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1

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

2

PREFACE: Water in confined geometries  

Microsoft Academic Search

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

Mauro Rovere

2004-01-01

3

Twisted coil geometry in plasma confinement devices  

NASA Astrophysics Data System (ADS)

Twisted coils, ie., coils for which windings do not lie in a plane, are used widely in plasma confinement devices, especially those in the general class of stellerator-type devices. In the design of these devices ad hoc expressions for the positions of turns and the outer envelope of the windings are usually assumed. However, these expressions do not correctly represent the true shape taken by windings as successive turns and layers of turns are applied to a curved surface. In the present work, the techniques of differential geometry are used to determine the actual location of turns as they are wound on arbitrary surfaces. In the process, a set of natural winding coordinates is derived; the Biot Savart law for calculation of magnetic fields is expressed in terms of these natural coordinates. Next, the advantages of using a class of surfaces, called developables, for winding surfaces are discussed. A particular developable, called the rectifying developable, offers the additional advantages that the turns on it are geodesies and that wide flat conductors can be wound on it to minimize bending strains. Finally, the problem of windings with conductors of finite thickness is briefly discussed.

Walstrom, P. L.

1987-09-01

4

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

5

Superconductivity of gallium in various confined geometries  

Microsoft Academic Search

The superconductivity of gallium in porous glasses with various pore sizes and in opals is studied using a superconducting quantum interference device magnetometer. The single and double superconducting phase transitions are observed for different samples. Magnetization hysteresis loops are also measured and found to be dependent on pore sizes and geometry. The changes in magnetization below about 6.4 K are

E. V. Charnaya; C. Tien; K. J. Lin; C. S. Wur; Yu. A. Kumzerov

1998-01-01

6

Thermodynamic Properties of Alkanes in Confined Geometries  

NASA Astrophysics Data System (ADS)

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

Sheehan, Joseph F., III

7

Plasma confinement by circularly polarized electromagnetic field in toroidal geometry  

SciTech Connect

A novel plasma confinement concept based on plasma confinement by electromagnetic pressure of circularly polarized electromagnetic fields is proposed. Practical implementation of this concept in a toroidal device is suggested. In this concept the confining field frequency is in the lower range such that the size of the device is much smaller than the vacuum wavelength. Most of the previous radio-frequency (rf) confinement concepts of unmagnetized plasma were related to confinement in rf cavities which operated at high frequency for which the size of the cavity is comparable to the wavelength. Operation at lower frequencies simplifies rf design, reduces Ohmic losses in the conducting walls and probably makes application of superconductors for wall materials more feasible. It is demonstrated that circular (or nearly circular) polarization of the electromagnetic field is required for confinement from both the equilibrium and stability considerations. Numerical analysis of plasma confinement for magnetohydrodynamic plasma model in two-dimensional toroidal geometry is performed. Within this model plasma is confined by the applied rf fields and its equilibrium is stable. Technically feasible compact and medium size toroidal plasma confinement devices based on this concept are proposed. Application of this approach to the fusion reactor requires use of superconducting materials for the toroidal shell to reduce the Ohmic losses. Further theoretical and experimental studies are required for a more reliable conclusion about the attractiveness of this plasma confinement concept.

Svidzinski, Vladimir A. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); and Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-10-15

8

Dynamics of supercooled water in confined geometry  

NASA Astrophysics Data System (ADS)

As with most liquids, it is possible to supercool water; this generally involves cooling the liquid below its melting temperature (avoiding crystallization) until it eventually forms a glass. The viscosity and related relaxation times (?) of glass-forming liquids typically show non-Arrhenius temperature (T) dependencies. Liquids with highly non-Arrhenius behaviour in the supercooled region are termed `fragile'. In contrast, liquids whose behaviour is close to the Arrhenius law (ln? ~ 1/T) are termed `strong' ( ref. 5). A unique `fragile-strong' transition around 228K has been proposed for supercooled water; however, experimental studies of bulk supercooled water in this temperature range are generally hampered because crystallization occurs. Here we use broad-band dielectric spectroscopy to study the relaxation dynamics of supercooled water in a wide temperature range, including the usually inaccessible temperature region. This is possible because the supercooled water is held within a layered vermiculite clay-the geometrical confinement and presence of intercalated sodium ions prevent most of the water from crystallizing. We find a relaxational process with an Arrhenius temperature dependence, consistent with the proposed strong nature of deeply supercooled bulk water. Because water that is less supercooled has been established as highly fragile, our results support the existence of a fragile-strong transition.

Bergman, R.; Swenson, J.

2000-01-01

9

Dynamics of supercooled water in confined geometry  

PubMed

As with most liquids, it is possible to supercool water; this generally involves cooling the liquid below its melting temperature (avoiding crystallization) until it eventually forms a glass. The viscosity and related relaxation times (tau) of glass-forming liquids typically show non-Arrhenius temperature (T) dependencies. Liquids with highly non-Arrhenius behaviour in the supercooled region are termed 'fragile'. In contrast, liquids whose behaviour is close to the Arrhenius law (In tau infinity 1/T) are termed 'strong'. A unique 'fragile-strong' transition around 228 K has been proposed for supercooled water; however, experimental studies of bulk supercooled water in this temperature range are generally hampered because crystallization occurs. Here we use broad-band dielectric spectroscopy to study the relaxation dynamics of supercooled water in a wide temperature range, including the usually inaccessible temperature region. This is possible because the supercooled water is held within a layered vermiculite clay-the geometrical confinement and presence of intercalated sodium ions prevent most of the water from crystallizing. We find a relaxational process with an Arrhenius temperature dependence, consistent with the proposed strong nature of deeply supercooled bulk water. Because water that is less supercooled has been established as highly fragile, our results support the existence of a fragile-strong transition. PMID:10659841

Bergman; Swenson

2000-01-20

10

Cauchy flights in confining potentials  

NASA Astrophysics Data System (ADS)

We analyze confining mechanisms for Lévy flights evolving under an influence of external potentials. Given a stationary probability density function (pdf), we address the reverse engineering problem: design a jump-type stochastic process whose target pdf (eventually asymptotic) equals the preselected one. To this end, dynamically distinct jump-type processes can be employed. We demonstrate that one “targeted stochasticity” scenario involves Langevin systems with a symmetric stable noise. Another derives from the Lévy-Schrödinger semigroup dynamics (closely linked with topologically induced super-diffusions), which has no standard Langevin representation. For computational and visualization purposes, the Cauchy driver is employed to exemplify our considerations.

Garbaczewski, Piotr

2010-03-01

11

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

12

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

PubMed

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

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

2007-05-28

13

Critical comparison between magnetic and inertial confinement schemes and their geometries  

Microsoft Academic Search

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

Salingaros

1995-01-01

14

A molecular dynamics study of freezing in a confined geometry  

NASA Technical Reports Server (NTRS)

The dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls is studied by computer simulation. The time development of ordering is quantified and a novel freezing mechanism is observed. The liquid forms layers and subsequent in-plane ordering within a layer is accompanied by a sharpening of the layer in the transverse direction. The effects of channel size, the methods of quench, the liquid-wall interaction and the roughness of walls on the freezing mechanism are elucidated. Comparison with recent experiments on freezing in confined geometries is presented.

Ma, Wen-Jong; Banavar, Jayanth R.; Koplik, Joel

1992-01-01

15

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

16

Statistical geometry of cavities in a metastable confined fluid  

SciTech Connect

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

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

2000-07-01

17

Reaction kinetics in confined geometries: Lonely adatoms in space  

NASA Astrophysics Data System (ADS)

There is a close relation between the problems of second-layer nucleation in epitaxial crystal growth and chemical surface reactions, such as hydrogen recombination, on interstellar dust grains. In both cases, standard rate equation analysis has been found to fail because the process takes place in a confined geometry, and under typical conditions the mean number of reactant particles on the surface is small compared to unity (the lonely adatom regime). Using scaling arguments developed in the context of second-layer nucleation, I present a simple derivation of the hydrogen recombination rate for small and large grains. I clarify the reasons for the failure of rate equations for small grains, and point out a logarithmic correction to the reaction rate when the reaction is limited by the desorption of hydrogen atoms (the second-order reaction regime).

Krug, Joachim

2003-06-01

18

Dynamics of suspensions of elastic capsules flowing in confined geometries  

NASA Astrophysics Data System (ADS)

Modeling the behavior of fluid-filled capsules (a simple representation of red blood cells and vesicles), is not only important to understand biological processes, such as blood flow in the microcirculation, but also to help design and improve microfluidic devices for characterizing or separating such particles. The present work describes simulations of large numbers of deformable capsules with various properties in confined geometries. Our algorithm incorporates a General-Geometry-Ewald-Like method (GGEM) for efficiently calculating hydrodynamic interactions (O(N)) in an immersed-boundary method. With our algorithm, we have addressed several issues. The ability to quickly simulate large number of particles enables examinations of not only of the competition between shear-induced diffusion and wall-induced hydrodynamic migration of single particles, but also exploration of concentration effects and segregation by size, shape and/or deformability. Combined with the simulation of grooved channels, we propose a methodology to separate these cells depending on their deformability and size. Finally, the effect of addition of long-chained polymer molecules in blood flow, known to lower blood pressure, is investigated.

Pranay, Pratik; Janseen, Pieter J. A.; Graham, Michael

2009-11-01

19

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

20

Confining potential in momentum space  

NASA Technical Reports Server (NTRS)

A method is presented for the solution in momentum space of the bound state problem with a linear potential in r space. The potential is unbounded at large r leading to a singularity at small q. The singularity is integrable, when regulated by exponentially screening the r-space potential, and is removed by a subtraction technique. The limit of zero screening is taken analytically, and the numerical solution of the subtracted integral equation gives eigenvalues and wave functions in good agreement with position space calculations.

Norbury, John W.; Kahana, David E.; Maung, Khin Maung

1992-01-01

21

Effective pair potential between confined charged colloidal particles  

Microsoft Academic Search

The pair correlation function g(r) between like-charged colloidal particles in quasi-two-dimensional geometries is measured by optical microscopy for a wide range of particle concentrations and various degrees of confinement. The effective pair potential u(r) is obtained by deconvoluting g(r) via Monte Carlo computer simulations. Our results confirm the existence of a long-range attractive component of u(r) and the appearance of

Angeles Ramírez-Saito; Martín Chávez-Páez; Jesús Santana-Solano; José Luis Arauz-Lara

2003-01-01

22

Yukawa particles in a confining potential.  

PubMed

We study the density distribution of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show that the mean-field theory is able to accurately account for the particle distribution. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. For strongly correlated systems, we construct a density functional theory which provides an excellent description of the particle distribution, without any adjustable parameters. PMID:25005276

Girotto, Matheus; Dos Santos, Alexandre P; Colla, Thiago; Levin, Yan

2014-07-01

23

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

24

Vortex distribution in a confining potential  

NASA Astrophysics Data System (ADS)

We study a model of interacting vortices in a type II superconductor. In the weak coupling limit, we constructed a mean-field theory which allows us to accurately calculate the vortex density distribution inside a confining potential. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. Contrary to recent suggestions, this does not imply failure of the Boltzmann-Gibbs statistical mechanics, as we clearly demonstrate by comparing the results of molecular dynamics and Monte Carlo simulations.

Girotto, Matheus; dos Santos, Alexandre P.; Levin, Yan

2013-09-01

25

Vortex distribution in a confining potential.  

PubMed

We study a model of interacting vortices in a type II superconductor. In the weak coupling limit, we constructed a mean-field theory which allows us to accurately calculate the vortex density distribution inside a confining potential. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. Contrary to recent suggestions, this does not imply failure of the Boltzmann-Gibbs statistical mechanics, as we clearly demonstrate by comparing the results of molecular dynamics and Monte Carlo simulations. PMID:24125224

Girotto, Matheus; Dos Santos, Alexandre P; Levin, Yan

2013-09-01

26

Ambipolar potential formation and axial confinement in TMX  

Microsoft Academic Search

TMX experimental data on ambipolar potential control and on the accompanying electrostatic confinement are reported. In the radial core of the central cell, measurements of electrostatic potentials of 150 V which augment axial ion confinement are in agreement with predictions using the Maxwell-Boltzmann result. Central-cell ion confinement was observed to scale according to electrostatic potential theory up to average enhancement

D. L. Correll; S. L. Allen; T. A. Capser; J. F. Clauser; P. Coakley; F. H. Coensgen; W. Condit; W. F. Cummins; J. C. Davis; R. P. Drake; J. H. Foote; A. H. Futch; R. K. Goodman; D. P. Grubb; G. A. Hallock; E. B. Hooper; R. S. Hornady; A. L. Hunt; C. V. Karmendy; A. W. Molvik; W. E. Nexsen; W. L. Pickles; P. Poulsen; T. C. Simonen; B. W. Stallard; O. T. Strand

1982-01-01

27

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

PubMed

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

Peters, Michael H

2011-01-14

28

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

NASA Astrophysics Data System (ADS)

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

Peters, Michael H.

2011-01-01

29

Saturn-ring defects around microspheres suspended in nematic liquid crystals: an analogy between confined geometries and magnetic fields.  

PubMed

Particles suspended in a nematic liquid crystal exhibit characteristic dipolar and Saturn-ring configurations. Using results on the magnetic-field behavior of these configurations, we explain the recent observation of the Saturn-ring defect in confined geometries based on the idea that a confining geometry and a magnetic field generate a similar "confinement" for the nematic phase. PMID:12366166

Stark, Holger

2002-09-01

30

tt* Geometry and Closed String Tachyon Potential  

Microsoft Academic Search

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

Atish Dabholkar; Cumrun Vafa

2002-01-01

31

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

32

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

33

Beam-ion confinement for different injection geometries  

NASA Astrophysics Data System (ADS)

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

Heidbrink, W. W.; Murakami, M.; Park, J. M.; Petty, C. C.; Van Zeeland, M. A.; Yu, J. H.; McKee, G. R.

2009-12-01

34

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

35

A theoretical model for tissue growth in confined geometries  

NASA Astrophysics Data System (ADS)

It is known that cells proliferate and produce extracellular matrix in response to biochemical and mechanical stimuli. Constitutive models considering these phenomena are needed to quantitatively describe the process of tissue growth in the context of tissue engineering and regenerative medicine. In this paper we re-examine the theoretical framework provided by Ambrosi and Guana (2007) and Ambrosi and Guillou (2007). We show how a volumetric growth rate term can be obtained (both in a large and small strain setting), which is consistent with the laws of thermodynamics and then apply the model to a simple geometry of tissue growth within a circular pore. The model, despite its simplicity, is comparable with experimental measurements of tissue growth and highlights the contribution of the mechanical stresses produced during tissue growth on the growth rate itself.

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

2010-08-01

36

Statistical Thermodynamics of Homopolymer Mixtures in Bulk and Confined Geometries In a Recursive Lattice Approach  

Microsoft Academic Search

We present a new lattice theory of a regular model of multicomponent polymer mixtures in bulk and in confined geometries, which goes beyond the random- mixing approximation of the Flory-Huggins theory. The theory is obtained by solving exactly the regular model on a recursive lattice (RL) and has been successfully applied to investigate thermodynamic and percolative properties, as many examples

P. D. Gujrati; Mukesh Chhajer; T. F. George; X. Sun; G. Zhang

37

Generalized Bertlmann-Martin inequalities for confining potentials  

NASA Astrophysics Data System (ADS)

The generalized Bertlmann-Martin inequalities for the moments of the ground state wave function of a two-body system are shown to be saturated within a few percent for confining potentials. Two kinds of potentials are investigated: the superposition of 1/r and rp, and the anharmonic oscillator potentials. The application to qq¯ hadrons is discussed.

Lombard, R. J.; Mareš, J.

1999-04-01

38

Plasma Confinement in Glass Microcavities: Dependence of Plasma Properties on Microcavity Geometry.  

NASA Astrophysics Data System (ADS)

Arrays of glass microcavities having diameters of 50-200 ?m and controllable geometries have been successfully fabricated by micropowder blasting techniques. Anisotropic or isotropic microcavities, including cavities with ellipsoidal geometry have been fabricated in large scale arrays with high resolution and various shapes of microcavities were prepared precisely. Arrays having as much as 1000 microcavities were fabricated on 400 ?m thick soda lime glasses and a pair of these glasses was aligned and sealed to form a closed microdischarge cell. The cross-sectional microcavity shape in the discharge cell is designed from the calculation of electric field distribution. Powered by electrodes located outside the microcavity with ac frequencies of 20-100 kHz, the stable, uniform discharges and confinement of plasma in entire microcavity was observed at 300-800 Torr of noble gases. From the spatially-resolved measurement of emission from a microcavity, the device has better plasma confinement and increased emission intensity in higher gas pressures. Discharge performance in various gas or gas mixtures and its dependence on microcavity geometry will be discussed.

Sung, S. H.; Berger, A. G.; Kim, J.-Y.; Park, S.-J.; Eden, J. G.

2007-10-01

39

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

PubMed

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

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

2013-06-01

40

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

41

A software package to manipulate space dependencies and geometry in magnetic confinement fusion  

SciTech Connect

Improvement in the performance of magnetic confinement devices for nuclear fusion relies on the optimization of the geometry of the plasma: either the two-dimensional (2D) cross-section shape in tokamaks with toroidal symmetry or the 3D magnetic configuration in stellerators. The variation in time and space of the plasma parameters in these devices is measured using tomographic or imaging systems with a large number of detectors. To integrate the geometrical manipulations required for the analysis of experimental data, the description of the confining magnetic field configuration and the modeling and simulation of the physical processes within the plasma, an object oriented software package has been developed. Classes in this package are used to describe several coordinate systems, including magnetic flux coordinates, the geometry of the measurement systems, the configuration of the magnetic field and space, and time dependent functions representing plasma parameters. Methods applied on these classes can then easily implement coordinate system transformations, as well as interpolation of and integro-differential calculus on, space and time dependent functions. The geometrical description and characteristics of the magnetic flux surfaces have a natural representation in this environment, allowing the ready computation of the intersection of measurement viewing lines with a coordinate mesh and with flux surfaces, as well as the calculation of the corresponding transfer matrix used in tomographic inversion. The selected numerical methods used in these manipulations and their performances are also presented.

Moret, J.-M. [CRPP-EPFL, Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

2005-07-15

42

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

PubMed

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

Khirevich, Siarhei; Höltzel, Alexandra; Tallarek, Ulrich

2011-06-28

43

Inertial confinement fusion: present status and future potential  

Microsoft Academic Search

Power from inertial confinement fusion holds much promise for society. This paper points out many of the benefits relative to combustion of hydrocarbon fuels and fission power. Potential problems are also identified and put in perspective. The progress toward achieving inertial fusion power is described and results of recent work at the Lawrence Livermore National Laboratory are presented. Key phenomenological

Hogan

1984-01-01

44

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

PubMed

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

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

2013-03-01

45

Inertial confinement fusion: present status and future potential  

SciTech Connect

Power from inertial confinement fusion holds much promise for society. This paper points out many of the benefits relative to combustion of hydrocarbon fuels and fission power. Potential problems are also identified and put in perspective. The progress toward achieving inertial fusion power is described and results of recent work at the Lawrence Livermore National Laboratory are presented. Key phenomenological uncertainties are described and experimental goals for the Nova laser system are given. Several ICF reactor designs are discussed.

Hogan, W.J.

1984-07-16

46

Controlled Evaporative Self-Assembly of Poly(acrylic acid) in a Confined Geometry for Fabricating Patterned Polymer Brushes.  

PubMed

A simple yet robust approach was exploited to fabricate large-scaled patterned polymer brushes by combining controlled evaporative self-assembly (CESA) in a confined geometry and self-initiated photografting and photopolymerization (SIPGP). Our method was carried out without any sophisticated instruments, free of lithography, overcoming current difficulties in fabricating polymer patterns by using complex instruments. PMID:24702600

Men, Yonghong; Xiao, Peng; Chen, Jing; Fu, Jun; Huang, Youju; Zhang, Jiawei; Xie, Zhengchao; Wang, Wenqin; Chen, Tao

2014-04-29

47

LETTER TO THE EDITOR: Does temperature fluctuate? Indirect proof by dynamic glass transition in confined geometries  

NASA Astrophysics Data System (ADS)

The Gibbs canonical distribution, dw ~ exp ( - E ( p , q ) / kB T ) dp dq , seems one of the most solid pillars of statistical physics. Thermodynamics is believed to be a derivative of this distribution. Since the temperature T is introduced, de facto , from a heat bath by the zeroth law of thermodynamics, this distribution cannot represent a genuine temperature fluctuation; all fluctuations are derived from energy fluctuations (icons/Journals/Common/delta" ALT="delta" ALIGN="TOP"/> E ). Increasingly, nanoscale problems are attacked by physics (e.g. glass transition), physical chemistry (e.g. nucleation), or biology (e.g. protein folding). The fluctuations are relatively large because the nano-subsystems are small. The fluctuations should, therefore, completely be collected. The von Laue approach [1 - 3] to subsystem thermodynamics via minimal work for generation of fluctuations also allows the temperature to fluctuate (icons/Journals/Common/delta" ALT="delta" ALIGN="TOP"/> T ). For this alternative, statistical physics is a derivative of thermodynamics. Here we show that a decision between the alternatives is possible by a calorimetric determination of the characteristic length of dynamic glass transition in confined geometries.

Donth, E.; Hempel, E.; Schick, C.

2000-04-01

48

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

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

Heavy tetraquark confining potential in Coulomb gauge QCD  

NASA Astrophysics Data System (ADS)

We present an analytic nonperturbative solution of the Yakubovsky equation for tetraquark states in the case of equal separations and energies, and demonstrate a direct connection between the tetraquark confinement potential and the temporal gluon propagator. To this end we employ a leading-order heavy quark mass expansion of the Coulomb gauge QCD action, and use the dressed two-point functions of the Yang-Mills sector only. As a result, we find a bound state energy that rises linearly with distance and a string tension twice as large as in a qq¯-system.

Popovici, Carina; Fischer, Christian S.

2014-06-01

51

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

52

Brane-world black hole solutions via a confining potential  

SciTech Connect

Using a confining potential, we consider spherically symmetric vacuum (static black hole) solutions in a brane-world scenario. Working with a constant curvature bulk, two interesting cases/solutions are studied. A Schwarzschild-de Sitter black hole solution similar to the standard solution in the presence of a cosmological constant is obtained which confirms the idea that an extra term in the field equations on the brane can play the role of a positive cosmological constant and may be used to account for the accelerated expansion of the universe. The other solution is one in which we can have a proper potential to explain the galaxy rotation curves without assuming the existence of dark matter and without working with new modified theories (modified Newtonian dynamics)

Heydari-Fard, M.; Sepangi, H. R. [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839 (Iran, Islamic Republic of); Razmi, H. [Department of Physics, University of Qom, Qom 37185-359 (Iran, Islamic Republic of)

2007-09-15

53

Spectral singularity in confined PT symmetric optical potential  

SciTech Connect

We present an analytical study for the scattering amplitudes (Reflection ?R? and Transmission ?T?), of the periodic PT symmetric optical potential V(x)=W{sub 0}cos{sup 2}x+iV{sub 0}sin2x confined within the region 0 ?x?L, embedded in a homogeneous medium having uniform potential W{sub 0}. The confining length L is considered to be some integral multiple of the period ?. We give some new and interesting results. Scattering is observed to be normal (?T?{sup 2}? 1, ?R?{sup 2}? 1) for V{sub 0}? 0.5, when the above potential can be mapped to a Hermitian potential by a similarity transformation. Beyond this point (V{sub 0} > 0.5) scattering is found to be anomalous (?T?{sup 2}, ?R?{sup 2} not necessarily ?1). Additionally, in this parameter regime of V{sub 0}, one observes infinite number of spectral singularities E{sub SS} at different values of V{sub 0}. Furthermore, for L= 2n?, the transition point V{sub 0}= 0.5 shows unidirectional invisibility with zero reflection when the beam is incident from the absorptive side (Im[V(x)] < 0) but with finite reflection when the beam is incident from the emissive side (Im[V(x)] > 0), transmission being identically unity in both cases. Finally, the scattering coefficients ?R?{sup 2} and ?T?{sup 2} always obey the generalized unitarity relation : ?T|{sup 2}?1|=?(|R{sub R}|{sup 2}|R{sub L}|{sup 2}), where subscripts R and L stand for right and left incidence, respectively.

