Fortran programs for the time-dependent Gross-Pitaevskii equation in a fully anisotropic trap
NASA Astrophysics Data System (ADS)
Muruganandam, P.; Adhikari, S. K.
2009-10-01
Here we develop simple numerical algorithms for both stationary and non-stationary solutions of the time-dependent Gross-Pitaevskii (GP) equation describing the properties of Bose-Einstein condensates at ultra low temperatures. In particular, we consider algorithms involving real- and imaginary-time propagation based on a split-step Crank-Nicolson method. In a one-space-variable form of the GP equation we consider the one-dimensional, two-dimensional circularly-symmetric, and the three-dimensional spherically-symmetric harmonic-oscillator traps. In the two-space-variable form we consider the GP equation in two-dimensional anisotropic and three-dimensional axially-symmetric traps. The fully-anisotropic three-dimensional GP equation is also considered. Numerical results for the chemical potential and root-mean-square size of stationary states are reported using imaginary-time propagation programs for all the cases and compared with previously obtained results. Also presented are numerical results of non-stationary oscillation for different trap symmetries using real-time propagation programs. A set of convenient working codes developed in Fortran 77 are also provided for all these cases (twelve programs in all). In the case of two or three space variables, Fortran 90/95 versions provide some simplification over the Fortran 77 programs, and these programs are also included (six programs in all). Program summaryProgram title: (i) imagetime1d, (ii) imagetime2d, (iii) imagetime3d, (iv) imagetimecir, (v) imagetimesph, (vi) imagetimeaxial, (vii) realtime1d, (viii) realtime2d, (ix) realtime3d, (x) realtimecir, (xi) realtimesph, (xii) realtimeaxial Catalogue identifier: AEDU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDU_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
C programs for solving the time-dependent Gross-Pitaevskii equation in a fully anisotropic trap
NASA Astrophysics Data System (ADS)
Vudragović, Dušan; Vidanović, Ivana; Balaž, Antun; Muruganandam, Paulsamy; Adhikari, Sadhan K.
2012-09-01
We present C programming language versions of earlier published Fortran programs (Muruganandam and Adhikari (2009) [1]) for calculating both stationary and non-stationary solutions of the time-dependent Gross-Pitaevskii (GP) equation. The GP equation describes the properties of dilute Bose-Einstein condensates at ultra-cold temperatures. C versions of programs use the same algorithms as the Fortran ones, involving real- and imaginary-time propagation based on a split-step Crank-Nicolson method. In a one-space-variable form of the GP equation, we consider the one-dimensional, two-dimensional, circularly-symmetric, and the three-dimensional spherically-symmetric harmonic-oscillator traps. In the two-space-variable form, we consider the GP equation in two-dimensional anisotropic and three-dimensional axially-symmetric traps. The fully-anisotropic three-dimensional GP equation is also considered. In addition to these twelve programs, for six algorithms that involve two and three space variables, we have also developed threaded (OpenMP parallelized) programs, which allow numerical simulations to use all available CPU cores on a computer. All 18 programs are optimized and accompanied by makefiles for several popular C compilers. We present typical results for scalability of threaded codes and demonstrate almost linear speedup obtained with the new programs, allowing a decrease in execution times by an order of magnitude on modern multi-core computers. New version program summary Program title: GP-SCL package, consisting of: (i) imagtime1d, (ii) imagtime2d, (iii) imagtime2d-th, (iv) imagtimecir, (v) imagtime3d, (vi) imagtime3d-th, (vii) imagtimeaxial, (viii) imagtimeaxial-th, (ix) imagtimesph, (x) realtime1d, (xi) realtime2d, (xii) realtime2d-th, (xiii) realtimecir, (xiv) realtime3d, (xv) realtime3d-th, (xvi) realtimeaxial, (xvii) realtimeaxial-th, (xviii) realtimesph. Catalogue identifier: AEDU_v2_0. Program Summary URL: http://cpc.cs.qub.ac.uk/summaries/AEDU_v2_0.html
Vortex dynamics in anisotropic traps
McEndoo, S.; Busch, Th.
2010-07-15
We investigate the dynamics of linear vortex lattices in anisotropic traps in two dimensions and show that the interplay between the rotation and the anisotropy leads to a rich but highly regular dynamics.
Optical trapping of anisotropic nanocylinder
NASA Astrophysics Data System (ADS)
Bareil, Paul B.; Sheng, Yunlong
2013-09-01
The T-matrix method with the Vector Spherical Wave Function (VSWF) expansions represents some difficulties for computing optical scattering of anisotropic particles. As the divergence of the electric field is nonzero in the anisotropic medium and the VSWFs do not satisfy the anisotropic wave equations one questioned whether the VSWFs are still a suitable basis in the anisotropic medium. We made a systematic and careful review on the vector basis functions and the VSWFs. We found that a field vector in Euclidean space can be decomposed to triplet vectors {L, M, N}, which as non-coplanar. Especially, the vector L is designed to represent non-zero divergence component of the vector solution, so that the VSWF basis is sufficiently general to represent the solutions of the anisotropic wave equation. The mathematical proof can be that when the anisotropic wave equations is solved in the Fourier space, the solution is expanded in the basis of the plan waves with angular spectrum amplitude distributions. The plane waves constitute an orthogonal and complete set for the anisotropic solutions. Furthermore, the plane waves are expanded into the VSWF basis. These two-step expansions are equivalent to the one-step direct expansion of the anisotropic solution to the VSWF basis. We used direct VSWF expansion, along with the point-matching method in the T-matrix, and applied the boundary condition to the normal components displacement field in order to compute the stress and the related forces and torques and to show the mechanism of the optical trap of the anisotropic nano-cylinders.
NASA Astrophysics Data System (ADS)
Satarić, Bogdan; Slavnić, Vladimir; Belić, Aleksandar; Balaž, Antun; Muruganandam, Paulsamy; Adhikari, Sadhan K.
2016-03-01
We present hybrid OpenMP/MPI (Open Multi-Processing/Message Passing Interface) parallelized versions of earlier published C programs (Vudragović et al. 2012) for calculating both stationary and non-stationary solutions of the time-dependent Gross-Pitaevskii (GP) equation in three spatial dimensions. The GP equation describes the properties of dilute Bose-Einstein condensates at ultra-cold temperatures. Hybrid versions of programs use the same algorithms as the C ones, involving real- and imaginary-time propagation based on a split-step Crank-Nicolson method, but consider only a fully-anisotropic three-dimensional GP equation, where algorithmic complexity for large grid sizes necessitates parallelization in order to reduce execution time and/or memory requirements per node. Since distributed memory approach is required to address the latter, we combine MPI programming paradigm with existing OpenMP codes, thus creating fully flexible parallelism within a combined distributed/shared memory model, suitable for different modern computer architectures. The two presented C/OpenMP/MPI programs for real- and imaginary-time propagation are optimized and accompanied by a customizable makefile. We present typical scalability results for the provided OpenMP/MPI codes and demonstrate almost linear speedup until inter-process communication time starts to dominate over calculation time per iteration. Such a scalability study is necessary for large grid sizes in order to determine optimal number of MPI nodes and OpenMP threads per node.
Two atoms in an anisotropic harmonic trap
Idziaszek, Z.; Calarco, T.
2005-05-15
We consider the system of two interacting atoms confined in axially symmetric harmonic trap. Within the pseudopotential approximation, we solve the Schroedinger equation exactly, discussing the limits of quasi-one-and quasi-two-dimensional geometries. Finally, we discuss the application of an energy-dependent pseudopotential, which allows us to extend the validity of our results to the case of tight traps and large scattering lengths.
Absorption-induced trapping in an anisotropic magneto-optical trap.
Greenberg, Joel A; Oriá, M; Dawes, Andrew M C; Gauthier, Daniel J
2007-12-24
We report on a simple anisotropic magneto-optical trap for neutral atoms that produces a large sample of cold atoms confined in a cylindrically-shaped volume with a high aspect ratio (100:1). Due to the large number of trapped atoms, the laser beams that propagate along the optically thick axis of the trap to cool the atoms are substantially attenuated. We demonstrate that the resulting intensity imbalance produces a net force that spatially localizes the atoms. This limits both the trap length and the total number of trapped atoms. Rotating the cooling beams by a small angle relative to the trap axis avoids the problem of attenuation, and atoms can be trapped throughout the entire available trapping volume. Numerical and experimental results are reported that demonstrate the effects of absorption in an anisotropic trap, and a steady-state, line-center optical path length of 55 is measured for a probe beam propagating along the length of the trap.
Global sound modes in mirror traps with anisotropic pressure
Skovorodin, D. I.; Zaytsev, K. V.; Beklemishev, A. D.
2013-10-15
Global oscillations of inhomogeneous plasma with frequencies close to the bounce frequency of ions in mirror traps have been studied. It has been shown that, in some cases, the sound can be reflected from the axial plasma inhomogeneity. The ideal magnetohydrodynamic (MHD) model with Chew-Goldberger-Low approximation has been utilized to determine conditions of existence of the standing waves in the mirror-confined plasma. Linearized wave equation for the longitudinal plasma oscillations in thin anisotropic inhomogeneous plasma with finite β has been derived. The wave equation has been treated numerically. The oscillations are studied for the case of the trap with partially filled loss-cone and the trap with sloshing ions. It has been shown that in cells of the multiple-mirror trap standing waves can exist. The frequency of the wave is of the order of the mean bounce-frequency of ions. In the trap with sloshing ions, the mode supported by the pressure of fast ions could exist. The results of oscillations observation in the experiment on the Gas Dynamic Trap have been presented.
Elastic waves trapped by a homogeneous anisotropic semicylinder
Nazarov, S A
2013-11-30
It is established that the problem of elastic oscillations of a homogeneous anisotropic semicylinder (console) with traction-free lateral surface (Neumann boundary condition) has no eigenvalues when the console is clamped at one end (Dirichlet boundary condition). If the end is free, under additional requirements of elastic and geometric symmetry, simple sufficient conditions are found for the existence of an eigenvalue embedded in the continuous spectrum and generating a trapped elastic wave, that is, one which decays at infinity at an exponential rate. The results are obtained by generalizing the methods developed for scalar problems, which however require substantial modification for the vector problem in elasticity theory. Examples are given and open questions are stated. Bibliography: 53 titles.
Laser trapping in anisotropic fluids and polarization-controlled particle dynamics.
Smalyukh, Ivan I; Kachynski, Aliaksandr V; Kuzmin, Andrey N; Prasad, Paras N
2006-11-28
Anisotropic fluids are widespread, ranging from liquid crystals used in displays to ordered states of a biological cell interior. Optical trapping is potentially a powerful technique in the fundamental studies and applications of anisotropic fluids. We demonstrate that laser beams in these fluids can generate anisotropic optical trapping forces, even for particles larger than the trapping beam wavelength. Immersed colloidal particles modify the fluid's ordered molecular structures and locally distort its optic axis. This distortion produces a refractive index "corona" around the particles that depends on their surface characteristics. The laser beam can trap such particles not only at their center but also at the high-index corona. Trapping forces in the beam's lateral plane mimic the corona and are polarization-controlled. This control allows the optical forces to be reversed and cause the particle to follow a prescribed trajectory. Anisotropic particle dynamics in the trap varies with laser power because of the anisotropy of both viscous drag and trapping forces. Using thermotropic liquid crystals and biological materials, we show that these phenomena are quite general for all anisotropic fluids and impinge broadly on their quantitative studies using laser tweezers. Potential applications include modeling thermodynamic systems with anisotropic polarization-controlled potential wells, producing optically tunable photonic crystals, and fabricating light-controlled nano- and micropumps.
Autoionization of spin-polarized metastable helium in tight anisotropic harmonic traps
Beams, Timothy J.; Whittingham, Ian B.; Peach, Gillian
2007-12-15
Spin-dipole mediated interactions between tightly confined metastable helium atoms couple the spin-polarized quintet {sup 5}{sigma}{sub g}{sup +} state to the singlet {sup 1}{sigma}{sub g}{sup +} state from which autoionization is highly probable, resulting in finite lifetimes for the trap eigenstates. We extend our earlier study on spherically symmetric harmonic traps to the interesting cases of axially symmetric anisotropic harmonic traps and report results for the lowest 10 states in 'cigarlike' and 'pancakelike' traps with average frequencies of 100 kHz and 1 MHz. We find that there is a significant suppression of ionization, and subsequent increase in lifetimes, at trap aspect ratios A=p/q, where p and q are integers, for those states that are degenerate in the absence of collisions or spin-dipole interactions.
Inter-comparison of isotropic and anisotropic sea ice rheology in a fully coupled model
NASA Astrophysics Data System (ADS)
Roberts, A.; Cassano, J. J.; Maslowski, W.; Osinski, R.; Seefeldt, M. W.; Hughes, M.; Duvivier, A.; Nijssen, B.; Hamman, J.; Hutchings, J. K.; Hunke, E. C.
2015-12-01
We present the sea ice climate of the Regional Arctic System Model (RASM), using a suite of new physics available in the Los Alamos Sea Ice Model (CICE5). RASM is a high-resolution fully coupled pan-Arctic model that also includes the Parallel Ocean Program (POP), the Weather Research and Forecasting Model (WRF) and Variable Infiltration Capacity (VIC) land model. The model domain extends from ~45˚N to the North Pole and is configured to run at ~9km resolution for the ice and ocean components, coupled to 50km resolution atmosphere and land models. The baseline sea ice model configuration includes mushy-layer sea ice thermodynamics and level-ice melt ponds. Using this configuration, we compare the use of isotropic and anisotropic sea ice mechanics, and evaluate model performance using these two variants against observations including Arctic buoy drift and deformation, satellite-derived drift and deformation, and sea ice volume estimates from ICESat. We find that the isotropic rheology better approximates spatial patterns of thickness observed across the Arctic, but that both rheologies closely approximate scaling laws observed in the pack using buoys and RGPS data. A fundamental component of both ice mechanics variants, the so called Elastic-Viscous-Plastic (EVP) and Anisotropic-Elastic-Plastic (EAP), is that they are highly sensitive to the timestep used for elastic sub-cycling in an inertial-resolving coupled framework, and this has a significant affect on surface fluxes in the fully coupled framework.
NASA Astrophysics Data System (ADS)
Martin, A. D.; Blakie, P. B.
2012-11-01
We study theoretically Bose-Einstein condensates with polarized dipolar interactions in anisotropic traps. We map the parameter space by varying the trap frequencies and dipolar interaction strengths and find an irregular-shaped region of parameter space in which density-oscillating condensate states occur, with maximum density away from the trap center. These density-oscillating states may be biconcave (red-blood-cell-shaped), or have two or four peaks. For all trap frequencies, the condensate becomes unstable to collapse for sufficiently large dipole interaction strength. The collapse coincides with the softening of an elementary excitation. When the condensate mode is density oscillating, the character of the softening excitation is related to the structure of the condensate. We classify these excitations by linear and angular characteristics. We also find excited solutions to the Gross-Pitaevskii equation, which are always unstable.
Aspect Ratio Analysis for Ground States of Bosons in Anisotropic Traps
Ilinski, Kirill N.; Moroz, Alexander
1996-01-01
Characteristics of the initial condensate in the recent experiment on Bose-Einstein condensation (BEC) of 87Rb atoms in an anisotropic magnetic trap are discussed. Given the aspect ratio R, the quality of BEC is estimated. A simple analytical ansatz for the initial condensate wave function is proposed as a function of the aspect ratio which, in contrast to the Baym-Pethick trial wave function, can be used for any interaction strength, reproduces both the weak and the strong interaction limits, and which is in better agreement with numerical results than the latter. PMID:27805109
Buckling Behavior of Long Anisotropic Plates Subjected to Fully Restrained Thermal Expansion
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.
2003-01-01
An approach for synthesizing buckling results and behavior for thin, balanced and unbalanced symmetric laminates that are subjected to uniform heating or cooling and which are fully-restrained against thermal expansion or contraction is presented. This approach uses a nondimensional analysis for infinitely long, flexurally anisotropic plates that are subjected to combined mechanical loads and is based on useful nondimensional parameters. In addition, stiffness-weighted laminate thermal-expansion parameters are derived and used to determine critical temperature changes in terms of physically intuitive mechanical buckling coefficients. The effects of membrane orthotropy and anisotropy are included. Many results are presented for some common laminates that are intended to facilitate a structural designer's transition to the use of the generic buckling design curves that are presented in the paper. Several generic buckling design curves are presented that provide physical insight into buckling response and provide useful design data. Examples are presented that demonstrate the use of generic design curves. The analysis approach and generic results indicate the effects and characteristics of laminate thermal expansion, membrane orthotropy and anisotropy, and flexural orthotropy and anisotropy in a very general, unifying manner.
Buckling Behavior of Long Anisotropic Plates Subjected to Fully Restrained Thermal Expansion
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.
2001-01-01
An approach for synthesizing buckling results and behavior for thin balanced and unbalanced symmetric laminates that are subjected to uniform heating or cooling and fully restrained against thermal expansion or contraction is presented. This approach uses a nondimensional analysis for infinitely long, flexurally anisotropic plates that are subjected to combined mechanical loads and is based on useful nondimensional parameters. In addition, stiffness-weighted laminate thermal-expansion parameters are derived that are used to determine critical temperatures in terms of physically intuitive mechanical buckling coefficients, and the effects of membrane orthotropy and membrane anisotropy are included. Many results are presented for some common laminates that are intended to facilitate a structural designer's transition to the use of the generic buckling design curves that are presented in the paper. Several generic buckling design curves are presented that provide physical insight into the buckling response in addition to providing useful design data. Examples are presented that demonstrate the use of the generic design curves. The analysis approach and generic results indicate the effects and characteristics of laminate thermal expansion, membrane orthotropy and anisotropy, and flexural orthotropy and anisotropy in a very general and unifying manner.
Effenberger, F.; Fichtner, H.; Scherer, K.; Barra, S.; Kleimann, J.; Strauss, R. D.
2012-05-10
The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the most general case, be fully anisotropic, i.e., one has to distinguish three diffusion axes in a local, field-aligned frame. We reexamine the transformation for the diffusion tensor from this local to a global frame, in which the Parker transport equation for energetic particles is usually formulated and solved. Particularly, we generalize the transformation formulae to allow for an explicit choice of two principal local perpendicular diffusion axes. This generalization includes the 'traditional' diffusion tensor in the special case of isotropic perpendicular diffusion. For the local frame, we describe the motivation for the choice of the Frenet-Serret trihedron, which is related to the intrinsic magnetic field geometry. We directly compare the old and the new tensor elements for two heliospheric magnetic field configurations, namely the hybrid Fisk and Parker fields. Subsequently, we examine the significance of the different formulations for the diffusion tensor in a standard three-dimensional model for the modulation of galactic protons. For this, we utilize a numerical code to evaluate a system of stochastic differential equations equivalent to the Parker transport equation and present the resulting modulated spectra. The computed differential fluxes based on the new tensor formulation deviate from those obtained with the 'traditional' one (only valid for isotropic perpendicular diffusion) by up to 60% for energies below a few hundred MeV depending on heliocentric distance.
Fully kinetic simulation study of ion-acoustic solitons in the presence of trapped electrons.
Hosseini Jenab, S M; Spanier, F
2017-05-01
The nonlinear fluid theory developed by Schamel suggests a modified KdV equation to describe the temporal evolution of ion acoustic (IA) solitons in the presence of trapped electrons. The validity of this theory is studied here by verifying solitons' main characteristic, i.e., stability against successive mutual collisions. We have employed a kinetic model as a more comprehensive theory than the fluid one, and utilized a fully kinetic simulation approach (both ions and electrons are treated based on the Vlasov equation). In the simulation approach, these solitons are excited self-consistently by employing the nonlinear process of IA solitons formation from an initial density perturbation (IDP). The effect of the size of IDPs on the chain formation is proved by the simulation code as a benchmark test. It is shown that the IA solitons, in the presence of trapped electrons, can retain their features (both in spatial and velocity direction) after successive mutual collisions. The collisions here include encounters of IA solitons with the same trapping parameter, while differing in size. Kinetic simulation results reveal a complicated behavior during a collision between IA solitons in contrast to the fluid theory predictions and simulations. In the range of parameters considered here, two oppositely propagating solitons rotate around their collective center in the phase space during a collision, independent of their trapping parameters. Furthermore, they exchange some portions of their trapped populations.
Fully kinetic simulation study of ion-acoustic solitons in the presence of trapped electrons
NASA Astrophysics Data System (ADS)
Hosseini Jenab, S. M.; Spanier, F.
2017-05-01
The nonlinear fluid theory developed by Schamel suggests a modified KdV equation to describe the temporal evolution of ion acoustic (IA) solitons in the presence of trapped electrons. The validity of this theory is studied here by verifying solitons' main characteristic, i.e., stability against successive mutual collisions. We have employed a kinetic model as a more comprehensive theory than the fluid one, and utilized a fully kinetic simulation approach (both ions and electrons are treated based on the Vlasov equation). In the simulation approach, these solitons are excited self-consistently by employing the nonlinear process of IA solitons formation from an initial density perturbation (IDP). The effect of the size of IDPs on the chain formation is proved by the simulation code as a benchmark test. It is shown that the IA solitons, in the presence of trapped electrons, can retain their features (both in spatial and velocity direction) after successive mutual collisions. The collisions here include encounters of IA solitons with the same trapping parameter, while differing in size. Kinetic simulation results reveal a complicated behavior during a collision between IA solitons in contrast to the fluid theory predictions and simulations. In the range of parameters considered here, two oppositely propagating solitons rotate around their collective center in the phase space during a collision, independent of their trapping parameters. Furthermore, they exchange some portions of their trapped populations.
Lowest-Landau-level description of a Bose-Einstein condensate in a rapidly rotating anisotropic trap
NASA Astrophysics Data System (ADS)
Fetter, Alexander L.
2007-01-01
A rapidly rotating Bose-Einstein condensate in a symmetric two-dimensional trap can be described with the lowest Landau-level set of states. In this case, the condensate wave function ψ(x,y) is a Gaussian function of r2=x2+y2 , multiplied by an analytic function P(z) of the single complex variable z=x+iy ; the zeros of P(z) denote the positions of the vortices. Here, a similar description is used for a rapidly rotating anisotropic two-dimensional trap with arbitrary anisotropy (ωx/ωy⩽1) . The corresponding condensate wave function ψ(x,y) has the form of a complex anisotropic Gaussian with a phase proportional to xy , multiplied by an analytic function P(ζ) , where ζ∝x+iβ-y and 0⩽β-⩽1 is a real parameter that depends on the trap anisotropy and the rotation frequency. The zeros of P(ζ) again fix the locations of the vortices. Within the set of lowest Landau-level states at zero temperature, an anisotropic parabolic density profile provides an absolute minimum for the energy, with the vortex density decreasing slowly and anisotropically away from the trap center.
