to the available data for limiter discharges than the combined ohmic/auxiliary heating model of Goldston.

  4. Innovative confinement concepts workshop

    SciTech Connect

    Kirkpatrick, R.C.

    1998-06-01

    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.

  5. Topological confinement and superconductivity

    SciTech Connect

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

    2008-01-01

    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.

  6. Classical confined particles

    NASA Technical Reports Server (NTRS)

    Horzela, Andrzej; Kapuscik, Edward

    1993-01-01

    An alternative picture of classical many body mechanics is proposed. In this picture particles possess individual kinematics but are deprived from individual dynamics. Dynamics exists only for the many particle system as a whole. The theory is complete and allows to determine the trajectories of each particle. It is proposed to use our picture as a classical prototype for a realistic theory of confined particles.

  7. The Properties of Confined Water and Fluid Flow at the Nanoscale

    SciTech Connect

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

    2009-03-09

    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.

  8. Potential change in flaw geometry of an initially shallow finite-length surface flaw during a pressurized-thermal-shock transient

    SciTech Connect

    Shum, D.K.; Bryson, J.W.; Merkle, J.G. [Oak Ridge National Lab., TN (United States)

    1993-09-01

    This study presents preliminary estimates on whether an shallow, axially oriented, inner-surface finite-length flaw in a PWR-RPV would tend to elongate in the axial direction and/or deepen into the wall of the vessel during a postulated PTS transient. Analysis results obtained based on the assumptions of (1) linear-elastic material response, and (2) cladding with same toughness as the base metal, indicate that a nearly semicircular flaw would likely propagate in the axial direction followed by propagation into the wall of the vessel. Note that these results correspond to initiation within the lower-shelf fracture toughness temperature range, and that their general validity within the lower-transition temperature range remains to be determined. The sensitivity of the numerical results aid conclusions to the following analysis assumptions are evaluated: (1) reference flaw geometry along the entire crack front and especially within the cladding region; (2) linear-elastic vs elastic-plastic description of material response; and (3) base-material-only vs bimaterial cladding-base vessel-model assumption. The sensitivity evaluation indicates that the analysis results are very sensitive to the above assumptions.

  9. Christian Bar Differential Geometry

    E-print Network

    Baer, Christian

    .5 Trigonometry in spaces of constant curvature . . . . . . . . . . . . . . . . 133 5 Riemannian Geometry 143 5 apply differential geometry to derive the laws of trigonometry on spaces of constant curvature. One

  10. Inverted critical adsorption of polyelectrolytes in confinement

    E-print Network

    Sidney J. de Carvalho; Ralf Metzler; Andrey G. Cherstvy

    2015-03-06

    What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer-surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density $\\sigma_c$-defining the adsorption-desorption transition-are in excellent agreement with our analytical calculations based on the ground-state analysis of the Edwards equation. In particular, we confirm the magnitude and scaling of $\\sigma_c$ for the concave interfaces versus the Debye screening length $1/\\kappa$ and the extent of confinement $a$ for these three interfaces for small $\\kappa a$ values. For large $\\kappa a$ the critical adsorption condition approaches the planar limit. The transition between the two regimes takes place when the radius of surface curvature or half of the slit thickness $a$ is of the order of $1/\\kappa$. We also rationalize how $\\sigma_c(\\kappa)$ gets modified for semi-flexible versus flexible chains under external confinement. We examine the implications of the chain length onto critical adsorption-the effect often hard to tackle theoretically-putting an emphasis on polymers inside attractive spherical cavities.

  11. Spatially confined assembly of nanoparticles.

    PubMed

    Jiang, Lin; Chen, Xiaodong; Lu, Nan; Chi, Lifeng

    2014-10-21

    The ability to assemble NPs into ordered structures that are expected to yield collective physical or chemical properties has afforded new and exciting opportunities in the field of nanotechnology. Among the various configurations of nanoparticle assemblies, two-dimensional (2D) NP patterns and one-dimensional (1D) NP arrays on surfaces are regarded as the ideal assembly configurations for many technological devices, for example, solar cells, magnetic memory, switching devices, and sensing devices, due to their unique transport phenomena and the cooperative properties of NPs in assemblies. To realize the potential applications of NP assemblies, especially in nanodevice-related applications, certain key issues must still be resolved, for example, ordering and alignment, manipulating and positioning in nanodevices, and multicomponent or hierarchical structures of NP assemblies for device integration. Additionally, the assembly of NPs with high precision and high levels of integration and uniformity for devices with scaled-down dimensions has become a key and challenging issue. Two-dimensional NP patterns and 1D NP arrays are obtained using traditional lithography techniques (top-down strategies) or interfacial assembly techniques (bottom-up strategies). However, a formidable challenge that persists is the controllable assembly of NPs in desired locations over large areas with high precision and high levels of integration. The difficulty of this assembly is due to the low efficiency of small features over large areas in lithography techniques or the inevitable structural defects that occur during the assembly process. The combination of self-assembly strategies with existing nanofabrication techniques could potentially provide effective and distinctive solutions for fabricating NPs with precise position control and high resolution. Furthermore, the synergistic combination of spatially mediated interactions between nanoparticles and prestructures on surfaces may play an increasingly important role in the controllable assembly of NPs. In this Account, we summarize our approaches and progress in fabricating spatially confined assemblies of NPs that allow for the positioning of NPs with high resolution and considerable throughput. The spatially selective assembly of NPs at the desired location can be achieved by various mechanisms, such as, a controlled dewetting process, electrostatically mediated assembly of particles, and confined deposition and growth of NPs. Three nanofabrication techniques used to produce prepatterns on a substrate are summarized: the Langmuir-Blodgett (LB) patterning technique, e-beam lithography (EBL), and nanoimprint lithography (NPL). The particle density, particle size, or interparticle distance in NP assemblies strongly depends on the geometric parameters of the template structure due to spatial confinement. In addition, with smart design template structures, multiplexed NPs can be assembled into a defined structure, thus demonstrating the structural and functional complexity required for highly integrated and multifunction applications. PMID:25244100

  12. Comparison of select polarizable and non-polarizable water models in predicting solvation dynamics of water confined between MgO slabs.

    PubMed

    Kamath, Ganesh; Deshmukh, Sanket A; Sankaranarayanan, Subramanian K R S

    2013-07-31

    We present a molecular dynamics simulation study in which we compare and contrast the performance of a polarizable shell water potential model and non-polarizable water force field-extended simple point charge (SPC/EF) model in predicting the solvation dynamics of confined water molecules sandwiched between MgO(100) slabs. Structural features based on radial distribution functions, atomic density profiles, adsorption patterns, orientational ordering and dynamical correlations such as diffusional characteristics, hydrogen bonding lifetimes and residence probabilities are used as metrics for comparison. The simulations yield significant ordering of water molecules in the two layers adjacent to the oxide interface and the extent of ordering decreases with increasing distance from the oxide-water interface. These results elucidate that the dependence of local ordering and solvation dynamics on the molecular geometry and charge distribution, observed for typical three- and four-site water models, is generally lost for confined water if polarization is explicitly included. While the interfacial water structure predicted by the polarizable and non-polarizable models are similar, the confinement and interface proximity effects on the solvation dynamics are seen to be more pronounced for polarizable water models in comparison to non-polarizable ones. The study also shows that the polarizable water model over predicts the orientational order and under predicts the transport properties of confined water. In addition, analysis of the orientational preferences and hydrogen bonding characteristics of water near oxide interfaces suggests a higher degree of tetrahedral disorder in the polarizable shell compared to the non-polarizable SPC/E flexible model. The origin of the differences in solvation behavior of confined water between oxide slabs is analyzed based on the energetic contributions of the dispersive and electrostatic terms in the two force fields. Our findings suggest some new considerations regarding the role of polarization terms in predicting confinement and interface proximity effects that may guide future development of reliable polarizable water models for confined liquids. PMID:23819970

  13. Comparison of select polarizable and non-polarizable water models in predicting solvation dynamics of water confined between MgO slabs

    NASA Astrophysics Data System (ADS)

    Kamath, Ganesh; Deshmukh, Sanket A.; Sankaranarayanan, Subramanian K. R. S.

    2013-07-01

    We present a molecular dynamics simulation study in which we compare and contrast the performance of a polarizable shell water potential model and non-polarizable water force field-extended simple point charge (SPC/EF) model in predicting the solvation dynamics of confined water molecules sandwiched between MgO(100) slabs. Structural features based on radial distribution functions, atomic density profiles, adsorption patterns, orientational ordering and dynamical correlations such as diffusional characteristics, hydrogen bonding lifetimes and residence probabilities are used as metrics for comparison. The simulations yield significant ordering of water molecules in the two layers adjacent to the oxide interface and the extent of ordering decreases with increasing distance from the oxide-water interface. These results elucidate that the dependence of local ordering and solvation dynamics on the molecular geometry and charge distribution, observed for typical three- and four-site water models, is generally lost for confined water if polarization is explicitly included. While the interfacial water structure predicted by the polarizable and non-polarizable models are similar, the confinement and interface proximity effects on the solvation dynamics are seen to be more pronounced for polarizable water models in comparison to non-polarizable ones. The study also shows that the polarizable water model over predicts the orientational order and under predicts the transport properties of confined water. In addition, analysis of the orientational preferences and hydrogen bonding characteristics of water near oxide interfaces suggests a higher degree of tetrahedral disorder in the polarizable shell compared to the non-polarizable SPC/E flexible model. The origin of the differences in solvation behavior of confined water between oxide slabs is analyzed based on the energetic contributions of the dispersive and electrostatic terms in the two force fields. Our findings suggest some new considerations regarding the role of polarization terms in predicting confinement and interface proximity effects that may guide future development of reliable polarizable water models for confined liquids.

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

    SciTech Connect

    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

    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.

  15. Study of the Potential Earthquake Risk in the Western United States by the LURR Method Based on the Seismic Catalogue, Fault Geometry and Focal Mechanisms

    NASA Astrophysics Data System (ADS)

    Zhang, Yongxian; Yikilmaz, M. Burak; Rundle, John B.; Yin, Xiangchu; Liu, Yue; Zhang, Langping; Wang, Zijin

    2015-03-01

    Based on the load/unload response ratio (LURR) theory, spatial and temporal variation of Y/Y c (value of LURR/critical value of LURR under 90 % confidence) in the western United States and its adjacent area (31°-44°N, -128° to -112°E) during the period from 1980 to 2011 was studied. The selected study area was zoned into 20 sub-regions, in each of which the fault geometry and the focal mechanisms were very similar such that the stress fields were almost uniform. The loading and unloading periods were determined by calculating perturbations in the Coulomb failure stress in each sub-regions induced by earth tides. Earthquakes occurring in these sub-regions were identified as a loading or unloading type, and the response rate was chosen as the Benioff strain that can be calculated from earthquake magnitude M. With a time window of 1 year, a time moving step of 1 month, a space window of a circle region with a radius of 100 km, and a space moving step of 0.5° latitudinally and longitudinally, snapshots of the evolution of Y/Y c were generated. Scanning results show that obvious Y/Y c anomalies can be detected near the epicenter of all big earthquakes larger than M6.5 in regions with reasonable seismic monitoring abilities. They also show Y/Y c anomalies occurred several years prior to the big earthquakes and the lasting time of the anomaly is from one year to several years. For some LURR anomalous regions, however, no earthquakes occurred. According to the characteristics of LURR anomalies, two regions with a high risk of big earthquakes were detected. One is between the northern region of the Bay Area and the Mendocino triple junction (38°-40°N, -124° to -122°E) and the other is between Lake Tahoe and Mono Lake (37.5°-39.5°N, -120° to -118°E) along the border of California and Nevada.

  16. Dynamics of Confined Water Molecules in Aqueous Salt Hydrates

    SciTech Connect

    Werhahn, Jasper C.; Pandelov, S.; Yoo, Soohaeng; Xantheas, Sotiris S.; Iglev, H.

    2011-04-01

    The unusual properties of water are largely dictated by the dynamics of the H bond network. A single water molecule has more H bonding sites than atoms, hence new experimental and theoretical investigations about this peculiar liquid have not ceased to appear. Confinement of water to nanodroplets or small molecular clusters drastically changes many of the liquid’s properties. Such confined water plays a major role in the solvation of macro molecules such as proteins and can even be essential to their properties. Despite the vast results available on bulk and confined water, discussions about the correlation between spectral and structural properties continue to this day. The fast relaxation of the OH stretching vibration in bulk water, and the variance of sample geometries in the experiments on confined water obfuscate definite interpretation of the spectroscopic results in terms of structural parameters. We present first time-resolved investigations on a new model system that is ideally suited to overcome many of the problems faced in spectroscopical investigation of the H bond network of water. Aqueous hydrates of inorganic salts provide water molecules in a crystal grid, that enables unambiguous correlations of spectroscopic and structural features. Furthermore, the confined water clusters are well isolated from each other in the crystal matrix, so different degrees of confinement can be achieved by selection of the appropriate salt.

  17. PROJECTIVE GEOMETRY KRISTIN DEAN

    E-print Network

    May, J. Peter

    PROJECTIVE GEOMETRY KRISTIN DEAN Abstract. This paper investigates the nature of finite geometries. It will focus on the finite geometries known as projective planes and conclude with the example of the Fano plane. Contents 1. Basic Definitions 1 2. Axioms of Projective Geometry 2 3. Linear Algebra

  18. Geometry and Categoricity

    E-print Network

    Baldwin, John T.

    Analytic Structures Geometry and Categoricity John T. Baldwin January 8, 2012 #12;Geometry and Categoricity Homogeneity Zariski Structures Analytic Structures Whig History #12;Geometry and Categoricity John T. Baldwin in (C, +, ·) by `analytically' definable. Response #12;Geometry and Categoricity John T. Baldwin

  19. Geometry in Medias Res

    ERIC Educational Resources Information Center

    Cukier, Mimi; Asdourian, Tony; Thakker, Anand

    2012-01-01

    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…

  20. Confinement Vessel Dynamic Analysis

    SciTech Connect

    R. Robert Stevens; Stephen P. Rojas

    1999-08-01

    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.

  1. Hadrosynthesis and Quark Confinement

    NASA Astrophysics Data System (ADS)

    Satz, Helmut

    2014-04-01

    Multihadron production in high energy collisions, from e+e- annihilation to heavy ion interactions, shows remarkable thermal behaviour, specified by a universal "Hagedorn" temperature. We argue that this hadronic radiation is formed by tunnelling through the event horizon of colour confinement, i.e., that it is the QCD counterpart of Hawking-Unruh radiation from black holes. It is shown to be emitted at a universal temperature TH ? (?/2?)1/2, where ? denotes the string tension. Since the event horizon does not allow information transfer, the radiation is thermal "at birth".

