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.
PREFACE: Water in confined geometries
NASA Astrophysics Data System (ADS)
Rovere, Mauro
2004-11-01
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.
Dislocation dynamics in confined geometry
NASA Astrophysics Data System (ADS)
Gómez-García, D.; Devincre, B.; Kubin, L.
1999-05-01
A simulation of dislocation dynamics has been used to calculate the critical stress for a threading dislocation moving in a confined geometry. The optimum conditions for conducting simulations in systems of various sizes, down to the nanometer range, are defined. The results are critically compared with the available theoretical and numerical estimates for the problem of dislocation motion in capped layers.
Amoeboid motion in confined geometry
NASA Astrophysics Data System (ADS)
Wu, Hao; Thiébaud, M.; Hu, W.-F.; Farutin, A.; Rafaï, S.; Lai, M.-C.; Peyla, P.; Misbah, C.
2015-11-01
Many eukaryotic cells undergo frequent shape changes (described as amoeboid motion) that enable them to move forward. We investigate the effect of confinement on a minimal model of amoeboid swimmer. A complex picture emerges: (i) The swimmer's nature (i.e., either pusher or puller) can be modified by confinement, thus suggesting that this is not an intrinsic property of the swimmer. This swimming nature transition stems from intricate internal degrees of freedom of membrane deformation. (ii) The swimming speed might increase with increasing confinement before decreasing again for stronger confinements. (iii) A straight amoeoboid swimmer's trajectory in the channel can become unstable, and ample lateral excursions of the swimmer prevail. This happens for both pusher- and puller-type swimmers. 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. In this study, we combine numerical and theoretical analyses.
Planar geometry inertial electrostatic confinement fusion device
NASA Astrophysics Data System (ADS)
Knapp, Daniel R.
2015-03-01
In the classic gridded inertial electrostatic confinement (IEC) fusion reactor, ion bombardment of the grid leads to heating, thermionic electron emission, significant power loss, and ultimately melting of the grid. Gridless IEC devices have sought to overcome these limitations. Klein reported a gridless device in which ions are circulated as a linear beam in an electrostatic analogue of an optical resonator. To overcome limits of stored ions due to space charge effects at the turning regions, the device employed multiple overlapping traps. The work reported here seeks to further increase the turning region space in a gridless trap by employing a planar geometry. Ion trapping in the planar device was examined by simulating trajectories of 2H+ ions with SIMION 8.1 software. Simulations were carried out using multiple potentials as in Klein's device and for a single potential trap as a planar analogue of the anharmonic ion trap. Scattering by background gas was simulated using a hard sphere collision model, and the results suggested the device will require operation at low pressure with a separate ion source.
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)
Dirac equations with confining potentials
NASA Astrophysics Data System (ADS)
Noble, J. H.; Jentschura, U. D.
2015-01-01
This paper is devoted to a study of relativistic eigenstates of Dirac particles which are simultaneously bound by a static Coulomb potential and added linear confining potentials. Under certain conditions, despite the addition of radially symmetric, linear confining potentials, specific bound-state energies surprisingly preserve their exact Dirac-Coulomb values. The generality of the "preservation mechanism" is investigated. To this end, a Foldy-Wouthuysen transformation is used to calculate the corrections to the spin-orbit coupling induced by the linear confining potentials. We find that the matrix elements of the effective operators obtained from the scalar, and time-like confining potentials mutually cancel for specific ratios of the prefactors of the effective operators, which must be tailored to the preservation mechanism. The result of the Foldy-Wouthuysen transformation is used to verify that the preservation is restricted (for a given Hamiltonian) to only one reference state, rather than traceable to a more general relationship among the obtained effective low-energy operators. The results derived from the nonrelativistic effective operators are compared to the fully relativistic radial Dirac equations. Furthermore, we show that the preservation mechanism does not affect antiparticle (negative-energy) states.
2D Colloidal Wigner crystals in confined geometries
NASA Astrophysics Data System (ADS)
Higler, Ruben; Sprakel, Joris
2015-03-01
Crystallization of bulk systems has been widely studied using colloids as a model system. However, study into colloidal crystallization in confined geometries has been sparse and little is known about the effects of strong confinement on the dynamics of colloidal crystal. In our research we prepare 2D crystals from charged colloids in an apolar solvent to study crystal dynamics, formation, and structure in circular confinements. These confining geometries are made using softlithography techniques from SU-8. In order to broaden the parameter space we can reach in experiments we employ brownian dynamics simulations to supplement our experimental results. Using single-particle tracking we have subpixel resolution positional information of every particle in the system. We study the vibrational modes of our confined crystals and find well defined modes unique to confined systems, such as a radially symmetric compression (or breathing) mode, a collective rotation mode, and distinct resonance modes. Furthermore, due to the circular nature of our constrictions, defectless crystals are impossible, we find, for sufficiently high area fractions, that the defects order at well defined points at the edge. The effect of this ``defect-localization'' has a clear influence on the vibrational modes.
Schwinger effect and entanglement entropy in confining geometries
NASA Astrophysics Data System (ADS)
Ghodrati, Mahdis
2015-09-01
By using AdS /CFT , we study the critical electric field, the Schwinger pair creation rate and the potential phase diagram for the quark and antiquark in four confining supergravity backgrounds which are the Witten QCD (WQCD), the Maldacena-Nunez (MN), the Klebanov-Tseytlin (KT) and the Klebanov-Strassler (KS) models. We compare the rate of phase transition in these models and compare it also with the conformal case. We then present the phase diagrams of the entanglement entropy of a strip in these geometries and find the predicted butterfly shape in the diagrams. We found that the phase transitions have a higher rate in WQCD and KT relative to MN and KS. Finally we show the effect of turning on an additional magnetic field on the rate of pair creation by using the imaginary part of the Euler-Heisenberg effective Lagrangian. The result is increasing the parallel magnetic field would increase the pair creation rate and increasing the perpendicular magnetic field would decrease the rate.
Multiple patterns of diblock copolymer confined in irregular geometries with soft surface
NASA Astrophysics Data System (ADS)
Li, Ying; Sun, Min-Na; Zhang, Jin-Jun; Pan, Jun-Xing; Guo, Yu-Qi; Wang, Bao-Feng; Wu, Hai-Shun
2015-12-01
The different confinement shapes can induce the formation of various interesting and novel morphologies, which might inspire potential applications of materials. In this paper, we study the directed self-assembly of diblock copolymer confined in irregular geometries with a soft surface by using self-consistent field theory. Two types of confinement geometries are considered, namely, one is the concave pore with one groove and the other is the concave pore with two grooves. We obtain more novel and different structures which could not be produced in other two-dimensional (2D) confinements. Comparing these new structures with those obtained in regular square confinement, we find that the range of ordered lamellae is enlarged and the range of disordered structure is narrowed down under the concave pore confinement. We also compare the different structures obtained under the two types of confinement geometries, the results show that the effect of confinement would increase, which might induce the diblock copolymer to form novel structures. We construct the phase diagram as a function of the fraction of B block and the ratio of h/L of the groove. The simulation reveals that the wetting effect of brushes and the shape of confinement geometries play important roles in determining the morphologies of the system. Our results improve the applications in the directed self-assembly of diblock copolymer for fabricating the irregular structures. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20121404110004), the Research Foundation for Excellent Talents of Shanxi Provincial Department of Human Resources and Social Security, China, and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province, China.
Adsorbed molecules in external fields: Effect of confining potential.
Tyagi, Ashish; Silotia, Poonam; Maan, Anjali; Prasad, Vinod
2016-12-01
We study the rotational excitation of a molecule adsorbed on a surface. As is well known the interaction potential between the surface and the molecule can be modeled in number of ways, depending on the molecular structure and the geometry under which the molecule is being adsorbed by the surface. We explore the effect of change of confining potential on the excitation, which is largely controlled by the static electric fields and continuous wave laser fields. We focus on dipolar molecules and hence we restrict ourselves to the first order interaction in field-molecule interaction potential either through permanent dipole moment or/and the molecular polarizability parameter. It is shown that confining potential shapes, strength of the confinement, strongly affect the excitation. We compare our results for different confining potentials. PMID:27387127
A molecular dynamics study of freezing in a confined geometry
NASA Technical Reports Server (NTRS)
Ma, Wen-Jong; Banavar, Jayanth R.; Koplik, Joel
1992-01-01
The dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls is studied by computer simulation. The time development of ordering is quantified and a novel freezing mechanism is observed. The liquid forms layers and subsequent in-plane ordering within a layer is accompanied by a sharpening of the layer in the transverse direction. The effects of channel size, the methods of quench, the liquid-wall interaction and the roughness of walls on the freezing mechanism are elucidated. Comparison with recent experiments on freezing in confined geometries is presented.
Binding of two helium atoms in confined geometries
Kilic, S. |; Krotscheck, E.; Zillich, R.
1999-08-01
The authors carry out a comprehensive study of the binding of two helium atoms in unrestricted and, in particular, in restricted geometries in both two and three dimensions. Besides the well known binding of the {sup 4}He dimer in unrestricted geometry in two and three dimensions, the authors also find weakly bound states of the {sup 3}He-{sup 4}He molecule and the {sup 3}He dimer in 2 dimensions. Furthermore, any combination of two {sup 4}He or {sup 3}He atoms can form a molecule if their motion is sufficiently confined. The calculations are carried out by numerically solving the Schroedinger equation as well as by constructing a suitable variational wave function.
Drying of a colloidal suspension in confined geometry
NASA Astrophysics Data System (ADS)
Leng, Jacques
2010-08-01
We describe experiments on drying of a hard-sphere colloidal suspension in confined geometry where a drop of the suspension is squeezed in between two circular transparent plates and allowed to dry. In this situation, the geometry controls the vapor removal rate and leads to a facilitated observation directly inside the drop. We monitor the drying kinetics of colloids of two sizes and several volume fractions; in most cases, the drying kinetics leads to the formation of a crust at the level of the meniscus which can be either crystalline or glassy, the transition between the two cases being triggered by the local deposition velocity, itself slaved to the evaporation rate. It yields a final dry state which is either polycrystalline or amorphous. The crust is also responsible for a shape instability of the quasi-two-dimensional drop shrinking upon evaporation but with a crust opposing mechanical and flow resistance, and possibly a partial adhesion on the substrate.
Investigation of properties of lithium niobate crystals in confined geometries
NASA Astrophysics Data System (ADS)
Veenhuizen, Keith; Stone, Greg; Knabe, Bastian; McAnany, Sean; Buse, Karsten; Jain, Himanshu; Dierolf, Volkmar
The properties of ferroelectric materials in confined geometries, specifically lithium niobate nanocrystals and crystal lines in glass, were studied. Batches of LiNbO3 nanocrystals have been synthesized from various initial ratios of lithium to niobium using the sol-gel method. The batches were analyzed via Raman spectroscopy and SEM imaging to gain information about their size, morphology, stoichiometry, and defect content. The nanocrystals are very sensitive to the initial stoichiometric ratio in the synthesis step. Raman spectra reveal the resultant nanocrystal stoichiometry depends on the initial stoichiometry of the batch, the spectra also reveal an extra phase is present besides LiNbO3 in some batches, and high quality spherical nanocrystals can be synthesized at certain initial stoichiometric ratios. In addition, lines of LiNbO3 were crystallized in lithium-niobo-silica glass systems with varying amounts of silica to understand and control the nucleation and crystallization of the crystals in glass.
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.
Confining potential in momentum space
NASA Technical Reports Server (NTRS)
Norbury, John W.; Kahana, David E.; Maung, Khin Maung
1992-01-01
A method is presented for the solution in momentum space of the bound state problem with a linear potential in r space. The potential is unbounded at large r leading to a singularity at small q. The singularity is integrable, when regulated by exponentially screening the r-space potential, and is removed by a subtraction technique. The limit of zero screening is taken analytically, and the numerical solution of the subtracted integral equation gives eigenvalues and wave functions in good agreement with position space calculations.
Liquid crystal orientational order in confined geometries: A NMR perspective
NASA Astrophysics Data System (ADS)
Zeng, Huairen
Liquid crystals are a very rich physical system where it is possible to study many phenomena both theoretically as well as experimentally. In almost all applications, liquid crystals exist in contact with some kind of substrate. Liquid crystals properties are greatly affected by a nearby surface: confinement alignment, phase transition temperatures, the critical behavior of the thermodynamic quantities and several other of their properties change. Researching confined liquid crystals to study surface effects will be beneficial for basic physics understanding and provide results perhaps extrapolated to the applied world. An important concept in a microscopic description of a liquid crystal phase is the order parameter, each of the phases is characterized by one or more such parameters. It is therefore of interest to quantify and measure the degree of order of a particular phase 2H-NMR, as a microscopic measurement at the molecular level, has a number of unique features that make it a useful technique to study liquid crystals. NMR can distinguish between spatial and time averages whereas other methods such as birefringence can not. And, most importantly, deuterium NMR is sensitive to the orientational order present in the system. In fact, through NMR lineshape analysis, we can derive the configuration of the nematic director field, and thus determine liquid crystal alignment in random interconnected host. In this work I will use thermotropic liquid crystals and confine them in Millipore membranes, silica Aerogel porous glass and silica Aerosil spheres. Millipore membranes are made from pure, biologically inert mixtures of cellulose acetate and cellulose nitrate. It is a randomly interconnected host geometry with a high porosity, and available in a variety of void sizes, for my research I will use sizes from 8.0 mum to 0.025 mum. Silica Aerogel is a connected pore network, available in many different densities. Our work will cover densities ranging from 0.068 to 0
Electronic quantum confinement in cylindrical potential well
NASA Astrophysics Data System (ADS)
Baltenkov, Arkadiy S.; Msezane, Alfred Z.
2016-04-01
The effects of quantum confinement on the momentum distribution of electrons confined within a cylindrical potential well have been analyzed. The motivation is to understand specific features of the momentum distribution of electrons when the electron behavior is completely controlled by the parameters of a non-isotropic potential cavity. It is shown that studying the solutions of the wave equation for an electron confined in a cylindrical potential well offers the possibility to analyze the confinement behavior of an electron executing one- or two-dimensional motion in the three-dimensional space within the framework of the same mathematical model. Some low-lying electronic states with different symmetries have been considered and the corresponding wave functions have been calculated; the behavior of their nodes and their peak positions with respect to the parameters of the cylindrical well has been analyzed. Additionally, the momentum distributions of electrons in these states have been calculated. The limiting cases of the ratio of the cylinder length H and its radius R0 have been considered; when the cylinder length H significantly exceeds its radius R0 and when the cylinder radius is much greater than its length. The cylindrical quantum confinement effects on the momentum distribution of electrons in these potential wells have been analyzed. The possible application of the results obtained here for the description of the general features in the behavior of electrons in nanowires with metallic type of conductivity (or nanotubes) and ultrathin epitaxial films (or graphene sheets) are discussed. Possible experiments are suggested where the quantum confinement can be manifested. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by Gerardo Delgado Barrio, Andrey Solov'Yov, Pablo Villarreal, Rita Prosmiti.
Colloidal electrodynamics, electrohydrodynamics and thermodynamics in confined geometries
NASA Astrophysics Data System (ADS)
Han, Yilong
We use digital video microscopy and liquid structure theory to measure pair potentials of charged stabilized colloidal spheres in an equilibrium monolayer. Anomalous attraction is founded between like-charged spheres in different degree of confinement, different composition of spheres or substrates, at high ionic strength, or for larger spheres. Error analysis is developed to rule out artifacts. We show that one wall is enough to induce the attraction and gold substrate can enhance such effect. The recently derived configuration temperature is generalized to a hierarchy of hyperconfigurational temperatures. We show their relation to the hypervirial theorem. These temperature definitions are successfully tested experimentally for the first time via colloidal systems. The results confirmed our anomalous attractions measured in the previous chapter. As a set of constrains, hyperconfigurational temperatures are used to determine free parameters in an unknown potential. Other applications and thermodynamic considerations are discussed. The complicate electrohydrodynamic interplay of microions' fluxes and macroions in an electric field can induce many instabilities. A zoo of self-organized colloidal patterns are discovered in electrolysis of a horizontal layer of aqueous colloid. At low voltage, spheres cooperatively form various quasi-stationary microscopic clusters. At higher bias, spheres passively trace the electroconvection which is more nonlinear than its thermal analogy, the Raleigh-Benard convection. Explaining these patterns provides new challenge in pattern formation, electrokinetic of colloid and electrochemistry.
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
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.
Electron Confinement in Cylindrical Potential Well
NASA Astrophysics Data System (ADS)
Baltenkov, A. S.; Msezane, A. Z.
2016-05-01
We show that studying the solutions of the wave equation for an electron confined in a cylindrical potential well offers the possibility to analyze the confinement behavior of an electron executing one- or two-dimensional motion in the remaining three-dimensional space within the framework of the same mathematical model of the potential well. Some low-lying electronic states with different symmetries are considered and the corresponding wave functions are calculated. The behavior of their nodes and their peak positions with respect to the parameters of the cylindrical well is analyzed. Additionally, the momentum distributions of electrons in these states are calculated. The limiting cases of the ratio of the cylinder length H to its radius R0 are considered; when H significantly exceeds R0 and when R0 is much greater than H. The possible application of the results obtained here for the description of the general features in the behavior of electrons in nanowires with metallic type of conductivity (or nanotubes) and ultrathin epitaxial films (or graphene sheets) are discussed. Possible experiments are suggested as well where the quantum confinement can be manifested. Work supported by the Uzbek Foundation (ASB) and by the U.S. DOE, Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, Office of Energy Research (AZM).
Self-Diffusiophoresis of Janus Catalytic Micromotors in Confined Geometries.
Yang, Fengchang; Qian, Shizhi; Zhao, Yiping; Qiao, Rui
2016-06-01
The self-diffusiophoresis of Janus catalytic micromotors (JCMs) in confined environment is studied using direct numerical simulations. The simulations revealed that, on average, the translocation of a JCM through a short pore is moderately slowed down by the confinement. This slowdown is far weaker compared to the transport of particles through similar pores driven by forces induced by external means or passive diffusiophoresis. Pairing of two JCMs facilitates the translocation of the one JCM entering the pore first but slows down the second JCM. Depending on its initial orientation, a JCM near the entrance of a pore can exhibit different rotational motion, which determines whether it can enter the pore. Once a JCM enters a narrow pore, it can execute a self-alignment process after which it becomes fully aligned with the pore axis and moves to the center line of the pore. Analysis of these results showed that, in addition to hydrodynamic effect, the translation and rotation of JCM is also affected by the "chemical effects", i.e., the modification of the chemical species concentration around a JCM by confining walls and neighboring JCMs. These chemical effects are unique to the self-diffusiophoresis of JCMs and should be considered in design and operations of JCMs in confined environment. PMID:27186661
Polymer escape from a confining potential
Mökkönen, Harri; Ikonen, Timo; Jónsson, Hannes; Ala-Nissila, Tapio
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
NASA Astrophysics Data System (ADS)
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.
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, ΔHm (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.
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.
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.
Podgornik, R.; Parsegian, V.A. )
1992-02-01
By definition, membrane or macromolecular assembly is an event of molecular confinement against the configurational entropy of a disordered state. Bilayer membranes under progressive confinement experience a continual damping of undulatory fluctuations, first interpreted as a steric force (Helfrich. Z. Naturforsch. 1978). This paper uses a new, diffusion-equation formalism based on the Feynman-type variational principle to describe how direct interbilayer forces - of hydration, electrostatic double layers, and van der Waals attraction - confine membrane fluctuations. We recover theoretical results to examine measured forces in multilamellar arrays showing that [open quotes]soft[close quotes] collisions, through long-range forces, create a mutual enhancement of both the direct forces and the undulatory steric interactions. Thus, there is yet another way to resolve the old, but false, dilemma to choose between steric and direct forces driving membrane assembly. One may develop a systematic connection between bilayer charge, hydration, and flexibility and the action of configurational entropic forces. The results make clear that one should measure forces between membranes or macromolecules in a way that allows them to express their native mechanical freedom. 15 refs., 3 figs.
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.
Comparison of shear flow of hexadecane in a confined geometry and in bulk
Stevens, M.J.; Mondello, M.; Grest, G.S.; Cui, S.T.; Cochran, H.D.; Cummings, P.T.
1997-05-01
We examine the shear flow of hexadecane confined between plates with separation of 1{endash}10 nm using molecular dynamics simulations. We also performed non-equilibrium molecular dynamics (NEMD) simulations of bulk hexadecane to compare with the simulations in the confined geometry. The stiffness of hexadecane and its high melting temperature result in a tendency to crystallize at room temperature or large load. We find that when confined between hydrocarbon walls, shearing hexadecane exhibits a velocity profile with substantial slip at the wall and essentially constant velocity over most of the interior space between the walls. As the strength of the wall-fluid interaction increases the amount of slip decreases, but slip always occurs at the boundary for the range of parameters studied. The results are compared with recent surface force apparatus experiments on hexadecane and with similar simulations of model bead-spring fluids. {copyright} {ital 1997 American Institute of Physics.}
A simple model of a vesicle drop in a confined geometry
NASA Astrophysics Data System (ADS)
Owczarek, A. L.; Prellberg, T.