Sinha, Anjana [Department of Instrumentation Science, Jadavpur University, Kolkata - 700 032 (India)] [Department of Instrumentation Science, Jadavpur University, Kolkata - 700 032 (India); Roychoudhury, R. [Department of Mathematics, Bethune College, Kolkata - 700 006, India and Advanced Centre for Nonlinear and Complex Phenomena, 1175 Survey Park, Kolkata - 700075 (India)] [Department of Mathematics, Bethune College, Kolkata - 700 006, India and Advanced Centre for Nonlinear and Complex Phenomena, 1175 Survey Park, Kolkata - 700075 (India)

2013-11-15

54

Stress Induced Microcrack Geometry at Failure in Unconfined and Confined Axial Compressive Tests.  

National Technical Information Service (NTIS)

Cylindrical specimens of Indiana limestone have been tested in uniaxial, confined and partially confined compression. A low melting point metal alloy was used as a pore fluid. At the stress of interest this alloy was solidified in place to preserve the st...

Z. Zheng L. R. Myer N. G. W. Cook

1989-01-01

55

Stress induced microcrack geometry at failure in unconfined and confined axial compressive tests  

Microsoft Academic Search

Cylindrical specimens of Indiana limestone have been tested in uniaxial, confined and partially confined compression. A low melting point metal alloy was used as a pore fluid. At the stress of interest this alloy was solidified in place to preserve the stress induced microcracks. Optical and electron micrographs of cross sections from the specimens were used to study the density,

Z. Zheng; L. R. Myer; N. G. W. Cook

1989-01-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

57

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

58

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

59

From first-passage times of random walks in confinement to geometry-controlled kinetics  

NASA Astrophysics Data System (ADS)

We present a general theory which allows one to accurately evaluate the mean first-passage time (FPT) for regular random walks in bounded domains, and its extensions to related first-passage observables such as splitting probabilities and occupation times. It is showed that this analytical approach provides a universal scaling dependence of the mean FPT on both the volume of the confining domain and the source-target distance in the case of general scale invariant processes. This analysis is applicable to a broad range of stochastic processes characterized by scale-invariance properties. The full distribution of the FPT can be obtained using similar tools, and displays universal features. This allows to quantify the fluctuations of the FPT in confinement, and to reveal the key role that can be played by the starting position of the random walker. Applications to reaction kinetics in confinement are discussed.

Bénichou, O.; Voituriez, R.

2014-06-01

60

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

61

Effect of magnetic geometry on transport of neutral particles locally entering confined plasma volume  

SciTech Connect

The effect of the position where neutral particles enter the confined plasma region with closed magnetic surfaces on the radial profiles of the neutral flux and plasma density is numerically investigated. The case of elongated magnetic surfaces with X-point, in whose vicinity the metric coefficients are varying very fast with the radius of magnetic surfaces, is considered.

Tokar, M. Z. [Institut fuer Energieforschung-Plasmaphysik, Forschungszentrum Juelich GmbH, Association FZJ-Euratom, 52425 Juelich (Germany)

2009-09-15

62

Correlation studies in weakly confining quantum dot potentials  

NASA Astrophysics Data System (ADS)

We investigate the electron correlation in few-electron closed-shell atomic systems and similarly in few-electron quantum dots under weak confinement. As usual we start with restricted Hartree-Fock (HF) calculations and add electron correlation in steps in a series of approximations based on the single particle Green's function approach: (i) second-order Green function (GF); (ii) 2ph-Tamm-Dancoff approximation (TDA); and (iii) an extended version thereof which introduces ground-state correlation into the TDA. Our studies exhibit similarities and differences between weakly confined quantum dots and standard atomic systems. The calculations support the application of HF, GF, and TDA techniques in the modeling of three-dimensional quantum dot systems. The observed differences emphasize the significance of confinement and electronic features unique to quantum dots, such as the increased binding of electrons with higher angular momentum and thus - compared to atomic systems - modified shell-filling sequences.

Kimani, Peter; Jones, Preston; Winkler, Peter

63

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

Microsoft Academic Search

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

G. Liu; Y. Li; J. Jonas

1991-01-01

64

Transport phenomena and dynamics of externally and self-propelled colloids in confined geometry  

NASA Astrophysics Data System (ADS)

Over the last decades, colloidal suspensions have been proven as powerful model systems to reveal fundamental questions in soft matter or general physics. In this work, we will focus on the influence of interaction and confinement to the mobility of colloidal particles as well as to the transport behavior of particles over obstacles placed in a micro-channel. Both experiments are supported with Brownian dynamics simulations to complete the experimental work. The paper concludes with the investigation of the behavior of single active swimmers close to a wall.

Kreuter, C.; Siems, U.; Nielaba, P.; Leiderer, P.; Erbe, A.

2013-11-01

65

Geometry  

NSDL National Science Digital Library

This collection, created by Salman Khan of the Khan Academy, features videos on geometry. A basic understanding of Algebra I necessary to understand the fundamental elements featured in this collection. Altogether, the site contains 23 videos the cover an array of topics under the field of geometry. After these lessons, you'll certainly be ready for Trigonometry.

Khan, Salman

2011-01-03

66

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

67

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

68

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

Microsoft Academic Search

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

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

1990-01-01

69

Quantum chemistry of confined systems: structure and vibronic spectra of a confined hydrogen molecule  

Microsoft Academic Search

Structure and spectral properties of the hydrogen molecule confined in a spherically symmetric harmonic oscillator potential were studied using the configuration interaction method. Increased strength of the confining potential exerts significant influence on the geometry of the molecule as well as on the vibronic transitions between the electronic ground and lowest excited singlet states. With increasing confinement strength the bond

Geerd H. F Diercksen; Mariusz Klobukowski

2001-01-01

70

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

71

Diffusion of water in confined geometry: The case of a multilamellar bilayer  

NASA Astrophysics Data System (ADS)

The diffusion of water confined in a stack of GM3 ganglioside bilayers is studied by computer simulation. A theoretical analysis of the behavior of the mean square displacement parallel and perpendicular to the bilayer surface is also provided in terms of diffusion equations in a very long time interval, between 2 ps and 2 ns. Such an analysis has allowed us to identify two different time regimes, to clarify the nature of nonlinear time dependence of the mean square displacement, and to give an interpretation to the origin of the often used time dependent diffusion coefficient. Both the effects of spatial inhomogeneities and boundary conditions are demonstrated to be the key points for the interpretation of all these results within a consistent theoretical framework.

Sega, Marcello; Vallauri, Renzo; Melchionna, Simone

2005-10-01

72

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

73

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

SciTech Connect

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

Warren, R.P.; Caspi, S.

1981-08-01

74

On the generation of nonlinear travelling waves in confined geometries using electric fields.  

PubMed

We investigate electrostatically induced interfacial instabilities and subsequent generation of nonlinear coherent structures in immiscible, viscous, dielectric multi-layer stratified flows confined in small-scale channels. Vertical electric fields are imposed across the channel to produce interfacial instabilities that would normally be absent in such flows. In situations when the imposed vertical fields are constant, interfacial instabilities emerge due to the presence of electrostatic forces, and we follow the nonlinear dynamics via direct numerical simulations. We also propose and illustrate a novel pumping mechanism in microfluidic devices that does not use moving parts. This is achieved by first inducing interfacial instabilities using constant background electric fields to obtain fully nonlinear deformations. The second step involves the manipulation of the imposed voltage on the lower electrode (channel wall) to produce a spatio-temporally varying voltage there, in the form of a travelling wave with pre-determined properties. Such travelling wave dielectrophoresis methods are shown to generate intricate fluid-surface-structure interactions that can be of practical value since they produce net mass flux along the channel and thus are candidates for microfluidic pumps without moving parts. We show via extensive direct numerical simulations that this pumping phenomenon is a result of an externally induced nonlinear travelling wave that forms at the fluid-fluid interface and study the characteristics of the generated velocity field inside the channel. PMID:24936019

Cimpeanu, R; Papageorgiou, D T

2014-07-28

75

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

76

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

SciTech Connect

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

Not Available

1993-12-31

77

Influence of confinement on the electrostatic interaction between charged colloids: a (N,V,T) Monte Carlo study within hyperspherical geometry.  

PubMed

Monte Carlo simulations within closed hyperspherical geometry are used to analyze the ionic distribution around two confined charged colloids to determine the origin of the net attraction recently reported in the literature. A scaling procedure is used to compare our numerical results obtained with small ideal colloids with the conclusion of the measurements performed with large silica colloids. Although no electrostatic attraction is detected under confinement, our simulations exhibit a significant reduction of the electrostatic repulsion between charged colloids confined between two weakly charged walls. After rescaling to reproduce the electrostatic repulsion between large confined colloids, our numerical results are qualitatively consistent with the reported attraction because we reasonably expect a reduction of the electrostatic force between such confined colloids below the order of magnitude of their van der Waals attraction. PMID:16851954

Delville, A

2005-04-28

78

Confined quantum time of arrival for the vanishing potential  

SciTech Connect

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

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

2005-12-15

79

Collective modes and dielectric and superconducting properties of electronic systems in confined geometries  

SciTech Connect

The dielectric response function of electronic systems in restricted geometries is studied as well as some of the consequences, using the self-consistent field method. These consequences include: 1) existence of multiple branches of longitudinal slender acoustic plasma oscillations (SAP) in thin wires; 2) a new superconductivity mechanism in thin wires via the exchange of SAPs by the electrons forming the Cooper pairs, and 3) reduction of the static screening offered by the valence electrons in a thin semiconductor film with respect to the bulk case. The SAP modes are collective modes shown to exist only in thin wires and neither in a bulk system nor in a thin film. They have linear dispersion relations with phase velocities smaller than the Fermi velocity of the system and are not Landau-damped. Numerical examples of these SAP modes in metallic and semiconductor wires are presented, showing that they sould be more easily observable in semiconductor structures. The SAP-induced mechanism of superconductivity is shown to possibly give higher critical temperature T/sub c/ than the phonon mechanism in thin wires. The author presents a semi-rigorous calculation of T/sub c/ and shows that by increasing the frequency of the SAP modes and having a small effective electron mass one would be able to increase T/sub c/. He also shows that the dielectric function of a thin semiconductor slab is wavenumber dependent even at long wavelengths and is not a constant as in the bulk case.

Ulloa, S.E.

1984-01-01

80

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

SciTech Connect

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

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

2013-05-15

81

Testing confining potentials through meson/baryon hyperfine splittings  

SciTech Connect

In this paper, we discuss a quantity that can be derived from the hadronic spectrum-the ratio between the color hyperfine splitting of a K meson and that of a {sigma} baryon. It is shown that within the constituent quark model this ratio depends only on the ratio of contact probabilities in the hadrons. We compute this ratio assuming several phenomenological potential models, and show that the best agreement with data is obtained from the Cornell potential - Coulomb + linear. Thus, the analysis of color hyperfine interactions corroborates the preference for the Cornell potential based on quarkonium spectra.

Keren-Zur, Boaz [School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv (Israel)], E-mail: kerenzu@post.tau.ac.il

2008-03-15

82

Rotating Bose-Einstein condensates confined in an anharmonic potential  

SciTech Connect

We consider bosonic atoms that rotate in an anharmonic trapping potential. Using numerical diagonalization of the Hamiltonian, we get evidence for various phases of the gas for different values of the coupling between the atoms and of the rotational frequency of the trap. These include vortex excitation of single and multiple quantization, the phase of center-of-mass excitation, and the unstable phase.

Bargi, S.; Kavoulakis, G. M.; Reimann, S. M. [Mathematical Physics, LTH, Lund University, P.O. Box 118, SE-22100, Lund (Sweden)

2006-03-15

83

Potential energy profile of colloidal nanoparticles in optical confinement.  

PubMed

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

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

2013-10-15

84

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

85

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

86

Structure and correlations in two-dimensional classical artificial atoms confined by a Coulomb potential.  

PubMed

The ordering of N equally charged particles (-e) moving in two dimensions and confined by a Coulomb potential, resulting from a displaced positive charge Ze is discussed. This is a classical model system for atoms. We obtain the configurations of charged particles which, depending on the value of N and Z, may result in ring structures, hexagonal-type configurations, and for N/Z approximately 1 in an inner structure of particles which is separated by an outer ring of particles. For N/Z<1, the Hamiltonian of the parabolic confinement case is recovered. For N/Z approximately 1, the configurations are very different from those found in the case of a parabolic confinement potential. A hydrodynamic analysis is presented in order to highlight the correlations effects. PMID:12786503

Ferreira, W P; Matulis, A; Farias, G A; Peeters, F M

2003-04-01

87

The Electrophoretic Mobility of a Polyelectrolyte within a Radially Confining Potential Well  

NASA Astrophysics Data System (ADS)

We demonstrate that a polyelectrolyte electrophoresing while radially confined by a mechanical force has a conformationally dependent electrophoretic mobility that differs from its free-draining value. The mobility increases as a function of the confining harmonic potential and in the absence of solid walls. Mesoscale MPCD-MD hybrid simulations that include electro-hydrodynamics through a mean-field Debye H"uckel approximation will be presented for a variety of well widths and contour lengths, demonstrating that mobility increases with confinement after a critical point but remains independent of polymerization. For this reason, models based on a change of monomer friction coefficient at the confinement boundary (such as those recently put forward to explain experimentally measured mobility polyelectrolytes confined within nano- and microfluidic channels) are not sufficient to explain our observations. Since the potential acts perpendicular to the electric field and only on the monomers, the Electro-Hydrodynamic Equivalence Principle does not predict the mobility to differ. We present a course-grained theory explaining these findings in terms of hydrodynamic coupling within overlapping diffuse layers.

Shendruk, Tyler; Bertrand, Martin; Slater, Gary W.

2013-03-01

88

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

PubMed

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

Sanghi, T; Aluru, N R

2012-01-14

89

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

90

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

NASA Astrophysics Data System (ADS)

A lateral resonant tunneling field effect transistor has been fabricated with a gate electrode in the form of a railway such that the two rails form a lateral double barrier potential at the GaAs/AlGaAs interface. The ties confine the electrons in the third dimension forming an array of potential boxes or three dimensionally confined potential wells. The width of the ties and rails is 50nm; the spacings between the ties and between the two rails are 230nm and 150nm respectively. The ties are 750nm long and extend beyond the the two rails forming one dimensional wires on either side. Conductance oscillations are observed in the drain current at 4.2K as the gate voltage is scanned. Comparison with devices with a solid gate, and with a monorail gate with ties fabricated on the same wafer suggest that these conductance oscillations are electron resonant tunneling from one dimensional wires through the quasi-bound states of the three dimensionally confined potential wells. Comparison with a device with a two rail gate without ties (previously published) indicates that additional confinement due to the ties enhances the strength of the conductance oscillations.

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

91

Structure and correlations in two-dimensional classical artificial atoms confined by a Coulomb potential  

Microsoft Academic Search

The ordering of N equally charged particles (-e) moving in two dimensions and confined by a Coulomb potential, resulting from a displaced positive charge Ze is discussed. This is a classical model system for atoms. We obtain the configurations of charged particles which, depending on the value of N and Z, may result in ring structures, hexagonal-type configurations, and for

W. P. Ferreira; A. Matulis; G. A. Farias; F. M. Peeters

2003-01-01

92

Electronic structure and electron correlation in weakly confining spherical quantum dot potentials  

NASA Astrophysics Data System (ADS)

The electronic structure and electron correlations in weakly confining spherical quantum dots potentials are investigated. Following a common practice, the investigation starts with the restricted Hartree-Fock (HF) approximation. Then electron correlation is added in steps in a series of approximations based on the single particle Green's function approach: (i) Second-order Green function (GF) (ii) 2ph-Tamm-Dancoff approximation (TDA) and (iii) an extended version thereof (XTDA) which introduces ground-state correlation into the TDA. The study includes as well Hartree-Fock V (N-1) potential approximation in which framework the Hartree-Fock virtual orbitals are calculated in the field of the N-1 electrons as opposed to the regular but unphysical N-electron field Hartree-Fock calculation of virtual orbitals. For contrast and comparison, the same approximation techniques are applied to few-electron closed-shell atoms and few-electron negative ions for which pertinent data is readily available. The results for the weakly confining spherical quantum dot potentials and the standard atomic systems exhibit fundamental similarities as well as significant differences. For the most part the results of these calculations are in favor of application of HF, GF, and TDA techniques in the modeling of three-dimensional weakly confining quantum dot potentials. The observed differences emphasize the significance of confinement and electronic features unique to quantum dots such as the increased binding of electrons with higher angular momentum and the modified shell filling sequences.

Kimani, Peter Borgia Ndungu

93

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

94

Realistic confinement potential for a square-patterned two-dimensional semiconductor quantum dot and its approximated circular counterpart  

NASA Astrophysics Data System (ADS)

Two-dimensional semiconductor quantum-dot systems are typical nanoscale structures in which a few number of electrons is confined in a small region of space by applying external electric gate potentials. While the detailed form of the confining potential depends on the specific experimental setup, the parabolic confinement model has commonly been used because of its simplicity. Clearly, on those instances in which the experimental setup involves placement of gate potentials with sharp geometric features, the area depleted of electrons; thus, the quantum-dot region cannot be considered circular. If, for simplicity, we consider the confinement region of the electrons as square in shape, then an accurate calculation of the properties of such square-patterned quantum dot should be made using a realistic confinement potential originating from that particular configuration. We calculated exactly such a confinement potential for a square quantum dot. The particular analytic form of this realistic potential is complicated given its dependence on the two-dimensional position coordinates, rather than simply the distance from the center of the quantum dot. In this work, we choose to substitute the realistic confinement potential for a square-patterned quantum dot with an approximated circular symmetric potential. We assess the quality of this approximation and discuss instances in which one can reliably use the approximated simplified potential instead of the computationally unyielding exact one.

Ciftja, Orion

2012-11-01

95

Electronic structure and electron correlation in weakly confining spherical quantum dot potentials  

Microsoft Academic Search

The electronic structure and electron correlations in weakly confining spherical quantum dots potentials are investigated. Following a common practice, the investigation starts with the restricted Hartree-Fock (HF) approximation. Then electron correlation is added in steps in a series of approximations based on the single particle Green's function approach: (i) Second-order Green function (GF) (ii) 2ph-Tamm-Dancoff approximation (TDA) and (iii) an

Peter Borgia Ndungu Kimani

2008-01-01

96

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

NASA Astrophysics Data System (ADS)

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

2014-03-01

97

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

NASA Technical Reports Server (NTRS)

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

Wiese, Michael R.

1987-01-01

98

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

99

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

PubMed

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 are both accompanied by increased cell polarization. Disruption of this polarization occurs 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; Kumar, Sanjay

2013-08-01

100

Model of waterlike fluid under confinement for hydrophobic and hydrophilic particle-plate interaction potentials.  

PubMed

Molecular dynamic simulations were employed to study a waterlike model confined between hydrophobic and hydrophilic plates. The phase behavior of this system is obtained for different distances between the plates and particle-plate potentials. For both hydrophobic and hydrophilic walls, there are the formation of layers. Crystallization occurs at lower temperature at the contact layer than at the middle layer. In addition, the melting temperature decreases as the plates become more hydrophobic. Similarly, the temperatures of maximum density and extremum diffusivity decrease with hydrophobicity. PMID:24580175

Krott, Leandro B; Barbosa, Marcia C

2014-01-01

101

Variation of the confinement potential of a quasi-one-dimensional electron gas by lateral p-n junctions  

Microsoft Academic Search

We present the first study of a new system where the confinement potential of a high mobility quasi-one-dimensional electron gas on the (100) GaAs surface is varied using two, two-dimensional hole gases produced on the adjacent (311)A surfaces. The structure consists of two lateral two-dimensional p-n junctions, placed back-to-back to form a p-n-p structure. The confinement potential of the narrow

R. J. Evans; T. M. Burke; J. H. Burroughes; M. P. Grimshaw; D. A. Ritchie; M. Pepper

1996-01-01

102

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

NASA Astrophysics Data System (ADS)

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

Shuryak, E.; Sulejmanpasic, T.

2013-10-01

103

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

104

Theoretical study on quasi-confined optical phonon modes in a free-standing cylindrical GaN nanowire with ring geometry: A resonant Raman scattering  

NASA Astrophysics Data System (ADS)

We have investigated quasi-confined (QC) optical resonant Raman scattering in GaN nanowires (NWs) with ring geometry. We consider the Fröhlich electron-phonon interaction in the framework of the dielectric continuum approach. The selection rules are studied. For small ring radius, our results show that the main contribution to the differential cross section (DCS) comes from high-frequency of the QC phonons, with a minor contribution from the LO phonons. The peak of the DCS is mainly attributed to the electron-QC coupling strength can get the maximum value as the anisotropic effect of wurtzite nitride crystal. Moreover, the lower orders of the QC phonons, the larger the DCS.

Tan, Qi-Ren; Liu, Cui-Hong

2013-12-01

105

Screening of the confinement potential in the SU(2) lattice gauge theory with scalar matter  

NASA Astrophysics Data System (ADS)

Using the SU (2) Higgs system with dynamical scalar matter fields as a model for analyzing screening properties of the confining potential in gauge theories, we examine the Wilson loop W (T, R) and the gauge invariant 2-point function G(T, R) by Monte Carlo simulations on a 164 lattice. For small values of the hopping parameter k these quantities show non-asymptotic area law behavior which changes to asymptotic perimeter law behavior as k increases. Close to the Higgs phase transition we find an indication that both these asymptotic and nonasymptotic terms are present simultaneously within the lattice at different distances R and T and that the breaking of the confining flux tube by matter pair production occurs within the lattice. Introducing an appropriate ansatz for W(T, R) and G(T, R), respectively, we determine in this complex situation the string tension, the screening energy of the external sources, and the order parameter introduced by Fredenhagen and Marcu.

Bock, W.; Evertz, H. G.; Jansen, K.; Jersák, J.; Kanaya, K.; Kastrup, H. A.; Landau, D. P.; Neuhaus, T.; Xu, J. L.

1990-12-01

106

Heavy mesons in a simple quark-confining two-step potential model  

NASA Astrophysics Data System (ADS)

We study the mass spectra and decay widths of ? resonances in a simple quark-confining, analytically solvable, two-step potential model used earlier to study the charmonium system and even the light mesons such as ?, ?, K, .... Results are found to be in good agreement with experiments and also with the values predicted by others. We predict the BB¯ threshold at 10.242 GeV, which means in our model the first three radial ? excitations ?(9.4345), ?'(9.9930), and ?''(10.1988) are stable with respect to the Zweig-rule-allowed decay ?-->BB¯. The mass spectrum and thresholds of the anticipated tt¯ states are also studied as a function of quark mass.

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

1982-11-01

107

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

108

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

PubMed Central

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

2014-01-01

109

The Potential Role of Electric Fields and Plasma Barotropic Diffusion on the Inertial Confinement Fusion Database  

NASA Astrophysics Data System (ADS)

The generation of strong, self-generated electric fields ( 1-10 GV/m) in direct-drive, inertial-confinement-fusion capsules has been reported [1], prompting the question whether such fields can have observable consequences on target performance. Two anomalies in the inertial confinement fusion database are well known: (1) an observed 2x greater-than-expected deficit of neutrons in an equimolar D^3He fuel mixture compared with hydrodynamically equivalent DD [2] mixtures, and (2) a similar shortfall of neutrons when trace amounts of argon are mixed with DD fuel in indirect-drive implosions [3]. A new mechanism based on barodiffusion (or pressure gradient-driven diffusion) in a plasma is proposed that incorporates the presence of shock-generated electric fields to explain the reported anomalies. For Omega-scale implosions the (low Mach number) return shock has an appreciable scale length over which the lighter DD ions can diffuse away from fuel center. The depletion of DD fuel is estimated and found to yield a corresponding reduction in neutrons, consistent with the anomalies observed in experiments for both argon-doped DD fuels and D^3He equimolar mixtures. The reverse diffusion of the heavier ions towards fuel center also increases the pressure, potentially resulting in lower stagnation pressures and larger imploded cores in agreement with gated self-emission x-ray imaging data. The theory is applied to studying the degree of potential fractionation of THD fuel mixtures for an upcoming ignition tuning campaign on the National Ignition Facility.[4pt] [1] Rygg et al., Science 319, 1223 (2008), Li et al., PRL 100, 225001 (2008)[0pt] [2] Rygg et al., PoP 13, 052702 (2006)[0pt] [3] Lindl et al., PoP 11, 339 (2004).

Amendt, Peter

2010-11-01

110

Geometry-induced potential on a two-dimensional section of a wormhole: Catenoid  

SciTech Connect

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, in a honeycomb lattice with an array of dislocations, or in nanoscale waveguides in the shape of a catenoid.