Buckling analysis of fully anisotropic plates containing cutouts and elastically restrained edges
NASA Technical Reports Server (NTRS)
Jones, Kevin M.; Klang, Eric C.
1992-01-01
An analysis is developed which combines the Ritz and collocation methods for the stability solution of an anisotropic plate with a cutout and elastically restrained edges. Results are presented which agree closely with experiment for isotropic and orthotropic materials. Results are also given for restrained anisotropic plates with circular holes loaded in compression and shear. Difference is noted in the critical buckling loads between displacement and stress loaded panels as hole size is increased. Clamping is also seen to affect the trends in buckling associated with hole size.
Bohn, Holger F; Federle, Walter
2004-09-28
Pitcher plants of the genus Nepenthes have highly specialized leaves adapted to attract, capture, retain, and digest arthropod prey. Several mechanisms have been proposed for the capture of insects, ranging from slippery epicuticular wax crystals to downward-pointing lunate cells and alkaloid secretions that anesthetize insects. Here we report that perhaps the most important capture mechanism has thus far remained overlooked. It is based on special surface properties of the pitcher rim (peristome) and insect "aquaplaning." The peristome is characterized by a regular microstructure with radial ridges of smooth overlapping epidermal cells, which form a series of steps toward the pitcher inside. This surface is completely wettable by nectar secreted at the inner margin of the peristome and by rain water, so that homogenous liquid films cover the surface under humid weather conditions. Only when wet, the peristome surface is slippery for insects, so that most ant visitors become trapped. By measuring friction forces of weaver ants (Oecophylla smaragdina) on the peristome surface of Nepenthes bicalcarata, we demonstrate that the two factors preventing insect attachment to the peristome, i.e., water lubrication and anisotropic surface topography, are effective against different attachment structures of the insect tarsus. Peristome water films disrupt attachment only for the soft adhesive pads but not for the claws, whereas surface topography leads to anisotropic friction only for the claws but not for the adhesive pads. Experiments on Nepenthes alata show that the trapping mechanism of the peristome is also essential in Nepenthes species with waxy inner pitcher walls.
Fully dense anisotropic nanocomposite Sm(Co,Fe,Zr,Cu,B)z (z=7.5-12) magnets
NASA Astrophysics Data System (ADS)
Huang, M. Q.; Turgut, Z.; Wheeler, B.; Lee, D.; Liu, S.; Ma, B. M.; Peng, Y. G.; Chu, S. Y.; Laughlin, D. E.; Horwath, J. C.; Fingers, R. T.
2005-05-01
Fully dense anisotropic nanocomposite Sm(Co0.58Fe0.31Zr0.05Cu0.04B0.02)z (z =7.5-12) magnets have been synthesized via rapid hot pressing and hot deformation processes. The highest (BH)max˜10.6MGOe was observed for a magnet with z =10. X-ray diffraction and M-H measurements indicated that the easy magnetization direction of magnets prefers to be in the hot pressing direction. Transmission electron microscopy investigation confirmed that plastic deformation is an important route for forming magnetic anisotropy in the Sm-Co-type nanocomposite magnets. Some stripe and/or platelike patterns have been observed inside the nanograins (50-200nm ), which may present as twins, and stacking faults. The (0001) twins have been observed in the 2:17R phase.
NASA Astrophysics Data System (ADS)
Gutfleisch, O.; Eckert, D.; Schäfer, R.; Müller, K. H.; Panchanathan, V.
2000-05-01
Two types of textured, fully dense NdFeB hydrogenation, disproportionation, desorption, and recombination (HDDR) magnets were produced. The first type was produced by hot pressing isotropic HDDR powder followed by die upsetting; the second, by hot pressing prealigned, anisotropic HDDR powder (MQA-T). Studies of the magnetization processes revealed that for isotropic HDDR powder and its hot pressed and die-upset magnets a much larger initial susceptibility is found after thermal demagnetization than after reverse dc-field demagnetization. Prealigned, hot pressed magnets made from MQA-T material showed a different virgin magnetization curve, indicating a unique coercivity mechanism. Interaction domains larger than the average grain size can be observed in both cases by Kerr microscopy, with the MQA-T type showing significantly broader interaction domains.
Carr, Sam T.; Quintanilla, Jorge; Betouras, Joseph J.
2010-07-15
We consider a two-dimensional model of noninteracting chains of spinless fermions weakly coupled via a small interchain hopping and a repulsive interchain interaction. The phase diagram of this model has a surprising feature: an abrupt change in the Fermi surface as the interaction is increased. We study in detail this metanematic transition and show that the well-known 2(1/2)-order Lifshitz transition is the critical end point of this first-order quantum phase transition. Furthermore, in the vicinity of the end point, the order parameter has a nonperturbative BCS-type form. We also study a competing crystallization transition in this model and derive the full phase diagram. This physics can be demonstrated experimentally in dipolar ultracold atomic or molecular gases. In the presence of a harmonic trap, it manifests itself as a sharp jump in the density profile.
Chin, Siu A.; Krotscheck, Eckhard
2005-09-01
By implementing the exact density matrix for the rotating anisotropic harmonic trap, we derive a class of very fast and accurate fourth-order algorithms for evolving the Gross-Pitaevskii equation in imaginary time. Such fourth-order algorithms are possible only with the use of forward, positive time step factorization schemes. These fourth-order algorithms converge at time-step sizes an order-of-magnitude larger than conventional second-order algorithms. Our use of time-dependent factorization schemes provides a systematic way of devising algorithms for solving this type of nonlinear equations.
Effects of Rapid High Temperature Cyclic Aging on a Fully-Formulated Lean NOx Trap Catalyst
Ottinger, Nathan; Nguyen, Ke; Bunting, Bruce G; Toops, Todd J; Howe, Janet E
2009-01-01
In this study, high-temperature deactivation of a fully-formulated lean NOx trap (LNT) is investigated with an accelerated aging protocol where accelerated aging is accomplished by rapid temperature cycling and by higher temperatures. Thermal aging is carried out in a bench-flow reactor at nominal temperatures of 700, 800, 900, and 1000 C using an aging cycle consisting of a 130s lean-phase and a 50s rich-phase. After a prescribed number of lean/rich aging cycles, the NOx conversion of the aged LNT is evaluated at 200, 300, and 400 C. The NOx performance is obtained at a GHSV of 30,000 h-1 using an evaluation cycle consisting of a 60s lean-phase and 5s rich-phase. The effects of aging on the LNT washcoat are determined with EPMA, XRD, STEM/EDS, and BET. Aging at 700 and 800 C has a minimal effect on LNT performance and material properties. However, at aging temperatures of 900 and 1000 C reduction in surface area and sintering of PGM particles are observed and result in a drastic reduction in NOx conversion. Additionally, after aging at 900 C and 1000 C the NOx storage medium, BaCO3, is no longer visible in the XRD patterns, even though a Ba-phase identified by EPMA still exists in all aged samples. BaAl2O4 is not identified at any aging temperatures; possibly due to stabilization effects provided by washcoat additives present in this particular LNT.
Study of trapping effect on ion-acoustic solitary waves based on a fully kinetic simulation approach
NASA Astrophysics Data System (ADS)
Hosseini Jenab, S. M.; Spanier, F.
2016-10-01
A fully kinetic simulation approach, treating each plasma component based on the Vlasov equation, is adopted to study the disintegration of an initial density perturbation into a number of ion-acoustic solitary waves (IASWs) in the presence of the trapping effect of electrons. The nonlinear fluid theory developed by Schamel [Plasma Phys. 13, 491 (1971); J. Plasma Phys. 7, 1 (1972); Plasma Phys. 14, 905 (1972); J. Plasma Phys. 9, 377 (1973); Phys. Scr. 20, 306 (1979)] has identified three separate regimes of ion-acoustic solitary waves based on the trapping parameter. Here, the disintegration process and the resulting self-consistent IASWs are studied in a wide range of trapping parameters covering all the three regimes continuously. The dependency of features such as the time of disintegration, the number, speed, and size of IASWs on the trapping parameter are focused upon. It is shown that an increase in this parameter slows down the propagation of IASWs while decreases their sizes in the phase space. These features of IASWs tend to saturate for large values of trapping parameters. The disintegration time shows a more complicated behavior than what was predicted by the theoretical approach. Also for the case of trapping parameters bigger than one, propagation of IASWs is observed in contrast with the theoretical predictions. The kinetic simulation results unveil a smooth and well-defined dependency of solitary waves' features on the trapping parameter, showing the possibility of bridging all the three regimes. Finally, it is shown that for β around zero, the electron phase space structure of the accompanying vortex stays symmetric. The effect of the electron-to-ion temperature ratio on the disintegration and the propagation of IASWs are considered as a benchmarking test of the simulation code (in the nonlinear regime).
Weakly nonlinear dynamics and fully nonlinear simulations of trapped waves on jet currents
NASA Astrophysics Data System (ADS)
Slunyaev, Alexey; Shrira, Victor
2014-05-01
The asymptotic modal approach developed in Shrira & Slunyaev (2014) for waves trapped by an opposing jet current is extended by examining the weakly nonlinear dynamics of trapped waves due to four-wave resonances. Evolution equations governing dynamics of an arbitrary number of wave packets have been derived. In particular, for a single mode the asymptotic procedure yields the integrable one-dimensional nonlinear Schrodinger equation (NLS). The NLS describes the evolution of modes along the current, while the modal structure is specified by the corresponding boundary value problem (BVP). When the current is weak in comparison with the wave celerity, the BVP reduces to the classic stationary Schrodinger equation with conditions of decay outside the jet, which allows exact solutions for a number of model current profiles. This enables us to find analytically the interaction coefficients in the dynamic equations. Thus, to the leading order a variety of analytic solutions to the evolution equation and the BVP specifying the trapped modes is readily available. A few such asymptotic solutions are tested in numerical simulations of the Euler equations. The equations are solved by means of the adapted High Order Spectral Method (West et al, 1987). Single trapped mode solutions are simulated: the uniform waves train, modulated wave train, and solitary wave packets. The weakly nonlinear theory is shown to be a reasonable first approximation to the solution even in the case of rather steep waves. Solitary patterns of trapped waves were found to be robust, though an insignificant radiation is observed in the course of their propagation, which suggests that the solitary wave patterns represent important elements of nonlinear dynamics of gravity waves on jet currents. Their presence in the stochastic wave field may result in significant deviation from the Gaussianity, and increase the extreme wave probability. Shrira, V.I., Slunyaev, A.V. Trapped waves on jet currents
NASA Astrophysics Data System (ADS)
Badavi, Francis F.; Nealy, John E.; Wilson, John W.
2011-10-01
The International Space Station (ISS) provides the proving ground for future long duration human activities in space. Ionizing radiation measurements in ISS form the ideal tool for the experimental validation of radiation environmental models, nuclear transport code algorithms and nuclear reaction cross sections. Indeed, prior measurements on the Space Transportation System (STS; Shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the Low Earth Orbit (LEO) environment. Previous studies using Computer Aided Design (CAD) models of the evolving ISS configurations with Thermo-Luminescent Detector (TLD) area monitors, demonstrated that computational dosimetry requires environmental models with accurate non-isotropic as well as dynamic behavior, detailed information on rack loading, and an accurate six degree of freedom (DOF) description of ISS trajectory and orientation. It is imperative that we understand ISS exposures dynamically for crew career planning, and insure that the regulatory requirements of keeping exposure as low as reasonably achievable (ALARA) are adequately implemented. This is especially true as ISS nears some form of completion with increasing complexity, resulting in a larger drag coefficient, and requiring operation at higher altitudes with increased exposure rates. In this paper ISS environmental model is configured for 11A (circa mid 2005), and uses non-isotropic and dynamic geomagnetic transmission and trapped proton models. ISS 11A and LEO model validations are important steps in preparation for the design and validation for the next generation manned vehicles. While the described cutoff rigidity, trapped proton and electron formalisms as coded in a package named GEORAD (GEOmagnetic RADiation) and a web interface named OLTARIS (On-line Tool for the Assessment of Radiation in Space) are applicable to the LEO, Medium Earth Orbit (MEO) and
NASA Astrophysics Data System (ADS)
Ishizuka, Ryosuke; Yoshida, Norio
2013-08-01
An extended molecular Ornstein-Zernike (XMOZ) integral equation is formulated to calculate the spatial distribution of solvent around a solute of arbitrary shape and solid surfaces. The conventional MOZ theory employs spherical harmonic expansion technique to treat the molecular orientation of components of solution. Although the MOZ formalism is fully exact analytically, the truncation of the spherical harmonic expansion requires at a finite order for numerical calculation and causes the significant error for complex molecules. The XMOZ integral equation is the natural extension of the conventional MOZ theory to a rectangular coordinate system, which is free from the truncation of spherical harmonic expansion with respect to solute orientation. In order to show its applicability, we applied the XMOZ theory to several systems using the hypernetted-chain (HNC) and Kovalenko-Hirata approximations. The quality of results obtained within our theory is discussed by comparison with values from the conventional MOZ theory, molecular dynamics simulation, and three-dimensional reference interaction site model theory. The spatial distributions of water around the complex of non-charged sphere and dumbbell were calculated. Using this system, the approximation level of the XMOZ and other methods are discussed. To assess our theory, we also computed the excess chemical potentials for three realistic molecules (water, methane, and alanine dipeptide). We obtained the qualitatively reasonable results by using the XMOZ/HNC theory. The XMOZ theory covers a wide variety of applications in solution chemistry as a useful tool to calculate solvation thermodynamics.
Ji, Yaying; Easterling, Vencon; Graham, Uschi; Fisk, Courtney; Crocker, Mark; Choi, Jae-Soon
2011-01-01
In order to elucidate the effect of washcoat composition on lean NO{sub x} trap (LNT) aging characteristics, fully formulated monolithic LNT catalysts containing varying amounts of Pt, Rh and BaO were subjected to accelerated aging on a bench reactor. Subsequent catalyst evaluation revealed that in all cases aging resulted in deterioration of the NO{sub x} conversion as a consequence of impaired NO{sub x} storage and NO{sub x} reduction functions, while increased selectivity to NH{sub 3} was observed in the temperature range 250--450 C. Elemental analysis, H{sub 2} chemisorption and TEM data revealed two main changes which account for the degradation in LNT performance. First, residual sulfur in the catalysts, associated with the Ba phase, decreased catalyst NO{sub x} storage capacity. Second, sintering of the precious metals in the washcoat occurred, resulting in decreased contact between the Pt and Ba, and hence in less efficient NO{sub x} spillover from Pt to Ba during NO{sub x} adsorption, as well as decreased rates of reductant spillover from Pt to Ba and reverse NO{sub x} spillover during catalyst regeneration. For the aged catalysts, halving the Pt loading from 100 to 50 g/ft{sup 3} was found to result in a significant decrease in overall NO{sub x} conversion, while for catalysts with the same 100 g/ft{sup 3} Pt loading, increasing the relative amount of Pt on the NO{sub x} storage components (BaO and La-stabilized CeO{sub 2}), as opposed to an Al{sub 2}O{sub 3} support material (where it was co-located with Rh), was found to be beneficial. The effect of Rh loading on aged catalyst performance was found to be marginal within the range studied (10--20 g/ft{sup 3}), as was the effect of BaO loading in the range 30--45 g/L.
NASA Astrophysics Data System (ADS)
Kim, Seong Kwang; Lee, Jungmin; Geum, Dae-Myeong; Park, Min-Su; Choi, Won Jun; Choi, Sung-Jin; Kim, Dae Hwan; Kim, Sanghyeon; Kim, Dong Myong
2016-08-01
We report characterization of the interface trap distribution (Dit(E)) over the bandgap in III-V metal-oxide-semiconductor field-effect transistors (MOSFETs) on insulator. Based only on the experimental subthreshold current data and differential coupling factor, we simultaneously obtained Dit(E) and a nonlinear mapping of the gate bias (VGS) to the trap level (Et) via the effective surface potential (ψS,eff). The proposed technique allows direct extraction of the interface traps at the In0.53Ga0.47As-on insulator (-OI) MOSFETs only from the experimental subthreshold current data. Applying the technique to the In0.53Ga0.47As channel III-V-OI MOSFETs with the gate width/length W/L = 100/50, 100/25, and 100/10 μm/μm, we obtained Dit(E) ≅ 1011-1012 eV-1 cm-2 over the bandgap without the dimension dependence.
NASA Astrophysics Data System (ADS)
Rushton, J. A.; Aldous, M.; Himsworth, M. D.
2014-12-01
Experiments using laser cooled atoms and ions show real promise for practical applications in quantum-enhanced metrology, timing, navigation, and sensing as well as exotic roles in quantum computing, networking, and simulation. The heart of many of these experiments has been translated to microfabricated platforms known as atom chips whose construction readily lend themselves to integration with larger systems and future mass production. To truly make the jump from laboratory demonstrations to practical, rugged devices, the complex surrounding infrastructure (including vacuum systems, optics, and lasers) also needs to be miniaturized and integrated. In this paper we explore the feasibility of applying this approach to the Magneto-Optical Trap; incorporating the vacuum system, atom source and optical geometry into a permanently sealed micro-litre system capable of maintaining 10-10 mbar for more than 1000 days of operation with passive pumping alone. We demonstrate such an engineering challenge is achievable using recent advances in semiconductor microfabrication techniques and materials.
Rushton, J. A.; Aldous, M.; Himsworth, M. D.
2014-12-15
Experiments using laser cooled atoms and ions show real promise for practical applications in quantum-enhanced metrology, timing, navigation, and sensing as well as exotic roles in quantum computing, networking, and simulation. The heart of many of these experiments has been translated to microfabricated platforms known as atom chips whose construction readily lend themselves to integration with larger systems and future mass production. To truly make the jump from laboratory demonstrations to practical, rugged devices, the complex surrounding infrastructure (including vacuum systems, optics, and lasers) also needs to be miniaturized and integrated. In this paper we explore the feasibility of applying this approach to the Magneto-Optical Trap; incorporating the vacuum system, atom source and optical geometry into a permanently sealed micro-litre system capable of maintaining 10{sup −10} mbar for more than 1000 days of operation with passive pumping alone. We demonstrate such an engineering challenge is achievable using recent advances in semiconductor microfabrication techniques and materials.
NASA Astrophysics Data System (ADS)
Li, Hui; Wyart, Jean-François; Dulieu, Olivier; Lepers, Maxence
2017-06-01
The efficiency of optical trapping is determined by the atomic dynamic dipole polarizability, whose real and imaginary parts are associated with the potential energy and photon-scattering rate, respectively. In this article we develop a formalism to calculate analytically the real and imaginary parts of the scalar, vector, and tensor polarizabilities of lanthanide atoms. We assume that the sum-over-state formula comprises only transitions involving electrons in the valence orbitals like 6 s ,5 d ,6 p , and 7 s , while transitions involving 4 f core electrons are neglected. Applying this formalism to the ground level of configuration 4 fq6 s2 , we restrict the sum to transitions implying the 4 fq6 s 6 p configuration, which yields polarizabilities depending on two parameters: an effective transition energy and an effective transition dipole moment. Then, by introducing configuration-interaction mixing between 4 fq6 s 6 p and other configurations, we demonstrate that the imaginary part of the scalar, vector, and tensor polarizabilities is very sensitive to configuration-interaction coefficients, whereas the real part is not. The magnitude and anisotropy of the photon-scattering rate are thus strongly related to the details of the atomic electronic structure. Those analytical results agree with our detailed electronic-structure calculations of the energy levels, Landé g factors, transition probabilities, polarizabilities, and van der Waals C6 coefficients, previously performed on erbium and dysprosium and presently performed on holmium. Our results show that, although the density of states decreases with increasing q , the configuration interaction between 4 fq6 s 6 p ,4 fq -15 d 6 s2 , and 4 fq -15 d26 s is surprisingly stronger in erbium (q =12 ) than in holmium (q =11 ), itself stronger than in dysprosium (q =10 ).
NASA Astrophysics Data System (ADS)
Andrews, S. J.; Hackenberg, S. C.; Carpenter, L. J.
2015-04-01
The oceans are a key source of a number of atmospherically important volatile gases. The accurate and robust determination of trace gases in seawater is a significant analytical challenge, requiring reproducible and ideally automated sample handling, a high efficiency of seawater-air transfer, removal of water vapour from the sample stream, and high sensitivity and selectivity of the analysis. Here we describe a system that was developed for the fully automated analysis of dissolved very short-lived halogenated species (VSLS) sampled from an under-way seawater supply. The system can also be used for semi-automated batch sampling from Niskin bottles filled during CTD (conductivity, temperature, depth) profiles. The essential components comprise a bespoke, automated purge and trap (AutoP & T) unit coupled to a commercial thermal desorption and gas chromatograph mass spectrometer (TD-GC-MS). The AutoP & T system has completed five research cruises, from the tropics to the poles, and collected over 2500 oceanic samples to date. It is able to quantify >25 species over a boiling point range of 34-180 °C with Henry's law coefficients of 0.018 and greater (CH22l, kHcc dimensionless gas/aqueous) and has been used to measure organic sulfurs, hydrocarbons, halocarbons and terpenes. In the eastern tropical Pacific, the high sensitivity and sampling frequency provided new information regarding the distribution of VSLS, including novel measurements of a photolytically driven diurnal cycle of CH22l within the surface ocean water.
NASA Astrophysics Data System (ADS)
Andrews, S. J.; Hackenberg, S. C.; Carpenter, L. J.
2014-12-01
The oceans are a key source of a number of atmospherically important volatile gases. The accurate and robust determination of trace gases in seawater is a significant analytical challenge, requiring reproducible and ideally automated sample handling, a high efficiency of seawater-air transfer, removal of water vapour from the sample stream, and high sensitivity and selectivity of the analysis. Here we describe a system that was developed for the fully automated analysis of dissolved very short-lived halogenated species (VSLS) sampled from an under-way seawater supply. The system can also be used for semi-automated batch sampling from Niskin bottles filled during CTD (Conductivity, Temperature, Depth) profiles. The essential components comprise of a bespoke, automated purge and trap (AutoP & T) unit coupled to a commercial thermal desorption and gas chromatograph-mass spectrometer (TD-GC-MS). The AutoP & T system has completed five research cruises, from the tropics to the poles, and collected over 2500 oceanic samples to date. It is able to quantify >25 species over a boiling point range of 34-180 °C with Henry's Law coefficients of 0.018 and greater (CH2I2, kHcc dimensionless gas/aqueous) and has been used to measure organic sulfurs, hydrocarbons, halocarbons and terpenes. In the east tropical Pacific, the high sensitivity and sampling frequency provided new information regarding the distribution of VSLS, including novel measurements of a photolytically driven diurnal cycle of CH2I2 within the surface ocean water.
