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
PREFACE: Water in confined geometries
NASA Astrophysics Data System (ADS)
Rovere, Mauro
2004-11-01
The study of water confined in complex systems in solid or gel phases and/or in contact with macromolecules is relevant to many important processes ranging from industrial applications such as catalysis and soil chemistry, to biological processes such as protein folding or ionic transport in membranes. Thermodynamics, phase behaviour and the molecular mobility of water have been observed to change upon confinement depending on the properties of the substrate. In particular, polar substrates perturb the hydrogen bond network of water, inducing large changes in the properties upon freezing. Understanding how the connected random hydrogen bond network of bulk water is modified when water is confined in small cavities inside a substrate material is very important for studies of stability and the enzymatic activity of proteins, oil recovery or heterogeneous catalysis, where water-substrate interactions play a fundamental role. The modifications of the short-range order in the liquid depend on the nature of the water-substrate interaction, hydrophilic or hydrophobic, as well as on its spatial range and on the geometry of the substrate. Despite extensive study, both experimentally and by computer simulation, there remain a number of open problems. In the many experimental studies of confined water, those performed on water in Vycor are of particular interest for computer simulation and theoretical studies since Vycor is a porous silica glass characterized by a quite sharp distribution of pore sizes and a strong capability to absorb water. It can be considered as a good candidate for studying the general behaviour of water in hydrophilic nanopores. But there there have been a number of studies of water confined in more complex substrates, where the interpretation of experiments and computer simulation is more difficult, such as in zeolites or in aerogels or in contact with membranes. Of the many problems to consider we can mention the study of supercooled water. It is particularly important to understand whether the glass transition temperature could be experimentally accessible for confined water. In this respect the modifications induced by the confinement on the dynamics of water on supercooling are of extreme interest and a number of experimental and computer simulation studies have been devoted in recent years to this topic. This special section contains papers from different groups which have contributed with various experimental and computer simulation techniques to the progress made in the study of water in confined geometry. I thank all of the authors for their stimulating contributions. I am very pleased in particular that Sow-Hsin Chen agreed to contribute since he has done pioneering experimental work on the dynamical properties of confined water upon supercooling, and he is still very active in the field. The work presented by the group of J Swenson concerns also the glass transition of confined water. The Messina group (Crupi et al) is very active in the study of dynamical properties of confined water and they present their results on water in zeolites. From the experimental side there is also a contribution from J Dore's group, one of the first to perform neutron scattering studies on confined water. The work of J Klein looks at the mobility of water molecules confined in subnanometre films. Important contributions on the computer simulation side come from the Geiger group (Brovchenko et al). They performed very accurate simulations of water in nanopores, exploring a large portion of the phase space. Puibasset et al were able to build a very realistic model to simulate water inside Vycor. Zangi et al review the extensive work performed on confined water. Jedlovszky is an expert on the model potential for water and studied how the hydrogen bond network of water can be modified by the presence of an interface. The special issue is intended to stimulate interest and future work on this important subject.
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.
Viral nematics in confined geometries
O. V. Manyuhina; K. B. Lawlor; M. C. Marchetti; M. J. Bowick
2015-06-19
Motivated by recent experiments on the rod-like virus bacteriophage fd, confined to circular and annular domains, we present a theoretical study of structural transitions in these geometries. Using the continuum theory of nematic liquid crystals, we examine the competition between bulk elasticity and surface anchoring, mediated by the formation of topological defects. We show analytically that bulk defects are unstable with respect to defects sitting at the boundary. Moreover, in case of an annulus, whose topology does not require the presence of topological defects, under weak anchoring conditions we find that nematic textures with boundary defects are stable compared to the defect free configurations. Thus our simple approach, with no fitting parameters, suggests a possible symmetry breaking mechanism responsible for the formation of one-, two- and three-fold textures under annular confinement.
Viral nematics in confined geometries.
Manyuhina, O V; Lawlor, K B; Marchetti, M C; Bowick, M J
2015-08-14
Motivated by recent experiments on the rod-like virus bacteriophage fd, confined to circular and annular domains, we present a theoretical study of structural transitions in these geometries. Using the continuum theory of nematic liquid crystals, we examine the competition between bulk elasticity and surface anchoring, mediated by the formation of topological defects. We show analytically that bulk defects are unstable with respect to defects sitting at the boundary. In the case of an annulus, whose topology does not require the presence of topological defects, we find that nematic textures with boundary defects are stable compared to defect-free configurations when the anchoring is weak. Our simple approach, with no fitting parameters, suggests a possible symmetry breaking mechanism responsible for the formation of one-, two- and three-fold textures under annular confinement. PMID:26135676
Confinement of nonneutral plasma in unconventional geometries
Turner, L.
1990-01-01
Our interest in efficient storage of cold, nonneutral plasma has been motivated by the elegant studies on cryogenic nonneutral electron plasmas at UCSD and by the remarkable results obtained from the laser-cooled ion plasmas at the NIST, Boulder, Colorado. Also motivating our study is the perceived need to develop the most expedient means of storing antimatter, whether it be antiprotons for gravitational studies or positrons for a variety of physics experiments and diagnostic purposes. One of the most explored technologies of confining nonneutral plasmas is the Penning trap. The maximum number density of cold nonneutral plasma that can be stored in such a trap is B{sup 2}/2{mu}{sub 0}mc{sup 2}, in which B{sup 2}/2{mu}{sub 0} is the (homogeneous) magnetic energy density and mc{sup 2} is the rest energy of the stored charges. In this paper, we shall present a synopsis of the results of our theoretical exploration of the effect on this hydrostatic limit, the so-called Brillouin'' limit, of altering the geometry of the confining vacuum magnetic field while maintaining the field's azimuthal symmetry. In particular, we shall analyze equilibrium confinement by, first, a poloidal magnetic field, B{sub 4}(r,z){cflx r} + B{sub z}(r,z){cflx z}, and second, a toroidal magnetic field, along with the concomitant electrostatic fields.
Limiting Spectra from Confining Potentials.
ERIC Educational Resources Information Center
Nieto, Michael Martin; Simmons, L. M., Jr.
1979-01-01
The author explains that, for confining potentials and large quantum numbers, the bound-state energies rise more rapidly as a function of n the more rapidly the potential rises with distance. However, the spectrum can rise no faster than n squared in the nonrelativistic case, or n in the relativistic case. (Author/GA)
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 ...
Hertz Potentials and Differential Geometry
Bouas, Jeffrey David
2011-08-08
I review the construction of Hertz potentials in vector calculus starting from Maxwell's equations. From here, I lay the minimal foundations of differential geometry to construct Hertz potentials for a general (spatially compact) Lorentzian...
Plasma confinement. [Physics for magnetic geometries
Boozer, A.H.
1985-03-01
The physics of plasma confinement by a magnetic field is developed from the basic properties of plasmas through the theory of equilibrium, stability, and transport in toroidal and open-ended configurations. The close relationship between the theory of plasma confinement and Hamiltonian mechanics is emphasized, and the modern view of macroscopic instabilities as three-dimensional equilibria is given.
Asymmetrical microbubble streaming in a confined geometry
NASA Astrophysics Data System (ADS)
Tsai, J.-C.; Hansen, David; Hilgenfeldt, Sascha
2007-11-01
Ultrasound-driven oscillating microbubbles situated on a substrate induce steady streaming flows that show great potential in cellular-scale force actuation for bioengineering or in microfluidic applications [1-3]. We have demonstrated for a streaming flow of azimuthal symmetry around a single bubble that the presence of a second wall opposite to the substrate does not compromise the flow speed but instead enhances the circulation efficiency. Additionally, we show here that a continuous spectrum of flow patterns ranging from localized vortex circulations to transport-dominated directional flows can be created by breaking the symmetry either passively (by changing the subtrate topology) or actively (by imposing a large-scale flow field). The spatial confinement provides a dominant lengthscale that simplifies the flow patterns and enhances the transport efficiency. Asymmetrical microbubble streaming, with its capability to fine-tune the relative strength between the circulation and forward transport, offers a continuously adjustable tool for microfluidic applications that demand the simultaneous optimization of mixing rate and transport efficiency. Ref: [1] P. Marmottant and S. Hilgenfeldt, Nature 423, 153 (2003). [2] P. Marmottant and S. Hilgenfeldt, Proc. Natl. Acad. Science USA, 101, 9523 (2004). [3] P. Marmottant, J.-P. Raven, H. Gardeniers, J. G. Bomer, and S. Hilgenfeldt, J. Fluid Mech., vol.568, 109 (2006).
Temperature-resonant cyclotron spectra in confined geometries
Andrey Pototsky; Peter Hänggi; Fabio Marchesoni; Sergey Savel'ev
2011-05-22
We consider a two-dimensional gas of colliding charged particles confined to finite size containers of various geometries and subjected to a uniform orthogonal magnetic field. The gas spectral densities are characterized by a broad peak at the cyclotron frequency. Unlike for infinitely extended gases, where the amplitude of the cyclotron peak grows linearly with temperature, here confinement causes such a peak to go through a maximum for an optimal temperature. In view of the fluctuation-dissipation theorem, the reported resonance effect has a direct counterpart in the electric susceptibility of the confined magnetized gas.
Sedimenting particle-laden flows in confined geometries
Dalziel, Stuart
;Summary This thesis investigates the characteristics of particle-laden flows in confined geometries, such as the flow in wastewater treatment tanks. Particle-laden flows also occur in a variety of geophysical the comparison of the laboratory experiments with wastewater treatment tanks, and specific recommendations
Taming Lévy flights in confined crowded geometries.
Cie?la, Micha?; Dybiec, Bart?omiej; Sokolov, Igor; Gudowska-Nowak, Ewa
2015-04-28
We study two-dimensional diffusive motion of a tracer particle in restricted, crowded anisotropic geometries. The underlying medium is formed from a monolayer of elongated molecules [Cie?la J. Chem. Phys. 140, 044706 (2014)] of known concentration. Within this mesh structure, a tracer molecule is allowed to perform a Cauchy random walk with uncorrelated steps. Our analysis shows that the presence of obstacles significantly influences the motion, which in an obstacle-free space would be of a superdiffusive type. At the same time, the selfdiffusive process reveals different anomalous properties, both at the level of a single trajectory realization and after the ensemble averaging. In particular, due to obstacles, the sample mean squared displacement asymptotically grows sublinearly in time, suggesting a non-Markov character of motion. Closer inspection of survival probabilities indicates, however, that the underlying diffusion is memoryless over long time scales despite a strong inhomogeneity of the motion induced by the orientational ordering. PMID:25933788
Taming Lévy flights in confined crowded geometries
NASA Astrophysics Data System (ADS)
Cie?la, Micha?; Dybiec, Bart?omiej; Sokolov, Igor; Gudowska-Nowak, Ewa
2015-04-01
We study two-dimensional diffusive motion of a tracer particle in restricted, crowded anisotropic geometries. The underlying medium is formed from a monolayer of elongated molecules [Cie?la J. Chem. Phys. 140, 044706 (2014)] of known concentration. Within this mesh structure, a tracer molecule is allowed to perform a Cauchy random walk with uncorrelated steps. Our analysis shows that the presence of obstacles significantly influences the motion, which in an obstacle-free space would be of a superdiffusive type. At the same time, the selfdiffusive process reveals different anomalous properties, both at the level of a single trajectory realization and after the ensemble averaging. In particular, due to obstacles, the sample mean squared displacement asymptotically grows sublinearly in time, suggesting a non-Markov character of motion. Closer inspection of survival probabilities indicates, however, that the underlying diffusion is memoryless over long time scales despite a strong inhomogeneity of the motion induced by the orientational ordering.
Two-body problems with confining potentials
Joseph Day; Joseph McEwen; Zoltan Papp
2009-05-21
A formalism is presented that allows an asymptotically exact solution of non-relativistic and semi-relativistic two-body problems with infinitely rising confining potentials. We consider both linear and quadratic confinement. The additional short-range terms are expanded in a Coulomb-Sturmian basis. Such kinds of Hamiltonians are frequently used in atomic, nuclear, and particle physics.
Confining potential and mass of elementary particles
L. I. Buravov
2014-11-21
In this paper we consider a model in which the masses of elementary particles are formed and stabilized thanks to confining potential, which is caused by recoil momentum at emission of specific virtual bosons by particle itself. The calculation of this confining potential is carried out. It is shown that $\\Phi$(R) may be in the form const $R^3$ or const $R^2$ depending on continuous or discrete nature of the spectrum of emitted bosons.
Diffusion of finite-size particles in confined geometries
Maria Bruna; S. Jonathan Chapman
2012-12-19
The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle's dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion which depends on both the excluded-volume and the narrow confinement. By including both these effects the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined.
Modeling smectic layers in confined geometries: Order parameter and defects
NASA Astrophysics Data System (ADS)
Pevnyi, Mykhailo Y.; Selinger, Jonathan V.; Sluckin, Timothy J.
2014-09-01
We identify problems with the standard complex order parameter formalism for smectic-A (SmA) liquid crystals and discuss possible alternative descriptions of smectic order. In particular, we suggest an approach based on the real smectic density variation rather than a complex order parameter. This approach gives reasonable numerical results for the smectic layer configuration and director field in sample geometries and can be used to model smectic liquid crystals under nanoscale confinement for technological applications.
Modeling smectic layers in confined geometries: order parameter and defects.
Pevnyi, Mykhailo Y; Selinger, Jonathan V; Sluckin, Timothy J
2014-09-01
We identify problems with the standard complex order parameter formalism for smectic-A (SmA) liquid crystals and discuss possible alternative descriptions of smectic order. In particular, we suggest an approach based on the real smectic density variation rather than a complex order parameter. This approach gives reasonable numerical results for the smectic layer configuration and director field in sample geometries and can be used to model smectic liquid crystals under nanoscale confinement for technological applications. PMID:25314465
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.
Trigonometric quark confinement potential of QCD traits
C. B. Compean; M. Kirchbach
2007-08-20
We make the case that the Coulomb- plus linear quark confinement potential predicted by lattice QCD is an approximation to the exactly solvable trigonometric Rosen-Morse potential that has the property to interpolate between the Coulomb- and the infinite wells. We test the predictive power of this potential in the description of the nucleon (considered as a quark-diquark system) and provide analytic expressions for its mass spectrum and the proton electric form factor. We compare the results obtained in this fashion to data and find quite good agreement. We obtain an effective gluon propagator in closed form as the Fourier transform of the potential under investigation.
Random Matrices in Non-confining Potentials
NASA Astrophysics Data System (ADS)
Allez, Romain; Dumaz, Laure
2015-08-01
We consider invariant matrix processes diffusing in non-confining cubic potentials of the form . 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 at a critical value . If , then the potential presents a well near deep enough to confine all the particles inside, and the spectral density is supported on a compact interval. If however, the steady state is in fact dynamical with a macroscopic stationary flux of particles flowing across the system. We prove that this flux displays a second order phase transition at the critical value such that when where is an explicit constant. In the subcritical regime, the eigenvalues allocate according to a stationary density profile with full support in , flanked with heavy tails such that as . Our method applies to other non-confining 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.
Yukawa particles in a confining potential
Girotto, Matheus Levin, Yan; Santos, Alexandre P. dos; Colla, Thiago
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.
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.
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.
Polymer escape from a confining potential
Harri Mökkönen; Timo Ikonen; Tapio Ala-Nissila; Hannes Jónsson
2015-03-26
The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.
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.
Polymer escape from a confining potential.
Mökkönen, Harri; Ikonen, Timo; Jónsson, Hannes; Ala-Nissila, Tapio
2014-02-01
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. PMID:24511979
Confined H(1s) and H(2p) under different geometries
NASA Astrophysics Data System (ADS)
Micca Longo, G.; Longo, S.; Giordano, D.
2015-08-01
In this paper the diffusion Monte Carlo method is applied to the confined hydrogen atom with different confinement geometries. This approach is validated using the much studied spherical and cylindrical confinements and then applied to cubical and squared ones, for which data are not available, as new applications of the method relevant to solid state physics. The energy eigenvalues of the ground state and one low-lying excited state are reported as a function of the characteristic confinement length.
Massive field theory approach for polymer chains in confined geometries
NASA Astrophysics Data System (ADS)
Romeis, D.; Usatenko, Z.
2009-12-01
Using the massive field theory approach directly at fixed dimensions d = 3 we calculated the depletion interaction potential and the depletion force between two repulsive, two inert and one repulsive and one inert wall confining a dilute solution of long flexible polymer chains. The obtained calculations for all cases of polymer-surface interactions were performed for an ideal chain and a real polymer chain with excluded volume interactions (EVI) in the wide slit regime. Besides, we used some assumptions which allowed us to estimate the depletion interaction potential in the region of narrow slit. The obtained results are in very good agreement with previous theoretical investigations and with the results of Monte Carlo simulations for the case of two repulsive walls. Taking into account the Derjaguin approximation we obtained good qualitative agreement with the experimental data for the depletion potential between a spherical colloidal particle of big radius and repulsive wall. The obtained results confirm that the depletion interaction potential and the resulting depletion force between two repulsive walls are weaker for chains with EVI than for ideal chains, because the EVI effectively reduces the depletion effect near the walls.
NASA Astrophysics Data System (ADS)
Yu, Bin; Deng, Jian-Hua; Wang, Zheng; Li, Bao-Hui; Shi, An-Chang
2015-04-01
The self-assembly of symmetric diblock copolymers confined in the channels of variously shaped cross sections (regular triangles, squares, and ellipses) is investigated using a simulated annealing technique. In the bulk, the studied symmetric diblock copolymers form a lamellar structure with period LL. The geometry and surface property of the confining channels have a large effect on the self-assembled structures and the orientation of the lamellar structures. Stacked perpendicular lamellae with period LL are observed for neutral surfaces regardless of the channel shape and size, but each lamella is in the shape of the corresponding channel's cross section. In the case of triangle-shaped cross sections, stacked parallel lamellae are the majority morphologies for weakly selective surfaces, while morphologies including a triangular-prism-shaped B-cylinder and multiple tridentate lamellae are obtained for strongly selective surfaces. In the cases of square-shaped and ellipse-shaped cross sections, concentric lamellae are the signature morphology for strongly selective surfaces, whereas for weakly selective surfaces, stacked parallel lamellae, and several types of folding lamellae are obtained in the case of square-shaped cross sections, and stacked parallel lamellae are the majority morphologies in the case of ellipse-shaped cross sections when the length of the minor axis is commensurate with the bulk lamellar period. The mean-square end-to-end distance, the average contact number between different species and the surface concentration of the A-monomers are computed to elucidate the mechanisms of the formation of the different morphologies. It is found that the resulting morphology is a consequence of competition among the chain stretching, interfacial energy, and surface energy. Our results suggest that the self-assembled morphology and the orientation of lamellae can be manipulated by the shape, the size, and the surface property of the confining channels. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204215, 51302187, 20990234, 20925414, 21204040, and 91227121), the Natural Science Foundation of Tianjin City, China (Grant Nos. 12JCYBJC32500 and 14JCZDJC32100), the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) (Grant No. IRT1257), and the 111 Project. A. C. Shi gratefully acknowledges the supports from the Natural Sciences and Engineering Research Council (NSERC) of Canada.
Hubbard Models in Confined Geometries: Statistical Mechanics of Inhomogeneous Systems
NASA Astrophysics Data System (ADS)
Cone, James David
Optical lattice experiments (OLE) with cold atoms provide an exciting new testing ground for quantum many body models, like the fermion Hubbard model. The conditions of OLE experiments, however, differ in significant ways from our current theoretical models- such as 1) the use of an inhomogeneous potential for trapping atoms and 2) an environment characterized by constant entropy, rather than constant temperature. For experimenters, these differences complicate the identification of phase transitions and comparisons of experimental results with numerical simulations. This research simulates the effects of these experimental constraints with current numerical models and analyzes the impact of these effects on identifying critical phases and phase transitions in OLEs. The results provide potential guidance for OLE experimenters in the exploration of important theoretical questions like the nature and onset of Mott insulating or d-wave super-conducting phases. For the 2D fermion Hubbard model, the research analyzes the impact of several current and proposed methods for trapping atoms in OLEs. Using Quantum Monte Carlo results under constant entropy, we evaluate the effects of these trapping methods on magnetic order and d-wave pairing correlations for the resulting inhomogeneous systems. The goal is to identify the confinement techniques which maximize the likelihood for observing magnetic order or superconductivity in optical lattices
Chan, Derek Y C
Long-Range Electrostatic Attractions between Identically Charged Particles in Confined Geometries colloidal particles that are immersed in an electrolyte and confined by a third charged body.1-13 It has-Landau-Verwey-Over- beek (DLVO),14,15,16 for the pairwise interaction of two isolated identically charged particles, which
tt* Geometry and Closed String Tachyon Potential
Atish Dabholkar; Cumrun Vafa
2002-01-01
We propose a closed string tachyon action including kinetic and potential terms for non-supersymmetric orbifolds. The action is given in terms of solutions to tt* equations which captures the geometry of vacua of the corresponding N = 2 worldsheet theory. In certain cases the solutions are well studied. In case of tachyons of Bbb C\\/Bbb Zn, solutions to affine toda
Spectra generated by a confined softcore Coulomb potential
NASA Astrophysics Data System (ADS)
Hall, Richard L.; Saad, Nasser
2014-08-01
Analytic and approximate solutions for the energy eigenvalues generated by a confined softcore Coulomb potentials of the form a/(r + ?) in d > 1 dimensions are constructed. The confinement is effected by linear and harmonic-oscillator potential terms, and also through "hard confinement" by means of an impenetrable spherical box. A byproduct of this work is the construction of polynomial solutions for a number of linear differential equations with polynomial coefficients, along with the necessary and sufficient conditions for the existence of such solutions. Very accurate approximate solutions for the general problem with arbitrary potential parameters are found by use of the asymptotic iteration method.
Dynamics of laser-blow-off induced Li plume in confined geometry
Kumar, Bhupesh; Singh, R K; Kumar, Ajai
2013-08-15
Dynamics of Li plasma plume created by laser-blow-off technique in air ambient is reported. Plasma plume dynamics and its optical emission are investigated in planar and confined geometries using time resolved shadowgraph imaging and optical emission spectroscopy. Significant differences in the plasma characteristics in confined geometry are quantitatively investigated by comparing the plasma parameters (temperature and density) in free expansion and confined geometry configurations. Dynamics and physical parameters of the primary as well as the reflected shock waves (in confined geometry) and their interactions with expanding plasma are briefly addressed. A large enhancement in the emission intensities of Li I 610.3 nm (2p {sup 2}P{sub 1/2,3/2}? 3d {sup 2}P{sub 3/2,5/2}) and 670.8 nm (2s {sup 2}S{sub 1/2}? 2p {sup 2}P{sub 1/2,3/2}) is correlated with the shock wave dynamics in the two geometries. Strong self reversal in the neutral emission infers an increase in the population density of neutrals within the confined plasma plume.
Crystals and liquid crystals confined to curved geometries
Vinzenz Koning; Vincenzo Vitelli
2014-01-20
This review introduces the elasticity theory of two-dimensional crystals and nematic liquid crystals on curved surfaces, the energetics of topological defects (disclinations, dislocations and pleats) in these ordered phases, and the interaction of defects with the underlying curvature. This chapter concludes with two cases of three-dimensional nematic phases confined to spaces with curved boundaries, namely a torus and a spherical shell.
Evaporation of liquids and solutions in confined geometry.
Clément, F; Leng, J
2004-08-01
We describe a drying setup where a liquid droplet is confined between two circular glass plates and allowed to evaporate. Optical imaging of the shrinking droplet provides the temporal evolution of the solvent volume. For a pure liquid, we measure the diffusion coefficient of the evaporating gas with a good accuracy. For a solution, the slowing down of evaporation by progessive concentration of the solute yields a direct measurement of the solvent activity. PMID:15274550
Studies of Superfluid 3He Confined to a Regular Submicron Slab Geometry, Using SQUID NMR
NASA Astrophysics Data System (ADS)
Casey, Andrew; Córcoles, Antonio; Lusher, Chris; Cowan, Brian; Saunders, John
2006-09-01
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.
Topological superfluids confined in a nanoscale slab geometry
NASA Astrophysics Data System (ADS)
Saunders, John
2013-03-01
Nanofluidic samples of superfluid 3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid 3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of 3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe 3He-B with a surface induced planar distortion. 3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter. Nanofluidic samples of superfluid 3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid 3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of 3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe 3He-B with a surface induced planar distortion. 3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter. Supported by EPSRC (UK) GR/J022004/1 and European Microkelvin Consortium, FP7 grant 228464
Spin probe dynamics of n-hexadecane in confined geometry
NASA Astrophysics Data System (ADS)
Lukešová, Miroslava; Švajdlenková, Helena; Sippel, Pit; Macová, Eva; Berek, Dušan; Loidl, Alois; Bartoš, Josef
2015-02-01
A combined study of the rotational dynamics of the stable free radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and the phase behavior of n-hexadecane (n-HXD) in the bulk and the confined states in a series of silica gels (SG) by means of ESR and DSC is presented. A slow to fast motion transition of the spin probe TEMPO in the bulk n-HXD occurs at T50 G,bulk ? Tm,bulk, i.e., well below the melting temperature due to its trapping and localized mobility in the interlamellar gap of the crystallites [J. Bartoš, H. Švajdlenková, M. Zaleski, M. Edelmann, M. Lukešová, Physica B 430, 99 (2013)]. On the other hand, the dynamics of the TEMPO in the confined systems is strongly slowing down with T50 G (Dpore) >Tm(Dpore) and slightly increases with the pore size Dpore = 60, 100 and 300 Å of the SG's. At the same time, both the corresponding melting temperature, Tm (Dpore), and melting enthalpy, ?Hm (Dpore), decrease with Dpore together with the mutual anti-correlation between T50 G and Tm as a function of the inverse of pore diameter, 1/Dpore. Moreover, the dynamic heterogeneity of the TEMPO in the confined state below T50 G (Dpore) is closely related to the phase transformation. The strong slowing down of the spin probe motion likely results from its preferential localization at the interface layer of the matrix pore due to specific interaction of TEMPO molecules with the polar silanol groups of the SG matrix. This is supported by special study on a series of the variously filled n-HXD/SG systems, other similar experimental findings as well as by theoretical spectral argument.
Modeling exact exchange potential in spherically confined atoms.
Vyboishchikov, Sergei F
2015-10-15
In this work, local exchange potentials corresponding to the Hartree-Fock (HF) electron density have been obtained using the Zhao-Morrison-Parr method for a number of closed-shell confined atoms and ions. The exchange potentials obtained and the resulting density were compared with those given by the Becke-Johnson (BJ) model potential. It is demonstrated that introducing a scaling factor to the BJ potential allows improving the quality of the resulting density. The optimum scaling factor increases with decreasing confinement radius. The performance of Karasiev and Ludeña's SC?-LDA method as well as of the Becke-88 exchange potential for reproducing the HF electron densities in confined atoms has been also examined. © 2015 Wiley Periodicals, Inc. PMID:26255863
Phase separation in binary mixtures confined in a strip geometry
NASA Astrophysics Data System (ADS)
Bhattacharya, Aniket; Rao, Madan; Chakrabarti, Amitabha
1994-01-01
We study the kinetics of phase separation of a model binary fluid confined within a narrow strip in two dimensions by numerically integrating the Cahn-Hilliard-Cook equation. We explore the systematics of the time evolution of domain shapes as a function of temperature and wetting field. The domains exhibit similar configurations as seen in recent Monte Carlo simulations of a related lattice model. We provide a quantitative estimate of the breakdown of power-law growth of domains once the domain size becomes comparable with the strip width, and show the relevance of the model to domain growth in Vycor glasses. Next we argue for the incorporation of an anisotropic kinetic coefficient in the coarse-grained dynamical equations. We find that even the slightest amount of anisotropy modifies the shapes of domains drastically and allows for complete phase separation.
Hysteretic Spin-density-wave Ordering in Confined Geometries
Fullerton, E. E. [San Jose Research Center; Robertson, Lee [ORNL; Prinsloo, A. R. [Rand Afrikaans University, South Africa; Alberts, H, L. [Rand Afrikaans University, South Africa; Bader, S. D. [Argonne National Laboratory (ANL)
2003-01-01
We have measured the antiferromagnetic spin-density-wave (SDW) order in Cr/Cr{sub 97.5}Mn{sub 2.5}(001) superlattices. The Mn doping creates a high Neel temperature layer that confines the incommensurate SDW order within the Cr layers. With temperature cycling we observe a transition from commensurate to incommensurate SDW order and discrete changes in the SDW period. We find that these transitions show significant hysteresis (up to 75 K) when the number of SDW nodes within the Cr layer changes by an odd number, while there is no hysteresis for changes of an even number of nodes. This results from the competition between maintaining the spin structure at the interfaces and introducing a spin slip at the nodes of the Cr SDW.
O. Berk Usta; Anthony J. C. Ladd; Jason E. Butler
2005-01-01
A numerical method to simulate the dynamics of polymer solutions in confined geometries has been implemented and tested. The method combines a fluctuating lattice-Boltzmann model of the solvent [Ladd, Phys. Rev. Lett. 70, 1339 (1993)] with a point-particle model of the polymer chains. A friction term couples the monomers to the fluid [Ahlrichs and Dünweg, J. Chem. Phys. 111, 8225
Self-organization of helically forced MHD flow in confined cylindrical geometries
NASA Astrophysics Data System (ADS)
Roberts, Malcolm; Leroy, Matthieu; Morales, Jorge; Bos, Wouter; Schneider, Kai
2014-12-01
The dynamics of a magnetically forced conducting fluid in confined geometries is studied. A pseudospectral method with volume penalisation is used to solve the resistive magnetohydrodynamic equations. A helical magnetic field is imposed via boundary conditions, which generates a response in the velocity field for large enough magnitudes. Different helical structures are observed in the flow depending on the magnitude and direction of the forcing and the cross-sectional geometry of the fluid domain. A computational technique for finding a solenoidal vector field which can be used in complex geometries is also proposed.
Study of the nonlinear instability of confined geometries
NASA Astrophysics Data System (ADS)
Okawa, Hirotada; Cardoso, Vitor; Pani, Paolo
2014-11-01
The discovery of a "weakly turbulent" instability of anti-de Sitter spacetime supports the idea that confined fluctuations eventually collapse to black holes and suggests that similar phenomena might be possible in asymptotically flat spacetime, for example in the context of spherically symmetric oscillations of stars or nonradial pulsations of ultracompact objects. Here we present a detailed study of the evolution of the Einstein-Klein-Gordon system in a cavity, with different types of deformations of the spectrum, including a mass term for the scalar and Neumann conditions at the boundary. We provide numerical evidence that gravitational collapse always occurs, at least for amplitudes that are three orders of magnitude smaller than Choptuik's critical value and corresponding to more than 105 reflections before collapse. The collapse time scales as the inverse square of the initial amplitude in the small-amplitude limit. In addition, we find that fields with nonresonant spectrum collapse earlier than in the fully resonant case, a result that is at odds with the current understanding of the process. Energy is transferred through a direct cascade to high frequencies when the spectrum is resonant, but we observe both direct- and inverse-cascade effects for nonresonant spectra. Our results indicate that a fully resonant spectrum might not be a crucial ingredient of the conjectured turbulent instability and that other mechanisms might be relevant. We discuss how a definitive answer to this problem is essentially impossible within the present framework.
Binary mixtures of condensates in generic confining potentials
P. Facchi; G. Florio; S. Pascazio; F. V. Pepe
2011-05-12
We study a binary mixture of Bose-Einstein condensates, confined in a generic potential, in the Thomas-Fermi approximation. We search for the zero-temperature ground state of the system, both in the case of fixed numbers of particles and fixed chemical potentials.
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.
Planform geometry and channel migration of confined meandering rivers on the Canadian prairies
NASA Astrophysics Data System (ADS)
Nicoll, Tami J.; Hickin, Edward J.
2010-03-01
The planform geometry and migration behaviour of confined meandering rivers at 23 locations in Alberta and British Columbia are examined. Relationships among planform geometry variables are generally consistent with those described for freely meandering rivers with small but significant differences because of the unique meander pattern of confined meanders. These exceptions are the ratio channel wavelength ( l)/channel width ( w) and the bend curvature ( rm/ w); in these confined meanders, the ratios exceed ( l/ w ? 17; rm/ w = 4.1) the free-meander norms ( l/ w = 8-14; rm/ w = 2-3). In general, these migrating confined meandering rivers do not develop cutoffs, and meander bends appear to migrate downstream as a coherent waveform. Migration rates vary greatly, from 0.01 to 5.8 m/y, consistent with the general distribution of published rates for freely meandering rivers. Attempts to seek correlations between migration rate and channel flow and morphometry data are modestly successful. Stream power offers the best statistical predictor of migration rate, accounting for up to 52% of variance in migration rate, greater than that provided by valley slope (34%), bankfull width (32%), and mean annual flood (30%). Overall, the findings indicate that confined meandering rivers within western Canada may be more usefully regarded as part of a continuum of a meandering river pattern rather than as a unique river planform.
Helium confined to a restricted geometry: A study of lower dimensionality crossover and universality
NASA Astrophysics Data System (ADS)
Kimball, Mark O.
This thesis tests the ideas of finite-size scaling theory using homogeneous confinements in well characterized geometries. We use structures which are homogeneously small in one dimension, thus leading to two-dimensional (2D) crossover; and, structures which are small in all three dimensions leading to 0D crossover. These confinements are created using photolithography of silicon oxide thermally grown on two inch silicon wafers. Two wafers are bonded together to complete the structure and create a cell. High precision heat capacity measurements are made using a modified AC technique which involves oscillating the sample temperature while simultaneously regulating the average cell temperature. The superfluid fraction of helium is also measured in order to test scaling theory. We make use of a superfluid oscillation between a helium reservoir outside the cell and the cell itself. The frequency at resonance is proportional to the amount of fluid in the superfluid phase of the confined helium. We call this Adiabatic Fountain Resonance (AFR) since the mass flow is driven with minimal heat transport. This work also includes the use of 3He-4He mixtures and compares this to previous work with pure 4He. Mixtures are not expected to change the physics except to increase an intrinsic length which characterizes the critical behavior. We find that the heat capacity of mixtures in a planar geometry do not scale with the data of pure 4He in the same geometry unless a metric factor is introduced to the scaling variable of the mixtures. The mixture superfluid density data also do not scale well unless an additional confinement length is included in the analysis. We cannot scale the 0D heat capacity data since we only have one cell with 0D confinement. However, we attempt to scale mixtures and pure 4He data. We find that these data do not scale and that the mixture data for 0D confinement have an unusual behavior below the superfluid transition.
McCune, Matthew A.; Chakraborty, Himadri S. [Department of Chemistry and Physics, Northwest Missouri State University, Maryville, Missouri 64468 (United States); Madjet, Mohamed E. [Institute of Chemistry and Biochemistry, Free University, Fabeckstrasse 36a, D-14195 Berlin (Germany)
2009-07-15
In the photoionization of an atom endohedrally confined in a fullerene the electrons directly ionized from the atom partially reflect from the cage. However, the valence atomic electrons can also eject from the cage collaterally with their direct emission. The reflective and the collateral amplitudes oscillate in the electron's momentum space with frequencies determined by their path differences from the direct amplitude. Resulting cross sections reveal the confining geometry in the Fourier conjugate domain. The frequency pattern distinguishes the atomic emission from the fullerene emission.
Plasmonic mode interactions with organic semiconductor gain media in nano-confined geometries
NASA Astrophysics Data System (ADS)
Goodman, Sarah; O'Carroll, Deirdre M.
2014-10-01
Coupling of gain materials to metallic nanostructures and thin films offers an avenue for amplification of plasmonic modes in both confined and extended geometries. In the past decade, a deeply sub-wavelength analogue to the laser, using surface plasmons instead of photons, has been proposed and demonstrated. Additionally, propagating surface plasmon polaritons on extended metallic films have been amplified using gain media to achieve chip-scale propagation lengths. Here, we investigate a core-shell nanoparticle structure amenable to amplification of resonant surface plasmon modes using a gold nanorod as the core and an organic polymer semiconductor gain medium as the shell. Organic semiconducting polymer gain media are of interest because, unlike laser dye molecules, they do not undergo significant concentration quenching in the solid-state and, therefore, can result in a high chromophore density in the optical near-field of the metal nanostructure. For investigations of resonant surface plasmon mode amplification, we fabricate gold nanorod-F8BT core-shell nanoparticles through a miniemulsion synthesis process. A more distinct threshold in emitted intensity as a function of optical pump energy is observed from these hybrid structures and neat F8BT nanoparticles compared to dissolved F8BT molecules. However, spectral narrowing is not observed from these structures, potentially due to the low heterostructure yield and poor spectral overlap between the absorption and emission bands of the F8BT with the pump laser and the longitudinal surface plasmon resonance of the nanorods, respectively. Future work will focus on increasing heterostructure yield, employing a red-emitting gain material such as MEH-PPV to couple to longitudinal surface plasmon modes and alternative thin-film geometries in which plasmonic mode-emitter interactions can be easier to control.
The capillarity of nanometric water menisci confined inside closed-geometry viral cages
Carrasco, C.; Douas, M.; Miranda, R.; Castellanos, M.; Serena, P. A.; Carrascosa, J. L.; Mateu, M. G.; Marqués, M. I.; de Pablo, P. J.
2009-01-01
We present an investigation of water menisci confined in closed geometries by studying the structural effects of their capillary forces on viruses during the final stage of desiccation. We used individual particles of the bacteriophage ?29 and the minute virus of mice. In both cases the genomic DNA was ejected from the capsid. However, although the structural integrity of the minute virus of mice was essentially preserved, the ?29 capsid underwent a wall-to-wall collapse. We provide evidence that the capillary forces of water confined inside the viruses are mainly responsible for these effects. Moreover, by performing theoretical simulations with a lattice gas model, we found that some structural differences between these 2 viruses may be crucial to explain the different ways in which they are affected by water menisci forces confined at the nanoscale. PMID:19307554
O. Berk Usta; Anthony J. C. Ladd; Jason E. Butler
2005-01-01
A numerical method to simulate the dynamics of polymer solutions in confined geometries has been implemented and tested. The method combines a fluctuating lattice-Boltzmann model of the solvent [Ladd, Phys. Rev. Lett. 70, 1339 (1993)] with a point-particle model of the polymer chains. A friction term couples the monomers to the fluid [Ahlrichs and Du¨nweg, J. Chem. Phys. 111, 8225
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 ...
Three-quark confinement potential from the Faddeev equation
NASA Astrophysics Data System (ADS)
Popovici, C.; Watson, P.; Reinhardt, H.
2011-01-01
In the heavy quark limit of Coulomb gauge QCD and by truncating the Yang-Mills sector to include only dressed two-point functions, an analytic nonperturbative solution to the Faddeev equation for three-quark bound states in the case of equal quark separations is presented. A direct connection between the temporal gluon propagator and the three-quark confinement potential is provided and it is shown that only color-singlet qqq (baryon) states are physically allowed.
NASA Astrophysics Data System (ADS)
Reinmüller, A.; Palberg, T.; Schöpe, H. J.
2013-06-01
A new experimental setup for optical microscopic studies of charged colloidal model systems under confinement between two flat walls is presented. The measurement cell consists of optically flat quartz substrates attached to piezo actuators. Those facilitate fast and flexible adjustment of the confining geometry. Optionally, the local cell height can be quantitatively controlled by in situ interferometric measurements. Proper choice of materials guarantees sufficient chemical inertia against contamination with salt ions. For efficient preparation of charged colloidal suspensions under strongly deionized conditions, the cell can be connected to a conventional pump circuit including a mixed bed ion exchanger column. The usefulness of this setup, in particular for investigating the equilibrium phase behavior of colloids at low background salt concentrations, is demonstrated recalling recent experiments.
S. Condamin; V. Tejedor; O. Benichou
2008-06-03
We consider a random walk in confined geometry, starting from a site and eventually reaching a target site. We calculate analytically the distribution of the occupation time on a third site, before reaching the target site. The obtained distribution is exact, and completely explicit in the case or parallepipedic confining domains. We discuss implications of these results in two different fields: The mean first passage time for the random trap model is computed in dimensions greater than 1, and is shown to display a non-trivial dependence with the source and target positions ; The probability of reaction with a given imperfect center before being trapped by another one is also explicitly calculated, revealing a complex dependence both in geometrical and chemical parameters.
Colloidal spheres confined by liquid droplets: Geometry, physics, and physical chemistry
NASA Astrophysics Data System (ADS)
Manoharan, Vinothan N.