  2. Monistic conception of geometry

    E-print Network

    Yuri A. Rylov

    2010-09-15

    One considers the monistic conception of a geometry, where there is only one fundamental quantity (world function). All other geometrical quantities a derivative quantities (functions of the world function). The monisitc conception of a geometry is compared with pluralistic conceptions of a geometry, where there are several independent fundamental geometrical quantities. A generalization of a pluralistic conception of the proper Euclidean geometry appears to be inconsistent, if the generalized geometry is inhomogeneous. In particular, the Riemannian geometry appears to be inconsistent, in general, if it is obtained as a generalization of the pluralistic conception of the Euclidean geometry.

  3. Singular diffusion in a confined sandpile

    NASA Astrophysics Data System (ADS)

    Pires, R. S.; Moreira, A. A.; Carmona, H. A.; Andrade, J. S., Jr.

    2015-01-01

    We investigate the behavior of a two-state sandpile model subjected to a confining potential in one and two dimensions. From the microdynamical description of this simple model with its intrinsic exclusion mechanism, it is possible to derive a continuum nonlinear diffusion equation that displays singularities in both the diffusion and drift terms. The stationary-state solutions of this equation, which maximizes the Fermi-Dirac entropy, are in perfect agreement with the spatial profiles of time-averaged occupancy obtained from model numerical simulations in one as well as in two dimensions. Surprisingly, our results also show that, regardless of dimensionality, the presence of a confining potential can lead to the emergence of a power-law tail in the distribution of avalanche sizes.

  4. Inertial electrostatic confinement (IEC) neutron sources

    SciTech Connect

    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

    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.

  5. Inertial electrostatic confinement (IEC) neutron sources

    SciTech Connect

    Nebel, R.A.; Barnes, D.C.; Caramana, E.J.; Janssen, R.D.; Nystrom, W.D.; Tiouririne, T.N.; Trent, B.C. [Los Alamos National Lab., NM (United States); Miley, G.H.; Javedani, J. [Univ. of Illinois, Urbana, IL (United States)

    1995-12-31

    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 {times} 10{sup 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.

  6. Computational Information Geometry From Euclidean to flat Pythagorean geometries

    E-print Network

    Nielsen, Frank

    geometry: Customize geometries to datasets, generic non-Euclidean algorithmic toolboxes. George E. P. BoxComputational Information Geometry From Euclidean to flat Pythagorean geometries Frank Nielsen persistence), Recover intrinsic geometry (eg., distance learning, invariants) Computational information

  7. Geometry is Great Fun

    NSDL National Science Digital Library

    Mrs Burch

    2006-12-08

    Geometrical shapes can be the beginning of a strong geometrical foundation Geometry can be great fun. Check out these websites and start having some fun with shapes. Spend 10 minutes with this siteGeometry- Making Our Own Shapes. After you have made some shapes, check out this site Geometry is Great! to see that Geometry is Great. You can spend time on this site Groovy Geometry if you ...

  8. Statistical mechanics of confined quantum particles

    E-print Network

    Vishnu M. Bannur; K. M. Udayanandan

    2006-02-02

    We develop statistical mechanics and thermodynamics of Bose and Fermi systems in relativistic harmonic oscillator (RHO) confining potential, which may be applicable in quark gluon plasma (QGP), astrophysics, Bose-Einstein condensation (BEC), condensed matter physics etc. Detailed study of QGP system is carried out and compared with lattice results. Further, as an application, our equation of state (EoS) of QGP is used to study compact stars like quark star.

  9. Color Confinement and Massive Gluons

    E-print Network

    M. Chaichian; K. Nishijima

    2005-11-15

    Color confinement is one of the central issues in QCD so that there are various interpretations of this feature. In this paper we have adopted the interpretation that colored particles are not subject to observation just because colored states are unphysical in the sense of Eq. (2.16). It is shown that there are two phases in QCD distinguished by different choices of the gauge parameter. In one phase, called the "confinement phase", color confinement is realized and gluons turn out to be massive. In the other phase, called the "deconfinement phase", color confinement is not realized, but the gluons remain massless.

  10. AN INTRODUCTION TO SYMPLECTIC GEOMETRY,

    E-print Network

    Schürmann, Michael

    AN INTRODUCTION TO SYMPLECTIC GEOMETRY, HAMILTON SYSTEMS, AND COMPLEX GEOMETRY Rainer Schimming Szczecin 2002 #12; AN INTRODUCTION TO SYMPLECTIC GEOMETRY, HAMILTON SYSTEMS, AND COMPLEX GEOMETRY Rainer Poisson and symplectic geometries 8 2.1 Poisson manifolds

  11. Inertial Electrostatic Confinement Modeling and Comparison to Experiments

    Microsoft Academic Search

    Gilbert Emmert; John Santarius; Eric Alderson; David Donovan

    2010-01-01

    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

  12. Signatures of Spacetime Geometry Fluctuations

    NASA Astrophysics Data System (ADS)

    Ford, L. H.; Thompson, R. T.

    The operational meaning of quantum fluctuations of spacetime geometry will be discussed. Three potential signatures of these fluctuations will be considered: luminosity fluctuations of a distant source, angular blurring of images, and broadening of spectral lines. To leading order, luminosity fluctuations arise only from passive geometry fluctuations, those driven by quantum fluctuations of the stress tensor. This effect can be described by a Langevin version of the Raychaudhuri equation. Angular blurring and line broadening can arise both from passive fluctuations and from the active fluctuations of the quantized gravitational field, and can be given a unified geometrical description using the Riemann tensor correlation function.

  13. Physics as Spacetime Geometry

    NASA Astrophysics Data System (ADS)

    Petkov, Vesselin

    As there have been no major advancements in fundamental physics in the past decades it seems reasonable to reexamine the major explicit and especially implicit assumptions in fundamental physics to ensure that all logically possible research directions are identified. The purpose of this chapter is to outline such a direction. Minkowski's program of regarding four-dimensional physics as spacetime geometry is rigorously and consistently employed to the already geometrized general relativity with the most stunning implication that gravitational phenomena are fully explained in the theory without the need to assume that they are caused by gravitational interaction. Then the real open question in gravitational physics seems to be how matter curves spacetime, not how to quantize the apparent gravitational interaction. In view of the difficulties encountered by quantum gravity, even the radical option that gravity is not a physical interaction deserves careful scrutiny due to its potential impact on fundamental physics as a whole. The chapter discusses the possible implications of this option for the physics of gravitational waves and for quantum gravity and ends with an example where regarding physics as spacetime geometry provides a straightforward explanation of a rather subtle issue in relativity - propagation of light in noninertial reference frames.

  14. Exploring Geometry Using Cabri Jr. Geometry App

    Microsoft Academic Search

    Leah A. Nillas

    2010-01-01

    This is a Hands-on session and an introduction to the Cabri Jr. Geometry App. Participants will learn basic commands in using the Cabri Jr. Geometry App as well as explore geometric constructions and relationships. Activities in this session are designed to engage students in discovering geometric relationships and making mathematical connections. Topics that will be covered include lines, angles, triangles,

  15. Learning Geometry through Dynamic Geometry Software

    ERIC Educational Resources Information Center

    Forsythe, Sue

    2007-01-01

    In this article, the author investigates effective teaching and learning of geometrical concepts using dynamic geometry software (DGS). Based from her students' reactions to her project, the author found that her students' understanding of the concepts was better than if they had learned geometry through paper-based tasks. However, mixing computer…

  16. Drift and diffusion of a confined semiflexible chain.

    PubMed

    Nam, G; Johner, A; Lee, N-K

    2010-06-01

    We study the transverse and longitudinal linear response function of rigid chains subjected to an external force. Our main concern are stiff polymers confined in narrow pores with diameter less than their persistence length. We explicitly consider confinement in a transverse harmonic potential and generalize results by scaling arguments. Our results describe the drift of the filament under an external force, time evolution of the filament shape, and filament diffusion. Diffusion of a confined filament resembles the celebrated reptation process for flexible chains, albeit with distinct kinetic exponents. The limiting case of stiff free filaments is also mentioned. PMID:20577775

  17. ITER confinement capability

    SciTech Connect

    Uckan, N.A.; Hogan, J.T.

    1990-01-01

    The confinement capability of ITER was examined for a number of operational scenarios. The reference ITER physics baseline scenario (I = 22 MA) allows ignited burn under H-mode conditions ({tau}{sub E}(H-mode) {approximately} 2 {times} {tau}{sub E}(L-mode)). At higher currents (I = 25--28 MA) at which ITER can operate for limited pulse duration, there is an increased ignition margin if low-q operation proves acceptable. About a factor of 2 reduction in helium ash concentration (from the baseline value of 10% to 5%) in the reference ITER scenario has about the same impact on ignition capability as increasing the plasma current by about 15% (from the baseline value of 22 MA to {ge}25 MA). It might be possible to further optimize the ignition capability of ITER if some of the limits on operational boundaries can be relaxed by tailoring plasma profiles. 9 refs., 4 figs.

  18. Toward a Measurement of the Cosmological Geometry at z~2: Predicting Lyman-alpha Forest Correlation in Three Dimensions, and the Potential of Future Data Sets

    E-print Network

    Patrick McDonald

    2001-08-03

    The correlation between Lyman-alpha absorption in the spectra of quasar pairs can be used to measure the transverse distance scale at z~2, which is sensitive to the cosmological constant (Omega_Lambda) or other forms of vacuum energy. Using Hydro-PM simulations, I compute the three-dimensional power spectrum of the Lyman-alpha forest flux, P_F(k,mu), from which the redshift-space anisotropy of the correlation can be obtained. I find that box size ~40 Mpc/h and resolution ~40 Kpc/h are necessary for convergence of the calculations to <5% on all relevant scales, although somewhat poorer resolution can be used for large scales. I compute directly the linear theory bias parameters of the Lyman-alpha forest, potentially allowing simulation results to be extended to arbitrarily large scales. I investigate the dependence of P_F(k,mu) on the primordial power spectrum, the temperature-density relation of the gas, and the mean flux decrement, finding that the redshift-space anisotropy is relatively insensitive to these parameters. A table of results is provided for different parameter variations. I investigate the constraint that can be obtained on Omega_Lambda using quasars from a large survey. Assuming 13 (theta/1')^2 pairs at separation

  19. Nernst branes from special geometry

    E-print Network

    Dempster, Paul; Mohaupt, Thomas

    2015-01-01

    We construct new black brane solutions in $U(1)$ gauged ${\\cal N}=2$ supergravity with a general cubic prepotential, which have entropy density $s\\sim T^{1/3}$ as $T \\rightarrow 0$ and thus satisfy the Nernst Law. By using the real formulation of special geometry, we are able to obtain analytical solutions in closed form as functions of two parameters, the temperature $T$ and the chemical potential $\\mu$. Our solutions interpolate between hyperscaling violating Lifshitz geometries with $(z,\\theta)=(0,2)$ at the horizon and $(z,\\theta)=(1,-1)$ at infinity. In the zero temperature limit, where the entropy density goes to zero, we recover the extremal Nernst branes of Barisch et al, and the parameters of the near horizon geometry change to $(z,\\theta)=(3,1)$.

  20. Nernst branes from special geometry

    E-print Network

    Paul Dempster; David Errington; Thomas Mohaupt

    2015-02-27

    We construct new black brane solutions in $U(1)$ gauged ${\\cal N}=2$ supergravity with a general cubic prepotential, which have entropy density $s\\sim T^{1/3}$ as $T \\rightarrow 0$ and thus satisfy the Nernst Law. By using the real formulation of special geometry, we are able to obtain analytical solutions in closed form as functions of two parameters, the temperature $T$ and the chemical potential $\\mu$. Our solutions interpolate between hyperscaling violating Lifshitz geometries with $(z,\\theta)=(0,2)$ at the horizon and $(z,\\theta)=(1,-1)$ at infinity. In the zero temperature limit, where the entropy density goes to zero, we recover the extremal Nernst branes of Barisch et al, and the parameters of the near horizon geometry change to $(z,\\theta)=(3,1)$.

  1. Variable geometry Darrieus wind machine

    NASA Astrophysics Data System (ADS)

    Pytlinski, J. T.; Serrano, D.

    1983-08-01

    A variable geometry Darrieus wind machine is proposed. The lower attachment of the blades to the rotor can move freely up and down the axle allowing the blades of change shape during rotation. Experimental data for a 17 m. diameter Darrieus rotor and a theoretical model for multiple streamtube performance prediction were used to develop a computer simulation program for studying parameters that affect the machine's performance. This new variable geometry concept is described and interrelated with multiple streamtube theory through aerodynamic parameters. The computer simulation study shows that governor behavior of a Darrieus turbine can not be attained by a standard turbine operating within normally occurring rotational velocity limits. A second generation variable geometry Darrieus wind turbine which uses a telescopic blade is proposed as a potential improvement on the studied concept.

  2. Performance of Polywell inertial-electrostatic confinement for applications

    Microsoft Academic Search

    J. F. Santarius; K. H. Simmons

    1995-01-01

    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

  3. H. Stachel, Professor A Way to Geometry Through Descriptive Geometry

    E-print Network

    Stachel, Hellmuth

    motions in [9]. The correspondence be- tween non-Euclidean differential geometry and the geometryH. Stachel, Professor A Way to Geometry Through Descriptive Geometry Vienna University of geometry and on my contributions to Descriptive Geometry education. Descriptive Geometry in Austria

  4. Inertial Electrostatic Confinement (IEC) devices

    Microsoft Academic Search

    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

    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

  5. The virial theorem for the smoothly and sharply, penetrably and impenetrably confined hydrogen atom

    SciTech Connect

    Katriel, Jacob [Department of Chemistry, Technion, Haifa 32000 (Israel) and Nazareth Academic Institute, Nazareth 16100 (Israel); Montgomery, H. E. Jr. [Chemistry Program, Centre College, Danville, Kentucky 40422 (United States)

    2012-09-21

    Confinement of atoms by finite or infinite boxes containing sharp (discontinuous) jumps has been studied since the fourth decade of the previous century, modelling the effect of external pressure. Smooth (continuous) counterparts of such confining potentials, that depend on a parameter such that in an appropriate limit they coincide with the sharp confining potentials, are investigated, with an emphasis on deriving the corresponding virial and Hellmann-Feynman theorems.