Anisotropic Interactions between Cold Rydberg Atoms
2015-09-28
AFRL-AFOSR-CL-TR-2015-0002 Anisotropic interactions between cold Rydberg atoms Luis Marcassa INSTITUTO DE FISICA DE SAO CARLOS Final Report 09/28...34Anisotropic Interactions Between Cold Rydberg Atoms " 5a. CONTRACT NUMBER FA9550-12-1-0434 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...processes in an atomic sample trapped in a CO2 optical dipole trap. The process was investigated as a function of: i) atomic density; ii) dc electric
NASA Astrophysics Data System (ADS)
Young-S., Luis E.; Vudragović, Dušan; Muruganandam, Paulsamy; Adhikari, Sadhan K.; Balaž, Antun
2016-07-01
We present new version of previously published Fortran and C programs for solving the Gross-Pitaevskii equation for a Bose-Einstein condensate with contact interaction in one, two and three spatial dimensions in imaginary and real time, yielding both stationary and non-stationary solutions. To reduce the execution time on multicore processors, new versions of parallelized programs are developed using Open Multi-Processing (OpenMP) interface. The input in the previous versions of programs was the mathematical quantity nonlinearity for dimensionless form of Gross-Pitaevskii equation, whereas in the present programs the inputs are quantities of experimental interest, such as, number of atoms, scattering length, oscillator length for the trap, etc. New output files for some integrated one- and two-dimensional densities of experimental interest are given. We also present speedup test results for the new programs.
Anisotropic universe with anisotropic sources
Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha E-mail: sukanta@iiserb.ac.in E-mail: snigdha@iiserb.ac.in
2013-12-01
We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived. Dynamical systems approach is used to study the evolution of these equations. The asymptotic stable fixed points for all the evolution equations are found. We also check our analytic results with numerical analysis of these dynamical equations. The evolution of the state observables are studied both in cosmic time and using a dimensionless time variable. Then we repeat the same analysis with a more realistic scenario, adding the isotropic (dust like dark) matter and a cosmological constant (dark energy) to our anisotropic sources, to study their co-evolution. The universe now approaches a de Sitter space asymptotically dominated by the cosmological constant. The cosmic microwave background anisotropy maps due to shear are also generated in this scenario, assuming that the universe contains anisotropic matter along with the usual (dark) matter and vacuum (dark) energy since decoupling. We find that they contribute dominantly to the CMB quadrupole. We also constrain the current level of anisotropy and also search for any cosmic preferred axis present in the data. We use the Union 2 Supernovae data to this extent. An anisotropy axis close to the mirror symmetry axis seen in the cosmic microwave background data from Planck probe is found.
Monte Carlo ICRH simulations in fully shaped anisotropic plasmas
Jucker, M.; Graves, J. P.; Cooper, W. A.; Mellet, N.; Brunner, S.
2008-11-01
In order to numerically study the effects of Ion Cyclotron Resonant Heating (ICRH) on the fast particle distribution function in general plasma geometries, three codes have been coupled: VMEC generates a general (2D or 3D) MHD equilibrium including full shaping and pressure anisotropy. This equilibrium is then mapped into Boozer coordinates. The full-wave code LEMan then calculates the power deposition and electromagnetic field strength of a wave field generated by a chosen antenna using a warm model. Finally, the single particle Hamiltonian code VENUS combines the outputs of the two previous codes in order to calculate the evolution of the distribution function. Within VENUS, Monte Carlo operators for Coulomb collisions of the fast particles with the background plasma have been implemented, accounting for pitch angle and energy scattering. Also, ICRH is simulated using Monte Carlo operators on the Doppler shifted resonant layer. The latter operators act in velocity space and induce a change of perpendicular and parallel velocity depending on the electric field strength and the corresponding wave vector. Eventually, the change in the distribution function will then be fed into VMEC for generating a new equilibrium and thus a self-consistent solution can be found. This model is an enhancement of previous studies in that it is able to include full 3D effects such as magnetic ripple, treat the effects of non-zero orbit width consistently and include the generation and effects of pressure anisotropy. Here, first results of coupling the three codes will be shown in 2D tokamak geometries.
Monte Carlo ICRH simulations in fully shaped anisotropic plasmas
NASA Astrophysics Data System (ADS)
Jucker, M.; Graves, J. P.; Cooper, W. A.; Mellet, N.; Brunner, S.
2008-11-01
In order to numerically study the effects of Ion Cyclotron Resonant Heating (ICRH) on the fast particle distribution function in general plasma geometries, three codes have been coupled: VMEC[1] generates a general (2D or 3D) MHD equilibrium including full shaping and pressure anisotropy. This equilibrium is then mapped into Boozer coordinates. The full-wave code LEMan[2], [3] then calculates the power deposition and electromagnetic field strength of a wave field generated by a chosen antenna using a warm model. Finally, the single particle Hamiltonian code VENUS [4, 5] combines the outputs of the two previous codes in order to calculate the evolution of the distribution function. Within VENUS, Monte Carlo operators for Coulomb collisions of the fast particles with the background plasma have been implemented, accounting for pitch angle and energy scattering. Also, ICRH is simulated using Monte Carlo operators on the Doppler shifted resonant layer. The latter operators act in velocity space and induce a change of perpendicular and parallel velocity depending on the electric field strength and the corresponding wave vector. Eventually, the change in the distribution function will then be fed into VMEC for generating a new equilibrium and thus a self-consistent solution can be found. This model is an enhancement of previous studies in that it is able to include full 3D effects such as magnetic ripple, treat the effects of non-zero orbit width consistently and include the generation and effects of pressure anisotropy. Here, first results of coupling the three codes will be shown in 2D tokamak geometries.
Neuman, Keir C.; Block, Steven M.
2006-01-01
Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on—and the measurement of nanometer-level displacements of—optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications. PMID:16878180
Thompson, W.I.
1958-09-30
A cold trap is presented for removing a condensable component from a gas mixture by cooling. It consists of a shell, the exterior surface of which is chilled by a refrigerant, and conductive fins welded inside the shell to condense the gas, and distribute the condensate evenly throughout the length of the trap, so that the trap may function until it becomes completely filled with the condensed solid. The contents may then be removed as either a gas or as a liquid by heating the trap. This device has particuinr use as a means for removing uranium hexafluoride from the gaseous diffusion separation process during equipment breakdown and repair periods.
An engineered anisotropic nanofilm with unidirectional wetting properties
NASA Astrophysics Data System (ADS)
Malvadkar, Niranjan A.; Hancock, Matthew J.; Sekeroglu, Koray; Dressick, Walter J.; Demirel, Melik C.
2010-12-01
Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly(p-xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release droplet ratchet mechanism. Droplet retention forces in the pin and release directions differ by up to 80μN, which is over ten times greater than the values reported for other engineered anisotropic surfaces. The nanofilm provides a microscale smooth surface on which to transport microlitre droplets, and is also relatively easy to synthesize by a bottom-up vapour-phase technique. An accompanying comprehensive model successfully describes the film's anisotropic wetting behaviour as a function of measurable film morphology parameters.
An engineered anisotropic nanofilm with unidirectional wetting properties.
Malvadkar, Niranjan A; Hancock, Matthew J; Sekeroglu, Koray; Dressick, Walter J; Demirel, Melik C
2010-12-01
Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly(p-xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release droplet ratchet mechanism. Droplet retention forces in the pin and release directions differ by up to 80 μN, which is over ten times greater than the values reported for other engineered anisotropic surfaces. The nanofilm provides a microscale smooth surface on which to transport microlitre droplets, and is also relatively easy to synthesize by a bottom-up vapour-phase technique. An accompanying comprehensive model successfully describes the film's anisotropic wetting behaviour as a function of measurable film morphology parameters.
Anisotropic Artificial Impedance Surfaces
NASA Astrophysics Data System (ADS)
Quarfoth, Ryan Gordon
Anisotropic artificial impedance surfaces are a group of planar materials that can be modeled by the tensor impedance boundary condition. This boundary condition relates the electric and magnetic field components on a surface using a 2x2 tensor. The advantage of using the tensor impedance boundary condition, and by extension anisotropic artificial impedance surfaces, is that the method allows large and complex structures to be modeled quickly and accurately using a planar boundary condition. This thesis presents the theory of anisotropic impedance surfaces and multiple applications. Anisotropic impedance surfaces are a generalization of scalar impedance surfaces. Unlike the scalar version, anisotropic impedance surfaces have material properties that are dependent on the polarization and wave vector of electromagnetic radiation that interacts with the surface. This allows anisotropic impedance surfaces to be used for applications that scalar surfaces cannot achieve. Three of these applications are presented in this thesis. The first is an anisotropic surface wave waveguide which allows propagation in one direction, but passes radiation in the orthogonal direction without reflection. The second application is a surface wave beam shifter which splits a surface wave beam in two directions and reduces the scattering from an object placed on the surface. The third application is a patterned surface which can alter the scattered radiation pattern of a rectangular shape. For each application, anisotropic impedance surfaces are constructed using periodic unit cells. These unit cells are designed to give the desired surface impedance characteristics by modifying a patterned metallic patch on a grounded dielectric substrate. Multiple unit cell geometries are analyzed in order to find the setup with the best performance in terms of impedance characteristics and frequency bandwidth.
Formation of Anisotropic Block Copolymer Gels
NASA Astrophysics Data System (ADS)
Liaw, Chya Yan; Shull, Kenneth; Henderson, Kevin; Joester, Derk
2011-03-01
Anisotropic, fibrillar gels are important in a variety of processes. Biomineralization is one example, where the mineralization process often occurs within a matrix of collagen or chitin fibers that trap the mineral precursors and direct the mineralization process. We wish to replicate this type of behavior within block copolymer gels. Particularly, we are interested in employing gels composed of cylindrical micelles, which are anisotropic and closely mimic biological fibers. Micelle geometry is controlled in our system by manipulating the ratio of molecular weights of the two blocks and by controlling the detailed thermal processing history of the copolymer solutions. Small-Angle X-ray Scattering and Dynamic Light Scattering are used to determine the temperature dependence of the gel formation process. Initial experiments are based on a thermally-reversible alcohol-soluble system, that can be subsequently converted to a water soluble system by hydrolysis of a poly(t-butyl methacrylate) block to a poly (methacrylic acid) block. MRSEC.
Anisotropic Nanoparticles and Anisotropic Surface Chemistry.
Burrows, Nathan D; Vartanian, Ariane M; Abadeer, Nardine S; Grzincic, Elissa M; Jacob, Lisa M; Lin, Wayne; Li, Ji; Dennison, Jordan M; Hinman, Joshua G; Murphy, Catherine J
2016-02-18
Anisotropic nanoparticles are powerful building blocks for materials engineering. Unusual properties emerge with added anisotropy-often to an extraordinary degree-enabling countless new applications. For bottom-up assembly, anisotropy is crucial for programmability; isotropic particles lack directional interactions and can self-assemble only by basic packing rules. Anisotropic particles have long fascinated scientists, and their properties and assembly behavior have been the subjects of many theoretical studies over the years. However, only recently has experiment caught up with theory. We have begun to witness tremendous diversity in the synthesis of nanoparticles with controlled anisotropy. In this Perspective, we highlight the synthetic achievements that have galvanized the field, presenting a comprehensive discussion of the mechanisms and products of both seed-mediated and alternative growth methods. We also address recent breakthroughs and challenges in regiospecific functionalization, which is the next frontier in exploiting nanoparticle anisotropy.
Egedal, Jan; Le, Ari; Daughton, William
2013-06-15
From spacecraft data, it is evident that electron pressure anisotropy develops in collisionless plasmas. This is in contrast to the results of theoretical investigations, which suggest this anisotropy should be limited. Common for such theoretical studies is that the effects of electron trapping are not included; simply speaking, electron trapping is a non-linear effect and is, therefore, eliminated when utilizing the standard methods for linearizing the underlying kinetic equations. Here, we review our recent work on the anisotropy that develops when retaining the effects of electron trapping. A general analytic model is derived for the electron guiding center distribution f(v{sub ∥},v{sub ⊥}) of an expanding flux tube. The model is consistent with anisotropic distributions observed by spacecraft, and is applied as a fluid closure yielding anisotropic equations of state for the parallel and perpendicular components (relative to the local magnetic field direction) of the electron pressure. In the context of reconnection, the new closure accounts for the strong pressure anisotropy that develops in the reconnection regions. It is shown that for generic reconnection in a collisionless plasma nearly all thermal electrons are trapped, and dominate the properties of the electron fluid. A new numerical code is developed implementing the anisotropic closure within the standard two-fluid framework. The code accurately reproduces the detailed structure of the reconnection region observed in fully kinetic simulations. These results emphasize the important role of pressure anisotropy for the reconnection process. In particular, for reconnection geometries characterized by small values of the normalized upstream electron pressure, β{sub e∞}, the pressure anisotropy becomes large with p{sub ∥}≫p{sub ⊥} and strong parallel electric fields develop in conjunction with this anisotropy. The parallel electric fields can be sustained over large spatial scales and
NASA Astrophysics Data System (ADS)
Egedal, Jan; Le, Ari; Daughton, William
2013-06-01
From spacecraft data, it is evident that electron pressure anisotropy develops in collisionless plasmas. This is in contrast to the results of theoretical investigations, which suggest this anisotropy should be limited. Common for such theoretical studies is that the effects of electron trapping are not included; simply speaking, electron trapping is a non-linear effect and is, therefore, eliminated when utilizing the standard methods for linearizing the underlying kinetic equations. Here, we review our recent work on the anisotropy that develops when retaining the effects of electron trapping. A general analytic model is derived for the electron guiding center distribution f¯(v∥,v⊥) of an expanding flux tube. The model is consistent with anisotropic distributions observed by spacecraft, and is applied as a fluid closure yielding anisotropic equations of state for the parallel and perpendicular components (relative to the local magnetic field direction) of the electron pressure. In the context of reconnection, the new closure accounts for the strong pressure anisotropy that develops in the reconnection regions. It is shown that for generic reconnection in a collisionless plasma nearly all thermal electrons are trapped, and dominate the properties of the electron fluid. A new numerical code is developed implementing the anisotropic closure within the standard two-fluid framework. The code accurately reproduces the detailed structure of the reconnection region observed in fully kinetic simulations. These results emphasize the important role of pressure anisotropy for the reconnection process. In particular, for reconnection geometries characterized by small values of the normalized upstream electron pressure, βe∞, the pressure anisotropy becomes large with p∥≫p⊥ and strong parallel electric fields develop in conjunction with this anisotropy. The parallel electric fields can be sustained over large spatial scales and, therefore, become important for
NASA Astrophysics Data System (ADS)
Lam, Wai Sze Tiffany
Optical components made of anisotropic materials, such as crystal polarizers and crystal waveplates, are widely used in many complex optical system, such as display systems, microlithography, biomedical imaging and many other optical systems, and induce more complex aberrations than optical components made of isotropic materials. The goal of this dissertation is to accurately simulate the performance of optical systems with anisotropic materials using polarization ray trace. This work extends the polarization ray tracing calculus to incorporate ray tracing through anisotropic materials, including uniaxial, biaxial and optically active materials. The 3D polarization ray tracing calculus is an invaluable tool for analyzing polarization properties of an optical system. The 3x3 polarization ray tracing P matrix developed for anisotropic ray trace assists tracking the 3D polarization transformations along a ray path with series of surfaces in an optical system. To better represent the anisotropic light-matter interactions, the definition of the P matrix is generalized to incorporate not only the polarization change at a refraction/reflection interface, but also the induced optical phase accumulation as light propagates through the anisotropic medium. This enables realistic modeling of crystalline polarization elements, such as crystal waveplates and crystal polarizers. The wavefront and polarization aberrations of these anisotropic components are more complex than those of isotropic optical components and can be evaluated from the resultant P matrix for each eigen-wavefront as well as for the overall image. One incident ray refracting or reflecting into an anisotropic medium produces two eigenpolarizations or eigenmodes propagating in different directions. The associated ray parameters of these modes necessary for the anisotropic ray trace are described in Chapter 2. The algorithms to calculate the P matrix from these ray parameters are described in Chapter 3 for
Shortcut to Adiabaticity for an Anisotropic Gas Containing Quantum Defects.
Papoular, D J; Stringari, S
2015-07-10
We present a shortcut to adiabaticity (STA) protocol applicable to 3D unitary Fermi gases and 2D weakly interacting Bose gases containing defects such as vortices or solitons. Our protocol relies on a new class of exact scaling solutions in the presence of anisotropic time-dependent harmonic traps. It connects stationary states in initial and final traps having the same frequency ratios. The resulting scaling laws exhibit a universal form and also apply to the classical Boltzmann gas. The duration of the STA can be made very short so as to realize a quantum quench from one stationary state to another. When applied to an anisotropically trapped superfluid gas, the STA conserves the shape of the quantum defects hosted by the cloud, thereby acting like a perfect microscope, which sharply contrasts with their strong distortion occurring during the free expansion of the cloud.
Capillary interactions between anisotropic colloidal particles.
Loudet, J C; Alsayed, A M; Zhang, J; Yodh, A G
2005-01-14
We report on the behavior of micron-sized prolate ellipsoids trapped at an oil-water interface. The particles experience strong, anisotropic, and long-ranged attractive capillary interactions which greatly exceed the thermal energy k(B)T. Depending on surface chemistry, the particles aggregate into open structures or chains. Using video microscopy, we extract the pair interaction potential between ellipsoids and show it exhibits a power law behavior over the length scales probed. Our observations can be explained using recent calculations, if we describe the interfacial ellipsoids as capillary quadrupoles.
Geomagnetically trapped anomalous cosmic rays
Selesnick, R.S.; Cummings, A.C.; Cummings, J.R.
1995-06-01
Since its launch in July 1992, the polar-orbiting satellite SAMPEX has been collecting data on geomagnetically trapped heavy ions, predominantly O, N, and Ne, at energies {ge}15 MeV/nucleon and in a narrow L shell range L = 2. Their location, elemental composition, energy spectra, pitch angle distribution, and time variations all support the theory that these particles originated as singly ionized interplanetary anomalous cosmic rays that were stripped of electrons in the Earth`s upper atmosphere and subsequently trapped. The O are observed primarily at pitch angles outside the atmospheric loss cones, consistent with a trapped population, and their distribution there is nearly isotropic. The abundances relative to O of the N, possible Ne, and especially C are lower than the corresponding interplanetary values, which may be indicative of the trapping efficiencies. The distributions of trapped N, O, and Ne in energy and L shell suggest that most of the ions observed at the SAMPEX altitude of {approximately}600 km are not fully stripped when initially trapped. A comparison of the trapped intensity with the much lower interplanetary intensity of anomalous cosmic rays provides model-dependent estimates of the product of the trapping probability and the average trapped particle lifetime against ionization losses in the residual atmosphere for particles that mirror near the SAMPEX altitude. 36 refs., 13 figs., 1 tab.
Anisotropic contrast optical microscope
NASA Astrophysics Data System (ADS)
Peev, D.; Hofmann, T.; Kananizadeh, N.; Beeram, S.; Rodriguez, E.; Wimer, S.; Rodenhausen, K. B.; Herzinger, C. M.; Kasputis, T.; Pfaunmiller, E.; Nguyen, A.; Korlacki, R.; Pannier, A.; Li, Y.; Schubert, E.; Hage, D.; Schubert, M.
2016-11-01
An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent, or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. These images are obtained from sets of multiple images obtained under various polarizer, analyzer, and compensator settings. Up to 16 independent Mueller matrix images can be obtained, while our current setup is limited to 11 images normalized by the unpolarized intensity. We demonstrate the anisotropic contrast optical microscope by measuring lithographically defined micro-patterned anisotropic filters, and we quantify the adsorption of an organic self-assembled monolayer film onto the anisotropic filter. Comparison with an isotropic glass slide demonstrates the image enhancement obtained by our method over microscopy without the use of an anisotropic filter. In our current instrument, we estimate the limit of detection for organic volumetric mass within the object plane of ≈49 fg within ≈7 × 7 μm2 object surface area. Compared to a quartz crystal microbalance with dissipation instrumentation, where contemporary limits require a total load of ≈500 pg for detection, the instrumentation demonstrated here improves
Molecular anisotropic magnetoresistance
NASA Astrophysics Data System (ADS)
Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy
2015-12-01
Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by 3 d transition-metal wires. We show that a gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symmetry filtering properties of the molecules. We further discuss how this molecular anisotropic magnetoresistance (MAMR) can be tuned by the proper choice of materials and their electronic properties.
Anisotropic contrast optical microscope.
Peev, D; Hofmann, T; Kananizadeh, N; Beeram, S; Rodriguez, E; Wimer, S; Rodenhausen, K B; Herzinger, C M; Kasputis, T; Pfaunmiller, E; Nguyen, A; Korlacki, R; Pannier, A; Li, Y; Schubert, E; Hage, D; Schubert, M
2016-11-01
An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent, or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. These images are obtained from sets of multiple images obtained under various polarizer, analyzer, and compensator settings. Up to 16 independent Mueller matrix images can be obtained, while our current setup is limited to 11 images normalized by the unpolarized intensity. We demonstrate the anisotropic contrast optical microscope by measuring lithographically defined micro-patterned anisotropic filters, and we quantify the adsorption of an organic self-assembled monolayer film onto the anisotropic filter. Comparison with an isotropic glass slide demonstrates the image enhancement obtained by our method over microscopy without the use of an anisotropic filter. In our current instrument, we estimate the limit of detection for organic volumetric mass within the object plane of ≈49 fg within ≈7 × 7 μm(2) object surface area. Compared to a quartz crystal microbalance with dissipation instrumentation, where contemporary limits require a total load of ≈500 pg for detection, the instrumentation demonstrated here improves
NASA Astrophysics Data System (ADS)
Butler, E.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Cesar, C. L.; Chapman, S.; Charlton, M.; Deller, A.; Eriksson, S.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jenkins, M. J.; Jonsell, S.; Jørgensen, L. V.; Kemp, S. L.; Kurchaninov, L.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sarid, E.; Seif el Nasr, S.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.
Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art magnetic-minimum atom traps have well depths of only ˜1 T (˜0.5 K for ground state antihydrogen atoms). The atoms annihilate on contact with matter and must be `born' inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic potential energy per particle is on the order of electronvolts, more than 104 times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations due to antihydrogen atoms that had been trapped for at least 172 ms and then released—the first instance of a purely antimatter atomic system confined for any length of time (Andresen et al., Nature 468:673, 2010). We present a description of the main components of the ALPHA traps and detectors that were key to realising this result. We discuss how the antihydrogen atoms were identified and how they were discriminated from the background processes. Since the results published in Andresen et al. (Nature 468:673, 2010), refinements in the antihydrogen production technique have allowed many more antihydrogen atoms to be trapped, and held for much longer times. We have identified antihydrogen atoms that have been trapped for at least 1,000 s in the apparatus (Andresen et al., Nature Physics 7:558, 2011). This is more than sufficient time to interrogate the atoms spectroscopically, as well as to ensure that they have relaxed to their ground state.
NASA Astrophysics Data System (ADS)
Butler, E.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Cesar, C. L.; Chapman, S.; Charlton, M.; Deller, A.; Eriksson, S.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jenkins, M. J.; Jonsell, S.; Jørgensen, L. V.; Kemp, S. L.; Kurchaninov, L.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Rasmussen, C. Ø.; Robicheaux, F.; Sarid, E.; Seif el Nasr, S.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.
2012-12-01
Precision spectroscopic comparison of hydrogen and antihydrogen holds the promise of a sensitive test of the Charge-Parity-Time theorem and matter-antimatter equivalence. The clearest path towards realising this goal is to hold a sample of antihydrogen in an atomic trap for interrogation by electromagnetic radiation. Achieving this poses a huge experimental challenge, as state-of-the-art magnetic-minimum atom traps have well depths of only ˜1 T (˜0.5 K for ground state antihydrogen atoms). The atoms annihilate on contact with matter and must be `born' inside the magnetic trap with low kinetic energies. At the ALPHA experiment, antihydrogen atoms are produced from antiprotons and positrons stored in the form of non-neutral plasmas, where the typical electrostatic potential energy per particle is on the order of electronvolts, more than 104 times the maximum trappable kinetic energy. In November 2010, ALPHA published the observation of 38 antiproton annihilations due to antihydrogen atoms that had been trapped for at least 172 ms and then released—the first instance of a purely antimatter atomic system confined for any length of time (Andresen et al., Nature 468:673, 2010). We present a description of the main components of the ALPHA traps and detectors that were key to realising this result. We discuss how the antihydrogen atoms were identified and how they were discriminated from the background processes. Since the results published in Andresen et al. (Nature 468:673, 2010), refinements in the antihydrogen production technique have allowed many more antihydrogen atoms to be trapped, and held for much longer times. We have identified antihydrogen atoms that have been trapped for at least 1,000 s in the apparatus (Andresen et al., Nature Physics 7:558, 2011). This is more than sufficient time to interrogate the atoms spectroscopically, as well as to ensure that they have relaxed to their ground state.
Anisotropic eddy viscosity models
NASA Technical Reports Server (NTRS)
Carati, D.; Cabot, W.
1996-01-01
A general discussion on the structure of the eddy viscosity tensor in anisotropic flows is presented. The systematic use of tensor symmetries and flow symmetries is shown to reduce drastically the number of independent parameters needed to describe the rank 4 eddy viscosity tensor. The possibility of using Onsager symmetries for simplifying further the eddy viscosity is discussed explicitly for the axisymmetric geometry.
Fractures in anisotropic media
NASA Astrophysics Data System (ADS)
Shao, Siyi
Rocks may be composed of layers and contain fracture sets that cause the hydraulic, mechanical and seismic properties of a rock to be anisotropic. Coexisting fractures and layers in rock give rise to competing mechanisms of anisotropy. For example: (1) at low fracture stiffness, apparent shear-wave anisotropy induced by matrix layering can be masked or enhanced by the presence of a fracture, depending on the fracture orientation with respect to layering, and (2) compressional-wave guided modes generated by parallel fractures can also mask the presence of matrix layerings for particular fracture orientations and fracture specific stiffness. This report focuses on two anisotropic sources that are widely encountered in rock engineering: fractures (mechanical discontinuity) and matrix layering (impedance discontinuity), by investigating: (1) matrix property characterization, i.e., to determine elastic constants in anisotropic solids, (2) interface wave behavior in single-fractured anisotropic media, (3) compressional wave guided modes in parallel-fractured anisotropic media (single fracture orientation) and (4) the elastic response of orthogonal fracture networks. Elastic constants of a medium are required to understand and quantify wave propagation in anisotropic media but are affected by fractures and matrix properties. Experimental observations and analytical analysis demonstrate that behaviors of both fracture interface waves and compressional-wave guided modes for fractures in anisotropic media, are affected by fracture specific stiffness (controlled by external stresses), signal frequency and relative orientation between layerings in the matrix and fractures. A fractured layered medium exhibits: (1) fracture-dominated anisotropy when the fractures are weakly coupled; (2) isotropic behavior when fractures delay waves that are usually fast in a layered medium; and (3) matrix-dominated anisotropy when the fractures are closed and no longer delay the signal. The
Parallel Anisotropic Tetrahedral Adaptation
NASA Technical Reports Server (NTRS)
Park, Michael A.; Darmofal, David L.
2008-01-01
An adaptive method that robustly produces high aspect ratio tetrahedra to a general 3D metric specification without introducing hybrid semi-structured regions is presented. The elemental operators and higher-level logic is described with their respective domain-decomposed parallelizations. An anisotropic tetrahedral grid adaptation scheme is demonstrated for 1000-1 stretching for a simple cube geometry. This form of adaptation is applicable to more complex domain boundaries via a cut-cell approach as demonstrated by a parallel 3D supersonic simulation of a complex fighter aircraft. To avoid the assumptions and approximations required to form a metric to specify adaptation, an approach is introduced that directly evaluates interpolation error. The grid is adapted to reduce and equidistribute this interpolation error calculation without the use of an intervening anisotropic metric. Direct interpolation error adaptation is illustrated for 1D and 3D domains.
Anisotropic blockade using pendular long-range Rydberg molecules
NASA Astrophysics Data System (ADS)
Eiles, Matthew T.; Lee, Hyunwoo; Pérez-Ríos, Jesús; Greene, Chris H.
2017-05-01
We propose an experiment to demonstrate a blockade mechanism caused by long-range anisotropic interactions in an ultracold dipolar gas composed of the recently observed "butterfly" Rydberg molecules. At the blockade radius, the strong intermolecular interaction between two adjacent molecules shifts their molecular states out of resonance with the photoassociation laser, preventing their simultaneous excitation. When the molecules are prepared in a quasi-one-dimensional (Q1D) trap, the interaction's strength can be tuned via a weak external field. The molecular density thus depends strongly on the angle between the trap axis and the field. The available Rydberg and internal molecular states provide a wide range of tunability.
Anisotropic blockade using pendular long-range Rydberg molecules
NASA Astrophysics Data System (ADS)
Eiles, M. T.; Lee, H.; Pérez-Ríos, J.; Greene, C. H.
2017-07-01
We propose an experiment to demonstrate a novel blockade mechanism caused by long-range anisotropic interactions in an ultracold dipolar gas composed of the recently observed "butterfly" Rydberg molecules. At the blockade radius, the strong intermolecular interaction between two adjacent molecules shifts their molecular states out of resonance with the photoassociation laser, preventing their simultaneous excitation. When the molecules are prepared in a quasi-one-dimensional (Q1D) trap, the interaction's strength can be tuned via a weak external field. The molecular density thus depends strongly on the angle between the trap axis and the field. The available Rydberg and molecular states provide a wide range of tunability.
Combined acoustic and optical trapping
Thalhammer, G.; Steiger, R.; Meinschad, M.; Hill, M.; Bernet, S.; Ritsch-Marte, M.
2011-01-01
Combining several methods for contact free micro-manipulation of small particles such as cells or micro-organisms provides the advantages of each method in a single setup. Optical tweezers, which employ focused laser beams, offer very precise and selective handling of single particles. On the other hand, acoustic trapping with wavelengths of about 1 mm allows the simultaneous trapping of many, comparatively large particles. With conventional approaches it is difficult to fully employ the strengths of each method due to the different experimental requirements. Here we present the combined optical and acoustic trapping of motile micro-organisms in a microfluidic environment, utilizing optical macro-tweezers, which offer a large field of view and working distance of several millimeters and therefore match the typical range of acoustic trapping. We characterize the acoustic trapping forces with the help of optically trapped particles and present several applications of the combined optical and acoustic trapping, such as manipulation of large (75 μm) particles and active particle sorting. PMID:22025990
Anisotropic Total Variation Filtering
Grasmair, Markus; Lenzen, Frank
2010-12-15
Total variation regularization and anisotropic filtering have been established as standard methods for image denoising because of their ability to detect and keep prominent edges in the data. Both methods, however, introduce artifacts: In the case of anisotropic filtering, the preservation of edges comes at the cost of the creation of additional structures out of noise; total variation regularization, on the other hand, suffers from the stair-casing effect, which leads to gradual contrast changes in homogeneous objects, especially near curved edges and corners. In order to circumvent these drawbacks, we propose to combine the two regularization techniques. To that end we replace the isotropic TV semi-norm by an anisotropic term that mirrors the directional structure of either the noisy original data or the smoothed image. We provide a detailed existence theory for our regularization method by using the concept of relaxation. The numerical examples concluding the paper show that the proposed introduction of an anisotropy to TV regularization indeed leads to improved denoising: the stair-casing effect is reduced while at the same time the creation of artifacts is suppressed.
Ehrsam, Eric; Kallini, Joseph R.; Lebas, Damien; Modiano, Philippe; Cotten, Hervé
2016-01-01
Fully regressive melanoma is a phenomenon in which the primary cutaneous melanoma becomes completely replaced by fibrotic components as a result of host immune response. Although 10 to 35 percent of cases of cutaneous melanomas may partially regress, fully regressive melanoma is very rare; only 47 cases have been reported in the literature to date. AH of the cases of fully regressive melanoma reported in the literature were diagnosed in conjunction with metastasis on a patient. The authors describe a case of fully regressive melanoma without any metastases at the time of its diagnosis. Characteristic findings on dermoscopy, as well as the absence of melanoma on final biopsy, confirmed the diagnosis. PMID:27672418
Feshbach resonances of harmonically trapped atoms
Schneider, Philipp-Immanuel; Vanne, Yulian V.; Saenz, Alejandro
2011-03-15
Employing a short-range two-channel description, we derive an analytic model of atoms in isotropic and anisotropic harmonic traps at a Feshbach resonance. On this basis we obtain a parametrization of the energy-dependent scattering length that differs from the one previously employed. We validate the model by comparison to full numerical calculations for {sup 6}Li-{sup 87}Rb and explain quantitatively the experimental observation of a resonance shift and trap-induced molecules in exited bands. Finally, we analyze the bound state admixture and Landau-Zener transition probabilities.
NASA Technical Reports Server (NTRS)
2006-01-01
3 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the margin of a lava flow on a cratered plain in the Athabasca Vallis region of Mars. Remarkably, the cratered plain in this scene is essentially free of bright, windblown ripples. Conversely, the lava flow apparently acted as a trap for windblown materials, illustrated by the presence of the light-toned, wave-like texture over much of the flow. That the lava flow surface trapped windblown sand and granules better than the cratered plain indicates that the flow surface has a rougher texture at a scale too small to resolve in this image.
Location near: 10.7oN, 204.5oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter
Cosmic anisotropic doomsday in Bianchi type I universes
NASA Astrophysics Data System (ADS)
Cataldo, Mauricio; Cid, Antonella; Labraña, Pedro; Mella, Patricio
2016-11-01
In this paper we study finite time future singularities in anisotropic Bianchi type I models. It is shown that there exist future singularities similar to Big Rip ones (which appear in the framework of phantom Friedmann-Robertson-Walker cosmologies). Specifically, in an ellipsoidal anisotropic scenario or in a fully anisotropic scenario, the three directional and average scale factors may diverge at a finite future time, together with energy densities and anisotropic pressures. We call these singularities "Anisotropic Big Rip Singularities." We show that there also exist Bianchi type I models filled with matter, where one or two directional scale factors may diverge. Another type of future anisotropic singularities is shown to be present in vacuum cosmologies, i.e., Kasner spacetimes. These singularities are induced by the shear scalar, which also blows up at a finite time. We call such a singularity "Vacuum Rip." In this case one directional scale factor blows up, while the other two and average scale factors tend to zero.
Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates.
Yang, Tao; Hu, Zhi-Qiang; Zou, Shan; Liu, Wu-Ming
2016-07-28
Dynamics of vortex clusters is essential for understanding diverse superfluid phenomena. In this paper, we examine the dynamics of vortex quadrupoles in a trapped two-dimensional (2D) Bose-Einstein condensate. We find that the movement of these vortex-clusters fall into three distinct regimes which are fully described by the radial positions of the vortices in a 2D isotropic harmonic trap, or by the major radius (minor radius) of the elliptical equipotential lines decided by the vortex positions in a 2D anisotropic harmonic trap. In the "recombination" and "exchange" regimes the quadrupole structure maintains, while the vortices annihilate each other permanently in the "annihilation" regime. We find that the mechanism of the charge flipping in the "exchange" regime and the disappearance of the quadrupole structure in the "annihilation" regime are both through an intermediate state where two vortex dipoles connected through a soliton ring. We give the parameter ranges for these three regimes in coordinate space for a specific initial configuration and phase diagram of the vortex positions with respect to the Thomas-Fermi radius of the condensate. We show that the results are also applicable to systems with quantum fluctuations for the short-time evolution.
Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates
Yang, Tao; Hu, Zhi-Qiang; Zou, Shan; Liu, Wu-Ming
2016-01-01
Dynamics of vortex clusters is essential for understanding diverse superfluid phenomena. In this paper, we examine the dynamics of vortex quadrupoles in a trapped two-dimensional (2D) Bose-Einstein condensate. We find that the movement of these vortex-clusters fall into three distinct regimes which are fully described by the radial positions of the vortices in a 2D isotropic harmonic trap, or by the major radius (minor radius) of the elliptical equipotential lines decided by the vortex positions in a 2D anisotropic harmonic trap. In the “recombination” and “exchange” regimes the quadrupole structure maintains, while the vortices annihilate each other permanently in the “annihilation” regime. We find that the mechanism of the charge flipping in the “exchange” regime and the disappearance of the quadrupole structure in the “annihilation” regime are both through an intermediate state where two vortex dipoles connected through a soliton ring. We give the parameter ranges for these three regimes in coordinate space for a specific initial configuration and phase diagram of the vortex positions with respect to the Thomas-Fermi radius of the condensate. We show that the results are also applicable to systems with quantum fluctuations for the short-time evolution. PMID:27464981
NASA Astrophysics Data System (ADS)
Go, Gi-Hyun; Heo, Seungjin; Cho, Jong-Hoi; Yoo, Yang-Seok; Kim, Minkwan; Park, Chung-Hyun; Cho, Yong-Hoon
2017-03-01
As interest in anisotropic particles has increased in various research fields, methods of tracking such particles have become increasingly desirable. Here, we present a new and intuitive method to monitor the Brownian motion of a nanowire, which can construct and visualize multi-dimensional motion of a nanowire confined in an optical trap, using a dual particle tracking system. We measured the isolated angular fluctuations and translational motion of the nanowire in the optical trap, and determined its physical properties, such as stiffness and torque constants, depending on laser power and polarization direction. This has wide implications in nanoscience and nanotechnology with levitated anisotropic nanoparticles.
Go, Gi-Hyun; Heo, Seungjin; Cho, Jong-Hoi; Yoo, Yang-Seok; Kim, MinKwan; Park, Chung-Hyun; Cho, Yong-Hoon
2017-01-01
As interest in anisotropic particles has increased in various research fields, methods of tracking such particles have become increasingly desirable. Here, we present a new and intuitive method to monitor the Brownian motion of a nanowire, which can construct and visualize multi-dimensional motion of a nanowire confined in an optical trap, using a dual particle tracking system. We measured the isolated angular fluctuations and translational motion of the nanowire in the optical trap, and determined its physical properties, such as stiffness and torque constants, depending on laser power and polarization direction. This has wide implications in nanoscience and nanotechnology with levitated anisotropic nanoparticles. PMID:28272445
Go, Gi-Hyun; Heo, Seungjin; Cho, Jong-Hoi; Yoo, Yang-Seok; Kim, MinKwan; Park, Chung-Hyun; Cho, Yong-Hoon
2017-03-08
As interest in anisotropic particles has increased in various research fields, methods of tracking such particles have become increasingly desirable. Here, we present a new and intuitive method to monitor the Brownian motion of a nanowire, which can construct and visualize multi-dimensional motion of a nanowire confined in an optical trap, using a dual particle tracking system. We measured the isolated angular fluctuations and translational motion of the nanowire in the optical trap, and determined its physical properties, such as stiffness and torque constants, depending on laser power and polarization direction. This has wide implications in nanoscience and nanotechnology with levitated anisotropic nanoparticles.
Anisotropic Weyl symmetry and cosmology
Moon, Taeyoon; Oh, Phillial; Sohn, Jongsu E-mail: ploh@skku.edu
2010-11-01
We construct an anisotropic Weyl invariant theory in the ADM formalism and discuss its cosmological consequences. It extends the original anisotropic Weyl invariance of Hořava-Lifshitz gravity using an extra scalar field. The action is invariant under the anisotropic transformations of the space and time metric components with an arbitrary value of the critical exponent z. One of the interesting features is that the cosmological constant term maintains the anisotropic symmetry for z = −3. We also include the cosmological fluid and show that it can preserve the anisotropic Weyl invariance if the equation of state satisfies P = zρ/3. Then, we study cosmology of the Einstein-Hilbert-anisotropic Weyl (EHaW) action including the cosmological fluid, both with or without anisotropic Weyl invariance. The correlation of the critical exponent z and the equation of state parameter ω-bar provides a new perspective of the cosmology. It is also shown that the EHaW action admits a late time accelerating universe for an arbitrary value of z when the anisotropic conformal invariance is broken, and the anisotropic conformal scalar field is interpreted as a possible source of dark energy.
On the relativistic anisotropic configurations
NASA Astrophysics Data System (ADS)
Shojai, F.; Kohandel, M.; Stepanian, A.
2016-06-01
In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov equations, we explore the relativistic anisotropic Lane-Emden equations. We find how the anisotropic pressure affects the boundary conditions of these equations. Also we argue that the behavior of physical quantities near the center of star changes in the presence of anisotropy. For constant density, a class of exact solution is derived with the aid of a new ansatz and its physical properties are discussed.
Salisbury hospital's steam trap success.
Baillie, Jonathan
2011-03-01
With the Carbon Reduction Commitment now fully in force, and the NHS tasked with achieving tough carbon emission reduction targets in line with both UK and EU mandates, healthcare estates teams across the country are seeking cost-effective ways to reduce energy consumption. Against this backdrop, Salisbury District Hospital has implemented a concerted energy-saving programme, key elements of which include replacing existing bucket steam traps with higher performing, lower maintenance, and more effective GEM venturi steam traps from Thermal Energy International (TEI), installing a new gas CHP engine, and looking into fitting a TEI condensate economiser system.
Andresen, G B; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jonsell, S; Jørgensen, L V; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; el Nasr, S Seif; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y
2010-12-02
Antimatter was first predicted in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 10(14) for the frequency of the 1s-to-2s transition), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 10(7) antiprotons and 7 × 10(8) positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4 ± 1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.
Anisotropic multiple bounce models
NASA Astrophysics Data System (ADS)
Bacalhau, Anna Paula; Peter, Patrick; Vitenti, Sandro D. P.
2017-07-01
We analyze the Galileon ghost condensate implementation of a bouncing cosmological model in the presence of a non-negligible anisotropic stress. We exhibit its structure, which we find to be far richer than previously thought. In particular, even restricting attention to a single set of underlying microscopic parameters, we obtain, numerically, many qualitatively different regimes: depending on the initial conditions on the scalar field leading the dynamics of the Universe, the contraction phase can evolve directly towards a singularity, avoid it by bouncing once, or even bounce many times before settling into an ever-expanding phase. We clarify the behavior of the anisotropies in these various situations.
Dickakian, G. B.
1985-11-05
An improved process for preparing an optically anisotropic pitch which comprises heating a pitch feed material at a temperature within the range of about 350/sup 0/ C. to 450/sup 0/ C. while passing an inert gas therethrough at a rate of at least 2.5 SCFH/lb of pitch feed material and agitating said pitch feed material at a stirrer rate of from about 500 to 600 rpm to obtain an essentially 100% mesophase pitch product suitable for carbon production.
Anisotropic spinfoam cosmology
NASA Astrophysics Data System (ADS)
Rennert, Julian; Sloan, David
2014-01-01
The dynamics of a homogeneous, anisotropic universe are investigated within the context of spinfoam cosmology. Transition amplitudes are calculated for a graph consisting of a single node and three links—the ‘Daisy graph’—probing the behaviour a classical Bianchi I spacetime. It is shown further how the use of such single node graphs gives rise to a simplification of states such that all orders in the spin expansion can be calculated, indicating that it is the vertex expansion that contains information about quantum dynamics.
Lew, H.S.
1988-02-09
A solar trap for collecting solar energy at a concentrated level is described comprising: (a) a compound light funnel including a pair of light reflecting substantially planar members arranged into a trough having a substantially V-shaped cross section; (b) a two dimensional Fresnel lens cover covering the opening of the compound light funnel, the opening being the open diverging end of the substantially V-shaped cross section of the compound light funnel; (c) at least one conduit for carrying a heat transfer fluid disposed substantially adjacent and substantially parallel to the apex line of the compound light funnel.
Gordon, H.S.
1959-09-15
An improved adsorption vacuum trap for use in vacuum systems was designed. The distinguishing feature is the placement of a plurality of torsionally deformed metallic fins within a vacuum jacket extending from the walls to the central axis so that substantially all gas molecules pass through the jacket will impinge upon the fin surfaces. T fins are heated by direct metallic conduction, thereby ol taining a uniform temperature at the adeorbing surfaces so that essentially all of the condensible impurities from the evacuating gas are removed from the vacuum system.
Milleron, N.
