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1

Effect of confinement potential geometry on entanglement in quantum dot-based nanostructures  

E-print Network

We calculate the spatial entanglement between two electrons trapped in a nanostructure for a broad class of confinement potentials, including single and double quantum dots, and core-shell quantum dot structures. By using a parametrized confinement potential, we are able to switch from one structure to the others with continuity and to analyze how the entanglement is influenced by the changes in the confinement geometry. We calculate the many-body wave function by `exact' diagonalization of the time independent Schr\\"odinger equation. We discuss the relationship between the entanglement and specific cuts of the wave function, and show that the wave function at a single highly symmetric point could be a good indicator for the entanglement content of the system. We analyze the counterintuitive relationship between spatial entanglement and Coulomb interaction, which connects maxima (minima) of the first to minima (maxima) of the latter. We introduce a potential quantum phase transition which relates quantum states characterized by different spatial topology. Finally we show that by varying shape, range and strength of the confinement potential, it is possible to induce strong and rapid variations of the entanglement between the two electrons. This property may be used to tailor nanostructures according to the level of entanglement required by a specific application.

S. Abdullah; J. P. Coe; I. D'Amico

2009-08-19

2

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

Microsoft Academic Search

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

S. Ashforth-Frost; K. Jambunathan

1996-01-01

3

Freezing in confined geometries  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

4

Reactive collisions in confined geometries  

E-print Network

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.

Idziaszek, Zbigniew; Julienne, Paul S

2014-01-01

5

Reactive collisions in confined geometries  

E-print Network

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.

Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne

2015-02-06

6

Reactive collisions in confined geometries  

E-print Network

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.

Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne

2014-12-08

7

PREFACE: Water in confined geometries  

NASA Astrophysics Data System (ADS)

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.

Rovere, Mauro

2004-11-01

8

Amoeboid motion in confined geometry  

E-print Network

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...

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

2015-01-01

9

Amoeboid motion in confined geometry  

E-print Network

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.

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

2015-02-13

10

Ionic liquids in confined geometries.  

PubMed

Over recent years the Surface Force Apparatus (SFA) has been used to carry out model experiments revealing structural and dynamic properties of ionic liquids confined to thin films. Understanding characteristics such as confinement induced ion layering and lubrication is of primary importance to many applications of ionic liquids, from energy devices to nanoparticle dispersion. This Perspective surveys and compares SFA results from several laboratories as well as simulations and other model experiments. A coherent picture is beginning to emerge of ionic liquids as nano-structured in pores and thin films, and possessing complex dynamic properties. The article covers structure, dynamics, and colloidal forces in confined ionic liquids; ionic liquids are revealed as a class of liquids with unique and useful confinement properties and pertinent future directions of research are highlighted. PMID:22301770

Perkin, Susan

2012-04-21

11

Glass Transition in Confined Geometry  

NASA Astrophysics Data System (ADS)

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 mode-coupling theory 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 transition line as a result of the structural changes related to layering.

Lang, Simon; Bo?an, Vitalie; Oettel, Martin; Hajnal, David; Franosch, Thomas; Schilling, Rolf

2010-09-01

12

Limiting Spectra from Confining Potentials.  

ERIC Educational Resources Information Center

The author explains that, for confining potentials and large quantum numbers, the bound-state energies rise more rapidly as a function of n the more rapidly the potential rises with distance. However, the spectrum can rise no faster than n squared in the nonrelativistic case, or n in the relativistic case. (Author/GA)

Nieto, Michael Martin; Simmons, L. M., Jr.

1979-01-01

13

Dirac equations with confining potentials  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

14

Layer-by-layer assembly in confined geometries  

E-print Network

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 ...

DeRocher, Jonathan P

2011-01-01

15

Temperature-resonant cyclotron spectra in confined geometries  

E-print Network

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.

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

2011-05-22

16

Adsorption potentials for nonplanar geometries  

NASA Astrophysics Data System (ADS)

We present a method to compute, assuming a continuous distribution of sources, the elementary potential created by a differential element of volume of matter, whose integral generates a known adsorption field V(z) for a planar surface. We show that this elementary potential is univocally determined by the original field and can be used to generate adsorption potentials for other nontrivial geometries. We illustrate the method for the Chizmeshya-Cole-Zaremba physisorption potential and discuss several examples and applications.

Hernando, A.; Hernández, E. S.; Mayol, R.; Pi, M.

2007-09-01

17

Helically forced MHD flows in confined cylindrical geometries  

E-print Network

to control MHD flows more efficiently. In this paper we explore the behaviour of a conducting fluidHelically forced MHD flows in confined cylindrical geometries Malcolm Roberts1 , Matthieu Leroy1 the resistive magnetohydrodynamic (MHD) equations. A helical magnetic field is imposed via boundary conditions

Boyer, Edmond

18

Modeling smectic layers in confined geometries: Order parameter and defects  

NASA Astrophysics Data System (ADS)

We identify problems with the standard complex order parameter formalism for smectic-A (SmA) liquid crystals and discuss possible alternative descriptions of smectic order. In particular, we suggest an approach based on the real smectic density variation rather than a complex order parameter. This approach gives reasonable numerical results for the smectic layer configuration and director field in sample geometries and can be used to model smectic liquid crystals under nanoscale confinement for technological applications.

Pevnyi, Mykhailo Y.; Selinger, Jonathan V.; Sluckin, Timothy J.

2014-09-01

19

Dirac Equations with Linear Confining Potentials  

E-print Network

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. It has recently been shown that, despite the addition of radially symmetric, linear confining potentials, some specific bound-state energies surprisingly retain their exact Dirac-Coulomb values (in the sense of an "exact symmetry"). This observation raises pertinent questions as to the generality of the cancellation mechanism. A Foldy-Wouthuysen transformation is used to find the relevant nonrelativistic physical degrees of freedom, which include additional spin-orbit couplings induced by the linear confining potentials. 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 cancellation mechanism. The result of the Foldy-Wouthuysen transformation is used to explicitly show that the cancellation is accidental and 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. Furthermore, we show that the cancellation mechanism does not affect anti-particle (negative-energy) states.

J. H. Noble; U. D. Jentschura

2014-10-03

20

Confinement-dependent localization of diffusing aggregates in cellular geometries  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

21

Binding of two helium atoms in confined geometries  

SciTech Connect

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.

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

22

Superfluid Phases of 3He in a Periodic Confined Geometry  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

23

Critical comparison between magnetic and inertial confinement schemes and their geometries  

SciTech Connect

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

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

1995-05-01

24

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

SciTech Connect

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.

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

2011-03-15

25

Clustering of branching Brownian motions in confined geometries.  

PubMed

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

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

2014-10-01

26

Universal properties of branching random walks in confined geometries  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

27

Clustering of branching Brownian motions in confined geometries  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

28

Polymer escape from a confining potential  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

29

Polymer escape from a confining potential  

SciTech Connect

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.

Mökkönen, Harri, E-mail: harri.mokkonen@aalto.fi [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Ikonen, Timo [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Jónsson, Hannes [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States); Ala-Nissila, Tapio [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States)

2014-02-07

30

A molecular dynamics study of freezing in a confined geometry Wen-Jong Ma and Jayanth R. Banavaf)  

E-print Network

of freezing in restricted geometries. The primary difficulty in analytic studies is that freezing is a complexA molecular dynamics study of freezing in a confined geometry Wen-Jong Ma and Jayanth R. Banavaf in confined geometries is presented. I. INTRODUCTION The properties of liquids and solids confined in very

31

Structure of charged polymer chains in confined geometry.  

SciTech Connect

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.

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

2000-12-15

32

Hertz Potentials and Differential Geometry  

E-print Network

, and I present techniques for introducing gauge terms of arbitrary order. Finally, I give a treatment of one application of Hertz potentials, namely calculating electromagnetic Casimir interactions for a couple of systems....

Bouas, Jeffrey David

2011-08-08

33

FAST TRACK COMMUNICATION: Thermal stability of ionic liquid in confined geometry  

NASA Astrophysics Data System (ADS)

The thermal stability of imidazolium based ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMI][PF6]) in a confined geometry is analysed. It has been found that the decomposition of IL starts at an earlier temperature upon confinement in nanopores. Early decomposition of confined IL is due to the breaking of end group alkyl chains of the [BMI] ring, which is explained by a phenomenological 'hinged spring' model.

Pratap Singh, Manish; Singh, Rajendra Kumar; Chandra, Suresh

2010-03-01

34

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

SciTech Connect

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.

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

35

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

36

Self-assembled morphologies of diblock copolymers confined in nanochannels: Effects of confinement geometry  

Microsoft Academic Search

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,

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

2007-01-01

37

Adsorption and desorption in confined geometries: A discrete hopping model  

NASA Astrophysics Data System (ADS)

We study the adsorption and desorption kinetics of interacting particles moving on a one-dimensional lattice. Confinement is introduced by limiting the number of particles on a lattice site. Adsorption and desorption are found to proceed at different rates, and are strongly influenced by the concentration-dependent transport diffusion. Analytical solutions for the transport and self-diffusion are given for systems of length 1 and 2 and for a zero-range process. In the last situation the self- and transport diffusion can be calculated analytically for any length.

Becker, T.; Nelissen, K.; Cleuren, B.; Partoens, B.; Van den Broeck, C.

2014-12-01

38

Studies of Superfluid 3He Confined to a Regular Submicron Slab Geometry, Using SQUID NMR  

SciTech Connect

The effect on the superfluid ground state of confining p-wave superfluid 3He in regular geometries of characteristic size comparable to the diameter of the Cooper pair remains relatively unexplored, in part because of the demands placed by experiments on the sensitivity of the measuring technique. In this paper we report preliminary experiments aimed at the study of 3He confined to a slab geometry. The NMR response of a series of superfluid samples has been investigated using a SQUID NMR amplifier. The sensitivity of this NMR spectrometer enables samples of order 1017 spins, with low filling factor, to be studied with good resolution.

Casey, Andrew; Corcoles, Antonio; Lusher, Chris; Cowan, Brian; Saunders, John [Department of Physics, Royal Holloway University of London, Egham, Surrey, TW20 0EX (United Kingdom)

2006-09-07

39

Topological superfluids confined in a nanoscale slab geometry  

NASA Astrophysics Data System (ADS)

Nanofluidic samples of superfluid ^3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid ^3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of ^3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe ^3He-B with a surface induced planar distortion. ^3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter.[4pt] In collaboration with L.V. Levitin, R.G. Bennett, A.J. Casey, B. Cowan, J. Parpia, E.V. Surovtsev

Saunders, John

2013-03-01

40

Self-organisation of helically forced MHD flows in confined cylindrical geometries  

E-print Network

and can help to control MHD flows more efficiently. In this paper we explore the behaviour of a conductingSelf-organisation of helically forced MHD flows in confined cylindrical geometries Malcolm Roberts1 to solve the resistive magnetohydrodynamic (MHD) equations. A helical magnetic field is imposed via

Roberts, Malcolm

41

Long-Range Electrostatic Attractions between Identically Charged Particles in Confined Geometries and the  

E-print Network

Long-Range Electrostatic Attractions between Identically Charged Particles in Confined Geometries, 1999 There has been much speculation about the origin of long-range electrostatic attractions between the mechanism behind the phenomenon of long- range electrostatic attraction between identically charged

Chan, Derek Y C

42

Potential Well Structures in Spherical Inertial Electrostatic Confinement Devices  

Microsoft Academic Search

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

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

2005-01-01

43

tt* Geometry and Closed String Tachyon Potential  

NASA Astrophysics Data System (ADS)

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 equations determine the action. We study the particular case of Bbb C/Bbb Z3?Bbb C in detail and find that the Tachyon action is determined in terms of a solution to Painleve III equation.

Dabholkar, Atish; Vafa, Cumrun

2002-02-01

44

Plasmonic mode interactions with organic semiconductor gain media in nano-confined geometries  

NASA Astrophysics Data System (ADS)

Coupling of gain materials to metallic nanostructures and thin films offers an avenue for amplification of plasmonic modes in both confined and extended geometries. In the past decade, a deeply sub-wavelength analogue to the laser, using surface plasmons instead of photons, has been proposed and demonstrated. Additionally, propagating surface plasmon polaritons on extended metallic films have been amplified using gain media to achieve chip-scale propagation lengths. Here, we investigate a core-shell nanoparticle structure amenable to amplification of resonant surface plasmon modes using a gold nanorod as the core and an organic polymer semiconductor gain medium as the shell. Organic semiconducting polymer gain media are of interest because, unlike laser dye molecules, they do not undergo significant concentration quenching in the solid-state and, therefore, can result in a high chromophore density in the optical near-field of the metal nanostructure. For investigations of resonant surface plasmon mode amplification, we fabricate gold nanorod-F8BT core-shell nanoparticles through a miniemulsion synthesis process. A more distinct threshold in emitted intensity as a function of optical pump energy is observed from these hybrid structures and neat F8BT nanoparticles compared to dissolved F8BT molecules. However, spectral narrowing is not observed from these structures, potentially due to the low heterostructure yield and poor spectral overlap between the absorption and emission bands of the F8BT with the pump laser and the longitudinal surface plasmon resonance of the nanorods, respectively. Future work will focus on increasing heterostructure yield, employing a red-emitting gain material such as MEH-PPV to couple to longitudinal surface plasmon modes and alternative thin-film geometries in which plasmonic mode-emitter interactions can be easier to control.

Goodman, Sarah; O'Carroll, Deirdre M.

2014-10-01

45

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

NASA Astrophysics Data System (ADS)

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.

Xu, Jun

46

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

Microsoft Academic Search

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

D. W. Colucci; R. Viskanta

1996-01-01

47

Occupation times of random walks in confined geometries: From random trap model to diffusion limited reactions  

E-print Network

We consider a random walk in confined geometry, starting from a site and eventually reaching a target site. We calculate analytically the distribution of the occupation time on a third site, before reaching the target site. The obtained distribution is exact, and completely explicit in the case or parallepipedic confining domains. We discuss implications of these results in two different fields: The mean first passage time for the random trap model is computed in dimensions greater than 1, and is shown to display a non-trivial dependence with the source and target positions ; The probability of reaction with a given imperfect center before being trapped by another one is also explicitly calculated, revealing a complex dependence both in geometrical and chemical parameters.

S. Condamin; V. Tejedor; O. Benichou

2008-06-03

48

Intervalley coupling by quantum dot confinement potentials in monolayer transition metal dichalcogenides  

NASA Astrophysics Data System (ADS)

Monolayer transition metal dichalcogenides (TMDs) offer new opportunities for realizing quantum dots (QDs) in the ultimate two-dimensional (2D) limit. Given the rich control possibilities of electron valley pseudospin discovered in the monolayers, this quantum degree of freedom can be a promising carrier of information for potential quantum spintronics exploiting single electrons in TMD QDs. An outstanding issue is to identify the degree of valley hybridization, due to the QD confinement, which may significantly change the valley physics in QDs from its form in the 2D bulk. Here we perform a systematic study of the intervalley coupling by QD confinement potentials on extended TMD monolayers. We find that the intervalley coupling in such geometry is generically weak due to the vanishing amplitude of the electron wavefunction at the QD boundary, and hence valley hybridization will be well quenched by the much stronger spin–valley coupling in monolayer TMDs and the QDs can well inherit the valley physics of the 2D bulk. We also discover sensitive dependence of intervalley coupling strength on the central position and the lateral length scales of the confinement potentials, which may possibly allow tuning of intervalley coupling by external controls.

Liu, Gui-Bin; Pang, Hongliang; Yao, Yugui; Yao, Wang

2014-10-01

49

Heavy quarks, gluons and the confinement potential in Coulomb gauge  

SciTech Connect

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

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

2011-05-23

50

Protection from Potential Exposure for the Chernobyl New Safe Confinement  

SciTech Connect

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

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

2004-03-24

51

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

SciTech Connect

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.

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

52

Light-Front Holographic QCD and the Confinement Potential  

NASA Astrophysics Data System (ADS)

Light-Front Hamiltonian theory, derived from the quantization of the QCD Lagrangian at fixed light-front time ?=t+z/c, provides a rigorous frame-independent framework for solving nonperturbative QCD. The eigenvalues of the light-front QCD Hamiltonian predict the hadronic mass spectrum, and the corresponding eigensolutions provide the light-front wavefunctions which describe hadron structure. The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrödinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. In fact, the potential U has a unique form if one requires that the action for zero quark mass remains conformally invariant. We also show that the holographic mapping of gravity in AdS space to QCD with a specific soft-wall dilaton yields the same light-front Schrödinger equation. Light-front holography also leads to a precise relation between the bound-state amplitudes in the fifth dimension z of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The predictions of the LF equations of motion include a zero-mass pion in the chiral mq?0 limit, and linear Regge trajectories M2(n,L)?n+L with the same slope in the radial quantum number n and orbital angular momentum L. The light-front AdS/QCD holographic approach thus gives a frame-independent representation of color-confining dynamics, Regge spectroscopy, and the excitation spectra of relativistic light-quark meson and baryon bound states in QCD in terms of a single mass parameter. We also briefly discuss the implications of the underlying conformal template of QCD for renormalization scale-setting and the implications of light-front quantization for the value of the cosmological constant.

Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter

2014-06-01

53

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

ERIC Educational Resources Information Center

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

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

2012-01-01

54

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

PubMed Central

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

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

2009-01-01

55

Resonant dipole-dipole interaction in confined and strong-coupling dielectric geometries  

NASA Astrophysics Data System (ADS)

Using the electromagnetic response function of an electric dipole located within a dielectric geometry, we derive the mathematical equivalence between the classical response and quantum mechanical resonant dipole-dipole interaction between two quantum objects (atoms, quantum dots, etc). Cooperative spontaneous emission likewise emerges from this equivalence. We introduce a practical numerical technique using finite difference time domain for calculating both dipole-dipole interaction and collective spontaneous emission in confined dielectric structures, where strong light-matter coupling might arise. This method is capable of obtaining resonant dipole-dipole interaction over a wide range of frequencies in a single run. Our method recaptures the results of quantum mechanical second order perturbation theory for weak light-matter coupling. In strong coupling situations such as near a photonic band edge, second order Rayleigh-Schrödinger perturbation theory leads to divergences, and instead Brillouin-Wigner perturbation theory is required. This is equivalent to the use of a variational wavefunction to describe the exciton transfer between initial and final states. We introduce a system of coupled classical oscillators, that describes resonant dipole-dipole interaction and vacuum Rabi splitting in the strong-coupling regime, and that provides an effective numerical scheme based on the finite difference time domain method. This includes the effects of quantum entanglement and the correlation of quantum fluctuations. We discuss the crossover to Forster energy transfer when quantum correlations between the dipoles are damped by strong environmental interactions.

El-Ganainy, Ramy; John, Sajeev

2013-08-01

56

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)

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.

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

2012-06-01

57

Solution of Two-Body Bound State Problems with Confining Potentials  

SciTech Connect

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

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

2010-11-12

58

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

59

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

NASA Astrophysics Data System (ADS)

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.

Dolganov, P. V.; Cluzeau, P.

2014-12-01

60

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

Microsoft Academic Search

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

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

2006-01-01

61

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

62

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)

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.

Ghobadi, Ahmadreza F.; Elliott, J. Richard

2014-09-01

63

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

E-print Network

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

Doyle, Patrick S.

64

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

SciTech Connect

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.

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

65

Spectroscopic results in helium from the NASA Lewis Bumpy Torus plasma. [ion heating by Penning discharge in confinement geometry  

NASA Technical Reports Server (NTRS)

Spectroscopic measurements were carried out on the NASA Lewis Bumpy Torus experiment in which a steady state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. Electron temperatures in pure helium are measured from the ratio of spectral line intensities. Measured electron temperatures range from 10 to 100 eV. Relative electron densities are also measured over the range of operating conditions. Radial profiles of temperature and relative density are measured in the two basic modes of operation of the device called the low and high pressure modes. The electron temperatures are used to estimate particle confinement times based on a steady state particle balance.

Richardson, R. W.

1974-01-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

67

Sensitivity of exciton spin relaxation in quantum dots to confining potential  

Microsoft Academic Search

We observe a strong dependence of the exciton spin relaxation in CdTe quantum dots on the average dot size and the depth of the confining potential. After rapid thermal annealing, which increases the average dot size and leads to weaker confinement, we measure the spin relaxation time of the quantum dot excitons to be 1.5 ns, as compared to 4.8

S. Mackowski; T. Gurung; H. E. Jackson; L. M. Smith; W. Heiss; J. Kossut; G. Karczewski

2005-01-01

68

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

SciTech Connect

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.

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

69

Electrical Double-Layer Interaction between Charged Particles near Surfaces and in Confined Geometries  

E-print Network

Electrical Double-Layer Interaction between Charged Particles near Surfaces and in Confined The proximity effect of one or two flat surfaces on the double- layer interaction between two identically. INTRODUCTION The electrical double-layer interaction between two charged spheres immersed in an unbounded

Chan, Derek Y C

70

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

Microsoft Academic Search

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

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

1997-01-01

71

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

Microsoft Academic Search

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

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

1995-01-01

72

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

SciTech Connect

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.

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

1995-12-31

73

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

PubMed

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

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

2014-08-01

74

Geometry  

NSDL National Science Digital Library

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.

Rusin, Dave

75

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

76

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

E-print Network

We consider a long, semiflexible polymer, with persistence length $P$ and contour length $L$, fluctuating in a narrow cylindrical channel of diameter $D$. In the regime $D\\ll P\\ll L$ the free energy of confinement $\\Delta F$ and the length of the channel $R_\\parallel$ occupied by the polymer are given by Odijk's relations $\\Delta F/R_\\parallel=A_\\circ k_BTP^{-1/3}D^{-2/3}$ and $R_\\parallel=L[1-\\alpha_\\circ(D/P)^{2/3}]$, where $A_\\circ$ and $\\alpha_\\circ$ are dimensionless amplitudes. Using a simulation algorithm inspired by PERM (Pruned Enriched Rosenbluth Method), which yields results for very long polymers, we determine $A_\\circ$ and $\\alpha_\\circ$ and the analogous amplitudes for a channel with a rectangular cross section. For a semiflexible polymer confined to the surface of a cylinder, the corresponding amplitudes are derived with an exact analytic approach. The results are relevant for interpreting experiments on biopolymers in microchannels or microfluidic devices.

Yingzi Yang; Theodore W. Burkhardt; Gerhard Gompper

2007-04-19

77

Simulation method for resonant light scattering of exciton confined to arbitrary geometry.  

PubMed

We develop an electromagnetic (EM) simulation method based on a finite-element method (FEM) for an exciton confined to a semiconductor nanostructure. The EM field inside the semiconductor excites two transverse exciton polariton and a single longitudinal exciton at a given frequency. Established EM simulation methods cannot be applied directly to semiconductor nanostructures because of this multimode excitation; however, the present method overcomes this difficulty by introducing an additional boundary condition. To avoid spurious solutions and enhance the precision, we propose a hybrid edge-nodal element formulation in which edge and nodal elements are employed to represent the transverse and longitudinal polarizations, respectively. We apply the developed method to the EM-field scattering and distributions of exciton polarizations of spherical and hexagonal-disk quantum dots. PMID:24787834

Uemoto, Mitsuharu; Ajiki, Hiroshi

2014-04-21

78

Electron leakage through magnetic cusps in the polywell (tradename) confinement geometry  

SciTech Connect

The approach taken here is to proceed from a relatively simple model to a more complex description, examining each one in turn. The first model relates to the computer calculations of Maffei, in which electrons of constant energy are reflected by cusp mirror magnetic fields on the faces of a truncated cube, but no electric field is present. The analytic model invoked here for this system analyzes a single face cusp of a truncated cube configuration as representative of the complete polyhedral pattern. Electron reflection coefficients, losses and other features and characteristics of this single-face model are found to give good agreement with the results of the Monte Carlo calculation; conditions for low loss rates are indicated. These analyses are all limited to single particle behavior, the basic cusp mirror reflection mode of electron confinement.

Bussard, R.W.; Krall, N.A.

1991-02-01

79

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

NASA Astrophysics Data System (ADS)

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.

Sussman, Daniel M.; Schweizer, Kenneth S.

2011-10-01

80

A POTENTIAL ALGORITHM FOR TARGET CLASSIFICATION IN BISTATIC SONAR GEOMETRIES  

Microsoft Academic Search

The recent evolution in oceanographic sensing and platforms, including the availability of Autonomous Underwater Vehicles (AUVs), is encouraging the investigation of new high-resolution sonar concepts based on multistatic geometries. The rationale behind this concept is that multistatic systems, in particular if the geometry can be adapted with the experiment, can be located in the regions where the scattered signal is

MARIO COSCI; ANDREA CAITI; PHILIPPE BLONDEL; NISABHA JAYASUNDERE

81

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

PubMed

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

Aydemir, Erdo?an; Ulas, Abdullah

2011-02-15

82

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

PubMed

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

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

2015-02-01

83

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

84

Effect of external fields on the energies of hydrogenic donor with the anharmonic confinement potential  

NASA Astrophysics Data System (ADS)

The impurity binding energy in the GaAs -Ga1-xAlx As system is studied with an anharmonic type confinement potential by taking into account the influence of the external electric and magnetic fields within the framework of the effective mass approximation and asymptotic iteration method (AIM). The influence of the external electromagnetic fields and anharmonicity on a donor binding energy is examined systematically. It is shown that the donor binding energy is highly dependent on the external electric and magnetic fields and the confinement potential shapes. Both the electric and magnetic fields are increased, the binding energies increase for each of them. However, the behaviors of increase in the weak and strong fields' regimes have different character a bit. Furthermore, when the more anharmonicity is considered, the binding energy of donor slightly increases as well.

Aciksoz, E.; Bayrak, O.; Soylu, A.

2015-01-01

85

Analytic eigenenergies of Dirac equation under a confining linear potential using basis functions localized in spacetime  

E-print Network

This paper presents analytical eigenenergies for a pair of confined fundamental fermion and antifermion under a linear potential derived from the Wilson loop for the non-Abelian Yang-Mills field. We use basis functions localized in spacetime, and the Hamiltonian matrix of the Dirac equation is analytically diagonalized. 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.