  6. The virial theorem for the smoothly and sharply, penetrably and impenetrably confined hydrogen atom.

    PubMed

    Katriel, Jacob; Montgomery, H E

    2012-09-21

    Confinement of atoms by finite or infinite boxes containing sharp (discontinuous) jumps has been studied since the fourth decade of the previous century, modelling the effect of external pressure. Smooth (continuous) counterparts of such confining potentials, that depend on a parameter such that in an appropriate limit they coincide with the sharp confining potentials, are investigated, with an emphasis on deriving the corresponding virial and Hellmann-Feynman theorems. PMID:22998251

  7. Spherical microwave confinement and ball lightning

    NASA Astrophysics Data System (ADS)

    Robinson, William Richard

    This dissertation presents the results of research done on unconventional energy technologies from 1995 to 2009. The present civilization depends on an infrastructure that was constructed and is maintained almost entirely using concentrated fuels and ores, both of which will run out. Diffuse renewable energy sources rely on this same infrastructure, and hence face the same limitations. I first examined sonoluminescence directed toward fusion, but demonstrated theoretically that this is impossible. I next studied Low Energy Nuclear Reactions and developed methods for improving results, although these have not been implemented. In 2000, I began Spherical Microwave Confinement (SMC), which confines and heats plasma with microwaves in a spherical chamber. The reactor was designed and built to provide the data needed to investigate the possibility of achieving fusion conditions with microwave confinement. A second objective was to attempt to create ball lightning (BL). The reactor featured 20 magnetrons, which were driven by a capacitor bank and operated in a 0.2 s pulse mode at 2.45 GHz. These provided 20 kW to an icosahedral array of 20 antennas. Video of plasmas led to a redesign of the antennas to provide better coupling of the microwaves to the plasma. A second improvement was a grid at the base of the antennas, which provided corona electrons and an electric field to aid quick formation of plasmas. Although fusion conditions were never achieved and ball lightning not observed, experience gained from operating this basic, affordable system has been incorporated in a more sophisticated reactor design intended for future research. This would use magnets that were originally planned. The cusp geometry of the magnetic fields is suitable for electron cyclotron resonance in the same type of closed surface that in existing reactors has generated high-temperature plasmas. Should ball lightning be created, it could be a practical power source with nearly ideal characteristics that could solve many of our current energy-production problems.

  8. Geometry and Topology

    NSDL National Science Digital Library

    Geometry and Topology is "a fully refereed international journal dealing with all aspects of geometry and topology and their applications." The publisher, Geometry & Topology Publications (GTP), is a non-profit organization based in the Mathematics Department of the University of Warwick at Coventry, UK. Visitors can browse the journal, available free of charge electronically, or search by keyword or author. The moderate collection within the Geometry and Topology Monographs series includes research monographs and refereed conference proceedings.

  9. Non-Euclidean Geometry

    Microsoft Academic Search

    John Stillwell

    \\u000a Surprisingly, the geometry of curved surfaces throws light on the geometry of the plane. More than 2000 years after Euclid\\u000a formulated axioms for plane geometry, differential geometry showed that the parallel axiom does not follow from the other axioms of Euclid. It had long been hoped that the parallel axiom followed from the others, but no proof had ever been

  10. Recent Results on Field Reversed Configurations from the Translation, Confinement and Sustainment Experiment

    Microsoft Academic Search

    Houyang Guo

    2005-01-01

    The field-reversed configuration (FRC) offers an attractive alternative approach to magnetically confined fusion because of its extremely high beta, simple linear geometry, and natural divertor for helium ash removal. Multi-hundred eV and high density FRCs have been produced using the standard Field Reversed Theta Pinch (RFTP) method, with a confinement scaling that leads to fusion conditions. These FRCs are, however,

  11. On the Lorentz nature of confinement

    SciTech Connect

    Kalashnikova, Yulia S. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation)

    1998-05-29

    The Lorentz structure of the long-range confining force in the heavy quark approximation is studied within the model of QCD vacuum which is described by the bilocal gluonic correlators and assures the area law asymptotics for the isolated Wilson loop. The effective Dirac-type equation is written out for the quark propagating in such vacuum in the presence of static antiquark source. In the heavy quark limit the effective interaction is reduced to the potential one, with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement. The next-to-leading in {radical}({sigma})/m corrections are calculated, and the sign and the coefficient at the spin-orbit term is found to be in agreement with both Eichten-Feinberg-Gromes results and demands of heavy quarkonia phenomenology.

  12. On the Lorentz nature of confinement

    NASA Astrophysics Data System (ADS)

    Kalashnikova, Yulia S.

    1998-05-01

    The Lorentz structure of the long-range confining force in the heavy quark approximation is studied within the model of QCD vacuum which is described by the bilocal gluonic correlators and assures the area law asymptotics for the isolated Wilson loop. The effective Dirac-type equation is written out for the quark propagating in such vacuum in the presence of static antiquark source. In the heavy quark limit the effective interaction is reduced to the potential one, with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement. The next-to-leading in ?? /m corrections are calculated, and the sign and the coefficient at the spin-orbit term is found to be in agreement with both Eichten-Feinberg-Gromes results and demands of heavy quarkonia phenomenology.

  13. Confinement made simple in the Coulomb gauge

    NASA Astrophysics Data System (ADS)

    Cucchieri, Attilio; Zwanziger, Daniel

    2002-03-01

    In Gribov's scenario in Coulomb gauge, confinement of color charge is due to a long-range instantaneous color-Coulomb potential V( R). This may be determined numerically from the instantaneous part of the gluon propagator D44,inst = V( R)?( t). Confinement of gluons is reflected in the vanishing at k = 0 of the equal-time three-dimensionally transverse would-be physical gluon propagator Dtr( k). We present exact analytic results on D44 and Dtr (which have also been investigated numerically, A. Cucchieri, T. Mendes, and D. Zwanziger, this conference), in particular the vanishing of Dtr( k) at k = 0, and the determination of the running coupling constant from x0g2( k) = k2D44,inst, where x0 = 12 N/(11 N - 2 N f).

  14. Confinement made simple in the Coulomb gauge

    NASA Astrophysics Data System (ADS)

    Cucchieri, Attilio; Zwanziger, Daniel

    In Gribov's scenario in Coulomb gauge, confinement of color charge is due to a long-range instantaneous color-Coulomb potential V(R). This may be determined numerically from the instantaneous part of the gluon propagator D44,inst = V(R)?(t). Confinement of gluons is reflected in the vanishing at k = 0 of the equal-time three-dimensionally transverse would-be physical gluon propagator Dtr(k). We present exact analytic results on D44 and Dtr (which have also been investigated numerically, A. Cucchieri, T. Mendes, and D. Zwanziger, this conference), in particular the vanishing of Dtr(k) at k = 0, and the determination of the running coupling constant from x0g2(k) = k2 D44,inst, where x0 = 12N/(11N - 2Nf).

  15. Cooperative Length Scale and Fragility of Polystyrene under Confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Chuan; Guo, Yunlong; Priestley, Rodney

    2012-02-01

    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.

  16. Oriented projective geometry

    Microsoft Academic Search

    Jorge Stolfi

    1987-01-01

    Oriented projective geometry is a model for geometric computation that combines the elegance of classical projective geometry with the ability to talk about oriented lines and planes, signed angles, line segments, convex figures, and many other concepts that cannot be defined within the classical version. Classical projective geometry is the implicit framework of many geometric computations, since it underlies the

  17. Algebraic Geometry Jean Gallier

    E-print Network

    Gallier, Jean

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 2 Dimension, Local Theory, Projective Geometry 69 2.1 Dimension TheoryAlgebraic Geometry Jean Gallier and Stephen S. Shatz Department of Computer and Information, 2011 #12;2 #12;Contents 1 Elementary Algebraic Geometry 7 1.1 History and Problems

  18. Algebraic Geometry Jean Gallier

    E-print Network

    Gallier, Jean

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 2 Dimension, Local Theory, Projective Geometry 67 2.1 Dimension TheoryAlgebraic Geometry Jean Gallier and Stephen S. Shatz Department of Computer and Information #12;2 #12;Contents 1 Elementary Algebraic Geometry 5 1.1 History and Problems

  19. TRIANGLES IN HYPERBOLIC GEOMETRY

    Microsoft Academic Search

    LAURA VALAAS

    This paper derives the Law of Cosines, Law of Sines, and the Pythagorean Theorem for triangles in Hyperbolic Geometry. The Poincar e model for Hyperbolic Geometry is used. In order to accomplish this the paper reviews Inversion in Hyperbolic Geometry, Radical Axes and Powers of circles and expressions for hyperbolic cosine, hyperbolic sine, and hyperbolic tangent. A brief history of

  20. Spectral Geometry Bruno Iochum

    E-print Network

    Paris-Sud XI, Université de

    Spectral Geometry Bruno Iochum Aix-Marseille Université, CNRS UMR 7332, CPT, 13288 Marseille France Abstract The goal of these lectures is to present some fundamentals of noncommutative geometry looking primary objects defined for manifolds will be generalized to reach the level of noncommutative geometry

  1. Geometry Formulas and Facts

    NSDL National Science Digital Library

    Levy, Silvio

    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.

  2. Hydrodynamic fluctuations in confined emulsions

    E-print Network

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

    2013-01-23

    When an ensemble of particles interact hydrodynamically, they generically display large-scale transient structures such as swirls in sedimenting particles [1], or colloidal strings in sheared suspensions [2]. Understanding these nonequilibrium fluctuations is a very difficult problem, yet they are of great importance for a wide range of processes including pigment deposition in cosmetic or paint films, the transport of microfluidic droplets, ... All these samples concern rigidly confined fluids, which we consider in this paper. We address the collective dynamics of non-Brownian droplets cruising in a shallow microchannel. We 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 theory which quantitatively accounts for our experimental findings. By doing so we demonstrate that the fluctuation spectrum of this nonequilibrium system is shaped by the combination of truly long-range hydrodynamic interactions and local collisions.

  3. Trapping ultracold atoms in a time-averaged adiabatic potential

    SciTech Connect

    Gildemeister, M.; Nugent, E.; Sherlock, B. E.; Kubasik, M.; Sheard, B. T.; Foot, C. J. [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)

    2010-03-15

    We report an experimental realization of ultracold atoms confined in a time-averaged, adiabatic potential (TAAP). This trapping technique involves using a slowly oscillating ({approx}kHz) bias field to time-average the instantaneous potential given by dressing a bare magnetic potential with a high-frequency ({approx}MHz) magnetic field. The resultant potentials provide a convenient route to a variety of trapping geometries with tunable parameters. We demonstrate the TAAP trap in a standard time-averaged orbiting potential trap with additional Helmholtz coils for the introduction of the radio frequency dressing field. We have evaporatively cooled 5x10{sup 4} atoms of {sup 87}Rb to quantum degeneracy and observed condensate lifetimes of longer than 3 s.

  4. The role of jet inlet geometry in impinging jet heat transfer, modeling and experiments

    Microsoft Academic Search

    M. F. Koseoglu; S. Baskaya

    2010-01-01

    Effects of jet inlet geometry and aspect ratio on local and average heat transfer characteristics of totally nine confined impinging jets have been investigated experimentally using thermochromic liquid crystals and numerically by using a 3-D low Reynolds number k–? model. Experimental study by using liquid crystals for temperature measurement was conducted for three different jet exit geometries (circular, elliptic, rectangular).

  5. Inertial confinement fusion

    SciTech Connect

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

    1992-01-01

    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.

  6. Weapons Activities/ Inertial Confinement Fusion Ignition

    E-print Network

    Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY 2012 Congressional Budget Inertial Confinement Fusion Ignition and High Yield Campaign Funding Profile by Subprogram FY 2010 Actual Appropriation FY 2011 Request FY 2012 Request Inertial Confinement Fusion Ignition

  7. Dynamics and density distribution of strongly confined noninteracting nonaligning self-propelled particles in a nonconvex boundary

    NASA Astrophysics Data System (ADS)

    Fily, Yaouen; Baskaran, Aparna; Hagan, Michael F.

    2015-01-01

    We study the dynamics of nonaligning, noninteracting self-propelled particles confined to a box in two dimensions. In the strong confinement limit, when the persistence length of the active particles is much larger than the size of the box, particles stay on the boundary and align with the local boundary normal. It is then possible to derive the steady-state density on the boundary for arbitrary box shapes. In nonconvex boxes, the nonuniqueness of the boundary normal results in hysteretic dynamics and the density is nonlocal, i.e., it depends on the global geometry of the box. These findings establish a general connection between the geometry of a confining box and the behavior of an ideal active gas it confines, thus providing a powerful tool to understand and design such confinements.

  8. Psychopathological effects of solitary confinement.

    PubMed

    Grassian, S

    1983-11-01

    Psychopathological reactions to solitary confinement were extensively described by nineteenth-century German clinicians. In the United States there have been several legal challenges to the use of solitary confinement, based on allegations that it may have serious psychiatric consequences. The recent medical literature on this subject has been scarce. The author describes psychiatric symptoms that appeared in 14 inmates exposed to periods of increased social isolation and sensory restriction in solitary confinement and asserts that these symptoms form a major, clinically distinguishable psychiatric syndrome. PMID:6624990

  9. Geometry Dependence of Stellarator Turbulence

    SciTech Connect

    H.E. Mynick, P. Xanthopoulos and A.H. Boozer

    2009-08-10

    Using the nonlinear gyrokinetic code package GENE/GIST, we study the turbulent transport in a broad family of stellarator designs, to understand the geometry-dependence of the microturbulence. By using a set of flux tubes on a given flux surface, we construct a picture of the 2D structure of the microturbulence over that surface, and relate this to relevant geometric quantities, such as the curvature, local shear, and effective potential in the Schrodinger-like equation governing linear drift modes.

  10. Impact of surface charges on the solvation forces in confined colloidal solutions

    NASA Astrophysics Data System (ADS)

    Grandner, Stefan; Zeng, Yan; Klitzing, Regine v.; Klapp, Sabine H. L.

    2009-10-01

    Combining computer simulations and experiments we address the impact of charged surfaces on the solvation forces of a confined, charged colloidal suspension (slit-pore geometry). Investigations based on the colloidal-probe atomic-force-microscope technique indicate that an increase in surface charges markedly enhances the oscillations of the force in terms of their amplitude. To understand this effect on a theoretical level we perform grand-canonical Monte-Carlo simulations (GCMC) of a coarse-grained model system. It turns out that various established approaches of the interaction between a charged colloid and a charged wall, such as linearized Poisson-Boltzmann (PB) theory involving the bulk screening length, do not reproduce the experimental observations. We thus introduce a modified PB potential with a space-dependent screening parameter. The latter takes into account, in an approximate way, the fact that the charged walls release additional (wall) counterions which accumulate in a thin layer at the surface(s). The resulting, still purely repulsive fluid-wall potential displays a nonmonotonic behavior as function of the surface potential with respect to the strength and range of repulsion. GCMC simulations based on this potential reproduce the experimentally observed charge-induced enhancement in the force oscillations. We also show, both by experiment and by simulations, that the asymptotic wave- and decay length of the oscillating force do not change with the wall charge, in agreement with predictions from density functional theory.

  11. Diffusion Enhancement in Core-softened fluid confined in nanotubes

    E-print Network

    José R. Bordin; Alan B. de Oliveira; Alexandre Diehl; Marcia C. Barbosa

    2012-08-05

    We study the effect of confinement in the dynamical behavior of a core-softened fluid. The fluid is modeled as a two length scales potential. This potential in the bulk reproduces the anomalous behavior observed in the density and in the diffusion of liquid water. A series of $NpT$ Molecular Dynamics simulations for this two length scales fluid confined in a nanotube were performed. We obtain that the diffusion coefficient increases with the increase of the nanotube radius for wide channels as expected for normal fluids. However, for narrow channels, the confinement shows an enhancement in the diffusion coefficient when the nanotube radius decreases. This behavior, observed for water, is explained in the framework of the two length scales potential.