2010-08-01
We present the exact solution of a two-dimensional directed walk model of a drop, or half-vesicle, confined between two walls, and attached to one wall. This model is also a generalization of a polymer model of steric stabilization recently investigated. We explore the competition between a sticky potential on the two walls and the effect of a pressure-like term in the system. We show that a negative pressure ensures the drop/polymer is unaffected by confinement when the walls are a macroscopic distance apart.
Kelvin-Helmhotz instability and Bénard-Von Karman vortex street in a confined geometry
NASA Astrophysics Data System (ADS)
Lebon, Luc; Boniface, Paul; Receveur, Mathieu; Limat, Laurent
2014-11-01
We have experimentally investigated the appearance of Kelvin-Helmhotz vortices in a confined geometry: in a closed rectangular tank a tape is pulled at high speed on the water surface. This induces a flow in the same direction as the tape, and by conservation a backward flow in the opposite direction. With an appropriate choose of the experiment parameters (water height, tape speed) the backward flow takes place on the sides of the tank: this creates a strong shear that can induces a Kelvin-Helmhotz instability on each side of the tank. As long as the tape width stays small enough compared to the tank width, we can observe the appearance of well organized vortex rows on each sides of the tank. In this case, the vortex rows are coupled like a Bénard-Von Karman vortex street, but without the classical forcing of a wake behind an obstacle. All our experiments are in agreement with a theoretical prediction by Rosenhead which extended the Bénard-Von Karman vortex street stability calculation to a confined geometry. Our work seems to be one of the first experimental verification of this 80 years old model.
Khirevich, Siarhei; Höltzel, Alexandra; Tallarek, Ulrich
2011-06-28
We study the time and length scales of hydrodynamic dispersion in confined monodisperse sphere packings as a function of the conduit geometry. By a modified Jodrey-Tory algorithm, we generated packings at a bed porosity (interstitial void fraction) of ε=0.40 in conduits with circular, rectangular, or semicircular cross section of area 100πd(p)(2) (where d(p) is the sphere diameter) and dimensions of about 20d(p) (cylinder diameter) by 6553.6d(p) (length), 25d(p) by 12.5d(p) (rectangle sides) by 8192d(p) or 14.1d(p) (radius of semicircle) by 8192d(p), respectively. The fluid-flow velocity field in the generated packings was calculated by the lattice Boltzmann method for Péclet numbers of up to 500, and convective-diffusive mass transport of 4×10(6) inert tracers was modelled with a random-walk particle-tracking technique. We present lateral porosity and velocity distributions for all packings and monitor the time evolution of longitudinal dispersion up to the asymptotic (long-time) limit. The characteristic length scales for asymptotic behaviour are explained from the symmetry of each conduit's velocity field. Finally, we quantify the influence of the confinement and of a specific conduit geometry on the velocity dependence of the asymptotic dispersion coefficients. PMID:21576163
NASA Astrophysics Data System (ADS)
Datta, Preeta; Efimenko, Kirill; Genzer, Jan
2014-03-01
Bulk free radical polymerization reactions lead to highly polydisperse polymers (polydispersity index, PDI >> 1.5). In the past, researchers have shown that polymerization in porous microreactors can lower polydispersity (PDI ~1.5-1.7) by promoting gelation. We employ free-radical thermal frontal polymerization reaction of acrylamide (AAm) in DMSO in highly confined reactors (height <1mm) to produce high molecular weight (~300 kDa) PAAm of relatively low PDI (~1.2). In frontal polymerization systems, a localized reaction zone propagates in space along the direction of heat transfer, sustained by the interplay of heat diffusion and Arrhenius reaction kinetics. The directional heat transfer assists in maintaining the uniformity of the front temperature. While convection improves thermal transport, it causes inhomogeneity in the propagating front in horizontal reactors. In highly confined systems, convection is heavily suppressed, as manifested by the ``flattening'' of the reaction front and the absence of ``fingering''. Gelation lowers termination rate and increases the life time of the active reaction centers. Elimination of convection in confined geometries coupled with directional heat transfer and gelation results in polymers with high molecular weights and low PDIs.
Sánchez-Arellano, Enrique; Olivares, Wilmer; Lozada-Cassou, Marcelo; Jiménez-Angeles, Felipe
2009-02-15
The electrokinetic properties (such as capillary conductance, electroviscosity, and the streaming potential) are obtained for a restricted primitive model electrolyte confined in a slitlike nanopore made up of two infinite parallel plates and in a cylindrical cavity of infinite extension. The hypernetted chain/mean spherical approximation (HNC/MSA) is used to obtain the equilibrium ionic concentration profiles inside the pores, which in turn are used to calculate the electrokinetic properties via linear hydrodynamic equations. Our results are compared with those obtained via the classical Poisson-Boltzmann (PB) theory. Important quantitative and qualitative effects, attributed to geometry and to the proper consideration of short-range correlations by HNC/MSA, are discussed. PMID:19062031
Random lasing in dye doped nematic liquid crystals: the role of confinement geometry
NASA Astrophysics Data System (ADS)
Strangi, G.; Ferjani, S.; Barna, V.; De Luca, A.; Versace, C.; Scaramuzza, N.; Bartolino, R.
2007-05-01
The first experimental evidence of random laser action in a partially ordered, dye doped nematic liquid crystal with long-range dielectric tensor fluctuations is reported. Above a given pump power the fluorescence curve collapses and discrete sharp peaks emerge above the residual spontaneous emission spectrum. The spectral linewidth of these emission peaks is narrow banded, typically around 0.5nm. The unexpected surviving of interference effects in recurrent multiple scattering of the emitted photons provide the required optical feedback for lasing in nematic liquid crystalline materials. Light waves coherent backscattering in orientationally ordered nematics manifests a weak localization, strongly supporting the diffusive laser action phenomenon in the presence of a gain medium. Unlike distributed feedback mirror-less laser, this system can be considered as a cavity-less microlaser where the disorder unexpectedly plays the most important role, behaving as randomly distributed feedback laser. The far field spatial distribution of the emission intensity shows a huge number of bright tiny spots spatially overlapped and the intensity of each pulse strongly fluctuates in time and space. Here, we report the main characteristics of this novel systems for various confinement geometries and under different conditions. A brief presentation of boundary-less systems such as free standing and freely suspended dye doped nematic films and droplets is also introduced, revealing unique emission features because of the complete absence of confining borders.
Advancing Edge Speeds of Epithelial Monolayers Depend on Their Initial Confining Geometry.
Kollimada, Somanna A; Kulkarni, Ankur H; Ravan, Aniket; Gundiah, Namrata
2016-01-01
Collective cell migrations are essential in several physiological processes and are driven by both chemical and mechanical cues. The roles of substrate stiffness and confinement on collective migrations have been investigated in recent years, however few studies have addressed how geometric shapes influence collective cell migrations. Here, we address the hypothesis that the relative position of a cell within the confinement influences its motility. Monolayers of two types of epithelial cells--MCF7, a breast epithelial cancer cell line, and MDCK, a control epithelial cell line--were confined within circular, square, and cross-shaped stencils and their migration velocities were quantified upon release of the constraint using particle image velocimetry. The choice of stencil geometry allowed us to investigate individual cell motility within convex, straight and concave boundaries. Cells located in sharp, convex boundaries migrated at slower rates than those in concave or straight edges in both cell types. The overall cluster migration occurred in three phases: an initial linear increase with time, followed by a plateau region and a subsequent decrease in cluster speeds. An acto-myosin contractile ring, present in the MDCK but absent in MCF7 monolayer, was a prominent feature in the emergence of leader cells from the MDCK clusters which occurred every ~125 μm from the vertex of the cross. Further, coordinated cell movements displayed vorticity patterns in MDCK which were absent in MCF7 clusters. We also used cytoskeletal inhibitors to show the importance of acto-myosin bounding cables in collective migrations through translation of local movements to create long range coordinated movements and the creation of leader cells within ensembles. To our knowledge, this is the first demonstration of how bounding shapes influence long-term migratory behaviours of epithelial cell monolayers. These results are important for tissue engineering and may also enhance our
Advancing Edge Speeds of Epithelial Monolayers Depend on Their Initial Confining Geometry
Kollimada, Somanna A.; Kulkarni, Ankur H.; Ravan, Aniket; Gundiah, Namrata
2016-01-01
Collective cell migrations are essential in several physiological processes and are driven by both chemical and mechanical cues. The roles of substrate stiffness and confinement on collective migrations have been investigated in recent years, however few studies have addressed how geometric shapes influence collective cell migrations. Here, we address the hypothesis that the relative position of a cell within the confinement influences its motility. Monolayers of two types of epithelial cells—MCF7, a breast epithelial cancer cell line, and MDCK, a control epithelial cell line—were confined within circular, square, and cross-shaped stencils and their migration velocities were quantified upon release of the constraint using particle image velocimetry. The choice of stencil geometry allowed us to investigate individual cell motility within convex, straight and concave boundaries. Cells located in sharp, convex boundaries migrated at slower rates than those in concave or straight edges in both cell types. The overall cluster migration occurred in three phases: an initial linear increase with time, followed by a plateau region and a subsequent decrease in cluster speeds. An acto-myosin contractile ring, present in the MDCK but absent in MCF7 monolayer, was a prominent feature in the emergence of leader cells from the MDCK clusters which occurred every ~125 μm from the vertex of the cross. Further, coordinated cell movements displayed vorticity patterns in MDCK which were absent in MCF7 clusters. We also used cytoskeletal inhibitors to show the importance of acto-myosin bounding cables in collective migrations through translation of local movements to create long range coordinated movements and the creation of leader cells within ensembles. To our knowledge, this is the first demonstration of how bounding shapes influence long-term migratory behaviours of epithelial cell monolayers. These results are important for tissue engineering and may also enhance our
Rovibrational states of Wigner molecules in spherically symmetric confining potentials.
Cioslowski, Jerzy
2016-08-01
The strong-localization limit of three-dimensional Wigner molecules, in which repulsively interacting particles are confined by a weak spherically symmetric potential, is investigated. An explicit prescription for computation of rovibrational wavefunctions and energies that are asymptotically exact at this limit is presented. The prescription is valid for systems with arbitrary angularly-independent interparticle and confining potentials, including those involving Coulombic and screened (i.e., Yukawa/Debye) interactions. The necessary derivations are greatly simplified by explicit constructions of the Eckart frame and the parity-adapted primitive wavefunctions. The performance of the new formalism is illustrated with the three- and four-electron harmonium atoms at their strong-correlation limits. In particular, the involvement of vibrational modes with the E symmetry is readily pinpointed as the origin of the "anomalous" weak-confinement behavior of the (1)S+ state of the four-electron species that is absent in its (1)D+ companion of the strong-confinement regime. PMID:27497548
Rovibrational states of Wigner molecules in spherically symmetric confining potentials
NASA Astrophysics Data System (ADS)
Cioslowski, Jerzy
2016-08-01
The strong-localization limit of three-dimensional Wigner molecules, in which repulsively interacting particles are confined by a weak spherically symmetric potential, is investigated. An explicit prescription for computation of rovibrational wavefunctions and energies that are asymptotically exact at this limit is presented. The prescription is valid for systems with arbitrary angularly-independent interparticle and confining potentials, including those involving Coulombic and screened (i.e., Yukawa/Debye) interactions. The necessary derivations are greatly simplified by explicit constructions of the Eckart frame and the parity-adapted primitive wavefunctions. The performance of the new formalism is illustrated with the three- and four-electron harmonium atoms at their strong-correlation limits. In particular, the involvement of vibrational modes with the E symmetry is readily pinpointed as the origin of the "anomalous" weak-confinement behavior of the 1S+ state of the four-electron species that is absent in its 1D+ companion of the strong-confinement regime.
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.
Confining Potential from Interacting Magnetic and Torsion Fields
NASA Astrophysics Data System (ADS)
Gaete, Patricio; Helaÿel-Neto, José A.
Adopting the gauge-invariant but path-dependent variables formalism, we study the coupling of torsion fields with photons in the presence of an external background electromagnetic. We explicitly show that, in the case of a constant electric field strength expectation value, the static potential remains Coulombic, while in the case of a constant magnetic field strength expectation value a confining potential is obtained. This result displays a marked qualitative departure from the usual coupling of axionlike particles with photons in the presence of an external magnetic field.
NASA Astrophysics Data System (ADS)
Saito, Fumikazu; Kishimura, Hiroaki; Suzuki, Takanori
2013-06-01
In order to characterize dynamic fracture of borosilicate glass, we performed laser-shock-experiments of both an aluminum-ablator mounted glass and a glass with plasma confinement geometry in pure water by Q-switched Nd3+:YAG laser. The incident beam with 440 mJ were focused onto the target approximately 300 μm in diameter. The dynamic fracture of the glass targets is observed with high-speed digital framing-camera photography. For the aluminum-ablator mounted glass, propagation of the shock wave in water was observed, and the shock-wave velocity is obtained to be 1.65 +/- 0.02 km/s using image processing. Shock-pressure applied the target is estimated to be 180 MPa by Hugoniot relation. For the glass with plasma confinement geometry, generation of the micro-fragments from the rear side of the target was observed. This result indicates that shock-induced fragmentation by laser irradiation is enhanced by the plasma confinement effect. The soft-recovered fragments are separated according the size with PET mesh having deferent mesh size. As a result, the glass with plasma confinement geometry generated smaller fragment than the aluminum-ablator mounted glass.
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…
Heavy quarks, gluons and the confinement potential in Coulomb gauge
NASA Astrophysics Data System (ADS)
Popovici, Carina; Watson, Peter; Reinhardt, Hugo
2011-05-01
We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.
Heavy quarks, gluons and the confinement potential in Coulomb gauge
Popovici, Carina; Watson, Peter; Reinhardt, Hugo
2011-05-23
We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.
Influence of pore size on the Knight shift in liquid tin and mercury in a confined geometry
NASA Astrophysics Data System (ADS)
Tien, Cheng; Charnaya, E. V.; Lee, M. K.; Kumzerov, Yu A.
2007-03-01
119Sn and 199Hg NMR studies were carried out for metallic tin and mercury embedded in synthetic opals and porous glasses. The Knight shift for confined liquid tin and mercury was found to decrease monotonically with decreasing pore size, evidence for the reduction of electron susceptibility. Size-induced alterations in the Knight shift were more pronounced for confined mercury than for tin. The influence of pore filling on the NMR line shape and Knight shift was observed for tin within opal. The reasons for the decreasing Knight shift for liquid metals in a confined geometry are discussed. Correlations between the alteration in the Knight shift and atomic number are shown, the changes in fractional values of the Knight shift remaining almost identical.
States of the Dirac Equation in Confining Potentials
Giachetti, Riccardo; Sorace, Emanuele
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.
Spectral singularity in confined PT symmetric optical potential
Sinha, Anjana; Roychoudhury, R.
2013-11-15
We present an analytical study for the scattering amplitudes (Reflection ‖R‖ and Transmission ‖T‖), of the periodic PT symmetric optical potential V(x)=W{sub 0}cos{sup 2}x+iV{sub 0}sin2x confined within the region 0 ⩽x⩽L, embedded in a homogeneous medium having uniform potential W{sub 0}. The confining length L is considered to be some integral multiple of the period π. We give some new and interesting results. Scattering is observed to be normal (‖T‖{sup 2}⩽ 1, ‖R‖{sup 2}⩽ 1) for V{sub 0}⩽ 0.5, when the above potential can be mapped to a Hermitian potential by a similarity transformation. Beyond this point (V{sub 0} > 0.5) scattering is found to be anomalous (‖T‖{sup 2}, ‖R‖{sup 2} not necessarily ⩽1). Additionally, in this parameter regime of V{sub 0}, one observes infinite number of spectral singularities E{sub SS} at different values of V{sub 0}. Furthermore, for L= 2nπ, the transition point V{sub 0}= 0.5 shows unidirectional invisibility with zero reflection when the beam is incident from the absorptive side (Im[V(x)] < 0) but with finite reflection when the beam is incident from the emissive side (Im[V(x)] > 0), transmission being identically unity in both cases. Finally, the scattering coefficients ‖R‖{sup 2} and ‖T‖{sup 2} always obey the generalized unitarity relation : ‖T|{sup 2}−1|=√(|R{sub R}|{sup 2}|R{sub L}|{sup 2}), where subscripts R and L stand for right and left incidence, respectively.
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.
NASA Technical Reports Server (NTRS)
Richardson, R. W.
1974-01-01
Spectroscopic measurements were carried out on the NASA Lewis Bumpy Torus experiment in which a steady state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. Electron temperatures in pure helium are measured from the ratio of spectral line intensities. Measured electron temperatures range from 10 to 100 eV. Relative electron densities are also measured over the range of operating conditions. Radial profiles of temperature and relative density are measured in the two basic modes of operation of the device called the low and high pressure modes. The electron temperatures are used to estimate particle confinement times based on a steady state particle balance.
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 μm) 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.
An x-ray setup to investigate the atomic order of confined liquids in slit geometry
Lippmann, M.; Ehnes, A.; Seeck, O. H.
2014-01-15
A setup has been designed to investigate thin films of confined liquids with the use of X-ray scattering methods. The confinement is realized between the flat culets of a pair of diamonds by positioning and orienting the lower diamond with nanometer and micro radian accuracy. We routinely achieve gaps between 5 and 50 nm at culet diameters of 200 μm. With this setup and a micro focused X-ray beam we have investigated the in-plane and the out-off-plane atomic order of benzene with atomic resolution.
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 τ = 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
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
Correlation studies in weakly confining quantum dot potentials
NASA Astrophysics Data System (ADS)
Kimani, Peter; Jones, Preston; Winkler, Peter
We investigate the electron correlation in few-electron closed-shell atomic systems and similarly in few-electron quantum dots under weak confinement. As usual we start with restricted Hartree-Fock (HF) calculations and add electron correlation in steps in a series of approximations based on the single particle Green's function approach: (i) second-order Green function (GF); (ii) 2ph-Tamm-Dancoff approximation (TDA); and (iii) an extended version thereof which introduces ground-state correlation into the TDA. Our studies exhibit similarities and differences between weakly confined quantum dots and standard atomic systems. The calculations support the application of HF, GF, and TDA techniques in the modeling of three-dimensional quantum dot systems. The observed differences emphasize the significance of confinement and electronic features unique to quantum dots, such as the increased binding of electrons with higher angular momentum and thus - compared to atomic systems - modified shell-filling sequences.
Rigas, Fotis; Sklavounos, Spyros
2005-05-20
Accidental blast wave generation and propagation in the surroundings poses severe threats for people and property. The prediction of overpressure maxima and its change with time at specified distances can lead to useful conclusions in quantitative risk analysis applications. In this paper, the use of a computational fluid dynamics (CFD) code CFX-5.6 on dense explosive detonation events is described. The work deals with the three-dimensional simulation of overpressure wave propagation generated by the detonation of a dense explosive within a small-scale branched tunnel. It also aids at validating the code against published experimental data as well as to study the way that the resulting shock wave propagates in a confined space configuration. Predicted overpressure histories were plotted and compared versus experimental measurements showing a reasonably good agreement. Overpressure maxima and corresponding times were found close to the measured ones confirming that CFDs may constitute a useful tool in explosion hazard assessment procedures. Moreover, it was found that blast wave propagates preserving supersonic speed along the tunnel accompanied by high overpressure levels, and indicating that space confinement favors the formation and maintenance of a shock rather than a weak pressure wave. PMID:15885402
Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry
Wang, Siyuan; Jain, Chhavi; Wondraczek, Katrin; Kobelke, Jens; Wondraczek, Lothar; Troles, Johann; Caillaud, Celine; Schmidt, Markus A.
2015-05-18
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.
Ghobadi, Ahmadreza F.; Elliott, J. Richard
2014-09-07
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-γ WCA, is able to reproduce the specific orientation of hydrophilic head and hydrophobic tail of 1-alkanols at the vapor-liquid interface of water.
NASA Astrophysics Data System (ADS)
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-γ WCA, is able to reproduce the specific orientation of hydrophilic head and hydrophobic tail of 1-alkanols at the vapor-liquid interface of water.
Hydrodynamic interactions in colloidal systems confined to linear geometries with a singular corner
NASA Astrophysics Data System (ADS)
Lin, Binhua; Zarcone, Ryan; Rice, Stuart A.
Here we investigate the question of whether or not the requirement that particles diffuse around a corner affects their hydrodynamic coupling. We report the results of studies of the collective diffusion coefficients of particles in quasi-one-dimensional linear channels of widths 3 and 5um, each with a singular central corner of angle: 60-, 90-, 120-, and 180-degrees. We find that for large angles, the channels are so close in their geometry to 180-degrees that the corner has very little to no effect on the hydrodynamic coupling of particles on opposite sides of the apex. For small angles, the corner's effect is to increase the particle separation at which the maximum hydrodynamic coupling occurs. U Chicago MRSEC (NSF-DMR-1420709), Dreyfus Foundation (Agency Award #: SI-14-014).