Fukushima, Kimichika

2015-01-01

86

Analytic eigenenergies of Dirac equation under a confining linear potential using basis functions localized in spacetime  

E-print Network

This paper presents analytical eigenenergies for a pair of confined fundamental fermion and antifermion under a linear potential derived from the Wilson loop for the non-Abelian Yang-Mills field. We use basis functions localized in spacetime, and the Hamiltonian matrix of the Dirac equation is analytically diagonalized. 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.

Kimichika Fukushima; Hikaru Sato

2015-01-20

87

Analytic eigenenergies of Dirac equation under a confining linear potential using basis functions localized in spacetime  

E-print Network

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.

Kimichika Fukushima; Hikaru Sato

2015-01-26

88

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

SciTech Connect

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.

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

89

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

90

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

SciTech Connect

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

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

1992-10-01

91

Transforming potential and matrix stiffness co-regulate confinement sensitivity of tumor cell migration  

PubMed Central

It is now well established that tumor cell invasion through tissue is strongly regulated by the microstructural and mechanical properties of the extracellular matrix (ECM). However, it remains unclear how these physical microenvironmental inputs are jointly processed with oncogenic lesions to drive invasion. In this study, we address this open question by combining a microfabricated polyacrylamide channel (?PAC) platform that enables independent control of ECM stiffness and confinement with an isogenically-matched breast tumor progression series in which the oncogenes ErbB2 and 14-3-3? are overexpressed independently or in tandem. We find that increasing channel confinement and overexpressing ErbB2 both promote cell migration to a similar degree when other parameters are kept constant. In contrast, 14-3-3? overexpression slows migration speed, and does so in a fashion that dwarfs effects of ECM confinement and stiffness. We also find that ECM stiffness dramatically enhances cell motility when combined with ErbB2 overexpression, demonstrating that biophysical cues and cell-intrinsic parameters promote cell invasion in an integrative manner. Morphometric analysis of cells inside the ?PAC platform reveals that the rapid cell migration induced by narrow channels and ErbB2 overexpression both are accompanied by increased cell polarization. Disruption of this polarization by pharmacological inhibition of Rac GTPase phenocopies 14-3-3? overexpression by reducing cell polarization and slowing migration. By systematically measuring migration speed as a function of matrix stiffness and confinement, we also quantify for the first time the sensitivity of migration speed to microchannel properties and transforming potential. These results demonstrate that oncogenic lesions and ECM biophysical properties can synergistically interact to drive invasive migration, and that both inputs may act through common molecular mechanisms to enhance migration speed. PMID:23832051

Pathak, Amit

2013-01-01

92

Geometry and earthquake potential of the shoreline fault, central California  

USGS Publications Warehouse

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.

Hardebeck, Jeanne L.

2013-01-01

93

Deriving geological contact geometry from potential field data  

NASA Astrophysics Data System (ADS)

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.

Ugalde, Hernan; Morris, William A.

2010-02-01

94

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

E-print Network

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. ...

Low, Guang Hao

95

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

NASA Astrophysics Data System (ADS)

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.

Moradi, M.; Hashemi, S.

2011-11-01

96

Spectral geometry of power-law potentials in quantum mechanics  

NASA Astrophysics Data System (ADS)

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.

Hall, Richard L.

1989-06-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

98

Selective Metallization of Well Aligned PS-b-P2VP Block Copolymers in Thin Films and in Confined Geometries  

Microsoft Academic Search

Well aligned, microphase-separated structures of styrene-2-vinylpyridine block copolymers are being used as templates for macromolecule-metal nanocomposites. These composites are either prepared as thin films or confined in nanoporous aluminum oxide membranes. Under optimal conditions, templates are prepared as thin films or confined nanorods and metallized without disturbing the ordered structure. We have developed a procedure that deposits metal within the

James D. Sievert; James J. Watkins; Thomas P. Russell

2006-01-01

99

Exploring the potential high energy locations and intensities in confined work spaces of waveguide dimensions  

NASA Astrophysics Data System (ADS)

Adequately identifying and managing hazards at the workplace can be a tedious task which extends into the realm of uncertainty, probability and prediction models in order to fully comprehend the nature of the hazard. As such, organizations cannot be blamed for knowledge gaps in the training of personnel they contract to ensure a safe and healthy work environment, especially where there are latent hazards. Electromagnetic wave propagation at frequencies in the SAR (specific absorption rate) region is a special concern to authorities involved in setting RF (radiofrequency) and microwave exposure guidelines. Despite that there is no conclusive evidence to suggest that non-ionizing electromagnetic radiation causes adverse health effects other than thermal, no effort should be lost to ensure that workers and the public at large are adequately protected from unnecessary exposure to radiation. Standards however set exposure limits for free space, plane wave propagation but fall short in compiling information on intensities of these waves after they undergo reflection and diffraction from wall surfaces. Waveguide technology has managed to constrain microwaves to remain within set boundaries, with fixed frequencies that force the waves to behave differently to if they were moving in free space. This technology has offered the ability to transport more energy for communication purposes other than transmission lines. The size of a waveguide may be to the order of a few centimetres and can guide RF of wavelengths of the order of centimetres also but what if spaces of larger dimensions are capable of being waveguides and can guide waves of larger wavelengths such as those that correspond to frequencies between 30MHz to 300MHz? Such RF waves belong to the SAR region of the spectrum where strict exposure limits are set for health and safety protection since a standing man acts as a dipole antenna for this radiation and can absorb maximum energy from propagating RF waves. This review visits the likelihood for potential energy build-up due to RF propagation in confined spaces that are of waveguide design but with larger dimensions. Such confined spaces include silos, tanks, pipes, manholes, air-condition ducts, tunnels, wells, engine rooms and operator rooms on board vessels. In these confined spaces waves reflect off of the walls and combine constructively or destructively with incident waves producing reinforcement or cancellation respectively. Where there is reinforcement, the intensity of the wave for a particular distance in accordance with the standard, may exceed the exposure limit for this distance from the source thereby exposing the worker to larger intensities than the accepted limit and presenting a potential health and safety threat.

Rodriguez, Ricardo; Lewis, Winston G.

2014-07-01

100

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

101

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

Microsoft Academic Search

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

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

2005-01-01

102

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

PubMed

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

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

2012-11-21

103

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

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

104

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

SciTech Connect

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

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

2010-08-01

105

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

PubMed

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

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

2015-01-14

106

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

107

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

108

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

PubMed

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

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

2014-01-01

109

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

Microsoft Academic Search

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

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

1995-01-01

110

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

PubMed Central

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

Chen, A.; Sooryakumar, R.

2013-01-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

112

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

E-print Network

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.

Rossen Dandoloff; Avadh Saxena; Bjorn Jensen

2009-12-11

113

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

NASA Astrophysics Data System (ADS)

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.

Kushwaha, Manvir S.

2014-12-01

114

POTENTIAL OF CONFINED ANIMAL FEED OPERATIONS (CAFOS) TO CONTRIBUTE ESTROGENS TO THE ENVIRONMENT  

EPA Science Inventory

Confined Animal Feed Operations (CAFOs) are a growing industry, with a trend towards fewer operations with higher concentrations of animals. Animals are either fed and/or treated with many different types of pharmaceuticals, including antibiotics and hormones, which can end up in...

115

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

Microsoft Academic Search

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

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

2005-01-01

116

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

PubMed

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

K, Rohini; Swathi, R S

2013-07-18

117

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

E-print Network

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.

Nigel Cundy; Yongmin Cho; Weonjong Lee

2014-11-04

118

A three-dimensional potential-flow program with a geometry package for input data generation  

NASA Technical Reports Server (NTRS)

Information needed to run a computer program for the calculation of the potential flow about arbitrary three dimensional lifting configurations is presented. The program contains a geometry package which greatly reduces the task of preparing the input data. Starting from a very sparse set of coordinate data, the program automatically augments and redistributes the coordinates, calculates curves of intersection between components, and redistributes coordinates in the regions adjacent to the intersection curves in a suitable manner for use in the potential flow calculations. A brief summary of the program capabilities and options is given, as well as detailed instructions for the data input, a suggested structure for the program overlay, and the output for two test cases.

Halsey, N. D.

1978-01-01

119

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

USGS Publications Warehouse

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.

Magirl, Christopher S.; Olsen, Theresa D.

2009-01-01

120

Yukawa particles confined in a channel and subject to a periodic potential: ground state and normal modes  

E-print Network

We consider a classical system of two-dimensional (2D) charged particles, which interact through a repulsive Yukawa potential $exp(-r/\\lambda)/r$, confined in a parabolic channel which limits the motion of the particles in the $y$-direction. Along the $x$-direction, the particles are also subject to a periodic potential substrate. The ground state configurations and the normal mode spectra of the system are obtained as function of the periodicity and strength of the periodic potential ($V_0$), and density. An interesting set of tunable ground state configurations are found, with first and second order structural transitions between them. A magic configuration with particles aligned in each minimum of the periodic potential is obtained for V_0 larger than some critical value which has a power law dependence on the density. The phonon spectrum of different configurations were also calculated. A localization of the modes into a small frequency interval is observed for a sufficient strength of the periodic potential. A tunable band-gap is found as a function of $V_0$. This model system can be viewed as a generalization of the Frenkel and Kontorova model.

J. C. N. Carvalho; W. P. Ferreira; G. A. Farias; F. M. Peeters

2010-06-10

121

Yukawa particles confined in a channel and subject to a periodic potential: Ground state and normal modes  

NASA Astrophysics Data System (ADS)

We consider a classical system of two-dimensional (2D) charged particles, interacting through a repulsive Yukawa potential exp(-r/?)/r, and confined in a parabolic channel that limits the motion of the particles in the y direction. Along the x direction, the particles are subject to a periodic potential. The ground-state configurations and the normal-mode spectra of the system are obtained as a function of the periodicity and strength of the periodic potential (V0) and density. An interesting set of tunable ground-state configurations are found, with first- or second-order structural transitions between them. A configuration with particles aligned, perpendicular to the x direction, in each minimum of the periodic potential is obtained for V0 larger than some critical value that has a power-law dependence on the density. The phonon spectrum of different configurations was also calculated. A localization of the modes into a small frequency interval is observed for sufficiently large strength of the periodic potential, and a tunable gap in the phonon spectrum is found as a function of V0.

Carvalho, J. C. N.; Ferreira, W. P.; Farias, G. A.; Peeters, F. M.

2011-03-01

122

Modelling smectics in confined geometries  

Microsoft Academic Search

We examine a continuum theory for smectic liquid crystals which allows some variation in the smectic layer spacing as well as the director tilt. The theory can model configurations beyond the scope of a constant director tilt approach. Two applications of the continuum description are discussed. The first models equilibrium configurations of a planar smectic C cell, where a variation

G McKay

2004-01-01

123

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

PubMed

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 N(1/(? + 1)), where ? is the power-law exponent, and a function periodic in N(1/3). The amplitude of the fluctuating component, which originates mostly from the irregular dependence of the Thomson energy E(Th)(n) on n, also scales like N(1/(? + 1)). PMID:24050343

Cioslowski, Jerzy; Albin, Joanna

2013-09-14

124

Persistent currents in a two-component Bose–Einstein condensate confined in a ring potential  

NASA Astrophysics Data System (ADS)

We present variational and numerical solutions for the problem of stability of persistent currents in a two-component Bose–Einstein condensate of distinguishable atoms which rotate in a ring potential. We consider the general class of solutions of constant density in the two components separately, thus providing an alternative approach to the solution of the same problem given recently by Wu and Zaremba (2013 Phys. Rev. A 88 063640). Our approach provides a physically transparent solution for this delicate problem. Finally, we give a unified and simple picture of the lowest energy state of the system for large values of the coupling.

Smyrnakis, J.; Magiropoulos, M.; Efremidis, Nikolaos K.; Kavoulakis, G. M.

2014-11-01

125

Reduced neutron spectroscopic factors when using potential geometries constrained by Hartree-Fock calculations  

E-print Network

We carry out a systematic analysis of angular distribution measurements for selected ground-state to ground-state (d,p) and (p,d) neutron transfer reactions, including the calcium isotopes. We propose a consistent three-body model reaction methodology in which we constrain the transferred-neutron bound state and nucleon-target optical potential geometries using modern Hartree-Fock calculations. Our deduced neutron spectroscopic factors are found to be suppressed by ~30% relative to independent-particle shell-model values, from 40Ca through 49Ca. The other nuclei studied, ranging from B to Ti, show similar average suppressions with respect to large-basis shell-model expectations. Our results are consistent with deduced spectroscopic strengths for neutrons and protons from intermediate energy nucleon knockout reactions, and for protons from (e,e'p) reactions, on well-bound nuclei. PACS: 24.50.+g, 24.10.Eq, 25.40.-h, 25.45.-z

Jenny Lee; J. A. Tostevin; B. A. Brown; F. Delaunay; W. G. Lynch; M. J. Saelim; M. B. Tsang

2006-01-27

126

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

127

Anomalous magnetotransport properties of a ballistic non-interacting three-dimensional electron gas confined to narrow potential wells with corrugated barriers  

SciTech Connect

The classical dynamics of ballistic non-interacting electrons confined to a narrow electrostatic potential well with corrugated barriers in uniform magnetic field was numerically studied. Trajectories in phase space were analyzed and longitudinal and transversal resistivities were calculated. Commensurability oscillations and negative magnetoresistance similar to those found in antidot lattice devices were observed.

Sotomayor, N. M.; Davila, L. Y. D.; Lima, B. C. [Universidade Federal do Tocantins, Campus de Araguaina, Araguaina TO (Brazil); Gusev, G. M. [Instituto de Física da Universidade de São Paulo, 135960-170, São Paulo, SP (Brazil)

2013-12-04

128

High Resolution Spatio-temporal Detection of Potentially Harmful Dinoflagellates in Confined Waters of the NW Mediterranean  

Microsoft Academic Search

A systematic sampling programme was carried out in a large number of confined waters (principally harbours) along the Catalan coast (NW Mediterranean) in the context of a new Monitoring Pro- gramme. This Monitoring Programme was associated not only with areas subject to aquaculture activities, and therefore under legislation, but also with confined areas with a high risk of harmful algal

MAGDA VILA; JORDI CAMP; ESTHER GARCÉS; MERCEDES MASÓ; MAXIMINO DELGADO

2001-01-01

129

Internal geometry, seismic facies, and petroleum potential of canyons and inner fan channels of the Indus submarine fan  

SciTech Connect

The Indus Fan, the second largest submarine fan in the world, covers 1,250,000 km/sup 2/ (500,000 mi/sup 2/) and contains sediment more than 7 km (23,000 ft) thick. Multichannel (24-fold) CDP seismic data provide the bases for evaluating the Indus Fan and consist of four seismic facies. Of these, only the high-amplitude, discontinuous (H-D) facies is thought to contain reservoir-quality sandstones. The H-D facies is confined to the axes of leveed channels. Canyon-channel systems that fed the fan in the past can be divided into three zones. The degradational zone is composed of an erosional canyon complex filled by prodelta mud. The transitional zone, located near the canyon mouth, consists of superimposed channels that initially were erosional but eventually aggraded and developed levees. The headward termination of the H-D facies occurs in this zone. The aggradational zone consists of superimposed leveed channels confined solely by their own levees. The proximal termination of the H-D facies near canyon mouths implies the presence of reservoir-quality sandstone surrounded by source/seal mudstone in the transitional zone. This stratigraphic trapping geometry and structural leads may represent a vast, untapped petroleum province.

McHargue, T.R.; Webb, J.E.

1986-02-01

130

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

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

131

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

SciTech Connect

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.

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

132

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)

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.

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

2014-12-01

133

Extreme sensitivity of the spin-splitting and 0.7 anomaly to confining potential in one-dimensional nanoelectronic devices.  

PubMed

Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron many-body effects such as the 0.7 × 2e(2)/h anomaly. We report on the dependence of the 1D Landé g-factor g and 0.7 anomaly on electron density and confinement in QPCs with two different top-gate architectures. We obtain g values up to 2.8 for the lowest 1D subband, significantly exceeding previous in-plane g-factor values in AlGaAs/GaAs QPCs and approaching that in InGaAs/InP QPCs. We show that g is highly sensitive to confinement potential, particularly for the lowest 1D subband. This suggests careful management of the QPC's confinement potential may enable the high g desirable for spintronic applications without resorting to narrow-gap materials such as InAs or InSb. The 0.7 anomaly and zero-bias peak are also highly sensitive to confining potential, explaining the conflicting density dependencies of the 0.7 anomaly in the literature. PMID:22830617

Burke, A M; Klochan, O; Farrer, I; Ritchie, D A; Hamilton, A R; Micolich, A P

2012-09-12

134

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

Microsoft Academic Search

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

Michael Filatov; Dieter Cremer

2003-01-01

135

Race, Poverty, and Potential Exposure of Middle-School Students to Air Emissions from Confined Swine Feeding Operations  

PubMed Central

Previous studies suggest that airborne effluent from swine confined animal feeding operations (CAFOs) may affect the health and quality of life of adults and the prevalence of asthma symptoms among children. To investigate the extent to which public school students may be exposed to airborne effluent from swine CAFOs and to evaluate the association between schools’ demographic characteristics and swine CAFO exposures, we assessed the proximity of 226 schools to the nearest swine CAFO and conducted a survey of school employees to identify schools with noticeable livestock odor. We used publicly available information describing the enrollment of each school to assess the association between race and socioeconomic status (SES) and swine CAFO exposure. Odor from livestock was noticeable outside (n = 47, 21%) and inside (n = 19, 8%) school buildings. Schools with < 63% enrollment of white students and ?47% of students receiving subsidized lunches at school were located closer to swine CAFOs (mean = 4.9 miles) than were the remaining schools (mean = 10.8 miles) and were more likely to be located within 3 miles of an operation than were schools with high-white/high-SES enrollment (prevalence ratio = 2.63; 95% confidence interval, 1.59–4.33). The prevalence of reported livestock odor varied with SES (low SES, 25%; high SES, 17%). These analyses indicate that the potential for in-school exposure to pollution arising from swine CAFOs in North Carolina and the environmental health risks associated with such exposures vary according to the racial and economic characteristics of enrolled students. PMID:16581551

Mirabelli, Maria C.; Wing, Steve; Marshall, Stephen W.; Wilcosky, Timothy C.

2006-01-01

136

Turbulence in Magnetically Confined Plasmas  

NASA Astrophysics Data System (ADS)

Experimental characterization of plasma fluctuations has lead to significant insights into the dynamics of turbulent transport processes in magnetically confined fusion plasmas. Fluctuations on the scale of the ion gyroradius result in cross-field transport of particles, energy and momentum at rates that significantly exceed collisional (neoclassical) transport. The energy confinement time and, ultimately, fusion power are thus strongly dependent on this turbulent-driven transport. Turbulent eddy structures are found to be highly anisotropic (k||k), with the magnetic field defining a symmetry direction: parallel wavelengths scale with machine size, while perpendicular wavelengths scale with gyroradius. Measurement techniques using optical, microwave, beam, and laser-based methods have been developed to remotely probe relevant fluctuations in density, temperature, potential and velocity, including density imaging. Measured fluctuation characteristics are generally consistent with gyrokinetic simulations of drift wave turbulence: correlation lengths scale with ion gyroradius (?I); amplitudes scale with &*circ;(=?I/a); decorrelation rates scale with the acoustic timescale, ?c˜a/cs; and wavenumber spectra peak near k??I˜0.25 and kr?I˜0. Measurements of potential fluctuations and poloidal turbulence flows show evidence for n=0, m=0 zonal flows, including the coherent geodesic acoustic mode. These nonlinearly driven flows saturate turbulence via flow shearing. Such flows appear crucial to L-H confinement transitions and core barrier formation. Dependencies of turbulence on critical transport parameters will be reviewed in tokamak, stellarator and spherical torus geometries. Understanding these dependencies, as well as challenging and validating simulations, will be crucial to confidently predicting transport and confinement in burning plasmas.

McKee, G. R.

2012-10-01

137

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

Microsoft Academic Search

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

M. A. “Curt” Koenders; Steffen Reymann

2000-01-01

138

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

USGS Publications Warehouse

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.

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

2000-01-01

139

Symplectic Geometry Metric geometry  

E-print Network

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

Wolpert, Scott A.

140

Using Transmural Regularization and Dynamic Modeling for Non-Invasive Cardiac Potential Imaging of Endocardial Pacing with Imprecise Thoracic Geometry  

PubMed Central

Cardiac electrical imaging from body surface potential measurements is increasingly being seen as a technology with the potential for use in the clinic, for example for pre-procedure planning or during-treatment guidance for ventricular arrhythmia ablation procedures. However several important impediments to widespread adoption of this technology remain to be effectively overcome. Here we address two of these impediments: the difficulty of reconstructing electric potentials on the inner (endocardial) as well as outer (epicardial) surfaces of the ventricles, and the need for full anatomical imaging of the subject’s thorax to build an accurate subject-specific geometry. We introduce two new features in our reconstruction algorithm: a non-linear low-order dynamic parameterization derived from the measured body surface signals, and a technique to jointly regularize both surfaces. With these methodological innovations in combination, it is possible to reconstruct endocardial activation from clinically acquired measurements with an imprecise thorax geometry. In particular we test the method using body surface potentials acquired from three subjects during clinical procedures where the subjects’ hearts were paced on their endocardia using a catheter device. Our geometric models were constructed using a set of CT scans limited in axial extent to the immediate region near the heart. The catheter system provides a reference location to which we compare our results. We compare our estimates of pacing site localization, in terms of both accuracy and stability, to those reported in a recent clinical publication [1], where a full set of CT scans were available and only epicardial potentials were reconstructed. PMID:24595345

Erem, Burak; Coll-Font, Jaume; Orellana, Ramon Martinez; Štóví?ek, Petr; Brooks, Dana H.

2014-01-01

141

On the nonminimal vector coupling in the Duffin-Kemmer-Petiau theory and the confinement of massive bosons by a linear potential  

E-print Network

Vector couplings in the Duffin-Kemmer-Petiau theory are revised. It is shown that minimal and nonminimal vector potentials behave differently under charge-conjugation and time-reversal transformations. In particular, it is shown that nonminimal vector potentials have been erroneously applied to the description of elastic meson-nucleus scatterings and that the space component of the nonminimal vector potential plays a crucial role for the confinement of bosons. The DKP equation with nonminimal vector linear potentials is mapped into the nonrelativistic harmonic oscillator problem and the behavior of the solutions for this sort of DKP oscillator is discussed in detail. Furthermore, the absence of Klein's paradox and the localization of bosons in the presence of nonminimal vector interactions are discussed.

Cardoso, T R; De Castro, A S

2009-01-01

142

On the Geometry of the Dirac Matter with the Fermionic Potentials and its Quantum Properties  

NASA Astrophysics Data System (ADS)

We consider the torsional completion of gravity with electrodynamics for Dirac matter fields; we will see that these Dirac matter field equations will develop torsionally-induced non-linear interactions, which can be manipulated in order to be rearranged in the form of self-fermion potentials of a specific structure: we will see that this structure is formally equivalent to the one arising from quantum properties.

Fabbri, Luca

2014-11-01

143

Electrostatic Patch Effect in Cylindrical Geometry. I. Potential and Energy between Slightly Non-Coaxial Cylinders  

E-print Network

We study the effect of any uneven voltage distribution on two close cylindrical conductors with parallel axes that are slightly shifted in the radial and by any length in the axial direction. The investigation is especially motivated by certain precision measurements, such as the Satellite Test of the Equivalence Principle (STEP). By energy conservation, the force can be found as the energy gradient in the vector of the shift, which requires determining potential distribution and energy in the gap. The boundary value problem for the potential is solved, and energy is thus found to the second order in the small transverse shift, and to lowest order in the gap to cylinder radius ratio. The energy consists of three parts: the usual capacitor part due to the uniform potential difference, the one coming from the interaction between the voltage patches and the uniform voltage difference, and the energy of patch interaction, entirely independent of the uniform voltage. Patch effect forces and torques in the cylindrical configuration are derived and analyzed in the next two parts of this work.

Valerio Ferroni; Alexander Silbergleit

2010-09-16

144

Modeling of high-order terms in potential energy surface expansions using the reference-geometry Harris-Foulkes method.  

PubMed

The reference-geometry Harris-Foulkes (RGHF) approach has been used to model high-order terms within the expansion of multi-dimensional potential energy surfaces (PES) as needed within the calculation of accurate vibrational frequencies beyond the harmonic approximation. The key step of this method is a localization of the electron density to the atoms of the molecule at a given reference structure and a subsequent transfer of these atom-centered partial densities to the atom positions of distorted structures. This concept has been used to evaluate the 3-mode coupling terms of a multi-mode expansion of the PES as arising in the Watson Hamiltonian. Systematic benchmark calculations for vibrational frequencies obtained from vibrational configuration interaction (VCI) theory have been performed in order to study the effects of this approximation on the fundamental modes of a test suite of 28 molecules. PMID:23525154

Meier, Patrick; Bellchambers, Greg; Klepp, Julian; Manby, Frederick R; Rauhut, Guntram

2013-07-01

145

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

Microsoft Academic Search

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

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

2005-01-01

146

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

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

Dhar, Jayabrata; Ghosh, Uddipta; Chakraborty, Suman

2014-03-01

147

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

SciTech Connect

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

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

2010-08-15

148

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

PubMed

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

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

2015-01-14

149

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

SciTech Connect

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.

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

1993-12-01

150

Dynamics of potentially harmful microalgae in a confined Mediterranean Gulf—Assessing the risk of bloom formation  

Microsoft Academic Search

The population dynamics of potentially harmful microalgae was investigated in the semi-enclosed shallow Gulf of Kalloni, Greece (Aegean Sea, Eastern Mediterranean), during a 2-year period from August 2004 to March 2006. A total of 21 potentially harmful microalgae (bloom-forming and\\/or toxic) were identified including 3 diatoms and 18 dinoflagellates. The densities of each species were analyzed in time and space

Sofie Spatharis; Nicolas P. Dolapsakis; Athena Economou-Amilli; George Tsirtsis; Daniel B. Danielidis

2009-01-01

151

Guiding and confining light in void nanostructure  

Microsoft Academic Search

We present a novel waveguide geometry for enhancing and confining light in a nanometer-wide low-index material. Light enhancement and confinement is caused by large discontinuity of the electric field at high- index-contrast interfaces. We show that by use of such a structure the field can be confined in a 50-nm-wide low-index region with a normalized intensity of 20 mm 22

Vilson R. Almeida; Qianfan Xu; Carlos A. Barrios; Michal Lipson

2004-01-01

152

Tropical geometric interpretation of ultradiscrete singularity confinement  

NASA Astrophysics Data System (ADS)

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.