  12. Interplay of explosive thermal reaction dynamics and structural confinement

    NASA Astrophysics Data System (ADS)

    Perry, W. Lee; Zucker, Jonathan; Dickson, Peter M.; Parker, Gary R.; Asay, Blaine W.

    2007-04-01

    Explosives play a significant role in human affairs; however, their behavior in circumstances other than intentional detonation is poorly understood. Accidents may have catastrophic consequences, especially if additional hazardous materials are involved. Abnormal ignition stimuli, such as impact, spark, friction, and heat may lead to a very violent outcome, potentially including detonation. An important factor influencing the behavior subsequent to abnormal ignition is the strength and inertia of the vessel confining the explosive, i.e., the near-field structural/mechanical environment, also known as confinement (inertial or mechanical). However, a comprehensive and quantified understanding of how confinement affects reaction violence does not yet exist. In the research discussed here, we have investigated a wide range of confinement conditions and related the explosive response to the fundamentals of the combustion process in the explosive. In our experiments, a charge of an octahydrotetranitrotetrazine-based plastic bonded explosive (PBX 9501) was loaded into a gun assembly having variable confinement conditions and subjected to a heating profile. The exploding charge breached the confinement and accelerated a projectile down the gun barrel. High bandwidth pressure and volume measurements were made and a first-law analysis was used to obtain enthalpy and power from the raw data. These results were then used to quantify reaction violence. Enthalpy change and power ranged from 0-1.8 kJ and 0-12 MW for 300 mg charges, respectively. Below a confinement strength of 20 MPa, violence was found to decline precipitously with decreasing confinement, while the violence for the heaviest confinement experiments was found to be relatively constant. Both pressure and pressurization rate were found to have critical values to induce and sustain violent reaction.

  13. Perturbation theory for confined systems

    E-print Network

    Francisco M. Fernández

    2010-04-14

    We discuss the application of perturbation theory to a system of particles confined in a spherical box. A simple argument shows that the particles behave almost independently in sufficiently strong confinement. We choose the helium atom with a moving nucleus as a particular example and compare results of first order with those for the nucleus clamped at the center of the box. We provide a suitable explanation for some numerical results obtained recently by other authors.

  14. Snyder-Yang algebra and confinement of color particles

    E-print Network

    V. V. Khruschov

    2010-12-21

    A model of color particle confinement is considered. The model is based on the Snyder-Yang algebra, which takes into account a non-commutativity of generalized momenta and coordinates of a color particle and contains two new constants. An extended kinematical invariance in a quantum phase space of a color particle gives rise to an invariant equation with an oscillator rising potential. The presence of the oscillator rising potential can simulate a confinement of a color particle. Mass and lenght parameters involved in the Snyder-Yang commutation relations along with parameters of current and constituent quarks are estimated.

  15. The Geometry Junkyard

    NSDL National Science Digital Library

    Provided by David Eppstein, professor of Information and Computer Science at the University of California-Irvine, the Geometry Junkyard is a metasite covering classical geometry theory and current research in the area of computation geometry. A few examples of the many topics included in the Geometry Junkyard are: combination geometry, fractals, multi-dimensional geometry, and open problems (most of which are illustrated with diagrams). Dr. Eppstein's thoughtful selection of links point users to numerous discussions and solutions to problems; in addition, he has added several pages on topics not well covered (My Own Junk), and has highlighted newly added material (New Junk). This site is more of a gold mine than a junkyard, based on the vast amount of information provided and the fun spin placed on many of the topics.

  16. Engineering tube shapes to control confined transport

    NASA Astrophysics Data System (ADS)

    Reguera, D.; Rubi, J. M.

    2014-12-01

    Transport of particles in confined structures can be modeled by means of diffusion in a potential of entropic nature. The entropic transport model proposes a drift-diffusion kinetic equation for the evolution of the probability density in which the diffusion coefficient depends on position and the drift term contains an entropic force. The model has been applied to analyze transport in single cavities and through periodic structures of different shape, and to investigate the nature of non-equilibrium fluctuations as well. The transport characteristics depends strongly on the contour of the region through which particles move, which defines the entropic potential. We show that the form of the entropic potential can be properly designed to optimize and govern how molecules diffuse and get drifted in tortuous channels. The shape of a tube or channel can be smartly engineered to control transport for the desired application.

  17. High Temperature Confinement in SU(N) Gauge Theories

    E-print Network

    Michael C. Ogilvie; Peter N. Meisinger

    2008-11-13

    SU(N) gauge theories, extended with adjoint fermions having periodic boundary conditions, are confining at high temperature for sufficiently light fermion mass m. Lattice simulations indicate that this confining region is smoothly connected to the confining region of low-temperature pure SU(N) gauge theory. In the high temperature confining region, the one-loop effective potential for Polyakov loops has a Z(N)-symmetric confining minimum. String tensions associated with Polyakov loops are smooth functions of m/T. In the magnetic sector, the Polyakov loop plays a role similar to a Higgs field, leading to a breaking of SU(N) to U(1)^{N-1}. This is turn yields an effective theory where magnetic monopoles give rise to string tensions for spatial Wilson loops. These string tensions are calculable semiclassically. There are many analytical predictions for the high-temperature region that can be tested by lattice simulations, but lattice work will be crucial for exploring the crossover from this region to the low-temperature confining behavior of pure gauge theories.

  18. Potentially active copies of the gypsy retroelement are confined to the Y chromosome of some strains of Drosophila melanogaster possibly as the result of the female-specific effect of the flamenco gene.

    PubMed

    Chalvet, F; di Franco, C; Terrinoni, A; Pelisson, A; Junakovic, N; Bucheton, A

    1998-04-01

    Gypsy is an endogenous retrovirus present in the genome of Drosophila melanogaster. This element is mobilized only in the progeny of females which contain active gypsy elements and which are homozygous for permissive alleles of a host gene called flamenco (flam). Some data strongly suggest that gypsy elements bearing a diagnostic HindIII site in the central region of the retrovirus body represent a subfamily that appears to be much more active than elements devoid of this site. We have taken advantage of this structural difference to assess by the Southern blotting technique the genomic distribution of active gypsy elements. In some of the laboratory Drosophila stocks tested, active gypsy elements were found to be restricted to the Y chromosome. Further analyses of 14 strains tested for the permissive vs. restrictive status of their flamenco alleles suggest that the presence of permissive alleles of flam in a stock tends to be associated with the confinement of active gypsy elements to the Y chromosome. This might be the result of the female-specific effect of flamenco on gypsy activity. PMID:9541538

  19. Geometry Here, Geometry There, Geomerty is EVERYWHERE!

    NSDL National Science Digital Library

    Miss Tiller

    2012-02-05

    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 ...

  20. Interactive Geometry Dictionary: Areas in Geometry

    NSDL National Science Digital Library

    2011-01-01

    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.

  1. Confinement of conjugated polymers into soft nanoparticles: molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Wijesinghe, Sidath; Perahia, Dvora; Grest, Gary S.

    2013-03-01

    The structure and dynamics of conjugated polymers confined into soft nanoparticles (SNPs) have been studies by molecular dynamic simulations. This new class of tunable luminescent SNPs exhibits an immense potential as bio-markers as well as targeted drug delivery agents where tethering specific groups to the surface particles offers a means to target specific applications. Of particular interest are SNPs that consist of non- crosslinked polymers, decorated with polar groups. These SNPs are potentially tunable through the dynamics of the polymer chains, whereas the polar entity serves as internal stabilizer and surface encore. Confinement of a polymer whose inherent conformation is extended impacts not only their dynamics and as a result their optical properties. Here we will present insight into the structure and dynamics of dialkyl poly para phenylene ethynylene (PPE), decorated by a carboxylate groups, confined into a soft particle. The conformation and dynamics of polymer within SNP will be discussed and compared with that of the linear chain in solution.

  2. The geometry of thermodynamic control

    E-print Network

    Zulkowski, Patrick R; Crooks, Gavin E; DeWeese, Michael R

    2012-01-01

    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 novel 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 directl...

  3. Geometry Professionalized for Teachers.

    ERIC Educational Resources Information Center

    Christofferson, Halbert Carl

    Written in 1933, this book grew out of the author's concern that college matehmatics sequences of the day, although appropriate in algebra preparation, did not adequately prepare teachers of geometry. This book describes a course intended to remedy this by providing for both a comprehensive study of geometry as an axiomatically defined structure…

  4. Projective Geometry Image Analysis

    E-print Network

    Paris-Sud XI, Université de

    Projective Geometry for Image Analysis A Tutorial given at ISPRS, Vienna, July 1996 Roger Mohr A Hierarchy of Geometries 25 4.1 From Projective to Affine Space and Bill Triggs GRAVIR, project MOVI INRIA, 655 avenue de l'Europe F-38330 Montbonnot St Martin France E

  5. Geometry + Technology = Proof

    ERIC Educational Resources Information Center

    Lyublinskaya, Irina; Funsch, Dan

    2012-01-01

    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…

  6. Geometry of multihadron production

    SciTech Connect

    Bjorken, J.D.

    1994-10-01

    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.

  7. Euclidean Geometry via Programming.

    ERIC Educational Resources Information Center

    Filimonov, Rossen; Kreith, Kurt

    1992-01-01

    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…

  8. An electrostatically and a magnetically confined electron gun lens system

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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 second gun lens system is a simpler three-lens system suitable for use in a uniform, solenoidal magnetic field. While the focusing properties of such a magnetically confined lens systenm are simpler to deal with, the system does illustrate features of electron extraction and Brillouin flow that have not been suitably emphasized in the literature.

  9. Some links between turtle geometry and analytic geometry

    Microsoft Academic Search

    Neil C. Rowe

    1985-01-01

    The computer language LOGO facilitates the teaching of analytic geometry and calculus from the notion of curvature, through its ‘turtle geometry’ facility [2]. We provide some theoretical basis for finding turtle geometry equivalents of familiar curves in analytic geometry, and vice versa, by some simple methods which apparently have not been noticed previously. In particular, we study turtle geometry programs

  10. Geometry of membrane fission.

    PubMed

    Frolov, Vadim A; Escalada, Artur; Akimov, Sergey A; Shnyrova, Anna V

    2015-01-01

    Cellular membranes define the functional geometry of intracellular space. Formation of new membrane compartments and maintenance of complex organelles require division and disconnection of cellular membranes, a process termed membrane fission. Peripheral membrane proteins generally control membrane remodeling during fission. Local membrane stresses, reflecting molecular geometry of membrane-interacting parts of these proteins, sum up to produce the key membrane geometries of fission: the saddle-shaped neck and hour-glass hemifission intermediate. Here, we review the fundamental principles behind the translation of molecular geometry into membrane shape and topology during fission. We emphasize the central role the membrane insertion of specialized protein domains plays in orchestrating fission in vitro and in cells. We further compare individual to synergistic action of the membrane insertion during fission mediated by individual protein species, proteins complexes or membrane domains. Finally, we describe how local geometry of fission intermediates defines the functional design of the protein complexes catalyzing fission of cellular membranes. PMID:25062896

  11. Aspects of spinorial geometry

    E-print Network

    U. Gran; J. Gutowski; G. Papadopoulos; D. Roest

    2006-12-14

    We review some aspects of the spinorial geometry approach to the classification of supersymmetric solutions of supergravity theories. In particular, we explain how spinorial geometry can be used to express the Killing spinor equations in terms of a linear system for the fluxes and the geometry of spacetime. The solutions of this linear system express some of the fluxes in terms of the spacetime geometry and determine the conditions on the spacetime geometry imposed by supersymmetry. We also present some of the recent applications like the classification of maximally supersymmetric G-backgrounds in IIB, this includes the most general pp-wave solution preserving 1/2 supersymmetry, and the classification of N=31 backgrounds in ten and eleven dimensions.

  12. Experimental and Theoretical Studies of Electrostatic Confinement

    NASA Astrophysics Data System (ADS)

    Park, Jaeyoung; Nebel, Richard

    2002-11-01

    Experimental and Theoretical Studies of Electrostatic Confinement J. Park, R. A. Nebel, C. P. Munson, W. G. Rellergert, M. D. Sekora Los Alamos National Laboratory Previous theoretical work [R. A. Nebel, D. C. Barnes, Fusion Technology (1998) and D. C. Barnes, R. A. Nebel, Phys. Plasmas (1998)] suggested that an ion cloud confined by a stable oscillating virtual cathode may undergo a self=similar collapse producing periodic and simultaneous attainment of high densities and temperatures. We are currently conducting experiments to test the stability of these virtual cathodes. Emissive probes have been used to measure time and space resolved potential and electron density profiles. Fluctuations in the plasma have been measured by a passive receiver and a combination of an external driver and a receiver. The observed virtual cathode exhibits a bifurcation between states where the well depth is 60potential. The transition is a function of the injected electron flux, grid biases, and the gas pressure. Experimental results on fluctuation and stability of a driven virtual cathode will be presented and compared with theoretical predictions [R. A. Nebel, J. M. Finn, Phys. Plasmas (2001)].

  13. CORRELATIONS IN CONFINED QUANTUM PLASMAS

    SciTech Connect

    DUFTY J W

    2012-01-11

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

  14. Hydrodynamics of Confined Active Fluids

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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).

  15. Polyelectrolyte stars in planar confinement

    E-print Network

    Martin Konieczny; Christos N. Likos

    2006-04-18

    We employ monomer-resolved Molecular Dynamics simulations and theoretical considerations to analyze the conformations of multiarm polyelectrolyte stars close to planar, uncharged walls. We identify three mechanisms that contribute to the emergence of a repulsive star-wall force, namely: the confinement of the counterions that are trapped in the star interior, the increase in electrostatic energy due to confinement as well as a novel mechanism arising from the compression of the stiff polyelectrolyte rods approaching the wall. The latter is not present in the case of interaction between two polyelectrolyte stars and is a direct consequence of the impenetrable character of the planar wall.

  16. Spatial Variations in Carbon Storage along Headwater Fluvial Networks with Differing Valley Geometry

    NASA Astrophysics Data System (ADS)

    Wohl, E. E.; Dwire, K. A.; Polvi, L. E.; Sutfin, N. A.; Bazan, R. A.

    2011-12-01

    We distinguish multiple valley types along headwater fluvial networks in the Colorado Front Range based on valley geometry (downstream gradient and valley-bottom width relative to active channel width) and the presence of biotic drivers (beaver dams or channel-spanning logjams associated with old-growth forest) capable of creating a multi-thread channel pattern. Valley type influences storage of fine sediment, organic matter, and carbon. Deep, narrow valleys have limited storage potential, whereas wide, shallow valleys with multi-thread channels have substantial storage potential. Multi-thread channels only occur in the presence of a biotic driver. Given the importance of headwater streams in the global carbon cycle, it becomes important to understand the spatial distribution and magnitude of carbon storage along these streams, as well as the processes governing patterns of storage. We compare carbon stored in three reservoirs: riparian vegetation (live, dead, and litter), instream and floodplain large wood, and floodplain soils for 100-m-long valley segments in seven different valley types. The valley types are (i) laterally confined valleys in old-growth forest, (ii) partly confined valleys in old-growth forest, (iii) laterally unconfined valleys with multi-thread channels in old-growth forest, (iv) laterally unconfined valleys with single-thread channels in old-growth forest, (v) laterally confined valleys in younger forest, (vi) recently abandoned beaver-meadow complexes with multi-thread channels and willow thickets, and (vii) longer abandoned beaver-meadow complexes with single-thread channels and very limited woody vegetation. Preliminary results suggest that, although multi-thread channel segments driven by beavers or logjams cover less than 25 percent of the total length of headwater river networks in the study area, they account for more than three-quarters of the carbon stored along the river network. Historical loss of beavers and old-growth forest has thus likely resulted in continuing loss of carbon storage in these headwater river networks.