2006-09-01
I discuss how colloidal particles organize when they are confined by emulsion droplets. In these systems, the interplay between surface tension and interparticle repulsion drives the formation of complex, non-crystalline 3D arrangements. These can be classified into three groups: colloidosomes, or Pickering emulsions, structures that form when particles are bound to the interface of a spherical droplet; colloidal clusters, small polyhedral configurations of colloids formed by capillary forces generated in an evaporating emulsion droplet; and supraparticles, ball-shaped crystallites formed in the interior of emulsion droplets. I discuss the preparation, properties, and structure of each of these systems, using relevant results from geometry to describe how the particles organize.
Schneider, Kai
2015-01-01
Immersed boundary methods for computing confined fluid and plasma flows in complex geometries are reviewed. The mathematical principle of the volume penalization technique is described and simple examples for imposing Dirichlet and Neumann boundary conditions in one dimension are given. Applications for fluid and plasma turbulence in two and three space dimensions illustrate the applicability and the efficiency of the method in computing flows in complex geometries, for example in toroidal geometries with asymmetric poloidal cross-sections.
Layer-by-layer deposition of all-nanoparticle multilayers in confined geometries.
DeRocher, Jonathan P; Mao, Pan; Kim, Jun Young; Han, Jongyoon; Rubner, Michael F; Cohen, Robert E
2012-01-01
Nanofluidic arrays containing high-aspect-ratio nanochannels were used as a platform for the deposition of all nanoparticle multilayers. LbL assembly of 6 nm titania and 15 nm silica nanoparticles resulted in conformal multilayers of uniform thickness throughout the nanochannels. These multilayers are inherently nanoporous with void volume fractions of about 0.5. Compared to unconfined assembly of the same materials on flat substrates, thinner multilayer films were observed for the case of deposition within confined channel geometries because of surface charge-induced electrostatic depletion of the depositing species. Additionally, systematic and reproducible bridging of the nanochannels occurred as multilayer assembly progressed, a phenomenon not seen in our earlier work involving polyelectrolytes. This behavior was attributed to relatively weak nanoparticle adsorption and the resulting formation of large aggregates. These results demonstrate a new route by which confined geometries can be coated and even bridged with a nanoporous multilayer without the need for calcination or other postassembly steps to introduce porosity into the conformal coating. PMID:22181001
States of the Dirac Equation in Confining Potentials
Giachetti, Riccardo; Sorace, Emanuele [Dipartimento di Fisica, Universita di Firenze (Italy) and Istituto Nazionale di Fisica Nucleare, Sezione di Firenze (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Firenze (Italy)
2008-11-07
We study the Dirac equation in confining potentials with pure vector coupling, proving the existence of metastable states with longer and longer lifetimes as the nonrelativistic limit is approached and eventually merging with continuity into the Schroedinger bound states. The existence of these states could concern high energy models and possible resonant scattering effects in systems like graphene. We present numerical results for the linear and the harmonic cases and we show that the density of the states of the continuous spectrum is well described by a sum of Breit-Wigner lines. The width of the line with lowest positive energy well reproduces the Schwinger pair production rate for a linear potential: this gives an explanation of the Klein paradox for bound states and a new concrete way to get information on pair production in unbounded, nonuniform electric fields, where very little is known.
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.
Light-Front Holographic QCD and the Confinement Potential
Stanley J. Brodsky; Guy F. de Téramond; Hans Günter Dosch
2013-08-23
Light-Front Hamiltonian theory, derived from the quantization of the QCD Lagrangian at fixed light-front time \\tau = 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 eigensolutions provide the light-front wavefunctions describing 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 Schrodinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. The potential U has a unique form if one requires that the action for zero quark mass remains conformally invariant. The holographic mapping of gravity in AdS space to QCD with a specific soft-wall dilaton yields the same light-front Schrodinger equation. It also gives 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 include a zero-mass pion in the chiral limit, and linear Regge trajectories 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 and the excitation spectra of light-quark hadrons in terms of a single mass parameter. We also 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.
Potential for general relativity and its geometry
NASA Astrophysics Data System (ADS)
Gabadadze, Gregory; Hinterbichler, Kurt; Pirtskhalava, David; Shang, Yanwen
2013-10-01
The unique ghost-free mass and nonlinear potential terms for general relativity are presented in a diffeomorphism and local Lorentz invariant vierbein formalism. This construction requires an additional two-index Stückelberg field, beyond the four scalar fields used in the metric formulation, and unveils a new local SL(4) symmetry group of the mass and potential terms, not shared by the Einstein-Hilbert term. The new field is auxiliary but transforms as a vector under two different Lorentz groups, one of them the group of local Lorentz transformations, the other an additional global group. This formulation enables a geometric interpretation of the mass and potential terms for gravity in terms of certain volume forms. Furthermore, we find that the decoupling limit is much simpler to extract in this approach; in particular, we are able to derive expressions for the interactions of the vector modes. We also note that it is possible to extend the theory by promoting the two-index auxiliary field into a Nambu-Goldstone boson nonlinearly realizing a certain spacetime symmetry, and show how it is “eaten up” by the antisymmetric part of the vierbein.
Protection from Potential Exposure for the Chernobyl New Safe Confinement
Shipler, Dillard B.; Rudko, Vladimir; Batiy, Valeriy; Timmins, Douglas C.; Brothers, Alan J.; Schmidt, John P.; Swearingen, Gary L.; Schmieman, Eric A.
2004-03-24
The Bechtel/EDF/Battelle Consortium has recently completed developing the conceptual design for the Chernobyl New Safe Confinement (NSC). Battelle has the scope of work related to environment and safety of the design. As part of the safety analysis, an analysis was performed to determine the degree of protection to be provided during the construction and 100-year operation period for expected upsets and lower-probability events that would occur from errors, procedures, other human factors, and equipment failures, i.e., ''potential exposures'' other than normal operations. The analysis was based on results of the Preliminary Hazards Analysis. The potential exposure analysis was performed in accordance with existing Ukranian regulations and working processes and procedures in place at the Shelter Object. KSK (a Ukranian Consortium), a subcontractor to the Bechtel/EDF/Battelle Consortium, performed much of the dose analysis. The analysis concluded that potential exposures, outside of those expected during normal operations, would be acceptable and that design criteria and features, and preventative and mitigative measures currently in place at the Shelter would be sufficient to meet operating exposure limits.
Men, Yonghong; Xiao, Peng; Chen, Jing; Fu, Jun; Huang, Youju; Zhang, Jiawei; Xie, Zhengchao; Wang, Wenqin; Chen, Tao
2014-04-29
A simple yet robust approach was exploited to fabricate large-scaled patterned polymer brushes by combining controlled evaporative self-assembly (CESA) in a confined geometry and self-initiated photografting and photopolymerization (SIPGP). Our method was carried out without any sophisticated instruments, free of lithography, overcoming current difficulties in fabricating polymer patterns by using complex instruments. PMID:24702600
NASA Astrophysics Data System (ADS)
Baxamusa, S.; Field, J.; Dylla-Spears, R.; Kozioziemski, B.; Suratwala, T.; Sater, J.
2014-03-01
Growth of high-quality single-crystal hydrogen in confined geometries relies on the in situ formation of seed crystals. Generation of deuterium-tritium seed crystals in a confined geometry is governed by three effects: self-heating due to tritium decay, external thermal environment, and latent heat of phase change at the boundary between hydrogen liquid and vapor. A detailed computation of the temperature profile for liquid hydrogen inside a hollow shell, as is found in inertial confinement fusion research, shows that seeds are likely to form at the equatorial plane of the shell. Radioactive decay of tritium to helium slowly alters the composition of the hydrogen vapor, resulting in a modified temperature profile that encourages seed formation at the top of the shell. We show that the computed temperature profile is consistent with a variety of experimental observations.
Baxamusa, S. Field, J.; Dylla-Spears, R.; Kozioziemski, B.; Suratwala, T.; Sater, J.
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.
ERIC Educational Resources Information Center
Miyazaki, Mikio; Kimiho, Chino; Katoh, Ryuhei; Arai, Hitoshi; Ogihara, Fumihiro; Oguchi, Yuichi; Morozumi, Tatsuo; Kon, Mayuko; Komatsu, Kotaro
2012-01-01
Three-dimensional dynamic geometry software has the power to enhance students' learning of spatial geometry. The purpose of this research is to clarify what potential using three-dimensional dynamic geometry software can offer us in terms of how to develop the spatial geometry curriculum in lower secondary schools. By focusing on the impacts the…
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.
Inverting Asymmetric Confinement Potentials in Core/Thick-Shell Nanocrystals.
Paulite, Melissa; Acharya, Krishna P; Nguyen, Hue Minh; Hollingsworth, Jennifer A; Htoon, Han
2015-02-19
We investigate CdSe/ZnSe core/thick-shell nanocrystals (a.k.a. giant-nanocrystal quantum dots [g-NQDs]) that have an asymmetric electron/hole confinement potential opposite to nonblinking CdSe/CdS g-NQDs. We deconstruct the photon streams into five different photoluminescence (PL) intensity levels and analyze second-order photon correlation (g((2))) traces of each PL intensity level. This analysis allows us to decouple the contribution of exciton charging from the g((2)) experiment and determine the quantum yield of neutral biexciton states to be in the range of ?20-50%, a value comparable to that of CdSe/CdS g-NQDs. We also show that the Auger recombination rate of positive trion states is suppressed compared to that of negative trions. This suppression, however, is shown not to be strong enough to yield complete suppression of PL fluctuations due to the heavy effective mass of holes. Strong intensity fluctuations also result from the fact that hole charging occurs more readily in CdSe/ZnSe g-NQDs than electron charging in CdSe/CdS g-NQDs. PMID:26262490
Resonant dipole-dipole interaction in confined and strong-coupling dielectric geometries
NASA Astrophysics Data System (ADS)
El-Ganainy, Ramy; John, Sajeev
2013-08-01
Using the electromagnetic response function of an electric dipole located within a dielectric geometry, we derive the mathematical equivalence between the classical response and quantum mechanical resonant dipole-dipole interaction between two quantum objects (atoms, quantum dots, etc). Cooperative spontaneous emission likewise emerges from this equivalence. We introduce a practical numerical technique using finite difference time domain for calculating both dipole-dipole interaction and collective spontaneous emission in confined dielectric structures, where strong light-matter coupling might arise. This method is capable of obtaining resonant dipole-dipole interaction over a wide range of frequencies in a single run. Our method recaptures the results of quantum mechanical second order perturbation theory for weak light-matter coupling. In strong coupling situations such as near a photonic band edge, second order Rayleigh-Schrödinger perturbation theory leads to divergences, and instead Brillouin-Wigner perturbation theory is required. This is equivalent to the use of a variational wavefunction to describe the exciton transfer between initial and final states. We introduce a system of coupled classical oscillators, that describes resonant dipole-dipole interaction and vacuum Rabi splitting in the strong-coupling regime, and that provides an effective numerical scheme based on the finite difference time domain method. This includes the effects of quantum entanglement and the correlation of quantum fluctuations. We discuss the crossover to Forster energy transfer when quantum correlations between the dipoles are damped by strong environmental interactions.
Geometry of a Quantized Spacetime: The Quantum Potential Approach
NASA Astrophysics Data System (ADS)
Mirza, Babur M.
2014-03-01
Quantum dynamics in a curved spacetime can be studied using a modified Lagrangian approach directly in terms of the spacetime variables [Mirza, B.M., Quantum Dynamics in Black Hole Spacetimes, IC-MSQUARE 2012]. Here we investigate the converse problem of determining the nature of the background spacetime when quantum dynamics of a test particle is known. We employ the quantum potential formalism here to obtain the modifications introduced by the quantum effects to the background spacetime. This leads to a novel geometry for the spacetime in which a test particle modifies the spacetime via interaction through the quantum potential. We present here the case of a Gaussian wave packet, and a localized quantum soliton, representing the test particle, and determine the corresponding geometries that emerge.
Dynamics of a ±1/2 defect pair in a confined geometry: A thin hybrid aligned nematic cell
NASA Astrophysics Data System (ADS)
Lu, Li-Xia; Zhang, Zhi-Dong
2015-02-01
Confined geometry can change the defect structure and its properties. In this paper, we investigate numerically the dynamics of a dipole of ±1/2 parallel wedge disclination lines in a confined geometry: a thin hybrid aligned nematic (HAN) cell, based on the Landau–de Gennes theory. When the cell gap d is larger than a critical value of 12? (where ? is the characteristic length for order-parameter change), the pair annihilates. A pure HAN configuration without defect is formed in an equilibrium state. In the confined geometry of d ? 12?, the diffusion process is discovered for the first time and an eigenvalue exchange configuration is formed in an equilibrium state. The eigenvalue exchange configuration is induced by different essential reasons. When 10? < d ? 12?, the two defects coalesce and annihilate. The biaxial wall is created by the inhomogeneous distortion of the director, which results in the eigenvalue exchange configuration. When d ? 10?, the defects do not collide and the eigenvalue exchange configuration originates from the biaxial seeds concentrated at the defects. Project supported by the National Natural Science Foundation of China (Grant No. 11374087) and the Key Subject Construction Project of Hebei Province University.
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.
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. PMID:25615113
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.
Levin, Yan
Yukawa particles in a confining potential Matheus Girotto, Alexandre P. dos Santos, Thiago Colla (2014) Yukawa particles in a confining potential Matheus Girotto,1,a) Alexandre P. dos Santos,2,3,b of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show
Unusual large-pitch banding in poly(L-lactic acid): Effects of composition and geometry confinement
Woo, Eamor M.; Lugito, Graecia; Hsieh, Ya-Ting; Nurkhamidah, Siti
2014-02-24
Lamellar patterns and orientations in blends of two crystalline polymers: poly(ethylene oxide) (PEO) and low-molecular-weight poly(L-lactic acid) (PLLA) were investigated using polarizing light optical microscopy (POM), and atomic and scanning electron microscopy (AFM, SEM). Specific etching off of PEO was used to reveal the complex earlier-grown PLLA lamellae patterns with various PEO content in blends. Banding of extremely long pitch (50 ?m) in crystallized PLLA spherulites was induced by two kinetic factors: geometry confinement by top cover and introduction of diluent such as PEO. The mechanisms and correlation among the lamellar assembly, ring bands, and cracks are exemplified. Lamellar patterns and ring-band types in blends were found to vary with respect to not only blend compositions, but also confinement of top-cover.
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.
Dynamics and statistics of wave-particle interactions in a confined geometry.
Gilet, Tristan
2014-11-01
A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors. PMID:25493868
Chan, Derek Y C
Electrical Double-Layer Interaction between Charged Particles near Surfaces and in Confined are presented for the interaction of (i) two particles in the vicinity of a charged flat surface and (ii) two electrolyte concentrations has been reported when the particles are in the vicinity of a charged surface
Animal studies of potential chronic lung disease of workers in swine confinement buildings.
Donham, K J; Leininger, J R
1984-05-01
The pathologic changes in laboratory animals housed in a swine confinement building were studied to predict potential chronic health effects on persons working in these buildings. Rabbits and guinea pigs were maintained for 12 months either in a confined nursery-grower unit (test animals) or in conventional laboratory animal housing (controls). Necropsies and histopathologic examinations were performed on animals that died prematurely or were killed at termination of the study. Blood serum from the animals was examined for antibodies to extracts from swine confinement house dust. The confinement atmosphere was monitored for environmental pollutants. Concentrations of gases and dust in the air of the confinement building were comparable to those found in a typical swine confinement building. Pulmonic lesions seen in the test rabbits and guinea pigs included diffuse interstitial histiocytic pneumonia. Tracheal and nasal turbinate lesions included epithelial hyperplasia and metaplasia, with submucosal infiltration of plasma cells and heterophils. Blood from the test animals contained serum precipitins to dust extract from confinement houses. The presence of precipitins combined with the microscopic appearance of the lungs indicated that an immunologic process, such as hypersensitivity pneumonitis, may be used to explain the basis of the observed lung lesions. The tracheal and turbinate lesions are best explained as a reaction to a chronic low-grade irritation. PMID:6732025
DNA electrophoresis in confined, periodic geometries: A new lakes-straits model
NASA Astrophysics Data System (ADS)
Laachi, Nabil; Dorfman, Kevin D.
2010-12-01
We present a method to study the dynamics of long DNA molecules inside a cubic array of confining spheres, connected through narrow openings. Our method is based on the coarse-grained, lakes-straits model of Zimm and is therefore much faster than Brownian dynamics simulations. In contrast to Zimm's approach, our method uses a standard stochastic kinetic simulation to account for the mass transfer through the narrow straits and the formation of new lakes. The different rates, or propensities, of the reactions are obtained using first-passage time statistics and a Monte Carlo sampling to compute the total free energy of the chain. The total free energy takes into account the self-avoiding nature of the chain as well as confinement effects from the impenetrable spheres. The mobilities of various chains agree with biased reptation theory at low and high fields. At moderate fields, confinement effects lead to a new regime of reptation where the mobility is a linear function of molecular weight and the dispersion is minimal.
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.
Path integral Monte Carlo applications to quantum fluids in confined geometries
Manousakis, Efstratios
2001 Path integral Monte Carlo is an exact simulation method for calculating thermodynamic properties of bosonic systems. Properties such as superfluidity and bose condensation are directly related geometries, such as helium and hydrogen on surfaces and in droplets are reviewed. © 2001 American Institute
Quasi-confined optical phonon modes in a free-standing GaN nanowire with ring geometry
NASA Astrophysics Data System (ADS)
Tan, Qi-Ren; Liu, Cui-Hong
2013-03-01
Within the framework of the dielectric continuum model and Loudons uniaxial crystal model, the quasi-confined (QC) phonon modes and corresponding Fröhlich-like Hamiltonian in GaN nanowires with ring geometry are investigated. The dispersion relations and electron-QC phonon coupling strength are calculated numerically. Results reveal that the dispersions of the QC modes are obvious only when the wave number kz and the azimuthal quantum number m are small. Meanwhile, the behaviors of QC modes reducing to surface optical phonon modes are observed. Moreover, the lower-order QC modes in the higher frequency region make more contributions to the electron-QC phonon coupling strengths. Furthermore, the electron-QC coupling functions sometimes can get the maximum value at certain kz and m, which is attributed to the "modulating" effect of the dielectric functions ratio (?z/?t) due to the anisotropy of the wurtzite nitride crystals.
Quasilinear theory of collisionless Fermi acceleration in a multicusp magnetic confinement geometry
Robert L. Dewar; Carmen I. Ciubotariu
1999-09-30
Particle motion in a cylindrical multiple-cusp magnetic field configuration is shown to be highly (though not completely) chaotic, as expected by analogy with the Sinai billiard. This provides a collisionless, linear mechanism for phase randomization during monochromatic wave heating. A general quasilinear theory of collisionless energy diffusion is developed for particles with a Hamiltonian of the form $H_0+H_1$, motion in the \\emph{unperturbed} Hamiltonian $H_0$ being assumed chaotic, while the perturbation $H_1$ can be coherent (i.e. not stochastic). For the multicusp geometry, two heating mechanisms are identified --- cyclotron resonance heating of particles temporarily mirror-trapped in the cusps, and nonresonant heating of nonadiabatically reflected particles (the majority). An analytically solvable model leads to an expression for a transit-time correction factor, exponentially decreasing with increasing frequency. The theory is illustrated using the geometry of a typical laboratory experiment.
W. Richard Bowen; Paul M. Williams
2002-01-01
Published experimental data has shown a long-range attractive interaction between identical colloidal particles close to a charged surface. However, previous numerical calculations for a capillary geometry, which indicated that such attractions could arise from solution of the non-linear Poisson–Boltzmann equation (PBE) have been shown to be both qualitatively and quantitatively in error. The present paper uses a finite difference method
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.
Free energy and extension of a semiflexible polymer in cylindrical confining geometries
Yingzi Yang; Theodore W. Burkhardt; Gerhard Gompper
2007-04-19
We consider a long, semiflexible polymer, with persistence length $P$ and contour length $L$, fluctuating in a narrow cylindrical channel of diameter $D$. In the regime $D\\ll P\\ll L$ the free energy of confinement $\\Delta F$ and the length of the channel $R_\\parallel$ occupied by the polymer are given by Odijk's relations $\\Delta F/R_\\parallel=A_\\circ k_BTP^{-1/3}D^{-2/3}$ and $R_\\parallel=L[1-\\alpha_\\circ(D/P)^{2/3}]$, where $A_\\circ$ and $\\alpha_\\circ$ are dimensionless amplitudes. Using a simulation algorithm inspired by PERM (Pruned Enriched Rosenbluth Method), which yields results for very long polymers, we determine $A_\\circ$ and $\\alpha_\\circ$ and the analogous amplitudes for a channel with a rectangular cross section. For a semiflexible polymer confined to the surface of a cylinder, the corresponding amplitudes are derived with an exact analytic approach. The results are relevant for interpreting experiments on biopolymers in microchannels or microfluidic devices.
Chen, Zhonghui
Selective manipulation of InAs quantum dot electronic states using a lateral potential confinement-0241 Received 8 July 2002; accepted 4 September 2002 To further the objective of controlled manipulation and excited electron and hole states. The energy states of InAs/In0.15Ga0.85As QDs are manipulated using 10
A POTENTIAL ALGORITHM FOR TARGET CLASSIFICATION IN BISTATIC SONAR GEOMETRIES
MARIO COSCI; ANDREA CAITI; PHILIPPE BLONDEL; NISABHA JAYASUNDERE
The recent evolution in oceanographic sensing and platforms, including the availability of Autonomous Underwater Vehicles (AUVs), is encouraging the investigation of new high-resolution sonar concepts based on multistatic geometries. The rationale behind this concept is that multistatic systems, in particular if the geometry can be adapted with the experiment, can be located in the regions where the scattered signal is
Optical probing of MgZnO/ZnO heterointerface confinement potential energy levels
NASA Astrophysics Data System (ADS)
Solovyev, V. V.; Van'kov, A. B.; Kukushkin, I. V.; Falson, J.; Zhang, D.; Maryenko, D.; Kozuka, Y.; Tsukazaki, A.; Smet, J. H.; Kawasaki, M.
2015-02-01
Low-temperature photoluminescence and reflectance measurements were employed to study the optical transitions present in two-dimensional electron systems confined at MgxZn1-xO/ZnO heterojunctions. Transitions involving A- and B-holes and electrons from the two lowest subbands formed within the confinement potential are detected. In the studied density range of 2.0-6.5 × 1011 cm-2, the inter-subband splitting is measured and the first excited electron subband is shown to be empty of electrons.
Novel steady state of a microtubule assembly in a confined geometry
Bindu S. Govindan; William. B. Spillman, Jr.
2004-01-04
We study the steady state of an assembly of microtubules in a confined volume, analogous to the situation inside a cell where the cell boundary forms a natural barrier to growth. We show that the dynamical equations for growing and shrinking microtubules predict the existence of two steady states, with either exponentially decaying or exponentially increasing distribution of microtubule lengths. We identify the regimes in parameter space corresponding to these steady states. In the latter case, the apparent catastrophe frequency near the boundary was found to be significantly larger than that in the interior. Both the exponential distribution of lengths and the increase in the catastrophe frequency near the cell margin is in excellent agreement with recent experimental observations.
Persistent currents in dipolar Bose-Einstein condensates confined in annular potentials
Malet, F.; Reimann, S. M. [Mathematical Physics, Lund University, LTH, P.O. Box 118, SE-22100 Lund (Sweden); Kavoulakis, G. M. [Technological Educational Institute of Crete, P.O. Box 1939, GR-71004, Heraklion (Greece)
2011-10-15
We consider a dipolar Bose-Einstein condensate confined in an annular potential, with all the dipoles being aligned along some arbitrary direction. In addition to the dipole-dipole interaction, we also assume a zero-range hard-core potential. We investigate the stability of the system against collapse, as well as the stability of persistent currents as a function of the orientation of the dipoles and of the strength of the hard-core interaction.
Seismic behavior of wide-flange steel column with confined potential plastic hinge
Y. Xiao; H. Li; T. Zhou
2009-01-01
This experimental project investigates and validates an innovative method to confine the potential plastic hinge zone of hot-rolled H-shape (or wide-flange) steel column for improved seismic behavior. Based on fundamental mechanics, the concept aims at controlling the local buckling of the flange and web elements of the H-shape steel in the potential plastic hinge region of a column. In the
NASA Astrophysics Data System (ADS)
Scelsi, Lino; Auhl, Dietmar; Klein, Harley; Mackley, Malcolm R.
2008-07-01
Experimental observations on the way High Density Polyethylene (HDPE) and Polypropylene (PP) can crystallize under flow in a Multi-pass Rheometer (MPR) are reported. Both deep and shallow flow geometries were chosen for the rheo-optical study. Preliminary linear viscoelastic rheological tests enabled the temperature window for quiescent crystallization to be established. Flow-induced crystallization (FIC) studies were performed in a temperature regime above the normal quiescent crystallization conditions. In the case of HDPE in a contraction-expansion cell, FIC occurred during flow at the sidewalls of the slit and in localized regions downstream and the processing pressure increased during the piston movement. In the case of PP, flow-induced crystallization was generally observed after flow cessation and the processing pressure did not change during flow. For PP, FIC also occurred preferentially at the walls in the form of elongated crystallites but the fibres gradually emerged after flow cessation. The difference in the FIC behavior was attributed to differences in the crystal growth kinetics of the two materials at the particular super-cooling used. 2D numerical simulations of the polymers flowing in a deep slit geometry were performed using Flowsolve, an Arbitrary Lagrangian Eulerian solver developed at Leeds University (Harlen OG et al., 1995 [10]). The local principal stress difference, orientation and stretch of the molecules in the flow at the onset of crystallization were determined for a range of conditions.
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
2014-01-01
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)
Campos, L. Q. Costa; Apolinario, S. W. S.
2015-01-01
We implement Brownian dynamics to investigate the static properties of colloidal particles confined anisotropically and interacting via a potential which can be tailored in a repulsive-attractive-respulsive fashion as the interparticle distance increases. A diverse number of structural phases are self-assembled, which were classified according to two aspects, that is, their macroscopic and microscopic patterns. Concerning the microscopic phases we found the quasicrystalline, triangular, square, and mixed orderings, where this latter is a combination of square and triangular cells in a 3 ×2 proportion, i.e., the so-called (33,42) Archimedian lattice. On the macroscopic level the system could self-organize in a compact or perforated single cluster surrounded or not by fringes. All the structural phases are summarized in detailed phases diagrams, which clearly show that the different phases are extended as the confinement potential becomes more anisotropic.
Fukushima, Kimichika
2015-01-01
This paper presents analytical eigenenergies for a pair of confined fundamental fermion and antifermion under a linear potential derived from the Wilson loop for the non-Abelian Yang-Mills field. We use basis functions localized in spacetime, and the Hamiltonian matrix of the Dirac equation is analytically diagonalized. The squared system eigenenergies are proportional to the string tension and the absolute value of the Dirac's relativistic quantum number related to the total angular momentum, consistent with the expectation.
Potential optimisation of the ATLAS reconstruction geometry description.
Andrews, Holly
2015-01-01
The offline reconstruction software of high energy physics experiments often uses a simplified geometry and material model in order to speed up the process of material effect integration within the event reconstruction. This geometry model is also often used for fast simulation purposes, in ATLAS for the fast track simulation FATRAS. As part of a 12 week summer project undertaken at CERN, the use of material property maps within the FATRAS software were explored. A new material properties map was developed that relies on less data storage, allowing for a higher level of geometric properties to be stored over a greater range of the geometry. This is done by compressing to an acceptable memory level. A new manipulator tool was also created that is able to correct the quantity of material assigned to individual layers within the tracking geometry via an array of scaling factors for each layer, which leads to more accuracy in reconstruction parameters. This new tool has been developed within the ATLAS offline fra...
Broughton, S. Allen
Introduction Basic Structure Symmetries Labelling and Potential Energy Future Work Geometry from by NSF Award DMR-0304487 #12;Introduction Basic Structure Symmetries Labelling and Potential Energy and Potential Energy local potential energy terms 5 Future Work #12;Introduction Basic Structure Symmetries
NASA Astrophysics Data System (ADS)
Motoyasu, Tatsunori; Namba, Shinichi; Takiyama, Ken
2014-10-01
Spatial distributions of the electric field were measured in inertial-electrostatic confinement plasmas generated in a glided cylindrical hollow cathode in He gas as a function of the applied voltage using laser-induced fluorescence polarization spectroscopy to obtain profiles of the potential and the charge density. With increasing applied voltage, the potential difference between the center of the plasma and the cathode decreased, while a virtual anode due to converging positive ions was clearly appeared at the center of the cathode. These are probably caused by the increase in the number of electrons emitted from the cathode surface due to the increasing ion bombardment with increasing applied voltage.
Edge-mediated skyrmion chain and its collective dynamics in a confined geometry.
Du, Haifeng; Che, Renchao; Kong, Lingyao; Zhao, Xuebing; Jin, Chiming; Wang, Chao; Yang, Jiyong; Ning, Wei; Li, Runwei; Jin, Changqing; Chen, Xianhui; Zang, Jiadong; Zhang, Yuheng; Tian, Mingliang
2015-01-01
The emergence of a topologically nontrivial vortex-like magnetic structure, the magnetic skyrmion, has launched new concepts for memory devices. Extensive studies have theoretically demonstrated the ability to encode information bits by using a chain of skyrmions in one-dimensional nanostripes. Here, we report experimental observation of the skyrmion chain in FeGe nanostripes by using high-resolution Lorentz transmission electron microscopy. Under an applied magnetic field, we observe that the helical ground states with distorted edge spins evolve into individual skyrmions, which assemble in the form of a chain at low field and move collectively into the interior of the nanostripes at elevated fields. Such a skyrmion chain survives even when the width of the nanostripe is much larger than the size of single skyrmion. This discovery demonstrates a way of skyrmion formation through the edge effect, and might, in the long term, shed light on potential applications. PMID:26446692
Effect of the confining potential on the magneto-optical spectrum of a quantum dot
NASA Astrophysics Data System (ADS)
Geerinckx, F.; Peeters, F. M.; Devreese, J. T.
1990-10-01
The energy levels of electrons confined to a circular quantum well with hard walls are calculated in the presence of a perpendicular magnetic field. The results are compared with the case of soft-wall confinement (parabolic potential). There are important differences in the transition energies of the magneto-optical spectrum: (i) in contrast to the parabolic case where only two transition energies are found, in the hard-wall case there are many transitions possible which have different energies. Only a small number of them however have sufficient oscillator strength to be observable; (ii) with increasing magnetic field the energies approach the two-dimensional results much faster than for the soft-wall case. In quantum dots with many electrons we calculate the Fermi energy as a function of the magnetic field.
Nonlinear Poisson-Nernst-Planck equations for ion flux through confined geometries
NASA Astrophysics Data System (ADS)
Burger, M.; Schlake, B.; Wolfram, M.-T.
2012-04-01
The mathematical modelling and simulation of ion transport through biological and synthetic channels (nanopores) is a challenging problem, with direct application in biophysics, physiology and chemistry. At least two major effects have to be taken into account when creating such models: the electrostatic interaction of ions and the effects due to size exclusion in narrow regions. While mathematical models and methods for electrostatic interactions are well-developed and can be transferred from other flow problems with charged particles, e.g. semiconductor devices, less is known about the appropriate macroscopic modelling of size exclusion effects. Recently several papers proposed simple or sophisticated approaches for including size exclusion effects into entropies, in equilibrium as well as off equilibrium. The aim of this paper is to investigate a second potentially important modification due to size exclusion, which often seems to be ignored and is not implemented in currently used models, namely the modification of mobilities due to size exclusion effects. We discuss a simple model derived from a self-consisted random walk and investigate the stationary solutions as well as the computation of conductance. The need of incorporating nonlinear mobilities in high density situations is demonstrated in an investigation of conductance as a function of bath concentrations, which does not lead to obvious saturation effects in the case of linear mobility.
Leandro B. Krott; Marcia C. Barbosa
2013-09-24
Molecular dynamic simulations were employed to study a water-like model confined between hydrophobic and hydrophilic plates. The phase behavior of this system is obtained for different distances between the plates and particle-plate potentials. For both hydrophobic and hydrophilic walls there are the formation of layers. Crystallization occurs at lower temperature at the contact layer than at the middle layer. In addition, the melting temperature decreases as the plates become more hydrophobic. Similarly, the temperatures of maximum density and extremum diffusivity decrease with hydrophobicity.
NSDL National Science Digital Library
Ms. Walker
2008-03-31
Shapes, lines, and more! Here are some fun games to practice geometry and not get bored! Here\\'s a review to help you through the fun... Identify Geometric Shapes and then you will be on your way! After you have reviewed...show me all you know with this Shape Quiz and then all the fun begins!!! Is it a polygon or not? You tell me. Drag them into the bins and we will see! ...
NASA Astrophysics Data System (ADS)
Sussman, Daniel; Schweizer, Ken
2012-02-01
We have developed a first-principles theory of the transverse confinement potential in an entangled needle fluid based on exactly enforcing uncrossability at the two-rod level while self-consistently renormalizing many-particle effects [Sussman & Schweizer PRL 107, 078102 (2011); J. Chem. Phys. 135, 131104 (2011)]. The predicted tube radius and long-time diffusion constant are consistent with the asymptotic reptation scaling laws under quiescent conditions, but in contrast with the usual tube model strong anharmonicities soften the confinement potential in a manner that quantitatively agrees with experiments on heavily entangled F-actin solutions. This weakening of entanglement constraints has multiple dramatic consequences under applied deformation: tube dilation, accelerated reptation, reduction of the transverse entropic barrier, and a critical stress or strain beyond which tube localization is destroyed. The degree-of-entanglement-dependent competition between reptative and transverse-hopping relaxation is established as a function of stress and strain. A mapping between rigid rods and flexible chain systems is also proposed, allowing predictions to be made for the tube diameter, entanglement onset, and transport properties of chain polymer liquids.
Dose reduction potential of the scanning geometry CT D'OR: a simulation study
NASA Astrophysics Data System (ADS)
de las Heras, Hugo; Tischenko, Oleg; Schlattl, Helmut; Xu, Yuan; Hoeschen, Christoph
2009-02-01
The sampling geometry of CT-scanners plays an important role in the reconstruction of images. We have previously reported a test-device that directly collects the Radon data within a special scanning geometry, whose acquired data can be efficiently treated with series expansion algorithms such as, for example, OPED (Orthogonal Polynomial Expansion on Disc). This geometry has the potential of reducing the radiation exposure of the patient by about a factor of two. However, a fourth of the data must be obtained by interpolation within the measured projections. In this contribution, we show by a Monte Carlo simulation that this interpolation has no significant influence on the quality of the reconstructions.
Lagomarsino, Marco Cosentino; Tanase, Catalin; Vos, Jan W.; Emons, Anne Mie C.; Mulder, Bela M.; Dogterom, Marileen
2007-01-01
Microtubules or microtubule bundles in cells often grow longer than the size of the cell, which causes their shape and organization to adapt to constraints imposed by the cell geometry. We test the reciprocal role of elasticity and confinement in the organization of growing microtubules in a confining box-like geometry, in the absence of other (active) microtubule organizing processes. This is inspired, for example, by the cortical microtubule array of elongating plant cells, where microtubules are typically organized in an aligned array transverse to the cell elongation axis. The method we adopt is a combination of analytical calculations, in which the polymers are modeled as inextensible filaments with bending elasticity confined to a two-dimensional surface that defines the limits of a three-dimensional space, and in vitro experiments, in which microtubules are polymerized from nucleation seeds in microfabricated chambers. We show that these features are sufficient to organize the polymers in aligned, coiling configurations as for example observed in plant cells. Though elasticity can account for the regularity of these arrays, it cannot account for a transverse orientation of microtubules to the cell's long axis. We therefore conclude that an additional active, force-generating process is necessary to create a coiling configuration perpendicular to the long axis of the cell. PMID:17098802
Sameer M. Ikhdair
2011-10-03
We obtain the exact energy spectra and corresponding wave functions of the radial Schr\\"odinger equation (RSE) for any (n,l) state in the presence of a combination of psudoharmonic, Coulomb and linear confining potential terms using an exact analytical iteration method. The interaction potential model under consideration is Cornell-modified plus harmonic (CMpH) type which is a correction form to the harmonic, Coulomb and linear confining potential terms. It is used to investigates the energy of electron in spherical quantum dot and the heavy quarkonia (QQ-onia).
Effective potential of the confinement order parameter in the Hamiltonian approach
NASA Astrophysics Data System (ADS)
Reinhardt, Hugo; Heffner, Jan
2013-08-01
The effective potential of the order parameter for confinement is calculated for SU(N) Yang-Mills theory in the Hamiltonian approach. Compactifying one spatial dimension and using a background gauge fixing, this potential is obtained within a variational approach by minimizing the energy density for given background field. In this formulation the inverse length of the compactified dimension represents the temperature. Using Gaussian trial wave functionals we establish an analytic relation between the propagators in the background gauge at finite temperature and the corresponding zero-temperature propagators in Coulomb gauge. In the simplest truncation, neglecting the ghost and using the ultraviolet form of the gluon energy, we recover the Weiss potential. Neglecting the ghost and using for the gluon energy ?(p) the approximate Gribov formula ?(p)?p+M2/p one finds a critical temperature of 3M/?. We explicitly show that the omission of the ghost drastically increases the transition temperature. From the full nonperturbative potential (with the ghost included) we extract a critical temperature of the deconfinement phase transition of 269 MeV for the gauge group SU(2) and 283 MeV for SU(3).
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.
NASA Astrophysics Data System (ADS)
Amendt, Peter
2010-11-01
The generation of strong, self-generated electric fields ( 1-10 GV/m) in direct-drive, inertial-confinement-fusion capsules has been reported [1], prompting the question whether such fields can have observable consequences on target performance. Two anomalies in the inertial confinement fusion database are well known: (1) an observed 2x greater-than-expected deficit of neutrons in an equimolar D^3He fuel mixture compared with hydrodynamically equivalent DD [2] mixtures, and (2) a similar shortfall of neutrons when trace amounts of argon are mixed with DD fuel in indirect-drive implosions [3]. A new mechanism based on barodiffusion (or pressure gradient-driven diffusion) in a plasma is proposed that incorporates the presence of shock-generated electric fields to explain the reported anomalies. For Omega-scale implosions the (low Mach number) return shock has an appreciable scale length over which the lighter DD ions can diffuse away from fuel center. The depletion of DD fuel is estimated and found to yield a corresponding reduction in neutrons, consistent with the anomalies observed in experiments for both argon-doped DD fuels and D^3He equimolar mixtures. The reverse diffusion of the heavier ions towards fuel center also increases the pressure, potentially resulting in lower stagnation pressures and larger imploded cores in agreement with gated self-emission x-ray imaging data. The theory is applied to studying the degree of potential fractionation of THD fuel mixtures for an upcoming ignition tuning campaign on the National Ignition Facility.[4pt] [1] Rygg et al., Science 319, 1223 (2008), Li et al., PRL 100, 225001 (2008)[0pt] [2] Rygg et al., PoP 13, 052702 (2006)[0pt] [3] Lindl et al., PoP 11, 339 (2004).
NASA Astrophysics Data System (ADS)
Rodriguez, Ricardo; Lewis, Winston G.
2014-07-01
Adequately identifying and managing hazards at the workplace can be a tedious task which extends into the realm of uncertainty, probability and prediction models in order to fully comprehend the nature of the hazard. As such, organizations cannot be blamed for knowledge gaps in the training of personnel they contract to ensure a safe and healthy work environment, especially where there are latent hazards. Electromagnetic wave propagation at frequencies in the SAR (specific absorption rate) region is a special concern to authorities involved in setting RF (radiofrequency) and microwave exposure guidelines. Despite that there is no conclusive evidence to suggest that non-ionizing electromagnetic radiation causes adverse health effects other than thermal, no effort should be lost to ensure that workers and the public at large are adequately protected from unnecessary exposure to radiation. Standards however set exposure limits for free space, plane wave propagation but fall short in compiling information on intensities of these waves after they undergo reflection and diffraction from wall surfaces. Waveguide technology has managed to constrain microwaves to remain within set boundaries, with fixed frequencies that force the waves to behave differently to if they were moving in free space. This technology has offered the ability to transport more energy for communication purposes other than transmission lines. The size of a waveguide may be to the order of a few centimetres and can guide RF of wavelengths of the order of centimetres also but what if spaces of larger dimensions are capable of being waveguides and can guide waves of larger wavelengths such as those that correspond to frequencies between 30MHz to 300MHz? Such RF waves belong to the SAR region of the spectrum where strict exposure limits are set for health and safety protection since a standing man acts as a dipole antenna for this radiation and can absorb maximum energy from propagating RF waves. This review visits the likelihood for potential energy build-up due to RF propagation in confined spaces that are of waveguide design but with larger dimensions. Such confined spaces include silos, tanks, pipes, manholes, air-condition ducts, tunnels, wells, engine rooms and operator rooms on board vessels. In these confined spaces waves reflect off of the walls and combine constructively or destructively with incident waves producing reinforcement or cancellation respectively. Where there is reinforcement, the intensity of the wave for a particular distance in accordance with the standard, may exceed the exposure limit for this distance from the source thereby exposing the worker to larger intensities than the accepted limit and presenting a potential health and safety threat.
