Physisorption in confined geometry
NASA Astrophysics Data System (ADS)
Derycke, I.; Vigneron, J. P.; Lambin, Ph.; Lucas, A. A.; Derouane, E. G.
1991-03-01
The physisorption of molecules in confined geometry, i.e., in pores of atomic size such as found in zeolites, has been investigated using a simple pairwise-additive Lennard-Jones potential and an effective-medium model. In a spherical geometry, it is found that the equilibrium distance D corresponding to the lowest equilibrium energy is reduced to about 90% of the pair equilibrium distance ?e. This originates from the increased dominance of long-range forces in the condensed state. The enhancement of the physisorption energy due to surface curvature and confinement effects reaches its maximum value of 5.05, relative to the flat surface, when D=0.899?e. This value must be compared to the factor of 8 which was derived previously [D. H. Everett and P. C. Powl, J. Chem. Soc. Faraday Trans. 1 72, 619 (1976); E. G. Derouane, J.-M. André, and A. A. Lucas, Chem. Phys. Lett. 137, 336 (1987)] using a simple van der Waals model neglecting repulsion forces. It is also concluded that molecules can be strongly trapped in pores which are substantially narrower than their free (gaseous phase) sizes, the situation of lowest energy corresponding to R=D=0.899?e and the sorption energy remaining negative down to R=D=0.749?e (R denotes the pore radius).
Freezing in confined geometries
NASA Technical Reports Server (NTRS)
Sokol, P. E.; Ma, W. J.; Herwig, K. W.; Snow, W. M.; Wang, Y.; Koplik, Joel; Banavar, Jayanth R.
1992-01-01
Results of detailed structural studies, using elastic neutron scattering, of the freezing of liquid O2 and D2 in porous vycor glass, are presented. The experimental studies have been complemented by computer simulations of the dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls. Results point to a new simple physical interpretation of freezing in confined geometries.
Diffusion in confined geometries.
Burada, P Sekhar; Hänggi, Peter; Marchesoni, Fabio; Schmid, Gerhard; Talkner, Peter
2009-01-12
Diffusive transport of particles or, more generally, small objects, is a ubiquitous feature of physical and chemical reaction systems. In configurations containing confining walls or constrictions, transport is controlled both by the fluctuation statistics of the jittering objects and the phase space available to their dynamics. Consequently, the study of transport at the macro- and nanoscales must address both Brownian motion and entropic effects. Herein we report on recent advances in the theoretical and numerical investigation of stochastic transport occurring either in microsized geometries of varying cross sections or in narrow channels wherein the diffusing particles are hindered from passing each other (single-file diffusion). For particles undergoing biased diffusion in static suspension media enclosed by confining geometries, transport exhibits intriguing features such as 1) a decrease in nonlinear mobility with increasing temperature or also 2) a broad excess peak of the effective diffusion above the free diffusion limit. These paradoxical aspects can be understood in terms of entropic contributions resulting from the restricted dynamics in phase space. If, in addition, the suspension medium is subjected to external, time-dependent forcing, rectification or segregation of the diffusing Brownian particles becomes possible. Likewise, the diffusion in very narrow, spatially modulated channels is modified via contact particle-particle interactions, which induce anomalous sub-diffusion. The effective sub-diffusion constant for a driven single file also develops a resonance-like structure as a function of the confining coupling constant. PMID:19025741
Reactive collisions in confined geometries
Zbigniew Idziaszek; Krzysztof Jachymski; Paul S. Julienne
2015-02-06
We consider low energy threshold reactive collisions of particles interacting via a van der Waals potential at long range in the presence of external confinement and give analytic formulas for the confinement modified scattering in such circumstances. The reaction process is described in terms of the short range reaction probability. Quantum defect theory is used to express elastic and inelastic or reaction collision rates analytically in terms of two dimensionless parameters representing phase and reactivity. We discuss the modifications to Wigner threshold laws for quasi-one-dimensional and quasi-two-dimensional geometries. Confinement-induced resonances are suppressed due to reactions and are completely absent in the universal limit where the short-range loss probability approaches unity.
Amoeboid motion in confined geometry
Wu, Hao; Hu, Wei-Fan; Farutin, Alexander; Rafaï, Salima; Lai, Ming-Chih; Peyla, Philippe; Misbah, Chaouqi
2015-01-01
Cells of the immune system, as well as cancer cells, migrating in confined environment of tissues undergo frequent shape changes (described as amoeboid motion) that enable them to move forward through these porous media without the assistance of adhesion sites. In other words, they perform amoeboid swimming (AS) while using extracellular matrices and cells of tissues as support. We introduce a simple model of AS in a confined geometry solved by means of 2D numerical simulations. We find that confinement promotes AS, unless being so strong that it restricts shape change amplitude. A straight AS trajectory in the channel is found to be unstable, and ample lateral excursions of the swimmer prevail. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. This is a spontaneous symmetry-breaking bifurcation. We find that there exists an optimal confinement for migration. We provide numerical results as...
Amoeboid motion in confined geometry
Hao Wu; Marine Thiébaut; Wei-Fan Hu; Alexander Farutin; Salima Rafaï; Ming-Chih Lai; Philippe Peyla; Chaouqi Misbah
2015-02-13
Cells of the immune system, as well as cancer cells, migrating in confined environment of tissues undergo frequent shape changes (described as amoeboid motion) that enable them to move forward through these porous media without the assistance of adhesion sites. In other words, they perform amoeboid swimming (AS) while using extracellular matrices and cells of tissues as support. We introduce a simple model of AS in a confined geometry solved by means of 2D numerical simulations. We find that confinement promotes AS, unless being so strong that it restricts shape change amplitude. A straight AS trajectory in the channel is found to be unstable, and ample lateral excursions of the swimmer prevail. For weak confinement, these excursions are symmetric, while they become asymmetric at stronger confinement, whereby the swimmer is located closer to one of the two walls. This is a spontaneous symmetry-breaking bifurcation. We find that there exists an optimal confinement for migration. We provide numerical results as well as scaling laws. This study raises the question of the relevance of these scenarios to complex situations encountered in vivo.
Particle swarms in confining geometries
NASA Astrophysics Data System (ADS)
Boomsma, Eric Robert
The transport of micro- and nano-particles in subsurface fluid deposits is an area of increasing interest due to the rising use of these particles for consumer and industrial purposes. Subsurface particle transport is complicated by the presence of fractures and fracture networks which govern the paths that particles will be able to take. In this thesis, subsurface particle transport will be investigated using particle swarms; collections of hydro-dynamically interacting particles which exhibit group behavior. The effects of fluid viscosity, particle properties, fracture geometry, and fracture aperture on swarm behavior were experimentally investigated. Swarm parameters were examined in time with an emphasis on geometry (height, width) and speed. Fracture geometry and aperture strongly affected these parameters. As a result, swarms in artificial fluid filled fractures displayed behavior that was not obvious or expected based on current theory. The most significant of these is what we have termed the "Enhanced Transport Regime." In uniform aperture fractures (two finite parallel plates), a range of apertures exists in which swarms travel more quickly than swarms in larger apertures. This behavior was observed in 3 separate experimental sets using different combinations of bulk fluid and particles. In fractures with variable apertures, swarms changed shape and speed in response to fracture features: accelerating/elongating when apertures increased and decelerating/expanding when apertures decreased. Experiments and numerical models were also undertaken to investigate the importance of finite fractures on particle swarms. Closing the open boundaries on the sides and bottom of the uniform aperture fracture had a dramatic effect on the behavior of particle swarms, either eliminating or enhancing the enhanced transport regime. This was investigated with a numerical model which determined that a finite fracture allows fluid to exit the confined space and requires that fluid re-enter at a different location. This creates global scale fluid flow that interacts with particle swarms in ways that are impossible if the fracture has infinite length. The experimental results demonstrate the critical importance of the collective nature of particle swarms. As collections of particles that are free to move relative to each other, swarms are able to respond to fractures in ways that a single spherical object cannot (i.e. expanding, contracting, elongating, etc.). Additionally, the finite sizes of the fractures used in these experiments play a significant role in governing the behavior of particle swarms.
Ionic liquids in confined geometries.
Perkin, Susan
2012-04-21
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
Compaction of granular material inside confined geometries
Benjy Marks; Bjørnar Sandnes; Guillaume Dumazer; Jon Alm Eriksen; Knut Jørgen Måløy
2015-05-15
In both nature and engineering, loosely packed granular materials are often compacted inside confined geometries. Here, we explore such behaviour in a quasi-two dimensional geometry, where parallel rigid walls provide the confinement. We use the discrete element method to investigate the stress distribution developed within the granular packing as a result of compaction due to the displacement of a rigid piston. We observe that the stress within the packing increases exponentially with the length of accumulated grains, and show an extension to current analytic models which fits the measured stress. The micromechanical behaviour is studied for a range of system parameters, and the limitations of existing analytic models are described. In particular, we show the smallest sized systems which can be treated using existing models. Additionally, the effects of increasing piston rate, and variations of the initial packing fraction, are described.
Polymer Statics and Dynamics in Confined Geometries
NASA Astrophysics Data System (ADS)
Kalb, Joshua; Chakraborty, Bulbul
2006-03-01
Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. Little is known about the possibility of inducing a glass transition through pure dimensional confinement. We are concerned with whether or not there is a critical value of the confining length scale. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain by measuring quantities such as the magnitude end-to-end vector, the radius of gyration, and single monomer motion (JACS 124, 20 (2004)). A primary question is whether the self-avoidance constraint manifests itself in a manner similar to kinetically constrained models of the glass transition. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.
Layer-by-layer assembly in confined geometries
DeRocher, Jonathan P
2011-01-01
The fundamental nature of layer-by-layer (LbL) assembly in confined geometries was investigated for a number of different chemical systems. The first part of this thesis concerns the modification of microfluidic and ...
Temperature-resonant cyclotron spectra in confined geometries.
Pototsky, A; Hänggi, P; Marchesoni, F; Savel'ev, S
2011-07-01
We consider a two-dimensional gas of colliding charged particles confined to finite size containers of various geometries and subjected to a uniform orthogonal magnetic field. The gas spectral densities are characterized by a broad peak at the cyclotron frequency. Unlike for infinitely extended gases, where the amplitude of the cyclotron peak grows linearly with temperature, here confinement causes such a peak to go through a maximum for an optimal temperature. In view of the fluctuation-dissipation theorem, the reported resonance effect has a direct counterpart in the electric susceptibility of the confined magnetized gas. PMID:21867113
Target Finding Mechanism of Microtubules in a Confined Geometry
NASA Astrophysics Data System (ADS)
Shojania Feizabadi, Mitra
2007-03-01
Discovery of a non-equilibrium dynamic of microtubules, called dynamic instability, raised this question: is stochastic polymerization dynamic of microtubules an advantage in the process of finding a chromosome as a target? Previous studies showed that compared to usual reversible polymerization, dynamic instability of microtubules with decreasing length distribution reduced the time required to find a target by several order of magnitude [1]. Dynamic Equations for growing and shrinking microtubules in a confined geometry is theoretically modeled by Govinden and Spillman [2]. This work calculates the target finding time for microtubules with exponentially increasing length distribution in a confined geometry. The efficiency of target finding mechanism based upon different dynamical parameters is discussed. [1] Holy TE, Leibler S. 1994, Proc. Natl. Acad. Sci. USA 91, 5682. [2] Govindan B, Spillman W. 2004, Phys. Rev. E 70, 032901.
Confinement of a Dirac Particle to a Hard-Wall Confining Potential Induced by Noninertial Effects
NASA Astrophysics Data System (ADS)
Bakke, K.
2013-01-01
In this contribution, we discuss the influence of noninertial effects on a Dirac particle in the Minkowski spacetime by showing that the geometry of the manifold can play the role of a hard-wall confining potential. Thus, we discuss a limit case where the relativistic bound states can be achieved in analogous way to having a Dirac particle confined to a quantum dot. We discuss the application of this mathematical model in studies of noninertial effects on condensed matter systems described by the Dirac equation, and compare the nonrelativistic limit of the energy levels with the spectrum of energy of a spin-½ particle confined to a quantum dot [E. Tsitsishvili et al., Phys. Rev. B70 (2004) 115316].
Confining potential in momentum space
NASA Technical Reports Server (NTRS)
Norbury, John W.; Kahana, David E.; Maung, Khin Maung
1992-01-01
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.
Excitons confined by split-gate potentials
NASA Astrophysics Data System (ADS)
Cocoletzi, Gregorio H.; Ulloa, Sergio E.
1994-03-01
Quasi-one-dimensional excitons in a GaAs-AlxGa1-xAs quantum well are studied; they are produced by an applied twin-split-gate potential which confines the particles laterally and allows free motion in one dimension. A variational approach is used to calculate the binding energies Eex and oscillator strength fex of these excitonic transitions as functions of the applied voltage and width of the induced potential wells. In the limit of high electrostatic confinement the excitons are strongly polarized and the system resembles a type II structure where electron and hole are spatially separated. The resulting Eex and fex show a strong dependence on applied voltage and structure width. Strong oscillations are found, which should be observed experimentally, as a consequence of subtle competition between confinement and Coulomb attraction.
A molecular dynamics study of freezing in a confined geometry
NASA Technical Reports Server (NTRS)
Ma, Wen-Jong; Banavar, Jayanth R.; Koplik, Joel
1992-01-01
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.
Binding of two helium atoms in confined geometries
Kilic, S. [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik] [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik; [Univ. of Split (Croatia). Faculty of Natural Sciences; Krotscheck, E.; Zillich, R. [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik] [Johannes Kepler Univ., Linz (Austria). Inst. fuer Theoretische Physik
1999-08-01
The authors carry out a comprehensive study of the binding of two helium atoms in unrestricted and, in particular, in restricted geometries in both two and three dimensions. Besides the well known binding of the {sup 4}He dimer in unrestricted geometry in two and three dimensions, the authors also find weakly bound states of the {sup 3}He-{sup 4}He molecule and the {sup 3}He dimer in 2 dimensions. Furthermore, any combination of two {sup 4}He or {sup 3}He atoms can form a molecule if their motion is sufficiently confined. The calculations are carried out by numerically solving the Schroedinger equation as well as by constructing a suitable variational wave function.
Yukawa particles in a confining potential
Girotto, Matheus, E-mail: matheus.girotto@ufrgs.br; Levin, Yan, E-mail: levin@if.ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil); Santos, Alexandre P. dos, E-mail: alexandreps@ufcspa.edu.br [Departamento de Educação e Informação em Saúde, Universidade Federal de Ciências da Saúde de Porto Alegre, 90050-170, Porto Alegre, RS (Brazil); Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina (Brazil); Colla, Thiago, E-mail: thiago.colla@ufrgs.br [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria)
2014-07-07
We study the density distribution of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show that the mean-field theory is able to accurately account for the particle distribution. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. For strongly correlated systems, we construct a density functional theory which provides an excellent description of the particle distribution, without any adjustable parameters.
Critical comparison between magnetic and inertial confinement schemes and their geometries
Salingaros, N.A. [Univ. of Texas, San Antonio, TX (United States)
1995-05-01
The interaction mechanism between the plasma and magnetic field in a tokamak does not provide complete magnetic confinement as is usually imagined. Also, the toroidal geometry itself is not particularly well suited for containing a hot plasma. Qualitative arguments reveal an intrinsic superiority of the inertial confinement spherical geometry over any geometry of magnetic confinement for fusion purposes. Moreover, from the point of view of applications, spherical devices such as the inertial electrostatic confinement device and the inertial confinement fusion-spherical pinch are giving immediate spin-offs of industrial interest. 12 refs., 1 fig.
Collisional aspects of bosonic and fermionic dipoles in quasi-two-dimensional confining geometries
D'Incao, Jose P.; Greene, Chris H. [Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)
2011-03-15
Fundamental aspects of ultracold collisions between identical bosonic or fermionic dipoles are studied under quasi-two-dimensional (Q2D) confinement. In the strongly dipolar regime, bosonic and fermion species are found to share important collisional properties as a result of the confining geometry, which suppresses the inelastic rates irrespective of the quantum statistics obeyed. A potential negative is that the confinement causes dipole-dipole resonances to be extremely narrow, which could make it difficult to explore Q2D dipolar gases with tunable interactions. Such properties are shown to be universal, and a simple WKB model reproduces most of our numerical results. In order to shed light on the many-body behavior of dipolar gases in Q2D we have analyzed the scattering amplitude and developed an energy-analytic form of the pseudopotentials for dipoles.
Random Matrices in Non-confining Potentials
NASA Astrophysics Data System (ADS)
Allez, Romain; Dumaz, Laure
2015-05-01
We consider invariant matrix processes diffusing in non-confining cubic potentials of the form V_a(x)= x^3/3 - a x, ain {R} . We construct the trajectories of such processes for all time by restarting them whenever an explosion occurs, from a new (well chosen) initial condition, insuring continuity of the eigenvectors and of the non exploding eigenvalues. We characterize the dynamics of the spectrum in the limit of large dimension and analyze the stationary state of this evolution explicitly. We exhibit a sharp phase transition for the limiting spectral density ? _a at a critical value a=a^* . If a? a^* , then the potential V_a presents a well near x=?{a} deep enough to confine all the particles inside, and the spectral density ? _a is supported on a compact interval. If aconfining potentials and we further investigate a family of quartic potentials, which were already studied in (Brezin et al. in Commun Math Phys 59:35-51, 1978) to count planar diagrams.
Clustering of branching Brownian motions in confined geometries
NASA Astrophysics Data System (ADS)
Zoia, A.; Dumonteil, E.; Mazzolo, A.; de Mulatier, C.; Rosso, A.
2014-10-01
We study the evolution of a collection of individuals subject to Brownian diffusion, reproduction, and disappearance. In particular, we focus on the case where the individuals are initially prepared at equilibrium within a confined geometry. Such systems are widespread in physics and biology and apply for instance to the study of neutron populations in nuclear reactors and the dynamics of bacterial colonies, only to name a few. The fluctuations affecting the number of individuals in space and time may lead to a strong patchiness, with particles clustered together. We show that the analysis of this peculiar behavior can be rather easily carried out by resorting to a backward formalism based on the Green's function, which allows the key physical observables, namely, the particle concentration and the pair correlation function, to be explicitly derived.
Clustering of branching Brownian motions in confined geometries.
Zoia, A; Dumonteil, E; Mazzolo, A; de Mulatier, C; Rosso, A
2014-10-01
We study the evolution of a collection of individuals subject to Brownian diffusion, reproduction, and disappearance. In particular, we focus on the case where the individuals are initially prepared at equilibrium within a confined geometry. Such systems are widespread in physics and biology and apply for instance to the study of neutron populations in nuclear reactors and the dynamics of bacterial colonies, only to name a few. The fluctuations affecting the number of individuals in space and time may lead to a strong patchiness, with particles clustered together. We show that the analysis of this peculiar behavior can be rather easily carried out by resorting to a backward formalism based on the Green's function, which allows the key physical observables, namely, the particle concentration and the pair correlation function, to be explicitly derived. PMID:25375449
Polymer escape from a confining potential
Mökkönen, Harri, E-mail: harri.mokkonen@aalto.fi [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Ikonen, Timo [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Jónsson, Hannes [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States); Ala-Nissila, Tapio [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland) [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States)
2014-02-07
The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.
Plasma confinement by circularly polarized electromagnetic field in toroidal geometry
Wisconsin at Madison, University of
on this concept are proposed. Application of this approach to the fusion reactor requires use of superconducting is stable. Technically feasible compact and medium size toroidal plasma confinement devices based are proportional to . The conclusions of early publications late 1950s on this approach to fusion power where
Studies of Superfluid 3He Confined to a Regular Submicron Slab Geometry, Using SQUID NMR
Casey, Andrew; Corcoles, Antonio; Lusher, Chris; Cowan, Brian; Saunders, John [Department of Physics, Royal Holloway University of London, Egham, Surrey, TW20 0EX (United Kingdom)
2006-09-07
The effect on the superfluid ground state of confining p-wave superfluid 3He in regular geometries of characteristic size comparable to the diameter of the Cooper pair remains relatively unexplored, in part because of the demands placed by experiments on the sensitivity of the measuring technique. In this paper we report preliminary experiments aimed at the study of 3He confined to a slab geometry. The NMR response of a series of superfluid samples has been investigated using a SQUID NMR amplifier. The sensitivity of this NMR spectrometer enables samples of order 1017 spins, with low filling factor, to be studied with good resolution.
Buckling transition of nematic gels in confined geometry
Guangnan Meng; Robert B. Meyer
2009-10-17
A spontaneous buckling transition in thin layers of monodomain nematic liquid crystalline gel was observed by polarized light microscopy. The coupling between the orientational ordering of liquid crystalline solvent and the translational ordering of crosslinked polymer backbones inside the nematic gel contributes to such buckling transition. As the nematic mesogens become more ordered when the gel is cooled down from a higher gelation temperature, the polymeric backbones tend to elongate along the direction parallel to the nematic director, which is perpendicular to the rigid glass surfaces in the experimental setup. The shape change of such confined gel sample lead to the spontaneous buckling of polymeric network and the spatial modulation of nematic liquid crystalline director, which is observed as the stripe patterns. The instability analysis was used to explain such transitions, and the relationship between the critical field, stripe's wavelength and temperature can be explained qualitatively by the rubber elasticity theory for liquid crystalline gels.
Quantum confinement of hot image-potential state electrons.
Schouteden, K; Van Haesendonck, C
2009-12-31
Discrete image-potential state (IS) resonances at Co nanoislands on Au(111) are probed using scanning tunneling microscopy and spectroscopy. We observe particle-in-box-type standing wave patterns, which is surprising in view of the high energy of the IS electrons when compared to the confining potential imposed by the island edges. The weak confining potential experienced by the IS electrons results in electronic interaction effects between closely spaced islands. Probing high-energy ISs hence provides a novel route to investigate electronic coupling between nanoislands on surfaces. PMID:20366332
Potential Well Structures in Spherical Inertial Electrostatic Confinement Devices
Ryan M. Meyer; Sudarshan K. Loyalka; Mark A. Prelas
2005-01-01
Inertial electrostatic confinement (IEC) devices are of interest as neutron generators for many applications. Experiments by Hirsch inspired further efforts to decipher the potential distribution within IEC devices. In this paper, previous analyzes of potential distributions in IEC devices are reviewed and extended. Three types of IEC systems are classified and analyzed according to the arrangement of electrodes and the
Yongkun Liu; C. L. Cox; R. J. Diefendorf
1998-01-01
A simple mathematical model based on atomic drift and diffusion is advanced to describe electromigration-induced stress in confined metal lines. Using a finite element approach, a MATLAB program was developed to simulate stress evolution in lines with variable geometry and microstructure under different boundary conditions. The simulation results show that the contact pads connected to the line end in the
Stochastic resonance in bistable confining potentials. On the role of confinement
NASA Astrophysics Data System (ADS)
Heinsalu, E.; Patriarca, M.; Marchesoni, F.
2009-05-01
We study the effects of the confining conditions on the occurrence of stochastic resonance (SR) in continuous bistable systems. We model such systems by means of double-well potentials that diverge like |x|q for |x|??. For super-harmonic (hard) potentials with q > 2 the SR peak sharpens with increasing q, whereas for sub-harmonic (soft) potentials, q < 2, it gets suppressed.
Deformable cells in confined geometries: From hemolysis to hydrodynamic interactions
NASA Astrophysics Data System (ADS)
Abkarian, Manouk; Faivre, Magalie; Stone, Howard A.
2004-11-01
Recent developments in microfluidics allow a wide range of possibilities for studying cellular-scale hydrodynamics. Here we use microfluidic technology to address several open questions in the blood flow literature where cell deformation and hydrodynamic interactions are significant. In particular, we investigate the pressure-driven flow of a dilute suspension in a channel and characterize the transition from steady axisymmetric cell shapes (for which numerical calculations exist) to asymmetric, highly extended shapes, which are precursors to hemolysis (i.e. destruction of the cell). In addition, we examine the influence of geometry on hydrodynamic interactions of deformable cells by contrasting one-dimensional motion of a train of particles in a channel with two-dimensional motions in a Hele-Shaw cell. This study can help to understand flow of cells in microcirculation from the unidirectional flow in capillaries to the two-dimensional flow in the lung alveoli and provides the basic steps to understand certain aspects of microcirculatory deseases like sickle cell anemia for example.
A calorimetric study of liquid crystalline phase transitions in confined geometries
Indira Amarangani Weerasekera
1998-01-01
The behavior of the mesophase to isotropic transitions of liquid crystals in confined geometries has been studied using differential scanning calorimetry in an effort to understand the effects of finite size on the transition temperature and the latent heat. Liquid crystals 4-5-alkyl-4sp'-cyanobiphenyl, 4-10-alkyl-4sp '-cyanobiphenyl, 4-5-alkoxy-4sp'-cyanobiphenyl, and 4-10-alkoxy-4sp'-cyanobiphenyl were confined in a series of porous silica glasses with mean pore radii
Taboo search by successive confinement: Surveying a potential energy surface
NASA Astrophysics Data System (ADS)
Chekmarev, Sergei F.
2001-09-01
A taboo search for minima on a potential energy surface (PES) is performed by means of confinement molecular dynamics: the molecular dynamics trajectory of the system is successively confined to various basins on the PES that have not been sampled yet. The approach is illustrated for a 13-atom Lennard-Jones cluster. It is shown that the taboo search radically accelerates the process of surveying the PES, with the probability of finding a new minimum defined by a propagating Fermi-like distribution.
Higgs potential and confinement in Yang-Mills theory on exotic R^4
Torsten Asselmeyer-Maluga; Jerzy Król
2013-03-07
We show that pure SU(2) Yang-Mills theory formulated on certain exotic R^4 from the radial family shows confinement. The condensation of magnetic monopoles and the qualitative form of the Higgs potential are derived from the exotic R^4, e. A relation between the Higgs potential and inflation is discussed. Then we obtain a formula for the Higgs mass and discuss a particular smoothness structure so that the Higgs mass agrees with the experimental value. The singularity in the effective dual U(1) potential has its cause by the exotic 4-geometry and agrees with the singularity in the maximal abelian gauge scenario. We will describe the Yang-Mills theory on e in some limit as the abelian-projected effective gauge theory on the standard R^4. Similar results can be derived for SU(3) Yang-Mills theory on an exotic R^4 provided dual diagonal effective gauge bosons propagate in the exotic 4-geometry.
Vortex core behaviour in confined and unconfined geometries: a quasi-one-dimensional model
NASA Astrophysics Data System (ADS)
Darmofal, D. L.; Khan, R.; Greitzer, E. M.; Tan, C. S.
2001-12-01
Axisymmetric vortex core flows, in unconfined and confined geometries, are examined using a quasi-one-dimensional analysis. The goal is to provide a simple unified view of the topic which gives insight into the key physical features, and the overall parametric dependence, of the core area evolution due to boundary geometry or far-field pressure variation. The analysis yields conditions under which waves on vortex cores propagate only downstream (supercritical flow) or both upstream and downstream (subcritical flow), delineates the conditions for a Kelvin Helmholtz instability arising from the difference in core and outer flow axial velocities, and illustrates the basic mechanism for suppression of this instability due to the presence of swirl. Analytic solutions are derived for steady smoothly, varying vortex cores in unconfined geometries with specified far-field pressure and in confined flows with specified bounding area variation. For unconfined vortex cores, a maximum far-field pressure rise exists above which the vortex cannot remain smoothly varying; this coincides with locally critical conditions (axial velocity equal to wave speed) in terms of wave propagation. Comparison with axisymmetric Navier Stokes simulations and experimental results indicate that this maximum correlates with the appearance of vortex breakdown and marked core area increase in the simulations and experiments. For confined flows, the core stagnation pressure defect relative to the outer flow is found to be the dominant factor in determining conditions for large increases in core size. Comparisons with axisymmetric Navier Stokes computations show that the analysis captures qualitatively, and in many instances, quantitatively, the evolution of vortex cores in confined geometries. Finally, a strong analogy with quasi-one-dimensional compressible flow is demonstrated by construction of continuous and discontinuous flows as a function of imposed downstream core edge pressure.
Ma, Minglin
The self-assembly of gyroid-forming diblock copolymers confined in cylindrical geometry is studied using a combination of computer simulations and experiments. The simulations, based on a system qualitatively representative ...
Heavy quarks, gluons and the confinement potential in Coulomb gauge
Popovici, Carina; Watson, Peter; Reinhardt, Hugo [Institut fuer Theoretische Physik, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)
2011-05-23
We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.
A software package to manipulate space dependencies and geometry in magnetic confinement fusion
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
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.
Khirevich, Siarhei; Höltzel, Alexandra; Tallarek, Ulrich
2011-06-28
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
NASA Astrophysics Data System (ADS)
Datta, Preeta; Efimenko, Kirill; Genzer, Jan
2014-03-01
Bulk free radical polymerization reactions lead to highly polydisperse polymers (polydispersity index, PDI >> 1.5). In the past, researchers have shown that polymerization in porous microreactors can lower polydispersity (PDI ~1.5-1.7) by promoting gelation. We employ free-radical thermal frontal polymerization reaction of acrylamide (AAm) in DMSO in highly confined reactors (height <1mm) to produce high molecular weight (~300 kDa) PAAm of relatively low PDI (~1.2). In frontal polymerization systems, a localized reaction zone propagates in space along the direction of heat transfer, sustained by the interplay of heat diffusion and Arrhenius reaction kinetics. The directional heat transfer assists in maintaining the uniformity of the front temperature. While convection improves thermal transport, it causes inhomogeneity in the propagating front in horizontal reactors. In highly confined systems, convection is heavily suppressed, as manifested by the ``flattening'' of the reaction front and the absence of ``fingering''. Gelation lowers termination rate and increases the life time of the active reaction centers. Elimination of convection in confined geometries coupled with directional heat transfer and gelation results in polymers with high molecular weights and low PDIs.
Spectral singularity in confined PT symmetric optical potential
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
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.
NASA Astrophysics Data System (ADS)
M, Haritha; P, Durganandini
2015-06-01
We study the scattering and confinement of Dirac particles in external electrostatic and Lorentz scalar potentials. We use a numerical finite difference time -domain method to solve the equation and obtain the particle dynamics. We find qualitatively different dynamical behavior for electrostatic and Lorentz scalar potentials. Electrostatic potentials lead to Klein tunneling and do not exhibit confinement, while Lorentz scalar potentials inhibit Klein tunneling and exhibit confinement.
Confined geometry effects on reorientational dynamics of molecular liquids in porous silica glasses
NASA Astrophysics Data System (ADS)
Liu, G.; Li, Y.; Jonas, J.
1991-11-01
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 143 Å over the temperature range from 260 to 310 K. Molecular liquids studied include strongly interacting polar liquids such as pyridine-d5, aniline-d5, and nitrobenzene-d5, whereas the saturated cyclic hydrocarbon liquids of cyclohexane-d12 and cis-decalin-d18 represent the weakly interacting liquids. In a first approximation, toluene-d1 and dioxane-d18 are chosen as examples of liquids with intermediate interactions with the silica surface. The experimental relaxation data are analyzed by using the two-state, fast-exchange model which is found to be valid for the strongly interacting liquids and liquids with intermediate interactions. In terms of this model, the viscosity of the surface layer for pyridine-d5 is about 30 times higher than that for bulk liquid pyridine. The importance of the two-dimensional approach to describe motional dynamics of liquids confined to pores smaller than 30 Å is illustrated in the case of weakly interacting liquid of cyclohexane-d12. Additional information on the relative role of surface interactions and the pure topological effects on the dynamics of liquids in confined geometries was obtained by using surface-modified glasses in which the surface hydroxyl groups were replaced by OSi(CH3)2OC2H5 groups. Indeed, the effects of surface modifications on the 2H T-11 are most pronounced for strongly interacting liquids whereas they are absent for cyclohexane. In agreement with the concept of two-dimensional behavior of liquids in small pores, one finds that the low-frequency relaxation times, namely, the spin-spin relaxation time T2, and the spin-lattice relaxation time in the rotating coordinate frame, T1?, remain unchanged by surface modification. In fact, this is a consequence of logarithmic enhancement of the spectral density at low frequencies so that the effect of pure geometrical confinement on the T-12 and T-11? relaxation rates is much larger than any relaxation rate changes arising from surface modification. Several selected NMR T1 experiments on pyridine-d5 confined to anopore and zeolites are also presented.
NASA Astrophysics Data System (ADS)
Chakrabarty, Ayan; Wang, Feng; Joshi, Bhuwan; Wei, Qi-Huo
2011-03-01
Recent studies shows that the boomerang shaped molecules can form various kinds of liquid crystalline phases. One debated topic related to boomerang molecules is the existence of biaxial nematic liquid crystalline phase. Developing and optical microscopic studies of colloidal systems of boomerang particles would allow us to gain better understanding of orientation ordering and dynamics at ``single molecule'' level. Here we report the fabrication and experimental studies of the Brownian motion of individual boomerang colloidal particles confined between two glass plates. We used dark-field optical microscopy to directly visualize the Brownian motion of the single colloidal particles in a quasi two dimensional geometry. An EMCCD was used to capture the motion in real time. An indigenously developed imaging processing algorithm based on MatLab program was used to precisely track the position and orientation of the particles with sub-pixel accuracy. The experimental finding of the Brownian diffusion of a single boomerang colloidal particle will be discussed.
Diffusion-limited reactions and mortal random walkers in confined geometries
Ingo Lohmar; Joachim Krug
2008-11-24
Motivated by the diffusion-reaction kinetics on interstellar dust grains, we study a first-passage problem of mortal random walkers in a confined two-dimensional geometry. We provide an exact expression for the encounter probability of two walkers, which is evaluated in limiting cases and checked against extensive kinetic Monte Carlo simulations. We analyze the continuum limit which is approached very slowly, with corrections that vanish logarithmically with the lattice size. We then examine the influence of the shape of the lattice on the first-passage probability, where we focus on the aspect ratio dependence: Distorting the lattice always reduces the encounter probability of two walkers and can exhibit a crossover to the behavior of a genuinely one-dimensional random walk. The nature of this transition is also explained qualitatively.
Diffusion-Limited Reactions and Mortal Random Walkers in Confined Geometries
NASA Astrophysics Data System (ADS)
Lohmar, Ingo; Krug, Joachim
2009-01-01
Motivated by the diffusion-reaction kinetics on interstellar dust grains, we study a first-passage problem of mortal random walkers in a confined two-dimensional geometry. We provide an exact expression for the encounter probability of two walkers, which is evaluated in limiting cases and checked against extensive kinetic Monte Carlo simulations. We analyze the continuum limit which is approached very slowly, with corrections that vanish logarithmically with the lattice size. We then examine the influence of the shape of the lattice on the first-passage probability, where we focus on the aspect ratio dependence: Distorting the lattice always reduces the encounter probability of two walkers and can exhibit a crossover to the behavior of a genuinely one-dimensional random walk. The nature of this transition is also explained qualitatively.
Slow Kinetics of Capillary Condensation in Confined Geometry: Experiment and Theory
F. Restagno; L. Bocquet; J. Crassous; E. Charlaix
2001-09-04
When two solid surfaces are brought in contact, water vapor present in the ambient air may condense in the region of the contact to form a liquid bridge connecting the two surfaces : this is the so-called capillary condensation. This phenomenon has drastic consequences on the contact between solids, modifying the macroscopic adhesion and friction properties. In this paper, we present a survey of the work we have performed both experimentally and theoretically to understand the microscopic foundations of the kinetics of capillary condensation. From the theoretical point of view, we have computed the free energy barrier associated with the condensation of the liquid from the gas in a confined system. These calculations allow to understand the existence of very large hysteresis, which is often associated with capillary condensation. This results are compatible with experimental results obtained with a surface forces apparatus in a vapor atmosphere, showing a large hysteris of the surface energy of two parallel planes as a function of their distance. In the second part, we present some experiments on the influence of humidity on the avalanche angle of granular media. We show that the ageing in time of this avalanche angle can be explained by the slow kinetics of capillary condensation in a random confined geometry.
Baxamusa, S., E-mail: baxamusa1@llnl.gov; Field, J.; Dylla-Spears, R.; Kozioziemski, B.; Suratwala, T.; Sater, J. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)
2014-03-28
Growth of high-quality single-crystal hydrogen in confined geometries relies on the in situ formation of seed crystals. Generation of deuterium-tritium seed crystals in a confined geometry is governed by three effects: self-heating due to tritium decay, external thermal environment, and latent heat of phase change at the boundary between hydrogen liquid and vapor. A detailed computation of the temperature profile for liquid hydrogen inside a hollow shell, as is found in inertial confinement fusion research, shows that seeds are likely to form at the equatorial plane of the shell. Radioactive decay of tritium to helium slowly alters the composition of the hydrogen vapor, resulting in a modified temperature profile that encourages seed formation at the top of the shell. We show that the computed temperature profile is consistent with a variety of experimental observations.
Light-Front Holographic QCD and the Confinement Potential
NASA Astrophysics Data System (ADS)
Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter
2014-06-01
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.
Solution of Two-Body Bound State Problems with Confining Potentials
Hadizadeh, M R; 10.1063/1.3523199
2011-01-01
The homogeneous Lippmann-Schwinger integral equation is solved in momentum space by using confining potentials. Since the confining potentials are unbounded at large distances, they lead to a singularity at small momentum. In order to remove the singularity of the kernel of the integral equation, a regularized form of the potentials is used. As an application of the method, the mass spectra of heavy quarkonia, mesons consisting from heavy quark and antiquark $(\\Upsilon(b\\bar{b}), \\psi(c\\bar{c}))$, are calculated for linear and quadratic confining potentials. The results are in good agreement with configuration space and experimental results.
Solution of Two-Body Bound State Problems with Confining Potentials
M. R. Hadizadeh; Lauro Tomio
2011-04-19
The homogeneous Lippmann-Schwinger integral equation is solved in momentum space by using confining potentials. Since the confining potentials are unbounded at large distances, they lead to a singularity at small momentum. In order to remove the singularity of the kernel of the integral equation, a regularized form of the potentials is used. As an application of the method, the mass spectra of heavy quarkonia, mesons consisting from heavy quark and antiquark $(\\Upsilon(b\\bar{b}), \\psi(c\\bar{c}))$, are calculated for linear and quadratic confining potentials. The results are in good agreement with configuration space and experimental results.
Solution of Two-Body Bound State Problems with Confining Potentials
Hadizadeh, M. R. [Instituto de Fisica Teorica (IFT), Universidade Estadual Paulista (UNESP), Barra Funda, 01140-070, Sao Paulo (Brazil); Tomio, Lauro [Instituto de Fisica Teorica (IFT), Universidade Estadual Paulista (UNESP), Barra Funda, 01140-070, Sao Paulo (Brazil); Instituto de Fisica, Universidade Federal Fluminense, 24210-346, Niteroi, RJ (Brazil)
2010-11-12
The homogeneous Lippmann-Schwinger integral equation is solved in momentum space by using confining potentials. Since the confining potentials are unbounded at large distances, they lead to a singularity at small momentum. In order to remove the singularity of the kernel of the integral equation, a regularized form of the potentials is used. As an application of the method, the mass spectra of heavy quarkonia, mesons consisting from heavy quark and antiquark ({Upsilon}(bb-bar), {psi}(cc-bar)), are calculated for linear and quadratic confining potentials. The results are in good agreement with configuration space and experimental results.
Ferromagnetic 1D oxide nanostructures grown from chemical solutions in confined geometries.
Carretero-Genevrier, A; Puig, T; Obradors, X; Mestres, N
2014-04-01
This review summarizes the capabilities and recent developments of nanoporous polymeric template systems directly supported on different substrates for the confined growth of epitaxial ferromagnetic complex oxide 1D nanostructures. In particular, we describe the versatility and potentiality of chemical solutions combined with track-etched polymers to synthesize (i) vertical polycrystalline La0.7Sr0.3MnO3 nanorods on top of single crystal perovskites, (ii) single crystalline manganese based octahedral molecular sieve (OMS) nanowires on silicon substrates, and (iii) the epitaxial directional single crystal OMS nanowires on top of fluorite-type substrates. The influence of the distinct growth parameters on the nanostructural evolution of the resulting nanostructures and their magnetic properties is further discussed in detail. PMID:24091495
NASA Astrophysics Data System (ADS)
Dolganov, P. V.; Cluzeau, P.
2014-12-01
We study the topology of the c -director field near topological defects with point core and with a droplet in the core of the defect in nonpolar smectic-C and ferroelectric smectic-C * freestanding films using polarized optical microscopy. Free and confined geometry of topological defects and droplets with strong outer boundary condition are compared. The c -director field can be remarkably different around a point defect and a droplet with the same topological charge S =+1 . In ferroelectric films, splay deformation of the c -director transforms into bend deformation after droplet nucleation. Heating a ferroelectric film with an S =+1 droplet leads to a dramatic change of the c -director topology from bend to splay. In confined geometry we found spiral structures in which the c -director has opposite direction of rotation along the inner and outer boundaries of the island. Our observations are discussed on the basis of theories taking into account both the influence of polarity and of confined geometry on elasticity and topology of the c -director field.
Space potential profiles in relativistic spherical inertial electrostatic confinement (SIEC) devices
Ryan M. Meyer; Sudarshan K. Loyalka; Mark A. Prelas
2006-01-01
Summary form only given. Spherical inertial electrostatic confinement (SIEC) devices could potentially be used as neutron generators for a number of applications. Since Hirsch put forward the hypothesis that a number of alternating virtual electrodes at the center of these devices could be acting as a confinement mechanism, a modest amount of research has been dedicated to verify the existence
The potential role of electric fields and plasma barodiffusion on the inertial confinement fusion. Related Articles Investigating inertial confinement fusion target fuel conditions through x-ray spectroscopy Phys. Plasmas 19, 056312 (2012) Analytic criteria for shock ignition of fusion reactions
NASA Astrophysics Data System (ADS)
Ghobadi, Ahmadreza F.; Elliott, J. Richard
2014-09-01
In Paper I [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 139(23), 234104 (2013)], we showed that how a third-order Weeks-Chandler-Anderson (WCA) Thermodynamic Perturbation Theory and molecular simulation can be integrated to characterize the repulsive and dispersive contributions to the Helmholtz free energy for realistic molecular conformations. To this end, we focused on n-alkanes to develop a theory for fused and soft chains. In Paper II [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 141(2), 024708 (2014)], we adapted the classical Density Functional Theory and studied the microstructure of the realistic molecular fluids in confined geometries and vapor-liquid interfaces. We demonstrated that a detailed consistency between molecular simulation and theory can be achieved for both bulk and inhomogeneous phases. In this paper, we extend the methodology to molecules with partial charges such as carbon dioxide, water, 1-alkanols, nitriles, and ethers. We show that the electrostatic interactions can be captured via an effective association potential in the framework of Statistical Associating Fluid Theory (SAFT). Implementation of the resulting association contribution in assessing the properties of these molecules at confined geometries and interfaces presents satisfactory agreement with molecular simulation and experimental data. For example, the predicted surface tension deviates less than 4% comparing to full potential simulations. Also, the theory, referred to as SAFT-? WCA, is able to reproduce the specific orientation of hydrophilic head and hydrophobic tail of 1-alkanols at the vapor-liquid interface of water.
NASA Astrophysics Data System (ADS)
Verdoolaege, Geert; Karagounis, Giorgos; Van Oost, Guido
2013-08-01
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.
Effect of confining wall potential on charged collimated dust beam in low-pressure plasma
Kausik, S. S.; Kakati, B.; Saikia, B. K. [Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402 (India)] [Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402 (India)
2013-05-15
The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10{sup ?4} millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (?pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.
Light-Cone Kaluza-Klein Geometry: Confined Propagation as a Particle Model
Donald E. Jennings
2000-04-24
A modified Kaluza-Klein theory is proposed in which propagation takes place only at the speed of light. The propagation can be confined to a small volume, forming a particle with rest mass. The usual four space-time coordinates locate the confinement volume, and Kaluza's fifth coordinate is replaced by an internal degree of freedom. Electromagnetism corresponds to a gauge field on the phase of the internal motion. Self-gravity might create the confinement, as in a geon, but the particle would have a Planck mass. This large mass could be made closer to the masses of observed particles if gravity were allowed to increase in strength within the confinement volume.
Tzonev, I.V.; DeMora, J.M.; Miley, G.H. [Univ. of Illinois, Urbana, IL (United States)
1995-12-31
Prior Inertial Electrostatic Confinement (IEC) studies have assumed that very low angular momentum (zero in the ideal case) is necessary to achieve a potential well structure capable of trapping energetic ions in the center of a spherical device. However, the present study shows that high-current ion beams having large-angular-momentum spread can also form deep potential well traps.