  17. Experimental study of proton rate density in a spherical inertial electrostatic confinement fusion device

    Microsoft Academic Search

    Yibin Gu

    1998-01-01

    The concept of spherical inertial-electrostatic confinement (SIEC) is to focus and accelerate ions and electrons radially inward into the center of a negatively biased, highly transparent spherical grid to create a space-charge double-potential well (a negative-potential well nested inside a positive-potential well) which confines the high-energy ions in the dense central core region such that appreciable nuclear fusion reactions are

  18. Induced geometry from disformal transformation

    E-print Network

    Fang-Fang Yuan; Peng Huang

    2015-02-08

    In this note, we use the disformal transformation to induce a geometry from the manifold which is originally Riemannian. The new geometry obtained here can be considered as a generalization of Weyl integrable geometry. Based on these results, we further propose a geometry which is naturally a generalization of Weyl geometry.

  19. Geometrie im Internet Wolfgang Rath

    E-print Network

    Stachel, Hellmuth

    Geometrie im Internet Wolfgang Rath Institut für Geometrie, TU Wien rath@geometrie.tuwien.ac.at http://www.geometrie.tuwien.ac.at/rath Version 1999-11-15 #12;Geometrie im Internet - Wolfgang Rath......................................................................................... 5 1.1 SCHNELLER EINSTIEG INS INTERNET

  20. The Bifurcation Approach Hyperbolic Geometry

    E-print Network

    Ungar, Abraham A.

    to which Euclidean geometry bifurcates into two mutually dual branches of hyperbolic geometry in its transition to non­ Euclidean geometry. One of the two resulting branches turns out to be the standard of the geometry generate, that al­ lows Euclidean and hyperbolic geometry to be unified in terms of analogies

  1. Flavors of Geometry MSRI Publications

    E-print Network

    Kapovich, Misha

    of non-Euclidean geometry, that is, a geometry that discards one of Euclid's axioms. Einstein and Minkowski found in non-Euclidean geometry a This work was supported in part by The Geometry Center of the twentieth century every serious student of mathematics and physics studied non-Euclidean geometry. This has

  2. www.postersession.com Inertial Electrostatic Confinement Fusion for Spacecraft

    E-print Network

    de Weck, Olivier L.

    Laboratory, Fusion Power and Propulsion Group Nuclear fusion has been identified as a potentially abundantprinted by www.postersession.com Inertial Electrostatic Confinement Fusion for Spacecraft Dr functionality is a result of the extraordinary energy density of the relevant fusion reactions in combination

  3. Inertial electrostatic confinement as a power source for electric propulsion

    Microsoft Academic Search

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

    1993-01-01

    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.

  4. Inertial-electrostatic confinement (IEC) fusion for space power

    Microsoft Academic Search

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

    1991-01-01

    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,

  5. Improved virtual cathode formation in Inertial Electrostatic Confinement

    Microsoft Academic Search

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

    2009-01-01

    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

  6. Open-ended magnetic confinement systems for fusion

    SciTech Connect

    Post, R.F.; Ryutov, D.D.

    1995-05-01

    Magnetic confinement systems that use externally generated magnetic fields can be divided topologically into two classes: ``closed`` and `open``. The tokamak, the stellarator, and the reversed-field-pinch approaches are representatives of the first category, while mirror-based systems and their variants are of the second category. While the recent thrust of magnetic fusion research, with its emphasis on the tokamak, has been concentrated on closed geometry, there are significant reasons for the continued pursuit of research into open-ended systems. The paper discusses these reasons, reviews the history and the present status of open-ended systems, and suggests some future directions for the research.

  7. Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles

    SciTech Connect

    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

    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.

  8. Quench Dynamics in Confined 1+1-Dimensional Systems

    E-print Network

    Engelhardt, Dalit

    2015-01-01

    We present a scheme for investigating the response of confined 1+1-dimensional systems to a quantum quench and consider the extent to which a system whose post-quench dynamics are near-integrable may be analyzed by an application of boundary CFT techniques. As the main example we present a model of a split-momentum quench in a finite 1D geometry, a setup analogous to that of the experiment of Kinoshita, Wenger, and Weiss [Nature 440, 900 (2006)]. We analytically derive the form of the expected momentum distributions and describe how such information may be used to assess the extent of integrability breaking in realistic systems.

  9. Magnetospheric vortex formation: self-organized confinement of charged particles.

    PubMed

    Yoshida, Z; Saitoh, H; Morikawa, J; Yano, Y; Watanabe, S; Ogawa, Y

    2010-06-11

    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. PMID:20867249

  10. Changes in EEG alpha frequency and evoked response latency during solitary confinement

    Microsoft Academic Search

    Paul Gendreau; N. L. Freedman; G. J. Wilde; G. D. Scott

    1972-01-01

    1 wk. of solitary confinement of 20 18-45 yr. old prison inmates produced significant changes in their EEG frequency and visual evoked potentials (VEP) that parallel those reported in laboratory studies of sensory deprivation. EEG frequency declined in a nonlinear manner over the 7-day period. VEP latency, which decreased with continued solitary confinement, was shorter for these Ss than for

  11. DEVELOPMENT OF A METHODOLOGY FOR REGIONAL EVALUATION OF CONFINING BED INTEGRITY

    EPA Science Inventory

    For safe underground injection of liquid waste, confining formations must be thick, extensive, and have low permeability. Recognition of faults that extend from the potential injection zone to underground sources of drinking water is critical for evaluation of confining-bed integ...

  12. Collective motion of squirmers in a quasi-2D geometry

    NASA Astrophysics Data System (ADS)

    ZöTtl, Andreas; Stark, Holger

    2013-03-01

    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.

  13. Confinement Driven by Scalar Field in 4d Non Abelian Gauge Theories

    SciTech Connect

    Chabab, Mohamed [LPHEA, Physics Department, Faculty of Science Semlalia, Cadi-Ayyad University, 40000-Marrakech (Morocco)

    2007-01-12

    We review some of the most recent work on confinement in 4d gauge theories with a massive scalar field (dilaton). Emphasis is put on the derivation of confining analytical solutions to the Coulomb problem versus dilaton effective couplings to gauge terms. It is shown that these effective theories can be relevant to model quark confinement and may shed some light on confinement mechanism. Moreover, the study of interquark potential, derived from Dick Model, in the heavy meson sector proves that phenomenological investigation of tmechanism is more than justified and deserves more efforts.

  14. Native American geometry

    NSDL National Science Digital Library

    2007-12-12

    This website focuses on Native American use of the physical, proportional geometry that originates from the simple circle. Aimed at 4th to 9th grade teachers, the site is divided into four sections: foundations, anthropology, designs, and education. It was selected by Britannica.com, February 2000, as a best Internet site. Other keywords: geometric shapes, geometric constructions, proportional geometry, proportional constants, polygons, hexagons, equilateral triangles, dodecagons, squares, octagons, connect the dot, art, square roots, irrational numbers, non-random geometry. (Includes about 25 relevant website links and 50 published references)

  15. Influence of Geometry and Flow Variation on Jet Mixing and NO Formation in a Model Staged Combustor Mixer with Eight Orifices

    NASA Technical Reports Server (NTRS)

    Samuelsen, G. S.; Sowa, W. A.; Hatch, M. S.

    1996-01-01

    A series of non-reacting parametric experiments was conducted to investigate the effect of geometric and flow variations on mixing of cold jets in an axis-symmetric, heated cross flow. The confined, cylindrical geometries tested represent the quick mix region of a Rich-Burn/Quick-Mix/Lean-Burn (RQL) combustor. The experiments show that orifice geometry and jet to mainstream momentum-flux ratio significantly impact the mixing characteristic of jets in a cylindrical cross stream. A computational code was used to extrapolate the results of the non-reacting experiments to reacting conditions in order to examine the nitric oxide (NO) formation potential of the configurations examined. The results show that the rate of NO formation is highest immediately downstream of the injection plane. For a given momentum-flux ratio, the orifice geometry that mixes effectively in both the immediate vicinity of the injection plane, and in the wall regions at downstream locations, has the potential to produce the lowest NO emissions. The results suggest that further study may not necessarily lead to a universal guideline for designing a low NO mixer. Instead, an assessment of each application may be required to determine the optimum combination of momentum-flux ratio and orifice geometry to minimize NO formation. Experiments at reacting conditions are needed to verify the present results.

  16. Detection of confinement and jumps in single-molecule membrane trajectories

    NASA Astrophysics Data System (ADS)

    Meilhac, N.; Le Guyader, L.; Salomé, L.; Destainville, N.

    2006-01-01

    We propose a variant of the algorithm by [R. Simson, E. D. Sheets, and K. Jacobson, Biophys. 69, 989 (1995)]. Their algorithm was developed to detect transient confinement zones in experimental single-particle tracking trajectories of diffusing membrane proteins or lipids. We show that our algorithm is able to detect confinement in a wider class of confining potential shapes than that of Simson Furthermore, it enables to detect not only temporary confinement but also jumps between confinement zones. Jumps are predicted by membrane skeleton fence and picket models. In the case of experimental trajectories of ? -opioid receptors, which belong to the family of G-protein-coupled receptors involved in a signal transduction pathway, this algorithm confirms that confinement cannot be explained solely by rigid fences.

  17. Capillary Condensation in Confined Media

    Microsoft Academic Search

    Elisabeth Charlaix; Matteo Ciccotti

    2009-01-01

    We review here the physics of capillary condensation of liquids in confined media, with a special regard to the application in nanotechnologies. The thermodynamics of capillary condensation and thin film adsorption are first exposed along with all the relevant notions. The focus is then shifted to the modelling of capillary forces, to their measurements techniques (including SFA, AFM and crack

  18. Confined Fluids as Strain Meters

    Microsoft Academic Search

    Gunnar Bodvarsson

    1970-01-01

    Earth dilatations due to earth tides and seismic waves cause periodic fluctuations of the fluid pressure within saturated porous formations. Pressures and water levels in wells that are connected with sufficiently confined subsurface fluids are also affected and provide a means of obtaining quantitative data on the earth strain. A theory is given of strain-induced pressure fluctuations in a well-aquifer

  19. Inertial confinement fusion (ICF) review

    SciTech Connect

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

    1996-03-01

    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.

  20. Psychiatric Effects of Solitary Confinement

    Microsoft Academic Search

    Stuart Grassian

    2006-01-01

    The author, Dr. Grassian, is a Board Certified Psychiatrist who was on the faculty of the Harvard Medical School for over twenty-five years. He has had extensive experience in evaluating the psychiatric effects of solitary confinement, and in the course of his professional involvement, has been involved as an expert regarding the psychiatric impact of federal and state segregation and

  1. String Theory and Quark Confinement

    E-print Network

    A. Polyakov

    1997-11-01

    This article is based on a talk given at the ``Strings'97'' conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed.

  2. Momentum Confinement at Low Torque

    SciTech Connect

    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

    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.

  3. Flex Circuitry for Confined Spaces

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, J. B.; Maier, L. C.

    1986-01-01

    To facilitate installation of electronic equipment in confined spaces, circuitry preassembled on flexible wiring. Mother boards, large bypass capacitors, and interface connectors mounted on flexible wiring and tested before installation. Flexible circuits eliminate need for in-place hardwiring and allow smaller enclosures to be used.

  4. Deriving confinement via RG decimations

    E-print Network

    E. T. Tomboulis

    2007-10-10

    We present the general framework and building blocks of a recent derivation of the fact that the SU(2) LGT is in a confining phase for all values of the coupling $0 decimations that are shown to constrain the exact partition function and order parameters from above and below, and flow from the weak to the strong coupling regime without encountering a fixed point.

  5. Scaling behaviour for the water transport in nanoconfined geometries

    PubMed Central

    Chiavazzo, Eliodoro; Fasano, Matteo; Asinari, Pietro; Decuzzi, Paolo

    2014-01-01

    The transport of water in nanoconfined geometries is different from bulk phase and has tremendous implications in nanotechnology and biotechnology. Here molecular dynamics is used to compute the self-diffusion coefficient D of water within nanopores, around nanoparticles, carbon nanotubes and proteins. For almost 60 different cases, D is found to scale linearly with the sole parameter ? as D(?)=DB[1+(DC/DB?1)?], with DB and DC the bulk and totally confined diffusion of water, respectively. The parameter ? is primarily influenced by geometry and represents the ratio between the confined and total water volumes. The D(?) relationship is interpreted within the thermodynamics of supercooled water. As an example, such relationship is shown to accurately predict the relaxometric response of contrast agents for magnetic resonance imaging. The D(?) relationship can help in interpreting the transport of water molecules under nanoconfined conditions and tailoring nanostructures with precise modulation of water mobility. PMID:24699509

  6. Scaling behaviour for the water transport in nanoconfined geometries

    NASA Astrophysics Data System (ADS)

    Chiavazzo, Eliodoro; Fasano, Matteo; Asinari, Pietro; Decuzzi, Paolo

    2014-04-01

    The transport of water in nanoconfined geometries is different from bulk phase and has tremendous implications in nanotechnology and biotechnology. Here molecular dynamics is used to compute the self-diffusion coefficient D of water within nanopores, around nanoparticles, carbon nanotubes and proteins. For almost 60 different cases, D is found to scale linearly with the sole parameter ? as D(?)=DB[1+(DC/DB-1)?], with DB and DC the bulk and totally confined diffusion of water, respectively. The parameter ? is primarily influenced by geometry and represents the ratio between the confined and total water volumes. The D(?) relationship is interpreted within the thermodynamics of supercooled water. As an example, such relationship is shown to accurately predict the relaxometric response of contrast agents for magnetic resonance imaging. The D(?) relationship can help in interpreting the transport of water molecules under nanoconfined conditions and tailoring nanostructures with precise modulation of water mobility.

  7. Stark effect on a geometry defined by a cake' slice

    E-print Network

    Reyes-Esqueda, J A; Castillo-Mussot, M; Vazquez, G J; Reyes-Esqueda, Jorge-Alejandro; Mendoza, Carlos I.; Castillo-Mussot, Marcelo del; Vazquez, Gerardo J.