Dandoloff, Rossen; Saxena, Avadh; Jensen, Bjoern [Laboratoire de Physique Theorique et Modelisation, Universite de Cergy-Pontoise, F-95302 Cergy-Pontoise (France); Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Vestfold University College, Faculty of Science and Engineering, N-3103 Toensberg (Norway)

2010-01-15

111

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

PubMed Central

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

Wing, Steve; Freedman, Stephanie; Band, Lawrence

2002-01-01

112

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

PubMed

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

Wing, Steve; Freedman, Stephanie; Band, Lawrence

2002-04-01

113

Elastic anisotropy and pore space geometry of schlieren granite: direct 3-D measurements at high confining pressure combined with microfabric analysis  

NASA Astrophysics Data System (ADS)

Pore space geometry of granitic rocks and its evolution with depth are key factors in large-scale seismics or in projects of enhanced geothermal systems or of deep hazardous waste repositories. In this study, we studied macroscopically anisotropic schlieren-bearing granite by experimental P-wave velocity (VP) measurements on spherical sample in 132 directions at seven different confining pressures in the range 0.1-400 MPa. In order to discriminate the phenomena affecting the rock elastic properties we analysed the orientation of microcracks and of grain boundaries and we measured the anisotropy of magnetic susceptibility of the rock. Three sets of microcracks were defined, with two of them linked to the massif exfoliation process and one to cooling contraction of the massif. During pressurization the measured mean VP and VP anisotropy degree at ambient pressure and at highest confinement (400 MPa) yielded 3.3 km s-1 and 24 per cent, and 6.2 km s-1 and 3 per cent, respectively. The associated VP anisotropy pattern was transversely isotropic and governed by the schlieren, with a minimum VP direction perpendicular to them and a girdle of high VP directions parallel to them. The highest change in VP was observed between 0.1 and 10 MPa, suggesting a significant closure of porosity below depths of 500 m. Change of the VP anisotropy pattern to orthorhombic together with increase of mean VP and VP anisotropy degree during depressurization was attributed to inelastic response of one of the sets of microcracks to the loading-unloading cycle.

Stan?k, Martin; Géraud, Yves; Lexa, Ondrej; Špa?ek, Petr; Ulrich, Stanislav; Diraison, Marc

2013-07-01

114

On the nonlinear electrical properties of molecules in confined spaces - From cylindrical harmonic potential to carbon nanotube cages  

NASA Astrophysics Data System (ADS)

In this contribution, the effect of spatial confinement on the linear and nonlinear electrical properties of LiF, LiH, HF and HCl is analyzed based on the results of ab initio quantum chemical calculations. Central to this study is the comparison of different models of spatial confinement. The harmonic oscillator potential of cylindrical symmetry as well as a more sophisticated model, based on the supermolecular approximation, are applied in order to establish the correspondence between the real chemical environment and their approximate representation in the form of analytical potential. In the case of supermolecular approach, the molecular cages are represented by carbon nanotubes and nanotube-like helium clusters. The results of calculations show that the spatial confinement strongly influences the electric properties of investigated molecules.

Koz?owska, Justyna; Zale?ny, Robert; Bartkowiak, Wojciech

2014-01-01

115

Normal modes of a small bilayer system of binary classical charged particles trapped in a parabolic confinement potential  

Microsoft Academic Search

The normal modes and the melting character of a bilayer system consisting of binary charged particles with different charge and\\/or different mass, interacting through a Coulomb potential and confined in a parabolic trap are investigated. The normal mode spectrum is discussed as a function of the charge ratio (CR) and mass ratio (MR) of the two kinds of charged particles

Xin Lu; Baowen Li; Chang-Qin Wu

2008-01-01

116

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

117

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

NASA Astrophysics Data System (ADS)

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.

Chen, A.; Sooryakumar, R.

2013-11-01

118

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

PubMed

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

119

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.

Chen, A.; Sooryakumar, R.

2013-01-01

120

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

121

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...

122

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

123

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

124

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

PubMed Central

Objective The steady-state visual evoked potential (SSVEP) is an electroencephalographic response to flickering stimuli generated partly in primary visual area V1. The typical “cruciform” geometry and retinotopic organization of V1 is such that certain neighboring visual regions project to neighboring cortical regions of opposite orientation. Here, we explored ways to exploit this organization in order to boost scalp SSVEP amplitude via oscillatory summation. Approach We manipulated flicker-phase offsets among angular segments of a large annular stimulus in three ways, and compared the resultant SSVEP power to a conventional condition with no temporal phase offsets. 1) we divided the annulus into standard octants for all subjects, and flickered upper horizontal octants with opposite temporal phase to the lower horizontal ones, and left vertical octants opposite to the right vertical ones; 2) we individually adjusted the boundaries between the 8 contiguous segments of the standard octants condition to coincide with cruciform-consistent, early-latency topographical shifts in pattern-pulse multifocal visual-evoked potentials (PPMVEP) derived for each of 32 equal-sized segments; 3) we assigned phase offsets to stimulus segments following an automatic algorithm based on the relative amplitudes of vertically- and horizontally-oriented PPMVEP components. Main results The three flicker-phase manipulations resulted in a significant enhancement of normalized SSVEP power of 1) 202%, 2) 383%, and 3) 300%, respectively. Significance We have thus demonstrated a means to obtain more reliable measures of visual evoked activity purely through consideration of cortical geometry. This principle stands to impact both basic and clinical research using SSVEPs.

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

2013-01-01

125

Linear transport of domain walls confined to propagating 1-D potential wells  

NASA Astrophysics Data System (ADS)

We present a method of controllably propagating domain walls (DWs) in magnetic nanowires over extended linear distances by confining them to geometrically defined energy minima. Using simple models, magnetic transmission soft x-ray microscopy and magneto-optic Kerr effect measurements, we show that the technique allows DWs to be moved at arbitrary, user-defined velocities and be positioned with micrometer precision. Our approach is expected to be of utility in applications where the precise transport and positioning of DWs take precedent over the absolute speed of propagation, for example, where the fields produced by DWs are used to trap and transport magnetized particles.

Negotia, M.; Hodges, M. P. P.; Bryan, M. T.; Fry, P. W.; Im, M.-Y.; Fischer, P.; Allwood, D. A.; Hayward, T. J.

2013-10-01

126

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

NASA Astrophysics Data System (ADS)

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

Bhattacharjee, S.

2012-09-01

127

e-beam probe potential diagnostic in spherical electrostatic-inertial plasma confinement (SEIC) (abstract)  

Microsoft Academic Search

A new e-beam probe is developed to study the potential structure inside a SEIC device [G. H. Miley etal., Fusion Technol. 19, 840 (1991)]. The device has a spherical grid negatively biased inside a spherical vacuum chamber. Ions oscillate through the highly transparent grid, forming a single potential well inside the cathode. The potential in turn attracts electrons from ionization

Y. B. Gu; G. H. Miley; L. Turner

1992-01-01

128

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

PubMed

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

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

2012-06-01

129

Confining Dirac electrons on a topological insulator surface using potentials and a magnetic field  

NASA Astrophysics Data System (ADS)

We study the effects of extended and localized potentials and a magnetic field on the Dirac electrons residing at the surface of a three-dimensional topological insulator like Bi2Se3. We use a lattice model to numerically study the various states; we show how the potentials can be chosen in a way which effectively avoids the problem of fermion doubling on a lattice. We show that extended potentials of different shapes can give rise to states which propagate freely along the potential but decay exponentially away from it. For an infinitely long potential barrier, the dispersion and spin structure of these states are unusual and these can be varied continuously by changing the barrier strength. In the presence of a magnetic field applied perpendicular to the surface, these states become separated from the gapless surface states by a gap, thereby giving rise to a quasi-one-dimensional system. Similarly, a magnetic field along with a localized potential can give rise to exponentially localized states which are separated from the surface states by a gap and thereby form a zero-dimensional system. Finally, we show that a long barrier and an impurity potential can produce bound states which are localized at the impurity, and an "L"-shaped potential can have both bound states at the corner of the L and extended states which travel along the arms of the potential. Our work opens the way to constructing wave guides for Dirac electrons.

Seshadri, Ranjani; Sen, Diptiman

2014-06-01

130

Effects of ambipolar potential in a two-component gasdynamic confinement system  

SciTech Connect

Ambipolar effects stemming from the presence of a peak in the density of fast electrons can influence the velocity at which cold plasma flows out of a gasdynamic confinement system containing a two-component plasma is studied. There are two very different limits of this outflow. In the first, the density of fast particles at the peak, n(/sub T/, is lower than the density (n/sub D/0) of the bulk plasma in the uniform region. In the second case, the opposite relation holds. In the first case, the loss rate is found from the solution of the problem of the gas flow from a Laval nozzle. Depending on the value of N(/sub T/, the sonic point is either at the location of the maximum mirror ratio or at the peak in the fast-particle density. If N(/sub T/ varies smoothly, the position of the point at which the velocity of sound is crossed changes abruptly, and there are also abrupt changes in all the spatial characteristics of the flow. In the second case, the loss rate is determined by a method similar to that used for tandem mirrors with a short mean free path. A distinctive feature of this problem is that, because of the low ion temperature of the bulk plasma, a pronounced ambipolar-plugging effect is possible even if N(/sub T/ is only slightly greater than n/sub D/0.

Kotel'nikov, I.A.; Ryutov, D.D.

1985-10-01

131

Near-surface, marine seismic-reflection data defines potential hydrogeologic confinement bypass in a tertiary carbonate aquifer, southeastern Florida  

USGS Publications Warehouse

Approximately 210 km of near-surface, high-frequency, marine seismic-reflection data were acquired on the southeastern part of the Florida Platform between 2007 and 2011. Many high-resolution, seismic-reflection profiles, interpretable to a depth of about 730 m, were collected on the shallow-marine shelf of southeastern Florida in water as shallow as 1 m. Landward of the present-day shelf-margin slope, these data image middle Eocene to Pleistocene strata and Paleocene to Pleistocene strata on the Miami Terrace. This high-resolution data set provides an opportunity to evaluate geologic structures that cut across confining units of the Paleocene to Oligocene-age carbonate rocks that form the Floridan aquifer system.Seismic profiles image two structural systems, tectonic faults and karst collapse structures, which breach confining beds in the Floridan aquifer system. Both structural systems may serve as pathways for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability rocks in the Floridan aquifer system. The tectonic faults occur as normal and reverse faults, and collapse-related faults have normal throw. The most common fault occurrence delineated on the reflection profiles is associated with karst collapse structures. These high-frequency seismic data are providing high quality structural analogs to unprecedented depths on the southeastern Florida Platform. The analogs can be used for assessment of confinement of other carbonate aquifers and the sealing potential of deeper carbonate rocks associated with reservoirs around the world.

Cunningham, Kevin J.; Walker, Cameron; Westcott, Richard L.

2012-01-01

132

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

133

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

SciTech Connect

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

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

2011-05-15

134

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

PubMed

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

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

2013-07-01

135

Normal modes of a small bilayer system of binary classical charged particles trapped in a parabolic confinement potential.  

PubMed

The normal modes and the melting character of a bilayer system consisting of binary charged particles with different charge and/or different mass, interacting through a Coulomb potential and confined in a parabolic trap are investigated. The normal mode spectrum is discussed as a function of the charge ratio (CR) and mass ratio (MR) of the two kinds of charged particles as well as the interlayer separation. We show that the dependence of the normal modes on the excited states can be tuned by varying the CR, the MR, and the interlayer distance. Once the interlayer distance is larger than a critical value, the first excited state corresponds only to the intershell rotation mode. In addition, the intershell rotation melting temperature is discussed as a function of the CR and MR as well as the interlayer separation. PMID:18999421

Lu, Xin; Li, Baowen; Wu, Chang-Qin

2008-10-01

136

Asymmetric confinement of an electron in a double-well potential and its relation with molecular lasers  

NASA Astrophysics Data System (ADS)

The confinement of an electron in an asymmetric double-well is proposed as an alternative system in which transitions and tunneling between bound states can have a similar behavior as in double-square well structures, regarding lasing properties. We show that this system would be more reliable than actual devices, since the relevant factor related to its efficiency is sharper and can be shifted in wavelength in a wide range as compared with, namely, its closest partner, the square double-well potential. Since nowadays technology allows the deposition of atom by atom (or molecule by molecule) layers of active materials, we think that such a device is feasible of construction, and represents a very attractive subject for research at both experimental and theoretical physics.

Marin-Enriquez, Ivan; Marin-Flores, Jose Luis; Campoy-Guere˜A, German; Riera-Aroche, Raul

2006-03-01

137

Resonances in ultracold collisions confined by atomic traps  

NASA Astrophysics Data System (ADS)

We have developed a method for treating ultracold pair collisions in confined geometry of tight atomic waveguides. With this approach we have predicted and analyzed a few novel resonant and multichannel effects induced by confining traps in ultracold atomic collisions. In this report we discuss our model yielding the shifts and widths of magnetic Feshbach resonances in tight atomic waveguides. We also briefly discuss a resonant mechanism of molecule formation in atomic traps with transferring the energy release to the center-of-mass excitation while forming molecule and dipolar confinement-induced resonances in waveguides. These results could potentially be used experimentally.

Melezhik, Vladimir S.

2014-04-01

138

Preliminary studies of potential well measurement in inertial-electrostatic confinement fusion experiments  

Microsoft Academic Search

IECF experiments with auxiliary discharges in outer region were made. Operation pressure of IECF is successfully reduced to about 0.5 Pa when auxiliary discharges are turned on. Neutron measurement shows 2×106\\/sec fusion occurred at 45 kV, 15 mA discharge. Proof of principle experiment of the potential well measurement using Stark effect shows the method works but several improvements are required

Y. Yamamoto; M. Hasegawa; M. Ohnishi; K. Yoshikawa; N. Inoue

1997-01-01

139

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

140

High confinement in fusion oriented plasmas with kV-order potential, ion, and electron temperatures with controlled radial turbulent transport in GAMMA 10  

NASA Astrophysics Data System (ADS)

The tandem mirror system has achieved improved energy confinement times (> 60-90 ms) with radial transport dominating the Pastukhov axial energy confinement time (> 100 ms). This high confinement regime establishes a proof of principle that the combination of electrostatic and magnetic mirror confinement can successfully insulate electrons from thermal ions. ECH controlled hot-layer formation facilitates plasma-rotation profile formation with a radially localized high-vorticity layer. In the vicinity of the layer, a radial transport barrier is formed [1], showing similar properties to ITB in toroidal plasmas. Coaxially nested intense E(r)xB sheared flow [2] in the GAMMA 10 core plasma realizes an upgraded stable regime having (i) > 0.75 keV bulk central electron temperature with (ii) an achievement of larger stored energy for axially potential-confined ions exceeding that (i.e., diamagnetism) for central magnetically confined ions ( 7 keV). The radially sheared flow having peak-on-axis high vorticity guards and improves whole core plasma confinement, and is controlled by (iii) improved 3 kV ion-confining potential due to simultaneous central and plug ECH. X-ray imaging of the suppression of turbulent structures [1-3] will be shown [1,2]. [1] T. Cho et al., Phys. Rev. Lett. 97, 055001 (2006). [2] T. Cho et al., Phys. Rev. Lett. 94, 085002 (2005). [3] J. Pratt and W. Horton, Phys. Plasmas 13, 042513 (2006). Collaborators; W. Horton^1, J. Pratt^1, M. Hirata, J. Kohagura, T. Numakura, H. Hojo, M. Ichimura, A. Itakura, T. Kariya, I. Katanuma, R. Minami, Y. Nakashima, M. Yoshikawa, Y. Miyata, Y. Yamaguchi, T. Imai, V. P. Pastukhov^2, S. Miyoshi, GAMMA 10 Group (^1IFS, Univ. Texas at Austin, ^2Kurchatov Institute, Russia)

Cho, Teruji

2007-11-01

141

Correlated motions of two hydrodynamically coupled particles confined in separate quadratic potential wells.  

PubMed

We report a study of the correlated motions of two hydrodynamically coupled colloidal particles, each of which is trapped in a quadratic potential well defined by optical tweezers (optical traps). By setting one of the trapped particles into forced oscillation using oscillating optical tweezers, we measure the displacement and phase shift of each of the particles over a wide frequency range. From the in-phase and out-of-phase motions of both of the particles in the traps, we determine the correlated motions of the coupled mechanical system as a function of frequency. A theoretical model is developed to calculate the response tensor of the coupled mechanical system. The experimental results are in agreement with the prediction of the theoretical model. This method may be extended to more general applications, such as the investigation of the micromechanical properties of viscoelastic and/or heterogeneous media. PMID:11863562

Hough, L A; Ou-Yang, H D

2002-02-01

142

Three-dimensional assessment of left atrial appendage orifice geometry and potential implications for device closure.  

PubMed

Transcatheter placement of left atrial closure device is an attractive therapy for patients with atrial fibrillation (AF), to avoid anticoagulation and reduce cerebrovascular events; however peri-device leaks occur. The geometry of the left atrial appendage (LAA) is not well understood, largely owing to limitations of 2-dimensional imaging techniques. We sought to better define the LAA orifice geometry, by performing 3-dimensional multi-detector computed tomography measurements. We prospectively recruited 105 consecutive patients referred for pulmonary vein ablation (PVA) and age-matched controls. Area, short and long-axis measurements were performed. Eccentricity was calculated as 1-(short axis/long axis). Multiple clinical variables were tested for their ability to predict appendage orifice eccentricity using univariate linear regression models. The PVA cohort demographics included; 25 (24%) females, mean age 59 years (SD = 10), median height (1.55-2.03), weight 89 (56-139) kg and body surface area 2.1 (1.61-2.58). In the PVA cohort, there was a significant difference between the long and short-axis; median short-axis dimension was 20.5 (12.9-35.4) mm, versus long-axis median 30.4 (17.7-43.8) (p < 0.001). Mean eccentricity score was 0.4. When compared with controls, there was a significant difference in the short and long-axis measurements (p < 0.001) as well as eccentricity (p = 0.04). All clinical variables tested showed limited ability to predict appendage eccentricity (p = NS). LAA ostium is an elliptical structure in the setting of AF with a high eccentricity index and uniformly significant differences between short and long-axis. There were significant differences between these parameters when compared with controls. A deeper appreciation of LAA geometry and eccentricity may allow for reduction in peri-closure leaks. PMID:24599646

O'Brien, Julie; Al-Hassan, Donya; Ng, Justin; Joshi, Madalsa; Hague, Cameron; Chakrabarti, Santabhanu; Leipsic, Jonathon

2014-04-01

143

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

NASA Astrophysics Data System (ADS)

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

Soldatkina, E. I.; Bagryansky, P. A.; Solomakhin, A. L.

2008-04-01

144

Using transmural regularization and dynamic modeling for noninvasive cardiac potential imaging of endocardial pacing with imprecise thoracic geometry.  

PubMed

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 nonlinear 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 , 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; Stovícek, Petr; Brooks, Dana H

2014-03-01

145

Spinning geometry = Twisted geometry  

NASA Astrophysics Data System (ADS)

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

Freidel, Laurent; Ziprick, Jonathan

2014-02-01

146

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

147

The confining trailing string  

NASA Astrophysics Data System (ADS)

We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.

Kiritsis, Elias; Mazzanti, Liuba; Nitti, Francesco

2014-02-01

148

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

Microsoft Academic Search

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

Timothy J. Dunkerton; Richard K. Scott

2008-01-01

149

Electrostatic-Inertial Plasma Confinement.  

National Technical Information Service (NTIS)

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

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

1970-01-01

150

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.

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

2006-01-01

151

Race, poverty, and potential exposure of middle-school students to air emissions from confined swine feeding operations.  

PubMed

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 > or = 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

2006-04-01

152

The effect of donor groups and geometry on the redox potential of copper Schiff base complexes  

Microsoft Academic Search

We report a study which correlates the metrical parameters of the unsubstituted tetradentate copper Schiff base complexes containing N2O2, N2N2 and N2S2 donors with their respective redox potentials. To achieve this aim we were required to structurally characterise many of the seminal species including, [CuAmbpr-H2], [CuH4Amben][ClO4]2, [CuH4Ambpr][ClO4]2, [CuH4Ambbu][ClO4]2, CuH4Salpr and [Cu(SSalen)2][ClO4]2 which were absent from the crystallographic catalogue. The oxidative

Michelle K. Taylor; John Reglinski; Leonard E. A. Berlouis; Alan R. Kennedy

2006-01-01

153

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

DOEpatents

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

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

1981-01-01

154

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

155

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

156

Peculiarities of gallium crystallization in confined geometry  

Microsoft Academic Search

The freezing and melting phase transitions for gallium embedded into a porous glass with a pore size of about 8 nm were studied\\u000a using acoustic, NMR, and x-ray techniques. It was shown that the broadened solidification and melting transitions upon deep\\u000a cooling up to complete freezing at 165 K were due to the formation of ?-Ga within pores. The offset

B. F. Borisov; E. V. Charnaya; A. V. Gartvik; Cheng Tien; Yu. A. Kumzerov; V. K. Lavrentev

2004-01-01

157

Modeling UW Gridded Inertial-Electrostatic Confinement Fusion Experiments  

Microsoft Academic Search

Gridded inertial-electrostatic confinement (IEC) devices accelerate and focus ions using voltage differences between nearly transparent concentric grids in spherical or cylindrical geometry. High voltages can be produced relatively easily between the grids, giving the accelerated ions energies (>50 keV) suitable for producing fusion of advanced fuels, such as D-3He. The resulting fusion products potentially can produce radioisotopes useful for positron

John F. Santarius

2002-01-01

158

Experimental Characterization of Quasi-Fermi Potential Profile in the Channel of a Silicon Nanowire Field-Effect Transistor with Four-Terminal Geometry  

Microsoft Academic Search

Using the four-terminal geometry, quasi-Fermi potential profiles in the channel of silicon nanowire (SiNW) metal--oxide--semiconductor field-effect transistors (MOSFETs) have been successfully characterized during MOSFET operation, for the first time. We measured the voltages of two branches attached to the SiNW channel under various conditions of gate and drain voltages for MOSFET operation, and evaluated the quasi-Fermi potential profile. The experimental

Soshi Sato; Kenji Ohmori; Kuniyuki Kakushima; Parhat Ahmet; Kenji Natori; Keisaku Yamada; Hiroshi Iwai

2011-01-01

159

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

NASA Astrophysics Data System (ADS)

A set of weakly interacting spin- 1/2 > Fermions, confined by a harmonic oscillator potential, and interacting with each other via a contact potential, is a model system which closely represents the physics of a dilute gas of two-component fermionic atoms confined in a magneto-optic trap. In the present work, our aim is to present a Fortran 90 computer program which, using a basis set expansion technique, solves the Hartree-Fock (HF) equations for spin- 1/2 > Fermions confined by a three-dimensional harmonic oscillator potential, and interacting with each other via pair-wise delta-function potentials. Additionally, the program can also account for those anharmonic potentials which can be expressed as a polynomial in the position operators x, y, and z. Both the restricted-HF (RHF), and the unrestricted-HF (UHF) equations can be solved for a given number of Fermions, with either repulsive or attractive interactions among them. The option of UHF solutions for such systems also allows us to study possible magnetic properties of the physics of two-component confined atomic Fermi gases, with imbalanced populations. Using our code we also demonstrate that such a system exhibits shell structure, and follows Hund's rule. Program summaryProgram title: trap.x Catalogue identifier: AEBB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 17 750 No. of bytes in distributed program, including test data, etc.: 205 138 Distribution format: tar.gz Programming language: mostly Fortran 90 Computer: PCs—SUN, HP Alpha, IBM Operating system: Linux, Solaris, Tru64, AIX Classification: 7.7 Nature of problem: The simplest description of a spin 1/2 >; trapped system at the mean field level is given by the Hartree-Fock method. This program presents an efficient approach to solving these equations. Additionally, this program can solve for time-independent Gross-Pitaevskii and Hartree-Fock equations for bosonic atoms confined in a harmonic trap. Thus the combined program can handle mean-field equations for both the Fermi and the Bose particles. Solution method: The solutions of the Hartree-Fock equation corresponding to the Fermi systems in atomic traps are expanded as linear combinations of simple-harmonic oscillator eigenfunctions. Thus, the Hartree-Fock equations which comprise a set of nonlinear integro-differential equations, are transformed into a matrix eigenvalue problem. Thereby, solutions are obtained in a self-consistent manner, using methods of computational linear algebra. Running time: The run times of example jobs are from a few seconds to a few minutes. For jobs involving very large basis sets, the run time can extend into hours.

Pal, Hridis Kumar; Shukla, Alok

2008-08-01

160

Kinetics of Diffusing Polymer Encounter in Confined Cellular Microdomains  

NASA Astrophysics Data System (ADS)

We study the mean first time that two monomers, located on the same polymer, encounter in a confined microdomain. Approximating the confined geometry by a harmonic potential well, we obtain an asymptotic expression for the mean first encounter time (MFETC) as a function of the radius ? around one monomer. By studying the end-to-end distance of the polymer in a ball using the Edwards' formalism, we derive an other estimation of the MFETC. We validate the asymptotic formulas using Brownian simulations and derive their range of validity in terms of the polymer length. We apply the present models to compute the mean time for a gene located far away from a promoter site to be activated during looping in confined genomic territories.