Ormerod, Christopher M.

2013-08-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

154

A quantum-mechanical description of ion motion within the confining potentials of voltage-gated ion channels.  

PubMed

Voltage-gated channel proteins cooperate in the transmission of membrane potentials between nerve cells. With the recent progress in atomic-scaled biological chemistry, it has now become established that these channel proteins provide highly correlated atomic environments that may maintain electronic coherences even at warm temperatures. Here we demonstrate solutions of the Schrödinger equation that represent the interaction of a single potassium ion within the surrounding carbonyl dipoles in the Berneche-Roux model of the bacterial KcsA model channel. We show that, depending on the surrounding carbonyl-derived potentials, alkali ions can become highly delocalized in the filter region of proteins at warm temperatures. We provide estimations on the temporal evolution of the kinetic energy of ions depending on their interaction with other ions, their location within the oxygen cage of the proteins filter region, and depending on different oscillation frequencies of the surrounding carbonyl groups. Our results provide the first evidence that quantum mechanical properties are needed to explain a fundamental biological property such as ion selectivity in transmembrane ion currents and the effect on gating kinetics and shaping of classical conductances in electrically excitable cells. PMID:22744820

Summhammer, Johann; Salari, Vahid; Bernroider, Gustav

2012-06-01

155

Confined Brownian ratchets  

E-print Network

We analyze the dynamics of Brownian ratchets in a confined environment. The motion of the particles is described by a Fick-Jakobs kinetic equation in which the presence of boundaries is modeled by means of an entropic potential. The cases of a flashing ratchet, a two-state model and a ratchet under the influence of a temperature gradient are analyzed in detail. We show the emergence of a strong cooperativity between the inherent rectification of the ratchet mechanism and the entropic bias of the fluctuations caused by spatial confinement. Net particle transport may take place in situations where none of those mechanisms leads to rectification when acting individually. The combined rectification mechanisms may lead to bidirectional transport and to new routes to segregation phenomena. Confined Brownian ratchets (CBR) could be used to control transport in mesostructures and to engineer new and more efficient devices for transport at the nanoscale.

Malgaretti, Paolo; Rubi, J Miguel

2013-01-01

156

A reactive transport model for the geochemical response, detection and potential mitigation of CO2 leakage into a confined aquifer  

NASA Astrophysics Data System (ADS)

Long-term storage of anthropogenic CO2 in the subsurface generally assumes that caprock formations will serve as physical barriers to upward migration of CO2. Stability and coherence of the caprocks are thus important criteria for site selection, but caprock integritycannot be guaranteed with total certainty over the lifetime of the project. As a result, carbon capture and storage projects require reliable techniques to monitor geologic storage sites for newly formed leaks, and the ability to rapidly deploy mitigation measures should leakage occur. Here, we present two-dimensional reactive transport simulations to evaluate the hydrogeochemical characteristics of a newly formed CO2 leak into an overlying reservoir. Simulations use the ToughReact multi-component reactive transport code and hypothetical reservoir characteristics. We focus on the comparatively short time period of days to months following formation of the leak to consider (1) geochemical shifts in formation water indicative of the leak, (2) hydrodynamics of pumping wells in the vicinity of the leak, and (3) delivery of a sealant to the leak through an adjacent well bore. Our results suggest that characteristic shifts in pH and dissolved inorganic carbon might be detected in down-gradient mentoring wells prior to the breakthrough of CO2, and could offer a potential means of identifying small and newly formed leaks. Injecting water into the aquifer through pumping wells in the vicinity of the leak provides a hydrodynamic control that can prevent CO2 from reaching the top of the reservoir, but this action will likely have only minor influence on the rate of leakage through the caprock defect. Injection of a hypothetical sealant through an adjacent pumping well is considered using an aqueous solute with pH-dependent equilibrium constraints such that the species is soluble in the basic pH range but forms a precipitate at neutral to acidic pH conditions associated with CO2-rich water. Injection of this species in an alkaline fluid allows for delivery of the sealant to the edge of the CO2 plume where the sharp decrease in pH is leveraged to facilitate precipitation. Our results indicate that the solubilized sealant can be delivered to the edge of the plume and high rates of precipitation are achieved. However, the sealant is not able to reach the interior of the plume unless the leakage rate is extremely small, thus delivery to the precise location of the caprock defect within the plume is significantly more challenging.

Maher, K.; Druhan, J. L.; Vialle, S.; Benson, S. M.; Agarwal, A.

2013-12-01

157

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

PubMed

The gradient for the fragment molecular orbital (FMO) method interfaced with effective fragment potentials (EFP), denoted by FMO?EFP, was developed and applied to polypeptides solvated in water. The structures of neutral and zwitterionic tetraglycine immersed in water layers of 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5 A? are investigated by performing FMO?EFP geometry optimizations at the RHF?cc-pVDZ level of theory for the solutes. The geometries optimized with FMO-RHF?EFP are compared to those from the conventional RHF?EFP and are found to be in very close agreement. Using the optimized geometries, the stability of the hydrated zwitterionic and neutral structures is discussed structurally and in terms of energetics at the second-order Møller-Plesset theory (MP2)?cc-pVDZ level. To demonstrate the potential of the method for proteins, the geometry of hydrated chignolin (protein data bank ID: 1UAO) was optimized, and the importance of the inclusion of water was examined by comparing the solvated and gas phase structures of chignolin with the experimental NMR structure. PMID:21261333

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

2011-01-21

158

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

159

Geometry induced entanglement transitions in nanostructures  

E-print Network

We model quantum dot nanostructures using a one-dimensional system of two interacting electrons. We show that strong and rapid variations may be induced in the spatial entanglement by varying the nanostructure geometry. We investigate the position-space information entropy as an indicator of the entanglement in this system. We also consider the expectation value of the Coulomb interaction and the ratio of this expectation to the expectation of the confining potential and their link to the entanglement. We look at the first derivative of the entanglement and the position-space information entropy to infer information about a possible quantum phase transition.

J. P. Coe; S. Abdullah; I. D'Amico

2010-03-19

160

Elmo bumpy square plasma confinement device  

DOEpatents

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

Owen, L.W.

1985-01-01

161

Dust confinement in anodic plasmas  

SciTech Connect

Experiments on dust confinement in a magnetized plasma region in front of a small positively biased electrode are analyzed. The axial confinement of d = 1{mu}m particles can be quantitatively described by a balance of ion drag and electric field force. Radial confinement is due to strong electric fields. It is demonstrated that this anodic plasma has a distinctly different discharge mechanism from fireballs with ionizing double layers. The plasma is stable against potential relaxations but shows a strong ion cyclotron mode in the shear layer at the anode edge.

Piel, A.; Trottenberg, T.; Block, D. [IEAP, Christian-Albrechts-University, D-24098 Kiel (Germany)

2005-10-31

162

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

163

Alternative approaches to plasma confinement  

NASA Technical Reports Server (NTRS)

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.

Roth, J. R.

1977-01-01

164

Quark confinement and metric fluctuations  

E-print Network

We analyse, by doing very simple calculations, the internal degree of freedom leading to the de Broglie frequency associated to a material particle, as well, the confinement of quarks provided both by the Cornell potential and by the MIT bag model.We propose that the driving forces behind these confining models could be originated in the fluctuations of the metric, namely the particle interacting self-gravitationally, when its mass fluctuates in position throught of a distance equal to the Planck length.

P. R. Silva

2009-08-23

165

Hydrogen-bonded complexes upon spatial confinement: structural and energetic aspects.  

PubMed

In the present study we consider structural and energetic aspects of spatial confinement of the H-bonded systems. The model dimeric systems: HF···HF, HCN···HCN and HCN···HCCH have been chosen for a case study. Two-dimensional harmonic oscillator potential, mimicking a cylindrical confinement, was applied in order to render the impact of orbital compression on the analyzed molecular complexes. The calculations have been performed employing the MP2 method as well as the Kohn-Sham formulation of density functional theory. In the latter case, two exchange-correlation potentials have been used, namely B3LYP and M06-2X. The geometries of studied complexes have been optimized (without any constraints) in the presence of the applied model confining potential. A thorough analysis of topological parameters characterizing hydrogen bonds upon orbital compression has been performed within the Quantum Theory of Atoms in Molecules (QTAIM). Furthermore, an energetic analysis performed for the confined H-bonded complexes has shown a different trend in the interaction energy changes. Additionally, a variational-perturbational decomposition scheme was applied to study the interaction energy components in the presence of spatial confinement. PMID:24296646

Lipkowski, Pawe?; Koz?owska, Justyna; Roztoczy?ska, Agnieszka; Bartkowiak, Wojciech

2014-01-28

166

Geometries, singlet-triplet separations, dipole moments, ionization potentials, and vibrational frequencies in methylene (CH2) and halocarbenes (CHF, CF2, CCl2, CBr2, and CI2)  

NASA Astrophysics Data System (ADS)

The geometrical structure, harmonic vibrational frequencies, ionization potentials, and singlet-triplet gaps of simple substituted halocarbenes (CHF, CF2, CCl2, CBr2, and CI2) have been investigated by using the linear combination of Gaussian-type-orbital local-spin-density method. Optimized geometries, as well as vibrational frequencies, are in good agreement with available experimental data. The obtained values of singlet-triplet splittings (?EST) computed taking into account the nonlocal corrections are very close to experimental and previous theoretical investigations employing extended configuration interaction contributions. Many of the calculated properties obtained here have not yet been determined both experimentally and theoretically.

Russo, Nino; Sicilia, Emilia; Toscano, Marirosa

1992-10-01

167

Confinement induced instability of thin elastic film  

E-print Network

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.

Animangsu Ghatak

2005-05-02

168

Developments in special geometry  

E-print Network

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.

Thomas Mohaupt; Owen Vaughan

2011-12-13

169

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

NASA Astrophysics Data System (ADS)

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

Oglesby, David D.; Mai, P. Martin

2012-03-01

170

Understanding Confinement From Deconfinement  

E-print Network

We use effective magnetic SU(N) pure gauge theory with cutoff M and fixed gauge coupling g_m to calculate non-perturbative magnetic properties of the deconfined phase of SU(N) Yang-Mills theory. We obtain the response to an external closed loop of electric current by reinterpreting and regulating the calculation of the one loop effective potential in Yang-Mills theory. This effective potential gives rise to a color magnetic charge density, the counterpart in the deconfined phase of color magnetic currents introduced in effective dual superconductor theories of the confined phase via magnetically charged Higgs fields. The resulting spatial Wilson loop has area law behavior. Using values of M and g_m determined in the confined phase, we find SU(3) spatial string tensions compatible with lattice simulations in the temperature interval 1.5T_c < T < 2.5T_c. Use of the effective theory to analyze experiments on heavy ion collisions will provide applications and further tests of these ideas.

M. Baker

2007-12-03

171

Calculation of distribution of potential and electron concentration in the dust-electron thermal plasma with the axial geometry particles  

NASA Astrophysics Data System (ADS)

We obtained the equation, which describes the distribution of the potential and the electron density in an equilibrium dust-electron plasma taking into account parameters of the electron gas inside the axial geomtry dust particles. The inclusion of these parameters performed on the basis of the model of "solid-state plasma," considering the condensed particle system as the ion core and the free electron gas.

Dautov, G.; Fayrushin, I.; Kashapov, N.

2014-11-01

172

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

SciTech Connect

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

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

2003-08-01

173

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

SciTech Connect

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.

Oie, Tetsuro

1980-07-28

174

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

SciTech Connect

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

Oie, Tetsuro

1980-01-01

175

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

PubMed

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

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

2012-01-11

176

Geometry and Nanolength Scales versus Interface Interactions: Water Dynamics in AOT Lamellar Structures and  

E-print Network

Geometry and Nanolength Scales versus Interface Interactions: Water Dynamics in AOT Lamellar@stanford.edu Abstract: To determine the relative importance of the confining geometry and nanoscopic length scale versus in confined aqueous systems? Is it the geometry of the system with some nanolength scale determined

Fayer, Michael D.

177

Three s-wave-interacting fermions under anisotropic harmonic confinement: Dimensional crossover of energetics and virial coefficients  

NASA Astrophysics Data System (ADS)

We present highly accurate solutions of the Schrödinger equation for three fermions in two different spin states with zero-range s-wave interactions under harmonic confinement. Our approach covers spherically symmetric, strictly two-dimensional, strictly one-dimensional, cigar-shaped, and pancake-shaped traps. In particular, we discuss the transition from quasi-one-dimensional to strictly one-dimensional and from quasi-two-dimensional to strictly two-dimensional geometries. We determine and interpret the eigenenergies of the system as a function of the trap geometry and the strength of the zero-range interactions. The eigenenergies are used to investigate the dependence of the second- and third-order virial coefficients, which play an important role in the virial expansion of the thermodynamic potential, on the geometry of the trap. We show that the second- and third-order virial coefficients for anisotropic confinement geometries are, for experimentally relevant temperatures, very well approximated by those for the spherically symmetric confinement for all s-wave scattering lengths.

Gharashi, Seyed Ebrahim; Daily, K. M.; Blume, D.

2012-10-01

178

Quantum Confinement in Hydrogen Bond  

E-print Network

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.

Santos, Carlos da Silva dos; Ricotta, Regina Maria

2015-01-01

179

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

PubMed

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

Zhu, H; Braun, W

1999-02-01

180

Geometry optimization, HOMO and LUMO energy, molecular electrostatic potential, NMR, FT-IR and FT-Raman analyzes on 4-nitrophenol  

NASA Astrophysics Data System (ADS)

In the present work, the equilibrium geometry, HOMO-LUMO energy gap, chemical shifts, vibrational frequencies, IR and Raman intensities and thermodynamic parameters of 4-nitrophenol molecule was calculated using the methods of HF and DFT/B3YLP employing 6-311+G basis set. Theoretically calculated geometrical parameters such as bond length and bond angle were compared with the corresponding experimental X-ray diffraction values. The highest occupied (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of the 4-NP molecule have been calculated. The study was extended to calculate the energy gap, ionization potential, electron affinity and chemical hardness. HOMO-LUMO electronic transition of 3.76 eV is obtained from the contribution of the bands. The reacting electrophilic and nucleophilic sites of the molecule were analyzed with the help of molecular electrostatic potential (MEP) surface analysis. The different proton and carbon environment of the grown crystal was analyzed by 1H and 13C NMR analyses. All vibrational frequencies were assigned and compared with the calculated frequencies in detail.

Gandhimathi, Rajendran; Dheivamalar, Sethuraman; Dhanasekaran, Ramasamy

2015-01-01

181

Industrial Applications to the Inertial Electrostatic Confinement Configuration  

Microsoft Academic Search

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

Elijah Martin; Steve Shannon; Mohamed Bourham

2009-01-01

182

Current-induced skyrmion dynamics in constricted geometries.  

PubMed

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

Iwasaki, Junichi; Mochizuki, Masahito; Nagaosa, Naoto

2013-10-01

183

Geometry compression  

Microsoft Academic Search

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

Michael Deering

1995-01-01

184

Computer simulations of charged colloids in confinement.  

PubMed

We study by computer simulations the interaction between two similarly charged colloidal particles confined between parallel planes, in salt free conditions. Both the colloids and ions are simulated explicitly, in a fine-mesh lattice, and the electrostatic interaction is calculated using Ewald summation in two dimensions. The internal energy is measured by setting the colloidal particles at a given position and equilibrating the ions, whereas the free energy is obtained introducing a bias (attractive) potential between the colloids. Our results show that upon confining the system, the internal energy decreases, resulting in an attractive contribution to the interaction potential for large charges and strong confinement. However, the loss of entropy of the ions is the dominant mechanism in the interaction, irrespective of the confinement of the system. The interaction potential is therefore repulsive in all cases, and is well described by the DLVO functional form, but effective values have to be used for the interaction strength and Debye length. PMID:25460717

Puertas, Antonio M; de Las Nieves, F Javier; Cuetos, Alejandro

2015-02-15

185

Quantum confinement of nanocrystals within amorphous matrices  

NASA Astrophysics Data System (ADS)

Nanocrystals encapsulated within an amorphous matrix are computationally analyzed to quantify the degree to which the matrix modifies the nature of their quantum-confinement power—i.e., the relationship between nanocrystal size and the gap between valence- and conduction-band edges. A special geometry allows exactly the same amorphous matrix to be applied to nanocrystals of increasing size to precisely quantify changes in confinement without the noise typically associated with encapsulating structures that are different for each nanocrystal. The results both explain and quantify the degree to which amorphous matrices redshift the character of quantum confinement. The character of this confinement depends on both the type of encapsulating material and the separation distance between the nanocrystals within it. Surprisingly, the analysis also identifies a critical nanocrystal threshold below which quantum confinement is not possible—a feature unique to amorphous encapsulation. Although applied to silicon nanocrystals within an amorphous silicon matrix, the methodology can be used to accurately analyze the confinement softening of other amorphous systems as well.

Lusk, Mark T.; Collins, Reuben T.; Nourbakhsh, Zahra; Akbarzadeh, Hadi

2014-02-01

186

Bifurcated equilibria in centrifugally confined plasma  

SciTech Connect

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

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

2008-12-15

187

Gaspé Belt subsurface geometry in the northern Québec Appalachians as revealed by an integrated geophysical and geological study: 2 — Seismic interpretation and potential field modelling results  

NASA Astrophysics Data System (ADS)

Geological information, seismic reflection profiles and potential field data are used to study the geometry of the Middle Paleozoic Gaspé Belt (eastern Canada) that has been interpreted in various ways in the past. On the western edge of the Gaspé Belt, in the Matapédia area, growth strata are imaged on seismic profiles and testify of normal (or transtensional) motion during the period spanning the Silurian (and possibly Late Ordovician) to earliest Devonian along several faults, including the Shickshock-Sud Fault. In this area, Acadian deformation during the Middle to Late Devonian is associated with relatively modest shortening (less than 20%) accommodated by broad open folds, steeply-dipping neo-formed faults and inversion of previously formed faults. Neo-formed faults cut the entire Middle Paleozoic succession and offset the Ordovician Taconian unconformity suggesting that no sedimentary interval acted as an efficient décollement level. Toward the SE, the Sainte-Florence Fault divides rock assemblages with different paleogeographic settings and structural styles. Increase in tectonic complexity and amount of shortening to the south of the fault is interpreted as resulting of a vise effect between two basement blocks.

Pinet, Nicolas

2013-03-01

188

Enhancement of confinement in tokamaks  

SciTech Connect

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

Furth, H.P.

1986-05-01

189

Progress in toroidal confinement and fusion research  

SciTech Connect

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

Furth, H.P.

1987-10-01

190

Differential geometry  

Microsoft Academic Search

\\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

Lajos Tamássy

191

Algebra = Geometry Sandor Kovacs  

E-print Network

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

Kovács, Sándor

192

Programmed environment management of confined microsocieties  

NASA Technical Reports Server (NTRS)

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.

Emurian, Henry H.

1988-01-01

193

New developments in special geometry  

E-print Network

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.

Thomas Mohaupt

2006-02-17

194

Confinement Aquaculture. Final Report.  

ERIC Educational Resources Information Center

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

Delaplaine School District, AR.

195

Hazard Alert: Confined Spaces  

MedlinePLUS

... NIOSH. www.cpwr.com What is a confined space? Ask questions It is the employer’s responsibility to ... union. Call OSHA 1-800-321-OSHA COnFIned SpACeS Get training Your employer must train you for ...

196

Hot electron confinement in a microwave heated spindle cusp  

NASA Astrophysics Data System (ADS)

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

Prelas, M. A.

1991-08-01

197

Algebraic Geometry  

NSDL National Science Digital Library

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

Rusin, David J., 1957-

2007-12-18

198

Negative ions in inertial electrostatic confinement devices  

Microsoft Academic Search

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

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

2009-01-01

199

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

NASA Astrophysics Data System (ADS)

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.

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

1981-06-01

200

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

E-print Network

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 \

Patra, Binoy Krishna

2014-01-01

201

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

E-print Network

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 \

Binoy Krishna Patra; Himanshu Khanchandani

2014-12-16

202

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

SciTech Connect

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.

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

203

Computer simulation studies of confined liquid-crystal films  

NASA Astrophysics Data System (ADS)

In this paper we present results from molecular dynamics simulations performed using a system of Gay-Berne particles confined between two substrates in a slab geometry. We use a nonseparable anisotropic molecule-substrate interaction potential and investigate weak and moderate molecule-substrate coupling strengths. We find that for both coupling strengths a well-defined, tilted molecular layer forms at each wall and that the pretilt angle and layer density are only weakly dependent on temperature as the central region is cooled through isotropiclike and nematiclike regions. The orientationally ordered fluid formed at the center of the film is tilted in sympathy with the surface layers. At low temperatures, however, where the central region adopts a layered arrangement, a sharp change is observed in the pretilt angle. This transition is more marked in the weak-coupling system where the high-temperature tilted surface layers adopt an approximately planar arrangement at low temperatures and the system resembles a bookshelf-geometry smectic film. In the moderate-coupling system, the surface layers maintain some tilt in the presence of the layered central region, leading to a smectic-stripe phase arrangement.

Wall, Greg D.; Cleaver, Douglas J.

1997-10-01

204

Precision platform for convex lens-induced confinement microscopy  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

205

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

206

Fusion, magnetic confinement  

SciTech Connect

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.

Berk, H.L.

1992-08-06

207

Lattice QCD Study for Confinement in Hadrons  

SciTech Connect

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

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

2011-10-21

208

Fractal Geometry  

NSDL National Science Digital Library

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

Frame, Michael; Mandelbrot, Benoit

2004-11-30

209

Engaging All Students with "Impossible Geometry"  

ERIC Educational Resources Information Center

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…

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

2010-01-01

210

Noncommutative geometry  

Microsoft Academic Search

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

Alain Connes

1994-01-01

211

Fractal Geometry  

NSDL National Science Digital Library

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

Frame, Michael; Mandelbrot, Benoit; Neger, Nial

212

Connectivity in Dense Networks Confined within Right Prisms  

E-print Network

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

Dettmann, Carl

213

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

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

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

2014-11-01

214

Manipulation of confined bubbles in a thin microchannel: Drag and acoustic Bjerknes forces  

E-print Network

Manipulation of confined bubbles in a thin microchannel: Drag and acoustic Bjerknes forces David walls of microchannels experience an increased drag compared to freestanding bubbles. We measure of the microchannel geometry, defined by the two parallel plates and a rectangular cross-section. Under confinement

Boyer, Edmond

215

Nonequilibrium melting of icy soil in confined geometries on Mars  

NASA Astrophysics Data System (ADS)

While applicable to natural phenomena such as landslides, the study reported here was motivated by concerns about radioactive power sources (RPS) that might be emplaced just below the martian surface as a result of a landing "anomaly." Mars is best described as a cold, dry desert in the sense that water (in any form) is not circulated by precipitation or other means. Thus, while the phase diagram supports liquid water in many places, over time it would all migrate to the coldest locations, primarily at the poles or just beneath the surface at high latitudes. Transient water can be formed, however, when this equilibrium is disturbed by introduction of a heat source. Since the crash of a spacecraft might deposit a halo of microbial contamination in the vicinity of an RPS, such transient sources of water could provide breeding areas that would violate planetary protection treaties. The Mars Odyssey spacecraft has identified vast stretches of high latitude terrain as zones where liquid water could easily be formed in this scenario. To address both the extent and the duration of wet soil, certain scenarios have been modeled in two dimensions using both a finite difference time-marching method and by one dimensional analytical approximation. Considered in the analysis are the diffusion of both heat and water vapor, capillary forces on liquid water, latent heat exchange, surface processes such as radiation, evaporation, and convection, and continuous equilibration between the liquid, vapor, and solid phases. Results indicate that the initial ice content of the soil, a proxy for thermal conductivity, exerts the greatest influence on the progress of the wetting and drying cycle. Ice can be melted at distances of almost a meter from a 250W power source and may, under certain circumstances, persist for months. It is not yet clear, however, whether the result suggests a planetary protection risk.

Hecht, M. H.

2004-12-01

216

Rayleigh-Taylor mixing: confinement by stratification and geometry  

E-print Network

to the interface in the direction from the light to the heavy fluid. The instability leads to the distortion of the interface and in miscible fluids, their mixing, driven by the baroclinic genera- tion of vorticity which arises from the misaligment of pressure... water tunnel with two inlet streams (one for each density), from which a spatially evolving steady state Rayleigh-Taylor instability was created and much more precise growth rate measure- ments have been made with this apparatus. Even with such accurate...

Lawrie, Andrew

2010-03-16

217

Transport and boundary scattering in confined geometries: Analytical results  

Microsoft Academic Search

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.

R. A. Richardson; Franco Nori

1993-01-01

218

Charge Transport through Organized Organic Assemblies in Confined Geometries  

E-print Network

......................................... 73 xvii FIGURE Page 3.4 IR spectra of pure porphyrin monolayers on Au/Cr/Si after (A) 1 day, (B) 2 days, (C) 4 days, (D...) 8 days and (E) 12 days soaking time .............. 74 3.5 IR spectra of porphyrin thiol in (A) KBr pellets and (B) DFT calculated . 76 3.6 AFM topography images of pure porphyrin thiol monolayer on Au(111) after (A & B) 1 day and (C & D) 4...

Schuckman, Amanda Eileen

2012-07-16

219

Dynamics of rod eutectic growth patterns in confined geometry  

NASA Astrophysics Data System (ADS)

The dynamics of rod-like eutectics are examined using a directional solidification setup, which allows real-time observation of the whole solidification front in specimens of transparent eutectic alloys -here, succinonitrile-(D)camphor. In steady-state, rod eutectic growth patterns consist of triangular arrays, more or less disturbed by topological defects. In the absence of strong convection and of crystallographic anisotropy, the long-time evolution of the pattern is dominated by "imperfections" of the system, such as misalignment of the temperature gradient, and finite-size. In this study, we present experimental results on the finite-size effects on rod eutectics and show that a rod to lamella transition takes place as a result of finite-size effect only, at a given alloy concentration.

?erefo?lu, Melis; Bottin-Rousseau, S.; Akamatsu, S.; Faivre, G.

2012-01-01

220

Spinor geometry  

E-print Network

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.