    2005-01-01

    By using a variational calculation, we study the effect of an external applied electric field on the ground state of electrons confined in a quantum box with a geometry defined by a slice of a cake. This geometry is a first approximation for a tip of a cantilever of an Atomic Force Microscope (AFM). By modeling the tip with the slice, we calculate the electronic ground state energy as function of the slice's diameter, its angular aperture, its thickness and the intensity of the external electric field applied along the slice. For the applied field pointing to the wider part of the slice, a confining electronic effect in the opposite side is clearly observed. This effect is sharper as the angular slice's aperture is smaller and there is more radial space to manifest itself.

  8. Stark effect on a geometry defined by a cake' slice

    E-print Network

    Jorge-Alejandro Reyes-Esqueda; Carlos I. Mendoza; Marcelo del Castillo-Mussot; Gerardo J. Vazquez

    2006-02-23

    By using a variational calculation, we study the effect of an external applied electric field on the ground state of electrons confined in a quantum box with a geometry defined by a slice of a cake. This geometry is a first approximation for a tip of a cantilever of an Atomic Force Microscope (AFM). By modeling the tip with the slice, we calculate the electronic ground state energy as function of the slice's diameter, its angular aperture, its thickness and the intensity of the external electric field applied along the slice. For the applied field pointing to the wider part of the slice, a confining electronic effect in the opposite side is clearly observed. This effect is sharper as the angular slice's aperture is smaller and there is more radial space to manifest itself.

  9. Gingerbread-House Geometry.

    ERIC Educational Resources Information Center

    Emenaker, Charles E.

    1999-01-01

    Describes a sixth-grade interdisciplinary geometry unit based on Charles Dickens's "A Christmas Carol". Focuses on finding area, volume, and perimeter, and working with estimation, decimals, and fractions in the context of making gingerbread houses. (ASK)

  10. Functional Differential Geometry

    E-print Network

    Sussman, Gerald Jay

    2005-02-02

    Differential geometry is deceptively simple. It is surprisingly easyto get the right answer with unclear and informal symbol manipulation.To address this problem we use computer programs to communicate aprecise understanding ...

  11. Geometry (MathPages)

    NSDL National Science Digital Library

    Brown, Kevin

    "Informal notes" by Kevin Brown on geometry: constructing the heptadecagon, what mirrors do, the golden pentagon, the grazing goat and the lune, Napoleon's theorem, chess boards, Diophantine geodesic boxes, Zeno's mice and the logarithmic spiral, and many more.

  12. Geometry and Science Fiction

    ERIC Educational Resources Information Center

    Potter, Gretchen

    1976-01-01

    After a unit on Euclidean geometry which stresses both the development of intuition and the use of deductive methods, non-Euclidean concepts are introduced by having students read and consider science fiction stories. (SD)

  13. Droplet microfluidics driven by gradients of confinement.

    PubMed

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

    2013-01-15

    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

  14. Hydrodynamic instabilities in inertial confinement fusion

    SciTech Connect

    Hoffman, N.M.

    1994-12-01

    The focus of the paper is on buoyancy-driven instabilities of the Rayleigh-Taylor type, which are commonly regarded as the most important kind of hydrodynamic instability in inertial-confinement-fusion implosions. The paper is intended to be pedagogical rather than research-oriented, and so is by no means a comprehensive review of work in this field. Rather, it is hoped that the student will find here a foundation on which to build an understanding of current research, and the experienced researcher will find a compilation of useful results. The aim of the paper is to discuss the evolution of a single Rayleigh-Taylor-unstable mode, from its linear phase to its late-stage constant-velocity bubble growth, with a brief consideration of the saturation of linear growth. The influence of other modes in invoked only in the short-range sense (in wavenumber space) of the Haan saturation model. Owing to limitations of space, the treatment of other instabilities such as Richtmyer-Meshkov and Kelvin-Helmholtz is necessarily very brief, and entirely inadequate as an introductory discussion. Likewise, there is no reference to the effect of convergent geometry, to long-range mode coupling, or to shape effects in three-dimensional growth. Furthermore, there is no reference to the large body of experimental research related to hydrodynamic instabilities.

  15. Azimuthal field instability in a confined ferrofluid

    NASA Astrophysics Data System (ADS)

    Dias, Eduardo O.; Miranda, José A.

    2015-02-01

    We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.

  16. Droplet microfluidics driven by gradients of confinement

    PubMed Central

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

    2013-01-01

    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

  17. Geometry without Topology

    Microsoft Academic Search

    Yuri A. Rylov

    2000-01-01

    The proper Euclidean geometry is considered to be metric space and described\\u000ain terms of only metric and finite metric subspaces (sigma-immanent\\u000adescription). Constructing the geometry, one does not use topology and\\u000atopological properties. For instance, the straight, passing through points A\\u000aand B, is defined as a set of such points R that the area S(A,B,R) of the\\u000atriangle

  18. Quantum Computation as Geometry

    E-print Network

    Michael A. Nielsen; Mark R. Dowling; Mile Gu; Andrew C. Doherty

    2006-03-21

    Quantum computers hold great promise, but it remains a challenge to find efficient quantum circuits that solve interesting computational problems. We show that finding optimal quantum circuits is essentially equivalent to finding the shortest path between two points in a certain curved geometry. By recasting the problem of finding quantum circuits as a geometric problem, we open up the possibility of using the mathematical techniques of Riemannian geometry to suggest new quantum algorithms, or to prove limitations on the power of quantum computers.

  19. Non-Euclidean Geometry

    Microsoft Academic Search

    José Natário

    \\u000a In this chapter we discuss the non-Euclidean geometry of curved surfaces, using the sphere as our primary example. We find\\u000a that all the information about the geometry of the surface is contained in the expression for the distance between two nearby\\u000a points in some coordinate system, called the metric. For example, the distance between two distant points can be found

  20. Ion separation effects in mixed-species ablators for inertial-confinement-fusion implosions

    NASA Astrophysics Data System (ADS)

    Amendt, Peter; Bellei, Claudio; Ross, J. Steven; Salmonson, Jay

    2015-02-01

    Recent efforts to demonstrate significant self-heating of the fuel and eventual ignition at the National Ignition Facility make use of plastic (CH) ablators [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014), 10.1063/1.4874330]. Mainline simulation techniques for modeling CH capsule implosions treat the ablator as an average-atom fluid and neglect potential species separation phenomena. The mass-ablation process for a mixture is shown to lead to the potential for species separation, parasitic energy loss according to thermodynamic arguments, and reduced rocket efficiency. A generalized plasma barometric formula for a multispecies concentration gradient that includes collisionality and steady flows in spherical geometry is presented. A model based on plasma expansion into a vacuum is used to interpret reported experimental evidence for ablator species separation in an inertial-confinement-fusion target [J. S. Ross et al., Rev. Sci. Instrum. 83, 10E323 (2012)]. The possibility of "runaway" hydrogen ions in the thermoelectric field of the ablation front is conjectured.

  1. 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.

  2. SOC and Fractal Geometry

    NASA Astrophysics Data System (ADS)

    McAteer, R. T. J.

    2013-06-01

    When Mandelbrot, the father of modern fractal geometry, made this seemingly obvious statement he was trying to show that we should move out of our comfortable Euclidean space and adopt a fractal approach to geometry. The concepts and mathematical tools of fractal geometry provides insight into natural physical systems that Euclidean tools cannot do. The benet from applying fractal geometry to studies of Self-Organized Criticality (SOC) are even greater. SOC and fractal geometry share concepts of dynamic n-body interactions, apparent non-predictability, self-similarity, and an approach to global statistics in space and time that make these two areas into naturally paired research techniques. Further, the iterative generation techniques used in both SOC models and in fractals mean they share common features and common problems. This chapter explores the strong historical connections between fractal geometry and SOC from both a mathematical and conceptual understanding, explores modern day interactions between these two topics, and discusses how this is likely to evolve into an even stronger link in the near future.

  3. Landscape as a Model: The Importance of Geometry

    PubMed Central

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

    2007-01-01

    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. PMID:17967050

  4. Quantum Computing in Non Euclidean Geometry

    E-print Network

    Germano Resconi; Ignazio Licata

    2009-11-04

    The recent debate on hyper-computation has raised new questions both on the computational abilities of quantum systems and the Church-Turing Thesis role in Physics. We propose here the idea of geometry of effective physical process as the essentially physical notion of computation. In Quantum mechanics we cannot use the traditional Euclidean geometry but we introduce more sophisticate non Euclidean geometry which include a new kind of information diffuse in the entire universe and that we can represent as Fisher information or active information. We remark that from the Fisher information we can obtain the Bohm and Hiley quantum potential and the classical Schrodinger equation. We can see the quantum phenomena do not affect a limited region of the space but is reflected in a change of the geometry of all the universe. In conclusion any local physical change or physical process is reflected in all the universe by the change of its geometry, This is the deepest meaning of the entanglement in Quantum mechanics and quantum computing. We stress the connection between metric and information as measure of change. Because computation is not restricted to calculus but is the environment changing via physical processes, super-Turing potentialities derive from an incomputable information source embedded into the geometry of the universe in accordance with Bell's constraints. In the general relativity we define the geometry of the space time. In our approach quantum phenomena define the geometry of the parameters of the probability distribution that include also the space time parameters. To study this new approach to the computation we use the new theory of Morphogenic systems.

  5. Nonlinear stability of rotating plasmas in a mirror geometry

    Microsoft Academic Search

    A. Y. Aydemir

    2006-01-01

    In a previous work, we studied the magnetohydrodynamic (MHD) equilibrium and stability of a mirror plasma in which a strong azimuthal rotation is driven by an externally applied radial electric field^1. Although the interchange-stabilization through flow-shear^2 was confirmed, centrifugally confined ``detached states'' obtained in this geometry were found to be linearly unstable to a wide range of other fluid modes

  6. Structure and catalytic activities of ferrous centers confined on the interface between carbon nanotubes and humic acid.

    PubMed

    Wang, Bing; Zhou, Xiaoyan; Wang, Dongqi; Yin, Jun-Jie; Chen, Hanqing; Gao, Xingfa; Zhang, Jing; Ibrahim, Kurash; Chai, Zhifang; Feng, Weiyue; Zhao, Yuliang

    2015-01-28

    Preparation of heterogeneous catalysts with active ferrous centers is of great significance for industrial and environmental catalytic processes. Nanostructured carbon materials (NCM), which possess free-flowing ? electrons, can coordinate with transition metals, provide a confinement environment for catalysis, and act as potential supports or ligands to construct analogous complexes. However, designing such catalysts using NCM is still seldom studied to date. Herein, we synthesized a sandwich structured ternary complex via the coordination of Fe-loaded humic acid (HA) with C[double bond, length as m-dash]C bonds in the aromatic rings of carbon nanotubes (CNTs), in which the O/N-Fe-C interface configuration provides the confinement environment for the ferrous sites. The experimental and theoretical results revealed octahedrally/tetrahedrally coordinated geometry at Fe centers, and the strong hybridization between CNT C ?* and Fe 3d orbitals induces discretization of the atomic charges on aromatic rings of CNTs, which facilitates O2 adsorption and electron transfer from carbon to O2, which enhances O2 activation. The O2 activation by the novel HA/Fe-CNT complex can be applied in the oxidative degradation of phenol red (PR) and bisphenol A (BPA) in aqueous media. PMID:25580558

  7. Theory of supercoupling, squeezing wave energy, and field confinement in narrow channels and tight bends using ? near-zero metamaterials

    NASA Astrophysics Data System (ADS)

    Silveirinha, Mário G.; Engheta, Nader

    2007-12-01

    In this work, we investigate the detailed theory of the supercoupling, anomalous tunneling effect, and field confinement originally identified by Silveirinha and Engheta [Phys. Rev. Lett. 97, 157403 (2006)], where we demonstrated the possibility of using materials with permittivity ? near zero to drastically improve the transmission of electromagnetic energy through a narrow irregular channel with very subwavelength transverse cross section. Here, we present additional physical insights, describe applications of the tunneling effect in relevant waveguide scenarios (e.g., the “perfect” or “super” waveguide coupling), and study the effect of metal losses in the metallic walls and the possibility of using near-zero ? materials to confine energy in a subwavelength cavity with gigantic field enhancement. In addition, we systematically study the propagation of electromagnetic waves through narrow channels filled with anisotropic near-zero ? materials. It is demonstrated that these materials may have interesting potentials, and that for some particular geometries, the reflectivity of the channel is independent of the specific dimensions or parameters of near-zero ? transition. We also describe several realistic metamaterial implementations of the studied problems, based on standard metallic waveguides, microstrip line configurations, and wire media.

  8. Inertial-Electrostatic Confinement (IEC) Fusion for Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using EEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois@Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  9. Inertial-Electrostatic Confinement (IEC) Fusion For Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using IEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois @ Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  10. Multiple reentrant glass transitions in confined hard-sphere glasses

    E-print Network

    S. Mandal; S. Lang; M. Gross; M. Oettel; D. Raabe; T. Franosch; F. Varnik

    2014-06-20

    Glass forming liquids exhibit a rich phenomenology upon confinement. This is often related to the effects arising from wall-fluid interactions. Here we focus on the interesting limit where the separation of the confining walls becomes of the order of a few particle diameters. For a moderately polydisperse, densely packed hard-sphere fluid confined between two smooth hard walls, we show via event-driven molecular dynamics simulations the emergence of a multiple reentrant glass transition scenario upon a variation of the wall separation. Using thermodynamic relations, this reentrant phenomenon is shown to persist also under constant chemical potential. This allows straightforward experimental investigation and opens the way to a variety of applications in micro- and nanotechnology, where channel dimensions are comparable to the size of the contained particles. The results are in-line with theoretical predictions obtained by a combination of density functional theory and the mode-coupling theory of the glass transition.

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

    SciTech Connect

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

    1996-03-01

    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.

  12. Confinement of electron plasma by levitating dipole magnet

    SciTech Connect

    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

    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.

  13. Multiple reentrant glass transitions in confined hard-sphere glasses

    NASA Astrophysics Data System (ADS)

    Mandal, Suvendu; Lang, Simon; Gross, Markus; Oettel, Martin; Raabe, Dierk; Franosch, Thomas; Varnik, Fathollah

    2014-07-01

    Glass-forming liquids exhibit a rich phenomenology upon confinement. This is often related to the effects arising from wall-fluid interactions. Here we focus on the interesting limit where the separation of the confining walls becomes of the order of a few particle diameters. For a moderately polydisperse, densely packed hard-sphere fluid confined between two smooth hard walls, we show via event-driven molecular dynamics simulations the emergence of a multiple reentrant glass transition scenario upon a variation of the wall separation. Using thermodynamic relations, this reentrant phenomenon is shown to persist also under constant chemical potential. This allows straightforward experimental investigation and opens the way to a variety of applications in micro- and nanotechnology, where channel dimensions are comparable to the size of the contained particles. The results are in line with theoretical predictions obtained by a combination of density functional theory and the mode-coupling theory of the glass transition.