Not Available
1993-12-31
The authors have been constructing a special purpose small angle neutron scattering spectrometer (SAND) in collaboration with IPNS of Argonne National Laboratory and Texaco Research Laboratories in Beacon, New York. The spectrometer, having a moderate neutron flux, will be uniquely suited for detailed studies of complex fluids in their various phases. This spectrometer will be fully available to general users of the small angle scattering community after a year of testing and upon installation of the auxiliary equipment. The general research objective of the MIT group is to continue studies of the microstructural relationship to phase-behavior in three-component microemulsion systems. Specifically, they shall study the (1) variation of bulk structures when a microemulsion undergoes a non-wetting to wetting transition, (2) correlating interfacial reflectivity measurements of these wetting transitions to the SANS results, (3) use the contrast variation technique they recently developed for measuring the mean and Gaussian curvatures of the surfactant sheet to study the structural inversion of water-in-oil to oil-in-water microemulsions and the transition of disordered bicontinuous microemulsion to ordered lamellar phases, (4) investigation of the effects of spatial confinement on the phase behavior and structure of bicontinuous microemulsions, and finally (5) they shall continue the study of the recently discovered non-exponential relaxation of droplet density fluctuations near the critical and percolation points in water-in-oil droplet microemulsions.
NASA Astrophysics Data System (ADS)
Anthistle, T.; Fletcher, D. I.; Tyas, A.
2016-03-01
Explosions in confined spaces lead to complicated patterns of shock wave reflection and interactions which are best investigated by use of experimental tests or numerical simulations. This paper describes the design and outcome of a series of experiments using a test cell to measure the pressures experienced when structures were placed inside to alter the propagation of shock waves, utilising quarter symmetry to reduce the size of the required test cell and charge. An 80 g charge of PE4 (a conventional RDX-based plastic explosive) was placed at half height in one corner of the test cell, which represents the centre of a rectangular enclosure when symmetry is taken into consideration. Steel cylinders and rectangular baffles were placed within the test cell at various locations. Good reproducibility was found between repeated tests in three different arrangements, in terms of both the recorded pressure data and the calculated cumulative impulse. The presence of baffles within the test cell made a small difference to the pressures and cumulative impulse experienced compared to tests with no baffles present; however, the number and spacing of baffles was seen to make minimal difference to the experienced pressures and no noticeable difference to the cumulative impulse history. The paper presents useful experimental data that may be used for three-dimensional code validation.
NASA Astrophysics Data System (ADS)
Gupta, A.; Sbragaglia, M.; Scagliarini, A.
2015-06-01
We propose numerical simulations of viscoelastic fluids based on a hybrid algorithm combining Lattice-Boltzmann models (LBM) and Finite Differences (FD) schemes, the former used to model the macroscopic hydrodynamic equations, and the latter used to model the polymer dynamics. The kinetics of the polymers is introduced using constitutive equations for viscoelastic fluids with finitely extensible non-linear elastic dumbbells with Peterlin's closure (FENE-P). The numerical model is first benchmarked by characterizing the rheological behavior of dilute homogeneous solutions in various configurations, including steady shear, elongational flows, transient shear and oscillatory flows. As an upgrade of complexity, we study the model in presence of non-ideal multicomponent interfaces, where immiscibility is introduced in the LBM description using the "Shan-Chen" interaction model. The problem of a confined viscoelastic (Newtonian) droplet in a Newtonian (viscoelastic) matrix under simple shear is investigated and numerical results are compared with the predictions of various theoretical models. The proposed numerical simulations explore problems where the capabilities of LBM were never quantified before.
On the generation of nonlinear travelling waves in confined geometries using electric fields.
Cimpeanu, R; Papageorgiou, D T
2014-07-28
We investigate electrostatically induced interfacial instabilities and subsequent generation of nonlinear coherent structures in immiscible, viscous, dielectric multi-layer stratified flows confined in small-scale channels. Vertical electric fields are imposed across the channel to produce interfacial instabilities that would normally be absent in such flows. In situations when the imposed vertical fields are constant, interfacial instabilities emerge due to the presence of electrostatic forces, and we follow the nonlinear dynamics via direct numerical simulations. We also propose and illustrate a novel pumping mechanism in microfluidic devices that does not use moving parts. This is achieved by first inducing interfacial instabilities using constant background electric fields to obtain fully nonlinear deformations. The second step involves the manipulation of the imposed voltage on the lower electrode (channel wall) to produce a spatio-temporally varying voltage there, in the form of a travelling wave with pre-determined properties. Such travelling wave dielectrophoresis methods are shown to generate intricate fluid-surface-structure interactions that can be of practical value since they produce net mass flux along the channel and thus are candidates for microfluidic pumps without moving parts. We show via extensive direct numerical simulations that this pumping phenomenon is a result of an externally induced nonlinear travelling wave that forms at the fluid-fluid interface and study the characteristics of the generated velocity field inside the channel. PMID:24936019
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
Banc, Amélie; Desbat, Bernard; Renard, Denis; Popineau, Yves; Mangavel, Cécile; Navailles, Laurence
2009-08-01
Mechanisms leading to the assembly of wheat storage proteins into proteins bodies within the endoplasmic reticulum (ER) of endosperm cells are unresolved today. In this work, physical chemistry parameters which could be involved in these processes were explored. To model the confined environment of proteins within the ER, the dynamic behavior of gamma-gliadins inserted inside lyotropic lamellar phases was studied using FRAP experiments. The evolution of the diffusion coefficient as a function of the lamellar periodicity enabled to propose the hypothesis of an interaction between gamma-gliadins and membranes. This interaction was further studied with the help of phospholipid Langmuir monolayers. gamma- and omega-gliadins were injected under DMPC and DMPG monolayers and the two-dimensional (2D) systems were studied by Brewster angle microscopy (BAM), polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and surface tension measurements. Results showed that both gliadins adsorbed under phospholipid monolayers, considered as biological membrane models, and formed micrometer-sized domains at equilibrium. However, their thicknesses, probed by reflectance measurements, were different: omega-gliadins aggregates displayed a constant thickness, consistent with a monolayer, while the thickness of gamma-gliadins aggregates increased with the quantity of protein injected. These different behaviors could find some explanations in the difference of aminoacid sequence distribution: an alternate repeated - unrepeated domain within gamma-gliadin sequence, while one unique repeated domain was present within omega-gliadin sequence. All these findings enabled to propose a model of gliadins self-assembly via a membrane interface and to highlight the predominant role of wheat prolamin repeated domain in the membrane interaction. In the biological context, these results would mean that the repeated domain could be considered as an anchor for the interaction with
Confined quantum time of arrival for the vanishing potential
Galapon, Eric A.; Caballar, Roland F.; Bahague, Ricardo
2005-12-15
We give full account of our recent report in E. A. Galapon, R. Caballar, and R. Bahague, Phys. Rev. Lett. 93, 180406 (2004), where it is shown that formulating the free quantum time of arrival problem in a segment of the real line suggests rephrasing the quantum time of arrival problem to finding a complete set of states that evolve to unitarily arrive at a given point at a definite time. For a spatially confined particle, here it is shown explicitly that the problem admits a solution in the form of an eigenvalue problem of a class of compact and self-adjoint time of arrival operators derived by a quantization of the classical time of arrival. The eigenfunctions of these operators are numerically demonstrated to unitarily arrive at the origin at their respective eigenvalues.
Structure and rheology of star polymers in confined geometries: a mesoscopic simulation study.
Zheng, Feiwo; Goujon, Florent; Mendonça, Ana C F; Malfreyt, Patrice; Tildesley, Dominic J
2015-11-28
Mesoscopic simulations of star polymer melts adsorbed onto solid surfaces are performed using the dissipative particle dynamics (DPD) method. A set of parameters is developed to study the low functionality star polymers under shear. The use of a new bond-angle potential between the arms of the star creates more rigid chains and discriminates between different functionalities at equilibrium, but still allows the polymers to deform appropriately under shear. The rheology of the polymer melts is studied by calculating the kinetic friction and viscosity and there is good agreement with experimental properties of these systems. The study is completed with predictive simulations of star polymer solutions in an athermal solvent. PMID:26435466
Edge-mediated skyrmion chain and its collective dynamics in a confined geometry
NASA Astrophysics Data System (ADS)
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
2015-10-01
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.
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 confining wall potential on charged collimated dust beam in low-pressure plasma
Kausik, S. S.; Kakati, B.; Saikia, B. K.
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.
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.
Rotating Bose-Einstein condensates confined in an anharmonic potential
NASA Astrophysics Data System (ADS)
Bargi, S.; Kavoulakis, G. M.; Reimann, S. M.
2006-03-01
We consider bosonic atoms that rotate in an anharmonic trapping potential. Using numerical diagonalization of the Hamiltonian, we get evidence for various phases of the gas for different values of the coupling between the atoms and of the rotational frequency of the trap. These include vortex excitation of single and multiple quantization, the phase of center-of-mass excitation, and the unstable phase.
Universal potential-barrier penetration by initially confined wave packets
Granot, Er'el; Marchewka, Avi
2007-07-15
The dynamics of an initially sharp-boundary wave packet in the presence of an arbitrary potential barrier is investigated. It is shown that the penetration through the barrier is universal in the sense that it depends only on the values of the wave function and its derivatives at the boundary. The dependence on the derivatives vanishes at long distances from the barrier, where the dynamics is governed solely by the initial value of the wave function at the boundary.
Interacting Bose gas confined in a Kronig-Penney potential
NASA Astrophysics Data System (ADS)
Rodríguez, O. A.; Solís, M. A.
We analyze the effect of the 1D periodic Kronig-Penney potential, composed of barriers of width b and separated a distance a, over an interacting Bose gas. At T = 0 , the Gross-Pitaevskii equation is solved analytically in terms of the Jacobi elliptic functions for repulsive or attractive interaction between bosons. By applying the boundary conditions for periodic solutions as well as the normalization of the wave function, we arrive to a set of nonlinear equations from which we obtain the density profile and the chemical potential of the condensate as a function of the particle momentum. The profiles for attractive and repulsive interactions are compared with that of the non-interacting case. For attractive interaction we are able to observe a pronounced spatial localization in the middle of every two barriers. We reproduce the well known results when the Kronig-Penney potential becomes a Dirac Comb. We acknowledge partial support from Grants PAPIIT IN111613 and CONACyT 221030.
Ligand-Mediated Control of the Confinement Potential in Semiconductor Quantum Dots
NASA Astrophysics Data System (ADS)
Amin, Victor
This thesis describes the mechanisms by which organic surfactants, particularly thiophenols and phenyldithiocarbamates, reduce the confinement potential experienced by the exciton of semiconductor quantum dots (QDs). The reduction of the confinement potential is enabled by the creation of interfacial electronic states near the band edge of the QD upon ligand adsorption. In the case of thiophenols, we find that this ligand adsorbs in two distinct binding modes, (i) a tightly bound mode capable of exciton delocalization, and (ii) a more weakly bound mode that has no discernable effect on exciton confinement. Both the adsorption constant and reduction in confinement potential are tunable by para substitution and are generally anticorrelated. For tightly bound thiophenols and other moderately delocalizing ligands, the degree of delocalization induced in the QD is approximately linearly proportional to the fractional surface area occupied by the ligand for all sizes of QDs. In the case of phenyldithiocarbamates, the reduction in the confinement potential is much greater, and ligand adjacency must be accounted for to model exciton delocalization. We find that at high surface coverages, exciton delocalization by phenyldithiocarbamates and other highly delocalizing ligands is dominated by ligand packing effects. Finally, we construct a database of electronic structure calculations on organic molecules and propose an algorithm that combines experimental and computational screening to find novel delocalizing ligands.
Quantum-Carnot engine for particle confined to cubic potential
Sutantyo, Trengginas Eka P. Belfaqih, Idrus H. Prayitno, T. B.
2015-09-30
Carnot cycle consists of isothermal and adiabatic processes which are reversible. Using analogy in quantum mechanics, these processes can be well explained by replacing variables in classical process with a quantum system. Quantum system which is shown in this paper is a particle that moves under the influence of a cubic potential which is restricted only to the state of the two energy levels. At the end, the efficiency of the system is shown as a function of the width ratio between the initial conditions and the farthest wall while expanding. Furthermore, the system efficiency will be considered 1D and 2D cases. The providing efficiencies are different due to the influence of the degeneration of energy and the degrees of freedom of the system.
On the calculation of the absolute grand potential of confined smectic-A phases
NASA Astrophysics Data System (ADS)
Huang, Chien-Cheng; Baus, Marc; Ryckaert, Jean-Paul
2015-09-01
We determine the absolute grand potential Λ along a confined smectic-A branch of a calamitic liquid crystal system enclosed in a slit pore of transverse area A and width L, using the rod-rod Gay-Berne potential and a rod-wall potential favouring perpendicular orientation at the walls. For a confined phase with an integer number of smectic layers sandwiched between the opposite walls, we obtain the excess properties (excess grand potential Λexc, solvation force fs and adsorption Γ) with respect to the bulk phase at the same μ (chemical potential) and T (temperature) state point. While usual thermodynamic integration methods are used along the confined smectic branch to estimate the grand potential difference as μ is varied at fixed L, T, the absolute grand potential at one reference state point is obtained via the evaluation of the absolute Helmholtz free energy in the (N, L, A, T) canonical ensemble. It proceeds via a sequence of free energy difference estimations involving successively the cost of localising rods on layers and the switching on of a one-dimensional harmonic field to keep layers integrity coupled to the elimination of inter-layers and wall interactions. The absolute free energy of the resulting set of fully independent layers of interacting rods is finally estimated via the existing procedures. This work opens the way to the computer simulation study of phase transitions implying confined layered phases.
NASA Astrophysics Data System (ADS)
Choudhury, Kaushik; Singh, R. K.; Narayan, Surya; Srivastava, Atul; Kumar, Ajai
2016-04-01
An experimental investigation of the laser produced plasma induced shock wave in the presence of confining walls placed along the axial as well as the lateral direction has been performed. A time resolved Mach Zehnder interferometer is set up to track the primary as well as the reflected shock waves and its effect on the evolving plasma plume has been studied. An attempt has been made to discriminate the electronic and medium density contributions towards the changes in the refractive index of the medium. Two dimensional spatial distributions for both ambient medium density and plasma density (electron density) have been obtained by employing customised inversion technique and algorithm on the recorded interferograms. The observed density pattern of the surrounding medium in the presence of confining walls is correlated with the reflected shock wave propagation in the medium. Further, the shock wave plasma interaction and the subsequent changes in the shape and density of the plasma plume in confined geometry are briefly described.
NASA Astrophysics Data System (ADS)
Zhao, Xujun; Hernandez-Ortiz, Juan; Karpeyev, Dmitry; de Pablo, Juan; Smith, Barry
In this work, we present an efficient parallel particle-in-mesh method for Brownian Dynamics simulations of many-particle systems confined in micro- and nano-fluidic devices. A general geometry Ewald-like method (GGEM) combined with finite element method is used to account for the hydrodynamic interaction. A fast parallel Krylov-type iterative solver with hybrid preconditioning techniques is developed for solving the large sparse systems of equations arising from finite element discretization of the Stokes equations. In addition, the current computer code is developed based on PETSc, a scalable library of numerical algorithms developed at Argonne, SLEPc - Scalable Library for Eigenvalue Problem Computations, and libMesh, a finite element library for numerical solution of PDEs built on top of PETSc, which allows for direct simulation of large scale systems with arbitrary confined geometries. This scheme is applied to Brownian dynamics simulations of flowing confined polymer solutions and colloidal dispersions in micro-fluid channels. The effects of hydrodynamics interactions and geometric confinement on the migration phenomena are illustrated.
Electronic structure and electron correlation in weakly confining spherical quantum dot potentials
NASA Astrophysics Data System (ADS)
Kimani, Peter Borgia Ndungu
The electronic structure and electron correlations in weakly confining spherical quantum dots potentials are investigated. Following a common practice, the investigation starts with the restricted Hartree-Fock (HF) approximation. Then electron correlation is added in steps in a series of approximations based on the single particle Green's function approach: (i) Second-order Green function (GF) (ii) 2ph-Tamm-Dancoff approximation (TDA) and (iii) an extended version thereof (XTDA) which introduces ground-state correlation into the TDA. The study includes as well Hartree-Fock V (N-1) potential approximation in which framework the Hartree-Fock virtual orbitals are calculated in the field of the N-1 electrons as opposed to the regular but unphysical N-electron field Hartree-Fock calculation of virtual orbitals. For contrast and comparison, the same approximation techniques are applied to few-electron closed-shell atoms and few-electron negative ions for which pertinent data is readily available. The results for the weakly confining spherical quantum dot potentials and the standard atomic systems exhibit fundamental similarities as well as significant differences. For the most part the results of these calculations are in favor of application of HF, GF, and TDA techniques in the modeling of three-dimensional weakly confining quantum dot potentials. The observed differences emphasize the significance of confinement and electronic features unique to quantum dots such as the increased binding of electrons with higher angular momentum and the modified shell filling sequences.
Optical probing of MgZnO/ZnO heterointerface confinement potential energy levels
Solovyev, V. V.; Van'kov, A. B.; Kukushkin, I. V.; Falson, J.; Kozuka, Y.; Zhang, D.; Smet, J. H.; Maryenko, D.; Tsukazaki, A.; Kawasaki, M.
2015-02-23
Low-temperature photoluminescence and reflectance measurements were employed to study the optical transitions present in two-dimensional electron systems confined at Mg{sub x}Zn{sub 1–x}O/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 × 10{sup 11 }cm{sup −2}, the inter-subband splitting is measured and the first excited electron subband is shown to be empty of electrons.
Perfect Abelian dominance of confinement in quark-antiquark potential in SU(3) lattice QCD
NASA Astrophysics Data System (ADS)
Suganuma, Hideo; Sakumichi, Naoyuki
2016-01-01
In the context of the dual superconductor picture for the confinement mechanism, we study maximally Abelian (MA) projection of quark confinement in SU(3) quenched lattice QCD with 324 at β=6.4 (i.e., a ≃ 0.058 fm). We investigate the static quark-antiquark potential V(r), its Abelian part VAbel(r) and its off-diagonal part Voff(r), respectively, from the on-axis lattice data. As a remarkable fact, we find almost perfect Abelian dominance for quark confinement, i.e., σAbel ≃ σ for the string tension, on the fine and large-volume lattice. We find also a nontrivial summation relation of V (r) ≃ VAbel(r)+Voff(r).
Dielectric confinement influenced screened Coulomb potential for a semiconductor quantum wire
NASA Astrophysics Data System (ADS)
Aharonyan, K. H.; Margaryan, N. B.
2016-01-01
A formalism of the Thomas-Fermi method has been applied for studying the screening effect due to quasi-one-dimensional electron gas in a semiconductor cylindrical quantum wire embedded in the barrier environment. With taking into account of strongly low dielectric properties of the barrier material, an applicability of the quantum wire effective interaction potential of the confined charge carriers has been revealed. Both screened quasi- one-dimensional interaction potential and effective screening length analytical expressions are derived in the first time. It is shown that in the long wavelength moderate limit dielectric confinement effect enhances strength of the screening potential depending on the both radius of the wire and effective screening length, whereas in the long wavelength strong limit the screening potential solely is determined by barrier environment dielectric properties.
High-density plasma production with potential confinement in the GAMMA 10 tandem mirror
NASA Astrophysics Data System (ADS)
Ichimura, M.; Cho, T.; Hirata, M.; Hojo, H.; Ishii, K.; Itakura, A.; Katanuma, I.; Kohagura, J.; Nakashima, Y.; Saito, T.; Tamano, T.; Tanaka, S.; Tatematsu, Y.; Yatsu, K.; Yoshikawa, M.
2001-05-01
The improvement of potential confinement was attained in the GAMMA 10 tandem mirror [Phys. Rev. Lett. 55, 939 (1985); Proceedings of the 13th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Washington, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 2, p. 539] by axisymmetrization of heating systems for the plasma production, heating, and potential formation. A significant increase of the density and diamagnetism by the potential confinement was observed. In the previous experiment, it was difficult to increase the central cell density higher than 2.7×1018m-3. One of the possible mechanisms is the density clamping due to the eigenmode formation of the ion-cyclotron-range of frequency (ICRF) waves in the axial direction. With high harmonic ICRF waves (RF3), the experiments to overcome this problem have been performed. In preliminary experiments with RF3 and NBI the maximum density of 4×1018m-3 was attained.
Quantum-Carnot engine for particle confined to 2D symmetric potential well
Belfaqih, Idrus Husin Sutantyo, Trengginas Eka Putra Prayitno, T. B.; Sulaksono, Anto
2015-09-30
Carnot model of heat engine is the most efficient cycle consisting of isothermal and adiabatic processes which are reversible. Although ideal gas usually used as a working fluid in the Carnot engine, Bender used quantum particle confined in 1D potential well as a working fluid. In this paper, by following Bender we generalize the situation to 2D symmetric potential well. The efficiency is express as the ratio of the initial length of the system to the final length of the compressed system. The result then is shown that for the same ratio, 2D potential well is more efficient than 1D potential well.
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.
The photino sector and a confining potential in a supersymmetric Lorentz-symmetry-violating model
NASA Astrophysics Data System (ADS)
Belich, H.; Bernald, L. D.; Gaete, Patricio; Helayël-Neto, J. A.