1963-03-12
An improved linear-flow cold trap is designed for highvacuum applications such as mitigating back migration of diffusion pump oil moiecules. A central pot of liquid nitrogen is nested within and supported by a surrounding, vertical, helical coil of metai sheet, all enveloped by a larger, upright, cylindrical, vacuum vessel. The vertical interstices between successive turns of the coil afford lineal, axial, high-vacuum passages between open mouths at top and bottom of said vessel, while the coil, being cold by virtue of thermal contact of its innermost turn with the nitrogen pot, affords expansive proximate condensation surfaces. (AEC)
Inhomogeneous anisotropic cosmology
NASA Astrophysics Data System (ADS)
Kleban, Matthew; Senatore, Leonardo
2016-10-01
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Inhomogeneous anisotropic cosmology
Kleban, Matthew; Senatore, Leonardo
2016-10-12
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with “flat” (including toroidal) and “open” (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are “flat” or “open”. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with “flat” or “open” topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Inhomogeneous anisotropic cosmology
Kleban, Matthew; Senatore, Leonardo
2016-10-12
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here in this paper, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with "flat'' (including toroidal) and "open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarilymore » large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with "flat'' or "open" topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.« less
Inhomogeneous anisotropic cosmology
Kleban, Matthew; Senatore, Leonardo
2016-10-12
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here in this paper, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with "flat'' (including toroidal) and "open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with "flat'' or "open" topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Anisotropic Particles in Turbulence
NASA Astrophysics Data System (ADS)
Voth, Greg A.; Soldati, Alfredo
2017-01-01
Anisotropic particles are common in many industrial and natural turbulent flows. When these particles are small and neutrally buoyant, they follow Lagrangian trajectories while exhibiting rich orientational dynamics from the coupling of their rotation to the velocity gradients of the turbulence field. This system has proven to be a fascinating application of the fundamental properties of velocity gradients in turbulence. When particles are not neutrally buoyant, they experience preferential concentration and very different preferential alignment than neutrally buoyant tracer particles. A vast proportion of the parameter range of anisotropic particles in turbulence is still unexplored, with most existing research focusing on the simple foundational cases of axisymmetric ellipsoids at low concentrations in homogeneous isotropic turbulence and in turbulent channel flow. Numerical simulations and experiments have recently developed a fairly comprehensive picture of alignment and rotation in these cases, and they provide an essential foundation for addressing more complex problems of practical importance. Macroscopic effects of nonspherical particle dynamics include preferential concentration in coherent structures and drag reduction by fiber suspensions. We review the models used to describe nonspherical particle motion, along with numerical and experimental methods for measuring particle dynamics.
Anisotropic power-law inflation
Kanno, Sugumi; Soda, Jiro; Watanabe, Masa-aki E-mail: jiro@tap.scphys.kyoto-u.ac.jp
2010-12-01
We study an inflationary scenario in supergravity model with a gauge kinetic function. We find exact anisotropic power-law inflationary solutions when both the potential function for an inflaton and the gauge kinetic function are exponential type. The dynamical system analysis tells us that the anisotropic power-law inflation is an attractor for a large parameter region.
A hybrid-stress finite element for linear anisotropic elasticity
NASA Technical Reports Server (NTRS)
Fly, Gerald W.; Oden, J. Tinsley; Pearson, Mark L.
1988-01-01
Standard assumed displacement finite elements with anisotropic material properties perform poorly in complex stress fields such as combined bending and shear and combined bending and torsion. A set of three dimensional hybrid-stress brick elements were developed with fully anisotropic material properties. Both eight-node and twenty-node bricks were developed based on the symmetry group theory of Punch and Atluri. An eight-node brick was also developed using complete polynomials and stress basis functions and reducing the order of the resulting stress parameter matrix by applying equilibrium constraints and stress compatibility constraints. Here the stress compatibility constraints must be formulated assuming anisotropic material properties. The performance of these elements was examined in numerical examples covering a broad range of stress distributions. The stress predictions show significant improvement over the assumed displacement elements but the calculation time is increased.
Anisotropic Kepler and anisotropic two fixed centres problems
NASA Astrophysics Data System (ADS)
Maciejewski, Andrzej J.; Przybylska, Maria; Szumiński, Wojciech
2017-02-01
In this paper we show that the anisotropic Kepler problem is dynamically equivalent to a system of two point masses which move in perpendicular lines (or planes) and interact according to Newton's law of universal gravitation. Moreover, we prove that generalised version of anisotropic Kepler problem as well as anisotropic two centres problem are non-integrable. This was achieved thanks to investigation of differential Galois groups of variational equations along certain particular solutions. Properties of these groups yield very strong necessary integrability conditions.
Thermodynamics of anisotropic branes
NASA Astrophysics Data System (ADS)
Ávila, Daniel; Fernández, Daniel; Patiño, Leonardo; Trancanelli, Diego
2016-11-01
We study the thermodynamics of flavor D7-branes embedded in an anisotropic black brane solution of type IIB supergravity. The flavor branes undergo a phase transition between a `Minkowski embedding', in which they lie outside of the horizon, and a `black hole embedding', in which they fall into the horizon. This transition depends on the black hole temperature, its degree of anisotropy, and the mass of the flavor degrees of freedom. It happens either at a critical temperature or at a critical anisotropy. A general lesson we learn from this analysis is that the anisotropy, in this particular realization, induces similar effects as the temperature. In particular, increasing the anisotropy bends the branes more and more into the horizon. Moreover, we observe that the transition becomes smoother for higher anisotropies.
WANTED: Fully Automated Indexing.
ERIC Educational Resources Information Center
Purcell, Royal
1991-01-01
Discussion of indexing focuses on the possibilities of fully automated indexing. Topics discussed include controlled indexing languages such as subject heading lists and thesauri, free indexing languages, natural indexing languages, computer-aided indexing, expert systems, and the need for greater creativity to further advance automated indexing.…
An In-Depth Tutorial on Constitutive Equations for Elastic Anisotropic Materials
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.
2011-01-01
An in-depth tutorial on the constitutive equations for elastic, anisotropic materials is presented. Basic concepts are introduced that are used to characterize materials, and notions about how anisotropic material deform are presented. Hooke s law and the Duhamel-Neuman law for isotropic materials are presented and discussed. Then, the most general form of Hooke s law for elastic anisotropic materials is presented and symmetry requirements are given. A similar presentation is also given for the generalized Duhamel-Neuman law for elastic, anisotropic materials that includes thermal effects. Transformation equations for stress and strains are presented and the most general form of the transformation equations for the constitutive matrices are given. Then, specialized transformation equations are presented for dextral rotations about the coordinate axes. Next, concepts of material symmetry are introduced and criteria for material symmetries are presented. Additionally, engineering constants of fully anisotropic, elastic materials are derived from first principles and the specialized to several cases of practical importance.
NASA Technical Reports Server (NTRS)
Bearman, Gregory H.; Bradley, James G.
1993-01-01
Micromachined traps devised to capture dust particles for analysis without contaminating them. Based on micromachined structures retaining particles, rather than adhesives or greases interfering with scanning-electron-microscope analysis or x-ray imaging. Unlike maze traps and traps enmeshing particles in steel wool or similar materials, micromachined traps do not obscure trapped particles. Internal geometries of traps range from simple cones to U-shapes, all formed by etching silicon.
Propagation characteristics of an extremely anisotropic metamaterial loaded helical guide.
Sharma, Dushyant K; Pathak, Surya K
2016-12-26
In this study, we report slow wave propagation characteristics of an extremely anisotropic metamaterial loaded helical guide (EAMLHG). An analytical expression has been theoretically derived and numerically computed to get exact solutions of all possible guided modes of propagation. Anisotropy is defined in terms of positive longitudinal permittivity (ϵz > 0) and negatives transverse permittivity value (ϵt < 0). The waveguide supports hybrid (HE) mode propagation and possesses characteristics of backward wave (BW) mode, forward wave (FW) mode, zero-group velocity and mode-degeneracy. The large value of effective index of BW mode and mode-degeneracy mechanism leads to slowing and trapping of electromagnetic (EM) wave. Closed-form guided mode energy propagation expressions has been also derived and computed which exhibits zero power flow at mode degeneracy point. A comparative study is also carried out between extremely anisotropic metamaterial helical waveguide (EAMLHG) and conventional extremely anisotropic metamaterial cylindrical guide (EAMCG), which reveals enhanced slow wave behaviour. Engineering feasible design and analysis is also presented by combining alternate disks of silver and glass as an extremely anisotropic medium which exhibits lossy and dispersive properties. This type of waveguide can find applications as a filter, phase shifter, and delay lines in microwave to THz applications and, as an optical buffer in optoelectronics applications.
On the Penning trap coherent states
NASA Astrophysics Data System (ADS)
Genkin, M.; Lindroth, E.
2009-07-01
Recently, a class of coherent states of a particle in a Penning trap was derived by Fernández and Velázquez (2009 J. Phys. A: Math. Theor. 42 085304). By means of the Wigner function and density matrix associated with these states, we show that they are fully consistent with Morikawa's definition of the decoherence degree and hence they provide a possibility to directly access the decoherence process in a Penning trap.
Cracking on anisotropic neutron stars
NASA Astrophysics Data System (ADS)
Setiawan, A. M.; Sulaksono, A.
2017-07-01
We study the effect of cracking of a local anisotropic neutron star (NS) due to small density fluctuations. It is assumed that the neutron star core consists of leptons, nucleons and hyperons. The relativistic mean field model is used to describe the core of equation of state (EOS). For the crust, we use the EOS introduced by Miyatsu et al. [1]. Furthermore, two models are used to describe pressure anisotropic in neutron star matter. One is proposed by Doneva-Yazadjiev (DY) [2] and the other is proposed by Herrera-Barreto (HB) [3]. The anisotropic parameter of DY and HB models are adjusted in order the predicted maximum mass compatible to the mass of PSR J1614-2230 [4] and PSR J0348+0432 [5]. We have found that cracking can potentially present in the region close to the neutron star surface. The instability due cracking is quite sensitive to the NS mass and anisotropic parameter used.
[Fully implantable hearing systems].
Maurer, J
2009-03-01
As yet comparatively little experience has been gained with fully implantable hearing systems, as the two systems available at present have only recently received CE permission for Europe and the FDA permissions are still pending in the USA. Additionally the technology is expensive and usually not covered by insurance companies. However, it could be shown that by careful patient selection and very careful surgical techniques, good results can be achieved with this highly sensitive technology, often with better patient satisfaction and hearing quality than with conventional hearing aids. To spread the technology further, the systems must also show reliable results on a broad application. Further surgery to change the batteries should not be necessary more frequently than with cardiac pacemakers. Not all technical problems are finally solved. However, it is to be foreseen that fully implantable hearing systems will be a good long-term alternative to conventional hearing aids for some patients.
Cryogenic surface-electrode ion trap apparatus
NASA Astrophysics Data System (ADS)
Dubielzig, Timko; Carsjens, Martina; Kohnen, Matthias; Grondkowski, Sebastian; Ospelkaus, Christian
2014-05-01
In this talk we describe the infrastructure necessary to operate a surface-electrode ion trap with integrated microwave conductors for near-field quantum control of 9Be+ in a cryogenic environment. These traps are promising systems for analog quantum simulators and for quantum logic applications. Our group recently developed a trap with an integrated meander-like microwave guide for driving motional sidebands on an 9Be+ ion. The trap will be operated in a cryogenic vacuum chamber. We will discuss the vibrational isolated closed cycle cryostat and the design of the vacuum chamber with all electrical supplies necessary to apply two different microwave currents, dc voltages and three independent rf supplies to generate a reconfigurable rf trapping potential. We will also discuss the used hyperfine qubit and the laser systems required to cool and repump. Furthermore we will present the cryogenic, high aperture and fully acromatic imaging system.
Actuation performances of anisotropic gels
NASA Astrophysics Data System (ADS)
Nardinocchi, P.; Teresi, L.
2016-12-01
We investigated the actuation performances of anisotropic gels driven by mechanical and chemical stimuli, in terms of both deformation processes and stroke-curves, and distinguished between the fast response of gels before diffusion starts and the asymptotic response attained at the steady state. We also showed as the range of forces that an anisotropic hydrogel can exert when constrained is especially wide; indeed, changing fiber orientation allows us to induce shear as well as transversely isotropic extensions.
Anisotropic assembly and pattern formation
NASA Astrophysics Data System (ADS)
von Brecht, James H.; Uminsky, David T.
2017-01-01
We investigate the role of anisotropy in two classes of individual-based models for self-organization, collective behavior and self-assembly. We accomplish this via first-order dynamical systems of pairwise interacting particles that incorporate anisotropic interactions. At a continuum level, these models represent the natural anisotropic variants of the well-known aggregation equation. We leverage this framework to analyze the impact of anisotropic effects upon the self-assembly of co-dimension one equilibrium structures, such as micelles and vesicles. Our analytical results reveal the regularizing effect of anisotropy, and isolate the contexts in which anisotropic effects are necessary to achieve dynamical stability of co-dimension one structures. Our results therefore place theoretical limits on when anisotropic effects can be safely neglected. We also explore whether anisotropic effects suffice to induce pattern formation in such particle systems. We conclude with brief numerical studies that highlight various aspects of the models we introduce, elucidate their phase structure and partially validate the analysis we provide.
Anisotropic microsrheology of self-assembling collagen networks
NASA Astrophysics Data System (ADS)
Dutov, Pavel
Collagen is the main component of human connective tissue and extracellular matrix. Here we report multiple novel methods for utilizing optical tweezers to measure mechanical properties of different hierarchical levels of collagenous materials. First, we introduce a method for optical trap calibration that is suitable for viscoelastic material. The method is designed for use on experimental setups with two optical tweezers and is based on pulling a trapped particle with one trap while holding it with the other. The method combines advantages of commonly known PSD-fitting and fast-sweeping methods, allowing calibration of a completely fixed trap in a fluid of unknown viscosity/viscoelasticity without additional expensive equipment. Then we report an approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found in vivo and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. The approach also avoids the traditional drying-soaking cycle, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. Lastly, we report a new method for characterizing anisotropic viscoelastic response of collagenous matrices. Anisotropic collagenous extracellular matrices are used in biomedicine to enhance the wound healing process by directing fibroblast proliferation. We utilize an optical trap to monitor the thermal fluctuations of microspheres embedded into collagenous network to extract a viscoelastic response function of the network along the principal axes of anisotropy.
An active bubble trap and debubbler for microfluidic systems.
Skelley, Alison M; Voldman, Joel
2008-10-01
We present a novel, fully integrated microfluidic bubble trap and debubbler. The 2-layer structure, based on a PDMS valve design, utilizes a featured membrane to stop bubble progression through the device. A pneumatic chamber directly above the trap is evacuated, and the bubble is pulled out through the gas-permeable PDMS membrane. Normal device operation, including continuous flow at atmospheric pressure, is maintained during the entire trapping and debubbling process. We present a range of trap sizes, from 2 to 10 mm diameter, and can trap and remove bubbles up to 25 microL in under 3 h.
Characteristics of trapped proton anisotropy at Space Station Freedom altitudes
Armstrong, T.W.; Colborn, B.L.; Watts, J.W.
1990-10-01
The ionizing radiation dose for spacecraft in low-Earth orbit (LEO) is produced mainly by protons trapped in the Earth's magnetic field. Current data bases describing this trapped radiation environment assume the protons to have an isotropic angular distribution, although the fluxes are actually highly anisotropic in LEO. The anisotropy of the trapped proton exposure has not been an important practical consideration for most previous LEO missions because the random spacecraft orientation during passage through the radiation belt averages out the anisotropy. Thus, in spite of the actual exposure anisotropy, cumulative radiation effects over many orbits can be predicted as if the environment were isotropic when the spacecraft orientation is variable during exposure. However, Space Station Freedom will be gravity gradient stabilized to reduce drag, and, due to this fixed orientation, the cumulative incident proton flux will remain anisotropic. The anisotropy could potentially influence several aspects of Space Station design and operation, such as the appropriate location for radiation sensitive components and experiments, location of workstations and sleeping quarters, and the design and placement of radiation monitors. Also, on-board mass could possible be utilized to counteract the anisotropy effects and reduce the dose exposure. Until recently only omnidirectional data bases for the trapped proton environment were available. However, a method to predict orbit-average, angular dependent (vector) trapped proton flux spectra has been developed from the standard omnidirectional trapped proton data bases.
Light propagation through anisotropic turbulence.
Toselli, Italo; Agrawal, Brij; Restaino, Sergio
2011-03-01
A wealth of experimental data has shown that atmospheric turbulence can be anisotropic; in this case, a Kolmogorov spectrum does not describe well the atmospheric turbulence statistics. In this paper, we show a quantitative analysis of anisotropic turbulence by using a non-Kolmogorov power spectrum with an anisotropic coefficient. The spectrum we use does not include the inner and outer scales, it is valid only inside the inertial subrange, and it has a power-law slope that can be different from a Kolmogorov one. Using this power spectrum, in the weak turbulence condition, we analyze the impact of the power-law variations α on the long-term beam spread and scintillation index for several anisotropic coefficient values ς. We consider only horizontal propagation across the turbulence cells, assuming circular symmetry is maintained on the orthogonal plane to the propagation direction. We conclude that the anisotropic coefficient influences both the long-term beam spread and the scintillation index by the factor ς(2-α).
Trapping polar molecules in an ac trap
Bethlem, Hendrick L.; Veldhoven, Jacqueline van; Schnell, Melanie; Meijer, Gerard
2006-12-15
Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell's equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of {sup 15}ND{sub 3} ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270 mm{sup 3} (m/s){sup 3} remain trapped. This corresponds to a trap depth of about 5 mK and a trap volume of about 20 mm{sup 3}.
Filson, Simon A; Yarhi, Danielle; Ramon, Yitzhak
2016-11-01
The authors present 25 cases and an in-depth 4-minute video of fully awake aesthetic breast reduction, which was made possible by thoracic epidural anesthesia. There are obvious and important advantages to this technique. Not only does this allow for intraoperative patient cooperation (i.e., patient self-positioning and opinion for comparison of breasts), meaning a shorter and more efficient intraoperative time, there also is a reduction in postoperative pain, complications, recovery, and discharge times. The authors have also enjoyed great success and no complications with this technique in over 150 awake abdominoplasty/total body lift patients. The authors feel that the elimination of the need for general anesthesia by thoracic epidural sensorial-only anesthesia is a highly effective and efficient technique, with very few disadvantages/complications, providing advantages to both patients and surgeons. Therapeutic, IV.
Fully automated protein purification
Camper, DeMarco V.; Viola, Ronald E.
2009-01-01
Obtaining highly purified proteins is essential to begin investigating their functional and structural properties. The steps that are typically involved in purifying proteins can include an initial capture, intermediate purification, and a final polishing step. Completing these steps can take several days and require frequent attention to ensure success. Our goal was to design automated protocols that will allow the purification of proteins with minimal operator intervention. Separate methods have been produced and tested that automate the sample loading, column washing, sample elution and peak collection steps for ion-exchange, metal affinity, hydrophobic interaction and gel filtration chromatography. These individual methods are designed to be coupled and run sequentially in any order to achieve a flexible and fully automated protein purification protocol. PMID:19595984
On the boundary of the region containing trapped surfaces
Senovilla, Jose M. M.
2009-05-01
The boundary of the region in spacetime containing future-trapped closed surfaces is considered. In asymptotically flat spacetimes, this boundary does not need to be the event horizon nor a dynamical/trapping horizon. Some properties of this boundary and its localization are analyzed, and illustrated with examples. In particular, fully explicit future-trapped compact surfaces penetrating into flat portions of a Vaidya spacetime are presented.
Anisotropic lattice models of electrolytes
NASA Astrophysics Data System (ADS)
Kobelev, Vladimir; Kolomeisky, Anatoly B.
2002-11-01
Systems of charged particles on anisotropic three-dimensional lattices are investigated theoretically using Debye-Huckel theory. It is found that the thermodynamics of these systems strongly depends on the degree of anisotropy. For weakly anisotropic simple cubic lattices, the results indicate the existence of order-disorder phase transitions and a tricritical point, while the possibility of low-density gas-liquid coexistence is suppressed. For strongly anisotropic lattices this picture changes dramatically: The low-density gas-liquid phase separation reappears and the phase diagram exhibits critical, tricritical, and triple points. For body-centered lattices, the low-density gas-liquid phase coexistence is suppressed for all degrees of anisotropy. These results show that the effect of anisotropy in lattice models of electrolytes amounts to reduction of spatial dimensionality.
Fluctuation relations for anisotropic systems
NASA Astrophysics Data System (ADS)
Villavicencio-Sanchez, R.; Harris, R. J.; Touchette, H.
2014-02-01
Currents of particles or energy in driven non-equilibrium steady states are known to satisfy certain symmetries, referred to as fluctuation relations, determining the ratio of the probabilities of positive fluctuations to negative ones. A generalization of these fluctuation relations has been proposed recently for extended non-equilibrium systems of dimension greater than one, assuming, crucially, that they are isotropic (Hurtado P. I., Pérez-Espigares C., del Pozo J. J. and Garrido P. L., Proc. Natl. Acad. Sci. U.S.A., 108 (2011) 7704). Here we relax this assumption and derive a fluctuation relation for d-dimensional systems having anisotropic bulk driving rates. We test the validity of this anisotropic fluctuation relation by calculating the particle current fluctuations in the 2d anisotropic zero-range process, using both exact and fluctuating hydrodynamic approaches.
Anisotropically structured magnetic aerogel monoliths
NASA Astrophysics Data System (ADS)
Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus
2014-10-01
Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and
Synthetic waveform modelling of SS precursors from anisotropic upper-mantle discontinuities
NASA Astrophysics Data System (ADS)
Rychert, Catherine A.; Harmon, Nicholas; Schmerr, Nicholas
2014-03-01
SS precursors are a powerful tool for interrogating upper-mantle discontinuity structure. Some of these discontinuities may be defined fully or partially by a variation in anisotropy with depth. Therefore, a careful evaluation of SS precursor waveform predictions from anisotropic discontinuities is required. Here, we perform synthetic waveform modelling to evaluate the potential for using SS precursors to constrain anisotropic discontinuities. We investigate SS precursor amplitudes from models with azimuthally anisotropic discontinuities with assumed hexagonal symmetry. We demonstrate that SS precursor polarity variations are robust across a wide range of earthquake source polarizations for our anisotropic models. While polarity variations are not unique among all potential two-layer models with anisotropic discontinuities, other observables, such as the relative arrival time of the precursor and tectonic settings, may be used to constrain anisotropic structure. We discuss implications for previous imaging of upper-mantle discontinuities that may be anisotropic, such as the Lehmann discontinuity, and discontinuities in depth range of the lithosphere-asthenosphere boundary beneath the Pacific.