  14. Silica nanoparticle suspensions under confinement of thin liquid films.

    PubMed

    Zeng, Yan; Schön, Sebastian; von Klitzing, Regine

    2015-07-01

    The paper deals with the effect of geometrical confinement on the structuring of Silica nanoparticle suspensions in thin films. The confinement is produced by a Colloidal Probe AFM. Approaching of the two outer surface leads to oscillatory forces. The force profile reflects the pair correlation function and its period the average distance between the nanoparticles under confinement. The nanoparticle structuring is compared to the particle distribution in bulk by small angle X-ray scattering (SAXS). The SAXS structure factor which presents the Fourier transform of the pair correlation function gives the same interparticle distance for the bulk as the oscillation period of the AFM force curves. The distance scales with particle number density ? as ?(-1/3) and is very robust against different suspension parameters (nanoparticle size, ionic strength) and parameters of the outer surfaces (surface potential, roughness and elasticity). PMID:25823979

  15. Multiple reentrant glass transitions in confined hard-sphere glasses.

    PubMed

    Mandal, Suvendu; Lang, Simon; Gross, Markus; Oettel, Martin; Raabe, Dierk; Franosch, Thomas; Varnik, Fathollah

    2014-01-01

    Glass-forming liquids exhibit a rich phenomenology upon confinement. This is often related to the effects arising from wall-fluid interactions. Here we focus on the interesting limit where the separation of the confining walls becomes of the order of a few particle diameters. For a moderately polydisperse, densely packed hard-sphere fluid confined between two smooth hard walls, we show via event-driven molecular dynamics simulations the emergence of a multiple reentrant glass transition scenario upon a variation of the wall separation. Using thermodynamic relations, this reentrant phenomenon is shown to persist also under constant chemical potential. This allows straightforward experimental investigation and opens the way to a variety of applications in micro- and nanotechnology, where channel dimensions are comparable to the size of the contained particles. The results are in line with theoretical predictions obtained by a combination of density functional theory and the mode-coupling theory of the glass transition. PMID:25033741

  16. Quantum chromodynamics near the confinement limit

    SciTech Connect

    Quigg, C.

    1985-09-01

    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.

  17. Deuterium anions in inertial electrostatic confinement devices

    NASA Astrophysics Data System (ADS)

    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

    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.

  18. Deuterium anions in inertial electrostatic confinement devices.

    PubMed

    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

    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

  19. The Importance of Radial Electric Fields in Magnetic Confinement

    SciTech Connect

    Oost, Guido van [Ghent University (Belgium)

    2004-03-15

    The importance of radial electric fields was already recognised early in the research on controlled thermonuclear fusion. An initial description of electric field effects in toroidal confinement was given by Budker{sup 1} Such a configuration with combined magnetic and electric confinement ('magnetoelectric confinement', where the electric field provides a toroidal equilibrium configuration without rotational transform) was studied by Stix{sup 2}, who suggested that a reactor-grade plasma under magnetoelectric confinement (electric fields of order 1 MV/cm) may reach a quasi-steady-state with ambipolar loss of electrons and some suprathermal ions (e.g. 3.5 MeV {alpha}-particles). Experiments such as on the Electric Field Bumpy Torus EFBT{sup 3,4} provided quite favourable scaling for particle confinement. The possible importance of radial electric fields for transport was in the past repeatedly established{sup 5,6,7,8}. Since the early days the plasma potential has been measured in tokamaks such as ST{sup 9}, TM-4{sup 10} and ISX-B{sup 11}, but because no significant effects of the radial electric field E{sub r} on plasma transport were observed, no further research was conducted in tokamaks.

  20. Shape and Current Profile Effects on Runaway Electron Confinement

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    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.

  1. A double-layer based model of ion confinement in electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Mascali, D.; Neri, L.; Celona, L.; Castro, G.; Torrisi, G.; Gammino, S.; Sorbello, G.; Ciavola, G.

    2014-02-01

    The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this "barrier" confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.

  2. BOOK REVIEW: Instabilities in a confined plasma

    NASA Astrophysics Data System (ADS)

    Glasser, A. H.

    1999-05-01

    This is a large and important work by one of the leading Russian contributors to this subject. It covers topics of central importance to magnetic fusion energy research with a breadth, depth and clarity not found elsewhere. It is intended as a reference book and guide to the original literature for serious practitioners of the field. The book is divided into 8 large parts, listed below, and further subdivided into 31 chapters. The preface states, ``A need was identified to summarize the large amount of information on the topic of instabilities. This information is scattered throughout many papers on certain special subjects on the theory of toroidal-plasma instabilities. This book aims to treat it from a unified point of view.'' This is a good description of the aims and approach. The range of topics is large and the treatment deep and thorough. This is often accomplished by assuming considerable knowledge on the part of the reader, most appropriate for mature researchers in the field. The pace is fast. The requisite background includes extensive knowledge of a wide range of physics, ordinary and partial differential equations, integral equations, differential geometry and special functions. The preface also states, ``The author starts with the fundamental principles, so that no special knowledge of plasma physics is necessary before reading the book. It will therefore be useful for researchers, postgraduates, high-school teachers and students specializing in plasma physics and controlled fusion.'' In the opinion of this reviewer, that may be overly ambitious. The terse approach, characteristic of the whole book, as well as the steep price, would make it rather challenging for such an audience. For example, in the opening chapter, `General results of equilibrium theory', the properties of non-orthogonal, curvilinear co-ordinates are stated tersely without much explanation or derivation, more as a review than a first presentation. It is common for physics students, at least in the USA, to encounter this material first in a course on general relativity, which they might not have taken previously when specializing in plasma physics. While good efforts are made by the author to provide an intuitive understanding of the many analytical results, this is often done with such brevity that a substantial level of maturity is required to comprehend the ideas. Another quote from the preface is, ``The book is based on analytical approaches and should therefore be useful for everybody who is interested in the topic.'' In a field where complex geometry and dynamics and the importance of practical results have required much novel and creative computational work over the past 25 years, there is no mention, no acknowledgment, no hint of its importance. The analytical approach presented here certainly fills an important need, and there is no need for the same work to cover numerical work in depth, but some recognition of the importance of numerical work and its relationship with the analytical side of the theory might have been justified. Despite these shortcomings, this book is a major and welcome addition to the literature on plasma instabilities which I heartily recommend. Contents: 1. Equilibrium of a plasma in toroidal confinement systems; 2. Internal magnetohydrodynamic modes in the cylindrical approximation; 3. Small-scale magnetohydrodynamic instabilities in toroidal confinement systems; 4. Magnetohydrodynamic internal kink modes in toroidal geometry; 5. Magnetohydrodynamic modes in collisionless and neoclassical regimes; 6. Drift-magnetohydrodynamic modes; 7. External kink modes; 8. Alfvén eigenmodes and their interaction with high-energy particles; References; Index.

  3. MATH 348 --TOPICS IN GEOMETRY FURTHER READING Euclidean Geometry

    E-print Network

    Do, Norman

    MATH 348 -- TOPICS IN GEOMETRY FURTHER READING Euclidean Geometry The Elements by Euclid://faculty.evansville.edu/ck6/encyclopedia/ETC.html The Geometer's Sketchpad This is a program for drawing Euclidean geometry for drawing Euclidean geometry diagrams which I quite like. Unlike The Geometer's Sketchpad, the full program

  4. Students Discovering Spherical Geometry Using Dynamic Geometry Software

    ERIC Educational Resources Information Center

    Guven, Bulent; Karatas, Ilhan

    2009-01-01

    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…

  5. TOPICAL REVIEW: Biopolymer organization upon confinement

    Microsoft Academic Search

    D. Marenduzzo; C. Micheletti; E. Orlandini

    2010-01-01

    Biopolymers in vivo are typically subject to spatial restraints, either as a result of molecular crowding in the cellular medium or of direct spatial confinement. DNA in living organisms provides a prototypical example of a confined biopolymer. Confinement prompts a number of biophysics questions. For instance, how can the high level of packing be compatible with the necessity to access

  6. Two-electron atoms under spherical confinement

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, S.; Saha, J. K.; Mukhopadhyay, T. K.

    2014-04-01

    The effect of spherical confinement on the ground state of helium-like have been calculated by using correlated Hylleraas basis sets within the variational framework. The thermodynamic pressure on the ions in the ground state due to confinement and the critical values of the confining radii close to fragmentation limit are also estimated.

  7. Soft Confinement for Polymer Solutions

    E-print Network

    Yutaka Oya; Toshihiro Kawakatsu

    2014-05-09

    As a model of soft confinement for polymers, we investigated equilibrium shapes of a flexible vesicle that contains a phase-separating polymer solution. To simulate such a system, we combined the phase field theory (PFT) for the vesicle and the self-consistent field theory (SCFT) for the polymer solution. We observed a transition from a symmetric prolate shape of the vesicle to an asymmetric pear shape induced by the domain structure of the enclosed polymer solution. Moreover, when a non-zero spontaneous curvature of the vesicle is introduced, a re-entrant transition between the prolate and the dumbbell shapes of the vesicle is observed. This re-entrant transition is explained by considering the competition between the loss of conformational entropy and that of translational entropy of polymer chains due to the confinement by the deformable vesicle. This finding is in accordance with the recent experimental result reported by Terasawa, et al.

  8. Influence of confinement on thermodiffusion

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

  9. Physics of magnetic confinement fusion

    NASA Astrophysics Data System (ADS)

    Wagner, F.

    2013-06-01

    Fusion is the energy source of the universe. The local conditions in the core of the Sun allow the transfer of mass into energy, which is finally released in the form of radiation. Technical fusion melts deuterons and tritons to helium releasing large amounts of energy per fusion process. Because of the conditions for fusion, which will be deduced, the fusion fuel is in the plasma state. Here we report on the confinement of fusion plasmas by magnetic fields. Different confinement concepts — tokamaks and stellarators — will be introduced and described. The first fusion reactor, ITER, and the most modern stellarator, Wendelstein 7-X, are under construction. Their basic features and objectives will be presented.

  10. The redemption of singularity confinement

    NASA Astrophysics Data System (ADS)

    Ramani, A.; Grammaticos, B.; Willox, R.; Mase, T.; Kanki, M.

    2015-03-01

    We present a novel way to apply the singularity confinement property as a discrete integrability criterion. We shall use what we call a full deautonomization approach, which consists in treating the free parameters in the mapping as functions of the independent variable, applied to a mapping complemented with terms that are absent in the original mapping but which do not change the singularity structure. We shall show, on a host of examples including the well-known mapping of Hietarinta–Viallet, that our approach offers a way to compute the algebraic entropy for these mappings exactly, thereby allowing one to distinguish between the integrable and non-integrable cases even when both have confined singularities.

  11. Integrable Background Geometries

    NASA Astrophysics Data System (ADS)

    Calderbank, David M. J.

    2014-03-01

    This work has its origins in an attempt to describe systematically the integrable geometries and gauge theories in dimensions one to four related to twistor theory. In each such dimension, there is a nondegenerate integrable geometric structure, governed by a nonlinear integrable differential equation, and each solution of this equation determines a background geometry on which, for any Lie group G, an integrable gauge theory is defined. In four dimensions, the geometry is selfdual conformal geometry and the gauge theory is selfdual Yang-Mills theory, while the lower-dimensional structures are nondegenerate (i.e., non-null) reductions of this. Any solution of the gauge theory on a k-dimensional geometry, such that the gauge group H acts transitively on an ?-manifold, determines a (k+?)-dimensional geometry (k+??4) fibering over the k-dimensional geometry with H as a structure group. In the case of an ?-dimensional group H acting on itself by the regular representation, all (k+?)-dimensional geometries with symmetry group H are locally obtained in this way. This framework unifies and extends known results about dimensional reductions of selfdual conformal geometry and the selfdual Yang-Mills equation, and provides a rich supply of constructive methods. In one dimension, generalized Nahm equations provide a uniform description of four pole isomonodromic deformation problems, and may be related to the {SU}(?) Toda and dKP equations via a hodograph transformation. In two dimensions, the {Diff}(S^1) Hitchin equation is shown to be equivalent to the hyperCR Einstein-Weyl equation, while the {SDiff}(?^2) Hitchin equation leads to a Euclidean analogue of Plebanski's heavenly equations. In three and four dimensions, the constructions of this paper help to organize the huge range of examples of Einstein-Weyl and selfdual spaces in the literature, as well as providing some new ! ones. The nondegenerate reductions have a long ancestry. More ! recently , degenerate or null reductions have attracted increased interest. Two of these reductions and their gauge theories (arguably, the two most significant) are also described.

  12. Supersymmetric strings and colour confinement

    Microsoft Academic Search

    M. Ademollo; L. Brink; A. D'Adda; R. D'Auria; E. Napolitano; S. Sciuto; E. del Giudice; P. di Vecchia; S. Ferrara; F. Gliozzi; R. Musto; R. Pettorino

    1976-01-01

    The (infinite-dimensional) supersymmetry algebra in 1 + 1 space-time dimension is extended in order to incorporate, in a non-trivial way, an internal symmetry. It turns out that this requirement implies that the internal symmetry is realized as a local gauge symmetry. Moreover, it is possible to construct string-like models with this underlying symmetry, where colour confinement is exactly realized as

  13. Gluon confinement and quantum censorship

    E-print Network

    Janos Polonyi

    2010-09-19

    The dynamical Maxwell-cut, a degeneracy is shown to be a precursor of condensate in the phi4 and the sine-Gordon models. The difference of the way the Maxwell-cut is obtained is pointed out and quantum censorship, the generation of semiclassically looking phenomenon by loop-corrections is conjectured in the sine-Gordon model. It is argued that quantum censorship and gluon confinement exclude each other.

  14. Feynman amplitudes with confinement included

    SciTech Connect

    Simonov, Yu. A. [Institute of Theoretical and Experimental Physics (Russian Federation)

    2009-07-15

    Amplitudes for any multipoint Feynman diagram are written taking into account vacuum background confining field. Higher order gluon exchanges are treated within background perturbation theory. For amplitudes with hadrons in initial or final states vertices are shown to be expressed by the corresponding wave function with the renormalized z factors. Examples of two-point functions, three-point functions (form factors), and decay amplitudes are explicitly considered.

  15. Inertial-confinement-fusion targets

    SciTech Connect

    Hendricks, C.D.

    1981-11-16

    Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques have been devised for producing the targets. Glass and metal shells are made by using drop and bubble techniques. Solid hydrogen shells are also produced by adapting old methods to the solution of modern problems. Some of these techniques, problems and solutions are discussed. In addition, the applications of many of the techniques to fabrication of ICF targets is presented.

  16. Split Special Lagrangian Geometry

    E-print Network

    Harvey, F Reese

    2010-01-01

    One purpose of this article is to draw attention to the seminal work of J. Mealy in 1989 on calibrations in semi-riemannian geometry where split SLAG geometry was first introduced. The natural setting is provided by doing geometry with the complex numbers C replaced by the double numbers D, where i with i^2 = -1 is replaced by tau with tau^2 = 1. A rather surprising amount of complex geometry carries over, almost untouched, and this has been the subject of many papers. We briefly review this material and, in particular, we discuss Hermitian D-manifolds with trivial canonical bundle, which provide the background space for the geometry of split SLAG submanifolds. A removable singularities result is proved for split SLAG subvarieties. It implies, in particular, that there exist no split SLAG cones, smooth outside the origin, other than planes. This is in sharp contrast to the complex case. Parallel to the complex case, space-like Lagrangian submanifolds are stationary if and only if they are theta-split SLAG for...