Ivon V. Tzonev; John M. DeMora; George H. Miley
1995-01-01
Prior inertial electrostatic confinement (IEC) studies have assumed that very low angular momentum (zero in the ideal case) is necessary to achieve a potential well structure capable of trapping energetic ions in the center of a spherical device. However, the present study shows that high-current ion beams having large-angular-momentum spread can also form deep potential well traps
M. Ohnishi; K. H. Sato; Y. Yamamoto; K. Yoshikawa
1997-01-01
The electrostatic potential well in inertial electrostatic confinement (IEC) is studied using two approaches. First, the equilibrium potential profile is obtained by solving the charge neutrality condition, i.e. ni=ne, assuming the appropriate distribution functions for the ions and the electrons. The formation of a double well structure is demonstrated, with a depth depending upon the ratio between the focus radii
Dynamics and statistics of wave-particle interactions in a confined geometry
NASA Astrophysics Data System (ADS)
Gilet, Tristan
2014-11-01
A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors.
Universal potential barrier penetration by initially confined wavepackets
Er'el Granot; Avi Marchewka
2006-08-09
The dynamics of an initially sharp-boundary wavepacket in the presence of an arbitrary potential barrier are investigated. It is shown that the penetration through the barrier is universal in the sense that it depends only on the values of the wavefunction and its derivatives at the boundary. The dependence on the derivatives vanishes at long distances from the barrier, where the dynamics are governed solely by the initial value of the wavefunction at the boundary.
Fractional Brownian motion and generalized Langevin equation motion in confined geometries
Jae-Hyung Jeon; Ralf Metzler
2010-01-06
Motivated by subdiffusive motion of bio-molecules observed in living cells we study the stochastic properties of a non-Brownian particle whose motion is governed by either fractional Brownian motion or the fractional Langevin equation and restricted to a finite domain. We investigate by analytic calculations and simulations how time-averaged observables (e.g., the time averaged mean squared displacement and displacement correlation) are affected by spatial confinement and dimensionality. In particular we study the degree of weak ergodicity breaking and scatter between different single trajectories for this confined motion in the subdiffusive domain. The general trend is that deviations from ergodicity are decreased with decreasing size of the movement volume, and with increasing dimensionality. We define the displacement correlation function and find that this quantity shows distinct features for fractional Brownian motion, fractional Langevin equation, and continuous time subdiffusion, such that it appears an efficient measure to distinguish these different processes based on single particle trajectory data.
NSDL National Science Digital Library
Rusin, Dave
A short article designed to provide an introduction to geometry, including classical Euclidean geometry and synthetic (non-Euclidean) geometries; analytic geometry; incidence geometries (including projective planes); metric properties (lengths and angles); and combinatorial geometries such as those arising in finite group theory. Many results in this area are basic in either the sense of simple, or useful, or both. History; applications and related fields and subfields; textbooks, reference works, and tutorials; software and tables; other web sites with this focus.
Periodically driven dynamics of a particle moving in the field of Coulomb plus confining potential
D. U. Matrasulov; P. K. Khabibullaev; F. C. Khanna; D. M. Otajanov
2011-06-24
Periodically driven dynamics of a particle moving in the field Coulomb plus confining potential is treated for one and three dimensional cases. Critical value of the external field strength at which chaotization will occur is evaluated analytically based on the resonance overlap criterion. The analysis of the phase-space dynamics is presented.
Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry
NASA Astrophysics Data System (ADS)
Wang, Siyuan; Jain, Chhavi; Wondraczek, Lothar; Wondraczek, Katrin; Kobelke, Jens; Troles, Johann; Caillaud, Celine; Schmidt, Markus A.
2015-05-01
The flow of high-viscosity liquids inside micrometer-size holes can be substantially different from the flow in the bulk, non-confined state of the same liquid. Such non-Newtonian behavior can be employed to generate structural anisotropy in the frozen-in liquid, i.e., in the glassy state. Here, we report on the observation of non-Newtonian flow of an ultralow melting chalcogenide glass inside a silica microcapillary, leading to a strong deviation of the shear viscosity from its value in the bulk material. In particular, we experimentally show that the viscosity is radius-dependent, which is a clear indication that the microscopic rearrangement of the glass network needs to be considered if the lateral confinement falls below a certain limit. The experiments have been conducted using pressure-assisted melt filling, which provides access to the rheological properties of high-viscosity melt flow under previously inaccessible experimental conditions. The resulting flow-induced structural anisotropy can pave the way towards integration of anisotropic glasses inside hybrid photonic waveguides.
Rigas, Fotis; Sklavounos, Spyros
2005-05-20
Accidental blast wave generation and propagation in the surroundings poses severe threats for people and property. The prediction of overpressure maxima and its change with time at specified distances can lead to useful conclusions in quantitative risk analysis applications. In this paper, the use of a computational fluid dynamics (CFD) code CFX-5.6 on dense explosive detonation events is described. The work deals with the three-dimensional simulation of overpressure wave propagation generated by the detonation of a dense explosive within a small-scale branched tunnel. It also aids at validating the code against published experimental data as well as to study the way that the resulting shock wave propagates in a confined space configuration. Predicted overpressure histories were plotted and compared versus experimental measurements showing a reasonably good agreement. Overpressure maxima and corresponding times were found close to the measured ones confirming that CFDs may constitute a useful tool in explosion hazard assessment procedures. Moreover, it was found that blast wave propagates preserving supersonic speed along the tunnel accompanied by high overpressure levels, and indicating that space confinement favors the formation and maintenance of a shock rather than a weak pressure wave. PMID:15885402
Electron leakage through magnetic cusps in the polywell (tradename) confinement geometry
Bussard, R.W.; Krall, N.A.
1991-02-01
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.
Simulation method for resonant light scattering of exciton confined to arbitrary geometry.
Uemoto, Mitsuharu; Ajiki, Hiroshi
2014-04-21
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
A numerical study on the thermal initiation of a confined explosive in 2-D geometry.
Aydemir, Erdo?an; Ulas, Abdullah
2011-02-15
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
A. Gupta; M. Sbragaglia; A. Scagliarini
2014-06-11
We propose numerical simulations of viscoelastic fluids based on a hybrid algorithm combining Lattice-Boltzmann models (LBM) and Finite Differences (FD) schemes, the former used to model the macroscopic hydrodynamic equations, and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible non-linear elastic dumbbells with Peterlin's closure (FENE-P). The numerical model is first benchmarked by characterizing the rheological behaviour of dilute homogeneous solutions in various configurations, including steady shear, elongational flows, transient shear and oscillatory flows. As an upgrade of complexity, we study the model in presence of non-ideal multicomponent interfaces, where immiscibility is introduced in the LBM description using the "Shan-Chen" model. The problem of a confined viscoelastic (Newtonian) droplet in a Newtonian (viscoelastic) matrix under simple shear is investigated and numerical results are compared with the predictions of various theoretical models. The proposed numerical simulations explore problems where the capabilities of LBM were never quantified before.
NASA Astrophysics Data System (ADS)
Gupta, A.; Sbragaglia, M.; Scagliarini, A.
2015-06-01
We propose numerical simulations of viscoelastic fluids based on a hybrid algorithm combining Lattice-Boltzmann models (LBM) and Finite Differences (FD) schemes, the former used to model the macroscopic hydrodynamic equations, and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible non-linear elastic dumbbells with Peterlin's closure (FENE-P). The numerical model is first benchmarked by characterizing the rheological behavior of dilute homogeneous solutions in various configurations, including steady shear, elongational flows, transient shear and oscillatory flows. As an upgrade of complexity, we study the model in presence of non-ideal multicomponent interfaces, where immiscibility is introduced in the LBM description using the "Shan-Chen" interaction model. The problem of a confined viscoelastic (Newtonian) droplet in a Newtonian (viscoelastic) matrix under simple shear is investigated and numerical results are compared with the predictions of various theoretical models. The proposed numerical simulations explore problems where the capabilities of LBM were never quantified before.
On the generation of nonlinear travelling waves in confined geometries using electric fields.
Cimpeanu, R; Papageorgiou, D T
2014-07-28
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
NASA Astrophysics Data System (ADS)
Aciksoz, E.; Bayrak, O.; Soylu, A.
2015-01-01
The impurity binding energy in the GaAs -Ga1-xAlx As system is studied with an anharmonic type confinement potential by taking into account the influence of the external electric and magnetic fields within the framework of the effective mass approximation and asymptotic iteration method (AIM). The influence of the external electromagnetic fields and anharmonicity on a donor binding energy is examined systematically. It is shown that the donor binding energy is highly dependent on the external electric and magnetic fields and the confinement potential shapes. Both the electric and magnetic fields are increased, the binding energies increase for each of them. However, the behaviors of increase in the weak and strong fields' regimes have different character a bit. Furthermore, when the more anharmonicity is considered, the binding energy of donor slightly increases as well.
Morikawa, Kyojiro; Kazoe, Yutaka; Mawatari, Kazuma; Tsukahara, Takehiko; Kitamori, Takehiko
2015-02-01
Understanding liquid structure and the electrical properties of liquids confined in extended nanospaces (10-1000 nm) is important for nanofluidics and nanochemistry. To understand these liquid properties requires determination of the dielectric constant of liquids confined in extended nanospaces. A novel dielectric constant measurement method has thus been developed for extended nanospaces using a streaming potential method. We focused on the nonsteady-state streaming potential in extended nanospaces and successfully measured the dielectric constant of liquids within them without the use of probe molecules. The dielectric constant of water was determined to be significantly reduced by about 3 times compared to that of the bulk. This result contributes key information toward further understanding of the chemistry and fluidics in extended nanospaces. PMID:25569302
Deep sub-nanosecond reversal of vortex cores confined in a spin-wave potential well
Dong, Xinwei; Wang, Zhenyu; Wang, Ruifang, E-mail: wangrf@xmu.edu.cn [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China)
2014-03-17
A spin-wave potential well is created in a permalloy nanodisk by setting up a cylindrical cavity in the center of the sample. We then apply a single-harmonic external magnetic field perpendicular to the disk plane to switch the vortex polarity of the sample. Our micromagnetic numerical studies establish that the effective spin-wave confinement by the potential well leads to much stronger magnetization oscillation in the sample. Therefore, the vortex core can be reversed well below 200 ps and over a wide range of field frequency. Our findings present an additional efficient means for ultrafast switching of magnetic vortices.
Escape rate of Lévy particles from truncated confined and unconfined potentials
NASA Astrophysics Data System (ADS)
Bai, Zhan-Wu; Hu, Meng
2015-06-01
For a double-well potential consisting of a truncated quartic potential and a truncated harmonic potential, the inter-well escape rates of Lévy particles are investigated numerically, and analytically for the Cauchy case, with focus on the former. The escape rate of Lévy particles from the truncated confined quartic potential well possesses qualitatively different characteristics compared with that from the truncated harmonic potential well, as reflected in the noise intensity dependence and Lévy index dependence of the escape rate. Two kinds of different escape mechanisms exist for low noise and high noise intensities. As the noise intensity increases, the escaping particles in quasi-stationary state present a noise-induced phase transition phenomenon, wherein the distribution of Lévy particles transits from a bimodal narrow distribution to a unimodal wide distribution. The characteristics of the escape rate in low and high noise intensities can be understood by the distributions of Lévy particles and the features of Lévy noise.
The photino sector and a confining potential in a supersymmetric Lorentz-symmetry-violating model
NASA Astrophysics Data System (ADS)
Belich, H.; Bernald, L. D.; Gaete, Patricio; Helayël-Neto, J. A.
2013-11-01
We study the spectrum of the minimal supersymmetric extension of the Carroll-Field-Jackiw model for Electrodynamics with a topological Chern-Simons-like Lorentz-symmetry violating term. We identify a number of independent background fermion condensates, work out the gaugino dispersion relation and propose a photonic effective action to consider aspects of confinement induced by the SUSY background fermion condensates, which also appear to signal Lorentz-symmetry violation in the photino sector of the action. Our calculations of the static potential are carried out within the framework of the gauge-invariant but path-dependent variables formalism which are alternative to the Wilson loop approach. Our results show that the interaction energy contains a linear term leading to the confinement of static probe charges.
Nadler, J.H. (U.S. Department of Energy, Field Office, Idaho, Idaho Falls, Idaho 83401 (United States)); Gu, Y.B.; Miley, G.H. (Fusion Studies Laboratory, University of Illinois, Urbana, Illinois 61801 (United States))
1992-10-01
A collimated proton detector has been developed for spatial resolved proton measurements in inertial-electrostatic plasma confinement (IEC) fusion experiments. These are the first proton measurements used to infer potential well profiles on an IEC device. This paper describes a new technique for investigating the existence of multiple potential wells inside IEC devices. Analysis of the observed proton energy and source profile indicates that (for a 12-mA cathode current, a 30-kV cathode voltage in a 4-mTorr D{sub 2} background) predominantly beam-background fusion occurs. Computer simulation suggests that a positive space charge potential approximately half that of the applied voltage is formed inside the cathode. These results establish the first measurement of a positive potential well structure inside an ion-injected IEC device.
Malet, F.; Reimann, S. M. [Mathematical Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund (Sweden); Kristensen, T. [Ecole Normale Superieure de Cachan, Cachan cedex, F-94230 Cachan (France); Kavoulakis, G. M. [Technological Educational Institute of Crete, P.O. Box 1939, GR-71004 Heraklion (Greece)
2011-03-15
We study the rotational properties of a dipolar Bose-Einstein condensate confined in a quasi-two-dimensional anisotropic trap for an arbitrary orientation of the dipoles with respect to their plane of motion. Within the mean-field approximation, we find that the lowest-energy state of the system depends strongly on the relative strength between the dipolar and the contact interactions, as well as on the size and the orientation of the dipoles and the size and the orientation of the deformation of the trapping potential.
NSDL National Science Digital Library
Mr. Edwards
2010-09-29
Geometric concepts Thanks to all who have contributed to this site. Your hard work is appreciated. Geogebra Interactive manipulation of geometric figures National Library of Virtual Manipulatives Utah State University internet site with lots of math games Pythagorean Theorem Find out how the Greek philosopher figured the lengths of lines in a right triangle Triangles Build, name and see triangles in 3-D Great Geometry Play a matching game with polygons Learn to sort the different types of triangles Groovy Geometry Make different shapes and sizes ...
NASA Astrophysics Data System (ADS)
Lumb, Shalini; Lumb, Sonia; Prasad, Vinod
2014-09-01
The energy spectra of spherically confined hydrogen atom embedded in an exponential-cosine-screened Coulomb potential is worked out by using the Bernstein-polynomial method. The interaction of short laser pulses in the femtosecond range with the system is studied in detail. The effect of shape of laser pulse, confinement radius, Debye screening length as well as different laser parameters on the dynamics of the system has been explored and analyzed.
NASA Technical Reports Server (NTRS)
Wiese, Michael R.
1987-01-01
Documented is an aeronautical geometry conversion package which translates wave-drag geometry into the Langley Wireframe Geometry Standard (LaWGS) format and then into a format which is used by the Supersonic Implicit Marching Potential (SIMP) program. The programs described were developed by Computer Sciences Corporation for the Advanced Vehicles Division/Advanced Concepts Branch at NASA Langley Research Center. Included also are the input and output from a benchmark test case.
Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D; Sebastiani, Daniel
2012-11-21
We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials. PMID:23181297
Three-layer dielectric models for generalized Coulomb potential calculation in ellipsoidal geometry
Changfeng Xue; Shaozhong Deng
2011-01-01
This paper concerns a basic electrostatic problem: how to calculate generalized Coulomb and self-polarization potentials in heterogeneous dielectric media. In particular, with simulations of ellipsoidal semiconductor quantum dots and elongated biomacromolecules being its target applications, this paper extends the so-called three-layer dielectric models for generalized Coulomb and self-polarization potential calculation from the spherical and the spheroidal geometries to the triaxial
P. Bicudo
2010-03-04
We study the string tension as a function of temperature, fitting the SU(3) lattice QCD finite temperature free energy potentials computed by the Bielefeld group. We compare the string tension points with order parameter curves of ferromagnets, superconductors or string models, all related to confinement. We also compare the SU(3) string tension with the one of SU(2) Lattice QCD. With the curve providing the best fit to the finite temperature string tensions, the spontaneous magnetization curve, we then show how to include finite temperature, in the state of the art confining and chiral invariant quark models.
Bicudo, P. [CFTP, Departamento de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)
2010-08-01
We study the string tension as a function of temperature, fitting the SU(3) lattice QCD finite temperature free energy potentials computed by the Bielefeld group. We compare the string tension points with order parameter curves of ferromagnets, superconductors, or string models, all related to confinement. We also compare the SU(3) string tension with the one of SU(2) lattice QCD. With the curve providing the best fit to the finite temperature string tensions, the spontaneous magnetization curve, we then show how to include finite temperature, in the state of the art confining and chiral invariant quark models.
Potential flow model of cavitation-induced interfacial fracture in a confined ductile layer
NASA Astrophysics Data System (ADS)
Zhang, Sulin; Hsia, K. Jimmy; Pearlstein, Arne J.
2002-03-01
Fracture of a thin ductile layer sandwiched between stiff substrates often results from growth and coalescence of microscopic cavities ahead of an extending crack. Cavitation induced by plastic flow in a confined, ductile layer is analyzed here to evaluate the interfacial fracture toughness of such sandwich structures. For rigid-plastic materials, a new method is proposed in which the potential flow field of a fluid is used to approximate the plastic deformation. The principle of virtual work rate is applied to determine the equivalent traction-separation law. The method is demonstrated and validated for spherically symmetric cavity growth, for which an exact solution exists. We then study in detail the growth of an initially spherical cavity in a cylindrical bar of finite length subject to uniform traction at its ends. The results show that the stress-separation curves depend strongly on initial cavity size and the strain-hardening exponent, and weakly on the nominal strain. The method has clear advantages over numerical methods, such as finite-element analysis, for parametric study of cavity growth with large plastic deformation.
Euán-Díaz, Edith C; Herrera-Velarde, Salvador; Misko, Vyacheslav R; Peeters, François M; Castañeda-Priego, Ramón
2015-01-14
We report on the ordering and dynamics of interacting colloidal particles confined by a parabolic potential. By means of Brownian dynamics simulations, we find that by varying the magnitude of the trap stiffness, it is possible to control the dimension of the system and, thus, explore both the structural transitions and the long-time self-diffusion coefficient as a function of the degree of confinement. We particularly study the structural ordering in the directions perpendicular and parallel to the confinement. Further analysis of the local distribution of the first-neighbors layer allows us to identify the different structural phases induced by the parabolic potential. These results are summarized in a structural state diagram that describes the way in which the colloidal suspension undergoes a structural re-ordering while increasing the confinement. To fully understand the particle dynamics, we take into account hydrodynamic interactions between colloids; the parabolic potential constricts the available space for the colloids, but it does not act on the solvent. Our findings show a non-linear behavior of the long-time self-diffusion coefficient that is associated to the structural transitions induced by the external field. PMID:25591382
William McCaffrey; Benjamin Kneller
Stratigraphic trapping at pinch-out margins is a key feature of many turbidite-hosted hydrocarbon reservoirs. In systems confined by lat- eral or oblique frontal slopes, outcrop studies show that there is a continuum between two geometries of pinch-out configuration. In type A, turbidites thin onto the confining surface—although the final sandstone pinch-out is commonly abrupt—and individual beds tend not to erode
NASA Astrophysics Data System (ADS)
Ghosal, Amit; Ash, Biswarup; Chakrabarti, Jaydeb
2015-03-01
We investigate the dynamics of Coulomb-interacting confined particles over a range of temperatures capturing the crossover from a Wigner molecule to a liquid-like phase. Dynamical signatures, derived from the Van-Hove correlations, develop pivotal understanding of the phases as well as the intervening crossover, which are inaccessible from the study of static correlations alone. The motion of the particles shows frustrations, produces heterogeneities depending on the observation time-scales and temperatures and results into a non-Gaussian behavior. The extent and nature of the departure of the behavior of spatio-temporal correlations from the conventional wisdom depends crucially on the symmetry of the confinements. In particular, we find that the decay of correlations follow a stretched-exponential form in traps that lack any symmetry. Our data offers a broad support to a theoretical model that integrates the non-Gaussian behavior arising from the convolution of Gaussian fluctuations weighted by appropriate diffusivities, consistent with local dynamics. The richness of information from the dynamic correlation will be shown to improve the understanding of melting in confined systems in a powerful manner.
Bent waveguides for matter-waves: supersymmetric potentials and reflectionless geometries
Campo, Adolfo del; Boshier, Malcolm G.; Saxena, Avadh
2014-01-01
Non-zero curvature in a waveguide leads to the appearance of an attractive quantum potential which crucially affects the dynamics in matter-wave circuits. Using methods of supersymmetric quantum mechanics, pairs of bent waveguides are found whose geometry-induced potentials share the same scattering properties. As a result, reflectionless waveguides, dual to the straight waveguide, are identified. Strictly isospectral waveguides are also found by modulating the depth of the trapping potential. Numerical simulations are used to demonstrate the efficiency of these approaches in tailoring and controlling curvature-induced quantum-mechanical effects. PMID:24919423
Numerical simulation of a laterally confined double dot with tunable interaction potential
Finck, Aaron David Kiyoshi
2005-01-01
Recent technological advances have allowed for the construction of small (on the order of 100-1000 nm) systems of confined electrons called quantum dots. Often kept within semiconductor heterostructures, these systems are ...
Potential change in flaw geometry during pressurized-thermal-shock transients
D. K. M. Shum; J. W. Bryson; J. G. Merkle; J. Keeney-Walker; T. L. Dickson; B. R. Bass
1993-01-01
This study presents preliminary estimates on the potential change in flaw geometry of an initially shallow, axially oriented, inner-surface finite-length flaw in a PWR-RPV during the course of a postulated PTS transient. Specifically, the question being addressed is whether a shallow, axially oriented, finite-length surface flaw would tend to elongate in the axial direction and\\/or deepen into the wall of
Application of a full potential method for analysis of complex aircraft geometries
NASA Technical Reports Server (NTRS)
Jones, Kenneth M.; Talcott, Noel A., Jr.
1986-01-01
A supersonic potential flow solver was developed to analyze the flow over complex realistic aircraft geometries. Enhancements to the method were made to accommodate regions of subsonic flow, the effect of trailing wakes on other aircraft components, and the modeling/gridding of complete configurations. Validation of the method was demonstrated by comparisons with experimental aerodynamic force and surface pressure measurements. The predicted results are in very good agreement with the experimental data. The bibliography contains additional information on the use of the potential flow code to predict the aerodynamics of high-speed wing/body configurations, waverider concepts, TAV, and the Space Shuttle orbiter package.
M. Ohnishi; Y. Yamamoto; K. Yoshikawa; K. Sato
1995-01-01
The electrostatic potential well in an inertial-electrostatic confinement (IEC) is calculated by performing the numerical simulations based on the particle-in-cell method. The single, double and triple wells, depending on the amount of the injected ion current, are observed to be formed for the ions with a mono-energetic distribution. The well in the center of the multi-well structure is unstable and
Mohamed, T. [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Physics department, Faculty of Science, Beni-Suef University (Egypt); Mohri, A. [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Yamazaki, Y. [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Institute of Physics, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902 (Japan)
2013-01-15
Confinement of high density electron plasmas in a strong uniform magnetic field was experimentally studied in a multi-ring trap (MRT). The trap was housed inside a bore tube and surrounded by a superconducting solenoid. A 5 T magnetic field was used to provide radial confinement while an electrostatic harmonic or rectangular potential well was used for axial confinement. For trapped electrons of N = 1.2 Multiplication-Sign 10{sup 10} in a harmonic potential well (HPW) with the trap length of L{sub T} = 320 mm, the plasma lifetime was about 10{sup 4} s and it became much longer at lower N = 4.5 Multiplication-Sign 10{sup 9}. Such long holding times were achieved without application of rotating electric fields. Contrastingly, in a rectangular potential well (RPW), the plasma of N = 1.2 Multiplication-Sign 10{sup 10} under the same trap length expanded to cover the whole Faraday Cup within 200 s, where its radial expansion rate was {eta} = 3.2 Multiplication-Sign 10{sup -2} mm/s, which was 20 times faster than HPW. The lifetime for RPW became shorter with increasing L{sub T} and scaled as 1/[L{sub T}]{sup 2}. This scaling found for high density plasmas is similar to the obtained one with different Penning-Malmberg traps at UC San Diego (USCD).
Three-layer dielectric models for generalized Coulomb potential calculation in ellipsoidal geometry.
Xue, Changfeng; Deng, Shaozhong
2011-05-01
This paper concerns a basic electrostatic problem: how to calculate generalized Coulomb and self-polarization potentials in heterogeneous dielectric media. In particular, with simulations of ellipsoidal semiconductor quantum dots and elongated biomacromolecules being its target applications, this paper extends the so-called three-layer dielectric models for generalized Coulomb and self-polarization potential calculation from the spherical and the spheroidal geometries to the triaxial ellipsoidal geometry. Compared to the simple steplike dielectric model, these three-layer dielectric models can overcome the mathematical divergence in the self-polarization energy by employing continuous radial dielectric functions. More specifically, in this paper, the quasiharmonic three-layer dielectric model for the ellipsoidal geometry is discussed, and the explicit analytical series solutions of the corresponding electrostatic problem are obtained in terms of the ellipsoidal harmonics. Then a robust numerical procedure working for general three-layer dielectric models is developed. The key component of the numerical method is to subdivide the transition layer of the underlying three-layer model into multiple sublayers and then in each one of them approximate the select dielectric function of the transition layer by one of the quasiharmonic functional form rather than simply by a constant value as one would normally do. As a result, the numerical method has no numerical divergence. PMID:21728695
Three-layer dielectric models for generalized Coulomb potential calculation in ellipsoidal geometry
NASA Astrophysics Data System (ADS)
Xue, Changfeng; Deng, Shaozhong
2011-05-01
This paper concerns a basic electrostatic problem: how to calculate generalized Coulomb and self-polarization potentials in heterogeneous dielectric media. In particular, with simulations of ellipsoidal semiconductor quantum dots and elongated biomacromolecules being its target applications, this paper extends the so-called three-layer dielectric models for generalized Coulomb and self-polarization potential calculation from the spherical and the spheroidal geometries to the triaxial ellipsoidal geometry. Compared to the simple steplike dielectric model, these three-layer dielectric models can overcome the mathematical divergence in the self-polarization energy by employing continuous radial dielectric functions. More specifically, in this paper, the quasiharmonic three-layer dielectric model for the ellipsoidal geometry is discussed, and the explicit analytical series solutions of the corresponding electrostatic problem are obtained in terms of the ellipsoidal harmonics. Then a robust numerical procedure working for general three-layer dielectric models is developed. The key component of the numerical method is to subdivide the transition layer of the underlying three-layer model into multiple sublayers and then in each one of them approximate the select dielectric function of the transition layer by one of the quasiharmonic functional form rather than simply by a constant value as one would normally do. As a result, the numerical method has no numerical divergence.
K. Noborio; Y. Yamamoto; Y. Ueno; S. Konishi
2005-01-01
We have simulated an IECF (inertial electrostatic confinement fusion) device by developing and using a particle code. Because a virtual anode is built up at large current region, which decelerates ions and reduces neutron yield, suppression of this virtual anode by supply of electrons from an additional electrode inside the cathode has been tried in the simulations. The simulation results
Plasma confinement by a radio frequency plugging potential in an axisymmetric mirror-cusp device
R. Kumazawa; S. Okamura; K. Adati; T. Aoki; H. Fujita; K. Hattori; S. Hidekuma; T. Kawamoto; Y. Okubo; T. Sato
1986-01-01
The RFC-XX-M is a magnetohydrodynamic (MHD) stable and axisymmetric mirror-cusp device with radio frequency (RF) plugging. The plasma is produced by ion cyclotron resonant heating (ICRH) with gas puffing at the central mirror. The total ion energy confinement time including axial loss, electron drag, and charge exchange is improved by a factor of three by the RF plugging and reaches
Bandopadhyay, Aditya; Chakraborty, Suman
2015-03-21
By considering an ion moving inside an imaginary sphere filled with a power-law fluid, we bring out the implications of the fluid rheology and the influence of the proximity of the other ions towards evaluating the conduction current in an ionic solution. We show that the variation of the conductivity as a function of the ionic concentration is both qualitatively and quantitatively similar to that predicted by the Kohlrausch law. We then utilize this consideration for estimating streaming potentials developed across narrow fluidic confinements as a consequence of the transport of ions in a convective medium constituting a power-law fluid. These estimates turn out to be in sharp contrast to the classical estimates of streaming potential for non-Newtonian fluids, in which the effect of rheology of the solvent is merely considered to affect the advection current, disregarding its contributions to the conduction current. Our results have potential implications of devising a new paradigm of consistent estimation of streaming potentials for non-Newtonian fluids, with combined considerations of the confinement effect and fluid rheology in the theoretical calculations. PMID:25693753
Nigel Cundy; Yongmin Cho; Weonjong Lee
2014-11-04
In the past few years, we have presented a new way of considering quark confinement. Through a careful choice of a Cho-Duan-Ge Abelian Decomposition, we can construct the QCD Wilson Loop in terms of an Abelian restricted field. The relationship between the QCD and restricted string tensions is exact; and we do not need to gauge fix, apply any path ordering of gauge links, or additional path integrals. This hints at why mesons are colour neutral. Furthermore, the Abelian restricted field contains two parts: a Maxwell term, and a topological term. The topological term can describe magnetic monopoles and other topological objects, which can be studied both numerically and theoretically. By examining the topological part of the restricted field strength we have found evidence suggesting that these objects, which will contribute to confinement if present, are indeed there. Previous studies have used simplifications, breaking the exact relationship between the restricted and QCD string tensions, but it was found that the topological term dominated the restricted string tension. Here we remove those simplifications, and show that the Abelian restricted field does indeed fully explain confinement. However, our results for how much of the restricted string tension arises from the topological objects show strong dependence on the lattice spacing and level of smearing, so we are not yet able to draw a definitive conclusion.
Ramirez Caballero, Gustavo
2012-02-14
metallic thin films, molecular water dissociation can occur. When ethylene was located in the gap between Ti/Pt thin films, the molecule converts in an anion radical adopting the geometry and structure of the activated monomer necessary to initiate chain...
2011-01-01
We investigate the effect of an external magnetic field on the carrier states that are localized at a potential kink and a kink-antikink in bilayer graphene. These chiral states are localized at the interface between two potential regions with opposite signs. PACS numbers: 71.10.Pm, 73.21.-b, 81.05.Uw PMID:21756331
The whistling potentiality of an orifice in a confined flow using an energetic criterion
P. Testud; Y. Aurégan; P. Moussou; A. Hirschberg
2009-01-01
Using a two-source method, the scattering matrices of 10 sharp-edged thin orifices are measured under different subsonic flow conditions. The data are analysed in terms of net acoustical energy balance: the potential whistling frequency range is defined as the one associated with acoustical energy production.A Strouhal number describing the maximum whistling potentiality is found to be equal to 0.2–0.35, based
Phase Separation in Confined Geometries
NASA Astrophysics Data System (ADS)
Binder, Kurt; Puri, Sanjay; Das, Subir K.; Horbach, Jürgen
2010-02-01
The kinetics of phase separation or domain growth, subsequent to temperature quenches of binary mixtures from the one-phase region into the miscibility gap, still remains a challenging problem of nonequilibrium statistical mechanics. We have an incomplete understanding of many aspects of the growth of concentration inhomogeneities, including the effect of surfaces on this process, and the interplay with wetting phenomena and finite-size effects in thin films. In the present paper, an overview of the simulation approaches to this problem is given, with an emphasis on solutions of a diffusive Ginzburg-Landau model. We also discuss two recent alternative approaches: a local molecular field approximation to the Kawasaki spin exchange model on a lattice; and molecular dynamics simulations of a fluid binary Lennard-Jones mixture. A brief outlook to open questions is also given.
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
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.
NASA Astrophysics Data System (ADS)
Ribeiro, M. S.; Nobre, F. D.; Curado, E. M. F.
2012-12-01
By comparing numerical and analytical results, it is shown that a system of interacting particles under overdamped motion is very well described by a nonlinear Fokker-Planck equation, which can be associated with nonextensive statistical mechanics. The particle-particle interactions considered are repulsive, motivated by three different physical situations: (i) modified Bessel function, commonly used in vortex-vortex interactions, relevant for the flux-front penetration in disordered type-II superconductors; (ii) Yukawa-like forces, useful for charged particles in plasma, or colloidal suspensions; (iii) derived from a Gaussian potential, common in complex fluids, like polymer chains dispersed in a solvent. Moreover, the system is subjected to a general confining potential, ?( x) = ( ?| x| z )/ z ( ? > 0 , z > 1), so that a stationary state is reached after a sufficiently long time. Recent numerical and analytical investigations, considering interactions of type (i) and a harmonic confining potential ( z = 2), have shown strong evidence that a q-Gaussian distribution, P( x,t), with q = 0, describes appropriately the particle positions during their time evolution, as well as in their stationary state. Herein we reinforce further the connection with nonextensive statistical mechanics, by presenting numerical evidence showing that: (a) in the case z = 2, different particle-particle interactions only modify the diffusion parameter D of the nonlinear Fokker-Planck equation; (b) for z ? 2, all cases investigated fit well the analytical stationary solution P st( x), given in terms of a q-exponential (with the same index q = 0) of the general external potential ?( x). In this later case, we propose an approximate time-dependent P( x,t) (not known analytically for z ? 2), which is in very good agreement with the simulations for a large range of times, including the approach to the stationary state. The present work suggests that a wide variety of physical phenomena, characterized by repulsive interacting particles under overdamped motion, present a universal behavior, in the sense that all of them are associated with the same entropic form and nonlinear Fokker-Planck equation.
Importance of the energy-dependent geometry in the /sup 16/O+ /sup 16/O optical model potential
Pantis, G.; Ioannidis, K.; Poirier, P.
1985-08-01
Optical model potentials with various forms of energy-dependent geometry have been considered for the description of /sup 16/O+ /sup 16/O elastic scattering. It is shown that the variation with energy of the imaginary radius leads to a reasonable fit of the cross-section data, throughout the energy range.
In 1995, EPA completed a risk assessment for potential air emissions from the operation of a proposed confined disposal facility (CDF) to be constructed and operated by the U.S. Army Corps of Engineers for dredged sediments from the Indiana Harbor and Shipping Canal in East Chica...
NASA Astrophysics Data System (ADS)
Bakke, K.
2015-07-01
The behaviour of the Landau-Aharonov-Casher system is discussed by showing a case where the external electric field cannot yield the Landau-Aharonov-Casher quantization under the influence of rotating effects in the cosmic string spacetime, but it can yield bound states solutions to the Schrödinger-Pauli equation analogous to having the Landau-Aharonov-Casher system confined to a hard-wall confining potential under the influence of rotating effects and the topology of the cosmic string spacetime (by assuming ? ??1 and neglecting the effects of a gravitational self-force on the particle).
Ohnishi, Masami; Yamamoto, Yasushi; Yoshikawa, Kiyoshi [Kyoto Univ., Uji, Kyoto (Japan). Inst. of Atomic Energy; Sato, Kunihiro [Himeji Inst. of Tech., Himeji, Hyogo (Japan)
1995-12-31
The electrostatic potential well in an inertial-electrostatic confinement (IEC) is calculated by performing the numerical simulations based on the particle-in-cell method. The single, double and triple wells, depending on the amount of the injected ion current, are observed to be formed for the ions with a mono-energetic distribution. The well in the center of the multi-well structure is unstable and oscillates at the period much longer than the ion plasma frequency. A double well structure can be formed even for the ions with a spread energy distribution when the ion current is larger than the threshold value. The time-averaged neutron production in D-D fusion events is found to be proportional to the third power of the ion current where the double well structure is formed. The numerical simulation reveals that an IEC possesses the favorable dependence of fusion reactions on the injected ion current for the application to a neutron source or a fusion reactor.
M. A. “Curt” Koenders; Steffen Reymann
2000-01-01
The interparticle force due to electrostatic\\/ionic origin in thermal equilibrium is modeled for two particles in close contact in an ion-laden fluid. The space between the particles presents approximately a wedge-shaped geometry. Two methods are used to ascertain the value of the interparticle force: an analytical approximation (equivalent to the traditional Debye–Hückel (DH) method) and a simulation of the ionic
Langenheim, Victoria E.; Griscom, Andrew; Jachens, R.C.; Hildenbrand, T.G.
2000-01-01
Gravity and magnetic data provide new insights on the structural underpinnings of the San Fernando Basin region, which may be important to ground motion models. Gravity data indicate that a deep basin (>5 km) underlies the northern part of the San Fernando Valley; this deep basin is required to explain the lowest gravity values over the Mission Hills thrust fault. Gravity modeling, constrained by well data and density information, shows that the basin may reach a thickness of 8 km, coinciding with the upper termination of the 1994 Northridge earthquake mainshock rupture. The basin is deeper than previous estimates by 2 to 4 km; this estimate is the result of high densities for the gravels of the Pliocene-Pleisocene Saugus Formation. The geometry of the southern margin of the deep basin is not well-constrained by the gravity data, but may dip to the south. Recently acquired seismic data along the LARSE (Los Angeles Regional Seismic Experiment) II profile may provide constraints to determine the location and attitude of the basin edge. Gravity and aeromagnetic models across the eastern margin of the San Fernando Valley indicate that the Verdugo fault may dip to the southwest along its southern extent and therefore have a normal fault geometry whereas it clearly has a thrust fault geometry along its northern strand.
E. Kiritsis; L. Mazzanti; F. Nitti
2014-12-03
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.
Mezeme, M Essone; Brosseau, C
2012-07-30
In this work, we describe finite element simulations of the plasmonic resonance (PLR) properties of a self-similar chain of plasmonic nanostructures. Using a broad range of conditions, we find strong numerical evidence that the electric field confinement behaves as (?/?)(PLR)[proporationality] EFE(-?), where EFE is the electric field enhancement, ?is the linear size of the focusing length, and ? is the wavelength of the resonant excitation. We find that the exponent ? is close to 1, i.e. significantly lower than the 1.5 found for two-dimensional nanodisks. This scaling law provides support for the hypothesis of a universal regime in which the sub-optical wavelength electric field confinement is controlled by the Euclidean dimensionality and is independent of nanoparticle size, metal nature, or embedding medium permittivity. PMID:23038312
Symplectic Geometry Metric geometry
Wolpert, Scott A.
surfaces, metric space geometry, as well as the analytic/algebraic geometry of curvature, characteristicBasics Symplectic Geometry Curvature Metric geometry Random geodesics Weil-Petersson sampler;Basics Symplectic Geometry Curvature Metric geometry Random geodesics Table of contents 1 Introduction
Edge Currents for Quantum Hall Systems, I. One-Edge, Unbounded Geometries
Peter D. Hislop; Eric Soccorsi
2007-02-27
Devices exhibiting the integer quantum Hall effect can be modeled by one-electron Schroedinger operators describing the planar motion of an electron in a perpendicular, constant magnetic field, and under the influence of an electrostatic potential. The electron motion is confined to unbounded subsets of the plane by confining potential barriers. The edges of the confining potential barrier create edge currents. In this, the first of two papers, we prove explicit lower bounds on the edge currents associated with one-edge, unbounded geometries formed by various confining potentials. This work extends some known results that we review. The edge currents are carried by states with energy localized between any two Landau levels. These one-edge geometries describe the electron confined to certain unbounded regions in the plane obtained by deforming half-plane regions. We prove that the currents are stable under various potential perturbations, provided the perturbations are suitably small relative to the magnetic field strength, including perturbations by random potentials. For these cases of one-edge geometries, the existence of, and the estimates on, the edge currents imply that the corresponding Hamiltonian has intervals of absolutely continuous spectrum. In the second paper of this series, we consider the edge currents associated with two-edge geometries describing bounded, cylinder-like regions, and unbounded, strip-like, regions.
Erem, Burak; Coll-Font, Jaume; Orellana, Ramon Martinez; Štóví?ek, Petr; Brooks, Dana H.
2014-01-01
Cardiac electrical imaging from body surface potential measurements is increasingly being seen as a technology with the potential for use in the clinic, for example for pre-procedure planning or during-treatment guidance for ventricular arrhythmia ablation procedures. However several important impediments to widespread adoption of this technology remain to be effectively overcome. Here we address two of these impediments: the difficulty of reconstructing electric potentials on the inner (endocardial) as well as outer (epicardial) surfaces of the ventricles, and the need for full anatomical imaging of the subject’s thorax to build an accurate subject-specific geometry. We introduce two new features in our reconstruction algorithm: a non-linear low-order dynamic parameterization derived from the measured body surface signals, and a technique to jointly regularize both surfaces. With these methodological innovations in combination, it is possible to reconstruct endocardial activation from clinically acquired measurements with an imprecise thorax geometry. In particular we test the method using body surface potentials acquired from three subjects during clinical procedures where the subjects’ hearts were paced on their endocardia using a catheter device. Our geometric models were constructed using a set of CT scans limited in axial extent to the immediate region near the heart. The catheter system provides a reference location to which we compare our results. We compare our estimates of pacing site localization, in terms of both accuracy and stability, to those reported in a recent clinical publication [1], where a full set of CT scans were available and only epicardial potentials were reconstructed. PMID:24595345
Erem, Burak; Coll-Font, Jaume; Orellana, Ramon Martinez; Stovícek, Petr; Brooks, Dana H
2014-03-01
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
Naiedja, H.; Quentin, P. [Centre d'Etudes Nucleaires de Bordeaux-Gradignan, Universite Bordeaux-I and CNRS/IN2P3, B.P. 120, F-33175 Gradignan (France); Bencheikh, K. [Departement de Physique, Laboratoire de Physique Quantique et Systemes Dynamiques, Universite de Setif, Setif 19000 (Algeria); Bartel, J. [Institut Pluridisciplinaire Hubert Curien, Universite de Strasbourg and CNRS/IN2P3, B.P. 28, F-67037 Strasbourg (France)
2011-05-15
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).
Role of flow shear in enhanced core confinement regimes
Hahm, T.S. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Burrell, K.H. [General Atomics, San Diego, CA (United States)
1996-03-01
The importance of the ExB flow shear in various enhanced confinement regimes is discussed in terms of the turbulence suppression criterion in toroidal geometry. This criterion is then further generalized to include the poloidal angle dependence of the equilibrium electrostatic potential. The implication of the recently observed in-out asymmetry in the fluctuation behavior in DIII-D VH-mode is discussed.
Extrapolating potential energy surfaces by scaling electron correlation at a single geometry
NASA Astrophysics Data System (ADS)
Varandas, A. J. C.; Piecuch, P.
2006-10-01
It is shown that the molecular potential energy surface corresponding to a high level of ab initio theory can be accurately predicted by performing calculations with smaller basis sets and then scaling the electron correlation at a single point calculated with the larger target basis set.
On the geometry of the Dirac matter with the Fermionic potentials and its quantum properties
Luca Fabbri
2014-05-22
We consider the torsional completion of gravity with electrodynamics for Dirac matter fields; we will see that these Dirac matter field equations will develop torsionally-induced non-linear interactions, which can be manipulated in order to be rearranged in the form of self-fermion potentials of a specific structure: eventually we will see that these non-linear interactions result into dynamical effects that are formally equivalent to those due to the quantum corrections.
Deheng Shi; Yufang Liu; Jinfeng Sun; Zunlue Zhu; Xiangdong Yang
2005-01-01
The accurate dissociation energy and equilibrium geometry of the b3? state of 7LiH molecule is calculated using a symmetry-adapted-cluster configuration-interaction method in full active space. And the calculated results are 0.2580 eV and 0.1958 nm for the dissociation energy and equilibrium geometry, respectively. The whole potential energy curve for the b3? state is also calculated over the internuclear separation range
NASA Astrophysics Data System (ADS)
Hansen, J. S.; Daivis, Peter J.; Todd, B. D.
2009-10-01
In this paper we present equilibrium molecular-dynamics results for the shear, rotational, and spin viscosities for fluids composed of linear molecules. The density dependence of the shear viscosity follows a stretched exponential function, whereas the rotational viscosity and the spin viscosities show approximately power-law dependencies. The frequency-dependent shear and spin viscosities are also studied. It is found that viscoelastic behavior is first manifested in the shear viscosity and that the real part of the spin viscosities features a maximum for nonzero frequency. The calculated transport coefficients are used together with the extended Navier-Stokes equations to investigate the effect of the coupling between the intrinsic angular momentum and linear momentum for highly confined fluids. Both steady and oscillatory flows are studied. It is shown, for example, that the fluid flow rate for Poiseuille flow is reduced by up to 10% in a 2 nm channel for a buta-triene fluid at density 236kgm-3 and temperature 306 K. The coupling effect may, therefore, become very important for nanofluidic applications.