Amitai, A.; Kupka, I.; Holcman, D.

2013-12-01

161

Isothermal Confinement  

NASA Astrophysics Data System (ADS)

The concept of isothermal confinement is presented. The idea is a revival of the early magnetic fusion concepts with new insight. The plasma core is confined magnetically and is surrounded by a quasi-vacuum region. The temperature of the core is uniform and the turbulence associated with the temperature gradient is absent. The quasi-vacuum region is unstable against the pressure gradient and the turbulent transport rate is much larger than that of the core. Two modes of operation, pulsed and steady state, are considered. Recent experimental results in LHD and CDX-U appear to support the concept.

Ohkawa, Tihiro

162

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

163

Z2 Symmetry Breaking in Multi-Band Bosonic Atoms Confined by a Two-Dimensional Harmonic Potential  

NASA Astrophysics Data System (ADS)

When a two-dimensional harmonic potential is applied to bosonic cold atoms, the atoms become a cigar shape and the radial energy level is discretized. If the strength of the potential or the total number of atoms is tuned, the atoms can occupy not only the lowest radial band but also higher bands. This paper shows that when both the lowest band and the second lowest doubly-degenerate bands are filled, the repulsive interaction among atoms induces a ground state circulating along the trap axis, in which the Z2 reflection symmetry is spontaneously broken.

Sato, Masahiro; Tokuno, Akiyuki

2009-06-01

164

Manipulation of gel emulsions by variable microchannel geometry.  

PubMed

In this article we investigate the morphology and manipulation of monodisperse emulsions at high dispersed phase volume fractions (gel emulsions) in a microfluidic environment. Confined monodisperse gel emulsions self-organize into well-ordered droplet arrangements, which may be stable or metastable, depending on the geometry of the confining microchannel. Three arrangements are considered, in which the droplets are aligned in a single file, a two row, or a three row arrangement. We explore the potential for induced transitions between these distinct droplet arrangements as a tool for droplet-based microfluidic processing. Transitions are readily achieved by means of localized (geometrical) features in channel geometry, however the onset of the transition is strongly dependent on the subtleties of the microfluidic system, e.g. volume fraction, droplet size, and feature dimensions. The transitions can be achieved via fixed channel features or, when the continuous phase is a ferrofluid, by a virtual channel constriction created using a magnetic field. PMID:19107292

Surenjav, Enkhtuul; Priest, Craig; Herminghaus, Stephan; Seemann, Ralf

2009-01-21

165

A Pearson Effective Potential for Monte-Carlo simulation of quantum confinement effects in various MOSFET architectures  

Microsoft Academic Search

A Pearson Effective Potential model for including quantization effects in the\\u000asimulation of nanoscale nMOSFETs has been developed. This model, based on a\\u000arealistic description of the function representing the non zero-size of the\\u000aelectron wave packet, has been used in a Monte-Carlo simulator for bulk, single\\u000agate SOI and double-gate SOI devices. In the case of SOI capacitors, the

M.-A. Jaud; S. Barraud; P. Dollfus; H. Jaouen

2008-01-01

166

Confined Brownian ratchets  

NASA Astrophysics Data System (ADS)

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 could be used to control transport in mesostructures and to engineer new and more efficient devices for transport at the nanoscale.

Malgaretti, Paolo; Pagonabarraga, Ignacio; Rubi, J. Miguel

2013-05-01

167

Developments in special geometry  

NASA Astrophysics Data System (ADS)

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

Mohaupt, Thomas; Vaughan, Owen

2012-02-01

168

Geometry and Physics Today  

NASA Astrophysics Data System (ADS)

Geometry,” in the sense of the classical differential geometry of smooth manifolds (CDG), is put under scrutiny from the point of view of Abstract Differential Geometry (ADG). We explore potential physical implications of viewing things under the light of ADG, especially matters concerning the “ gauge theories” of modern physics, when the latter are viewed (as they are actually regarded currently) as “ physical theories of a geometrical character.” Thence, “ physical geometry,” in connection with physical laws and the associated with them, within the background spacetime manifoldless context of ADG, “ differential” equations, are also being discussed.

Mallios, Anastasios

2006-08-01

169

Characteristics of electron transport through vertical double-barrier quantum-dot structures: Effects of symmetric and asymmetric variations of the lateral confinement potentials  

Microsoft Academic Search

We report on a theoretical study of the electron transport through laterally-confined, vertical double-barrier resonant-tunneling (DBRT) structures, defined as one-dimensional (1D)-0D-1D systems, with a tunable lateral confinement. The current and the differential conductance of the systems are calculated and the influence caused by varying the lateral confinement on the device characteristics is investigated. Three representative systems are studied. First of

Dan Csontos; H. Q. Xu

2002-01-01

170

Electrohydrodynamics of DNA in confinement  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

171

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

PubMed Central

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

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

2013-01-01

172

Numerical solution of the potential due to dipole sources in volume conductors with arbitrary geometry and conductivity.  

PubMed

The integral conservation equation for biological volume conductors with general geometry and arbitrary distribution of electrical conductivity is solved using a finite volume method. An effective conductivity was defined for the boundaries between regions with abrupt change of the conductivity to allow the simultaneous solution of the entire domain although the derivatives are not continuous. The geometrical singularities arising from the spherical topology of the coordinate system are removed using the conservation law. The resulting finite volume solution method is efficient both in central processing unit (CPU) time and memory requirements, allowing the solution of the volume conductor equation using a large number of mesh points (of the order of 10(5)) even on small workstations (like SGI Indigo). It results in very accurate solutions, as several comparisons with analytical solutions of head models reveal. The proposed finite volume method is an attractive alternative to the finite element and boundary element methods that are more common in bioelectric applications. PMID:9216139

Rosenfeld, M; Tanami, R; Abboud, S

1996-07-01

173

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

174

Geometry Information  

NSDL National Science Digital Library

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

2010-01-01

175

Two interacting electrons confined in a 3D parabolic cylindrically symmetric potential, in presence of axial magnetic field: A finite element approach  

NASA Astrophysics Data System (ADS)

In this work, we explore the performance and accuracy of finite element numerical simulations for the relevant and well-known problem of two interacting electrons confined in a parabolic cylindrically symmetric potential, and under the influence of axial magnetic field. By using a full configuration interaction method as reference, we compare two different ways to obtain the eigenvalues of the system by finite element simulations, one of which approximately separates the Coulomb interaction and averages the longitudinal part. We find that in the regime of low aspect ratios, the results from the approximate scheme with approximation are quite optimal (<0.05% of difference respect to the reference), but once the dots turn more and more thicker, the results become just acceptable (>0.5% of difference), due to underestimation of the Coulomb interaction. On the other hand, for the non-approximated finite element approach the results are consistently reliable along the different field and aspect ratio regimes (<0.02% of difference respect to the reference). This allows us to present a novel, efficient and highly accurate method for obtaining electronic structure of interacting particles in 0D nanostructures.

Ramírez, Hanz Y.; Santana, Alejandro

2012-08-01

176

Projective Geometry  

NSDL National Science Digital Library

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

177

Connecting Geometry  

NSDL National Science Digital Library

A fully credited high school distance learning geometry course offered via the Internet to students throughout the Hawaiian islands as part of a grant-funded pilot project through the Hawaii Department of Education. During this E-School (electronic school) course Cathi Sanders, a teacher at Punahou School in Honolulu, and her students communicate through a Web page and via e-mail. Chapters include: 1. Communicating in Geometry; 2. Symmetry and Transformations; 3. Theorems in Geometry; 4. Congruent Triangles; 5. Triangle Properties; 6. Right Triangles; 7. Parallel Lines and Planes; 8. Polygons; 9. Similar Triangles; 10. Circles; 11. Perimeter and Area; 12. Surface Areas and Volumes.

Sanders, Cathleen V.

2007-02-24

178

Characteristics of electron transport through vertical double-barrier quantum-dot structures: Effects of symmetric and asymmetric variations of the lateral confinement potentials  

NASA Astrophysics Data System (ADS)

We report on a theoretical study of the electron transport through laterally-confined, vertical double-barrier resonant-tunneling (DBRT) structures, defined as one-dimensional (1D)-0D-1D systems, with a tunable lateral confinement. The current and the differential conductance of the systems are calculated and the influence caused by varying the lateral confinement on the device characteristics is investigated. Three representative systems are studied. First of all, a 1D-0D-1D device, symmetric with respect to the current flow, with a variable lateral confinement in the double-barrier quantum-well (DBQW) region, is investigated. This device would in an experimental setup correspond to the structure in which a thin, lateral metallic gate is placed in the DBQW region. Subsequently, calculations are performed for two asymmetric 1D-0D-1D devices, in which the strongest, but varying, lateral confinement is placed either in the collector or in the emitter region. In experiments, these two devices would correspond to the situations where a lateral metallic gate is positioned below or on top of the DBQW structure. The calculations predict several phenomena for the device characteristics. It is shown that as the lateral confinement increases, in addition to those normally observed current onsets and pinch-offs that move toward higher bias voltages, several current onsets and pinch-offs move towards lower bias voltages. These negative shifts of the current onsets and pinch-offs with increasing of the lateral confinement have so far not been expected for gated DBRT devices. It is also found that the threshold voltages, at which the current onsets and pinch-offs appear, depend strongly on the strength and position of the lateral confinement and on the Fermi levels in the collector and the emitter. The models that explain these predictions are presented and discussed.

Csontos, Dan; Xu, H. Q.

2002-11-01

179

Geometry Adventure  

NSDL National Science Digital Library

You are going on a geometry adventure! Your first task is to become an Angle Investigator Then you\\'re off to the Shape Factory to help out. Finally, you will complete 10 rounds of the Triangle Sort ...

Craighill, Miss

2007-11-12

180

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

181

Decoupling of Confined Normal 3He  

NASA Astrophysics Data System (ADS)

Anodic bonding was used to fabricate a 10 mm diameter × 640 nm tall annular geometry suitable for torsion pendulum studies of confined 3He. For pure 3He at saturated vapor pressure the inertia of the confined fluid was seen to be only partially coupled to the pendulum at 160 mK. Below 100 mK the liquid’s inertial contribution was negligible, indicating a complete decoupling of the 3He from the pendulum.

Dimov, S. G.; Bennett, R. G.; Ilic, B.; Verbridge, S. S.; Levitin, L. V.; Fefferman, A. D.; Casey, A.; Saunders, J.; Parpia, J. M.

2010-01-01

182

Holographic Schwinger effect in confining phase  

NASA Astrophysics Data System (ADS)

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

Sato, Yoshiki; Yoshida, Kentaroh

2013-09-01

183

A Review of Quantum Confinement  

SciTech Connect

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

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

2009-12-03

184

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

185

Numerical analysis of seismoelectromagnetic field conversion at confined geological units  

NASA Astrophysics Data System (ADS)

It is well known that at material boundaries in fluid-saturated porous media, an incoming seismic wave can give rise to electric and magnetic fields due to electrokinetic coupling effects. Given its sensitivity to rock parameters governing fluid flow, this so-called seismoelectromagnetic (or seismoelectric, if only the electric field is considered) interface response is of strong interest with a view to hydro geophysical and petroleum exploration applications. However, the understanding of the correspondence of the converting interface geometry on the one hand and electric and magnetic field characteristics on the other hand is still poor. By means of two-dimensional finite-element modeling in the time domain, we here investigate the character of the seismoelectromagnetic interface response for the special case of spatially confined geological units, which may be representative for clay lenses embedded in an aquifer or petroleum deposits in a host rock. In the numerical analysis we consider the interface response generated by both compressional and shear wave. The modeling results, which are analyzed in terms of snapshots, time slices, and electro and magneto grams, reveal a significant influence of the confined geological units on the generation and character of the seismoelectro-magnetic interface response. The different conversion patterns can be attributed to the induced streaming currents at the interfaces caused by the oscillation of the seismic body waves. Pattern analysis of the interface responses is done with a view to an improved qualitative understanding of their spatio-temporal occurrence and evolution relative to the geometry of the converting interfaces. Our time-lapse simulations illustrate that the seismoelectromagnetic interface response captures characteristics of the geometry of the converting geological unit, indicating the potential of the seismoelectromagnetic method in particular for exploration of confined targets.

Kroeger, B.; Kemna, A.

2010-12-01

186

Noncommutative geometry induced by spin effects  

SciTech Connect

In this paper we study the nonlocal effects of noncommutative spacetime on simple physical systems. Our main point is the assumption that the noncommutative effects are consequences of a background field which generates a local spin structure. So, we reformulate some simple electrostatic models in the presence of a spin-deformation contribution to the geometry of the motion, and we obtain an interesting correlation amongst the deformed area vector, the 3D noncommutative effects, and the usual spin vector S-vector given in quantum mechanics framework. Remarkably we can observe that a spin-orbit coupling term comes to light on the spatial sector of a potential written in terms of noncommutative coordinates which indicates that bound states are particular cases in this procedure. Concerning confined or bounded particles in this noncommutative domain, we verify that the kinetic energy is modified by a deformation factor. Finally, we discuss perspectives.

Colatto, L.P.; Penna, A.L.A.; Santos, W.C. [Departamento de Fisica, Centro de Ciencias Exatas, Universidade Federal do Espirito Santo, Avenue Fernando Ferrari, 514, CEP 29075-910, Vitoria, ES (Brazil); Instituto de Fisica, Universidade de Brasilia, CEP 70919-970, Brasilia, DF (Brazil)

2006-05-15

187

Computational Geometry  

NSDL National Science Digital Library

A short article designed to provide an introduction to computational geometry, intended for topics whose geometric aspects are fairly straightforward, but for which the main questions involve efficient, accurate computation. A number of geometric questions arise involving large sets of points (e.g. which of these points are closest together?) which are arguably combinatorics or statistics, but which have been included here.

Rusin, David J., 1957-

2007-12-14

188

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

PubMed Central

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.

Zhu, H.; Braun, W.

1999-01-01

189

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

190

Noncommutative geometry and reality  

Microsoft Academic Search

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

Alain Connes

1995-01-01

191

Inflation from Quantum Geometry  

Microsoft Academic Search

Quantum geometry predicts that a universe evolves through an inflationary phase at small volume before exiting gracefully into a standard Friedmann phase. This does not require the introduction of additional matter fields with ad hoc potentials; rather, it occurs because of a quantum gravity modification of the kinetic part of ordinary matter Hamiltonians. An application of the same mechanism can

Martin Bojowald

2002-01-01

192

Tuning the ordered states of folded rods by isotropic confinement.  

PubMed

The packing of elastic objects is increasingly studied in the framework of out-of-equilibrium statistical mechanics and thus these appear to be similar to glassy systems. Here, we present a two-dimensional experiment whereby a rod is confined by a parabolic potential. The setup enables spanning a wide range of folded configurations of the rod. Measurements of the distributions of length and curvature in the system reveal the importance of a stacking process whereby many layers of the rod are grouped into branches. The geometrical order of patterns increases with the confinement strength. Measurements of the distributions of energies lead to the definition of an energy scale that is correlated with the elastic energy of the stacked parts of the rod. This scale imposes energy partition in the system and might be relevant to the framework of the thermodynamics of disordered systems. Following these observations, we describe the patterns as excited states of a ground state corresponding to the most ordered geometry. Eventually, we provide evidence that the disordered state of a folded rod becomes spontaneously closer to the ground state as confinement is increased. PMID:24580237

Bayart, E; Boudaoud, A; Adda-Bedia, M

2014-01-01

193

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

SciTech Connect

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

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

2010-10-15

194

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

PubMed

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

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

2010-10-01

195

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

196

Electron confinement and long-range interactions in 1-D atom chains  

Microsoft Academic Search

In nanostructures, when electrons are confined to reduced dimensions, the geometry of the confinement leads to the formation of quantized electronic states. In turn, these quantized states determine the energetic stability of a particular geometry. For systems that are self assembled, where thermodynamics and the cohesive energy can play a key role in the formation process, this interplay between the

Daniel T. Pierce

2007-01-01

197

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

Microsoft Academic Search

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

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

1996-01-01

198

Cascade inertial confinement fusion reactor concept.  

National Technical Information Service (NTIS)

The Cascade reactor concept has the potential of converting inertial confinement fusion (ICF) energy into electrical power safely, efficiently, and with low activation. Its flexibility permits a number of options for materials, blankets, fuel-pellet desig...

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

1990-01-01

199

Dependence of electromagnetically induced transparency on pressure and temperature in a quantum dot with flat cylindrical geometry  

NASA Astrophysics Data System (ADS)

We demonstrate an electromagnetically induced transparency in a quantum dot having disk geometry under two radiation fields. It is found that electromagnetically induced transparency occurs in the system. Analytical expressions for the complex electric susceptibility, absorption, dispersion and group index are presented. The combined effects of external factors such as magnetic field, hydrostatic pressure, temperature and confinement length on the electromagnetically induced transparency are investigated. Our results may have potential applications in optical communication and quantum information processing.

Gambhir, Monica; Gumber, Sukirti; Jha, P. K.; Mohan, Man

2014-07-01

200

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

201

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

NASA Astrophysics Data System (ADS)

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

Jancovici, B.; Samaj, L.

2005-05-01

202

Aperture method to determine the density and geometry of antiparticle plasmas  

NASA Astrophysics Data System (ADS)

The density and geometry of p¯ and e + plasmas in realistic trapping potentials are required if the rate of antihydrogen formation from them is to be understood. A new measurement technique determines these properties of trapped positron (e +) and antiproton (p¯) plasmas, the latter for the first time. The method does not require the common assumption of a spheroidal plasma geometry, which only pertains for a perfect electrostatic quadrupole trapping potential. Plasma densities, diameters, aspect ratios and angular momenta are deduced by comparing the number of particles that survive transmission through an aperture, to that obtained from self-consistent solutions of Poisson's equation. For p¯ the results differ substantially from the spheroid plasmas of an ideal Penning trap. The angular momentum of the plasma emerges as smooth function of the number of particles in the plasma, independent of the depth of the potential well that confines them.

Oxley, P.; Bowden, N. S.; Parrott, R.; Speck, A.; Storry, C. H.; Tan, J. N.; Wessels, M.; Gabrielse, G.; Grzonka, D.; Oelert, W.; Schepers, G.; Sefzick, T.; Walz, J.; Pittner, H.; Hänsch, T. W.; Hessels, E. A.; Atrap Collaboration

2004-08-01

203

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

204

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

205

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

206

Efficient light confinement with nanostructured optical microfiber tips  

NASA Astrophysics Data System (ADS)

Nanostructured optical microfiber tips are proposed and experimentally demonstrated to efficiently confine light beyond the diffraction limit at high powers. Focused ion beam milling was used for the nanostructuring of gold-coated optical microfiber tips with both single-ramp and wedge geometries. Small apertures were formed by flat cutting or hole drilling and optical spot sizes of ˜?/10 with high transmission efficiency were achieved. Numerical simulations were carried out to optimize the device design with circularly polarized light. Enhanced transmission efficiencies (higher than 10-2) were recorded by optimizing the overall light throughput along the fiber tips. The tip thermal behavior was investigated by launching high powers into the device and recording the tip position in a scanning near-field optical microscopy set-up. This nanostructured optical microfiber tip has the potential for applications in optical recording, scanning near-field optical microscopy and lithography.

Ding, Ming; Fenwick, Oliver; Di Stasio, Francesco; Ou, Jun-Yu; Sessions, Neil; Jung, Yongmin; Cacialli, Franco; Brambilla, Gilberto

2012-10-01

207

Hydrodynamic Fluctuations in Confined Particle-Laden Fluids  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

208

Hydrodynamic fluctuations in confined particle-laden fluids.  

PubMed

We address the collective dynamics of non-Brownian particles cruising in a confined microfluidic geometry and provide a comprehensive characterization of their spatiotemporal density fluctuations. We show that density excitations freely propagate at all scales, and in all directions even though the particles are neither affected by potential forces nor by inertia. We introduce a kinetic theory which quantitatively accounts for our experimental findings, demonstrating that the fluctuation spectrum of this nonequilibrium system is shaped by the combination of truly long-range hydrodynamic interactions and local collisions. We also demonstrate that the free propagation of density waves is a generic phenomenon which should be observed in a much broader range of hydrodynamic systems. PMID:24074122

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

2013-09-13

209

A theoretical model for tissue growth in confined geometries  

Microsoft Academic Search

It is known that cells proliferate and produce extracellular matrix in response to biochemical and mechanical stimuli. Constitutive models considering these phenomena are needed to quantitatively describe the process of tissue growth in the context of tissue engineering and regenerative medicine. In this paper we re-examine the theoretical framework provided by Ambrosi and Guana (2007) and Ambrosi and Guillou (2007).

J. W. C. Dunlop; F. D. Fischer; E. Gamsjäger; P. Fratzl

2010-01-01

210

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

211

Geometry Online  

NSDL National Science Digital Library

Projects that use realtime data available from the Internet, and collaborative projects that use the Internet's potential to reach peers and experts around the world. The site lists currently sponsored projects by level, with an archive of past sponsored projects, each with a brief desciption and links to the National Science Standards and NCTM math standards it supports. Also at http://k12science.stevens-tech.edu/currichome.html. From the Center for Improved Engineering and Science Education (CIESE) at Stevens Institute of Technology.

Lanius, Cynthia

2001-04-29

212

Boundary effects in the pressure of a confined magnetized electron gas  

NASA Astrophysics Data System (ADS)

The role of boundary effects in the pressure of a magnetized quantum plasma is determined by evaluating the spatial dependence of the mechanical pressure tensor for several simplified model systems, namely for a non-interacting magnetized electron gas in either a slab geometry or in a harmonic confining potential. From the pressure profiles it is shown that the bulk and surface values of the pressure are related in such a way that an earlier result on the difference between the thermodynamic and the mechanical pressure in a magnetized quantum plasma is confirmed.

John, P.; Suttorp, L. G.

1994-09-01

213

129Xe NMR as a probe of the dynamics of gas confined in porous Vycor.  

PubMed

We use 129Xe NMR to probe the diffusion of xenon gas in the porous network of Vycor glass, by monitoring its relaxation properties. When the mean free path of the diffusing gas is larger than the pore size (Knudsen conditions), both 129Xe chemical shifts and relaxation rates are sensitive to the confinement of xenon gas within a porous solid. The influence of both temperature and xenon pressure are recorded on the 129Xe chemical shifts and relaxation rates, in order to characterise the xenon/Vycor interactions. Monte Carlo (MC) and Molecular Dynamics (MD) simulations, using a numerical model of Vycor, are required to interpret the relaxation properties of xenon. MD simulations clearly establish the occurrence of confined diffusion of xenon within Vycor, related to the geometry of this porous media. This work shows the potentiality of NMR relaxation to obtain dynamical information on the diffusion within porous media. PMID:8970126

Pasquier, V; Levitz, P; Tinet, D; Delville, A

1996-01-01

214

Plasma confinement in the TMX tandem mirror  

SciTech Connect

Plasma confinement in the Tandem Mirror Experiment (TMX) is described. Axially confining potentials are shown to exist throughout the central 20-cm core of TMX. Axial electron-confinement time is up to 100 times that of single-cell mirror machines. Radial transport of ions is smaller than axial transport near the axis. It has two parts at large radii: nonambipolar, in rough agreement with predictions from resonant-neoclassical transport theory, and ambipolar, observed near the plasma edge under certain conditions, accompanied by a low-frequency, m = 1 instability or strong turbulence.

Hooper, E.B. Jr.; Allen, S.L.; Casper, T.A.

1981-04-29

215

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

216

Confinement of Pure Ion Plasma in a Cylindrical Current Sheet  

Microsoft Academic Search

A novel method for containing a pure ion plasma at thermonuclear densities and temperatures has been modeled. The method combines the confinement properties of a Penning-Malmberg trap and some aspects of the magnetic field geometry of a pulsed theta-pinch. A conventional Penning trap can confine a uniform-density plasma of about 5x1011 cm-3 with a 30-Tesla magnetic field. However, if the

C. K. Phillips; E. H. Chao; R. C. Davidson; S. F. Paul

1999-01-01

217

Confining ensemble of dyons  

SciTech Connect

We construct the integration measure over the moduli space of an arbitrary number of N kinds of dyons of the pure SU(N) gauge theory at finite temperatures. The ensemble of dyons governed by the measure is mathematically described by a (supersymmetric) quantum field theory that is exactly solvable and is remarkable for a number of striking features: (i) The free energy has the minimum corresponding to the zero average Polyakov line, as expected in the confining phase; (ii) the correlation function of two Polyakov lines exhibits a linear potential between static quarks in any N-ality nonzero representation, with a calculable string tension roughly independent of temperature; (iii) the average spatial Wilson loop falls off exponentially with its area and the same string tension; (iv) at a critical temperature, the ensemble of dyons rearranges and deconfines; and (v) the estimated ratio of the critical temperature to the square root of the string tension is in excellent agreement with the lattice data.