2013-11-01
We study the spectrum of the minimal supersymmetric extension of the Carroll-Field-Jackiw model for Electrodynamics with a topological Chern-Simons-like Lorentz-symmetry violating term. We identify a number of independent background fermion condensates, work out the gaugino dispersion relation and propose a photonic effective action to consider aspects of confinement induced by the SUSY background fermion condensates, which also appear to signal Lorentz-symmetry violation in the photino sector of the action. Our calculations of the static potential are carried out within the framework of the gauge-invariant but path-dependent variables formalism which are alternative to the Wilson loop approach. Our results show that the interaction energy contains a linear term leading to the confinement of static probe charges.
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.
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.
Pathak, Amit; Kumar, Sanjay
2013-08-01
It is now well established that tumor cell invasion through tissue is strongly regulated by the microstructural and mechanical properties of the extracellular matrix (ECM). However, it remains unclear how these physical microenvironmental inputs are jointly processed with oncogenic lesions to drive invasion. In this study, we address this open question by combining a microfabricated polyacrylamide channel (μPAC) platform that enables independent control of ECM stiffness and confinement with an isogenically-matched breast tumor progression series in which the oncogenes ErbB2 and 14-3-3ζ are overexpressed independently or in tandem. We find that increasing channel confinement and overexpressing ErbB2 both promote cell migration to a similar degree when other parameters are kept constant. In contrast, 14-3-3ζ overexpression slows migration speed, and does so in a fashion that dwarfs effects of ECM confinement and stiffness. We also find that ECM stiffness dramatically enhances cell motility when combined with ErbB2 overexpression, demonstrating that biophysical cues and cell-intrinsic parameters promote cell invasion in an integrative manner. Morphometric analysis of cells inside the μPAC platform reveals that the rapid cell migration induced by narrow channels and ErbB2 overexpression are both accompanied by increased cell polarization. Disruption of this polarization occurs by pharmacological inhibition of Rac GTPase phenocopies 14-3-3ζ overexpression by reducing cell polarization and slowing migration. By systematically measuring migration speed as a function of matrix stiffness and confinement, we also quantify for the first time the sensitivity of migration speed to microchannel properties and transforming potential. These results demonstrate that oncogenic lesions and ECM biophysical properties can synergistically interact to drive invasive migration, and that both inputs may act through common molecular mechanisms to enhance migration speed. PMID:23832051
Impurity with two electrons in the spherical quantum dot with Unite confinement potential
NASA Astrophysics Data System (ADS)
Baghdasaryan, D. A.; Ghaltaghchyan, H. Ts; Kazaryan, E. M.; Sarkisyan, H. A.
2016-01-01
Two-electron states in a spherical QD with the hydrogenic impurity located in the center and with a finite height confinement potential barrier are investigated. The effective mass mismatch have been taken into account. The dependence of ground state energy and Coulomb electron-electron interaction energy correction on the QD size is studied. The problem of the state exchange time control in QD is discussed, taking into account the spins of the electrons in the Russell-Saunders approximation. The effect of quantum emission has been shown.
Quantum dynamics of a hydrogen molecule confined in a cylindrical potential
NASA Astrophysics Data System (ADS)
Yildirim, Taner; Harris, A. B.
2003-06-01
We study the coupled rotation-vibration levels of a hydrogen molecule in a confining potential with cylindrical symmetry. We include the coupling between rotations and translations and show how this interaction is essential to obtain the correct degeneracies of the energy level scheme. We applied our formalism to study the dynamics of H2 molecules inside a “smooth” carbon nanotube as a function of tube radius. The results are obtained both by numerical solution of the (2J+1)-component radial Schrödinger equation and by developing an effective Hamiltonian to describe the splitting of a manifold of states of fixed angular momentum J and number of phonons N. For nanotube radius smaller than ≈3.5 Å, the confining potential has a parabolic shape and the results can be understood in terms of a simple toy model. For larger radius, the potential has the “Mexican hat” shape and therefore the H2 molecule is off centered, yielding radial and tangential translational dynamics in addition to rotational dynamics of H2 molecule which we also describe by a simple model. Finally, we make several predictions for the the neutron scattering observation of various transitions between these levels.
On PT-Symmetric Periodic Potential, Quark Confinement, and Other Impossible Pursuits
NASA Astrophysics Data System (ADS)
Christianto, V.; Smarandache, Florentin
2009-04-01
As we know, it has been quite common nowadays for particle physicists to think of six impossible things before breakfast, just like what their cosmology fellows used to do. In the present paper, we discuss a number of those impossible things, including PT-symmetric periodic potential, its link with condensed matter nuclear science, and possible neat link with Quark confinement theory. In recent years, the PT-symmetry and its related periodic potential have gained considerable interests among physicists. We begin with a review of some results from a preceding paper discussing derivation of PT-symmetric periodic potential from biquaternion Klein-Gordon equation and proceed further with the remaining issues. Further observation is of course recommended in order to refute or verify this proposition.
Importance of the energy-dependent geometry in the 16O+ 16O optical model potential
NASA Astrophysics Data System (ADS)
Pantis, G.; Ioannidis, K.; Poirier, P.
1985-08-01
Optical model potentials with various forms of energy-dependent geometry have been considered for the description of 16O+ 16O elastic scattering. It is shown that the variation with energy of the imaginary radius leads to a reasonable fit of the cross-section data, throughout the energy range.
Wehmeyer, Christoph; Falk von Rudorff, Guido; Wolf, Sebastian; Kabbe, Gabriel; Schärf, Daniel; Kühne, Thomas D; Sebastiani, Daniel
2012-11-21
We present a stochastic, swarm intelligence-based optimization algorithm for the prediction of global minima on potential energy surfaces of molecular cluster structures. Our optimization approach is a modification of the artificial bee colony (ABC) algorithm which is inspired by the foraging behavior of honey bees. We apply our modified ABC algorithm to the problem of global geometry optimization of molecular cluster structures and show its performance for clusters with 2-57 particles and different interatomic interaction potentials. PMID:23181297
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.
Monte Carlo study of one-dimensional confined fluids with Gay-Berne intermolecular potential
NASA Astrophysics Data System (ADS)
Moradi, M.; Hashemi, S.
2011-11-01
The thermodynamic quantities of a one dimensional system of particles with Gay-Berne model potential confined between walls have been obtained by means of Monte Carlo computer simulations. For a number of temperatures, the systems were considered and their density profiles, order parameter, pressure, configurational temperature and average potential energy per particle are reported. The results show that by decreasing the temperature, the soft particles become more ordered and they align to the walls and also they don't show any tendency to be near the walls at very low temperatures. We have also changed the structure of the walls by embedding soft ellipses in them, this change increases the total density near the wall whereas, increasing or decreasing the order parameter depend on the angle of embedded ellipses.
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
Black hole accretion disks in brane gravity via a confining potential
NASA Astrophysics Data System (ADS)
Heydari-Fard, Malihe
2010-12-01
Accretion disks are among the most luminous and ubiquitous sources in astrophysics and they have drawn a good deal of attention from the observational and theoretical communities. In this paper, we study the process of matter forming thin accretion disks around black hole solutions in the context of the brane-world scenario where our universe is a three-brane embedded in an m-dimensional bulk and localization of matter on the brane is achieved by means of a confining potential. The physical properties of thin accretion disks including the time averaged energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and the results are compared with the DMPR, CFM and BMD brane black holes and the standard general relativistic Schwarzschild solution.
Tong, Lianming; Miljković, Vladimir D; Johansson, Peter; Käll, Mikael
2011-11-01
The understanding of interaction forces between nanoparticles in colloidal suspension is central to a wide range of novel applications and processes in science and industry. However, few methods are available for actual characterization of such forces at the single particle level. Here we demonstrate the first measurements of colloidal interactions between two individual diffusing nanoparticles using a colorimetric assay based on plasmon hybridization, that is, strong near-field coupling between localized surface plasmon resonances. The measurements are possible because individual gold nanoparticle pairs can be loosely confined in an optical potential well created by a laser tweezers. We quantify the degree of plasmon hybridization for a large number of individual particle pairs as a function of increasing salt concentration. The data reveal a considerable heterogeneity at the single particle level but the estimated average surface separations are in excellent agreements with predictions based on the classical theory of Derjaguin, Landau, Verwey, and Overbeek. PMID:21142200
NASA Astrophysics Data System (ADS)
Rodriguez, Ricardo; Lewis, Winston G.
2014-07-01
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.
Energy spectra of a particle confined in a finite ellipsoidal shaped potential well
NASA Astrophysics Data System (ADS)
Kereselidze, Tamaz; Tchelidze, Tamar; Nadareishvili, Teimuraz; Kezerashvili, Roman Ya.
2016-07-01
A charged particle confined in a strongly prolate ellipsoidal shaped finite potential well is studied. In the case when a distance R between foci is large and accordingly R-1 is small, the asymptotic solutions of quasiradial and quasiangular equations in prolate spheroidal coordinates are found. We demonstrate that quasiangular wave functions inside and outside of the potential well coincide on the entire surface of strongly prolate ellipsoid if separation parameters are chosen appropriately. This allows us to obtain the transcendental equation for the energy levels by equating the quasiradial wave function and its derivative on the surface of ellipsoid. The obtained equation is solved numerically and algebraically. The calculated energies are in good qualitative and quantitative agreement with the results obtained earlier for the infinitely high ellipsoidal potential well via a numerical solution of the quasiradial and quasiangular equations. An importance of the actual shape of ellipsoidal potential well for calculation of the energy spectrum for the trapped particle is shown. A dependence of the energy spectrum on the effective mass when it is a different constant inside and outside of the ellipsoid is addressed.
Geometry-induced potential on a two-dimensional section of a wormhole: Catenoid
Dandoloff, Rossen; Saxena, Avadh; Jensen, Bjoern
2010-01-15
We show that a two-dimensional wormhole geometry is equivalent to a catenoid, a minimal surface. We then obtain the curvature-induced geometric potential and show that the ground state with zero energy corresponds to a reflectionless potential. By introducing an appropriate coordinate system we also obtain bound states for different angular momentum channels. Our findings can be realized in suitably bent bilayer graphene sheets with a neck, in a honeycomb lattice with an array of dislocations, or in nanoscale waveguides in the shape of a catenoid.
Application of a full potential method for analysis of complex aircraft geometries
NASA Technical Reports Server (NTRS)
Jones, Kenneth M.; Talcott, Noel A., Jr.
1986-01-01
A supersonic potential flow solver was developed to analyze the flow over complex realistic aircraft geometries. Enhancements to the method were made to accommodate regions of subsonic flow, the effect of trailing wakes on other aircraft components, and the modeling/gridding of complete configurations. Validation of the method was demonstrated by comparisons with experimental aerodynamic force and surface pressure measurements. The predicted results are in very good agreement with the experimental data. The bibliography contains additional information on the use of the potential flow code to predict the aerodynamics of high-speed wing/body configurations, waverider concepts, TAV, and the Space Shuttle orbiter package.
The potential impact of flooding on confined animal feeding operations in eastern North Carolina.
Wing, Steve; Freedman, Stephanie; Band, Lawrence
2002-01-01
Thousands of confined animal feeding operations (CAFOs) have been constructed in eastern North Carolina. The fecal waste pit and spray field waste management systems used by these operations are susceptible to flooding in this low-lying region. To investigate the potential that flood events can lead to environmental dispersion of animal wastes containing numerous biologic and chemical hazards, we compared the geographic coordinates of 2,287 CAFOs permitted by the North Carolina Division of Water Quality (DWQ) with estimates of flooding derived from digital satellite images of eastern North Carolina taken approximately 1 week after Hurricane Floyd dropped as much as 15-20 inches of rain in September 1999. Three cattle, one poultry, and 237 swine operations had geographic coordinates within the satellite-based flooded area. DWQ confirmed 46 operations with breached or flooded fecal waste pits in the same area. Only 20 of these 46 CAFOs were within the satellite-based estimate of the inundated area. CAFOs within the satellite-based flood area were located in 132 census block groups with a population of 171,498 persons in the 2000 census. African Americans were more likely than whites to live in areas with flooded CAFOs according to satellite estimates, but not according to DWQ reports. These areas have high poverty rates and dependence on wells for drinking water. Our analysis suggests that flood events have a significant potential to degrade environmental health because of dispersion of wastes from industrial animal operations in areas with vulnerable populations. PMID:11940456
NASA Astrophysics Data System (ADS)
Borgoo, Alex; Tozer, David; Geerlings, Paul; de Proft, Frank
2009-03-01
When a molecule is placed as a guest inside a zeolite pore, its electronic structure will be altered, among others by the effect of the so-called ``confinement". It has been established that the compression of the molecular orbitals influences a system's reactivity. In this work we use a simple potential barrier method to quantify the importance of confinement effects on chemical reactivity. In the first part, excitation energies and molecular orbital energy gaps are evaluated for molecules placed in cavities of different sizes. Our results for ethylene and formaldehyde reveal an increase in excitation energy and the gap between the occupied and the unoccupied levels. In the case of the larger molecules naphthalene and anthracene, the HOMO-LUMO gap shows very little sensitivity to the confinement. To investigate the role of confinement effects on local aspects of chemical reactivity and on regioselectivity, we evaluated its effect on the Fukui function and the molecular electrostatic potential, reactivity indices that are central in the description of orbital and charge controlled reactions. The results indicate that confinement can influence the regioselectivity and that the reactivity of anions is expected to change, due to the artificial binding of the exess electron.
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
Bose-Hubbard models in confining potentials: Inhomogeneous mean-field theory
NASA Astrophysics Data System (ADS)
Pai, Ramesh V.; Kurdestany, Jamshid Moradi; Sheshadri, K.; Pandit, Rahul
2012-06-01
We present an extensive study of Mott insulator (MI) and superfluid (SF) shells in Bose-Hubbard (BH) models for bosons in optical lattices with harmonic traps. For this we apply the inhomogeneous mean-field theory developed by Sheshadri [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.75.4075 75, 4075 (1995)]. Our results for the BH model with one type of spinless bosons agree quantitatively with quantum Monte Carlo simulations. Our approach is numerically less intensive than such simulations, so we are able to perform calculations on experimentally realistic, large three-dimensional systems, explore a wide range of parameter values, and make direct contact with a variety of experimental measurements. We also extend our inhomogeneous mean-field theory to study BH models with harmonic traps and (a) two species of bosons or (b) spin-1 bosons. With two species of bosons, we obtain rich phase diagrams with a variety of SF and MI phases and associated shells when we include a quadratic confining potential. For the spin-1 BH model, we show, in a representative case, that the system can display alternating shells of polar SF and MI phases, and we make interesting predictions for experiments in such systems.
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
NASA Astrophysics Data System (ADS)
Zhu, Hua-Gui; Huang, Guo-Qiang; Luo, Cui-Lan
2016-02-01
We investigate the reciprocal of the mean quantum Fisher information per particle (RMQFIP) and phase sensitivity of atomic Josephson junctions with a bosonic species confined by a double-well potential. Here we are focus on the Rabi oscillation energy's influence on RMQFIP and phase sensitivity. The better quantum entanglement and phase sensitivity may be achieved by decreasing the Rabi oscillation energy.
Bicudo, P.
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)
van Hooydonk, G.
2016-03-01
We review harmonic oscillator theory for closed, stable quantum systems. The H2 potential energy curve (PEC) of Mexican hat-type, calculated with a confined Kratzer oscillator, is better than the Rydberg-Klein-Rees (RKR) H2 PEC. Compared with QM, the theory of chemical bonding is simplified, since a confined Kratzer oscillator can also lead to the long sought for universal function, once called the Holy Grail of Molecular Spectroscopy. This is validated by reducing PECs for different bonds H2, HF, I2, N2 and O2 to a single one. The equal probability for H2, originating either from HA + HB or HB + HA, is quantified with a Gauss probability density function. At the Bohr scale, a confined harmonic oscillator behaves properly at the extremes of bound two-nucleon quantum systems.
A three-dimensional potential-flow program with a geometry package for input data generation
NASA Technical Reports Server (NTRS)
Halsey, N. D.
1978-01-01
Information needed to run a computer program for the calculation of the potential flow about arbitrary three dimensional lifting configurations is presented. The program contains a geometry package which greatly reduces the task of preparing the input data. Starting from a very sparse set of coordinate data, the program automatically augments and redistributes the coordinates, calculates curves of intersection between components, and redistributes coordinates in the regions adjacent to the intersection curves in a suitable manner for use in the potential flow calculations. A brief summary of the program capabilities and options is given, as well as detailed instructions for the data input, a suggested structure for the program overlay, and the output for two test cases.
Magirl, Christopher S.; Olsen, Theresa D.
2009-01-01
Using discharge and channel geometry measurements from U.S. Geological Survey streamflow-gaging stations and data from a geographic information system, regression relations were derived to predict river depth, top width, and bottom width as a function of mean annual discharge for rivers in the State of Washington. A new technique also was proposed to determine bottom width in channels, a parameter that has received relatively little attention in the geomorphology literature. These regression equations, when combined with estimates of mean annual discharge available in the National Hydrography Dataset, enabled the prediction of hydraulic geometry for any stream or river in the State of Washington. Predictions of hydraulic geometry can then be compared to thresholds established by the Washington State Department of Natural Resources to determine navigability potential of rivers. Rivers with a mean annual discharge of 1,660 cubic feet per second or greater are 'probably navigable' and rivers with a mean annual discharge of 360 cubic feet per second or less are 'probably not navigable'. Variance in the dataset, however, leads to a relatively wide range of prediction intervals. For example, although the predicted hydraulic depth at a mean annual discharge of 1,660 cubic feet per second is 3.5 feet, 90-percent prediction intervals indicate that the actual hydraulic depth may range from 1.8 to 7.0 feet. This methodology does not determine navigability - a legal concept determined by federal common law - instead, this methodology is a tool for predicting channel depth, top width, and bottom width for rivers and streams in Washington.
Patterned time-orbiting potentials for the confinement and assembly of magnetic dipoles
Chen, A.; Sooryakumar, R.
2013-01-01
We present an all-magnetic scheme for the assembly and study of magnetic dipoles within designed confinement profiles that are activated on micro-patterned permalloy films through a precessing magnetic field. Independent control over the confinement and dipolar interactions is achieved by tuning the strength and orientation of the revolving field. The technique is demonstrated with superparamagnetic microspheres field-driven to assemble into closely packed lattice sheets, quasi-1D and other planar structures expandable into dipolar arrays that mirror the patterned surface motifs. PMID:24185093
Lee, Jenny; Brown, B.A.; Delaunay, F.; Lynch, W.G.; Saelim, M. J.; Tsang, M.B.; Tostevin, J.A.
2006-04-15
We carry out a systematic analysis of angular distribution measurements for selected ground-state to ground-state (d,p) and (p,d) neutron transfer reactions, including the calcium isotopes. We propose a consistent three-body model reaction methodology in which we constrain the transferred-neutron bound state and nucleon-target optical potential geometries using modern Hartree-Fock calculations. Our deduced neutron spectroscopic factors are found to be suppressed by {approx}30% relative to independent-particle shell-model values, from {sup 40}Ca through {sup 49}Ca. The other nuclei studied, ranging from B to Ti, show similar average suppressions with respect to large-basis shell-model expectations. Our results are consistent with deduced spectroscopic strengths for neutrons and protons from intermediate-energy nucleon knockout reactions and for protons from (e,e{sup '}p) reactions on well-bound nuclei.
Hovering rotor airload prediction using a full potential flow analysis with realistic wake geometry
NASA Technical Reports Server (NTRS)
Egolf, T. A.; Sparks, S. P.
1985-01-01
A three-dimensional, full potential flow analysis with realistic hover wake geometry is presented for the prediction of hovering rotor airloads. The method of analysis is based on the concept of matching inner and outer domain solutions in three dimensions. The inner domain nonlinear solution is obtained using a finite difference analysis and the outer domain solution is based on prescribed wake methodology. This formulation which includes three-dimensional wake influence, was initially validated using a fixed-wing analysis, and has been extended to hovering rotor flight. Detailed chordwise and spanwise loading results are compared with subsonic and transonic test results from two rotor configurations to illustrate the predictive capabilities of the analysis. The extension of the method to steady-level forward flight is also discussed.
Kushwaha, Manvir S.
2014-12-15
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
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
NASA Astrophysics Data System (ADS)
Johnson, C. B.; Furlong, K. P.; Kirby, E.
2004-12-01
The cause of high elevations in the Marin County - Mt. Tamalpais region is enigmatic. Because the region is adjacent to a segment of the San Andreas fault with essentially no transpression, fault-normal shortening is unlikely to be the cause of the uplift. Rather it has been proposed that the uplift may be associated with blind thrust(s) in the area (Furlong and Kirby 2004, this meeting). If such structures do indeed exist, then their extent and orientation would be a key component in assessing earthquake potential for the area. This study examines the specific geometries of possible blind thrusts that could produce the Mt. Tamalpais uplift, and the seismogenic implications. The study area, bounded by the Point Reyes - Tomales Bay segment of the San Andreas (on the west) and the Hayward/Rodgers Creek fault system (on the east), increases in elevation significantly from north to south. Mt. Tamalpais sits at the southernmost extent of the uplifted area with the highest elevations at 780 meters above sea level. We have utilized 2-D and 3-D elastic deformation models to evaluate the orientation and spatial extent of possible blind thrusts that could generate the uplift. The combination of potential fault area and rate of deformation (shortening across the structure) allows us to place limits on the possible size of earthquakes that could occur on such blind faults. Preliminary analyses indicate that structures in the Marin County - Mt. Tamalpais could host up to a M = 6 event with a recurrence time of 1000 years.