Three-quark potential and Abelian dominance of confinement in SU(3) QCD
Naoyuki Sakumichi; Hideo Suganuma
2015-08-03
We study the baryonic three-quark (3Q) potential and its Abelian projection in terms of the dual-superconductor picture in SU(3) quenched lattice QCD. The non-Abelian SU(3) gauge theory is projected onto Abelian U(1)$^2$ gauge theory in the maximal Abelian gauge. We investigate the 3Q potential and its Abelian part for more than 300 different patterns of static 3Q systems in total at $\\beta=5.8$ on $16^332$ and at $\\beta=6.0$ on $20^332$ with 1000-2000 gauge configurations. For all the distances, both the 3Q potential and Abelian part are found to be well described by the Y ansatz, i.e., two-body Coulomb term plus three-body Y-type linear term $\\sigma_{3\\mathrm{Q}} L_{\\mathrm{min}}$, where $L_{\\mathrm{min}}$ is the minimum flux-tube length connecting the three quarks. We find equivalence between the three-body string tension $\\sigma_{3\\mathrm{Q}}$ and its Abelian part $\\sigma_{3\\mathrm{Q}}^{\\rm Abel}$ with an accuracy within a few percent deviation, i.e., $\\sigma_{3\\mathrm{Q}} \\simeq \\sigma_{3\\mathrm{Q}}^{\\rm Abel}$, which means Abelian dominance of the quark-confining force in 3Q systems.
Three-quark potential and Abelian dominance of confinement in SU(3) QCD
Naoyuki Sakumichi; Hideo Suganuma
2015-08-26
We study the baryonic three-quark (3Q) potential and its Abelian projection in terms of the dual-superconductor picture in SU(3) quenched lattice QCD. The non-Abelian SU(3) gauge theory is projected onto Abelian U(1)$^2$ gauge theory in the maximal Abelian gauge. We investigate the 3Q potential and its Abelian part for more than 300 different patterns of static 3Q systems in total at $\\beta=5.8$ on $16^332$ and at $\\beta=6.0$ on $20^332$ with 1000-2000 gauge configurations. For all the distances, both the 3Q potential and Abelian part are found to be well described by the Y ansatz, i.e., two-body Coulomb term plus three-body Y-type linear term $\\sigma_{3\\mathrm{Q}} L_{\\mathrm{min}}$, where $L_{\\mathrm{min}}$ is the minimum flux-tube length connecting the three quarks. We find equivalence between the three-body string tension $\\sigma_{3\\mathrm{Q}}$ and its Abelian part $\\sigma_{3\\mathrm{Q}}^{\\rm Abel}$ with an accuracy within a few percent deviation, i.e., $\\sigma_{3\\mathrm{Q}} \\simeq \\sigma_{3\\mathrm{Q}}^{\\rm Abel}$, which means Abelian dominance of the quark-confining force in 3Q systems.
Three-quark potential and Abelian dominance of confinement in SU(3) QCD
NASA Astrophysics Data System (ADS)
Sakumichi, Naoyuki; Suganuma, Hideo
2015-08-01
We study the baryonic three-quark (3Q) potential and its Abelian projection in terms of the dual-superconductor picture in SU(3) quenched lattice QCD. The non-Abelian SU(3) gauge theory is projected onto Abelian U(1 ) 2 gauge theory in the maximal Abelian gauge. We investigate the 3Q potential and its Abelian part for more than 300 different patterns of static 3Q systems in total at ? =5.8 on 16332 and at ? =6.0 on 20332 with 1000-2000 gauge configurations. For all the distances, both the 3Q potential and Abelian part are found to be well described by the Y ansatz, i.e., two-body Coulomb term plus three-body Y-type linear term ?3 QLmin , where Lmin is the minimum flux-tube length connecting the three quarks. We find equivalence between the three-body string tension ?3 Q and its Abelian part ?3Q Abel with an accuracy within a few percent deviation, i.e., ?3 Q??3Q Abel, which means Abelian dominance of the quark-confining force in 3Q systems.
NASA Astrophysics Data System (ADS)
Koz?owska, Justyna; Zale?ny, Robert; Bartkowiak, Wojciech
2014-01-01
In this contribution, the effect of spatial confinement on the linear and nonlinear electrical properties of LiF, LiH, HF and HCl is analyzed based on the results of ab initio quantum chemical calculations. Central to this study is the comparison of different models of spatial confinement. The harmonic oscillator potential of cylindrical symmetry as well as a more sophisticated model, based on the supermolecular approximation, are applied in order to establish the correspondence between the real chemical environment and their approximate representation in the form of analytical potential. In the case of supermolecular approach, the molecular cages are represented by carbon nanotubes and nanotube-like helium clusters. The results of calculations show that the spatial confinement strongly influences the electric properties of investigated molecules.
NASA Astrophysics Data System (ADS)
Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D.; Sebastiani, Daniel
2012-11-01
We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials.
The potential impact of flooding on confined animal feeding operations in eastern North Carolina.
Wing, Steve; Freedman, Stephanie; Band, Lawrence
2002-04-01
Thousands of confined animal feeding operations (CAFOs) have been constructed in eastern North Carolina. The fecal waste pit and spray field waste management systems used by these operations are susceptible to flooding in this low-lying region. To investigate the potential that flood events can lead to environmental dispersion of animal wastes containing numerous biologic and chemical hazards, we compared the geographic coordinates of 2,287 CAFOs permitted by the North Carolina Division of Water Quality (DWQ) with estimates of flooding derived from digital satellite images of eastern North Carolina taken approximately 1 week after Hurricane Floyd dropped as much as 15-20 inches of rain in September 1999. Three cattle, one poultry, and 237 swine operations had geographic coordinates within the satellite-based flooded area. DWQ confirmed 46 operations with breached or flooded fecal waste pits in the same area. Only 20 of these 46 CAFOs were within the satellite-based estimate of the inundated area. CAFOs within the satellite-based flood area were located in 132 census block groups with a population of 171,498 persons in the 2000 census. African Americans were more likely than whites to live in areas with flooded CAFOs according to satellite estimates, but not according to DWQ reports. These areas have high poverty rates and dependence on wells for drinking water. Our analysis suggests that flood events have a significant potential to degrade environmental health because of dispersion of wastes from industrial animal operations in areas with vulnerable populations. PMID:11940456
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.
NASA Astrophysics Data System (ADS)
Guan, Huan; Yao, Peijun; Yu, Wenhai; Wang, Pei; Ming, Hai
2012-11-01
Single quantum dot-cavity system with a deep confinement potential quantum dot is detailedly investigated, with both s- and p-exciton incoherent pump. Through gradually increasing pump rate (about 10-4=ps ˜ 12=ps), the mean photon number shows a linear-dependence on pump power, the photon probability distribution, characterized by g(2)(0), transforms from antibunching to bunching through Poisson, and the spectra go from the doublet to a singlet, the linewidth shows clear reduction in the lasing region. If we increase pump rate further, the mean photon number decreases monotonically to zero, g(2)(0) reaches its maximum value 2, and all the electrons stack at upper lasing level, indicating thermal light generation. The results show, the deep QD-cavity system under s- and p-exciton pump can generate laser although it is not an ideal coherent light, and with only p-exciton pump considered, in spite of the coherent light generated, this pump method is unreasonable to simulate the experimental conditions for the negligible energy spacing between s-exciton and p-exciton.
Azaizeh, Hassan; Kurzbaum, Eyal; Said, Ons; Jaradat, Husain; Menashe, Ofir
2015-10-01
Olive mill wastewater (OMWW) is claimed to be one of the most polluting effluents produced by agro-food industries, providing high contaminants load that encase cytotoxic agents such as phenolic and polyphenolic compounds. Therefore, a significant and continuous stress episode is induced once the mixed liquor of the wastewater treatment plants (WWTP's) is being exposed to OMWW. The use of bio-augmentation treatment procedures can be useful to eliminate or reduce such stress episodes. In this study, we have estimated the use of autochthonous biomass implementation within small bioreactor platform (SBP) particles as a bio-augmentation method to challenge against WWTPs stress episodes. Our results showed that SBP particles significantly reduced the presence of various phenolics: tannic, gallic and caffeic acid in a synthetic medium and in crude OMWW matrix. Moreover, the SBP particles succeeded to biodegrade a very high concentration of phenol blend (3000 mg L(-1)). Our findings indicated that the presence of the SBP microfiltration membrane has reduced the phenol biodegradation rate by 50 % compared to the same suspended culture. Despite the observed reduction in biodegradation rate, encapsulation in a confined environment can offer significant values such as overcoming the grazing forcers and dilution, thus achieving a long-term sufficient biomass. The potential for reducing stress episodes caused by cytotoxic agents through bio-augmentation treatment procedure using the SBP technology is discussed. PMID:26250809
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 ...
NASA Astrophysics Data System (ADS)
Tan, Qi-Ren; Liu, Cui-Hong
2013-12-01
We have investigated quasi-confined (QC) optical resonant Raman scattering in GaN nanowires (NWs) with ring geometry. We consider the Fröhlich electron-phonon interaction in the framework of the dielectric continuum approach. The selection rules are studied. For small ring radius, our results show that the main contribution to the differential cross section (DCS) comes from high-frequency of the QC phonons, with a minor contribution from the LO phonons. The peak of the DCS is mainly attributed to the electron-QC coupling strength can get the maximum value as the anisotropic effect of wurtzite nitride crystal. Moreover, the lower orders of the QC phonons, the larger the DCS.
NASA Astrophysics Data System (ADS)
Padukka, Prabha; Zhou, Hsiao-Ling; Manson, Steven T.
2014-05-01
Relativistic Breit-Pauli R-Matrix calculations of the photoionization cross sections of the inner 2p shell of free Mg and Mg confined in a C60 molecule have been performed. The C60 confinement potential is modeled as an attractive spherical potential of inner radius 5.8 a.u., thickness of 1.89 a.u. and a depth U0 of 0.302 a.u. Multi-configuration wave functions for the final states of the ion core (target states) were obtained using modified MCHF and HF codes. The calculations were performed for a variety of well depths up to 0.302 a.u in order to study the evolution of the photoionization cross section from free Mg to Mg@C60. Particular attention was paid to the autoionizing resonances arising from the excitation 2p1/2 and 2p3/2; the lowest five series are given as 2p5(2 P3/2) ns[3/2], 2p5(2 P1/2) ns[1/2], 2p5(2 P3/2) nd[3/2], 2p5(2 P3/2) nd[1/2], 2p5(2 P1/2) nd[3/2]. The resonances were identified and characterized using the eigenphase derivative technique, the QB method, and quantum defect theory. A complex pattern of changes occur with increasing well depth, with some of the resonances moving to lower photon energy and some to higher. This behavior is explained in terms of how the discrete orbitals are altered by the increasing depth of the well.
Z. Usatenko
2010-12-07
The universal density-force relation is analyzed and the correspondent universal amplitude ratio $B_{real}$ is obtained using the massive field theory approach in fixed space dimensions d=3 up to one-loop order. The layer monomer density profiles of ideal chains and real polymer chains with excluded volume interaction in a good solvent between two parallel repulsive walls, one repulsive and one inert wall are obtained. Besides, taking into account the Derjaguin approximation the layer monomer density profiles for dilute polymer solution confined in semi-infinite space containing mesoscopic spherical particle of big radius are calculated. The last mentioned situation is analyzed for both cases when wall and particle are repulsive and for the mixed case of repulsive wall and inert particle. The obtained results are in good agreement with previous theoretical results and with the results of Monte Carlo simulations.
Mohamed, T.; Mohri, A.; Yamazaki, Y.
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).
cameras, visible diode and array, survey spectrometer Fluctuations Edge Isat and Vf probes, Mirnov coils, Isat, and floating potential probes In development reflectometer for density profile (peak density
NASA Astrophysics Data System (ADS)
Kushwaha, Manvir S.
2014-12-01
Semiconducting quantum dots - more fancifully dubbed artificial atoms - are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement - or the lack of any degree of freedom for the electrons (and/or holes) - in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines' random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level transitions are seen to be forbidden. The spherical quantum dots have an edge over the strictly two-dimensional quantum dots in that the additional (magnetic) quantum number makes the physics richer (but complex). A deeper grasp of the Coulomb blockade, quantum coherence, and entanglement can lead to a better insight into promising applications involving lasers, detectors, storage devices, and quantum computing.
Mech, Agnieszka; Monguzzi, Angelo; Meinardi, Francesco; Mezyk, Jakub; Macchi, Giorgio; Tubino, Riccardo
2010-04-01
A new hybrid material, based on Er(3+) exchanged zeolite L loaded with DFB molecules, is proposed as an efficient emitter in the third telecommunication window. The close proximity between the Er(3+) ions and perfluorinated dyes, induced by the restricted geometry of the zeolite nanochannels, allows sensitized emission at 1.5 mum, with a lifetime >2 orders of magnitude longer than that for classic erbium organic complexes using nonfluorinated ligands. This approach, circumventing the requirement of the creation of real chemical bonds between the organic species and the metal ion, opens the way to using as an efficient antenna, the organic molecules for which the complexation to the metal ions cannot be realized. PMID:20232810
POTENTIAL OF CONFINED ANIMAL FEED OPERATIONS (CAFOS) TO CONTRIBUTE ESTROGENS TO THE ENVIRONMENT
Confined Animal Feed Operations (CAFOs) are a growing industry, with a trend towards fewer operations with higher concentrations of animals. Animals are either fed and/or treated with many different types of pharmaceuticals, including antibiotics and hormones, which can end up in...
Türkcan, Silvan; Masson, Jean-Baptiste; Casanova, Didier; Mialon, Geneviève; Gacoin, Thierry; Boilot, Jean-Pierre; Popoff, Michel R.; Alexandrou, Antigoni
2012-01-01
We track single toxin receptors on the apical cell membrane of MDCK cells with Eu-doped oxide nanoparticles coupled to two toxins of the pore-forming toxin family: ?-toxin of Clostridium septicum and ?-toxin of Clostridium perfringens. These nonblinking and photostable labels do not perturb the motion of the toxin receptors and yield long uninterrupted trajectories with mean localization precision of 30 nm for acquisition times of 51.3 ms. We were thus able to study the toxin-cell interaction at the single-molecule level. Toxins bind to receptors that are confined within zones of mean area 0.40 ± 0.05 ?m2. Assuming that the receptors move according to the Langevin equation of motion and using Bayesian inference, we determined mean diffusion coefficients of 0.16 ± 0.01 ?m2/s for both toxin receptors. Moreover, application of this approach revealed a force field within the domain generated by a springlike confining potential. Both toxin receptors were found to experience forces characterized by a mean spring constant of 0.30 ± 0.03 pN/?m at 37°C. Furthermore, both toxin receptors showed similar distributions of diffusion coefficient, domain area, and spring constant. Control experiments before and after incubation with cholesterol oxidase and sphingomyelinase show that these two enzymes disrupt the confinement domains and lead to quasi-free motion of the toxin receptors. Our control data showing cholesterol and sphingomyelin dependence as well as independence of actin depolymerization and microtubule disruption lead us to attribute the confinement of both receptors to lipid rafts. These toxins require oligomerization to develop their toxic activity. The confined nature of the toxin receptors leads to a local enhancement of the toxin monomer concentration and may thus explain the virulence of this toxin family. PMID:22677383
Messinger-Rapport, B J; Rudy, Y
1990-04-01
The inverse problem in electrocardiography implies the reconstruction of electrical events within the heart from information measured noninvasively on the body surface. Deduction of these electrical events is possible from measured epicardial potentials, and, thus, a noninvasive method of recovering epicardial potentials from body surface data is useful in experimental and clinical studies. In the present study, an inverse method that uses Tikhonov regularization was shown to reconstruct, with good accuracy, important events in cardiac excitation. The inverse procedure was employed on data obtained from a human-torso tank in which a beating canine heart was placed in the correct anatomical position. Comparison with the actual, measured epicardial potentials indicates that positions and shapes of potential features (maxima, minima, zero potential line, saddles, etc.) are recovered with good accuracy throughout the QRS. An error in position of up to 1 cm is typical, while amplitudes are slightly diminished. In addition, application was extended from the above setting, in which the geometry was precisely known and potentials at a large number of leads were measured accurately, to a situation that is more representative of clinical and experimental settings. Effects of inaccuracy in location of the position of the heart were examined. A stylized torso that approximates the actual geometry was designed, and its performance in the inverse computations was evaluated. A systematic method of reduction of the number of leads on the body surface was proposed, and the resulting lead configurations were evaluated in terms of the accuracy of inverse solutions. The results indicate that the inverse problem can be stabilized with respect to different types of uncertainties in measured data and offer promise in the use of the inverse procedure in clinical and experimental situations. PMID:2317885
Potential change in flaw geometry during pressurized-thermal-shock transients
Shum, D.K.M.; Bryson, J.W.; Merkle, J.G.; Keeney-Walker, J.; Dickson, T.L.; Bass, B.R.
1993-04-01
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 the vessel during the transient. In the first part of the study, estimates are obtained based on the assumptions of linear-elastic material response. The thermo-elastic properties of the cladding and base material are explicitly considered. The flaw geometry corresponds to a family of modified-elliptical flaws characterized by the flaw`s half-length to maximum depth (aspect ratio). Requirements for numerical convergence of the finite element results are examined. In the second part of the study, the sensitivity of the numerical results and conclusions obtained in the first part of the study to the following three analysis assumptions are evaluated: (1) Reference flaw geometry along the entire crack front and especially within the cladding region; (2) Linear-elastic versus elastic-plastic description of material response; (3) Base-material-only vs bi-material cladding-base vessel-model assumption.
Potential change in flaw geometry during pressurized-thermal-shock transients
Shum, D.K.M.; Bryson, J.W.; Merkle, J.G.; Keeney-Walker, J.; Dickson, T.L.; Bass, B.R.
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 the vessel during the transient. In the first part of the study, estimates are obtained based on the assumptions of linear-elastic material response. The thermo-elastic properties of the cladding and base material are explicitly considered. The flaw geometry corresponds to a family of modified-elliptical flaws characterized by the flaw's half-length to maximum depth (aspect ratio). Requirements for numerical convergence of the finite element results are examined. In the second part of the study, the sensitivity of the numerical results and conclusions obtained in the first part of the study to the following three analysis assumptions are evaluated: (1) Reference flaw geometry along the entire crack front and especially within the cladding region; (2) Linear-elastic versus elastic-plastic description of material response; (3) Base-material-only vs bi-material cladding-base vessel-model assumption.
K, Rohini; Swathi, R S
2013-07-18
We have considered push-pull molecules, aminonitroacetylene and aminonitrodiacetylene (O2N-(C?C)n-NH2; n = 1 and 2) as the basic units to design a series of molecular aggregates containing favorable hydrogen bonding interactions. Linear, closed, and stacked geometries of dimers, trimers, tetramers, and pentamers formed from these molecules are found to have very good stabilization energies due to the strong hydrogen bonding abilities of the terminal -NO2 and -NH2 groups. The closed hydrogen-bonded assemblies can act as supramolecular hosts for accommodating some molecules and ions as guests. We have been able to find substantial host-guest interaction energies for the complexes of the hydrogen-bonded closed assemblies with some highly reactive molecules like hexahydro-1,3,5-trinitro-s-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), pentafluoroethane (R-125), and difluoromethane (R-32). Further investigations on the interaction of the ions Li(+), Na(+), K(+), Mg(2+), Ca(2+), Al(3+), F(-), Cl(-), and Br(-) with the monomers as well as the oligomers reveal the formation of strong ion-? complexes, unlike the conventional weak ion-? complexes found in similar acetylenic systems without the end groups. This opens up the possibility of tuning the nature of ionic interactions in ?-systems by varying the terminal groups. PMID:23772692
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.
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
Cunningham, Kevin J.; Walker, Cameron; Westcott, Richard L.
2012-01-01
Approximately 210 km of near-surface, high-frequency, marine seismic-reflection data were acquired on the southeastern part of the Florida Platform between 2007 and 2011. Many high-resolution, seismic-reflection profiles, interpretable to a depth of about 730 m, were collected on the shallow-marine shelf of southeastern Florida in water as shallow as 1 m. Landward of the present-day shelf-margin slope, these data image middle Eocene to Pleistocene strata and Paleocene to Pleistocene strata on the Miami Terrace. This high-resolution data set provides an opportunity to evaluate geologic structures that cut across confining units of the Paleocene to Oligocene-age carbonate rocks that form the Floridan aquifer system.Seismic profiles image two structural systems, tectonic faults and karst collapse structures, which breach confining beds in the Floridan aquifer system. Both structural systems may serve as pathways for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability rocks in the Floridan aquifer system. The tectonic faults occur as normal and reverse faults, and collapse-related faults have normal throw. The most common fault occurrence delineated on the reflection profiles is associated with karst collapse structures. These high-frequency seismic data are providing high quality structural analogs to unprecedented depths on the southeastern Florida Platform. The analogs can be used for assessment of confinement of other carbonate aquifers and the sealing potential of deeper carbonate rocks associated with reservoirs around the world.
J. C. N. Carvalho; W. P. Ferreira; G. A. Farias; F. M. Peeters
2010-06-10
We consider a classical system of two-dimensional (2D) charged particles, which interact through a repulsive Yukawa potential $exp(-r/\\lambda)/r$, confined in a parabolic channel which limits the motion of the particles in the $y$-direction. Along the $x$-direction, the particles are also subject to a periodic potential substrate. The ground state configurations and the normal mode spectra of the system are obtained as function of the periodicity and strength of the periodic potential ($V_0$), and density. An interesting set of tunable ground state configurations are found, with first and second order structural transitions between them. A magic configuration with particles aligned in each minimum of the periodic potential is obtained for V_0 larger than some critical value which has a power law dependence on the density. The phonon spectrum of different configurations were also calculated. A localization of the modes into a small frequency interval is observed for a sufficient strength of the periodic potential. A tunable band-gap is found as a function of $V_0$. This model system can be viewed as a generalization of the Frenkel and Kontorova model.
INFLUENCE OF END POTENTIAL PLATES ON PLASMA HEATING AND CONFINEMENT Sergey Yu. Taskaev
Taskaev, Sergey Yur'evich
is Fig. 1. Scheme of AMBAL-M experiments. 1-- mirror coils, 2 -- gun solenoid, 3 -- plasma gun, 4 additional heating in an open trap AMBAL-M from arc source (gun) located behind the mirror [1]. The plasma will be formulated. Note that end potential plates in this very experiment mean potential electrodes of a plasma gun
Holographic description of confinement and screening through brane cosmology
F. A. Brito; D. C. Moreira
2014-12-23
We compute the holographic quark potential in the realm of brane cosmology. We show that under certain conditions the very geometry due to an inflationary 3-brane induces a D3-D7-brane system. The cosmological constant that appears involved in the original geometry is attributed to the D7-brane position itself in its embedding process. We address the issues of confinement at low distances, screening effects at sufficiently large distances, and quark condensate.
On the twisted chiral potential in 2d and the analogue of rigid special geometry for 4-folds
NASA Astrophysics Data System (ADS)
Kaste, Peter
1999-06-01
We discuss how to obtain an N = (2,2) supersymmetric SU(3) gauge theory in two dimensions via geometric engineering from a Calabi-Yau 4-fold and compute its non-perturbative twisted chiral potential tilde W(?). The relevant compact part of the 4-fold geometry consists of two intersecting Bbb P1's fibered over Bbb P2. The rigid limit of the local mirror of this geometry is a complex surface that generalizes the Seiberg-Witten curve and on which there exist two holomorphic 2-forms. These stem from the same meromorphic 2-form as derivatives w.r.t. the two moduli, respectively. The middle periods of this meromorphic form give directly the twisted chiral potential. The explicit computation of these and of the four-point Yukawa couplings allows for a non-trivial test of the analogue of rigid special geometry for a 4-fold with several moduli.
The whistling potentiality of an orifice in a confined flow using an energetic criterion
NASA Astrophysics Data System (ADS)
Testud, P.; Aurégan, Y.; Moussou, P.; Hirschberg, A.
2009-09-01
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 on the orifice thickness and the orifice jet velocity. It appears to depend on the Reynolds number and on the ratio of orifice to pipe diameters. Tests are performed to compare theoretically and experimentally the potential whistling frequency to the actual whistling frequency. They are found to coincide within the measurement uncertainty.
NASA Astrophysics Data System (ADS)
Göktürkler, G.; Balkaya, Ç.
2012-10-01
Three naturally inspired meta-heuristic algorithms—the genetic algorithm (GA), simulated annealing (SA) and particle swarm optimization (PSO)—were used to invert some of the self-potential (SP) anomalies originated by some polarized bodies with simple geometries. Both synthetic and field data sets were considered. The tests with the synthetic data comprised of the solutions with both noise-free and noisy data; in the tests with the field data some SP anomalies observed over a copper belt (India), graphite deposits (Germany) and metallic sulfide (Turkey) were inverted. The model parameters included the electric dipole moment, polarization angle, depth, shape factor and origin of the anomaly. The estimated parameters were compared with those from previous studies using various optimization algorithms, mainly least-squares approaches, on the same data sets. During the test studies the solutions by GA, PSO and SA were characterized as being consistent with each other; a good starting model was not a requirement to reach the global minimum. It can be concluded that the global optimization algorithms considered in this study were able to yield compatible solutions with those from widely used local optimization algorithms.
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.
One-dimensional extended Bose Hubbard model with a confining potential: a DMRG analysis
NASA Astrophysics Data System (ADS)
Urba, Laura; Lundh, Emil; Rosengren, Anders
2006-12-01
The extended Bose-Hubbard model in a quadratic trap potential is studied using a finite-size density-matrix renormalization group method (DMRG). We compute the boson density profiles, the local compressibility and the hopping correlation functions. We observe the phase separation induced by the trap in all the quantities studied and conclude that the local density approximation is valid in the extended Bose-Hubbard model. From the plateaus obtained in the local compressibility it was possible to obtain the phase diagram of the homogeneous system which is in agreement with previous results.
Persistent currents in a two-component Bose-Einstein condensate confined in a ring potential
J. Smyrnakis; M. Magiropoulos; Nikolaos K. Efremidis; G. M. Kavoulakis
2014-12-10
We present variational and numerical solutions for the problem of stability of persistent currents in a two-component Bose-Einstein condensate of distinguishable atoms which rotate in a ring potential. We consider the general class of solutions of constant density in the two components separately, thus providing an alternative approach of the solution of the same problem given recently by Zhigang Wu and Eugene Zaremba [Phys. Rev. A {\\bf 88}, 063640 (2013)]. Our approach provides a physically transparent solution of this delicate problem. Finally, we give a unified and simple picture of the lowest-energy state of the system for large values of the coupling.
Exciton states and interband absorption of cylindrical quantum dot with Morse confining potential
NASA Astrophysics Data System (ADS)
Hayrapetyan, D. B.; Kazaryan, E. M.; Kotanjyan, T. V.; Tevosyan, H. Kh.
2015-02-01
In this paper the exciton and electron sates in cylindrical quantum dot with Morse potential made of GaAs are studied. For the regime of strong size quantization, energy spectrum with the parabolic approximation case are compared. For strong and weak size quantization regimes analytic expressions for the particle energy spectrum, absorption coefficient and dependencies of effective threshold frequencies of absorption on the geometrical parameters quantum dot are obtained. For the intermediate size quantization regime the problem solved in the framework of variation method. The selection rules corresponding to different transitions between quantum levels are found. The size dispersion distribution of growing quantum dots by the radius and height by two experimentally realizing distribution functions have been taken into account. Distribution functions of Gauss, Lifshits-Slezov have been considered.
Lourenco, Stella F; Cabrera, Janine
2015-12-01
Accumulating evidence demonstrates that humans and other animals use geometric information, such as the shape of a surrounding space, to recover from disorientation. Less clear is to what extent human children integrate geometry with featural cues, such as the color of walls within an enclosed space, for this purpose. One view holds that reorientation relies on a cognitive module that processes geometric information independently of features. Here we provide evidence against this position by demonstrating that prior exposure to features within a kite-shaped space facilitated the use of geometry in 3- and 4-year-old children, as has been shown with nonhuman animals. Children were tasked with localizing a hidden object within a kite space following disorientation. Their performance was compared across two blocks of trials. We found that children first exposed to features (two black walls and two white walls) within the kite space (first block) were subsequently better at relying on the space's geometry to localize the target object (second block) than children not previously exposed to features. Follow-up experiments ruled out nonspecific effects of practice and attention. Not only did featural cues interact with the processing of geometry, but also features specifically enhanced children's representations of the space's geometry, which they used for reorientation. We suggest that this potentiation of geometry was possible because the placement of wall colors highlighted the major axis of the kite space, which may be critical for aiding the encoding of global shape or for maintaining the representation of a complex geometry in memory. PMID:26254274
Singh, Gargi; Pruden, Amy; Widdowson, Mark A
2012-06-01
A field survey was conducted following the Deepwater Horizon blowout and it was noted that resulting coastal petroleum deposits possessed distinct geometries, ranging from small tar balls to expansive horizontal oil sheets. A subsequent laboratory study evaluated the effect of oil deposit geometry on localized gradients of electron acceptors and microbial community composition, factors that are critical to accurately estimating biodegradation rates. One-dimensional top-flow sand columns with 12-h simulated tidal cycles compared two contrasting geometries (isolated tar "balls" versus horizontal "sheets") relative to an oil-free control. Significant differences in the effluent dissolved oxygen and sulfate concentrations were noted among the columns, indicating presence of anaerobic zones in the oiled columns, particularly in the sheet condition. Furthermore, quantification of genetic markers of terminal electron acceptor and catabolic processes via quantitative polymerase chain reaction of dsrA (sulfate-reduction), mcrA (methanogenesis), and cat23 (oxygenation of aromatics) genes in column cores suggested more extensive anaerobic conditions induced by the sheet relative to the ball geometry. Denaturing gradient gel electrophoresis similarly revealed that distinct gradients of bacterial communities established in response to the different geometries. Thus, petroleum deposit geometry impacts local dominant electron acceptor conditions and may be a key factor for advancing attenuation models and prioritizing cleanup. PMID:22574781
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...
Sotomayor, N. M.; Davila, L. Y. D.; Lima, B. C.; Gusev, G. M.
2013-12-04
The classical dynamics of ballistic non-interacting electrons confined to a narrow electrostatic potential well with corrugated barriers in uniform magnetic field was numerically studied. Trajectories in phase space were analyzed and longitudinal and transversal resistivities were calculated. Commensurability oscillations and negative magnetoresistance similar to those found in antidot lattice devices were observed.
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).
Baldwin, David E. (Danville, CA); Logan, B. Grant (Danville, CA)
1981-01-01
The invention provides a method and apparatus for raising the potential of a magnetic mirror cell by pumping charged particles of the opposite sign of the potential desired out of the mirror cell through excitation, with the pumping being done by an externally imposed field at the bounce frequency of the above charged particles. These pumped simple mirror cells then provide end stoppering for a center mirror cell for the tandem mirror plasma confinement apparatus. For the substantially complete pumping case, the end plugs of a tandem mirror can be up to two orders of magnitude lower in density for confining a given center mirror cell plasma than in the case of end plugs without pumping. As a result the decrease in recirculating power required to keep the system going, the technological state of the art required, and the capital cost are all greatly lowered.
Turbulence in Magnetically Confined Plasmas
NASA Astrophysics Data System (ADS)
McKee, G. R.
2012-10-01
Experimental characterization of plasma fluctuations has lead to significant insights into the dynamics of turbulent transport processes in magnetically confined fusion plasmas. Fluctuations on the scale of the ion gyroradius result in cross-field transport of particles, energy and momentum at rates that significantly exceed collisional (neoclassical) transport. The energy confinement time and, ultimately, fusion power are thus strongly dependent on this turbulent-driven transport. Turbulent eddy structures are found to be highly anisotropic (k||k), with the magnetic field defining a symmetry direction: parallel wavelengths scale with machine size, while perpendicular wavelengths scale with gyroradius. Measurement techniques using optical, microwave, beam, and laser-based methods have been developed to remotely probe relevant fluctuations in density, temperature, potential and velocity, including density imaging. Measured fluctuation characteristics are generally consistent with gyrokinetic simulations of drift wave turbulence: correlation lengths scale with ion gyroradius (?I); amplitudes scale with &*circ;(=?I/a); decorrelation rates scale with the acoustic timescale, ?c˜a/cs; and wavenumber spectra peak near k??I˜0.25 and kr?I˜0. Measurements of potential fluctuations and poloidal turbulence flows show evidence for n=0, m=0 zonal flows, including the coherent geodesic acoustic mode. These nonlinearly driven flows saturate turbulence via flow shearing. Such flows appear crucial to L-H confinement transitions and core barrier formation. Dependencies of turbulence on critical transport parameters will be reviewed in tokamak, stellarator and spherical torus geometries. Understanding these dependencies, as well as challenging and validating simulations, will be crucial to confidently predicting transport and confinement in burning plasmas.
Minimizing manganin/system noise for potential use in small geometry experiments
Phillips, D; May, C; Vandersall, K; Garcia, F
2008-10-02
Manganin gauges are piezo resistive devices often used for pressure measurements on larger, planer impact experiments. These gauges function in this capacity as a result of their ability to change resistance in a consistent fashion relative to the pressure exerted against them. Pressures to 400 kbar have been reliably recorded (H.C. Vantine et al.[1]). Because the mini-manganin is significantly physically smaller than other types, there has been interest in the ability to place these gauges on small geometry (detonator) type experiments. Of primary concern is that the detonator shock front has significant curvature associated with it--especially at small geometries--and that this curvature will cause unknown distortion (stretching) of the manganin gauge and therefore may indicate erroneous data. A problem encountered while configuring this experiment was noise as a result of the proximity and high current levels of the fireset to the manganin gauge. Initial results indicate noise on the order of 130 mV peak-to-peak (p-p) and running as long as the CVR signal from the ringdown charge voltage of 775 V. These noise problems significantly worsened while discharging the full charge voltage of 1500 V on the fireset through the chip slapper.
M. L. Glasser; L. M. Nieto
2015-05-17
Motivated by current interest in quantum confinement potentials, especially with respect to the Stark spectroscopy of new types of quantum wells, we examine several novel one-dimensional singular oscillators. A Green function method is applied, the construction of the necessary resolvents is reviewed and several new ones are introduced. In addition, previous work on the singular harmonic oscillator model, introduced by Avakian et al. is reproduced to verify the method and results. A novel features is the determination of the spectra of asymmetric hybrid linear and quadratic potentials. As in previous work, the singular perturbations are modeled by delta functions.
A geometric approach to confining a Dirac neutral particle in analogous way to a quantum dot
Knut Bakke
2012-10-31
We discuss a geometric approach to confining a Dirac neutral particle with a permanent magnetic dipole moment interacting with external fields to a hard-wall confining potential in the Minkowski spacetime through noninertial effects. We discuss the behaviour of external fields induced by noninertial effects, and a case where relativistic bound states can be achieved in analogous way to having a Dirac particle confined to a quantum dot. We show that this confinement of a Dirac neutral particle analogous to a quantum dot arises from noninertial effects that give rise to the geometry of the manifold playing the role of a hard-wall confining potential. We also discuss the possible use of this mathematical model in studies of noninertial effects on condensed matter systems described by the Dirac equation.
NASA Ames potential flow analysis (POTFAN) geometry program (POTGEM), version 1
NASA Technical Reports Server (NTRS)
Medan, R. T.; Bullock, R. B.
1976-01-01
A computer program known as POTGEM is reported which has been developed as an independent segment of a three-dimensional linearized, potential flow analysis system and which is used to generate a panel point description of arbitrary, three-dimensional bodies from convenient engineering descriptions consisting of equations and/or tables. Due to the independent, modular nature of the program, it may be used to generate corner points for other computer programs.
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
Colloidal glass transition observed in confinement
Carolyn R. Nugent; Kazem V. Edmond; Hetal N. Patel; Eric R. Weeks
2007-05-16
We study a colloidal suspension confined between two quasi-parallel walls as a model system for glass transitions in confined geometries. The suspension is a mixture of two particle sizes to prevent wall-induced crystallization. We use confocal microscopy to directly observe the motion of colloidal particles. This motion is slower in confinement, thus producing glassy behavior in a sample which is a liquid in an unconfined geometry. For higher volume fraction samples (closer to the glass transition), the onset of confinement effects occurs at larger length scales.
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
NASA Astrophysics Data System (ADS)
Pal, Hridis Kumar; Shukla, Alok
2008-08-01
A set of weakly interacting spin- 1/2 > Fermions, confined by a harmonic oscillator potential, and interacting with each other via a contact potential, is a model system which closely represents the physics of a dilute gas of two-component fermionic atoms confined in a magneto-optic trap. In the present work, our aim is to present a Fortran 90 computer program which, using a basis set expansion technique, solves the Hartree-Fock (HF) equations for spin- 1/2 > Fermions confined by a three-dimensional harmonic oscillator potential, and interacting with each other via pair-wise delta-function potentials. Additionally, the program can also account for those anharmonic potentials which can be expressed as a polynomial in the position operators x, y, and z. Both the restricted-HF (RHF), and the unrestricted-HF (UHF) equations can be solved for a given number of Fermions, with either repulsive or attractive interactions among them. The option of UHF solutions for such systems also allows us to study possible magnetic properties of the physics of two-component confined atomic Fermi gases, with imbalanced populations. Using our code we also demonstrate that such a system exhibits shell structure, and follows Hund's rule. Program summaryProgram title: trap.x Catalogue identifier: AEBB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 17 750 No. of bytes in distributed program, including test data, etc.: 205 138 Distribution format: tar.gz Programming language: mostly Fortran 90 Computer: PCs—SUN, HP Alpha, IBM Operating system: Linux, Solaris, Tru64, AIX Classification: 7.7 Nature of problem: The simplest description of a spin 1/2 >; trapped system at the mean field level is given by the Hartree-Fock method. This program presents an efficient approach to solving these equations. Additionally, this program can solve for time-independent Gross-Pitaevskii and Hartree-Fock equations for bosonic atoms confined in a harmonic trap. Thus the combined program can handle mean-field equations for both the Fermi and the Bose particles. Solution method: The solutions of the Hartree-Fock equation corresponding to the Fermi systems in atomic traps are expanded as linear combinations of simple-harmonic oscillator eigenfunctions. Thus, the Hartree-Fock equations which comprise a set of nonlinear integro-differential equations, are transformed into a matrix eigenvalue problem. Thereby, solutions are obtained in a self-consistent manner, using methods of computational linear algebra. Running time: The run times of example jobs are from a few seconds to a few minutes. For jobs involving very large basis sets, the run time can extend into hours.
Steven Kenneth Kauffmann
2010-05-06
For Abelian gauge theory a properly relativistic gauge is developed by supplementing the Lorentz condition with causal determination of the time component of the four-vector potential by retarded Coulomb transformation of the charge density. This causal Lorentz gauge agrees with the Coulomb gauge for static charge densities, but allows the four-vector potential to have a longitudinal component that is determined by the time derivative of the four-vector potential's time component. Just as in Coulomb gauge, the two transverse components of the four-vector potential are its sole dynamical part. The four-vector potential in this gauge covariantly separates into a dynamical transverse four-vector potential and a nondynamical timelike/longitudinal four-vector potential, where each of these two satisfies the Lorentz condition. In fact, analogous partition of the conserved four-current shows each to satisfy a Lorentz-condition Maxwell equation system with its own conserved four-current. Because of this complete separation, either of these four-vector potentials can be tinkered with without affecting its counterpart. Since it satisfies the Lorentz condition, the nondynamical four-vector potential times a constant with dimension of inverse length squared is itself a conserved four-current, and so can be fed back into its own source current, which transforms its time component into an extended Yukawa, with both exponentially decaying and exponentially growing components. The latter might be the mechanism of quark-gluon confinement: in non-Abelian color gauge theory the Yukawa mixture ratio ought to be tied to color, with palpable consequences for "colorful" hot quark-gluon plasmas.
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.
NASA Astrophysics Data System (ADS)
Mack, Tobias; Cierpka, Christian; Kähler, Christian J.
2012-11-01
Astigmatism-PTV is a method that allows to measure with a single camera the fully three-dimensional, three-component velocity field. The technique is ideally suited for microfluidic velocity measurements without errors due to in-plane and out-of-plane averaging (Cierpka et al. Meas Scie Tech 21, 2010). Recently it was shown, that the interface between two fluids or the surrounding fluid and droplets or bubbles can be estimated as well with the technique (Rossi et al., Meas Scie Tech 22, 2010). In this contribution the advantages of both techniques are combined to measure the shape of a droplet inside a micro channel along with the internal 3D flow field of the droplet induced by the surrounding fluid. For the current investigation, particles were only distributed within oil-droplets. Therefore the shape of the droplet could be later reconstructed by the volumetric particle positions and the velocity can be estimated tracking the same particles in consecutive frames of the same dataset. The procedure allows the simultaneous determination of the shape and the droplet velocity as well as the inner flow field and offers a great potential for current research.
