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Streaks to Rings to Vortex Grids: Generic Patterns in Transient Convective Spin Up of an Evaporating Fluid

Physical Review Letters 2010年第4期105卷 044504-044504页

作者： J.-Q. Zhong M. D. Patterson J. S. Wettlaufer Department of Geology & Geophysics Yale University New Haven Connecticut 06520-8109 USA Faculty of Engineering & Design University of Bath Bath BA2 7AY United Kingdom Department of Physics Yale University New Haven Connecticut 06520-8109 USA Program in Applied Mathematics Yale University New Haven Connecticut 06520-8109 USA

We observe the transient formation of a ringed pattern state during spin up of an evaporating fluid on a time scale of order a few Ekman spin up times. The ringed state is probed using infrared thermometry and particle image velocimetry and it is demonstrated to be a consequence of the transient balance between Coriolis and viscous forces which dominate inertia, each of which are extracted from the measured velocity field. The breakdown of the ringed state is quantified in terms of the antiphasing of these force components which drives a Kelvin-Helmholtz instability and we show that the resulting vortex grid spacing scales with the ring wavelength. This is the fundamental route to quasi-two-dimensional turbulent vortex flow and thus may have implications in astrophysics and geophysics wherein rotating convection is ubiquitous.

关键词： Vortex flow

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A solution for the two-dimensional transport equation for photons and electrons in a rectangular domain by the Laplace transform technique

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International Journal of Nuclear Energy Science and Technology 2010年第1期5卷 25-40页

作者： Do Amaral Rodriguez, Bárbara D. Vilhena, Marco Túllio Borges, Volnei Instituto de Matemática Estatística e Física Universidade Federal Do Rio Grande - FURG Campus Carreiros Av. Itália Km 8 s/n Rio Grande Rio Grande do Sul Brazil Pure and Applied Mathematics Department Universidade Federal Do Rio Grande Do sul - UFRGS Avenida Bento Gonçalves 9500 Porto Alegre Rio Grande do Sul Brazil Mechanical Engineering Post-Graduation Program Universidade Federal Rio Grande Do sul - UFRGS Rua Sarmento Leite 425 sala 314 Porto Alegre Rio Grande do Sul Brazil

In the first part of this paper, we describe a review in the Laplace transform technique applied to SN two-dimensional transport equation in a rectangular domain considering Compton scattering. In Compton scattering the incident photon interacts with an electron of the irradiated medium, giving the electron kinetic energy, and also producing a scattered photon. In order to track that electron, in the second part of this paper, we apply the P N approximation to X,Y-geometry electron transport problems. In this derivation, the energy deposited by the free electron is taken into account. To reach this objective we solve two model problems: the first one for the transport of photons, assuming the Klein-Nishina scattering kernel as the scattering differential cross-section as well as the multigroup model in the energy variable;and the second one for the transport of free electrons considering the screened Rutherford scattering kernel. The results are presented under absorbed energy form in several points of interest. We report numerical simulations and comparisons with results obtained by using the Geant4 version 9.1 program which applies the Monte Carlo's technique to low energy libraries for both two-dimensional problems. Copyright © 2010 Inderscience Enterprises Ltd.

关键词： Photons

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Phase behavior of colloidal superballs: Shape interpolation from spheres to cubes

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Physical Review E 2010年第6期81卷 061105-061105页

作者： Robert D. Batten Frank H. Stillinger Salvatore Torquato Department of Chemical Engineering Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08544 USA

The phase behavior of hard superballs is examined using molecular dynamics within a deformable periodic simulation box. A superball’s interior is defined by the inequality |x|2q+|y|2q+|z|2q≤1, which provides a versatile family of convex particles (q≥0.5) with cubelike and octahedronlike shapes as well as concave particles (q<0.5) with octahedronlike shapes. Here, we consider the convex case with a deformation parameter q between the sphere point (q=1) and the cube (q=∞). We find that the asphericity plays a significant role in the extent of cubatic ordering of both the liquid and crystal phases. Calculation of the first few virial coefficients shows that superballs that are visually similar to cubes can have low-density equations of state closer to spheres than to cubes. Dense liquids of superballs display cubatic orientational order that extends over several particle lengths only for large q. Along the ordered, high-density equation of state, superballs with 1

关键词： Spheres

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Nonspherical laser-induced cavitation bubbles