A. Nicolaidis; V. Kiosses

2012-01-03

221

Beam optics in inertial electrostatic confinement fusion  

Microsoft Academic Search

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

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

2000-01-01

222

Theory of confinement-induced interlayer molecular resonances  

E-print Network

We study theoretically the interaction between two species of bosons confined parabolically in one transverse direction but with a finite separation between the centers of the confining potentials. We demonstrate the existence of new types of confinement-induced Feshbach resonances that can be tuned by changing separation between the layers. They are much sharper than usual two-dimensional confinement-induced resonances, and can be observed in the shaking spectrum of the two-dimensional layers, as shown by detailed many-body calculations for a thermal Bose gas.

Márton Kanász-Nagy; Eugene A. Demler; Gergely Zaránd

2014-01-22

223

The Geometry Algebraicizing  

E-print Network

The Geometry of 2 Ã? 2 Matrices William M. Goldman Algebraicizing geometry Euclidean geometry Spherical geometry Triangle tilings Stereographic projection Hyperbolic Geometry Matrices as geometric objects Conclusion The Geometry of 2 Ã? 2 Matrices William M. Goldman Department of Mathematics, University

Goldman, William

224

The entropic cost of polymer confinement.  

PubMed

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

Smyda, Mark R; Harvey, Stephen C

2012-09-01

225

Confinement of quarks  

Microsoft Academic Search

A general introduction to the topological mechanism responsible for the absolute confinement of quarks inside hadronic bound states is given, including the effects of a finite instanton angle. We then propose a calculational technique for computing these states and their properties, where instead of topology we rely on a perturbative mechanism. It assumes that already before the topological mechanism can

Gerard't Hooft

2003-01-01

226

Hazard Alert: Confined Spaces  

MedlinePLUS

... on your worksite. Do not enter without proper training. Never enter alone. A self-employed handyman died in this water service manhole. He had been called to fix a water leak in an adjacent rental house and was working alone. Know the basics… ... SpACeS Get training Your employer must train you for confined space ...

227

Electrokinetic confinement of axonal growth for dynamically configurable neural networks  

PubMed Central

Axons in the developing nervous system are directed via guidance cues, whose expression varies both spatially and temporally, to create functional neural circuits. Existing methods to create patterns of neural connectivity in vitro use only static geometries, and are unable to dynamically alter the guidance cues imparted on the cells. We introduce the use of AC electrokinetics to dynamically control axonal growth in cultured rat hippocampal neurons. We find that the application of modest voltages at frequencies on the order of 105 Hz can cause developing axons to be stopped adjacent to the electrodes while axons away from the electric fields exhibit uninhibited growth. By switching electrodes on or off, we can reversibly inhibit or permit axon passage across the electrodes. Our models suggest that dielectrophoresis is the causative AC electrokinetic effect. We make use of our dynamic control over axon elongation to create an axon-diode via an axon-lock system that consists of a pair of electrode `gates' that either permit or prevent axons from passing through. Finally, we developed a neural circuit consisting of three populations of neurons, separated by three axon-locks to demonstrate the assembly of a functional, engineered neural network. Action potential recordings demonstrate that the AC electrokinetic effect does not harm axons, and Ca2+ imaging demonstrated the unidirectional nature of the synaptic connections. AC electrokinetic confinement of axonal growth has potential for creating configurable, directional neural networks. PMID:23314575

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

2013-01-01

228

Geometry of thermodynamic control  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

229

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)

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.

Behera, Laxmidhar; Sen, Mrinal K.

2014-10-01

230

Dynamics of strongly confined self propelled particles in non convex boundaries  

E-print Network

We study the dynamics of non-aligning, non-interacting 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 non-convex boxes, the non-uniqueness of the boundary normal results in hysteretic dynamics and the density is non-local, 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 the active suspension it confines, thus providing a powerful tool to understand and design such confinements.

Yaouen Fily; Aparna Baskaran; Michael F. Hagan

2014-10-20

231

The Properties of Confined Water and Fluid Flow at the Nanoscale  

SciTech Connect

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

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

2009-03-09

232

Topological confinement and superconductivity  

SciTech Connect

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

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

2008-01-01

233

Inertial Confinement fusion targets  

NASA Technical Reports Server (NTRS)

Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques were 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.

Hendricks, C. D.

1982-01-01

234

Geometry and Picturing the  

E-print Network

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

Gideon, Rudy A.

235

Spatially confined assembly of nanoparticles.  

PubMed

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

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

2014-10-21

236

Christian Bar Differential Geometry  

E-print Network

.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

Baer, Christian

237

CUSP Energetic Particles: Confinement, Acceleration and Implications  

NASA Technical Reports Server (NTRS)

The cusp energetic particle (CEP) event is a new magnetospheric phenomenon. The events were detected in the dayside cusp for hours, in which the measured helium ions had energies up to 8 MeV. All of these events were associated with a dramatic decrease and large fluctuations in the local magnetic field strength. During January 1999 - December 1999 covered by this report, I have studied the CEP events by analyzing the POLAR, GEOTAIL, and WIND particle and magnetic field data measured during the geomagnetic quiet periods in 1996 and one geomagnetic storm period in 1998. The simultaneous observations indicated that the ion fluxes in the CEP events were higher than that in both the upstream and the downstream from the bow shock. The pitch angle distribution of the helium ions in the CEP events was found to peak around 90 deg. It was found that the mirror parameter, defined as the ratio of the square root of the integration of the parallel turbulent power spectral component over the ultra-low frequency (ULF) ranges to the mean field in the cusp, is correlated with the intensity of the cusp MeV helium flux, which is a measure of the influence of mirroring interactions and an indication of local effect. It was also found that the turbulent power of the local magnetic field in the ultra-low frequency (ULF) ranges is correlated with the intensity of the cusp energetic helium ions. Such ULF ranges correspond to periods of about 0.33-500 seconds that cover the gyroperiods, the bounce periods, and the drift periods of the tens keV to MeV charged particles when they are temporarily confined in the high-altitude dayside cusp. These observations represent a discovery that the high-altitude dayside cusp is a new acceleration and dynamic trapping region of the magnetosphere. The cusp geometry is connected via gradient and curvature drift of these energized ions to the equatorial plasma sheet as close as the geostationary orbit at local midnight. It implies that the dayside cusp is potentially an important source of magnetospheric particles. The discovery of the CEP events has been recognized as one of the most significant results from POLAR. I was invited to give a talk at 1999 IUGG meeting to interpret the CEP events. This discovery has also been written into the web-based Space Physics Text Book (http://www.oulu.fi/- spaceweb/textbook/cusp.html).

Chen, Jiasheng

1999-01-01

238

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

SciTech Connect

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

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

1999-11-01

239

Confinement studies in TFTR  

SciTech Connect

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

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

1985-06-01

240

Dynamics of Confined Water Molecules in Aqueous Salt Hydrates  

SciTech Connect

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.

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

2011-04-01

241

Confinement Contains Condensates  

SciTech Connect

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

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

2012-03-12

242

Theory of plasma confinement in non-axisymmetric magnetic fields  

NASA Astrophysics Data System (ADS)

The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced.

Helander, Per

2014-08-01

243

Effect of confining overlay in micro scale laser bulge forming  

NASA Astrophysics Data System (ADS)

Micro scale laser bulge forming (?LBF) shows great potential in fabricating high precision and high-aspect-ratio metallic micro components. The present paper investigated the effect of the confining overlay in ?LBF experimentally. The surface morphology of micro bulged parts of pure copper foils with and without confining overlay was explored through the scanning electron microscope. The surface features of quartz glasses with different thickness shocked by single and multiple laser pulses were observed using the optical microscope. The effect of thickness of the confining overlay on the maximum bulging height of micro parts was investigated. Experiments reveal that the application of the confining overlay in ?LBF has significant influence on both the surface morphology and plastic deformation of micro bulged parts. The change of laser ablation mode is responsible for forming results. In addition, there is a moderate thickness of the confining overlay to induce noticeable plastic deformation without failure.

Zheng, Chao; Sun, Sheng; Zhang, Guofang; Song, Libin; Ji, Zhong

2013-11-01

244

Confinement from gluodynamics in curved space-time  

SciTech Connect

We determine the static potential for a heavy quark-antiquark pair from gluodynamics in curved space-time. Our calculation is done within the framework of the gauge-invariant, path-dependent, variables formalism. The potential energy is the sum of a Yukawa and a linear potential, leading to the confinement of static charges.

Gaete, Patricio; Spallucci, Euro [Departamento de Fisica, Universidad Tecnica Federico Santa Maria, Valparaiso (Chile); Dipartimento di Fisica Teorica, Universita di Trieste and INFN, Sezione di Trieste (Italy)

2008-01-15

245

Thermal Conductivity of Liquid He-4 near the Superfluid Transition in Restricted Geometries  

NASA Technical Reports Server (NTRS)

We present measurements of the thermal conductivity near the superfluid transition of He-4 in confined geometries. The confinements we have studied include: cylindrical geometries with radii L=.5 and 1.0 microns, and parallel plates with 5 micron spacing. For L=1.0 microns, measurements at six pressures were conducted, whereas only SVP measurements have been done for other geometries. For the 1-D confinement in cylinders, the data are consistent with a universal scaling for all pressures at and above T(sub lambda). There are indications of breakdown of scaling and universality below T(sub lambda). For the 2-D confinement between parallel plates, the preliminary results indicate that the thermal conductivity is finite at the bulk superfluid transition temperature. Further analyses are needed to compare the 2-D results with those in bulk and 1-D confinement.

Liu, Yuanming

2003-01-01

246

Inertial electrostatic confinement (IEC) neutron sources  

SciTech Connect

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

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

1995-01-01

247

Inertial electrostatic confinement (IEC) neutron sources  

SciTech Connect

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2 {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.

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

248

Statistical mechanics of confined quantum particles  

E-print Network

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.

Vishnu M. Bannur; K. M. Udayanandan

2006-02-02

249

Crystallization under nanoscale confinement.  

PubMed

Classical crystal growth models posit that crystallization outcomes are determined by nuclei that resemble mature crystal phases, but at a critical size where the volume free energy of nuclei begins to offset the unfavorable surface free energy arising from the interface with the growth medium. Crystallization under nanoscale confinement offers an opportunity to examine nucleation and phase transformations at length scales corresponding to the critical size, at which kinetics and thermodynamics of nucleation and growth intersect and dramatic departures in stability compared to bulk crystals can appear. This tutorial review focuses on recent investigations of the crystallization of organic compounds in nanoporous matrices that effectively provide millions of nanoscale reactors in a single sample, ranging from controlled porous glass (CPG) beads to nanoporous block-copolymer monoliths to anodic aluminum oxide (AAO) membranes. Confinement of crystal growth in this manner provides a snapshot of the earliest stages of crystal growth, with insights into nucleation, size-dependent polymorphism, and thermotropic behavior of nanoscale crystals. Moreover, these matrices can be used to screen for crystal polymorphs and assess their stability as nanocrystals. The well-aligned cylindrical nanoscale pores of polymer monoliths or AAO also allow determination of preferred orientation of embedded nanocrystals, affording insight into the competitive nature of nucleation, critical sizes, and phase transition mechanisms. Collectively, these investigations have increased our understanding of crystallization at length scales that are deterministic while suggesting strategies for controlling crystallization outcomes. PMID:24081010

Jiang, Qi; Ward, Michael D

2014-04-01

250

PROJECTIVE GEOMETRY KRISTIN DEAN  

E-print Network

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

May, J. Peter

251

Geometry in Medias Res  

ERIC Educational Resources Information Center

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

Cukier, Mimi; Asdourian, Tony; Thakker, Anand

2012-01-01

252

Geometry and Categoricity  

E-print Network

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

Baldwin, John T.

253

Confinement vessel analysis final report  

SciTech Connect

The overall purpose of the confinement vessel analysis program was to aid Los Alamos in validation of a new confinement vessel configuration. This was done in two steps: First, we developed a finite element analysis model of the benchmark confinement vessel and compared the results against test results to verify the accuracy of the model and analysis technique. We then changed the finite element model to represent the new confinement vessel configuration and predicted the response of the new vessel for specified loading conditions. This report describes the work done to achieve the objective.

Lewis, B.B. [APTEK, Inc., Colorado Springs, CO (United States)

1992-05-06

254

Monistic conception of geometry  

E-print Network

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.

Yuri A. Rylov

2010-09-15

255

Fusion radioactivity confinement and application to postulated ITER accidents  

SciTech Connect

An assessment of the ITER radioactivity confinement shows reduction of potential accidental releases to the environment by two orders of magnitude. Important credits are the 1% volume/day confinement leakage rate, radioactivity decay for short-lived isotopes, resumption of detritiation/negative pressure within seven days of the accident, and wind meander during the slow confinement leakage. Achieving this two order of magnitude credit in practice requires appropriate design details, especially the leakage rate and detritiation/negative pressure equipment, and research to validate some key assumptions. The confinement maximizes dependence on passive safety features, thereby working toward using fusion's potential safety advantages. The confinement includes several confinement zones with varying human access allowances. Some confinement areas are normally isolated from the environment, the closed ventilation zone. Some areas have an inert cover gas to inhibit combustion. If future assessments of accidental overpressure show the need, we propose a filter/vent system. This report documents our work for the ITER Conceptual Design Activity (CDA). The report is consistent with the final CDA design reports and descriptions, except that our analysis includes a filter/vent. For gaseous or vapor tritium and for most activated aerosols, the reference release fraction is about 2%. For short-lived tungsten-rhenium aerosols, the reference release fraction is somewhat lower, as low as 0.5% for some accident scenarios. Even without resumption of detritiation/decontamination or negative pressure within seven days of the accident, the release fraction for stays below 4%.

Piet, S.J.; Brereton, S.J.

1991-03-01

256

Inertial confinement fusion method producing line source radiation fluence  

DOEpatents

An inertial confinement fusion method in which target pellets are imploded in sequence by laser light beams or other energy beams at an implosion site which is variable between pellet implosions along a line. The effect of the variability in position of the implosion site along a line is to distribute the radiation fluence in surrounding reactor components as a line source of radiation would do, thereby permitting the utilization of cylindrical geometry in the design of the reactor and internal components.

Rose, Ronald P. (Peters Township, Washington County, PA)

1984-01-01

257

Inertial Electrostatic Confinement Modeling and Comparison to Experiments  

Microsoft Academic Search

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

Gilbert Emmert; John Santarius; Eric Alderson; David Donovan

2010-01-01

258

Descriptions and Conflicts in Dynamic Geometry  

ERIC Educational Resources Information Center

We expand the theoretical perspective based on the notions of description and conflict, which was previously used to the learning of functions and calculus, to the learning of deductive geometry supported by Dynamic Geometry (DG) environments. Based on prior studies on functions and on the potential role of a DG software, we analyze a case study…

Giraldo, Victor; Belfort, Elizabeth; Carvalho, Luiz Mariano

2004-01-01

259

Performance of Polywell inertial-electrostatic confinement for applications  

Microsoft Academic Search

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

J. F. Santarius; K. H. Simmons

1995-01-01

260

AN INTRODUCTION TO SYMPLECTIC GEOMETRY,  

E-print Network

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

Schürmann, Michael

261

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

SciTech Connect

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.

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

262

Inertial Electrostatic Confinement (IEC) devices  

Microsoft Academic Search

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

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

1994-01-01

263

UNIVERSITY OF WASHINGTON CONFINED SPACE EVALUATION FORM  

E-print Network

UNIVERSITY OF WASHINGTON CONFINED SPACE EVALUATION FORM ENVIRONMENTAL HEALTH & SAFETY DateYour Name. Building/Area Room # Location Key # CONFINED SPACE AND PERMIT REQUIRED CONFINED SPACE This section must be filled out for both CS (Confined Space) and PRCS (Permit Required Confined Space). SIZE: Can a person get

Wilcock, William

264

Learning Geometry through Dynamic Geometry Software  

ERIC Educational Resources Information Center

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…

Forsythe, Sue

2007-01-01

265

Viscous fingering and liquid crystals in confinement  

NASA Astrophysics Data System (ADS)

This thesis focuses on two problems lying within the field of soft condensed matter: the viscous fingering or Saffman-Taylor instability and nematic liquid crystals in confinement. Whenever a low viscosity fluid displaces a high viscosity fluid in a porous medium, for example water pushing oil out of oil reservoirs, the interface between the two fluids is rendered unstable. Viscous fingers develop, grow and compete until a single finger spans all the way from inlet to outlet. Here, using a free energy lattice Boltzmann algorithm, we examine the Saffman-Taylor instability for two different wetting situations: (a) when neither of the two fluids wet the walls of the channel and (b) when the displacing fluids completely wets the walls. We demonstrate that curvature effects in the third dimension, which arise because of the wetting boundary conditions, can lead to a novel suppression of the instability. Recent experiments in microchannels using colloid-polymer mixtures support our findings. In the second part of the thesis we examine nematic liquid crystals confined in wedge-structured geometries. In these systems the final stable configuration of the liquid crystal system is controlled by the complex interplay between confinement, elasticity and surface anchoring. Varying the wedge opening angle this competition leads to a splay to bend transition mediated by a defect in the bulk of the wedge. Using a hybrid lattice Boltzmann algorithm we study the splay-bend transition and compare to recent experiments on {em fd} virus particles in microchannels. Our numerical results, in quantitative agreement with the experiments, enable us to predict the position of the defect as a function of opening angle, and elucidate its role in the change of director structure. This has relevance to novel energy saving, liquid crystal devices which rely on defect motion and pinning to create bistable director configurations.

Zacharoudiou, Ioannis

266

Confinement of Fractional Quantum Hall States  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

267

The Geometry Junkyard  

NSDL National Science Digital Library

The Geometry Junkyard website provides a broad introduction to the specifics of geometry. The site, designed by David Eppstein of UC-Irvine, provides all the basics of geometry for students and teachers alike. Topics range from the mathematics of shapes to fractals and multi-dimensional geometry, to name only a few. Also provided are various lesson plans for different levels of education. The information on this site could be used to build lesson plans, to design projects, or to better understand the basics of college-level geometry. This simple website will be useful for geometry enthusiasts of all levels.

Eppstein, David

268

Nernst branes from special geometry  

E-print Network

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 $(z,\\theta)=(3,1)$.

Dempster, Paul; Mohaupt, Thomas

2015-01-01

269

Nernst branes from special geometry  

E-print Network

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 $(z,\\theta)=(3,1)$.

Paul Dempster; David Errington; Thomas Mohaupt

2015-01-30

270

Initial results on positron confinement in a magnetospheric configuration  

NASA Astrophysics Data System (ADS)

Creation of positron-electron plasma in a laboratory is an interesting and challenging subject, which may open many scientific applications. Although single-component plasma is stably confined in linear traps, for example Penning-Malmberg trap, it is not straightforward to simultaneously confine electrons and positrons as plasma. Toroidal geometries have advantages for solving this problem. For this purpose, studies on toroidal non-neutral plasma have been conducted in the levitated magnetospheric configuration, RT-1. Stable confinement and self-organization of toroidal non-neutral plasma was realized in RT-1; rigid-rotating pure electron plasma is confined for more than 300s [Z. Yoshida et al., PRL 104, 235004 (2010)]. As the initial step toward the formation of magnetospheric antimatter plasmas, we installed a 1MBq Na-22 radiation source in RT-1. Annihilation gamma-rays were observed by a NaI(TI) scintillator detector, for the estimation of basic injection and confinement properties of positrons in the magnetospheric configuration. Numerical analysis of positron orbits in RT-1 and the initial experimental results will be presented.

Saitoh, Haruhiko; Yoshida, Zensho; Yano, Yoshihisa; Morikawa, Junji

2011-11-01

271

Cooperative Length Scale and Fragility of Polystyrene under Confinement  

NASA Astrophysics Data System (ADS)

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

Zhang, Chuan; Guo, Yunlong; Priestley, Rodney

2012-02-01

272

GaAs (Ga, Al)As double quantum rings: confinement and magnetic field effects  

NASA Astrophysics Data System (ADS)

Here we address a theoretical study of concentric GaAs-(Ga, Al)As double quantum rings, under a magnetic field applied perpendicularly to the ring plane. Electron-hole transition energies are calculated as a function of the system geometry confinement, following a single-particle picture, neglecting interaction effects. We adopted an effective-mass approximation, within a hard potential model calculation, exactly solved by using confluent hypergeometric functions. A huge dependence on the barrier width value and on the external ring width of the Ga1-xAlxAs coupled rings is found for the transition energy values. The results show a high competition between geometric and magnetic-field confinement, leading to an increase of the electron-hole energies with the magnetic field, and a reducing behavior as the outer ring width is assumed to be larger. Our results are in quite good agreement with the experimental data by Mano et al (2005 Nano Lett. 5 425).

Culchac, F. J.; Porras-Montenegro, N.; Latgé, A.

2008-07-01

273

Geometry and Dynamics of the Brane-World  

Microsoft Academic Search

Recent developments in string theory have led to 5-dimensional warped spacetime models in which standard-model fields are confined to a 3-brane (the observed universe), while gravity can propagate in the fifth dimension. Gravity is localized near the brane at low energies, even if the extra dimension is noncompact. A review is given of the classical geometry and dynamics of these

Roy Maartens

2001-01-01

274

Confinement of semiflexible polymers  

NASA Astrophysics Data System (ADS)

A variational framework is developed to examine the equilibrium states of a semiflexible polymer that is constrained to lie on a fixed surface. As an application the confinement of a closed polymer loop of fixed length 2?R within a spherical cavity of smaller radius, R0, is considered. It is shown that an infinite number of distinct periodic completely attached equilibrium states exist, labeled by two integers: n=2,3,4,⋯ and p=1,2,3,⋯, the number of periods of the polar and azimuthal angles, respectively. Small loops oscillate about a geodesic circle: n=2, p=1 is the stable ground state; states with higher n exhibit instabilities. If R?2R0 new states appear as oscillations about a doubly covered geodesic circle; the state n=3,p=2 replaces the twofold as the ground state in a finite band of values of R. With increasing R, loop states make a transition from oscillatory and orbital behavior on crossing the poles, returning to oscillation upon collapse to a multiple cover of a geodesic circle (signaled, respectively, by an increase in p and an increase in n). The force transmitted to the surface does not increase monotonically with loop size, but does asymptotically. It behaves discontinuously where n changes. The contribution to energy from geodesic curvature is bounded. In large loops, the energy becomes dominated by a state independent contribution proportional to the loop size; the energy gap between the ground state and excited states disappears.

Guven, Jemal; Vázquez-Montejo, Pablo

2012-02-01

275

Inertial confinement fusion  

SciTech Connect

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

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

1992-01-01

276

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.

277

Confinement of ultracold atoms in a Laguerre-Gaussian laser beam created with diffractive optics  

E-print Network

We report 2D confinement of Rb 87 atoms in a Laguerre-Gaussian laser beam. Changing of the sign of the detuning from the atomic resonance dramatically alters the geometry of the confinement. With the laser detuned to the blue, the atoms are confined to the dark, central node of the Laguerre-Gaussian laser mode. This trapping method leads to low ac Stark shifts to the atomic levels. Alternatively, by detuning the laser to the red of the resonance, we confine atoms to the high intensity outer ring in a multiply-connected, toroidal configuration. We model the confined atoms to determine azimuthal intensity variations of the trapping laser, caused by slight misalignments of the Laguerre-Gaussian mode generating optics.

Kennedy, Sharon A; Farrar, J Tom; Akin, T G; Krzyzewski, S; Abraham, E R I

2013-01-01

278

Quantum confinement and host/guest chemistry: probing a new dimension.  

PubMed

Nanoparticulate metals and semiconductors that have atomic arrangements at the interface of molecular clusters and "infinite" solid-state arrays of atoms have distinctive properties determined by the extent of confinement of highly delocalized valence electrons. At this interface, the total number of atoms and the geometrical disposition of each atom can be used to significantly modify the electronic and photonic response of the medium. In addition to teh novel inherent physical properties of the quantum-confined moieties, their "packaging" into nanocomposite bulk materials can be used to define the confinement surface states and environment, intercluster interactions, the quantum-confinement geometry, and the effective charge-carrier density of the bulk. Current approaches for generating nanostructures of conducting materials are briefly reviewed, especially the use of three-dimensional crystalline superlattices as hosts for quantum-confined semiconductor atom arrays (such as quantum wires and dots) with controlled inter-quantum-structure tunneling. PMID:17771883

Stucky, G D; Mac Dougall, J E

1990-02-01

279

Numerical Studies of Properties of Confined Helium  

NASA Technical Reports Server (NTRS)

We carry out state of the art simulations of properties of confined liquid helium near the superfluid transition to a degree of accuracy which allows to make predictions for the outcome of fundamental physics experiments in microgravity. First we report our results for the finite-size scaling behavior of heat capacity of superfluids for cubic and parallel-plate geometry. This allows us to study the crossover from zero and two dimensions to three dimensions. Our calculated scaling functions are in good agreement with recently measured specific heat scaling functions for the above mentioned geometries. We also present our results of a quantum simulation of submonolayer of molecular hydrogen deposited on an ideal graphite substrate using path-integral quantum Monte Carlo simulation. We find that the monolayer phase diagram is rich and very similar to that of helium monolayer. We are able to uncover the main features of the complex monolayer phase diagram, such as the commensurate solid phases and the commensurate to incommensurate transition, in agreement with the experiments and to find some features which are missing from the experimental analysis.

Manousakis, Efstratios

2003-01-01

280

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

281

Partial confinement photonic crystal waveguides  

SciTech Connect

One-dimensional photonic crystal waveguides with an incomplete photonic band gap are modeled and proposed for an integration application that exploits their property of partial angular confinement. Planar apodized photonic crystal structures are deposited by plasma enhanced chemical vapor deposition and characterized by reflectivity as a function of angle and polarization, validating a partial confinement design for light at 850 nm wavelength. Partial confinement identifies an approach for tailoring waveguide properties by the exploitation of conformal film deposition over a substrate with angularly dependent topology. An application for an optoelectronic transceiver is demonstrated.