Kimichika Fukushima; Hikaru Sato
2015-07-27
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 lowest eigenenergy (as a function of the relativistic quantum number when the rotational energy is large compared to the composite particle masses) is 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.
NASA Astrophysics Data System (ADS)
Amitai, A.; Holcman, D.
2013-06-01
Is it possible to extract the size and structure of chromosomal territories (confined domain) from the encounter frequencies of chromosomal loci? To answer this question, we estimate the mean time for two monomers located on the same polymer to encounter, which we call the mean first encounter time in a confined microdomain (MFETC). We approximate the confined domain geometry by a harmonic potential well and obtain an asymptotic expression that agrees with Brownian simulations for the MFETC as a function of the polymer length, the radius of the confined domain, and the activation distance radius ? at which the two searching monomers meet. We illustrate the present approach using chromosome capture data for the encounter rate distribution of two loci depending on their distances along the DNA. We estimate the domain size that restricts the motion of one of these loci for chromosome II in yeast.
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
Dynamics of supercooled water in confined geometry
R. Bergman; J. Swenson
2000-01-01
As with most liquids, it is possible to supercool water; this generally involves cooling the liquid below its melting temperature (avoiding crystallization) until it eventually forms a glass. The viscosity and related relaxation times (tau) of glass-forming liquids typically show non-Arrhenius temperature (T) dependencies. Liquids with highly non-Arrhenius behaviour in the supercooled region are termed `fragile'. In contrast, liquids whose
Geng, Dongsheng; Ding, Ning; Hor, T S Andy; Chien, Sheau Wei; Liu, Zhaolin; Zong, Yun
2015-10-01
With new chemistry and advantageous configuration, the lithium-oxygen (Li-O2 ) battery promises a much higher specific energy than traditional lithium-ion batteries. The limited understanding on the complicated battery reactions therein, however, has become a major bottleneck of its development for applications requiring a high energy efficiency and long cycle-life. Herein, in a confined potential window with negligible electrolyte degradation, we studied the rechargeability of Li-O2 cathodes with pre-filled well-defined discharge products of Li2 O2 , Li2 CO3 , LiOH, or their combinations. Our results suggest Li2 CO3 as the most difficult species to be electrochemically decomposed among the three lithium compounds, whereas the presence of LiOH notably increases the initial charge potential. The clearly visible difference in the charge behavior and cycling stability of these artificially "discharged" electrodes provides a guideline for the development of future high-performance Li-O2 batteries. PMID:26011604
NASA Astrophysics Data System (ADS)
Maher, K.; Druhan, J. L.; Vialle, S.; Benson, S. M.; Agarwal, A.
2013-12-01
Long-term storage of anthropogenic CO2 in the subsurface generally assumes that caprock formations will serve as physical barriers to upward migration of CO2. Stability and coherence of the caprocks are thus important criteria for site selection, but caprock integritycannot be guaranteed with total certainty over the lifetime of the project. As a result, carbon capture and storage projects require reliable techniques to monitor geologic storage sites for newly formed leaks, and the ability to rapidly deploy mitigation measures should leakage occur. Here, we present two-dimensional reactive transport simulations to evaluate the hydrogeochemical characteristics of a newly formed CO2 leak into an overlying reservoir. Simulations use the ToughReact multi-component reactive transport code and hypothetical reservoir characteristics. We focus on the comparatively short time period of days to months following formation of the leak to consider (1) geochemical shifts in formation water indicative of the leak, (2) hydrodynamics of pumping wells in the vicinity of the leak, and (3) delivery of a sealant to the leak through an adjacent well bore. Our results suggest that characteristic shifts in pH and dissolved inorganic carbon might be detected in down-gradient mentoring wells prior to the breakthrough of CO2, and could offer a potential means of identifying small and newly formed leaks. Injecting water into the aquifer through pumping wells in the vicinity of the leak provides a hydrodynamic control that can prevent CO2 from reaching the top of the reservoir, but this action will likely have only minor influence on the rate of leakage through the caprock defect. Injection of a hypothetical sealant through an adjacent pumping well is considered using an aqueous solute with pH-dependent equilibrium constraints such that the species is soluble in the basic pH range but forms a precipitate at neutral to acidic pH conditions associated with CO2-rich water. Injection of this species in an alkaline fluid allows for delivery of the sealant to the edge of the CO2 plume where the sharp decrease in pH is leveraged to facilitate precipitation. Our results indicate that the solubilized sealant can be delivered to the edge of the plume and high rates of precipitation are achieved. However, the sealant is not able to reach the interior of the plume unless the leakage rate is extremely small, thus delivery to the precise location of the caprock defect within the plume is significantly more challenging.
Experimental study of flame propagation in semiconfined geometries with obstacles
Urtiew, P.A.; Brandeis, J.; Hogan, W.J.
1982-02-08
Accidents in which large quantities of liquefied natural gas (LNG) or other combustible materials are spilled can potentially lead to disastrous consequences, especially if the dispersing combustible cloud finds a suitable ignition source. So far, very little is known about the detailed behavior of a large burning cloud. Full-scale experiments are economically prohibitive, and therefore one must rely on laboratory and field experiments of smaller size, scaling up the results to make predictions about larger spill accidents. In this paper we describe our laboratory-scale experiments with a combustible propane/air mixture in various partially confined geometries. We summarize the experimental results and compare them with calculated results based on numerical simulations of the experiments. Our observations suggest that the geometry of the partial confinement is of primary importance; turbulence-producing obstacles can cause acceleration in the flame front and, more important, can cause a faster burnout of the combustible vapor.
Effects of confinement on the thermodynamics of supercooled water
NASA Astrophysics Data System (ADS)
Strekalova, Elena G.
The main focus of this thesis is to understand how confinement alters the phase diagram of supercooled liquid water by employing methods of statistical mechanics and numerical simulations. Water is very complex and anomalous when compared to simple liquids. For example, experimental data for liquid water reveals the presence of a temperature of maximum density (TMD) below which the density decreases under isobaric cooling. Another anomaly is the hypothesized liquid--liquid phase transition (LLPT) between two types of liquid water with different densities. In this thesis we study how confinement affects such anomalies as TMD and LLPT in supercooled liquid water. This thesis is separated into three parts: (i) Monte Carlo simulations of a 2D coarse-grained model of a water layer confined in a fixed disordered matrix of hydrophobic nanoparticles, (ii) molecular dynamics simulations of a Jagla ramp model of liquid confined in fixed ordered and disordered matrices of hydrophobic nanoparticles, and (iii) all-atom simulations of trehalose and maltose in aqueous solution of lysozyme. In Part (i), we perform Monte Carlo simulations and find that a nanoparticle concentration as small as 2.4% is enough to destroy the LLPT for pressure P > 0.14 GPa. Moreover, we find a substantial (more than 90%) decrease of compressibility, thermal expansion coefficient and specific heat at high P and low temperature T upon increase of nanoparticle concentration from 0% to 25%. In Part (ii), we ask how, for single component systems interacting via a soft-core isotropic potential with two characteristic length scales, the geometry of hydrophobic confinement affects the phase diagram. We use molecular dynamics simulations to study particles interacting through a ramp potential and a shoulder potential, each confined in a fixed matrix of nanoscopic particles with a fixed volume fraction. We find a substantial weakening of the LLPT and the disappearance of TMD upon the increase of disorder in the confining geometry. In Part (iii), we study aqueous systems with all-atom simulations. We are currently investigating the mechanism of water-trehalose-protein and water-maltose-protein interaction upon supercooling for its relevance to bioprotection.
Gorenstein, D G; Luxon, B A; Findlay, J B
1977-03-01
CNDO and ab initio calculations on the dimethyl phosphate monoanion demonstrate that geometry optimization can dramatically alter the relative energies of the conformational isomers of the phosphate ester. Thus, with geometry optimization (particularly of the diester RO-P-OR bond angle) the energy differences between the gauche-gauche, gauche-trans, and trans-trans conformations is less than 1 kcal/mol rather than approximately 7 kcal/mol previously reported. A torsional energy map for the two ester torsional angles which includes ester bond angle optimization is presented. Ab initio (STO-3G level) and CNDO calculations confirm the strong coupling of the diester RO-P-OR bond angle to the torsional conformation. PMID:849444
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.
C. A. Rogers
\\u000a The Geometry of Numbers is concerned with a study of the relationships between point lattices and sets of points. In this\\u000a course of lectures I want to give an account of some of the basic general results of the subject. I will confine my attention\\u000a to the study of what may be called homogeneous problems, and will say nothing about
Carroll, Gerard M; Schimpf, Alina M; Tsui, Emily Y; Gamelin, Daniel R
2015-09-01
Electronically doped colloidal semiconductor nanocrystals offer valuable opportunities to probe the new physical and chemical properties imparted by their excess charge carriers. Photodoping is a powerful approach to introducing and controlling free carrier densities within free-standing colloidal semiconductor nanocrystals. Photoreduced (n-type) colloidal ZnO nanocrystals possessing delocalized conduction-band (CB) electrons can be formed by photochemical oxidation of EtOH. Previous studies of this chemistry have demonstrated photochemical electron accumulation, in some cases reaching as many as >100 electrons per ZnO nanocrystal, but in every case examined to date this chemistry maximizes at a well-defined average electron density of ?Nmax? ? (1.4 ± 0.4) × 10(20) cm(-3). The origins of this maximum have never been identified. Here, we use a solvated redox indicator for in situ determination of reduced ZnO nanocrystal redox potentials. The Fermi levels of various photodoped ZnO nanocrystals possessing on average just one excess CB electron show quantum-confinement effects, as expected, but are >600 meV lower than those of the same ZnO nanocrystals reduced chemically using Cp*2Co, reflecting important differences between their charge-compensating cations. Upon photochemical electron accumulation, the Fermi levels become independent of nanocrystal volume at ?N? above ?2 × 10(19) cm(-3), and maximize at ?Nmax? ? (1.6 ± 0.3) × 10(20) cm(-3). This maximum is proposed to arise from Fermi-level pinning by the two-electron/two-proton hydrogenation of acetaldehyde, which reverses the EtOH photooxidation reaction. PMID:26263400
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.
Decoupling of Confined Normal 3He
NASA Astrophysics Data System (ADS)
Dimov, S. G.; Bennett, R. G.; Ilic, B.; Verbridge, S. S.; Levitin, L. V.; Fefferman, A. D.; Casey, A.; Saunders, J.; Parpia, J. M.
2010-01-01
Anodic bonding was used to fabricate a 10 mm diameter × 640 nm tall annular geometry suitable for torsion pendulum studies of confined 3He. For pure 3He at saturated vapor pressure the inertia of the confined fluid was seen to be only partially coupled to the pendulum at 160 mK. Below 100 mK the liquid’s inertial contribution was negligible, indicating a complete decoupling of the 3He from the pendulum.
On the applicability of entropy potentials in transport problems
Berezhkovskii, Alexander M.; Bezrukov, Sergey M.
2015-01-01
Transport in confined structures of varying geometry has become the subject of growing attention in recent years since such structures are ubiquitous in biology and technology. In analyzing transport in systems of this type, the notion of entropy potentials is widely used. Entropy potentials naturally arise in one-dimensional description of equilibrium distributions in multidimensional confined structures. However, their application to transport problems requires some caution. In this article we discuss such applications and summarize the results of recent studies exploring the limits of applicability. We also consider an example of a transport problem in a system of varying geometry, where the conventional approach is inapplicable since the geometry changes abruptly. In addition, we demonstrate how the entropy potential can be used to analyze optimal transport through a tree-dimensional cosine-shaped channel.
Semiflexible Chains in Confined Spaces
Greg Morrison; D. Thirumalai
2008-08-12
We develop an analytical method for studying the properties of a non-interacting 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 MF 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.
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.
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.
Li, Jun; Kathmann, Shawn M.; Schenter, Gregory K.; Gutowski, Maciej S.
2007-02-07
Boron-nitrogen-hydrogen (BNHx) materials are polar analogs of hydrocarbons with potential applications as media for hydrogen storage. As H(NH?BH?)nH oligomers result from dehydrogenation of NH?BH? and NH?BH? materials, understanding the geometries, stabilities, and electronic structure of these oligomers is essential for developing chemical methods of hydrogen release and regeneration of the BNHx-based hydrogen storage materials. In this work we have performed computational modeling on the H(NH?BH?)nH (n = 1 – 6) oligomers using density functional theory (DFT). We have investigated linear chain structures and the stabilizing effects of coiling, biradicalization, and branching through Car-Parrinello molecular dynamics simulations and geometry optimizations. We find that the zig-zag linear oligomers are unstable with respect to the coiled, square-wave chain, and branched structures, with the coiled structures being the most stable. Dihydrogen bonding in oligomers, where protic H??(N) hydrogens interact with hydridic H??(B) hydrogens, plays a crucial role in stabilizing different isomers and conformers. The results are consistent with structures of products that are seen in experimental NMR studies of dehydrogenated ammonia borane.
Impact of improved confinement on fusion research
NASA Astrophysics Data System (ADS)
Itoh, Kimitaka; Itoh, Sanae-I.; Fukuyama, A.
1990-12-01
The effect of the improvement of the plasma confinement on fusion research is investigated for the ITER grade plasma. The impact of the confinement improvement is quantitatively evaluated from the viewpoints of necessity and cost, the engineering research and development, the economic potential, and reduction of the ambiguity in the design of future devices. It is shown that confinement improvement has a strong and favorable influence on these aspects.
Facilitated diffusion on confined DNA
NASA Astrophysics Data System (ADS)
Foffano, G.; Marenduzzo, D.; Orlandini, E.
2012-02-01
In living cells, proteins combine three-dimensional bulk diffusion and one-dimensional sliding along the DNA to reach a target faster. This process is known as facilitated diffusion and we investigate its dynamics in the physiologically relevant case of confined DNA. The confining geometry and DNA elasticity are key parameters: We find that facilitated diffusion is most efficient inside an isotropic volume and on a flexible polymer. By considering the typical copy numbers of proteins in vivo, we show that the speedup due to sliding becomes insensitive to fine tuning of parameters, rendering facilitated diffusion a robust mechanism to speed up intracellular diffusion-limited reactions. The parameter range we focus on is relevant for in vitro systems and for facilitated diffusion on yeast chromatin.
Hydrogenic systems confined by infinite tubes
P. Duclos; H. Hogreve
2010-01-01
We consider a hydrogen atom or ion confined within a straight infinite tube. Modelled by an appropriate nonrelativistic Schrödinger operator with Dirichlet boundary conditions, basic properties of the discrete and continuous spectrum of the system are investigated by rigorous methods. This includes the behaviour of energies and ionization potentials when the size of the confining region is changing. For the
Tuning the ordered states of folded rods by isotropic confinement.
Bayart, E; Boudaoud, A; Adda-Bedia, M
2014-01-01
The packing of elastic objects is increasingly studied in the framework of out-of-equilibrium statistical mechanics and thus these appear to be similar to glassy systems. Here, we present a two-dimensional experiment whereby a rod is confined by a parabolic potential. The setup enables spanning a wide range of folded configurations of the rod. Measurements of the distributions of length and curvature in the system reveal the importance of a stacking process whereby many layers of the rod are grouped into branches. The geometrical order of patterns increases with the confinement strength. Measurements of the distributions of energies lead to the definition of an energy scale that is correlated with the elastic energy of the stacked parts of the rod. This scale imposes energy partition in the system and might be relevant to the framework of the thermodynamics of disordered systems. Following these observations, we describe the patterns as excited states of a ground state corresponding to the most ordered geometry. Eventually, we provide evidence that the disordered state of a folded rod becomes spontaneously closer to the ground state as confinement is increased. PMID:24580237
A fresh look at the confinement mechanism
Kurt Langfeld
2010-07-06
Topological configurations, monopoles and vortices, successfully describe quark confinement and the spontaneous breakdown of chiral symmetry. Despite their infinite action, these configurations are relevant due to a subtle cancellation between action and entropy. A natural explanation for this intrinsic fine-tuning is that smooth low action configurations exist which confine and which appear as singular topological objects in certain gauges. To reveal these confining semi-classical configurations, a new cooling method is proposed which largely reduces the action while preserving the asymptotic quark-antiquark potential. First numerical results for a SU(2) gauge theory show that confining configurations with an average plaquette as high as 0.95 do exist.
NASA Astrophysics Data System (ADS)
Gandhimathi, Rajendran; Dheivamalar, Sethuraman; Dhanasekaran, Ramasamy
2015-01-01
In the present work, the equilibrium geometry, HOMO-LUMO energy gap, chemical shifts, vibrational frequencies, IR and Raman intensities and thermodynamic parameters of 4-nitrophenol molecule was calculated using the methods of HF and DFT/B3YLP employing 6-311+G basis set. Theoretically calculated geometrical parameters such as bond length and bond angle were compared with the corresponding experimental X-ray diffraction values. The highest occupied (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of the 4-NP molecule have been calculated. The study was extended to calculate the energy gap, ionization potential, electron affinity and chemical hardness. HOMO-LUMO electronic transition of 3.76 eV is obtained from the contribution of the bands. The reacting electrophilic and nucleophilic sites of the molecule were analyzed with the help of molecular electrostatic potential (MEP) surface analysis. The different proton and carbon environment of the grown crystal was analyzed by 1H and 13C NMR analyses. All vibrational frequencies were assigned and compared with the calculated frequencies in detail.
Quantum Confinement in Hydrogen Bond
Santos, Carlos da Silva dos; Ricotta, Regina Maria
2015-01-01
In this work, the quantum confinement effect is proposed as the cause of the displacement of the vibrational spectrum of molecular groups that involve hydrogen bonds. In this approach the hydrogen bond imposes a space barrier to hydrogen and constrains its oscillatory motion. We studied the vibrational transitions through the Morse potential, for the NH and OH molecular groups inside macromolecules in situation of confinement (when hydrogen bonding is formed) and non-confinement (when there is no hydrogen bonding). The energies were obtained through the variational method with the trial wave functions obtained from Supersymmetric Quantum Mechanics (SQM) formalism. The results indicate that it is possible to distinguish the emission peaks related to the existence of the hydrogen bonds. These analytical results were satisfactorily compared with experimental results obtained from infrared spectroscopy.
Quantum Confinement in Hydrogen Bond
Carlos da Silva dos Santos; Elso Drigo Filho; Regina Maria Ricotta
2015-02-09
In this work, the quantum confinement effect is proposed as the cause of the displacement of the vibrational spectrum of molecular groups that involve hydrogen bonds. In this approach the hydrogen bond imposes a space barrier to hydrogen and constrains its oscillatory motion. We studied the vibrational transitions through the Morse potential, for the NH and OH molecular groups inside macromolecules in situation of confinement (when hydrogen bonding is formed) and non-confinement (when there is no hydrogen bonding). The energies were obtained through the variational method with the trial wave functions obtained from Supersymmetric Quantum Mechanics (SQM) formalism. The results indicate that it is possible to distinguish the emission peaks related to the existence of the hydrogen bonds. These analytical results were satisfactorily compared with experimental results obtained from infrared spectroscopy.
NSDL National Science Digital Library
This site departs from the common themes taught in general geometry classes and introduces projective geometry, which has to do with special properties resulting from the intersection of lines, planes, and points. The coincidence of such elements is what is referred to as an incidence, and this is the basis of the topic. The site makes extensive use of animated figures to demonstrate principles involved in projective geometry, such as path curves, pivot transforms, and the curious concept of counter space. The author does a good job of explaining what is depicted in the figures as well as the underlying theory.
Optical studies of quantum confined nanostructures
NASA Astrophysics Data System (ADS)
Vamivakas, Anthony Nickolas
Recent advances in material growth techniques have led to the laboratory realization of quantum confined nanostructures. By engineering the geometry of these systems it is possible to tailor their optical, electrical and vibrational properties. We now envision integrated electronic and optical devices potentially harnessing quantum mechanical properties of photons, electrons or even phonons. The realization of these next generation devices requires parallel advances in both electrical and optical characterization techniques. In this dissertation we study the optical properties of both zero-dimensional (0D) InAs/GaAs semiconductor quantum dots (QDs) and one-dimensional (1D) single wall carbon nanotubes (SWNTs). We utilize high resolution optical microscopy and spectroscopy techniques to experimentally study both individual QDs and SWNTs. The effect of quantum confinement on light-matter interaction in SWNTs is theoretically investigated. InAs QDs grown by Stranski-Krastanow self-assembly are buried in a GaAs matrix. The planar barriers presented by the dielectric boundary between the GaAs and the host medium limits the optical access to the InAs QDs. Incorporating a numerical aperture increasing microlens (NAIL) into a fiber-based confocal microscope we demonstrate improved ability to couple photons to and from a single InAs QD. With such immersion lens techniques we measure a record 12% extinction of a far-field laser by a single InAs QD. Even typical QD extinction of 6% is visible using a dc power-meter without the need for phase sensitive lock-in detection. This experimental advance will make possible the study of single QDs interacting with engineered vector laser beams. In the optical characterization of SWNTs, one-phonon resonant Raman scattering is employed to measure a tube's electronic resonances and determine the physical diameter and chirality of the tube under study. Recent work has determined excitons dominate the optical response of semiconducting SWNTs. We develop a theory to model the exciton mediated resonant Raman scattering cross-section from a 1D system looking for excitonic signatures in the scattering line shape. Additionally, we theoretically study phonon confinement to a 1D SWNT and use these results to extract the electron-phonon coupling in SWNTs from our Raman measurements. Knowledge of the electron-phonon coupling is a crucial piece of information to characterize a SWNTs electrical transport properties.
Bifurcated equilibria in centrifugally confined plasma
Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)
2008-12-15
A bifurcation theory and associated computational model are developed to account for abrupt transitions observed recently on the Maryland Centrifugal eXperiment (MCX) [R. F. Ellis et al. Phys. Plasmas 8, 2057 (2001)], a supersonically rotating magnetized plasma that relies on centrifugal forces to prevent thermal expansion of plasma along the magnetic field. The observed transitions are from a well-confined, high-rotation state (HR-mode) to a lower-rotation, lesser-confined state (O-mode). A two-dimensional time-dependent magnetohydrodynamics code is used to simulate the dynamical equilibrium states of the MCX configuration. In addition to the expected viscous drag on the core plasma rotation, a momentum loss term is added that models the friction of plasma on the enhanced level of neutrals expected in the vicinity of the insulators at the throats of the magnetic mirror geometry. At small values of the external rotation drive, the plasma is not well-centrifugally confined and hence experiences the drag from near the insulators. Beyond a critical value of the external drive, the system makes an abrupt transition to a well-centrifugally confined state in which the plasma has pulled away from the end insulator plates; more effective centrifugal confinement lowers the plasma mass near the insulators allowing runaway increases in the rotation speed. The well-confined steady state is reached when the external drive is balanced by only the viscosity of the core plasma. A clear hysteresis phenomenon is shown.
Strongly interacting confined quantum systems in one dimension
A. G. Volosniev; D. V. Fedorov; A. S. Jensen; M. Valiente; N. T. Zinner
2015-05-24
In one dimension, the study of magnetism dates back to the dawn of quantum mechanics when Bethe solved the famous Heisenberg model that describes quantum behaviour in magnetic systems. In the last decade, one-dimensional systems have become a forefront area of research driven by the realization of the Tonks-Girardeau gas using cold atomic gases. Here we prove that one-dimensional fermionic and bosonic systems with strong short-range interactions are solvable in arbitrary confining geometries by introducing a new energy-functional technique and obtaining the full spectrum of energies and eigenstates. As a first application, we calculate spatial correlations and show how both ferro- and anti-ferromagnetic states are present already for small system sizes that are prepared and studied in current experiments. Our work demonstrates the enormous potential for quantum manipulation of magnetic correlations at the microscopic scale.
Strongly interacting confined quantum systems in one dimension.
Volosniev, A G; Fedorov, D V; Jensen, A S; Valiente, M; Zinner, N T
2014-01-01
In one dimension, the study of magnetism dates back to the dawn of quantum mechanics when Bethe solved the famous Heisenberg model that describes quantum behaviour in magnetic systems. In the last decade, one-dimensional (1D) systems have become a forefront area of research driven by the realization of the Tonks-Girardeau gas using cold atomic gases. Here we prove that 1D fermionic and bosonic systems with strong short-range interactions are solvable in arbitrary confining geometries by introducing a new energy-functional technique and obtaining the full spectrum of energies and eigenstates. As a first application, we calculate spatial correlations and show how both ferro- and antiferromagnetic states are present already for small system sizes that are prepared and studied in current experiments. Our work demonstrates the enormous potential for quantum manipulation of magnetic correlations at the microscopic scale. PMID:25366925
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
Confinement and screening in tachyonic matter
F. A. Brito; M. L. F. Freire; W. Serafim
2014-11-20
In this paper we consider confinement and screening of the electric field. We study the behavior of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the phenomenon of `anti-screening' in a medium with exotic dielectric. We show that tachyon matter behaves like an exotic way whose associated dielectric function modifies the Maxwell's equations and affects the fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that the confining regime coincides with the tachyon condensation, which resembles the effect of confinement due to condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance which is associated with {a screening phase
Confinement and screening in tachyonic matter
NASA Astrophysics Data System (ADS)
Brito, F. A.; Freire, M. L. F.; Serafim, W.
2014-12-01
In this paper we consider confinement and screening of the electric field. We study the behavior of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the phenomenon of `anti-screening' in a medium with exotic dielectric. We show that tachyon matter behaves like in an exotic way whose associated dielectric function modifies the Maxwell equations and affects the fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that the confining regime coincides with the tachyon condensation, which resembles the effect of confinement due to the condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance, which is associated with a screening phase.
Hydrophobicity of protein surfaces: Separating geometry from chemistry
Hydrophobicity of protein surfaces: Separating geometry from chemistry Nicolas Giovambattista, Princeton University, Princeton, NJ 08544; and Department of Chemistry and Biochemistry and Institute molecular dynamics simulation the structure and thermodynamics of water confined between two protein
Extreme Lagrangian acceleration in confined turbulent flow.
Kadoch, Benjamin; Bos, Wouter J T; Schneider, Kai
2008-05-01
A Lagrangian study of two-dimensional turbulence for two different geometries, a periodic and a confined circular geometry, is presented to investigate the influence of solid boundaries on the Lagrangian dynamics. It is found that the Lagrangian acceleration is even more intermittent in the confined domain than in the periodic domain. The flatness of the Lagrangian acceleration as a function of the radius shows that the influence of the wall on the Lagrangian dynamics becomes negligible in the center of the domain, and it also reveals that the wall is responsible for the increased intermittency. The transition in the Lagrangian statistics between this region, not directly influenced by the walls, and a critical radius which defines a Lagrangian boundary layer is shown to be very sharp with a sudden increase of the acceleration flatness from about 5 to about 20. PMID:18518379
Noncommutative geometry and reality
Alain Connes
1995-01-01
We introduce the notion of realstructure in our spectral geometry. This notion is motivated by Atiyah’s KR-theory and by Tomita’s involution J. It allows us to remove two unpleasant features of the ‘‘Connes–Lott’’ description of the standard model, namely, the use of bivector potentials and the asymmetry in the Poincare´ duality and in the unimodularity condition.
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.
Enhancement of confinement in tokamaks
Furth, H.P.
1986-05-01
A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime.
Valchev, Galin; Dantchev, Daniel
2015-07-01
We study, using general scaling arguments and mean-field type calculations, the behavior of the critical Casimir force and its interplay with the van der Waals force acting between two parallel slabs separated at a distance L from each other, confining some fluctuating fluid medium, say a nonpolar one-component fluid or a binary liquid mixture. The surfaces of the slabs are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials ensuring the so-called (+,+) boundary conditions. The slabs, on the other hand, influence the fluid by long-range competing dispersion potentials, which represent irrelevant interactions in renormalization-group sense. Under such conditions, one usually expects attractive Casimir force governed by universal scaling function, pertinent to the extraordinary surface universality class of Ising type systems, to which the dispersion potentials provide only corrections to scaling. We demonstrate, however, that below a given threshold thickness of the system L_{crit} for a suitable set of slabs-fluid and fluid-fluid coupling parameters the competition between the effects due to the coatings and the slabs can result in sign change of the Casimir force acting between the surfaces confining the fluid when one changes the temperature T, the chemical potential of the fluid ?, or L. The last implies that by choosing specific materials for the slabs, coatings, and the fluid for L?L_{crit} one can realize repulsive Casimir force with nonuniversal behavior which, upon increasing L, gradually turns into an attractive one described by a universal scaling function, depending only on the relevant scaling fields related to the temperature and the excess chemical potential, for L?L_{crit}. We present arguments and relevant data for specific substances in support of the experimental feasibility of the predicted behavior of the force. It can be of interest, e.g., for designing nanodevices and for governing behavior of objects, say colloidal particles, at small distances. We formulate the corresponding criterion for determination of L_{crit}. The universality is regained for L?L_{crit}. We also show that for systems with L?L_{crit}, the capillary condensation phase diagram suffers modifications which one does not observe in systems with purely short-ranged interactions. PMID:26274136
NASA Astrophysics Data System (ADS)
Valchev, Galin; Dantchev, Daniel
2015-07-01
We study, using general scaling arguments and mean-field type calculations, the behavior of the critical Casimir force and its interplay with the van der Waals force acting between two parallel slabs separated at a distance L from each other, confining some fluctuating fluid medium, say a nonpolar one-component fluid or a binary liquid mixture. The surfaces of the slabs are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials ensuring the so-called (+,+) boundary conditions. The slabs, on the other hand, influence the fluid by long-range competing dispersion potentials, which represent irrelevant interactions in renormalization-group sense. Under such conditions, one usually expects attractive Casimir force governed by universal scaling function, pertinent to the extraordinary surface universality class of Ising type systems, to which the dispersion potentials provide only corrections to scaling. We demonstrate, however, that below a given threshold thickness of the system Lcrit for a suitable set of slabs-fluid and fluid-fluid coupling parameters the competition between the effects due to the coatings and the slabs can result in sign change of the Casimir force acting between the surfaces confining the fluid when one changes the temperature T , the chemical potential of the fluid ? , or L . The last implies that by choosing specific materials for the slabs, coatings, and the fluid for L ?Lcrit one can realize repulsive Casimir force with nonuniversal behavior which, upon increasing L , gradually turns into an attractive one described by a universal scaling function, depending only on the relevant scaling fields related to the temperature and the excess chemical potential, for L ?Lcrit . We present arguments and relevant data for specific substances in support of the experimental feasibility of the predicted behavior of the force. It can be of interest, e.g., for designing nanodevices and for governing behavior of objects, say colloidal particles, at small distances. We formulate the corresponding criterion for determination of Lcrit. The universality is regained for L ?Lcrit . We also show that for systems with L ?Lcrit , the capillary condensation phase diagram suffers modifications which one does not observe in systems with purely short-ranged interactions.
Spectral properties of endohedrally confined helium atom
NASA Astrophysics Data System (ADS)
Fang, Shuai-Shuai; Hao-Xue, Qiao
2015-08-01
Based on the B-spline basis method, the properties of the helium atom confined inside an endohedral environment, such as buckminster fullerene, are studied. In our calculations, the endohedral environment is a parabolic potential well. In this situation, the phenomenon of “mirror collapse” is exhibited for energy levels of a confined helium atom. The “giant resonance” of oscillator strength of the dipole transition emerges with the variation of depth of the confining well. The physical mechanisms of these phenomena are analyzed in this paper. Project supported by the National Natural Science Foundation of China (Grant No. 11274246.)
Galin Valchev; Daniel Dantchev
2015-06-10
We study the behavior of the critical Casimir force and its interplay with the van der Waals force acting between two parallel slabs separated at a distance $L$ from each other confining a non-polar simple fluid or a binary liquid mixture. The surfaces of the slabs are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture. The slabs influence the fluid by long-range competing dispersion potentials. Under such conditions one usually expects {\\it attractive} Casimir force governed by universal scaling function to which the dispersion potentials provide only corrections to scaling. We demonstrate, however, that below a given $L
Programmed environment management of confined microsocieties
NASA Technical Reports Server (NTRS)
Emurian, Henry H.
1988-01-01
A programmed environment is described that assists the implementation and management of schedules governing access to all resources and information potentially available to members of a confined microsociety. Living and work schedules are presented that were designed to build individual and group performance repertoires in support of study objectives and sustained adaptation by participants. A variety of measurement requirements can be programmed and standardized to assure continuous assessment of the status and health of a confined microsociety.
Fayer, Michael D.
Geometry and Nanolength Scales versus Interface Interactions: Water Dynamics in AOT Lamellar@stanford.edu Abstract: To determine the relative importance of the confining geometry and nanoscopic length scale versus criteria: surface-to-surface dimensions to study the effect of confining length scales, and water
ERIC Educational Resources Information Center
Desseyn, H. O.; And Others
1985-01-01
Compares linear-nonlinear and planar-nonplanar geometry through the valence-shell electron pairs repulsion (V.S.E.P.R.), Mulliken-Walsh, and electrostatic force theories. Indicates that although the V.S.E.P.R. theory has more advantages for elementary courses, an explanation of the best features of the different theories offers students a better…
NSDL National Science Digital Library
Rusin, David J., 1957-
A short article designed to provide an introduction to computational geometry, intended for topics whose geometric aspects are fairly straightforward, but for which the main questions involve efficient, accurate computation. A number of geometric questions arise involving large sets of points (e.g. which of these points are closest together?) which are arguably combinatorics or statistics, but which have been included here.
Hot electron confinement in a microwave heated spindle cusp
Prelas, M.A.
1991-08-01
The Plasma Research Laboratory at the University of Missouri-Columbia was established with awards from the McDonnel Douglas Foundation, ARMCO, Union Electric, Black and Vetch, Kansas City Power and Light, the National Science Foundation, and DOE. The Plasma Research Lab's major effort is the Missouri Magnetic Mirror (MMM or M{sup 3}) Project. The technical goals of MMM have been (1) Diagnostic Development, (2) Plasma Physics in the Cusp geometry, (3) plasma-wall interactions, (4) impurity effects in a steady-state plasma, and (5) Development of Diagnostics for use in harsh plasma processing environments. The other major goal of MMM has remained providing a facility for hands-on training in experimental plasma physics. The major experimental facility of MMM is the MMM Modified Experiment (M4X). Other research efforts in the Plasma Research Laboratory include small efforts in cold fusion, toroidal magnetic confinement, and inertial confinement and a potentially major effort in direct conversion of nuclear energy.
Grooms, Daniel L; Kroll, Lee Anne K
2015-07-01
Indoor confined feedlots offer advantages that make them desirable in northern climates where high rainfall and snowfall occur. These facilities increase the risk of certain health risks, including lameness and tail injuries. Closed confinement can also facilitate the rapid spread of infectious disease. Veterinarians can help to manage these health risks by implementing management practices to reduce their occurrence. PMID:26139194
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…
... NIOSH. www.cpwr.com What is a confined space? Ask questions It is the employer’s responsibility to ... union. Call OSHA 1-800-321-OSHA COnFIned SpACeS Get training Your employer must train you for ...
NASA Astrophysics Data System (ADS)
Kep?ija, N.; Huang, T.-J.; Klappenberger, F.; Barth, J. V.
2015-03-01
Quantum confinement of a two-dimensional electron gas by supramolecular nanoporous networks is investigated using the boundary elements method based on Green's functions for finite geometries and electron plane wave expansion for periodic systems. The "particle in a box" picture was analyzed for cases with selected symmetries that model previously reported architectures constructed from organic and metal-organic scattering centers confining surface state electrons of Ag(111) and Cu(111). First, by analyzing a series of cases with systematically defined parameters (scattering geometry, potentials, and effective broadening), we demonstrate how the scattering processes affect the properties of the confined electrons. For the features of the local density of states reported by scanning tunneling spectroscopy (STS), we disentangle the contributions of lifetime broadening and splitting of quantum well states due to coupling of neighboring quantum dots. For each system, we analyze the local electron density distribution and relate it to the corresponding band structure as calculated within the plane-wave expansion framework. Then, we address two experimental investigations, where in one case only STS data and in the other case mainly angle-resolved photoemission spectroscopy (ARPES) data were reported. In both cases, the experimental findings can be successfully simulated. Furthermore, the missing information can be complemented because our approach allows to correlate the information obtained by STS with that of ARPES. The combined analysis of several observations suggests that the scattering potentials created by the network originate primarily from the adsorbate-induced changes of the local surface dipole barrier.
Diakonov, Dmitri; Petrov, Victor [St. Petersburg NPI, Gatchina, 188 300, St. Petersburg (Russian Federation)
2007-09-01
We construct the integration measure over the moduli space of an arbitrary number of N kinds of dyons of the pure SU(N) gauge theory at finite temperatures. The ensemble of dyons governed by the measure is mathematically described by a (supersymmetric) quantum field theory that is exactly solvable and is remarkable for a number of striking features: (i) The free energy has the minimum corresponding to the zero average Polyakov line, as expected in the confining phase; (ii) the correlation function of two Polyakov lines exhibits a linear potential between static quarks in any N-ality nonzero representation, with a calculable string tension roughly independent of temperature; (iii) the average spatial Wilson loop falls off exponentially with its area and the same string tension; (iv) at a critical temperature, the ensemble of dyons rearranges and deconfines; and (v) the estimated ratio of the critical temperature to the square root of the string tension is in excellent agreement with the lattice data.
Energy confinement in Doublet III with high-Z limiters
Marcus, F.B.; Adcock, S.J.; Baker, D.R.; Blau, F.P.; Brooks, N.H.; Chase, R.P.; DeBoo, J.C.; Ejima, S.; Fairbanks, E.S.; Fisher, R.K.
1980-02-01
This report describes the experimental measurements and data analysis techniques used to evaluate the energy confinement in noncircular plasmas produced in Doublet III. Major aspects of the confinement measurements and analysis techniques are summarized. Machine parameters, diagnostic systems and discharge parameters relavent to the confinement measurements are given. Magnetic analysis techniques used to determine the plasma shape are reviewed. Scaling of the on-axis values of electron temperature, confinement time and Z/sub eff/ with plasma density is presented. Comparison with scaling results from other circular tokamaks is discussed. Numerical and analytic techniques developed for calculating the plasma energy confinement time and self-consistent profiles of density, temperature, current, and flux in non-circular geometries are described. These techniques are applied to the data and used to determine the central and global electron energy confinement time for a typical doublet plasma. Additional aspects of the confinement such as the radial dependence of the electron thermal conductivity and the estimated ion temperature are explored with the aid of a non-circular transport simulation code. The results of the confinement measurements are summarized and discussed. A brief summary of the theoretically expected effects of noncircularity on plasma confinement is included for reference as Appendix I.
Influence of Confinement on Dynamical Heterogeneities in Dense Colloidal Samples
Kazem V. Edmond; Carolyn R. Nugent; Eric R. Weeks
2012-01-30
We study a dense colloidal suspension confined between two quasiparallel glass plates as a model system for a supercooled liquid in confined geometries. We directly observe the three-dimensional Brownian motion of the colloidal particles using laser scanning confocal microscopy. The particles form dense layers along the walls, but crystallization is avoided as we use a mixture of two particle sizes. A normally liquid-like sample, when confined, exhibits slower diffusive motion. Particle rearrangements are spatially heterogeneous, and the shapes of the rearranging regions are strongly influenced by the layering. These rearranging regions become more planar upon confinement. The wall-induced layers and changing character of the spatially heterogeneous dynamics appear strongly connected to the confinement induced glassiness.
Elementary framework for cold field emission: Incorporation of quantum-confinement effects
Patterson, A. A. Akinwande, A. I.
2013-12-21
Although the Fowler-Nordheim (FN) equation serves as the foundation of cold field emission theory, it may not be suitable for predicting the emitted current density (ECD) from emitters with a quantum-confined electron supply. This work presents an analytical framework for treating cold field emission from metals that includes the effects of a quantum-confined electron supply. Within the framework, quantum confinement in emitters is classified into transverse and normal quantum confinement based on the orientation of the confinement relative to the emission direction. The framework is used to generate equations predicting the ECD from rectangular and cylindrical emitter geometries comprised of electron supplies of reduced dimensionality. Transverse quantum confinement of the electron supply leads to a reduction in the total ECD as transverse emitter dimensions decrease and normal quantum confinement results in an oscillatory ECD as a function of the normal quantum well width. Incorporating a geometry-dependent field enhancement factor into the model reveals an optimal transverse well width for which quantum confinement of the electron supply and field enhancement equally affect the ECD and a maximum total ECD for the emitter geometry at a given applied field is obtained. As a result, the FN equation over-predicts the ECD from emitters with transverse dimensions under approximately 5?nm, and in those cases, geometry-specific ECD equations incorporating quantum-confinement effects should be employed instead.