Diffusion Geometry Diffusion Geometry
Hirn, Matthew
Diffusion Geometry Diffusion Geometry for High Dimensional Data Matthew J. Hirn July 3, 2013 #12;Diffusion Geometry Introduction Embedding of closed curve Figure: Left: A closed, non-self-intersecting curve in 3 dimensions. Right: Its embedding as a circle. #12;Diffusion Geometry Introduction Cartoon
NASA Astrophysics Data System (ADS)
Prabhakar, Sanjay; Raynolds, James
2009-03-01
Among recent proposals for next-generation, non-charge-based logic is the notion that a single electron can be trapped and its spin can be manipulated through the application of gate voltages (Rev. Mod. Phys.79, 1217 (2007)). In this talk we present numerical simulations of Berry Phase of electron spins in single electron devices for realistic asymmetric confining potentials in support of experimental work at the University at Albany, State University of New York aimed at the practical development of post-CMOS concepts and devices. We solve the Schr"odinger equation including spin-orbit effects using a numerical finite-element based technique. We will discuss the calculation of Berry Phase for electrons (Phys. Rev. B 73, 125330 (2006)) in electrostatically defined quantum dots including the Rashba and Dresselhaus spin-orbit interactions computed numerically from realistic asymmetric confining potentials. The new simulation results open the possibility of spin manipulation through the gate induced Berry phase. This work is supported through funding from the DARPA/NRI INDEX center.
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
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.
Zhang, Du; Peng, Degao; Zhang, Peng; Yang, Weitao
2015-01-14
The energy gradient for electronic excited states is of immense interest not only for spectroscopy but also for the theoretical study of photochemical reactions. We present the analytic excited state energy gradient of the particle-particle random phase approximation (pp-RPA). The analytic gradient formula is developed from an approach similar to that of time-dependent density-functional theory (TDDFT). The formula is verified for both the Hartree-Fock and (Generalized) Kohn-Sham reference states via comparison with finite difference results. The excited state potential energy surfaces and optimized geometries of some small molecules are investigated, yielding results of similar or better quality compared to adiabatic TDDFT. The singlet-to-triplet instability in TDDFT resulting in underestimated energies of the lowest triplet states is eliminated by pp-RPA. Charge transfer excitations and double excitations, which are challenging for most adiabatic TDDFT methods, can be reasonably well captured by pp-RPA. Within this framework, ground state potential energy surfaces of stretched single bonds can also be described well. PMID:25410624
Edge Currents for Quantum Hall Systems, II. Two-Edge, Bounded and Unbounded Geometries
Peter D. Hislop; Eric Soccorsi
2007-02-27
Devices exhibiting the integer quantum Hall effect can be modeled by one-electron Schroedinger operators describing the planar motion of an electron in a perpendicular, constant magnetic field, and under the influence of an electrostatic potential. The electron motion is confined to bounded or unbounded subsets of the plane by confining potential barriers. The edges of the confining potential barriers create edge currents. This is the second of two papers in which we review recent progress and prove explicit lower bounds on the edge currents associated with one- and two-edge geometries. In this paper, we study various unbounded and bounded, two-edge geometries with soft and hard confining potentials. These two-edge geometries describe the electron confined to unbounded regions in the plane, such as a strip, or to bounded regions, such as a finite length cylinder. We prove that the edge currents are stable under various perturbations, provided they are suitably small relative to the magnetic field strength, including perturbations by random potentials. The existence of, and the estimates on, the edge currents are independent of the spectral type of the operator.
Spectra of Confined Atoms and Molecules
D. Bielinska-Waz
2003-01-01
The properties of spectra of atoms and molecules confined by an external potential are analyzed. The effects of spatial confinement are studied using quantum-chemical models. The confinement of the system is described by an external one-particle potential. Two-electron atoms confined in a spherically symmetric harmonic oscillator potential are investigated in detail [1]. In this case the interplay between the effects
Guzowski, R.V. [Science Applications International Corp., Albuquerque, NM (United States); Newman, G. [GRAM, Inc., Albuquerque, NM (United States)
1993-12-01
The Greater Confinement Disposal location is being evaluated to determine whether defense-generated transuranic waste buried at this location complies with the Containment Requirements established by the US Environmental Protection Agency. One step in determining compliance is to identify those combinations of events and processes (scenarios) that define possible future states of the disposal system for which performance assessments must be performed. An established scenario-development procedure was used to identify a comprehensive set of mutually exclusive scenarios. To assure completeness, 761 features, events, processes, and other listings (FEPS) were compiled from 11 references. This number was reduced to 205 primarily through the elimination of duplications. The 205 FEPs were screened based on site-specific, goal-specific, and regulatory criteria. Four events survived screening and were used in preliminary scenario development: (1) exploratory drilling penetrates a GCD borehole, (2) drilling of a withdrawal/injection well penetrates a GCD borehole, (3) subsidence occurs at the RWMS, and (4) irrigation occurs at the RWMS. A logic diagram was used to develop 16 scenarios from the four events. No screening of these scenarios was attempted at this time. Additional screening of the currently retained events and processes will be based on additional data and information from site-characterization activities. When screening of the events and processes is completed, a final set of scenarios will be developed and screened based on consequence and probability of occurrence.
Kimichika Fukushima; Hikaru Sato
2015-04-07
Considering the propagation of fields in the spacetime continuum and the well-defined features of fields with finite degrees of freedom, the wave function is expanded in terms of a finite set of basis functions localized in spacetime. This paper presents the analytic eigenenergies derived for a confined fundamental fermion-antifermion pair under a linear potential obtained from the Wilson loop for the non-Abelian Yang-Mills field. The Hamiltonian matrix of the Dirac equation is analytically diagonalized using basis functions localized in spacetime. The squared system eigenenergies are proportional to the string tension and the absolute value of the Dirac's relativistic quantum number related to the total angular momentum, consistent with the expectation.
Kimichika Fukushima; Hikaru Sato
2015-06-08
Considering the propagation of fields in the spacetime continuum and the well-defined features of fields with finite degrees of freedom, the wave function is expanded in terms of a finite set of basis functions localized in spacetime. This paper presents the analytic eigenenergies derived for a confined fundamental fermion-antifermion pair under a linear potential obtained from the Wilson loop for the non-Abelian Yang-Mills field. The Hamiltonian matrix of the Dirac equation is analytically diagonalized using basis functions localized in spacetime. The squared system eigenenergies are proportional to the string tension and the absolute value of the Dirac's relativistic quantum number related to the total angular momentum, consistent with the expectation.
Turner, D L; Costa, H S; Coutinho, I B; Legall, J; Xavier, A V
1997-01-15
Cytochrome c551.5 is a trihaem cytochrome of the cytochrome c3 family isolated from Desulfuromonas acetoxidans. Although several X-ray structures are available for tetrahaem cytochromes of this family, there is no X-ray structure for trihaem cytochromes. Cytochrome C551.5 was studied in the oxidized form by means of two-dimensional NMR. The pattern of observed interhaem NOESY connectivities is in agreement with the haem core structure previously determined by NMR for the reduced protein [Coutinho, I. B., Turner, D. L., Liu, M. Y., LeGall, J. & Xavier, A. V. (1996) J. Biol. Inorg. Chem. 1, 305-311]. The similarities found between the haem core structure and the amino acid sequence of cytochrome c551.5 and those of tetrahaem cytochromes c3 allows each of the haems to be specifically assigned in the polypeptide sequence, and the attribution of the midpoint redox potentials to the individual haems. This also allows individual redox potentials to be assigned to each haem in the NMR spectrum. The paramagnetic shifts of the 13C resonances of the haem substituents were analyzed in terms of pi molecular orbitals with perturbed D4h symmetry. The parameters of this analysis have been shown to be controlled by the orientation of the axial ligands in several other bis-His-coordinated haems and hence the ligand geometry was deduced for cytochrome C551.5. The structural analogy between the relative haem plane orientations in cytochrome c551.5 and the tetrahaem cytochromes c3 is found to extend to the axial ligands with the largest differences being in the vicinity of the deleted fourth haem, using the numbering of cytochrome c3 haems. PMID:9030775
H. Belich; K. Bakke
2015-04-27
The behaviour of a relativistic scalar particle subject to a scalar potential under the effects of the violation of the Lorentz symmetry in the cosmic string spacetime is discussed. It is considered two possible scenarios of the Lorentz symmetry breaking in the CPT-even gauge sector of the Standard Model Extension defined by a tensor $\\left(K_{F}\\right)_{\\mu\
Heavy Quark Potential at Finite Temperature in a Dual Gravity Closer to Large N QCD
Binoy Krishna Patra; Himanshu Khanchandani
2015-04-01
In gauge-gravity duality, the heavy quark potential at finite temperature is usually calculated with the pure AdS background, which does not capture the renormalization group (RG) running in the gauge theory part. In addition, the potential does not contain any confining term in the deconfined phase. Following the Klebanov-Strassler geometry, we employ a geometry, which captures the RG flow similar to QCD, to obtain the heavy quark potential by analytically continuing the string configurations into the complex plane. In addition to the attractive terms, the obtained potential has confining terms both at $T = 0$ and $T \
Subwavelength metallic waveguides as a tool for extreme confinement of THz surface waves
Gacemi, D.; Mangeney, J.; Colombelli, R.; Degiron, A.
2013-01-01
Research on surface waves supported by metals at THz frequencies is experiencing a tremendous growth due to their potential for imaging, biological sensing and high-speed electronic circuits. Harnessing their properties is, however, challenging because these waves are typically poorly confined and weakly bound to the metal surface. Many design strategies have been introduced to overcome these limitations and achieve increased modal confinement, including patterned surfaces, coated waveguides and a variety of sub-wavelength geometries. Here we provide evidence, using a combination of numerical simulations and time-resolved experiments, that shrinking the transverse size of a generic metallic structure always leads to solutions with extreme field confinement. The existence of such a general behavior offers a new perspective on energy confinement and should benefit future developments in THz science and technology. PMID:23463351
Polymers under Cylindrical Confinement
NASA Astrophysics Data System (ADS)
Russell, Thomas
2009-03-01
Anodized alumina oxide (AAO) membranes offer a unique platform to investigate polymers under confinement. AAO membranes have been prepared where the diameters of the nanopores in the membrane have been varied from 8 to 50 nm by varying the anodization conditions. Capillary force is sufficiently large to draw high molecular weight polymers into the membrane, producing either nanotubes or nanorods. Polymer solutions can also be used place a thin film on the walls of the nanopores, forming nanotubes. With pore diameters less than the radius of gyration, a quantitative understanding of perturbations to chain dynamics due to geometric constraints was examined. We found a weak molecular weight-dependent mobility of polymers confined within AAO nanopores having diameters smaller than the dimension of the chains in the bulk. The measured mobility of polymers in the confined geometry was much higher than the mobility of the unconfined chain. Rayleigh instabilities in thin polymer films confined within nanoporous alumina membranes were also found where periodic undulations on the film surface were found to increase with time, eventually bridging across the cylindrical nanopore, resulting in the formation of polymer nanorods with a periodic array of encapsulated holes. With microphase separated block copolymers, where the characteristic period of the BCP morphology is comparable to the pore diameter, significant deviations from the bulk morphology as revealed by electron tomography. Small angle neutron scattering was also used to investigate the influence of cylindrical confinement on the order-to-disordered transition. This work was done in collaboration with T. J. McCarthy (UMass), K. Shin (Seoul National University), H. Jinnai (Kyoto University), D. Chen, J. Chen, H. Xiang, T. Kim, and P. Dobriyal, and was supported by the DOE, NSF MRSEC, NSF CHM.
Thermal noise in confined fluids.
Sanghi, T; Aluru, N R
2014-11-01
In this work, we discuss a combined memory function equation (MFE) and generalized Langevin equation (GLE) approach (referred to as MFE/GLE formulation) to characterize thermal noise in confined fluids. Our study reveals that for fluids confined inside nanoscale geometries, the correlation time and the time decay of the autocorrelation function of the thermal noise are not significantly different across the confinement. We show that it is the strong cross-correlation of the mean force with the molecular velocity that gives rise to the spatial anisotropy in the velocity-autocorrelation function of the confined fluids. Further, we use the MFE/GLE formulation to extract the thermal force a fluid molecule experiences in a MD simulation. Noise extraction from MD simulation suggests that the frequency distribution of the thermal force is non-Gaussian. Also, the frequency distribution of the thermal force near the confining surface is found to be different in the direction parallel and perpendicular to the confinement. We also use the formulation to compute the noise correlation time of water confined inside a (6,6) carbon-nanotube (CNT). It is observed that inside the (6,6) CNT, in which water arranges itself in a highly concerted single-file arrangement, the correlation time of thermal noise is about an order of magnitude higher than that of bulk water. PMID:25381537
Thermal noise in confined fluids
NASA Astrophysics Data System (ADS)
Sanghi, T.; Aluru, N. R.
2014-11-01
In this work, we discuss a combined memory function equation (MFE) and generalized Langevin equation (GLE) approach (referred to as MFE/GLE formulation) to characterize thermal noise in confined fluids. Our study reveals that for fluids confined inside nanoscale geometries, the correlation time and the time decay of the autocorrelation function of the thermal noise are not significantly different across the confinement. We show that it is the strong cross-correlation of the mean force with the molecular velocity that gives rise to the spatial anisotropy in the velocity-autocorrelation function of the confined fluids. Further, we use the MFE/GLE formulation to extract the thermal force a fluid molecule experiences in a MD simulation. Noise extraction from MD simulation suggests that the frequency distribution of the thermal force is non-Gaussian. Also, the frequency distribution of the thermal force near the confining surface is found to be different in the direction parallel and perpendicular to the confinement. We also use the formulation to compute the noise correlation time of water confined inside a (6,6) carbon-nanotube (CNT). It is observed that inside the (6,6) CNT, in which water arranges itself in a highly concerted single-file arrangement, the correlation time of thermal noise is about an order of magnitude higher than that of bulk water.
Inertial electrostatic confinement: Theoretical and experimental studies of spherical devices
Ryan Meyer
2007-01-01
Inertial Electrostatic Confinement (IEC) is a means to confine ions for fusion purposes with electrostatic fields in a converging geometry. Its engineering simplicity makes it appealing when compared to magnetic confinement devices. It is hoped that such a device may one day be a net energy producer, but it has near term applications as a neutron generator. We study spherical
Dirk Rollmann; David E. Miller
2015-05-26
We discuss the forces on the internal constituents of the hadrons based on the bag model. The ground state of the hadrons forms a color singlet so that the effects of the colored internal states are neutralized. From the breaking of the dilatation and conformal symmetries under the strong interactions the corresponding currents are not conserved. These currents give rise to the forces changing the motion of the internal particles which causes confinement.
Elmo bumpy square plasma confinement device
Owen, L.W.
1985-01-01
The invention is an Elmo bumpy type plasma confinement device having a polygonal configuration of closed magnet field lines for improved plasma confinement. In the preferred embodiment, the device is of a square configuration which is referred to as an Elmo bumpy square (EBS). The EBS is formed by four linear magnetic mirror sections each comprising a plurality of axisymmetric assemblies connected in series and linked by 90/sup 0/ sections of a high magnetic field toroidal solenoid type field generating coils. These coils provide corner confinement with a minimum of radial dispersion of the confined plasma to minimize the detrimental effects of the toroidal curvature of the magnetic field. Each corner is formed by a plurality of circular or elliptical coils aligned about the corner radius to provide maximum continuity in the closing of the magnetic field lines about the square configuration confining the plasma within a vacuum vessel located within the various coils forming the square configuration confinement geometry.
Confined helium on Lagrange meshes
Daniel Baye; Jérémy Dohet-Eraly
2015-06-01
The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.
Confined helium on Lagrange meshes
Baye, Daniel
2015-01-01
The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.
CCSD(T) calculations of stabilities and properties of confined systems
NASA Astrophysics Data System (ADS)
Holka, F.; Urban, M.; Melicher?ík, M.; Neogrády, P.; Paldus, J.
2015-01-01
We analyze energies, electron affinities and polarizabilities of small anions exposed to an external confinement. The second electron in free O2- and S2- anions is unbound. We investigate the stabilizing effect of the spherical harmonic-oscillator confining potential ?. on these anions employing the Hartree-Fock stability analysis as introduced by ?ížek and Paldus. With increasing strength of the external harmonic-oscillator confinement potential ? the broken symmetry (BS) solutions are systematically eliminated. For ? larger than 0.1 all BS solutions for O2- disappear. For ? larger than 0.13 the CCSD(T) energy of O2- becomes more negative than the energy of the singly charged O- anion. We relate the harmonic-oscillator confining potential to a crystalline environment in which the O2- and S2- anions are stable. We also present a model allowing calculations of the in-crystal polarizabilities of anions. The model is based on CCSD(T) calculations of static polarizabilities of selected anions exposed to the spherical harmonic-oscillator confining potential ? This artificial confinement potential ? is then related to the ionic radii of the cation in representative crystal lattices. We investigate the polarizability of O2- and S2- anions in MgO, MgS, CaO, CaS, SrO, SrS, BaO and BaS crystals. We compare our results with alternative models for in-crystal polarizabilities. External confinement also stabilizes the uracil anion U-, as is shown by calculations with a stepwise micro-hydration of U-. Upon hydration is the CCSD(T) adiabatic electron affinity (AEA) of uracil enhanced by about 250 up to 570 meV in comparison with AEA of the isolated molecule, depending on the geometry of the hydrated uracil anion complex. We tried to find an analogy of the stabilization effect of the external confinement on the otherwise unstable anions. In uracil and its anion is the external confinement represented by the polarized continuum solvation model with dielectric constant as a variational parameter. The physical behavior of ions exposed to an artificial external, spherical harmonic-oscillator confining potential ?, the environment represented by a crystal structure and the confinement represented by the solvent, all have considerable stabilizing effect on the otherwise unstable free anion.
Quark confinement and metric fluctuations
P. R. Silva
2009-08-23
We analyse, by doing very simple calculations, the internal degree of freedom leading to the de Broglie frequency associated to a material particle, as well, the confinement of quarks provided both by the Cornell potential and by the MIT bag model.We propose that the driving forces behind these confining models could be originated in the fluctuations of the metric, namely the particle interacting self-gravitationally, when its mass fluctuates in position throught of a distance equal to the Planck length.
Alternative approaches to plasma confinement
NASA Technical Reports Server (NTRS)
Roth, J. R.
1977-01-01
The potential applications of fusion reactors, the desirable properties of reactors intended for various applications, and the limitations of the Tokamak concept are discussed. The principles and characteristics of 20 distinct alternative confinement concepts are described, each of which may be an alternative to the Tokamak. The devices are classed as Tokamak-like, stellarator-like, mirror machines, bumpy tori, electrostatically assisted, migma concept, and wall-confined plasma.
Particle Segregation and Dynamics in Confined Flows
Di Carlo, Dino; Edd, Jon F.; Humphry, Katherine J.; Stone, Howard A.; Toner, Mehmet
2015-01-01
Nonlinearity in finite-Reynolds-number flow results in particle migration transverse to fluid streamlines, producing the well-known “tubular pinch effect” in cylindrical pipes. Here we investigate these nonlinear effects in highly confined systems where the particle size approaches the channel dimensions. Experimental and numerical results reveal distinctive dynamics, including complex scaling of lift forces with channel and particle geometry. The unique behavior described in this Letter has broad implications for confined particulate flows. PMID:19392526
Semiflexible chains in confined spaces
NASA Astrophysics Data System (ADS)
Morrison, Greg; Thirumalai, D.
2009-01-01
We develop an analytical method for studying the properties of a noninteracting wormlike chain (WLC) in confined geometries. The mean-field-like theory replaces the rigid constraints of confinement with average constraints, thus allowing us to develop a tractable method for treating a WLC wrapped on the surface of a sphere, and fully encapsulated within it. The efficacy of the theory is established by reproducing the exact correlation functions for a WLC confined to the surface of a sphere. In addition, the coefficients in the free energy are exactly calculated. We also describe the behavior of a surface-confined chain under external tension that is relevant for single molecule experiments on histone-DNA complexes. The force-extension curves display spatial oscillations, and the extension of the chain, whose maximum value is bounded by the sphere diameter, scales as f-1 at large forces, in contrast to the unconfined chain that approaches the contour length as f-1/2 . A WLC encapsulated in a sphere, that is relevant for the study of the viral encapsulation of DNA, can also be treated using the mean-field approach. The predictions of the theory for various correlation functions are in excellent agreement with Langevin simulations. We find that strongly confined chains are highly structured by examining the correlations using a local winding axis. The predicted pressure of the system is in excellent agreement with simulations but, as is known, is significantly lower than the pressures seen for DNA packaged in viral capsids.
NASA Astrophysics Data System (ADS)
Heryadi, Dodi; Yeager, Danny L.; Golab, Joseph T.; Nichols, Jeffrey A.
1995-06-01
In a recent paper in The Journal of Chemical Physics, we showed the potential energy curves for several cation states of O2 obtained using the multiconfigurational spin tensor electron propagator method (MCSTEP) with a <5s4p3d> basis set. In this communication we present vertical ionization potential calculations to the same O2 states. However, for the results reported here, exactly the same basis sets and geometries are used that were used for two other forefront methods; the coupled-cluster reference electron propagator theory (CC-EPT) and the Fock space multireference coupled-cluster method (FSMRCC). Hence, more direct comparisons and contrasts among these methods are now available.
NASA Astrophysics Data System (ADS)
Christina lily Jasmine, P.; John Peter, A.; Lee, Chang Woo
2015-05-01
Electronic and optical properties of a hydrogenic donor impurity in a CdTe/Zn0.2Cd0.8Te/ZnTe core/shell/shell quantum dot are discussed taking into consideration of geometrical confinement effect. The confining potentials on both the sides of the barrier are different and a two parametrical potential of Smorodinsky-Winternitz is considered in this problem. The dielectric mismatch is included in the Hamiltonian. The position dependent effective mass is applied. The electronic properties are studied using variational method and the optical properties are investigated using the density matrix approach. The intersubband optical absorption, the oscillator strength and the radiative life time between ground and the excited states are studied based on the wave functions and the confined energies with and without the impurity with various dot radii. The results show that the absorption wavelength in type-II core and shell semiconducting nanomaterials can be tuned over a wider range of wavelengths by altering their size and the composition.
Developments in special geometry
Thomas Mohaupt; Owen Vaughan
2012-01-19
We review the special geometry of N = 2 supersymmetric vector and hypermultiplets with emphasis on recent developments and applications. A new formulation of the local c-map based on the Hesse potential and special real coordinates is presented. Other recent developments include the Euclidean version of special geometry, and generalizations of special geometry to non-supersymmetric theories. As applications we disucss the proof that the local r-map and c-map preserve geodesic completeness, and the construction of four- and five-dimensional static solutions through dimensional reduction over time. The shared features of the real, complex and quaternionic version of special geometry are stressed throughout.
Developments in special geometry
Mohaupt, Thomas
2011-01-01
We review the special geometry of N = 2 supersymmetric vector and hypermultiplets with emphasis on recent developments and applications. A new formulation of the local c-map based on the Hesse potential and special real coordinates is presented. Other recent developments include the Euclidean version of special geometry, and generalizations of special geometry to non-supersymmetric theories. As applications we disucss the proof that the local r-map and c-map preserve geodesic completeness, and the construction of four- and five-dimensional static solutions through dimensional reduction over time. The shared features of the real, complex and quaternionic version of special geometry are stressed throughout.
Casimir effects for classical and quantum liquids in slab geometry: A brief review
NASA Astrophysics Data System (ADS)
Biswas, Shyamal
2015-05-01
We analytically explore Casimir effects for confinement of classical and quantum fluctuations in slab (film) geometry (i) for classical (critical) fluctuations over 4He liquid around the ? point, and (ii) for quantum (phonon) fluctuations of Bogoliubov excitations over an interacting Bose-Einstein condensate. We also briefly review Casimir effects for confinement of quantum vacuum fluctuations confined to two plates of different geometries.
R. L. Davidson; G. D. Earle; J. H. Klenzing; R. A. Heelis
2010-01-01
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
Immel, S; Schmitt, G E; Lichtenthaler, F W
1998-12-01
Cyclofructins composed of six (1, "CF6") to ten (5, "CF10") beta-(1-->2)-linked fructofuranose units were subjected to conformational analysis using Monte Carlo simulations based on the PIMM91 force-field. Breaking the molecular symmetry partially by alternating inclination of the spiro-type anellated fructofuranoses relative to the crown ether ring core, i.e. the 3-OH groups pointing either towards or away from the molecular center, substantially lowers the strain energy of the cyclofructins. The global energy-minimum geometries of CF6, CF8, and CF10 exhibit Cn/2 rotational symmetry, whilst the odd-membered macrocycles in CF7 and CF9 adopt C1 symmetry. Identical conformations of the solid-state geometry of CF6 (1) and its computer-generated form manifest the reliability of the computational analysis. The molecular surfaces calculated for the energy-minimum structures establish a disk-type shape for CF6 (1), CF7 (2), and CF8 (3), whereas further ring enlargement to CF9 (4) and CF10 (5) leads to torus-shaped molecules with through-going cavities. Color-coded projection of the molecular lipophilicity patterns (MLPs) and the electrostatic potential profiles (MEPs) onto these surfaces cogently displays the crown ether-like properties, favoring the complexation of metal cations via strong electrostatic interactions through the 3-OH groups located on the hydrophilic molecular side. The central cavities of CF9 and CF10 are characterized not only by significantly enhanced hydrophobicity, but also by highly negative electrostatic potentials around the narrow aperture of the tori made up by the 3-OH/4-OH groups, and positive potentials on the opposite rim. Accordingly, CF9 and CF10 are capable to form inclusion complexes, the cavity of the latter being approximately as large as the one of alpha-cyclodextrin. Calculation of the inclusion complex geometries of CF9 with beta-alanine and of CF10 with p-aminobenzoic acid revealed the guest to be deeply incorporated into the respective cavities, masking the guest's hydrophobic parts. Analysis of the electrostatic interactions at the interface of the zwitter-ionic guests with the oppositely polarized hosts predicts a high degree of regiospecificity for complex formation. PMID:9880905
A potentially pure test of cosmic geometry: galaxy clusters and the real space Alcock-Paczynski test
Young-Rae Kim; Rupert Croft
2006-10-10
We investigate the possibility of probing dark energy by measuring the isotropy of the galaxy cluster autocorrelation function (an Alcock-Paczynski test). The correlation function is distorted in redshift space because of the cluster peculiar velocities, but if these are known and can be subtracted, the correlation function measurement becomes in principle a pure test of cosmic geometry. Galaxy cluster peculiar velocities can be measured using the kinetic Sunyaev Zel'dovich (kSZ) effect. Upcoming CMB surveys, e.g., ACT, SPT, Planck, are expected to do this with varying levels of accuracy, dependent on systematic errors due to cluster temperature measurements, radio point sources, and the primary CMB anisotropy. We use the Hubble volume N-body simulation and the hydrodynamic simulation results of Nagai et. al (2003) to simulate various kSZ surveys. We find by model fitting that a measurement of the correlation function distortion can be used to recover the cosmological parameters that have been used to generate the simulation. However, the low space density of galaxy clusters requires larger surveys than are taking place at present to place tight constraints on cosmology. For example, with the SPT and ACT surveys, Omega_Lambda could be measured to within 0.1 and 0.2 respectively at one sigma, but only upper limits on the equation of state parameter w will be possible. Nevertheless, with accurate measurements of the kSZ effect, this test can eventually be used to probe the dark energy equation of state and its evolution with redshift, with different systematic errors than other methods.
Scaling of confined and interacting comb polymers
NASA Astrophysics Data System (ADS)
Yeh, Catherine; Pincus, Philip
2011-03-01
We study the scaling of polymer chains grafted to a line, i.e. a 1-D brush or comb polymer, on a repulsive plane in good solvent using classical molecular dynamics. The grafting density is large enough to cause chain stretching. The confined comb geometry is motivated by intermediate filaments where the unstructured monomer c-termini form annular rings that can be modeled as a confined comb bent into a ring. We find that the scaling of brush size as a function of the number of monomers per chain is the same for a comb with and without confinement by a repulsive plane. We also consider the transition of a line of parallel interacting combs to the planar brush geometry as they are compressed from isolated combs; we present results for the dependence of brush height on the distance between combs.
Oie, Tetsuro
1980-01-01
A purpose of the present studies is twofold: (1) development of an empirical potential function (EPF) and (2) application of it to the studies of photoreaction center chlorophyll a dimer. The reliable estimate of geometric structures and energies of large molecules by quantum mechanical methods is not possible at the present time. An alternative method is, therefore, needed for the studies of large molecular systems, and Chapter I is dedicated to the development of this tool, i.e., an empirical potential function, which could suffice this purpose. Because of a large number of variable chemical compositions and functional groups characteristically present in a large molecule, it is important to include a large number of structurally diverse molecules in the development of the EPF. In Chapter II, the EPF is applied to study the geometrical structure of a chlorophyll a (Chl a) dimer, which is believed to exist at the photoreaction center of green plants and is known to play an essential role in photosynthetic energy conversion. Although various models have been proposed for this dimer structure, there is still a great need for information concerning the detailed geometric structure of this dimer. Therefore, in this chapter the structural stabilities of various dimer models are examined by the EPF, and detailed and quantitative information on the structure and stability of these models is provided.
Oie, Tetsuro
1980-07-28
A purpose of the present studies is twofold: (1) development of an empirical potential function (EDF) and (2) application of it to the studies of photoreaction center chlorophyll a dimer. The reliable estimate of geometric structures and energies of large molecules by quantum mechanical methods is not possible at the present time. An alternative method is, therefore, needed for the studies of large molecular systems, and Chapter I is dedicated to the development of this tool, i.e., an empirical potential function, which could suffice this purpose. Because of a large number of variable chemical compositions and functional groups characteristically present in a large molecule, it is important to include a large number of structurally diverse molecules in the development of the EPF. In Chapter II, the EPF is applied to study the geometrical structure of a chlorophyll a (Ch1 a) dimer, which is believed to exist at the photoreaction center of green plants and is known to play an essential role in photosynthetic energy conversion. Although various models have been proposed for this dimer structure, there is still a great need for information concerning the detailed geometric structure of this dimer. Therefore, in this chapter the structural stabilities of various dimer models are examined by the EPF, and detailed and quantitative information on the structure and stability of these models is provided.
NASA Astrophysics Data System (ADS)
Gharashi, Seyed Ebrahim; Daily, K. M.; Blume, D.
2012-10-01
We present highly accurate solutions of the Schrödinger equation for three fermions in two different spin states with zero-range s-wave interactions under harmonic confinement. Our approach covers spherically symmetric, strictly two-dimensional, strictly one-dimensional, cigar-shaped, and pancake-shaped traps. In particular, we discuss the transition from quasi-one-dimensional to strictly one-dimensional and from quasi-two-dimensional to strictly two-dimensional geometries. We determine and interpret the eigenenergies of the system as a function of the trap geometry and the strength of the zero-range interactions. The eigenenergies are used to investigate the dependence of the second- and third-order virial coefficients, which play an important role in the virial expansion of the thermodynamic potential, on the geometry of the trap. We show that the second- and third-order virial coefficients for anisotropic confinement geometries are, for experimentally relevant temperatures, very well approximated by those for the spherically symmetric confinement for all s-wave scattering lengths.
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
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
Quantum confined nanocrystalline silicon
NASA Astrophysics Data System (ADS)
Guan, Tianyuan; Kendrick, Chito; Theingi, San; Bagolini, Luigi; Riskey, Kory; Vitti, Lauren; Klafehn, Grant; Taylor, Craig; Lusk, Mark; Gorman, Brain; Collins, Reuben; Fields, Jeremy; Stradins, Pauls
2014-03-01
Quantum confined (QC) semiconductors have drawn much attention in photovoltaics due to their tunable optoelectronic properties and potential for efficiency improvements. Here, we report a study of nanocrystalline silicon (nc-Si:H), consisting of silicon nano-particles (SiNPs) embedded in hydrogenated amorphous silicon (a-Si:H) matrix. Films were grown by depositing the SiNPs and a-Si:H sequentially from separate plasma reactors in a common deposition chamber. Several characterizations were used to ensure the material had low defect density and that the SiNPs were highly crystalline and well within the QC regime. Optical properties of hybrid SiNP/a-Si:H films were explored using visible to near infrared photoluminescence (PL). At low temperature, PL revealed two primary emission features, one from conventional a-Si:H ~ 1.3 eV and a second peak which can be attributed to recombination in SiNPs. The energy of this peak is higher than the bulk c-Si bandgap (~ 1.2 eV), and with decreasing SiNP size, it increases to ~ 1.7 eV. This quantum confinement effect agrees with Density Functional Theory predictions. In addition, we also see that the PL peak for SiNPs surrounded by a-Si:H shifts to lower energy relative to the isolated SiNPs. This shift is also consistent with the modeling results which show that surrounding SiNPs with a-Si:H leads to a softening of the confinement barrier and a redshift in the optical gap.
Heavy quark potential at finite temperature in a dual gravity closer to large N QCD
NASA Astrophysics Data System (ADS)
Patra, Binoy Krishna; Khanchandani, Himanshu
2015-03-01
In gauge-gravity duality, heavy quark potential at finite temperature is usually calculated with the pure AdS background, which does not capture the renormalisation group (RG) running in the gauge theory part and the potential also does not contain any confining term in the deconfined phase. Following the developments on the Klebanov-Strassler geometry, we employ a geometry which captures the RG flow similar to QCD, to obtain the heavy quark potential by analytically continuing the string configurations into the complex plane. In addition to the attractive terms, the obtained potential has confining terms both at T = 0 and T ? 0 , compared to the calculations usually done in the literature, where only Coulomb like term is present in the deconfined phase. The potential also develops an (negative) imaginary part above a critical separation, rc (=0.53 zh) . Moreover our potential exhibits a behaviour, different from the usual Debye screening obtained from the perturbation theory.
G. Giavaras; P. A. Maksym; M. Roy
2009-01-01
Massless Dirac particles cannot be confined by an electrostatic potential. This is a problem for making graphene quantum dots but confinement can be achieved with a magnetic field and here general conditions for confined and deconfined states are derived. There is a class of potentials for which the character of the state can be controlled at will. Then a confinement-deconfinement
Microstructure and viscoelasticity of confined semiflexible polymer networks
Bausch, Andreas
LETTERS Microstructure and viscoelasticity of confined semiflexible polymer networks M. M. A. E of polymers to external confinement has potential implications both for technology and for our understanding-filament fluctuations. Enforcing progressively narrower confinement is found to induce a reduction of polymer
Industrial Applications to the Inertial Electrostatic Confinement Configuration
Elijah Martin; Steve Shannon; Mohamed Bourham
2009-01-01
Since Fransworth's observation of inertial electrostatic confinement in the 1930's several applications have been proposed and studied with fusion being the main focus. Inertial electrostatic confinement is a scheme in which ions are focused and confined by means of either an electrostatic field or a combination of electrostatic and magnetic fields to produce an effective spherical potential well. Due to
Molecular modeling of confined polymers
NASA Astrophysics Data System (ADS)
Hehmeyer, Owen J.
Molecular Dynamics (MD) simulation, Monte Carlo (MC) simulation, and Mean Field (MF) theory were used to study the structure and thermodynamics of polymers in confined geometries. Molecular simulation is a valuable tool for accessing structural and thermodynamic information in systems where experiments are difficult to perform or where analytical theories are inadequate. End-tethered polyelectrolytes and polymers confined in a slit geometry are two such difficult systems. Analytical theories are limited because of the long-range nature of electrostatic interactions. Physical inaccessibility limits experiments. The effect of confinement on the phase behavior of lattice homopolymers was studied using grand canonical MC simulations in conjunction with multihistogram reweighting. The scaling of critical parameters and chain dimensions with chain length was determined for lattice homopolymers in strictly two dimensional and slab geometries, and compared to the bulk results. The influence of confinement on critical behavior persists even in a thick slab due to the diverging correlation length of density fluctuations. MD simulations were used to examine a model system that approximates a flexible polyelectrolyte, such as sodium polystyrene sulfonate, grafted to two apposing walls. The effect of the polymer grafting density, chain length, and gap width on the structure and pressure was examined. The apposing brushes seek to avoid interpenetration as the gap between the walls narrows. The avoidance of interpenetration may be the origin of lubrication in tethered polyelectrolyte systems. The structure of tethered polyelectrolytes on a single wall was studied using MC and single-chain MF theory. The monomer and counterion density profiles and the brush height were investigated as a function of grafting density, chain length, and charge strength. It was found that MF theory that incorporates counterion condensation agrees well with MC results. Grafting density is found to have only a mild effect on brush height. Grafted polymers carrying a single charge at the free-ends were studied with MC simulation. The brush height was found to change substantially with the surface charge density. The interaction of the same brush with adsorbing protein was examined with MC and MF. It was found that the brush hinders protein adsorption.
NSDL National Science Digital Library
2010-01-01
This article from New Zealand maths contains justifications for teaching geometry in the elementary grades and thoughts on how children learn geometry, including ideas from Piaget and the van Hieles. The article concludes with an example of how adults in a non-school setting would apply the van Hiele stages in an unfamiliar space.
Michael Deering
1995-01-01
This paper introduces the concept of Geometry Compression, al- lowing 3D triangle data to be represented with a factor of 6 to 10 times fewer bits than conventional techniques, with only slight loss- es in object quality. The technique is amenable to rapid decompres- sion in both software and hardware implementations; if 3D render- ing hardware contains a geometry decompression
NSDL National Science Digital Library
Ms. Hocutt
2010-02-03
Play these fun games to see how good your geometry skills are and learn more about geometry. First, let's see if you can Feed Billy Bug. Then, see if you can help in the Space Rescue. If you're ready, play this fun game about angles find out what is your angle ?. ...
Particle focusing mechanisms in curving confined flows.
Gossett, Daniel R; Di Carlo, Dino
2009-10-15
Particles in finite-inertia confined channel flows are known to segregate and focus to equilibrium positions whose number corresponds with the fold of symmetry of the channel's cross section. The addition of curvature into channels presumably modifies these equilibrium inertial focusing positions, because of the secondary flow induced in curved channels. Here, we identify the critical interaction of the secondary flow field with inertial lift forces to create complex sets of particle focusing positions that vary with the channel Reynolds number (Re(C)) and the inertial force ratio, which is a new dimensionless parameter that is based on the ratio of inertial lift to drag forces from the secondary flow. We use these results to identify microfluidic channel geometries to focus particles at rates an order of magnitude higher than previously shown (channel Reynolds number, Re(C) = 270) and develop design criteria for the focusing of potentially arbitrary-sized particles. In addition, our results indicate that channel curvature can lead to microfluidic designs with reduced fluidic resistance, useful for lower power inertial focusing or separation. These results will enable design of practical particle/cell separation, filtration, and focusing systems for critical applications in biomedicine and environmental cleanup. PMID:19761190
The Role of Confinement on Biologically Derived Liquid Crystals
NASA Astrophysics Data System (ADS)
Brown, Marguerite; Blair, Daniel
2013-03-01
Suspensions of stabilized, dilute microtubules provide a versatile model system for understanding the structure of confined liquid crystals. Microtubule solutions are easily transported as a simple monomeric fluid that can easily be polymerized into rod-like macromolecules after they are confined within quasi-2D geometries (microfluidics). Using polarization and confocal microscopy, we analyze the structure of liquid crystals in a variety of geometries. We will present results on the role of confinement, boundary conditions and concentration, specifically discussing how each variable alters nematic ordering. Suspensions of stabilized, dilute microtubules provide a versatile model system for understanding the structure of confined liquid crystals. Microtubule solutions are easily transported as a simple monomeric fluid that can easily be polymerized into rod-like macromolecules after they are confined within quasi-2D geometries (microfluidics). Using polarization and confocal microscopy, we analyze the structure of liquid crystals in a variety of geometries. We will present results on the role of confinement, boundary conditions and concentration, specifically discussing how each variable alters nematic ordering. ARCS Fellowship: General Dynamics Corporation Scholar
Jiang, Yan-xia; Chen, Zuo-feng; Ding, Nan; Sun, Shi-gang
2004-04-01
Palladium nanoparticles (nm-Pd) were synthesized in the supercages of Y-zeolite via "ship-in-a-bottle". Polyvinyl chloride (PVC) and Nafion were used as bonds respectively to prepare zeolite-modified electrode loading nm-Pd by mixed coat and steped coat. IR optical properties of adsorbed CO (COad) were studied by in situ electrochemical FTIR spectrum on zeolite-modified electrode surface prepared by different bond and coating method. Results display the same enhanced IR absorption of COad and different response rate to potential as well as the ability of electron transfer on PVC and Nafion film. Time-dependent vCOB shift was studied for obtaining the information of response rate to potential and electron transfer ability of PVC and Nafion coating. A larger potential lag on PVC coating electrode and a very small potential lag on Nafion coating film were found, showing that different bond and prepared method affect response rate to potential of zeolite-modified electrode. These findings are significant in understanding special optical performance and the electron transfer mechanism of zeolite-modified electrode. PMID:15766147
Algebra = Geometry Sandor Kovacs
Kovács, Sándor
Algebra = Geometry S´andor Kov´acs University of Washington #12;Motto "To me, algebraic geometry is algebra with a kick" Solomon Lefschetz #12;Geometry Geometry = Space + Functions #12;Geometry Geometry = Space + Functions Type of function Type of Geometry #12;Geometry Geometry = Space + Functions Type
Lajos Tamássy
\\u000a In the thirties of the 19th century János Bolyai and Nikolai Ivanovi? Lobacevskii created the hyperbolic geometry. Thus they proved that not only the\\u000a Euclidean but also other geometries may exist. Concerning its geometrical importance, this discovery can be compared to the\\u000a change which replaced the Ptolemaic geocentric concept of astronomy by the heliocentric point of view of Copernicus. Hyperbolic
Progress in toroidal confinement and fusion research
Furth, H.P.
1987-10-01
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.
Confinement-Induced Colloidal Attractions in Equilibrium
NASA Astrophysics Data System (ADS)
Han, Yilong; Grier, David G.
2003-07-01
The Poisson-Boltzmann theory for colloidal electrostatic interactions predicts that charged colloidal spheres dispersed in water should repel each other, even when confined by charged surfaces. Direct measurements on highly charged polystyrene spheres, however, reveal strong, long-ranged confinement-induced attractions that have yet to be explained. We demonstrate that anomalous attractions also characterize the equilibrium pair potential for more weakly charged colloidal silica spheres sedimented into a monolayer above a glass surface. This observation substantially expands the range of conditions for which mean-field theory incorrectly predicts the sign of macroions' interactions, and provides new insights into how confinement induces long-ranged like-charge attractions.
Confinement-Induced Colloidal Attractions in Equilibrium
Yilong Han; David G. Grier
2003-01-01
The Poisson-Boltzmann theory for colloidal electrostatic interactions predicts that charged colloidal spheres dispersed in water should repel each other, even when confined by charged surfaces. Direct measurements on highly charged polystyrene spheres, however, reveal strong, long-ranged confinement-induced attractions that have yet to be explained. We demonstrate that anomalous attractions also characterize the equilibrium pair potential for more weakly charged colloidal
Interacting Living Polymers Confined between Two Surfaces
NASA Astrophysics Data System (ADS)
Besseling, Nicolaas A. M.; Korobko, Alexander V.
2013-11-01
We present predictions on the equilibrium behavior of solutions of living polymers confined in a gap between surfaces, including the ensuing potential of mean force between those surfaces (the disjoining potential). We highlight the occurrence of a transition upon narrowing the gap, which arises from a cooperative simultaneous increase of the local density and degree of polymerization. At this transition, many properties of the confined solution, including the disjoining potential, change by orders of magnitude over a minute change of the surface separation. These results were obtained owing to two extensions to a previously introduced self-consistent field-propagator formalism. (i) We derive this formalism from a free-energy functional of the distribution of chain lengths and configurations. This enables evaluation of thermodynamic properties, including the disjoining potential. (ii) We solved for a system confined between two surfaces.
Confinement Aquaculture. Final Report.
ERIC Educational Resources Information Center
Delaplaine School District, AR.
The Delaplaine Agriculture Department Confinement Project, begun in June 1988, conducted a confinement aquaculture program by comparing the growth of channel catfish raised in cages in a pond to channel catfish raised in cages in the Black River, Arkansas. The study developed technology that would decrease costs in the domestication of fish, using…
Negative ions in inertial electrostatic confinement devices
D. R. Boris; J. F. Santarius; G. L. Kulcinski
2009-01-01
The UW-Inertial Electrostatic Confinement (IEC) device is comprised of concentric, nearly transparent, spherical metallic grids within a cylindrical vacuum vessel. The central grid, which can be held at high negative potentials (~ -100 to -200 kV) is the device cathode, while the outer grid, held at ground potential, is the device anode. This configuration accelerates ions, created near the anode,
NSDL National Science Digital Library
Rusin, David J., 1957-
A short article designed to provide an introduction to algebraic geometry, which combines the algebraic with the geometric for the benefit of both. Thus the recent proof of "Fermat's Last Theorem" - ostensibly a statement in number theory - was proved with geometric tools. Conversely, the geometry of sets defined by equations is studied using quite sophisticated algebraic machinery. This is an enticing area but the important topics are quite deep. This area includes elliptic curves. Applications and related fields and subfields; textbooks, reference works, and tutorials; software and tables; other web sites with this focus.