Making Conjectures in Dynamic Geometry: The Potential of a Particular Way of Dragging
ERIC Educational Resources Information Center
Mariotti, Maria Alessandra; Baccaglini-Frank, Anna
2011-01-01
When analyzing what has changed in the geometry scenario with the advent of dynamic geometry systems (DGS), one can notice a transition from the traditional graphic environment made of paper-and-pencil, and the classical construction tools like the ruler and compass, to a virtual graphic space, made of a computer screen, graphical tools that are…
Linear transport of domain walls confined to propagating 1-D potential wells
NASA Astrophysics Data System (ADS)
Negotia, M.; Hodges, M. P. P.; Bryan, M. T.; Fry, P. W.; Im, M.-Y.; Fischer, P.; Allwood, D. A.; Hayward, T. J.
2013-10-01
We present a method of controllably propagating domain walls (DWs) in magnetic nanowires over extended linear distances by confining them to geometrically defined energy minima. Using simple models, magnetic transmission soft x-ray microscopy and magneto-optic Kerr effect measurements, we show that the technique allows DWs to be moved at arbitrary, user-defined velocities and be positioned with micrometer precision. Our approach is expected to be of utility in applications where the precise transport and positioning of DWs take precedent over the absolute speed of propagation, for example, where the fields produced by DWs are used to trap and transport magnetized particles.
Yuan, Baohong; Pei, Yanbo; Kandukuri, Jayanth
2013-01-01
Our recently developed ultrasound-switchable fluorescence (USF) imaging technique showed that it was feasible to conduct high-resolution fluorescence imaging in a centimeter-deep turbid medium. Because the spatial resolution of this technique highly depends on the ultrasound-induced temperature focal size (UTFS), minimization of UTFS becomes important for further improving the spatial resolution USF technique. In this study, we found that UTFS can be significantly reduced below the diffraction-limited acoustic intensity focal size via nonlinear acoustic effects and thermal confinement by appropriately controlling ultrasound power and exposure time, which can be potentially used for deep-tissue high-resolution imaging. PMID:23479498
NASA Astrophysics Data System (ADS)
Tuncel, Eylul; Suzuki, Yasuhito; Iossifidis, Agathaggelos; Steinhart, Martin; Butt, Hans-Jurgen; Floudas, George; Duran, Hatice
Structure formation, thermodynamic stability, phase and dynamic behaviors of polypeptides are strongly affected by confinement. Since understanding the changes in these behaviors will allow their rational design as functional devices with tunable properties, herein we investigated Poly-Z-L-lysine (PZLL) and Poly-L-alanine (PAla) homopolypeptides confined in nanoporous alumina containing aligned cylindrical nanopores as a function of pore size by differential scanning calorimetry (DSC), Fourier Transform Infrared Spectroscopy, Solid-state NMR, X-ray diffraction, Dielectric spectroscopy(DS). Bulk PZLL exhibits a glass transition temperature (Tg) at about 301K while PZLL nanorods showed slightly lower Tg (294K). The dynamic investigation by DS also revealed a decrease (4K) in Tg between bulk and PZLL nanorods. DS is a very sensitive probe of the local and global secondary structure relaxation through the large dipole to study effect of confinement. The results revealed that the local segmental dynamics, associated with broken hydrogen bonds, and segmental dynamics speed-up on confinement.
McHargue, T.R.; Webb, J.E.
1986-02-01
The Indus Fan, the second largest submarine fan in the world, covers 1,250,000 km/sup 2/ (500,000 mi/sup 2/) and contains sediment more than 7 km (23,000 ft) thick. Multichannel (24-fold) CDP seismic data provide the bases for evaluating the Indus Fan and consist of four seismic facies. Of these, only the high-amplitude, discontinuous (H-D) facies is thought to contain reservoir-quality sandstones. The H-D facies is confined to the axes of leveed channels. Canyon-channel systems that fed the fan in the past can be divided into three zones. The degradational zone is composed of an erosional canyon complex filled by prodelta mud. The transitional zone, located near the canyon mouth, consists of superimposed channels that initially were erosional but eventually aggraded and developed levees. The headward termination of the H-D facies occurs in this zone. The aggradational zone consists of superimposed leveed channels confined solely by their own levees. The proximal termination of the H-D facies near canyon mouths implies the presence of reservoir-quality sandstone surrounded by source/seal mudstone in the transitional zone. This stratigraphic trapping geometry and structural leads may represent a vast, untapped petroleum province.
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
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.
A geometry package for generation of input data for a three-dimensional potential-flow program
NASA Technical Reports Server (NTRS)
Halsey, N. D.; Hess, J. L.
1978-01-01
The preparation of geometric data for input to three-dimensional potential flow programs was automated and simplified by a geometry package incorporated into the NASA Langley version of the 3-D lifting potential flow program. Input to the computer program for the geometry package consists of a very sparse set of coordinate data, often with an order of magnitude of fewer points than required for the actual potential flow calculations. Isolated components, such as wings, fuselages, etc. are paneled automatically, using one of several possible element distribution algorithms. Curves of intersection between components are calculated, using a hybrid curve-fit/surface-fit approach. Intersecting components are repaneled so that adjacent elements on either side of the intersection curves line up in a satisfactory manner for the potential-flow calculations. Many cases may be run completely (from input, through the geometry package, and through the flow calculations) without interruption. Use of the package significantly reduces the time and expense involved in making three-dimensional potential flow calculations.
NASA Astrophysics Data System (ADS)
Amendt, Peter; Wilks, S. C.; Bellei, C.; Li, C. K.; Petrasso, R. D.
2011-05-01
The generation of strong, self-generated electric fields (GV/m) in direct-drive, inertial-confinement-fusion (ICF) capsules has been reported [Rygg et al., Science 319, 1223 (2008); Li et al., Phys. Rev. Lett. 100, 225001 (2008)]. A candidate explanation for the origin of these fields based on charge separation across a plasma shock front was recently proposed [Amendt et al., Plasma Phys. Controlled Fusion 51 124048 (2009)]. The question arises whether such electric fields in imploding capsules can have observable consequences on target performance. Two well-known anomalies come to mind: (1) an observed ≈2× greater-than-expected deficit of neutrons in an equimolar D3He fuel mixture compared with hydrodynamically equivalent D [Rygg et al., Phys. Plasmas 13, 052702 (2006)] and DT [Herrmann et al., Phys. Plasmas 16, 056312 (2009)] fuels, and (2) a similar shortfall of neutrons when trace amounts of argon are mixed with D in indirect-drive implosions [Lindl et al., Phys. Plasmas 11, 339 (2004)]. A new mechanism based on barodiffusion (or pressure gradient-driven diffusion) in a plasma is proposed that incorporates the presence of shock-generated electric fields to explain the reported anomalies. For implosions performed at the Omega laser facility [Boehly et al., Opt. Commun. 133, 495 (1997)], the (low Mach number) return shock has an appreciable scale length over which the lighter D ions can diffuse away from fuel center. The depletion of D fuel is estimated and found to lead to a corresponding reduction in neutrons, consistent with the anomalies observed in experiments for both argon-doped D fuels and D3He equimolar mixtures. The reverse diffusional flux of the heavier ions toward fuel center also increases the pressure from a concomitant increase in electron number density, resulting in lower stagnation pressures and larger imploded cores in agreement with gated, self-emission, x-ray imaging data.
NASA Astrophysics Data System (ADS)
Ross, J. Ole; Ceranna, Lars
2016-04-01
The radionuclide component of the International Monitoring System (IMS) to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is in place to detect tiny traces of fission products from nuclear explosions in the atmosphere. The challenge for the interpretation of IMS radionuclide data is to discriminate radionuclide sources of CTBT relevance against emissions from nuclear facilities. Remarkable activity concentrations of Ba/La-140 occurred at the IMS radionuclide stations RN 37 (Okinawa) and RN 58 (Ussurysk) mid of May 2010. In those days also an elevated Xe-133 level was measured at RN 38 (Takasaki). Additional regional measurements of radioxenon were reported in the press and further analyzed in various publications. The radionuclide analysis gives evidence for the presence of a nuclear fission source between 10 and 12 May 2010. Backward Atmospheric Transport Modelling (ATM) with HYSPLIT driven by 0.2° ECMWF meteorological data for the IMS samples indicates that, assuming a single source, a wide range of source regions is possible including the Korean Peninsula, the Sea of Japan (East Sea), and parts of China and Russia. Further confinement of the possible source location can be provided by atmospheric backtracking for the assumed sampling periods of the reported regional xenon measurements. New studies indicate a very weak seismic event at the DPRK test site on early 12 May 2010. Forward ATM for a pulse release caused by this event shows fairly good agreement with the observed radionuclide signature. Nevertheless, the underlying nuclear fission scenario remains quite unclear and speculative even if assuming a connection between the waveform and the radionuclide event.
Langenheim, V.E.; Griscom, Andrew; Jachens, R.C.; Hildenbrand, T.G.
2000-01-01
Gravity and magnetic data provide new insights on the structural underpinnings of the San Fernando Basin region, which may be important to ground motion models. Gravity data indicate that a deep basin (>5 km) underlies the northern part of the San Fernando Valley; this deep basin is required to explain the lowest gravity values over the Mission Hills thrust fault. Gravity modeling, constrained by well data and density information, shows that the basin may reach a thickness of 8 km, coinciding with the upper termination of the 1994 Northridge earthquake mainshock rupture. The basin is deeper than previous estimates by 2 to 4 km; this estimate is the result of high densities for the gravels of the Pliocene-Pleisocene Saugus Formation. The geometry of the southern margin of the deep basin is not well-constrained by the gravity data, but may dip to the south. Recently acquired seismic data along the LARSE (Los Angeles Regional Seismic Experiment) II profile may provide constraints to determine the location and attitude of the basin edge. Gravity and aeromagnetic models across the eastern margin of the San Fernando Valley indicate that the Verdugo fault may dip to the southwest along its southern extent and therefore have a normal fault geometry whereas it clearly has a thrust fault geometry along its northern strand.
Cioslowski, Jerzy; Albin, Joanna
2013-09-14
Energies E(N) of assemblies of equicharged particles subject to spherically symmetric power-law confining potentials vary in a convoluted fashion with the particle totalities N. Accurate rigorous upper bounds to these energies, which are amenable to detailed mathematical analysis, are found to comprise terms with smooth, oscillatory, and fluctuating dependences on N. The smooth energy component is obtained as a power series in N(-2/3) with the first two terms corresponding to the bulk and Madelung energies. The oscillatory component possesses the large-N asymptotics given by a product of N(1/(λ + 1)), where λ is the power-law exponent, and a function periodic in N(1/3). The amplitude of the fluctuating component, which originates mostly from the irregular dependence of the Thomson energy E(Th)(n) on n, also scales like N(1/(λ + 1)). PMID:24050343
NASA Astrophysics Data System (ADS)
Cho, Teruji
2007-11-01
The tandem mirror system has achieved improved energy confinement times (> 60-90 ms) with radial transport dominating the Pastukhov axial energy confinement time (> 100 ms). This high confinement regime establishes a proof of principle that the combination of electrostatic and magnetic mirror confinement can successfully insulate electrons from thermal ions. ECH controlled hot-layer formation facilitates plasma-rotation profile formation with a radially localized high-vorticity layer. In the vicinity of the layer, a radial transport barrier is formed [1], showing similar properties to ITB in toroidal plasmas. Coaxially nested intense E(r)xB sheared flow [2] in the GAMMA 10 core plasma realizes an upgraded stable regime having (i) > 0.75 keV bulk central electron temperature with (ii) an achievement of larger stored energy for axially potential-confined ions exceeding that (i.e., diamagnetism) for central magnetically confined ions ( 7 keV). The radially sheared flow having peak-on-axis high vorticity guards and improves whole core plasma confinement, and is controlled by (iii) improved 3 kV ion-confining potential due to simultaneous central and plug ECH. X-ray imaging of the suppression of turbulent structures [1-3] will be shown [1,2]. [1] T. Cho et al., Phys. Rev. Lett. 97, 055001 (2006). [2] T. Cho et al., Phys. Rev. Lett. 94, 085002 (2005). [3] J. Pratt and W. Horton, Phys. Plasmas 13, 042513 (2006). Collaborators; W. Horton^1, J. Pratt^1, M. Hirata, J. Kohagura, T. Numakura, H. Hojo, M. Ichimura, A. Itakura, T. Kariya, I. Katanuma, R. Minami, Y. Nakashima, M. Yoshikawa, Y. Miyata, Y. Yamaguchi, T. Imai, V. P. Pastukhov^2, S. Miyoshi, GAMMA 10 Group (^1IFS, Univ. Texas at Austin, ^2Kurchatov Institute, Russia)
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, φ( x) = ( α| x| z )/ z ( α > 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 φ( 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
Cioslowski, Jerzy; Albin, Joanna
2013-09-21
Asymptotic equivalence of the shell-model and local-density (LDA) descriptions of Coulombic systems confined by radially symmetric potentials in two and three dimensions is demonstrated. Tight upper bounds to the numerical constants that enter the LDA expressions for the Madelung energy are derived and found to differ by less than 0.5% from the previously known approximate values. Thanks to the variational nature of the shell-model approximate energies, asymptotic expressions for other properties, such as mean radial positions of the particles and number densities, are also obtained. A conjecture that generalizes the present results to confining potentials with arbitrary symmetries is formulated. PMID:24070281
Decay rates of charmonia within a quark-antiquark confining potential
NASA Astrophysics Data System (ADS)
Smruti, Patel; Vinodkumar, P. C.; Shashank, Bhatnagar
2016-05-01
In this work, we investigate the spectroscopy and decay rates of charmonia within the framework of the non-relativistic Schrödinger equation by employing an approximate inter quark-antiquark potential. The spin hyperfine, spin-orbit and tensor components of the one gluon exchange interaction are employed to compute the spectroscopy of the excited S states and a few low-lying P and D waves. The resultant wave functions at zero inter-quark separation as well as some finite separations are employed to predict the di-gamma, di-leptonic and di-gluon decay rates of charmonia states using the conventional Van Royen-Weisskopf formula. The di-gamma and di-leptonic decay widths are also computed by incorporating the relativistic corrections of order v 4 within the NRQCD formalism. We have observed that the NRQCD predictions with their matrix elements computed at finite radial separation yield results which are found to be in better agreement with experimental values for both di-gamma and di-leptonic decays. The same scenario is seen in the case when di-gamma and di-leptonic decay widths are computed with the Van Royen-Weisskopf formula. It is also observed that the di-gluon decay width with the inclusion of binding energy effects are in better agreement with the experimental data available for 1S-2S and 1P. The di-gluon decay width of 3S and 2P waves waves are also predicted. Thus, the present study of decay rates clearly indicates the importance of binding energy effects. Supported by Major Research Project NO. F. 40-457/2011(SR), UGC, India
Mitra, S.
1986-09-01
Duplexes and imbricate thrust systems form some of the most complex hydrocarbon traps in overthrust belts. The geometry of a duplex is controlled by the ramp angle (theta) and height (h/sub r/), the final spacing between adjacent thrusts (a'), and the relative displacements on them (d/sub 1/-d/sub 2/). For constant theta and h/sub r/, three different classes are recognized: (1) independent ramp anticlines and hinterland sloping duplexes, (2) true duplexes, and (3) overlapping ramp anticlines. Several types of duplexes and imbricate thrust systems form important hydrocarbon traps. Examples include the system of independent anticlines of the Turner Valley and Highwood oil and gas fields, the hinterland sloping duplex consisting of the Chestnut Ridge-Sandy Ridge system of the Ben Hur oil field, the partly overlapping anticlines of the Waterton and Savanna Creek gas fields, and the completely overlapping anticlines of the Rose Hill oil field. 27 figures.
Soldatkina, E. I.; Bagryansky, P. A.; Solomakhin, A. L.
2008-04-15
One of the most important problems to be studied in the gas-dynamic trap (GDT) facility is the investigation of MHD stability and cross-field transport in a plasma with a relatively high value of {beta} = {pi}p/B{sup 2}. Recent experiments demonstrated that the radial electric field produced in the plasma by using radial limiters and coaxial end plasma collectors improves plasma stability in axisymmetric magnetic mirror systems without applying special MHD stabilizers. The experimental data presented in this work show that stable plasma confinement can be achieved by producing a radial potential drop across a narrow region near the plasma boundary. Creating radial electric fields of strength 15-40 V/cm causes a shear plasma flow, thereby substantially increasing the plasma confinement time. When all the radial electrodes were grounded, the confinement was unstable and the plasma confinement time was much shorter than the characteristic time of plasma outflow through the magnetic mirrors. Measurements of cross-field plasma fluxes with the use of a specially designed combined probe show that, in confinement modes with differential plasma rotation, transverse particle losses are negligibly small as compared to longitudinal ones and thus can be ignored. It is also shown that, when the GDT plasma is in electric contact with the radial limiters and end collectors, the growth rate of interchange instability decreases considerably; such a contact, however, does not ensure complete MHD stability when the electrodes are at the same potential.
NASA Astrophysics Data System (ADS)
Bartolo, Denis; Bricard, Antoine; Caussin, Jean-Baptiste; Savoie, Charles; Das, Debasish; Chepizhko, Oleskar; Peruani, Fernando; Saintillan, David
2014-11-01
It is well established that geometrical confinement have a significant impact on the structure and the flow properties of complex fluids. Prominent examples include the formation of topological defects in liquid crystals, and the flow instabilities of viscoelastic fluids in curved geometries. In striking contrast very little is known about the macroscopic behavior of confined active fluids. In this talk we show how to motorize plastic colloidal beads and turn them into self-propelled particles. Using microfluidic geometries we demonstrate how confinement impacts their collective motion. Combining quantitative experiments, analytical theory and numerical simulations we show how a population of motile bodies interacting via alignement and repulsive interactions self-organizes into a single heterogeneous macroscopic vortex that lives on the verge of a phase separation.
In 1995, EPA completed a risk assessment for potential air emissions from the operation of a proposed confined disposal facility (CDF) to be constructed and operated by the U.S. Army Corps of Engineers for dredged sediments from the Indiana Harbor and Shipping Canal in East Chica...
NASA Astrophysics Data System (ADS)
Bakke, K.
2015-07-01
The behaviour of the Landau-Aharonov-Casher system is discussed by showing a case where the external electric field cannot yield the Landau-Aharonov-Casher quantization under the influence of rotating effects in the cosmic string spacetime, but it can yield bound states solutions to the Schrödinger-Pauli equation analogous to having the Landau-Aharonov-Casher system confined to a hard-wall confining potential under the influence of rotating effects and the topology of the cosmic string spacetime (by assuming ω ρ≪1 and neglecting the effects of a gravitational self-force on the particle).
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.
Castro, Luis B.; Castro, Antonio S. de
2014-12-15
We point out a misleading treatment in the recent literature regarding confining solutions for a scalar potential in the context of the Duffin–Kemmer–Petiau theory. We further present the proper bound-state solutions in terms of the generalized Laguerre polynomials and show that the eigenvalues and eigenfunctions depend on the solutions of algebraic equations involving the potential parameter and the quantum number.
Mirabelli, Maria C; Wing, Steve; Marshall, Stephen W; Wilcosky, Timothy C
2006-04-01
Previous studies suggest that airborne effluent from swine confined animal feeding operations (CAFOs) may affect the health and quality of life of adults and the prevalence of asthma symptoms among children. To investigate the extent to which public school students may be exposed to airborne effluent from swine CAFOs and to evaluate the association between schools' demographic characteristics and swine CAFO exposures, we assessed the proximity of 226 schools to the nearest swine CAFO and conducted a survey of school employees to identify schools with noticeable livestock odor. We used publicly available information describing the enrollment of each school to assess the association between race and socioeconomic status (SES) and swine CAFO exposure. Odor from livestock was noticeable outside (n = 47, 21%) and inside (n = 19, 8%) school buildings. Schools with < 63% enrollment of white students and > or = 47% of students receiving subsidized lunches at school were located closer to swine CAFOs (mean = 4.9 miles) than were the remaining schools (mean = 10.8 miles) and were more likely to be located within 3 miles of an operation than were schools with high-white/high-SES enrollment (prevalence ratio = 2.63; 95% confidence interval, 1.59-4.33). The prevalence of reported livestock odor varied with SES (low SES, 25%; high SES, 17%). These analyses indicate that the potential for in-school exposure to pollution arising from swine CAFOs in North Carolina and the environmental health risks associated with such exposures vary according to the racial and economic characteristics of enrolled students. PMID:16581551
Global geometry optimization of silicon clusters described by three empirical potentials
NASA Astrophysics Data System (ADS)
Yoo, S.; Zeng, X. C.