Saini, S.; Hong, C.-Y.; Pfaff, N.; Kimerling, L. C.; Michel, J. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2008-12-29

282

Alpha particle confinement in tokamaks  

SciTech Connect

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

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

1988-11-01

283

Spectral Geometry Bruno Iochum  

E-print Network

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

Paris-Sud XI, Université de

284

TRIANGLES IN HYPERBOLIC GEOMETRY  

Microsoft Academic Search

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

LAURA VALAAS

285

Energy-dependent ?-wave confinement-induced resonances  

NASA Astrophysics Data System (ADS)

The universal aspects of two-body collisions in the presence of a harmonic confinement are investigated for both bosons and fermions. The main focus of this study are the confinement-induced resonances (CIRs) which are attributed to different angular momentum states ?, and we explicitly show that in alkaline collisions only four universal ?-wave CIRs emerge given that the interatomic potential is deep enough. Going beyond the single mode regime the energy dependence of ?-wave CIRs is studied. In particular we show that all the ?-wave CIRs may emerge even when the underlying two-body potential cannot support any bound state. We observe that the intricate dependence on the energy yields resonant features where the colliding system within the confining potential experiences an effective free-space scattering. Our analysis is done within the framework of the generalized K-matrix theory, and the relevant analytical calculations are in very good agreement with the corresponding ab initio numerical scattering simulations.

Heß, Benjamin; Giannakeas, Panagiotis; Schmelcher, Peter

2014-05-01

286

New crisis in geometry?  

E-print Network

The first crisis in the geometry arose in the beginning of XIXth century, when the mathematicians rejected the non-Euclidean geometry as a possible geometry of the real world. Now we observe unreasonable rejection of the non-Riemannian geometry by the official representatives of the contemporary geometry. Class of the Riemannian geometries appears to be too narrow for physical applications. The microcosm physics needs expansion of the class of possible geometries appropriate for the role of space-time geometry. In the framework of the non-Riemannian geometry one can construct the space-time geometry, where the motion of free particles is primordially stochastic, and this stochasticity depends on the particle mass. At the same time the geometry in itself is not stochastic in the sense that the space-time intervals are deterministic. Principles of quantum mechanics can be deduced from such a space-time geometry. The crisis situation in geometry appears to be connected with some preconceptions concerning the foundation of the geometry. The preconceptions as well as the crisis generated by them are not purely scientific phenomena. The human factor (social aspect) is rather strong in the crisis phenomena. The preconceptions and the human factor appear to be so strong, that usual logical arguments are not perceived, and the usual formal mathematical language appears to be inappropriate for perception of an analysis of the crisis origin and of a possibility of its overcoming. In the paper the history and motives of the non-Riemannian geometry construction are presented. There is a hope that such a less formal way of presentation helps to understand and to overcome the existing preconceptions.

Yuri A. Rylov

2005-03-14

287

Quantum Confined Silicon Clathrate Quantum Dots  

NASA Astrophysics Data System (ADS)

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

Lusk, Mark; Brawand, Nicholas

2013-03-01

288

Confined Hard Disk System Model  

NSDL National Science Digital Library

The Confined Hard Disk System is an idealized statistical mechanics model that simulates a two-dimensional system of hard disks confined to a box with a constant temperature thermal reservoir at one end and a movable piston at the other. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The model computes and plots the time evolution of the kinetic energy K per particle, the pressure P, and the volume V. The model also displays histograms and mean values of these quantities. The Confined Hard Disk System was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_hd_ConfinedHardDiskSystem.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-12-27

289

Snyder-Yang algebra and confinement of color particles  

E-print Network

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.

V. V. Khruschov

2010-12-21

290

Spin asymmetries for confined Dirac particles  

SciTech Connect

We study the Bjorken x (or equivalently Nachtmann {xi}) dependence of the virtual photon spin asymmetry in polarized deep inelastic scattering of electrons from hadrons. We use an exactly solved relativistic potential model of the hadron, treating the constituents as independent massless Dirac particles confined to an infinitely massive force center. The importance of including the p--wave components of the Dirac wave function is demonstrated. Comparisons are made to the observed data on the proton by taking into account the observed flavor dependence of the valence quark distribution functions.

Mark Paris; V.R. Pandharipande; Ingo Sick

2004-06-01

291

Engineering tube shapes to control confined transport  

NASA Astrophysics Data System (ADS)

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.

Reguera, D.; Rubi, J. M.

2014-12-01

292

a Quark-Independent Description of Confinement  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

293

Example of an explicit function for confining classical Yang-Mills fields with quantum fluctuations in path integral scheme  

E-print Network

This article reports an explicit function of confining classical Yang-Mills vector potentials as well as quantum fluctuations around the classical field. The classical vector potential, which is composed of a confining localized function and an unlocalized function, satisfies the classical Yang-Mills equation. The confining localized function contributes to the Wilson loop, while the unlocalized function has no contribution to this loop. The confining linear potential between a pair of a heavy fermion particle and an antiparticle is due to the Lie algebra and the form of the confining localized function, which have opposite signs at positions of the particle and antiparticles along the Wilson loop in the time direction. Some classical confining parts of vector potentials also have the opposite sign for the inversion of coordinate of the axis perpendicular to the axis between two particles. The localized functions of vector potentials are squeezed around the axis connecting two particles, and the string tensio...

Fukushima, Kimichika

2014-01-01

294

High Temperature Confinement in SU(N) Gauge Theories  

E-print Network

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.

Michael C. Ogilvie; Peter N. Meisinger

2008-11-13

295

Single fiber transport in a confined channel: Microfluidic experiments and numerical study  

NASA Astrophysics Data System (ADS)

We present an experimental and numerical study on the transport of a single fiber confined in a microfluidic Hele-Shaw geometry. The fiber has a square cross-section and a typical aspect ratio of ten. We address the question of the fiber velocity as it is freely transported by the flow, and study in particular its dependence on the fiber orientation and confinement in the channel, defined as the ratio of the fiber height with the channel height. Both experiments and simulations are set so that the fiber suspended in the middle of the channel height does not interact with the lateral flow boundaries. At low confinements, the fiber velocity is independent of the fiber orientation with the flow direction and tends to the maximal velocity of the fluid when the confinement tends to zero. The fiber slows down as the confinement increases. We find that as the confinement reaches approximately 0.5, the orientation affects the fiber velocity: a fiber perpendicular to the flow direction moves faster than a parallel one. Consequently, a confined fiber transported in a microchannel at an angle different from 0° or 90° with the flow direction will drift towards a lateral wall, in the opposite direction found in sedimenting fibers. We also characterize the perturbation caused by the presence of the fiber on the flow field, and find that it drops very quickly as the fiber confinement decreases.

Berthet, Helene; Fermigier, Marc; Lindner, Anke

2013-10-01

296

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.

297

Generalized Kähler Geometry  

NASA Astrophysics Data System (ADS)

Generalized Kähler geometry is the natural analogue of Kähler geometry, in the context of generalized complex geometry. Just as we may require a complex structure to be compatible with a Riemannian metric in a way which gives rise to a symplectic form, we may require a generalized complex structure to be compatible with a metric so that it defines a second generalized complex structure. We prove that generalized Kähler geometry is equivalent to the bi-Hermitian geometry on the target of a 2-dimensional sigma model with (2, 2) supersymmetry. We also prove the existence of natural holomorphic Courant algebroids for each of the underlying complex structures, and that these split into a sum of transverse holomorphic Dirac structures. Finally, we explore the analogy between pre-quantum line bundles and gerbes in the context of generalized Kähler geometry.

Gualtieri, Marco

2014-10-01

298

What is Computational Geometry?  

Microsoft Academic Search

Voronoi Diagrams, Springer-Verlag, 1989.[Ko86] Kostovskii, A., Geometrical Constructions with Compasses Only, Mir Publishers,Moscow, 1986.[Kr92] Kreveld, M. van, New Results on Data Structures in Computational Geometry, Universityof Utrecht, 1992.[KS92] Karasik, Y. B. and Sharir, M., "Optical computational geometry," Proc. 8th ACM Symposiumon Computational Geometry, Berlin, June 10-12, 1992, pp. 232-241.[Le02] Lemoine, E., Geometrographie, C. Naud, Paris, 1902.[LPS88] Lenhart, W.,...

Godfried T. Toussaint

299

Achieving optical gain in waveguide-confined nanocluster-sensitized erbium by pulsed excitation  

E-print Network

Achieving optical gain in waveguide-confined nanocluster-sensitized erbium by pulsed excitation for optical gain in nanocluster sensitized erbium in a slot waveguide geometry. We determine the viability to erbium. We show that pulsed excitation of a 10 nm layer achieves a modal gain of 0.9 dB/cm during each

Atwater, Harry

300

An electrostatically and a magnetically confined electron gun lens system  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

301

Coronal Electron Confinement by Double Layers  

E-print Network

In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons (T.C. Li, J.F. Drake, and M. Swisdak, 2012, ApJ, 757, 20). The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations, and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and find also a linear scaling with the hot e...

Li, T C; Swisdak, M

2014-01-01

302

Experimental and Theoretical Studies of Electrostatic Confinement  

NASA Astrophysics Data System (ADS)

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)].

Park, Jaeyoung; Nebel, Richard

2002-11-01

303

Fluctuations and confinement in ATF  

SciTech Connect

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

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

1993-10-01

304

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

PubMed

The dynamical behavior of single-component two-dimensional colloidal crystals confined in a slit geometry is studied by Langevin dynamics simulation of a simple model. The colloids are modeled as pointlike particles, interacting with the repulsive part of the Lennard-Jones potential, and the fluid molecules in the colloidal suspension are not explicitly considered. Considering a crystalline strip of triangular lattice structure with n=30 rows, the (one-dimensional) walls confining the strip are chosen as two rigidly fixed crystalline rows at each side, commensurate with the lattice structure and, thus, stabilizing long-range order. The case when the spacing between the walls is incommensurate with the ideal triangular lattice is also studied, where (due to a transition in the number of rows, n ? n-1) the confined crystal is incommensurate with the confining boundaries, and a soliton staircase forms along the walls. It is shown that mean-square displacements (MSDs) of particles as a function of time show an overshoot and then saturate at a horizontal plateau in the commensurate case, the value of the plateau being largest in the center of the strip. Conversely, when solitons are present, MSDs are largest in the rows containing the solitons, and all MSDs do not settle down at well-defined plateaus in the direction parallel to the boundaries, due to the lack of positional long-range order in ideal two-dimensional crystals. The MSDs of the solitons (which can be treated like quasiparticles at very low temperature) have also been studied and their dynamics are found to be about an order of magnitude slower than that of the colloidal particles themselves. Finally, transport of individual colloidal particles by diffusion processes is studied: both standard vacancy-interstitial pair formation and cooperative ring rotation processes are identified. These processes require thermal activation, with activation energies of the order of 10T(m) (T(m) being the melting temperature of the crystal), while the motions due to long-wavelength phonons decrease only linearly in temperature. PMID:23214781

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

2012-11-01

305

Inertial-electrostatic confinement (IEC) fusion for space power  

Microsoft Academic Search

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

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

1991-01-01

306

Improved virtual cathode formation in Inertial Electrostatic Confinement  

Microsoft Academic Search

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

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

2009-01-01

307

Inertial electrostatic confinement as a power source for electric propulsion  

Microsoft Academic Search

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

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

1993-01-01

308

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...

309

Quantum confined Stark effect in Gaussian quantum wells: A tight-binding study  

SciTech Connect

The main characteristics of the quantum confined Stark effect (QCSE) are studied theoretically in quantum wells of Gaussian profile. The semi-empirical tight-binding model and the Green function formalism are applied in the numerical calculations. A comparison of the QCSE in quantum wells with different kinds of confining potential is presented.

Ramírez-Morales, A.; Martínez-Orozco, J. C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad Esquina Con Paseo La Bufa S/N, 98060 Zacatecas, Zac. (Mexico)

2014-05-15

310

Transient nonlinear spectroscopy of indium arsenide quantum dots: Coherent and incoherent dynamics of confined excitons  

Microsoft Academic Search

The three-dimensional confinement created by the ultrasmall semiconductor structures known as quantum dots greatly modifies the optical properties of the spatially localized carriers. These systems are presently of great interest to the research community, both for the improved understanding of the physics of confined structures, and for the potential applications of these systems to areas such as optoelectronics and quantum

Anthony Stephen Lenihan

2002-01-01

311

Progressive geometry compression  

Microsoft Academic Search

We propose a new progressive compression scheme for arbitrary topology, highly detailed and densely sampled meshes arising from geometry scanning. We observe that meshes consist of three distinct components: geometry, parameter, and connectivity information. The latter two do not contribute to the reduction of error in a compression setting. Using semi-regular meshes, parameter and connectivity information can be virtually eliminated.

Andrei Khodakovsky; Peter Schröder; Wim Sweldens

2000-01-01

312

Geometry + Technology = Proof  

ERIC Educational Resources Information Center

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

Lyublinskaya, Irina; Funsch, Dan

2012-01-01

313

Geometry and High School  

E-print Network

geometry texts in the U.S. came to be that way. #12;Geometry and Proof John T. Baldwin Background Hilbert Hilbert's Critique Three Frameworks High School Curriculum My background 1 Model theory research (35 years to change slash & back to just ampersand to get the site.) or just google glencoe. Why does it take six

Baldwin, John T.

314

Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles  

SciTech Connect

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

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

2010-06-11

315

Quench Dynamics in Confined 1+1-Dimensional Systems  

E-print Network

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.

Engelhardt, Dalit

2015-01-01

316

Some links between turtle geometry and analytic geometry  

Microsoft Academic Search

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

Neil C. Rowe

1985-01-01

317

Aspects of spinorial geometry  

E-print Network

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.

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

2006-12-14

318

The Geometry of Time  

NASA Astrophysics Data System (ADS)

A description of the geometry of space-time with all the questions and issues explained without the need for formulas. As such, the author shows that this is indeed geometry, with actual constructions familiar from Euclidean geometry, and which allow exact demonstrations and proofs. The formal mathematics behind these constructions is provided in the appendices. The result is thus not a textbook introducing readers to the theory of special relativity so they may calculate formally, but rather aims to show the connection with synthetic geometry. It presents the relation to projective geometry and uses this to illustrate the starting points of general relativity. Written at an introductory level for undergraduates, this novel presentation will also benefit teaching staff.

Liebscher, Dierck-Ekkehard

2005-04-01

319

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

SciTech Connect

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

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

1996-11-01

320

Confined Fluids as Strain Meters  

Microsoft Academic Search

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

Gunnar Bodvarsson

1970-01-01

321

String Theory and Quark Confinement  

E-print Network

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.

A. Polyakov

1997-11-01

322

Confinement regime transitions in ASDEX  

Microsoft Academic Search

The authors give an overview of the different confinement regimes observed on ASDEX and compare the changes during the transition phases with qualitative tendencies suggested by theoretical models. The transitions discussed are those between purely Ohmic heating and additional heating in the L-regime between the L- and the H-regime and between discharges with flat and peaked electron density profiles.

K. Lackner; O. Gruber; F. Wagner; G. Becker; M. Bessenrodt-Weberpals; B. Bomba; H.-S. Bosch; H. Bruhns; R. Buchse; A. Carlson; G. Dodel; A. Eberhagen; H.-U. Fahrbach; G. Fussmann; O. Gehre; J. Gernhardt; L. Giannone; S. von Goeler; K. Grassie; G. Haas; H. Herrmann; J. Hofmann; E. Holzhauer; K. Hubner; G. Janeschitz; A. Kallenbach; F. Karger; M. Kaufmann; O. Kluber; M. Kornherr; K. Krieger; J. Kucinski; R. Lang; G. Lisitano; H. M. Mayer; K. McCormick; D. Meisel; V. Mertens; E. R. Muller; H. D. Murmann; J. Neuhauser; H. Niedermeyer; R. Nolte; J. M. Noterdaeme; W. Poschenrieder; L. B. Ran; D. E. Roberts; H. Rohr; J. Roth; A. Rudyj; F. Ryter; W. Sandmann; F. Schneider; U. Schneider; W. Schneider; G. Siller; E. Speth; F. X. Soldner; A. Stabler; K. H. Steuer; U. Stroth; J. Szigeti; E. Taglauer; N. Tsois; H. Verbeek; O. Vollmer; R. Wunderlich; H. Wurz; H. R. Yang; H. Zohm

1989-01-01

323

Encapsulating Objects with Confined Types  

E-print Network

Encapsulating Objects with Confined Types Kevin O'Neill CS 711 September 15, 2003 A Security Breach Identity[] getSigners() { Identity[] pub; pub = new Identity[signers.length]; for (int i=0; ipub[i] = signers[i]; return pub; } } An Ad-hoc Fix: Is this fix good enough? · The better get

Myers, Andrew C.

324

Prospects of inertial confinement fusion  

Microsoft Academic Search

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

J. Meyer-ter-Vehn

1997-01-01

325

Momentum Confinement at Low Torque  

SciTech Connect

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

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

2007-06-26

326

String theory and quark confinement  

Microsoft Academic Search

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.

Alexandre M. Polyakov

1998-01-01

327

Inertial confinement fusion (ICF) review  

SciTech Connect

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

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

1996-03-01

328

Flex Circuitry for Confined Spaces  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

329

Scattering for Nonlinear Schrödinger Equation Under Partial Harmonic Confinement  

NASA Astrophysics Data System (ADS)

We consider the nonlinear Schrödinger equation under a partial quadratic confinement. We show that the global dispersion corresponding to the direction(s) with no potential is enough to prove global in time Strichartz estimates, from which we infer the existence of wave operators, thanks to suitable vector-fields. Conversely, given an initial Cauchy datum, the solution is global in time and asymptotically free, provided that confinement affects one spatial direction only. This stems from anisotropic Morawetz estimates, involving a marginal of the position density.

Antonelli, Paolo; Carles, Rémi; Silva, Jorge Drumond

2014-09-01

330

The Schwinger pair production rate in confining theories via holography  

E-print Network

We study the Schwinger pair production in confining theories. The production rate in an external electric field E is numerically evaluated by using the holographic description. There exist two kinds of critical values of the electric field, i) E=E_c, above which there is no potential barrier and particles are freely generated, ii) E=E_s, below which the confining string tension dominates the electric field and the pair production does not occur. We argue the universal exponents associated with the critical behaviors.

Daisuke Kawai; Yoshiki Sato; Kentaroh Yoshida

2014-06-02

331

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)

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.

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

1996-01-01

332

Induced geometry from disformal transformation  

E-print Network

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.

Fang-Fang Yuan; Peng Huang

2015-02-08

333

Induced geometry from disformal transformation  

E-print Network

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.

Yuan, Fang-Fang

2015-01-01

334

Thickness of the Mississippi River Valley confining unit, eastern Arkansas  

USGS Publications Warehouse

Concern arose in the late 1980s over the vulnerability of the Mississippi Valley alluvial aquifer to contamination from potential surface sources related to pesticide or fertilizer use, industrial activity, landfills, or livestock operations. In 1990 a study was begun to locate areas in Arkansas where the groundwater flow system is susceptible to contamination by surface contaminants. As a part of that effort, the thickness of the clay confining unit overlying the alluvial aquifer in eastern Arkansas was mapped. The study area included all or parts of 27 counties in eastern Arkansas that are underlain by the alluvial aquifer and its overlying confining unit. A database of well attributes was compiled based on data from driller's logs and from published data and stored in computer files. A confining-unit thickness map was created from the driller's-log database using geographic information systems technology. A computer program was then used to contour the data. Where the confining unit is present, it ranges in thickness from 0 feet in many locations in the study area to 140 feet in northeastern Greene County and can vary substantially over short distances. Although general trends in the thickness of the confining unit are apparent, the thickness has great spatial variability. An apparent relation exists between thickness of the confining unit and spatial variability in thickness. In areas where the thickness of the confining unit is 40 feet or less, such as in Clay, eastern Craighead, northwestern Mississippi, and Woodruff Counties, thickness of the unit tends robe more uniform than in areas where the thickness of the unit generally exceeds 40 feet, such as in Arkansas, Lonoke, and Prairie Counties. At some sites the confining unit is very thick compared to its thickness in the immediate surrounding area. Locations of abandoned Mississippi River meander channels generally coincide with location of locally thick confining unit. Deposition of the confining unit onto the coarser alluvial aquifer deposits has reduced the relief of the land surface. Hence, the altitude of the top of the alluvial aquifer varies more than the altitude of the land surface and is indicative of a depositional setting.

Gonthier, Gerard J.; Mahon, Gary L.

1993-01-01

335

Hydrodynamic instabilities in inertial confinement fusion  

SciTech Connect

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.

Hoffman, N.M.

1994-12-01

336

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

PubMed

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

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

337

Inertial-Electrostatic Confinement (IEC) Fusion For Space Propulsion  

NASA Technical Reports Server (NTRS)

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.

Nadler, Jon

1999-01-01

338

Inertial-Electrostatic Confinement (IEC) Fusion for Space Propulsion  

NASA Technical Reports Server (NTRS)

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.

Nadler, Jon

1999-01-01

339

Quantum-confined strain gradient effect in semiconductor nanomembranes  

NASA Astrophysics Data System (ADS)

Semiconductor nanomembranes can exhibit strain gradients that lead to quantum confinement effects similar to the well known quantum-confined Stark effect (QCSE) in semiconductor quantum wells. The deformation of square well into triangular well potential leads to modifications of the exciton resonance, but important differences between the quantum-confined strain gradient effect (QCsgE) and the QCSE include (i) the versatility of the QCsgE in which conduction and valence bands can have different slopes (even reverse slopes are possible), and (ii) the fact that in the QCsgE exciton shifts are determined by the gradients in the heavy-hole and light-hole energies as well as a gradient in the heavy-hole and light-hole coupling.

Binder, R.; Gu, B.; Kwong, N. H.

2014-11-01

340

Multiple reentrant glass transitions in confined hard-sphere glasses  

E-print Network

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.

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

2014-06-20

341

Native American Geometry  

NSDL National Science Digital Library

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

Forum, Math; Hardaker, Chris

2000-01-01

342

Scaling behaviour for the water transport in nanoconfined geometries  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

343

Deuterium anions in inertial electrostatic confinement devices.  

PubMed

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

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

2009-09-01

344

NUMERICAL SIMULATION OF MULTIPOLE CONFINEMENT (Examples)  

E-print Network

NUMERICAL SIMULATION OF MULTIPOLE CONFINEMENT (Examples) by J. R. Patau and J. C. Sprott April 1974 in a zero-dimensional calculation. l "Numerical Simulation of r..1ultipole Confinement, " J. R. Patau and J

Sprott, Julien Clinton

345

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

346

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

SciTech Connect

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.

Mascali, D., E-mail: davidmascali@lns.infn.it; Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy)] [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Torrisi, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy) [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Università Mediterranea di Reggio Calabria, Dipartimento di Ingegneria dell’Informazione, delle Infrastrutture e dell’Energia Sostenibile, Via Graziella, I-89100 Reggio Calabria (Italy); Sorbello, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy) [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Ingegneria Elettrica Elettronica ed Informatica, Viale Andrea Doria 6, 95125 Catania (Italy)

2014-02-15

347

Shape and Current Profile Effects on Runaway Electron Confinement  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

348

Complex Algebraic Geometry Jean Gallier  

E-print Network

Complex Algebraic Geometry Jean Gallier and Stephen S. Shatz Department of Computer is Geometry & What is Complex Algebraic Geometry? . . . . . . . . . . . . . . . . . . 7 1.2 Local Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 2.3 Hodge I, Analytic Preliminaries

Gallier, Jean

349

Swirl, confinement and nozzle effects on confined turbulent flow  

NASA Technical Reports Server (NTRS)

Predictions of swirl, confinement and nozzle effects on confined turbulent flow are exhibited and compared with five-hole pitot-probe time-mean velocity measurements. Two sets of computations are given, one using the standard k-epsilon turbulence model and the other using a C sub mu formulation model deduced from recent six-orientation single-wire hot-wire measurements. Results confirm that the accuracy of the latter model is superior. To highlight the effects of confinement and exit nozzle area on this flow, three expansion ratios and two contraction ratios are used. Predictions are given for a full range of swirl strengths using measured inlet conditions for axial, radial and swirl velocity profiles. The predicted velocity profiles illustrate the large-scale effects of inlet swirl on flowfields. It appears that a strong contraction nozzle has a pronounced effect, on swirl flow cases, with discouragement of central recirculation zones, and forward flow in highly swirled vortex core regions. The expansion ratio value has large-scale effects on the size and location of the recirculation zones.

Abujelala, M. T.; Lilley, D. G.

1984-01-01

350

Quark confinement and the renormalization group.  

PubMed

Recent approaches to quark confinement are reviewed, with an emphasis on their connection to renormalization group (RG) methods. Basic concepts related to confinement are introduced: the string tension, Wilson loops and Polyakov lines, string breaking, string tension scaling laws, centre symmetry breaking and the deconfinement transition at non-zero temperature. Current topics discussed include confinement on R(3)×S(1), the real-space RG, the functional RG and the Schwinger-Dyson equation approach to confinement. PMID:21646275

Ogilvie, Michael C

2011-07-13

351

Nozzle-geometry effects in liquid jet impingement heat transfer  

Microsoft Academic Search

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

Suresh V. Garimella; Boris Nenaydykh

1996-01-01

352

What Is Geometry?  

ERIC Educational Resources Information Center

Discussed are the major historical developments of geometry. Euclid, Descartes, Klein's Erlanger Program, Gaus and Riemann, globalization, topology, Elie Cartan, and an application to molecular biology are included as topics. (KR)

Chern, Shiing-Shen

1990-01-01

353

Flyby Geometry Optimization Tool  

NASA Technical Reports Server (NTRS)

The Flyby Geometry Optimization Tool is a computer program for computing trajectories and trajectory-altering impulsive maneuvers for spacecraft used in radio relay of scientific data to Earth from an exploratory airplane flying in the atmosphere of Mars.

Karlgaard, Christopher D.

2007-01-01

354

Functional Differential Geometry  

E-print Network

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 ...

Sussman, Gerald Jay

2005-02-02

355

Gingerbread-House Geometry.  

ERIC Educational Resources Information Center

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)

Emenaker, Charles E.

1999-01-01

356

Exploratorium: Geometry Playground  

NSDL National Science Digital Library

You've probably been to a playground, but have you been to the Geometry Playground? It's just as much fun, and it may change the way you think about geometry. Created by the good folks at the Exploratorium in San Francisco, this exhibit is meant to complement the traveling exhibit which has been featured in other science museums around the United States. The exhibit here contains three sections: Seeing, Moving, and Fitting Things Together. In the Seeing exhibit, visitors can make their way through a fine photo essay about the invisible geometry of light, while the Moving section gets interested parties up and exploring geometry with their bodies. Each of these sections has great photo essays, complemented by animations and fun activities.