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Physical Review E 2010年第1期81卷 016308-016308页

作者： Kang Yuan Lim Pedro A. Quinto-Su Evert Klaseboer Boo Cheong Khoo Vasan Venugopalan Claus-Dieter Ohl Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 637371 Singapore Institute of High Performance Computing Fusionopolis 1 Fusionopolis Way #16-16 Connexis Singapore 138632 Singapore Department of Mechanical Engineering National University of Singapore 10 Kent Ridge Crescent Singapore 119260 Singapore Department of Chemical Engineering and Materials Science and Laser Microbeam and Medical Program Beckman Laser Institute University of California Irvine California 92697-2575 USA

The generation of arbitrarily shaped nonspherical laser-induced cavitation bubbles is demonstrated with a optical technique. The nonspherical bubbles are formed using laser intensity patterns shaped by a spatial light modulator using linear absorption inside a liquid gap with a thickness of 40 μm. In particular we demonstrate the dynamics of elliptic, toroidal, square, and V-shaped bubbles. The bubble dynamics is recorded with a high-speed camera at framing rates of up to 300 000 frames per second. The observed bubble evolution is compared to predictions from an axisymmetric boundary element simulation which provides good qualitative agreement. Interesting dynamic features that are observed in both the experiment and simulation include the inversion of the major and minor axis for elliptical bubbles, the rotation of the shape for square bubbles, and the formation of a unidirectional jet for V-shaped bubbles. Further we demonstrate that specific bubble shapes can either be formed directly through the intensity distribution of a single laser focus, or indirectly using secondary bubbles that either confine the central bubble or coalesce with the main bubble. The former approach provides the ability to generate in principle any complex bubble geometry.

关键词： High speed cameras

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An inventory of potentially habitable environments on Mars: Geological and biological perspectives

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Special Paper of the Geological Society of America 2011年 483卷 317-347页

作者： Dohm, J.M. Miyamoto, H. Ori, G.G. Fairén, A.G. Davila, A.F. Komatsu, G. Mahaney, W.C. Williams, J.-P. Joye, S.B. Di Achille, G. Oehler, D.Z. Marzo, G.A. Schulze-Makuch, D. Acocella, V. Glamoclija, M. Pondrelli, M. Boston, P. Hart, K.M. Anderson, R.C. Baker, V.R. Fink, W. Kelleher, B.P. Furfaro, R. Gross, C. Hare, T.M. Frazer, A.R. Ip, F. Allen, C.C.R. Kim, K.J. Maruyama, S. McGuire, P.C. Netoff, D. Parnell, J. Wendt, L. Wheelock, S.J. Steele, A. Hancock, R.G.V. Havics, R.A. Costa, P. Krinsley, D. Department of Hydrology and Water Resources University of Arizona Tucson AZ United States University Museum Tokyo Japan International Research School of Planetary Sciences Università d'Annunzio Pescara Italy Space Sciences and Astrobiology Division National Aeronautics and Space Administration Ames Research Center Moffett Field CA United States SETI Institute Mountain View CA United States Planetary Exploration Research Center Chiba Institute of Technology Chiba Japan Quaternary Surveys Toronto ON Canada Division of Geological and Planetary Sciences California Institute of Technology Pasadena CA United States Ashima Research Pasadena CA United States Department of Marine Sciences University of Georgia Athens GA United States Laboratory for Atmospheric and Space Physics University of Colorado Boulder CO United States Astromaterials Research and Exploration Science NASA Johnson Space Center Houston TX United States Bay Area Environmental Research Institute Sonoma CA United States School of Earth and Environmental Sciences Washington State University Pullman WA United States Dipartimento Science Geologiche Università Roma Tre Rome Italy Geophysical Laboratory Carnegie Institution of Washington Carnegie WA United States Department of Earth and Environmental Science New Mexico Tech Socorro NM United States School of Chemical Sciences Dublin City University Dublin Ireland Jet Propulsion Laboratory California Institute of Technology Pasadena CA United States Division of Physics Mathematics and Astronomy California Institute of Technology Pasadena CA United States Departments of Electrical and Computer Engineering and Biomedical Engineering University of Arizona Tucson AZ United States Department of Aerospace and Mechanical Engineering University of Arizona Tucson AZ United States Institute of Geological Sciences-Planetary Sciences and Remote Sensing Freie Universität Berlin Malteserstrasse Berlin Germany U.S. Geological Survey Flagstaff