Thermodynamics of water structural reorganization due to geometric confinement
NASA Astrophysics Data System (ADS)
Stroberg, Wylie; Lichter, Seth
2015-03-01
Models of aqueous solvation have successfully quantified the behavior of water near convex bodies. However, many important processes occurring in aqueous solution involve interactions between solutes and surfaces with complicated non-convex geometries. Examples include the folding of proteins, hydrophobic association of solutes, ligand-receptor binding, and water confined within nanotubes and pores. For these geometries, models for solvation of convex bodies fail to account for the added interactions associated with structural confinement. Due to water's propensity to form networks of hydrogen bonds, small alterations to the confining geometry can induce large structural rearrangement within the water. We perform systematic Monte Carlo simulations of water confined to cylindrical cavities of varying aspect ratio to investigate how small geometric changes to the confining geometry may cause large changes to the structure and thermodynamic state of water. Using the Wang-Landau algorithm, we obtain free energies, enthalpies, entropies, and heat capacities across a broad range of temperatures, and show how these quantities are influenced by the structural rearrangement of water molecules due to geometric perturbations.
Kenichi Konishi; Yutaka Ookouchi
2009-09-21
The smallest integer t for which the Wilson loop W^{t} fails to exhibit area law is known as the confinement index of a given field theory. The confinement index provides us with subtle information on the vacuum properties of the system. We study the behavior of the Wilson and 't Hooft loops and compute the confinement index in a wide class of N=1 supersymmetric gauge theories. All possible electric and magnetic screenings are taken into account. The results found are consistent with the theta periodicity, and whenever such a check is available, with the factorization property of Seiberg-Witten curves.
Masanori Hara; Noriyuki Hayashi; Keishi Shiotsuki; Masanori Akazaki
1982-01-01
Lateral profiles of electric field and ion current density at ground level were measured precisely in a unipolar\\/bipolar line to plane geometry under different wind conditions and different dc voltages. Furthermore, the relationship between the field and current density is discussed. In the case of unipolar line in still air, the normalized profiles are approximately independent of the magnitude of
NASA Astrophysics Data System (ADS)
Sarkar, Kanchan; Bhattacharyya, S. P.
2013-08-01
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
2013-08-21
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
NSDL National Science Digital Library
Ms. Yost
2009-10-26
Let's practice some geometry skills. First, try to feed Billy Bug all the grubs in Billy Bug: Quadrant I. Just click on "Start," move Billy Bug with the arrow keys on the screen, and click "Feed" when you're at the coordinate where the grub is located. If you're up for a challenge, try Billy Bug: All Quadrants! Then, in Robo Packer, you will ...
Heat-capacity scaling function for confined superfluids
NASA Astrophysics Data System (ADS)
Nho, Kwangsik; Manousakis, Efstratios
2003-11-01
We study the specific-heat scaling function of confined superfluids using Monte Carlo simulation. While the scaling function is insensitive to the microscopic details, it depends on the confining geometry and boundary conditions (BC’s). In the present work we have studied (a) cubic geometry with open BC’s in all three directions and (b) parallel-plate (film) geometry using open BC’s along the finite dimension and periodic BC’s along the other two dimensions. We find that the specific-heat scaling function is significantly different for the two different geometries studied. The scaling function for each geometry (a) or (b) is very different when compared to that obtained for the same geometry but with periodic BC’s. On the contrary, we find that in case (b) the calculated scaling function is very close to the earlier calculated using Dirichlet instead of open BC’s. This demonstrates that Dirichlet and open boundary conditions act in a similar way. Our results for both scaling functions obtained for the parallel-plate geometry and for cubic geometry with open BC’s along the finite dimensions are in very good agreement with recent very-high-quality experimental measurements with no free parameters.
Dynamics and energetics of hydrophobically confined water
NASA Astrophysics Data System (ADS)
Bauer, Brad A.; Ou, Shuching; Patel, Sandeep; Siva, Karthik
2012-05-01
The effects of water confined in regions between self-assembling entities is relevant to numerous contexts such as macromolecular association, protein folding, protein-ligand association, and nanomaterials self-assembly. Thus assessing the impact of confined water, and the ability of current modeling techniques to capture the salient features of confined water is important and timely. We present molecular dynamics simulation results investigating the effect of confined water on qualitative features of potentials of mean force describing the free energetics of self-assembly of large planar hydrophobic plates. We consider several common explicit water models including the TIP3P, TIP4P, SPC/E, TIP4P-FQ, and SWM4-NDP, the latter two being polarizable models. Examination of the free energies for filling and unfilling the volume confined between the two plates (both in the context of average number of confined water molecules and “depth” of occupancy) suggests TIP4P-FQ water molecules generally occupy the confined volume at separation distances larger than observed for other models under the same conditions. The connection between this tendency of TIP4P-FQ water and the lack of a pronounced barrier in the potential of mean force for plate-plate association in TIP4P-FQ water is explored by artificially, but systematically, populating the confined volume with TIP4P-FQ water at low plate-plate separation distances. When the critical separation distance [denoting the crossover from an unoccupied (dry) confined interior to a filled (wet) interior] for TIP4P-FQ is reduced by 0.5 Å using this approach, a barrier is observed; we rationalize this effect based on increased resistant forces introduced by confined water molecules at these low separations. We also consider the dynamics of water molecules in the confined region between the hydrophobes. We find that the TIP4P-FQ water model exhibits nonbulklike dynamics, with enhanced lateral diffusion relative to bulk. This is consistent with the reduced intermolecular water-water interaction indicated by a decreased molecular dipole moment in the interplate region. Analysis of velocity autocorrelation functions and associated power spectra indicate that the interplate region for TIP4P-FQ at a plate separation of 14.4 Å approaches characteristics of the pure water liquid-vapor interface. This is in stark contrast to the other water models (including the polarizable SWM4-NDP model).
Dynamics and energetics of hydrophobically confined water.
Bauer, Brad A; Ou, Shuching; Patel, Sandeep; Siva, Karthik
2012-05-01
The effects of water confined in regions between self-assembling entities is relevant to numerous contexts such as macromolecular association, protein folding, protein-ligand association, and nanomaterials self-assembly. Thus assessing the impact of confined water, and the ability of current modeling techniques to capture the salient features of confined water is important and timely. We present molecular dynamics simulation results investigating the effect of confined water on qualitative features of potentials of mean force describing the free energetics of self-assembly of large planar hydrophobic plates. We consider several common explicit water models including the TIP3P, TIP4P, SPC/E, TIP4P-FQ, and SWM4-NDP, the latter two being polarizable models. Examination of the free energies for filling and unfilling the volume confined between the two plates (both in the context of average number of confined water molecules and "depth" of occupancy) suggests TIP4P-FQ water molecules generally occupy the confined volume at separation distances larger than observed for other models under the same conditions. The connection between this tendency of TIP4P-FQ water and the lack of a pronounced barrier in the potential of mean force for plate-plate association in TIP4P-FQ water is explored by artificially, but systematically, populating the confined volume with TIP4P-FQ water at low plate-plate separation distances. When the critical separation distance [denoting the crossover from an unoccupied (dry) confined interior to a filled (wet) interior] for TIP4P-FQ is reduced by 0.5 Å using this approach, a barrier is observed; we rationalize this effect based on increased resistant forces introduced by confined water molecules at these low separations. We also consider the dynamics of water molecules in the confined region between the hydrophobes. We find that the TIP4P-FQ water model exhibits nonbulklike dynamics, with enhanced lateral diffusion relative to bulk. This is consistent with the reduced intermolecular water-water interaction indicated by a decreased molecular dipole moment in the interplate region. Analysis of velocity autocorrelation functions and associated power spectra indicate that the interplate region for TIP4P-FQ at a plate separation of 14.4 Å approaches characteristics of the pure water liquid-vapor interface. This is in stark contrast to the other water models (including the polarizable SWM4-NDP model). PMID:23004766
NASA Astrophysics Data System (ADS)
Wilking, Connie; Weitz, David
2010-03-01
Bacterial cells can display differentiation between several developmental pathways, from planktonic to matrix-producing, depending upon the colony conditions. We study the confinement of bacteria in hydrogels as well as in liquid-liquid double emulsion droplets and observe the growth and morphology of these colonies as a function of time and environment. Our results can give insight into the behavior of bacterial colonies in confined spaces that can have applications in the areas of food science, cosmetics, and medicine.
Modeling Non-Confined Coronal Flares: Dynamics and X-Ray Diagnostics
F. Reale; F. Bocchino; G. Peres
2001-12-14
Long-lasting, intense, stellar X-ray flares may approach conditions of breaking magnetic confinement and evolving in open space. We explore this hypothesis with hydrodynamic simulations of flares occurring in a non-confined corona: model flares are triggered by a transient impulsive heating injected in a plane-parallel stratified corona. The plasma evolution is described by means of a numerical 2-D model in cylindrical geometry R,Z. We explore the space of fundamental parameters. As a reference model, we consider a flare triggered by a heating pulse that would cause a 20 MK flare if delivered in a 40000 km long closed loop. The modeled plasma evolution is described. The X-ray emission, spectra and light curves at the ASCA/SIS focal plan, and in two intense X-ray lines (Mg XI at 9.169 A and Fe XXI at 128.752 A), have been synthesized from the models. The results are discussed and compared to features of confined events, and scaling laws are derived. The light curves invariably show a very rapid rise, a constant phase as long as the constant heating is on, and then a very fast decay, on time scales of few seconds, followed by a more gradual one (few minutes). We show that this evolution of the emission, and especially the fast decay, together with other potentially observable effects, are intrinsic to the assumption of non-confinement. Their lack indicates that observed long-lasting stellar X-ray flares should involve plasma strongly confined by magnetic fields.
Sanna, Daniele; Ugone, Valeria; Lubinu, Giuseppe; Micera, Giovanni; Garribba, Eugenio
2014-11-01
The coordination modes and geometry assumed in solution by the potent antitumor oxidovanadium(IV) complexes formed by different flavonoids were studied by spectroscopic (Electron Paramagnetic Resonance, EPR) and computational (Density Functional Theory, DFT) methods. A series of bidentate flavonoid ligands (L) with increasing structural complexity was examined, which can involve (CO, O(-)) donors and formation of five- and six-membered chelate rings, or (O(-), O(-)) donors and five-membered chelate rings. The geometry corresponding to these coordination modes can be penta-coordinated, [VOL2], or cis-octahedral, cis-[VOL2(H2O)]. The results show that, at physiological pH, ligands provided with (CO, O(-)) donor set yield cis-octahedral species with "maltol-like" coordination when five-membered chelate rings are formed (as with 3-hydroxyflavone), while penta-coordinated structures with "acetylacetone-like" coordination are preferred when the chelate rings are six-membered (as with chrysin). When both the binding modes are possible, as with morin, the "acetylacetone-like" coordination is observed. For the ligands containing a catecholic donor set, such as 7,8-dihydroxyflavone, baicalein, fisetin, quercetin and rutin, the formation of square pyramidal complexes with (O(-), O(-)) "catechol-like" coordination and five-membered chelate rings is preferred at physiological pH. The determination of the different coordination modes and geometry is important to define the biotransformation in the blood and the interaction of these complexes with the biological membranes. PMID:25127230
Semiflexible Polymer Confined to a Spherical Surface Andrew J. Spakowitz and Zhen-Gang Wang
Straight, Aaron
Semiflexible Polymer Confined to a Spherical Surface Andrew J. Spakowitz and Zhen-Gang Wang, persistence length lp, and sphere radius R.We predict two qualitatively different behaviors for a long polymerRevLett.91.166102 PACS numbers: 68.47.Pe, 05.20.y, 36.20.Ey A polymer in a confined geometry
Polymer Statics and Dynamics Under Box Confinement
NASA Astrophysics Data System (ADS)
Kalb, Joshua; Chakraborty, Bulbul
2007-03-01
Current work on biological systems and glass forming polymers (JCP 106, 6176 (1997)) has led to an interest in the study of single polymer systems. The main questions concern relaxation phenomena and the shape adopted by single polymers under hard and soft boundaries. We are concerned with whether or not there is a critical length scale for a confined polymer system. Both structure and relaxation can be described using scaling arguments and tested with Monte Carlo simulations using the bond-fluctuation algorithm (Macromolecules 21,2819 (1988)), which uses a lattice representation of the polymer chain with excluded volume effects. We look at the effects of confinement on a single polymer chain confined to a box by measuring dynamical quantities such as the end-to-end vector and single monomer positions (JACS 124, 20 (2004)). A primary question is how spatial correlations between monomers, `blob's, influence the dynamics. Understanding how these quantities change with various confining geometries will lead to a deeper understanding of biological structures and glass formation. Work supported by NSF-DMR 0403997.
Water Flow in Fractured Rock Under Changeable Confining Pressure
W. Liu; X. Song
2008-01-01
Fluid flow in fractured rocks is largely governed by the properties of the fractures. In turn, fracture geometry can be affected by confining pressure. There is thus a feedback between fluid flow and rock properties. To better understand the interaction between fluid pressure and fracture properties, we have integrated results from experimental, analytical and numerical methods. In the experiments, we
NSDL National Science Digital Library
Frame, Michael
This is one of the best online resources about fractals, and is "meant to support a first course in fractal geometry for students without especially strong mathematical preparation." The site is incredibly deep, providing everything from the most basic definitions and non-technical discussions to involved mathematical formulations. Interactive Java applets, downloadable software for the PC and Macintosh, and laboratory activities are also presented. A particularly interesting section of the site explores about 100 places in nature and society where fractals are found.
Structure factor of a Gaussian chain confined between two parallel plates.
Liao, Yi; Miao, Bing
2015-04-28
We study the structure factor of a single Gaussian chain confined between two macroscopic parallel plates theoretically. The chain propagator is constructed in terms of the eigen-spectrum of the Laplace operator under the Dirichlet boundary condition enforced at the two plates, by which the confinement effect enters the treatment through size-dependent eigen-spectrum. In terms of the series expansion solution for the chain propagator, we first calculate the confinement free energy and the confinement force for an arbitrary confinement strength. It is found that the confinement force scales to the distance between the two confining surfaces with a power of -3 for strong confinements and of -2 for weak confinements. Based on the ground state dominance approximation for strong confinements and the Euler-Maclaurin formula for weak confinements, we develop approximation theories for the two limit situations, which agree with the numerical results well. We further calculate the structure factor of the confined Gaussian chain in this slit geometry. While the scattering function of the transverse chain fluctuations perpendicular to the confinement direction is still a Debye function form, the structure factor for the longitudinal fluctuations along the confinement dimension starts with the monotonic Debye function behavior for weak confinements and develops a decaying oscillation behavior with the increase of confinements. The numerical results for the structure factor are also interpreted by developing approximation theories in different confinement regimes. Finally, the orientational average of the anisotropic structure factor is performed and an analytic expression for the averaged structure factor is derived under the ground state dominance approximation for strong confinements. PMID:25933787
Glow discharges with electrostatic confinement of fast electrons
NASA Astrophysics Data System (ADS)
Kolobov, V. I.; Metel, A. S.
2015-06-01
This review presents a unified treatment of glow discharges with electrostatic confinement of fast electrons. These discharges include hollow cathode discharges, wire and cage discharges, reflect discharges with brush and multirod cathodes, and discharges in crossed electric and magnetic fields. Fast electrons bouncing inside electrostatic traps provide efficient ionization of gas at very low gas pressures. The electrostatic trap effect (ETE) was first observed by Paschen in hollow cathode discharges almost a century ago. The key parameters that define fundamental characteristics of ETE discharges are the ionization length ?N, the penetration range, ?, and the diffusion length ? of the fast electrons, and two universal geometric parameters of the traps: effective width a and length L. Peculiarities of electron kinetics and ion collection mechanism explain experimental observations for different trap geometries. The ETE is observed only at ??>?a, when the penetration range of the ?-electrons emitted by the cathode exceeds the trap width. In the optimal pressure range, when ?N?>?a, and ??potential fall Uc is independent of gas pressure p. With increasing current, Uc tends to its upper limit W/e??, where ? is the percentage of ions arriving at the cathode and W is the gas ionization cost. In the low-pressure range, ??>?L, Uc rises from hundreds to thousands of volts. The sign of the anode potential fall, Ua, depends on the anode surface Sa and its position. When Sa is large compared to a critical value S*, Ua is negative and small. At Sa?confinement of fast electrons are described.
Micelle fragmentation and wetting in confined flow
Mona Habibi; Colin Denniston; Mikko Karttunen
2014-09-30
We use coarse-grained molecular-dynamics (MD) simulations to investigate the structural and dynamical properties of micelles under non-equilibrium Poiseuille flow in a nano-confined geometry. The effects of flow, confinement, and the wetting properties of die-channel walls on spherical sodium dodecyl sulfate (SDS) micelles are explored when the micelle is forced through a die-channel slightly smaller than its equilibrium size. Inside the channel, the micelle may fragment into smaller micelles. In addition to the flow rate, the wettability of the channel surfaces dictates whether the micelle fragments and determines the size of the daughter micelles: The overall behavior is determined by the subtle balance between hydrodynamic forces, micelle-wall interactions and self-assembly forces.
Confinement and Mayer cluster expansions
NASA Astrophysics Data System (ADS)
Bourgine, Jean-Emile
2014-05-01
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.
Modelling the confinement of spilled oil with floating booms
Song-Ping Zhu; Dmitry Strunin
2001-01-01
An effective mechanical method of confining the oil spills in an open ocean is to use barriers such as floating booms. However, the confined oil may leak beneath a boom if either the towing speed of the boom or the amount of oil is too large. In this paper a simple mathematical model based on the potential theory is presented
Prospects of confined flow boiling in thermal management of microsystems
S. Lin; K. Sefiane; J. R. E. Christy
2002-01-01
This paper presents a review of prospects of confined flow boiling in future thermal management of microsystems such as microelectronics, optoelectronics, and microreactors. With the trend towards miniaturisation, heat removal has become the major bottleneck in microsystem development. In view of this we briefly discuss available cooling strategies, then assess studies of confined flow boiling and potential applications in heat
Beam optics in inertial electrostatic confinement fusion
Masami Ohnishi; Chikara Hoshino; Kiyoshi Yoshikawa; Kai Masuda; Yasushi Yamamoto
2000-01-01
We study the transport of ions and electrons near the cathode of the inertial electrostatic confinement fusion that is expected to be a portable neutron source. We carry out a PIC particle simulation in order to obtain the self-consistent electrostatic potential and the transparency of the cathode for the accelerated ions. The transparency is shown to be much less than
Transitions Within a Vertically Confined Plasma Crystal
Ke Qiao; Truell Hyde
2004-01-01
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
NASA Astrophysics Data System (ADS)
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
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.
Charge Transport through Organized Organic Assemblies in Confined Geometries
Schuckman, Amanda Eileen
2012-07-16
characterized on Au(111) surfaces. A variety of surface characterization techniques such as Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS) have been implemented in order to obtain...
Charge Transport through Organized Organic Assemblies in Confined Geometries
Schuckman, Amanda Eileen
2012-07-16
............................................................... 54 2.2 STM and STS .......................................................................... 54 2.3 AFM ........................................................................................ 56 2.4 IR Spectroscopy... ......................................................................................................................... 239 xiv LIST OF FIGURES FIGURE Page 1.1 Porphyrin thiol derivatives. M- 2H+ or Zn2+; R- H or F...
Transport and boundary scattering in confined geometries: Analytical results
R. A. Richardson; Franco Nori
1993-01-01
We utilize a geometric argument to determine the effects of boundary scattering on the carrier mean free path in samples of various cross sections. Analytic expressions for samples with rectangular and circular cross sections are obtained. We also outline a method for incorporating these results into calculations of the thermal conductivity.
Anomalous diffusion in confined turbulent convection.
Boffetta, G; De Lillo, F; Musacchio, S
2012-06-01
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
Self-organized wrinkling patterns of a liquid crystalline polymer in surface wetting confinement.
Na, Jun-Hee; Kim, Se-Um; Sohn, Youngjoo; Lee, Sin-Doo
2015-06-28
Self-organized wrinkling patterns of a liquid crystalline polymer, dictated by the chemico-physically anisotropic nature of surface wettability, are demonstrated in confined geometries. The symmetry of the geometrical constraints of the confinement primarily governs the periodic wrinkling patterns of such a polymer in the wetting region. In a circular geometry, the number of the radial domains with multi-fold symmetries is linearly proportional to the radius of the confinement. The physical origin of the wrinkling process comes from the periodic bend-splay distortions through the relaxation of the curvature elasticity. PMID:25971924
Electrokinetic confinement of axonal growth for dynamically configurable neural networks
Honegger, Thibault; Scott, Mark A.; Yanik, Mehmet F.; Voldman, Joel
2013-01-01
Axons in the developing nervous system are directed via guidance cues, whose expression varies both spatially and temporally, to create functional neural circuits. Existing methods to create patterns of neural connectivity in vitro use only static geometries, and are unable to dynamically alter the guidance cues imparted on the cells. We introduce the use of AC electrokinetics to dynamically control axonal growth in cultured rat hippocampal neurons. We find that the application of modest voltages at frequencies on the order of 105 Hz can cause developing axons to be stopped adjacent to the electrodes while axons away from the electric fields exhibit uninhibited growth. By switching electrodes on or off, we can reversibly inhibit or permit axon passage across the electrodes. Our models suggest that dielectrophoresis is the causative AC electrokinetic effect. We make use of our dynamic control over axon elongation to create an axon-diode via an axon-lock system that consists of a pair of electrode `gates' that either permit or prevent axons from passing through. Finally, we developed a neural circuit consisting of three populations of neurons, separated by three axon-locks to demonstrate the assembly of a functional, engineered neural network. Action potential recordings demonstrate that the AC electrokinetic effect does not harm axons, and Ca2+ imaging demonstrated the unidirectional nature of the synaptic connections. AC electrokinetic confinement of axonal growth has potential for creating configurable, directional neural networks. PMID:23314575
Electrokinetic confinement of axonal growth for dynamically configurable neural networks.
Honegger, Thibault; Scott, Mark A; Yanik, Mehmet F; Voldman, Joel
2013-02-21
Axons in the developing nervous system are directed via guidance cues, whose expression varies both spatially and temporally, to create functional neural circuits. Existing methods to create patterns of neural connectivity in vitro use only static geometries, and are unable to dynamically alter the guidance cues imparted on the cells. We introduce the use of AC electrokinetics to dynamically control axonal growth in cultured rat hippocampal neurons. We find that the application of modest voltages at frequencies on the order of 10(5) Hz can cause developing axons to be stopped adjacent to the electrodes while axons away from the electric fields exhibit uninhibited growth. By switching electrodes on or off, we can reversibly inhibit or permit axon passage across the electrodes. Our models suggest that dielectrophoresis is the causative AC electrokinetic effect. We make use of our dynamic control over axon elongation to create an axon-diode via an axon-lock system that consists of a pair of electrode 'gates' that either permit or prevent axons from passing through. Finally, we developed a neural circuit consisting of three populations of neurons, separated by three axon-locks to demonstrate the assembly of a functional, engineered neural network. Action potential recordings demonstrate that the AC electrokinetic effect does not harm axons, and Ca(2+) imaging demonstrated the unidirectional nature of the synaptic connections. AC electrokinetic confinement of axonal growth has potential for creating configurable, directional neural networks. PMID:23314575
Asymmetric confinement in a noisy bistable device
NASA Astrophysics Data System (ADS)
Borromeo, M.; Marchesoni, F.
2004-12-01
A Brownian particle hopping in a symmetric double-well potential can be statistically confined to a single well by the simultaneous action of a) two periodic input signals, one tilting the minima, the other one modulating the barrier height; b) an additive and a purely multiplicative random signal, generated by a unique source and thus preserving a certain degree of statistical correlation. In view of technological implementation, such a basic mechanism for asymmetric confinement can be conveniently maximized by tuning the input signal parameters (correlation time, phase/time lag, amplitudes), thus revealing a resonant localization mechanism of wide applicability.
Tension of confining strings at low temperature
NASA Astrophysics Data System (ADS)
Giataganas, Dimitrios; Goldstein, Kevin
2015-02-01
In the low temperature confining phase of QCD or QCD-like theories it is challenging to capture the temperature dependence of observables through AdS/CFT. Using the blackfold approach we compute the quark-anti-quark linear static potential in the low temperature confining phase, taking into account the thermal excitations of the string. We find the explicit temperature dependence of the string tension and notice that, as naturally expected, tension decreases as temperature increases. We have also generalized the blackfold approach for the computation of the Wilson loops, making it directly applicable to a large class of backgrounds.
Gerard't Hooft
2003-01-01
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
NASA Astrophysics Data System (ADS)
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.
2013-09-01
We report an experimental and theoretical study of single-molecule inner-shell photoemission measured over an extended range of photon energies. The vibrational intensity ratios I(?=1)/I(?=0) from the C 1s photoelectron spectra of carbon monoxide, although mostly determined by the bond length change upon ionization, are shown to be affected also by photoelectron recoil and by scattering from the neighboring oxygen atom. Static-exchange density functional theory (DFT) is used to encompass all these effects in a unified theoretical treatment. The ab initio calculations show that the vibrational ratio as a function of the photoelectron momentum is sensitive to both the ground-state internuclear distance and its contraction upon photoionization. We present a proof-of-principle application of DFT calculations as a quantitative structural analysis tool for extracting the dynamic and static molecular geometry parameters simultaneously.
Radial Distribution Function for Semiflexible Polymers Confined in Microchannels
Patrick Levi; Klaus Mecke
2006-12-22
An analytic expression is derived for the distribution $G(\\vec{R})$ of the end-to-end distance $\\vec{R}$ of semiflexible polymers in external potentials to elucidate the effect of confinement on the mechanical and statistical properties of biomolecules. For parabolic confinement the result is exact whereas for realistic potentials a self-consistent ansatz is developed, so that $G(\\vec{R})$ is given explicitly even for hard wall confinement. The theoretical result is in excellent quantitative agreement with fluorescence microscopy data for actin filaments confined in rectangularly shaped microchannels. This allows an unambiguous determination of persistence length $L_P$ and the dependence of statistical properties such as Odijk's deflection length $\\lambda$ on the channel width $D$. It is shown that neglecting the effect of confinement leads to a significant overestimation of bending rigidities for filaments.
Confinement-induced colloidal attractions in equilibrium.
Han, Yilong; Grier, David G
2003-07-18
The Poisson-Boltzmann theory for colloidal electrostatic interactions predicts that charged colloidal spheres dispersed in water should repel each other, even when confined by charged surfaces. Direct measurements on highly charged polystyrene spheres, however, reveal strong, long-ranged confinement-induced attractions that have yet to be explained. We demonstrate that anomalous attractions also characterize the equilibrium pair potential for more weakly charged colloidal silica spheres sedimented into a monolayer above a glass surface. This observation substantially expands the range of conditions for which mean-field theory incorrectly predicts the sign of macroions' interactions, and provides new insights into how confinement induces long-ranged like-charge attractions. PMID:12906461
Simulating tumor growth in confined heterogeneous environments
NASA Astrophysics Data System (ADS)
Gevertz, Jana L.; Gillies, George T.; Torquato, Salvatore
2008-09-01
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.
Confinement induced splay-to-bend transition of colloidal rods.
Dammone, Oliver J; Zacharoudiou, Ioannis; Dullens, Roel P A; Yeomans, Julia M; Lettinga, M P; Aarts, Dirk G A L
2012-09-01
We study the nematic phase of rodlike f d-virus particles confined to channels with wedge-structured walls. Using laser scanning confocal microscopy we observe a splay-to-bend transition at the single particle level as a function of the wedge opening angle. Lattice Boltzmann simulations reveal the underlying origin of the transition and its dependence on nematic elasticity and wedge geometry. Our combined work provides a simple method to estimate the splay-to-bend elasticity ratios of the virus and offers a way to control the position of defects through the confining boundary conditions. PMID:23005336
Confinement Induced Splay-to-Bend Transition of Colloidal Rods
NASA Astrophysics Data System (ADS)
Dammone, Oliver J.; Zacharoudiou, Ioannis; Dullens, Roel P. A.; Yeomans, Julia M.; Lettinga, M. P.; Aarts, Dirk G. A. L.
2012-09-01
We study the nematic phase of rodlike fd-virus particles confined to channels with wedge-structured walls. Using laser scanning confocal microscopy we observe a splay-to-bend transition at the single particle level as a function of the wedge opening angle. Lattice Boltzmann simulations reveal the underlying origin of the transition and its dependence on nematic elasticity and wedge geometry. Our combined work provides a simple method to estimate the splay-to-bend elasticity ratios of the virus and offers a way to control the position of defects through the confining boundary conditions.
Topological confinement and superconductivity
Al-hassanieh, Dhaled A [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory
2008-01-01
We derive a Kondo Lattice model with a correlated conduction band from a two-band Hubbard Hamiltonian. This mapping allows us to describe the emergence of a robust pairing mechanism in a model that only contains repulsive interactions. The mechanism is due to topological confinement and results from the interplay between antiferromagnetism and delocalization. By using Density-Matrix-Renormalization-Group (DMRG) we demonstrate that this mechanism leads to dominant superconducting correlations in aID-system.
Energy confinement in tokamaks
Sugihara, M.; Singer, C.
1986-08-01
A straightforward generalization is made of the ohmic heating energy confinement scalings of Pfeiffer and Waltz and Blackwell et. al. The resulting model is systematically calibrated to published data from limiter tokamaks with ohmic, electron cyclotron, and neutral beam heating. With considerably fewer explicitly adjustable free parameters, this model appears to give a better fit to the available data for limiter discharges than the combined ohmic/auxiliary heating model of Goldston.
F. Lenz
2009-09-17
By superposition of regular gauge instantons or merons, ensembles of gauge fields are constructed which describe the confining phase of SU(2) Yang-Mills theory. Various properties of the Wilson loops, the gluon condensate and the topological susceptibility are found to be in qualitative agreement with phenomenology or results of lattice calculations. Limitations in the application to the glueball spectrum and small size Wilson loops are discussed.
NASA Astrophysics Data System (ADS)
Bhargava, Rameshwar
2001-03-01
When the size of Tb3+ doped Y2O3 nanoparticles is decreased from about 10 nm to 3 nm, the luminescent efficiency of Tb3+ green-emission (f-f transition) is increased by an order of magnitude1. This enhancement of oscillator strength is interpreted due to modulation of excited-states of the Tb3+ ion, brought about by the confinement-boundary of the Y2O3 nanocrystal2. This high efficiency of 'caged' single Tb3+ or Eu3+ ion in Y2O3 has led to the first observation of an atomic blinking3. The Quantum Confined Atoms (QCA) provide a novel way to modulate the luminescent properties of a single activator atom via quantum confinement of higher excited states. This QCA-effect occurs when the size of the host is about 5 to 10 times the size of the radius of the excited-state atom. This discovery is expected to impact many applications in the area of nanotechnology. 1. R.N Bhargava, V. Chhabra, B. Kulkarni and J.V. Veliadis Phys. stat. sol. (b) 210, 621 (1998) 2. R.N. Bhargava Jour. of Crystal Growth 214, 926 (2000) 3. M. Barnes, A. Mehta, T. Thundant, R.N. Bhargava, V. Chhabra, B .Kulkarni Jour. Chem. Phys. B 104, 6099 (2000)
D. V. Anderson; J. Breazeal; C. H. Finan; B. M. Johnston
1976-01-01
ABCXYZ is a computer code for obtaining the Cartesian components of the vector potential and the magnetic field on an observed grid from an arrangement of current-carrying wires. Arbitrary combinations of straight line segments, arcs, and loops are allowed in the specification of the currents. Arbitrary positions and orientations of the current-carrying elements are also allowed. Specification of the wire
BOWERS,RICHARD; CHANDLER,GORDON A.; HEBRON,DAVID E.; LEEPER,RAMON J.; MATUSLKA,WALTER; MOCK,RAYMOND CECIL; NASH,THOMAS J.; OLSON,CRAIG L.; PETERSON,BOB; PETERSON,DARRELL; RUGGLES,LAURENCE E.; SANFORD,THOMAS W. L.; SIMPSON,WALTER W.; STRUVE,KENNETH W.; VESEY,ROGER A.
1999-11-01
Hohlraums of full ignition scale (6-mm diameter by 7-mm length) have been heated by x-rays from a z-pinch magnet on Z to a variety of temperatures and pulse shapes which can be used to simulate the early phases of the National Ignition Facility (NIF) temperature drive. The pulse shape is varied by changing the on-axis target of the z pinch in a static-wall-hohlraum geometry. A 2-{micro}m-thick walled Cu cylindrical target of 8-mm diameter filled with 10 mg/cm{sup 3} CH, for example, produces foot-pulse conditions of {approx}85 eV for a duration of {approx}10 ns, while a solid cylindrical target of 5-mm diameter and 14-mg/cm{sup 3} CH generates first-step-pulse conditions of {approx}122 eV for a duration of a few ns. Alternatively, reducing the hohlraum size (to 4-mm diameter by 4-mm length) with the latter target has increased the peak temperature to {approx}150 eV, which is characteristic of a second-step-pulse temperature. In general, the temperature T of these x-ray driven hohlraums is in agreement with the Planckian relation T{approx}(P/A){sup 1/4}. P is the measured x-ray input power and A is the surface area of the hohlraum. Fully-integrated 2-D radiation-hydrodynamic simulations of the z pinch and subsequent hohlraum heating show plasma densities within the useful volume of the hohlraums to be on the order of air or less.
Thermal Conductivity of Liquid He-4 near the Superfluid Transition in Restricted Geometries
NASA Technical Reports Server (NTRS)
Liu, Yuanming
2003-01-01
We present measurements of the thermal conductivity near the superfluid transition of He-4 in confined geometries. The confinements we have studied include: cylindrical geometries with radii L=.5 and 1.0 microns, and parallel plates with 5 micron spacing. For L=1.0 microns, measurements at six pressures were conducted, whereas only SVP measurements have been done for other geometries. For the 1-D confinement in cylinders, the data are consistent with a universal scaling for all pressures at and above T(sub lambda). There are indications of breakdown of scaling and universality below T(sub lambda). For the 2-D confinement between parallel plates, the preliminary results indicate that the thermal conductivity is finite at the bulk superfluid transition temperature. Further analyses are needed to compare the 2-D results with those in bulk and 1-D confinement.
Entropic stochastic resonance without external force in oscillatory confined space
NASA Astrophysics Data System (ADS)
Ding, Huai; Jiang, Huijun; Hou, Zhonghuai
2015-05-01
We have studied the dynamics of Brownian particles in a confined geometry of dumbbell-shape with periodically oscillating walls. Entropic stochastic resonance (ESR) behavior, characterizing by a maximum value of the coherent factor Q at some optimal level of noise, is observed even without external periodic force in the horizontal direction, which is necessary for conventional ESR where the wall is static and the particle is subjected to the force. Interestingly, the ESR can be remarkably enhanced by the particle gravity G, in contrast to the conventional case. In addition, Q decreases (increases) with G in the small (large) noise limit, respectively, while it non-monotonically changes with G for moderate noise levels. We have applied an effective 1D coarsening description to illustrate such a nontrivial dependence on G, by investigating the property of the 1D effective potential of entropic nature and paying special attention to the excess part resulting from the boundary oscillation. Dependences of the ESR strength with other related parameters are also discussed.
Entropic stochastic resonance without external force in oscillatory confined space.
Ding, Huai; Jiang, Huijun; Hou, Zhonghuai
2015-05-21
We have studied the dynamics of Brownian particles in a confined geometry of dumbbell-shape with periodically oscillating walls. Entropic stochastic resonance (ESR) behavior, characterizing by a maximum value of the coherent factor Q at some optimal level of noise, is observed even without external periodic force in the horizontal direction, which is necessary for conventional ESR where the wall is static and the particle is subjected to the force. Interestingly, the ESR can be remarkably enhanced by the particle gravity G, in contrast to the conventional case. In addition, Q decreases (increases) with G in the small (large) noise limit, respectively, while it non-monotonically changes with G for moderate noise levels. We have applied an effective 1D coarsening description to illustrate such a nontrivial dependence on G, by investigating the property of the 1D effective potential of entropic nature and paying special attention to the excess part resulting from the boundary oscillation. Dependences of the ESR strength with other related parameters are also discussed. PMID:26001449
Dynamics of Confined Water Molecules in Aqueous Salt Hydrates
Werhahn, Jasper C.; Pandelov, S.; Yoo, Soohaeng; Xantheas, Sotiris S.; Iglev, H.
2011-04-01
The unusual properties of water are largely dictated by the dynamics of the H bond network. A single water molecule has more H bonding sites than atoms, hence new experimental and theoretical investigations about this peculiar liquid have not ceased to appear. Confinement of water to nanodroplets or small molecular clusters drastically changes many of the liquid’s properties. Such confined water plays a major role in the solvation of macro molecules such as proteins and can even be essential to their properties. Despite the vast results available on bulk and confined water, discussions about the correlation between spectral and structural properties continue to this day. The fast relaxation of the OH stretching vibration in bulk water, and the variance of sample geometries in the experiments on confined water obfuscate definite interpretation of the spectroscopic results in terms of structural parameters. We present first time-resolved investigations on a new model system that is ideally suited to overcome many of the problems faced in spectroscopical investigation of the H bond network of water. Aqueous hydrates of inorganic salts provide water molecules in a crystal grid, that enables unambiguous correlations of spectroscopic and structural features. Furthermore, the confined water clusters are well isolated from each other in the crystal matrix, so different degrees of confinement can be achieved by selection of the appropriate salt.
NASA Astrophysics Data System (ADS)
Musia?, A.; Gold, P.; Andrzejewski, J.; Löffler, A.; Misiewicz, J.; Höfling, S.; Forchel, A.; Kamp, M.; Sek, G.; Reitzenstein, S.
2014-07-01
In this paper we present a comprehensive and detailed analysis of carrier/exciton wave function extension in large low-strain In0.3Ga0.7As quantum dots (QDs). They exhibit rather shallow confinement potential with electron/hole localization energy below 30 meV and confinement strength substantially weakened in comparison to typical epitaxial quasi-zero-dimensional semiconductor nanostructures. The aim of this study is to investigate the influence of different factors on the wave function (probability density distribution) for carriers or excitons in this regime, i.e., object shape anisotropy as well as strain, piezoelectricity, and Coulomb interactions, and to identify the physical mechanisms determining the properties of optical emission. To probe the wave function symmetry, polarization-resolved photoluminescence has been performed, and the spatial extensions of the corresponding probability densities have been verified in magneto-optical measurements. The observed diamagnetic coefficients in the range of (15-31) ?eV/T2 reflect large in-plane QD size. These studies also enable us to investigate the importance of light hole states admixture to the valence band ground state in such nanostructures, which can be addressed via the degree of linear polarization of emission as well as the exciton gX factor. The linear-polarization-resolved measurements revealed an exceptionally low exciton fine structure splitting of 5?eV on average as well as a low emission polarization degree of -0.05, with the polarization perpendicular to the QD elongation direction dominating. The increased light hole contribution to the lowest energy hole level is reflected in the decreased exciton gX factor (in the range of 0-1) and is consistent with the results of the eight-band k.p modelling. Based on the temperature dependence of the diamagnetic coefficient, the problem of individual QD uniformity has additionally been discussed. To evaluate the impact of the confinment potential and the structure geometry on the optical properties of the QDs, a comparison between the investigated dots and InAs/InGaAlAs/InP quantum dashes exhibiting a much deeper confining potential is presented.
Theory of plasma confinement in non-axisymmetric magnetic fields.
Helander, Per
2014-08-01
The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced. PMID:25047050
Inertial electrostatic confinement (IEC) neutron sources
Nebel, R.A.; Barnes, D.C.; Caramana, E.J.; Janssen, R.D.; Nystrom, W.D.; Tiouririne, T.N.; Trent, B.C. [Los Alamos National Lab., NM (United States); Miley, G.H.; Javedani, J. [Univ. of Illinois, Urbana, IL (United States)
1995-12-31
Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2 {times} 10{sup 10} neutrons/sec in steady state. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. This paper discusses the IEC concept and how it can be adapted to a steady-state assaying source and an intense pulsed neutron source. Theoretical modeling and experimental results are presented.
Inertial electrostatic confinement (IEC) neutron sources
Barnes, D.C.; Caramana, E.J.; Janssen, R.D.; Nystrom, W.D.; Tiouririne, T.N.; Trent, B.C.; Miley, G.H.; Javedani, J.
1995-01-01
Inertial electrostatic confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2 x 10(exp 10) neutrons/sec in steady state. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. This paper discusses the IEC concept and how it can be adapted to a steady-state assaying source and an intense pulsed neutron source. Theoretical modeling and experimental results are presented.
Aerofractures in Confined Granular Media
NASA Astrophysics Data System (ADS)
Eriksen, Fredrik K.; Turkaya, Semih; Toussaint, Renaud; Måløy, Knut J.; Flekkøy, Eirik G.
2015-04-01
We will present the optical analysis of experimental aerofractures in confined granular media. The study of this generic process may have applications in industries involving hydraulic fracturing of tight rocks, safe construction of dams, tunnels and mines, and in earth science where phenomena such as mud volcanoes and sand injectites are results of subsurface sediment displacements driven by fluid overpressure. It is also interesting to increase the understanding the flow instability itself, and how the fluid flow impacts the solid surrounding fractures and in the rest of the sample. Such processes where previously studied numerically [Niebling 2012a, Niebling 2012b] or in circular geometries. We will here explore experimentally linear geometries. We study the fracturing patterns that form when air flows into a dense, non-cohesive porous medium confined in a Hele-Shaw cell - i.e. into a packing of dry 80 micron beads placed between two glass plates separated by ~1mm. The cell is rectangular and fitted with a semi-permeable boundary to the atmosphere - blocking beads but not air - on one short edge, while the other three edges are impermeable. The porous medium is packed inside the cell between the semi-permeable boundary and an empty volume at the sealed side where the air pressure can be set and kept at a constant overpressure (1-2bar). Thus, for the air trapped inside the cell to release the overpressure it has to move through the solid. At high enough overpressures the air flow deforms the solid and increase permeability in some regions along the air-solid interface, which results in unstable flow and aerofracturing. Aerofractures are thought to be an analogue to hydrofractures, and an advantage of performing aerofracturing experiments in a Hele-Shaw cell is that the fracturing process can easily be observed in the lab. Our experiments are recorded with a high speed camera with a framerate of 1000 frames per second. In the analysis, by using various image processing techniques, we segment out and study the aerofractures over time looking at growth dynamics, fractal dimension and characteristics such as average finger thickness as function of depth into the solid. Also, by performing image correlation on two subsequent frames we estimate displacement fields and investigate the surrounding stress and strain fields in the solid around the fractures. Several experiments are performed with various overpressures and packing densities, and we compare the results. In a directly related project, acoustic emissions are recorded on a cell plate during experiments, and one of our goals is to correlate acoustic events and observations. We will also compare the dependence of the patterns on the saturation of the initial deformable porous material, by comparing experiments performed by air injection in air saturated granular media, to some in liquid saturated granular media. References: MJ Niebling, R Toussaint, EG Flekkøy, KJ Måløy, 2012, Dynamic aerofracture of dense granular packings, 2012, Physical Review E 86 (6), 061315 M Niebling, R Toussaint, EG Flekkøy, KJ Måløy, 2012, Numerical studies of aerofractures in porous media, Revista Cubana de Fisica 29 (1E), pp. 1E66-1E70
Not Available
1990-07-01
The program objective is to demonstrate efficient removal of fine particulates to sufficiently low levels to meet proposed small scale coal combustor emission standards using a cleanup technology appropriate to small scale coal combustors. This to be accomplished using a novel particulate removal device, the Confined Vortex Scrubber (CVS), which consists of a cylindrical vortex chamber with tangential flue gas inlets. The clean gas exit is via vortex finder outlets, one at either end of the tube. Liquid is introduced into the chamber and is confined within the vortex chamber by the centrifugal force generated by the gas flow itself. This confined liquid forms a layer through which the flue gas is then forced to bubble, producing a strong gas/liquid interaction, high inertial separation forces and efficient particulate cleanup. During this quarter a comprehensive series of cleanup experiments have been made for three CVS configurations. The first CVS configuration tested gave very efficient fine particulate removal at the design air mass flow rate (1 MM BUT/hr combustor exhaust flow), but had over 20{double prime}WC pressure drop. The first CVS configuration was then re-designed to produce the same very efficient particulate collection performance at a lower pressure drop. The current CVS configuration produces 99.4 percent cleanup of ultra-fine fly ash at the design air mass flow at a pressure drop of 12 {double prime}WC with a liquid/air flow ratio of 0.31/m{sup 3}. Unlike venturi scrubbers, the collection performance of the CVS is insensitive to dust loading and to liquid/air flow ratio.