Lifting a large object from an anisotropic porous bed
NASA Astrophysics Data System (ADS)
Karmakar, Timir; Raja Sekhar, G. P.
2016-09-01
An analytical study of two dimensional problem of lifting an object from the top of a fully saturated rigid porous bed is discussed. It is assumed that the porous bed is anisotropic in nature. The flow within the gap region between the object and the porous bed is assumed to be governed by Stokes equation while the flow within the porous bed is governed by Brinkman equation. The breakout phenomenon for different kinds of soil is reported. The effect of mechanical properties like anisotropic permeability, grain diameter size, and porosity on streamlines, velocity, and force is analyzed. Relevant comparison with C. C. Mei, R. W. Yeung, and K. F. Liu ["Lifting a large object from a porous bed," J. Fluid. Mech. 152, 203-215 (1985)] and Y. Chang, L. H. Huang and F. P. Y. Yang ["Two-dimensional lift-up problem for a rigid porous bed," Phys. Fluids, 27, 053101 (2015)] is done.
Anisotropic mesh adaptivity for multi-scale ocean modelling.
Piggott, M D; Farrell, P E; Wilson, C R; Gorman, G J; Pain, C C
2009-11-28
Research into the use of unstructured mesh methods in oceanography has been growing steadily over the past decade. The advantages of this approach for domain representation and non-uniform resolution are clear. However, a number of issues remain, in particular those related to the computational cost of models produced using unstructured mesh methods compared with their structured mesh counterparts. Mesh adaptivity represents an important means to improve the competitiveness of unstructured mesh models, where high resolution is only used when and where necessary. In this paper, an optimization-based approach to mesh adaptivity is described where emphasis is placed on capturing anisotropic solution characteristics. Comparisons are made between the results obtained with uniform isotropic resolution, isotropic adaptive resolution and fully anisotropic adaptive resolution.
NASA Technical Reports Server (NTRS)
Barrington, A. E.; Caruso, A. J.
1970-01-01
Modified sorption trap for use in high vacuum systems contains provisions for online regeneration of sorbent material. Trap is so constructed that it has a number of encapsulated resistance heaters and a valving and pumping device for removing gases from heated sorbing material. Excessive downtime is eliminated with this trap.
Hamlet, Benjamin Roger
2009-02-01
Ion traps present a potential architecture for future quantum computers. These computers are of interest due to their increased power over classical computers stemming from the superposition of states and the resulting capability to simultaneously perform many computations. This paper describes a software application used to prepare and visualize simulations of trapping and maneuvering ions in ion traps.
Fully non-linear cosmological perturbations of multicomponent fluid and field systems
NASA Astrophysics Data System (ADS)
Hwang, Jai-chan; Noh, Hyerim; Park, Chan-Gyung
2016-09-01
We present fully non-linear and exact cosmological perturbation equations in the presence of multiple components of fluids and minimally coupled scalar fields. We ignore the tensor-type perturbation. The equations are presented without taking the temporal gauge condition in the Friedmann background with general curvature and the cosmological constant. We include the anisotropic stress. Even in the absence of anisotropic stress of individual component, the multiple component nature introduces the anisotropic stress in the collective fluid quantities. We prove the Newtonian limit of multiple fluids in the zero-shear gauge and the uniform-expansion gauge conditions, present the Newtonian hydrodynamic equations in the presence of general relativistic pressure in the zero-shear gauge, and present the fully non-linear equations and the third-order perturbation equations of the non-relativistic pressure fluids in the CDM-comoving gauge.
NASA Astrophysics Data System (ADS)
Casas, Ricard; Cardiel-Sas, Laia; Castander, Francisco J.; Jiménez, Jorge; de Vicente, Juan
2014-08-01
The focal plane of the PAU camera is composed of eighteen 2K x 4K CCDs. These devices, plus four spares, were provided by the Japanese company Hamamatsu Photonics K.K. with type no. S10892-04(X). These detectors are 200 μm thick fully depleted and back illuminated with an n-type silicon base. They have been built with a specific coating to be sensitive in the range from 300 to 1,100 nm. Their square pixel size is 15 μm. The read-out system consists of a Monsoon controller (NOAO) and the panVIEW software package. The deafualt CCD read-out speed is 133 kpixel/s. This is the value used in the calibration process. Before installing these devices in the camera focal plane, they were characterized using the facilities of the ICE (CSIC- IEEC) and IFAE in the UAB Campus in Bellaterra (Barcelona, Catalonia, Spain). The basic tests performed for all CCDs were to obtain the photon transfer curve (PTC), the charge transfer efficiency (CTE) using X-rays and the EPER method, linearity, read-out noise, dark current, persistence, cosmetics and quantum efficiency. The X-rays images were also used for the analysis of the charge diffusion for different substrate voltages (VSUB). Regarding the cosmetics, and in addition to white and dark pixels, some patterns were also found. The first one, which appears in all devices, is the presence of half circles in the external edges. The origin of this pattern can be related to the assembly process. A second one appears in the dark images, and shows bright arcs connecting corners along the vertical axis of the CCD. This feature appears in all CCDs exactly in the same position so our guess is that the pattern is due to electrical fields. Finally, and just in two devices, there is a spot with wavelength dependence whose origin could be the result of a defectous coating process.
NASA Astrophysics Data System (ADS)
Spassky, D. A.; Nagirnyi, V.; Mikhailin, V. V.; Savon, A. E.; Belsky, A. N.; Laguta, V. V.; Buryi, M.; Galashov, E. N.; Shlegel, V. N.; Voronina, I. S.; Zadneprovski, B. I.
2013-10-01
Charge carrier trapping centers have been studied in molybdates CaMoO4, SrMoO4 and PbMoO4 with the scheelite crystal structure as well as in ZnMoO4, which crystallize in a-ZnMoO4 structural type. The trap parameters such as activation energies and frequency factors have been determined. It is shown for the first time that both electrons and holes are trapped by the elements of regular crystal structure in ZnMoO4. The effect of the charge carrier trapping on luminescence properties is demonstrated. Potential influence of the traps on the scintillation process is discussed.
Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving.
Li, Jiaming; de Melo, Leonardo F; Luo, Le
2017-03-30
We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling. This experimental protocol starts with a magneto-optical trap (MOT) that is loaded by a Zeeman slower. The precooled atoms in the MOT are then transferred to an ODT, and a bias magnetic field is applied to create an interacting Fermi gas. We then lower the trapping potential to prepare a cold Fermi gas near the degenerate temperature. After that, we sweep the magnetic field to the noninteracting regime of the Fermi gas, in which the parametric cooling can be manifested by modulating the intensity of the optical trapping beams. We find that the parametric cooling effect strongly depends on the modulation frequencies and amplitudes. With the optimized frequency and amplitude, we measure the dependence of the cloud energy on the modulation time. We observe that the cloud energy is changed in an anisotropic way, where the energy of the axial direction is significantly reduced by parametric driving. The cooling effect is limited to the axial direction because the dominant anharmonicity of the crossed-beam ODT is along the axial direction. Finally, we propose to extend this protocol for the trapping potentials of large anharmonicity in all directions, which provides a promising scheme for cooling quantum gases using external driving.
Trapping in TITANs Cooler Penning Trap
NASA Astrophysics Data System (ADS)
Kootte, Brian; Lascar, Daniel; Paul, Stefan; Gwinner, Gerald; Dilling, Jens; Titan Collaboration
2016-09-01
Penning trap mass spectrometry provides an excellent means of determining the masses of nuclei to high precision. Highly Charged Ions (HCIs) have been successfully used at TRIUMFs Ion Trap for Atomic and Nuclear science (TITAN) to enhance the precision of mass measurements for short-lived species. The gain in precision can theoretically scale with the charge state of the ion, but recent measurements of beam properties have shown that the process of charge breeding ions to higher charge states increases the energy spread of the ion bunch sent to the Penning trap. This reduces the gain from using HCIs. In order to maximize the precision of mass measurements, we are currently performing offline commissioning of a Cooler PEnning Trap (CPET) with the purpose of sympathetically cooling HCI bunches to an energy of 1 eV/q using a plasma of electrons. This will require implementing a nested potential configuration to trap the ions and electrons in the same region so they can interact via coulomb scattering. Recent progress in testing the trapping of electrons and singly charged ions in CPET, leading towards the cooling of HCIs prior to mass measurements in TITANs will be discussed.
Anisotropic ripple deformation in phosphorene
Kou, Liangzhi; Ma, Yandong; Smith, Sean C.; Chen, Changfeng
2015-04-07
Here, two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS_{2}. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classical elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.
Anisotropic ripple deformation in phosphorene
Kou, Liangzhi; Ma, Yandong; Smith, Sean C.; ...
2015-04-07
Here, two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classical elasticitymore » theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.« less
Yield surfaces for anisotropic plates
NASA Astrophysics Data System (ADS)
Walker, J. D.; Thacker, B. H.
2000-04-01
Aerospace systems are incorporating composite materials into their structures. The composite materials are often anisotropic in mechanical response due to their geometric layout. For many years, the failure surfaces of anisotropic materials were thought to be characterizable by a quadratic function in the stress, referred to as a Tsai-Wu yield surface, or, in a more restrictive form, a Tsai-Hill yield surface. Such a representation does not work for materials that are strong in two directions and weak in one direction, which is the case of most interest since it represents fiber/epoxy composite plates. This paper demonstrates the impossibility of modeling the failure surface with either the Tsai-Wu or Tsai-Hill failure surfaces. A yield surface is presented based on the lemniscate, which is quartic in the stress. This new yield surface addresses the case of strong in two directions and weak in one.
Conductivity in an anisotropic background
Lee, Bum-Hoon; Nam, Siyoung; Pang, Da-Wei; Park, Chanyong
2011-03-15
By using the gauge/gravity duality, we investigate the dual field theories of the anisotropic backgrounds, which are exact solutions of Einstein-Maxwell-dilaton theory with a Liouville potential. When we turn on the bulk gauge field fluctuation A{sub x} with a nontrivial dilaton coupling, the AC conductivity of this dual field theory is proportional to the frequency with an exponent depending on parameters of the anisotropic background. In some parameter regions, we find that this conductivity can have the negative exponent like the strange metal. In addition, we also investigate another U(1) gauge field fluctuation, which is not coupled with a dilaton field. We classify all possible conductivities of this system and find that the exponent of the conductivity is always positive.
Anisotropic Ripple Deformation in Phosphorene.
Kou, Liangzhi; Ma, Yandong; Smith, Sean C; Chen, Changfeng
2015-05-07
Two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classical elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.
Cracking in charged anisotropic cylinder
NASA Astrophysics Data System (ADS)
Sharif, M.; Sadiq, Sobia
2017-06-01
In this paper, we study the stability of static charged anisotropic cylindrically symmetric compact object through cracking. The Einstein-Maxwell field equations and conservation equation are formulated. We then apply local density perturbation and study the behavior of force distribution function. Finally, the cracking is explored for two models satisfying specific form of Chaplygin equation of state. It is found that these models exhibit cracking and the instability increases as the value of charge parameter is increased.
Determination of the hydrodynamic friction matrix for various anisotropic particles
NASA Astrophysics Data System (ADS)
Kraft, Daniela; Wittkowksi, Raphael; Löwen, Hartmut; Pine, David
2013-03-01
The relationship between the shape of a colloidal particle and its Brownian motion can be captured by the hydrodynamic friction matrix. It fully describes the translational and rotational diffusion along the particle's main axes as well as the coupling between rotational and translational diffusion. We observed a wide variety of anisotropic colloidal particles with confocal microscopy and calculated the hydrodynamic friction matrix from the particle trajectories. We find that symmetries in the particle shape are reflected in the entries of the friction matrix. We compare our experimentally obtained results with numerical simulations and theoretical predictions. Financial support through a Rubicon grant by the Netherlands Organisation for Scientific Research.
Viscoacoustic anisotropic full waveform inversion
NASA Astrophysics Data System (ADS)
Qu, Yingming; Li, Zhenchun; Huang, Jianping; Li, Jinli
2017-01-01
A viscoacoustic vertical transverse isotropic (VTI) quasi-differential wave equation, which takes account for both the viscosity and anisotropy of media, is proposed for wavefield simulation in this study. The finite difference method is used to solve the equations, for which the attenuation terms are solved in the wavenumber domain, and all remaining terms in the time-space domain. To stabilize the adjoint wavefield, robust regularization operators are applied to the wave equation to eliminate the high-frequency component of the numerical noise produced during the backward propagation of the viscoacoustic wavefield. Based on these strategies, we derive the corresponding gradient formula and implement a viscoacoustic VTI full waveform inversion (FWI). Numerical tests verify that our proposed viscoacoustic VTI FWI can produce accurate and stable inversion results for viscoacoustic VTI data sets. In addition, we test our method's sensitivity to velocity, Q, and anisotropic parameters. Our results show that the sensitivity to velocity is much higher than that to Q and anisotropic parameters. As such, our proposed method can produce acceptable inversion results as long as the Q and anisotropic parameters are within predefined thresholds.
Yield Surfaces for Anisotropic Plates
NASA Astrophysics Data System (ADS)
Walker, J. D.; Thacker, B. H.
1999-06-01
Modern aerospace systems are incorporating composite materials into their structures. Often, the composite materials are anisotropic in their mechanical response due to the geometric layout of fibers. For many years, the failure surfaces of anisotropic materials were thought to be characterizable by a quadratic function in the stress, often referred to as a Tsai-Wu yield surface, or, in a more restrictive form, a Tsai-Hill yield surface. Such a representation does not work for materials that are strong in two directions and weak in one direction, which, unfortunately, is the case of most interest since it represents most composite plates. This paper demonstrates the impossibility of modeling the failure surface with both the Tsai-Wu and Tsai-Hill failure surfaces. We then present a yield surface based on the lemniscate, which is quartic in the stress. This new yield surface addresses the case of strong in two directions and weak in one. Calculations with a fragment impacting a composite plate modeled with the new yield surface are presented. Modifications of the yield surface are presented to allow, in a limited way, materials that are both anisotropic and have differing strengths in tension and compression.
Anisotropic characterization of magnetorheological materials
NASA Astrophysics Data System (ADS)
Dohmen, E.; Modler, N.; Gude, M.
2017-06-01
For the development of energy efficient lightweight parts novel function integrating materials are needed. Concerning this field of application magnetorheological (MR) fluids, MR elastomers and MR composites are promising materials allowing the adjustment of mechanical properties by an external magnetic field. A key issue for operating such structures in praxis is the magneto-mechanical description. Most rheological properties are gathered at laboratory conditions for high magnetic flux densities and a single field direction, which does not correspond to real praxis conditions. Although anisotropic formation of superstructures can be observed in MR suspensions (Fig. 1) or experimenters intentionally polymerize MR elastomers with anisotropic superstructures these MR materials are usually described in an external magnetic field as uniform, isotropic materials. This is due to missing possibilities for experimentally measuring field angle dependent properties and ways of distinguishing between material properties and frictional effects. Just a few scientific works experimentally investigated the influence of different field angles (Ambacher et al., 1992; Grants et al., 1990; Kuzhir et al., 2003) [1-3] or the influence of surface roughness on the shear behaviour of magnetic fluids (Tang and Conrad, 1996) [4]. The aim of this work is the introduction of a novel field angle cell allowing the determination of anisotropic mechanical properties for various MR materials depending on the applied magnetic field angle.
Characteristics of trapped proton anisotropy at Space Station Freedom altitudes
NASA Technical Reports Server (NTRS)
Armstrong, T. W.; Colborn, B. L.; Watts, J. W.
1990-01-01
The ionizing radiation dose for spacecraft in low-Earth orbit (LEO) is produced mainly by protons trapped in the Earth's magnetic field. Current data bases describing this trapped radiation environment assume the protons to have an isotropic angular distribution, although the fluxes are actually highly anisotropic in LEO. The general nature of this directionality is understood theoretically and has been observed by several satellites. The anisotropy of the trapped proton exposure has not been an important practical consideration for most previous LEO missions because the random spacecraft orientation during passage through the radiation belt 'averages out' the anisotropy. Thus, in spite of the actual exposure anisotropy, cumulative radiation effects over many orbits can be predicted as if the environment were isotropic when the spacecraft orientation is variable during exposure. However, Space Station Freedom will be gravity gradient stabilized to reduce drag, and, due to this fixed orientation, the cumulative incident proton flux will remain anisotropic. The anisotropy could potentially influence several aspects of Space Station design and operation, such as the appropriate location for radiation sensitive components and experiments, location of workstations and sleeping quarters, and the design and placement of radiation monitors. Also, on-board mass could possible be utilized to counteract the anisotropy effects and reduce the dose exposure. Until recently only omnidirectional data bases for the trapped proton environment were available. However, a method to predict orbit-average, angular dependent ('vector') trapped proton flux spectra has been developed from the standard omnidirectional trapped proton data bases. This method was used to characterize the trapped proton anisotropy for the Space Station orbit (28.5 degree inclination, circular) in terms of its dependence on altitude, solar cycle modulation (solar minimum vs. solar maximum), shielding thickness
Characteristics of trapped proton anisotropy at Space Station Freedom altitudes
NASA Astrophysics Data System (ADS)
Armstrong, T. W.; Colborn, B. L.; Watts, J. W.
1990-10-01
The ionizing radiation dose for spacecraft in low-Earth orbit (LEO) is produced mainly by protons trapped in the Earth's magnetic field. Current data bases describing this trapped radiation environment assume the protons to have an isotropic angular distribution, although the fluxes are actually highly anisotropic in LEO. The general nature of this directionality is understood theoretically and has been observed by several satellites. The anisotropy of the trapped proton exposure has not been an important practical consideration for most previous LEO missions because the random spacecraft orientation during passage through the radiation belt 'averages out' the anisotropy. Thus, in spite of the actual exposure anisotropy, cumulative radiation effects over many orbits can be predicted as if the environment were isotropic when the spacecraft orientation is variable during exposure. However, Space Station Freedom will be gravity gradient stabilized to reduce drag, and, due to this fixed orientation, the cumulative incident proton flux will remain anisotropic. The anisotropy could potentially influence several aspects of Space Station design and operation, such as the appropriate location for radiation sensitive components and experiments, location of workstations and sleeping quarters, and the design and placement of radiation monitors. Also, on-board mass could possible be utilized to counteract the anisotropy effects and reduce the dose exposure. Until recently only omnidirectional data bases for the trapped proton environment were available. However, a method to predict orbit-average, angular dependent ('vector') trapped proton flux spectra has been developed from the standard omnidirectional trapped proton data bases. This method was used to characterize the trapped proton anisotropy for the Space Station orbit (28.5 degree inclination, circular) in terms of its dependence on altitude, solar cycle modulation (solar minimum vs. solar maximum), shielding thickness
Trap style influences wild pig behavior and trapping success
Williams, B.L.; Holtfreter, R.W.; Ditchkoff, S.S.; Grand, J.B.
2011-01-01
Despite the efforts of many natural resource professionals, wild pig (Sus scrofa) populations are expanding in many areas of the world. Although many creative techniques for controlling pig populations are being explored, trapping has been and still is themost commonly usedmethod of population control formany public and private land managers. We conducted an observational study to examine the efficiency of 2 frequently used trap styles: a small, portable box-style trap and a larger, semi-permanent, corral-style trap.We used game cameras to examine patterns of trap entry by wild pigs around each style of trap, and we conducted a trapping session to compare trapping success between trap styles. Adult female and juvenile wild pigs entered both styles of trap more readily than did adult males, and adult males seemed particularly averse to entering box traps. Less than 10% of adult male visits to box traps resulted in entries, easily the least percentage of any class at any style of trap. Adult females entered corral traps approximately 2.2 times more often per visit than box traps and re-entered corral traps >2 times more frequently. Juveniles entered and reentered both box and corral traps at similar rates. Overall (all-class) entry-per-visit rates at corral traps (0.71) were nearly double that of box traps (0.37). Subsequent trapping data supported these preliminary entry data; the capture rate for corral traps was >4 times that of box traps. Our data suggest that corral traps are temporally and economically superior to box traps with respect to efficiency; that is, corral traps effectively trap more pigs per trap night at a lower cost per pig than do box traps. ?? 2011 The Wildlife Society.
High anisotropy of fully hydrogenated borophene.
Wang, Zhiqiang; Lü, Tie-Yu; Wang, Hui-Qiong; Feng, Yuan Ping; Zheng, Jin-Cheng
2016-11-23
We have studied the mechanical properties and phonon dispersions of fully hydrogenated borophene (borophane) under strains by first principles calculations. Uniaxial tensile strains along the a- and b-direction, respectively, and biaxial tensile strain have been considered. Our results show that the mechanical properties and phonon stability of borophane are both highly anisotropic. The ultimate tensile strain along the a-direction is only 0.12, but it can be as large as 0.30 along the b-direction. Compared to borophene and other 2D materials (graphene, graphane, silicene, silicane, h-BN, phosphorene and MoS2), borophane presents the most remarkable anisotropy in in-plane ultimate strain, which is very important for strain engineering. Furthermore, the phonon dispersions under the three applied strains indicate that borophane can withstand up to 5% and 15% uniaxial tensile strain along the a- and b-direction, respectively, and 9% biaxial tensile strain, indicating that mechanical failure in borophane is likely to originate from phonon instability.
Ecological and evolutionary traps
Schlaepfer, Martin A.; Runge, M.C.; Sherman, P.W.
2002-01-01
Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become 'trapped' by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid 'trapping' them.
Microfabricated ion trap array
Blain, Matthew G.; Fleming, James G.
2006-12-26
A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.
Pack, Michael Vern
2008-12-01
This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.
Evaluating steam trap performance
Fuller, N.Y.
1985-08-08
This paper presents a method for evaluating the performance level of steam traps by preparing an economic analysis of several types to determine the equivalent uniform annual cost. A series of tests on steam traps supplied by six manufacturers provided data for determining the relative efficiencies of each unit. The comparison was made using a program developed for the Texas Instruments T1-59 programmable calculator to evaluate overall steam trap economics.
Self-trapping of incoherent light beams
NASA Astrophysics Data System (ADS)
Mitchell, Matthew L.