ISBN: (纸本)9780813724836

On Earth, biology, hydrology, and geology are interlinked such that certain types of life are often associated with specifi c conditions, including rock type, pressure, temperature, and chemistry. Life on Earth has established itself in diverse and extreme niches, presenting the possibility that Mars, too, may hold records of fossilized and/or extant life in diverse environments. Geologic, paleohydrologic, and climatic conditions through the evolution of Mars are similar in many respects to conditions occurring during the evolution of Earth and, as such, may point to environments on Mars with potential to have supported living systems. Here, we discuss examples of those Martian settings. Such extraterrestrial environments should be targeted by international robotic and/or manned missions to explore potential fossilized or extant life on Mars. © 2011 Geological Society of America.

关键词： Geology

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Exact constructions of a family of dense periodic packings of tetrahedra

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Physical Review E 2010年第4期81卷 041310-041310页

作者： S. Torquato Y. Jiao Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08540 USA Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA

The determination of the densest packings of regular tetrahedra (one of the five Platonic solids) is attracting great attention as evidenced by the rapid pace at which packing records are being broken and the fascinating packing structures that have emerged. Here we provide the most general analytical formulation to date to construct dense periodic packings of tetrahedra with four particles per fundamental cell. This analysis results in six-parameter family of dense tetrahedron packings that includes as special cases recently discovered “dimer” packings of tetrahedra, including the densest known packings with density ϕ=40004671=0.856347…. This study strongly suggests that the latter set of packings are the densest among all packings with a four-particle basis. Whether they are the densest packings of tetrahedra among all packings is an open question, but we offer remarks about this issue. Moreover, we describe a procedure that provides estimates of upper bounds on the maximal density of tetrahedron packings, which could aid in assessing the packing efficiency of candidate dense packings.

关键词： constructions family tetrahedra tetrahedrons family Dense Platonic solid

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Origin of broad polydispersion in functionalized dendrimers and its effects on cancer-cell binding affinity

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Physical Review E 2010年第3期82卷 036108-036108页

作者： Jack N. Waddell Douglas G. Mullen Bradford G. Orr Mark M. Banaszak Holl Leonard M. Sander Department of Mathematics University of Michigan Ann Arbor Michigan 48109 USA Program in Macromolecular Science and Engineering Ann Arbor Michigan 48109 USA Michigan Nanotechnology Institute for Medicine and Biological Sciences Ann Arbor Michigan 48109 USA Michigan Nanotechnology Institute for Medicine and Biological Sciences University of Michigan Ann Arbor Michigan 48109 USA Program in Applied Physics University of Michigan Ann Arbor Michigan 48109 USA Department of Physics University of Michigan Ann Arbor Michigan 48109 USA Department of Chemistry University of Michigan Ann Arbor Michigan 48109 USA Michigan Center for Theoretical Physics University of Michigan Ann Arbor Michigan 48109 USA

Nanoparticles with multiple ligands have been proposed for use in nanomedicine. The multiple targeting ligands on each nanoparticle can bind to several locations on a cell surface facilitating both drug targeting and uptake. Experiments show that the distribution of conjugated ligands is unexpectedly broad, and the desorption rate appears to depend exponentially upon the mean number of attached ligands. These two findings are explained with a model in which ligands conjugate to the nanoparticle with a positive cooperativity of ≈4 kT, and that nanoparticles bound to a surface by multiple bonds are permanently affixed. This drives new analysis of the data, which confirms that there is only one time constant for desorption, that of a nanoparticle bound to the surface by a single bond.

关键词： Nanoparticles

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Dislocation climb strengthening in systems with immobile obstacles: Three-dimensional level-set simulation study

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Physical Review B 2010年第5期81卷 054104-054104页

作者： Zi Chen Kevin T. Chu David J. Srolovitz Jeffrey M. Rickman Mikko P. Haataja Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08540 USA Princeton Institute for the Science and Technology of Materials (PRISM) Princeton University Princeton New Jersey 08540 USA Vitamin D Inc. Menlo Park California 94025 USA Institute of High Performance Computing Singapore Singapore Department of Materials Science and Engineering Lehigh University Bethlehem Pennsylvania 18015 USA Department of Physics Lehigh University Bethlehem Pennsylvania 18015 USA Program in Applied and Computational Mathematics (PACM) Princeton University Princeton New Jersey 08540 USA