2012-04-20

357

Geometry (MathPages)  

NSDL National Science Digital Library

"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.

Brown, Kevin

2007-12-11

358

Analysis of No-Flow Boundaries in Mixed Unconfined-Confined Aquifer Systems  

E-print Network

flow influence. This study has used Girinskii’s Potential in combination with MATLAB to depict how changes in aquifer dimensions, hydraulic properties, regional flow rates, and pumping rates affect the size and shape of the unconfined-confined boundary...

Langerlan, Kent A.

2010-07-14

359

PT-symmetric knotting of coordinates: a new, topological mechanism of quantum confinement  

E-print Network

We construct an exactly solvable PT-symmetric example of Sturmian bound states which exist in the absence of any confining potential. Their origin is purely topological -- these states live on certain nontrivial contours of complex coordinates.

Miloslav Znojil

2008-01-03

360

Static use-based object confinement  

Microsoft Academic Search

The confinement of object references is a significant se- curity concern for modern programming languages. We define a language that serves as a uniform model for a va- riety of confined object reference systems. A use-based approach to confinement is adopted, which we argue is more expressive than previous communication-based ap- proaches. We then develop a readable, expressive type system

Christian Skalka; Scott F. Smith

2005-01-01

361

Quantum Computation as Geometry  

E-print Network

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.

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

2006-03-19

362

Fractal energy spectrum of a polariton gas in a Fibonacci quasiperiodic potential.  

PubMed

We report on the study of a polariton gas confined in a quasiperiodic one-dimensional cavity, described by a Fibonacci sequence. Imaging the polariton modes both in real and reciprocal space, we observe features characteristic of their fractal energy spectrum such as the opening of minigaps obeying the gap labeling theorem and log-periodic oscillations of the integrated density of states. These observations are accurately reproduced solving an effective 1D Schrödinger equation, illustrating the potential of cavity polaritons as a quantum simulator in complex topological geometries. PMID:24765996

Tanese, D; Gurevich, E; Baboux, F; Jacqmin, T; Lemaître, A; Galopin, E; Sagnes, I; Amo, A; Bloch, J; Akkermans, E

2014-04-11

363

Fractal Energy Spectrum of a Polariton Gas in a Fibonacci Quasiperiodic Potential  

NASA Astrophysics Data System (ADS)

We report on the study of a polariton gas confined in a quasiperiodic one-dimensional cavity, described by a Fibonacci sequence. Imaging the polariton modes both in real and reciprocal space, we observe features characteristic of their fractal energy spectrum such as the opening of minigaps obeying the gap labeling theorem and log-periodic oscillations of the integrated density of states. These observations are accurately reproduced solving an effective 1D Schrödinger equation, illustrating the potential of cavity polaritons as a quantum simulator in complex topological geometries.

Tanese, D.; Gurevich, E.; Baboux, F.; Jacqmin, T.; Lemaètre, A.; Galopin, E.; Sagnes, I.; Amo, A.; Bloch, J.; Akkermans, E.

2014-04-01

364

Soft Confinement for Polymer Solutions  

E-print Network

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.

Oya, Yutaka

2014-01-01

365

Nano-confined Polymer Crystallization in Self-assembled Block Copolymers*  

NASA Astrophysics Data System (ADS)

A convenient and effective method to study nano-confined polymer crystallization is to use self-assembled block copolymers as templates. Various confined geometries can be achieved using diblock copolymers on a nanometer length scale, such as lamellae, cylinders, spheres, double gyroids, and perforated layers. In this research, nano-confined polymer crystallization is studied in a poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer system. PEO crystal orientations within various confined geometries have been found to be dependent upon the crystallization temperatures (Tc). In addition to a lamellar confined environment, a cylinder-forming PEO-b-PS/PS blend shows that the PEO crystal c-axis changes from inclined to perpendicular to the cylinder axis with increasing Tc. In a hexagonal-perforated-layer (HPL) sample, the orientation of the PEO crystal c-axis changes from parallel to inclined to the layers with increasing Tc. At high Tcs in the HPL phase, the PEO lamellar crystals grow specifically along the (100) planes of the hexagonal lattice. These specific crystal orientations have been found in early stages of the PEO crystal growth.

Cheng, S. Z. D.; Zhu, L.; Huang, P.; Calhoun, B. H.; Ge, Q.; Quirk, R. P.; Thomas, E. L.; Hsiao, B. S.; Yeh, F.; Liu, L.; Lotz, B.

2001-03-01

366

Ion beam inertial confinement target  

DOEpatents

A target for implosion by ion beams composed of a spherical shell of frozen DT surrounded by a low-density, low-Z pusher shell seeded with high-Z material, and a high-density tamper shell. The target has various applications in the inertial confinement technology. For certain applications, if desired, a low-density absorber shell may be positioned intermediate the pusher and tamper shells.

Bangerter, Roger O. (Danville, CA); Meeker, Donald J. (Livermore, CA)

1985-01-01

367

Effects of resistive interchange instabilities on energy confinement in reversed-field pinch  

SciTech Connect

Electron conduction losses due to magnetic flutter produced by resistive interchange instabilities and the resulting confinement deterioration mechanism are investigated analytically. Using approximate solutions of MHD equations for even and odd potential parities, the potential and magnetic perturbation levels at saturation are estimated. These results are used to calculate the stochastic magnetic field diffusion coefficients. An expression for the anomalous electron thermal conductivity is then derived for collision-less and collisional regimes. Scaling laws for energy confinement are inferred therefrom.

AN Zhi-gang; Diamond, P.H.

1986-01-01

368

Spectral properties of a confined nonlinear quantum oscillator in one and three dimensions  

SciTech Connect

We analyze the spectral behaviour of a nonlinear quantum oscillator model under confinement. The underlying potential is given by a harmonic oscillator interaction plus a nonlinear term that can be weakened or strengthened through a parameter. Numerical eigenvalues of the model in one and three dimensions are presented. The asymptotic behaviour of the eigenvalues for confinement relaxation and for vanishing nonlinear term in the potential is investigated. Our findings are compared with existing results.

Schulze-Halberg, Axel; Gordon, Christopher R. [Department of Mathematics and Actuarial Science, Indiana University Northwest, 3400 Broadway, Gary, Indiana 46408 (United States)] [Department of Mathematics and Actuarial Science, Indiana University Northwest, 3400 Broadway, Gary, Indiana 46408 (United States)

2013-04-15

369

Denaturation and renaturation behaviors of short DNA in a confined space  

NASA Astrophysics Data System (ADS)

A deep understanding to the denaturation and renaturation behaviors of DNA in a confined state is fundamentally important to control the self-assembly of DNA in a chamber or channel for various applications. In this report, we study the denaturation and renaturation behaviors of short DNA confined in cylindrical and spherical spaces with the 3-Site-Per-Nucleotide coarse-grained DNA model applying the replica exchange molecular dynamics technology. It is found that as the confinement size decreases, the melting temperature Tm increases and the transition becomes broad. The analysis of the potential of mean force shows that the confinement increases the relative free energy of the denatured state of DNA and decreases the renaturation energy barrier. Besides the denatured and native states, the metastable parallel-stranded structure is also found. The simulation results show that the shapes of the confinement spaces and the short DNA sequences remarkably affect the renaturation behavior. In the cylindrical space, the DNA renaturation changes from random-binding to slithering-binding with the size of the confinement space decreasing. In contrast, the DNA renaturation in the spherical and symmetrical confinement space proceeds through strand binding and rolling. The relationship between the melting temperature and the confinement size, ?Tm/Tm ˜ Rc-?, is estimated and the exponential index ? equals about 1.32 and 1.75 in the cylindrical and spherical confinements, respectively. It is further compared with the theoretical result of the rigid rod model and a qualitative agreement with the simulation is achieved.

Li, Huaping; Wang, Zilu; Li, Ningning; He, Xuehao; Liang, Haojun

2014-07-01

370

Order in very cold confined plasmas  

SciTech Connect

The study of the structure and dynamic properties of classical systems of charged particles confined by external forces, and cooled to very low internal energies, is the subject of this talk. An infinite system of identical charged particles has been known for some time to form a body-centered cubic lattice and is a simple classical prototype for condensed matter. Recent technical developments in storage rings, ion traps, and laser cooling of ions, have made it possible to produce such systems in the laboratory, though somewhat modified because of their finite size. I would like to discuss what one may expect in such systems and also show some examples of experiments. If we approximate the potential of an ion trap with an isotropic harmonic force F = {minus}Kr then the Hamiltonian for this collection of ions is the same as that for J. J. Thomson`s ``plum pudding`` model of the atom, where electrons were thought of as discrete negative charges imbedded in a larger, positive, uniformly charged sphere. The harmonic force macroscopically is canceled by the average space-charge forces of the plasma-, and this fixes the overall radius of the distribution. What remains, are the residual two-body Coulomb interactions that keep the particles within the volume as nearly equidistant as possible in order to minimize the potential energy. The configurations obtained for the minimum energy of small ionic systems [2] in isotropic confinement are shown in figure 1. Indeed this is an `Exotic Atom` and fits well into the subject of this symposium honoring the 60th birthday of Professor Toshi Yamazaki.

Schiffer, J.P. [Argonne National Lab., IL (United States)]|[Univ. of Chicago, Chicago, IL (United States)

1995-12-31

371

Students Discovering Spherical Geometry Using Dynamic Geometry Software  

ERIC Educational Resources Information Center

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

Guven, Bulent; Karatas, Ilhan

2009-01-01

372

Thermodynamics, Structure, and Dynamics of Water Confined between Hydrophobic Plates  

E-print Network

We perform molecular dynamics simulations of 512 water-like molecules that interact via the TIP5P potential and are confined between two smooth hydrophobic plates that are separated by 1.10 nm. We find that the anomalous thermodynamic properties of water are shifted to lower temperatures relative to the bulk by $\\approx 40$ K. The dynamics and structure of the confined water resemble bulk water at higher temperatures, consistent with the shift of thermodynamic anomalies to lower temperature. Due to this $T$ shift, our confined water simulations (down to $T = 220$ K) do not reach sufficiently low temperature to observe a liquid-liquid phase transition found for bulk water at $T\\approx 215$ K using the TIP5P potential. We find that the different crystalline structures that can form for two different separations of the plates, 0.7 nm and 1.10 nm, have no counterparts in the bulk system, and discuss the relevance to experiments on confined water.

Pradeep Kumar; Sergey V. Buldyrev; Francis W. Starr; Nicolas Giovambattista; H. Eugene Stanley

2005-07-05

373

Inertial Confinement Fusion R&D and Nuclear Proliferation  

SciTech Connect

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.

Robert J. Goldston

2011-04-28

374

Proton radiography of PBX 9502 detonation shock dynamics confinement sandwich test  

SciTech Connect

Recent results utilizing proton radiography (P-Rad) during the detonation of the high explosive PBX 9502 are presented. Specifically, the effects of confinement of the detonation are examined in the LANL detonation confinement sandwich geometry. The resulting detonation velocity and detonation shock shape are measured. In addition, proton radiography allows one to image the reflected shocks through the detonation products. Comparisons are made with detonation shock dynamics (DSD) and reactive flow models for the lead detonation shock and detonation velocity. In addition, predictions of reflected shocks are made with the reactive flow models.

Aslam, Tariq D [Los Alamos National Laboratory; Jackson, Scott I [Los Alamos National Laboratory; Morris, John S [Los Alamos National Laboratory

2009-01-01

375

Graphene growth under Knudsen molecular flow on a confined catalytic metal coil  

NASA Astrophysics Data System (ADS)

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

Bong, Hyojin; Jo, Sae Byeok; Kang, Boseok; Lee, Seong Kyu; Kim, Hyun Ho; Lee, Seung Goo; Cho, Kilwon

2015-01-01

376

An Introduction to Projective Geometry  

NSDL National Science Digital Library

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/.

Birchfield, Stan

2008-09-19

377

The Bifurcation Approach Hyperbolic Geometry  

E-print Network

1 The Bifurcation Approach To Hyperbolic Geometry Abraham A. Ungar Department of Mathematics North of relativity physics gives rise to important isometries in hyperbolic geometry that expose analogies with Eu­ clidean geometry. These, in turn, suggest our bifurcation approach to hy­ perbolic geometry, according

Ungar, Abraham A.

378

Three-Dimensional Geometry and  

E-print Network

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

Landweber, Laura

379

Geometry, noncommutative algebra and representations  

E-print Network

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

Wirosoetisno, Djoko

380

Geometry and Cloaking Devices  

NASA Astrophysics Data System (ADS)

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

Ochiai, T.; Nacher, J. C.

2011-09-01

381

Origins of cellular geometry  

PubMed Central

Cells are highly complex and orderly machines, with defined shapes and a startling variety of internal organizations. Complex geometry is a feature of both free-living unicellular organisms and cells inside multicellular animals. Where does the geometry of a cell come from? Many of the same questions that arise in developmental biology can also be asked of cells, but in most cases we do not know the answers. How much of cellular organization is dictated by global cell polarity cues as opposed to local interactions between cellular components? Does cellular structure persist across cell generations? What is the relationship between cell geometry and tissue organization? What ensures that intracellular structures are scaled to the overall size of the cell? Cell biology is only now beginning to come to grips with these questions. PMID:21880160

2011-01-01

382

Noncommutative Geometry and Arithmetic  

E-print Network

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.

Matilde Marcolli

2010-03-18

383

Five dimensional microstate geometries  

NASA Astrophysics Data System (ADS)

In this thesis, we discuss the possibility of exploring the statistical mechanics description of a black hole from the point view of supergravity. Specifically, we study five dimensional microstate geometries of a black hole or black ring. At first, we review the method to find the general three-charge BPS supergravity solutions proposed by Bena and Warner. By applying this method, we show the classical merger of a black ring and black hole on [Special characters omitted.] base space in general are irreversible. On the other hand, we review the solutions on ambi-polar Gibbons-Hawking (GH) base which are bubbled geometries. There are many possible microstate geometries among the bubbled geometries. Particularly, we show that a generic blob of GH points that satisfy certain conditions can be either microstate geometry of a black hole or black ring without horizon. Furthermore, using the result of the entropy analysis in classical merger as a guide, we show that one can have a merger of a black-hole blob and a black-ring blob or two black-ring blobs that corresponds to a classical irreversible merger. From the irreversible mergers, we find the scaling solutions and deep microstates which are microstate geometries of a black hole/ring with macroscopic horizon. These solutions have the same AdS throats as classical black holes/rings but instead of having infinite throats, the throat is smoothly capped off at a very large depth with some local structure at the bottom. For solutions that produced from U (1) × U (1) invariant merger, the depth of the throat is limited by flux quantization. The mass gap is related with the depth of this throat and we show the mass gap of these solutions roughly match with the mass gap of the typical conformal-field-theory (CFT) states. Therefore, based on AdS/CFT correspondence, they can be dual geometries of the typical CFT states that contribute to the entropy of a black hole/ring. On the other hand, we show that for the solutions produced from more general merger (without U (1) × U (1) invariance), the throat can be arbitrarily deep. This presents a puzzle from the point view of AdS/CFT correspondence. We propose that this puzzle may be solved by some quantization of the angle or promoting the flux vectors to quantum spins. Finally, we suggest some future directions of further study including the puzzle of arbitrary long AdS throat and a general coarse-graining picture of microstate geometries.

Wang, Chih-Wei

384

Geometry in Action  

NSDL National Science Digital Library

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).

Eppstein, David

385

Fast particle confinement with optimized coil currents in the W7-X stellarator  

NASA Astrophysics Data System (ADS)

One of the principal goals of the W7-X stellarator is to demonstrate good confinement of energetic ions at finite ?. This confinement, however, is sensitive to the magnetic field configuration and is thus vulnerable to design modifications of the coil geometry. The collisionless drift orbit losses for 60 keV protons in W7-X are studied using the ANTS code. Particles in this energy range will be produced by the neutral beam injection (NBI) system being constructed for W7-X, and are particularly important because protons at this energy accurately mimick the behaviour of 3.5 MeV ?-particles in a HELIAS reactor. To investigate the possibility of improved fast particle confinement, several approaches to adjust the coil currents (5 main field coil currents +2 auxiliary coil currents) were explored. These strategies include simple rules of thumb as well as computational optimization of various properties of the magnetic field. It is shown that significant improvement of collisionless fast particle confinement can be achieved in W7-X for particle populations similar to ? particles produced in fusion reactions. Nevertheless, the experimental goal of demonstrating confinement improvement with rising plasma pressure using an NBI-generated population appears to be difficult based on optimization of the coil currents only. The principal reason for this difficulty is that the NBI deposition profile is broader than the region of good fast-ion confinement around the magnetic axis.

Drevlak, M.; Geiger, J.; Helander, P.; Turkin, Y.

2014-07-01

386

Spherical particle immersed in a nematic liquid crystal: Effects of confinement on the director field configurations  

NASA Astrophysics Data System (ADS)

The effects of confinement on the director field configurations are studied for a spherical particle immersed in a nematic liquid crystal. The liquid crystal is confined in a cylindrical geometry and the particle is located on the axis of symmetry. A finite element method is used to minimize the Frank free energy for various sizes of the system. The liquid crystal is assumed to possess strong anchoring at all the surfaces in the system. Two structures are examined for strong homeotropic anchoring at the surface of the particle: configuration with a Saturn ring disclination line and configuration with a satellite point defect (hedgehog defect). It is shown that the equilibrium locations of the Saturn ring and of the hedgehog point defect change with confinement. It is also found that confinement induces an increase in the elastic free energy that differs substantially with the type of topological defect under consideration. In particular, the evaluation of the total free energy that includes an approximate contribution for the core defect shows that, for micrometer-sized particles in confined systems, the Saturn ring configuration appears to be more stable than the hedgehog defect. This result is in contrast to the bulk situation, where the hedgehog is more stable than the Saturn ring, and it helps explain recent experimental observations of Saturn ring defects around confined micrometer-sized solid particles.

Grollau, S.; Abbott, N. L.; de Pablo, J. J.

2003-01-01

387

Example of an explicit function for confining classical Yang-Mills fields with quantum fluctuations in the path integral scheme  

E-print Network

This article reports an explicit function form for confining classical Yang-Mills vector potentials and quantum fluctuations around the classical field. The classical vector potential, which is composed of a confining localized function and an unlocalized function, satisfies the classical Yang-Mills equation. The confining localized function contributes to the Wilson loop, while the unlocalized function makes no contribution to this loop. The confining linear potential between a heavy fermion and antifermion is due to (1) the Lie algebra and (2) the form of the confining localized function which has opposite signs at the positions of the particle and antiparticle along the Wilson loop in the time direction. Some classical confining parts of vector potentials also change sign on inversion of the coordinates of the axis perpendicular to the axis joining the two particles. The localized parts of the vector potentials are squeezed around the axis connecting the two particles, and the string tension of the confining linear potential is derived. Quantum fluctuations are formulated using a field expression in terms of local basis functions in real spacetime. The quantum path integral gives the Coulomb potential between the two particles in addition to the linear potential due to the classical fields.

Kimichika Fukushima; Hikaru Sato

2014-02-03

388

Rheology of confined granular flows  

SciTech Connect

The properties of confined granular flows on a heap are studied through numerical simulations and experiments. We address how such system can be simulated with period boundaries in the flow direction. The packing fraction and velocity profiles are found to be described by one length scale. The dependence of the kinematic properties on the number of grains and on micromechanical parameters (coefficient of restitution and coefficient of friction) is described. Our results show that the friction at the sidewalls gradually decreases and that this decrease can be explained by the intermittent motion of the grains in the quasistatic part of the flow.

Richard, Patrick; Valance, Alexandre; Metayer, Jean-Francois; Crassous, Jerome; Delannay, Renaud [Universite Rennes 1, Institut de Physique de Rennes, UMR CNRS 6251, 263 av. General Leclerc, 35042 Rennes cedex FRANCE (France); Louge, Michel [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 (United States)

2010-05-05

389

Theory of rheology in confinement  

E-print Network

The viscosity of fluids is generally understood in terms of kinetic mechanisms, i.e., particle collisions, or thermodynamic ones as imposed through structural distortions upon e.g. applying shear. Often the former is less relevant, and (damped) Brownian particles are considered good fluid model systems. We formulate a general theoretical approach for rheology in confinement, based on the many particle diffusion equation, evaluated via classical density functional theory. We discuss the viscosity for the situation of two parallel walls in relative motion as a function of wall-to-wall distance.

Artem A. Aerov; Matthias Krüger

2014-12-12

390

In-situ Fabrication and Electronic Characterization of Junction-confined Single Layer Graphene Nanoribbons  

NASA Astrophysics Data System (ADS)

We report electronic measurements on high quality single layer junction-confined graphene nanoribbons fabricated in a transmission electron microscope (TEM). In this work, a process is demonstrated for the fabrication and confirmation of pristine single layer graphene nanoribbons using high vacuum current annealing and precision nano-sculpting, both conducted within the vacuum chamber of a TEM. Briefly, CVD-grown graphene is patterned into a freely-suspended nanoribbon connected to large area contacts. The sample is then mounted on a TEM holder with electrical feedthroughs to allow for simultaneous imaging and in-situ electrical transport measurements within the TEM. A focused electron beam is used to progressively narrow the ribbon, providing a platform to controllably sculpt and define the device geometry while characterizing its electrical properties. In-situ electrical measurements and TEM imaging with sub-nm resolution revealed the dependence of the nanoribbon resistance as a function of width in the range 17 -- 280 nm. Monolayer graphene were found to sustain current densities in excess of 5 x 10^9 A/cm^2, orders of magnitude higher than copper while the conductance varied approximately as w^0.75, where w is the ribbon width in nanometers. These results demonstrates graphene's potential as a next generation, high performance interconnects material with the ability to reach single-digit technology nodes at the level of a single atomic layer.

Qi, Zhengqing John; Rodriguez-Manzo, Julio; Hong, Sung Ju; Drndic, Marija; Johnson, A. T. Charlie

2013-03-01

391

Galilean invariance in confined quantum systems: Implications on spectral gaps, superfluid flow, and periodic order  

E-print Network

Galilean invariance leaves its imprint on the energy spectrum and eigenstates of $N$ quantum particles, bosons or fermions, confined in a bounded domain. It endows the spectrum with a recurrent structure which in capillaries or elongated traps of length $L$ and cross-section area $s_\\perp$ leads to spectral gaps $n^2h^2s_\\perp\\rho/(2mL)$ at wavenumbers $2n\\pi s_\\perp\\rho$, where $\\rho$ is the number density and $m$ is the particle mass. In zero temperature superfluids, in toroidal geometries, it causes the quantization of the flow velocity with the quantum $h/(mL)$ or that of the circulation along the toroid with the known quantum $h/m$. Adding a "friction" potential which breaks Galilean invariance, the Hamiltonian can have a superfluid ground state at low flow velocities but not above a critical velocity which may be different from the velocity of sound. In the limit of infinite $N$ and $L$, if $N/L=s_\\perp\\rho$ is kept fixed, translation invariance is broken, the center of mass has a periodic distribution, while superfluidity persists at low flow velocities. This conclusion holds for the Lieb-Liniger model.

Andras Suto

2014-03-12

392

Probing confinement resonances by photoionizing Xe inside a C60+ molecular cage  

NASA Astrophysics Data System (ADS)

Double photoionization accompanied by loss of n C atoms (n=0, 2, 4, 6) was investigated by merging beams of Xe@C60+ ions and synchrotron radiation and measuring the yields of product ions. The giant 4d dipole resonance of the caged Xe atom has a prominent signature in the cross section for these product channels, which together account for 6.2 ± 1.4 of the total Xe 4d oscillator strength of 10. Compared to that for a free Xe atom, the oscillator strength is redistributed in photon energy due to multipath interference of outgoing Xe 4d photoelectron waves that may be transmitted or reflected by the spherical C60+ molecular cage, yielding so-called confinement resonances. The data are compared with an earlier measurement and with theoretical predictions for this single-molecule photoelectron interferometer system. Relativistic R-matrix calculations for the Xe atom in a spherical potential shell representing the fullerene cage show the sensitivity of the interference pattern to the molecular geometry.

Phaneuf, R. A.; Kilcoyne, A. L. D.; Aryal, N. B.; Baral, K. K.; Esteves-Macaluso, D. A.; Thomas, C. M.; Hellhund, J.; Lomsadze, R.; Gorczyca, T. W.; Ballance, C. P.; Manson, S. T.; Hasoglu, M. F.; Schippers, S.; Müller, A.

2013-11-01

393

Galilean Invariance in Confined Quantum Systems: Implications for Spectral Gaps, Superfluid Flow, and Periodic Order  

NASA Astrophysics Data System (ADS)

Galilean invariance leaves its imprint on the energy spectrum and eigenstates of N quantum particles, bosons, or fermions, confined in a bounded domain. It endows the spectrum with a recurrent structure, which in capillaries or elongated traps of length L and cross-section area s? leads to spectral gaps n2h2s??/(2mL) at wave numbers 2n?s??, where ? is the number density and m is the particle mass. In zero temperature superfluids, in toroidal geometries, it causes the quantization of the flow velocity with the quantum h/(mL) or that of the circulation along the toroid with the known quantum h/m. Adding a "friction" potential, which breaks Galilean invariance, the Hamiltonian can have a superfluid ground state at low flow velocities but not above a critical velocity, which may be different from the velocity of sound. In the limit of infinite N and L, if N/L=s?? is kept fixed, translation invariance is broken, and the center of mass has a periodic distribution, while superfluidity persists at low flow velocities. This conclusion holds for the Lieb-Liniger model.