1998-09-01
This thesis presents an experimental and theoretical study of self-trapping beams of light from incoherent sources such as light emitting diodes and sunlight. The self-trapping of an optical beam occurs when a beam of light induces a change in the index of refraction through a nonlinear interaction. This induced index change can then fully compensate for diffraction of the optical beam in both transverse directions. When this process occurs, the trapped light is called a soliton. Until 1996, all experimental and theoretical studies of optical spatial solitons in nature employed a coherent beam, either in space, time, or both. In 1996 I demonstrated for the first time that self-trapping of beams upon which the phase varied randomly in time/space across any plane was possible. The optical beams were self-trapped by making use of the photorefractive nonlinearity. The self-trapping of these incoherent light sources has opened up a new subfield in the study of optical spatial solitons. Experimental and theoretical results of self-trapping both bright and dark incoherent solitons will be presented. In the first experiment, a quasi-monochromatic partially spatially-incoherent light beam was self-trapped, while the second experiment shows the self-trapping of an incoherent white light beam originating from an incandescent light bulb. In this second experiment, the self-trapped beam contained wavelengths between 380 and 720 nm. Theoretical work has shown that these incoherent light sources create effective multi-mode solitons. Existence conditions and the resulting coherence properties of such self-trapped beams have been examined. The theoretical methods used in describing these effects are general and can be extended for use with any form of nonlinearity. Experimental and theoretical results of creating dark incoherent solitons shows the possibility of self- trapping a dark notch sitting upon an incoherent background beam. Theoretical work shows that such dark incoherent
Anisotropic Turbulence Modeling for Accurate Rod Bundle Simulations
Baglietto, Emilio
2006-07-01
An improved anisotropic eddy viscosity model has been developed for accurate predictions of the thermal hydraulic performances of nuclear reactor fuel assemblies. The proposed model adopts a non-linear formulation of the stress-strain relationship in order to include the reproduction of the anisotropic phenomena, and in combination with an optimized low-Reynolds-number formulation based on Direct Numerical Simulation (DNS) to produce correct damping of the turbulent viscosity in the near wall region. This work underlines the importance of accurate anisotropic modeling to faithfully reproduce the scale of the turbulence driven secondary flows inside the bundle subchannels, by comparison with various isothermal and heated experimental cases. The very low scale secondary motion is responsible for the increased turbulence transport which produces a noticeable homogenization of the velocity distribution and consequently of the circumferential cladding temperature distribution, which is of main interest in bundle design. Various fully developed bare bundles test cases are shown for different geometrical and flow conditions, where the proposed model shows clearly improved predictions, in close agreement with experimental findings, for regular as well as distorted geometries. Finally the applicability of the model for practical bundle calculations is evaluated through its application in the high-Reynolds form on coarse grids, with excellent results. (author)
NASA Astrophysics Data System (ADS)
Jørgensen, L. V.; Andresen, G.; Bertsche, W.; Boston, A.; Bowe, P. D.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Fujiwara, M. C.; Funakoshi, R.; Gill, D. R.; Hangst, J. S.; Hayano, R. S.; Hydomako, R.; Jenkins, M. J.; Kurchaninov, L.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Page, R. D.; Povilus, A.; Robicheaux, F.; Sarid, E.; Silveira, D. M.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.; Alpha Collaboration
2008-02-01
Substantial progress has been made in the last few years in the nascent field of antihydrogen physics. The next big step forward is expected to be the trapping of the formed antihydrogen atoms using a magnetic multipole trap. ALPHA is a new international project that started to take data in 2006 at CERN's Antiproton Decelerator facility. The primary goal of ALPHA is stable trapping of cold antihydrogen atoms to facilitate measurements of its properties. We discuss the status of the ALPHA project and the prospects for antihydrogen trapping.
Details of tetrahedral anisotropic mesh adaptation
NASA Astrophysics Data System (ADS)
Jensen, Kristian Ejlebjerg; Gorman, Gerard
2016-04-01
We have implemented tetrahedral anisotropic mesh adaptation using the local operations of coarsening, swapping, refinement and smoothing in MATLAB without the use of any for- N loops, i.e. the script is fully vectorised. In the process of doing so, we have made three observations related to details of the implementation: 1. restricting refinement to a single edge split per element not only simplifies the code, it also improves mesh quality, 2. face to edge swapping is unnecessary, and 3. optimising for the Vassilevski functional tends to give a little higher value for the mean condition number functional than optimising for the condition number functional directly. These observations have been made for a uniform and a radial shock metric field, both starting from a structured mesh in a cube. Finally, we compare two coarsening techniques and demonstrate the importance of applying smoothing in the mesh adaptation loop. The results pertain to a unit cube geometry, but we also show the effect of corners and edges by applying the implementation in a spherical geometry.
Chen, Qian
2008-01-01
The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.
NASA Astrophysics Data System (ADS)
Chen, Qian
The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.
Constitutive Equation for Anisotropic Rock
NASA Astrophysics Data System (ADS)
Cazacu, O.
2006-12-01
In many rocks, due to the existence of well-defined fabric elements such as bedding, layering, foliation or lamination planes, or due to the existence of linear structures, anisotropy can be important. The symmetries most frequently encountered are: transverse isotropy and orthotropy. By adopting both theoretical and experimental approaches, many authors have investigated the effect of the presence within the rock of pronounced anisotropic feature on the mechanical behavior in the elastic regime and on strength properties. Fewer attempts however have been made to capture the anisotropy of rocks in the plastic range. In this paper an elastic/viscoplastic non-associated constitutive equation for an initially transversely isotropic material is presented. The model captures the observed dependency of the elastic moduli on the stress state. The limit of the elastic domain is given by an yield function whose expression is a priori unknown and is determined from data. The basic assumption adopted is that the type of anisotropy of the rock does not change during the deformation process. The anisotropy is thus described by a fourth order tensor invariant with respect to any transformation belonging to the symmetry group of the material. This tensor is assumed to be constant: it does not depend on time nor on deformation; A is involved in the expression of the flow rule, of the yield function, and of the failure criterion in the form of a transformed stress tensor. The components of the anisotropic tensor A are determined from the compressive strengths in conjunction with an anisotropic short- term failure The irreversibility is supposed to be due to transient creep, the irreversible stress work per unit volume being considered as hardening parameter. The adequacy of the model is demonstrated by applying it to a stratified sedimentary rock, Tournemire shale.
Search for trapped antihydrogen
NASA Astrophysics Data System (ADS)
Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Bray, C. C.; Butler, E.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayano, R. S.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jonsell, S.; Jørgensen, L. V.; Kurchaninov, L.; Lambo, R.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Seif El Nasr, S.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wilding, D.; Wurtele, J. S.; Yamazaki, Y.; Alpha Collaboration
2011-01-01
We present the results of an experiment to search for trapped antihydrogen atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator. Sensitive diagnostics of the temperatures, sizes, and densities of the trapped antiproton and positron plasmas have been developed, which in turn permitted development of techniques to precisely and reproducibly control the initial experimental parameters. The use of a position-sensitive annihilation vertex detector, together with the capability of controllably quenching the superconducting magnetic minimum trap, enabled us to carry out a high-sensitivity and low-background search for trapped synthesised antihydrogen atoms. We aim to identify the annihilations of antihydrogen atoms held for at least 130 ms in the trap before being released over ∼30 ms. After a three-week experimental run in 2009 involving mixing of 10 7 antiprotons with 1.3×10 positrons to produce 6×10 antihydrogen atoms, we have identified six antiproton annihilation events that are consistent with the release of trapped antihydrogen. The cosmic ray background, estimated to contribute 0.14 counts, is incompatible with this observation at a significance of 5.6 sigma. Extensive simulations predict that an alternative source of annihilations, the escape of mirror-trapped antiprotons, is highly unlikely, though this possibility has not yet been ruled out experimentally.
Hundal, Rolv
1976-01-01
A cold trap assembly for removing impurities from a liquid metal being provided with a hole between the incoming impure liquid metal and purified outgoing liquid metal which acts as a continuous bleed means and thus prevents the accumulation of cover gases within the cold trap assembly.
Anisotropic inflation from vector impurity
Kanno, Sugumi; Kimura, Masashi; Soda, Jiro; Yokoyama, Shuichiro E-mail: mkimura@sci.osaka-cu.ac.jp E-mail: shu@a.phys.nagoya-u.ac.jp
2008-08-15
We study an inflationary scenario with a vector impurity. We show that the universe undergoes anisotropic inflationary expansion due to a preferred direction determined by the vector. Using the slow roll approximation, we find a formula for determining the anisotropy of the inflationary universe. We discuss possible observable predictions of this scenario. In particular, it is stressed that primordial gravitational waves can be induced from curvature perturbations. Hence, even in low scale inflation, a sizable amount of primordial gravitational waves may be produced during inflation.
Anisotropic Geometrodynamics in Cosmological Problems
NASA Astrophysics Data System (ADS)
Siparov, Sergey
2010-10-01
Anisotropic geometrodynamics (AGD) is the GRT modification that takes into account the dependence of metric on the velocities of the sources which follows from the equivalence principle and from the inseparability of the field equations and geodesics equations. The AGD provides the explanation for the flat character of the rotation curves of spiral galaxies, for Tully-Fisher law, for some specific features of globular clusters behavior and for the essential excess of the observable gravitational lens effect over the predicted one. Neither dark matter nor arbitrary change of dynamics equations as in known approaches appears to be needed. Important cosmological consequences are discussed.
Light Propagation through Anisotropic Turbulence
2011-03-01
Kolmogorov stratospheric turbulence on star image motion,” Proc. SPIE 3126, 113–123 (1997). 5. B. E . Stribling, B. M . Welsh, and M . C. Roggemann...746407 (2009). 10. M . Chang, C. O. Font, F. Santiago, Y. Luna, E . Roura, and S. Restaino, “Marine environment optical propagation measure- ments,” Proc...Anisotropic factor as a function of alpha for several zeta values. Toselli et al. Vol. 28, No. 3 / March 2011 / J. Opt. Soc. Am. A 487 14. M . S
Granular Segregation with Anisotropic Particles
NASA Astrophysics Data System (ADS)
Sykes, Tim
2005-11-01
The results from experimental investigations of horizontally vibrated mixtures of anisotropic poppy seeds and long chains of linked spheres will be presented. A critical packing fraction was observed to be required to initiate a transition to segregation. The average size of the resulting patterns was measured and the concentration ratio of the mixtures was varied by changing the number of chains present in the mixtures. A change in the order of the transition, from second to first order with associated hysteresis, was observed as the chain number was reduced. This gave rise to three distinct regions of behaviour: segregated, mixed and a bi-stable state.
Signature of anisotropic bubble collisions
Salem, Michael P.
2010-09-15
Our universe may have formed via bubble nucleation in an eternally inflating background. Furthermore, the background may have a compact dimension--the modulus of which tunnels out of a metastable minimum during bubble nucleation--which subsequently grows to become one of our three large spatial dimensions. When in this scenario our bubble universe collides with other ones like it, the collision geometry is constrained by the reduced symmetry of the tunneling instanton. While the regions affected by such bubble collisions still appear (to leading order) as disks in an observer's sky, the centers of these disks all lie on a single great circle, providing a distinct signature of anisotropic bubble nucleation.
Optical trapping of nanoparticles.
Bergeron, Jarrah; Zehtabi-Oskuie, Ana; Ghaffari, Saeedeh; Pang, Yuanjie; Gordon, Reuven
2013-01-15
Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec, which has serious implications for biological matter. A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure. The double-nanohole structure has been shown to give a strong local field enhancement. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres and 3.4 nm hydrodynamic radius
Fully anisotropic 3-D EM modelling on a Lebedev grid with a multigrid pre-conditioner
NASA Astrophysics Data System (ADS)
Jaysaval, Piyoosh; Shantsev, Daniil V.; de la Kethulle de Ryhove, Sébastien; Bratteland, Tarjei
2016-12-01
We present a numerical algorithm for 3-D electromagnetic (EM) simulations in conducting media with general electric anisotropy. The algorithm is based on the finite-difference discretization of frequency-domain Maxwell's equations on a Lebedev grid, in which all components of the electric field are collocated but half a spatial step staggered with respect to the magnetic field components, which also are collocated. This leads to a system of linear equations that is solved using a stabilized biconjugate gradient method with a multigrid preconditioner. We validate the accuracy of the numerical results for layered and 3-D tilted transverse isotropic (TTI) earth models representing typical scenarios used in the marine controlled-source EM method. It is then demonstrated that not taking into account the full anisotropy of the conductivity tensor can lead to misleading inversion results. For synthetic data corresponding to a 3-D model with a TTI anticlinal structure, a standard vertical transverse isotropic (VTI) inversion is not able to image a resistor, while for a 3-D model with a TTI synclinal structure it produces a false resistive anomaly. However, if the VTI forward solver used in the inversion is replaced by the proposed TTI solver with perfect knowledge of the strike and dip of the dipping structures, the resulting resistivity images become consistent with the true models.
Nonlinear integrable ion traps
Nagaitsev, S.; Danilov, V.; /SNS Project, Oak Ridge
2011-10-01
Quadrupole ion traps can be transformed into nonlinear traps with integrable motion by adding special electrostatic potentials. This can be done with both stationary potentials (electrostatic plus a uniform magnetic field) and with time-dependent electric potentials. These potentials are chosen such that the single particle Hamilton-Jacobi equations of motion are separable in some coordinate systems. The electrostatic potentials have several free adjustable parameters allowing for a quadrupole trap to be transformed into, for example, a double-well or a toroidal-well system. The particle motion remains regular, non-chaotic, integrable in quadratures, and stable for a wide range of parameters. We present two examples of how to realize such a system in case of a time-independent (the Penning trap) as well as a time-dependent (the Paul trap) configuration.
NASA Astrophysics Data System (ADS)
Rossetti, R. F.; de Moraes Neto, G. D.; Egues, J. Carlos; Moussa, M. H. Y.
2016-09-01
Here we present a protocol for generating Lissajous curves with a trapped ion by engineering Rashba- and the Dresselhaus-type spin-orbit (SO) interactions in a Paul trap. The unique anisotropic Rashba αx , αy and Dresselhaus βx , βy couplings afforded by our setup also enable us to obtain an “unusual” Zitterbewegung, i.e., the semiconductor analog of the relativistic trembling motion of electrons, with cycloidal trajectories in the absence of magnetic fields. We have also introduced bounded SO interactions, confined to an upper-bound vibrational subspace of the Fock states, as an additional mechanism to manipulate the Lissajous motion of the trapped ion. We have also accounted for dissipative effects on the vibrational degrees of freedom of the ion and find that the Lissajous trajectories are still robust and well defined for realistic parameters.
NASA Astrophysics Data System (ADS)
Arahata, E.; Nikuni, T.
2013-05-01
We study sound propagation in a Bose-condensed gas confined in a highly elongated harmonic trap at finite temperatures. Our analysis is based on Zaremba-Nikuni-Griffin (ZNG) formalism, which consists of Gross-Pitaevskii equation for the condensate and the kinetic equation for a thermal cloud. We extend ZNG formalism to deal with a highly-anisotropic trap potential, and use it to simulate sound propagation in the two fluid hydrodynamic regime. We use the trap parameters for the experiment that has reported second sound propagation. Our simulation results show that propagation of two sound pulses corresponding to first and second sound can be observed in an intermediate temperature.
Anisotropic water reorientation around ions.
Tielrooij, K J; van der Post, S T; Hunger, J; Bonn, M; Bakker, H J
2011-11-03
We study the reorientation dynamics of water molecules around ions using terahertz dielectric relaxation spectroscopy and polarization-resolved femtosecond infrared pump-probe spectroscopy. The results are discussed in relation to the ion-specific Hofmeister series and the concomitant "structure-making" and "structure-breaking" effects of ions on water. We show that when a dissolved salt consists of a strongly hydrated ion with a weakly hydrated counterion the reorientation of water molecules around the strongly hydrated ion is anisotropic, in the sense that differently charged ions affect reorientation along different molecular axes: cations mainly slow the reorientation dynamics of the water dipole vectors, and anions mainly slow down the reorientation dynamics of the hydroxyl group that points toward the anion. In both cases, motion along only one molecular axis is impeded, so that the hydration shell is best described as semirigid. In this semirigid hydration picture, water molecules in the first hydration shell show anisotropic reorientation, whereas water molecules outside the first hydration shell remain unaffected. The inferred anisotropy in molecular motion explains why terahertz dielectric relaxation spectroscopy, which probes dipolar relaxation, is more sensitive to cation hydration effects while femtosecond infrared pump-probe spectroscopy, which is sensitive to reorientation of hydroxyl groups, is more sensitive to anion hydration effects. We also show that dissolution of CsI-a salt for which both cation and anion are weakly hydrated-has little effect on water reorientation dynamics, with hydration water displaying dynamics that are similar to those in bulk water.
Anisotropic Plasticity of BN Nanotubes
NASA Technical Reports Server (NTRS)
Madhu, Menon; Srivastava, Deepak; Woo, Alex (Technical Monitor)
1999-01-01
Plastic collapse of compressed BN nanotubes are investigated and compared with carbon nanotubes of similar nature. Using a generalized tight-binding molecular dynamics (GTBMD) method for system containing B, N and C atoms we compute stiffness and plastic collapse of BN and C nanotubes under axial compression. For small compressional strain, BN nanotubes are found to be about 92% as stiff as similar C nanotubes. Due to BN bond buckling effect, however, the elastic limit of BN nanotubes is found to be more than C nanotubes. A route to plasticity is explored in which we find that at elastic limit the accumulated strain is released by a local plastic deformation of the nanotube. The mechanism of strain release and the resulting plastic deformation, however. are anisotropic in nature. The strain is released preferentially towards N as leading edge of a buckled BN bond and the tube, compressed at both ends, plastically collapses preferentially towards one end. Details of the anisotropic plasticity and prospective applications will be discussed in this presentation.
NASA Astrophysics Data System (ADS)
Sur, Shouvik; Lee, Sung-Sik
2016-11-01
We study non-Fermi-liquid states that arise at the quantum critical points associated with the spin density wave (SDW) and charge density wave (CDW) transitions in metals with twofold rotational symmetry. We use the dimensional regularization scheme, where a one-dimensional Fermi surface is embedded in (3 -ɛ ) -dimensional momentum space. In three dimensions, quasilocal marginal Fermi liquids arise both at the SDW and CDW critical points: the speed of the collective mode along the ordering wave vector is logarithmically renormalized to zero compared to that of Fermi velocity. Below three dimensions, however, the SDW and CDW critical points exhibit drastically different behaviors. At the SDW critical point, a stable anisotropic non-Fermi-liquid state is realized for small ɛ , where not only time but also different spatial coordinates develop distinct anomalous dimensions. The non-Fermi liquid exhibits an emergent algebraic nesting as the patches of Fermi surface are deformed into a universal power-law shape near the hot spots. Due to the anisotropic scaling, the energy of incoherent spin fluctuations disperse with different power laws in different momentum directions. At the CDW critical point, on the other hand, the perturbative expansion breaks down immediately below three dimensions as the interaction renormalizes the speed of charge fluctuations to zero within a finite renormalization group scale through a two-loop effect. The difference originates from the fact that the vertex correction antiscreens the coupling at the SDW critical point whereas it screens at the CDW critical point.
Recent progress in anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Strickland, Michael
2017-03-01
The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, < pL2> ≪ < pT2>. In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.
Postbuckling of laminated anisotropic panels
NASA Technical Reports Server (NTRS)
Jeffrey, Glenda L.
1987-01-01
A two-part study of the buckling and postbuckling of laminated anisotropic plates with bending-extensional coupling is presented. The first part involves the development and application of a modified Rayleigh-Ritz analysis technique. Modifications made to the classical technique can be grouped into three areas. First, known symmetries of anisotropic panels are exploited in the selection of approximation functions. Second, a reduced basis technique based on these same symmetries is applied in the linear range. Finally, geometric boundary conditions are enforced via an exterior penalty function approach, rather than relying on choice of approximation functions to satisfy these boundary conditions. Numerical results are presented for both the linear and nonlinear range, with additional studies made to determine the effect of variation in penalty parameter and number of basis vectors. In the second part, six panels possessing anisotropy and bending-extensional coupling are tested. Detailed comparisons are made between experiment and finite element results in order to gain insight into the postbuckling and failure characteristics of such panels. The panels are constructed using two different lamination sequences, and panels with three different aspect ratios were constructed for each lamination sequence.
Anisotropic effects on ultrasonic guided waves propagation in composite bends.
Yu, Xudong; Ratassepp, Madis; Rajagopal, Prabhu; Fan, Zheng
2016-12-01
Ultrasonic guided waves have proven to be attractive to the long-range testing of composite laminates. As complex-shaped composite components are increasingly incorporated in high-performance structures, understanding of both anisotropic and geometric effects on guided waves propagation is needed to evaluate their suitability for the non-destructive testing (NDT) of such complex structures. This paper reports the Semi-Analytical Finite Element (SAFE) simulations revealing the capability of energy confinement carried by two types of guided modes in 90° carbon fiber/epoxy (CF/EP) bends. Existence of the phenomenon is cross-validated by both 3D Finite Element (FE) modeling and experimental measurements. The physics of such energy trapping effect is explained in view of geometric variation and anisotropic properties, and the frequency effect on the extent of energy concentration is discussed. Finally, the feasibility of using such confined guided waves for rapid inspection of bent composite plate structures is also discussed. Copyright © 2016 Elsevier B.V. All rights reserved.
Characterization of anisotropic acoustic metamaterial slabs
NASA Astrophysics Data System (ADS)
Park, Jun Hyeong; Lee, Hyung Jin; Kim, Yoon Young
2016-01-01
In an anisotropic acoustic metamaterial, the off-diagonal components of its effective mass density tensor should be considered in order to describe the anisotropic behavior produced by arbitrarily shaped inclusions. However, few studies have been carried out to characterize anisotropic acoustic metamaterials. In this paper, we propose a method that uses the non-diagonal effective mass density tensor to determine the behavior of anisotropic acoustic metamaterials. Our method accurately evaluates the effective properties of anisotropic acoustic metamaterials by separately dealing with slabs made of single and multiple unit cells along the thickness direction. To determine the effective properties, the reflection and transmission coefficients of an acoustic metamaterial slab are calculated, and then the wave vectors inside of the slab are determined using these coefficients. The effective material properties are finally determined by utilizing the spatial dispersion relation of the anisotropic acoustic metamaterial. Since the dispersion relation of an anisotropic acoustic metamaterial is explicitly used, its effective properties can be easily determined by only using a limited number of normal and oblique plane wave incidences into a metamaterial slab, unlike existing approaches requiring a large number of wave incidences. The validity of the proposed method is verified by conducting wave simulations for anisotropic acoustic metamaterial slabs with Z-shaped elastic inclusions of tilted principal material axes.