Elementary framework for cold field emission: Incorporation of quantum-confinement effects
NASA Astrophysics Data System (ADS)
Patterson, A. A.; Akinwande, A. I.
2013-12-01
Although the Fowler-Nordheim (FN) equation serves as the foundation of cold field emission theory, it may not be suitable for predicting the emitted current density (ECD) from emitters with a quantum-confined electron supply. This work presents an analytical framework for treating cold field emission from metals that includes the effects of a quantum-confined electron supply. Within the framework, quantum confinement in emitters is classified into transverse and normal quantum confinement based on the orientation of the confinement relative to the emission direction. The framework is used to generate equations predicting the ECD from rectangular and cylindrical emitter geometries comprised of electron supplies of reduced dimensionality. Transverse quantum confinement of the electron supply leads to a reduction in the total ECD as transverse emitter dimensions decrease and normal quantum confinement results in an oscillatory ECD as a function of the normal quantum well width. Incorporating a geometry-dependent field enhancement factor into the model reveals an optimal transverse well width for which quantum confinement of the electron supply and field enhancement equally affect the ECD and a maximum total ECD for the emitter geometry at a given applied field is obtained. As a result, the FN equation over-predicts the ECD from emitters with transverse dimensions under approximately 5 nm, and in those cases, geometry-specific ECD equations incorporating quantum-confinement effects should be employed instead.
Mobility in geometrically confined membranes
Domanov, Yegor A.; Aimon, Sophie; Toombes, Gilman E. S.; Renner, Marianne; Quemeneur, François; Triller, Antoine; Turner, Matthew S.; Bassereau, Patricia
2011-01-01
Lipid and protein lateral mobility is essential for biological function. Our theoretical understanding of this mobility can be traced to the seminal work of Saffman and Delbrück, who predicted a logarithmic dependence of the protein diffusion coefficient (i) on the inverse of the size of the protein and (ii) on the “membrane size” for membranes of finite size [Saffman P, Delbrück M (1975) Proc Natl Acad Sci USA 72:3111—3113]. Although the experimental proof of the first prediction is a matter of debate, the second has not previously been thought to be experimentally accessible. Here, we construct just such a geometrically confined membrane by forming lipid bilayer nanotubes of controlled radii connected to giant liposomes. We followed the diffusion of individual molecules in the tubular membrane using single particle tracking of quantum dots coupled to lipids or voltage-gated potassium channels KvAP, while changing the membrane tube radius from approximately 250 to 10 nm. We found that both lipid and protein diffusion was slower in tubular membranes with smaller radii. The protein diffusion coefficient decreased as much as 5-fold compared to diffusion on the effectively flat membrane of the giant liposomes. Both lipid and protein diffusion data are consistent with the predictions of a hydrodynamic theory that extends the work of Saffman and Delbrück to cylindrical geometries. This study therefore provides strong experimental support for the ubiquitous Saffman–Delbrück theory and elucidates the role of membrane geometry and size in regulating lateral diffusion. PMID:21768336
Transformation Composition Transformational Geometry
Ferguson, Thomas S.
Isomotries Transformation Composition Congruence Transformational Geometry Christopher Ograin Christopher Ograin Transformational Geometry #12;Isomotries Transformation Composition Congruence Geo Transformational Geometry #12;Isomotries Transformation Composition Congruence Definitions Transformation
Engaging All Students with "Impossible Geometry"
ERIC Educational Resources Information Center
Wiest, Lynda R.; Ayebo, Abraham; Dornoo, Michael D.
2010-01-01
Geometry is an area in which Australian students performed particularly poorly on the 2007 Trends in International Mathematics and Science Study (TIMSS). One innovative area of recreational geometry that has rich potential to engage and challenge a wide variety of students is "impossible geometry." An impossible geometric object is a…
MFU-type metal-organic frameworks as host materials of confined supercooled liquids
J. K. H. Fischer; P. Sippel; D. Denysenko; P. Lunkenheimer; D. Volkmer; A. Loidl
2015-08-13
In this work we examine the use of metal-organic framework (MOF) systems as host materials for the investigation of glassy dynamics in confined geometry. We investigate the confinement of the molecular glass former glycerol in three MFU-type MOFs with different pore sizes and study the dynamics of the confined liquid via dielectric spectroscopy. In accord with previous reports on confined glass formers, we find different degrees of deviations from bulk behavior depending on pore size, demonstrating that MOFs are well-suited host systems for confinement investigations.
The geometry behind double geometry
Martin Cederwall
2014-08-27
Generalised diffeomorphisms in double field theory rely on an O(d,d) structure defined on tangent space. We show that any (pseudo-)Riemannian metric on the doubled space defines such a structure, in the sense that the generalised diffeomorphisms defined using such a metric form an algebra, provided a covariant section condition is fulfilled. Consistent solutions of the section condition gives further restrictions. The case previously considered corresponds to a flat metric. The construction makes it possible to apply double geometry to a larger class of manifolds. Examples of curved defining metrics are given. We also comment on the role of the defining geometry for the symmetries of double field theory, and on the continuation of the present construction to the U-duality setting.
The importance of chemical potential in the determination of water slip in nanochannels
Marcello Sega; Mauro Sbragaglia; Luca Biferale; Sauro Succi
2015-07-28
We investigate the slip properties of water confined in graphite-like nano-channels by non-equilibrium molecular dynamics simulations, with the aim of identifying and analyze separately the influence of different physical quantities on the slip length. In a system under confinement but connected to a reservoir of fluid, the chemical potential is the natural control parameter: we show that two nanochannels characterized by the same macroscopic contact angle -- but a different microscopic surface potential -- do not exhibit the same slip length unless the chemical potential of water in the two channels is matched. Some methodological issues related to the preparation of samples for the comparative analysis in confined geometries are also discussed.
Lattice QCD Study for Confinement in Hadrons
Suganuma, H.; Iritani, T.; Yamamoto, A.; Okiharu, F.; Takahashi, T. T.
2011-10-21
We study three subjects on quark confinement in hadrons in SU(3)c lattice QCD. From the accurate lattice calculation for more than 300 different patterns of three-quark (3Q) systems, we find that the static 3Q potential is well described by Y-Ansatz, i.e., the Coulomb plus Y-type linear potential. We also study the multi-quark (4Q, 5Q) potentials in lattice QCD, and find that they are well described by the one-gluon-exchange (OGE) Coulomb plus string-theoretical linear potential, which supports the infrared string picture even for the multi-quarks. The second subject is a lattice-QCD determination of the relevant gluonic momentum component for confinement. The string tension (confining force) is found to be almost unchanged even after cutting off the high-momentum gluon component above 1.5GeV in the Landau gauge. In fact, quark confinement originates from the low-momentum gluon below about 1.5GeV. Finally, we consider a possible gauge of QCD for the quark potential model, by investigating 'instantaneous inter-quark potential' in generalized Landau gauge, which describes a continuous change from the Landau gauge to the Coulomb gauge.
Statics and dynamics of softly confined polymers
NASA Astrophysics Data System (ADS)
Scagliarini, Andrea; Sbragaglia, Mauro; Sega, Marcello
2015-03-01
A variety of biological and technological problems where long chain molecules are constrained in spaces small compared to the molecule size (like membrane nanopores or nanofluidic slits) motivated recently a growing effort to understand the dynamics and structural scaling properties of polymers confined by solid walls. Our focus is, instead, on polymers confined in different geometries by soft interfaces, mimicking, e.g., DNA packaging inside cell nuclei or, mutatis mutandis, viral capsids. Soft-confinement is achieved by a proper choice of the solvation energies such that the polymer is trapped in one of the two phases of a binary mixture of immiscible liquids. We perform Molecular Dynamics simulations of polymers coupled with a fluctuating lattice Boltzmann method for the embedding matrix. Slab and droplet configurations are considered. In the former case we address the transition among various regimes of size scaling at changing the slab width. Under shear, the droplet is distorted from its equilibrium spherical shape and we explore how the transition from an isotropic geometry to a quasi-tube-like one affects polymer size scaling and knotting degree. Finally, we show how the feedback on the solvent induces viscoelastic rheology that can be related to polymer entanglement.
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.
Berk, H.L.
1992-08-06
An overview is presented of the principles of magnetic confinement of plasmas for the purpose of achieving controlled fusion conditions. Sec. 1 discusses the different nuclear fusion reactions which can be exploited in prospective fusion reactors and explains why special technologies need to be developed for the supply of tritium or {sup 3}He, the probable fuels. In Sec. 2 the Lawson condition, a criterion that is a measure of the quality of confinement relative to achieving fusion conditions, is explained. In Sec. 3 fluid equations are used to describe plasma confinement. Specific confinement configurations are considered. In Sec. 4 the orbits of particle sin magneti and electric fields are discussed. In Sec. 5 stability considerations are discussed. It is noted that confinement systems usually need to satisfy stability constraints imposed by ideal magnetohydrodynamic (MHD) theory. The paper culminates with a summary of experimental progress in magnetic confinement. Present experiments in tokamaks have reached the point that the conditions necessary to achieve fusion are being satisfied.
Materials self-assembly and fabrication in confined spaces
Ramanathan, Nathan Muruganathan [ORNL; Kilbey, II, S Michael [ORNL; Ji, Dr. Qingmin [National Institute for Materials Science, Tsukuba, Japan; Hill, Dr. Jonathan P [National Institute for Materials Science, Tsukuba, Japan; Ariga, Katsuhiko [National Institute for Materials Science, Tsukuba, Japan
2012-01-01
Molecular assemblies have been mainly researched in open spaces for long time. However, recent researches have revealed that there are many interesting aspects remained in self-assemblies in confined spaces. Molecular association within nanospaces such as mesoporous materials provide unusual phenomena based on highly restricted molecular motions. Current research endeavors in materials science and technology are focused on developing either new class of materials or materials with novel/multiple functionalities which is often achived via molecular assembly in confined spaces. Template synthesis and guided assemblies are distinguishable examples for molecular assembly in confined spaces. So far, different aspects of molecular confinements are discussed separately. In this review, the focus is specifically to bring some potential developments in various aspects of confined spaces for molecular self-assembly under one roof. We arrange the sections in this review based on the nature of the confinements; accordingly the topological/geometrical confinements, chemical and biological confinements, and confinements within thin film, respectively. Following these sections, molecular confinements for practical applications are shortly described in order to show connections of these scientific aspects with possible practical uses. One of the most important facts is that the self-assembly in confined spaces stands at meeting points of top-down and bottom-up fabrications, which would be an ultimate key to push the limits of nanotechnology and nanoscience.
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.
Sala, Simon
2015-01-01
A detailed study of the anharmonicity-induced resonances caused by the coupling of center-of-mass and relative motion is presented for a system of two ultracold atoms in single-well potentials. As has been confirmed experimentally, these inelastic confinement-induced resonances are of interest, since they can lead to coherent molecule formation, losses, and heating in ultracold atomic gases. A perturbative model is introduced to describe the resonance positions and the coupling strengths. The validity of the model and the behavior of the resonances for different confinement geometries are analyzed in comparison with exact numerical ab initio calculations. While such resonances have so far only been detected for large positive values of the $s$-wave scattering length, it is found that they are present also for negative $s$-wave scattering lengths, i. e. for attractive interactions. The possibility to coherently tune the resonances by a variation of the external confinement geometry might pave the way for coher...
Simon Sala; Alejandro Saenz
2015-09-18
A detailed study of the anharmonicity-induced resonances caused by the coupling of center-of-mass and relative motion is presented for a system of two ultracold atoms in single-well potentials. As has been confirmed experimentally, these inelastic confinement-induced resonances are of interest, since they can lead to coherent molecule formation, losses, and heating in ultracold atomic gases. A perturbative model is introduced to describe the resonance positions and the coupling strengths. The validity of the model and the behavior of the resonances for different confinement geometries are analyzed in comparison with exact numerical ab initio calculations. While such resonances have so far only been detected for large positive values of the $s$-wave scattering length, it is found that they are present also for negative $s$-wave scattering lengths, i. e. for attractive interactions. The possibility to coherently tune the resonances by a variation of the external confinement geometry might pave the way for coherent molecule association where magnetic Feshbach resonances are inaccessible.
Ambipolar potential formation in TMX
Correll, D.L.; Allen, S.L.; Casper, T.A.
1981-05-05
TMX experimental data on ambipolar potential control and on the accompanying electrostatic confinement are reported. New results on the radial dependence of the central-cell confining potential are given. Radial and axial particle losses as well as scaling of the central-cell axial confinement are discussed.
Thermodynamic properties of a simple, confining model
NASA Astrophysics Data System (ADS)
Blaschke, David; Roberts, Craig D.; Schmidt, Sebastian
1998-04-01
We study the equilibrium thermodynamics of a simple, confining, DSE-model of 2-flavour QCD at finite temperature and chemical potential. The model has two phases: one characterised by confinement and dynamical chiral symmetry breaking; and the other by their absence. The phase boundary is defined by the zero of the vacuum-pressure difference between the confined and deconfined phases. Chiral symmetry restoration and deconfinement are coincident with the transition being of first order, except for ?=0, where it is second order. Nonperturbative modifications of the dressed-quark propagator persist into the deconfined domain and lead to a dispersion law modified by a dynamically-generated, momentum-dependent mass-scale. This entails that the Stefan-Boltzmann limit for the bulk thermodynamic quantities is attained only for large values of temperature and chemical potential. © 1998
Analysis of No-Flow Boundaries in Mixed Unconfined-Confined Aquifer Systems
Langerlan, Kent A.
2010-07-14
confining bed. This occurrence would create air pockets within the aquifer which then becomes depressurized and therefore unconfined. Girinskii?s Potential allows for a solution to be found for the location of this unconfined-confined boundary, as long...
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.
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
Rayleigh-Taylor mixing: confinement by stratification and geometry
Lawrie, Andrew
2010-03-16
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.2 Stencil pattern for upwinded u momentum. The hollow circle is the point being updated, the black dots and vestigial arrows depict data needed when u > 0 and v > 0. . . . . . . . . . . . . . . . . . . 35 3.3 Data in the black square... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Historical perspective . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2.1 Analytical studies . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2.2 Experimental studies . . . . . . . . . . . . . . . . . . . . . . . 4 1.2.3 Numerical...
The instability of monodisperse bubbles passing through a confined geometry
NASA Astrophysics Data System (ADS)
Li, Yuting; Wu, Ping; Zhang, Haifeng; Luo, Zhaofeng; Wang, Yong; Cheng, Zhengdong; He, Liqun
2014-11-01
The dispersed bubble experiences an impact of flow-focusing from the outer viscous liquid, and may break into satellite bubbles after flowing through the narrower section. We show that the number of satellite bubbles can be characterized by a phase diagram that depends on the capillary number and the Weber number. The number of satellite bubbles can be estimated through the Tgrow (the growth time of the daughter bubble), Tpinch (the pinch-off time of the daughter bubble), and Tpass (the time the initial microbubble need to pass the pore). We defined N = Tpass/(Tpinch + Tgrow) as the dimensionless time and the critical condition: N ˜ 1 to evaluate the bubble breakup. Our work shows that the breakup of the microbubble or droplet through a sudden narrowing joint is predictable and controllable.
Helically forced MHD flows in confined cylindrical geometries
Boyer, Edmond
, Jorge Morales2 , Wouter Bos2 , Kai Schneider1 1 M2P2, Aix-Marseille University, 38 Rue FrÂ´edÂ´eric Joliot-Curie 13451 Marseille, Cedex 20, France 2 LMFA, Ecole Centrale de Lyon, UMR 5509, CNRS, Universit
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...
Entropic Confinement of Colloidal Spheres in Corners on Silicon Substrates
Dinsmore, Tony
silicon facets intersected (as where a wall meets a floor). The entropic confinement potential increased a floor, as shown in Figure 1). This confinement is accompanied by an increase of the mixture's total normal to the top (polished) surface. The bottom surfaces of such wafers are covered with naturally
Wang, Yan; Vallabhaneni, Ajit; Hu, Jiuning; Qiu, Bo; Chen, Yong P; Ruan, Xiulin
2014-02-12
We show that thermal rectification (TR) in asymmetric graphene nanoribbons (GNRs) is originated from phonon confinement in the lateral dimension, which is a fundamentally new mechanism different from that in macroscopic heterojunctions. Our molecular dynamics simulations reveal that, though TR is significant in nanosized asymmetric GNRs, it diminishes at larger width. By solving the heat diffusion equation, we prove that TR is indeed absent in both the total heat transfer rate and local heat flux for bulk-size asymmetric single materials, regardless of the device geometry or the anisotropy of the thermal conductivity. For a deeper understanding of why lateral confinement is needed, we have performed phonon spectra analysis and shown that phonon lateral confinement can enable three possible mechanisms for TR: phonon spectra overlap, inseparable dependence of thermal conductivity on temperature and space, and phonon edge localization, which are essentially related to each other in a complicated manner. Under such guidance, we demonstrate that other asymmetric nanostructures, such as asymmetric nanowires, thin films, and quantum dots, of a single material are potentially high-performance thermal rectifiers. PMID:24393070
Seismic behavior of confined square CFT columns
X. Y. Mao; Y. Xiao
2006-01-01
The failure of conventional concrete filled tubes (CFT) under seismic loading is typically governed by the inelastic buckling and low cycle fatigue rupture. The second author has proposed to use additional confinement to control or delay the inelastic buckling of the steel tube at the potential plastic hinge zones of CFT members. Following the success of the previous studies on
Confined ring polymers as a model nucleoid
NASA Astrophysics Data System (ADS)
Ha, Bae-Yeun; Jeon, C.; Kim, J.; Jeong, H.; Jun, S.; Jung, Y.
2014-03-01
The bacterial chromosome is tightly packed in an intracellular space called the nucleoid with its loci linearly and precisely positioned. Here we propose a model nucleoid: a ring polymer confined in a cylindrical space. When the cylinder-ring parameters are chosen properly, our model describes the observed locus distributions of the E. coli chromosome surprisingly well. Our results illustrate how the geometry and function of the nucleoid are interrelated. This work was supported by the collaborative research contract funded by Korea Institute of Science & Technology Information (KISTI, Korea) and NSERC (Canada).
ATR confinement leakage determination
Kuan, P.; Buescher, B.J.
1998-06-01
The air leakage rate from the Advanced Test Reactor (ATR) confinement is an important parameter in estimating hypothesized accidental releases of radiation to the environment. The leakage rate must be determined periodically to assure that the confinement has not degraded with time and such determination is one of the technical safety requirements of ATR operation. This paper reviews the methods of confinement leakage determination and presents an analysis of leakage determination under windy conditions, which can complicate the interpretation of the determined leakage rates. The paper also presents results of analyses of building air exchange under windy conditions. High wind can enhance air exchange and this could increase the release rates of radioisotopes following an accident.
M. Avila
1998-01-04
The Regge behaviour of the solutions of a Dirac hamiltonian describing a heavy quark-light quark system in high orbital angular momentum states is analyzed. It is found that the solutions of a scalar confining potential are physically admissible while those of a vector confining potential are not. It is argued that with a Dirac hamiltonian a scalar confining potential is preferred over a vector confining potential for any value of the orbital angular momentum.
Perspectives on water science: transport and application of confined water
NASA Astrophysics Data System (ADS)
Zeng, XiPing; Wu, JinBo; Li, ShunBo; Chau, YeungYeung; He, GuangHong; Wen, WeiJia; Yang, GuoZhen
2014-05-01
The confinements of water can be divided into two main categories, namely, the confinements on surface or interface and the confinements in bulk water. By adding ions or applying electric field, the intensity and distribution of the hydrogen bonds can be greatly affected. These are collectively known as confinement on water surface or interface, which has potential applications in life science and industries involving evaporation control. Confined bulk water could be found everywhere in nature, such as in granular and porous materials, macromolecules and gels, etc. The investigation of the physical properties and the transports of the confined bulk water will contribute to understanding certain types of life activities such as the water transport in plant and in new application of extracting the shale oil and water.
NASA Astrophysics Data System (ADS)
Behera, Laxmidhar; Sen, Mrinal K.
2014-10-01
We have derived a shallow subsurface 2-D tomographic P-wave velocity image of the Deccan Volcanic Province (DVP) of India using first-arrival traveltime data along a 90-km-long N-S trending seismic profile in the Deccan Syneclise region. The tomographic image depicts smooth velocity variations of Quaternary and Tertiary (2.0-3.0 km s-1) sediments, basalts/traps (5.0-5.5 km s-1), sub-trappean Mesozoic sediments (4.3-4.5 km s-1) as well as the basement (5.9-6.1 km s-1) geometry down to a maximum depth of 5.0 km. Due to Late Cretaceous volcanism and outpouring of basaltic lava flows, this region is affected by numerous dyke intrusions and thick basaltic trap (2-3 km) exposed on the surface and surrounded by graben structures due to deep basinal faults forming a large igneous province. Although sub-basalt imaging is a major challenge for the oil industry, with the help of tomographic imaging technique of first-arrival seismic refraction data, we were able to image sub-trappean Mesozoic sediments (<0.75 km) deposited below the two sequences of thick basaltic flows above the basement. The imaged Mesozoic sediments are expected to contain hydrocarbon because of their wide extension in this sedimentary basin with suitable trapping mechanism due to basalts. The robustness of the velocity image is assessed through numerous tests like velocity perturbations, ?2 estimates, rms residuals of traveltime fit, uncertainty estimates through computation of ray-density or hits and series of checkerboard resolution tests with velocity anomalies having different cell size. The thickness of the basalt and the sub-trappean Mesozoic sediments along with the basement geometry obtained from tomography are constrained through ray-trace modelling and pre-stack depth migration (PSDM) of the wide-angle reflection phases for different shot gathers along the profile.
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.
Plasma confinement with an RF trap
Nebel, R.A.; Finn, J.M.; Glasser, A.H.
1996-12-31
A fusion device based on an RF trap is described. An RF trap combines the axial field of a Penning Trap with the pondermotive confinement of a Paul Trap. The pondermotive confinement is provided by standing electromagnetic waves in a resonant cavity, although driven electrostatic fields may also be employed if one wishes to operate at lower frequencies. The major advantage of this device is that the electrostatic breakdown problem for high energy Penning traps can be alleviated allowing one to utilize larger sizes and potentially higher fusion power densities than a standard Penning Trap. Also, multiple species can be confined and focused in this device permitting the utilization of advanced fuels in pure ion plasmas. The major disadvantage is that the device requires large standing wave energies which may lead to unacceptable wall dissipation. The equations describing the trap, spatial and temporal focusing criteria, and reactor embodiments of the device will be presented.
Holographic repulsion and confinement in gauge theory
NASA Astrophysics Data System (ADS)
Husain, Viqar; Kothawala, Dawood
2013-02-01
We show that for asymptotically anti-de Sitter (AdS) backgrounds with negative energy, such as the AdS soliton and regulated negative-mass AdS-Schwarzshild metrics, the Wilson loop expectation value in the AdS/CFT conjecture exhibits a Coulomb to confinement transition. We also show that the quark-antiquark (q \\bar{q}) potential can be interpreted as affine time along null geodesics on the minimal string worldsheet and that its intrinsic curvature provides a signature of transition to confinement phase. Our results suggest a generic (holographic) relationship between confinement in gauge theory and repulsive gravity, which in turn is connected with singularity avoidance in quantum gravity. Communicated by P R L V Moniz
Parabolic geometries BGG sequences
Drmota, Michael
Parabolic geometries BGG sequences Prolongation procedures BGG Sequences and Geometric sequences and overdetermined systems #12;Parabolic geometries BGG sequences Prolongation procedures Parabolic geometries are a large class of differential geometric structures, which can be described
Dynamics of strongly confined self propelled particles in non convex boundaries
Yaouen Fily; Aparna Baskaran; Michael F. Hagan
2014-10-20
We study the dynamics of non-aligning, non-interacting self-propelled particles confined to a box in two dimensions. In the strong confinement limit, when the persistence length of the active particles is much larger than the size of the box, particles stay on the boundary and align with the local boundary normal. It is then possible to derive the steady-state density on the boundary for arbitrary box shapes. In non-convex boxes, the non-uniqueness of the boundary normal results in hysteretic dynamics and the density is non-local, i.e. it depends on the global geometry of the box. These findings establish a general connection between the geometry of a confining box and the behavior of the active suspension it confines, thus providing a powerful tool to understand and design such confinements.
Shum, D.K.; Bryson, J.W.; Merkle, J.G. [Oak Ridge National Lab., TN (United States)
1993-09-01
This study presents preliminary estimates on whether an shallow, axially oriented, inner-surface finite-length flaw in a PWR-RPV would tend to elongate in the axial direction and/or deepen into the wall of the vessel during a postulated PTS transient. Analysis results obtained based on the assumptions of (1) linear-elastic material response, and (2) cladding with same toughness as the base metal, indicate that a nearly semicircular flaw would likely propagate in the axial direction followed by propagation into the wall of the vessel. Note that these results correspond to initiation within the lower-shelf fracture toughness temperature range, and that their general validity within the lower-transition temperature range remains to be determined. The sensitivity of the numerical results aid conclusions to the following analysis assumptions are evaluated: (1) reference flaw geometry along the entire crack front and especially within the cladding region; (2) linear-elastic vs elastic-plastic description of material response; and (3) base-material-only vs bimaterial cladding-base vessel-model assumption. The sensitivity evaluation indicates that the analysis results are very sensitive to the above assumptions.
The Properties of Confined Water and Fluid Flow at the Nanoscale
Schwegler, E; Reed, J; Lau, E; Prendergast, D; Galli, G; Grossman, J C; Cicero, G
2009-03-09
This project has been focused on the development of accurate computational tools to study fluids in confined, nanoscale geometries, and the application of these techniques to probe the structural and electronic properties of water confined between hydrophilic and hydrophobic substrates, including the presence of simple ions at the interfaces. In particular, we have used a series of ab-initio molecular dynamics simulations and quantum Monte Carlo calculations to build an understanding of how hydrogen bonding and solvation are modified at the nanoscale. The properties of confined water affect a wide range of scientific and technological problems - including protein folding, cell-membrane flow, materials properties in confined media and nanofluidic devices.
Dilation characteristics of confined concrete
Amir Mirmiran; Mohsen Shahawy
1997-01-01
SUMMARY Confinement of concrete enhances its strength and ductility by restraining lateral dilation. The accuracy of a confinement model depends on how well it captures the dilation tendency of concrete. In recent years, external confinement of concrete by fibre composites has become increasingly popular for civil infrastructure applications. This includes fibre-wrapping of existing columns or encasement of concrete in a
NASA Astrophysics Data System (ADS)
Zhang, Yongxian; Yikilmaz, M. Burak; Rundle, John B.; Yin, Xiangchu; Liu, Yue; Zhang, Langping; Wang, Zijin
2015-08-01
Based on the load/unload response ratio (LURR) theory, spatial and temporal variation of Y/ Y c (value of LURR/critical value of LURR under 90 % confidence) in the western United States and its adjacent area (31°-44°N, -128° to -112°E) during the period from 1980 to 2011 was studied. The selected study area was zoned into 20 sub-regions, in each of which the fault geometry and the focal mechanisms were very similar such that the stress fields were almost uniform. The loading and unloading periods were determined by calculating perturbations in the Coulomb failure stress in each sub-regions induced by earth tides. Earthquakes occurring in these sub-regions were identified as a loading or unloading type, and the response rate was chosen as the Benioff strain that can be calculated from earthquake magnitude M. With a time window of 1 year, a time moving step of 1 month, a space window of a circle region with a radius of 100 km, and a space moving step of 0.5° latitudinally and longitudinally, snapshots of the evolution of Y/ Y c were generated. Scanning results show that obvious Y/ Y c anomalies can be detected near the epicenter of all big earthquakes larger than M6.5 in regions with reasonable seismic monitoring abilities. They also show Y/ Y c anomalies occurred several years prior to the big earthquakes and the lasting time of the anomaly is from one year to several years. For some LURR anomalous regions, however, no earthquakes occurred. According to the characteristics of LURR anomalies, two regions with a high risk of big earthquakes were detected. One is between the northern region of the Bay Area and the Mendocino triple junction (38°-40°N, -124° to -122°E) and the other is between Lake Tahoe and Mono Lake (37.5°-39.5°N, -120° to -118°E) along the border of California and Nevada.
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.
Sandord, T.W.L.; Olson, R.E.; Chandler, G.A.; Hebron, D.E.; Mock, R.C.; Leeper, R.J.; Nash, T.J.; Ruggles, L.E.; Simpson, W.W.; Struve, K.W.; Vesey, R.A.; Bowers, R.L.; Matuska, W.; Peterson, D.L.; Peterson, R.R.
1999-08-25
Hohlraums of full ignition scale (6-mm diameter by 7-mm length) have been heated by x-rays from a z-pinch target on Z to a variety of temperatures and pulse shapes which can be used to simulate the early phases of the National Ignition Facility (NIF) temperature drive. The pulse shape is varied by changing the on-axis target of the z pinch in a static-wall-hohlraum geometry. A 2-{micro}m-thick walled Cu cylindrical target of 8-mm diameter filled with 10 mg/cm{sup 3} CH, for example, produces foot-pulse conditions of {minus}85 eV for a duration of {approximately} 10 ns, while a solid cylindrical target of 5-mm diameter and 14-mg/cm{sup 3} CH generates first-step-pulse conditions of {approximately} 122 eV for a duration of a few ns. Alternatively, reducing the hohlraum size (to 4-mm diameter by 4-mm length) with the latter target has increased the peak temperature to {approximately} 150 eV, which is characteristic of a second-step-pulse temperature. In general, the temperature T of these x-ray driven hohlraums is in agreement with the Planckian relation (T-(P/A){sup 1/4}). P is the measured x-ray input power and A is the surface area of the hohlraum. Fully-integrated 2-D radiation-hydrodynamic simulations of the z pinch and subsequent hohlraum heating show plasma densities within the useful volume of the hohlraums to be on the order of air or less.
Lewis, N.S.; Wrighton, M.S.
1984-05-10
Mediated outer-sphere redox processes have been examined at rotating disk Pt/(PQ/sup 2+/+/)/sub n/)/sub surf/ electrodes. The ((PQ/sup 2+/+/)/sub n/)/sub surf/ is a redox polymer anchored to the surface and is formed from N,N'-bis((trimethoxysilyl)propyl)-4,4'-bipyridinium, I. The polymer coverages for the electrodes selected for study are sufficiently great that Fe(phen)/sub 3//sup 3+/2+,E /sup 0/' = + 1.03 V vs. SCE, shows no electrochemical response near its E/sup 0/'. The mediated reduction of Fe(phen)/sub 3//sup 3 +/ and a number of other outer-sphere oxidants is mass-transport limited when the Pt/((PQ/sup 2+/+)/sub n/)/sub surf/ electrode is held approx. 100 mV more negative than E/sup 0/'((PQ/sup 2+/+)/sub n/)/sub surf/ = -0.45 V vs. SCE in CH/sub 3/CN/0.1 M (n-Bu/sub 1/N)ClO/sub 4/. However, contrary to theoretical expectations based only on the rate constant for reaction of Fe(phen)/sub 3//sup 3 +/ with a surface PQ/sup +/, the onset of current for the mediated reduction is at the onset for ((PQ/sup 2 +/)/sub n/)/sub surf/ ..-->.. ((PQ/sup +/)/sub n/)/sub surf/ reduction; in fact, the mediated reduction current in the onset region is directly proportional to the concentration of PQ/sup +/ in the surface-confined polymer. Data for Pt/((PQ/sup 2 +/ xFe(CN)/sub 6//sup 3-/4-/)/sub n/)/sub surf/ electrodes show directly that charge transport in the polymer can be a limitation to the maximum steady-state mediation current in aqueous electrolyte solution at the coverages of ((PQ/sup 2+/+)/sub n/)/sub surf/ that have been employed. The charge-transport properties of the polymer are concluded to control the current-potential profile, as has been reported previously for other surface-modified electrodes, for the large polymer coverages employed in these studies. 26 references, 13 figures, 1 table.
Inverted critical adsorption of polyelectrolytes in confinement.
de Carvalho, Sidney J; Metzler, Ralf; Cherstvy, Andrey G
2015-06-14
What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer-surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density ?c-defining the adsorption-desorption transition-are in excellent agreement with our analytical calculations based on the ground-state analysis of the Edwards equation. In particular, we confirm the magnitude and scaling of ?c for the concave interfaces versus the Debye screening length 1/? and the extent of confinement a for these three interfaces for small ?a values. For large ?a the critical adsorption condition approaches the known planar limit. The transition between the two regimes takes place when the radius of surface curvature or half of the slit thickness a is of the order of 1/?. We also rationalize how ?c(?) dependence gets modified for semi-flexible versus flexible chains under external confinement. We examine the implications of the chain length for critical adsorption-the effect often hard to tackle theoretically-putting an emphasis on polymers inside attractive spherical cavities. The applications of our findings to some biological systems are discussed, for instance the adsorption of nucleic acids onto the inner surfaces of cylindrical and spherical viral capsids. PMID:25940939
Inverted critical adsorption of polyelectrolytes in confinement
NASA Astrophysics Data System (ADS)
de Carvalho, Sidney J.; Metzler, Ralf; Cherstvy, Andrey G.
What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer-surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density $\\sigma_c$-defining the adsorption-desorption transition-are in excellent agreement with our analytical calculations based on the ground-state analysis of the Edwards equation. In particular, we confirm the magnitude and scaling of $\\sigma_c$ for the concave interfaces versus the Debye screening length $1/\\kappa$ and the extent of confinement $a$ for these three interfaces for small $\\kappa a$ values. For large $\\kappa a$ the critical adsorption condition approaches the planar limit. The transition between the two regimes takes place when the radius of surface curvature or half of the slit thickness $a$ is of the order of $1/\\kappa$. We also rationalize how $\\sigma_c(\\kappa)$ gets modified for semi-flexible versus flexible chains under external confinement. We examine the implications of the chain length onto critical adsorption-the effect often hard to tackle theoretically-putting an emphasis on polymers inside attractive spherical cavities.
Semiclassical construction of random wave functions for confined systems.
Urbina, Juan Diego; Richter, Klaus
2004-01-01
We develop a statistical description of chaotic wave functions in closed systems obeying arbitrary boundary conditions by combining a semiclassical expression for the spatial two-point correlation function with a treatment of eigenfunctions as Gaussian random fields. Thereby we generalize Berry's isotropic random wave model by incorporating confinement effects through classical paths reflected at the boundaries. Our approach allows one to explicitly calculate highly nontrivial statistics, such as intensity distributions, in terms of usually few short orbits, depending on the energy window considered. We compare with numerical quantum results for the Africa billiard and derive nonisotropic random wave models for other prominent confinement geometries. PMID:15324114
Confinement of Equilibrium Polymers
NASA Astrophysics Data System (ADS)
Feng, Edward
2005-03-01
We consider supramolecular polymer systems in which reversible intermolecular bonding affects the thermodynamics of the system. While we have formulated models for a number of such systems, this presentation focuses on equilibrium polymers in which monomers can reversibly link together to form linear polymers. This serves as a model for giant micelles of surfactant molecules that can break and recombine at any point along the cylindrical micelle. While equilibrium polymers in bulk environments have been studied, we investigate their behavior in confined environments such as between two parallel plates. Our model features a continuous distribution of polymer lengths and assumes a favorable energy decrease when two monomers form a bond. We are interested in how confinement affects the density profile and the polymer length distribution, and we calculate these properties analytically using the ground state dominance approximation and computationally employing self-consistent field theory.
Totally confined explosive welding
NASA Technical Reports Server (NTRS)
Bement, L. J. (inventor)
1978-01-01
The undesirable by-products of explosive welding are confined and the association noise is reduced by the use of a simple enclosure into which the explosive is placed and in which the explosion occurs. An infrangible enclosure is removably attached to one of the members to be bonded at the point directly opposite the bond area. An explosive is completely confined within the enclosure at a point in close proximity to the member to be bonded and a detonating means is attached to the explosive. The balance of the enclosure, not occupied by explosive, is filled with a shaped material which directs the explosive pressure toward the bond area. A detonator adaptor controls the expansion of the enclosure by the explosive force so that the enclosure at no point experiences a discontinuity in expansion which causes rupture. The use of the technique is practical in the restricted area of a space station.
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.
Inertial Confinement fusion targets
NASA Technical Reports Server (NTRS)
Hendricks, C. D.
1982-01-01
Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques were devised for producing the targets. Glass and metal shells are made by using drop and bubble techniques. Solid hydrogen shells are also produced by adapting old methods to the solution of modern problems. Some of these techniques, problems, and solutions are discussed. In addition, the applications of many of the techniques to fabrication of ICF targets is presented.
H. P. Furth
1990-01-01
Fusion plasmas with reactorlike temperatures have been confined in magnetic-field configurations of the tokamak type. The measured rate of heat leakage from these plasmas is sufficiently small to be compatible with the requirements of a full-sized fusion power reactor. Improvements in other aspects of reactor performance are still needed, however, and the high cost of reactor-development steps has become an
H. P. Furth
1990-01-01
Fusion plasmas with reactorlike temperatures have been confined in magnetic-field configurations of the tokamak type. The measured rate of heat leakage from these plasmas is sufficiently small to be compatible with the requirements of a full-sized fusion power reactor. Improvements in other aspects of reactor performance are still needed, however, and the high cost of reactor-development steps has become an
Furth, H P
1990-09-28
Fusion plasmas with reactorlike temperatures have been confined in magnetic-field configurations of the tokamak type. The measured rate of heat leakage from these plasmas is sufficiently small to be compatible with the requirements of a full-sized fusion power reactor. Improvements in other aspects of reactor performance are still needed, however, and the high cost of reactor- development steps has become an obstacle on the path to practical fusion power. PMID:17748724
NASA Technical Reports Server (NTRS)
Horzela, Andrzej; Kapuscik, Edward
1993-01-01
An alternative picture of classical many body mechanics is proposed. In this picture particles possess individual kinematics but are deprived from individual dynamics. Dynamics exists only for the many particle system as a whole. The theory is complete and allows to determine the trajectories of each particle. It is proposed to use our picture as a classical prototype for a realistic theory of confined particles.
General approach to polymer chains confined by interacting boundaries.
Freed, Karl F; Dudowicz, Jacek; Stukalin, Evgeny B; Douglas, Jack F
2010-09-01
Polymer chains, confined to cavities or polymer layers with dimensions less than the chain radius of gyration, appear in many phenomena, such as gel chromatography, rubber elasticity, viscolelasticity of high molar mass polymer melts, the translocation of polymers through nanopores and nanotubes, polymer adsorption, etc. Thus, the description of how the constraints alter polymer thermodynamic properties is a recurrent theoretical problem. A realistic treatment requires the incorporation of impenetrable interacting (attractive or repulsive) boundaries, a process that introduces significant mathematical complications. The standard approach involves developing the generalized diffusion equation description of the interaction of flexible polymers with impenetrable confining surfaces into a discrete eigenfunction expansion, where the solutions are normally truncated at the first mode (the "ground state dominance" approximation). This approximation is mathematically well justified under conditions of strong confinement, i.e., a confinement length scale much smaller than the chain radius of gyration, but becomes unreliable when the polymers are confined to dimensions comparable to their typically nanoscale size. We extend a general approach to describe polymers under conditions of weak to moderate confinement and apply this semianalytic method specifically to determine the thermodynamics and static structure factor for a flexible polymer confined between impenetrable interacting parallel plate boundaries. The method is first illustrated by analyzing chain partitioning between a pore and a large external reservoir, a model system with application to chromatography. Improved agreement is found for the partition coefficients of a polymer chain in the pore geometry. An expression is derived for the structure factor S(k) in a slit geometry to assist in more accurately estimating chain dimensions from scattering measurements for thin polymer films. PMID:20831332
Spatially confined assembly of nanoparticles.