  17. Generalizing Optical Geometry

    E-print Network

    Rickard Jonsson; Hans Westman

    2007-08-21

    We show that by employing the standard projected curvature as a measure of spatial curvature, we can make a certain generalization of optical geometry (Abramowicz and Lasota 1997, Class. Quantum Grav. 14 (1997) A23). This generalization applies to any spacetime that admits a hypersurface orthogonal shearfree congruence of worldlines. This is a somewhat larger class of spacetimes than the conformally static spacetimes assumed in standard optical geometry. In the generalized optical geometry, which in the generic case is time dependent, photons move with unit speed along spatial geodesics and the sideways force experienced by a particle following a spatially straight line is independent of the velocity. Also gyroscopes moving along spatial geodesics do not precess (relative to the forward direction). Gyroscopes that follow a curved spatial trajectory precess according to a very simple law of three-rotation. We also present an inertial force formalism in coordinate representation for this generalization. Furthermore, we show that by employing a new sense of spatial curvature (Jonsson, Class. Quantum Grav. 23 (2006) 1) closely connected to Fermat's principle, we can make a more extensive generalization of optical geometry that applies to arbitrary spacetimes. In general this optical geometry will be time dependent, but still geodesic photons move with unit speed and follow lines that are spatially straight in the new sense. Also, the sideways experienced (comoving) force on a test particle following a line that is straight in the new sense will be independent of the velocity.

  18. Lorentz structure of the confining force in QCD

    NASA Astrophysics Data System (ADS)

    Kalashnikova, Yulia

    1999-02-01

    The effective potential for the heavy quark in the field of static antiquark source is considered. The QCD vacuum is modeled by the bilocal gluonic correlator which provides the area law for the Wilson loop expectation. A Diral-type equation which defines the spectrum of the system is derived, and the effective interaction in the heavy quark limit is found, which appears to be potential with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement. The sub-leading spin-orbit interaction is identified which stems both from Fermi-Breit reduction of the confining force and from the nonlocal corrections to the leading potential regime, with the net effect being in agreement with Eichten-Feinberg-Gromes relations.

  19. An Introduction to Projective Geometry

    NSDL National Science Digital Library

    Birchfield, Stan

    The contents of this paper include: The Projective Plane; Projective Space; Projective Geometry Applied to Computer Vision; Demonstration of Cross Ratio in P^1; and a bibliography. (Euclidean geometry is a subset of projective geometry, and there are two geometries between them: similarity and affine.) Also at http://vision.stanford.edu/~birch/projective/.

  20. Three-Dimensional Geometry and

    E-print Network

    Landweber, Laura

    Three-Dimensional Geometry and Topology William P. Thurston This book was the ori- gin of a grand spaces. To do this, he had to establish the strong connection of geometry to topology--the study- pression "Thurston-type geometry" has become a commonplace. Three-Dimensional Geometry and Topology had its

  1. Geometry, noncommutative algebra and representations

    E-print Network

    Wirosoetisno, Djoko

    Geometry, noncommutative algebra and representations Iain Gordon http://www.maths.ed.ac.uk/~igordon/ University of Edinburgh 16th December 2006 1 Iain Gordon Geometry, noncommutative algebra and representations #12;2 Iain Gordon Geometry, noncommutative algebra and representations #12;Outline 1 Geometry

  2. Topics in Geometry Olga Kharlampovich

    E-print Network

    Kharlampovich, Olga

    . Symmetry in the real world ² Euclidean and non-Euclidean geometry 1. History 2. Plane Euclidean geometry, 3 mathematics, AMS, Mathematical world, Vol. 5, 1996 P.J. Ryan, Euclidean and non-Euclidean geometry. A±ne transformations in the Euclidean plane, 4. Finite groups of isometries of E2 , 5. Geometry

  3. Treatment of confinement in the Faddeev approach to three-quark problems

    E-print Network

    J. McEwen; J. Day; A. Gonzalez; Z. Papp; W. Plessas

    2010-01-22

    A method is presented that allows to solve the Faddeev integral equations of the semirelativistic constituent quark model. In such a model the quark-quark interaction is modeled by a infinitely rising confining potential and the kinetic energy is taken in a relativistic form. We solve the integral equations in Coulomb-Sturmian basis. This basis facilitate an exact treatment of the confining potentials.

  4. Molecule-induced quantum confinement in single-walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Hida, Akira; Ishibashi, Koji

    2015-04-01

    A method of fabricating quantum-confined structures with single-walled carbon nanotubes (SWNTs) has been developed. Scanning tunneling spectroscopy revealed that a parabolic confinement potential appeared when collagen model peptides were attached to both ends of an individual SWNT via the formation of carboxylic anhydrides. On the other hand, the confinement potential was markedly changed by yielding the peptide bonds between the SWNT and the collagen model peptides. Photoluminescence spectroscopy measurements showed that a type-II quantum dot was produced in the obtained heterostructure.

  5. Geometry and Cloaking Devices

    NASA Astrophysics Data System (ADS)

    Ochiai, T.; Nacher, J. C.

    2011-09-01

    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.

  6. Strings on Bubbling Geometries

    E-print Network

    Hai Lin; Alexander Morisse; Jonathan P. Shock

    2011-07-27

    We study gauge theory operators which take the form of a product of a trace with a Schur polynomial, and their string theory duals. These states represent strings excited on bubbling AdS geometries which are dual to the Schur polynomials. These geometries generically take the form of multiple annuli in the phase space plane. We study the coherent state wavefunction of the lattice, which labels the trace part of the operator, for a general Young tableau and their dual description on the droplet plane with a general concentric ring pattern. In addition we identify a density matrix over the coherent states on all the geometries within a fixed constraint. This density matrix may be used to calculate the entropy of a given ensemble of operators. We finally recover the BMN string spectrum along the geodesic near any circle from the ansatz of the coherent state wavefunction.

  7. Order in very cold confined plasmas

    SciTech Connect

    Schiffer, J.P. [Argonne National Lab., IL (United States)]|[Univ. of Chicago, Chicago, IL (United States)

    1995-12-31

    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.

  8. Inertial Confinement Fusion R&D and Nuclear Proliferation

    SciTech Connect

    Robert J. Goldston

    2011-04-28

    In a few months, or a few years, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory may achieve fusion gain using 192 powerful lasers to generate x-rays that will compress and heat a small target containing isotopes of hydrogen. This event would mark a major milestone after decades of research on inertial confinement fusion (ICF). It might also mark the beginning of an accelerated global effort to harness fusion energy based on this science and technology. Unlike magnetic confinement fusion (ITER, 2011), in which hot fusion fuel is confined continuously by strong magnetic fields, inertial confinement fusion involves repetitive fusion explosions, taking advantage of some aspects of the science learned from the design and testing of hydrogen bombs. The NIF was built primarily because of the information it would provide on weapons physics, helping the United States to steward its stockpile of nuclear weapons without further underground testing. The U.S. National Academies' National Research Council is now hosting a study to assess the prospects for energy from inertial confinement fusion. While this study has a classified sub-panel on target physics, it has not been charged with examining the potential nuclear proliferation risks associated with ICF R&D. We argue here that this question urgently requires direct and transparent examination, so that means to mitigate risks can be assessed, and the potential residual risks can be balanced against the potential benefits, now being assessed by the NRC. This concern is not new (Holdren, 1978), but its urgency is now higher than ever before.

  9. Geometry in Action

    NSDL National Science Digital Library

    Eppstein, David

    This metasite "collects various areas in which ideas from discrete and computational geometry (meaning mainly low-dimensional Euclidean geometry) meet some real world applications," according to the site's provider, Dr. David Eppstein of the University of California at Irvine. Categories available include Geometric References and Techniques, Design and Manufacturing, Graphics and Visualization, Information Systems, Medicine and Biology, Physical Sciences, Robotics, Other Applications, and Recent Additions. The types of links included are data sets, patents, journal articles, and research pages (note: a few of the links don't work, but overall the site is useful).

  10. Noncommutative Geometry and Arithmetic

    E-print Network

    Matilde Marcolli

    2010-03-18

    This is an overview of recent results aimed at developing a geometry of noncommutative tori with real multiplication, with the purpose of providing a parallel, for real quadratic fields, of the classical theory of elliptic curves with complex multiplication for imaginary quadratic fields. This talk concentrates on two main aspects: the relation of Stark numbers to the geometry of noncommutative tori with real multiplication, and the shadows of modular forms on the noncommutative boundary of modular curves, that is, the moduli space of noncommutative tori. To appear in Proc. ICM 2010.

  11. Proton radiography of PBX 9502 detonation shock dynamics confinement sandwich test

    SciTech Connect

    Aslam, Tariq D [Los Alamos National Laboratory; Jackson, Scott I [Los Alamos National Laboratory; Morris, John S [Los Alamos National Laboratory

    2009-01-01

    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.

  12. Globally aligned states and hydrodynamic traffic jams in confined suspensions of active asymmetric particles.

    PubMed

    Lefauve, Adrien; Saintillan, David

    2014-02-01

    Strongly confined active liquids are subject to unique hydrodynamic interactions due to momentum screening and lubricated friction by the confining walls. Using numerical simulations, we demonstrate that two-dimensional dilute suspensions of fore-aft asymmetric polar swimmers in a Hele-Shaw geometry can exhibit a rich variety of novel phase behaviors depending on particle shape, including coherent polarized density waves with global alignment, persistent counterrotating vortices, density shocks and rarefaction waves. We also explain these phenomena using a linear stability analysis and a nonlinear traffic flow model, both derived from a mean-field kinetic theory. PMID:25353410

  13. Graphene growth under Knudsen molecular flow on a confined catalytic metal coil

    NASA Astrophysics Data System (ADS)

    Bong, Hyojin; Jo, Sae Byeok; Kang, Boseok; Lee, Seong Kyu; Kim, Hyun Ho; Lee, Seung Goo; Cho, Kilwon

    2015-01-01

    We have established a simple method for drastically improving the productivity of chemical vapor deposition in large-area graphene synthesis using a roll-stacked Ni coil as a catalyst. Our systematic investigation of the effects of a confined catalytic geometry has shown that the gas flow through interfacial gaps within the stack follows non-continuum fluid dynamics when the size of the gap decreases sufficiently, which enhances the dissolution of the carbon sources into the catalyst during synthesis. Quantitative criteria for graphene growth in the confined geometry are established through the introduction of the Knudsen number, Kn, which is the ratio of the mean-free-path of the gas molecules to the size of the gap. The criteria provided in this article for the synthesis of graphene in the confined geometry are expected to provide the foundations for the efficient mass production of large-area graphene. We also show that the evolution of the catalytic Ni surface in a stacked system results in larger grains in the (111) plane, and consequently in reproducible, uniform, and high-quality multi-layered graphene.We have established a simple method for drastically improving the productivity of chemical vapor deposition in large-area graphene synthesis using a roll-stacked Ni coil as a catalyst. Our systematic investigation of the effects of a confined catalytic geometry has shown that the gas flow through interfacial gaps within the stack follows non-continuum fluid dynamics when the size of the gap decreases sufficiently, which enhances the dissolution of the carbon sources into the catalyst during synthesis. Quantitative criteria for graphene growth in the confined geometry are established through the introduction of the Knudsen number, Kn, which is the ratio of the mean-free-path of the gas molecules to the size of the gap. The criteria provided in this article for the synthesis of graphene in the confined geometry are expected to provide the foundations for the efficient mass production of large-area graphene. We also show that the evolution of the catalytic Ni surface in a stacked system results in larger grains in the (111) plane, and consequently in reproducible, uniform, and high-quality multi-layered graphene. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04153d

  14. Euclidean geometry as algorithm for construction of generalized geometries

    E-print Network

    Yuri A. Rylov

    2005-11-23

    It is shown that the generalized geometries may be obtained as a deformation of the proper Euclidean geometry. Algorithm of construction of any proposition S of the proper Euclidean geometry E may be described in terms of the Euclidean world function sigma_E in the form S(sigma_E). Replacing the Euclidean world function sigma_E by the world function sigma of the geometry G, one obtains the corresponding proposition S(sigma) of the generalized geometry G. Such a construction of the generalized geometries (known as T-geometries) uses well known algorithms of the proper Euclidean geometry and nothing besides. This method of the geometry construction is very simple and effective. Using T-geometry as the space-time geometry, one can construct the deterministic space-time geometries with primordially stochastic motion of free particles and geometrized particle mass. Such a space-time geometry defined properly (with quantum constant as an attribute of geometry) allows one to explain quantum effects as a result of the statistical description of the stochastic particle motion (without a use of quantum principles).

  15. Weyl Geometries, Fisher Information and Quantum Entropy in Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Fiscaletti, Davide; Licata, Ignazio

    2012-11-01

    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.

  16. Catadioptric Projective Geometry

    Microsoft Academic Search

    Christopher Geyer; Konstantinos Daniilidis

    2001-01-01

    Catadioptric sensors are devices which utilize mirrors and lenses to form a projection onto the image plane of a camera. Central catadioptric sensors are the class of these devices having a single effective viewpoint. In this paper, we propose a unifying model for the projective geometry induced by these devices and we study its properties as well as its practical

  17. Noncommutative Projective Geometry

    Microsoft Academic Search

    J. T. Stafford

    \\u000a The aim of the three lectures I gave at Constanta was to introduce the audience to the theory of “Noncommutative Pro- jective\\u000a Geometry.” The material for these talks was taken from the survey article (6) and so this abstract will give a very brief discussion of this material leaving the reader to see (6) for the details.

  18. Conics and Finite Geometries.

    ERIC Educational Resources Information Center

    Shilgalis, Thomas W.

    1985-01-01

    The results of investigations into finite geometries, prompted by questions raised in a course for secondary school mathematics teachers, are presented. The discussion of points, lines, and incidences led to consideration of graphs of second-degree equations in finite projective planes. (MNS)

  19. Fractal geometry of music.

    PubMed Central

    Hsü, K J; Hsü, A J

    1990-01-01

    Music critics have compared Bach's music to the precision of mathematics. What "mathematics" and what "precision" are the questions for a curious scientist. The purpose of this short note is to suggest that the mathematics is, at least in part, Mandelbrot's fractal geometry and the precision is the deviation from a log-log linear plot. PMID:11607061

  20. Spacetime and Euclidean geometry

    NASA Astrophysics Data System (ADS)

    Brill, Dieter; Jacobson, Ted

    2006-04-01

    Using only the principle of relativity and Euclidean geometry we show in this pedagogical article that the square of proper time or length in a two-dimensional spacetime diagram is proportional to the Euclidean area of the corresponding causal domain. We use this relation to derive the Minkowski line element by two geometric proofs of the spacetime Pythagoras theorem.