2003-07-01
The "basic-hopping" global optimization technique developed by Wales and Doye is employed to study the global minima of silicon clusters Sin(3⩽n⩽30) with three empirical potentials: the Stillinger-Weber (SW), the modified Stillinger-Weber (MSW), and the Gong potentials. For the small-sized SW and Gong clusters (3⩽n⩽15), it is found that the global minima obtained based on the basin-hopping method are identical to those reported by using the genetic algorithm [Iwamatsu, J. Chem. Phys. 112, 10976 (2000)], as well as with those by using molecular dynamics and the steepest-descent quench (SDQ) method [Feuston, Kalia, and Vashishta, Phys. Rev. B 37, 6297 (1988)]. However, for the mid-sized SW clusters (16⩽n⩽20), the global minima obtained differ from those based on the SDQ method, e.g., the appearance of the endohedral atom with fivefold coordination starting at n=17, as opposed to n=19. For larger SW clusters (20⩽n⩽30), it is found that the "bulklike" endohedral atom with tetrahedral coordination starts at n=20. In particular, the overall structural features of SW Si21, Si23, Si25, and Si28 are nearly identical to the MSW counterparts. With the SW Si21 as the starting structure, a geometric optimization at the B3LYP/6-31G(d) level of density-functional theory yields an isomer similar to the ground-state- isomer of Si21 reported by Pederson et al. [Phys. Rev. B 54, 2863 (1996)].
NASA Astrophysics Data System (ADS)
Mandal, Arkajit; Sarkar, Sucharita; Ghosh, Arghya Pratim; Ghosh, Manas
2015-12-01
We make an extensive investigation of total optical absorption coefficient (TOAC) of impurity doped quantum dots (QDs) in presence and absence of Gaussian white noise. The TOAC profiles have been monitored against incident photon energy with special emphasis on the roles played by the electric field, magnetic field, and the dot confinement potential. Presence of impurity also influences the TOAC profile. In general, presence of noise causes enhancement of TOAC over that of noise-free condition. However, the interplay between the noise and the quantities like electric field, magnetic field, confinement potential and impurity potential bring about rich subtleties in the TOAC profiles. The said subtleties are often manifested by the alterations in TOAC peak intensity, extent of TOAC peak bleaching, and value of saturation intensity. The findings reveal some technologically relevant aspects of TOAC for the doped QD systems, specially in presence of noise.
Guo, Rui; Miele, Margherita; Gardner, Elizabeth M; Fournier, Frederic; Kornau, Kathryn M; Gould, Ian R; Klug, David R
2011-01-01
The ability to detect molecular complexes and determine their geometries is crucial to our understanding of all biological phenomena, including protein structures and functions. We recently demonstrated that a novel 2DIR technique, EVV 2DIR spectroscopy, can be used for this purpose. In this paper, we evaluate the potential utility of the method for the analysis of protein composition, structure and function. In order to do this we apply computational tools to a group of selected biological systems, for which our calculated spectra all showed features that can in principle be detected with existing sensitivities. We also investigate the possibility of using our technique to detect and analyse hydrogen-bonded systems through a tyrosine-water model. PMID:22457947
NASA Astrophysics Data System (ADS)
Filatov, Michael; Cremer, Dieter
2003-03-01
For the quasi-relativistic normalized elimination of small component using an effective potential (NESC-EP) method, analytical energy gradients were developed, programmed, and implemented in a standard quantum chemical program package. NESC-EP with analytical gradients was applied to determine geometry, vibrational frequencies, and dissociation enthalpies of ferrocene, tungsten hexafluoride, and tungsten hexacarbonyle. Contrary to non-relativistic calculations and calculations carried out with RECPs for the same compounds, NESC-EP provided reliable molecular properties in good agreement with experiment. The computational power of NESC-EP results from the fact that reliable relativistic corrections are obtained at a cost level only slightly larger than that of a non-relativistic calculation.
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.
Deforming baryons into confining strings
NASA Astrophysics Data System (ADS)
Hartnoll, Sean A.; Portugues, Rubén
2004-09-01
We find explicit probe D3-brane solutions in the infrared of the Maldacena-Nuñez background. The solutions describe deformed baryon vertices: q external quarks are separated in spacetime from the remaining N-q. As the separation is taken to infinity we recover known solutions describing infinite confining strings in N=1 gauge theory. We present results for the mass of finite confining strings as a function of length. We also find probe D2-brane solutions in a confining type IIA geometry, the reduction of a G2 holonomy M theory background. The relation between these deformed baryons and confining strings is not as straightforward.
NASA Astrophysics Data System (ADS)
Gustin, C.; Faniel, S.; Hackens, B.; Bayot, V.; de Poortere, E.; Shayegan, M.
2002-03-01
We report on the low temperature magnetoresistance of various quantum billiards, each with a different shape of the 2DEG (two-dimensional electron gas) confinement potential. The structures are patterned by electron beam lithography on three different high mobility GaAs/AlGaAs samples, namely a single heterojunction and two quantum wells with widths of 150 and 450Årespectively. By means of electrostatic gates, both the electron density and the shape of the billiard can be controlled, as well as the finite thickness of the 2DEG in the case of the wide quantum well. We discuss the results of low temperature magnetotransport measurements with the open dots subject to an phin-situ tilted magnetic field. More specifically we investigate the influence of the symmetry-asymmetry of the 2DEG confinement potential on the statistics of the universal conductance fluctuations (UCF).
Baldwin, David E.; Logan, B. Grant
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.
Baldwin, D.E.; Logan, B.G.
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 frequence 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 technical state of the art required, and the capital cost are all greatly lowered.
Thallmair, Sebastian; Roos, Matthias K; de Vivie-Riedle, Regina
2016-06-21
Quantum dynamics simulations require prior knowledge of the potential energy surface as well as the kinetic energy operator. Typically, they are evaluated in a low-dimensional subspace of the full configuration space of the molecule as its dimensionality increases proportional to the number of atoms. This entails the challenge to find the most suitable subspace. We present an approach to design specially adapted reactive coordinates spanning this subspace. In addition to the essential geometric changes, these coordinates take into account the relaxation of the non-reactive coordinates without the necessity of performing geometry optimizations at each grid point. The method is demonstrated for an ultrafast photoinduced bond cleavage in a commonly used organic precursor for the generation of electrophiles. The potential energy surfaces for the reaction as well as the Wilson G-matrix as part of the kinetic energy operator are shown for a complex chemical reaction, both including the relaxation of the non-reactive coordinates on equal footing. A microscopic interpretation of the shape of the G-matrix elements allows to analyze the impact of the non-reactive coordinates on the kinetic energy operator. Additionally, we compare quantum dynamics simulations with and without the relaxation of the non-reactive coordinates included in the kinetic energy operator to demonstrate its influence. PMID:27334151
NASA Astrophysics Data System (ADS)
Thallmair, Sebastian; Roos, Matthias K.; de Vivie-Riedle, Regina
2016-06-01
Quantum dynamics simulations require prior knowledge of the potential energy surface as well as the kinetic energy operator. Typically, they are evaluated in a low-dimensional subspace of the full configuration space of the molecule as its dimensionality increases proportional to the number of atoms. This entails the challenge to find the most suitable subspace. We present an approach to design specially adapted reactive coordinates spanning this subspace. In addition to the essential geometric changes, these coordinates take into account the relaxation of the non-reactive coordinates without the necessity of performing geometry optimizations at each grid point. The method is demonstrated for an ultrafast photoinduced bond cleavage in a commonly used organic precursor for the generation of electrophiles. The potential energy surfaces for the reaction as well as the Wilson G-matrix as part of the kinetic energy operator are shown for a complex chemical reaction, both including the relaxation of the non-reactive coordinates on equal footing. A microscopic interpretation of the shape of the G-matrix elements allows to analyze the impact of the non-reactive coordinates on the kinetic energy operator. Additionally, we compare quantum dynamics simulations with and without the relaxation of the non-reactive coordinates included in the kinetic energy operator to demonstrate its influence.
Davidson, R. L.; Earle, G. D.; Heelis, R. A.; Klenzing, J. H.
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.
NASA Astrophysics Data System (ADS)
Zhang, Xianren; Wang, Wenchuan
2006-12-01
In this work the effects of the wall-fluid interaction on the critical point shift are studied by using a discrete and attractive wall-fluid interaction and density functional theory. In contrast to the previous assumption, it is found that the dependence of critical temperature shift on the wall-fluid interaction does not simply show a monotonic manner, but increases with the strength of the interaction for weak surfaces, then decreases for strong surfaces. The similar trend holds for the systems with different fluid-fluid interactions and different confined spaces. Unlike the capillary critical temperature, the critical density of square-well fluids in a confined space increases monotonically as the wall-fluid interaction becomes more attractive.
Strongly confined fluids: Diverging time scales and slowing down of equilibration
NASA Astrophysics Data System (ADS)
Schilling, Rolf
2016-06-01
The Newtonian dynamics of strongly confined fluids exhibits a rich behavior. Its confined and unconfined degrees of freedom decouple for confinement length L →0 . In that case and for a slit geometry the intermediate scattering functions Sμ ν(q ,t ) simplify, resulting for (μ ,ν )≠(0 ,0 ) in a Knudsen-gas-like behavior of the confined degrees of freedom, and otherwise in S∥(q ,t ) , describing the structural relaxation of the unconfined ones. Taking the coupling into account we prove that the energy fluctuations relax exponentially. For smooth potentials the relaxation times diverge as L-3 and L-4, respectively, for the confined and unconfined degrees of freedom. The strength of the L-3 divergence can be calculated analytically. It depends on the pair potential and the two-dimensional pair distribution function. Experimental setups are suggested to test these predictions.
Edge states in confined active fluids
NASA Astrophysics Data System (ADS)
Souslov, Anton; Vitelli, Vincenzo
Recently, topologically protected edge modes have been proposed and realized in both mechanical and acoustic metamaterials. In one class of such metamaterials, Time-Reversal Symmetry is broken, and, to achieve this TRS breaking in mechanical and acoustic systems, an external energy input must be used. For example, motors provide a driving force that uses energy and, thus, explicitly break TRS. As a result, motors have been used as an essential component in the design of topological metamaterials. By contrast, we explore the design of topological metamaterials that use a class of far-from-equilibrium liquids, called polar active liquids, that spontaneously break TRS. We thus envision the confinement of a polar active liquid to a prescribed geometry in order to realize topological order with broken time-reversal symmetry. We address the design of the requisite geometries, for example a regular honeycomb lattice composed of annular channels, in which the active liquid may be confined. We also consider the physical character of the active liquid that, when introduced into the prescribed geometry, will spontaneously form the flow pattern of a metamaterial with topologically protected edge states. Finally, we comment on potential experimental realizations of such metamaterials.
NASA Astrophysics Data System (ADS)
Cunningham, K. J.; Walker, C.; Westcott, R. L.
2011-12-01
Continuous improvements in shallow-focused, high-resolution, marine seismic-reflection technology has provided the opportunity to evaluate geologic structures that breach confining units of the Floridan aquifer system within the southeastern Florida Platform. The Floridan aquifer system is comprised mostly of Tertiary platform carbonates. In southeastern Florida, hydrogeologic confinement is important to sustainable use of the Floridan aquifer system, where the saline lower part is used for injection of wastewater and the brackish upper part is an alternative source of drinking water. Between 2007 and 2011, approximately 275 km of 24- and 48-channel seismic-reflection profiles were acquired in canals of peninsular southeastern Florida, Biscayne Bay, present-day Florida shelf margin, and the deeply submerged Miami Terrace. Vertical to steeply dipping offsets in seismic reflections indicate faults, which range from Eocene to possible early Pliocene age. Most faults are associated with karst collapse structures; however, a few tectonic faults of early Miocene to early Pliocene age are present. The faults may serve as a pathway for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability in the Floridan aquifer system. The faults may collectively produce a regional confinement bypass system. In early 2011, twenty seismic-reflection profiles were acquired near the Key Biscayne submarine sinkhole located on the seafloor of the Miami Terrace. Here the water depth is about 365 m. A steeply dipping (eastward) zone of mostly deteriorated quality of seismic-reflection data underlies the sinkhole. Correlation of coherent seismic reflections within and adjacent to the disturbed zone indicates a series of faults occur within the zone. It is hypothesized that upward movement of groundwater within the zone contributed to development of a hypogenic karst system and the resultant overlying sinkhole
Fractional statistics and confinement
NASA Astrophysics Data System (ADS)
Gaete, P.; Wotzasek, C.
2005-02-01
It is shown that a pointlike composite having charge and magnetic moment displays a confining potential for the static interaction while simultaneously obeying fractional statistics in a pure gauge theory in three dimensions, without a Chern-Simons term. This result is distinct from the Maxwell-Chern-Simons theory that shows a screening nature for the potential.
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
Guzowski, R.V.; Newman, G.
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.
Dhar, Jayabrata; Ghosh, Uddipta; Chakraborty, Suman
2014-03-01
We study the coupled effect of electrokinetic phenomena and fluid rheology in altering the induced streaming potential in narrow fluidic confinements, which is manifested by establishing a time periodic pressure-driven flow in presence of electrical double layer phenomenon. However, in sharp contrast with reported literature, we take into account nonelectrostatic ion-ion interactions toward estimating the same in addition to electrostatic interactions and steric effects. We employ power law based rheological model for estimating the induced streaming potential. We bring out an intricate interaction between nonelectrostatic interactions and fluid rheology on the concerned electrokinetic phenomena, bearing immense consequences toward designing of integrated lab-on-a-chip-based microdevices and nanodevices. PMID:24132646
Kinetics of Diffusing Polymer Encounter in Confined Cellular Microdomains
NASA Astrophysics Data System (ADS)
Amitai, A.; Kupka, I.; Holcman, D.
2013-12-01
We study the mean first time that two monomers, located on the same polymer, encounter in a confined microdomain. Approximating the confined geometry by a harmonic potential well, we obtain an asymptotic expression for the mean first encounter time (MFETC) as a function of the radius ɛ around one monomer. By studying the end-to-end distance of the polymer in a ball using the Edwards' formalism, we derive an other estimation of the MFETC. We validate the asymptotic formulas using Brownian simulations and derive their range of validity in terms of the polymer length. We apply the present models to compute the mean time for a gene located far away from a promoter site to be activated during looping in confined genomic territories.
Liang, Yawei; Xu, Limin; Zhou, Yinglin; Zhang, Xinxiang; Huang, Jianbin; Yan, Yun
2013-10-14
Currently there is intense interest in decreasing the operating potential for hydrogen evolution in water electrolysis to considerably decrease the energy cost. In this work we report a significant decrease of the operating potential for hydrogen evolution from neutral water mediated by an iron based soft coordination polymer (Fe(III)-SCSP). The creation of a local acidic environment with a thickness in the range of ~40 nm on the surface of a glassy carbon electrode allows enrichment of H(+) on the GCE, so that the operating potentials were effectively decreased. This strategy thus generates a new paradigm for lowering the operating potential of hydrogen generation from neutral water without the use of additional acids and organic cosolvents. PMID:23949627
NASA Astrophysics Data System (ADS)
Koenig, Anne; Planat-Chrétien, Anne; Coutard, Jean-Guillaume; Hervé, Lionel; Brambilla, Marco; Josserand, Véronique; Coll, Jean-Luc; Dinten, Jean-Marc
2011-03-01
An instrument dedicated to the co-registration of optical and X-ray measurements is presented: specific acquisition protocol and reconstruction software have been developed for carrying out fluorescence diffuse optical tomography in a cylindrical geometry consistent with XCT. Actual animal geometry provided by the X-ray tomography is used to give animal boundaries to the diffuse optical tomography reconstruction algorithm. To evaluate performances of this new optical imaging system, experiments have been conducted on phantoms, mice with fluorescent capillaries, and finally on mice bearing tumors. The fluorescence reconstructions are shown to be geometrically consistent with X-ray ones. We determined that the sensibility limit of the system to detect fluorescence signal over intrinsic ones is 2 pmol for lungs area and 5 pmol for the abdomen area.
Energies and densities of electrons confined in elliptical and ellipsoidal quantum dots.
Halder, Avik; Kresin, Vitaly V
2016-10-01
We consider a droplet of electrons confined within an external harmonic potential well of elliptical or ellipsoidal shape, a geometry commonly encountered in work with semiconductor quantum dots and other nanoscale or mesoscale structures. For droplet sizes exceeding the effective Bohr radius, the dominant contribution to average system parameters in the Thomas-Fermi approximation comes from the potential energy terms, which allows us to derive expressions describing the electron droplet's shape and dimensions, its density, total and capacitive energy, and chemical potential. The analytical results are in very good agreement with experimental data and numerical calculations, and make it possible to follow the dependence of the properties of the system on its parameters (the total number of electrons, the axial ratios and curvatures of the confinement potential, and the dielectric constant of the material). An interesting feature is that the eccentricity of the electron droplet is not the same as that of its confining potential well. PMID:27502044
NASA Astrophysics Data System (ADS)
Ducharme, R.; da Paz, I. G.
2016-08-01
In two recent papers exact Hermite-Gaussian solutions to relativistic wave equations were obtained for both electromagnetic and particle beams. The solutions for particle beams correspond to those of the Schrödinger equation in the nonrelativistic limit. Here, it will be shown that each beam particle has additional 4-momentum resulting from transverse localization compared to a free particle traveling in the same direction as the beam with the same speed. This will be referred to as the quantum 4-potential term since it will be shown to play an analogous role in relativistic Hamiltonian quantum mechanics as the Bohm potential in the nonrelativistic quantum Hamilton-Jacobi equation. Low-order localization effects include orbital angular momentum, Gouy phase, and beam spreading. Toward a more systematic approach for calculating localization effects at all orders, it will be shown that both the electromagnetic and quantum 4-potentials couple into the canonical 4-momentum of a particle in a similar way. This offers the prospect that traditional methods used to calculate the affect of an electromagnetic field on a particle can now be adapted to take localization effects into account. The prospects for measuring higher order quantum 4-potential related effects experimentally are also discussed alongside some questions to challenge the quantum information and quantum field theorists.
Code of Federal Regulations, 2012 CFR
2007-09-06
... bacterial pathogens like salmonella. Wetlands created from swine waste-water effluent had 5-50 fold greater... Contamination from Animal Waste 228 Farmers for Clean Air & Water, Inc 229 EXAMINATION OF THE POTENTIAL HUMAN... while trying to save him. The waste can increase phosphorus levels in water, causing algal blooms...
NASA Astrophysics Data System (ADS)
Belich, H.; Bakke, K.
2016-03-01
The behavior of a relativistic scalar particle subject to a scalar potential under the effects of the violation of the Lorentz symmetry in the cosmic string space-time is discussed. It is considered two possible scenarios of the Lorentz symmetry breaking in the CPT-even gauge sector of the Standard Model Extension defined by a tensor (KF)μναβ. Then, by introducing a scalar potential as a modification of the mass term of the Klein-Gordon equation, it is shown that the Klein-Gordon equation in the cosmic string space-time is modified by the effects of the Lorentz symmetry violation backgrounds and bound state solution to the Klein-Gordon equation can be obtained.
Manipulation of gel emulsions by variable microchannel geometry.
Surenjav, Enkhtuul; Priest, Craig; Herminghaus, Stephan; Seemann, Ralf
2009-01-21
In this article we investigate the morphology and manipulation of monodisperse emulsions at high dispersed phase volume fractions (gel emulsions) in a microfluidic environment. Confined monodisperse gel emulsions self-organize into well-ordered droplet arrangements, which may be stable or metastable, depending on the geometry of the confining microchannel. Three arrangements are considered, in which the droplets are aligned in a single file, a two row, or a three row arrangement. We explore the potential for induced transitions between these distinct droplet arrangements as a tool for droplet-based microfluidic processing. Transitions are readily achieved by means of localized (geometrical) features in channel geometry, however the onset of the transition is strongly dependent on the subtleties of the microfluidic system, e.g. volume fraction, droplet size, and feature dimensions. The transitions can be achieved via fixed channel features or, when the continuous phase is a ferrofluid, by a virtual channel constriction created using a magnetic field. PMID:19107292
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.
Summhammer, Johann; Salari, Vahid; Bernroider, Gustav
2012-06-01
Voltage-gated channel proteins cooperate in the transmission of membrane potentials between nerve cells. With the recent progress in atomic-scaled biological chemistry, it has now become established that these channel proteins provide highly correlated atomic environments that may maintain electronic coherences even at warm temperatures. Here we demonstrate solutions of the Schrödinger equation that represent the interaction of a single potassium ion within the surrounding carbonyl dipoles in the Berneche-Roux model of the bacterial KcsA model channel. We show that, depending on the surrounding carbonyl-derived potentials, alkali ions can become highly delocalized in the filter region of proteins at warm temperatures. We provide estimations on the temporal evolution of the kinetic energy of ions depending on their interaction with other ions, their location within the oxygen cage of the proteins filter region, and depending on different oscillation frequencies of the surrounding carbonyl groups. Our results provide the first evidence that quantum mechanical properties are needed to explain a fundamental biological property such as ion selectivity in transmembrane ion currents and the effect on gating kinetics and shaping of classical conductances in electrically excitable cells. PMID:22744820
NASA Astrophysics Data System (ADS)
Jido, Daisuke; Sakashita, Minori
2016-08-01
The possibility of having a diquark configuration in heavy baryons, such as Λ and Λ, is examined by a nonrelativistic potential model with a heavy quark and a light scalar diquark. Assuming that the Λ and Λ baryons are composed of the heavy quark and the point-like scalar-isoscalar ud diquark, we solve the two-body Schrödinger equation with the Coulomb plus linear potential and obtain the energy spectra for the heavy baryons. Contrary to our expectation, it is found that the potential determined by the quarkonium spectra fails to reproduce the excitation spectra of the Λ and Λ in the quark-diquark picture, while the Λ and Λ spectra are reproduced with half the strength of the confinement string tension than for the quarkonium. The finite size effect of the diquark is also examined and it is found that the introduction of a finite size diquark would resolve the failure of the spectrum reproduction. The Ξ excitation energy is also calculated and is found to be smaller than Λ in the quark-diquark model. This is not consistent with experimental observations.