Diakonov, Dmitri; Petrov, Victor [St. Petersburg NPI, Gatchina, 188 300, St. Petersburg (Russian Federation)

2007-09-01

218

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

219

Effects of molecular potential and geometry on atomic core-level photoemission over an extended energy range - the case study of CO molecule  

NASA Astrophysics Data System (ADS)

We report an experimental and theoretical study of single-molecule inner-shell photoemission over an extended range of photon energies. The vibrational ratios v=1/v=0 from the C 1s photoelectron spectra, although mostly determined by the bond length change, are shown to be affected also by photoelectron recoil and scattering on the neighboring oxygen atom. Density functional theory is used to encompass all these effect in unified treatment. It is also demonstrated that the DFT calculations can be used as a means to extract dynamic and static molecular geometry values.

Kukk, E.; Ayuso, D.; Thomas, T. D.; Decleva, P.; Patanen, M.; Argenti, L.; Plésiat, E.; Palacios, A.; Kooser, K.; Travnikova, O.; Mondal, S.; Kimura, M.; Sakai, K.; Miron, C.; Martín, F.; Ueda, K.

2014-04-01

220

A microfluidic device to confine a single cardiac myocyte in a sub-nanoliter volume on planar microelectrodes for extracellular potential recordings.  

PubMed

A hybrid chip is described which combines a microfluidic network fabricated in a silicone elastomer (PDMS) with planar microelectrodes. It was used to measure extracellular potentials from single adult murine cardiac myocytes in a restricted extracellular space. The recorded variations in the extracellular potentials were caused by transmembrane currents associated with spontaneously initiated intracellular calcium waves. Single cells were trapped inside the 100 pl microchamber by pressure gradients and maintained for several hours by continuous perfusion. In addition, the localized delivery of drugs to a portion of the cell was demonstrated. The impedance of the electrodes was reduced by a factor of 10 to 20 after the electrodeposition of platinum black. Biopotentials recorded from single cells with platinum black electrodes showed a three-fold decrease in the noise, resulting in a maximum signal-to-noise ratio of 15:1. Characteristic variations in the frequency and shape of the extracellular potentials were observed among different cells which are most likely due to differences in the sarcoplasmic reticulum Ca(2+) load. Our device architecture permits the integration of electrochemical and optical sensors for multiparameter recordings. PMID:15269804

Werdich, Andreas A; Lima, Eduardo A; Ivanov, Borislav; Ges, Igor; Anderson, Mark E; Wikswo, John P; Baudenbacher, Franz J

2004-08-01

221

Inertial Confinement Fusion.  

National Technical Information Service (NTIS)

In these notes, we discuss inertially confined thermonuclear fusion obtained by means of spherically imploded deuterium-tritium fuel. The emphasis is on the 'inner part' of ICF physics, on the implosion dynamics, central fuel ignition, and energy gain, ra...

J. Meyer-ter-Vehn

1985-01-01

222

Colloidal Interactions in a Two-Dimensional Geometry  

NASA Astrophysics Data System (ADS)

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

Kepler, Grace Martinelli

223

Energy confinement in Doublet III with high-Z limiters  

SciTech Connect

This report describes the experimental measurements and data analysis techniques used to evaluate the energy confinement in noncircular plasmas produced in Doublet III. Major aspects of the confinement measurements and analysis techniques are summarized. Machine parameters, diagnostic systems and discharge parameters relavent to the confinement measurements are given. Magnetic analysis techniques used to determine the plasma shape are reviewed. Scaling of the on-axis values of electron temperature, confinement time and Z/sub eff/ with plasma density is presented. Comparison with scaling results from other circular tokamaks is discussed. Numerical and analytic techniques developed for calculating the plasma energy confinement time and self-consistent profiles of density, temperature, current, and flux in non-circular geometries are described. These techniques are applied to the data and used to determine the central and global electron energy confinement time for a typical doublet plasma. Additional aspects of the confinement such as the radial dependence of the electron thermal conductivity and the estimated ion temperature are explored with the aid of a non-circular transport simulation code. The results of the confinement measurements are summarized and discussed. A brief summary of the theoretically expected effects of noncircularity on plasma confinement is included for reference as Appendix I.

Marcus, F.B.; Adcock, S.J.; Baker, D.R.; Blau, F.P.; Brooks, N.H.; Chase, R.P.; DeBoo, J.C.; Ejima, S.; Fairbanks, E.S.; Fisher, R.K.

1980-02-01

224

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

NASA Astrophysics Data System (ADS)

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

Sarkar, Kanchan; Bhattacharyya, S. P.

2013-08-01

225

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

PubMed

We propose and implement a simple adaptive heuristic to optimize the geometries of clusters of point charges or ions with the ability to find the global minimum energy configurations. The approach uses random mutations of a single string encoding the geometry and accepts moves that decrease the energy. Mutation probability and mutation intensity are allowed to evolve adaptively on the basis of continuous evaluation of past explorations. The resulting algorithm has been called Completely Adaptive Random Mutation Hill Climbing method. We have implemented this method to search through the complex potential energy landscapes of parabolically confined 3D classical Coulomb clusters of hundreds or thousands of charges--usually found in high frequency discharge plasmas. The energy per particle (EN?N) and its first and second differences, structural features, distribution of the oscillation frequencies of normal modes, etc., are analyzed as functions of confinement strength and the number of charges in the system. Certain magic numbers are identified. In order to test the feasibility of the algorithm in cluster geometry optimization on more complex energy landscapes, we have applied the algorithm for optimizing the geometries of MgO clusters, described by Coulomb-Born-Mayer potential and finding global minimum of some Lennard-Jones clusters. The convergence behavior of the algorithm compares favorably with those of other existing global optimizers. PMID:23968071

Sarkar, Kanchan; Bhattacharyya, S P

2013-08-21

226

Bacteria in Confined Spaces  

NASA Astrophysics Data System (ADS)

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

Wilking, Connie; Weitz, David

2010-03-01

227

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

228

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

229

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

230

Atomic scale mixing for inertial confinement fusion associated hydro instabilities  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

231

Low-temperature dynamics of water confined in a hydrophobic mesoporous material  

NASA Astrophysics Data System (ADS)

Quasielastic neutron scattering was used to study the dynamics of three-dimensional confined water in a hydrophobic mesoporous material designated as CMK-1 in the temperature range from 250 to 170 K. We observe a crossover phenomenon at temperature TL . We find that TL of water confined in CMK-1 occurs in between previous observations of one-dimensional confined water in materials with different hydrophilicities. This provides the first evidence that besides the obvious surface effect brought about by the hydrophobic confinements, TL is also dependent on the dimensionality of the geometry of the confinement.

Chu, Xiang-Qiang; Liu, Kao-Hsiang; Tyagi, Madhu Sudan; Mou, Chung-Yuan; Chen, Sow-Hsin

2010-08-01

232

Compact inertial confinement multireactor concepts  

SciTech Connect

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

Pendergrass, J.H.

1985-01-01

233

Dynamics and energetics of hydrophobically confined water  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

234

ATR confinement leakage determination  

SciTech Connect

The air leakage rate from the Advanced Test Reactor (ATR) confinement is an important parameter in estimating hypothesized accidental releases of radiation to the environment. The leakage rate must be determined periodically to assure that the confinement has not degraded with time and such determination is one of the technical safety requirements of ATR operation. This paper reviews the methods of confinement leakage determination and presents an analysis of leakage determination under windy conditions, which can complicate the interpretation of the determined leakage rates. The paper also presents results of analyses of building air exchange under windy conditions. High wind can enhance air exchange and this could increase the release rates of radioisotopes following an accident.

Kuan, P.; Buescher, B.J.

1998-06-01

235

Multiscale confining dynamics from holographic RG flows  

NASA Astrophysics Data System (ADS)

We consider renormalization group flows between conformal field theories in five (six) dimensions with a string (M-theory) dual. By compactifying on a circle (torus) with appropriate boundary conditions, we obtain continuous families of confining fourdimensional theories parametrized by the ratio ?flow/?QCD, with ?flow the scale at which the flow between fixed points takes place and ?QCD the confinement scale. We construct the dual geometries explicitly and compute the spectrum of scalar bound states (glueballs). We find a `universal' subset of states common to all the models. We comment on the modifications of these models, and the corresponding fine-tuning, required for a parametrically light `dilaton' state to be present. We also comment on some aspects of these theories as probed by extended objects such as strings and branes.

Elander, Daniel; Faedo, Anton F.; Hoyos, Carlos; Mateos, David; Piai, Maurizio

2014-05-01

236

Math Forum: 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

237

Materials self-assembly and fabrication in confined spaces  

SciTech Connect

Molecular assemblies have been mainly researched in open spaces for long time. However, recent researches have revealed that there are many interesting aspects remained in self-assemblies in confined spaces. Molecular association within nanospaces such as mesoporous materials provide unusual phenomena based on highly restricted molecular motions. Current research endeavors in materials science and technology are focused on developing either new class of materials or materials with novel/multiple functionalities which is often achived via molecular assembly in confined spaces. Template synthesis and guided assemblies are distinguishable examples for molecular assembly in confined spaces. So far, different aspects of molecular confinements are discussed separately. In this review, the focus is specifically to bring some potential developments in various aspects of confined spaces for molecular self-assembly under one roof. We arrange the sections in this review based on the nature of the confinements; accordingly the topological/geometrical confinements, chemical and biological confinements, and confinements within thin film, respectively. Following these sections, molecular confinements for practical applications are shortly described in order to show connections of these scientific aspects with possible practical uses. One of the most important facts is that the self-assembly in confined spaces stands at meeting points of top-down and bottom-up fabrications, which would be an ultimate key to push the limits of nanotechnology and nanoscience.

Ramanathan, Nathan Muruganathan [ORNL; Kilbey, II, S Michael [ORNL; Ji, Dr. Qingmin [National Institute for Materials Science, Tsukuba, Japan; Hill, Dr. Jonathan P [National Institute for Materials Science, Tsukuba, Japan; Ariga, Katsuhiko [National Institute for Materials Science, Tsukuba, Japan

2012-01-01

238

Inertial-Electrostatic Confinement of Ionized Fusion Gases  

Microsoft Academic Search

The nonmagnetic, inertial-electrostatic confinement of ionized gases in spherical geometry is discussed theoretically, and associated experiments are described. Assuming monoenergetic ion and electron distribution functions, the Poisson equation for bipolar currents is solved numerically. The results indicate spatially periodic solutions which respresent the alternate formation of virtual anodes and virtual cathodes. Particle pressures are found to vary approximately as the

Robert L. Hirsch

1967-01-01

239

Confinement of Pure Ion Plasma in a Cylindrical Current Sheet.  

National Technical Information Service (NTIS)

A novel method for containing a pure ion plasma at thermonuclear densities and temperatures has been modeled. The method combines the confinement properties of a Penning-Malmberg trap and some aspects of the magnetic field geometry of a pulsed theta-pinch...

C. K. Phillips E. H. Chao R. C. Davidson S. F. Paul

1999-01-01

240

Order, Disorder and Confinement  

SciTech Connect

Studying the order of the chiral transition for Nf = 2 is of fundamental importance to understand the mechanism of color confinement. We present results of a numerical investigation on the order of the transition by use of a novel strategy in finite size scaling analysis. The specific heat and a number of susceptibilities are compared with the possible critical behaviours. A second order transition in the O(4) and O(2) universality classes are excluded. Substantial evidence emerges for a first order transition. Results are in agreement with those found by studying the scaling properties of a disorder parameter related to the dual superconductivity mechanism of color confinement.

D'Elia, M. [Dipartimento di Fisica dell'Universita di Genova, Via Dodecaneso 33, I-16146 Genova (Italy); INFN, Sezione di Genova, Via Dodecaneso 33, I-16146 Genova (Italy); Di Giacomo, A.; Pica, C. [Dipartimento di Fisica dell'Universita di Pisa, largo Pontecorvo 3, I-56127 Pisa (Italy); INFN, Sezione di Pisa, largo Pontecorvo 3, I-56127 Pisa (Italy)

2006-01-12

241

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

242

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

SciTech Connect

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

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

1999-08-25

243

Confinement and Mayer cluster expansions  

NASA Astrophysics Data System (ADS)

In this paper, we study a class of grand-canonical partition functions with a kernel depending on a small parameter ?. This class is directly relevant to Nekrasov partition functions of 𝒩 = 2 SUSY gauge theories on the 4d ?-background, for which ? is identified with one of the equivariant deformation parameter. In the Nekrasov-Shatashvili limit ??0, we show that the free energy is given by an on-shell effective action. The equations of motion take the form of a TBA equation. The free energy is identified with the Yang-Yang functional of the corresponding system of Bethe roots. We further study the associated canonical model that takes the form of a generalized matrix model. Confinement of the eigenvalues by the short-range potential is observed. In the limit where this confining potential becomes weak, the collective field theory formulation is recovered. Finally, we discuss the connection with the alternative expression of instanton partition functions as sums over Young tableaux.

Bourgine, Jean-Emile

2014-05-01

244

Anomalous diffusion in confined turbulent convection.  

PubMed

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

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

2012-06-01

245

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.

246

The interaction between membrane kinetics and membrane geometry in the transmission of action potentials in non-uniform excitable fibres: a finite element approach  

Microsoft Academic Search

By solving the partial differential equations for an axonal segment using a finite element method, the interaction between membrane kinetics and axonal inhomogeneities, measured by their influence on propagated action potentials and stochastic spike trains, is investigated for Morris–Lecar and Hodgkin–Huxley membrane models. To facilitate comparisons of both kinetic models, parameter values are matched to give approximately the same speed

R. Altenberger; K. A. Lindsay; J. M. Ogden; J. R. Rosenberg

2001-01-01

247

Type-based confinement  

Microsoft Academic Search

Confinement properties impose a structure on object graphs which can be used to enforce encapsulation properties. From a practical point of view, encapsulation is essential for building secure object-oriented systems as security requires that the interface between trusted and untrusted components of a system be clearly delineated and restricted to the smallest possible set of operations and data structures. This

Tian Zhao; Jens Palsberg; Jan Vitek

2006-01-01

248

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

249

Geometry Formulas and Facts  

NSDL National Science Digital Library

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

Levy, Silvio

2007-12-07

250

Groovy Green Geometry!  

NSDL National Science Digital Library

Gotta Getcha some Great Goofy Geometry Games! Billy Bug is so hungry! Move him to the right coordinate so that he can eat! Make the puzzle pieces bigger or smaller to fit the puzzle in Cyberchase Geometry! If you want a definition of any geometry term.. click the word Definition ...

Nieman, Ms.

2007-11-22

251

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

252

The Microcomputer and Instruction in Geometry.  

ERIC Educational Resources Information Center

The microcomputer has great potential for making high school geometry more stimulating and more easily understood by the students. The microcomputer can facilitate instruction in both the logico-deductive and spatial-visual aspects of geometry through graphics representations, simulation of motion, and its capability of interacting with the…

Kantowski, Mary Grace

1981-01-01

253

Inertial confinement fusion with light ion beams  

Microsoft Academic Search

The Particle Beam Fusion Accelerator II (PBFA II) is presently under construction and is the only existing facility with the potential of igniting thermonuclear fuel in the laboratory. The accelerator will generate up to 5 megamperes of lithium ions at 30 million electron volts and will focus them onto an inertial confinement fusion (ICF) target after beam production and focusing

J. P. VanDevender; D. L. Cook

1986-01-01

254

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

255

Fusion plasma confinement research at the gas dynamic trap  

Microsoft Academic Search

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

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

2011-01-01

256

THE ENVIRONMENTAL IMPACT OF SHEEP CONFINEMENT FEEDING SYSTEMS  

Microsoft Academic Search

SUMMARY Confinement feeding systems are being used increasingly in dryland Australia for the finishing of lambs, and for maintenance of the flock in drought conditions. They have great potential as part of the farming system to address other major issues, such as herbicide resistance, soil compaction and improved management of pastures through deferred grazing. Whilst the benefits of confinement feeding

E. A. DOWLING; E. K. CROSSLEY

257

Inertial Electrostatic Confinement (IEC) devices.  

National Technical Information Service (NTIS)

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

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

1994-01-01

258

Perspectives on water science: transport and application of confined water  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

259

Perspectives on water science: transport and application of confined water  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

260

Electron recirculation in electrostatic multicusp systems: 1. Confinement and losses in simple power law wells  

SciTech Connect

A large body of work over the past 35 years has been devoted to the study of cusp confinement of electrons, ions, and plasmas. Nearly all of this has examined single particle electron (or ion) motion or the motion of particles in neutral plasmas within cusped magnetic systems, generally without internal electric potential fields. In this note the problem of electron motion, confinement and losses is analyzed in the non-LTE, electron-rich plasma system with anisotropic radial energy in both species, in multicusp Polywell geometry. The bulk problem is treated as one-dimensional, with arbitrary spatial indices of radial B and E field variation. Bulk diamagnetic collective effects are modelled as they influence this 1-D spatial variation of B field, but electron entry into single cusp volumes includes elements of the geometric effects of the real 3-D configuration. Electron motions in mirror reflection regions are analyzed on the usual basis of conservation of magnetic moment of the electron at entry into the confining cusp. However, turning points of this motion are modified to account for the effects of diamagnetic currents on this process. Comparison with non-Polywell models is made where useful and appropriate. Further details are given in the following sections.

Bussard, R.W.; King, K.E.

1991-04-19

261

Totally confined explosive welding  

NASA Technical Reports Server (NTRS)

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

Bement, L. J. (inventor)

1978-01-01

262

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

263

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

264

Invariance principles and plasma confinement  

Microsoft Academic Search

If the equations that describe the observed anomalous transport in magnetic confinement systems are invariant under a scale transformation then any confinement time calculated from them must exhibit the same invariance, no matter how intractable the calculation. This principle places constraints on the form of the confinement time scaling which are characteristic of the plasma model represented by the equations.

J. W. Connor

1988-01-01

265

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.

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

2013-01-01

266

Simulating tumor growth in confined heterogeneous environments  

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

267

NN interaction in a relativistic harmonic model with confined gluons  

NASA Astrophysics Data System (ADS)

We investigate the effect of exchange of confined gluons among relativistically confined quarks in nucleon-nucleon (NN) scattering calculations. For quarks we use the relativistic harmonicoscillator Lorentz scalar plus vector (RHM) confinement model. For the confinement of gluons, we use the current confinement model (CCM) developed in the spirit of RHM. Making use of the confined gluon propagators we obtain the confined one-gluon-exchange potential (COGEP) between the quarks. We employ the resonating group method formalism to obtain the NN phase shifts and interaction. The main conclusions are: (i) The color magnetic terms of the COGEP yields both short-range repulsion and intermediate-range attraction for the 1S 0 and 3S 1 states; (ii) The tensor part of the COGEP has the right sign and the terms in the tensor part of the COGEP arising out of confinement of gluons contribute significantly to the attraction in the 3S 1 state; (iii) The spin-orbit potential of the COGEP has the right sign and right order of magnitude and is in agreement with the phenomenological spin-orbit potential; (iv) The pp and np differential cross sections (?(?)) obtained are in good agreement with the experimental ?(?) although the calculated phase shifts for higher partial waves do not compare well with the phenomenological phase shifts of Arndt et al.

Kumar, K. B. Vijaya; Khadkikar, S. B.

1993-05-01

268

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.

269

SGEMP Geometry Effects  

Microsoft Academic Search

Self-consistent, fully dynamic computer calculations were performed using the recently developed arbitrary body-of-revolution code ABORC for complex geometries in SGEMP environments to test the validity of simplifying geometry assumptions previously made in the solutions of these problems. Assumptions such as simple geometry representations of complex bodies and separability of inside and outside problems are tested. Effects of gaps, interior electrical

A. J. Woods; E. P. Wenaas

1975-01-01

270

The equilibrium of electron plasmas confined on magnetic surfaces  

NASA Astrophysics Data System (ADS)

The study of pure electron plasmas confined on magnetic surfaces has only recently begun, with much of the work being conducted by the Columbia Non-neutral Torus (CNT) group. This thesis describes a computational model used to solve the equilibrium equation of such plasmas, some general properties of the equilibrium predicted by the model, reconstructions of the equilibrium of experimental plasmas in the CNT and in the Compact Helical System (CHS), and some relevant experimental contributions to the CNT experiment. The first three-dimensional equilibrium solver, the PBS (Poisson-Boltzmann Solver) code, was designed to model the equilibrium of these plasmas. The nonlinear equilibrium equation for the electrostatic potential is solved using an iterative pseudo-spectral method, and a flexible singular value decomposition (SVD) method is used to enforce boundary conditions. This code was first used to model a variety of simple geometries and boundary conditions. The results of these calculations show an outward major radial shift of the plasma, a shift toward conductors, and an increase in plasma ellipticity with respect to the magnetic surfaces. Dependence of the equilibrium on Debye length has also been explored. The complicated CNT magnetic surface configuration has been implemented and the equilibrium of CNT plasmas modeled. Results show a factor of five axial variation in density, more than twice as large as expected for a Penning trap with similar mirror fields. A simple analytical expression has been derived that describes this variation. Reconstructions of CNT equilibria have been performed and agree well with experiment, while CHS reconstructions differ somewhat from experimental measurements, but in a consistent with known problem associated with the diagnostic techniques employed. Some experimental work done for the CNT is also described in this thesis. This includes the experimental verification of the CNT magnetic surface configuration, necessary for proper equilibrium reconstructions, and the construction of a copper mesh torus that conforms to the CNT outer magnetic surface, the implementation of which should improve confinement according to computational predictions.

Lefrancois, Remi Guy

271

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

PubMed

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

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

2011-10-10

272

The influence of duct geometry on unsteady premixed flames  

Microsoft Academic Search

Measurements of the frequency spectrum and intensity of pressure fluctuations have been obtained in the vicinity of confined, bluff-body stabilized premixed flames as a function of equivalence ratio. Methane and air were premixed in a swirl register (swirl was subsequently removed by honeycomb) which provided a closed upstream end to the various duct geometries. The ducts included a straight pipe

M. Katsuki; J. H. Whitelaw

1986-01-01

273

Geometry Dependence of Stellarator Turbulence  

SciTech Connect

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

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

2009-08-10

274

Interactive Geometry Dictionary: Areas in Geometry  

NSDL National Science Digital Library

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

2011-01-01

275

Inertial Electrostatic Confinement as a Power Source for Electric Propulsion.  

National Technical Information Service (NTIS)

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

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

1993-01-01

276

Inertial Electrostatic Confinement as a Power Source for Electric Propulsion.  

National Technical Information Service (NTIS)

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

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

1993-01-01

277

Chirally symmetric but confining dense, cold matter  

SciTech Connect

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

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

2008-03-01

278

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

279

Modons in spherical geometry  

Microsoft Academic Search

Spherical geometry equivalent modons are derived in analytical form, together with the dispersion relationship that related the modon's frequency, spatial extent, and interior wavenumber. Improved kinematic agreement with atmospheric blocking patterns are achieved by equivalent modons in spherical geometry in virtue of increasing asymmetry as the geographic pole is approached. Numerical experiments demonstrating the robustness of spherical modons to background

Joseph J. Tribbia

1984-01-01

280

Noncommutative geometry and gravity  

Microsoft Academic Search

We study a deformation of infinitesimal diffeomorphisms of a smooth manifold. The deformation is based on a general twist. This leads to a differential geometry on a noncommutative algebra of functions whose product is a star product. The class of noncommutative spaces studied is very rich. Non-anticommutative superspaces are also briefly considered. The differential geometry developed is covariant under deformed

Paolo Aschieri; Marija Dimitrijevic; Frank Meyer; Julius Wess

2006-01-01

281

Lectures on Noncommutative Geometry  

Microsoft Academic Search

These Lectures are based on a course on noncommutative geometry given by the author in 2003 at the University of Chicago. The lectures contain some standard material, such as Poisson and Gerstenhaber algebras, deformations, Hochschild cohomology, Serre functors, etc. We also discuss many less known as well as some new results, in particular, noncommutative Chern-Weil theory, noncommutative symplectic geometry, noncommutative

Victor Ginzburg

2005-01-01

282

Geometry of multihadron production  

SciTech Connect

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

Bjorken, J.D.