Süt?, András

2014-03-01

394

Pattern formation in confined chemical gardens  

NASA Astrophysics Data System (ADS)

Chemical gardens are plant-like mineral structures first described in the seventeenth century and popularly known from chemistry sets for children. They are classically grown in three-dimensional containers by placing a solid metal-salt seed into a silicate solution. When the metal salt starts dissolving in the silicate solution, a semi-permeable membrane forms by precipitation across which water is pumped by osmosis from the silicate solution into the metal salt solution, further dissolving the salt. Above a given pressure, the membrane breaks. The dissolved metal salt solution being generally less dense than the reservoir silicate solution, it rises as a buoyant jet through the broken membrane and further precipitates in contact with the silicate solution, producing a collection of mineral forms that resemble a garden. Such gardens are the subject of increased interest as a model system to understand pattern formation in sea-ice brinicles and hydrothermal vents on the seafloor, among others. All these self-organized precipitation structures at the interface between chemistry, fluid dynamics and mechanics share indeed common chemical, mechanical and electrical properties. In this framework, we study experimentally spatial patterns resulting from the growth of chemical gardens in confined quasi-two-dimensional (2D) geometries upon radial injection of a metallic salt solution into a silicate solution in a horizontal Hele-Shaw cell. We find a large variety of patterns including spirals, fingers, worms, filiform tubes, and flower-like patterns. By exploring the phase space of reactant concentrations and injection flow rates, we observe transitions between these spatio-temporal structures resulting from a coupling between the precipitation reaction, mechanical effects and hydrodynamic instabilities.

De Wit, Anne; Haudin, Florence; Brau, Fabian; Cartwright, Julyan

2014-05-01

395

Inertial electrostatic confinement I(IEC) neutron sources  

SciTech Connect

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2*10 [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.

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. [Illinois Univ., Urbana, IL (United States)

1995-12-01

396

Atomic processes in Inertial Electrostatic Confinement (IEC) devices  

SciTech Connect

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2*10{sup 10} neutrons/sec. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. Atomic physics effects strongly influence the performance of all of these systems. Important atomic effects include elastic scattering, ionization, excitation, and charge exchange. This paper discusses how an IEC system is influenced by these effects and how to design around them. Theoretical modeling and experimental results are presented.

Nebel, R.A.; Turner, L.; Tiouririne, T.N.; Barnes, D.C.; Nystrom, W.D. [Los Alamos National Lab., NM (United States); Bussard, R.W. [Energy/Matter Conversion Corp., Manassas, VA (United States); Miley, G.H.; Javedani, J.; Yamamoto, Y. [Illinois Univ., Urbana, IL (United States)

1993-12-31

397

Perfect Abelian dominance of quark confinement in SU(3) QCD  

NASA Astrophysics Data System (ADS)

We study the Abelian projection of quark confinement in SU(3) quenched lattice QCD, in terms of the dual superconductor picture. In the maximal Abelian gauge, we perform the Cartan decomposition of the non-Abelian gauge field on a 3 24 lattice with spacing a ?0.058 , 0.10 fm (i.e., ? =6.4 , 6.0), and investigate the interquark potential V (r ), the Abelian part VAbel(r ) , and the off-diagonal part Voff(r ). For the potential analysis, we use both on-axis data and several types of off-axis data, with larger numbers of gauge configurations. Remarkably, we find almost perfect Abelian dominance of the string tension (quark-confining force) on the large-volume lattice. Also, we find a simple but nontrivial relation of V (r )?VAbel(r )+Voff(r ) .

Sakumichi, Naoyuki; Suganuma, Hideo

2014-12-01

398

Discharge characteristics of the spherical inertial electrostatic confinement (IEC) device  

Microsoft Academic Search

The University of Illinois inertial electrostatic confinement (IEC) device provides 107 2.5 MeV D-D neutrons\\/second when operated with a steady-state deuterium discharge at 70 kV. Being compact and lightweight, the IEC potentially represents an attractive portable neutron source for activation analysis applications. The plasma discharge in the IEC is unique, using a spherical grid in a spherical vacuum vessel with

George H. Miley; Yibin Gu; John M. DeMora; Robert A. Stubbers; Timothy A. Hochberg; Jon H. Nadler; Robert A. Anderl

1997-01-01

399

Discharge characteristics of the spherical inertial electrostatic confinement (IEC) device  

Microsoft Academic Search

The inertial electrostatic confinement (IEC) device provides 10 7 2.5-MeV D-D neutrons\\/second, when operated with a deuterium discharge at 70 kV. This potentially provides an important portable neutron source for various activation analysis applications. The discharge involved is unique, in that it uses a spherical grid in a spherical vacuum vessel. The discharge is struck between the grid and the

G. H. Miley; Y. Gu; J. M. DeMora; R. A. Stubbers; T. A. Hochberg; J. H. Nadler; R. A. Anderl

1996-01-01

400

Differential Geometry: Circle Packings  

E-print Network

Differential Geometry: Circle Packings [CirclePack, Ken Stephenson] [A Circle Packing Algorithm if it preserves oriented angles. That is, the map sends "tiny" circles to circles. Re Re Re ImImIm f(z)=z2.2 f the curve to the unit disk. #12;Conformal Maps Intuition: Since conformal maps send "tiny" circles

Kazhdan, Michael

401

Quantum Entanglement and Geometry  

E-print Network

The phenomenon of quantum entanglement is thoroughly investigated, focussing especially on geometrical aspects and on bipartite systems. After introducing the formalism and discussing general aspects, some of the most important separability criteria and entanglement measures are presented. Finally, the geometry of 2x2- and 3x3-dimensional state spaces is analysed and visualised.

Andreas Gabriel

2010-03-19

402

in Noncommutative Geometry  

Microsoft Academic Search

In a one-dimensional lattice, the induced metric (from a noncommutative geometry calculation) breaks translation invariance. This leads to some inconsistencies among different spectator frames, in the observation of the hoppings of a test particle between lattice sites. To resolve the inconsistencies between the different spectator frames, we replace the test particle's bare mass by an effective locally dependent mass. This

E. Atzmon

403

Spacetime and Euclidean geometry  

NASA Astrophysics Data System (ADS)

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.

Brill, Dieter; Jacobson, Ted

2006-04-01

404

Noncommutative Geometry for Pedestrians  

E-print Network

A short historical review is made of some recent literature in the field of noncommutative geometry, especially the efforts to add a gravitational field to noncommutative models of space-time and to use it as an ultraviolet regulator. An extensive bibliography has been added containing reference to recent review articles as well as to part of the original literature.

J. Madore

1999-06-16

405

Fractal geometry of music.  

PubMed Central

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

Hsü, K J; Hsü, A J

1990-01-01

406

Geoff Giles and Geometry  

ERIC Educational Resources Information Center

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

Fielker, David

2007-01-01

407

Sliding vane geometry turbines  

DOEpatents

Various systems and methods are described for a variable geometry turbine. In one example, a turbine nozzle comprises a central axis and a nozzle vane. The nozzle vane includes a stationary vane and a sliding vane. The sliding vane is positioned to slide in a direction substantially tangent to an inner circumference of the turbine nozzle and in contact with the stationary vane.

Sun, Harold Huimin; Zhang, Jizhong; Hu, Liangjun; Hanna, Dave R

2014-12-30

408

The Geometry Tutor  

Microsoft Academic Search

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

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

1985-01-01

409

Computability in Computational Geometry  

Microsoft Academic Search

We promote the concept of object directed computability in computational geometry in order to faithfully generalise the well- established theory of computability for real numbers and real functions. In object directed computability, a geometric object is computable if it is the effective limit of a sequence of finitary objects of the same type as the original object, thus allowing a

Abbas Edalat; Ali Asghar Khanban; André Lieutier

2005-01-01

410

The Geometry of Viruses.  

ERIC Educational Resources Information Center

Presented is an activity in which students make models of viruses, which allows them to visualize the shape of these microorganisms. Included are some background on viruses, the biology and geometry of viruses, directions for building viruses, a comparison of cells and viruses, and questions for students. (KR)

Case, Christine L.

1991-01-01

411

Dragon Shapes: Geometry Challenge  

NSDL National Science Digital Library

This iOS app requires users to apply their knowledge of geometry to solve Tangram puzzles. The app introduces the challenge through a brief episode and then provides challenges of increasing difficulty throughout level 1. There are fourteen free puzzles in all, with additional puzzles available through an in app purchase.

Lighthouse Learning Studios Ltd

2013-10-14

412

Advanced geometries and regimes  

SciTech Connect

We review and discuss different schemes of laser ion acceleration as well as advanced target geometries in connection with the development of the laser-driven proton source for hadron therapy of oncological diseases, which is a part of the ELIMED project.

Bulanov, S. S. [Univeristy of California, Berkeley, CA, 94720 (United States)] [Univeristy of California, Berkeley, CA, 94720 (United States); Bulanov, S. V. [Kansai Photon Science Institute, JAEA, Kizugawa, Kyoto 619-0215 (Japan)] [Kansai Photon Science Institute, JAEA, Kizugawa, Kyoto 619-0215 (Japan); Turchetti, G. [Dipartimento di Fisica, Università di Bologna and INFN Sezione di Bologna, Via Irnerio, 46-I-40126 Bologna (Italy)] [Dipartimento di Fisica, Università di Bologna and INFN Sezione di Bologna, Via Irnerio, 46-I-40126 Bologna (Italy); Limpouch, J.; Klimo, O.; Psikal, J. [Institute of Physics of the ASCR, ELI-Beamlines/HiLASE project, Na Slovance 2, 18221 Prague, Czech Republic and Czech Technical University in Prague, FNSPE, Brehova 7, 115 19 Prague (Czech Republic)] [Institute of Physics of the ASCR, ELI-Beamlines/HiLASE project, Na Slovance 2, 18221 Prague, Czech Republic and Czech Technical University in Prague, FNSPE, Brehova 7, 115 19 Prague (Czech Republic); Antici, P. [Dipartimento di Energetica ed INFM, Università di Roma, La Sapienza, 00165 Roma (Italy)] [Dipartimento di Energetica ed INFM, Università di Roma, La Sapienza, 00165 Roma (Italy); Margarone, D.; Korn, G. [Institute of Physics of the ASCR, ELI-Beamlines/HiLASE project, Na Slovance 2, 18221 Prague (Czech Republic)] [Institute of Physics of the ASCR, ELI-Beamlines/HiLASE project, Na Slovance 2, 18221 Prague (Czech Republic)

2013-07-26

413

Holographic collisions in confining theories  

NASA Astrophysics Data System (ADS)

We study the gravitational dual of a high-energy collision in a confining gauge theory. We consider a linearized approach in which two point particles traveling in an AdS-soliton background suddenly collide to form an object at rest (presumably a black hole for large enough center-of-mass energies). The resulting radiation exhibits the features expected in a theory with a mass gap: late-time power law tails of the form t -3/2, the failure of Huygens' principle and distortion of the wave pattern as it propagates. The energy spectrum is exponentially suppressed for frequencies smaller than the gauge theory mass gap. Consequently, we observe no memory effect in the gravitational waveforms. At larger frequencies the spectrum has an upward-stairway structure, which corresponds to the excitation of the tower of massive states in the confining gauge theory. We discuss the importance of phenomenological cutoffs to regularize the divergent spectrum, and the aspects of the full non-linear collision that are expected to be captured by our approach.

Cardoso, Vitor; Emparan, Roberto; Mateos, David; Pani, Paolo; Rocha, Jorge V.

2014-01-01

414

Soft confinement for polymer solutions  

NASA Astrophysics Data System (ADS)

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. (Proc. Natl. Acad. Sci. U.S.A., 108 (2011) 5249).

Oya, Yutaka; Kawakatsu, Toshihiro

2014-07-01

415

Confinement time of dust particles in a Kingdon trap  

NASA Astrophysics Data System (ADS)

The electrostatic orrery is a device in which negatively-charged dust particles orbit a wire in vacuum (Kingdon trap). The particles are glass microballoons about 50 microns in diameter charged negatively with 5× 10^5 electrons. The central elect rode is a 6 mm diameter rod at a potential of +8 kV. The particles are confined axially by grounded end plates. The orbits decay gradually until the particles strike the rod. Experiments with gas pressures from 2× 10-4 to 2× 10-6 To rr indicate that the confinement is limited by molecular drag. The longest confinement times are about 6 hours. At lower pressure, there may be additional mechanisms which prevent the confinement time from being further increased. For example, there is additional dissipation caused by the motion of image charges in the walls of the trap. This is being investigated by varying the placement of the walls and by resistively loading the walls. Resistive dissipation may account for elliptical orbits becomi ng circular at a rate more rapid than predicted from molecular drag alone.

Mahr, C.; Walch, R.; Robertson, S.

1996-11-01

416

Molecular confinement influences protein structure and enhances thermal protein stability  

PubMed Central

The sol-gel method of encapsulating proteins in a silica matrix was investigated as a potential experimental system for testing the effects of molecular confinement on the structure and stability of proteins. We demonstrate that silica entrapment (1) is fully compatible with structure analysis by circular dichroism, (2) allows conformational studies in contact with solvents that would otherwise promote aggregation in solution, and (3) generally enhances thermal protein stability. Lysozyme, ?-lactalbumin, and metmyoglobin retained native-like solution structures following sol-gel encapsulation, but apomyoglobin was found to be largely unfolded within the silica matrix under control buffer conditions. The secondary structure of encapsulated apomyoglobin was unaltered by changes in pH and ionic strength of KCl. Intriguingly, the addition of other neutral salts resulted in an increase in the ?-helical content of encapsulated apomyoglobin in accordance with the Hofmeister ion series. We hypothesize that protein conformation is influenced directly by the properties of confined water in the pores of the silica. Further work is needed to differentiate the steric effects of the silica matrix from the solvent effects of confined water on protein structure and to determine the extent to which this experimental system mimics the effects of crowding and confinement on the function of macromolecules in vivo. PMID:11266611

Eggers, Daryl K.; Valentine, Joan S.

2001-01-01

417

Dynamics of harmonically-confined systems: Some rigorous results  

SciTech Connect

In this paper we consider the dynamics of harmonically-confined atomic gases. We present various general results which are independent of particle statistics, interatomic interactions and dimensionality. Of particular interest is the response of the system to external perturbations which can be either static or dynamic in nature. We prove an extended Harmonic Potential Theorem which is useful in determining the damping of the centre of mass motion when the system is prepared initially in a highly nonequilibrium state. We also study the response of the gas to a dynamic external potential whose position is made to oscillate sinusoidally in a given direction. We show in this case that either the energy absorption rate or the centre of mass dynamics can serve as a probe of the optical conductivity of the system. -- Highlights: •We derive various rigorous results on the dynamics of harmonically-confined atomic gases. •We derive an extension of the Harmonic Potential Theorem. •We demonstrate the link between the energy absorption rate in a harmonically-confined system and the optical conductivity.

Wu, Zhigang, E-mail: zwu@physics.queensu.ca; Zaremba, Eugene, E-mail: zaremba@sparky.phy.queensu.ca

2014-03-15

418

Composite mesostructures by nano-confinement  

Microsoft Academic Search

In a physically confined environment, interfacial interactions, symmetry breaking, structural frustration and confinement-induced entropy loss can play dominant roles in determining molecular organization. Here we present a systematic study of the confined assembly of silica-surfactant composite mesostructures within cylindrical nanochannels of varying diameters. Using exactly the same precursors and reaction conditions that form the two-dimensional hexagonal SBA-15 mesostructured thin film,

Yiying Wu; Guosheng Cheng; Kirill Katsov; Scott W. Sides; Jianfang Wang; Jing Tang; Glenn H. Fredrickson; Martin Moskovits; Galen D. Stucky

2004-01-01

419

Field-induced confined states in graphene  

SciTech Connect

We report an approach to confine the carriers in single-layer graphene, which leads to quantum devices with field-induced quantum confinement. We demonstrated that the Coulomb-blockade effect evolves under a uniform magnetic field perpendicular to the graphene device. Our experimental results show that field-induced quantum dots are realized in graphene, and a quantum confinement-deconfinement transition is switched by the magnetic field.

Moriyama, Satoshi, E-mail: MORIYAMA.Satoshi@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Morita, Yoshifumi [Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515 (Japan); Watanabe, Eiichiro; Tsuya, Daiju [Nanotechnology Innovation Station, NIMS, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

2014-02-03

420

The identity of Thalictrum confine (Ranunculaceae)  

Microsoft Academic Search

A history of the collecting and naming ofThalictrum confine Fern, is detailed in an attempt to clear up long-standing nomenclatural and taxonomic confusions.Thalictrum confine has traditionally been distinguished fromT. venulosum Trel. on the basis of its larger, falcate fruits; however the lectotype ofT. confine consists only of a packet of terete, subcylindric fruits, even smaller than those of the type

Richard S. Mitchell

1988-01-01

421

Detecting the vulnerability of groundwater in semi-confined aquifers using barometric response functions  

NASA Astrophysics Data System (ADS)

The use of barometric response functions (BRFs) for detecting the presence of fully penetrating, highly conductive bodies within aquifer confining layers that present potential pathways for contaminants is explored. BRFs are determined from borehole water level (WL) and barometric pressure (Bp) records. Past studies have shown that confining layer properties can be estimated from BRFs, providing a potential link between BRFs and the concept of groundwater vulnerability. Existing analytical models that predict the BRF from system properties assume homogeneity within the aquifer and its confining layer, conditions which are seldom satisfied in nature. The impact of partially and fully penetrating, high diffusivity heterogeneities within a confining layer (representing potential high flow pathways for contaminants) on the BRF is investigated through a suite of three-dimensional, transient numerical simulations of the confining layer-aquifer system. The results are interpreted through comparison with a modified pre-existing analytical model for the BRF. Comparison of numerically and analytically calculated BRFs reveals that the key effect of a localised, fully penetrating, high diffusivity heterogeneity within a low diffusivity confining layer is to reduce the BRF gain with only minor changes to the phase. This impact on the BRF decreases with increasing distance from the heterogeneity. The importance of heterogeneity size is secondary to distance from the borehole and partially penetrating heterogeneities affect the BRF to only a minor extent. Data from a study of the Chalk Aquifer (E. Yorkshire, England) which is semi-confined by heterogeneous glacial sediments display variations in BRFs which are qualitatively similar to those shown by the numerical results. It is suggested that the variation in BRFs estimated from borehole records across a semi-confined aquifer could be used to assess the degree of spatial continuity of low diffusivity lithologies within the confining layer which protect the aquifer against surface sourced contamination, and thus provide a tool to improve groundwater vulnerability assessment.

Odling, N. E.; Perulero Serrano, R.; Hussein, M. E. A.; Riva, M.; Guadagnini, A.

2015-01-01

422

Confined one- and two-center systems  

NASA Astrophysics Data System (ADS)

It is shown that the usual model for confined one-center systems can be extended to two-center systems and the theory is used to treat H2 and HeH2+. It is convenient to use spheroidal coordinates for the two-center problems and we use this formalism to compare hydrogenlike systems confined spheroidally with the more standard spherical confinement. A discussion of confinement by both penetrable and impenetrable barriers is given together with a technique for describing the effect of the external region.

Burrows, B. L.; Cohen, M.

2013-11-01

423

Math Forum: K-12 Geometry  

NSDL National Science Digital Library

The Geometry Forum is "An Electronic Community for Lovers of Geometry." An NSF-funded project at Swarthmore College, the Geometry Forum is a great place for geometry and math teachers to locate curriculum ideas, software for mathematics, Internet math projects, and information about professional organizations. The student center offers a problem of the week, project of the month, the Internet geometry hunt, student hangouts on the Internet (where students talk about school and math), and students publications. The Geometry Forum has been re-designed and is attractive, easy to navigate, and very friendly. The site is searchable, a Help Desk is included, and the staff is available for questions.

1997-01-01

424

Anisotropic dynamics of water ultra-confined in macroscopically oriented channels of single-crystal beryl: A multi-frequency analysis  

SciTech Connect

The properties of fluids can be significantly altered by the geometry of their confining environments. While there has been significant work on the properties of such confined fluids, the properties of fluids under ultraconfinement, environments where, at least in one plane, the dimensions of the confining environment are similar to that of the confined molecule, have not been investigated. This paper investigates the dynamic properties of water in beryl (Be3Al2Si6O18), the structure of which contains approximately 5-A-diam channels parallel to the c axis. Three techniques, inelastic neutron scattering, quasielastic neutron scattering, and dielectric spectroscopy, have been used to quantify these properties over a dynamic range covering approximately 16 orders of magnitude. Because beryl can be obtained in large single crystals we were able to quantify directional variations, perpendicular and parallel to the channel directions, in the dynamics of the confined fluid. These are significantly anisotropic and, somewhat counterintuitively, show that vibrations parallel to the c-axis channels are significantly more hindered than those perpendicular to the channels. The effective potential for vibrations in the c direction is harder than the potential in directions perpendicular to it. There is evidence of single-file diffusion of water molecules along the channels at higher temperatures, but below 150 K this diffusion is strongly suppressed. No such suppression, however, has been observed in the channel-perpendicular direction. Inelastic neutron scattering spectra include an intramolecular stretching O-H peak at 465 meV. As this is nearly coincident with that known for free water molecules and approximately 30 meV higher than that in liquid water or ice, this suggests that there is no hydrogen bonding constraining vibrations between the channel water and the beryl structure. However, dielectric spectroscopic measurements at higher temperatures and lower frequencies yield an activation energy for the dipole reorientation of 16.4 0.14 kJ/mol, close to the energy required to break a hydrogen bond in bulk water. This may suggest the presence of some other form of bonding between the water molecules and the structure, but the resolution of the apparent contradiction between the inelastic neutron and dielectric spectroscopic results remains uncertain.

Anovitz, Lawrence {Larry} M [ORNL; Mamontov, Eugene [ORNL] [ORNL; Ishai, Paul ben [The Hebrew University of Jerusalem, Israel] [The Hebrew University of Jerusalem, Israel; Kolesnikov, Alexander I [ORNL] [ORNL

2013-01-01

425

Effects of the Cathode Grid Wires on Fusion Proton Measurements in Inertial-Electrostatic Confinement Devices  

Microsoft Academic Search

Gridded inertial-electrostatic confinement (IEC) de- vices interest fusion researchers owing to their ability to burn advanced fusion fuels and have many near-term applications. In these devices, a high voltage (10-180 kV) accelerates ions radially between nearly transparent electrodes in spherical or cylindrical geometry. In this paper, we report experiments that study fusion reactions within the microchannels formed between the wires

S. Krupakar Murali; John F. Santarius; Gerald L. Kulcinski

2011-01-01

426

Self-confinement in Block Copolymer Thin Films Induced by Chemical Patterns Made from Electrooxidation Nanolithorgraphy  

Microsoft Academic Search

The effect of confinement from chemical patterns on the self-assembly of block copolymer and related wetting physics has been studied. A variety of geometries designed in a mesh fashion were chemically patterned on OTS modified silicon wafers by electro-oxidation nanolithography. Thin films of a cylinder-forming PS-b-PEO were spin coated onto these patterned substrates. Thermal annealing of these films showed that

Ji Xu; Antonio Checco; Benjamin Ocko; Soojin Park; Shiliu Wang; Thomas Russell

2009-01-01

427

Comment on "Vortex distribution in a confining potential".  

PubMed

A system of interacting vortices is considered as an appropriate model for describing properties of type-II superconductors, and it has been shown lately to be deeply associated with nonextensive statistical mechanics. Herein we comment on a recent investigation of this model [M. Girotto, A. P. dos Santos, and Y. Levin, Phys. Rev. E 88, 032118 (2013)], which tried to contradict this assertion, based on a mean-field type of solution, compared with numerical-simulation data that correspond typically to a regime characterized by low concentrations of particles, as well as very high temperatures. It is shown that the physical situations analyzed differ significantly from those of a real superconducting phase. The analytical solution obtained from such a mean-field approximation shows a discrepancy with respect to the results of molecular-dynamics numerical simulations, which increases as the temperature is lowered towards the superconducting phase, as expected. We demonstrate that these results, when interpreted properly by means of an analytical solution within the framework of nonextensive statistical mechanics, present a remarkable agreement between molecular-dynamics simulations and theoretical results, for all temperatures, specially for those temperatures associated with the existence of type-II superconductivity. PMID:25215852

Ribeiro, Mauricio S; Nobre, Fernando D; Curado, Evaldo M F

2014-08-01

428

Experimental investigation of converging shocks in water with various confinement materials  

NASA Astrophysics Data System (ADS)

Fluid-solid coupling typically plays a negligible role in confined converging shocks in gases because of the rigidity of the surrounding material and large acoustic impedance mismatch of wave propagation between it and the gas. However, this is not true for converging shocks in a liquid. In the latter case, the coupling can not be ignored and properties of the surrounding material have a direct influence on wave propagation. In shock focusing in water confined in a solid convergent geometry, the shock in the liquid transmits to the solid and both transverse and longitudinal waves propagate in the solid. Shock focusing in water for three types of confinement materials has been studied experimentally with schlieren and photoelasticity optical techniques. A projectile from a gas gun impacts a liquid contained in a solid convergent geometry. The impact produces a shock wave in water that develops even higher pressure when focused in the vicinity of the apex. Depending on the confining material, the shock speed in the water can be slower, faster, or in between wave speeds in the solid. For solid materials with higher wave speeds than the shock in water, regions in the water is put in tension and cavitation occurs. Materials with slower wave speeds will deform easily.

Eliasson, V.; Mello, M.; Rosakis, A. J.; Dimotakis, P. E.

2010-10-01

429

Confined jet impingement of liquid nitrogen onto different heat transfer surfaces  

NASA Astrophysics Data System (ADS)

Jet impingement of liquid nitrogen owns many applications in the cryogenic cooling aspects, such as, cooling of high-power chips in the electronic devices and cryoprobes in the cryosurgery. In the present study, we systematically investigated the confined jet impingement of liquid nitrogen from a tube of about 2.0 mm in diameter onto the heat transfer surfaces of about 5.0 mm in basement diameter with different heat transfer surface geometries and conditions, i.e., flat surface, hemispherical surface and flat surface with a needle. The effects of many influential factors, such as, the geometry of the heat transfer surface, jet velocity, distance between the nozzle exit and heat transfer surface, heat transfer surface condition, and some other, on the heat transfer were investigated. The heat transfer correlations were also proposed by using the experimental data, and it was found that the heat transfer mechanism of liquid impingement in the confined space was dominated by the convective evaporation rather than the nucleate boiling in the present case. The critical heat flux (CHF) of the confined jet impingement was measured and the visualization of the corresponding flow patterns of the confined jet impingement of liquid nitrogen was also conducted simultaneously to understand the heat transfer phenomena.

Zhang, P.; Xu, G. H.; Fu, X.; Li, C. R.

2011-06-01

430

Graphene growth under Knudsen molecular flow on a confined catalytic metal coil.  