Murakami, M.; Arunasalam, V.; Bell, J.D.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Boody, F.; Boyd, D.; Bretz, N.; Bush, C.E.
1985-06-01
The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B/sub T/ increased to 4.0 T, I/sub p/ to 2.0 MA, injection power (P/sub b/) to 5 MW with H/sup 0/ or D/sup 0/ beams anti n/sub e/ to 5 x 10/sup 19/ m/sup -3/, and Z/sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (tau/sub E/ = anti n/sub e/q) has been confirmed at higher I/sub p/ and B/sub T/, and the maximum tau/sub E/ of 0.4 sec has been achieved. With NBI at P/sub b/ substantially (by factor >2) higher than P/sub OH/, excellent power and particle accountability have been established. This suggests that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. tau/sub E/ is observed to scale approximately as I/sub p/ P/sub b//sup -0.5/ (independent of anti n/sub e/), consistent with previous L-mode scalings. With NBI we have achieved the maximum tau/sub E/ of 0.2 sec and the maximum T/sub i/(o) of 4.4 keV in the normal operating regime, and even higher T/sub i/(o) in the energetic-ion regime with low-n/sub e/ and low-I/sub p/ operation.
A new model of geometry-induced stochastic resonance
NASA Astrophysics Data System (ADS)
Zheng, Chunming; Guo, Wei; Du, Luchun; Mei, Dongcheng
2014-03-01
We propose a new model where entropic stochastic resonance and geometric stochastic resonance can both be observed by controlling the geometry parameters and the external force. Such stochastic resonance manifests a more adjustable character in small-scale systems where confinement and noise play a prominent role. The magnitude of the effect is sensitive to the geometry modification, thus leading to various resonance conditions. The novel phenomenon found could thus be beneficial for the control of the basic properties in these systems.
Confinement Vessel Dynamic Analysis
R. Robert Stevens; Stephen P. Rojas
1999-08-01
A series of hydrodynamic and structural analyses of a spherical confinement vessel has been performed. The analyses used a hydrodynamic code to estimate the dynamic blast pressures at the vessel's internal surfaces caused by the detonation of a mass of high explosive, then used those blast pressures as applied loads in an explicit finite element model to simulate the vessel's structural response. Numerous load cases were considered. Particular attention was paid to the bolted port connections and the O-ring pressure seals. The analysis methods and results are discussed, and comparisons to experimental results are made.
Confinement Contains Condensates
Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.
2012-03-12
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.
ERIC Educational Resources Information Center
Kuntz, Gilles
The first section of this paper on World Wide Web applications related to dynamic geometry addresses dynamic geometry and teaching, including the relationship between dynamic geometry and direct manipulation, key features of dynamic geometry environments, the importance of direct engagement of the learner using construction software for…
Baldwin, John T.
Analytic Structures Geometry and Categoricity John T. Baldwin January 8, 2012 #12;Geometry and Categoricity Homogeneity Zariski Structures Analytic Structures Whig History #12;Geometry and Categoricity John T. Baldwin in (C, +, Â·) by `analytically' definable. Response #12;Geometry and Categoricity John T. Baldwin
Gideon, Rudy A.
Projective Geometry and Pappus' Theorem Kelly McKinnie History Pappus' Theorem Geometries Picturing Kelly McKinnie History Pappus' Theorem Geometries Picturing the projective plane Lines in projective and Pappus' Theorem Kelly McKinnie History Pappus' Theorem Geometries Picturing the projective plane Lines
Electrostatic-Dipole (ED) Fusion Confinement Studies
NASA Astrophysics Data System (ADS)
Miley, George H.; Shrestha, Prajakti J.; Yang, Yang; Thomas, Robert
2004-11-01
The Electrostatic-Dipole (ED) concept significantly differs from a "pure" dipole confinement device [1] in that the charged particles are preferentially confined to the high-pressure region interior of the dipole coil by the assistance of a surrounding spherical electrostatic grid. In present ED experiments, a current carrying coil is embedded inside the grid of an IEC such as to produce a magnetic dipole field. Charged particles are injected axisymmetrically from an ion gun (or duo-plasmatron) into the center of the ED confinement grid/dipole ring where they oscillate along the magnetic field lines and pass the peak field region at the center of the dipole region. As particles begin accelerating away from the center region towards the outer electrostatic grid region, they encounter a strong electrostatic potential (order of 10's of kilovolts) retarding force. The particles then decelerate, reverse direction and re-enter the dipole field region where again magnetic confinement dominates. This process continues, emulating a complex harmonic oscillator motion. The resulting pressure profile averaged over the field curvature offers good plasma stability in the ED configuration. The basic concept and results from preliminary experiments will be described. [1] M.E. Mauel, et al. "Dipole Equilibrium and Stability," 18th IAEA Conference of Plasma Phys. and Control. Nuclear Fusion, Varenna, Italy 2000, IAEA-F1-CN-70/TH
Computational Information Geometry From Euclidean to flat Pythagorean geometries
Nielsen, Frank
geometry: Customize geometries to datasets, generic non-Euclidean algorithmic toolboxes. George E. P. BoxComputational Information Geometry From Euclidean to flat Pythagorean geometries Frank Nielsen persistence), Recover intrinsic geometry (eg., distance learning, invariants) Computational information
Gate-defined quantum confinement in suspended bilayer graphene.
Allen, M T; Martin, J; Yacoby, A
2012-01-01
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
Effect of Confinement: Polygons in Strips, Slabs and Rectangles
NASA Astrophysics Data System (ADS)
Guttmann, Anthony J.; Jensen, Iwan
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.
Magnon waveguide with nanoscale confinement constructed from topological magnon insulators
NASA Astrophysics Data System (ADS)
Mook, Alexander; Henk, Jürgen; Mertig, Ingrid
2015-05-01
Topological magnon insulators host spatially confined edge magnons brought about by the Dzyaloshinskii-Moriya interaction. Bringing two topological magnon insulators into contact results in topologically protected unidirectional interface magnons. These interface modes decay rapidly toward the bulk regions of the sample. As a result, heat and spin currents associated with these magnons are as well unidirectional and strongly confined to a few-nanometer-wide strip along the interface. On top of this, these interface currents follow any geometry owing to the topological nature of the magnons. In this theoretical study, we propose and analyze two recipes for composing magnon waveguides with nanoscale confinement, one from topologically different phases, another from identical phases. We further identify material classes to construct these magnon waveguides and propose an experiment to verify their topological nature.
Inertial confinement fusion method producing line source radiation fluence
Rose, Ronald P. (Peters Township, Washington County, PA)
1984-01-01
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.
Inertial Electrostatic Confinement Modeling and Comparison to Experiments
Gilbert Emmert; John Santarius; Eric Alderson; David Donovan
2010-01-01
In inertial-electrostatic confinement (IEC), a high voltage accelerates ions between concentric, nearly transparent grids, usually in spherical geometry. For typical parameters (˜0.3 Pa 2 mTorr, ˜100 kV, ˜30 mA, ˜0.5 m anode diameter), atomic and molecular processes dominate operation. A numerically solved integral equation[1,2] approach to modeling D^+, D2^+, D3^+, and D^- ions passing through D2 background gas will be
Crystallization under nanoscale confinement.
Jiang, Qi; Ward, Michael D
2014-04-01
Classical crystal growth models posit that crystallization outcomes are determined by nuclei that resemble mature crystal phases, but at a critical size where the volume free energy of nuclei begins to offset the unfavorable surface free energy arising from the interface with the growth medium. Crystallization under nanoscale confinement offers an opportunity to examine nucleation and phase transformations at length scales corresponding to the critical size, at which kinetics and thermodynamics of nucleation and growth intersect and dramatic departures in stability compared to bulk crystals can appear. This tutorial review focuses on recent investigations of the crystallization of organic compounds in nanoporous matrices that effectively provide millions of nanoscale reactors in a single sample, ranging from controlled porous glass (CPG) beads to nanoporous block-copolymer monoliths to anodic aluminum oxide (AAO) membranes. Confinement of crystal growth in this manner provides a snapshot of the earliest stages of crystal growth, with insights into nucleation, size-dependent polymorphism, and thermotropic behavior of nanoscale crystals. Moreover, these matrices can be used to screen for crystal polymorphs and assess their stability as nanocrystals. The well-aligned cylindrical nanoscale pores of polymer monoliths or AAO also allow determination of preferred orientation of embedded nanocrystals, affording insight into the competitive nature of nucleation, critical sizes, and phase transition mechanisms. Collectively, these investigations have increased our understanding of crystallization at length scales that are deterministic while suggesting strategies for controlling crystallization outcomes. PMID:24081010
Mejía-Salazar, J R; Porras-Montenegro, N; Oliveira, L E
2009-11-11
We have performed a theoretical study of the quantum confinement (geometrical and barrier potential confinements) and axis-parallel applied magnetic-field effects on the conduction-electron effective Landé g factor in GaAs-(Ga, Al)As cylindrical quantum dots. Numerical calculations of the g factor are performed by using the Ogg-McCombe effective Hamiltonian-which includes non-parabolicity and anisotropy effects-for the conduction-band electrons. The quantum dot is assumed to consist of a finite-length cylinder of GaAs surrounded by a Ga(1-x)Al(x)As barrier. Theoretical results are given as functions of the Al concentration in the Ga(1-x)Al(x)As barrier, radius, lengths and applied magnetic fields. We have studied the competition between the quantum confinement and applied magnetic field, finding that in this type of heterostructure the geometrical confinement and Al concentration determine the behavior of the electron effective Landé [Formula: see text] factor, as compared to the effect of the applied magnetic field. Present theoretical results are in good agreement with experimental reports in the limiting geometry of a quantum well, and with previous theoretical findings in the limiting case of a quantum well wire. PMID:21694007
The virial theorem for the smoothly and sharply, penetrably and impenetrably confined hydrogen atom.
Katriel, Jacob; Montgomery, H E
2012-09-21
Confinement of atoms by finite or infinite boxes containing sharp (discontinuous) jumps has been studied since the fourth decade of the previous century, modelling the effect of external pressure. Smooth (continuous) counterparts of such confining potentials, that depend on a parameter such that in an appropriate limit they coincide with the sharp confining potentials, are investigated, with an emphasis on deriving the corresponding virial and Hellmann-Feynman theorems. PMID:22998251
Performance of Polywell inertial-electrostatic confinement for applications
J. F. Santarius; K. H. Simmons
1995-01-01
Summary form only given, as follows. Recent ideas have motivated a fresh look at fusion based on inertial-electrostatic confinement (IEC). Inertial-electrostatic-confinement devices electrostatically focus ions into a dense core. The electrostatic potential is generated by either grids or magnetically trapped electrons (the polywell concept). Work will be reported on modeling Polywell particle and power balance, with an emphasis on moderate-Q
Rahaman, Obaidur; Estrada, Trilce P.; Doren, Douglas J.; Taufer, Michela; Brooks, Charles L.; Armen, Roger S.
2011-01-01
The performance of several two-step scoring approaches for molecular docking were assessed for their ability to predict binding geometries and free energies. Two new scoring functions designed for “step 2 discrimination” were proposed and compared to our CHARMM implementation of the linear interaction energy (LIE) approach using the Generalized-Born with Molecular Volume (GBMV) implicit solvation model. A scoring function S1 was proposed by considering only “interacting” ligand atoms as the “effective size” of the ligand, and extended to an empirical regression-based pair potential S2. The S1 and S2 scoring schemes were trained and five-fold cross validated on a diverse set of 259 protein-ligand complexes from the Ligand Protein Database (LPDB). The regression-based parameters for S1 and S2 also demonstrated reasonable transferability in the CSARdock 2010 benchmark using a new dataset (NRC HiQ) of diverse protein-ligand complexes. The ability of the scoring functions to accurately predict ligand geometry was evaluated by calculating the discriminative power (DP) of the scoring functions to identify native poses. The parameters for the LIE scoring function with the optimal discriminative power (DP) for geometry (step 1 discrimination) were found to be very similar to the best-fit parameters for binding free energy over a large number of protein-ligand complexes (step 2 discrimination). Reasonable performance of the scoring functions in enrichment of active compounds in four different protein target classes established that the parameters for S1 and S2 provided reasonable accuracy and transferability. Additional analysis was performed to definitively separate scoring function performance from molecular weight effects. This analysis included the prediction of ligand binding efficiencies for a subset of the CSARdock NRC HiQ dataset where the number of ligand heavy atoms ranged from 17 to 35. This range of ligand heavy atoms is where improved accuracy of predicted ligand efficiencies is most relevant to real-world drug design efforts. PMID:21644546
Nernst branes from special geometry
Paul Dempster; David Errington; Thomas Mohaupt
2015-02-27
We construct new black brane solutions in $U(1)$ gauged ${\\cal N}=2$ supergravity with a general cubic prepotential, which have entropy density $s\\sim T^{1/3}$ as $T \\rightarrow 0$ and thus satisfy the Nernst Law. By using the real formulation of special geometry, we are able to obtain analytical solutions in closed form as functions of two parameters, the temperature $T$ and the chemical potential $\\mu$. Our solutions interpolate between hyperscaling violating Lifshitz geometries with $(z,\\theta)=(0,2)$ at the horizon and $(z,\\theta)=(1,-1)$ at infinity. In the zero temperature limit, where the entropy density goes to zero, we recover the extremal Nernst branes of Barisch et al, and the parameters of the near horizon geometry change to $(z,\\theta)=(3,1)$.
Nernst branes from special geometry
Dempster, Paul; Mohaupt, Thomas
2015-01-01
We construct new black brane solutions in $U(1)$ gauged ${\\cal N}=2$ supergravity with a general cubic prepotential, which have entropy density $s\\sim T^{1/3}$ as $T \\rightarrow 0$ and thus satisfy the Nernst Law. By using the real formulation of special geometry, we are able to obtain analytical solutions in closed form as functions of two parameters, the temperature $T$ and the chemical potential $\\mu$. Our solutions interpolate between hyperscaling violating Lifshitz geometries with $(z,\\theta)=(0,2)$ at the horizon and $(z,\\theta)=(1,-1)$ at infinity. In the zero temperature limit, where the entropy density goes to zero, we recover the extremal Nernst branes of Barisch et al, and the parameters of the near horizon geometry change to $(z,\\theta)=(3,1)$.
Fry, D.J.; Adams, E.
1983-09-01
A submerged, negatively buoyant radial jet, discharging horizontally beneath a free surface into water of initially uniform density, was studied experimentally and theoretically. The situation relates to the operation of an ocean thermal energy conversion plant and is an example of buoyancy and confinement offering opposing influences on jet trajectory. For shallow submergence, the jet is attached to the free surface while for large submergence or greater (negative) buoyancy, the jet is detached. An experimental program yielded data on jet trajectory, temperature, velocity and discharge conditions associated with transition between attached and detached regimes. A hysteresis effect was noted as the conditions for attachment and detachment were different. Dimensional analysis yielded a single parameter of primary importance and two parameters of secondary importance in describing jet behavior. An integral jet analysis based on a spreading assumption was successfully adapted to include induced velocity and pressure effects on jet behavior.
Uckan, N.A.; Hogan, J.T.
1990-01-01
The confinement capability of ITER was examined for a number of operational scenarios. The reference ITER physics baseline scenario (I = 22 MA) allows ignited burn under H-mode conditions ({tau}{sub E}(H-mode) {approximately} 2 {times} {tau}{sub E}(L-mode)). At higher currents (I = 25--28 MA) at which ITER can operate for limited pulse duration, there is an increased ignition margin if low-q operation proves acceptable. About a factor of 2 reduction in helium ash concentration (from the baseline value of 10% to 5%) in the reference ITER scenario has about the same impact on ignition capability as increasing the plasma current by about 15% (from the baseline value of 22 MA to {ge}25 MA). It might be possible to further optimize the ignition capability of ITER if some of the limits on operational boundaries can be relaxed by tailoring plasma profiles. 9 refs., 4 figs.
Thermal Conductivty Measurements in Confined Liquid He^4 near the Lambda Point
Edgar Genio; Kerry Kuehn; Guenter Ahlers; Feng-Chuan Liu; Yuan-Ming Liu
2000-01-01
We present a cell design to study the effects of confinement on the thermal conductivity lambda(L,t) of liquid He^4 near the superfluid transition T_lambda (t ? T\\/T_lambda - 1). The confining geometry is a glass capillary array (GCA) consisting of densely-packed parallel cylindrical tubes of uniform radius L and a porosity near 0.5 in a glass matrix. The GCA is
Quantum Confined Semiconductors for High Efficiency Photovoltaics
NASA Astrophysics Data System (ADS)
Beard, Matthew
2014-03-01
Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photon-to-free energy conversion step. In this discussion, I will present the current status of research efforts towards utilizing the unique properties of colloidal quantum dots (NCs confined in three dimensions) in prototype solar cells and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion. The solar cells are constructed using a low temperature solution based deposition of PbS or PbSe QDs as the absorber layer. Different chemical treatments of the QD layer are employed in order to obtain good electrical communication while maintaining the quantum-confined properties of the QDs. We have characterized the transport and carrier dynamics using a transient absorption, time-resolved THz, and temperature-dependent photoluminescence. I will discuss the interplay between carrier generation, recombination, and mobility within the QD layers. A unique aspect of our devices is that the QDs exhibit multiple exciton generation with an efficiency that is ~ 2 to 3 times greater than the parental bulk semiconductor.
Effects of wetting and anchoring on capillary phenomena in a confined liquid crystal.
De Las Heras, D; Velasco, E; Mederos, L
2004-03-01
A fluid of hard spherocylinders of length-to-breadth ratio L/D=5 confined between two identical planar, parallel walls--forming a pore of slit geometry--has been studied using a version of the Onsager density-functional theory. The walls impose an exclusion boundary condition over the particle's centers of mass, while at the same time favoring a particular anchoring at the walls, either parallel or perpendicular to the substrate. We observe the occurrence of a capillary transition, i.e., a phase transition associated with the formation of a nematic film inside the pore at a chemical potential different from micro(b)-the chemical potential at the bulk isotropic-nematic transition. This transition terminates at an Ising-type surface critical point. In line with previous studies based on the macroscopic Kelvin equation and the mesoscopic Landau-de Gennes approach, our microscopic model indicates that the capillary transition is greatly affected by the wetting and anchoring properties of the semi-infinite system, i.e., when the fluid is in contact with a single wall or, equivalently, the walls are at a very large distance. Specifically, in a situation where the walls are preferentially wetted by the nematic phase in the semi-infinite system, one has the standard scenario with the capillary transition taking place at chemical potentials less than micro(b) (capillary nematization transition or capillary ordering transition). By contrast, if the walls tend to orientationally disorder the fluid, the capillary transition may occur at chemical potentials larger than micro(b), in what may be called a capillary isotropization transition or capillary disordering transition. Moreover, the anchoring transition that occurs in the semi-infinite system may affect very decisively the confinement properties of the liquid crystal and the capillary transitions may become considerably more complicated. PMID:15267357
Effects of wetting and anchoring on capillary phenomena in a confined liquid crystal
NASA Astrophysics Data System (ADS)
de las Heras, D.; Velasco, E.; Mederos, L.
2004-03-01
A fluid of hard spherocylinders of length-to-breadth ratio L/D=5 confined between two identical planar, parallel walls—forming a pore of slit geometry—has been studied using a version of the Onsager density-functional theory. The walls impose an exclusion boundary condition over the particle's centers of mass, while at the same time favoring a particular anchoring at the walls, either parallel or perpendicular to the substrate. We observe the occurrence of a capillary transition, i.e., a phase transition associated with the formation of a nematic film inside the pore at a chemical potential different from ?b—the chemical potential at the bulk isotropic-nematic transition. This transition terminates at an Ising-type surface critical point. In line with previous studies based on the macroscopic Kelvin equation and the mesoscopic Landau-de Gennes approach, our microscopic model indicates that the capillary transition is greatly affected by the wetting and anchoring properties of the semi-infinite system, i.e., when the fluid is in contact with a single wall or, equivalently, the walls are at a very large distance. Specifically, in a situation where the walls are preferentially wetted by the nematic phase in the semi-infinite system, one has the standard scenario with the capillary transition taking place at chemical potentials less than ?b (capillary nematization transition or capillary ordering transition). By contrast, if the walls tend to orientationally disorder the fluid, the capillary transition may occur at chemical potentials larger than ?b, in what may be called a capillary isotropization transition or capillary disordering transition. Moreover, the anchoring transition that occurs in the semi-infinite system may affect very decisively the confinement properties of the liquid crystal and the capillary transitions may become considerably more complicated.
H. Stachel, Professor A Way to Geometry Through Descriptive Geometry
Stachel, Hellmuth
motions in [9]. The correspondence be- tween non-Euclidean differential geometry and the geometryH. Stachel, Professor A Way to Geometry Through Descriptive Geometry Vienna University of geometry and on my contributions to Descriptive Geometry education. Descriptive Geometry in Austria
Inertial Electrostatic Confinement (IEC) devices
R. A. Nebel; L. Turner; T. N. Tiouririne; D. C. Barnes; W. D. Nystrom; R. W. Bussard; G. H. Miley; J. Javedani; Y. Yamamoto
1994-01-01
Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950's. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated
Tuning the confinement strength in a split-gate quantum wire
W. K. Hew; K. J. Thomas; I. Farrer; D. Anderson; D. A. Ritchie; M. Pepper
2008-01-01
We present conductance measurements of a quantum wire defined by gating techniques which demonstrate independent control over the strength of the confinement potential and the carrier density. This is achieved by the introduction of a top gate over the standard split gates, so that the Fermi level in the wire can be adjusted without strongly affecting the confinement potential, permitting
Quantum Confined Silicon Clathrate Quantum Dots
NASA Astrophysics Data System (ADS)
Lusk, Mark; Brawand, Nicholas
2013-03-01
Silicon (Si) allotropes can be synthesized in such a way that tetrahedrally bonded atoms form cage-like structures with bulk mechanical and opto-electronic properties distinct from those of diamond silicon (dSi). We use DFT, supplemented with many-body Green function analysis, to explore the structural stability of clathrate Si quantum dots (QDs) and to characterize their confinement as a function of crystal symmetry and size. Our results show that that there is a simple relationship between the confinement character of the QDs and the effective mass of the associated bulk crystals. Clathrate QDs and dSiQDs of the same size can exhibit differences of gap energies by as much as 2 eV. This offers the potential of synthesizing Si dots on the order of 1 nm that have optical gaps in the visible range but that do not rely on high-pressure routes such as those explored for the metastable BC8 and R8 phases. These results prompt the question as to how minimal quantum confinement can be in dots composed of Si. More broadly, clathrate QDs can in principle be synthesized for a wide range of semiconductors, and the design space can be further enriched via doping. Silicon (Si) allotropes can be synthesized in such a way that tetrahedrally bonded atoms form cage-like structures with bulk mechanical and opto-electronic properties distinct from those of diamond silicon (dSi). We use DFT, supplemented with many-body Green function analysis, to explore the structural stability of clathrate Si quantum dots (QDs) and to characterize their confinement as a function of crystal symmetry and size. Our results show that that there is a simple relationship between the confinement character of the QDs and the effective mass of the associated bulk crystals. Clathrate QDs and dSiQDs of the same size can exhibit differences of gap energies by as much as 2 eV. This offers the potential of synthesizing Si dots on the order of 1 nm that have optical gaps in the visible range but that do not rely on high-pressure routes such as those explored for the metastable BC8 and R8 phases. These results prompt the question as to how minimal quantum confinement can be in dots composed of Si. More broadly, clathrate QDs can in principle be synthesized for a wide range of semiconductors, and the design space can be further enriched via doping. NSF Renewable Energy Materials Research Science and Engineering Center (REMRSEC) and the Golden Energy Computing Organization (GECO)
Ultrasonic interferometer for first-sound measurements of confined liquid He4
NASA Astrophysics Data System (ADS)
Rojas, X.; Hauer, B. D.; MacDonald, A. J. R.; Saberi, P.; Yang, Y.; Davis, J. P.
2014-05-01
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.
John Stillwell
\\u000a Surprisingly, the geometry of curved surfaces throws light on the geometry of the plane. More than 2000 years after Euclid\\u000a formulated axioms for plane geometry, differential geometry showed that the parallel axiom does not follow from the other axioms of Euclid. It had long been hoped that the parallel axiom followed from the others, but no proof had ever been
The Dynamics of a Polymer Confined in Anodic Aluminum Oxide Nanopore
NASA Astrophysics Data System (ADS)
Xue, Gi; Sa, Ye
2015-03-01
The dynamics of poly (n-butyl methacrylate) confined in porous templates are investigated using DSC and Fluorescence nonradiative energy transfer. Two glass transition temperatures are obtained at a slow cooling rate of which one bulk-like phase reflects core layer while the other at much higher temperature indicates interfacial layer in the confined polymer glass. Because of cylindrical geometry, the glass transition energy barrier of interfacial layer is elevated, and the thereof temperature threshold to form one or two glass transitions is determined through adjusting infiltrating temperatures. In addition, the glass transition behavior is speculated to be meditated by the counterbalance of the size and interfacial effects in the confined space.
Anchoring and nematic-isotropic transitions in a confined nematic phase
NASA Astrophysics Data System (ADS)
Rodríguez-Ponce, I.; Romero-Enrique, J. M.; Velasco, E.; Mederos, L.; Rull, L. F.
2000-02-01
We present a study of a simple model of a nematic liquid crystal confined between two walls in slab geometry (slit pore). A rich phenomenology, associated with capillary effects as well as orientational transitions, arises. In a previous paper (1999 Phys. Rev. Lett. 82 2697) on the semi-infinite problem (a single wall) we found anchoring transitions whose existence depends on the values of the surface parameters and temperature. We discuss the persistence of this transition in the confined problem and the effects of the confinement on the nematic-isotropic transition.
NSDL National Science Digital Library
Levy, Silvio
Rewritten and updated excerpts from the 30th Edition of the CRC Standard Mathematical Tables and Formulas. Covers all of geometry, minus differential geometry. Very complete collection of definitions, formulas, tables and diagrams, divided into two- and three- dimensional geometry, and further into 16 subdivisions such as transformations, polygons, coordinate systems, isometries, polyhedra and spheres.
Numerical Studies of Properties of Confined Helium
NASA Technical Reports Server (NTRS)
Manousakis, Efstratios
2003-01-01
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.
On the study of quark confinement and the relativistic flux tube model
Y. H. Yuan
2005-09-15
The scalar potential, time component vector potential and flux tube quark confinements are studied in this paper. We find that the predictions of scalar confinement and time component vector confinement are in considerable conflict with measured values while the flux-tube confinement works well to explain the experimental data. We also study the relativistic flux tube model. From the comparison of the exact numerical solution with the analytic approximation solution for heavy-light mesons, we find that the solutions are much more in agreement with each other for higher excited states since the deep radial limit is better satisfied.
NASA Astrophysics Data System (ADS)
Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P. W.
This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1-2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; and the Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.
Powers, L.; Condouris, R.; Kotowski, M.; Murphy, P.W. (eds.)
1992-01-01
This issue of the ICF Quarterly contains seven articles that describe recent progress in Lawrence Livermore National Laboratory's ICF program. The Department of Energy recently initiated an effort to design a 1--2 MJ glass laser, the proposed National Ignition Facility (NIF). These articles span various aspects of a program which is aimed at moving forward toward such a facility by continuing to use the Nova laser to gain understanding of NIF-relevant target physics, by developing concepts for an NIF laser driver, and by envisioning a variety of applications for larger ICF facilities. This report discusses research on the following topics: Stimulated Rotational Raman Scattering in Nitrogen; A Maxwell Equation Solver in LASNEX for the Simulation of Moderately Intense Ultrashort Pulse Experiments; Measurements of Radial Heat-Wave Propagation in Laser-Produced Plasmas; Laser-Seeded Modulation Growth on Directly Driven Foils; Stimulated Raman Scattering in Large-Aperture, High-Fluence Frequency-Conversion Crystals; Fission Product Hazard Reduction Using Inertial Fusion Energy; Use of Inertial Confinement Fusion for Nuclear Weapons Effects Simulations.
Interplay of explosive thermal reaction dynamics and structural confinement
NASA Astrophysics Data System (ADS)
Perry, W. Lee; Zucker, Jonathan; Dickson, Peter M.; Parker, Gary R.; Asay, Blaine W.
2007-04-01
Explosives play a significant role in human affairs; however, their behavior in circumstances other than intentional detonation is poorly understood. Accidents may have catastrophic consequences, especially if additional hazardous materials are involved. Abnormal ignition stimuli, such as impact, spark, friction, and heat may lead to a very violent outcome, potentially including detonation. An important factor influencing the behavior subsequent to abnormal ignition is the strength and inertia of the vessel confining the explosive, i.e., the near-field structural/mechanical environment, also known as confinement (inertial or mechanical). However, a comprehensive and quantified understanding of how confinement affects reaction violence does not yet exist. In the research discussed here, we have investigated a wide range of confinement conditions and related the explosive response to the fundamentals of the combustion process in the explosive. In our experiments, a charge of an octahydrotetranitrotetrazine-based plastic bonded explosive (PBX 9501) was loaded into a gun assembly having variable confinement conditions and subjected to a heating profile. The exploding charge breached the confinement and accelerated a projectile down the gun barrel. High bandwidth pressure and volume measurements were made and a first-law analysis was used to obtain enthalpy and power from the raw data. These results were then used to quantify reaction violence. Enthalpy change and power ranged from 0-1.8 kJ and 0-12 MW for 300 mg charges, respectively. Below a confinement strength of 20 MPa, violence was found to decline precipitously with decreasing confinement, while the violence for the heaviest confinement experiments was found to be relatively constant. Both pressure and pressurization rate were found to have critical values to induce and sustain violent reaction.
Snyder-Yang algebra and confinement of color particles
V. V. Khruschov
2010-12-21
A model of color particle confinement is considered. The model is based on the Snyder-Yang algebra, which takes into account a non-commutativity of generalized momenta and coordinates of a color particle and contains two new constants. An extended kinematical invariance in a quantum phase space of a color particle gives rise to an invariant equation with an oscillator rising potential. The presence of the oscillator rising potential can simulate a confinement of a color particle. Mass and lenght parameters involved in the Snyder-Yang commutation relations along with parameters of current and constituent quarks are estimated.
Edge Currents for Quantum Hall Systems, II. Two-Edge, Bounded and Unbounded Geometries
Peter D. Hislop; Eric Soccorsi
2008-01-01
. Devices exhibiting the integer quantum Hall effect can be modeled by one-particle Schrödinger operators describing the planar\\u000a motion of an electron in a perpendicular, constant magnetic field, and under the influence of an electrostatic potential.\\u000a The electron motion is confined to bounded or unbounded subsets of the plane by confining potential barriers. The edges of\\u000a the confining potential barriers create
Properties of Confinement in Holography
Giataganas, Dimitrios
2015-01-01
We review certain properties of confinement with added focus on the ones we study with holography. Then we discuss observables whose unique behavior can indicate the presence of confinement. Using mainly the Wilson loop in the gauge/gravity formalism, we study two main features of the QCD string: the string tension dependence on the temperature while in the confining phase, and the logarithmic broadening of the flux tube between the heavy static charges that turns out to be a generic property of all confining theories. Finally, we review the k-string bound state and we show that for a wide class of generic theories the k-string observables can be expressed in terms of the single meson bound state observables.
Response of nonrelativistic confined systems
NASA Astrophysics Data System (ADS)
Gurvitz, S. A.; Rinat, A. S.
1993-06-01
We study the nonrelativistic response of a ``diquark'' bound by confining forces, for which perturbation theory in the interaction fails. As nonperturbative alternatives we consider the Gersch-Rodriguez-Smith (GRS) theory and a summation method. We show that, contrary to the case of singular repulsive forces, the GRS theory can generally be applied to confined systems. When expressed in the GRS-West kinematic variable y, the response has a standard asymptotic limit and calculable dominant corrections of orders 1/q, 1/q2. That theory therefore clearly demonstrates how constituents, confined before and after the absorption of the transferred momentum and energy, behave as asymptotically free particles. We compare the GRS results with those of a summation method for harmonic and square-well confinement and also discuss the convergence of the GRS series for the response in powers of 1/q.
Properties of Confinement in Holography
Dimitrios Giataganas
2015-05-26
We review certain properties of confinement with added focus on the ones we study with holography. Then we discuss observables whose unique behavior can indicate the presence of confinement. Using mainly the Wilson loop in the gauge/gravity formalism, we study two main features of the QCD string: the string tension dependence on the temperature while in the confining phase, and the logarithmic broadening of the flux tube between the heavy static charges that turns out to be a generic property of all confining theories. Finally, we review the k-string bound state and we show that for a wide class of generic theories the k-string observables can be expressed in terms of the single meson bound state observables.
Alternative approaches to plasma confinement
NASA Technical Reports Server (NTRS)
Roth, J. R.
1978-01-01
The paper discusses 20 plasma confinement schemes each representing an alternative to the tokamak fusion reactor. Attention is given to: (1) tokamak-like devices (TORMAC, Topolotron, and the Extrap concept), (2) stellarator-like devices (Torsatron and twisted-coil stellarators), (3) mirror machines (Astron and reversed-field devices, the 2XII B experiment, laser-heated solenoids, the LITE experiment, the Kaktus-Surmac concept), (4) bumpy tori (hot electron bumpy torus, toroidal minimum-B configurations), (5) electrostatically assisted confinement (electrostatically stuffed cusps and mirrors, electrostatically assisted toroidal confinement), (6) the Migma concept, and (7) wall-confined plasmas. The plasma parameters of the devices are presented and the advantages and disadvantages of each are listed.
An index for confined monopoles
Robert Wimmer
2012-06-08
We compute the index and associated spectral density for fluctuation operators which are defined via the Lagrangian of N=2 SQCD in the background of non-abelian confined multimonopoles. To this end we generalize the standard index calculations of Callias and Weinberg to the case of asymptotically nontrivial backgrounds. The resulting index is determined by topological charges. We conjecture that this index counts one quarter of the dimension of the moduli space of confined multimonopoles.
Isolation and confinement - Considerations for colonization
NASA Technical Reports Server (NTRS)
Akins, F. R.
1978-01-01
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.
Effects of nanoscopic-confinement on polymer dynamics.
Chrissopoulou, Kiriaki; Anastasiadis, Spiros H
2015-05-01
The static and dynamic behavior of polymers in confinement close to interfaces can be very different from that in the bulk. Among the various geometries, intercalated nanocomposites, in which polymer films of ?1 nm thickness reside between the parallel inorganic surfaces of layered silicates in a well-ordered multilayer, offer a unique avenue for the investigation of the effects of nanoconfinement on polymer structure and dynamics by utilizing conventional analytical techniques and macroscopic specimens. In this article, we provide a review of research activities mainly in our laboratory on polymer dynamics under severe confinement utilizing different polymer systems: polar and non-polar polymers were mixed with hydrophilic or organophilic silicates, respectively, whereas hyperbranched polymers were studied in an attempt to probe the effect of polymer-surface interactions by altering the number and the kinds of functional groups in the periphery of the branched polymers. The polymer dynamics was probed by quasielastic neutron scattering and dielectric relaxation spectroscopy and was compared with that of the polymers in the bulk. In all cases, very local sub-Tg processes related to the motion of side and/or end groups as well as the segmental ?-relaxation were identified with distinct differences recorded between the bulk and the confined systems. Confinement was found not to affect the very local motion in the case of the linear chains whereas it made it easier for hyperbranched polymers due to modifications of the hydrogen bond network. The segmental relaxation in confinement becomes faster than that in the bulk, exhibits Arrhenius temperature dependence and is observed even below the bulk Tg due to reduced cooperativity in the confined systems. PMID:25869864
V. T. Jacobson; R. D. Bengtson; R. G. Bussell; A. J. Wootton; F. R. Chang Díaz; J. P. Squire
1998-01-01
The Advanced Space Propulsion Laboratory at Johnson Space Center is developing a variable specific impulse rocket from a plasma confined in an asymmetric magnetic mirror geometry. The plasma is produced either with 2.45 GHz ECRH or a helicon with 8 or 13.56 MHz RF. Plasma parameters in the VASIMR experiment are measured using a fast reciprocating triple Langmuir probe. A
An electrostatically and a magnetically confined electron gun lens system
NASA Technical Reports Server (NTRS)
Bernius, Mark T.; Man, Kin F.; Chutjian, Ara
1988-01-01
Focal properties, electron trajectory calculations, and geometries are given for two electron 'gun' lens systems that have a variety of applications in, for example, electron-neutral and electron-ion scattering experiments. One nine-lens system utilizes only electrostatic confinement and is capable of focusing electrons onto a fixed target with extremely small divergence angles, over a range of final energies 1-790 eV. The second gun lens system is a simpler three-lens system suitable for use in a uniform, solenoidal magnetic field. While the focusing properties of such a magnetically confined lens systenm are simpler to deal with, the system does illustrate features of electron extraction and Brillouin flow that have not been suitably emphasized in the literature.
Defect topologies in chiral liquid crystals confined to mesoscopic channels
NASA Astrophysics Data System (ADS)
Schlotthauer, Sergej; Skutnik, Robert A.; Stieger, Tillmann; Schoen, Martin
2015-05-01
We present Monte Carlo simulations in the grand canonical and canonical ensembles of a chiral liquid crystal confined to mesochannels of variable sizes and geometries. The mesochannels are taken to be quasi-infinite in one dimension but finite in the two other directions. Under thermodynamic conditions chosen and for a selected value of the chirality coupling constant, the bulk liquid crystal exhibits structural characteristics of a blue phase II. This is established through the tetrahedral symmetry of disclination lines and the characteristic simple-cubic arrangement of double-twist helices formed by the liquid-crystal molecules along all three axes of a Cartesian coordinate system. If the blue phase II is then exposed to confinement, the interplay between its helical structure, various anchoring conditions at the walls of the mesochannels, and the shape of the mesochannels gives rise to a broad variety of novel, qualitative disclination-line structures that are reported here for the first time.
Transport in Fermi Liquids Confined by Rough Walls
NASA Astrophysics Data System (ADS)
Sharma, Priya
2014-10-01
I present theoretical calculations of the thermal conductivity of Fermi liquid 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 He in a slab geometry.
NASA Astrophysics Data System (ADS)
Wilms, Dorothea; Virnau, Peter; Snook, Ian K.; Binder, Kurt
2012-11-01
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.
DEVELOPMENT OF A METHODOLOGY FOR REGIONAL EVALUATION OF CONFINING BED INTEGRITY
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...
arXiv:hep-ph/9211265v12Nov92 Dynamical confinement in bosonized QCD2
FernÃ¡ndez de CÃ³rdoba, Pedro
of the confinement mechanism is that no quark can be liberated from a bound state. Let us characterize confinement a consequence of gauge freedom [4]. One can choose a gauge where the self-energy is perfectly finite. However we next show that one can find a relation between the self-energy and the interaction potential
Quantum confined Stark effect in Gaussian quantum wells: A tight-binding study
Ramírez-Morales, A.; Martínez-Orozco, J. C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad Esquina Con Paseo La Bufa S/N, 98060 Zacatecas, Zac. (Mexico)
2014-05-15
The main characteristics of the quantum confined Stark effect (QCSE) are studied theoretically in quantum wells of Gaussian profile. The semi-empirical tight-binding model and the Green function formalism are applied in the numerical calculations. A comparison of the QCSE in quantum wells with different kinds of confining potential is presented.
Inertial-electrostatic confinement (IEC) fusion for space power
George H. Miley; Jonathon H. Nadler; Timothy K. Hochberg; Olivier Barnouin; Yibin Gu
1991-01-01
Fusion offers the potential for a very high specific power, providing a large specific impulse that can be traded-off with thrust for mission optimization. Thus fusion is a leading candidate for missions beyond the moon. Here we discuss a new approach for space fusion power, namely Inertial-Electrostatic Confinement (IEC). This method offers a high power density in a relatively small,
Inertial electrostatic confinement as a power source for electric propulsion
G. H. Miley; R. Burton; J. Javedani; Y. Yamamoto; A. Satsangi; Y. Gu; P. Heck; R. Nebel; N. Schulze; J. Christensen
1993-01-01
The potential use of an INERTIAL ELECTROSTATIC CONFINEMENT (IEC) power source for space propulsion has previously been suggested by the authors and others. In the past, these discussions have generally followed the charged-particle electric-discharge engine (QED) concept proposed by Bussard, in which the IEC is used to generate an electron beam which vaporizes liquid hydrogen for use as a propellant.
Improved virtual cathode formation in Inertial Electrostatic Confinement
A. M. McEvoy; Y. H. Kim; H. W. Herrmann
2009-01-01
Summary form only given. Continued experimentation on the inertial electrostatic confinement (IEC) of ions in a virtual cathode potential well at Los Alamos National Laboratory (LANL) is presented. The IEC virtual cathode is formed by focusing six diametrically opposed electron beams to the center of a spherical vacuum chamber. The electrons are accelerated using two highly transparent, concentric spherical grids
Structures and phase transitions of a vertically confined plasma crystal
K. Qiao; T. W. Hyde
2004-01-01
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
Rare earth-doped confined structures for amplifiers and lasers
B Jacquier; E Lebrasseur; S Guy; A Belarouci; F Menchini
2000-01-01
Here, we present an overview of the specific spectroscopic properties of fluoride planar waveguides which emphasize the difference between rare earth-doped waveguide and bulk and demonstrate their potentiality to be used as lasers and amplifiers. We illustrate this with recent results obtained at strategic wavelengths for telecommunications. Furthermore, we are dealing with even more confined structures such as optical microcavities
Properties of non-neutral electron plasmas confined with a magnetic mirror field
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
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.
Geometry Here, Geometry There, Geomerty is EVERYWHERE!
NSDL National Science Digital Library
Miss Tiller
2012-02-05
See if you know your geometry by using coordinate planes! GAME 1 Space Boy To The Rescue! See if you can fly through space using coordinate pairs if you dare! Directions: Double click on the space astronaut on the right hand side of the screen. Your astronaut should ...
Some links between turtle geometry and analytic geometry
Neil C. Rowe
1985-01-01
The computer language LOGO facilitates the teaching of analytic geometry and calculus from the notion of curvature, through its ‘turtle geometry’ facility [2]. We provide some theoretical basis for finding turtle geometry equivalents of familiar curves in analytic geometry, and vice versa, by some simple methods which apparently have not been noticed previously. In particular, we study turtle geometry programs
Optimizing the Geometry of Patterned Polymer Separation Media
NASA Astrophysics Data System (ADS)
Hoagland, David; Strey, Helmut
2006-03-01
A quantitative understanding of polymer transport in patterned polymer separation media would guide the design of media with optimized pattern geometries. For example, one might desire to know what confinement geometry best separates linear polymers by molecular weight as a driving field is applied to a polymer mixture. By asserting that transport is controlled by steric interactions with a periodic pore structure, and that the driving field is low enough for a linearity in the relationship between transport rate and field magnitude, we have derived a simple, general expression for polymer mobility as a function of parameters characterizing polymer and pattern. Our expression can be used to derive optimized separation geometries that can be produced by micro- or nano-lithography methods. Analysis will be discussed for several pattern geometries that exert periodic constriction on migrating polymers. Financial support: UMass MRSEC
Euclidean Geometry via Programming.
ERIC Educational Resources Information Center
Filimonov, Rossen; Kreith, Kurt
1992-01-01
Describes the Plane Geometry System computer software developed at the Educational Computer Systems laboratory in Sofia, Bulgaria. The system enables students to use the concept of "algorithm" to correspond to the process of "deductive proof" in the development of plane geometry. Provides an example of the software's capability and compares it to…
ERIC Educational Resources Information Center
Lyublinskaya, Irina; Funsch, Dan
2012-01-01
Several interactive geometry software packages are available today to secondary school teachers. An example is The Geometer's Sketchpad[R] (GSP), also known as Dynamic Geometry[R] software, developed by Key Curriculum Press. This numeric based technology has been widely adopted in the last twenty years, and a vast amount of creativity has been…
Tone generation by flow past confined, deep cylindrical cavities
NASA Astrophysics Data System (ADS)
Jungowski, W. M.; Botros, K. K.; Studzinski, W.; Berg, D. H.
1987-10-01
Flow past a confined, deep, cylindrical cavity such as a side-branch can induce powerful pressure pulsations in piping systems. Oscillating pressures and velocities were monitored in two facilities where branch geometry, flow parameters and boundary conditions were varied over a wide range. These measurements showed the influence of various factors on tone generation, determined source output and impedances involved, and revealed pertinent phase relationships. Tone amplitude in the side-branches investigated depends on seven similarity numbers. The data collected and source model developed can help to estimate tone frequency and amplitude for any complex piping system.