1994-10-01

283

Twistors to twisted geometries  

SciTech Connect

In a previous paper we showed that the phase space of loop quantum gravity on a fixed graph can be parametrized in terms of twisted geometries, quantities describing the intrinsic and extrinsic discrete geometry of a cellular decomposition dual to the graph. Here we unravel the origin of the phase space from a geometric interpretation of twistors.

Freidel, Laurent [Perimeter Institute for Theoretical Physics, 31 Caroline Street N, ON N2L 2Y5, Waterloo (Canada); Speziale, Simone [Centre de Physique Theorique, CNRS-Luminy Case 907, 13288 Marseille Cedex 09 (France)

2010-10-15

284

Expansion, geometry, and gravity  

Microsoft Academic Search

In general-relativistic cosmological models, the expansion history, matter content, and geometry are closely intertwined. In this brief paper, we clarify the distinction between the effects of geometry and expansion history on the luminosity distance. We show that the cubic correction to the Hubble law, measured recently with high-redshift supernovae, is the first cosmological measurement, apart from the cosmic microwave background,

Robert R. Caldwell; Marc Kamionkowski

2004-01-01

285

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

286

Want to Play Geometry?  

ERIC Educational Resources Information Center

Students enter the geometry classroom with a strong concept of fairness and a sense of what it means to "play by the rules," yet many students have difficulty understanding the postulates, or rules, of geometry and their implications. Although they may never have articulated the properties of an axiomatic system, they have gained a practical…

Kaufmann, Matthew L.; Bomer, Megan A.; Powell, Nancy Norem

2009-01-01

287

Confined placental mosaicism.  

PubMed Central

In most pregnancies the chromosomal complement detected in the fetus is also present in the placenta. The detection of an identical chromosomal complement in both the fetus and its placenta has always been expected as both develop from the same zygote. However, in approximately 2% of viable pregnancies studied by chorionic villus sampling (CVS) at 9 to 11 weeks of gestation, the cytogenetic abnormality, most often trisomy, is confined to the placenta. This phenomenon is known as confined placental mosaicism (CPM). It was first described by Kalousek and Dill in term placentas of infants born with unexplained intrauterine growth restriction (IUGR). Contrary to generalised mosaicism, which is characterised by the presence of two or more karyotypically different cell lines within both the fetus and its placenta, CPM represents tissue specific chromosomal mosaicism affecting the placenta only. The diagnosis of CPM is most commonly made when, after the diagnosis of chromosomal mosaicism in a CVS sample, the second prenatal testing (amniotic fluid culture or fetal blood culture analysis) shows a normal diploid karyotype.

Kalousek, D K; Vekemans, M

1996-01-01

288

Novel diagnostic approaches to characterizing the performance of the Wisconsin inertial electrostatic confinement plasma  

Microsoft Academic Search

The inertial electrostatic confinement (IEC) device confines energetic ions in a spherically symmetric, negative potential well between two nearly transparent metallic grids. Diagnostics were developed and implemented to understand IEC device operation. A plasma diagnostic to measure concentrations of molecular deuterium ions in the edge plasma region of the UW-Inertial Electrostatic Confinement (IEC) fusion device was developed and implemented. This

David R. Boris

2009-01-01

289

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

PubMed

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

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

2013-07-31

290

On the geometry of stiff knots  

NASA Astrophysics Data System (ADS)

We analyse the geometry of a thin knotted string with bending rigidity. Two types of geometric properties are investigated. First, following the approach of von der Mosel [H. von der Mosel, Asymptotic Anal. 18, 49 (1998)], we derive upper bounds for the multiplicity of crossings and braids. Then, using a general inequality for the length of 3D curves derived by Chakerian [G.D. Chakerian, Proc. of the American Math. Soc. 15, 886 (1964)], we analyze the size and confinement of a knot

Pierre-Louis, O.

2009-09-01

291

Effect of charge transport in electrode-confined N,N'-dialkyl-4,4'-bipyridinium polymers on the current-potential response for mediated, outer-sphere electron-transfer reactions  

SciTech Connect

Mediated outer-sphere redox processes have been examined at rotating disk Pt/(PQ/sup 2+/+/)/sub n/)/sub surf/ electrodes. The ((PQ/sup 2+/+/)/sub n/)/sub surf/ is a redox polymer anchored to the surface and is formed from N,N'-bis((trimethoxysilyl)propyl)-4,4'-bipyridinium, I. The polymer coverages for the electrodes selected for study are sufficiently great that Fe(phen)/sub 3//sup 3+/2+,E /sup 0/' = + 1.03 V vs. SCE, shows no electrochemical response near its E/sup 0/'. The mediated reduction of Fe(phen)/sub 3//sup 3 +/ and a number of other outer-sphere oxidants is mass-transport limited when the Pt/((PQ/sup 2+/+)/sub n/)/sub surf/ electrode is held approx. 100 mV more negative than E/sup 0/'((PQ/sup 2+/+)/sub n/)/sub surf/ = -0.45 V vs. SCE in CH/sub 3/CN/0.1 M (n-Bu/sub 1/N)ClO/sub 4/. However, contrary to theoretical expectations based only on the rate constant for reaction of Fe(phen)/sub 3//sup 3 +/ with a surface PQ/sup +/, the onset of current for the mediated reduction is at the onset for ((PQ/sup 2 +/)/sub n/)/sub surf/ ..-->.. ((PQ/sup +/)/sub n/)/sub surf/ reduction; in fact, the mediated reduction current in the onset region is directly proportional to the concentration of PQ/sup +/ in the surface-confined polymer. Data for Pt/((PQ/sup 2 +/ xFe(CN)/sub 6//sup 3-/4-/)/sub n/)/sub surf/ electrodes show directly that charge transport in the polymer can be a limitation to the maximum steady-state mediation current in aqueous electrolyte solution at the coverages of ((PQ/sup 2+/+)/sub n/)/sub surf/ that have been employed. The charge-transport properties of the polymer are concluded to control the current-potential profile, as has been reported previously for other surface-modified electrodes, for the large polymer coverages employed in these studies. 26 references, 13 figures, 1 table.

Lewis, N.S.; Wrighton, M.S.

1984-05-10

292

Plasma confinement studies in open systems  

NASA Astrophysics Data System (ADS)

Studies in open systems in the world are reviewed from viewpoints of the potential confinement and magnetohydrodynamic (MHD) stability. The tandem mirror GAMMA 10 has shown the potential confinement of a high-ion-temperature plasma from an analysis of the time evolution of end-loss ion current and end-loss ion energy distributions. The central cell density was increased by 50% by the potential confinement. In the HIEI tandem mirror H-mode-like phenomena were observed with an increase in density and diamagnetic signal in a limiter biasing experiment. Potential formation phenomena in plasmas are studied by 0741-3335/41/3A/024/img1-like Upgrade under different magnetic field configurations and plasma conditions. The fully axisymmetric tandem mirror AMBAL-M is under construction and its end mirror system has been assembled. Heating experiments of a plasma gun produced plasma by neutral beam injection and ICRF heating are in progress. The gas dynamic trap (GDT) experiment has successfully produced an MHD-stable high-temperature, high-density plasma. In GOL-3-II, a high-density plasma with several 100 eV temperature is created by powerful relativistic electron beam injection. Construction of HANBIT has been completed and experiments on plasma production and ICRF heating have begun.

Yatsu, Kiyoshi

1999-03-01

293

Effect of confinement on the deformation of microfluidic drops.  

PubMed

We study the deformation of drops squeezed between the floor and ceiling of a microchannel and subjected to a hyperbolic flow. We observe that the maximum deformation of drops depends on both the drop size and the rate of strain of the external flow and can be described with power laws with exponents 2.59±0.28 and 0.91±0.05, respectively. We develop a theoretical model to describe the deformation of squeezed drops based on the Darcy approximation for shallow geometries and the use of complex potentials. The model describes the steady-state deformation of the drops as a function of a nondimensional parameter Ca?2, where Ca is the capillary number (proportional to the strain rate and the drop size) and ? is a confinement parameter equal to the drop size divided by the channel height. For small deformations, the theoretical model predicts a linear relationship between the deformation of drops and this parameter, in good agreement with the experimental observations. PMID:24730934

Ulloa, Camilo; Ahumada, Alberto; Cordero, María Luisa

2014-03-01

294

Instantons confined by monopole strings  

NASA Astrophysics Data System (ADS)

It is known that monopoles can be confined by vortex strings in d=3+1 while vortices can be confined by domain lines in d=2+1. Here, as a higher dimensional generalization of these, we show that Yang-Mills instantons can be confined by monopole strings in d=4+1. We achieve this by putting the system into the Higgs phase in which the configuration can be constructed inside a non-Abelian vortex sheet.

Nitta, Muneto

2013-03-01

295

A Phase Field Approach to No Slip Boundary Conditions in Dissipative Particle Dynamics and Other Particle Models for Fluid Flow in Geometrically Complex Confined Systems  

SciTech Connect

Dissipative particle dynamics (DPD) is an effective mesoscopic particle model with a lower computational cost than molecular dynamics because of the soft potentials that it employs. However, the soft potential is not strong enough to prevent the fluid DPD particles from penetrating solid boundaries represented by stationary DPD particles. A phase field variable, _(x,t) , is used to indicate the phase at point x and time t, with a smooth transition from -1 (phase 1) to +1 (phase 2) across the interface. We describe an efficient implementation of no-slip boundary conditions in DPD models that combine solid-liquid particle-particle interactions with reflection at a sharp boundary located with subgrid scale accuracy using the phase field. This approach can be used for arbitrarily complex flow geometries and other similar particle models (such as smoothed particle hydrodynamics), and the validity of the model is demonstrated by flow in confined systems with various geometries.

Paul Meakin; Zhijie Xu

2009-06-01

296

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

297

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

298

Native American geometry  

NSDL National Science Digital Library

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

2007-12-12

299

Effect of Confinement: Polygons in Strips, Slabs and Rectangles  

NASA Astrophysics Data System (ADS)

In this chapter we will be considering the effect of confining polygons to lie in a bounded geometry. This has already been briefly discussed in Chapters 2 and 3, but here we give many more results. The simplest, non-trivial case is that of SAP on the two-dimensional square lattice Z2, confined between two parallel lines, say x = 0 and x = w. This problem is essentially 1-dimensional, and as such is in principle solvable. As we shall show, the solution becomes increasingly unwieldy as the distance w between the parallel lines increases. Stepping up a dimension to the situation in which polygons in the simple-cubic lattice Z3 are confined between two parallel planes, that is essentially a two-dimensional problem, and as such is not amenable to exact solution.

Guttmann, Anthony J.; Jensen, Iwan

300

Gate-defined quantum confinement in suspended bilayer graphene.  

PubMed

Quantum-confined devices that manipulate single electrons in graphene are emerging as attractive candidates for nanoelectronics applications. Previous experiments have employed etched graphene nanostructures, but edge and substrate disorder severely limit device functionality. Here we present a technique that builds quantum-confined structures in suspended bilayer graphene with tunnel barriers defined by external electric fields that open a bandgap, thereby eliminating both edge and substrate disorder. We report clean quantum dot formation in two regimes: at zero magnetic field B using the energy gap induced by a perpendicular electric field and at B>0 using the quantum Hall ?=0 gap for confinement. Coulomb blockade oscillations exhibit periodicity consistent with electrostatic simulations based on local top-gate geometry, a direct demonstration of local control over the band structure of graphene. This technology integrates single electron transport with high device quality and access to vibrational modes, enabling broad applications from electromechanical sensors to quantum bits. PMID:22760633

Allen, M T; Martin, J; Yacoby, A

2012-01-01

301

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

302

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

303

Strain-induced pseudoheterostructure nanowires confining carriers at room temperature with nanoscale-tunable band profiles.  

PubMed

Semiconductor heterostructures play a vital role in photonics and electronics. They are typically realized by growing layers of different materials, complicating fabrication and limiting the number of unique heterojunctions on a wafer. In this Letter, we present single-material nanowires which behave exactly like traditional heterostructures. These pseudoheterostructures have electronic band profiles that are custom-designed at the nanoscale by strain engineering. Since the band profile depends only on the nanowire geometry with this approach, arbitrary band profiles can be individually tailored at the nanoscale using existing nanolithography. We report the first experimental observations of spatially confined, greatly enhanced (>200×), and wavelength-shifted (>500 nm) emission from strain-induced potential wells that facilitate effective carrier collection at room temperature. This work represents a fundamentally new paradigm for creating nanoscale devices with full heterostructure behavior in photonics and electronics. PMID:23758608

Nam, Donguk; Sukhdeo, David S; Kang, Ju-Hyung; Petykiewicz, Jan; Lee, Jae Hyung; Jung, Woo Shik; Vu?kovi?, Jelena; Brongersma, Mark L; Saraswat, Krishna C

2013-07-10

304

Integrating Transformation Geometry into Traditional High School Geometry.  

ERIC Educational Resources Information Center

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

Okolica, Steve; Macrina, Georgette

1992-01-01

305

Proof in Transformation Geometry  

ERIC Educational Resources Information Center

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

Bell, A. W.

1971-01-01

306

Noncommutative Geometry and Physics  

SciTech Connect

In this very short essay we shall describe a 'spectral' point of view on geometry which allows to start taking into account the lessons from both renormalization and of general relativity. We shall first do that for renormalization and explain in rough outline the content of our recent collaborations with Dirk Kreimer and Matilde Marcolli leading to the universal Galois symmetry of renormalizable quantum field theories provided by the renormalization group in its cosmic Galois group incarnation. As far as general relativity is concerned, since the functional integral cannot be treated in the traditional perturbative manner, it relies heavily as a 'sum over geometries' on the chosen paradigm of geometric space. This will give us the occasion to discuss, in the light of noncommutative geometry, the issue of 'observables' in gravity and our joint work with Ali Chamseddine on the spectral action, with a first attempt to write down a functional integral on the space of noncommutative geometries.

Connes, Alain [College de France, 3, rue d'Ulm, Paris, F-75005 France (France)

2006-11-03

307

Noncommutative Geometry and Physics  

NASA Astrophysics Data System (ADS)

In this very short essay we shall describe a ``spectral'' point of view on geometry which allows to start taking into account the lessons from both renormalization and of general relativity. We shall first do that for renormalization and explain in rough outline the content of our recent collaborations with Dirk Kreimer and Matilde Marcolli leading to the universal Galois symmetry of renormalizable quantum field theories provided by the renormalization group in its cosmic Galois group incarnation. As far as general relativity is concerned, since the functional integral cannot be treated in the traditional perturbative manner, it relies heavily as a ``sum over geometries'' on the chosen paradigm of geometric space. This will give us the occasion to discuss, in the light of noncommutative geometry, the issue of ``observables'' in gravity and our joint work with Ali Chamseddine on the spectral action, with a first attempt to write down a functional integral on the space of noncommutative geometries.

Connes, Alain

2006-11-01

308

Discrete and Convex Geometry  

Microsoft Academic Search

\\u000a Mathematical research in Hungary started with geometry: with the work of the two Bolyais early in the 19th century. The father,\\u000a Farkas Bolyai, showed that equal area polygons are equidecomposable. The son, János Bolyai, laid down the foundations of non-Euclidean\\u000a geometry. The study of geometric objects has been continuing ever since. The present chapter of this book is devoted to

Imre Bárány

309

View-dependent geometry  

Microsoft Academic Search

When constructing 3D geometry for use in cel animation, the reference drawings of the object or character often contain various view-specific distortions, which cannot be captured with conventional 3D models. In this work we present a technique called View-Dependent Geometry, wherein a 3D model changes shape based on the direction it is viewed from. A view-dependent model consists of a

Paul Rademacher

1999-01-01

310

Renormalizability conditions for almost-commutative geometries  

NASA Astrophysics Data System (ADS)

We formulate conditions for almost-commutative (spacetime) manifolds under which the asymptotically expanded spectral action is renormalizable. These conditions are of a graph-theoretical nature, involving the Krajewski diagrams that classify such geometries. This applies in particular to the Standard Model of particle physics, giving a graph-theoretical argument for its renormalizability. A promising potential application is in the selection of physical (renormalizable) field theories described by almost-commutative geometries, thereby going beyond the Standard Model.

van Suijlekom, Walter D.

2012-05-01

311

CMS Geometry Through 2020  

NASA Astrophysics Data System (ADS)

CMS faces real challenges with upgrade of the CMS detector through 2020 and beyond. One of the challenges, from the software point of view, is managing upgrade simulations with the same software release as the 2013 scenario. We present the CMS geometry description software model, its integration with the CMS event setup and core software. The CMS geometry configuration and selection is implemented in Python. The tools collect the Python configuration fragments into a script used in CMS workflow. This flexible and automated geometry configuration allows choosing either transient or persistent version of the same scenario and specific version of the same scenario. We describe how the geometries are integrated and validated, and how we define and handle different geometry scenarios in simulation and reconstruction. We discuss how to transparently manage multiple incompatible geometries in the same software release. Several examples are shown based on current implementation assuring consistent choice of scenario conditions. The consequences and implications for multiple/different code algorithms are discussed.

Osborne, I.; Brownson, E.; Eulisse, G.; Jones, C. D.; Lange, D. J.; Sexton-Kennedy, E.

2014-06-01

312

Confined volume blasting experiments: Description and analysis  

SciTech Connect

A series of bench-scale blasting experiments was conducted to produce rubble beds for use in retorting experiments. The experiments consisted of blasting oil shale with explosives within a confined volume containing 25% void. A variety of blasting geometries was used to control the fragment size distribution and void distribution in the rubble. The series of well controlled tests provided excellent data for use in validating rock fragmentation models. Analyses of the experiments with PRONTO, a dynamic finite element computer code, and a newly developed fracturing model provided good agreement between code predictions and experimental measurements of fracture extent and fragment size. CAROM, a dynamic distinct element code developed to model rock motion during blasting, was used to model the fully fragmented tests. Calculations of the void distribution agreed well with experimentally measured values. 9 refs., 11 figs., 1 tab.

Gorham-Bergeron, E.; Kuszmaul, J.S.; Bickel, T.C.; Shirey, D.L.

1987-01-01

313

Magnetic confinement fusion energy research  

Microsoft Academic Search

Controlled thermonuclear fusion offered a relatively clean energy solution with completely inexhaustible fuel and unlimited power capacity. The scientific and technological problem consisted in magnetically confining a hot, dense plasma for an appreciable fraction of a second. The scientific and mathematical problem was to describe the behavior, such as confinement, stability, flow, compression, heating, energy transfer and diffusion of this

H. Grad

1977-01-01

314

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

315

BRS Transformation and Color Confinement.  

National Technical Information Service (NTIS)

The condition of confinement of quarks and gluons in QCD is derived. It is shown that color confinement is realized when there exist massles scalar color-octet bound states of two Faddeev-Popov ghosts. (ERA citation 08:008561)

K. Nishijima

1982-01-01

316

Nanotube based hybrid plasmon polariton waveguide for propagation loss reduction and enhanced field confinement inside the gap region at the subwavelength scale  

NASA Astrophysics Data System (ADS)

We present a comprehensive numerical investigation on the guiding properties of a nanotube based hybrid plasmonic waveguide, which comprises a high-index dielectric nanotube placed above a metallic substrate. It is shown that the incorporation of the nanotube offers additional freedom for tuning the optical performance of the hybrid plasmonic structure when compared to the traditional nanowire based hybrid counterparts, which enables further reduction of the propagation loss and enhanced field confinement inside the gap region, while simultaneously maintaining a subwavelength mode size at appropriate geometries. Systematic geometric parameters mapping considering the size of the nanotube and the dimension of the gap reveals that the tradeoff between the confinement and loss could be further balanced through optimizing key physical parameters. These investigations potentially lay the groundwork for the further applications of nanotube based hybrid structures.

Bian, Yusheng; Gong, Qihuang

2014-06-01

317

Experimental study on confined two-phase jets  

SciTech Connect

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

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

1991-09-01

318

Geometry of PDE's. IV  

NASA Astrophysics Data System (ADS)

Following our previous results on this subject [R.P. Agarwal, A. Prástaro, Geometry of PDE's. III(I): Webs on PDE's and integral bordism groups. The general theory, Adv. Math. Sci. Appl. 17 (2007) 239-266; R.P. Agarwal, A. Prástaro, Geometry of PDE's. III(II): Webs on PDE's and integral bordism groups. Applications to Riemannian geometry PDE's, Adv. Math. Sci. Appl. 17 (2007) 267-285; A. Prástaro, Geometry of PDE's and Mechanics, World Scientific, Singapore, 1996; A. Prástaro, Quantum and integral (co)bordism in partial differential equations, Acta Appl. Math. (5) (3) (1998) 243-302; A. Prástaro, (Co)bordism groups in PDE's, Acta Appl. Math. 59 (2) (1999) 111-201; A. Prástaro, Quantized Partial Differential Equations, World Scientific Publishing Co, Singapore, 2004, 500 pp.; A. Prástaro, Geometry of PDE's. I: Integral bordism groups in PDE's, J. Math. Anal. Appl. 319 (2006) 547-566; A. Prástaro, Geometry of PDE's. II: Variational PDE's and integral bordism groups, J. Math. Anal. Appl. 321 (2006) 930-948; A. Prástaro, Th.M. Rassias, Ulam stability in geometry of PDE's, Nonlinear Funct. Anal. Appl. 8 (2) (2003) 259-278; I. Stakgold, Boundary Value Problems of Mathematical Physics, I, The MacMillan Company, New York, 1967; I. Stakgold, Boundary Value Problems of Mathematical Physics, II, Collier-MacMillan, Canada, Ltd, Toronto, Ontario, 1968], integral bordism groups of the Navier-Stokes equation are calculated for smooth, singular and weak solutions, respectively. Then a characterization of global solutions is made on this ground. Enough conditions to assure existence of global smooth solutions are given and related to nullity of integral characteristic numbers of the boundaries. Stability of global solutions are related to some characteristic numbers of the space-like Cauchy dataE Global solutions of variational problems constrained by (NS) are classified by means of suitable integral bordism groups too.

Prástaro, Agostino

2008-02-01

319

Integrable Background Geometries  

NASA Astrophysics Data System (ADS)

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

Calderbank, David M. J.

2014-03-01

320

Electron confinement in an annular Penning trap  

NASA Astrophysics Data System (ADS)

Electron confinement in an annular version of a Malmberg-Penning trap [S. Robertson and B. Walch, Rev. Sci. Instrum. 70, 2993 (1999)] has been investigated for conditions in which mobility is the dominant source of transport. A non-neutral plasma of electrons is contained in the annular region between coaxial cylinders. An axial magnetic field provides radial confinement and electric bias potentials provide axial confinement. The electric field that drives transport is determined primarily by the potential difference applied to the cylinders. The measured density decay rates have the expected dependence upon electric field, collision frequency and magnetic field and are within a factor of 2 of calculated values. Experiments are performed with an axial field of 5-18 mT, a radial electric field of 11-38 V/cm, a helium pressure of 0.01-0.13 mTorr, an initial electron density of ~106 cm-3, and the density decay times are 1-10 ms.

Robertson, Scott; Walch, Bob

2000-06-01

321

Degeneracy of confined D-dimensional harmonic oscillator  

NASA Astrophysics Data System (ADS)

Using the mathematical properties of the confluent hypergeometric functions, the conditions for the incidental, simultaneous, and interdimensional degeneracy of the confined D-dimensional (D > 1) harmonic oscillator energy levels are derived, assuming that the isotropic confinement is defined by an infinite potential well and a finite radius Rc. Very accurate energy eigenvalues are obtained numerically by finding the roots of the confluent hypergeometric functions that confirm the degeneracy conditions.

Montgomery, H. E., Jr.; Aquino, N. A.; Sen, K. D.

322

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

323

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

324

The Effect of Molecular Anchoring and Curvature on Confined Liquid Crystals  

Microsoft Academic Search

Nematic liquid crystals confined to curved geometries exhibit unique elastic and anchoring properties. One result of this study was the first simultaneous measurement of the azimuthal (W_phi) and polar (W_theta) anchoring strength and the saddle-splay surface elastic constant K_{24}. The technique confined 4^'-pentyl-4 -cyanobiphenyl (5CB) to submicrometer polyimide treated cylindrical cavities of polycarbonate (Nuclepore) membranes with concentric tangential anchoring conditions

Renate Johanna Ondris-Crawford

1993-01-01

325

Competition between capillarity, layering and biaxiality in a confined liquid crystal  

Microsoft Academic Search

.  The effect of confinement on the phase behaviour and structure of fluids made of biaxial hard particles (cuboids) is examined\\u000a theoretically by means of Onsager second-order virial theory in the limit where the long particle axes are frozen in a mutually\\u000a parallel configuration. Confinement is induced by two parallel planar hard walls (slit-pore geometry), with particle long\\u000a axes perpendicular to

Szabolcs Varga; Y. Mart?nez-Ratón; Enrique Velasco

2010-01-01

326

Incommensurability of a confined system under shear.  