Anisotropic de Gennes Narrowing in Confined Fluids
NASA Astrophysics Data System (ADS)
Nygârd, Kim; Buitenhuis, Johan; Kagias, Matias; Jefimovs, Konstantins; Zontone, Federico; Chushkin, Yuriy
2016-04-01
The collective diffusion of dense fluids in spatial confinement is studied by combining high-energy (21 keV) x-ray photon correlation spectroscopy and small-angle x-ray scattering from colloid-filled microfluidic channels. We find the structural relaxation in confinement to be slower compared to the bulk. The collective dynamics is wave vector dependent, akin to the de Gennes narrowing typically observed in bulk fluids. However, in stark contrast to the bulk, the structure factor and de Gennes narrowing in confinement are anisotropic. These experimental observations are essential in order to develop a microscopic theoretical description of collective diffusion of dense fluids in confined geometries.
Rosenfeld, M; Tanami, R; Abboud, S
1996-07-01
The integral conservation equation for biological volume conductors with general geometry and arbitrary distribution of electrical conductivity is solved using a finite volume method. An effective conductivity was defined for the boundaries between regions with abrupt change of the conductivity to allow the simultaneous solution of the entire domain although the derivatives are not continuous. The geometrical singularities arising from the spherical topology of the coordinate system are removed using the conservation law. The resulting finite volume solution method is efficient both in central processing unit (CPU) time and memory requirements, allowing the solution of the volume conductor equation using a large number of mesh points (of the order of 10(5)) even on small workstations (like SGI Indigo). It results in very accurate solutions, as several comparisons with analytical solutions of head models reveal. The proposed finite volume method is an attractive alternative to the finite element and boundary element methods that are more common in bioelectric applications. PMID:9216139
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 Li2O2, Li2CO3, LiOH, or their combinations. Our results suggest Li2CO3 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
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 ɛ 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.
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.
Baye, D; Dohet-Eraly, J
2015-12-21
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. PMID:25732054
NASA Astrophysics Data System (ADS)
Oglesby, David D.; Mai, P. Martin
2012-03-01
Using the 3-D finite-element method, we develop dynamic spontaneous rupture models of earthquakes on the North Anatolian Fault system in the Sea of Marmara, Turkey, considering the geometrical complexity of the fault system in this region. We find that the earthquake size, rupture propagation pattern and ground motion all strongly depend on the interplay between the initial (static) regional pre-stress field and the dynamic stress field radiated by the propagating rupture. By testing several nucleation locations, we observe that those far from an oblique normal fault stepover segment (near Istanbul) lead to large through-going rupture on the entire fault system, whereas nucleation locations closer to the stepover segment tend to produce ruptures that die out in the stepover. However, this pattern can change drastically with only a 10° rotation of the regional stress field. Our simulations also reveal that while dynamic unclamping near fault bends can produce a new mode of supershear rupture propagation, this unclamping has a much smaller effect on the speed of the peak in slip velocity along the fault. Finally, we find that the complex fault geometry leads to a very complex and asymmetric pattern of near-fault ground motion, including greatly amplified ground motion on the insides of fault bends. The ground-motion pattern can change significantly with different hypocentres, even beyond the typical effects of directivity. The results of this study may have implications for seismic hazard in this region, for the dynamics and ground motion of geometrically complex faults, and for the interpretation of kinematic inverse rupture models.
Confinement from spontaneous breaking of scale symmetry
NASA Astrophysics Data System (ADS)
Gaete, Patricio; Guendelman, Eduardo
2006-09-01
We show that one can obtain naturally the confinement of static charges from the spontaneous symmetry breaking of scale invariance in a gauge theory. At the classical level a confining force is obtained and at the quantum level, using a gauge invariant but path-dependent variables formalism, the Cornell confining potential is explicitly obtained. Our procedure answers completely to the requirements by 't Hooft for "perturbative confinement".
NASA Astrophysics Data System (ADS)
Zemánek, Pavel; Šiler, Martin; Brzobohatý, Oto; Jákl, Petr; Filip, Radim
2016-06-01
The noise-to-signal transitions belong to an exciting group of processes in physics. In Filip and Zemánek (2016, J. Opt. 18 065401) we theoretically analyse the stochastic noise-to-signal transition of overdamped Brownian motion of a particle in the cubic potential. In this part, we propose a feasible experimental setup for a proof-of-principle experiment that uses methods of optical trapping in shaped laser beams which provide cubic and quadratic potentials. Theoretical estimates and results from the numerical simulations indicate that the noise-to-signal transition can be observed under realistic experimental conditions.
Oie, Tetsuro
1980-07-28
A purpose of the present studies is twofold: (1) development of an empirical potential function (EDF) and (2) application of it to the studies of photoreaction center chlorophyll a dimer. The reliable estimate of geometric structures and energies of large molecules by quantum mechanical methods is not possible at the present time. An alternative method is, therefore, needed for the studies of large molecular systems, and Chapter I is dedicated to the development of this tool, i.e., an empirical potential function, which could suffice this purpose. Because of a large number of variable chemical compositions and functional groups characteristically present in a large molecule, it is important to include a large number of structurally diverse molecules in the development of the EPF. In Chapter II, the EPF is applied to study the geometrical structure of a chlorophyll a (Ch1 a) dimer, which is believed to exist at the photoreaction center of green plants and is known to play an essential role in photosynthetic energy conversion. Although various models have been proposed for this dimer structure, there is still a great need for information concerning the detailed geometric structure of this dimer. Therefore, in this chapter the structural stabilities of various dimer models are examined by the EPF, and detailed and quantitative information on the structure and stability of these models is provided.
Oie, Tetsuro
1980-01-01
A purpose of the present studies is twofold: (1) development of an empirical potential function (EPF) and (2) application of it to the studies of photoreaction center chlorophyll a dimer. The reliable estimate of geometric structures and energies of large molecules by quantum mechanical methods is not possible at the present time. An alternative method is, therefore, needed for the studies of large molecular systems, and Chapter I is dedicated to the development of this tool, i.e., an empirical potential function, which could suffice this purpose. Because of a large number of variable chemical compositions and functional groups characteristically present in a large molecule, it is important to include a large number of structurally diverse molecules in the development of the EPF. In Chapter II, the EPF is applied to study the geometrical structure of a chlorophyll a (Chl a) dimer, which is believed to exist at the photoreaction center of green plants and is known to play an essential role in photosynthetic energy conversion. Although various models have been proposed for this dimer structure, there is still a great need for information concerning the detailed geometric structure of this dimer. Therefore, in this chapter the structural stabilities of various dimer models are examined by the EPF, and detailed and quantitative information on the structure and stability of these models is provided.
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.
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(NH₂BH₂)nH oligomers result from dehydrogenation of NH₃BH₃ and NH₄BH₄ 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(NH₂BH₂)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 Hδ⁺(N) hydrogens interact with hydridic Hδ⁻(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.
A Review of Quantum Confinement
Connerade, Jean-Patrick
2009-12-03
A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker - henceforth cited as SW - in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell. The
Omogo, Benard; Gao, Feng; Bajwa, Pooja; Kaneko, Mizuho; Heyes, Colin D
2016-04-26
Currently, the most common way to reduce blinking in quantum dots (QDs) is accomplished by using very thick and/or perfectly crystalline CdS shells on CdSe cores. Ideally, a nontoxic material such as ZnS is preferred to be the outer material in order to reduce environmental and cytotoxic effects. Blinking suppression with multishell configurations of CdS and ZnS has been reported only for "giant" QDs of 15 nm or more. One of the main reasons for the limited progress is that the role that interfacial trap states play in blinking in these systems is not very well understood. Here, we show a "Goldilocks" effect to reduce blinking in small (∼7 nm) QDs by carefully controlling the thicknesses of the shells in multishell QDs. Furthermore, by correlating the fluorescence lifetime components with the fraction of time that a QD spends in the on-state, both with and without applying a threshold, we found evidence for two types of blinking that separately affect the average fluorescence lifetime of a single QD. A thorough characterization of the time-resolved fluorescence at the ensemble and single-particle level allowed us to propose a detailed physical model involving both short-lived interfacial trap states and long-lived surface trap states that are coupled. This model highlights a strategy of reducing QD blinking in small QDs by balancing the magnitude of the induced lattice strain, which results in the formation of interfacial trap states between the inner shell and the outer shell, and the confinement potential that determines how accessible the interfacial trap states are. The combination of reducing blinking while maintaining a small overall QD size and using a Cd-free outer shell of ZnS will be useful in a wide array of applications, particularly for advanced bioimaging. PMID:27058120
NASA Astrophysics Data System (ADS)
Cremer, Dieter; Dorofeeva, Olga V.; Mastryukov, Vladimir S.
1981-09-01
Restricted Hartree—Fock calculations on 21 planar and puckered conformers of azetidine have been done employing a split valence basis augmented by d functions. Complete geometry optimizations have been performed for eight conformers. In this way the puckering potential of azetidine is explored over the range -40° < ø (puckering angle) < 40°, for both sp3 and sp2 hybridization of the nitrogen atom. In its equatorial form, azetidine is slightly more puckered than cyclobutane. This is because of a decrease of van der Waals' repulsion between H atoms. Charge effects lead to destabilization of the axial forms. There is only moderate coupling between puckering and methylene group rocking. Previously published electron diffraction (ED) data are reinvestigated using vibrational corrections and information from the ab initio calculations. On the basis of this MO constrained ED (MOCED) analysis a puckering angle φ = 35.1(1.8)° is found. Observed rg and re bond distances are compared with ab initio values.
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…
NASA Astrophysics Data System (ADS)
Magalhães, José; Barbosa, José; Ribeiro, Vanessa; Oliveira, Jefferson; Filho, Osvaldo; Buarque, Bruno
2016-04-01
The study region encompasses a set of three basins located at Northeast Brazilian continental margin: Pernambuco (south sector), Paraíba and Natal platform (north sector). These basins were formed during the last stage of separation between South America and African plates during Cretaceous. The continental breakup in these regions occurred probably during the Middle-Upper Albian (~102 m.y). The adjacent basement rocks belong to Borborema Province (BP), which was formed due a complex superposition between Pre-Cambrian orogenic cycles. The structural framework of BP is dominated by large shear zones that divided this province in three main tectonic domains: South, Central and North. The Pernambuco Basin is located in the South Domain and the Paraíba and Natal platform basins are related to the Central Domain. The tectonic and magmatic evolution of the Pernambuco Basin was influenced by oblique rifting (~ 35° to rift axis) and a thermal anomaly probably caused by the Santa Helena hotspot. The north sector represents a continental shelf characterized by basement high with a narrow platform and an abrupt shelf break on transition to the abyssal plain. The continental platform break of this sector was parallel to the rift axis. In this way, we present a regional structural interpretation of these sectors of Brazilian rifted margin based on interpretation and 2D forward modeling of potential field and 2D seismic data. The magnetic maps (Reduction to magnetic pole and Analytic signal) revealed the influence of an alternating pattern of large narrow magnetic and non-magnetic lineaments, oriented NE-SW, E-W and NW-SE. In the Pernambuco Basin these lineaments (NE-SW and E-W) are related to shear zones in the hyperextended basement which is interpreted as a continuation of the granitic-gneissic and metasedimentary rocks of the South Domain of BP. The Paraíba and Natal platform basins show a slight change in the orientation of structures trending E-W (shear zones in
CCSD(T) calculations of stabilities and properties of confined systems
Holka, F.; Urban, M.; Melicherčík, M.; Neogrády, P.; Paldus, J.
2015-01-22
We analyze energies, electron affinities and polarizabilities of small anions exposed to an external confinement. The second electron in free O{sup 2−} and S{sup 2−} anions is unbound. We investigate the stabilizing effect of the spherical harmonic-oscillator confining potential ω. on these anions employing the Hartree-Fock stability analysis as introduced by Čížek and Paldus. With increasing strength of the external harmonic-oscillator confinement potential ω the broken symmetry (BS) solutions are systematically eliminated. For ω larger than 0.1 all BS solutions for O{sup 2−} disappear. For ω larger than 0.13 the CCSD(T) energy of O{sup 2−} becomes more negative than the energy of the singly charged O{sup −} anion. We relate the harmonic-oscillator confining potential to a crystalline environment in which the O{sup 2−} and S{sup 2−} anions are stable. We also present a model allowing calculations of the in-crystal polarizabilities of anions. The model is based on CCSD(T) calculations of static polarizabilities of selected anions exposed to the spherical harmonic-oscillator confining potential ω This artificial confinement potential ω is then related to the ionic radii of the cation in representative crystal lattices. We investigate the polarizability of O{sup 2−} and S{sup 2−} anions in MgO, MgS, CaO, CaS, SrO, SrS, BaO and BaS crystals. We compare our results with alternative models for in-crystal polarizabilities. External confinement also stabilizes the uracil anion U{sup −}, as is shown by calculations with a stepwise micro-hydration of U{sup −}. Upon hydration is the CCSD(T) adiabatic electron affinity (AEA) of uracil enhanced by about 250 up to 570 meV in comparison with AEA of the isolated molecule, depending on the geometry of the hydrated uracil anion complex. We tried to find an analogy of the stabilization effect of the external confinement on the otherwise unstable anions. In uracil and its anion is the external
NASA Astrophysics Data System (ADS)
Cembranos, J. A. R.; Dobado, A.; Maroto, A. L.
Extra-dimensional theories contain additional degrees of freedom related to the geometry of the extra space which can be interpreted as new particles. Such theories allow to reformulate most of the fundamental problems of physics from a completely different point of view. In this essay, we concentrate on the brane fluctuations which are present in brane-worlds, and how such oscillations of the own space-time geometry along curved extra dimensions can help to resolve the Universe missing mass problem. The energy scales involved in these models are low compared to the Planck scale, and this means that some of the brane fluctuations distinctive signals could be detected in future colliders and in direct or indirect dark matter searches.
Numerical analysis of seismoelectromagnetic field conversion at confined geological units
NASA Astrophysics Data System (ADS)
Kroeger, B.; Kemna, A.
2010-12-01
It is well known that at material boundaries in fluid-saturated porous media, an incoming seismic wave can give rise to electric and magnetic fields due to electrokinetic coupling effects. Given its sensitivity to rock parameters governing fluid flow, this so-called seismoelectromagnetic (or seismoelectric, if only the electric field is considered) interface response is of strong interest with a view to hydro geophysical and petroleum exploration applications. However, the understanding of the correspondence of the converting interface geometry on the one hand and electric and magnetic field characteristics on the other hand is still poor. By means of two-dimensional finite-element modeling in the time domain, we here investigate the character of the seismoelectromagnetic interface response for the special case of spatially confined geological units, which may be representative for clay lenses embedded in an aquifer or petroleum deposits in a host rock. In the numerical analysis we consider the interface response generated by both compressional and shear wave. The modeling results, which are analyzed in terms of snapshots, time slices, and electro and magneto grams, reveal a significant influence of the confined geological units on the generation and character of the seismoelectro-magnetic interface response. The different conversion patterns can be attributed to the induced streaming currents at the interfaces caused by the oscillation of the seismic body waves. Pattern analysis of the interface responses is done with a view to an improved qualitative understanding of their spatio-temporal occurrence and evolution relative to the geometry of the converting interfaces. Our time-lapse simulations illustrate that the seismoelectromagnetic interface response captures characteristics of the geometry of the converting geological unit, indicating the potential of the seismoelectromagnetic method in particular for exploration of confined targets.
Hydrogen-bonded complexes upon spatial confinement: structural and energetic aspects.
Lipkowski, Paweł; Kozłowska, Justyna; Roztoczyńska, Agnieszka; Bartkowiak, Wojciech
2014-01-28
In the present study we consider structural and energetic aspects of spatial confinement of the H-bonded systems. The model dimeric systems: HF···HF, HCN···HCN and HCN···HCCH have been chosen for a case study. Two-dimensional harmonic oscillator potential, mimicking a cylindrical confinement, was applied in order to render the impact of orbital compression on the analyzed molecular complexes. The calculations have been performed employing the MP2 method as well as the Kohn-Sham formulation of density functional theory. In the latter case, two exchange-correlation potentials have been used, namely B3LYP and M06-2X. The geometries of studied complexes have been optimized (without any constraints) in the presence of the applied model confining potential. A thorough analysis of topological parameters characterizing hydrogen bonds upon orbital compression has been performed within the Quantum Theory of Atoms in Molecules (QTAIM). Furthermore, an energetic analysis performed for the confined H-bonded complexes has shown a different trend in the interaction energy changes. Additionally, a variational-perturbational decomposition scheme was applied to study the interaction energy components in the presence of spatial confinement. PMID:24296646
Current-induced skyrmion dynamics in constricted geometries.
Iwasaki, Junichi; Mochizuki, Masahito; Nagaosa, Naoto
2013-10-01
Magnetic skyrmions--vortex-like swirling spin structures with a quantized topological number that are observed in chiral magnets--are appealing for potential applications in spintronics because it is possible to control their motion with ultralow current density. To realize skyrmion-based spintronic devices, it is essential to understand skyrmion motions in confined geometries. Here we show by micromagnetic simulations that the current-induced motion of skyrmions in the presence of geometrical boundaries is very different from that in an infinite plane. In a channel of finite width, transverse confinement results in steady-state characteristics of the skyrmion velocity as a function of current that are similar to those of domain walls in ferromagnets, whereas the transient behaviour depends on the initial distance of the skyrmion from the boundary. Furthermore, we show that a single skyrmion can be created by an electric current in a simple constricted geometry comprising a plate-shaped specimen of suitable size and geometry. These findings could guide the design of skyrmion-based devices in which skyrmions are used as information carriers. PMID:24013132
Anisotropic de Gennes Narrowing in Confined Fluids.
Nygård, Kim; Buitenhuis, Johan; Kagias, Matias; Jefimovs, Konstantins; Zontone, Federico; Chushkin, Yuriy
2016-04-22
The collective diffusion of dense fluids in spatial confinement is studied by combining high-energy (21 keV) x-ray photon correlation spectroscopy and small-angle x-ray scattering from colloid-filled microfluidic channels. We find the structural relaxation in confinement to be slower compared to the bulk. The collective dynamics is wave vector dependent, akin to the de Gennes narrowing typically observed in bulk fluids. However, in stark contrast to the bulk, the structure factor and de Gennes narrowing in confinement are anisotropic. These experimental observations are essential in order to develop a microscopic theoretical description of collective diffusion of dense fluids in confined geometries. PMID:27152823
Longitudinal response of confined semiflexible polymers
NASA Astrophysics Data System (ADS)
Thüroff, Florian; Obermayer, Benedikt; Frey, Erwin
2011-02-01
The longitudinal response of single semiflexible polymers to sudden changes in externally applied forces is known to be controlled by the propagation and relaxation of backbone tension. Under many experimental circumstances, realized, for example, in nanofluidic devices or in polymeric networks or solutions, these polymers are effectively confined in a channel- or tubelike geometry. By means of heuristic scaling laws and rigorous analytical theory, we analyze the tension dynamics of confined semiflexible polymers for various generic experimental setups. It turns out that in contrast to the well-known linear response, the influence of confinement on the nonlinear dynamics can largely be described as that of an effective prestress. We also study the free relaxation of an initially confined chain, finding a surprising superlinear ~t9/8 growth law for the change in end-to-end distance at short times.
Colloidal cholesteric liquid crystal in spherical confinement.
Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S; Lavrentovich, Oleg D; Kumacheva, Eugenia
2016-01-01
The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545
Colloidal cholesteric liquid crystal in spherical confinement
Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia
2016-01-01
The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545
WEST,WP; BURRELL,KH; deGRASSIE,JS; DOYLE,EJ; GREENFIELD,CM; LASNIER,CJ; SNYDER,PB; ZENG,L
2003-08-01
OAK-B135 The quiescent H-mode (QH-mode) is an ELM-free and stationary state mode of operation discovered on DIII-D. This mode achieves H-mode levels of confinement and pedestal pressure while maintaining constant density and radiated power. The elimination of edge localized modes (ELMs) and their large divertor loads while maintaining good confinement and good density control is of interest to next generation tokamaks. This paper reports on the correlations found between selected parameters in a QH-mode database developed from several hundred DIII-D counter injected discharges. Time traces of key plasma parameters from a QH-mode discharge are shown. On DIII-D the negative going plasma current (a) indicates that the beam injection direction is counter to the plasma current direction, a common feature of all QH-modes. The D{sub {alpha}} time behavior (c) shows that soon after high powered beam heating (b) is applied, the discharge makes a transition to ELMing H-mode, then the ELMs disappear, indicating the start of the QH period that lasts for the remainder of the high power beam heating (3.5 s). Previously published work showing density and temperature profiles indicates that long-pulse, high-triangularity QH discharges develop an internal transport barrier in combination with the QH edge barrier. These discharges are known as quiescent, double-barrier discharges (QDB). The H-factor (d) and stored energy (c) rise then saturate at a constant level and the measured axial and minimum safety factors remain above 1.0 for the entire QH duration. During QDB operation the performance of the plasma can be very good, with {beta}{sub N}*H{sub 89L} product reaching 7 for > 10 energy confinement times. These discharges show promise that a stationary state can be achieved.