Jiang, Lin; Chen, Xiaodong; Lu, Nan; Chi, Lifeng
2014-10-21
The ability to assemble NPs into ordered structures that are expected to yield collective physical or chemical properties has afforded new and exciting opportunities in the field of nanotechnology. Among the various configurations of nanoparticle assemblies, two-dimensional (2D) NP patterns and one-dimensional (1D) NP arrays on surfaces are regarded as the ideal assembly configurations for many technological devices, for example, solar cells, magnetic memory, switching devices, and sensing devices, due to their unique transport phenomena and the cooperative properties of NPs in assemblies. To realize the potential applications of NP assemblies, especially in nanodevice-related applications, certain key issues must still be resolved, for example, ordering and alignment, manipulating and positioning in nanodevices, and multicomponent or hierarchical structures of NP assemblies for device integration. Additionally, the assembly of NPs with high precision and high levels of integration and uniformity for devices with scaled-down dimensions has become a key and challenging issue. Two-dimensional NP patterns and 1D NP arrays are obtained using traditional lithography techniques (top-down strategies) or interfacial assembly techniques (bottom-up strategies). However, a formidable challenge that persists is the controllable assembly of NPs in desired locations over large areas with high precision and high levels of integration. The difficulty of this assembly is due to the low efficiency of small features over large areas in lithography techniques or the inevitable structural defects that occur during the assembly process. The combination of self-assembly strategies with existing nanofabrication techniques could potentially provide effective and distinctive solutions for fabricating NPs with precise position control and high resolution. Furthermore, the synergistic combination of spatially mediated interactions between nanoparticles and prestructures on surfaces may play an increasingly important role in the controllable assembly of NPs. In this Account, we summarize our approaches and progress in fabricating spatially confined assemblies of NPs that allow for the positioning of NPs with high resolution and considerable throughput. The spatially selective assembly of NPs at the desired location can be achieved by various mechanisms, such as, a controlled dewetting process, electrostatically mediated assembly of particles, and confined deposition and growth of NPs. Three nanofabrication techniques used to produce prepatterns on a substrate are summarized: the Langmuir-Blodgett (LB) patterning technique, e-beam lithography (EBL), and nanoimprint lithography (NPL). The particle density, particle size, or interparticle distance in NP assemblies strongly depends on the geometric parameters of the template structure due to spatial confinement. In addition, with smart design template structures, multiplexed NPs can be assembled into a defined structure, thus demonstrating the structural and functional complexity required for highly integrated and multifunction applications. PMID:25244100
Riahi, Siavash; Ganjali, Mohammad Reza; Moghaddam, Abdolmajid Bayandori; Norouzi, Parviz
2008-04-01
The electrode potential of 2-(4,5-dihydroxy-2-methylphenyl)-2-phenyl-2H-indene-1,3-dione (DMPID) in acetonitrile has been calculated. The calculations were performed using ab initio molecular orbital calculations (HF), and density functional theory (DFT) with the inclusion of entropic and thermochemical corrections to yield free energies of redox reactions. The electrode potential of DMPID was also obtained experimentally with the aid of an electrochemical technique (cyclic voltammetry). The values for geometric parameters and the vibrational frequencies of DMPID and 2-(6-methyl-3,4-dioxocyclohexa-1,5-dienyl)-2-phenyl-2H-indene-1,3-dione (MDPID) were also computed using the same levels with the basis set of 6-31G(d). The calculated IR spectrum of DMPID used for the assignment of IR frequencies was observed in the experimental FT-IR spectrum and the calculated IR and FT-IR observed spectra of DMPID were compared with correlation factor of 0.996. It should be mentioned that the present work is the first research on coagulant derivative molecules in which the electrode potential of a molecule is calculated. Optimized structures of 2-(6-methyl-3,4-dioxocyclohexa-1,5-dienyl)-2-phenyl-2H-indene-1,3-dione (MDPID). PMID:18274794
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…
CUSP Energetic Particles: Confinement, Acceleration and Implications
NASA Technical Reports Server (NTRS)
Chen, Jiasheng
1999-01-01
The cusp energetic particle (CEP) event is a new magnetospheric phenomenon. The events were detected in the dayside cusp for hours, in which the measured helium ions had energies up to 8 MeV. All of these events were associated with a dramatic decrease and large fluctuations in the local magnetic field strength. During January 1999 - December 1999 covered by this report, I have studied the CEP events by analyzing the POLAR, GEOTAIL, and WIND particle and magnetic field data measured during the geomagnetic quiet periods in 1996 and one geomagnetic storm period in 1998. The simultaneous observations indicated that the ion fluxes in the CEP events were higher than that in both the upstream and the downstream from the bow shock. The pitch angle distribution of the helium ions in the CEP events was found to peak around 90 deg. It was found that the mirror parameter, defined as the ratio of the square root of the integration of the parallel turbulent power spectral component over the ultra-low frequency (ULF) ranges to the mean field in the cusp, is correlated with the intensity of the cusp MeV helium flux, which is a measure of the influence of mirroring interactions and an indication of local effect. It was also found that the turbulent power of the local magnetic field in the ultra-low frequency (ULF) ranges is correlated with the intensity of the cusp energetic helium ions. Such ULF ranges correspond to periods of about 0.33-500 seconds that cover the gyroperiods, the bounce periods, and the drift periods of the tens keV to MeV charged particles when they are temporarily confined in the high-altitude dayside cusp. These observations represent a discovery that the high-altitude dayside cusp is a new acceleration and dynamic trapping region of the magnetosphere. The cusp geometry is connected via gradient and curvature drift of these energized ions to the equatorial plasma sheet as close as the geostationary orbit at local midnight. It implies that the dayside cusp is potentially an important source of magnetospheric particles. The discovery of the CEP events has been recognized as one of the most significant results from POLAR. I was invited to give a talk at 1999 IUGG meeting to interpret the CEP events. This discovery has also been written into the web-based Space Physics Text Book (http://www.oulu.fi/- spaceweb/textbook/cusp.html).
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
Self-assembly of Cylindrically Confined Block Copolymers in Core-Shell Electrospun Fibers
NASA Astrophysics Data System (ADS)
Ma, Minglin; Rutledge, Gregory
2008-03-01
We report the development of electrospun fibers with internal structure by two-fluid coaxial electrospinning of block copolymers. Microphase separated morphologies with a long-range order were obtained by annealing the fibers at a temperature greater than the glass transition temperature of either block of the copolymer core but less than the glass transition temperature of the polymer shell. Various interesting, unusual and in some cases unprecedented self-assembled morphologies of block copolymers have been observed. Based on quantitative analyses, confinement within the cylindrical geometry was found to affect both the microphase morphology and fundamental period of the block copolymer. These internally nanostructured fibers have both practical and fundamental intellectual importance. For example, these fibers have unique potential for applications in optics, photonics, drug delivery, and other uses because of their small diameter, unique internal structure, and continuous filamentary nature.
Confinement from gluodynamics in curved space-time
Gaete, Patricio; Spallucci, Euro [Departamento de Fisica, Universidad Tecnica Federico Santa Maria, Valparaiso (Chile); Dipartimento di Fisica Teorica, Universita di Trieste and INFN, Sezione di Trieste (Italy)
2008-01-15
We determine the static potential for a heavy quark-antiquark pair from gluodynamics in curved space-time. Our calculation is done within the framework of the gauge-invariant, path-dependent, variables formalism. The potential energy is the sum of a Yukawa and a linear potential, leading to the confinement of static charges.
Order-Disorder structural transition in a confined fluid
de la Calleja-Mora, Elsa M; Barbosa, Marcia C
2015-01-01
In this paper the amorphous/solid to disorder liquid structural phase transitions of an anomalous confined fluid is analyzed using their local fractal dimension. The model is a system of particles interacting through a two length scales potentials confined by two infinite plates. In the bulk, this fluid exhibit water-like anomalies and under confinement forms layers of particles. The particle distributions of them, present different arrangements related to amorphous/solid phases. Here only the contact layer is analyzed through fractal singularity spectrum. At high densities the structural transition its quantify by the order degree to determine the phases affected by the confinement. This mapping shows that the system as the temperature increased, the fractal dimension decreases, which is consistent with the behavior studying in such systems. This result suggests that under thermodynamic perturbations, an anomalous confined liquid, presents different phase transitions achieving be characterized by its fractal...
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
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
Lee, EokKyun
2011-01-01
fluids confined to micropores Hyungjun Kim,1,2,a) William A. Goddard III,1,2 Kyeong Hwan Han,3 Changho-dimensional hard sphere fluids confined to slit pores by applying Speedy and Reiss' interpretation of cavity space of fluids in restricted geometries has been of long-standing interest. Owing to the recent rapid development
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.
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.
Paolo Malgaretti; Ignacio Pagonabarraga; J. Miguel Rubi
2014-11-14
We analyze the performance of a Brownian ratchet in the presence of geometrical constraints. A two-state model that describes the kinetics of molecular motors is used to characterize the energetic cost when the motor proceeds under confinement, in the presence of an external force. We show that the presence of geometrical constraints has a strong effect on the performance of the motor. In particular, we show that it is possible to enhance the ratchet performance by a proper tuning of the parameters characterizing the environment. These results open the possibility of engineering entropically-optimized transport devices.
Self-organizing human cardiac microchambers mediated by geometric confinement
NASA Astrophysics Data System (ADS)
Ma, Zhen; Wang, Jason; Loskill, Peter; Huebsch, Nathaniel; Koo, Sangmo; Svedlund, Felicia L.; Marks, Natalie C.; Hua, Ethan W.; Grigoropoulos, Costas P.; Conklin, Bruce R.; Healy, Kevin E.
2015-07-01
Tissue morphogenesis and organ formation are the consequences of biochemical and biophysical cues that lead to cellular spatial patterning in development. To model such events in vitro, we use PEG-patterned substrates to geometrically confine human pluripotent stem cell colonies and spatially present mechanical stress. Modulation of the WNT/?-catenin pathway promotes spatial patterning via geometric confinement of the cell condensation process during epithelial-mesenchymal transition, forcing cells at the perimeter to express an OCT4+ annulus, which is coincident with a region of higher cell density and E-cadherin expression. The biochemical and biophysical cues synergistically induce self-organizing lineage specification and creation of a beating human cardiac microchamber confined by the pattern geometry. These highly defined human cardiac microchambers can be used to study aspects of embryonic spatial patterning, early cardiac development and drug-induced developmental toxicity.
Self-organizing human cardiac microchambers mediated by geometric confinement.
Ma, Zhen; Wang, Jason; Loskill, Peter; Huebsch, Nathaniel; Koo, Sangmo; Svedlund, Felicia L; Marks, Natalie C; Hua, Ethan W; Grigoropoulos, Costas P; Conklin, Bruce R; Healy, Kevin E
2015-01-01
Tissue morphogenesis and organ formation are the consequences of biochemical and biophysical cues that lead to cellular spatial patterning in development. To model such events in vitro, we use PEG-patterned substrates to geometrically confine human pluripotent stem cell colonies and spatially present mechanical stress. Modulation of the WNT/?-catenin pathway promotes spatial patterning via geometric confinement of the cell condensation process during epithelial-mesenchymal transition, forcing cells at the perimeter to express an OCT4+ annulus, which is coincident with a region of higher cell density and E-cadherin expression. The biochemical and biophysical cues synergistically induce self-organizing lineage specification and creation of a beating human cardiac microchamber confined by the pattern geometry. These highly defined human cardiac microchambers can be used to study aspects of embryonic spatial patterning, early cardiac development and drug-induced developmental toxicity. PMID:26172574
Self-organizing human cardiac microchambers mediated by geometric confinement
Ma, Zhen; Wang, Jason; Loskill, Peter; Huebsch, Nathaniel; Koo, Sangmo; Svedlund, Felicia L.; Marks, Natalie C.; Hua, Ethan W.; Grigoropoulos, Costas P.; Conklin, Bruce R.; Healy, Kevin E.
2015-01-01
Tissue morphogenesis and organ formation are the consequences of biochemical and biophysical cues that lead to cellular spatial patterning in development. To model such events in vitro, we use PEG-patterned substrates to geometrically confine human pluripotent stem cell colonies and spatially present mechanical stress. Modulation of the WNT/?-catenin pathway promotes spatial patterning via geometric confinement of the cell condensation process during epithelial–mesenchymal transition, forcing cells at the perimeter to express an OCT4+ annulus, which is coincident with a region of higher cell density and E-cadherin expression. The biochemical and biophysical cues synergistically induce self-organizing lineage specification and creation of a beating human cardiac microchamber confined by the pattern geometry. These highly defined human cardiac microchambers can be used to study aspects of embryonic spatial patterning, early cardiac development and drug-induced developmental toxicity. PMID:26172574
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
Holographic thermalization in a quark confining background
NASA Astrophysics Data System (ADS)
Ageev, D. S.; Aref'eva, I. Ya.
2015-03-01
We study holographic thermalization of a strongly coupled theory inspired by two colliding shock waves in a vacuum confining background. Holographic thermalization means a black hole formation, in fact, a trapped surface formation. As the vacuum confining background, we considered the well-know bottom-up AdS/QCD model that provides the Cornell potential and reproduces the QCD ?-function. We perturb the vacuum background by colliding domain shock waves that are assumed to be holographically dual to heavy ions collisions. Our main physical assumption is that we can make a restriction on the time of trapped surface formation, which results in a natural limitation on the size of the domain where the trapped surface is produced. This limits the intermediate domain where the main part of the entropy is produced. In this domain, we can use an intermediate vacuum background as an approximation to the full confining background. We find that the dependence of the multiplicity on energy for the intermediate background has an asymptotic expansion whose first term depends on energy as E 1/3, which is very similar to the experimental dependence of particle multiplicities on the colliding ion energy obtained from the RHIC and LHC. However, this first term, at the energies where the approximation of the confining metric by the intermediate background works, does not saturate the exact answer, and we have to take the nonleading terms into account.
The specific heat of confined helium near the lambda point
NASA Astrophysics Data System (ADS)
Nissen, J. A.; Chui, T. C. P.; Lipa, J. A.
1993-09-01
Heat capacity measurements of the liquid helium lambda transition in confined geometries have long been in disagreement with scaling theories of second order phase transitions. We present measurements of a 19 micron film which extend the results of Chen and Gasparini (CG) to near macroscopic size. We find that the new data as well as most of the CG data are in reasonable agreement with recent renormalization group theory calculations.
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.
Kalousek, D K; Vekemans, M
1996-01-01
In most pregnancies the chromosomal complement detected in the fetus is also present in the placenta. The detection of an identical chromosomal complement in both the fetus and its placenta has always been expected as both develop from the same zygote. However, in approximately 2% of viable pregnancies studied by chorionic villus sampling (CVS) at 9 to 11 weeks of gestation, the cytogenetic abnormality, most often trisomy, is confined to the placenta. This phenomenon is known as confined placental mosaicism (CPM). It was first described by Kalousek and Dill in term placentas of infants born with unexplained intrauterine growth restriction (IUGR). Contrary to generalised mosaicism, which is characterised by the presence of two or more karyotypically different cell lines within both the fetus and its placenta, CPM represents tissue specific chromosomal mosaicism affecting the placenta only. The diagnosis of CPM is most commonly made when, after the diagnosis of chromosomal mosaicism in a CVS sample, the second prenatal testing (amniotic fluid culture or fetal blood culture analysis) shows a normal diploid karyotype. PMID:8818935
Trapping ultracold atoms in a time-averaged adiabatic potential
Gildemeister, M.; Nugent, E.; Sherlock, B. E.; Kubasik, M.; Sheard, B. T.; Foot, C. J.
2010-03-15
We report an experimental realization of ultracold atoms confined in a time-averaged, adiabatic potential (TAAP). This trapping technique involves using a slowly oscillating ({approx}kHz) bias field to time-average the instantaneous potential given by dressing a bare magnetic potential with a high-frequency ({approx}MHz) magnetic field. The resultant potentials provide a convenient route to a variety of trapping geometries with tunable parameters. We demonstrate the TAAP trap in a standard time-averaged orbiting potential trap with additional Helmholtz coils for the introduction of the radio frequency dressing field. We have evaporatively cooled 5x10{sup 4} atoms of {sup 87}Rb to quantum degeneracy and observed condensate lifetimes of longer than 3 s.
Color Confinement and Massive Gluons
M. Chaichian; K. Nishijima
2005-11-15
Color confinement is one of the central issues in QCD so that there are various interpretations of this feature. In this paper we have adopted the interpretation that colored particles are not subject to observation just because colored states are unphysical in the sense of Eq. (2.16). It is shown that there are two phases in QCD distinguished by different choices of the gauge parameter. In one phase, called the "confinement phase", color confinement is realized and gluons turn out to be massive. In the other phase, called the "deconfinement phase", color confinement is not realized, but the gluons remain massless.
A cylindrical geometry for cardiac SPECT imaging
Chang, W.; Liu, J.; Yu, D.; Loncaric, S. [Rush Presbyterian-St. Luke`s Medical Center, Chicago, IL (United States)] [Rush Presbyterian-St. Luke`s Medical Center, Chicago, IL (United States)
1996-08-01
In SPECT imaging, a cylindrical detector geometry offers many advantages. Because the detector completely surrounds the patient, the cylindrical system geometry should provide more detector coverage than the rotating camera SPECT systems. This increased coverage means increased sensitivity, or improved resolution, and better image quality. Because the cylindrical detector system is stationary and the projection data is acquired through collimator rotation, this geometry simplifies system design and allows very stable imaging performance. They propose a cylindrical system geometry that features a large number of projections for a small FOV located at the center of the gantry. This geometry has potential for cardiac SPECT imaging, provided that the patient`s body can be offset properly and reliably to place his heart in the specified FOV. General design issues and potential configurations for such a cardiac SPECT system are presented.
Constraints on the magnetic field geometry of magnetars
H. Sotani; A. Colaiuda; K. D. Kokkotas
2008-01-01
We study the effect of the magnetic field geometry on the oscillation spectra of strongly magnetized stars. We construct a configuration of magnetic field where a toroidal component is added to the standard poloidal one. We consider a star with a type I superconductor core so that both components of the magnetic field are expelled from the core and confined
New confining force solution of QCD domain wall problem
Barr, S M
2014-01-01
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 axion dark energy.
The virial theorem for the smoothly and sharply, penetrably and impenetrably confined hydrogen atom
Katriel, Jacob [Department of Chemistry, Technion, Haifa 32000 (Israel) and Nazareth Academic Institute, Nazareth 16100 (Israel); Montgomery, H. E. Jr. [Chemistry Program, Centre College, Danville, Kentucky 40422 (United States)
2012-09-21
Confinement of atoms by finite or infinite boxes containing sharp (discontinuous) jumps has been studied since the fourth decade of the previous century, modelling the effect of external pressure. Smooth (continuous) counterparts of such confining potentials, that depend on a parameter such that in an appropriate limit they coincide with the sharp confining potentials, are investigated, with an emphasis on deriving the corresponding virial and Hellmann-Feynman theorems.
Track structure, chromosome geometry and chromosome aberrations.
Brenner, D J; Ward, J F; Sachs, R K
1994-01-01
The joint role of radiation track structure and chromosome geometry in determining yields of chromosome aberrations is discussed. Ideally, the geometric models of chromosomes used for analyzing aberration yields should have the same degree of realism as track structure models. However, observed chromosome aberrations are produced by processes on comparatively large scales, e.g., misrepair involving two DSB located on different chromosomes or two DSB separated by millions of base pairs on one chromosome, and quantitative models for chromatin on such large scales have to date almost never been attempted. We survey some recent data on large-scale chromosome geometry, mainly results obtained with fluorescence in situ hybridization ("chromosome painting") techniques. Using two chromosome models suggested by the data, we interpret the relative yields, at low and high LET, of inter-chromosomal aberrations compared to intra-chromosomal, inter-arm aberrations. The models consider each chromosome confined within its own "chromosome localization sphere," either as a random cloud of points in one model or as a confined Gaussian polymer in the other. In agreement with other approaches, our results indicate that at any given time during the G0/G1 part of the cell cycle a chromosome is largely confined to a sub-volume comprising less than 10% of the volume of the cell nucleus. The possible significance of the ratio of inter-chromosomal aberrations to intra-chromosomal, inter-arm aberrations as an indicator of previous exposure to high LET radiation is outlined. PMID:7755549
Confined volume blasting experiments: Description and analysis
Gorham-Bergeron, E.; Kuszmaul, J.S.; Bickel, T.C.; Shirey, D.L.
1987-01-01
A series of bench-scale blasting experiments was conducted to produce rubble beds for use in retorting experiments. The experiments consisted of blasting oil shale with explosives within a confined volume containing 25% void. A variety of blasting geometries was used to control the fragment size distribution and void distribution in the rubble. The series of well controlled tests provided excellent data for use in validating rock fragmentation models. Analyses of the experiments with PRONTO, a dynamic finite element computer code, and a newly developed fracturing model provided good agreement between code predictions and experimental measurements of fracture extent and fragment size. CAROM, a dynamic distinct element code developed to model rock motion during blasting, was used to model the fully fragmented tests. Calculations of the void distribution agreed well with experimentally measured values. 9 refs., 11 figs., 1 tab.
Confinement from a massive scalar in QCD
Rainer Dick
1998-02-28
A model is introduced with a massive scalar coupling to the Yang--Mills term in four--dimensional gauge theory. It is shown that the resulting potential of colour sources consists of a short range Coulomb interaction and a long range confining part. Far away from the source the scalar vanishes $\\sim r^{-1}$ while the potential diverges linearly $\\sim r$. Up to an $N_c$--dependent factor of order 1 the tension parameter in the model is $gmf$, where $m$ denotes the mass of the scalar and $f$ is a coupling scale entering the scalar--gluon coupling.
The Effect of Molecular Anchoring and Curvature on Confined Liquid Crystals
Renate Johanna Ondris-Crawford
1993-01-01
Nematic liquid crystals confined to curved geometries exhibit unique elastic and anchoring properties. One result of this study was the first simultaneous measurement of the azimuthal (W_phi) and polar (W_theta) anchoring strength and the saddle-splay surface elastic constant K_{24}. The technique confined 4^'-pentyl-4 -cyanobiphenyl (5CB) to submicrometer polyimide treated cylindrical cavities of polycarbonate (Nuclepore) membranes with concentric tangential anchoring conditions
NSDL National Science Digital Library
Geometry and Topology is "a fully refereed international journal dealing with all aspects of geometry and topology and their applications." The publisher, Geometry & Topology Publications (GTP), is a non-profit organization based in the Mathematics Department of the University of Warwick at Coventry, UK. Visitors can browse the journal, available free of charge electronically, or search by keyword or author. The moderate collection within the Geometry and Topology Monographs series includes research monographs and refereed conference proceedings.
Baldwin, John T.
with high school teachers on `how to teach geomety' 2 One session of History of Mathematics on `the the axiomatization of geometry affect the teaching of high school geometry? #12;Geometry and Proof John T. Baldwin conclusions? Checking the truth of the premises is 1 Mathematics if the premises are mathematical. #12
ERIC Educational Resources Information Center
McDonald, Nathaniel J.
2001-01-01
Chronicles a teacher's first year teaching geometry at the Hershey Montessori Farm School in Huntsburg, Ohio. Instructional methods relied on Euclid primary readings and combined pure abstract logic with practical applications of geometry on the land. The course included geometry background imparted by Montessori elementary materials as well as…
NSDL National Science Digital Library
Ms. Nieman
2007-11-22
Gotta Getcha some Great Goofy Geometry Games! Billy Bug is so hungry! Move him to the right coordinate so that he can eat! Make the puzzle pieces bigger or smaller to fit the puzzle in Cyberchase Geometry! If you want a definition of any geometry term.. click the word Definition ...
Geometries for Possible Kinematics
Chao-Guang Huang; Yu Tian; Xiao-Ning Wu; Zhan Xu; Bin Zhou
2010-07-21
The algebras for all possible Lorentzian and Euclidean kinematics with $\\frak{so}(3)$ isotropy except static ones are re-classified. The geometries for algebras are presented by contraction approach. The relations among the geometries are revealed. Almost all geometries fall into pairs. There exists $t \\leftrightarrow 1/(\
Coronal electron confinement by double layers
Li, T. C.; Drake, J. F.; Swisdak, M. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 (United States)
2013-12-01
In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons. The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and also find a linear scaling with the hot electron temperature. The DL strength obtained from the analytic calculation is comparable to that from the simulations. At the maximum strength, the DL is capable of confining a significant fraction of hot electrons in the source.
QUANTUM CONFINEMENT IN NANOCRYSTALLINE SILICON
M. L. Ciurea
Quantum confinement effects in different kinds of nanocrystalline silicon systems are experimentally and theoretically investigated. Porous silicon structured as a nanowire network and silicon nanodots embedded in amorphous silicon dioxide are studied. The main quantum confinement effect in both cases is represented by the appearance of new energy levels in the silicon band gap. The corresponding energies can be experimentally
Monopole confinement by flux tube
Chandrasekhar Chatterjee; Amitabha Lahiri
2006-10-24
We revisit Nambu's model of quark confinement by a tube of magnetic flux, with two additional features. The quarks are taken to be magnetic monopoles external to the tube, which seal the ends, and are also taken to be fermions. This ensures that the model is inconsistent unless there are at least two species of fermions being confined.
Cooperative Length Scale and Fragility of Polystyrene under Confinement
NASA Astrophysics Data System (ADS)
Zhang, Chuan; Guo, Yunlong; Priestley, Rodney
2012-02-01
While thin films are an attractive model system to investigate the impact of confinement on glassy behavior, extending studies beyond thin films to geometries of higher dimensionalities is vital from both scientific and technological viewpoints. In this talk, we present the impact of confinement on the characteristic length at the glass transition as well as the fragility for confined polystyrene (PS) nanoparticles under isochoric conditions. We measure the glass transition temperature (Tg), fictive temperature (Tf) and isochoric heat capacity of silica-capped PS nanoparticles as a function of diameter via differential scanning calorimetry. From the measurement of Tf, we obtain the isochoric fragility, and via the fluctuation formula, the characteristic length at the glass transition. We illustrate that confinement under isochoric conditions for PS nanoparticles leads to a significant increase in the isochoric fragility while the characteristic length is reduced with size. At the minimum the results demonstrate a relationship between fragility and the characteristics length of isochorically-confined polymer that is not intuitive from the Adam-Gibbs theory.
Density of States Simulations of Confined Glasses
NASA Astrophysics Data System (ADS)
Faller, Roland; Ghosh, Jayeeta
2008-03-01
Glassy systems under confinement have been studied with great enthusiasm and effort for the last decades. They are relevant both fundamentally and technically because there is still debate about the nature of glass transition in small geometries which is important for lithographic processes in the semiconductor and other industries. In this work we are using the Wang-Landau approach also known as Density of States Monte Carlo to study glassy systems in bulk and under confinement. We apply the technique to a model binary Lennard Jones glass as well as the small organic glass former Ortho-terphenyl (OTP). For Lennard Jones glasses we use a well tested model. For OTP we start from a united atom model and then derive systematically a coarse grained representation by replacing each phenyl ring with a bead and using the Iterative Boltzmann Inversion. The properties of bulk Lennard Jones model show very good agreement with literature values. The atomistic and coarse grained representations of ortho-terphenyl in the bulk are in good agreement with experiments. Unsupported freestanding films show a lower glass transition than the bulk value.
Viscous fingering and liquid crystals in confinement
NASA Astrophysics Data System (ADS)
Zacharoudiou, Ioannis
This thesis focuses on two problems lying within the field of soft condensed matter: the viscous fingering or Saffman-Taylor instability and nematic liquid crystals in confinement. Whenever a low viscosity fluid displaces a high viscosity fluid in a porous medium, for example water pushing oil out of oil reservoirs, the interface between the two fluids is rendered unstable. Viscous fingers develop, grow and compete until a single finger spans all the way from inlet to outlet. Here, using a free energy lattice Boltzmann algorithm, we examine the Saffman-Taylor instability for two different wetting situations: (a) when neither of the two fluids wet the walls of the channel and (b) when the displacing fluids completely wets the walls. We demonstrate that curvature effects in the third dimension, which arise because of the wetting boundary conditions, can lead to a novel suppression of the instability. Recent experiments in microchannels using colloid-polymer mixtures support our findings. In the second part of the thesis we examine nematic liquid crystals confined in wedge-structured geometries. In these systems the final stable configuration of the liquid crystal system is controlled by the complex interplay between confinement, elasticity and surface anchoring. Varying the wedge opening angle this competition leads to a splay to bend transition mediated by a defect in the bulk of the wedge. Using a hybrid lattice Boltzmann algorithm we study the splay-bend transition and compare to recent experiments on {em fd} virus particles in microchannels. Our numerical results, in quantitative agreement with the experiments, enable us to predict the position of the defect as a function of opening angle, and elucidate its role in the change of director structure. This has relevance to novel energy saving, liquid crystal devices which rely on defect motion and pinning to create bistable director configurations.
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.
Carrier Localization in Confined Vanadate Superlattices
NASA Astrophysics Data System (ADS)
Eaton, Craig; Zhang, Lei; Engel-Herbert, Roman
2015-03-01
Perovskite oxide heterostructures have attracted attention due to the wealth of phenomena emerging at the interface, as well as the presence of strong electron correlations with potential applications as active electronic material for logic application utilizing the metal-to-insulator transition. Successful monolithic integration of perovskite oxides with Si makes them an ideal material choice. Here we present the growth of cubic SrTiO3/SrVO3/SrTiO3 heterostructures on (La0.3Sr0.7) (Al0.65Ta0.35) O3 substrates and orthorhombically distorted CaTiO3/CaVO3/CaTiO3 heterostructures on (LaSrAlTa4) O3 substrates by hybrid molecular beam epitaxy, where alkaline earth metals were supplied using conventional effusion cells and the transition metals from the metal-organic precursor titanium-isopropoxide and vanadium oxi-tri-isopropoxide. Here, the interfaces are non-polar and carrier confinement in the correlated vanadate metals (d1 configuration, 1 electron per unit cell) is achieved using insulating titanates as barrier material. Growth challenges associated with optimizing conditions for cation and oxygen stoichiometry are discussed. Confined structures down to 2 ML have been studied to demonstrate the potential for tuning incipient 2D Mott transition from 3D correlated metal. Room temperature hall measurements revealed carrier concentration in SrVO3 films are 2 × 1022 cm-3 in thick films and decreases to 8 × 1020 cm-3 at 3 ML confinement, revealing the onset of strong carrier localization. Direct comparison between SrVO3 and CaVO3 structures are presented to elucidate the role of dimensional confinement and structural distortion.
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.
Confinement of ultracold atoms in a Laguerre-Gaussian laser beam created with diffractive optics
NASA Astrophysics Data System (ADS)
Kennedy, Sharon A.; Biedermann, G. W.; Farrar, J. T.; Akin, T. G.; Krzyzewski, S. P.; Abraham, E. R. I.
2014-06-01
We report 2D confinement of 87Rb atoms in a Laguerre-Gaussian laser beam. Changing of the sign of the detuning from the atomic resonance dramatically alters the geometry of the confinement. With the laser detuned to the blue, the atoms are confined to the dark, central node of the Laguerre-Gaussian laser mode. This trapping method leads to low ac Stark shifts to the atomic levels. Alternatively, by detuning the laser to the red of the resonance, we confine atoms to the high intensity outer ring in a multiply-connected, toroidal configuration. We model the confined atoms to determine azimuthal intensity variations of the trapping laser, caused by slight misalignments of the Laguerre-Gaussian mode generating optics.
Transport of Brownian particles confined to a weakly corrugated channel
Xinli Wang; German Drazer
2010-05-15
We investigate the average velocity of Brownian particles driven by a constant external force when constrained to move in two-dimensional, weakly-corrugated channels. We consider both the geometric confinement of the particles between solid walls as well as the soft confinement induced by a periodic potential. Using perturbation methods we show that the leading order correction to the marginal probability distribution of particles in the case of soft confinement is equal to that obtained in the case of geometric confinement, provided that the (configuration) integral over the cross-section of the confining potential is equal to the width of the solid channel. We then calculate the probability distribution and average velocity in the case of a sinusoidal variation in the width of the channels. The reduction on the average velocity is larger in the case of soft channels at small P\\'eclet numbers and for relatively narrow channels and the opposite is true at large P\\'eclet numbers and for wide channels. In the limit of large P\\'eclet numbers the convergence to bulk velocity is faster in the case of soft channels. The leading order correction to the average velocity and marginal probability distribution agree well with Brownian Dynamics simulations for the two types of confinement and over a wide range of P\\'eclet numbers.
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.
A confining quark model and new gauge symmetry
NASA Astrophysics Data System (ADS)
Hsu, Jong-Ping
2014-07-01
We discuss a confining model for quark-antiquark system with a new color SU3 gauge symmetry. New gauge transformations involve non-integrable phase factors and lead to the fourth-order gauge field equations and a linear potential. The massless gauge bosons have non-definite energies, which are not observable because they are permanently confined in quark systems by the linear potential. We use the empirical potentials of charmonium to determine the coupling strength of the color charge gs and find gs2/(4? ) ? 0.2. The rules for Feynman diagrams involve propagators with poles of order 2 associated with new gauge fields. The confining quark model may be renormalizable by power counting and compatible with perturbation theory.
Diffusion Enhancement in Core-softened fluid confined in nanotubes
José R. Bordin; Alan B. de Oliveira; Alexandre Diehl; Marcia C. Barbosa
2012-08-05
We study the effect of confinement in the dynamical behavior of a core-softened fluid. The fluid is modeled as a two length scales potential. This potential in the bulk reproduces the anomalous behavior observed in the density and in the diffusion of liquid water. A series of $NpT$ Molecular Dynamics simulations for this two length scales fluid confined in a nanotube were performed. We obtain that the diffusion coefficient increases with the increase of the nanotube radius for wide channels as expected for normal fluids. However, for narrow channels, the confinement shows an enhancement in the diffusion coefficient when the nanotube radius decreases. This behavior, observed for water, is explained in the framework of the two length scales potential.
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.
ITER EDA design confinement capability
Uckan, N.A.
1993-01-01
Major device parameters for ITER-EDA and CDA are given in this paper. Ignition capability of the EDA (and CDA) operational scenarios is evaluated using both the 1-1/2-D time-dependent transport simulations and 0-D global models under different confinement [[chi]([triangledown]T[sub e])[sub crit], empirical global energy confinement scalings, [chi](empirical), etc.] assumptions. Results from some of these transport simulations and confinement assessments are summarized in and compared with the ITER CDA reference ignition scenario.
ITER EDA design confinement capability
Uckan, N.A.
1993-06-01
Major device parameters for ITER-EDA and CDA are given in this paper. Ignition capability of the EDA (and CDA) operational scenarios is evaluated using both the 1-1/2-D time-dependent transport simulations and 0-D global models under different confinement [{chi}({triangledown}T{sub e}){sub crit}, empirical global energy confinement scalings, {chi}(empirical), etc.] assumptions. Results from some of these transport simulations and confinement assessments are summarized in and compared with the ITER CDA reference ignition scenario.
Confined explosive joining of tubes
NASA Technical Reports Server (NTRS)
Bement, L. J.
1979-01-01
Technique uses explosive ribbon to join and seal tubes hermetically while totally confining explosive products, such as smoke, light, and sound. Only click is audible. Process yields joints of the same strengths as parent metal.
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.
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.
Novel confinement of liquid crystals in Janus droplets
NASA Astrophysics Data System (ADS)
Wei, Wei-Shao; Jeong, Joonwoo; Collings, Peter J.; Lubensky, Tom C.; Yodh, A. G.
2015-03-01
In this work we create and investigate Janus droplets composed of liquid crystal (LC) and polymer. The Janus droplets are formed when homogeneous droplets of LC-polymer-solvent phase separate into LC and polymer regions during solvent evaporation through aqueous continuous phase. This scheme enables us to realize unique confinement geometries for LCs such as spherical caps and bowls, which are difficult to be achieved via other systems. The morphologies and surface anchoring conditions can be controlled by changing the size of droplets, the volume ratio between LC and polymer, and the type/concentration of surfactants in aqueous background phase. We explore a variety of defects in these novel confined geometries including dislocations and focal conic defects of smectic LCs. Nematic and cholesteric LCs are also explored. Models that balance the energetics of bulk elasticity and surface anchoring determine the director configurations of confined liquid crystals (LCs). This work is funded by NSF Grant DMR-1205463, NSF MRSEC Grant DMR-1120901, and NASA Grant NNX08AO0G.
Complex Plasmas in Narrow Channels: Impact of Confinement on the Local Order
Klumov, B. A.
2008-10-15
Two-dimensional (2D) and three-dimensional (3D) quasi-equilibrium configurations of a complex (dusty) plasma in narrow channels are investigated using the molecular dynamics simulations for various confining potentials (confinements). The dynamics of the microparticles is described within the framework of a Langevin thermostat with allowance for the pair interaction between charged particles, which is described by a screened Coulomb potential (Yukawa potential). Two types of confinement: the parabolic electrostatic potential and hard elastic wall are considered. It is shown that the confinement strongly affects the crystallization and the local order of the microparticles in the system under consideration; in particular, the appearance of a new quasicrystalline phase induced by the hard wall confinement is revealed in 3D case.
Heterogeneous catalysis and confinement effects
Stéphane Pariente; Philippe Trens; François Fajula; Francesco Di Renzo; Nathalie Tanchoux
2006-01-01
The aim of this study is to highlight the impact of confinement effects in catalysis for reactants confined in small mesopores. Double bond isomerization of 1-hexene at 343K has been chosen as model reaction and mesostructured aluminosilicates of the MCM-41 type with the very same chemical composition (Si\\/Al=400±20) and varying pore sizes (2.3–9.3nm) were used as catalysts. Adsorption isotherms of
Solvent cavitation under solvophobic confinement.
Ashbaugh, Henry S
2013-08-14
The stability of liquids under solvophobic confinement can tip in favor of the vapor phase, nucleating a liquid-to-vapor phase transition that induces attractive forces between confining surfaces. In the case of water adjacent to hydrophobic surfaces, experimental and theoretical evidence support confinement-mediated evaporation stabilization of biomolecular and colloidal assemblies. The macroscopic thermodynamic theory of cavitation under confinement establishes the connection between the size of the confining surfaces, interfacial free energies, and bulk solvent pressure with the critical evaporation separation and interfacial forces. While molecular simulations have confirmed the broad theoretical trends, a quantitative comparison based on independent measurements of the interfacial free energies and liquid-vapor coexistence properties has, to the best of our knowledge, not yet been performed. To overcome the challenges of simulating a large number of systems to validate scaling predictions for a three-dimensional fluid, we simulate both the forces and liquid-vapor coexistence properties of a two-dimensional Lennard-Jones fluid confined between solvophobic plates over a range of plate sizes and reservoir pressures. Our simulations quantitatively agree with theoretical predictions for solvent-mediated forces and critical evaporation separations once the length dependence of the solvation free energy of an individual confining plate is taken into account. The effective solid-liquid line tension length dependence results from molecular scale correlations for solvating microscopic plates and asymptotically decays to the macroscopic value for plates longer than 150 solvent diameters. The success of the macroscopic thermodynamic theory at describing two-dimensional liquids suggests application to surfactant monolayers to experimentally confirm confinement-mediated cavitation. PMID:23947875
Dynamical gluon mass and linear confinement
Cesar Ayala; Pedro Gonzalez; Vicente Vento
2015-09-04
We define a non-perturbative running coupling in terms of a gluon mass function, similar to that used in some Dyson-Schwinger approaches. From this coupling, which satisfies asymptotic freedom and describes correctly the singularity structure of confinement, a static quark-antiquark potential is constructed. We calculate the bottomonium and charmonium spectra below the first open flavor meson-meson thresholds and show that for a small range of values of the free parameter determining the gluon mass function a good agreement with data is attained.
Perlite for permanent confinement of cesium
NASA Astrophysics Data System (ADS)
Balencie, J.; Burger, D.; Rehspringer, J.-L.; Estournès, C.; Vilminot, S.; Richard-Plouet, M.; Boos, A.
2006-06-01
We present the potential use of expanded perlite, a metastable amorphous hydrated aluminium silicate, as a permanent medium for the long-term confinement of cesium. The method requires simply a loading by mixing an aqueous cesium nitrate solution and expanded perlite at 300 K followed by densification by sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, upon careful heat treatment is demonstrated by X-ray diffraction. Leaching tests on the resulting glass-ceramics reveal a very low Cs departure of 0.5 mg m-2 d-1.
Ice-Confined Basaltic Lava Flows: Review and Discussion
NASA Astrophysics Data System (ADS)
Skilling, I.; Edwards, B. R.