Quench Dynamics in Confined 1+1-Dimensional Systems
Dalit Engelhardt
2015-04-04
We present a framework for investigating the response of confined 1+1-dimensional systems to a quantum quench and consider the extent to which a system whose post-quench dynamics are near-integrable may be analyzed by an application of boundary conformal field theory techniques. As the main example we present a model of a split-momentum quench in a finite 1D geometry, a setup analogous to that of the experiment of Kinoshita, Wenger, and Weiss [Nature 440, 900 (2006)]. We analytically derive the form of the expected momentum distributions and demonstrate qualitative agreement with the experimental results.
Magnetospheric Vortex Formation: Self-Organized Confinement of 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
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.
Mixing of multiple jets with a confined subsonic crossflow
NASA Technical Reports Server (NTRS)
Holdeman, James D.
1993-01-01
An account is given of experimental and computational results on the mixing of single, double, and opposed rows of jets characterized by an either isothermal or variable temperature mainstream in a confined subsonic crossflow; these flow configurations are typical of gas turbine combustor dilution chambers. It is established that the momentum-flux ratio is the most significant flow variable. Combinations of flow and geometry yielding optimum mixing were identified from experimental and computational results. The orifice spacing and momentum-flux relationships affected jet structure, which was significantly different between jets injected from the inner wall of a turn and those injected from the outer wall.
Quench Dynamics in Confined 1+1-Dimensional Systems
Engelhardt, Dalit
2015-01-01
We present a scheme for investigating the response of confined 1+1-dimensional systems to a quantum quench and consider the extent to which a system whose post-quench dynamics are near-integrable may be analyzed by an application of boundary CFT techniques. As the main example we present a model of a split-momentum quench in a finite 1D geometry, a setup analogous to that of the experiment of Kinoshita, Wenger, and Weiss [Nature 440, 900 (2006)]. We analytically derive the form of the expected momentum distributions and describe how such information may be used to assess the extent of integrability breaking in realistic systems.
Bending of Elastic Fibers in Viscous Flow: the Influence of Confinement
NASA Astrophysics Data System (ADS)
Wexler, Jason; Berthet, Helene; Quennouz, Nawal; Du Roure, Olivia; Stone, Howard; Lindner, Anke
2011-11-01
Applications such as microfluidic flow sensors or living micro-organisms often involve the deformation of a slender deformable body attached to a rigid boundary. Here we investigate the deformation of an anchored elastic fiber subject to transverse flow in a microfluidic device. Our fiber protrudes into a Hele-Shaw cell, a geometry with a flow field that varies rapidly near the wall but is otherwise approximately uniform. We fabricate our fibers directly in the microchannel using a photopolymerization method. This approach allows us not only to tune the geometry of the fiber (width, length), but also to control the fiber confinement (ratio of fiber height compared to channel height). For varying flow rates we measure how the shape of the fiber changes as a function of its geometry and the confinement. We analyze our results using dimensionless analysis and discuss simplified models of the deflection. Support from European Project MODIFY.
Evolution of Quantum Confinement Effects in Lead Iodide Semiconductor Clusters
NASA Astrophysics Data System (ADS)
Sawamura, Makoto
1990-01-01
Molecular orbital theory is used in the context of ab initio Hartree-Fock calculations to study the origin of quantum confinement effects in layered Pb_7 I_{14} clusters. As the cluster geometry is energy optimized in several steps, the structure distends into two quasi-hemispherical iodine layers sandwiching a hexagonal lead layer. At the equilibrium geometry for the lowest electronic state, Pb-Pb in-plane interatomic distances are contracted by 11.3% compared to the experimental bulk PbI_2 values. Optical spectra are observed to be blue-shifted by 0.3 to 2.1 eV relative to the energy band gap of crystalline PbI _2.
Swimming of Vorticella in two-dimensional confinements
NASA Astrophysics Data System (ADS)
Sotelo, Luz; Park, Young-Gil; Jung, Sunghwan; Ryu, Sangjin
2015-03-01
Vorticellais a ciliate observed in the stalked sessile form (trophont), which consists of an inverted bell-shaped cell body (zooid) and a slender stalk attaching the zooid to a substrate. Having circular cilia bands around the oral part, the stalkless zooid of Vorticella can serve as a model system for microorganism swimming. Here we present how the stalkess trophont zooid of Vorticella swims in two-dimensional confined geometries which are similar to the Hele-Shaw cell. Having harvested stalkless Vorticella zooids, we observed their swimming in water between two glass surfaces using video microscopy. Based on measured swimming trajectories and distributions of zooid orientation and swimming velocity, we analyzed how Vorticella's swimming mobility was influenced by the geometry constraints. Supported by First Award grant from Nebraska EPSCoR.
Geometrie im Internet Wolfgang Rath
Stachel, Hellmuth
Geometrie im Internet Wolfgang Rath Institut für Geometrie, TU Wien rath@geometrie.tuwien.ac.at http://www.geometrie.tuwien.ac.at/rath Version 1999-11-15 #12;Geometrie im Internet - Wolfgang Rath......................................................................................... 5 1.1 SCHNELLER EINSTIEG INS INTERNET
Geometries for CAGD Helmut Pottmanna
Nawratil, Georg
, and non-Euclidean geometries. In all cases, we outline and illustrate applications of the respective modeling and addresses Euclidean, affine and projective geometry, as well as differential geometry in Projective Geometry Differential geometry in projective spaces requires some modifications over Euclidean
Flavors of Geometry MSRI Publications
Kapovich, Misha
of non-Euclidean geometry, that is, a geometry that discards one of Euclid's axioms. Einstein and Minkowski found in non-Euclidean geometry a This work was supported in part by The Geometry Center of the twentieth century every serious student of mathematics and physics studied non-Euclidean geometry. This has
Ion separation effects in mixed-species ablators for inertial-confinement-fusion implosions.
Amendt, Peter; Bellei, Claudio; Ross, J Steven; Salmonson, Jay
2015-02-01
Recent efforts to demonstrate significant self-heating of the fuel and eventual ignition at the National Ignition Facility make use of plastic (CH) ablators [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014)]. Mainline simulation techniques for modeling CH capsule implosions treat the ablator as an average-atom fluid and neglect potential species separation phenomena. The mass-ablation process for a mixture is shown to lead to the potential for species separation, parasitic energy loss according to thermodynamic arguments, and reduced rocket efficiency. A generalized plasma barometric formula for a multispecies concentration gradient that includes collisionality and steady flows in spherical geometry is presented. A model based on plasma expansion into a vacuum is used to interpret reported experimental evidence for ablator species separation in an inertial-confinement-fusion target [J. S. Ross et al., Rev. Sci. Instrum. 83, 10E323 (2012)]. The possibility of "runaway" hydrogen ions in the thermoelectric field of the ablation front is conjectured. PMID:25768614
Ion separation effects in mixed-species ablators for inertial-confinement-fusion implosions
NASA Astrophysics Data System (ADS)
Amendt, Peter; Bellei, Claudio; Ross, J. Steven; Salmonson, Jay
2015-02-01
Recent efforts to demonstrate significant self-heating of the fuel and eventual ignition at the National Ignition Facility make use of plastic (CH) ablators [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014), 10.1063/1.4874330]. Mainline simulation techniques for modeling CH capsule implosions treat the ablator as an average-atom fluid and neglect potential species separation phenomena. The mass-ablation process for a mixture is shown to lead to the potential for species separation, parasitic energy loss according to thermodynamic arguments, and reduced rocket efficiency. A generalized plasma barometric formula for a multispecies concentration gradient that includes collisionality and steady flows in spherical geometry is presented. A model based on plasma expansion into a vacuum is used to interpret reported experimental evidence for ablator species separation in an inertial-confinement-fusion target [J. S. Ross et al., Rev. Sci. Instrum. 83, 10E323 (2012)]. The possibility of "runaway" hydrogen ions in the thermoelectric field of the ablation front is conjectured.
Electrostatic confinement of electrons in an integrable graphene quantum dot.
Bardarson, J H; Titov, M; Brouwer, P W
2009-06-01
We compare the conductance of an undoped graphene sheet with a small region subject to an electrostatic gate potential for the cases that the dynamics in the gated region is regular (disc-shaped region) and classically chaotic (stadium). For the disc, we find sharp resonances that narrow upon reducing the area fraction of the gated region. We relate this observation to the existence of confined electronic states. For the stadium, the conductance loses its dependence on the gate voltage upon reducing the area fraction of the gated region, which signals the lack of confinement of Dirac quasiparticles in a gated region with chaotic classical electron dynamics. PMID:19658887
New confining force solution of QCD axion domain wall problem
S. M. Barr; Jihn E. Kim
2014-11-13
The serious cosmological problems created by the axion-string/axion-domain-wall system in standard axion models are alleviated by positing the existence of a new confining force. The instantons of this force can generate an axion potential that erases the axion strings long before QCD effects become important, thus preventing QCD-generated axion walls from ever appearing. Axion walls generated by the new confining force would decay so early as not to contribute significantly to the energy in axion dark matter.
The Schwinger pair production rate in confining theories via holography
Daisuke Kawai; Yoshiki Sato; Kentaroh Yoshida
2014-06-02
We study the Schwinger pair production in confining theories. The production rate in an external electric field E is numerically evaluated by using the holographic description. There exist two kinds of critical values of the electric field, i) E=E_c, above which there is no potential barrier and particles are freely generated, ii) E=E_s, below which the confining string tension dominates the electric field and the pair production does not occur. We argue the universal exponents associated with the critical behaviors.
Scattering for Nonlinear Schrödinger Equation Under Partial Harmonic Confinement
NASA Astrophysics Data System (ADS)
Antonelli, Paolo; Carles, Rémi; Silva, Jorge Drumond
2015-02-01
We consider the nonlinear Schrödinger equation under a partial quadratic confinement. We show that the global dispersion corresponding to the direction(s) with no potential is enough to prove global in time Strichartz estimates, from which we infer the existence of wave operators, thanks to suitable vector-fields. Conversely, given an initial Cauchy datum, the solution is global in time and asymptotically free, provided that confinement affects one spatial direction only. This stems from anisotropic Morawetz estimates, involving a marginal of the position density.
Screening Evaluations for Upland Confined Disposal Facility Effluent Quality
Paul Schroeder; Trudy Estes; Susan Bailey
PURPOSE: Section 404 of the Clean Water Act requires evaluation of the potential impacts of dredged material discharges from confined disposal facilities (CDFs). A joint U.S. Army Corps of Engineers (USACE) and U.S. Environmental Protection Agency (EPA) Technical Framework (USACE\\/EPA 2004) provides guidance for evaluation of potential contaminant pathways to determine if controls or management actions are required. Guidance for
Fractal energy spectrum of a polariton gas in a Fibonacci quasiperiodic potential.
Tanese, D; Gurevich, E; Baboux, F; Jacqmin, T; Lemaître, A; Galopin, E; Sagnes, I; Amo, A; Bloch, J; Akkermans, E
2014-04-11
We report on the study of a polariton gas confined in a quasiperiodic one-dimensional cavity, described by a Fibonacci sequence. Imaging the polariton modes both in real and reciprocal space, we observe features characteristic of their fractal energy spectrum such as the opening of minigaps obeying the gap labeling theorem and log-periodic oscillations of the integrated density of states. These observations are accurately reproduced solving an effective 1D Schrödinger equation, illustrating the potential of cavity polaritons as a quantum simulator in complex topological geometries. PMID:24765996
Fractal Energy Spectrum of a Polariton Gas in a Fibonacci Quasiperiodic Potential
NASA Astrophysics Data System (ADS)
Tanese, D.; Gurevich, E.; Baboux, F.; Jacqmin, T.; Lemaètre, A.; Galopin, E.; Sagnes, I.; Amo, A.; Bloch, J.; Akkermans, E.
2014-04-01
We report on the study of a polariton gas confined in a quasiperiodic one-dimensional cavity, described by a Fibonacci sequence. Imaging the polariton modes both in real and reciprocal space, we observe features characteristic of their fractal energy spectrum such as the opening of minigaps obeying the gap labeling theorem and log-periodic oscillations of the integrated density of states. These observations are accurately reproduced solving an effective 1D Schrödinger equation, illustrating the potential of cavity polaritons as a quantum simulator in complex topological geometries.
Scaling behaviour for the water transport in nanoconfined geometries
Chiavazzo, Eliodoro; Fasano, Matteo; Asinari, Pietro; Decuzzi, Paolo
2014-01-01
The transport of water in nanoconfined geometries is different from bulk phase and has tremendous implications in nanotechnology and biotechnology. Here molecular dynamics is used to compute the self-diffusion coefficient D of water within nanopores, around nanoparticles, carbon nanotubes and proteins. For almost 60 different cases, D is found to scale linearly with the sole parameter ? as D(?)=DB[1+(DC/DB?1)?], with DB and DC the bulk and totally confined diffusion of water, respectively. The parameter ? is primarily influenced by geometry and represents the ratio between the confined and total water volumes. The D(?) relationship is interpreted within the thermodynamics of supercooled water. As an example, such relationship is shown to accurately predict the relaxometric response of contrast agents for magnetic resonance imaging. The D(?) relationship can help in interpreting the transport of water molecules under nanoconfined conditions and tailoring nanostructures with precise modulation of water mobility. PMID:24699509
Landscape as a Model: The Importance of Geometry
Holland, E. Penelope; Aegerter, James N; Dytham, Calvin; Smith, Graham C
2007-01-01
In all models, but especially in those used to predict uncertain processes (e.g., climate change and nonnative species establishment), it is important to identify and remove any sources of bias that may confound results. This is critical in models designed to help support decisionmaking. The geometry used to represent virtual landscapes in spatially explicit models is a potential source of bias. The majority of spatial models use regular square geometry, although regular hexagonal landscapes have also been used. However, there are other ways in which space can be represented in spatially explicit models. For the first time, we explicitly compare the range of alternative geometries available to the modeller, and present a mechanism by which uncertainty in the representation of landscapes can be incorporated. We test how geometry can affect cell-to-cell movement across homogeneous virtual landscapes and compare regular geometries with a suite of irregular mosaics. We show that regular geometries have the potential to systematically bias the direction and distance of movement, whereas even individual instances of landscapes with irregular geometry do not. We also examine how geometry can affect the gross representation of real-world landscapes, and again show that individual instances of regular geometries will always create qualitative and quantitative errors. These can be reduced by the use of multiple randomized instances, though this still creates scale-dependent biases. In contrast, virtual landscapes formed using irregular geometries can represent complex real-world landscapes without error. We found that the potential for bias caused by regular geometries can be effectively eliminated by subdividing virtual landscapes using irregular geometry. The use of irregular geometry appears to offer spatial modellers other potential advantages, which are as yet underdeveloped. We recommend their use in all spatially explicit models, but especially for predictive models that are used in decisionmaking. PMID:17967050
The Glass Transition Temperature of Polymer Nanoparticles under Soft and Hard Confinement
NASA Astrophysics Data System (ADS)
Zhang, Chuan; Guo, Yunlong; Priestley, Rodney
2011-03-01
When confined to the nanoscale, the glass transition temperature (Tg) of polymers can deviate substantially from the bulk, i.e., the Tg-confinement effect. Due to ease of processing, most studies have focused on the size-dependent Tg of thin films, while few have extended investigations to other geometries. As polymers confined in higher geometrical dimensions become the enabling material in technologies ranging from drug delivery to plastic electronics, a greater understanding of size effects on Tg is warranted. Here, we investigate the effect of soft and hard three-dimensional confinement on the Tg of polymer nanoparticles. Via modulated differential scanning calorimetry, we show that Tg decreases with size for bare polymer nanoparticles, i.e., the case of soft confinement while Tg is invariant with size for silica-capped polymer nanoparticles, i.e., the case of hard confinement. These results suggest that the free surface is a key factor in Tg reductions of three-dimensionally confined polymer.
String theory and quark confinement
Alexandre M. Polyakov
1998-01-01
This article is based on a talk given at the “Strings '97” conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed.
Selenium Confined in Porous Membranes
Steve Ehrlich; David Narehood; Paul Sokol; Thomas Mallouk; Achim Amma
2001-01-01
Selenium posses many interesting and peculiar properties that are not entirely understood and that require further study. The bulk structure of selenium is a hexagonal structure with a small c\\/a ratio; while, under vaporization or high-pressure two monoclinic phases. In the two monoclinic phases (alpha and beta), the selenium forms long chains. No study of the effects of confinement on
Flex Circuitry for Confined Spaces
NASA Technical Reports Server (NTRS)
Fitzpatrick, J. B.; Maier, L. C.
1986-01-01
To facilitate installation of electronic equipment in confined spaces, circuitry preassembled on flexible wiring. Mother boards, large bypass capacitors, and interface connectors mounted on flexible wiring and tested before installation. Flexible circuits eliminate need for in-place hardwiring and allow smaller enclosures to be used.
Toolbox Safety Talk Confined Spaces
Pawlowski, Wojtek
and maintenance. Examples of confined spaces include manholes, storage tanks, boilers, vaults and pipelines material to drown, capture or asphyxiate an entrant. Examples include water, grains and soils. Other/Tag/Verify procedures when required. · Complete and record pre-entry air quality measurements. Continuously monitor
Momentum Confinement at Low Torque
Solomon, W M; Burrell, K H; deGrassie, J S; Budny, R; Groebner, R J; Heidbrink, W W; Kinsey, J E; Kramer, G J; Makowski, M A; Mikkelsen, D; Nazikian, R; Petty, C C; Politzer, P A; Scott, S D; Van Zeeland, M A; Zarnstorff, M C
2007-06-26
Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.
NSDL National Science Digital Library
2007-12-12
This website focuses on Native American use of the physical, proportional geometry that originates from the simple circle. Aimed at 4th to 9th grade teachers, the site is divided into four sections: foundations, anthropology, designs, and education. It was selected by Britannica.com, February 2000, as a best Internet site. Other keywords: geometric shapes, geometric constructions, proportional geometry, proportional constants, polygons, hexagons, equilateral triangles, dodecagons, squares, octagons, connect the dot, art, square roots, irrational numbers, non-random geometry. (Includes about 25 relevant website links and 50 published references)
Double Brillouin scattering geometry
NASA Astrophysics Data System (ADS)
Mroz, B.; Mielcarek, S.
2001-02-01
A procedure to optimize the collection of Brillouin spectra and to allow the simultaneous observation of phonons in two pairs of scattering geometries is proposed. The first geometry is used to observe the bulk phonons in right-angle- and back-scattering. This procedure reduces measurement time and requires the use of only one type of sample. The second geometry is used for simultaneous observation of bulk and surface phonons in transparent materials and can provide some valuable information on the relation between the bulk and surface elastic properties.
Hydrodynamic instabilities in inertial confinement fusion
Hoffman, N.M.
1994-12-01
The focus of the paper is on buoyancy-driven instabilities of the Rayleigh-Taylor type, which are commonly regarded as the most important kind of hydrodynamic instability in inertial-confinement-fusion implosions. The paper is intended to be pedagogical rather than research-oriented, and so is by no means a comprehensive review of work in this field. Rather, it is hoped that the student will find here a foundation on which to build an understanding of current research, and the experienced researcher will find a compilation of useful results. The aim of the paper is to discuss the evolution of a single Rayleigh-Taylor-unstable mode, from its linear phase to its late-stage constant-velocity bubble growth, with a brief consideration of the saturation of linear growth. The influence of other modes in invoked only in the short-range sense (in wavenumber space) of the Haan saturation model. Owing to limitations of space, the treatment of other instabilities such as Richtmyer-Meshkov and Kelvin-Helmholtz is necessarily very brief, and entirely inadequate as an introductory discussion. Likewise, there is no reference to the effect of convergent geometry, to long-range mode coupling, or to shape effects in three-dimensional growth. Furthermore, there is no reference to the large body of experimental research related to hydrodynamic instabilities.
Droplet microfluidics driven by gradients of confinement
Dangla, Rémi; Kayi, S. Cagri; Baroud, Charles N.
2013-01-01
The miniaturization of droplet manipulation methods has led to drops being proposed as microreactors in many applications of biology and chemistry. In parallel, microfluidic methods have been applied to generate monodisperse emulsions for applications in the pharmaceuticals, cosmetics, and food industries. To date, microfluidic droplet production has been dominated by a few designs that use hydrodynamic forces, resulting from the flowing fluids, to break drops at a junction. Here we present a platform for droplet generation and manipulation that does not depend on the fluid flows. Instead, we use devices that incorporate height variations to subject the immiscible interfaces to gradients of confinement. The resulting curvature imbalance along the interface causes the detachment of monodisperse droplets, without the need for a flow of the external phase. Once detached, the drops are self-propelled due to the gradient of surface energy. We show that the size of the drops is determined by the device geometry; it is insensitive to the physical fluid properties and depends very weakly on the flow rate of the dispersed phase. This allows us to propose a geometric theoretical model that predicts the dependence of droplet size on the geometric parameters, which is in agreement with experimental measurements. The approach presented here can be applied in a wide range of standard applications, while simplifying the device operations. We demonstrate examples for single-droplet operations and high-throughput generation of emulsions, all of which are performed in simple and inexpensive devices. PMID:23284169
Dipole Transport: a New Confinement Paradigm
NASA Astrophysics Data System (ADS)
Kesner, J.; Garnier, D.; Mauel, M.
2014-10-01
In a tokamak-like device turbulence will grow up to a level determined by non-linear processes. The associated transport, in combination with particle and energy sources then determines the density and temperature profiles of the plasma. This paradigm is fundamentally different for a plasma that is confined in a dipole field. In a dipole, levitated to avoid losses to the supports, the plasma will assume a stationary profile determined only by the specific volume, V (?) , (which is determined by the magnetic geometry). Independent of the source and sink profiles for particles and energy, turbulence will grow up to a sufficient level so that diffusion and pinch dynamics will establish stationary profiles characterized by ne ~ 1 / V and p ~ 1 /V 5 / 3 . This process is observed in magnetospheric plasmas and we have observed it in the laboratory in LDX. For example, with edge fueling in LDX we observed that the stationary (peaked) density profile (n ~ 1 / V) was established by a turbulence-driven density pinch whereas in recent experiments with core (pellet) fueling turbulence was observed to relax the density back to the stationary profile on a similar timescale. Supported by the NSF-DOE Partnership in Plasma Science Grants DE-FG02-00ER54585 and PHY-1201896.
Azimuthal field instability in a confined ferrofluid.
Dias, Eduardo O; Miranda, José A
2015-02-01
We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes. PMID:25768610
Azimuthal field instability in a confined ferrofluid
NASA Astrophysics Data System (ADS)
Dias, Eduardo O.; Miranda, José A.
2015-02-01
We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.
Electrophoretic Mobility of Polyelectrolytes within a Confining Well
Tyler N. Shendruk; Martin Bertrand; Gary W. Slater
2015-04-11
We present a numerical study of polyelectrolytes electrophoresing in free solution while squeezed by an axisymmetric confinement force transverse to their net displacement. Hybrid multi-particle collision dynamics and molecular dynamics simulations with mean-field finite Debye layers show that even though the polyelectrolyte chains remain "free-draining", their electrophoretic mobility increases with confinement in nanoconfining potential wells. The primary mechanism leading to the increase in mobility above the free-solution value, despite long-range hydrodynamic screening by counterion layers, is the orientation of polymer segments within Debye layers. The observed length-dependence of the electrophoretic mobility arises due to secondary effects of counterion condensation related to confinement compactification.
Inertial-Electrostatic Confinement (IEC) Fusion For Space Propulsion
NASA Technical Reports Server (NTRS)
Nadler, Jon
1999-01-01
An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using IEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois @ Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.
Inertial-Electrostatic Confinement (IEC) Fusion for Space Propulsion
NASA Technical Reports Server (NTRS)
Nadler, Jon
1999-01-01
An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using EEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois@Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.
Capillary smectization and layering in a confined liquid crystal.
de Las Heras, D; Velasco, E; Mederos, L
2005-01-14
Using density-functional theory, we have analyzed the phase behavior of a model liquid crystal confined between two parallel, planar surfaces (i.e., the so-called slit pore). As a result of confinement, a rich phase behavior arises. The complete liquid-crystal phase diagram of the confined fluid is mapped out as a function of wall separation and chemical potential. Strong commensuration effects in the film with respect to wall separation lead to enhanced smectic ordering, which gives capillary smectization (i.e., formation of a smectic phase in the pore), or frustrated smectic ordering, which suppresses capillary smectization. These effects also produce layering transitions. Our nonlocal density-functional-based analysis provides a unified picture of all the above phenomena. PMID:15698132
Capillary Smectization and Layering in a Confined Liquid Crystal
NASA Astrophysics Data System (ADS)
de Las Heras, D.; Velasco, E.; Mederos, L.
2005-01-01
Using density-functional theory, we have analyzed the phase behavior of a model liquid crystal confined between two parallel, planar surfaces (i.e., the so-called slit pore). As a result of confinement, a rich phase behavior arises. The complete liquid-crystal phase diagram of the confined fluid is mapped out as a function of wall separation and chemical potential. Strong commensuration effects in the film with respect to wall separation lead to enhanced smectic ordering, which gives capillary smectization (i.e., formation of a smectic phase in the pore), or frustrated smectic ordering, which suppresses capillary smectization. These effects also produce layering transitions. Our nonlocal density-functional-based analysis provides a unified picture of all the above phenomena.
Quantum Computing in Non Euclidean Geometry
Germano Resconi; Ignazio Licata
2009-11-04
The recent debate on hyper-computation has raised new questions both on the computational abilities of quantum systems and the Church-Turing Thesis role in Physics. We propose here the idea of geometry of effective physical process as the essentially physical notion of computation. In Quantum mechanics we cannot use the traditional Euclidean geometry but we introduce more sophisticate non Euclidean geometry which include a new kind of information diffuse in the entire universe and that we can represent as Fisher information or active information. We remark that from the Fisher information we can obtain the Bohm and Hiley quantum potential and the classical Schrodinger equation. We can see the quantum phenomena do not affect a limited region of the space but is reflected in a change of the geometry of all the universe. In conclusion any local physical change or physical process is reflected in all the universe by the change of its geometry, This is the deepest meaning of the entanglement in Quantum mechanics and quantum computing. We stress the connection between metric and information as measure of change. Because computation is not restricted to calculus but is the environment changing via physical processes, super-Turing potentialities derive from an incomputable information source embedded into the geometry of the universe in accordance with Bell's constraints. In the general relativity we define the geometry of the space time. In our approach quantum phenomena define the geometry of the parameters of the probability distribution that include also the space time parameters. To study this new approach to the computation we use the new theory of Morphogenic systems.
Deuterium anions in inertial electrostatic confinement devices.
Boris, D R; Alderson, E; Becerra, G; Donovan, D C; Egle, B; Emmert, G A; Garrison, L; Kulcinski, G L; Santarius, J F; Schuff, C; Zenobia, S J
2009-09-01
A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5 microA/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7 cm2. Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2(-), and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device. PMID:19905231
Proof in Transformation Geometry
ERIC Educational Resources Information Center
Bell, A. W.
1971-01-01
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)
ERIC Educational Resources Information Center
Emenaker, Charles E.
1999-01-01
Describes a sixth-grade interdisciplinary geometry unit based on Charles Dickens's "A Christmas Carol". Focuses on finding area, volume, and perimeter, and working with estimation, decimals, and fractions in the context of making gingerbread houses. (ASK)
Flyby Geometry Optimization Tool
NASA Technical Reports Server (NTRS)
Karlgaard, Christopher D.
2007-01-01
The Flyby Geometry Optimization Tool is a computer program for computing trajectories and trajectory-altering impulsive maneuvers for spacecraft used in radio relay of scientific data to Earth from an exploratory airplane flying in the atmosphere of Mars.
NSDL National Science Digital Library
Brown, Kevin
"Informal notes" by Kevin Brown on geometry: constructing the heptadecagon, what mirrors do, the golden pentagon, the grazing goat and the lune, Napoleon's theorem, chess boards, Diophantine geodesic boxes, Zeno's mice and the logarithmic spiral, and many more.
ERIC Educational Resources Information Center
Potter, Gretchen
1976-01-01
After a unit on Euclidean geometry which stresses both the development of intuition and the use of deductive methods, non-Euclidean concepts are introduced by having students read and consider science fiction stories. (SD)
Manuel Hohmann
2014-09-11
From general relativity we have learned the principles of general covariance and local Lorentz invariance, which follow from the fact that we consider observables as tensors on a spacetime manifold whose geometry is modeled by a Lorentzian metric. Approaches to quantum gravity, however, hint towards a breaking of these symmetries and the possible existence of more general, non-tensorial geometric structures. Possible implications of these approaches are non-tensorial transformation laws between different observers and an observer-dependent notion of geometry. In this work we review two different frameworks for observer dependent geometries, which may provide hints towards a quantization of gravity and possible explanations for so far unexplained phenomena: Finsler spacetimes and Cartan geometry on observer space. We discuss their definitions, properties and applications to observers, field theories and gravity.
José Natário
\\u000a In this chapter we discuss the non-Euclidean geometry of curved surfaces, using the sphere as our primary example. We find\\u000a that all the information about the geometry of the surface is contained in the expression for the distance between two nearby\\u000a points in some coordinate system, called the metric. For example, the distance between two distant points can be found
NSDL National Science Digital Library
2007-12-12
Science UTM offers online articles and activities for people who like science. Science U and the web-design and development company that owns and operates the website, Geometry Technologies, were formed as a result of the closure of The Geometry Center at the University of Minnesota. One of the conditions of that grant, which funded The Geometry Center and ended in 1998, was that the Center would find a way to keep their materials available to the public. In anticipation of the day when the Geometry Center goes offline, they are slowly migrating materials to this website. The Geometry Center section at Science U offers lessons on solids using interactive models, geometry tiling activities, an interactive fractal generator, and many other puzzles, articles and activities. Visitors can search their resources using an online query form or by browsing the topic index, subject listing or content listing. The content listing gives you an idea of the different types of resources available, such as articles, facts and figures, classroom materials, online simulations, hands-on-projects, or software. The Science U also offers other sections on astronomy, graphic arts, and a library with various online and print resources on science.
Quark Confinement and the Renormalization Group
Michael C. Ogilvie
2010-10-10
Recent approaches to quark confinement are reviewed, with an emphasis on their connection to renormalization group methods. Basic concepts related to confinement are introduced: the string tension, Wilson loops and Polyakov lines, string breaking, string tension scaling laws, center symmetry breaking, and the deconfinement transition at non-zero temperature. Current topics discussed include confinement on $R^3\\times S^1$, the real-space renormalization group, the functional renormalization group, and the Schwinger-Dyson equation approach to confinement.
Spectral properties of a confined nonlinear quantum oscillator in one and three dimensions
Schulze-Halberg, Axel; Gordon, Christopher R. [Department of Mathematics and Actuarial Science, Indiana University Northwest, 3400 Broadway, Gary, Indiana 46408 (United States)] [Department of Mathematics and Actuarial Science, Indiana University Northwest, 3400 Broadway, Gary, Indiana 46408 (United States)
2013-04-15
We analyze the spectral behaviour of a nonlinear quantum oscillator model under confinement. The underlying potential is given by a harmonic oscillator interaction plus a nonlinear term that can be weakened or strengthened through a parameter. Numerical eigenvalues of the model in one and three dimensions are presented. The asymptotic behaviour of the eigenvalues for confinement relaxation and for vanishing nonlinear term in the potential is investigated. Our findings are compared with existing results.
Treatment of confinement in the Faddeev approach to three-quark problems
J. McEwen; J. Day; A. Gonzalez; Z. Papp; W. Plessas
2010-01-22
A method is presented that allows to solve the Faddeev integral equations of the semirelativistic constituent quark model. In such a model the quark-quark interaction is modeled by a infinitely rising confining potential and the kinetic energy is taken in a relativistic form. We solve the integral equations in Coulomb-Sturmian basis. This basis facilitate an exact treatment of the confining potentials.
Lessons Learned in Confined Space Training
Denis E. Zeimet; John Van Ast
1996-01-01
A concern presently exists in industry regarding weak and inconsistent implementation of confined space programs which do not meet Occupational Safety and Health Administration requirements. To assist those personnel who are required to develop, implement, and evaluate a confined space program to achieve compliance with the regulation, an 8-hour Confined Space Program Management training session was held to present the
Vortex confinement by magnetic domains in superconductor-ferromagnet bilayers
NASA Astrophysics Data System (ADS)
Cieplak, Marta Z.; Adamus, Z.; Konczykowski, M.; Zhu, L. Y.; Chien, C. L.; Cheng, X. M.
2013-03-01
We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in between to avoid proximity effect. The magnetic domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the decreasing temperature the magnetic pinning increases but this increase is substantially weaker than that of the intrinsic pinning. The analysis of the initial flux penetration suggests that vortices may form various vortex structures, including disordered Abrikosov lattice or single and double vortex chains, in which minimal vortex-vortex distance is comparable to the magnetic penetration depth. We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in between to avoid proximity effect. The magnetic domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the decreasing temperature the magnetic pinning increases but this increase is substantially weaker than that of the intrinsic pinning. The analysis of the initial flux penetration suggests that vortices may form various vortex structures, including disordered Abrikosov lattice or single and double vortex chains, in which minimal vortex-vortex distance is comparable to the magnetic penetration depth. Supported by Polish NCS grant 2011/01/B/ST3/00462, by the French-Polish Program PICS 2012, by EU grant POIG.01.01.02-00-108/09, and by NSF grants DMR05-20491 and DMR-1053854.
Dynamics of Water Confined in Partially Hydrophobic Nanosized Cylindrical Sieves
NASA Astrophysics Data System (ADS)
Faraone, Antonio; Zhang, Yang; Liu, Kao-Hsiang; Mou, Chung-Yuan; Chen, Sow-Hsin
2009-03-01
Using three high resolution quasielastic neutron scattering spectrometers we have investigated the single particle dynamics of water confined in a hydrophobically modified MCM-41-S sample. This latter is a silica matrix containing cylindrical sieves with diameter < 20 å arranged in a hexagonal geometry. In the hydrophobically modified sample some of the sylanol groups in the pores' wall have been substituted with methanol groups resulting in a partially hydrophobic confining surface, which could be used as a model system. We have been able to analyze the data in the temperature range from 300 K to 210 K using a single consistent model, the Relaxing Cage Model (RCM) for the dynamics of supercooled water. Because of the heterogenous environment experienced by the water molecules in the pores, the relaxational dynamics show a broad distribution of relaxation times. However, the Fickian diffusive behaviour is retained. The obtained results help clarify the role that the chemical interaction between the water molecules and the walls of the confining host plays in determining the characteristics of the water dynamics, as compared to purely geometric constraints such as the size and shape of the pores.
Students Discovering Spherical Geometry Using Dynamic Geometry Software
ERIC Educational Resources Information Center
Guven, Bulent; Karatas, Ilhan
2009-01-01
Dynamic geometry software (DGS) such as Cabri and Geometers' Sketchpad has been regularly used worldwide for teaching and learning Euclidean geometry for a long time. The DGS with its inductive nature allows students to learn Euclidean geometry via explorations. However, with respect to non-Euclidean geometries, do we need to introduce them to…
Dynamics of confined water molecules
Gilijamse, J. J.; Lock, A. J.; Bakker, H. J.
2005-01-01
We present femtosecond midinfrared pump–probe measurements of the molecular motion and energy-transfer dynamics of a water molecule that is enclosed by acetone molecules. These confined water molecules show hydrogen-bond and orientational dynamics that are much slower than in bulk liquid water. This behavior is surprising because the hydrogen bonds to the C=O groups of the acetone molecules are weaker than the hydrogen bonds in bulk water. The energy transfer between the O—H groups of the confined water molecules has a time constant of 1.3 ± 0.2 ps, which is >20 times slower than in bulk water. We find that this energy transfer is governed completely by the rate at which hydrogen bonds are broken and reformed, and we identify the short-lived molecular complex that forms the transition state of this process. PMID:15722413
Influence of confinement on thermodiffusion
NASA Astrophysics Data System (ADS)
Hannaoui, Rachid; Galliero, Guillaume; Hoang, Hai; Boned, Christian
2013-09-01
This work focuses on a possible influence of a nanoporous medium on the thermodiffusion of a fluid "isotopic" mixture. To do so, we performed molecular dynamics simulations of confined Lennard-Jones binary equimolar mixtures using grand-canonical like and non-equilibrium approaches in sub- and super-critical conditions. The study was conducted in atomistic slit pore of three adsorbent natures for various widths (from 5 to 35 times the size of a molecule). The simulation results indicate that for all thermodynamic conditions and whatever the pore characteristics, the confinement has a negligible effect on the thermal diffusion factor/Soret coefficient. However, when considered separately, the mass diffusion and thermodiffusion coefficients have been found to be largely influenced by the pore characteristics. These two coefficients decrease noticeably when adsorption is stronger and pore width smaller, a behavior that is consistent with a simple hydrodynamic explanation.
F. V. Gubarev
2008-12-24
We critically reconsider our recent observation of confining string shrinkage in pure glue SU(2) lattice gauge theory near the continuum limit. Using the advanced numerical techniques we argue that imperfect overlap with the string ground state and corresponding ambiguities in T->\\infty extrapolation are likely to be the cause of the observed scaling violations. In particular, even in the limit of large Euclidean times the string shrinkage is apparent in torelon correlation function, however, in this case the best relevant overlap we could attain is of order 50%. To the contrary, when the ground state is selected properly the string width scales in physical units being ~0.3 fm for 1 fm long confining string.
Thermodynamics, Structure, and Dynamics of Water Confined between Hydrophobic Plates
Pradeep Kumar; Sergey V. Buldyrev; Francis W. Starr; Nicolas Giovambattista; H. Eugene Stanley
2005-07-05
We perform molecular dynamics simulations of 512 water-like molecules that interact via the TIP5P potential and are confined between two smooth hydrophobic plates that are separated by 1.10 nm. We find that the anomalous thermodynamic properties of water are shifted to lower temperatures relative to the bulk by $\\approx 40$ K. The dynamics and structure of the confined water resemble bulk water at higher temperatures, consistent with the shift of thermodynamic anomalies to lower temperature. Due to this $T$ shift, our confined water simulations (down to $T = 220$ K) do not reach sufficiently low temperature to observe a liquid-liquid phase transition found for bulk water at $T\\approx 215$ K using the TIP5P potential. We find that the different crystalline structures that can form for two different separations of the plates, 0.7 nm and 1.10 nm, have no counterparts in the bulk system, and discuss the relevance to experiments on confined water.
Continuous melting and thermal-history-dependent freezing in the confined Na-K eutectic alloy
NASA Astrophysics Data System (ADS)
Charnaya, E. V.; Lee, M. K.; Tien, Cheng; Chang, L. J.; Wu, Z.-J.; Kumzerov, Yu. A.; Bugaev, A. S.
2013-04-01
23Na NMR studies of the Na-K eutectic alloy embedded into porous glass with 7-nm pores showed that melting of Na2K confined nanoparticles is a continuous process with smooth changes in the Knight shift of a narrow resonance line and nuclear spin relaxation between those in the crystalline and liquid states. The intermediate state, which occurs upon melting is stable and more favorable than the liquid state. The inverse freezing transformation can be sharp as at a first-order transition or continuous depending on the initial temperature of cooling. The results suggest revision of theoretical predictions for the melting and freezing transitions in confined geometry.
Vacuum calculations in azimuthally symmetric geometry
M. S. Chance
1997-01-01
A robustly accurate and effective method is presented to solve Laplace{close_quote}s equation in general azimuthally symmetric geometry for the magnetic scalar potential in the region surrounding a plasma discharge which may or may not contain external conductors. These conductors can be topologically toroidal or spherical, and may have toroidal gaps in them. The solution is incorporated into the various magnetohydrodynamic
Vacuum calculations in azimuthally symmetric geometry
M. S. Chance
1997-01-01
A robustly accurate and effective method is presented to solve Laplace’s equation in general azimuthally symmetric geometry for the magnetic scalar potential in the region surrounding a plasma discharge which may or may not contain external conductors. These conductors can be topologically toroidal or spherical, and may have toroidal gaps in them. The solution is incorporated into the various magnetohydrodynamic
VACUUM calculation in azimuthally symmetric geometry
1996-01-01
A robustly accurate and effective method is presented to solve Laplace`s equation in general azimuthally symmetric geometry for the magnetic scalar potential in the region surrounding a plasma discharge which may or may not contain external conducting shells. These shells can be topologically toroidal or spherical, and may have toroidal gaps in them. The solution is incorporated into the various
Ion beam inertial confinement target
Bangerter, Roger O. (Danville, CA); Meeker, Donald J. (Livermore, CA)
1985-01-01
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.
Order in very cold confined plasmas
Schiffer, J.P. [Argonne National Lab., IL (United States)]|[Univ. of Chicago, Chicago, IL (United States)
1995-12-31
The study of the structure and dynamic properties of classical systems of charged particles confined by external forces, and cooled to very low internal energies, is the subject of this talk. An infinite system of identical charged particles has been known for some time to form a body-centered cubic lattice and is a simple classical prototype for condensed matter. Recent technical developments in storage rings, ion traps, and laser cooling of ions, have made it possible to produce such systems in the laboratory, though somewhat modified because of their finite size. I would like to discuss what one may expect in such systems and also show some examples of experiments. If we approximate the potential of an ion trap with an isotropic harmonic force F = {minus}Kr then the Hamiltonian for this collection of ions is the same as that for J. J. Thomson`s ``plum pudding`` model of the atom, where electrons were thought of as discrete negative charges imbedded in a larger, positive, uniformly charged sphere. The harmonic force macroscopically is canceled by the average space-charge forces of the plasma-, and this fixes the overall radius of the distribution. What remains, are the residual two-body Coulomb interactions that keep the particles within the volume as nearly equidistant as possible in order to minimize the potential energy. The configurations obtained for the minimum energy of small ionic systems [2] in isotropic confinement are shown in figure 1. Indeed this is an `Exotic Atom` and fits well into the subject of this symposium honoring the 60th birthday of Professor Toshi Yamazaki.
Graphene growth under Knudsen molecular flow on a confined catalytic metal coil
NASA Astrophysics Data System (ADS)
Bong, Hyojin; Jo, Sae Byeok; Kang, Boseok; Lee, Seong Kyu; Kim, Hyun Ho; Lee, Seung Goo; Cho, Kilwon
2015-01-01
We have established a simple method for drastically improving the productivity of chemical vapor deposition in large-area graphene synthesis using a roll-stacked Ni coil as a catalyst. Our systematic investigation of the effects of a confined catalytic geometry has shown that the gas flow through interfacial gaps within the stack follows non-continuum fluid dynamics when the size of the gap decreases sufficiently, which enhances the dissolution of the carbon sources into the catalyst during synthesis. Quantitative criteria for graphene growth in the confined geometry are established through the introduction of the Knudsen number, Kn, which is the ratio of the mean-free-path of the gas molecules to the size of the gap. The criteria provided in this article for the synthesis of graphene in the confined geometry are expected to provide the foundations for the efficient mass production of large-area graphene. We also show that the evolution of the catalytic Ni surface in a stacked system results in larger grains in the (111) plane, and consequently in reproducible, uniform, and high-quality multi-layered graphene.We have established a simple method for drastically improving the productivity of chemical vapor deposition in large-area graphene synthesis using a roll-stacked Ni coil as a catalyst. Our systematic investigation of the effects of a confined catalytic geometry has shown that the gas flow through interfacial gaps within the stack follows non-continuum fluid dynamics when the size of the gap decreases sufficiently, which enhances the dissolution of the carbon sources into the catalyst during synthesis. Quantitative criteria for graphene growth in the confined geometry are established through the introduction of the Knudsen number, Kn, which is the ratio of the mean-free-path of the gas molecules to the size of the gap. The criteria provided in this article for the synthesis of graphene in the confined geometry are expected to provide the foundations for the efficient mass production of large-area graphene. We also show that the evolution of the catalytic Ni surface in a stacked system results in larger grains in the (111) plane, and consequently in reproducible, uniform, and high-quality multi-layered graphene. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04153d
Confinement dynamics in the reversed field pinch
Schoenberg, K.F.
1988-01-01
The study of basic transport and confinement dynamics is central to the development of the reversed field pinch (RFP) as a confinement concept. Thus, the goal of RFP research is to understand the connection between processes that sustain the RFP configuration and related transport/confinement properties. Recently, new insights into confinement have emerged from a detailed investigation of RFP electron and ion physics. These insights derive from the recognition that both magnetohydrodynamic (MHD) and electron kinetic effects play an important and strongly coupled role in RFP sustainment and confinement dynamics. In this paper, we summarize the results of these studies on the ZT-40M experiment. 8 refs.