PubMed

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. PMID:25363512

Bong, Hyojin; Jo, Sae Byeok; Kang, Boseok; Lee, Seong Kyu; Kim, Hyun Ho; Lee, Seung Goo; Cho, Kilwon

2015-01-01

431

Prospects of inertial confinement fusion  

NASA Astrophysics Data System (ADS)

The present status of inertial confinement fusion (ICF) is briefly reviewed, emphasizing the National Ignition Facility (NIF) project in the US and the Megajoule project in France. Critical aspects of target performance such as symmetry and stability of capsule implosions and interaction physics in hohlraum targets are discussed. The advantages of heavy-ion beam drivers and corresponding research programs are pointed out with reference to the long-term prospects for ICF power production. The new concept of the fast ignition of precompressed fuel by petawatt, picosecond laser pulses is also covered. The laser plasma group at the Max-Planck-Institute for Quantum Optics (MPQ) is one of the European institutes funded by EURATOM for an ICF keep-in-touch activity, and we highlight results obtained at MPQ relevant to the recent progress of ICF.

Meyer-ter-Vehn, J.

1997-12-01

432

Multishell inertial confinement fusion target  

DOEpatents

A method of fabricating multishell fuel targets for inertial confinement fusion usage. Sacrificial hemispherical molds encapsulate a concentric fuel pellet which is positioned by fiber nets stretched tautly across each hemispherical mold section. The fiber ends of the net protrude outwardly beyond the mold surfaces. The joint between the sacrificial hemispheres is smoothed. A ceramic or glass cover is then deposited about the finished mold surfaces to produce an inner spherical surface having continuously smooth surface configuration. The sacrificial mold is removed by gaseous reaction accomplished through the porous ceramic cover prior to enclosing of the outer sphere by addition of an outer coating. The multishell target comprises the inner fuel pellet concentrically arranged within a surrounding coated cover or shell by fiber nets imbedded within the cover material.

Holland, James R. (Butler, PA); Del Vecchio, Robert M. (Vandergrift, PA)

1984-01-01

433

Multishell inertial confinement fusion target  

DOEpatents

A method of fabricating multishell fuel targets for inertial confinement fusion usage. Sacrificial hemispherical molds encapsulate a concentric fuel pellet which is positioned by fiber nets stretched tautly across each hemispherical mold section. The fiber ends of the net protrude outwardly beyond the mold surfaces. The joint between the sacrificial hemispheres is smoothed. A ceramic or glass cover is then deposited about the finished mold surfaces to produce an inner spherical surface having continuously smooth surface configuration. The sacrificial mold is removed by gaseous reactions accomplished through the porous ceramic cover prior to enclosing of the outer sphere by addition of an outer coating. The multishell target comprises the inner fuel pellet concentrically arranged within a surrounding coated cover or shell by fiber nets imbedded within the cover material.

Holland, James R. (Butler, PA); Del Vecchio, Robert M. (Vandergrift, PA)

1987-01-01

434

Monte Carlo simulations of proteins in cages: influence of confinement on the stability of intermediate states  

E-print Network

We present a theoretical study of the folding of small proteins inside confining potentials. Proteins are described in the framework of an effective potential model which contains the Ramachandran angles as degrees of freedom and does not need any {\\it a priori} information about the native state. Hydrogen bonds, dipole-dipole- and hydrophobic interactions are taken explicitly into account. An interesting feature displayed by this potential is the presence of some intermediates between the unfolded and native states. We consider different types of confining potentials in order to study the structural properties of proteins folding inside cages with repulsive or attractive walls. Using the Wang-Landau algorithm we determine the density of states (DOS) and analyze in detail the thermodynamical properties of the confined proteins for different sizes of the cages. We show that confinement dramatically reduces the phase space available to the protein and that the presence of intermediate states can be controlled by varying the properties of the confining potential. Cages with strongly attractive walls lead to the disappearance of the intermediate states and to a two-state folding into a less stable configuration. However, cages with slightly attractive walls make the native structure more stable than in the case of pure repulsive potentials, and the folding process occurs through intermediate configurations. In order to test the metastable states we analyze the free energy landscapes as a function of the configurational energy and of the end-to-end distance as an order parameter.

Pedro Ojeda; Aurora Londono; Nan-Yow Chen; Martin Garcia

2008-08-04

435

Shear Relaxations of Confined Liquids.  

NASA Astrophysics Data System (ADS)

Ultrathin (<40 A) films of octamethylcyclotetrasiloxane (OMCTS), hexadecane, and dodecane were subjected to linear and non-linear oscillatory shear between flat plates. Shearing frequencies of 0.1 to 800 s^{-1} were applied at pressures from zero to 0.8 MPa using a surface rheometer only recently developed. In most cases the plates were atomically smooth mica surfaces; the role of surface interactions was examined by replacing these with alkyl chain monolayers. OMCTS and hexadecane were examined at a temperature about 5 Celsius degrees above their melting points and tended to solidify. Newtonian plateaus having enormous viscosities were observed at low shear rates. The onset of shear thinning implied relaxation times of about 0.1 s in the linear structure of the confined liquids. Large activation volumes (~80 nm ^3) suggested that shear involved large-scale collective motion. Dodecane was studied at a much higher temperature relative to its melting point and showed no signs of impending solidification though it exhibited well-defined regions of Newtonian response and power law shear thinning. When treated with molecular sieves before use, dodecane had relaxation times which were short (0.02 s) compared to hexadecane, but still exhibited large-scale collective motion. When treated with silica gel, an unexplained long -time relaxation (10 s) was seen in the Newtonian viscosity of dodecane. The relaxation time of the linear structure, 0.005 s was very small, and the storage modulus was unresolvable. The small activation volume (7nm^3) indicated a much lower level of collective motion. The activation volume remained small when dodecane was confined between tightly bound, low energy, alkyl monolayers. At low strains the storage and loss moduli became very large (>10^4 Pa), probably due to interactions with flaws in the monolayers. Dramatic signs of wall slip were observed at large strains even at low pressures.

Carson, George Amos, Jr.

436

Failures of information geometry  

NASA Astrophysics Data System (ADS)

Information H is a unique relationship between probabilities, based on the property of independence which is central to scientific methodology. Information Geometry makes the tempting but fallacious assumption that a local metric (conventionally based on information) can be used to endow the space of probability distributions with a preferred global Riemannian metric. No such global metric can conform to H, which is "from-to" asymmetric whereas geometrical length is by definition symmetric. Accordingly, any Riemannian metric will contradict the required structure of the very distributions which are supposedly being triangulated. It follows that probabilities do not form a metric space. We give counter-examples in which alternative formulations of information, and the use of information geometry, lead to unacceptable results.

Skilling, John

2015-01-01

437

Puzzle geometry and rigidity  

NASA Astrophysics Data System (ADS)

We describe a new and robust method to prove rigidity results in complex dynamics. The new ingredient is the geometry of the critical puzzle pieces: under control of geometry and ``complex bounds'', two generalized polynomial-like maps which admit a topological conjugacy, quasiconformal outside the filled-in Julia set, are indeed quasiconformally conjugate. The proof uses a new abstract removability-type result for quasiconformal maps, following ideas of Heinonen and Koskela and of Kallunki and Koskela, optimized for applications in complex dynamics. We prove, as the first application of this new method, that, for even criticalities distinct from two, the period two cycle of the Fibonacci renormalization operator is hyperbolic with 1 -dimensional unstable manifold.

Smania, Daniel

2007-07-01

438

Gallery of Interactive Geometry  

NSDL National Science Digital Library

Provided by the Center for the Computation and Visualization of Geometric Structures, a National Science Foundation Science and Technology Center at the University of Minnesota, the Gallery of Interactive Geometry offers users ten web-based applications that explore different aspects of geometry. "Build a Rainbow," for example, allows users to manipulate the light entering a prism to see the effects of changes in angle and wavelength, while "QuasiTiler" draws Penrose tilings and their generalizations. The user interface is as consistent as can be expected given the range of subjects covered; most applications present the user with a form, and return .gif files based on the parameters entered. Each application also offers background lessons on the concepts involved, as well as help with the application itself. The site is a good example of how powerful computing can be brought to the desktop through the web.

439

Renyi Entropy and Geometry  

E-print Network

Entanglement entropy in even dimensional conformal field theories (CFTs) contains well-known universal terms arising from the conformal anomaly. Renyi entropies are natural generalizations of the entanglement entropy that are much less understood. Above two spacetime dimensions, the universal terms in the Renyi entropies are unknown for general entangling geometries. We conjecture a new structure in the dependence of the four-dimensional Renyi entropies on the intrinsic and extrinsic geometry of the entangling surface. We provide evidence for this conjecture by direct numerical computations in the free scalar and fermion field theories. The computation involves relating the four-dimensional free massless Renyi entropies across cylindrical entangling surfaces to corresponding three-dimensional massive Renyi entropies across circular entangling surfaces. Our numerical technique also allows us to directly probe other interesting aspects of three-dimensional Renyi entropy, including the massless renormalized Renyi entropy and calculable contributions to the perimeter law.

Jeongseog Lee; Lauren McGough; Benjamin R. Safdi

2014-03-06

440

Differential Geometry Based Multiscale Models  

PubMed Central

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

Wei, Guo-Wei

2010-01-01

441

Surveying Diffusion in Complex Geometries. An Essay  

E-print Network

The surrounding world surprises us by the beauty and variety of complex shapes that emerge from nanometric to macroscopic scales. Natural or manufactured materials (sandstones, sedimentary rocks and cement), colloidal solutions (proteins and DNA), biological cells, tissues and organs (lungs, kidneys and placenta), they all present irregularly shaped "scenes" for a fundamental transport "performance", that is, diffusion. Here, the geometrical complexity, entangled with the stochastic character of diffusive motion, results in numerous fascinating and sometimes unexpected effects like diffusion screening or localization. These effects control many diffusion-mediated processes that play an important role in heterogeneous catalysis, biochemical mechanisms, electrochemistry, growth phenomena, oil recovery, or building industry. In spite of a long and rich history of academic and industrial research in this field, it is striking to see how little we know about diffusion in complex geometries, especially the one which occurs in three dimensions. We present our recent results on restricted diffusion. We look into the role of geometrical complexity at different levels, from boundary microroughness to hierarchical structure and connectivity of the whole diffusion-confining domain. We develop a new approach which consists in combining fast random walk algorithms with spectral tools. The main focus is on studying diffusion in model complex geometries (von Koch boundaries, Kitaoka acinus, etc.), as well as on developing and testing spectral methods. We aim at extending this knowledge and at applying the accomplished arsenal of theoretical and numerical tools to structures found in nature and industry.

Denis Grebenkov

2009-09-08

442

RSensitivity of planar flows to forcing geometry  

NASA Astrophysics Data System (ADS)

We present experiments which reveal fundamental aspects of planar flows in confined geometries. The work has application to 2D flows in this films, geophysical flows, and MHD. We examine the laminar regime of the flow studied by Boubnov, Dalziel & Linden (1994). A planar flow is produced by source-sink forcing in a stably stratified fluid contained in a tank of square horizontal section. The source-sink forcing consists of 4 or 8 pairs of pipes connected to a peristaltic pump: each pair sucks and re-enters fluid from the same density layer. The Reynolds number based on the measured velocity field is O(10^2). We find that the resulting flow patterns are extremely sensitive to the configurations of the source-sink pairs in relation to the geometry of the flow domain. For some configurations, steady flows develop which resemble the inviscid eigenmodes for a homogeneous (unforced) boundary condition assuming a linear relation between the stream function and the vorticity. A dominant single vortex pattern which was identified in the previous work as the result of inverse energy cascade of 2D turbulence turned out to be one of the eigenmodes. For other configurations, the flow patterns change irregularly which provides a new mechanism of 2D mixing. We will also present the effect of viscosity which relates these laminar flows to 2D turbulent flows and Stokes flows.

Kanda, Isao; Linden, Paul F.

1999-11-01

443

Dynamics Determines Geometry  

NASA Astrophysics Data System (ADS)

The inverse problem of calculus of variations and s-equivalence are re-examined by using results obtained from non-commutative geometry ideas. The role played by the structure of the modified Poisson brackets is discussed in a general context and it is argued that classical s-equivalent systems may be non-equivalent at the quantum mechanical level. This last fact is explicitly discussed comparing different approaches to deal with the Nair-Polychronakos oscillator.

Hojman, Sergio A.; Gamboa, J.; Méndez, F.

2012-10-01

444

Unified Biplot Geometry  

Microsoft Academic Search

The fundamental geometry is outlined that underlies all biplots of a data-matrix X of n cases and p variables. Cases are represented by n points and variables by a reference system. The reference system for quantitative variables may be orthogonal Cartesian axes, other linear axes or nonlinear trajectories. The reference system for categorical variables is a set of category-level-points (CLPs)

John C. Gower

445

Circumference of Taxicab Geometry Circles.  

ERIC Educational Resources Information Center

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

Litwiller, Bonnie H.; Duncan, David R.

1991-01-01

446

A Lorentz Covariant Noncommutative Geometry  

E-print Network

A noncommutative geometry that preserves lorentz covariance was introduced by Hartland Snyder in 1947. We show that this geometry has unusual properties under momentum translation, and derive for it a form of star product.

A. Lewis Licht

2005-12-13

447

Geometry for the Secondary School  

ERIC Educational Resources Information Center

A sequential but non-axiomatic high school geometry course which includes Euclidean, transformation, and analytic geometry and vectors and matrices, and emphasizes the invariance property of transformations, is outlined. Sample problems, solutions, and comments are included. (MN)

Moalem, D.

1977-01-01

448

Noncommutative geometry and arithmetics  

NASA Astrophysics Data System (ADS)

We intend to illustrate how the methods of noncommutative geometry are currently used to tackle problems in class field theory. Noncommutative geometry enables one to think geometrically in situations in which the classical notion of space formed of points is no longer adequate, and thus a “noncommutative space” is needed; a full account of this approach is given in [3] by its main contributor, Alain Connes. The class field theory, i.e., number theory within the realm of Galois theory, is undoubtedly one of the main achievements in arithmetics, leading to an important algebraic machinery; for a modern overview, see [23]. The relationship between noncommutative geometry and number theory is one of the many themes treated in [22, 7-9, 11], a small part of which we will try to put in a more down-to-earth perspective, illustrating through an example what should be called an “application of physics to mathematics,” and our only purpose is to introduce nonspecialists to this beautiful area.

Almeida, P.

2009-09-01

449

Matter in Toy Dynamical Geometries  

E-print Network

One of the objectives of theories describing quantum dynamical geometry is to compute expectation values of geometrical observables. The results of such computations can be affected by whether or not matter is taken into account. It is thus important to understand to what extent and to what effect matter can affect dynamical geometries. Using a simple model, it is shown that matter can effectively mold a geometry into an isotropic configuration. Implications for "atomistic" models of quantum geometry are briefly discussed.

Tomasz Konopka

2009-03-25

450

Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas  

SciTech Connect

Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today’s magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today’s computers and modern linear and non?linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.

S.C. Jardin

2010-09-28

451

Confinement and focusing of geodesics in warped spacetimes  

NASA Astrophysics Data System (ADS)

We have explored certain characteristic features of test particle trajectories in five dimensional, warped bulk geometries with a single thick brane. After a brief introduction on such spacetimes, we have first discussed timelike geodesic motion. The geodesic equations, which reduce to a first order autonomous dynamical system, have been solved using analytical and numerical methods. We have demonstrated how a growing (decaying) warp factor leads to oscillatory (runaway) trajectories, suggesting confinement (deconfinement). Further, we have pointed out differences that arise when we have a cosmological brane and/or a time-dependent extra dimension. Next, we have moved on to the kinematics of geodesic congruences. The evolution of the kinematical variables (expansion, rotation and shear) along geodesic flows have been obtained using analytical and numerical approaches, with particular emphasis on the required conditions and occurence of geodesic focusing.

Kar, S.; Das Gupta, A.; Ghosh, S.; Nandan, H.

2014-03-01

452

Two-dimensional simulations of the inertial electrostatic confinement device  

NASA Astrophysics Data System (ADS)

We discuss the application of the CELESTE simulation package to the simulation of the experiments conducted at the Los Alamos Inertial Electrostatic Confinement (IEC) device. Recently considerable experimental advances have been made in understanding of the stability of the virtual cathode and in the physics of POPS. This momentous experimental advance requires a new simulation effort for explaining the new experimental findings, particularly in the area of stability of the configurations obtained experimentally. We have conducted a 2D stability study of the virtual cathode in the IEC device using the DEMOCRITUS package. DEMOCRITUS is a 2D general geometry electrostatic PIC code. In the present study we have done complete stability study and investigate the two-stream instability occuring in the IEC device.

Marocchino, Alberto; Lapenta, Giovanni; Evstatiev, Evstati; Nebel, Richard; Park, Jaeyoung

2006-04-01

453

Self-Assembled Biomolecular Materials Confined on Lithographic Surfaces  

NASA Astrophysics Data System (ADS)

Lithographically patterned Si-surfaces with different geometries (linear and circular channels) are used for confining and orienting assemblies of biomacromolecules. In order to direct the self assembly, the surfaces are coated with thin organic layers to change the hydrophobicity and surface charge. Droplet casting, spin coating and microinjection are used to fill the channels with biomaterials. In particular, the use of the microinjection technique allows us to control the formation of biomolecular assemblies for highly oriented x-ray samples as well as to fill single channels (width < 5?m) with dilute solutions for single molecule investigations. Biomaterials based on tubulin are our primary interest. We use fluorescence, confocal, and polarization microscopy to observe the polymerization of microtubules from tubulin and the formation of tubulin-cationic lipid complexes. Supported by NSF DMR-9972246, University of California Biotech Research, and Education Program Training Grant 99-14, DFG Pf 375/1-1.

Pfohl, Thomas; Kim, Joon Heon; Case, Ryan; Li, Youli; Safinya, Cyrus R.

2000-03-01

454

Climate conditions in bedded confinement buildings  

Technology Transfer Automated Retrieval System (TEKTRAN)

Confinement buildings are utilized for finishing cattle to allow more efficient collection of animal waste and to buffer animals against adverse climatic conditions. Environmental data were obtained from a 29 m wide x 318 m long bedded confinement building with the long axis oriented east to west. T...

455

Inertial electrostatic confinement (IEC) neutron sources  

Microsoft Academic Search

Inertial electrostatic confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 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

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

1995-01-01

456

Evaporation rate of water in hydrophobic confinement  

E-print Network

Evaporation rate of water in hydrophobic confinement Sumit Sharma and Pablo G. Debenedetti1, to compute the rate of capillary evaporation of water confined between two hydro- phobic surfaces separated to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes

457

INERT Atmosphere confinement operability test procedure  

Microsoft Academic Search

This Operability Test Procedure (OTP) provides instructions for testing operability of the Inert Atmosphere Confinement (IAC). The Inert Atmosphere Confinement was designed and built for opening cans of metal items that might have hydrided surfaces. Unreviewed Safety Question (USQ) PFP-97-005 addresses the discovery of suspected plutonium hydride forming on plutonium metal currently stored in the Plutonium Finishing Plant vaults. Plutonium

1999-01-01

458

Confinement and the safety factor profile  

SciTech Connect

The conjecture that the safety factor profile, q(r), controls the improvement in tokamak plasmas from poor confinement in the Low (L-) mode regime to improved confinement in the supershot regime has been tested in two experiments on the Tokamak Fusion Test Reactor (TFTR). First, helium was puffed into the beam-heated phase of a supershot discharge which induced a degradation from supershot to L-mode confinement in about 100 msec, far less than the current relaxation time. The q and shear profiles measured by a motional Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current ramps in supershot plasmas altered the q profile, but were observed not to change significantly the energy confinement. Thus, enhanced confinement in supershot plasmas is not due to a particular q profile which has enhanced stability or transport properties. The discharges making a continuous transition between supershot and L-mode confinement were also used to test the critical-electron-temperature-gradient transport model. It was found that this model could not reproduce the large changes in electron and ion temperature caused by the change in confinement.

Batha, S.H.; Levinton, F.M. [Fusion Physics and Technology, Torrance, CA (United States); Scott, S.D. [Princeton Univ., NJ (United States). Plasma Physics Lab.] [and others

1995-12-01

459

TOF Geometry TOF Software Review  

E-print Network

TOF Geometry W.J. Llope TOF Software Review Nov. 2008, BNL · the "jigsaw puzzle" · simple acceptance simulation · final tray-local geometry · installed tray locations · many ~20mil effects from manufacturing tolerances · upVPD-local geometry · geant simulations · positioning · summary #12

Llope, William J.

460

Geometry, noncommutative algebra and representations  

E-print Network

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 Outline 1 Geometry and Commutative Algebra 2 Singularities and Resolutions 3 Noncommutative Algebra

Gordon, Iain

461

The geometry package Hideo Umeki  

E-print Network

The geometry package Hideo Umeki hideo.umeki@toshiba.co.jp 1999/10/07 (v2.2) Abstract This package. Contents 1 Preface to Version 2 1 2 Introduction 2 3 Page Geometry 2 3.1 Layout Dimensions . . . . . . 2 3: · The geometry options using the keyval scheme can be set in the optional argument to the \\usepackage command

Gkioulekas, Eleftherios - Department of Mathematics, University of Texas

462

Geometry Textures Rodrigo de Toledo  

E-print Network

Geometry Textures Rodrigo de Toledo Tecgraf ­ PUC-Rio Rio de Janeiro - RJ, Brasil rtoledo but applied to the whole object. Tessel- lated models are converted into geometry textures, a geo- metric with LOD speed-up while preserving original quality. 1 Introduction The goal of geometry textures

Paris-Sud XI, Université de

463

Inertial electrostatic confinement and nuclear fusion in the interelectrode plasma of a nanosecond vacuum discharge. II: Particle-in-cell simulations  

SciTech Connect

Results of particle-in-sell simulations of ion acceleration by using the KARAT code in a cylindrical geometry in the problem formulation corresponding to an actual experiment with a low-energy vacuum discharge with a hollow cathode are presented. The fundamental role of the formed virtual cathode is analyzed. The space-time dynamics of potential wells related to the formation of the virtual cathode is discussed. Quasi-steady potential wells (with a depth of {approx}80% of the applied voltage) cause acceleration of deuterium ions to energies about the electron beam energy ({approx}50 keV). In the well, a quasi-isotropic velocity distribution function of fast ions forms. The results obtained are compared with available data on inertial electrostatic confinement fusion (IECF). In particular, similar correlations between the structure of potential wells and the neutron yield, as well as the scaling of the fusion power density, which increases with decreasing virtual cathode radius and increasing potential well depth, are considered. The chosen electrode configuration and potential well parameters provide power densities of nuclear DD fusion in a nanosecond vacuum discharge noticeably higher than those achieved in other similar IECF systems.

Kurilenkov, Yu. K.; Tarakanov, V. P. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation); Gus'kov, S. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

2010-12-15

464

Transient coexisting nanophases in ultrathin films confined between corrugated walls  

SciTech Connect

Grand-canonical Monte Carlo and microcanonical molecular dynamics methods have been used to simulate an ultrathin monatomic film confined to a slit-pore [i.e., between solid surfaces (walls)]. Both walls comprise atoms rigidly fixed in the face centered cubic (100) configuration; one wall is smooth on a nanoscale and the other is corrugated (i.e., scored with regularly spaced rectilinear grooves one to several nanometers wide). Properties of the film have been computed as a function of the lateral alignment (registry), with the temperature, chemical potential, and distance between the walls kept constant. Changing the registry carries the film through a succession of equilibrium states, ranging from all solid at one extreme to all fluid at the other. Over a range of intermediate registries the film consists of fluid and solid portions in equilibrium, that is fluid-filled nanocapillaries separated by solid strips. The range of registries over which such fluid--solid equilibria exist depends upon the width of the grooves and the frequency of the corrugation. For grooves of width comparable to the range of the interatomic potential, fluid and solid phases cease to coexist. In the limit of very wide grooves the character of the film is similar to that of the film confined by strictly smooth walls. The rich phase behavior of the confined film due to the coupling between molecular (registry) and nano (corrugation) scales has obvious implications for boundary lubrication.

Curry, J.E.; Zhang, F.; Cushman, J.H. (Lilly Hall of Life Sciences, Purdue University, West Lafayette, Indiana 47907 (United States)); Schoen, M. (Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)); Diestler, D.J. (Department of Agronomy, Keim Hall, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0915 (United States))

1994-12-15

465

Confinement of supernova explosions in a collapsing cloud  

E-print Network

We analyze the confining effect of cloud collapse on an expanding supernova shockfront. We solve the differential equation for the forces on the shockfront due to ram pressure, supernova energy, and gravity. We find that the expansion of the shockfront is slowed and in fact reversed by the collapsing cloud. Including radiative losses and a potential time lag between supernova explosion and cloud collapse shows that the expansion is reversed at smaller distances as compared to the non-radiative case. We also consider the case of multiple supernova explosions at the center of a collapsing cloud. For instance, if we scale our self-similar solution to a single supernova of energy 10^51 ergs occurring when a cloud of initial density 10^2 H/cm^3 has collapsed by 50%, we find that the shockfront is confined to ~15 pc in ~1 Myrs. Our calculations are pertinent to the observed unusually compact non-thermal radio emission in blue compact dwarf galaxies (BCDs). More generally, we demonstrate the potential of a collapsing cloud to confine supernovae, thereby explaining how dwarf galaxies would exist beyond their first generation of star formation.

M. M. Kasliwal; R. V. E. Lovelace; J. R. Houck

2005-05-13

466

Multicell Electrode Structure for Off-axis Plasma Confinement  

NASA Astrophysics Data System (ADS)

There are many potential applications of high-capacity and/or portable antimatter traps. One route towards this goal which we have been pursuing is the construction of a novel ``multicell'' trap acrchitecture, with the goal of storage of >=10^12 positrons using kV confinement potentials. Plasmas will be stored in separate Penning-Malmberg traps (``cells'') arranged in parallel off the magnetic axis. This utilizes efficiently the magnetic field volume, while minimizing the required confinement voltages. Other enabling techniques will be discussed including the excitation of autoresonant diocotron modes to inject plasmas into the off-axi cells, as well as novel beams that can be created from this type of trapped plasma. New experiements testing the confinement in off-axis cells will be presented. Anticipated uses of this device, including an experiment to create an electron-positron plasma in a stellerator,footnotetextT. S. Pedersen, et. al., NJP 14, 035010 (2012). will also be discussed.

Danielson, J. R.; Hurst, N. C.; Surko, C. M.

2012-10-01