2012-12-01
Basaltic lavas that are interpreted as having been emplaced in subglacial or ice-confined subaerial settings are known from several localities in Iceland, British Columbia and Antarctica. At least four different types of observations have been used to date to identify emplacement of basaltic lavas in an ice-rich environment: i) gross flow morphology, ii) surface structures, iii) evidence for ice-confined water during emplacement, and iv) lava fracture patterns. Five types of ice-confined lava are identified: sheets, lobes, mounds, linear ridges and sinuous ridges. While the appearance of lavas is controlled by the same factors as in the submarine environment, such as the geometry and configuration of vents and lava tubes, flow rheology and rates, and underlying topography, the presence of ice can lead to distinct features that are specific to the ice-confined setting. Other types have very similar or identical equivalents in submarine environment, albeit with some oversteepening/ice contact surfaces. Ice-confined lavas can form as (1) subaerial or subaqueous lavas emplaced against ice open to the air, (2) subaqueous lavas emplaced into pre-existing sub-ice drainage networks, and (3) subaqueous lavas emplaced into ponded water beneath ice. Their surface structures reflect the relationship between rates of lava flow emplacement at the site of ice-water-lava contact, ice melting and water drainage. Variations in local lava flow rates could be due to lava cooling, constriction, inflation, tube development, ice melting, ice collapse, lava collapse, changes in eruption rate etc. Episodes of higher lava flow rate would favour direct ice contact and plastic compression against the ice, generating oversteepened and/or overthickened chilled margins, cavities in the lava formed by melting of enveloped ice blocks (cryolith cavities) and structures such as flattened pillows and lava clasts embedded into the glassy margins. Melting back of the confining ice generates space to allow the formation of steep draping curtains of pillow tubes, breakout pillows and lava collapse breccias. Indications of the presence of water, such as pillow tubes in areas where there is no possibility of topographic confinement of former water or changes in sea level are also generally considered to be criteria for an ice-confined environment. Patterns of cooling contraction fractures can also be characteristic of ice-confined emplacement. While no one set of the four types of observations may be conclusive, taken in combination these observations can be used to discern the presence of ice during basaltic lava effusion.
Engineering tube shapes to control confined transport
NASA Astrophysics Data System (ADS)
Reguera, D.; Rubi, J. M.
2014-12-01
Transport of particles in confined structures can be modeled by means of diffusion in a potential of entropic nature. The entropic transport model proposes a drift-diffusion kinetic equation for the evolution of the probability density in which the diffusion coefficient depends on position and the drift term contains an entropic force. The model has been applied to analyze transport in single cavities and through periodic structures of different shape, and to investigate the nature of non-equilibrium fluctuations as well. The transport characteristics depends strongly on the contour of the region through which particles move, which defines the entropic potential. We show that the form of the entropic potential can be properly designed to optimize and govern how molecules diffuse and get drifted in tortuous channels. The shape of a tube or channel can be smartly engineered to control transport for the desired application.
Hyperbolic geometry of cosmological attractors
NASA Astrophysics Data System (ADS)
Carrasco, John Joseph M.; Kallosh, Renata; Linde, Andrei; Roest, Diederik
2015-08-01
Cosmological ? attractors give a natural explanation for the spectral index ns of inflation as measured by Planck while predicting a range for the tensor-to-scalar ratio r , consistent with all observations, to be measured more precisely in future B-mode experiments. We highlight the crucial role of the hyperbolic geometry of the Poincaré disk or half plane in the supergravity construction. These geometries are isometric under Möbius transformations, which include the shift symmetry of the inflaton field. We introduce a new Kähler potential frame that explicitly preserves this symmetry, enabling the inflaton to be light. Moreover, we include higher-order curvature deformations, which can stabilize a direction orthogonal to the inflationary trajectory. We illustrate this new framework by stabilizing the single superfield ? attractors.
Chalvet, F; di Franco, C; Terrinoni, A; Pelisson, A; Junakovic, N; Bucheton, A
1998-04-01
Gypsy is an endogenous retrovirus present in the genome of Drosophila melanogaster. This element is mobilized only in the progeny of females which contain active gypsy elements and which are homozygous for permissive alleles of a host gene called flamenco (flam). Some data strongly suggest that gypsy elements bearing a diagnostic HindIII site in the central region of the retrovirus body represent a subfamily that appears to be much more active than elements devoid of this site. We have taken advantage of this structural difference to assess by the Southern blotting technique the genomic distribution of active gypsy elements. In some of the laboratory Drosophila stocks tested, active gypsy elements were found to be restricted to the Y chromosome. Further analyses of 14 strains tested for the permissive vs. restrictive status of their flamenco alleles suggest that the presence of permissive alleles of flam in a stock tends to be associated with the confinement of active gypsy elements to the Y chromosome. This might be the result of the female-specific effect of flamenco on gypsy activity. PMID:9541538
Interactive Geometry Dictionary: Areas in Geometry
NSDL National Science Digital Library
2011-01-01
The applets in this Interactive Geometry Dictionary (IGD) will allow students an opportunity to explore finding the area of some common shapes. The applets demonstrate how to find the area of a triangle using the area of a parallelogram, which in turn can be found using the area of a rectangle. This tool also supports the lesson "What's My Area" cataloged separately.
Functional Differential Geometry Functional Differential Geometry
and culture, and we only sketch an idea using mathematical idioms. We are insufficiently precise to convey an idea to a person who does not share our culture. Our problem is that since we share the culture we find- ential geometry aimed at relativ
Uncertainty analysis of strength and ductility of confined reinforced concrete members
A. J Kappos; M. K Chryssanthopoulos; C Dymiotis
1999-01-01
The strength and ductility of reinforced concrete beam and column cross-sections with varying geometries and levels of confinement are investigated. Material properties are modelled as random variables and their effect on section behaviour is assessed through fibre modelling and the Response Surface Methodology. The section ductility is in many cases found to be mainly dependent on the ultimate concrete strain.
Finite-size and confinement effects in spin-polarized trapped Fermi gases
Mark Ku; Jens Braun; Achim Schwenk
2009-06-23
We calculate the energy of a single fermion interacting resonantly with a Fermi sea of different-species fermions in asymmetric traps, and show that finite particle numbers and the trap geometry impact the phase structure and the critical polarization. Our findings contribute to understanding some experimental discrepancies in spin-polarized Fermi gases as finite-size and confinement effects.
High Temperature Confinement in SU(N) Gauge Theories
Michael C. Ogilvie; Peter N. Meisinger
2008-11-13
SU(N) gauge theories, extended with adjoint fermions having periodic boundary conditions, are confining at high temperature for sufficiently light fermion mass m. Lattice simulations indicate that this confining region is smoothly connected to the confining region of low-temperature pure SU(N) gauge theory. In the high temperature confining region, the one-loop effective potential for Polyakov loops has a Z(N)-symmetric confining minimum. String tensions associated with Polyakov loops are smooth functions of m/T. In the magnetic sector, the Polyakov loop plays a role similar to a Higgs field, leading to a breaking of SU(N) to U(1)^{N-1}. This is turn yields an effective theory where magnetic monopoles give rise to string tensions for spatial Wilson loops. These string tensions are calculable semiclassically. There are many analytical predictions for the high-temperature region that can be tested by lattice simulations, but lattice work will be crucial for exploring the crossover from this region to the low-temperature confining behavior of pure gauge theories.
Twistors to twisted geometries
Freidel, Laurent; Speziale, Simone
2010-10-15
In a previous paper we showed that the phase space of loop quantum gravity on a fixed graph can be parametrized in terms of twisted geometries, quantities describing the intrinsic and extrinsic discrete geometry of a cellular decomposition dual to the graph. Here we unravel the origin of the phase space from a geometric interpretation of twistors.
Geometry of multihadron production
Bjorken, J.D.
1994-10-01
This summary talk only reviews a small sample of topics featured at this symposium: Introduction; The Geometry and Geography of Phase space; Space-Time Geometry and HBT; Multiplicities, Intermittency, Correlations; Disoriented Chiral Condensate; Deep Inelastic Scattering at HERA; and Other Contributions.
ERIC Educational Resources Information Center
Morris, Barbara H.
2004-01-01
This article describes a geometry project that used the beauty of stained-glass-window designs to teach middle school students about geometric figures and concepts. Three honors prealgebra teachers and a middle school mathematics gifted intervention specialist created a geometry project that covered the curriculum and also assessed students'…
Vector Electric Geometry Model
Wang Ju-feng; LiuYun; LiBin
2008-01-01
The classical electric geometry model unifies the thunder and lightning flashover characteristic logical circuit's structure size, very good explained the line shield expiration phenomenon. But the classical electric geometry model had not considered that the lightning leader the electrical field intensity influence, is being circled strikes the segmental arc is the zero hour, the line still had circles strikes the
Frolov, Vadim A; Escalada, Artur; Akimov, Sergey A; Shnyrova, Anna V
2015-01-01
Cellular membranes define the functional geometry of intracellular space. Formation of new membrane compartments and maintenance of complex organelles require division and disconnection of cellular membranes, a process termed membrane fission. Peripheral membrane proteins generally control membrane remodeling during fission. Local membrane stresses, reflecting molecular geometry of membrane-interacting parts of these proteins, sum up to produce the key membrane geometries of fission: the saddle-shaped neck and hour-glass hemifission intermediate. Here, we review the fundamental principles behind the translation of molecular geometry into membrane shape and topology during fission. We emphasize the central role the membrane insertion of specialized protein domains plays in orchestrating fission in vitro and in cells. We further compare individual to synergistic action of the membrane insertion during fission mediated by individual protein species, proteins complexes or membrane domains. Finally, we describe how local geometry of fission intermediates defines the functional design of the protein complexes catalyzing fission of cellular membranes. PMID:25062896
Spatial Variations in Carbon Storage along Headwater Fluvial Networks with Differing Valley Geometry
NASA Astrophysics Data System (ADS)
Wohl, E. E.; Dwire, K. A.; Polvi, L. E.; Sutfin, N. A.; Bazan, R. A.
2011-12-01
We distinguish multiple valley types along headwater fluvial networks in the Colorado Front Range based on valley geometry (downstream gradient and valley-bottom width relative to active channel width) and the presence of biotic drivers (beaver dams or channel-spanning logjams associated with old-growth forest) capable of creating a multi-thread channel pattern. Valley type influences storage of fine sediment, organic matter, and carbon. Deep, narrow valleys have limited storage potential, whereas wide, shallow valleys with multi-thread channels have substantial storage potential. Multi-thread channels only occur in the presence of a biotic driver. Given the importance of headwater streams in the global carbon cycle, it becomes important to understand the spatial distribution and magnitude of carbon storage along these streams, as well as the processes governing patterns of storage. We compare carbon stored in three reservoirs: riparian vegetation (live, dead, and litter), instream and floodplain large wood, and floodplain soils for 100-m-long valley segments in seven different valley types. The valley types are (i) laterally confined valleys in old-growth forest, (ii) partly confined valleys in old-growth forest, (iii) laterally unconfined valleys with multi-thread channels in old-growth forest, (iv) laterally unconfined valleys with single-thread channels in old-growth forest, (v) laterally confined valleys in younger forest, (vi) recently abandoned beaver-meadow complexes with multi-thread channels and willow thickets, and (vii) longer abandoned beaver-meadow complexes with single-thread channels and very limited woody vegetation. Preliminary results suggest that, although multi-thread channel segments driven by beavers or logjams cover less than 25 percent of the total length of headwater river networks in the study area, they account for more than three-quarters of the carbon stored along the river network. Historical loss of beavers and old-growth forest has thus likely resulted in continuing loss of carbon storage in these headwater river networks.
Searching for confined modes in graphene channels: the variable phase method
D. A. Stone; C. A. Downing; M. E. Portnoi
2012-09-07
Using the variable phase method, we reformulate the Dirac equation governing the charge carriers in graphene into a nonlinear first-order differential equation from which we can treat both confined-state problems in electron waveguides and above-barrier scattering problems for arbitrary-shaped potential barriers and wells, decaying at large distances. We show that this method agrees with a known analytic result for a hyperbolic secant potential and go on to investigate the nature of more experimentally realizable electron waveguides, showing that, when the Fermi energy is set at the Dirac point, truly confined states are supported in pristine graphene. In contrast to exponentially-decaying potentials, we discover that the threshold potential strength at which the first confined state appears is vanishingly small for potentials decaying at large distances as a power law, but nonetheless further confined states are formed when the strength and spread of the potential reach a certain threshold.
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.
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.
Polymer confinement in undulated membrane boxes and tubes
Dotera; Suzuki
2000-10-01
We consider quantum particle or Gaussian polymer confinement between two surfaces and in cylinders with sinusoidal undulations. In terms of the variational method, we show that the quantum-mechanical wave equations have lower ground-state energy in these geometries under long wavelength undulations, where bulges are formed and waves are localized in the bulges. It turns out correspondingly that Gaussian polymer chains in undulated boxes or tubes acquire higher entropy than in exactly flat or straight ones. These phenomena are explained by the uncertainty principle for quantum particles, and by a polymer confinement rule for Gaussian polymers. If membrane boxes or tubes are flexible, polymer-induced undulation instability is suggested. We find that the wavelength of undulations at the threshold of instability for a membrane box is almost twice the distance between two walls of the box. Surprisingly, we find that the instability for tubes begins with a shorter wavelength compared to the "Rayleigh" area-minimizing instability. PMID:11089093
NASA Technical Reports Server (NTRS)
Samuelsen, G. S.; Sowa, W. A.; Hatch, M. S.
1996-01-01
A series of non-reacting parametric experiments was conducted to investigate the effect of geometric and flow variations on mixing of cold jets in an axis-symmetric, heated cross flow. The confined, cylindrical geometries tested represent the quick mix region of a Rich-Burn/Quick-Mix/Lean-Burn (RQL) combustor. The experiments show that orifice geometry and jet to mainstream momentum-flux ratio significantly impact the mixing characteristic of jets in a cylindrical cross stream. A computational code was used to extrapolate the results of the non-reacting experiments to reacting conditions in order to examine the nitric oxide (NO) formation potential of the configurations examined. The results show that the rate of NO formation is highest immediately downstream of the injection plane. For a given momentum-flux ratio, the orifice geometry that mixes effectively in both the immediate vicinity of the injection plane, and in the wall regions at downstream locations, has the potential to produce the lowest NO emissions. The results suggest that further study may not necessarily lead to a universal guideline for designing a low NO mixer. Instead, an assessment of each application may be required to determine the optimum combination of momentum-flux ratio and orifice geometry to minimize NO formation. Experiments at reacting conditions are needed to verify the present results.
Water confined in hydrophobic environments
NASA Astrophysics Data System (ADS)
Han, Sungho
This thesis applies statistical physics approaches and computer simulation methods to investigate the dynamical properties and phase transitions of water confined in hydrophobic environments. A diffusion anomaly, an increase of diffusion upon compression, is one of many unexpected behaviors observed in water. To calculate the diffusion coefficient of confined water in the confining direction, we use the concept of the continuous random walk. We find that a diffusion anomaly of water is absent in the direction perpendicular to the confining walls down to 220 K, whereas there is a diffusion anomaly, similar to that in bulk water, in the direction parallel to the walls. Anomalous behaviors of water compared to simple liquids are generally ascribed to a hydrogen bond. From investigations of confinement effects on a hydrogen bond, we find that even if the average number and the lifetime of hydrogen bonds are affected by nanoconfinement, the characteristics of hydrogen bond dynamics in hydrophobic confined water are the same as in bulk water. The different physical properties of water in hydrophobic confinement compared to bulk water---such as ˜40 K temperature shift---may be primarily due to the reduction of the lifetime of hydrogen bonds in confined environments. We also find that the hydrogen bond autocorrelation function exhibits a power-law tail characterized by an exponent which depends on the system dimensionality. Vapor and liquid may transform into each other either discontinuously by crossing a first-order transition line or continuously without crossing a transition line, indicating an existence of the vapor-liquid critical point. In contrast to the phase transition line between vapor and liquid, the first-order transition line between solid and liquid is believed to persist indefinitely without terminating at a critical point. We show that either a first-order transition or a continuous transition between solid and liquid can occur for water confined in a quasi-two-dimensional hydrophobic nanopore slit. This finding indicates that the connection point between first-order and continuous transition lines might be a solid-liquid critical point with a tricritical nature.
A hybrid ion trap in a three-dimensional geometry
NASA Astrophysics Data System (ADS)
Wang, Ye; Yum, Dahyun; Zhang, Kuan; An, Shuoming; Kim, Kihwan
2015-05-01
We develop a three-dimensional (3D) monolithic ion trap that has the advantages of both 3D geometry, i.e., having a deep confining potential and surface trap, i.e., containing multiple zones for scaling up, no uncertainty between design and manufacture. The trap is fabricated by gold coating on a single layer of alumina plate sculpted by laser-machining technology. The axial trap frequencies are in the range from 230 kHz to 850 kHz with the average dc voltages from 20 V to 75V and the radial frequencies lie in 3 MHz with 3.5W input power of 40 MHz radio-frequency, which is well in agreement with numerical simulations. We successfully load Yb and Ba ions together and report the progress of the hybrid quantum operation with them. This work was supported by the National Basic Research Program of China under Grants No. 2011CBA00300 (No. 2011CBA00301), the National Natural Science Foundation of China 11374178.
Geometrie im Internet Wolfgang Rath
Havlicek, Hans
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
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.
Integrating Transformation Geometry into Traditional High School Geometry.
ERIC Educational Resources Information Center
Okolica, Steve; Macrina, Georgette
1992-01-01
Describes a geometry course that integrates transformation geometry into traditional high school geometry. Discussion of the scope and sequence of the course includes the topics of proof, congruence, translations, rotations, reflections, dilations, quadrilaterals, parallel lines, and similarity. (MDH)
Hessian geometry and entanglement thermodynamics
Hiroaki Matsueda
2015-08-11
We reconstruct entanglement thermodynamics by means of Hessian geometry, since this method exactly generalizes thermodynamics into much wider exponential family cases including quantum entanglement. Starting with the correct first law of entanglement thermodynamics, we derive that a proper choice of the Hessian potential leads to both of the entanglement entropy scaling for quantum critical systems and hyperbolic metric (or AdS space with imaginary time). We also derive geometric representation of the entanglement entropy in which the entropy is described as integration of local conserved current of information flowing across an entangling surface. We find that the entangling surface is equivalent to the domain boundary of the Hessian potential. This feature originates in a special property of critical systems in which we can identify the entanglement entropy with the Hessian potential after the second derivative by the canonical parameters, and this identification guarantees violation of extensive nature of the entropy.
Hessian geometry and entanglement thermodynamics
Matsueda, Hiroaki
2015-01-01
We reconstruct entanglement thermodynamics by means of Hessian geometry, since this method exactly generalizes thermodynamics into much wider exponential family cases including quantum entanglement. Starting with the correct first law of entanglement thermodynamics, we derive that a proper choice of the Hessian potential leads to both of the entanglement entropy scaling for quantum critical systems and hyperbolic metric (or AdS space with imaginary time). We also derive geometric representation of the entanglement entropy in which the entropy is described as integration of local conserved current of information flowing across an entangling surface. We find that the entangling surface is equivalent to the domain boundary of the Hessian potential. This feature originates in a special property of critical systems in which we can identify the entanglement entropy with the Hessian potential after the second derivative by the canonical parameters, and this identification guarantees violation of extensive nature of ...
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.
Confinement of dust particles in a double layer A. Barkan and R. L. Merlin0
Merlino, Robert L.
Confinement of dust particles in a double layer A. Barkan and R. L. Merlin0 Department of Physics) Negatively charged, micron-sized dust grains have been electrostatically confined in the high-potential region of an anode double layer formed in a single-ended Q-machine plasma. The levitated dust grains
Atomic scale mixing for inertial confinement fusion associated hydro instabilities
New York at Stoney Brook, State University of
Atomic scale mixing for inertial confinement fusion associated hydro instabilities J. Melvina, , P Alamos, NM 87545, USA Abstract Hydro instabilities have been identified as a potential cause- able. We find numerical convergence for this important quantity, in a purely hydro study, with only
Open-ended magnetic confinement systems for fusion
Post, R.F.; Ryutov, D.D.
1995-05-01
Magnetic confinement systems that use externally generated magnetic fields can be divided topologically into two classes: ``closed`` and `open``. The tokamak, the stellarator, and the reversed-field-pinch approaches are representatives of the first category, while mirror-based systems and their variants are of the second category. While the recent thrust of magnetic fusion research, with its emphasis on the tokamak, has been concentrated on closed geometry, there are significant reasons for the continued pursuit of research into open-ended systems. The paper discusses these reasons, reviews the history and the present status of open-ended systems, and suggests some future directions for the research.
Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles
Yoshida, Z.; Saitoh, H.; Morikawa, J.; Yano, Y.; Watanabe, S.; Ogawa, Y.
2010-06-11
A magnetospheric configuration gives rise to various peculiar plasma phenomena that pose conundrums to astrophysical studies; at the same time, innovative technologies may draw on the rich physics of magnetospheric plasmas. We have created a ''laboratory magnetosphere'' with a levitating superconducting ring magnet. Here we show that charged particles (electrons) self-organize a stable vortex, in which particles diffuse inward to steepen the density gradient. The rotating electron cloud is sustained for more than 300 s. Because of its simple geometry and self-organization, this system will have wide applications in confining single- and multispecies charged particles.
CORRELATIONS IN CONFINED QUANTUM PLASMAS
DUFTY J W
2012-01-11
This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed
Scaling behaviour for the water transport in nanoconfined geometries
NASA Astrophysics Data System (ADS)
Chiavazzo, Eliodoro; Fasano, Matteo; Asinari, Pietro; Decuzzi, Paolo
2014-04-01
The transport of water in nanoconfined geometries is different from bulk phase and has tremendous implications in nanotechnology and biotechnology. Here molecular dynamics is used to compute the self-diffusion coefficient D of water within nanopores, around nanoparticles, carbon nanotubes and proteins. For almost 60 different cases, D is found to scale linearly with the sole parameter ? as D(?)=DB[1+(DC/DB-1)?], with DB and DC the bulk and totally confined diffusion of water, respectively. The parameter ? is primarily influenced by geometry and represents the ratio between the confined and total water volumes. The D(?) relationship is interpreted within the thermodynamics of supercooled water. As an example, such relationship is shown to accurately predict the relaxometric response of contrast agents for magnetic resonance imaging. The D(?) relationship can help in interpreting the transport of water molecules under nanoconfined conditions and tailoring nanostructures with precise modulation of water mobility.
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
Constraints on the Magnetic Field Geometry of Magnetars
H. Sotani; A. Colaiuda; K. D. Kokkotas
2008-10-03
We study the effect of the magnetic field geometry on the oscillation spectra of strongly magnetized stars. The magnetic field distributions include both toroidal and poloidal contributions. We observe that the toroidal contribution does not influence significantly the torsional oscillations of the crust. Moreover, in the case that the core is a type I supercontactor and the magnetic fields are confined in the crust, the torsional oscillation spectrum is drastically affected by the presence of the strong magnetic fields. Comparison with results and estimations for the magnetic field strength, from observations, exclude the possibility that magnetars will have a magnetic field solely confined in the crust i.e. our results suggest that the magnetic field in whatever geometry has to permeate the whole star.
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
Polyelectrolyte stars in planar confinement
Martin Konieczny; Christos N. Likos
2006-04-18
We employ monomer-resolved Molecular Dynamics simulations and theoretical considerations to analyze the conformations of multiarm polyelectrolyte stars close to planar, uncharged walls. We identify three mechanisms that contribute to the emergence of a repulsive star-wall force, namely: the confinement of the counterions that are trapped in the star interior, the increase in electrostatic energy due to confinement as well as a novel mechanism arising from the compression of the stiff polyelectrolyte rods approaching the wall. The latter is not present in the case of interaction between two polyelectrolyte stars and is a direct consequence of the impenetrable character of the planar wall.
Towards assessing the violence of reaction during cookoff of confined energetic materials
Baer, M.R.; Kipp, M.E.; Schmitt, R.G.; Hobbs, M.L.
1996-11-01
An analysis of post-ignition events in a variable confinement cookoff test (VCCT) geometry is presented aimed toward predicting the level of violence during cookoff of confined thermally-degraded energetic materials. This study focuses on the dynamic events following thermal initiation whereby accelerated combustion interacts with confinement. Numerical simulations, based on a model of reactive multiphase mixtures, indicate that the response of energetic material is highly dependent upon thermal/mechanical damage states prior to ignition. These damaged states affect the rate of pressurization, dynamic compaction behavior and subsequent growth to detonation. Variations of the specific surface area and porosity produced by decomposition of the energetic material causes different responses ranging from pressure burst to detonation. Calculated stress histories are used in estimating breakup of the VCCT confinement based on Grady-Kipp fragmentation theory.
Nartowski, K P; Tedder, J; Braun, D E; Fábián, L; Khimyak, Y Z
2015-09-23
The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate - ROY (259.3 g mol(-1)). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical - indomethacin (IMC, 357.8 g mol(-1)), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids. PMID:26280634
Williams, Ian; O?uz, Erdal C; Jack, Robert L; Bartlett, Paul; Löwen, Hartmut; Royall, C Patrick
2014-03-14
The behaviour of materials under spatial confinement is sensitively dependent on the nature of the confining boundaries. In two dimensions, confinement within a hard circular boundary inhibits the hexagonal ordering observed in bulk systems at high density. Using colloidal experiments and Monte Carlo simulations, we investigate two model systems of quasi hard discs under circularly symmetric confinement. The first system employs an adaptive circular boundary, defined experimentally using holographic optical tweezers. We show that deformation of this boundary allows, and indeed is required for, hexagonal ordering in the confined system. The second system employs a circularly symmetric optical potential to confine particles without a physical boundary. We show that, in the absence of a curved wall, near perfect hexagonal ordering is possible. We propose that the degree to which hexagonal ordering is suppressed by a curved boundary is determined by the "strictness" of that wall. PMID:24628205
NASA Astrophysics Data System (ADS)
Williams, Ian; O?uz, Erdal C.; Jack, Robert L.; Bartlett, Paul; Löwen, Hartmut; Royall, C. Patrick
2014-03-01
The behaviour of materials under spatial confinement is sensitively dependent on the nature of the confining boundaries. In two dimensions, confinement within a hard circular boundary inhibits the hexagonal ordering observed in bulk systems at high density. Using colloidal experiments and Monte Carlo simulations, we investigate two model systems of quasi hard discs under circularly symmetric confinement. The first system employs an adaptive circular boundary, defined experimentally using holographic optical tweezers. We show that deformation of this boundary allows, and indeed is required for, hexagonal ordering in the confined system. The second system employs a circularly symmetric optical potential to confine particles without a physical boundary. We show that, in the absence of a curved wall, near perfect hexagonal ordering is possible. We propose that the degree to which hexagonal ordering is suppressed by a curved boundary is determined by the "strictness" of that wall.
Directed transport of confined Brownian particles with torque.
Radtke, Paul K; Schimansky-Geier, Lutz
2012-05-01
We investigate the influence of an additional torque on the motion of Brownian particles confined in a channel geometry with varying width. The particles are driven by random fluctuations modeled by an Ornstein-Uhlenbeck process with given correlation time ?_{c}. The latter causes persistent motion and is implemented as (i) thermal noise in equilibrium and (ii) noisy propulsion in nonequilibrium. In the nonthermal process a directed transport emerges; its properties are studied in detail with respect to the correlation time, the torque, and the channel geometry. Eventually, the transport mechanism is traced back to a persistent sliding of particles along the even boundaries in contrast to scattered motion at uneven or rough ones. PMID:23004706
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.
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.
Noncommutative Geometry and Physics
Connes, Alain
2006-11-03
In this very short essay we shall describe a 'spectral' point of view on geometry which allows to start taking into account the lessons from both renormalization and of general relativity. We shall first do that for renormalization and explain in rough outline the content of our recent collaborations with Dirk Kreimer and Matilde Marcolli leading to the universal Galois symmetry of renormalizable quantum field theories provided by the renormalization group in its cosmic Galois group incarnation. As far as general relativity is concerned, since the functional integral cannot be treated in the traditional perturbative manner, it relies heavily as a 'sum over geometries' on the chosen paradigm of geometric space. This will give us the occasion to discuss, in the light of noncommutative geometry, the issue of 'observables' in gravity and our joint work with Ali Chamseddine on the spectral action, with a first attempt to write down a functional integral on the space of noncommutative geometries.
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)
Complex Geometry and Supersymmetry
Ulf Lindstrom
2012-04-03
I stress how the form of sigma models with (2, 2) supersymmetry differs depending on the number of manifest supersymmetries. The differences correspond to different aspects/formulations of Generalized K\\"ahler Geometry.
Special Bohr - Sommerfeld geometry
Nikolay A. Tyurin
2015-08-27
We present a new approach to special lagrangian geometry which works for Bohr - Sommerfeld lagrangian submanifolds of symplectic manifolds with integer symplectic forms. This leads to construction of finite dimensional moduli spaces of SBS lagrangian cycles over algebraic varieties.
Algebraic Geometry Jean Gallier
Gallier, Jean
, 2011 #12;2 #12;Contents 1 Elementary Algebraic Geometry 7 1.1 History and Problems.2 Projective Fibre Bundles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 7.3 Projective . . . . . . . . . . . . . . . . . . . . . . . . . . 356 7.5 Finiteness Theorems for Projective Morphisms . . . . . . . . . . . . . . . . . 370 7.6 Serre
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)
Unsolved Problems in Geometry.
ERIC Educational Resources Information Center
Steen, Lynn Arthur
1979-01-01
Describes some unsolved problems in geometry, as well as some recently solved ones. Indicates that each advance generates more problems than it solves, thus ensuring a constant growth in unsolved problems. (GA)
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.
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
Electron-Hole Confinement Symmetry in Silicon Quantum Dots.
Mueller, Filipp; Konstantaras, Georgios; Spruijtenburg, Paul C; van der Wiel, Wilfred G; Zwanenburg, Floris A
2015-08-12
We report electrical transport measurements on a gate-defined ambipolar quantum dot in intrinsic silicon. The ambipolarity allows its operation as either an electron or a hole quantum dot of which we change the dot occupancy by 20 charge carriers in each regime. Electron-hole confinement symmetry is evidenced by the extracted gate capacitances and charging energies. The results demonstrate that ambipolar quantum dots offer great potential for spin-based quantum information processing, since confined electrons and holes can be compared and manipulated in the same crystalline environment. PMID:26134900
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.
On a Holographic Model for Confinement/Deconfinement
C. A. Ballon Bayona; Henrique Boschi-Filho; Nelson R. F. Braga; Leopoldo A. Pando Zayas
2008-03-06
We study the thermodynamics of the hard wall model, which consists in the introduction of an infrared cut-off in asymptotically AdS spaces. This is a toy model for confining backgrounds in the context of the gauge/gravity correspondence. We use holographic renormalization and reproduce the existence of a Hawking Page phase transition recently discussed by Herzog. We also show that the entropy jumps from $N^0$ to $N^2$, which reinforces the interpretation of this transition as the gravity dual of confinement/deconfinement. We also show that similar results hold for the phenomenologically motivated soft wall model, underlining the potential universality of our analysis.
On a holographic model for confinement/deconfinement
NASA Astrophysics Data System (ADS)
Bayona, C. A. Ballon; Boschi-Filho, Henrique; Braga, Nelson R. F.; Zayas, Leopoldo A. Pando
2008-02-01
We study the thermodynamics of the hard wall model, which consists of the introduction of an infrared cutoff in asymptotically AdS spaces. This is a toy model for confining backgrounds in the context of the gauge/gravity correspondence. We use holographic renormalization and reproduce the existence of a Hawking-Page phase transition recently discussed by Herzog. We also show that the entropy jumps from N0 to N2, which reinforces the interpretation of this transition as the gravity dual of confinement/deconfinement. We also show that similar results hold for the phenomenologically motivated soft wall model, underlining the potential universality of our analysis.
Geometry-induced electrostatic trapping of nanometric objects in a fluid.
Krishnan, Madhavi; Mojarad, Nassiredin; Kukura, Philipp; Sandoghdar, Vahid
2010-10-01
The ability to trap an object-whether a single atom or a macroscopic entity-affects fields as diverse as quantum optics, soft condensed-matter physics, biophysics and clinical medicine. Many sophisticated methodologies have been developed to counter the randomizing effect of Brownian motion in solution, but stable trapping of nanometre-sized objects remains challenging. Optical tweezers are widely used traps, but require sufficiently polarizable objects and thus are unable to manipulate small macromolecules. Confinement of single molecules has been achieved using electrokinetic feedback guided by tracking of a fluorescent label, but photophysical constraints limit the trap stiffness and lifetime. Here we show that a fluidic slit with appropriately tailored topography has a spatially modulated electrostatic potential that can trap and levitate charged objects in solution for up to several hours. We illustrate this principle with gold particles, polymer beads and lipid vesicles with diameters of tens of nanometres, which are all trapped without external intervention and independently of their mass and dielectric function. The stiffness and stability of our electrostatic trap is easily tuned by adjusting the system geometry and the ionic strength of the solution, and it lends itself to integration with other manipulation mechanisms. We anticipate that these features will allow its use for contact-free confinement of single proteins and macromolecules, and the sorting and fractionation of nanometre-sized objects or their assembly into high-density arrays. PMID:20930840
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.
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
Wang, Bing; Zhou, Xiaoyan; Wang, Dongqi; Yin, Jun-Jie; Chen, Hanqing; Gao, Xingfa; Zhang, Jing; Ibrahim, Kurash; Chai, Zhifang; Feng, Weiyue; Zhao, Yuliang
2015-02-14
Preparation of heterogeneous catalysts with active ferrous centers is of great significance for industrial and environmental catalytic processes. Nanostructured carbon materials (NCM), which possess free-flowing ? electrons, can coordinate with transition metals, provide a confinement environment for catalysis, and act as potential supports or ligands to construct analogous complexes. However, designing such catalysts using NCM is still seldom studied to date. Herein, we synthesized a sandwich structured ternary complex via the coordination of Fe-loaded humic acid (HA) with C=C bonds in the aromatic rings of carbon nanotubes (CNTs), in which the O/N-Fe-C interface configuration provides the confinement environment for the ferrous sites. The experimental and theoretical results revealed octahedrally/tetrahedrally coordinated geometry at Fe centers, and the strong hybridization between CNT C ?* and Fe 3d orbitals induces discretization of the atomic charges on aromatic rings of CNTs, which facilitates O2 adsorption and electron transfer from carbon to O2, which enhances O2 activation. The O2 activation by the novel HA/Fe-CNT complex can be applied in the oxidative degradation of phenol red (PR) and bisphenol A (BPA) in aqueous media. PMID:25580558
NASA Astrophysics Data System (ADS)
McAteer, R. T. J.
2013-06-01
When Mandelbrot, the father of modern fractal geometry, made this seemingly obvious statement he was trying to show that we should move out of our comfortable Euclidean space and adopt a fractal approach to geometry. The concepts and mathematical tools of fractal geometry provides insight into natural physical systems that Euclidean tools cannot do. The benet from applying fractal geometry to studies of Self-Organized Criticality (SOC) are even greater. SOC and fractal geometry share concepts of dynamic n-body interactions, apparent non-predictability, self-similarity, and an approach to global statistics in space and time that make these two areas into naturally paired research techniques. Further, the iterative generation techniques used in both SOC models and in fractals mean they share common features and common problems. This chapter explores the strong historical connections between fractal geometry and SOC from both a mathematical and conceptual understanding, explores modern day interactions between these two topics, and discusses how this is likely to evolve into an even stronger link in the near future.
Inertial confinement fusion (ICF) review
Hammer, D.; Dyson, F.; Fortson, N.; Novick, B.; Panofsky, W.
1996-03-11
During its 1996 Winter Study JASON reviewed the DOE Inertial Confinement Fusion (ICF) Program. This included the National Ignition Facility (NIF) and proposed studies. The result of the review was to comment on the role of the ICF program in support of the DOE Science Based Stockpile Stewardship program.
Mirror Confinement Systems: project summaries
Not Available
1980-07-01
This report contains descriptions of the projects supported by the Mirror Confinement Systems (MCS) Division of the Office of Fusion Energy. The individual project summaries were prepared by the principal investigators, in collaboration with MCS staff office, and include objectives and milestones for each project. In addition to project summaries, statements of Division objectives and budget summaries are also provided.
Inertial confinement fusion (ICF) review
Hammer, D.; Dyson, F.; Fortson, N.; Novick, B.; Panofsky, W.; Rosenbluth, M.; Treiman, S.; York, H.
1996-03-01
During its 1996 winter study JASON reviewed the DOE Inertial Confinement Fusion (ICF) program. This included the National Ignition Facility (NIF) and proposed studies. The result of the review was to comment on the role of the ICF program in support of the DOE Science Based Stockpile Stewardship program.
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.
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.
String Theory and Quark Confinement
A. Polyakov
1997-11-01
This article is based on a talk given at the ``Strings'97'' conference. It discusses the search for the universality class of confining strings. The key ingredients include the loop equations, the zigzag symmetry, the non-linear renormalization group. Some new tests for the equivalence between gauge fields and strings are proposed.
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.
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.
Multiple reentrant glass transitions in confined hard-sphere glasses
NASA Astrophysics Data System (ADS)
Mandal, Suvendu; Lang, Simon; Gross, Markus; Oettel, Martin; Raabe, Dierk; Franosch, Thomas; Varnik, Fathollah
2014-07-01
Glass-forming liquids exhibit a rich phenomenology upon confinement. This is often related to the effects arising from wall-fluid interactions. Here we focus on the interesting limit where the separation of the confining walls becomes of the order of a few particle diameters. For a moderately polydisperse, densely packed hard-sphere fluid confined between two smooth hard walls, we show via event-driven molecular dynamics simulations the emergence of a multiple reentrant glass transition scenario upon a variation of the wall separation. Using thermodynamic relations, this reentrant phenomenon is shown to persist also under constant chemical potential. This allows straightforward experimental investigation and opens the way to a variety of applications in micro- and nanotechnology, where channel dimensions are comparable to the size of the contained particles. The results are in line with theoretical predictions obtained by a combination of density functional theory and the mode-coupling theory of the glass transition.
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 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.
A double-layer based model of ion confinement in electron cyclotron resonance ion source
Mascali, D. Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G.; Torrisi, G.; Università Mediterranea di Reggio Calabria, Dipartimento di Ingegneria dell’Informazione, delle Infrastrutture e dell’Energia Sostenibile, Via Graziella, I-89100 Reggio Calabria ; Sorbello, G.; Università degli Studi di Catania, Dipartimento di Ingegneria Elettrica Elettronica ed Informatica, Viale Andrea Doria 6, 95125 Catania
2014-02-15
The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this “barrier” confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.
Quantum chromodynamics near the confinement limit
Quigg, C.
1985-09-01
These nine lectures deal at an elementary level with the strong interaction between quarks and its implications for the structure of hadrons. Quarkonium systems are studied as a means for measuring the interquark interaction. This is presumably (part of) the answer a solution to QCD must yield, if it is indeed the correct theory of the strong interactions. Some elements of QCD are reviewed, and metaphors for QCD as a confining theory are introduced. The 1/N expansion is summarized as a way of guessing the consequences of QCD for hadron physics. Lattice gauge theory is developed as a means for going beyond perturbation theory in the solution of QCD. The correspondence between statistical mechanics, quantum mechanics, and field theory is made, and simple spin systems are formulated on the lattice. The lattice analog of local gauge invariance is developed, and analytic methods for solving lattice gauge theory are considered. The strong-coupling expansion indicates the existence of a confining phase, and the renormalization group provides a means for recovering the consequences of continuum field theory. Finally, Monte Carlo simulations of lattice theories give evidence for the phase structure of gauge theories, yield an estimate for the string tension characterizing the interquark force, and provide an approximate description of the quarkonium potential in encouraging good agreement with what is known from experiment.
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
Deuterium anions in inertial electrostatic confinement devices
NASA Astrophysics Data System (ADS)
Boris, D. R.; Alderson, E.; Becerra, G.; Donovan, D. C.; Egle, B.; Emmert, G. A.; Garrison, L.; Kulcinski, G. L.; Santarius, J. F.; Schuff, C.; Zenobia, S. J.
2009-09-01
A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5?A/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7cm2 . Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2- , and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device.
NASA Astrophysics Data System (ADS)
Prástaro, Agostino
2008-02-01
Following our previous results on this subject [R.P. Agarwal, A. Prástaro, Geometry of PDE's. III(I): Webs on PDE's and integral bordism groups. The general theory, Adv. Math. Sci. Appl. 17 (2007) 239-266; R.P. Agarwal, A. Prástaro, Geometry of PDE's. III(II): Webs on PDE's and integral bordism groups. Applications to Riemannian geometry PDE's, Adv. Math. Sci. Appl. 17 (2007) 267-285; A. Prástaro, Geometry of PDE's and Mechanics, World Scientific, Singapore, 1996; A. Prástaro, Quantum and integral (co)bordism in partial differential equations, Acta Appl. Math. (5) (3) (1998) 243-302; A. Prástaro, (Co)bordism groups in PDE's, Acta Appl. Math. 59 (2) (1999) 111-201; A. Prástaro, Quantized Partial Differential Equations, World Scientific Publishing Co, Singapore, 2004, 500 pp.; A. Prástaro, Geometry of PDE's. I: Integral bordism groups in PDE's, J. Math. Anal. Appl. 319 (2006) 547-566; A. Prástaro, Geometry of PDE's. II: Variational PDE's and integral bordism groups, J. Math. Anal. Appl. 321 (2006) 930-948; A. Prástaro, Th.M. Rassias, Ulam stability in geometry of PDE's, Nonlinear Funct. Anal. Appl. 8 (2) (2003) 259-278; I. Stakgold, Boundary Value Problems of Mathematical Physics, I, The MacMillan Company, New York, 1967; I. Stakgold, Boundary Value Problems of Mathematical Physics, II, Collier-MacMillan, Canada, Ltd, Toronto, Ontario, 1968], integral bordism groups of the Navier-Stokes equation are calculated for smooth, singular and weak solutions, respectively. Then a characterization of global solutions is made on this ground. Enough conditions to assure existence of global smooth solutions are given and related to nullity of integral characteristic numbers of the boundaries. Stability of global solutions are related to some characteristic numbers of the space-like Cauchy dataE Global solutions of variational problems constrained by (NS) are classified by means of suitable integral bordism groups too.