An Introduction to Projective Geometry
NSDL National Science Digital Library
Birchfield, Stan
The contents of this paper include: The Projective Plane; Projective Space; Projective Geometry Applied to Computer Vision; Demonstration of Cross Ratio in P^1; and a bibliography. (Euclidean geometry is a subset of projective geometry, and there are two geometries between them: similarity and affine.) Also at http://vision.stanford.edu/~birch/projective/.
Topics in Geometry Olga Kharlampovich
Kharlampovich, Olga
. Symmetry in the real world Â² Euclidean and non-Euclidean geometry 1. History 2. Plane Euclidean geometry, 3 mathematics, AMS, Mathematical world, Vol. 5, 1996 P.J. Ryan, Euclidean and non-Euclidean geometry. AÂ±ne transformations in the Euclidean plane, 4. Finite groups of isometries of E2 , 5. Geometry
TRACTOR CALCULI FOR PARABOLIC GEOMETRIES
ANDREAS CAP; A. ROD GOVER
1999-01-01
Parabolic geometries may be considered as curved analogues of the homogeneous spaces G=P where G is a semisimple Lie group and P G a parabolic subgroup. Conformal geometries and CR geometries are exam- ples of such structures. We present a uniform description of a calculus, called tractor calculus, based on natural bundles with canonical linear connections for all parabolic geometries.
Hermitesche Relativitätstheorie, Chromodynamik und Confinement
NASA Astrophysics Data System (ADS)
Treder, H.-J.
Die Ausdehnung der Riemannschen Metrik der Allgemeinen Relativitätstheorie ins Komplexe bedeutet die Ersetzung der Symmetrie-Bedingungenfür den metrischen Tensor, Affinität und Ricci-Tensor durch die Hermiteschen BedingungenMit diesen Bedingungen führt das Einstein-Hilbert-Hamilton-Prinzipzu einer erweiterten Gravitationstheorie (Einstein), die im Sinne der EIH-Approximation neben der Newton-Einsteinschen Gravodynamik, auch die Chromodynamik der Elementarteilchenphysik enthält.Die von den Einstein-Schrödingerschen Feldgleichungen der Hermiteschen Relativitätstheorie implizierte Wechselwirkung zwischen Gravo- und Chromodynamik erzwingt das Confinement. Ohne dieses Confinement würde das Gravitationspotential divergieren, d.h., es könnte keine - nach Maßgabe der Einstein-Schrödingerschen Feldgleichungen - Riemannsche Raum-Zeit-Metrik gik = aik geben.
Kimichika Fukushima; Hikaru Sato
2014-10-04
This article reports an explicit function form for confining classical Yang-Mills vector potentials and quantum fluctuations around the classical field. The classical vector potential, which is composed of a confining localized function and an unlocalized function, satisfies the classical Yang-Mills equation. The confining localized function contributes to the Wilson loop, while the unlocalized function makes no contribution to this loop. The confining linear potential between a heavy fermion and antifermion is due to (1) the Lie algebra and (2) the form of the confining localized function which has opposite signs at the positions of the particle and antiparticle along the Wilson loop in the time direction. Some classical confining parts of vector potentials also change sign on inversion of the coordinates of the axis perpendicular to the axis joining the two particles. The localized parts of the vector potentials are squeezed around the axis connecting the two particles, and the string tension of the confining linear potential is derived. Quantum fluctuations are formulated using a field expression in terms of local basis functions in real spacetime. The quantum path integral gives the Coulomb potential between the two particles in addition to the linear potential due to the classical fields.
Integral Geometry and Holography
Czech, Bartlomiej; McCandlish, Samuel; Sully, James
2015-01-01
We present a mathematical framework which underlies the connection between information theory and the bulk spacetime in the AdS$_3$/CFT$_2$ correspondence. A key concept is kinematic space: an auxiliary Lorentzian geometry whose metric is defined in terms of conditional mutual informations and which organizes the entanglement pattern of a CFT state. When the field theory has a holographic dual obeying the Ryu-Takayanagi proposal, kinematic space has a direct geometric meaning: it is the space of bulk geodesics studied in integral geometry. Lengths of bulk curves are computed by kinematic volumes, giving a precise entropic interpretation of the length of any bulk curve. We explain how basic geometric concepts -- points, distances and angles -- are reflected in kinematic space, allowing one to reconstruct a large class of spatial bulk geometries from boundary entanglement entropies. In this way, kinematic space translates between information theoretic and geometric descriptions of a CFT state. As an example, we...
Magnetohydrodynamic equilibrium and stability of centrifugally confined plasmas
NASA Astrophysics Data System (ADS)
Huang, Yi-Min
Centrifugal confinement is an alternative approach to magnetic fusion, employing a magnetic field with an open field line configuration. In this scheme, a plasma with magnetic mirror geometry is made to rotate azimuthally at supersonic speeds. The resulting centrifugal forces, given the field line curvature, prevent the plasma from escaping along the field lines. This dissertation addresses the equilibrium and stability of this configuration within the framework of magnetohydrodynamics (MHD). Well confined equilibrium with desirable profiles is demonstrated by numerical simulation. As far as stability is concerned, four types of magnetohydrodynamic modes determine the overall stability of centrifugally confined plasmas: flute interchanges and the Kelvin-Helmholtz instability, in a low beta system, and the magnetorotational instability (MRI) and the Parker instability, in a high beta system. One of the underpinnings of the centrifugal confinement is that flute interchanges could be stabilized by the strong velocity shear accompanying the rotation. Numerical simulations show strong evidence of stabilization, provided that the shear flow is not unstable to Kelvin-Helmholtz (KH) modes. The KH modes are ideally stable if the generalized Rayleigh's Inflexion criterion is satisfied. Particle sources are shown to be important to both equilibrium and stability. In the absence of particle sources, density profiles relax under resistive diffusion to pile up to the outboard side of the confining vessel. Tailoring the density profiles by appropriately placing the particle sources could be used to achieve control over MHD stability, for both interchanges and KH modes. Analytic analysis of interchanges based on an extension of MHD which applicable for low density plasmas with VA ˜ c is presented. The interchange growth rates are reduced by a factor of 1+V2A/c2 compared to the usual MHD prediction. The physical mechanisms of both the MRI and the Parker instability are examined and an explanation of why the MRI mechanism is insufficient to destabilize the system while the Parker instability could occur is given. Numerical simulations of the nonlinear behavior of the Parker instability are presented. It is shown that clumping from the Parker instability could reinforce centrifugal confinement.
NSDL National Science Digital Library
Eppstein, David
This metasite "collects various areas in which ideas from discrete and computational geometry (meaning mainly low-dimensional Euclidean geometry) meet some real world applications," according to the site's provider, Dr. David Eppstein of the University of California at Irvine. Categories available include Geometric References and Techniques, Design and Manufacturing, Graphics and Visualization, Information Systems, Medicine and Biology, Physical Sciences, Robotics, Other Applications, and Recent Additions. The types of links included are data sets, patents, journal articles, and research pages (note: a few of the links don't work, but overall the site is useful).
Euclidean geometry as algorithm for construction of generalized geometries
Yuri A. Rylov
2005-11-23
It is shown that the generalized geometries may be obtained as a deformation of the proper Euclidean geometry. Algorithm of construction of any proposition S of the proper Euclidean geometry E may be described in terms of the Euclidean world function sigma_E in the form S(sigma_E). Replacing the Euclidean world function sigma_E by the world function sigma of the geometry G, one obtains the corresponding proposition S(sigma) of the generalized geometry G. Such a construction of the generalized geometries (known as T-geometries) uses well known algorithms of the proper Euclidean geometry and nothing besides. This method of the geometry construction is very simple and effective. Using T-geometry as the space-time geometry, one can construct the deterministic space-time geometries with primordially stochastic motion of free particles and geometrized particle mass. Such a space-time geometry defined properly (with quantum constant as an attribute of geometry) allows one to explain quantum effects as a result of the statistical description of the stochastic particle motion (without a use of quantum principles).
The Geometry of Quasar Outflows
NASA Astrophysics Data System (ADS)
Ganguly, Rajib
2012-10-01
Quasar outflows are important for understanding the accretion and growth processes of the central black hole, but also potentially play a role in feedback to the galaxy, halting star formation and infall of gas. A big uncertainty lies in the geometry and density of these outflows, especially as a function of ionization and velocity. We aim to tackle this using the archival COS M grating spectra of 266 quasars. We separate the geometry of outflows into two parts: the solid angle subtended around the black hole, and the distance of the outflow from the central engine. Large numbers of quasars with high resolution spectra are required for each aspect of this statistical investigation. First, we will determine which/how many absorption-line systems are intrinsic through both partial covering methods and statistical assessments. Second, we will consider the incidence of intrinsic absorbers as a function of quasar property {e.g., radio-loudness, SED shape, black hole mass, bolometric luminosity}. This will reveal what determines the solid angle. This can only be done at moderate redshifts where quasars with a larger range of properties are observable, and hence requires HST/COS. Third, we will use the wide range of diagnostic lines to constrain the physical conditions of the absorbers. We will target the CIII*1175 complex and apply photoionization models to constrain the densities and ionization parameters. This will provide the largest set yet of intrinsic absorbers with systematic distance constraints. In tandem with the solid angles, this work will inform models regarding the geometry of quasar outflows.
Formation of adhesion domains in stressed and confined membranes
Nadiv Dharan; Oded Farago
2015-03-23
The adhesion bonds connecting a lipid bilayer to an underlying surface may undergo a condensation transition resulting from an interplay between a short range attractive potential between them, and a long range fluctuation-induced potential of mean force. Here, we use computer simulations of a coarse-grained molecular model of supported lipid bilayers to study this transition in confined membranes, and in membranes subjected to a non-vanishing surface tension. Our results show that confinement may alter significantly the condensation transition of the adhesion bonds, whereas the application of surface tension has a very minor effect on it. We also investigate domain formation in membranes under negative tension which, in free membranes, causes enhancement of the amplitude of the membrane thermal undulations. Our results indicate that in supported membranes, this effect of a negative surface tension on the fluctuation spectrum is largely eliminated by the pressure resulting from the mixing entropy of the adhesion bonds.
Inertial electrostatic confinement I(IEC) neutron sources
Nebel, R.A.; Barnes, D.C.; Caramana, E.J.; Janssen, R.D.; Nystrom, W.D.; Tiouririne, T.N.; Trent, B.C. [Los Alamos National Lab., NM (United States); Miley, G.H.; Javedani, J. [Illinois Univ., Urbana, IL (United States)
1995-12-01
Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2*10 [10]. neutrons/sec in steady state. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. This paper discusses the IEC concept and how it can be adapted to a steady-state assaying source and an intense pulsed neutron source. Theoretical modeling and experimental results are presented.
Atomic processes in Inertial Electrostatic Confinement (IEC) devices
Nebel, R.A.; Turner, L.; Tiouririne, T.N.; Barnes, D.C.; Nystrom, W.D. [Los Alamos National Lab., NM (United States); Bussard, R.W. [Energy/Matter Conversion Corp., Manassas, VA (United States); Miley, G.H.; Javedani, J.; Yamamoto, Y. [Illinois Univ., Urbana, IL (United States)
1993-12-31
Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2*10{sup 10} neutrons/sec. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. Atomic physics effects strongly influence the performance of all of these systems. Important atomic effects include elastic scattering, ionization, excitation, and charge exchange. This paper discusses how an IEC system is influenced by these effects and how to design around them. Theoretical modeling and experimental results are presented.
Symmetry-Adapted Rotator Functions for Molecules in Cylindrical Confinement
Verberck, Bart
2011-01-01
We present a general description of the formalism of symmetry-adapted rotator functions (SARFs) for molecules in cylindrical confinement. Molecules are considered as clusters of interaction centers (ICs), can have any symmetry, and can display different types of ICs. Cylindrical confinement can be realized by encapsulation in a carbon nanotube (CNT). The potential energy of a molecule surrounded by a CNT can be calculated by evaluating a limited number of terms of an expansion into SARFs, which offers a significant reduction of the computation time. Optimal molecular orientations can be deduced from the resulting potential energy landscape. Examples, including the case of a molecule with cubic symmetry inside a CNT, are discussed. PMID:21339988
Elementary framework for cold field emission from quantum-confined, non-planar emitters
NASA Astrophysics Data System (ADS)
Patterson, A. A.; Akinwande, A. I.
2015-05-01
For suitably small field emitters, the effects of quantum confinement at the emitter tip may have a significant impact on the emitter performance and total emitted current density (ECD). Since the geometry of a quantum system uniquely determines the magnitude and distribution of its energy levels, a framework for deriving ECD equations from cold field electron emitters of arbitrary geometry and dimensionality is developed. In the interest of obtaining semi-analytical ECD equations, the framework is recast in terms of plane wave solutions to the Schrödinger equation via the use of the Jeffreys-Wentzel-Kramers-Brillouin approximation. To demonstrate the framework's consistency with our previous work and its capabilities in treating emitters with non-planar geometries, ECD equations were derived for the normally unconfined cylindrical nanowire (CNW) and normally confined (NC) CNW emitter geometries. As a function of the emitter radius, the NC CNW emitter ECD profile displayed a strong dependence on the Fermi energy and had an average ECD that exceeded the Fowler-Nordheim equation for typical values of the Fermi energy due to closely spaced, singly degenerate energy levels (excluding electron spin), comparatively large electron supply values, and the lack of a transverse, zero-point energy. Such characteristics suggest that emitters with non-planar geometries may be ideal for emission from both an electron supply and electrostatics perspective.
Thomson scattering from inertial confinement fusion plasmas
Glenzer, S.H.; Back, C.A.; Suter, L.J. [and others
1997-07-08
Thomson scattering has been developed at the Nova laser facility as a direct and accurate diagnostic to characterize inertial confinement fusion plasmas. Flat disks coated with thin multilayers of gold and beryllium were with one laser beam to produce a two ion species plasma with a controlled amount of both species. Thomson scattering spectra from these plasmas showed two ion acoustic waves belonging to gold and beryllium. The phase velocities of the ion acoustic waves are shown to be a sensitive function of the relative concentrations of the two ion species and are in good agreement with theoretical calculations. These open geometry experiments further show that an accurate measurement of the ion temperature can be derived from the relative damping of the two ion acoustic waves. Subsequent Thomson scattering measurements from methane-filled, ignition-relevant hohlraums apply the theory for two ion species plasmas to obtain the electron and ion temperatures with high accuracy. The experimental data provide a benchmark for two-dimensional hydrodynamic simulations using LASNEX, which is presently in use to predict the performance of future megajoule laser driven hohlraums of the National Ignition Facility (NIF). The data are consistent with modeling using significantly inhibited heat transport at the peak of the drive. Applied to NIF targets, this flux limitation has little effect on x- ray production. The spatial distribution of x-rays is slightly modified but optimal symmetry can be re-established by small changes in power balance or pointing. Furthermore, we find that stagnating plasma regions on the hohlraum axis are well described by the calculations. This result implies that stagnation in gas-filled hohlraums occurs too late to directly affect the capsule implosion in ignition experiments.
Cylindrical confinement of semiflexible polymers
NASA Astrophysics Data System (ADS)
Vázquez-Montejo, Pablo; McDargh, Zachary; Deserno, Markus; Guven, Jemal
2015-06-01
Equilibrium states of a closed semiflexible polymer binding to a cylinder are described. This may be either by confinement or by constriction. Closed completely bound states are labeled by two integers: the number of oscillations, n , and the number of times it winds the cylinder, p , the latter being a topological invariant. We examine the behavior of these states as the length of the loop is increased by evaluating the energy, the conserved axial torque, and the contact force. The ground state for a given p is the state with n =1 ; a short loop with p =1 is an elliptic deformation of a parallel circle; as its length increases it elongates along the cylinder axis with two hairpin ends. Excited states with n ?2 and p =1 possess n -fold axial symmetry. Short (long) loops possess energies ?p E0 (n E0 ), with E0 the energy of a circular loop with same radius as the cylinder; in long loops the axial torque vanishes. Confined bound excited states are initially unstable; however, above a critical length each n -fold state becomes stable: The folded hairpin cannot be unfolded. The ground state for each p is also initially unstable with respect to deformations rotating the loop off the surface into the interior. A closed planar elastic curve aligned along the cylinder axis making contact with the cylinder on its two sides is identified as the ground state of a confined loop. Exterior bound states behave very differently, if free to unbind, as signaled by the reversal in the sign of the contact force. If p =1 , all such states are unstable. If p ?2 , however, a topological obstruction to complete unbinding exists. If the loop is short, the bound state with p =2 and n =1 provides a stable constriction of the cylinder, partially unbinding as the length is increased. This motif could be relevant to an understanding of the process of membrane fission mediated by dynamin rings.
Substandard reinforced concrete members subjected to compression: FRP confining effects
Theodoros C. Rousakis; Athanasios I. Karabinis
2008-01-01
The investigation focuses on the effectiveness of fiber-reinforced polymer (FRP) confinement in upgrading ductility and strength\\u000a of reinforced concrete members under axial monotonic compression. An experimental program is presented that extends available\\u000a database to address the behavior of old type members with square section, having extremely low concrete strength and potential\\u000a longitudinal bars’ premature buckling. Reinforced concrete specimens were strengthened
Cyclically-Induced Pore Pressure at High Confining Stress
Michael K. Sharp; R. Scott Steedman
Experiments were conducted by the ERDC Centrifuge Research Team to investigate effective confining stress effects on liquefaction potential of fine, clean, Nevada sand, under the boundary and loading conditions of a centrifuge model. For this test series, twenty-six level ground models with either a dense layer over a loose layer or homogeneous profile were tested in an equivalent-shear-beam box. Some
Discharge characteristics of the spherical inertial electrostatic confinement (IEC) device
G. H. Miley; Y. Gu; J. M. DeMora; R. A. Stubbers; T. A. Hochberg; J. H. Nadler; R. A. Anderl
1996-01-01
The inertial electrostatic confinement (IEC) device provides 10 7 2.5-MeV D-D neutrons\\/second, when operated with a deuterium discharge at 70 kV. This potentially provides an important portable neutron source for various activation analysis applications. The discharge involved is unique, in that it uses a spherical grid in a spherical vacuum vessel. The discharge is struck between the grid and the
Discharge characteristics of the spherical inertial electrostatic confinement (IEC) device
George H. Miley; Yibin Gu; John M. DeMora; Robert A. Stubbers; Timothy A. Hochberg; Jon H. Nadler; Robert A. Anderl
1997-01-01
The University of Illinois inertial electrostatic confinement (IEC) device provides 107 2.5 MeV D-D neutrons\\/second when operated with a steady-state deuterium discharge at 70 kV. Being compact and lightweight, the IEC potentially represents an attractive portable neutron source for activation analysis applications. The plasma discharge in the IEC is unique, using a spherical grid in a spherical vacuum vessel with
Washington at Seattle, University of
chamber for confine- ment and sustainment, which offers engineering advan- tages for a fusion reactor.55.Lf, 52.35.Py, 52.55.Fa A field-reversed configuration (FRC) is a compact toroid with little connected magnetic geometry. This strongly self- organized compact toroid (CT) has been produced by various
ERIC Educational Resources Information Center
KLIER, KATHERINE M.
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…
Sliding vane geometry turbines
Sun, Harold Huimin; Zhang, Jizhong; Hu, Liangjun; Hanna, Dave R
2014-12-30
Various systems and methods are described for a variable geometry turbine. In one example, a turbine nozzle comprises a central axis and a nozzle vane. The nozzle vane includes a stationary vane and a sliding vane. The sliding vane is positioned to slide in a direction substantially tangent to an inner circumference of the turbine nozzle and in contact with the stationary vane.
NSDL National Science Digital Library
Hardaker, Chris.
This Website, sprung from a gifted-and-talented program for K-12 students in Arizona, presents the interesting world of Native American geometry, a system based on the proportional relationship between the radius and circumference of a circle. The eye-pleasing site, divided into sections that include Foundations, Education, Designs, and Anthropology, would be appealing to curious Web surfers along with mathematics students. Geometric principles of proportions and angles are presented in the context of Native American designs, joining art and science and allowing students to learn in a creative, applied fashion. Some highlights of the site include illustrated examples of how corporate logos such as those of Mitsubishi or CBS Television are based on this geometry and a page on the architectural geometries of archaeologic sites such as Chaco Canyon, NM. A brief discussion of the history of circle-based ("string and two sticks") geometry throughout the world and a list of references for teachers are also important parts of this site.
Baldwin, John T.
's Critique Three Frameworks High School Curriculum http://www.glencoe.com/sec/math/studytools/cgi- binGeometry and Proof John T. Baldwin Hilbert's Critique Three Frameworks High School Curriculum Frameworks High School Curriculum Outline 1 Hilbert's Critique 2 Three Frameworks 3 High School Curriculum
NSDL National Science Digital Library
2010-01-01
This activity allows learners to practice observation skills and to realize examples of geometric shapes are everywhere. This geometry scavenger hunt (PDF) contains a set of directions and a recording sheet to complete. Included also is a list of materials and extension ideas.
ERIC Educational Resources Information Center
Martin, John
2010-01-01
The cycloid has been called the Helen of Geometry, not only because of its beautiful properties but also because of the quarrels it provoked between famous mathematicians of the 17th century. This article surveys the history of the cycloid and its importance in the development of the calculus.
ERIC Educational Resources Information Center
Hartz, Viggo
1981-01-01
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)
Interactive Geometry Remeshing
Pierre Alliez USC; Mark Meyer Caltech; Mathieu Desbrun
We present a novel technique, both flexible and efficient, for inter- active remeshing of irregular geometry. First, the original (arbitrary genus) mesh is substituted by a series of 2D maps in parameter space. Using these maps, our algorithm is then able to take advan- tage of established signal processing and halftoning tools that offer real-time interaction and intricate control. The
Interactive geometry remeshing
Pierre Alliez; Mark Meyer; Mathieu Desbrun
2002-01-01
We present a novel technique, both flexible and efficient, for interactive remeshing of irregular geometry. First, the original (arbitrary genus) mesh is substituted by a series of 2D maps in parameter space. Using these maps, our algorithm is then able to take advantage of established signal processing and halftoning tools that offer real-time interaction and intricate control. The user can
ERIC Educational Resources Information Center
MacKeown, P. K.
1984-01-01
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)
ERIC Educational Resources Information Center
Fielker, David
2007-01-01
Geoff Giles died suddenly in 2005. He was a highly original thinker in the field of geometry teaching. As early as 1964, when teaching at Strathallen School in Perth, he was writing in "MT27" about constructing tessellations by modifying the sides of triangles and (irregular) quadrilaterals to produce what he called "trisides" and "quadrisides".…
Duality and asymptotic geometries
Harm Jan Boonstra; Bas Peeters; Kostas Skenderis
1997-01-01
We consider a series of duality transformations that leads to a constant shift in the harmonic functions appearing in the description of a configuration of branes. This way, for several intersections of branes, we can relate the original brane configuration which is asymptotically flat to a geometry of the type adSk × El × Sm. The implications of our results
NSDL National Science Digital Library
Terese Herrera
This resource guide from the Middle School Portal 2 project, written specifically for teachers, provides links to exemplary resources including background information, lessons, career information, and related national science education standards. The online resources featured in Geometry in 3-D actively engage students in exploring a variety of geometric shapes, at times through lessons that involve building models or creating paper nets that fold into three-dimensional shapes; at other times, through technology that allows students to rotate and zoom in on figures, noting their attributes and complexity. Other lessons offer problems on surface area and volume, a part of every middle school curriculum. The problems, each with a different twist on the subject, challenge students to reconsider their understanding of how to measure solids. Activities for developing spatial sense, another primary objective in teaching geometry, are also featured. Finally, there are online galleries of geometric solids, included for the rare opportunity they offer to show your students the beauty in mathematics. In Background Information, you will find workshop sessions developed for teachers and other materials that may interest you as a professional. Each resource deals specifically with three-dimensional geometry topics that align with the geometry and measurement standards recommended by NCTM.
Spacetime and Euclidean Geometry
Dieter Brill; Ted Jacobson
2004-08-04
Using only the principle of relativity and Euclidean geometry we show in this pedagogical article that the square of proper time or length in a two-dimensional spacetime diagram is proportional to the Euclidean area of the corresponding causal domain. We use this relation to derive the Minkowski line element by two geometric proofs of the "spacetime Pythagoras theorem".
Spacetime and Euclidean geometry
NASA Astrophysics Data System (ADS)
Brill, Dieter; Jacobson, Ted
2006-04-01
Using only the principle of relativity and Euclidean geometry we show in this pedagogical article that the square of proper time or length in a two-dimensional spacetime diagram is proportional to the Euclidean area of the corresponding causal domain. We use this relation to derive the Minkowski line element by two geometric proofs of the spacetime Pythagoras theorem.
Dynamics of harmonically-confined systems: Some rigorous results
Wu, Zhigang, E-mail: zwu@physics.queensu.ca; Zaremba, Eugene, E-mail: zaremba@sparky.phy.queensu.ca
2014-03-15
In this paper we consider the dynamics of harmonically-confined atomic gases. We present various general results which are independent of particle statistics, interatomic interactions and dimensionality. Of particular interest is the response of the system to external perturbations which can be either static or dynamic in nature. We prove an extended Harmonic Potential Theorem which is useful in determining the damping of the centre of mass motion when the system is prepared initially in a highly nonequilibrium state. We also study the response of the gas to a dynamic external potential whose position is made to oscillate sinusoidally in a given direction. We show in this case that either the energy absorption rate or the centre of mass dynamics can serve as a probe of the optical conductivity of the system. -- Highlights: •We derive various rigorous results on the dynamics of harmonically-confined atomic gases. •We derive an extension of the Harmonic Potential Theorem. •We demonstrate the link between the energy absorption rate in a harmonically-confined system and the optical conductivity.
Confining concrete cylinders using shape memory alloy wires
NASA Astrophysics Data System (ADS)
Choi, E.; Chung, Y.-S.; Cho, B.-S.; Nam, T.-H.
2008-05-01
This study proposed a new method to confine concrete cylinders or reinforced concrete columns using martensitic, Ti-49.7Ni (at %), or austenitic, Ti-50.3Ni (at %), shape-memory-alloy wires. Prestrained martensitic SMA wire was used to wrap a concrete cylinder and, then, was heated by a heating jacket. In the process, confining stress was developed around the cylinder by the SMA wire due to shape memory effect, which can increase the strength and ductility of the cylinder under axial compressive load. For austenitic shape memory wires, some prestraining was introduced in the wires during wrapping concrete cylinders on which post-tensioning stress was generated. In this study, 1.0 mm diameter of martensitic and austenitic SMA wire was used for confinement. Recovery tests were conducted for the martensitic and the austenitic shape memory wires to determine the recovery stress and superelastic behavior, respectively. The confinement by martensitic shape memory wires had increased the strength slightly and the ductility substantially. However, the austenitic shape memory wires only increased the ductility because the imposed prestress was too small. This study showed the potential of the proposed method to retrofit reinforced concrete columns using shape memory wires to protect themselves from earthquakes.
NASA Astrophysics Data System (ADS)
Odling, N. E.; Perulero Serrano, R.; Hussein, M. E. A.; Riva, M.; Guadagnini, A.
2015-01-01
The use of barometric response functions (BRFs) for detecting the presence of fully penetrating, highly conductive bodies within aquifer confining layers that present potential pathways for contaminants is explored. BRFs are determined from borehole water level (WL) and barometric pressure (Bp) records. Past studies have shown that confining layer properties can be estimated from BRFs, providing a potential link between BRFs and the concept of groundwater vulnerability. Existing analytical models that predict the BRF from system properties assume homogeneity within the aquifer and its confining layer, conditions which are seldom satisfied in nature. The impact of partially and fully penetrating, high diffusivity heterogeneities within a confining layer (representing potential high flow pathways for contaminants) on the BRF is investigated through a suite of three-dimensional, transient numerical simulations of the confining layer-aquifer system. The results are interpreted through comparison with a modified pre-existing analytical model for the BRF. Comparison of numerically and analytically calculated BRFs reveals that the key effect of a localised, fully penetrating, high diffusivity heterogeneity within a low diffusivity confining layer is to reduce the BRF gain with only minor changes to the phase. This impact on the BRF decreases with increasing distance from the heterogeneity. The importance of heterogeneity size is secondary to distance from the borehole and partially penetrating heterogeneities affect the BRF to only a minor extent. Data from a study of the Chalk Aquifer (E. Yorkshire, England) which is semi-confined by heterogeneous glacial sediments display variations in BRFs which are qualitatively similar to those shown by the numerical results. It is suggested that the variation in BRFs estimated from borehole records across a semi-confined aquifer could be used to assess the degree of spatial continuity of low diffusivity lithologies within the confining layer which protect the aquifer against surface sourced contamination, and thus provide a tool to improve groundwater vulnerability assessment.
Far-field approximation for hydrodynamic interactions in parallel-wall geometry
Gelfond, Michael
[Physica A 356 (2005) 294] for evaluating many-body hydrodynamic interactions in a suspension of sphericalFar-field approximation for hydrodynamic interactions in parallel-wall geometry S. Bhattacharya, J reserved. Keywords: Hydrodynamic interactions; Confined systems; Stokes flow; Suspensions; HeleShaw flow 1
A flexible polymer confined inside a cone-shaped nano-channel.
Nikoofard, Narges; Fazli, Hossein
2015-06-28
The nano-scale confinement of polymers in cone-shaped geometries occurs in many experimental situations. A flexible polymer confined in a cone-shaped nano-channel is studied theoretically and by using molecular dynamics simulations. Distribution of the monomers inside the channel, configuration of the confined polymer, the entropic force acting on the polymer, and their dependence on the channel and the polymer parameters are investigated. The theory and the simulation results are in very good agreement. The entropic force on the polymer that results from the asymmetric shape of the channel is measured in the simulations and its magnitude is found to be significant relative to thermal energy. The obtained dependence of the force on the channel parameters may be useful in the design of cone-shaped nano-channels. PMID:25994794
Confinement-induced resonances in quasi-one-dimensional traps with transverse anisotropy
Zhang Wei; Zhang Peng [Department of Physics, Renmin University of China, Beijing 100872 (China)
2011-05-15
We study atom-atom scattering in quasi-one-dimensional geometries with transverse anisotropy. By assuming an s-wave pseudopotential of contact interaction, we show that the system would exhibit a single confinement-induced resonance, where the scattering process degenerates to a total reflection as a one-dimensional gas of impenetrable bosons. For a general form of interaction, we present a formal calculation based on the two-channel model and draw the same qualitative conclusion of only one confinement-induced resonance. Our findings are inconsistent with a recent experiment by Haller et al. [Phys. Rev. Lett. 104, 153203 (2010)], where a splitting of confinement-induced resonances has been observed in an anisotropic quasi-one-dimensional quantum gas of Cs atoms.
Water confinement in three different substances
NASA Astrophysics Data System (ADS)
Mirshamsi, Sahar; Cheng, Hai-Ping
2014-03-01
Confined water in nano-pores of different materials appears in geological, physical, industrial and biological systems. Confined water demonstrates significantly different behavior than bulk water, which has motivated researchers to study the effects of confinement on structural and dynamical properties of water. We study the confinement of water in silica, carbon nanotubes, and gold nano-pores and compare the effect of these different materials on the properties of water. Compared to bulk water viscosity, we find that the viscosity of water increases in silica nano-pores but decreases when confined in carbon nanotubes. Increasing water density inside the silica nano-pores further increases water viscosity. Finally, we discuss how the diffusion coefficient of water and its density profile changes due to confinement. This work is supported by NSF/PHY-1068138.
S. Krupakar Murali; John F. Santarius; Gerald L. Kulcinski
2011-01-01
Gridded inertial-electrostatic confinement (IEC) de- vices interest fusion researchers owing to their ability to burn advanced fusion fuels and have many near-term applications. In these devices, a high voltage (10-180 kV) accelerates ions radially between nearly transparent electrodes in spherical or cylindrical geometry. In this paper, we report experiments that study fusion reactions within the microchannels formed between the wires
Confined compression of collagen hydrogels.
Busby, Grahame A; Grant, M Helen; Mackay, Simon P; Riches, Philip E
2013-02-22
Reconstituted collagen hydrogels are often used for in vitro studies of cell-matrix interaction and as scaffolds for tissue engineering. Understanding the mechanical and transport behaviours of collagen hydrogels is therefore extremely important, albeit difficult due to their very high water content (typically >99.5%). In the present study the mechanical behaviour of collagen hydrogels in confined compression was investigated using biphasic theory (J Biomechemical Engineering 102 (1980) 73), to ascertain whether the technique is sufficiently sensitive to determine differences in the characteristics of hydrogels of between 0.2% and 0.4% collagen. Peak stress, equilibrium stress, aggregate modulus and hydraulic permeability of the hydrogels exhibited sensitivity to collagen content, demonstrating that the technique is clearly able to discriminate between hydrogels with small differences in collagen content and may also be sensitive to factors that affect matrix remodelling. The results also offer additional insight into the deformation-dependent permeability of collagen hydrogels. This study suggests that confined compression, together with biphasic theory, is a suitable technique for assessing the mechanical properties of collagen hydrogels. PMID:23267779
Soft confinement for polymer solutions
NASA Astrophysics Data System (ADS)
Oya, Yutaka; Kawakatsu, Toshihiro
2014-07-01
As a model of soft confinement for polymers, we investigated equilibrium shapes of a flexible vesicle that contains a phase-separating polymer solution. To simulate such a system, we combined the phase field theory (PFT) for the vesicle and the self-consistent field theory (SCFT) for the polymer solution. We observed a transition from a symmetric prolate shape of the vesicle to an asymmetric pear shape induced by the domain structure of the enclosed polymer solution. Moreover, when a non-zero spontaneous curvature of the vesicle is introduced, a re-entrant transition between the prolate and the dumbbell shapes of the vesicle is observed. This re-entrant transition is explained by considering the competition between the loss of conformational entropy and that of translational entropy of polymer chains due to the confinement by the deformable vesicle. This finding is in accordance with the recent experimental result reported by Terasawa et al. (Proc. Natl. Acad. Sci. U.S.A., 108 (2011) 5249).
Field-induced confined states in graphene
Moriyama, Satoshi, E-mail: MORIYAMA.Satoshi@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Morita, Yoshifumi [Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515 (Japan); Watanabe, Eiichiro; Tsuya, Daiju [Nanotechnology Innovation Station, NIMS, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)
2014-02-03
We report an approach to confine the carriers in single-layer graphene, which leads to quantum devices with field-induced quantum confinement. We demonstrated that the Coulomb-blockade effect evolves under a uniform magnetic field perpendicular to the graphene device. Our experimental results show that field-induced quantum dots are realized in graphene, and a quantum confinement-deconfinement transition is switched by the magnetic field.
Confined jet impingement of liquid nitrogen onto different heat transfer surfaces
NASA Astrophysics Data System (ADS)
Zhang, P.; Xu, G. H.; Fu, X.; Li, C. R.
2011-06-01
Jet impingement of liquid nitrogen owns many applications in the cryogenic cooling aspects, such as, cooling of high-power chips in the electronic devices and cryoprobes in the cryosurgery. In the present study, we systematically investigated the confined jet impingement of liquid nitrogen from a tube of about 2.0 mm in diameter onto the heat transfer surfaces of about 5.0 mm in basement diameter with different heat transfer surface geometries and conditions, i.e., flat surface, hemispherical surface and flat surface with a needle. The effects of many influential factors, such as, the geometry of the heat transfer surface, jet velocity, distance between the nozzle exit and heat transfer surface, heat transfer surface condition, and some other, on the heat transfer were investigated. The heat transfer correlations were also proposed by using the experimental data, and it was found that the heat transfer mechanism of liquid impingement in the confined space was dominated by the convective evaporation rather than the nucleate boiling in the present case. The critical heat flux (CHF) of the confined jet impingement was measured and the visualization of the corresponding flow patterns of the confined jet impingement of liquid nitrogen was also conducted simultaneously to understand the heat transfer phenomena.
NASA Astrophysics Data System (ADS)
de Las Heras, D.; Velasco, E.; Mederos, L.
2006-07-01
A system of hard rods confined into a pore with slit geometry (two parallel planar substrates) is studied theoretically in the regime of high packing fraction. In this regime the bulk system exhibits a nematic phase as well as a smectic- A (spatially layered) phase. When the system is confined, strong commensuration effects between the layer spacing and the pore width bring about a rich phenomenology, with a phase diagram showing layering and capillary transitions. The latter include capillary smectization transitions whereby a confined smectic phase occurs at conditions of saturation different from those of the corresponding bulk fluid. These transitions are seen to be intimately connected with layering transitions involving discontinuous changes in the number of layers inside the pore. This rich phenomenology is obtained by use of a sophisticated density-functional, Onsager-theory-based approach, especially suited to deal with strongly inhomogeneous fluids. The theory allows for a unified description of ordering and phase behavior of the fluid in confined geometry, and permits us to correlate the above behavior with the wetting properties of the fluid on a single substrate.
de Las Heras, D; Velasco, E; Mederos, L
2006-07-01
A system of hard rods confined into a pore with slit geometry (two parallel planar substrates) is studied theoretically in the regime of high packing fraction. In this regime the bulk system exhibits a nematic phase as well as a smectic-A (spatially layered) phase. When the system is confined, strong commensuration effects between the layer spacing and the pore width bring about a rich phenomenology, with a phase diagram showing layering and capillary transitions. The latter include capillary smectization transitions whereby a confined smectic phase occurs at conditions of saturation different from those of the corresponding bulk fluid. These transitions are seen to be intimately connected with layering transitions involving discontinuous changes in the number of layers inside the pore. This rich phenomenology is obtained by use of a sophisticated density-functional, Onsager-theory-based approach, especially suited to deal with strongly inhomogeneous fluids. The theory allows for a unified description of ordering and phase behavior of the fluid in confined geometry, and permits us to correlate the above behavior with the wetting properties of the fluid on a single substrate. PMID:16907113
Abstract. Geometry and Complex Numbers GEOMETRY AND COMPLEX NUMBERS
Lee, Carl
Abstract. Geometry and Complex Numbers GEOMETRY AND COMPLEX NUMBERS JERZY DYDAK Contents 1. Introduction 2 2. Solving equations 10 3. Geometric proofs 20 Key words and phrases. Complex numbers. 1 #12-Euclidean, Projective, and Discrete' by Michael Henle (2nd edition, Prentice Hall). (2) `Complex numbers and geometry
Pedro Ojeda; Aurora Londono; Nan-Yow Chen; Martin Garcia
2008-08-04
We present a theoretical study of the folding of small proteins inside confining potentials. Proteins are described in the framework of an effective potential model which contains the Ramachandran angles as degrees of freedom and does not need any {\\it a priori} information about the native state. Hydrogen bonds, dipole-dipole- and hydrophobic interactions are taken explicitly into account. An interesting feature displayed by this potential is the presence of some intermediates between the unfolded and native states. We consider different types of confining potentials in order to study the structural properties of proteins folding inside cages with repulsive or attractive walls. Using the Wang-Landau algorithm we determine the density of states (DOS) and analyze in detail the thermodynamical properties of the confined proteins for different sizes of the cages. We show that confinement dramatically reduces the phase space available to the protein and that the presence of intermediate states can be controlled by varying the properties of the confining potential. Cages with strongly attractive walls lead to the disappearance of the intermediate states and to a two-state folding into a less stable configuration. However, cages with slightly attractive walls make the native structure more stable than in the case of pure repulsive potentials, and the folding process occurs through intermediate configurations. In order to test the metastable states we analyze the free energy landscapes as a function of the configurational energy and of the end-to-end distance as an order parameter.
Comment on "Vortex distribution in a confining potential"
NASA Astrophysics Data System (ADS)
Ribeiro, Mauricio S.; Nobre, Fernando D.; Curado, Evaldo M. F.
2014-08-01
A system of interacting vortices is considered as an appropriate model for describing properties of type-II superconductors, and it has been shown lately to be deeply associated with nonextensive statistical mechanics. Herein we comment on a recent investigation of this model [M. Girotto, A. P. dos Santos, and Y. Levin, Phys. Rev. E 88, 032118 (2013), 10.1103/PhysRevE.88.032118], which tried to contradict this assertion, based on a mean-field type of solution, compared with numerical-simulation data that correspond typically to a regime characterized by low concentrations of particles, as well as very high temperatures. It is shown that the physical situations analyzed differ significantly from those of a real superconducting phase. The analytical solution obtained from such a mean-field approximation shows a discrepancy with respect to the results of molecular-dynamics numerical simulations, which increases as the temperature is lowered towards the superconducting phase, as expected. We demonstrate that these results, when interpreted properly by means of an analytical solution within the framework of nonextensive statistical mechanics, present a remarkable agreement between molecular-dynamics simulations and theoretical results, for all temperatures, specially for those temperatures associated with the existence of type-II superconductivity.
Singular patterns for an aggregation model with a confining potential
NASA Astrophysics Data System (ADS)
Kolokolnikov, Theodore; Huang, Yanghong; Pavlovski, Mark
2013-10-01
We consider the aggregation equation with an attractive-repulsive force law. Recent studies (Kolokolnikov et al. (2011) [22]; von Brecht et al. (2012) [23]; Balague et al. (2013) [15]) have demonstrated that this system exhibits a very rich solution structure, including steady states consisting of rings, spots, annuli, N-fold symmetries, soccer-ball patterns etc. We show that many of these patterns can be understood as singular perturbations off lower-dimensional equilibrium states. For example, an annulus is a bifurcation from a ring; soccer-ball patterns bifurcate off solutions that consist of delta-point concentrations. We apply asymptotic methods to classify the form and stability of many of these patterns. To characterize spot solutions, a class of “semi-linear” aggregation problems is derived, where the repulsion is described by a nonlinear term and the attraction is linear but non-symmetric. For a special class of perturbations that consists of a Newtonian repulsion, the spot shape is shown to be an ellipse whose precise dimensions are determined via a complex variable method. For annular shapes, their width and radial density profile are described using perturbation techniques.
Differential geometry based multiscale models.
Wei, Guo-Wei
2010-08-01
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
Differential Geometry Based Multiscale Models
Wei, Guo-Wei
2010-01-01
Large chemical and biological systems such as fuel cells, ion channels, molecular motors, and viruses are of great importance to the scientific community and public health. Typically, these complex systems in conjunction with their aquatic environment pose a fabulous challenge to theoretical description, simulation, and prediction. In this work, we propose a differential geometry based multiscale paradigm to model complex macromolecular systems, and to put macroscopic and microscopic descriptions on an equal footing. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum mechanical description of the aquatic environment with the microscopic discrete atom-istic description of the macromolecule. Multiscale free energy functionals, or multiscale action functionals are constructed as a unified framework to derive the governing equations for the dynamics of different scales and different descriptions. Two types of aqueous macromolecular complexes, ones that are near equilibrium and others that are far from equilibrium, are considered in our formulations. We show that generalized Navier–Stokes equations for the fluid dynamics, generalized Poisson equations or generalized Poisson–Boltzmann equations for electrostatic interactions, and Newton's equation for the molecular dynamics can be derived by the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows. Comparison is given to classical descriptions of the fluid and electrostatic interactions without geometric flow based micro-macro interfaces. The detailed balance of forces is emphasized in the present work. We further extend the proposed multiscale paradigm to micro-macro analysis of electrohydrodynamics, electrophoresis, fuel cells, and ion channels. We derive generalized Poisson–Nernst–Planck equations that are coupled to generalized Navier–Stokes equations for fluid dynamics, Newton's equation for molecular dynamics, and potential and surface driving geometric flows for the micro-macro interface. For excessively large aqueous macromolecular complexes in chemistry and biology, we further develop differential geometry based multiscale fluid-electro-elastic models to replace the expensive molecular dynamics description with an alternative elasticity formulation. PMID:20169418
Kurilenkov, Yu. K.; Tarakanov, V. P. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation); Gus'kov, S. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
2010-12-15
Results of particle-in-sell simulations of ion acceleration by using the KARAT code in a cylindrical geometry in the problem formulation corresponding to an actual experiment with a low-energy vacuum discharge with a hollow cathode are presented. The fundamental role of the formed virtual cathode is analyzed. The space-time dynamics of potential wells related to the formation of the virtual cathode is discussed. Quasi-steady potential wells (with a depth of {approx}80% of the applied voltage) cause acceleration of deuterium ions to energies about the electron beam energy ({approx}50 keV). In the well, a quasi-isotropic velocity distribution function of fast ions forms. The results obtained are compared with available data on inertial electrostatic confinement fusion (IECF). In particular, similar correlations between the structure of potential wells and the neutron yield, as well as the scaling of the fusion power density, which increases with decreasing virtual cathode radius and increasing potential well depth, are considered. The chosen electrode configuration and potential well parameters provide power densities of nuclear DD fusion in a nanosecond vacuum discharge noticeably higher than those achieved in other similar IECF systems.