PubMed

We study a chain of harmonically interacting atoms confined between two sinusoidal substrate potentials, when the top substrate is driven through an attached spring with a constant velocity. This system is characterized by three inherent length scales and closely related to physical situations with confined lubricant films. We show that, contrary to the standard Frenkel-Kontorova model, the most favorable sliding regime is achieved by choosing chain-substrate incommensurabilities belonging to the class of cubic irrational numbers (e.g., the spiral mean). At large chain stiffness, the well known golden mean incommensurability reveals a very regular time-periodic dynamics with always higher kinetic friction values with respect to the spiral mean case. PMID:16090702

Braun, O M; Vanossi, A; Tosatti, E

2005-07-01

327

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

328

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

329

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

330

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

331

Ultrasonic interferometer for first-sound measurements of confined liquid He4  

NASA Astrophysics Data System (ADS)

We present a new technique for probing the properties of quantum fluids in restricted geometries. We have confined liquid He4 within microfluidic devices formed from glass wafers, in which one dimension is on the micrometer scale. Using an ultrasonic analog to Fabry-Pérot interferometry, we have measured the first sound of the confined liquid He4, which can be a probe of critical behavior near the lambda point (T?). All thermodynamic properties of liquid He4 can be derived from first-sound and heat capacity measurements, and although quite a bit of experimental work has been done on the latter, no measurement of first sound has been reported for a precisely confined geometry smaller than a few tens of micrometers. In this work, we report measurements of isobaric first sound in liquid He4 confined in cavities as small as ˜5 ?m. Our experimental setup allows us to pressurize the liquid up to ˜25 bar without causing deformation of the confined geometry, a pressure which is about four times larger than previously reported with similar microfluidic devices. Our preliminary results indicate that one can possibly observe finite-size effects and verify scaling laws, by using similar devices with smaller confinement.

Rojas, X.; Hauer, B. D.; MacDonald, A. J. R.; Saberi, P.; Yang, Y.; Davis, J. P.

2014-05-01

332

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

333

Chirowaveguides with complex geometry  

NASA Astrophysics Data System (ADS)

In this study, we examine the propagation of guided waves in chirowaveguides with complex geometry. The study is focused on discontinuous structures because these are of potential importance in practical circuit design for both passive and active devices. We concentrate on the development and application of numerical techniques to augment analytical solutions. First, we report on novel physical effects of semi-leaky waves in planar chirowaveguides. We derive the conditions under which leakage may occur, how large the leakage is, and the physical characteristics of the semi-leaky waves for a dielectric slab with chiral cladding. Second, we propose, develop and implement an exact numerical method to analyze the effect of discontinuities in open planar chirowaveguides. This method combines the building block approach of multi-mode network theory with a rigorous mode-matching procedure to bring new physical insight to chirowaveguide discontinuities and their effects. Features such as the symmetry properties of the structure are also investigated. Based on our research, numerical results are developed and displayed to demonstrate the usefulness of our approach and to discuss the mode conversion and radiation characteristics of discontinuities. Third, we provide a comprehensive study of two- and three-dimensional discontinuities in chirowaveguides. The multi-mode coupled-mode method is an effective numerical approach to analyze this problem. After obtaining the coupled-mode equations, we diagonalize the coupling matrix to obtain a multi-mode scattering matrix rather than the usual two-mode approximation. Based on our analysis, numerical and analytical results are displayed to discuss the effects of the chirality admittance and dielectric constant on scattering properties. We also find the relative influence of height and width of chiral obstacles in rectangular waveguides. Finally, we provide a rigorous mode-matching method combined with multi-mode network theory to analyze the scattering of guided wave in chiral periodic structure. We derive a new orthogonal relation for eigenmodes in a periodic array of chiral slabs to implement mode- matching. Symmetry properties of the structure are also employed to simplify the analysis. Numerical results are given to discuss physical properties for both low and high frequency cases.

Wu, Thomas Xinzhang

334

Designing Phoxonic Metamaterials with Fractal Geometry  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

335

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

336

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

NASA Astrophysics Data System (ADS)

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; Montgomery, H. E.

2012-09-01

337

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

PubMed

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

Katriel, Jacob; Montgomery, H E

2012-09-21

338

Ventilation, air confinement and high radon level in an underground gallery studied from profiles measurements.  

NASA Astrophysics Data System (ADS)

An horizontal closed-end tunnel, 128 m long and 2 m in diameter, located within the eastern margin of the Belledonne crystalline basement, French Alps, near the west shore of the Roselend artificial lake, 600 m NE of the dam, has been instrumented since 1995 for radon emanation and deformation measurements. Radon bursts are repeatedly associated with transient deformation events induced by variations in lake levels (Trique et al., 1999). This high radon anomalies (up to 30,000 Bq.m-3) in the air of the tunnel result from its particular geometry, its excellent confinement, the water and radium-226 contents of rocks, and the crossing of several faults. We calculated the equilibrium factor F, directly proportional to air ventilation, from the ratios of radon-222 gas activity measured with an AlphaGUARDTM, and the Potential Alpha Energy Concentration (PAEC, in ?J.m-3) of its short-lived daughters measured with a TracerlabTM, simultaneously in five locations along the tunnel. The calculated equilibrium factors of 0.60 to 0.78 show that confinement is very good all along the tunnel. Fast Fourier Transform of the radon-222 signals measured during six months simultaneously with six BarasolTM distributed along the tunnel shows also the poor ventilation and the weak influence of atmospheric pressure and air temperature.

Richon, P.; Perrier, F.; Sabroux, J.-C.; Pili, E.; Ferry, C.; Dezayes, C.; Voisin, V.

2003-04-01

339

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

PubMed

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

Ryabinkin, Ilya G; Staroverov, Viktor N

2011-12-28

340

Inhomogeneous melting in anisotropically confined two-dimensional clusters.  

PubMed

Molecular dynamic simulations are performed to investigate the melting process of two-dimensional clusters of classical charged particles trapped in an anisotropic parabolic potential. The confined particles interact through a repulsive potential. We find that the eccentricity of the confinement potential strongly affects the melting pattern of such clusters. Increasing the eccentricity of the confinement potential drives the system through three different melting regimes. Inhomogeneous melting is the typical melting process for anisotropically confined clusters and its appearance in small systems occurs in a distinct form called here internal intershell melting. The latter involves only particles in the center of the cluster while particles on the far left and right of the cluster are still ordered having a much higher melting temperature. Using the Lindemann's criterion the melting temperatures are determined as a function of the different parameters. The internal intershell melting process is found for both long-range (i.e., logarithmic) and short-range (i.e., screened Coulomb) interparticle interaction. Decreasing the range of the interparticle interaction increases the eccentricity of the confinement potential for which internal intershell melting can occur. PMID:17025594

Apolinario, S W S; Partoens, B; Peeters, F M

2006-09-01

341

The Common Geometry Module (CGM)  

Microsoft Academic Search

The Common Geometry Module (CGM) is a code library which provides geometry functionality used for mesh generation and other applications. This functionality includes that commonly found in solid modeling engines, like geometry creation, query and modification; CGM also includes capabilities not commonly found in solid modeling engines, like geometry decomposition tools and support for shared material interfaces. CGM is built

Tautges; Timothy James

2004-01-01

342

Magnetic Confinement Fusion Energy Research.  

National Technical Information Service (NTIS)

Controlled Thermonuclear Fusion offers probably the only relatively clean energy solution with completely inexhaustible fuel and unlimited power capacity. The scientific and technological problem consists in magnetically confining a hot, dense plasma (pre...

H. Grad

1977-01-01

343

Layering transition in confined silicon.  

PubMed

The structure of quasi-2D liquid silicon confined to slit nanopores has been investigated using molecular dynamics (MD) simulations. An obvious structural change from a low-density low-coordinated liquid to a high-density highly coordinated liquid has been found in the confined silicon with the increase of the slit size. This kind of structural transition results from layering in the confined silicon, which disappears with the increase of temperature. In the process of layering transition, the coordination distribution of quasi-2D liquid undergoes an evolutionary process from the initial non-uniform distribution to the final uniform distribution. In addition, our results also indicate that the increase of pressure will also induce a layering transition in the confined silicon. PMID:24609530

He, Yezeng; Li, Xiongying; Li, Hui; Jiang, Yanyan; Bian, Xiufang

2014-04-21

344

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

345

GEOMETRY, TENTATIVE GUIDES.  

ERIC Educational Resources Information Center

PRESENTED IS A FUSED COURSE IN PLANE, SOLID, AND COORDINATE GEOMETRY. ELEMENTARY SET THEORY, LOGIC, AND THE PRINCIPLE OF SEPARATION PROVIDE UNIFYING THREADS THROUGHOUT THE TEXT. THE TWO CURRICULUM GUIDES HAVE BEEN PREPARED FOR USE WITH TWO DIFFERENT TEXTS. EITHER CURRICULUM GUIDE MAY BE USED DEPENDING UPON THE CHOICE OF THE TEACHER AND THE NEEDS…

KLIER, KATHERINE M.

346

Seminar in Geometry  

NSDL National Science Digital Library

This course involves students taking turn giving lectures on geometry topics. Subjects such as Gauss maps, minimal surfaces and manifolds and geodesics were covered in the lectures. Course materials include lecture notes as well as student projects and examples. MIT presents OpenCourseWare as free educational material online. No registration or enrollment is required to use the materials.

Carberry, Emma Elizabeth, 1974-

2010-12-27

347

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

348

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.

Ltd, Lighthouse L.

2013-10-14

349

Geometry and physics  

PubMed Central

We review the remarkably fruitful interactions between mathematics and quantum physics in the past decades, pointing out some general trends and highlighting several examples, such as the counting of curves in algebraic geometry, invariants of knots and four-dimensional topology.

Atiyah, Michael; Dijkgraaf, Robbert; Hitchin, Nigel

2010-01-01

350

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

351

Noncommutative Geometry and Reality.  

National Technical Information Service (NTIS)

We introduce the notion of real structure in our spectral geometry. This notion is motivated by Atiyah's KR-theory and by Tomita's involution J. It allows us to remove two unpleasant features of the 'Connes-Lott' description of the standard model, namely ...

A. Connes

1995-01-01

352

Noncommutative Projective Geometry  

Microsoft Academic Search

\\u000a The aim of the three lectures I gave at Constanta was to introduce the audience to the theory of “Noncommutative Pro- jective\\u000a Geometry.” The material for these talks was taken from the survey article (6) and so this abstract will give a very brief discussion of this material leaving the reader to see (6) for the details.

J. T. Stafford

353

Prolog and Geometry Projects  

Microsoft Academic Search

Prolog is a userful tool for geometry and graphics implementations because its primitives, such as unification, match the requiements of many geometric algorithms. During the last two years, we have implemented programs to solve several problems in Prolog, including a subset of the Graphical Kernel System, convex-hull calculation, planar graph traversal, recognition of groupings of objects, Boolean combinations of polygons

W. R. Franklin; P. Y. F. Wu; Sumitro Samaddar; Margaret Nichols

1986-01-01

354

Gravity is Geometry.  

ERIC Educational Resources Information Center

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

MacKeown, P. K.

1984-01-01

355

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

356

Making Solid Geometry Solid.  

ERIC Educational Resources Information Center

Allowing students to use a polystyrene cutter to fashion their own three-dimensional models is suggested as a means of allowing individuals to experience problems and develop ideas related to solid geometry. A list of ideas that can lead to mathematical discovery is provided. (MP)

Hartz, Viggo

1981-01-01

357

Geometry of spinor regularization  

NASA Technical Reports Server (NTRS)

The Kustaanheimo theory of spinor regularization is given a new formulation in terms of geometric algebra. The Kustaanheimo-Stiefel matrix and its subsidiary condition are put in a spinor form directly related to the geometry of the orbit in physical space. A physically significant alternative to the KS subsidiary condition is discussed. Derivations are carried out without using coordinates.

Hestenes, D.; Lounesto, P.

1983-01-01

358

Spinorial Geometry and Supergravity  

Microsoft Academic Search

In the main part of this thesis, we present the foundations and initial results of the Spinorial Geometry formalism for solving Killing spinor equations. This method can be used for any supergravity theory, although we largely focus on D=11 supergravity. The D=5 case is investigated in an appendix. The exposition provides a comprehensive introduction to the formalism, and contains background

JOSEPH J. GILLARD

2006-01-01

359

Topics in Computational Geometry.  

National Technical Information Service (NTIS)

Two problems in computational geometry are solved. The first is to characterize the behavior of the nearest-neighbor search algorithm based on the k-d tree data structure. The k-d tree is a data structure useful in classification and analysis of multidime...

J. E. Zolnowsky

1978-01-01

360

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.

Hsu, K J; Hsu, A J

1990-01-01

361

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

NASA Astrophysics Data System (ADS)

We report 2D confinement of 87Rb 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.; Biedermann, G. W.; Farrar, J. T.; Akin, T. G.; Krzyzewski, S. P.; Abraham, E. R. I.

2014-06-01

362

Collective motion of squirmers in a quasi-2D geometry  

NASA Astrophysics Data System (ADS)

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

ZöTtl, Andreas; Stark, Holger

2013-03-01

363

A geometric realization of confinement  

Microsoft Academic Search

We study the geometric realization of the Higgs phenomenon in type II string compactification on Calabi-Yau manifolds. The string description is most directly phrased in terms of confinement of magnetic flux, with magnetic charged states arising from D-branes wrapped around chains as opposed to cycles. The rest of the closed cycle of the D-brane world-volume is manifested as a confining

Brian R. Greene; David R. Morrison; Cumrun Vafa

1996-01-01

364

A geometric realization of confinement  

Microsoft Academic Search

We study the geometric realization of the Higgs phenomenon in type II string compactifications on Calabi-Yau manifolds. The string description is most directly phrased in terms of confinement of magnetic flux, with magnetic charged states arising from D-branes wrapped around chains as opposed to cycles. The rest of the closed cycle of the D-brane world-volume is manifested as a confining

Brian R. Greene; David R. Morrison; Cumrun Vafa

1996-01-01

365

2XIIB plasma confinement experiments  

Microsoft Academic Search

The paper discusses results of plasma confinement experiments in the 2XIIB magnetic mirror device. Experiments attempting to achieve field-reversal using neutral-beam injection in which the central magnetic field is reduced by 90% but field lines are not closed are reported. Experiments with different neutral-beam aiming show that at constant beta both electron temperature and the energy-confinement parameter increase at larger

T. C. Simonen; J. F. Clauser; F. H. Coensgen; D. L. Correll; W. F. Cummins; J. H. Foote; A. H. Futch; R. K. Goodman; D. P. Grubb; R. P. Drake

1979-01-01

366

Heterogeneous catalysis and confinement effects  

Microsoft Academic Search

The aim of this study is to highlight the impact of confinement effects in catalysis for reactants confined in small mesopores. Double bond isomerization of 1-hexene at 343K has been chosen as model reaction and mesostructured aluminosilicates of the MCM-41 type with the very same chemical composition (Si\\/Al=400±20) and varying pore sizes (2.3–9.3nm) were used as catalysts. Adsorption isotherms of

Stéphane Pariente; Philippe Trens; François Fajula; Francesco Di Renzo; Nathalie Tanchoux

2006-01-01

367

Solvent cavitation under solvophobic confinement  

NASA Astrophysics Data System (ADS)

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

Ashbaugh, Henry S.

2013-08-01

368

Scaling behaviour for the water transport in nanoconfined geometries  

PubMed Central

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

2014-01-01

369

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

370

Confinement of atoms under general boundary conditions  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

371

Geometries and materials for subwavelength surface plasmon modes  

NASA Astrophysics Data System (ADS)

Plasmonic waveguides can guide light along metal-dielectric interfaces with propagating wave vectors of greater magnitude than are available in free space and hence with propagating wavelengths shorter than those in vacuum. This is a necessary, rather than sufficient, condition for subwavelength confinement of the optical mode. By use of the reflection pole method, the two-dimensional modal solutions for single planar waveguides as well as adjacent waveguide systems are solved. We demonstrate that, to achieve subwavelength pitches, a metal-insulator-metal geometry is required with higher confinement factors and smaller spatial extent than conventional insulator-metal-insulator structures. The resulting trade-off between propagation and confinement for surface plasmons is discussed, and optimization by materials selection is described.

Zia, Rashid; Selker, Mark D.; Catrysse, Peter B.; Brongersma, Mark L.

2004-12-01

372

Cold Dipolar Gases in Quasi-One-Dimensional Geometries  

SciTech Connect

We analyze the physics of cold dipolar gases in quasi-one-dimensional geometries, showing that the confinement-induced scattering resonances produced by the transversal trapping are crucially affected by the dipole-dipole interaction. As a consequence, the dipolar interaction may drastically change the properties of quasi-1D dipolar condensates, even for situations in which the dipolar interaction would be completely overwhelmed by the short-range interactions in a 3D environment.

Sinha, S. [S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Kolkata 700098 (India); Santos, L. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstr. 2, D-30167 Hannover (Germany)

2007-10-05

373

Cylindrical geometry hall thruster  

DOEpatents

An apparatus and method for thrusting plasma, utilizing a Hall thruster with a cylindrical geometry, wherein ions are accelerated in substantially the axial direction. The apparatus is suitable for operation at low power. It employs small size thruster components, including a ceramic channel, with the center pole piece of the conventional annular design thruster eliminated or greatly reduced. Efficient operation is accomplished through magnetic fields with a substantial radial component. The propellant gas is ionized at an optimal location in the thruster. A further improvement is accomplished by segmented electrodes, which produce localized voltage drops within the thruster at optimally prescribed locations. The apparatus differs from a conventional Hall thruster, which has an annular geometry, not well suited to scaling to small size, because the small size for an annular design has a great deal of surface area relative to the volume.

Raitses, Yevgeny (Princeton, NJ); Fisch, Nathaniel J. (Princeton, NJ)

2002-01-01

374

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

375

Rényi entropy and geometry  

NASA Astrophysics Data System (ADS)

Entanglement entropy in even-dimensional conformal field theories (CFTs) contains well-known universal terms arising from the conformal anomaly. Rényi entropies are natural generalizations of the entanglement entropy that are much less understood. Above two spacetime dimensions, the universal terms in the Rényi entropies are unknown for general entangling geometries. We conjecture a new structure in the dependence of the four-dimensional Rényi 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 Rényi entropies across cylindrical entangling surfaces to corresponding three-dimensional massive Rényi entropies across circular entangling surfaces. Our numerical technique also allows us to directly probe other interesting aspects of three-dimensional Rényi entropy, including the massless renormalized Rényi entropy and calculable contributions to the perimeter law.

Lee, Jeongseog; McGough, Lauren; Safdi, Benjamin R.

2014-06-01

376

Brane Universe: Global Geometry  

SciTech Connect

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

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

2010-06-23

377

Noncommutative Geometry Year 2000  

Microsoft Academic Search

\\u000a Our geometric concepts evolved first through the discovery of Non-Euclidean geometry. The discovery of quantum mechanics in\\u000a the form of the noncommuting coordinates on the phase space of atomic systems entails an equally drastic evolution. We describe\\u000a a basic construction which extends the familiar duality between ordinary spaces and commutative algebras to a duality between\\u000a Quotient spaces and Noncommutative algebras.

Alain Connes

2000-01-01

378

Gravity from Noncommutative Geometry  

Microsoft Academic Search

We introduce the linear connection in the noncommutative geometry model of\\u000athe product of continuous manifold and the discrete space of two points. We\\u000adiscuss its metric properties, define the metric connection and calculate the\\u000acurvature. We define also the Ricci tensor and the scalar curvature. We find\\u000athat the latter differs from the standard scalar curvature of the manifold

Andrzej Sitarz

1994-01-01

379

Curved geometry and Graphs  

NASA Astrophysics Data System (ADS)

Quantum Graphity is an approach to quantum gravity based on a background independent formulation of condensed matter systems on graphs. We summarize recent results obtained on the notion of emergent geometry from the point of view of a particle hopping on the graph. We discuss the role of connectivity in emergent Lorentzian perturbations in a curved background and the Bose-Hubbard (BH) model defined on graphs with particular symmetries.

Caravelli, Francesco

2012-05-01

380

Isolation and confinement - Considerations for colonization  

NASA Technical Reports Server (NTRS)

This paper discusses three types of isolation (sensory/perceptual, temporal, and social) that could adversely affect mankind in space. The literature dealing with laboratory and field experiments relevant to these areas is summarized and suggestions are given for dealing with these problems within the space colony community. Also, consideration is given to the potential effects of physical confinement and the need for usable space. Finally, a modification of Maslow's hierarchy of needs is proposed as a theoretical framework to understand and investigate mankind's psychological needs in space.

Akins, F. R.

1978-01-01

381

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

382

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

383

Persistent current through a semiconductor quantum dot with Gaussian confinement  

NASA Astrophysics Data System (ADS)

The persistent diamagnetic current in a GaAs quantum dot with Gaussian confinement is calculated. It is shown that except at very low temperature or at high temperature, the persistent current increases with decreasing temperature. It is also shown that as a function of the dot size, the diamagnetic current exhibits a maximum at a certain confinement length. It is furthermore shown that for a shallow potential, the persistent current shows an interesting maximum structure as a function of the depth of the potential. At low temperature, the peak structure is pretty sharp but becomes broader and broader with increasing temperature.

Boyacioglu, Bahadir; Chatterjee, Ashok

2012-09-01

384

The Common Geometry Module (CGM): A Generic, Extensible Geometry Interface  

Microsoft Academic Search

Geometry modeling has in the past five years emerge d as a commodity capability; several geometry model ing engines are available which provide largely the same capability , and most high-end CAD systems provide access to their geometry through APIs. However, subtle differences still exist betw een these modelers, both at the syntax level and in the underlying topological models.

Timothy J. Tautges; TIMOTHY J

2000-01-01

385

Hydrodynamics of Confined Active Fluids  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

386

Transport in Fermi Liquids Confined by Rough Walls  

NASA Astrophysics Data System (ADS)

I present theoretical calculations of the thermal conductivity of Fermi liquid ^3 He confined to a slab of thickness of order ˜ 100 nm. The effect of the roughness of the confining surfaces is included directly in terms of the surface roughness power spectrum which may be determined experimentally. Transport at low temperatures is limited by scattering off rough surfaces and evolves into the known high-temperature limit in bulk through an anomalous regime in which both inelastic quasiparticle scattering and elastic scattering off the rough surface coexist. I show preliminary calculations for the coefficients of thermal conductivity. These studies are applicable in the context of electrical transport in metal nanowires as well as experiments that probe the superfluid phase diagram of liquid ^3 He in a slab geometry.

Sharma, Priya

2014-04-01

387

Confinement induces actin flow in a meiotic cytoplasm  

PubMed Central

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

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

2012-01-01

388

Dipolar confinement-induced resonances of ultracold gases in waveguides.  

PubMed

We develop a nonperturbative theoretical framework to treat collisions with generic anisotropic interactions in quasi-one-dimensional geometries. Our method avoids the limitations of pseudopotential theory and allows us to include accurately long-range anisotropic interactions. For ultracold dipolar collisions in a harmonic waveguide we predict dipolar confinement-induced resonances (DCIRs) which are attributed to different angular momentum states. The analytically derived resonance condition reveals in detail the interplay of the confinement with the anisotropic nature of the dipole-dipole interactions. The results are in excellent agreement with ab initio numerical calculations confirming the robustness of the presented approach. The exact knowledge of the positions of DCIRs may pave the way for the experimental realization of, e.g., Tonks-Girardeau-like or super-Tonks-Girardeau-like phases in effective one-dimensional dipolar gases. PMID:24237514

Giannakeas, P; Melezhik, V S; Schmelcher, P

2013-11-01

389

Dipolar Confinement-Induced Resonances of Ultracold Gases in Waveguides  

NASA Astrophysics Data System (ADS)

We develop a nonperturbative theoretical framework to treat collisions with generic anisotropic interactions in quasi-one-dimensional geometries. Our method avoids the limitations of pseudopotential theory and allows us to include accurately long-range anisotropic interactions. For ultracold dipolar collisions in a harmonic waveguide we predict dipolar confinement-induced resonances (DCIRs) which are attributed to different angular momentum states. The analytically derived resonance condition reveals in detail the interplay of the confinement with the anisotropic nature of the dipole-dipole interactions. The results are in excellent agreement with ab initio numerical calculations confirming the robustness of the presented approach. The exact knowledge of the positions of DCIRs may pave the way for the experimental realization of, e.g., Tonks-Girardeau-like or super-Tonks-Girardeau-like phases in effective one-dimensional dipolar gases.