Buoyant jet behavior in confined regions
Fry, David J.
1981-01-01
Previous confined jet studies have emphasized the behavior of non-buoyant jets inside ducts or near plane boundaries (Coanda effect). Buoyancy, however, is a major factor in the confined jet behavior experienced in many ...
BOOK REVIEW: Instabilities in a confined plasma
NASA Astrophysics Data System (ADS)
Glasser, A. H.
1999-05-01
This is a large and important work by one of the leading Russian contributors to this subject. It covers topics of central importance to magnetic fusion energy research with a breadth, depth and clarity not found elsewhere. It is intended as a reference book and guide to the original literature for serious practitioners of the field. The book is divided into 8 large parts, listed below, and further subdivided into 31 chapters. The preface states, ``A need was identified to summarize the large amount of information on the topic of instabilities. This information is scattered throughout many papers on certain special subjects on the theory of toroidal-plasma instabilities. This book aims to treat it from a unified point of view.'' This is a good description of the aims and approach. The range of topics is large and the treatment deep and thorough. This is often accomplished by assuming considerable knowledge on the part of the reader, most appropriate for mature researchers in the field. The pace is fast. The requisite background includes extensive knowledge of a wide range of physics, ordinary and partial differential equations, integral equations, differential geometry and special functions. The preface also states, ``The author starts with the fundamental principles, so that no special knowledge of plasma physics is necessary before reading the book. It will therefore be useful for researchers, postgraduates, high-school teachers and students specializing in plasma physics and controlled fusion.'' In the opinion of this reviewer, that may be overly ambitious. The terse approach, characteristic of the whole book, as well as the steep price, would make it rather challenging for such an audience. For example, in the opening chapter, `General results of equilibrium theory', the properties of non-orthogonal, curvilinear co-ordinates are stated tersely without much explanation or derivation, more as a review than a first presentation. It is common for physics students, at least in the USA, to encounter this material first in a course on general relativity, which they might not have taken previously when specializing in plasma physics. While good efforts are made by the author to provide an intuitive understanding of the many analytical results, this is often done with such brevity that a substantial level of maturity is required to comprehend the ideas. Another quote from the preface is, ``The book is based on analytical approaches and should therefore be useful for everybody who is interested in the topic.'' In a field where complex geometry and dynamics and the importance of practical results have required much novel and creative computational work over the past 25 years, there is no mention, no acknowledgment, no hint of its importance. The analytical approach presented here certainly fills an important need, and there is no need for the same work to cover numerical work in depth, but some recognition of the importance of numerical work and its relationship with the analytical side of the theory might have been justified. Despite these shortcomings, this book is a major and welcome addition to the literature on plasma instabilities which I heartily recommend. Contents: 1. Equilibrium of a plasma in toroidal confinement systems; 2. Internal magnetohydrodynamic modes in the cylindrical approximation; 3. Small-scale magnetohydrodynamic instabilities in toroidal confinement systems; 4. Magnetohydrodynamic internal kink modes in toroidal geometry; 5. Magnetohydrodynamic modes in collisionless and neoclassical regimes; 6. Drift-magnetohydrodynamic modes; 7. External kink modes; 8. Alfvén eigenmodes and their interaction with high-energy particles; References; Index.
Integrable Background Geometries
NASA Astrophysics Data System (ADS)
Calderbank, David M. J.
2014-03-01
This work has its origins in an attempt to describe systematically the integrable geometries and gauge theories in dimensions one to four related to twistor theory. In each such dimension, there is a nondegenerate integrable geometric structure, governed by a nonlinear integrable differential equation, and each solution of this equation determines a background geometry on which, for any Lie group G, an integrable gauge theory is defined. In four dimensions, the geometry is selfdual conformal geometry and the gauge theory is selfdual Yang-Mills theory, while the lower-dimensional structures are nondegenerate (i.e., non-null) reductions of this. Any solution of the gauge theory on a k-dimensional geometry, such that the gauge group H acts transitively on an ?-manifold, determines a (k+?)-dimensional geometry (k+??4) fibering over the k-dimensional geometry with H as a structure group. In the case of an ?-dimensional group H acting on itself by the regular representation, all (k+?)-dimensional geometries with symmetry group H are locally obtained in this way. This framework unifies and extends known results about dimensional reductions of selfdual conformal geometry and the selfdual Yang-Mills equation, and provides a rich supply of constructive methods. In one dimension, generalized Nahm equations provide a uniform description of four pole isomonodromic deformation problems, and may be related to the {SU}(?) Toda and dKP equations via a hodograph transformation. In two dimensions, the {Diff}(S^1) Hitchin equation is shown to be equivalent to the hyperCR Einstein-Weyl equation, while the {SDiff}(?^2) Hitchin equation leads to a Euclidean analogue of Plebanski's heavenly equations. In three and four dimensions, the constructions of this paper help to organize the huge range of examples of Einstein-Weyl and selfdual spaces in the literature, as well as providing some new ! ones. The nondegenerate reductions have a long ancestry. More ! recently , degenerate or null reductions have attracted increased interest. Two of these reductions and their gauge theories (arguably, the two most significant) are also described.
Geometry, noncommutative algebra and representations
Wirosoetisno, Djoko
Geometry, noncommutative algebra and representations Iain Gordon http://www.maths.ed.ac.uk/~igordon/ University of Edinburgh 16th December 2006 1 Iain Gordon Geometry, noncommutative algebra and representations #12;2 Iain Gordon Geometry, noncommutative algebra and representations #12;Outline 1 Geometry
NASA Astrophysics Data System (ADS)
Jonsson, Rickard; Westman, Hans
2006-01-01
We show that by employing the standard projected curvature as a measure of spatial curvature, we can make a certain generalization of optical geometry (Abramowicz M A and Lasota J-P 1997 Class. Quantum Grav. A 14 23 30). This generalization applies to any spacetime that admits a hypersurface orthogonal shearfree congruence of worldlines. This is a somewhat larger class of spacetimes than the conformally static spacetimes assumed in standard optical geometry. In the generalized optical geometry, which in the generic case is time dependent, photons move with unit speed along spatial geodesics and the sideways force experienced by a particle following a spatially straight line is independent of the velocity. Also gyroscopes moving along spatial geodesics do not precess (relative to the forward direction). Gyroscopes that follow a curved spatial trajectory precess according to a very simple law of three-rotation. We also present an inertial force formalism in coordinate representation for this generalization. Furthermore, we show that by employing a new sense of spatial curvature (Jonsson R 2006 Class. Quantum Grav. 23 1)) closely connected to Fermat's principle, we can make a more extensive generalization of optical geometry that applies to arbitrary spacetimes. In general this optical geometry will be time dependent, but still geodesic photons move with unit speed and follow lines that are spatially straight in the new sense. Also, the sideways experienced (comoving) force on a test particle following a line that is straight in the new sense will be independent of the velocity.
NASA Astrophysics Data System (ADS)
Vassiliou, Peter J.
2009-10-01
Cartan's method of moving frames is briefly recalled in the context of immersed curves in the homogeneous space of a Lie group G. The contact geometry of curves in low dimensional equi-affine geometry is then made explicit. This delivers the complete set of invariant data which solves the G-equivalence problem via a straightforward procedure, and which is, in some sense a supplement to the equivariant method of Fels and Olver. Next, the contact geometry of curves in general Riemannian manifolds (M,g) is described. For the special case in which the isometries of (M,g) act transitively, it is shown that the contact geometry provides an explicit algorithmic construction of the differential invariants for curves in M. The inputs required for the construction consist only of the metric g and a parametrisation of structure group SO(n); the group action is not required and no integration is involved. To illustrate the algorithm we explicitly construct complete sets of differential invariants for curves in the Poincaré half-space H3 and in a family of constant curvature 3-metrics. It is conjectured that similar results are possible in other Cartan geometries.
Spectral properties of a confined nonlinear quantum oscillator in one and three dimensions
Schulze-Halberg, Axel; Gordon, Christopher R.
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.
Simulations of plasma confinement in an antihydrogen trap
Gomberoff, K.; Fajans, J.; Friedman, A.; Grote, D.; Vay, J.-L.; Wurtele, J. S. [Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States) and Physics Department, Technion, Haifa 32000 (Israel); Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States) and Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Heavy Ion Fusion Virtual National Laboratory, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States) and Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2007-10-15
The three-dimensional particle-in-cell (3-D PIC) simulation code WARP is used to study positron confinement in antihydrogen traps. The magnetic geometry is close to that of a UC Berkeley experiment conducted, with electrons, as part of the ALPHA collaboration [W. Bertsche et al., AIP Conf. Proc. 796, 301 (2005)]. In order to trap antihydrogen atoms, multipole magnetic fields are added to a conventional Malmberg-Penning trap. These multipole fields must be strong enough to confine the antihydrogen, leading to multipole field strengths at the trap wall comparable to those of the axial magnetic field. Numerical simulations reported here confirm recent experimental measurements of reduced particle confinement when a quadrupole field is added to a Malmberg-Penning trap. It is shown that, for parameters relevant to various antihydrogen experiments, the use of an octupole field significantly reduces the positron losses seen with a quadrupole field. A unique method for obtaining a 3-D equilibrium of the positrons in the trap with a collisionless PIC code was developed especially for the study of the antihydrogen trap; however, it is of practical use for other traps as well.
Simulations of plasma confinement in an antihydrogen trap
Gomberoff, K.; Fajans, J.; Friedman, A.; Grote, D.; Vay, J.-L.; Wurtele, J.S.
2007-10-15
The three-dimensional particle-in-cell (3-D PIC) simulation code WARP is used to study positron confinement in antihydrogen traps. The magnetic geometry is close to that of a UC Berkeley experiment conducted, with electrons, as part of the ALPHA collaboration (W. Bertsche et al., AIP Conf. Proc. 796, 301 (2005)). In order to trap antihydrogen atoms, multipole magnetic fields are added to a conventional Malmberg-Penning trap. These multipole fields must be strong enough to confine the antihydrogen, leading to multipole field strengths at the trap wall comparable to those of the axial magnetic field. Numerical simulations reported here confirm recent experimental measurements of reduced particle confinement when a quadrupole field is added to a Malmberg-Penning trap. It is shown that, for parameters relevant to various antihydrogen experiments, the use of an octupole field significantly reducesthe positron losses seen with a quadrupole field. A unique method for obtaining a 3-D equilibrium of the positrons in the trap with a collisionless PIC code was developed especially for the study of the antihydrogen trap; however, it is of practical use for other traps as well.
Capillary and winding transitions in a confined cholesteric liquid crystal
Daniel de las Heras; Enrique Velasco; Yuri Martínez-Ratón
2015-07-23
We consider a Lebwohl-Lasher model of chiral particles confined in a planar cell (slit pore) with different boundary conditions, and solve it using mean-field theory. The phase behaviour of the system with respect to temperature and pore width is studied. Two phenomena are observed: (i) an isotropic-cholesteric transition which exhibits an oscillatory structure with respect to pore width, and (ii) an infinite set of winding transitions caused by commensuration effects between cholesteric pitch and pore width. The latter transitions have been predicted and analysed by other authors for cholesterics confined in a fixed pore and subject to an external field promoting the uniaxial nematic phase; here we induce winding transitions solely from geometry by changing the pore width at zero external field (a setup recently explored in Atomic-Force Microscopy experiments). In contrast with previous studies, we obtain the phase diagrams in the temperature vs pore width plane, including the isotropic-cholesteric transition, the winding transitions and their complex relationship. In particular, the structure of winding transitions terminates at the capillary isotropic-cholesteric transition via triple points where the confined isotropic phase coexists with two cholesterics with different helix indices. For symmetric and asymmetric monostable plate anchorings the phase diagram are qualitatively similar.
Capillary and winding transitions in a confined cholesteric liquid crystal.
de Las Heras, Daniel; Velasco, Enrique; Martínez-Ratón, Yuri
2015-09-21
We consider a Lebwohl-Lasher model of chiral particles confined in a planar cell (slit pore) under different boundary conditions, and solve it using mean-field theory. The phase behaviour of the system with respect to temperature and pore width is studied. Two phenomena are observed: (i) an isotropic-cholesteric transition, which exhibits an oscillatory structure with respect to pore width, and (ii) an infinite set of winding transitions caused by commensuration effects between cholesteric pitch and pore width. The latter transitions have been predicted and analysed by other authors for cholesterics confined in a fixed pore and subjected to an external field promoting the uniaxial nematic phase; here we induce winding transitions solely from geometry by changing the pore width at zero external field (a setup recently explored in atomic-force microscopy experiments). In contrast with previous studies, we obtain the phase diagram in the temperature vs. pore width plane, including the isotropic-cholesteric transition, the winding transitions and their complex relationship. In particular, the structure of winding transitions terminates at the capillary isotropic-cholesteric transition via triple points where the confined isotropic phase coexists with two cholesterics with different helix indices. For symmetric and asymmetric monostable plate anchorings the phase diagrams are qualitatively similar. PMID:26246247
Understanding nanorheology and surface forces of confined thin films
NASA Astrophysics Data System (ADS)
Huang, Jun; Yan, Bin; Faghihnejad, Ali; Xu, Haolan; Zeng, Hongbo
2014-02-01
Understanding the nanorheology and associated intermolecular/surface forces of fluids in confined geometries or porous media is of both fundamental and practical importance, providing significant insights into various applications such as lubrication and micro/nanoelectromechanical systems. In this work, we briefly reviewed the fundamentals of nanoreheolgy, advances in experimental techniques and theoretical simulation methods, as well as important progress in the nanorheology of confined thin films. The advent of advanced experimental techniques such as surface forces apparatus (SFA), X-ray surface forces apparatus (XSFA) and atomic force microscope (AFM) and computational methods such as molecular dynamics simulations provides powerful tools to study a wide range of rheological phenomena at molecular level and nano scale. One of the most challenging issues unresolved is to elucidate the relationship between the rheological properties and structural evolution of the confined fluid films and particles suspensions. Some of the emerging research areas in the nanorheology field include, but are not limited to, the development of more advanced characterization techniques, design of multifunctional rheological fluids, bio-related nanorheology, and polymer brushes.
Dimension reduction for rotating Bose-Einstein condensates with anisotropic confinement
Florian Mehats; Christof Sparber
2015-07-10
We consider the three-dimensional time-dependent Gross-Pitaevskii equation arising in the description of rotating Bose-Einstein condensates and study the corresponding scaling limit of strongly anisotropic confinement potentials. The resulting effective equations in one or two spatial dimensions, respectively, are rigorously obtained as special cases of an averaged three dimensional limit model. In the particular case where the rotation axis is not parallel to the strongly confining direction the resulting limiting model(s) include a negative, and thus, purely repulsive quadratic potential, which is not present in the original equation and which can be seen as an effective centrifugal force counteracting the confinement.
NASA Astrophysics Data System (ADS)
Ochiai, T.; Nacher, J. C.
2011-09-01
Recently, the application of geometry and conformal mappings to artificial materials (metamaterials) has attracted the attention in various research communities. These materials, characterized by a unique man-made structure, have unusual optical properties, which materials found in nature do not exhibit. By applying the geometry and conformal mappings theory to metamaterial science, it may be possible to realize so-called "Harry Potter cloaking device". Although such a device is still in the science fiction realm, several works have shown that by using such metamaterials it may be possible to control the direction of the electromagnetic field at will. We could then make an object hidden inside of a cloaking device. Here, we will explain how to design invisibility device using differential geometry and conformal mappings.
2011-01-01
Cells are highly complex and orderly machines, with defined shapes and a startling variety of internal organizations. Complex geometry is a feature of both free-living unicellular organisms and cells inside multicellular animals. Where does the geometry of a cell come from? Many of the same questions that arise in developmental biology can also be asked of cells, but in most cases we do not know the answers. How much of cellular organization is dictated by global cell polarity cues as opposed to local interactions between cellular components? Does cellular structure persist across cell generations? What is the relationship between cell geometry and tissue organization? What ensures that intracellular structures are scaled to the overall size of the cell? Cell biology is only now beginning to come to grips with these questions. PMID:21880160
Proton radiography of PBX 9502 detonation shock dynamics confinement sandwich test
Aslam, Tariq D; Jackson, Scott I; Morris, John S
2009-01-01
Recent results utilizing proton radiography (P-Rad) during the detonation of the high explosive PBX 9502 are presented. Specifically, the effects of confinement of the detonation are examined in the LANL detonation confinement sandwich geometry. The resulting detonation velocity and detonation shock shape are measured. In addition, proton radiography allows one to image the reflected shocks through the detonation products. Comparisons are made with detonation shock dynamics (DSD) and reactive flow models for the lead detonation shock and detonation velocity. In addition, predictions of reflected shocks are made with the reactive flow models.
Concentric tetratic orientational order in a confined quasi-2D tubular system
NASA Astrophysics Data System (ADS)
Sánchez, Rodrigo; Aguirre-Manzo, Leopoldo A.
2015-09-01
Experimental evidence of two different forms of tetratic orientational order in granular submonolayers is presented. The system, which consists of tubular particles in a circular cell, essentially consists of a central region exhibiting conventional tetratic orientational order, reminiscent of that expected in the bulk for hard rectangles, as well as an outer region exhibiting ‘concentric’ tetratic order. The analysis used to quantify the latter’s degree of order and size, which requires suitably re-defining the relevant order parameters, can be readily extended to a wide variety of confining geometries, both with curved and straight confining walls.
Physics of magnetic confinement fusion
NASA Astrophysics Data System (ADS)
Wagner, F.
2013-06-01
Fusion is the energy source of the universe. The local conditions in the core of the Sun allow the transfer of mass into energy, which is finally released in the form of radiation. Technical fusion melts deuterons and tritons to helium releasing large amounts of energy per fusion process. Because of the conditions for fusion, which will be deduced, the fusion fuel is in the plasma state. Here we report on the confinement of fusion plasmas by magnetic fields. Different confinement concepts — tokamaks and stellarators — will be introduced and described. The first fusion reactor, ITER, and the most modern stellarator, Wendelstein 7-X, are under construction. Their basic features and objectives will be presented.
Simulations of artificial swimmers in confined flows
NASA Astrophysics Data System (ADS)
Brandt, Luca; Zhu, Lailai; Gjølberg, Eerik
2012-11-01
Miniature swimmming robots are potentially powerful for microobject manipulation, such as flow control in lab-on-a-chip, localized drug delivery and screening for diseases. Magnetically driven artificial bacterial flagella (ABF) performing helical motion is advantegous due to high swimming speed and accurate control. Using boundary element method, we numerically investigate the propulsion of ABF in free space and near solid boundaries. Step-out at high actuation frequencies, wobbling and near-wall drifting are documented, in qualitative agreement with recent experiments. We aim to explore the effect of swimmer shape on the performance, thus benefiting design of efficient microswimmers. Propulsion of ABF confined by a solid wall with and without background shear flow is also studied, with a focus on wall-induced hydrodynamic interaction and its influence on the stability of the motion. Funding by VR (the Swedish Research Council) and Linne flow centre at KTH is acknowledged.
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
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.
Deriving confinement via RG decimations
E. T. Tomboulis
2007-10-10
We present the general framework and building blocks of a recent derivation of the fact that the SU(2) LGT is in a confining phase for all values of the coupling $0 < \\beta < \\infty$, for space-time dimension $d \\leq 4$. The method employs approximate but explicitly computable RG decimations that are shown to constrain the exact partition function and order parameters from above and below, and flow from the weak to the strong coupling regime without encountering a fixed point.
Inertial-confinement-fusion targets
Hendricks, C.D.
1981-11-16
Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques have been devised for producing the targets. Glass and metal shells are made by using drop and bubble techniques. Solid hydrogen shells are also produced by adapting old methods to the solution of modern problems. Some of these techniques, problems and solutions are discussed. In addition, the applications of many of the techniques to fabrication of ICF targets is presented.
Electron states confined within nano-steps on metal surfaces.
Mitsuoka, Shigenori; Tamura, Akira
2011-02-01
To elucidate electron states confined within steps on metal surfaces, we demonstrated a new point of view that a linear step on a noble metal surface can be treated as a dipole potential composed of delta functions. For an electron confined by two pairs of dipole potentials, we derived quasi-stationary eigenstates whose eigenenergies are complex numbers which lead to the lifetime of the electron. To derive the local density of states (LDOS), scanning tunneling microscopy (STM) images and scanning tunneling spectra (STS) for stepped surfaces, we incorporated the lifetime effect on them and clarified the relation between the LDOS and the STM current by applying the expression for the STM current derived by Selloni et al (1985 Phys. Rev. B 31 2602). Although, in previous studies, the Fabry-Pérot interference mechanism has been used to explain electron states confined within two steps, it requires four fitting parameters, in contrast our method requires one fitting parameter which specifies the height of the delta functions. Our results for LDOS images, topographical images and STS are consistent with experimental ones for both the cases where electrons stay on a terrace confined by two steps and on a wide terrace outside the step, which confirms the validity of our model. PMID:21406882
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).
Heller, L.
1985-01-01
It is argued on theoretical and phenomenological grounds that confinement of quarks is intrinsically a many-body interaction. The Born-Oppenheimer approximation to the bag model is shown to give rise to a static potential energy that consists of a sum of two-body Coulomb terms and a many-body confining term. Following the success of this potential in heavy Q anti Q systems it is being applied to Q/sup 2/ anti Q/sup 2/. Preliminary calculations suggest that dimeson bound states with exotic flavor, such as bb anti s anti s, exist. 13 refs., 5 figs.
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.
Inertial Confinement Fusion R&D and Nuclear Proliferation
Robert J. Goldston
2011-04-28
In a few months, or a few years, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory may achieve fusion gain using 192 powerful lasers to generate x-rays that will compress and heat a small target containing isotopes of hydrogen. This event would mark a major milestone after decades of research on inertial confinement fusion (ICF). It might also mark the beginning of an accelerated global effort to harness fusion energy based on this science and technology. Unlike magnetic confinement fusion (ITER, 2011), in which hot fusion fuel is confined continuously by strong magnetic fields, inertial confinement fusion involves repetitive fusion explosions, taking advantage of some aspects of the science learned from the design and testing of hydrogen bombs. The NIF was built primarily because of the information it would provide on weapons physics, helping the United States to steward its stockpile of nuclear weapons without further underground testing. The U.S. National Academies' National Research Council is now hosting a study to assess the prospects for energy from inertial confinement fusion. While this study has a classified sub-panel on target physics, it has not been charged with examining the potential nuclear proliferation risks associated with ICF R&D. We argue here that this question urgently requires direct and transparent examination, so that means to mitigate risks can be assessed, and the potential residual risks can be balanced against the potential benefits, now being assessed by the NRC. This concern is not new (Holdren, 1978), but its urgency is now higher than ever before.
Effects of confinement on freezing and melting.
Alba-Simionesco, C; Coasne, B; Dosseh, G; Dudziak, G; Gubbins, K E; Radhakrishnan, R; Sliwinska-Bartkowiak, M
2006-02-15
We present a review of experimental, theoretical, and molecular simulation studies of confinement effects on freezing and melting. We consider both simple and more complex adsorbates that are confined in various environments (slit or cylindrical pores and also disordered porous materials). The most commonly used molecular simulation, theoretical and experimental methods are first presented. We also provide a brief description of the most widely used porous materials. The current state of knowledge on the effects of confinement on structure and freezing temperature, and the appearance of new surface-driven and confinement-driven phases are then discussed. We also address how confinement affects the glass transition. PMID:21697556
Effect of Aluminium Confinement on ANFO Detonation
NASA Astrophysics Data System (ADS)
Short, Mark; Jackson, Scott; Kiyanda, Charles; Shinas, Mike; Hare, Steve; Briggs, Matt
2013-06-01
Detonations in confined non-ideal high explosives often have velocities below the confiner sound speed. The effect on detonation propagation of the resulting subsonic flow in the confiner (such as confiner stress waves traveling ahead of the main detonation front or upstream wall deflection into the HE) has yet to be fully understood. Previous work by Sharpe and Bdzil (J. Eng. Math, 2006) has shown that for subsonic confiner flow, there is no limiting thickness for which the detonation dynamics are uninfluenced by further increases in wall thickness. The critical parameters influencing detonation behavior are the wall thickness relative to the HE reaction zone size, and the difference in the detonation velocity and confiner sound speed. Additional possible outcomes of subsonic flow are that for increasing thickness, the confiner is increasingly deflected into the HE upstream of the detonation, and that for sufficiently thick confiners, the detonation speed could be driven up to the sound speed in the confiner. We report here on a further series of experiments in which a mixture of ammonium nitrate and fuel oil (ANFO) is detonated in aluminum confiners with varying HE charge diameter and confiner thickness, and compare the results with the outcomes suggested by Sharpe and Bdzil.
ERIC Educational Resources Information Center
Case, Christine L.
1991-01-01
Presented is an activity in which students make models of viruses, which allows them to visualize the shape of these microorganisms. Included are some background on viruses, the biology and geometry of viruses, directions for building viruses, a comparison of cells and viruses, and questions for students. (KR)
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…
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)
NSDL National Science Digital Library
Carberry, Emma Elizabeth, 1974-
This course involves students taking turn giving lectures on geometry topics. Subjects such as Gauss maps, minimal surfaces and manifolds and geodesics were covered in the lectures. Course materials include lecture notes as well as student projects and examples. MIT presents OpenCourseWare as free educational material online. No registration or enrollment is required to use the materials.
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.
Atiyah, Michael; Dijkgraaf, Robbert; Hitchin, Nigel
2010-01-01
We review the remarkably fruitful interactions between mathematics and quantum physics in the past decades, pointing out some general trends and highlighting several examples, such as the counting of curves in algebraic geometry, invariants of knots and four-dimensional topology. PMID:20123740
COMPUTATIONAL REAL ALGEBRAIC GEOMETRY
Mishra, Bud
geometry studies various algorithmic questions dealing with the real solutions of a system of equalities by the power and elegance with which it solves a broad and general class of problems arising in robotics, vision, computer aided design, geometric theorem proving, etc. The algorithmic problems that arise
ERIC Educational Resources Information Center
Cooper, Brett D.; Barger, Rita
2009-01-01
The many connections between music and mathematics are well known. The length of a plucked string determines its tone, the time signature of a piece of music is a ratio, and note durations are measured in fractions. One connection commonly overlooked is that between music and geometry--specifically, geometric transformations, including…
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.
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.
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.
Advanced geometries and regimes
Bulanov, S. S.; Bulanov, S. V.; Turchetti, G.; Limpouch, J.; Klimo, O.; Psikal, J.; Margarone, D.; Korn, G.
2013-07-26
We review and discuss different schemes of laser ion acceleration as well as advanced target geometries in connection with the development of the laser-driven proton source for hadron therapy of oncological diseases, which is a part of the ELIMED project.
Algebraic Thinking and Geometry
ERIC Educational Resources Information Center
Grandau, Laura; Stephens, Ana C.
2006-01-01
This article describes how two middle school teachers incorporated algebraic thinking into their textbook-based geometry lessons. One teacher embedded algebraic concepts within an existing textbook lesson while the other teacher elicited algebraic thinking by extending a textbook lesson. (Contains 5 figures.)
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".…
Centrifugally Confined Plasmas: An Alternative Concept for Fusion
NASA Astrophysics Data System (ADS)
Hassam, A. B.
2000-10-01
The basic idea of centrifugal confinement is to use centrifugal forces from supersonic rotation to augment the conventional magnetic confinement. Optimizing this ``knob" results in a fusion device that features four advantages: steady state, no disruptions, superior crossfield confinement, and a simpler coil configuration. The idea rests on two prongs: first, centrifugal forces can confine plasmas to desired regions of shaped magnetic fields; second, the accompanying large velocity shear can stabilize even MHD instabilities. A third feature is that the velocity shear also viscously heats the plasma, no auxiliary heat is necessary to reach fusion temperatures. As far as transport goes, the velocity shear can also quell microturbulence, leading to fully classical confinement as there are no neoclassical effects. Classical parallel electron transport then determines the confinement time. These losses are minimized by a large Pastukhov factor resulting from the deep centrifugal potential well: at Mach 4-5, the Lawson Criterion is accessible. The key issue is whether velocity shear will be sufficient by itself to stabilize MHD interchanges. Numerical simulations indicate that laminar equilibria can be obtained at Mach numbers of 4-5 but that the progression towards laminarity with increasing Mach number is accompanied by residual convection from the interchanges. The central goal of the Maryland Centrifugal Torus (MCT), under construction at the University of Maryland, is to obtain MHD stability from velocity shear. As an assist to accessing laminarity, MCT will incorporate two unique features: plasma elongation and toroidal magnetic field. The former raises velocity shear efficiency, and modest magnetic shear should suppress residual convection.
An experiment to test centrifugal confinement for fusion
NASA Astrophysics Data System (ADS)
Ellis, R. F.; Hassam, A. B.; Messer, S.; Osborn, B. R.
2001-05-01
The basic idea of centrifugal confinement is to use centrifugal forces from supersonic rotation to augment conventional magnetic confinement. Optimizing this "knob" results in a fusion device that features four advantages: steady state, no disruptions, superior cross-field confinement, and a simpler coil configuration. The idea rests on two prongs: first, centrifugal forces can confine plasmas to desired regions of shaped magnetic fields; second, the accompanying large velocity shear can stabilize even magnetohydrodynamic (MHD) instabilities. A third feature is that the velocity shear also viscously heats the plasma; no auxiliary heating is necessary to reach fusion temperatures. Regarding transport, the velocity shear can also quell microturbulence, leading to fully classical confinement, as there are no neoclassical effects. Classical parallel electron transport then sets the confinement time. These losses are minimized by a large Pastukhov factor resulting from the deep centrifugal potential well: at Mach 4-5, the Lawson criterion is accessible. One key issue is whether velocity shear will be sufficient by itself to stabilize MHD interchanges. Numerical simulations indicate that laminar equilibria can be obtained at Mach numbers of 4-5 but that the progression toward laminarity with increasing Mach number is accompanied by residual convection from the interchanges. The central goal of the Maryland Centrifugal Torus (MCT) [R. F. Ellis et al., Bull. Am. Phys. Soc. 44, 48 (1998)] is to obtain MHD stability from velocity shear. As an assist to accessing laminarity, MCT will incorporate two unique features: plasma elongation and toroidal magnetic field. The former raises velocity shear efficiency, and modest magnetic shear should suppress residual convection.
Inertial confinement fusion with light ion beams.
Vandevender, J P; Cook, D L
1986-05-16
The Particle Beam Fusion Accelerator II (PBFA II) is presently under construction and is the only existing facility with the potential of igniting thermonuclear fuel in the laboratory. The accelerator will generate up to 5 megamperes of lithium ions at 30 million electron volts and will focus them onto an inertial confinement fusion (ICF) target after beam production and focusing have been optimized. Since its inception, the light ion approach to ICF has been considered the one that combines low cost, high risk, and high payoff. The beams are of such high density that their self-generated electric and magnetic fields were thought to prohibit high focal intensities. Recent advances in beam production and focusing demonstrate that these self-forces can be controlled to the degree required for ignition, break-even, and high gain experiments. ICF has been pursued primarily for its potential military applications. However, the high efficiency and cost-effectiveness of the light ion approach enhance its potential for commercial energy application as well. PMID:17755963
NASA Astrophysics Data System (ADS)
Süt?, András
2014-03-01
Galilean invariance leaves its imprint on the energy spectrum and eigenstates of N quantum particles, bosons, or fermions, confined in a bounded domain. It endows the spectrum with a recurrent structure, which in capillaries or elongated traps of length L and cross-section area s? leads to spectral gaps n2h2s??/(2mL) at wave numbers 2n?s??, where ? is the number density and m is the particle mass. In zero temperature superfluids, in toroidal geometries, it causes the quantization of the flow velocity with the quantum h/(mL) or that of the circulation along the toroid with the known quantum h/m. Adding a "friction" potential, which breaks Galilean invariance, the Hamiltonian can have a superfluid ground state at low flow velocities but not above a critical velocity, which may be different from the velocity of sound. In the limit of infinite N and L, if N/L=s?? is kept fixed, translation invariance is broken, and the center of mass has a periodic distribution, while superfluidity persists at low flow velocities. This conclusion holds for the Lieb-Liniger model.
Ion Extraction from a Helicon Plasma Source for an Inertial Electrostatic Confinement Fusion Device
NASA Astrophysics Data System (ADS)
Becerra, Gabriel; Kulcinski, Gerald; Santarius, John
2012-10-01
HELIOS, an inertial electrostatic confinement (IEC) fusion device designed for advanced fuel studies [1], uses an external helicon plasma source, from which ions are extracted and subsequently accelerated radially into an electrostatic potential well set up by a semi-transparent cathode grid inside a spherical chamber. A campaign is underway to raise fusion rates to allow for diagnostic studies of IEC physics with helium-3 fuel, in order to benchmark the single-atomic-species formalism of VICTER, a Volterra integral-equation code on spherically convergent ion flow [2]. The helicon plasma has been characterized through double probe measurements of plasma density and electron temperature for various rf antenna and magnetic field geometries. Measurements of the extracted ion current using a witness plate and a Faraday cup are also presented.[4pt] [1] G.R. Piefer et al., Fusion Sci. Technol. 47, 1255 (2005).[0pt] [2] G.A. Emmert and J.F. Santarius, Phys. Plasmas 17, 013502 (2010).
Molecular Dynamics simulation of evaporation processes of fluid bridges confined in slit-like pore
Katarzyna Bucior; Leonid Yelash; Kurt Binder
2009-01-23
A simple fluid, described by point-like particles interacting via the Lennard-Jones potential, is considered under confinement in a slit geometry between two walls at distance Lz apart for densities inside the vapor-liquid coexistence curve. Equilibrium then requires the coexistence of a liquid "bridge" between the two walls, and vapor in the remaining pore volume. We study this equilibrium for several choices of the wall-fluid interaction (corresponding to the full range from complete wetting to complete drying, for a macroscopically thick film), and consider also the kinetics of state changes in such a system. In particular, we study how this equilibrium is established by diffusion processes, when a liquid is inserted into an initially empty capillary (partial or complete evaporation into vacuum), or when the volume available for the vapor phase increases. We compare the diffusion constants describing the rates of these processes in such inhomogeneous systems to the diffusion constants in the corresponding bulk liquid and vapor phases.
Fast particle confinement with optimized coil currents in the W7-X stellarator
NASA Astrophysics Data System (ADS)
Drevlak, M.; Geiger, J.; Helander, P.; Turkin, Y.
2014-07-01
One of the principal goals of the W7-X stellarator is to demonstrate good confinement of energetic ions at finite ?. This confinement, however, is sensitive to the magnetic field configuration and is thus vulnerable to design modifications of the coil geometry. The collisionless drift orbit losses for 60 keV protons in W7-X are studied using the ANTS code. Particles in this energy range will be produced by the neutral beam injection (NBI) system being constructed for W7-X, and are particularly important because protons at this energy accurately mimick the behaviour of 3.5 MeV ?-particles in a HELIAS reactor. To investigate the possibility of improved fast particle confinement, several approaches to adjust the coil currents (5 main field coil currents +2 auxiliary coil currents) were explored. These strategies include simple rules of thumb as well as computational optimization of various properties of the magnetic field. It is shown that significant improvement of collisionless fast particle confinement can be achieved in W7-X for particle populations similar to ? particles produced in fusion reactions. Nevertheless, the experimental goal of demonstrating confinement improvement with rising plasma pressure using an NBI-generated population appears to be difficult based on optimization of the coil currents only. The principal reason for this difficulty is that the NBI deposition profile is broader than the region of good fast-ion confinement around the magnetic axis.
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.
Geometry independent game encapsulation for non-Euclidean geometries
de Figueiredo, Luiz Henrique
is able to render the encapsulated game in both Euclidean and non- Euclidean geometries, showcasing all geometric models, controlling its geometry through the use of shaders, in the GPU. By developing a simple
Impact of lateral carrier confinement on electro-optical tuning properties of polariton condensates
NASA Astrophysics Data System (ADS)
Brodbeck, S.; Suchomel, H.; Amthor, M.; Wolf, A.; Kamp, M.; Schneider, C.; Höfling, S.
2015-07-01
Electro-optical measurements on exciton-polaritons below and above the condensation threshold are performed on high quality, pin-doped microcavities with embedded GaAs quantum wells. Applying an external electric field shifts the polariton emission by hundreds of ?eV both in the linear and the nonlinear regime. We study three device geometries to investigate the influence of carrier confinement in the plane of the quantum well on the electro-optical tuning properties. In the conventional micropillar geometry, the electric field tuning behavior is dominated by the effects of carrier tunneling and electric field screening that manifest in a blueshift of the polariton emission. In stark contrast, for a planar sample geometry, we can significantly extend the range of electric fields and a redshift is observed. To separate the contributions of quantum confined Stark effect and reduced exciton oscillator strength to the energy shift, we study a third sample where the etching of micropillars is stopped just above the active region. In this semi-planar geometry, exciton and polariton emissions can be measured simultaneously. As for the planar geometry, redshifts of the polariton emission are observed below and above threshold that are well reproduced by theoretical shifts.
Pattern formation in confined chemical gardens
NASA Astrophysics Data System (ADS)
De Wit, Anne; Haudin, Florence; Brau, Fabian; Cartwright, Julyan
2014-05-01
Chemical gardens are plant-like mineral structures first described in the seventeenth century and popularly known from chemistry sets for children. They are classically grown in three-dimensional containers by placing a solid metal-salt seed into a silicate solution. When the metal salt starts dissolving in the silicate solution, a semi-permeable membrane forms by precipitation across which water is pumped by osmosis from the silicate solution into the metal salt solution, further dissolving the salt. Above a given pressure, the membrane breaks. The dissolved metal salt solution being generally less dense than the reservoir silicate solution, it rises as a buoyant jet through the broken membrane and further precipitates in contact with the silicate solution, producing a collection of mineral forms that resemble a garden. Such gardens are the subject of increased interest as a model system to understand pattern formation in sea-ice brinicles and hydrothermal vents on the seafloor, among others. All these self-organized precipitation structures at the interface between chemistry, fluid dynamics and mechanics share indeed common chemical, mechanical and electrical properties. In this framework, we study experimentally spatial patterns resulting from the growth of chemical gardens in confined quasi-two-dimensional (2D) geometries upon radial injection of a metallic salt solution into a silicate solution in a horizontal Hele-Shaw cell. We find a large variety of patterns including spirals, fingers, worms, filiform tubes, and flower-like patterns. By exploring the phase space of reactant concentrations and injection flow rates, we observe transitions between these spatio-temporal structures resulting from a coupling between the precipitation reaction, mechanical effects and hydrodynamic instabilities.
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.
Formation of adhesion domains in stressed and confined membranes.
Dharan, Nadiv; Farago, Oded
2015-05-21
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 the enhancement of the amplitude of 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. PMID:25833123
Formation of adhesion domains in stressed and confined membranes
Dharan, Nadiv
2015-01-01
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 adhes...
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.
Geometry dependence of stellarator turbulence
NASA Astrophysics Data System (ADS)
Mynick, H. E.; Xanthopoulos, P.; Boozer, A. H.
2009-11-01
Using the nonlinear gyrokinetic code package GENE/GIST [F. Jenko, W. Dorland, M. Kotschenreuther, and B. N. Rogers, Phys. Plasmas 7, 1904 (2000); P. Xanthopoulos, W. A. Cooper, F. Jenko, Yu. Turkin, A. Runov, and J. Geiger, Phys. Plasmas 16, 082303 (2009)], we study the turbulent transport in a broad family of stellarator designs, to understand the geometry dependence of the microturbulence. By using a set of flux tubes on a given flux surface, we construct a picture of the two-dimensional structure of the microturbulence over that surface and relate this to relevant geometric quantities, such as the curvature, local shear, and effective potential in the Schrödinger-like equation governing linear drift modes.
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.
The geometry of theThe geometry of the marketmarket
Vilela Mendes, Rui
market crises Redes de MercadoMarket networks Jan2008 28 Energy 73 Industrial 114 Consumer 44 Health 70 MercadoMarket networks Sep2001 28 Energy 73 Industrial 114 ConsumerThe geometry of theThe geometry of the marketmarket #12;ContentsContents 1 The Market Geometry