Surveying Diffusion in Complex Geometries. An Essay
Denis Grebenkov
2009-09-08
The surrounding world surprises us by the beauty and variety of complex shapes that emerge from nanometric to macroscopic scales. Natural or manufactured materials (sandstones, sedimentary rocks and cement), colloidal solutions (proteins and DNA), biological cells, tissues and organs (lungs, kidneys and placenta), they all present irregularly shaped "scenes" for a fundamental transport "performance", that is, diffusion. Here, the geometrical complexity, entangled with the stochastic character of diffusive motion, results in numerous fascinating and sometimes unexpected effects like diffusion screening or localization. These effects control many diffusion-mediated processes that play an important role in heterogeneous catalysis, biochemical mechanisms, electrochemistry, growth phenomena, oil recovery, or building industry. In spite of a long and rich history of academic and industrial research in this field, it is striking to see how little we know about diffusion in complex geometries, especially the one which occurs in three dimensions. We present our recent results on restricted diffusion. We look into the role of geometrical complexity at different levels, from boundary microroughness to hierarchical structure and connectivity of the whole diffusion-confining domain. We develop a new approach which consists in combining fast random walk algorithms with spectral tools. The main focus is on studying diffusion in model complex geometries (von Koch boundaries, Kitaoka acinus, etc.), as well as on developing and testing spectral methods. We aim at extending this knowledge and at applying the accomplished arsenal of theoretical and numerical tools to structures found in nature and industry.
Geometry for the Secondary School
ERIC Educational Resources Information Center
Moalem, D.
1977-01-01
A sequential but non-axiomatic high school geometry course which includes Euclidean, transformation, and analytic geometry and vectors and matrices, and emphasizes the invariance property of transformations, is outlined. Sample problems, solutions, and comments are included. (MN)
Soft and hard confinement of a two-electron quantum system
NASA Astrophysics Data System (ADS)
Hall, Richard L.; Saad, Nasser; Sen, K. D.
2014-12-01
A model physical problem is studied in which a system of two electrons is subject either to soft confinement by means of attractive oscillator potentials or by entrapment within an impenetrable spherical box of finite radius R. When hard confinement is present the oscillators can be switched off. Exact analytical solutions are found for special parameter sets, and highly accurate numerical solutions (18 decimal places) are obtained for general cases. Some interesting degeneracy questions are discussed at length.
NASA Astrophysics Data System (ADS)
Smania, Daniel
2007-07-01
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.
Nebeck, H.E.
1986-08-01
The MAZE mesh generator represents an arbitrary two dimensional region of space as an ordered collection of quadrilateral elements. Each element is defined by its four corner points (nodes) and an integer material number. Models are created by subdividing the region(s) of interest into one or more PARTS and specifying the element distribution in each part. Then, parts can be merged together to form the meshed representation of the entire region. Applying boundary conditions and describing material properties completes the model construction process. This activity takes place in three distinct phases: phase I-define geometry, subdivide regions into elements; phase II-refine geometry, establish interface and boundary conditions; phase III-describe material properties. This work presents explanations and examples of the phase I commands, along with an overview of the MAZE mesh generation process.
NON COMMUTATIVE DIFFERENTIAL GEOMETRY
Michel Dubois-Violette; Peter W. Michor
In commutative differential geometry the Frolicher-Nijenhuis bracket computes all kinds of curvatures and obstructions to integrability. In (1) the Frolicher- Nijenhuis bracket was developed for universal differential forms of non-commutative algebras, and several applications were given. In this paper this bracket and the Frolicher-Nijenhuis calculus will be developed for several kinds of differential graded algebras based on derivations, which were
Electroencephalography in ellipsoidal geometry
Fotini Kariotou
2004-01-01
The human brain is shaped in the form of an ellipsoid with average semiaxes equal to 6, 6.5 and 9 cm. This is a genuine 3-D shape that reflects the anisotropic characteristics of the brain as a conductive body. The direct electroencephalography problem in such anisotropic geometry is studied in the present work. The results, which are obtained through successively solving an
Urrutia, Ignacio
2015-06-28
Recently, new insights into the relation between the geometry of the vessel that confines a fluid and its thermodynamic properties were traced through the study of cluster integrals for inhomogeneous fluids. In this work, I analyze the thermodynamic properties of fluids confined in wedges or by edges, emphasizing on the question of the region to which these properties refer. In this context, the relations between the line-thermodynamic properties referred to different regions are derived as analytic functions of the dihedral angle ?, for 0 < ? < 2?, which enables a unified approach to both edges and wedges. As a simple application of these results, I analyze the properties of the confined gas in the low-density regime. Finally, using recent analytic results for the second cluster integral of the confined hard sphere fluid, the low density behavior of the line thermodynamic properties is analytically studied up to order two in the density for 0 < ? < 2? and by adopting different reference regions. PMID:26133452
NASA Astrophysics Data System (ADS)
Ahmad, Muhammad Raza; Jamil, Yasir; Qaiser Zakaria, M.; Hussain, Tousif; Ahmad, Riaz
2015-07-01
We introduce for the first time the novel idea of manipulating the momentum coupling coefficient using plasma confinement and shock wave reflection from the cavity walls. The plasma was confined using cylindrical geometries of various cavity aspect ratios to manipulate the momentum coupling coefficient (C m ). The Nd: YAG laser (532?nm, 5?ns pulse duration) was focused on the ferrite sample surface to produce plasma in a region surrounded by cylindrical cavity walls. The multiple reflections of the shockwaves from the cavity walls confined the laser-induced plasma to the central region of the cavity that subsequently resulted in a significant enhancement of the momentum coupling coefficient values. The plasma shielding effect has also been observed for particular values of laser fluencies and cavity aspect ratios. Compared with the direct ablation, the confined ablation provides an effective way to obtain high C m values.
Integral Geometry and Holography
Bartlomiej Czech; Lampros Lamprou; Samuel McCandlish; James Sully
2015-05-20
We present a mathematical framework which underlies the connection between information theory and the bulk spacetime in the AdS$_3$/CFT$_2$ correspondence. A key concept is kinematic space: an auxiliary Lorentzian geometry whose metric is defined in terms of conditional mutual informations and which organizes the entanglement pattern of a CFT state. When the field theory has a holographic dual obeying the Ryu-Takayanagi proposal, kinematic space has a direct geometric meaning: it is the space of bulk geodesics studied in integral geometry. Lengths of bulk curves are computed by kinematic volumes, giving a precise entropic interpretation of the length of any bulk curve. We explain how basic geometric concepts -- points, distances and angles -- are reflected in kinematic space, allowing one to reconstruct a large class of spatial bulk geometries from boundary entanglement entropies. In this way, kinematic space translates between information theoretic and geometric descriptions of a CFT state. As an example, we discuss in detail the static slice of AdS$_3$ whose kinematic space is two-dimensional de Sitter space.
Implicit Computation Geometry Henrik Blunck
Brodal, Gerth Stølting
Implicit Computation Geometry Henrik Blunck Department of Computer Science WWU M¨unster #12 Implicit Computation Geometry 1 #12;Motivation Traditional focus in algorithm design: Running Time Here/write)-memory Sensor Networks Car Navigation Henrik Blunck Implicit Computation Geometry 2 #12;In-Place Algorithms
Noncommutative geometry for arbitrary braidings
NASA Astrophysics Data System (ADS)
Marcinek, Wl/adysl/aw
1994-05-01
The noncommutative geometry corresponding to arbitrary braidings is studied in a purely algebraical way. The new and original proposal of the geometry is given in terms of the theory of braided monoidal categories. The quantum oscillator is considered as an example of application of our geometry.
Geometry for Santiago and Mathias
NSDL National Science Digital Library
Nora
2009-06-05
The Klings can practice their geometry skills through fun games. Test your geometry knowledge in Shape Hangman!! Practice what you know in the sort trianles. Do you reallyGrasp Geometry? Measuring area of rectangles, good for Santi Area of Rectangles BBC Cool Geoboard for Santi Interactive geoboard More area measuring Tutorial with game ...
Direct observation of electron confinement in epitaxial graphene nanoislands.
Phark, Soo-Hyon; Borme, Jérôme; Vanegas, Augusto León; Corbetta, Marco; Sander, Dirk; Kirschner, Jürgen
2011-10-25
One leading question for the application of graphene in nanoelectronics is how electronic properties depend on the size at the nanoscale. Direct observation of the quantized electronic states is central to conveying the relationship between electronic structures and local geometry. Scanning tunneling spectroscopy was used to measure differential conductance dI/dV patterns of nanometer-size graphene islands on an Ir(111) surface. Energy-resolved dI/dV maps clearly show a spatial modulation, indicating a modulated local density of states due to quantum confinement, which is unaffected by the edge configuration. We establish the energy dispersion relation with the quantized electron wave vector obtained from a Fourier analysis of dI/dV maps. The nanoislands preserve the Dirac Fermion properties with a reduced Fermi velocity. PMID:21942619
The theory of delamination during drying of confined colloidal suspensions.
Wallenstein, K J; Russel, W B
2011-05-18
Recent experiments on the drying of colloidal films in confined thin rectangular geometries show an interesting new phenomenon: the delamination of the colloidal suspension from the cavity wall. The theory developed in this paper explains the phenomenon by applying the Griffith energy criteria to a poroelastic film of Hertzian spheres. Prior to delamination, flow due to drying compresses the film in the direction of flow and generates tension in the transverse direction. Delamination allows relaxation in both the transverse tensile stresses and the axial compression. Preliminary numerical solutions suggest that the elastic energy recovered should increase linearly with the length of the close-packed film. That suggests a simple analytical solution that predicts the advancing of the delamination as the length of the close-packed region increases and explains qualitatively the essential features of the phenomenon. PMID:21525555
Confinement and focusing of geodesics in warped spacetimes
NASA Astrophysics Data System (ADS)
Kar, S.; Das Gupta, A.; Ghosh, S.; Nandan, H.
2014-03-01
We have explored certain characteristic features of test particle trajectories in five dimensional, warped bulk geometries with a single thick brane. After a brief introduction on such spacetimes, we have first discussed timelike geodesic motion. The geodesic equations, which reduce to a first order autonomous dynamical system, have been solved using analytical and numerical methods. We have demonstrated how a growing (decaying) warp factor leads to oscillatory (runaway) trajectories, suggesting confinement (deconfinement). Further, we have pointed out differences that arise when we have a cosmological brane and/or a time-dependent extra dimension. Next, we have moved on to the kinematics of geodesic congruences. The evolution of the kinematical variables (expansion, rotation and shear) along geodesic flows have been obtained using analytical and numerical approaches, with particular emphasis on the required conditions and occurence of geodesic focusing.
Fingering in Confined Elastic Layers
NASA Astrophysics Data System (ADS)
Biggins, John; Mahadevan, L.; Wei, Z.; Saintyves, Baudouin; Bouchaud, Elizabeth
2015-03-01
Fingering has recently been observed in soft highly elastic layers that are confined between and bonded to two rigid bodies. In one case an injected fluid invades the layer in finger-like protrusions at the layer's perimeter, a solid analogue of Saffman-Taylor viscous fingering. In a second case, separation of the rigid bodies (with maintained adhesion to the layer) leads air to the formation of similar fingers at the layer's perimeter. In both cases the finger formation is reversible: if the fluid is removed or the separation reduced, the fingers vanish. In this talk I will discuss a theoretical model for such elastic fingers that shows that the origin of the fingers is large-strain geometric non-linearity in the elasticity of soft solids. Our simplified elastic model unifies the two types of fingering and accurately estimates the thresholds and wavelengths of the fingers.
Capillary Condensation in Confined Media
Charlaix, Elisabeth
2009-01-01
We review here the physics of capillary condensation of liquids in confined media, with a special regard to the application in nanotechnologies. The thermodynamics of capillary condensation and thin film adsorption are first exposed along with all the relevant notions. The focus is then shifted to the modelling of capillary forces, to their measurements techniques (including SFA, AFM and crack tips) and to their influence on AFM imaging techniques as well as on the static and dynamic friction properties of solids (including granular heaps and sliding nanocontacts). A great attention is spent in investigating the delicate role of the surface roughness and all the difficulties involved in the reduction of the probe size to nanometric dimensions. Another major consequence of capillary condensation in nanosystems is the activation of several chemical and corrosive processes that can significantly alter the surface properties, such as dissolution/redeposition of solid materials and stress-corrosion crack propagati...
Magnetic confinement of cosmic clouds
NASA Technical Reports Server (NTRS)
Azar, Michel; Thompson, W. B.
1988-01-01
The role of the magnetic field in the confinement or compression of interstellar gas clouds is reconsidered. The virial theorem for an isolated magnetized cloud in the presence of distant magnetic sources is reformulated in terms of moments of the internal and external currents, and an equilibrium condition is derived. This condition is applied to the interaction between isolated clouds for the simple- and artificial-case in which the field of each cloud is a dipole. With the simplest of statistical assumptions, the probability of any given cloud being compressed is calculated as about 10 percent, the magnetic field acting as a medium which transmits the kinetic pressure between clouds. Even when compression occurs the magnetic pressure 1/2 B-squared may decrease on leaving the cloud surface.
Multishell inertial confinement fusion target
Holland, James R. (Butler, PA); Del Vecchio, Robert M. (Vandergrift, PA)
1987-01-01
A method of fabricating multishell fuel targets for inertial confinement fusion usage. Sacrificial hemispherical molds encapsulate a concentric fuel pellet which is positioned by fiber nets stretched tautly across each hemispherical mold section. The fiber ends of the net protrude outwardly beyond the mold surfaces. The joint between the sacrificial hemispheres is smoothed. A ceramic or glass cover is then deposited about the finished mold surfaces to produce an inner spherical surface having continuously smooth surface configuration. The sacrificial mold is removed by gaseous reactions accomplished through the porous ceramic cover prior to enclosing of the outer sphere by addition of an outer coating. The multishell target comprises the inner fuel pellet concentrically arranged within a surrounding coated cover or shell by fiber nets imbedded within the cover material.
Transient coexisting nanophases in ultrathin films confined between corrugated walls
Curry, J.E.; Zhang, F.; Cushman, J.H. (Lilly Hall of Life Sciences, Purdue University, West Lafayette, Indiana 47907 (United States)); Schoen, M. (Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)); Diestler, D.J. (Department of Agronomy, Keim Hall, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0915 (United States))
1994-12-15
Grand-canonical Monte Carlo and microcanonical molecular dynamics methods have been used to simulate an ultrathin monatomic film confined to a slit-pore [i.e., between solid surfaces (walls)]. Both walls comprise atoms rigidly fixed in the face centered cubic (100) configuration; one wall is smooth on a nanoscale and the other is corrugated (i.e., scored with regularly spaced rectilinear grooves one to several nanometers wide). Properties of the film have been computed as a function of the lateral alignment (registry), with the temperature, chemical potential, and distance between the walls kept constant. Changing the registry carries the film through a succession of equilibrium states, ranging from all solid at one extreme to all fluid at the other. Over a range of intermediate registries the film consists of fluid and solid portions in equilibrium, that is fluid-filled nanocapillaries separated by solid strips. The range of registries over which such fluid--solid equilibria exist depends upon the width of the grooves and the frequency of the corrugation. For grooves of width comparable to the range of the interatomic potential, fluid and solid phases cease to coexist. In the limit of very wide grooves the character of the film is similar to that of the film confined by strictly smooth walls. The rich phase behavior of the confined film due to the coupling between molecular (registry) and nano (corrugation) scales has obvious implications for boundary lubrication.
An EQT-cDFT approach to determine thermodynamic properties of confined fluids.
Mashayak, S Y; Motevaselian, M H; Aluru, N R
2015-06-28
We present a continuum-based approach to predict the structure and thermodynamic properties of confined fluids at multiple length-scales, ranging from a few angstroms to macro-meters. The continuum approach is based on the empirical potential-based quasi-continuum theory (EQT) and classical density functional theory (cDFT). EQT is a simple and fast approach to predict inhomogeneous density and potential profiles of confined fluids. We use EQT potentials to construct a grand potential functional for cDFT. The EQT-cDFT-based grand potential can be used to predict various thermodynamic properties of confined fluids. In this work, we demonstrate the EQT-cDFT approach by simulating Lennard-Jones fluids, namely, methane and argon, confined inside slit-like channels of graphene. We show that the EQT-cDFT can accurately predict the structure and thermodynamic properties, such as density profiles, adsorption, local pressure tensor, surface tension, and solvation force, of confined fluids as compared to the molecular dynamics simulation results. PMID:26133419
CONFINED SPACE ENTRY PERMIT University of Maryland
Rubloff, Gary W.
: Ventilation Lockout/Tagout Combustible gas Toxic contaminants Chemical/Biological Noise Other Personal Confined Space." 1. Check the UM Confined Space Inventory at www.des.umd.edu/os/csp to verify that the space that will be entered is listed in the inventory. If it is, use the information found
Weapons Activities/ Inertial Confinement Fusion Ignition
Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY 2012 a safe, secure, and reliable nuclear weapons stockpile without underground testing. Science-based weapons's Budget. Page 105 #12;Weapons Activities/ Inertial Confinement Fusion Ignition and High Yield Campaign FY
Inertial electrostatic confinement (IEC) neutron sources
R. A. Nebel; D. C. Barnes; E. J. Caramana; R. D. Janssen; W. D. Nystrom; T. N. Tiouririne; B. C. Trent; G. H. Miley; J. Javedani
1995-01-01
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
Confinement and the safety factor profile
Batha, S.H.; Levinton, F.M. [Fusion Physics and Technology, Torrance, CA (United States); Scott, S.D. [Princeton Univ., NJ (United States). Plasma Physics Lab.] [and others
1995-12-01
The conjecture that the safety factor profile, q(r), controls the improvement in tokamak plasmas from poor confinement in the Low (L-) mode regime to improved confinement in the supershot regime has been tested in two experiments on the Tokamak Fusion Test Reactor (TFTR). First, helium was puffed into the beam-heated phase of a supershot discharge which induced a degradation from supershot to L-mode confinement in about 100 msec, far less than the current relaxation time. The q and shear profiles measured by a motional Stark effect polarimeter showed little change during the confinement degradation. Second, rapid current ramps in supershot plasmas altered the q profile, but were observed not to change significantly the energy confinement. Thus, enhanced confinement in supershot plasmas is not due to a particular q profile which has enhanced stability or transport properties. The discharges making a continuous transition between supershot and L-mode confinement were also used to test the critical-electron-temperature-gradient transport model. It was found that this model could not reproduce the large changes in electron and ion temperature caused by the change in confinement.
Climate conditions in bedded confinement buildings
Technology Transfer Automated Retrieval System (TEKTRAN)
Confinement buildings are utilized for finishing cattle to allow more efficient collection of animal waste and to buffer animals against adverse climatic conditions. Environmental data were obtained from a 29 m wide x 318 m long bedded confinement building with the long axis oriented east to west. T...
Spectroscopic study of Gd nanostructures quantum confined in Fe corrals.
Cao, R X; Sun, L; Miao, B F; Li, Q L; Zheng, C; Wu, D; You, B; Zhang, W; Han, P; Bader, S D; Zhang, W Y; Ding, H F
2015-01-01
Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of the corrals and Gd structures trapped inside, are supported by tight-binding calculations. This demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects. PMID:26160318
Quantum confinement-induced tunable exciton states in graphene oxide
Lee, Dongwook; Seo, Jiwon; Zhu, Xi; Lee, Jiyoul; Shin, Hyeon-Jin; Cole, Jacqueline M.; Shin, Taeho; Lee, Jaichan; Lee, Hangil; Su, Haibin
2013-01-01
Graphene oxide has recently been considered to be a potential replacement for cadmium-based quantum dots due to its expected high fluorescence. Although previously reported, the origin of the luminescence in graphene oxide is still controversial. Here, we report the presence of core/valence excitons in graphene-based materials, a basic ingredient for optical devices, induced by quantum confinement. Electron confinement in the unreacted graphitic regions of graphene oxide was probed by high resolution X-ray absorption near edge structure spectroscopy and first-principles calculations. Using experiments and simulations, we were able to tune the core/valence exciton energy by manipulating the size of graphitic regions through the degree of oxidation. The binding energy of an exciton in highly oxidized graphene oxide is similar to that in organic electroluminescent materials. These results open the possibility of graphene oxide-based optoelectronic device technology. PMID:23872608
A noncommutative space approach to confined Dirac fermions in graphene
NASA Astrophysics Data System (ADS)
Dayi, Ömer F.; Jellal, Ahmed
2010-06-01
A generalized algebra of noncommutative coordinates and momenta embracing non-Abelian gauge fields is proposed. Through a two-dimensional realization of this algebra for a gauge field including electromagnetic vector potential and two spin-orbit-like coupling terms, a Dirac-like Hamiltonian in noncommutative coordinates is introduced. We established the corresponding energy spectrum and from that we derived the relation between the energy level quantum number and the magnetic field at the maxima of Shubnikov-de Haas oscillations. By tuning the noncommutativity parameter ? in terms of the values of magnetic field at the maxima of Shubnikov-de Haas oscillations, we accomplished the experimentally observed Landau plot of the peaks for graphene. Accepting that the experimentally observed behavior is due to the confinement of carriers, we conclude that our method of introducing noncommutative coordinates provides another formulation of the confined massless Dirac fermions in graphene.
The inertial electrostatic confinement approach to fusion power
Miley, G.H. [Univ. of Illinois, Urbana, IL (United States). Fusion Studies Lab.
1995-12-31
Inertial electrostatic confinement (IEC) of a non-Maxwellian beam-dominated plasma for fusion, originally proposed in the 1950s, has received little attention until recently. Experiments have shown that small IEC devices operating in a beam-background plasma mode are well-suited for a commercial portable low-level neutron source for activation analysis applications. However, the scaling to a high-power fusion reactor is uncertain, due to the lack of experimental data with the higher input currents necessary for beam-beam reactions. Three key issues need to be resolved: the stability of multiple potential well structures, the confinement time of energetic ions trapped in such wells, and the protection of grid structures during high-power operation. If these issues are positively resolved, conceptual design studies show that the resulting reactor would be economically and environmentally attractive and versatile.
Pulsed operation of spherical inertial-electrostatic confinement device
Gu, Y.; Williams, M.; Stubbers, R.; Miley, G. [Univ. of Illinois, Urbana, IL (United States)
1996-12-31
Inertial electrostatic confinement (IEC) fusion confines high energy ions in potential wells, where their increased energy and density yields a high fusion rate. Studies of the IEC at the University of Illinois (UI) initially concentrated on steady-state operation where neutron yields of approx.10{sup 6} D-D n/s are routinely obtained. However, the development of a pulsed configuration has been undertaken to provide higher neutron yields. Preliminary experiments have demonstrated I{sup 2} scaling during pulsed operation when the perveance threshold of 2.2 mA/kV{sup 3/2} is exceeded. Based on these results, it appears that the present IEC could be operated with 3-A, 100-kV repetitive pulses with a 10% duty factor to produce neutron yields of approx.10{sup 10} neutrons/second. 6 refs., 7 figs.
Spectroscopic study of Gd nanostructures quantum confined in Fe corrals
Cao, R. X.; Sun, L.; Miao, B. F.; Li, Q. L.; Zheng, C.; Wu, D.; You, B.; Zhang, W.; Han, P.; Bader, S. D.; Zhang, W. Y.; Ding, H. F.
2015-01-01
Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of the corrals and Gd structures trapped inside, are supported by tight-binding calculations. This demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects. PMID:26160318
Coulomb gauge confinement in the heavy quark limit
Popovici, C.; Watson, P.; Reinhardt, H. [Institut fuer Theoretische Physik, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)
2010-05-15
The relationship between the nonperturbative Green's functions of Yang-Mills theory and the confinement potential is investigated. By rewriting the generating functional of quantum chromodynamics in terms of a heavy quark mass expansion in Coulomb gauge, restricting to leading order in this expansion and considering only the two-point functions of the Yang-Mills sector, the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is shown to be exact in this case and an analytic, nonperturbative solution is presented. It is found that there is a direct connection between the string tension and the temporal gluon propagator. Further, it is shown that for the 4-point quark correlation functions, only confined bound states of color-singlet quark-antiquark (meson) and quark-quark (baryon) pairs exist.
Confinement-Induced Quorum Sensing of Individual Staphylococcus aureus Bacteria
Carnes, Eric C; Lopez, DeAnna M; Donegan, Niles P; Cheung, Ambrose; Gresham, Hattie; Timmins, Graham S; Brinker, CJ
2014-01-01
It is postulated that, in addition to cell density, other factors, such as the dimensions and diffusional characteristics of the environment, could influence quorum sensing (QS) and induction of genetic reprogramming. Modeling studies predict that QS may operate at the level of a single cell, but, due to experimental challenges, the potential benefits of QS by individual cells remain virtually unexplored. Here we report a physical system that mimics isolation of a bacterium, such as within an endosome or phagosome during infection, and maintains cell viability under conditions of complete chemical and physical isolation. For Staphylococcus aureus, we show quorum sensing and genetic re-programming to occur in a single isolated organism. Quorum sensing allows S. aureus to sense confinement and to activate virulence and metabolic pathways needed for survival. To demonstrate the benefit of confinement-induced quorum sensing to individuals, we showed quorum sensing bacteria to have significantly greater viability over non-QS bacteria. PMID:19935660
First-principles study of orbital-dependent quantum confinement in Si/Ge nanowire superlattices
NASA Astrophysics Data System (ADS)
Kim, Min-Kook; Choi, Hyoung Joon
2012-02-01
We study electronic structures of H-passivated Si/Ge nanowire superlattices (NWSLs) oriented along [110] direction, using an ab-initio pseudopotential density-functional method with the local density approximation. Obtained electronic structures of the Si/Ge NWSLs show both dispersive and non-dispersive bands in conduction and valence bands due to band-selective quantum confinement: the highest valence band and the lowest conduction band are not confined in either the Si- or Ge-nanowire segment but they are extended throughout the whole NWSLs, while there exist non-dispersive bands confined in either Si- or Ge-nanowire segment below the top of the valence band and above the bottom of the conduction band. This feature originates from strong orbital-dependence of quantum confinement of electronic states, making conventional band-offset diagrams for superlattices invalid in Si/Ge NWSLs. Effects of atomic geometries on the confinement are studied with different diameters and superlattice periodicities. This work was supported by NRF of Korea (Grant Nos. 2009-0081204 and 2011-0018306). Computational resources have been provided by KISTI Supercomputing Center (Project No. KSC-2011-C3-05).
Boosting the Light: X-ray Physics in Confinement
Rhisberger, Ralf [HASYLAB/ DESY
2010-01-08
Remarkable effects are observed if light is confined to dimensions comparable to the wavelength of the light. The lifetime of atomic resonances excited by the radiation is strongly reduced in photonic traps, such as cavities or waveguides. Moreover, one observes an anomalous boost of the intensity scattered from the resonant atoms. These phenomena results from the strong enhancement of the photonic density of states in such geometries. Many of these effects are currently being explored in the regime of vsible light due to their relevance for optical information processing. It is thus appealing to study these phenomena also for much shorter wavelengths. This talk illuminates recent experiments where synchrotron x-rays were trapped in planar waveguides to resonantly excite atomos ([57]Fe nuclei_ embedded in them. In fact, one observes that the radiative decay of these excited atoms is strongly accelerated. The temporal acceleration of the decay goes along with a strong boost of the radiation coherently scattered from the confined atmos. This can be exploited to obtain a high signal-to-noise ratio from tiny quantities of material, leading to manifold applications in the investigation of nanostructured materials. One application is the use of ultrathin probe layers to image the internal structure of magnetic layer systems.
Analytic Coleman-De Luccia geometries
Dong, Xi; Harlow, Daniel, E-mail: xidong@stanford.edu, E-mail: dharlow@stanford.edu [Stanford Institute for Theoretical Physics, Department of Physics, Stanford University, Stanford CA 94305 (United States)
2011-11-01
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(?), 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.
Analytic 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
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.
Confinement-induced resonances in anharmonic waveguides
Peng Shiguo [Department of Physics, Tsinghua University, Beijing 100084 (China); Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Hu Hui; Liu Xiaji; Drummond, Peter D. [Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia)
2011-10-15
We develop the theory of anharmonic confinement-induced resonances (ACIRs). These are caused by anharmonic excitation of the transverse motion of the center of mass (c.m.) of two bound atoms in a waveguide. As the transverse confinement becomes anisotropic, we find that the c.m. resonant solutions split for a quasi-one-dimensional (1D) system, in agreement with recent experiments. This is not found in harmonic confinement theories. A new resonance appears for repulsive couplings (a{sub 3D}>0) for a quasi-two-dimensional (2D) system, which is also not seen with harmonic confinement. After inclusion of anharmonic energy corrections within perturbation theory, we find that these ACIRs agree extremely well with anomalous 1D and 2D confinement-induced resonance positions observed in recent experiments. Multiple even- and odd-order transverse ACIRs are identified in experimental data, including up to N=4 transverse c.m. quantum numbers.
Diederichsen, Kyle M; Brow, Ryan R; Stoykovich, Mark P
2015-03-24
The topology and transport behavior of the lamellar morphology self-assembled by block copolymers in thin films are shown to depend on the length scale over which they are characterized and can be described by percolation in a network under confinement. Gold nanowires replicating the lamellar morphology were fabricated via self-assembled poly(styrene-block-methyl methacrylate) thin films and a lift-off pattern transfer process. The lamellar morphology exhibits long-range connectivity (macroscopic scale); however, characterization of electrical conduction over confined areas (5-500 ?m) demonstrates a discrete probability of disconnection that arises due to the underlying network structure and a lack of self-similarity at these microscale dimensions. In particular, it is proved that the lamellar network morphology under confinement has a conductance that is nonlinear with channel length or width. The experimental results are discussed in terms of percolation theory, and a simple, two-dimensional Monte Carlo model is shown to predict the key trends in the network topology and conductance in lamellar block copolymers, including the dependencies on composition, extent of spatial confinement, and confinement geometry. These results highlight the need to exquisitely control or engineer the self-assembled nanostructured pathways formed by block copolymers to ensure consistent device performance for any application that depends upon percolating material, ionic, or electrical transport, especially when confined in any dimension. It is also concluded that the two most promising approaches for enhancing conductivity in block copolymer materials may be achieved either at the limits of (1) perfectly oriented, single-crystalline or (2) high defect density, polycrystalline microphase separated morphologies and that nanostructured systems with intermediate defect densities would be detrimental to transport in confined systems. PMID:25756653
Layering transitions and solvation forces in an asymmetrically confined fluid
NASA Astrophysics Data System (ADS)
Stewart, M. C.; Evans, R.
2014-04-01
We consider a simple fluid confined between two parallel walls (substrates), separated by a distance L. The walls exert competing surface fields so that one wall is attractive and may be completely wet by liquid (it is solvophilic) while the other is solvophobic. Such asymmetric confinement is sometimes termed a "Janus Interface." The second wall is: (i) purely repulsive and therefore completely dry (contact angle ? = 180°) or (ii) weakly attractive and partially dry (? is typically in the range 160-170°). At low temperatures, but above the bulk triple point, we find using classical density functional theory (DFT) that the fluid is highly structured in the liquid part of the density profile. In case (i), a sequence of layering transitions occurs: as L is increased at fixed chemical potential ? close to bulk gas-liquid coexistence ?co, new layers of liquid-like density develop discontinuously. In contrast to confinement between identical walls, the solvation force is repulsive for all wall separations and jumps discontinuously at each layering transition and the excess grand potential exhibits many metastable minima as a function of the adsorption. For a fixed temperature T = 0.56TC, where TC is the bulk critical temperature, we determine the transition lines in the L, ? plane. In case (ii), we do not find layering transitions and the solvation force oscillates about zero. We discuss how our mean-field DFT results might be altered by including effects of fluctuations and comment on how the phenomenology we have revealed might be relevant for experimental and simulation studies of water confined between hydrophilic and hydrophobic substrates, emphasizing it is important to distinguish between cases (i) and (ii).
Layering transitions and solvation forces in an asymmetrically confined fluid.
Stewart, M C; Evans, R
2014-04-01
We consider a simple fluid confined between two parallel walls (substrates), separated by a distance L. The walls exert competing surface fields so that one wall is attractive and may be completely wet by liquid (it is solvophilic) while the other is solvophobic. Such asymmetric confinement is sometimes termed a "Janus Interface." The second wall is: (i) purely repulsive and therefore completely dry (contact angle ? = 180°) or (ii) weakly attractive and partially dry (? is typically in the range 160-170°). At low temperatures, but above the bulk triple point, we find using classical density functional theory (DFT) that the fluid is highly structured in the liquid part of the density profile. In case (i), a sequence of layering transitions occurs: as L is increased at fixed chemical potential ? close to bulk gas-liquid coexistence ?co, new layers of liquid-like density develop discontinuously. In contrast to confinement between identical walls, the solvation force is repulsive for all wall separations and jumps discontinuously at each layering transition and the excess grand potential exhibits many metastable minima as a function of the adsorption. For a fixed temperature T = 0.56TC, where TC is the bulk critical temperature, we determine the transition lines in the L, ? plane. In case (ii), we do not find layering transitions and the solvation force oscillates about zero. We discuss how our mean-field DFT results might be altered by including effects of fluctuations and comment on how the phenomenology we have revealed might be relevant for experimental and simulation studies of water confined between hydrophilic and hydrophobic substrates, emphasizing it is important to distinguish between cases (i) and (ii). PMID:24712805
Layering Transitions and Solvation Forces in an Asymmetrically Confined Fluid
Maria C. Stewart; Robert Evans
2014-08-29
We consider a simple fluid confined between two parallel walls (substrates), separated by a distance L. The walls exert competing surface fields so that one wall is attractive and may be completely wet by liquid (it is solvophilic) while the other is solvophobic. Such asymmetric confinement is sometimes termed a `Janus Interface'. The second wall is: (i) purely repulsive and therefore completely dry (contact angle 180 degrees) or (ii) weakly attractive and partially dry (the contact angle is typically in the range 160-170 degrees). At low temperatures, but above the bulk triple point, we find using classical density functional theory (DFT) that the fluid is highly structured in the liquid part of the density profile. In case (i) a sequence of layering transitions occurs: as L is increased at fixed chemical potential (mu) close to bulk gas--liquid coexistence, new layers of liquid-like density develop discontinuously. In contrast to confinement between identical walls, the solvation force is repulsive for all wall separations and jumps discontinuously at each layering transition and the excess grand potential exhibits many metastable minima as a function of the adsorption. For a fixed temperature T=0.56Tc, where Tc is the bulk critical temperature, we determine the transition lines in the L, mu plane. In case (ii) we do not find layering transitions and the solvation force oscillates about zero. We discuss how our mean-field DFT results might be altered by including effects of fluctuations and comment on how the phenomenology we have revealed might be relevant for experimental and simulation studies of water confined between hydrophilic and hydrophobic substrates, emphasizing it is important to distinguish between cases (i) and (ii).
Bergmair, Michael; Bruno, Giovanni; Cattelan, Denis; Cobet, Christoph; de Martino, Antonello; Fleischer, Karsten; Dohcevic-Mitrovic, Zorana; Esser, Norbert; Galliet, Melanie; Gajic, Rados; Hemzal, Dušan; Hingerl, Kurt; Humlicek, Josef; Ossikovski, Razvigor; Popovic, Zoran V.; Saxl, Ottilia
2009-01-01
This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems and devices at the nanoscale. These techniques include spectroscopic ellipsometry, polarimetry, and reflectance anisotropy. We give an overview of the various ellipsometry strategies for the measurement and analysis of nanometric films, metal nanoparticles and nanowires, semiconductor nanocrystals, and submicron periodic structures. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about process control, geometry factors, anisotropy, defects, and quantum confinement effects of nanostructures. PMID:21170135
Sobczyk, Garret
2007-01-01
The concept of number and its generalization has played a central role in the development of mathematics over many centuries and many civilizations. Noteworthy milestones in this long and arduous process were the developments of the real and complex numbers which have achieved universal acceptance. Serious attempts have been made at further extensions, such as Hamiltons quaternions, Grassmann's exterior algebra and Clifford's geometric algebra. By examining the geometry of moving planes, we show how new mathematics is within reach, if the will to learn these powerful methods can be found.
Garret Sobczyk
2007-09-29
The concept of number and its generalization has played a central role in the development of mathematics over many centuries and many civilizations. Noteworthy milestones in this long and arduous process were the developments of the real and complex numbers which have achieved universal acceptance. Serious attempts have been made at further extensions, such as Hamiltons quaternions, Grassmann's exterior algebra and Clifford's geometric algebra. By examining the geometry of moving planes, we show how new mathematics is within reach, if the will to learn these powerful methods can be found.
Yang-Hui He; Vishnu Jejjala; Cyril Matti; Brent D. Nelson; Michael Stillman
2014-08-28
We present an intriguing and precise interplay between algebraic geometry and the phenomenology of generations of particles. Using the electroweak sector of the MSSM as a testing ground, we compute the moduli space of vacua as an algebraic variety for multiple generations of Standard Model matter and Higgs doublets. The space is shown to have Calabi-Yau, Grassmannian, and toric signatures which sensitively depend on the number of generations of leptons, as well as inclusion of Majorana mass terms for right-handed neutrinos. We speculate as to why three generations is special.
NASA Astrophysics Data System (ADS)
Roberts, T. Maximillian
2014-10-01
Turbulence in a dipole-confined plasma is dominated by interchange fluctuations with complex dynamics and short coherence. We report the first laboratory demonstration of the regulation of interchange turbulence in a plasma torus confined by an axisymmetric dipole magnet using active feedback. Feedback is performed by varying the bias to an electrode in proportion to the electric potential measured at other locations. The phase and amplitude of the bias to the electrode is adjusted with a linear circuit, forming a relatively broad-band current-collection feedback system. Changing the gain and phase of collection results in modification of turbulent fluctuations, observed as amplification or suppression of turbulent spectrum. Significantly, power can be either extracted from or injected into the turbulence. When the gain and phase are adjusted to suppress turbulence, the external circuit becomes a controlled load extracting power from the plasma. This is analogous to the regulation of magnetospheric convection by ionospheric currents. When the gain and phase of the external circuit is adjusted to amplify turbulence, the direction of power flow from the electrode reverses, enhancing the fluctuations. Although we observe significant changes to the intensity and spectrum of plasma fluctuations, these changes appear only on those magnetic field lines within a region near the current collector equal in size to the turbulent correlation length and shifted in the direction of the electron magnetic drift. We conclude that the effects of this feedback on turbulence in a dipole plasma torus is localized. The clear influence of current-collection feedback on interchange turbulence suggests the possibility of global regulation of turbulent motion using multiple sensor and electrode pairs as well as the ability to perform controlled tests of bounce-averaged gyrokinetic theory of turbulence in the geometry of a dipole plasma torus. Supported by NSF-DOE Partnership for Plasma Science and DOE Grant DE-FG02-00ER54585 and NSF Award PHY-1201896.
Virtual Cathode in a Stationary Spherical Inertial Electrostatic Confinement
Momota, Hiromu; Miley, George H. [University of Illinois at Urbana-Champaign (United States)
2001-07-15
'Double-well' potential structure (virtual cathode formation) is studied in a stationary spherical inertial electrostatic confinement (SIEC) using the nonlinear Poisson's equation and particle densities derived from kinetic theory. A novel method to obtain a spherically symmetric stationary distribution function is introduced and an integral-differential equation is simplified by applying a relevant approximated formula for an integral. Electron and ion beams are collision-free, and their velocities are roughly aligned toward the spherical center, but with a slight divergence. Analyses show that the angular momentum of ions and the smaller one of electrons create a virtual cathode, i.e., a double-well structure, of the electrostatic potential on a potential hill near the center. The density limit of an SIEC is exhibited, and the condition relevant to form a deep potential well is presented.
Axisymmetric Tandem Mirrors: Stabilization and Confinement Studies
Post, R.F.; Fowler, T.K.; Bulmer, R.; Byers, J.; Hua, D.; Tung, L. [Lawrence Livermore National Laboratory (United States)
2005-01-15
The 'Kinetic Stabilizer' has been proposed as a means of MHD stabilizing an axisymmetric tandem mirror system. The K-S concept is based on theoretical studies by Ryutov, confirmed experimentally in the Gas Dynamic Trap experiment in Novosibirsk. In the K-S beams of ions are directed into the end of an 'expander' region outside the outer mirror of a tandem mirror. These ions, slowed, stagnated, and reflected as they move up the magnetic gradient, produce a low-density stabilizing plasma.At the Lawrence Livermore National Laboratory we have been conducting theoretical and computational studies of the K-S Tandem Mirror. These studies have employed a low-beta code written especially to analyze the beam injection/stabilization process,and a new code SYMTRAN (by Hua and Fowler)that solves the coupled radial and axial particle and energy transport in a K-S T-M. Also, a 'legacy' MHD stability code, FLORA, has been upgraded and employed to benchmark the injection/stabilization code and to extend its results to high beta values.The FLORA code studies so far have confirmed the effectiveness of the K-S in stabilizing high-beta (40%) plasmas with stabilizer plasmas the peak pressures of which are several orders of magnitude smaller than those of the confined plasma.Also the SYMTRAN code has shown D-T plasma ignition from alpha particle energy deposition in T-M regimes with strong end plugging.Our studies have confirmed the viability of the K-S T-M concept with respect to MHD stability and radial and axial confinement. We are continuing these studies in order to optimize the parameters and to examine means for the stabilization of possible residual instability modes, such as drift modes and 'trapped-particle' modes. These modes may in principle be controlled by tailoring the stabilizer plasma distribution and/or the radial potential distribution.In the paper the results to date of our studies are summarized and projected to scope out possible fusion-power versions of the K-S T-M.
Proterozoic Geomagnetic Field Geometry
NASA Astrophysics Data System (ADS)
Panzik, J. E.; Evans, D. A.
2011-12-01
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.
Yakov Itin
2007-11-27
The possible extensions of GR for description of fermions on a curved space, for supergravity and for loop quantum gravity require a richer set of 16 independent variables. These variables can be assembled in a coframe field, i.e., a local set of four linearly independent 1-forms. In the ordinary formulation, the coframe gravity does not have any connection to a specific geometry even being constructed from the geometrical meaningful objects. A geometrization of the coframe gravity is an aim of this paper. We construct a complete class of the coframe connections which are linear in the first order derivatives of the coframe field on an $n$ dimensional manifolds with and without a metric. The subclasses of the torsion-free, metric-compatible and flat connections are derived. We also study the behavior of the geometrical structures under local transformations of the coframe. The remarkable fact is an existence of a subclass of connections which are invariant when the infinitesimal transformations satisfy the Maxwell-like system of equations. In the framework of the coframe geometry construction, we propose a geometrical action for the coframe gravity. It is similar to the Einstein-Hilbert action of GR, but the scalar curvature is constructed from the general coframe connection. We show that this geometric Lagrangian is equivalent to the coframe Lagrangian up to a total derivative term. Moreover there is a family of coframe connections which Lagrangian does not include the higher order terms at all. In this case, the equivalence is complete.
Gao, Zhe; Dong, Mei; Wang, Guizhen; Sheng, Pei; Wu, Zhiwei; Yang, Huimin; Zhang, Bin; Wang, Guofu; Wang, Jianguo; Qin, Yong
2015-07-27
To design highly efficient catalysts, new concepts for optimizing the metal-support interactions are desirable. Here we introduce a facile and general template approach assisted by atomic layer deposition (ALD), to fabricate a multiply confined Ni-based nanocatalyst. The Ni nanoparticles are not only confined in Al2 O3 nanotubes, but also embedded in the cavities of Al2 O3 interior wall. The cavities create more Ni-Al2 O3 interfacial sites, which facilitate hydrogenation reactions. The nanotubes inhibit the leaching and detachment of Ni nanoparticles. Compared with the Ni-based catalyst supported on the outer surface of Al2 O3 nanotubes, the multiply confined catalyst shows a striking improvement of catalytic activity and stability in hydrogenation reactions. Our ALD-assisted template method is general and can be extended for other multiply confined nanoreactors, which may have potential applications in many heterogeneous reactions. PMID:26150352
Subsystem functional for confinement physics
NASA Astrophysics Data System (ADS)
Hao, Feng; Mattsson, Ann; Armiento, Rickard
2010-03-01
Recent success of the AM05 [1,2] functional shows that the subsystem functional scheme is a practical framework to construct well-performing functionals in density functional theory (DFT). The idea is to divide the real material system into regions with different characteristic physics that can be described by model systems. In AM05, subsystem functionals based on a surface model system and a uniform electron gas model system are combined to include both the edge and interior physics. By studying a harmonic oscillator model system restricted in one dimension, we are aiming to build a subsystem functional that can include ``confinement physics'' into the scheme. The new model system may help in constructing a more generally accurate functional working for both solid-state and chemical systems. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [1] R. Armiento, A.E. Mattsson, PRB 72, 085108 (2005), [2] A.E. Mattsson et al. JCP 128, 084714 (2008).