Tuning the energetics and tailoring the optical properties of silver clusters confined in zeolites.
Fenwick, Oliver; Coutiño-Gonzalez, Eduardo; Grandjean, Didier; Baekelant, Wouter; Richard, Fanny; Bonacchi, Sara; De Vos, Dirk; Lievens, Peter; Roeffaers, Maarten; Hofkens, Johan; Samorì, Paolo
2016-09-01
The integration of metal atoms and clusters in well-defined dielectric cavities is a powerful strategy to impart new properties to them that depend on the size and geometry of the confined space as well as on metal-host electrostatic interactions. Here, we unravel the dependence of the electronic properties of metal clusters on space confinement by studying the ionization potential of silver clusters embedded in four different zeolite environments over a range of silver concentrations. Extensive characterization reveals a strong influence of silver loading and host environment on the cluster ionization potential, which is also correlated to the cluster's optical and structural properties. Through fine-tuning of the zeolite host environment, we demonstrate photoluminescence quantum yields approaching unity. This work extends our understanding of structure-property relationships of small metal clusters and applies this understanding to develop highly photoluminescent materials with potential applications in optoelectronics and bioimaging. PMID:27270964
Simulations of Coulomb systems with slab geometry using an efficient 3D Ewald summation method
NASA Astrophysics Data System (ADS)
dos Santos, Alexandre P.; Girotto, Matheus; Levin, Yan
2016-04-01
We present a new approach to efficiently simulate electrolytes confined between infinite charged walls using a 3d Ewald summation method. The optimal performance is achieved by separating the electrostatic potential produced by the charged walls from the electrostatic potential of electrolyte. The electric field produced by the 3d periodic images of the walls is constant inside the simulation cell, with the field produced by the transverse images of the charged plates canceling out. The non-neutral confined electrolyte in an external potential can be simulated using 3d Ewald summation with a suitable renormalization of the electrostatic energy, to remove a divergence, and a correction that accounts for the conditional convergence of the resulting lattice sum. The new algorithm is at least an order of magnitude more rapid than the usual simulation methods for the slab geometry and can be further sped up by adopting a particle-particle particle-mesh approach.
Bifurcated equilibria in centrifugally confined plasma
Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R.
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.
Convection, evaporation, and condensation of binary fluids in confined geometries
NASA Astrophysics Data System (ADS)
Grigoriev, Roman; Qin, Tongran; Li, Yaofa; Chan, Benjamin; Yoda, Minami
2011-11-01
Phase change has a major effect on convection in liquid layers with a free surface. Significant latent heat generated at the free surface as a result of phase change can dramatically alter the interfacial temperature, inducing thermocapillary stresses. For binary fluids, differential evaporation leads to a variation in the concentration, and hence, induces solutocapillary stresses. This talk describes numerical and experimental studies of convection in alcohol-water mixtures due to a horizontal temperature gradient in the presence of phase change. Evaporation and condensation is known to be a notoriously difficult problem to model due to a poorly defined vapor transport problem which is strongly influenced by the presence/absence and flows of non-condensable gases (e.g., air). This issue is addressed by using a sealed cuvette heated at one end and cooled at the other. Both numerics and experiments show that, by adding or removing air from the cuvette, the direction of flow in a liquid layer covering the bottom of the cell can be reversed by emphasizing either thermocapillary or solutocapillary stresses. Supported by ONR.
Dynamics of rod eutectic growth patterns in confined geometry
NASA Astrophysics Data System (ADS)
Şerefoǧlu, Melis; Bottin-Rousseau, S.; Akamatsu, S.; Faivre, G.
2012-01-01
The dynamics of rod-like eutectics are examined using a directional solidification setup, which allows real-time observation of the whole solidification front in specimens of transparent eutectic alloys -here, succinonitrile-(D)camphor. In steady-state, rod eutectic growth patterns consist of triangular arrays, more or less disturbed by topological defects. In the absence of strong convection and of crystallographic anisotropy, the long-time evolution of the pattern is dominated by "imperfections" of the system, such as misalignment of the temperature gradient, and finite-size. In this study, we present experimental results on the finite-size effects on rod eutectics and show that a rod to lamella transition takes place as a result of finite-size effect only, at a given alloy concentration.
Diffusion of micrometer-sized soft particles in confinement
NASA Astrophysics Data System (ADS)
Jordan, Benjamin; Aptowicz, Kevin
We investigate the diffusion of micrometer sized poly(N-isopropylacrylamide) (PNIPAM) gel particles in confinement. The influence of confinement on the transport of small particles is becoming increasingly important for microfluidics and bio-fluidics. Analytical solutions to this problem are limited to very unique geometries or gross approximations. Computational methods have provided more insight into the problem as well as experimental investigations. However, most research has focused on the hard-sphere problem. In this work, we will explore the diffusion of soft particles in confinement. The dynamics of the particles confined between two parallel walls is captured with video-microscopy. In addition, we use a recently developed technique to measurement confinement of particles in-situ with a precision of 1%. This poster will present some preliminary results of how confinement affects the diffusion of these soft particles. We acknowledge support from Grant DMR-1206231.
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.
Protein Folding in Confined and Crowded Environments
Zhou, Huan-Xiang
2007-01-01
Confinement and crowding are two major factors that can potentially impact protein folding in cellular environments. Theories based on considerations of excluded volumes predict disparate effects on protein folding stability for confinement and crowding: confinement can stabilize proteins by over 10kBT but crowding has a very modest effect on stability. On the other hand, confinement and crowding are both predicted to favor conformations of the unfolded state which are compact, and consequently may increase the folding rate. These predictions are largely borne out by experimental studies of protein folding under confined and crowded conditions in the test tube. Protein folding in cellular environments is further complicated by interactions with surrounding surfaces and other factors. Concerted theoretical modeling and test-tube and in vivo experiments promise to elucidate the complexity of protein folding in cellular environments. PMID:17719556
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…
Confinement from constant field condensates
NASA Astrophysics Data System (ADS)
Gaete, Patricio; Guendelman, Eduardo; Spallucci, Euro
2007-01-01
For (2 + 1)- and (3 + 1)-dimensional reformulated SU (2) Yang-Mills theory, we compute the interaction potential within the framework of the gauge-invariant but path-dependent variables formalism. This reformulation is due to the presence of a constant gauge field condensate. Our results show that the interaction energy contains a linear term leading to the confinement of static probe charges. This result is equivalent to that of the massive Schwinger model.
Confinement of block copolymers
1995-12-31
The following were studied: confinement of block copolymers, free surface confinement, effects of substrate interactions, random copolymers at homopolymer interfaces, phase separation in thin film polymer mixtures, buffing of polymer surfaces, and near edge x-ray absorption fine structure spectroscopy.
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…
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
Elastic membranes in confinement.
Bostwick, J B; Miksis, M J; Davis, S H
2016-07-01
An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. PMID:27440257
Casimir effects for classical and quantum liquids in slab geometry: A brief review
Biswas, Shyamal
2015-05-15
We analytically explore Casimir effects for confinement of classical and quantum fluctuations in slab (film) geometry (i) for classical (critical) fluctuations over {sup 4}He liquid around the λ 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.
Effects of confinement on nanoparticle flows
NASA Astrophysics Data System (ADS)
Conrad, Jacinta
The transport properties of nanoparticles that are dispersed in complex fluids and flowed through narrow confining geometries affect a wide range of materials shaping and forming processes, including three-dimensional printing and nanocomposite processing. Here, I will describe two sets of experiments in which we use optical microscopy to probe the structure and transport properties of suspensions of particles that are confined geometrically. First, we investigate the structure and flow properties of dense suspensions of submicron particles, in which the particles interact via an entropic depletion attraction, that are confined in thin films and microchannels. Second, we characterize the transport properties of nanoparticles, dispersed at low concentration in water or in aqueous solutions of high-molecular weight polymers, that are confined in regular arrays of nanoposts or in disordered porous media. I will discuss our results and their practical implications for materials processing as well as for other applications that require confined transport of nanomaterials through complex media. Welch Foundation (E-1869) and NSF (CBET-1438204).
Elastic membranes in confinement
NASA Astrophysics Data System (ADS)
Bostwick, Joshua; Miksis, Michael; Davis, Stephen
2014-11-01
An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and DNA, have finer internal structure in which a membrane (or elastic member) is geometrically ``confined'' by another object. We study the shape stability of elastic membranes in a ``confining'' box and introduce repulsive van der Waals forces to prevent the membrane from intersecting the wall. We aim to define the parameter space associated with mitochondria-like deformations. We compare the confined to `unconfined' solutions and show how the structure and stability of the membrane shapes changes with the system parameters.
Arp, O.; Block, D.; Klindworth, M.; Piel, A.
2005-12-15
A model for the confinement of the recently discovered Coulomb balls is proposed. These spherical three-dimensional plasma crystals are trapped inside a rf discharge under gravity conditions and show an unusual structural order in complex plasmas. Measurements of the thermophoretic force acting on the trapped dust particles and simulations of the plasma properties of the discharge are presented. The proposed model of confinement considers thermophoretic, ion-drag, and electric field forces, and shows excellent agreement with the observations. The findings suggest that self-confinement does not significantly contribute to the structural properties of Coulomb balls.
Confinement effects of polymers in porous glasses
NASA Astrophysics Data System (ADS)
Crupi, V.; Majolino, D.; Migliardo, P.; Venuti, V.
1998-07-01
Recently, confinement effects on dynamical properties of liquids inside restricted volumes have been extensively studied, either from a theoretical or technological point of view, thanks to the large possibility of industrial applications (building of optical switches, membrane separation, catalysis). We performed depolarized light scattering measurements on propylene glycol (PG) and its oligomers poly(propylene glycols) (PPG) having different molecular weights ( Mw, 425, 725 and 4000 Da), in the bulk state and confined in a silica glass having 25 Å pores. Mainly, two relevant effects are responsible for the dynamical response of liquids that diffuse and reorient in a confined geometry: (a) the 'physical traps', related to both dead-end groups and the tortuosity of the percolated channels for diffusion; and (b) the 'chemical traps', related to the degree of the absorption of molecules on the active surface sites. Hence, by comparing the behaviour of bulk polymers with confined polymers we were able to analyse the confinement influence on the molecular mobility of hydrogen-bonded liquids with different steric hindrance. The experimental results showed a frustration of molecular mobility in the confined samples owing to chemical and physical traps whose main role was highlighted thanks to the opportunity to substitute the active silanol groups (SiOH) in the inner surfaces with the non-active groups in the surfaces (treatment with methanol). In particular, we found that, in the case of low molecular weight samples, the relevant retardation process is connected to the chemical traps while for long chain polymers the physical traps play the main role. Further, the fitting procedure provided a distribution of relaxation times in the bulk systems and in short chain systems when confined in modified glass showing, in particular in the first case, that the distribution of relaxation times increases with polymers weights, occurrence related to a variety of molecular
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.
ERIC Educational Resources Information Center
Cukier, Mimi; Asdourian, Tony; Thakker, Anand
2012-01-01
Geometry provides a natural window into what it is like to do mathematics. In the world of geometry, playful experimentation is often more fruitful than following a procedure, and logic plus a few axioms can open new worlds. Nonetheless, teaching a geometry course in a way that combines both rigor and play can be difficult. Many geometry courses…
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…
Polymer Crystallization under Confinement
NASA Astrophysics Data System (ADS)
Floudas, George
Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.
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.
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 μ , 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
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 μ, 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
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.
Structural and electronic properties of sodium clusters under confinement
NASA Astrophysics Data System (ADS)
Nagare, Balasaheb J.; Kanhere, Dilip G.; Chacko, Sajeev
2015-02-01
Using real-space density functional theory, electronic structure and equilibrium geometries of sodium clusters in the size range of 2-20 atoms have been calculated as a function of confinement. We have examined the evolution of the five lowest isomers as a function of volume for six different compressions. The minimum volume considered is about 1 /15 to 1 /10 of the free-space box volume. We observe a strong tendency for isomeric transitions in many cases, with the higher isomers evolving into the ground state under confinement. In general the clusters tend to become more spherical. The changes in the total energies and the geometries are not significant until the volume gets reduced beyond the 1/3 of the original volume. In this sense, the clusters are not easy to compress. Once the critical volume is reached, the changes in the total energies and geometries are rapid. It turns out that the increase in the total energy is mainly due to the ion-ion and Hartree energies of electrons. We also address how anisotropic confinement affects the geometry of clusters. We further show that geometries obtained with anisotropic confinement are strongly supported by the simulation of clusters inside a carbon nanotube using a hybrid quantum-mechanical and molecular-mechanics approach.
The development of a laterally confined laboratory fan delta under sediment supply reduction
NASA Astrophysics Data System (ADS)
Zhang, Xiaofeng; Wang, Siqiang; Wu, Xi; Xu, Shun; Li, Zhangyong
2016-03-01
In previous fan delta experiments, the effect of lateral confinement was generally ignored as these fans were usually unconfined with semiconical geometries. However, in gorge areas, fan development is usually laterally confined by valley walls. This study investigates autogenic processes of fan deltas in a laterally confined experimental tank. The experiment is divided into three phases. The sediment supply is held constant within each phase, so the autogenic processes of the fan are separated from the allogenic forcings. Results indicate that laterally confined fan deltas have higher progradation and aggradation potential, more regular channel braiding, and more even transverse sedimentation than unconfined fans. Besides, responses of fan deltas to sediment supply reduction are investigated in this research. At the initiation of the second and third phases, sediment feed rates are instantaneously reduced so that the allogenic forcings are predominant. Observations show that under sediment supply reduction, channelization on fan deltas are more pronounced and durations of the fluvial cycles are longer. The adjustment of fan morphology becomes slower as the self-regulation capacity of the fan decreases with reduced sediment supply.
Hot electron confinement in a microwave heated spindle cusp
NASA Astrophysics Data System (ADS)
Prelas, M. A.
1991-08-01
The Plasma Research Laboratory at the University of Missouri-Columbia was established with awards from the McDonnell Douglas Foundation, ARMCO, Union Electric, Black and Vetch, Kansas City Power and Light, the National Science Foundation, and DOE. The Plasma Research Lab's major effort is the Missouri Magnetic Mirror (MMM or M(exp 3)) Project. The technical goals of MMM have been (1) Diagnostic Development, (2) Plasma Physics in the Cusp geometry, (3) plasma-wall interactions, (4) impurity effects in a steady-state plasma, and (5) Development of Diagnostics for use in harsh plasma processing environments. The other major goal of MMM has remained providing a facility for hands-on training in experimental plasma physics. The major experimental facility of MMM is the MMM Modified Experiment (M4X). Other research efforts in the Plasma Research Laboratory include small efforts in cold fusion, toroidal magnetic confinement, and inertial confinement and a potentially major effort in direct conversion of nuclear energy.
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.
Investigation of failure mode transition in ceramics under confinement
Ravichandran, G.; Chen, W.; Ortiz, M.
1995-12-31
A newly developed experimental technique is used to investigate the failure behavior of ceramics in multi-axial compression. The axial loading is provided by a split Kolsky (Hopkinson) compression bar and the radial confinement is provided by shrink fit sleeves on the cylindrical specimens. Confinement pressures on the order of 1 GPa have been achieved. As the confinement is increased on the specimen, the failure mode changes from axial splitting under no confinement to conical faulting under moderate confinement. Experimental data have been obtained for several engineering ceramics in the strain rate range of 10{sup -3} to 10{sup 3} s{sup -1}. The peak or failure strength increases with increasing confinement. The increase in strength over its unconfined strength for a given level of confinement remains independent of the strain rate. The data from multiaxial loading experiments suggest that the engineering ceramics follow the Drucker-Prager model for pressure sensitive dilatant materials. This model is used to predict the localization modes in axi-symmetric geometries. The predictions are compared with experimental results for the limit load and the geometry of the fault. The implications of the proposed constitutive and failure model for the performance of engineering ceramics under multi-axial loading are discussed.
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, χ2 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.
NASA Astrophysics Data System (ADS)
Lourenço, S. A.; Teodoro, M. D.; González-Borrero, P. P.; Dias, I. F. L.; Duarte, J. L.; Marega, E.; Salamo, G. J.
2012-06-01
The competition between confinement potential fluctuations and band-gap renormalization (BGR) in GaAs/AlxGaAs quantum wells grown on [1 0 0] and [3 1 1]A GaAs substrates is evaluated. The results clearly demonstrate the coexistence of the band-tail states filling related to potential fluctuations and the band-gap renormalization caused by an increase in the density of photogenerated carriers during the photoluminescence (PL) experiments. Both phenomena have strong influence on temperature dependence of the PL-peak energy (EPL(T)). As the photon density increases, the EPL can shift to either higher or lower energies, depending on the sample temperature. The temperature at which the displacement changes from a blueshift to a redshift is governed by the magnitude of the potential fluctuations and by the variation of BGR with excitation density. A simple band-tail model with a Gaussian-like distribution of the density of state was used to describe the competition between the band-tail filling and the BGR effects on EPL(T).
Learning Geometry through Dynamic Geometry Software
ERIC Educational Resources Information Center
Forsythe, Sue
2007-01-01
In this article, the author investigates effective teaching and learning of geometrical concepts using dynamic geometry software (DGS). Based from her students' reactions to her project, the author found that her students' understanding of the concepts was better than if they had learned geometry through paper-based tasks. However, mixing computer…
Interfacial electrofluidics in confined systems
Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A.; Zhou, Guofu (G.F.)
2016-01-01
Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it’s potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films. PMID:27221211
Interfacial electrofluidics in confined systems
NASA Astrophysics Data System (ADS)
Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A.; Zhou, Guofu (G. F.)
2016-05-01
Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it’s potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films.
Interfacial electrofluidics in confined systems.
Tang, Biao; Groenewold, Jan; Zhou, Min; Hayes, Robert A; Zhou, Guofu G F
2016-01-01
Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it's potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films. PMID:27221211
Confinement & Stability in MAST
NASA Astrophysics Data System (ADS)
Akers, Rob
2001-10-01
Transition to H-mode has been achieved in the MAST spherical tokamak (ST) for both ohmically and neutral beam heated plasmas (P_NBI ~ 0.5-1.5MW), resulting in double-null diverted discharges containing both regular and irregular edge localised modes (ELMs). The observed L-H power threshold is ~10 times higher than predicted by established empirical scalings. L-H transition in MAST is accompanied by a sharp increase in edge density gradient, the efficient conversion of internal electron Bernstein waves into free space waves, the onset and saturation of edge poloidal rotation and a marked decrease in turbulence. During ELM free periods, a reduction in outboard power deposition width is observed using a Langmuir probe array. A novel divertor structure has been installed to counter the resulting increase in target heat-flux by applying a toroidally varying potential to the divertor plasma, theory suggesting that convective broadening of the scrape off layer will take place. Global confinement in H-mode is found to routinely exceed the international IPB(y,2) scaling, even for discharges approaching the Greenwald density. In an attempt to further extend the density range (densities in excess of Greenwald having been achieved for plasma currents up to 0.8MA) a multi-pellet injector has been installed at the low-field-side. In addition, high field side fuelling can be supplied via a gas-feed located at the centre-column mid-plane, this technique having been found to significantly enhance H-mode accessibility and quality. A range of stability issues will be discussed, including vertical displacement events, the rich variety of high frequency MHD seen in MAST and the physics of the Neoclassical Tearing Mode. This work was funded by the UK Department of Trade and Industry and by EURATOM. The NBI equipment is on loan from ORNL and the pellet injector was provided by FOM.
Condensation of topological defects and confinement
NASA Astrophysics Data System (ADS)
Gaete, Patricio; Wotzasek, Clovis
2004-11-01
We study the static quantum potential for a theory of antisymmetric tensor fields that results from the condensation of topological defects, within the framework of the gauge-invariant but path-dependent variables formalism. Our calculations show that the interaction energy is the sum of a Yukawa and a linear potentials, leading to the confinement of static probe charges.
On scale symmetry breaking and confinement in D = 3 models
NASA Astrophysics Data System (ADS)
Gaete, Patricio; Helaÿel-Neto, José A.
2008-10-01
Within the framework of the gauge-invariant, but path-dependent, variables formalism, we study the connection between scale symmetry breaking and confinement in three-dimensional gluodynamics. We explicitly show that the static potential profile contains a linear potential, leading to the confinement of static charges. Also, we establish a new type of equivalence among different three-dimensional effective theories.