We employ a parallel, three-dimensional level-set code to simulate the dynamics of isolated dislocation lines and loops in an obstacle-rich environment. This system serves as a convenient prototype of those in which extended, one-dimensional objects interact with obstacles and the out-of-plane motion of these objects is key to understanding their pinning-depinning behavior. In contrast to earlier models of dislocation motion, we incorporate long-ranged interactions among dislocation segments and obstacles to study the effect of climb on dislocation dynamics in the presence of misfitting penetrable obstacles/solutes, as embodied in an effective climb mobility. Our main observations are as follows. First, increasing climb mobility leads to more effective pinning by the obstacles, implying increased strengthening. Second, decreasing the range of interactions significantly reduces the effect of climb. The dependence of the critical stress on obstacle concentration and misfit strength is also explored and compared with existing models. In particular, our results are shown to be in reasonable agreement with the Friedel-Suzuki theory. Finally, the limitations inherent in the simplified model employed here, including the neglect of some lattice effects and the use of a coarse-grained climb mobility, are discussed.

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Renormalized spectral function for Co adatom on the Pt(111) surface

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Physical Review B 2010年第19期82卷 193403-193403页

作者： V. V. Mazurenko S. N. Iskakov A. N. Rudenko V. I. Anisimov A. I. Lichtenstein Theoretical Physics and Applied Mathematics Department Ural Federal University Mira Str. 19 620002 Ekaterinburg Russia Institute of Theoretical Physics University of Hamburg Jungiusstrasse 9 20355 Hamburg Germany Institute of Chemical Reaction Engineering Hamburg University of Technology Eissendorfer Str. 38 21073 Hamburg Germany Institute of Metal Physics Russian Academy of Sciences 620219 Ekaterinburg GSP-170 Russia

The strong Coulomb correlations effects in the electronic structure of magnetic Co adatom on the Pt(111) surface have been investigated. Using a realistic five d-orbital impurity Anderson model at low temperatures with parameters determined from first-principles calculations we found a striking change in the electronic structure in comparison with the local density approximation results. The spectral function calculated with full rotationally invariant Coulomb interaction is in good agreement with the quasiparticle region of the scanning tunneling spectroscopy conductance spectrum. Using the calculated spin-spin correlation functions we have analyzed the formation of the magnetic moments of the Co impurity orbitals.

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Ergodic directional switching in mobile insect groups

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Physical Review E 2010年第1期82卷 011926-011926页

作者： Carlos Escudero Christian A. Yates Jerome Buhl Iain D. Couzin Radek Erban Ioannis G. Kevrekidis Philip K. Maini ICMAT (CSIC-UAM-UC3M-UCM) Departamento de Matemáticas Facultad de Ciencias Universidad Autónoma de Madrid Ciudad Universitaria de Cantoblanco 28049 Madrid Spain Centre for Mathematical Biology Mathematical Institute University of Oxford 24-29 St. Giles’ Oxford OX1 3LB United Kingdom School of Biological Sciences and Centre for Mathematical Biology Heydon-Laurence Building A08 The University of Sydney Sydney New South Wales Australia Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey 08544 USA Oxford Centre for Collaborative Applied Mathematics Mathematical Institute University of Oxford 24-29 St. Giles’ Oxford OX1 3LB United Kingdom Department of Chemical Engineering Program in Applied and Computational Mathematics and Mathematics Princeton University Princeton New Jersey 08544 USA Department of Biochemistry Oxford Centre for Integrative Systems Biology University of Oxford South Parks Road Oxford OX1 3QU United Kingdom

We obtain a Fokker-Planck equation describing experimental data on the collective motion of locusts. The noise is of internal origin and due to the discrete character and finite number of constituents of the swarm. The stationary probability distribution shows a rich phenomenology including nonmonotonic behavior of several order and disorder transition indicators in noise intensity. This complex behavior arises naturally as a result of the randomness in the system. Its counterintuitive character challenges standard interpretations of noise induced transitions and calls for an extension of this theory in order to capture the behavior of certain classes of biologically motivated models. Our results suggest that the collective switches of the group’s direction of motion might be due to a random ergodic effect and, as such, they are inherent to group formation.

关键词： Fokker Planck equation

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