Giannakeas, P.; Melezhik, V. S.; Schmelcher, P.

2013-11-01

390

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

391

Stability of a Dense Plasma Confined by a Rotating Magnetic Field  

Microsoft Academic Search

The stability of a dense plasma (negligible skin depth) confined by a rotating magnetic field which is parallel to the surface is analyzed for plane and cylindrical geometries. This analysis culminates in an integrodifferential equation for each mode of deformation. Specific properties of the plasma enter only through the normal acoustic impedance. The concept of average stability is introduced. Very

Francis Troyon

1967-01-01

392

Confining the scalar field of the Kaluza-Klein wormhole soliton  

SciTech Connect

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

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

1989-08-01

393

Iqens study of the influence of confinement on diffusional dynamics of propylene glycol  

Microsoft Academic Search

The modification, compared to the bulk state, of the dynamics of liquids in confined geometry has attracted considerable interest in scientific research, also because of the close connection with many relevant technological problems, such as the building of optical switches, membrane separation, catalysis and tertiary oil recovery.We report the preliminary results of an Incoherent Quasi Elastic Neutron Scattering (IQENS) investigation

V. Crupi; A. J. Dianoux; F. Longo; D. Majolino; P. Migliardo; V. Venuti

2005-01-01

394

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

SciTech Connect

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

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

2011-09-01

395

Complex Plasmas in Narrow Channels: Impact of Confinement on the Local Order  

SciTech Connect

Two-dimensional (2D) and three-dimensional (3D) quasi-equilibrium configurations of a complex (dusty) plasma in narrow channels are investigated using the molecular dynamics simulations for various confining potentials (confinements). The dynamics of the microparticles is described within the framework of a Langevin thermostat with allowance for the pair interaction between charged particles, which is described by a screened Coulomb potential (Yukawa potential). Two types of confinement: the parabolic electrostatic potential and hard elastic wall are considered. It is shown that the confinement strongly affects the crystallization and the local order of the microparticles in the system under consideration; in particular, the appearance of a new quasicrystalline phase induced by the hard wall confinement is revealed in 3D case.

Klumov, B. A. [Max-Planck-Institut fuer Extraterrestrische Physik, D-85740 Garching (Germany)

2008-10-15

396

Geometry: Grades 10-12.  

ERIC Educational Resources Information Center

Behavioral objectives, each accompanied by six sample test items, for secondary school geometry are presented. Objectives were determined by surveying the most widely used secondary school geometry textbooks, and cover 14 major categories of geometry, with sections on set theory and introductory trigonometry. Answers are provided. Categories…

Instructional Objectives Exchange, Los Angeles, CA.

397

Computer-Aided Geometry Modeling  

NASA Technical Reports Server (NTRS)

Techniques in computer-aided geometry modeling and their application are addressed. Mathematical modeling, solid geometry models, management of geometric data, development of geometry standards, and interactive and graphic procedures are discussed. The applications include aeronautical and aerospace structures design, fluid flow modeling, and gas turbine design.

Shoosmith, J. N. (compiler); Fulton, R. E. (compiler)

1984-01-01

398

Differential geometry based multiscale models.  

PubMed

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

Wei, Guo-Wei

2010-08-01

399

Peptide encapsulation regulated by the geometry of carbon nanotubes.  

PubMed

In this work the encapsulation of an ?-helical peptide in single carbon nanotubes (CNTs) with similar diameter and length but different geometry (armchair and zigzag) was investigated through molecular dynamics simulations and free energy calculations. Our simulation results showed that in vacuo it makes no evident difference whether the investigated peptide is encapsulated in armchair or zigzag CNTs; however, in aqueous solution the armchair CNT encapsulates the peptide remarkably easier than the zigzag CNT does. A detailed analysis revealed that the equilibrium conformation of the water molecules inside the CNTs with varying geometry mediates the peptide encapsulation. It suggests that the water molecules play an important role in regulating behaviors of biomolecules in bio-systems. Then the impact of the CNT geometry on the conformational changes of the confined peptide was studied. Analyses of secondary structures showed the ?-helix of the peptide could be better maintained in the zigzag CNT. PMID:24290699

Zhang, Zhi-Sen; Kang, Yu; Liang, Li-Jun; Liu, Ying-Chun; Wu, Tao; Wang, Qi

2014-02-01

400

Effect of catheter tip-tissue surface contact on three-dimensional left atrial and pulmonary vein geometries: potential anatomic distortion of 3D ultrasound, fast anatomical mapping, and merged 3D CT-derived images.  

PubMed

Anatomic Distortion of 3D Mapping.?Background: Although catheter tip-tissue contact is known as a reliable basis for mapping and ablation of atrial fibrillation (AF), the effects of different mapping methods on 3-dimensional (3D) map configuration remain unknown. Methods and Results: Twenty AF patients underwent Carto-based 3D ultrasound (US) evaluation. Left atrium (LA)/pulmonary vein (PV) geometry was constructed with the 3D US system. The resulting geometry was compared to geometries created with a fast electroanatomical mapping (FAM) algorithm and 3D US merged with computed tomography (merged 3D US-CT). The 3D US-derived LA volumes were smaller than the FAM- and merged 3D US-CT-derived volumes (75 ± 21 cm(3) vs 120 ± 20 cm(3) and 125 ± 25 cm(3) , P < 0.0001 for both). Differences in anatomic PV orifice fiducials between 3D US- and FAM- and merged 3D US-CT-derived geometries were 6.0 (interquartile range 0-9.3) mm and 4.1 (0-7.0) mm, respectively. Extensive encircling PV isolation guided by 3D US images with real-time 2D intracardiac echocardiography-based visualization of catheter tip-tissue contact generated ablation point (n = 983) drop-out at 1.9 ± 3.8 mm beyond the surface of the 3D US-derived LA/PV geometry. However, these same points were located 1.5 ± 5.4 and 0.4 ± 4.1 mm below the FAM- and merged 3D US-CT-derived surfaces. Conclusions: Different mapping methods yield different 3D geometries. When AF ablation is guided by 3D US-derived images, ablation points fall beyond the 3D US surface but below the FAM- or merged 3D US-CT-derived surface. Our data reveal anatomic distortion of 3D images, providing important information for improving the safety and efficacy of 3D mapping-guided AF ablation. (J Cardiovasc Electrophysiol, Vol. 24, pp. 259-266, March 2013). PMID:23279593

Okumura, Yasuo; Watanabe, Ichiro; Kofune, Masayoshi; Nagashima, Koichi; Sonoda, Kazumasa; Mano, Hiroaki; Ohkubo, Kimie; Nakai, Toshiko; Sasaki, Naoko; Kogawa, Rikitake; Maruyama, Ayako; Hirayama, Atsushi

2013-03-01

401

Open-ended magnetic confinement systems for fusion  

SciTech Connect

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

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

1995-05-01

402

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

403

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

PubMed

A magnetospheric configuration gives rise to various peculiar plasma phenomena that pose conundrums to astrophysical studies; at the same time, innovative technologies may draw on the rich physics of magnetospheric plasmas. We have created a "laboratory magnetosphere" with a levitating superconducting ring magnet. Here we show that charged particles (electrons) self-organize a stable vortex, in which particles diffuse inward to steepen the density gradient. The rotating electron cloud is sustained for more than 300 s. Because of its simple geometry and self-organization, this system will have wide applications in confining single- and multispecies charged particles. PMID:20867249

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

2010-06-11

404

First-order Dyson coordinates and geometry.  

PubMed

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

Hermes, Matthew R; Hirata, So

2013-08-15

405

Proterozoic Geomagnetic Field Geometry  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

406

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

407

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

408

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

409

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

410

Classical energy confinement in Alcator  

Microsoft Academic Search

Nearly classical behaviour, from the viewpoint of energy confinement, is observed in the Alcator tokamak. A study of the energy balance of the central core of the plasma has been carried out in the regime 1014 cm-3 <=n¯e <= 6 × 1014 cm-3, 130 kA <= IP <= 160 kA and BT = 6 T. At the higheet densities the

A. Gondhalekar; D. Overskei; R. R. Parker

1979-01-01

411

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

412

Transitions Within a Vertically Confined Plasma Crystal  

NASA Astrophysics Data System (ADS)

Dusty plasmas consist of an ionized gas containing small (usually negatively charged) particles. Dusty plasmas are of interest in both astrophysics and space physics as well as in research in plasma processing and nanofabrication. In this work, the formation of plasma crystals confined in an external one-dimensional parabolic potential well is simulated for a normal experimental environment employing a computer code called BOX_TREE. Such crystals are layered systems, with each layer a 2D lattice composed of grain particles. The number of layers is dependent in part upon the external potential parameter. The transition from 1 to 2 layers is specifically analyzed with dispersion relations for the vertical dust lattice wave obtained at the transition point and the transition shown to be induced by the vertical dust lattice instability.

Qiao, Ke; Hyde, Truell

2004-10-01

413

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

414

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

415

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

416

Simulation of spheromak evolution and energy confinement  

SciTech Connect

Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and model the plasma energy confinement. The physics of magnetic reconnection during formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code [C. R. Sovinec, A. H. Glasser, T. A. Gianakon, D. C. Barnes, R. A. Nebel, S. E. Kruger, D. D. Schnack, S. J. Plimpton, A. Tarditi, and M. S. Chu, J. Comput. Phys. 195, 355 (2004)]. The simulation results are compared to data from the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. The simulation results are tracking SSPX with increasing fidelity (e.g., improved agreement with measured magnetic fields, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the experimental geometry, the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations confirm that controlling the magnetic fluctuations is influenced by the current drive history and by matching the gun current in sustainment approximately to the value corresponding to the eigenvalue in the flux-conserver for the parallel current in a force-free equilibrium.

Cohen, B.I.; Hooper, E.B.; Cohen, R.H.; Hill, D.N.; McLean, H.S.; Wood, R.D.; Woodruff, S.; Sovinec, C.R.; Cone, G.A. [University of California, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706-1609 (United States)

2005-05-15

417

Simulation of Spheromak Evolution and Energy Confinement  

SciTech Connect

Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and that model the energy confinement of the plasma. The physics of magnetic reconnection during spheromak formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code. The simulation results are compared to data from the SSPX spheromak experiment at the Lawrence Livermore National Laboratory. The simulation results are tracking the experiment with increasing fidelity (e.g., improved agreement with measurements of the magnetic field, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the geometry of the experiment (plasma gun and flux conserver), the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations are providing a better understanding of the dominant physics in SSPX, including when the flux surfaces close and the mechanisms limiting the efficiency of electrostatic drive.

Cohen, B; Hooper, E; Cohen, R; Hill, D; McLean, H; Wood, R; Woodruff, S; Sovinec, C; Cone, G

2004-11-09

418

Simulation of Spheromak Evolution and Energy Confinement  

SciTech Connect

Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and that model the energy confinement of the plasma. The physics of magnetic reconnection during spheromak formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code. The dimensional, simulation results are compared to data from the SSPX spheromak experiment at the Lawrence Livermore National Laboratory. The simulation results are tracking the experiment with increasing fidelity (e.g., improved agreement with measurements of the magnetic field, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the geometry of the experiment (plasma gun and flux conserver), the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations are providing a better understanding of the dominant physics in SSPX, including when the flux surfaces close and the mechanisms limiting the efficiency of electrostatic drive.

Cohen, B; Hooper, E; Cohen, R; Hill, D; McLean, H; Wood, R; Woodruff, S

2004-11-12

419

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

420

Progress toward ignition and burn propagation in inertial confinement fusion  

Microsoft Academic Search

To achieve efficient inertial confinement fusion one must produce a small hot spot within the imploding target from which thermonuclear burn can ignite. For the past decades, scientists throughout the world have pursued the dream of controlled thermonuclear fusion. The attraction of this goal is the enormous energy that is potentially available in fusion fuels and the view of fusion

John D. Lindl; E. M. Campbell; R. L. McCrory

1992-01-01

421

Electrostatic plasma-confinement experiments in a tandem mirror system  

Microsoft Academic Search

Results from the tandem mirror experiment are described. The configuration of axial density and potential profiles are created and sustained by neutral-beam injection and gas fueling. Plasma confinement in the center cell is shown to be improved by the end plugs by as much as a factor of 9. The electron temperature is higher than that achieved in our earlier

F. H. Coensgen; C. A. Anderson; T. A. Casper; J. F. Clauser; W. C. Condit; D. L. Correll; W. F. Cummins; J. C. Davis; R. P. Drake; J. H. Foote; A. H. Futch; R. K. Goodman; D. P. Grubb; G. A. Hallock; R. S. Hornady; A. L. Hunt; B. G. Logan; R. H. Munger; W. E. Nexsen; T. C. Simonen; D. R. Slaughter; B. W. Stallard; O. T. Strand

1980-01-01

422

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

423

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

424

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

425

Measuring the Probability Density of Quantum Confined States  

NASA Astrophysics Data System (ADS)

We show that it is possible to measure the probability density of a quantum-confined state using resonant magnetotunneling. We have measured the probability densities of the lowest three bound states formed in a semiconductor nanostructure and show that they are eigenstates of a parabolic potential.

Beton, P. H.; Wang, J.; Mori, N.; Eaves, L.; Main, P. C.; Foster, T. J.; Henini, M.

1995-09-01

426

Geometry from Gauge Theory  

SciTech Connect

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

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

2008-07-28

427

Null twisted geometries  

NASA Astrophysics Data System (ADS)

We define and investigate a quantization of null hypersurfaces in the context of loop quantum gravity on a fixed graph. The main tool we use is the parametrization of the theory in terms of twistors, which has already proved useful in discussing the interpretation of spin networks as the quantization of twisted geometries. The classical formalism can be extended in a natural way to null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra with spacelike faces, and SU(2) by the little group ISO(2). The main difference is that the simplicity constraints present in the formalism are all first class, and the symplectic reduction selects only the helicity subgroup of the little group. As a consequence, information on the shapes of the polyhedra is lost, and the result is a much simpler, Abelian geometric picture. It can be described by a Euclidean singular structure on the two-dimensional spacelike surface defined by a foliation of spacetime by null hypersurfaces. This geometric structure is naturally decomposed into a conformal metric and scale factors, forming locally conjugate pairs. Proper action-angle variables on the gauge-invariant phase space are described by the eigenvectors of the Laplacian of the dual graph. We also identify the variables of the phase space amenable to characterize the extrinsic geometry of the foliation. Finally, we quantize the phase space and its algebra using Dirac's algorithm, obtaining a notion of spin networks for null hypersurfaces. Such spin networks are labeled by SO(2) quantum numbers and are embedded nontrivially in the unitary, infinite-dimensional irreducible representations of the Lorentz group.

Speziale, Simone; Zhang, Mingyi

2014-04-01

428

Properties of non-neutral electron plasmas confined with a magnetic mirror field  

SciTech Connect

A low energy non-neutral electron plasma was confined with a magnetic mirror field and an electrostatic potential to investigate the basic confinement properties of a simple magnetic mirror trap. The mirror ratio of the magnetic field was increased up to 5. As expected the confinement time became longer as a function of the mirror ratio. The axially integrated radial density profiles in equilibrium were measured and compared with a theoretical model. The axial electrostatic oscillations of a confined electron plasma were also observed.

Higaki, H.; Ito, K.; Saiki, W.; Omori, Y.; Okamoto, H. [Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8530 (Japan)

2007-06-15

429

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...

430

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

Microsoft Academic Search

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

Yibin Gu

1998-01-01

431

Schwinger pair production rate in confining theories via holography  

NASA Astrophysics Data System (ADS)

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=Ec, above which there is no potential barrier and particles are freely generated, and (ii) E=Es, 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.

Kawai, Daisuke; Sato, Yoshiki; Yoshida, Kentaroh

2014-05-01

432

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

433

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

434

Emergent phenomena in manganites under spatial confinement  

NASA Astrophysics Data System (ADS)

It is becoming increasingly clear that the exotic properties displayed by correlated electronic materials such as high-Tc superconductivity in cuprates, colossal magnetoresistance (CMR) in manganites, and heavy-fermion compounds are intimately related to the coexistence of competing nearly degenerate states which couple simultaneously active degrees of freedom—charge, lattice, orbital, and spin states. The striking phenomena associated with these materials are due in a large part to spatial electronic inhomogeneities, or electronic phase separation (EPS). In many of these hard materials, the functionality is a result of the soft electronic component that leads to self-organization. In this paper, we review our recent work on a novel spatial confinement technique that has led to some fascinating new discoveries about the role of EPS in manganites. Using lithographic techniques to confine manganite thin films to length scales of the EPS domains that reside within them, it is possible to simultaneously probe EPS domains with different electronic states. This method allows for a much more complete view of the phases residing in a material and gives vital information on phase formation, movement, and fluctuation. Pushing this trend to its limit, we propose to control the formation process of the EPS using external local fields, which include magnetic exchange field, strain field, and electric field. We term the ability to pattern EPS “electronic nanofabrication." This method allows us to control the global physical properties of the system at a very fundamental level, and greatly enhances the potential for realizing true oxide electronics.

Shen, Jian; Z. Ward, T.; F. Yin, L.

2013-01-01

435

Physics of magnetic confinement fusion  

NASA Astrophysics Data System (ADS)

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

Wagner, F.

2013-06-01

436

Learning Geometry in Georgian England  

NSDL National Science Digital Library

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

Porcher, Thomas; Wardhaugh, Benjamin, 1979-

2012-09-21

437

Geometric Modeling and Industrial Geometry  

NSDL National Science Digital Library

The Geometric Modeling and Industrial Geometry group is part of the Institute of Discrete Mathematics and Geometry at the Vienna University of Technology. The group's goal is "to bridge the gap between academic and industrial research in geometry" by "performing application oriented fundamental research and industrial research closely connected to geometry." Its work currently emphasizes the recognition, inspection, manipulation, and design of geometric shapes. Short descriptions of the group's work and some articles are available on the academic research, covering topics such as Computational Line Geometry, Laguerre Geometry, approximation in the space of planes, the isophotic metric, and swept volumes. Visitors can also read about the group's industrial research on 3-D Computer Vision, reverse Engineering, and Industrial Inspection. The Application Areas section includes more articles and provides actual data from some of the objects it has scanned along with the resulting 3-D images.

438

Inertial-confinement-fusion targets  

SciTech Connect

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

Hendricks, C.D.

1981-11-16

439

Feynman amplitudes with confinement included  

SciTech Connect

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

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

2009-07-15

440

Two flavor QCD and confinement  

Microsoft Academic Search

We argue that the order of the chiral transition for Nf=2 is a sensitive probe of the QCD vacuum, in particular, of the mechanism of color confinement. A strategy is developed to investigate the order of the transition by use of finite size scaling analysis. An in-depth numerical investigation is performed with staggered fermions on lattices with Lt=4 and Ls=12,

Massimo D'Elia; Adriano di Giacomo; Claudio Pica

2005-01-01

441

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

442

Gluon Confinement and Quantum Censorship  

NASA Astrophysics Data System (ADS)

The dynamical Maxwell-cut, a degeneracy is shown to be a precursor of condensate in the ?4 and the sine-Gordon models. The difference of the way the Maxwell-cut is obtained is pointed out and quantum censorship, the generation of semiclassically looking phenomenon by loop-corrections is conjectured in the sine-Gordon model. It is argued that quantum censorship and gluon confinement exclude each other.

Polónyi, János

2011-04-01

443

Neutron Assay System for Confinement Vessel Disposition  

Microsoft Academic Search

Los Alamos National Laboratory has a number of spherical confinement vessels (CVs) remaining from tests involving nuclear materials. These vessels have an inner diameter of 6 feet with 1-inch thick steel walls. The goal of the Confinement Vessel Disposition (CVD) project is to remove debris and reduce contamination inside the CVs. The Confinement Vessel Assay System (CVAS) was developed to

Katherine C. Frame; Mark M. Bourne; William J. Crooks; Louise Evans; Douglas R. Mayo; David K. Miko; William R. Salazar; Sy Stange; Jose I. Valdez; Georgiana M. Vigil

2012-01-01

444

Comparison of reach-scale morphologic adjustment in confined and unconfined alluvial mountain rivers, Olympic Peninsula, Washington  

NASA Astrophysics Data System (ADS)

Over human time scales (10-1 - 102 yr), alluvial mountain rivers respond to changes in sediment input and discharge through adjustments in reach-scale morphology (width, depth, grain size, and, to some degree, slope). Channel confinement (valley-width relative to the bankfull channel width) in these systems can strongly influence the magnitude of channel response. We compared channel responsiveness to flood events (50-100 yr) within the last 5 years in unconfined and confined valley segments on the Olympic Peninsula, western Washington. Field measurements of cross-sectional averaged width and depth in 20 confined and 20 unconfined valleys are compared to the bankfull dimensions predicted from established downstream hydraulic geometry relationships for the region. We expect that measured bankfull geometry of confined reaches will be significantly greater than the predicted bankfull dimensions, which would suggest that the morphology of confined channels is more responsive to flood events. In unconfined channels floodplains are large enough to disperse over-bank flows, which can limit the effect of peak discharges on channel morphology, whereas confined channels are forced to disperse the extra energy exerted by peak flows into increased shear stress along their bed and banks. Results from this study can aid modeling efforts to predict future changes in channel geometry and aquatic habitat in response to climate change or land use at the basin scale.

Micheletty, P. D.; Goode, J.; Pierce, J. L.; Buffington, J. M.

2011-12-01

445

Industrial Applications to the Inertial Electrostatic Confinement Configuration  

NASA Astrophysics Data System (ADS)

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 the spherical symmetric configuration and the convergent non-Maxwellian ion beams IEC presents a unique energy spectrum that could enhance or enable a variety of industrial plasma applications from material processing to light sources. This work will present the possible industrial applications of the IEC configuration and initial characterization of an IEC source for these applications. The current industrial applications under consideration include materials synthesis, processing, and light production.

Martin, Elijah; Shannon, Steve; Bourham, Mohamed

2009-10-01

446

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

SciTech Connect

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

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

1996-03-01

447

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

448

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

449

Subwavelength confined terahertz waves on planar waveguides using metallic gratings.  

PubMed

A terahertz plasmonic waveguide is experimentally demonstrated using a plastic ribbon waveguide integrated with a diffraction metal grating to approach subwavelength-scaled confinement and long-distance delivery. Appropriately adjusting the metal-thickness and the periodical slit width of a grating greatly improves both guiding ability and field confinement in the hybrid waveguide structure. The measured lateral decay length of the bound terahertz surface waves on the hybrid waveguide can be reduced to less than ?/4 after propagating a waveguide of around 50mm-long in length. The subwavelength-confined field is potentially advantageous to biomolecular sensing or membrane detection because of the long interaction length between the THz field and analytes. PMID:23482169

You, Borwen; Lu, Ja-Yu; Chang, Wei-Lun; Yu, Chin-Ping; Liu, Tze-An; Peng, Jin-Long

2013-03-11

450

Planetary Image Geometry Library  

NASA Technical Reports Server (NTRS)

The Planetary Image Geometry (PIG) library is a multi-mission library used for projecting images (EDRs, or Experiment Data Records) and managing their geometry for in-situ missions. A collection of models describes cameras and their articulation, allowing application programs such as mosaickers, terrain generators, and pointing correction tools to be written in a multi-mission manner, without any knowledge of parameters specific to the supported missions. Camera model objects allow transformation of image coordinates to and from view vectors in XYZ space. Pointing models, specific to each mission, describe how to orient the camera models based on telemetry or other information. Surface models describe the surface in general terms. Coordinate system objects manage the various coordinate systems involved in most missions. File objects manage access to metadata (labels, including telemetry information) in the input EDRs and RDRs (Reduced Data Records). Label models manage metadata information in output files. Site objects keep track of different locations where the spacecraft might be at a given time. Radiometry models allow correction of radiometry for an image. Mission objects contain basic mission parameters. Pointing adjustment ("nav") files allow pointing to be corrected. The object-oriented structure (C++) makes it easy to subclass just the pieces of the library that are truly mission-specific. Typically, this involves just the pointing model and coordinate systems, and parts of the file model. Once the library was developed (initially for Mars Polar Lander, MPL), adding new missions ranged from two days to a few months, resulting in significant cost savings as compared to rewriting all the application programs for each mission. Currently supported missions include Mars Pathfinder (MPF), MPL, Mars Exploration Rover (MER), Phoenix, and Mars Science Lab (MSL). Applications based on this library create the majority of operational image RDRs for those missions. A Java wrapper around the library allows parts of it to be used from Java code (via a native JNI interface). Future conversions of all or part of the library to Java are contemplated.

Deen, Robert C.; Pariser, Oleg

2010-01-01

451

Analytic Coleman-de Luccia Geometries  

SciTech Connect

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

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

2012-02-16