March, Raymond E
2009-01-01
The extraordinary story of the three-dimensional radiofrequency quadrupole ion trap, accompanied by a seemingly unintelligible theoretical treatment, is told in some detail because of the quite considerable degree of commercial success that quadrupole technology has achieved. The quadrupole ion trap, often used in conjunction with a quadrupole mass filter, remained a laboratory curiosity until 1979 when, at the American Society for Mass Spectrometry Conference in Seattle, George Stafford, Jr., of Finnigan Corp., learned of the Masters' study of Allison Armitage of a combined quadrupole ion trap/quadrupole mass filter instrument for the observation of electron impact and chemical ionization mass spectra of simple compounds eluting from a gas chromatograph. Stafford developed subsequently the mass-selective axial instability method for obtaining mass spectra from the quadrupole ion trap alone and, in 1983, Finnigan Corp. announced the first commercial quadrupole ion trap instrument as a detector for a gas chromatograph. In 1987, confinement of ions generated externally to the ion trap was demonstrated and, soon after, the new technique of electrospray ionization was shown to be compatible with the ion trap. Copyright 2009 Wiley Periodicals, Inc.
Jiang, Xiangzhi; Xiang, Meichun; Liu, Xingzhong
2017-01-01
Nematode-trapping fungi are a unique and intriguing group of carnivorous microorganisms that can trap and digest nematodes by means of specialized trapping structures. They can develop diverse trapping devices, such as adhesive hyphae, adhesive knobs, adhesive networks, constricting rings, and nonconstricting rings. Nematode-trapping fungi have been found in all regions of the world, from the tropics to Antarctica, from terrestrial to aquatic ecosystems. They play an important ecological role in regulating nematode dynamics in soil. Molecular phylogenetic studies have shown that the majority of nematode-trapping fungi belong to a monophyletic group in the order Orbiliales (Ascomycota). Nematode-trapping fungi serve as an excellent model system for understanding fungal evolution and interaction between fungi and nematodes. With the development of molecular techniques and genome sequencing, their evolutionary origins and divergence, and the mechanisms underlying fungus-nematode interactions have been well studied. In recent decades, an increasing concern about the environmental hazards of using chemical nematicides has led to the application of these biological control agents as a rapidly developing component of crop protection.
Numerical study on the permeability in a tensorial form for laminar flow in anisotropic porous media
NASA Astrophysics Data System (ADS)
Galindo-Torres, S. A.; Scheuermann, A.; Li, L.
2012-10-01
Pore-scale flow simulations were conducted to investigate the permeability tensor of anisotropic porous media constructed using the Voronoi tessellation method. This construction method enabled the introduction of anisotropy to the media at the particle level in a random and yet controllable way. Simulations were carried out for media with different degrees of anisotropy through varying the mean aspect ratio of grain particles. The simulation results were then analyzed using the Kozeny-Carman (KC) model. The KC model describes the permeability of the anisotropic media in a tensor form with the anisotropy represented by different tortuosities along the three principal directions. The tortuosity tensor was found to be a complex function of the particle morphology, which is yet to be fully determined. However, the results presented have established the starting point for further theoretical development to formulate such a function and to build closed-form analytical permeability models for anisotropic porous media based on first principles.
Anisotropic rheology of a polycrystalline aggregate and convection in planetary mantles
NASA Astrophysics Data System (ADS)
Pouilloux, L. S.; Labrosse, S.; Kaminski, E.
2011-12-01
Observations of seismic anisotropy in the Earth mantle is often related to the crystal preferred orientation of polycrystalline aggregates. In this case, the physical properties depends on the direction and require the use of tensors to be fully described. In particular, the viscosity must be defined as a fourth order tensor whereas the thermal conductivity is a 2nd order tensor. However, the dynamical implications of such physical properties have received little attention until now. In this work, we present the mathematical formulation for an anisotropic medium and the relationship with dislocation creep deformation. We explore extensively the problem of the onset of Rayleigh-Bénard convection with such anisotropic properties. We finally presents some numerical results on the time-dependent problem using an orthotropic law for an ice polycrystal. Geophysical implications of this work related to the dynamics of planetary mantles are discussed, especially the potential of anisotropic rheology to localize deformation.
Not Available
1991-01-01
This volume contains studies of fields with traps that are mainly stratigraphic in nature. Structure plays a role in the traps of several fields, but overall, it is clear that the main trapping features with the group of fields in this volume are stratigraphic. The first six fields in this volume, Alabama Ferry, Rospo Mare, Walker Creek, Bindley, Lexington, and Newburg/South Westhope, have carbonate reservoirs. The latter two of these, Lexington and Newburg/South Westhope, also have sandstone reservoirs. The remaining fields, East Texas, East Clinton, Stockholm Southwest, Sorrento, Port Acres, and Lagoa Parda, have only sandstone reservoirs.
Grier, David G.; Roichman, Yael
2006-02-10
Holographic optical tweezers use computer-generated holograms to create arbitrary three-dimensional configurations of single-beam optical traps that are useful for capturing, moving, and transforming mesoscopic objects. Through a combination of beam-splitting, mode-forming, and adaptive wavefront correction, holographic traps can exert precisely specified and characterized forces and torques on objects ranging in size from a few nanometers to hundreds of micrometers. Offering nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps provide unsurpassed access to the microscopic world and have found applications in fundamental research, manufacturing, and materials processing.
Grier, David G; Roichman, Yael
2006-02-10
Holographic optical tweezers use computer-generated holograms to create arbitrary three-dimensional configurations of single-beam optical traps that are useful for capturing, moving, and transforming mesoscopic objects. Through a combination of beam-splitting, mode-forming, and adaptive wavefront correction, holographic traps can exert precisely specified and characterized forces and torques on objects ranging in size from a few nanometers to hundreds of micrometers. Offering nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps provide unsurpassed access to the microscopic world and have found applications in fundamental research, manufacturing, and materials processing.
Beau, Mathieu; Savoie, Baptiste
2014-05-15
In this paper, we rigorously investigate the reduced density matrix (RDM) associated to the ideal Bose gas in harmonic traps. We present a method based on a sum-decomposition of the RDM allowing to treat not only the isotropic trap, but also general anisotropic traps. When focusing on the isotropic trap, the method is analogous to the loop-gas approach developed by Mullin [“The loop-gas approach to Bose-Einstein condensation for trapped particles,” Am. J. Phys. 68(2), 120 (2000)]. Turning to the case of anisotropic traps, we examine the RDM for some anisotropic trap models corresponding to some quasi-1D and quasi-2D regimes. For such models, we bring out an additional contribution in the local density of particles which arises from the mesoscopic loops. The close connection with the occurrence of generalized-Bose-Einstein condensation is discussed. Our loop-gas-like approach provides relevant information which can help guide numerical investigations on highly anisotropic systems based on the Path Integral Monte Carlo method.
Vortex structures of rotating Bose-Einstein condensates in an anisotropic harmonic potential
Matveenko, S. I.
2010-09-15
We found an analytical solution for the vortex structure in a rapidly rotating trapped Bose-Einstein condensate in the lowest Landau level approximation. This solution is exact in the limit of a large number of vortices and is obtained for the case of a condensate in a anisotropic harmonic potential. The solution describes as limiting cases both a triangle vortex lattice in the symmetric potential trap and a quasi-one-dimensional structure of vortex rows in an asymmetric case, when the rotation frequency is very close to the lower trapping potential frequency. The shape of the density profile is found to be close to the Thomas-Fermi inverted paraboloid form, except in the vicinity of edges of a condensate cloud.
Kim, Hahn; Van Dung Doan; Cho, Woo Jong; Madhav, Miriyala Vijay; Kim, Kwang S.
2014-01-01
Although group (IV–VII) nonmetallic elements do not favor interacting with anionic species, there are counterexamples including the halogen bond. Such binding is known to be related to the charge deficiency because of the adjacent atom's electron withdrawing effect, which creates σ/π-holes at the bond-ends. However, a completely opposite behavior is exhibited by N2 and O2, which have electrostatically positive/negative character around cylindrical-bond-surface/bond-ends. Inspired by this, here we elucidate the unusual features and origin of the anisotropic noncovalent interactions in the ground and excited states of the 2nd and 3rd row elements belonging to groups IV–VII. The anisotropy in charge distributions and van der Waals radii of atoms in such molecular systems are scrutinized. This provides an understanding of their unusual molecular configuration, binding and recognition modes involved in new types of molecular assembling and engineering. This work would lead to the design of intriguing molecular systems exploiting anisotropic noncovalent interactions. PMID:25059645
Trapping and Probing Antihydrogen
Wurtele, Jonathan
2013-03-27
Precision spectroscopy of antihydrogen is a promising path to sensitive tests of CPT symmetry. The most direct route to achieve this goal is to create and probe antihydrogen in a magnetic minimum trap. Antihydrogen has been synthesized and trapped for 1000s at CERN by the ALPHA Collaboration. Some of the challenges associated with achieving these milestones will be discussed, including mixing cryogenic positron and antiproton plasmas to synthesize antihydrogen with kinetic energy less than the trap potential of .5K. Recent experiments in which hyperfine transitions were resonantly induced with microwaves will be presented. The opportunity for gravitational measurements in traps based on detailed studies of antihydrogen dynamics will be described. The talk will conclude with a discussion future antihydrogen research that will use a new experimental apparatus, ALPHA-I.
Ryan, M.J.
1987-05-04
A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (a hot finger) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more thermocouples for detecting condensate level and energy, while the cold finger contains a liquid with a lower boiling temperature than that of water. Vapor pressure from the liquid is used to do work such as displacing a piston or bellow in providing an indication of total energy (steam + condensate) of the system. Processing means coupled to and responsive to outputs from the hot and cold fingers subtracts the former from the latter to provide an indication of the presence of steam downstream from the trap indicating that the steam trap is malfunctioning. 2 figs.
Veldhoven, Jacqueline van; Bethlem, Hendrick L.; Schnell, Melanie; Meijer, Gerard
2006-06-15
A four electrode electrostatic trap geometry is demonstrated that can be used to combine a dipole, quadrupole, and hexapole field. A cold packet of {sup 15}ND{sub 3} molecules is confined in both a purely quadrupolar and hexapolar trapping field and additionally, a dipole field is added to a hexapole field to create either a double-well or a donut-shaped trapping field. The profile of the {sup 15}ND{sub 3} packet in each of these four trapping potentials is measured, and the dependence of the well-separation and barrier height of the double-well and donut potential on the hexapole and dipole term are discussed.
Time and spatial parity operations with trapped ions
NASA Astrophysics Data System (ADS)
Cheng, Xiao-Hang; Alvarez-Rodriguez, Unai; Lamata, Lucas; Chen, Xi; Solano, Enrique
2015-08-01
We propose a physical implementation of time and spatial parity transformations, as well as Galilean boosts, in a trapped-ion quantum simulator. By embedding the simulated model into an enlarged simulating Hilbert space, these fundamental symmetry operations can be fully realized and measured with ion traps. We illustrate our proposal with analytical and numerical techniques of prototypical examples with state-of-the-art trapped-ion platforms. These results pave the way for the realization of time and spatial parity transformations in other models and quantum platforms.
Anisotropic invariance in minisuperspace models
NASA Astrophysics Data System (ADS)
Chagoya, Javier; Sabido, Miguel
2016-06-01
In this paper we introduce invariance under anisotropic transformations to cosmology. This invariance is one of the key ingredients of the theory of quantum gravity at a Lifshitz point put forward by Hořava. We find that this new symmetry in the minisuperspace introduces characteristics to the model that can be relevant in the ultraviolet regime. For example, by canonical quantization we find a Schrödinger-type equation which avoids the problem of frozen time in quantum cosmology. For simple cases we obtain solutions to this quantum equation in a Kantowski-Sachs (KS) minisuperspace. At the classical level, we study KS and Friedmann-Robertson-Walker cosmologies, obtaining modifications to the solutions of general relativity that can be relevant in the early Universe.
Anisotropic Decomposition of Energetic Materials
Pravica, Michael; Quine, Zachary; Romano, Edward; Bajar, Sean; Yulga, Brian; Yang, Wenge; Hooks, Daniel
2008-01-17
Using a white x-ray synchrotron beam, we have dynamically studied radiation-induced decomposition in single crystalline PETN and TATB. By monitoring the integrated intensity of selected diffraction spots via a CCD x-ray camera as a function of time, we have found that the decomposition rate varies dramatically depending upon the orientation of the crystalline axes relative to polarized x-ray beam and for differing diffracting conditions (spots) within the same crystalline orientation. We suggest that this effect is due to Compton scattering of the polarized x-rays with electron clouds that is dependent upon their relative orientation. This novel effect may yield valuable insight regarding anisotropic detonation sensitivity in energetic materials such as PETN.
Anisotropic decomposition of energetic materials
Pravica, Michael; Quine, Zachary; Romano, Edward; Bajar, Sean; Yulga, Brian; Yang Wenge; Hooks, Daniel
2007-12-12
Using a white x-ray synchrotron beam, we have dynamically studied radiation-induced decomposition in single crystalline PETN and TATB. By monitoring the integrated intensity of selected diffraction spots via a CCD x-ray camera as a function of time, we have found that the decomposition rate varies dramatically depending upon the orientation of the crystalline axes relative to polarized x-ray beam and for differing diffracting conditions (spots) within the same crystalline orientation. We suggest that this effect is due to Compton scattering of the polarized x-rays with electron clouds that is dependent upon their relative orientation. This novel effect may yield valuable insight regarding anisotropic detonation sensitivity in energetic materials such as PETN.
Anisotropic grid adaptation in LES
NASA Astrophysics Data System (ADS)
Toosi, Siavash; Larsson, Johan
2016-11-01
The modeling errors depend directly on the grid (or filter) spacing in turbulence-resolving simulations (LES, DNS, DES, etc), and are typically at least as significant as the numerical errors. This makes adaptive grid-refinement complicated, since it prevents the estimation of the local error sources through numerical analysis. The present work attempts to address this difficulty with a physics-based error-source indicator that accounts for the anisotropy in the smallest resolved scales, which can thus be used to drive an anisotropic grid-adaptation process. The proposed error indicator is assessed on a sequence of problems, including turbulent channel flow and flows in more complex geometries. The formulation is geometrically general and applicable to complex geometries.
Mechanics of anisotropic spring networks
NASA Astrophysics Data System (ADS)
Zhang, T.; Schwarz, J. M.; Das, Moumita
2014-12-01
We construct and analyze a model for a disordered linear spring network with anisotropy. The modeling is motivated by, for example, granular systems, nematic elastomers, and ultimately cytoskeletal networks exhibiting some underlying anisotropy. The model consists of a triangular lattice with two different bond occupation probabilities, px and py, for the linear springs. We develop an effective medium theory (EMT) to describe the network elasticity as a function of px and py. We find that the onset of rigidity in the EMT agrees with Maxwell constraint counting. We also find beyond linear behavior in the shear and bulk modulus as a function of occupation probability in the rigid phase for small strains, which differs from the isotropic case. We compare our EMT with numerical simulations to find rather good agreement. Finally, we discuss the implications of extending the reach of effective medium theory as well as draw connections with prior work on both anisotropic and isotropic spring networks.
Modeling of Anisotropic Inelastic Behavior
Nikkel, D.J.; Nath, D.S.; Brown, A.A.; Casey, J.
2000-02-25
An experimental capability, developed at Lawrence Livermore National Laboratory (LLNL), is being used to study the yield behavior of elastic-plastic materials. The objective of our research is to develop better constitutive equations for polycrystalline metals. We are experimentally determining the multidimensional yield surface of the material, both in its initial state and as it evolves during large inelastic deformations. These experiments provide a more complete picture of material behavior than can be obtained from traditional uniaxial tests. Experimental results show that actual material response can differ significantly from that predicted by simple idealized models. These results are being used to develop improved constitutive models of anisotropic plasticity for use in continuum computer codes.
Thermodynamics of soft anisotropic interfaces.
Rey, Alejandro D
2004-01-22
The Gibbs-Duhem equation for interfaces between nematic liquid crystals and isotropic fluids is formulated and shown to be a generic equation for soft anisotropic surfaces. The one-to-one correspondence between the nematic and crystalline surface Gibbs-Duhem equations is established. Consistency between the surface Gibbs-Duhem equation and the classical equations of interfacial nematostatics is shown. Using a phase space that takes into account thermodynamics, liquid crystalline order, and geometric variables, the generalized nematic surface Gibbs-Duhem equation reveals the presence of couplings between shape, adsorption, temperature, and average molecular orientation. Merging the thermodynamic analysis with nematostatics results in a model for morphactancy, that is, adsorption-induced interfacial shape selection. The specific roles of gradient bulk Frank elasticity, interfacial tension, and anchoring energy are elucidated by analyzing particular paths in the thermodynamic-geometric phase space.
Optical trapping of nanoshells
NASA Astrophysics Data System (ADS)
Hester, Brooke C.; Crawford, Alice; Kishore, Rani B.; Helmerson, Kristian; Halas, Naomi J.; Levin, Carly
2007-09-01
We investigate near-resonant trapping of Rayleigh particles in optical tweezers. Although optical forces due to a near-resonant laser beam have been extensively studied for atoms, the situation for larger particles is that the laser wavelength is far from any absorption resonance. Theory predicts, however, that the trapping force exerted on a Rayleigh particle is enhanced, and may be three to fifty times larger for frequencies near resonance than for frequencies far off resonance. The ability to selectively trap only particles with a given absorption peak may have many practical applications. In order to investigate near-resonant trapping we are using nanoshells, particles with a dielectric core and metallic coating that can exhibit plasmon resonances. The resonances of the nanoshells can be tuned by adjusting the ratio of the radius of the dielectric core, r I, to the overall radius, r II, which includes the thickness of the metallic coating. Our nanoshells, fabricated at Rice University, consist of a silica core with a gold coating. Using back focal plane detection, we measure the trap stiffness of a single focus optical trap (optical tweezers), from a diode laser at 853 nm for nanoshells with several different r I/r II ratios.
Microfabricated cylindrical ion trap
Blain, Matthew G.
2005-03-22
A microscale cylindrical ion trap, having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale cylindrical ion trap to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The microscale CIT has a reduced ion mean free path, allowing operation at higher pressures with less expensive and less bulky vacuum pumping system, and with lower battery power than conventional- and miniature-sized ion traps. The reduced electrode voltage enables integration of the microscale cylindrical ion trap with on-chip integrated circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of microscale cylindrical ion traps can be realized in truly field portable, handheld microanalysis systems.
Anisotropic microstructure near the sun
NASA Astrophysics Data System (ADS)
Coles, W. A.; Grall, R. R.; Spangler, S. R.; Sakurai, T.; Harmon, J. K.
1996-07-01
Radio scattering observations provide a means of measuring a two-dimensional projection of the three-dimensional spatial spectrum of electron density, i.e., in the plane perpendicular to the line of sight. Earlier observations have shown that the microstructure at scales of the order of 10 km becomes highly field-aligned inside of 10 Rsolar [Armstrong et al., 1990]. Earlier work has also shown that density fluctuations at scales larger than 1000 km have a Kolmogorov spectrum, whereas the smaller scale structure has a flatter spectrum and is considerably enhanced above the Kolmogorov ``background'' [Coles et al., 1991]. Here we present new observations made during 1990 and 1992. These confirm the earlier work, which was restricted to one source on a few days, but they suggest that the anisotropy changes abruptly near 6 Rsolar which was not clear in the earlier data. The axial ratio measurements are shown on Figure 1 below. The new observations were made with a more uniform sampling of the spatial plane. They show that contours of constant correlation are elliptical. This is apparently inconsistent with the spatial correlation of the ISEE-3 magnetic field which shows a ``Maltese Cross'' shape [Matthaeus et al., 1990]. However this inconsistency may be only apparent: the magnetic field and density correlations need not have the same shape; the scale of the magnetic field correlations is at least 4 orders of magnitude larger; they are much further from the sun; and they are point measurements whereas ours are path-integrated. We also made two simultaneous measurements, at 10 Rsolar, of the anisotropy on scales of 200 to 4000 km. Significant anisotropy was seen on the smaller scales, but the larger scale structure was essentially isotropic. This suggests that the process responsible for the anisotropic microstructure is independent of the larger scale isotropic turbulence. It is then tempting to speculate that the damping of this anisotropic process inside of 6 Rsolar
Fully Integrating the Design Process
T.A. Bjornard; R.S. Bean
2008-03-01
The basic approach to designing nuclear facilities in the United States does not currently reflect the routine consideration of proliferation resistance and international safeguards. The fully integrated design process is an approach for bringing consideration of international safeguards and proliferation resistance, together with state safeguards and security, fully into the design process from the very beginning, while integrating them sensibly and synergistically with the other project functions. In view of the recently established GNEP principles agreed to by the United States and at least eighteen other countries, this paper explores such an integrated approach, and its potential to help fulfill the new internationally driven design requirements with improved efficiencies and reduced costs.
Pyramidal Magneto-Optical Atom Traps on a Chip
NASA Astrophysics Data System (ADS)
Pollock, Samuel; Cotter, Joseph; Laliotis, Athanasios; Ramirez-Martinez, Fernando; Trupke, Michael; Hinds, Ed
2009-05-01
We demonstrate the fabrication and development of scalable arrays of pyramidal magneto-optical micro-traps in silicon as an elegant and simple way of capturing atoms from a thermal vapour directly on the surface of atom chips. The integration of these devices offers good prospects for reducing the cost and complexity of atom-chip experiments. Potential applications range from using an array of small cold atom clouds to map local magnetic field variations or sensing inertial forces. The micropyramids could also serve as single-atom sources for loading integrated optical cavities, allowing for production of single photons on demand for applications in QIP. We form the pyramids using an anisotropic etching process, preferentially etching the 100 plane to produce hollow pyramids in the surface of the wafer. Further processes have been developed to effectively smooth the rough mirror surfaces resulting from the anisotropic etch whilst maintaining the planar structure. We have recently demonstrated that these microfabricated pyramids can trap atoms from a thermal vapour. We present experimental data and associated theoretical models to describe the capture and loss processes of the MOT, as well as the properties of the cold atomic sample in the sub-mm^3 trapping region of the micropyramids.
Ensuring Fully Soldered Through Holes
NASA Technical Reports Server (NTRS)
Blow, Raymond K.
1987-01-01
Simple differential-pressure soldering method provides visual evidence that hidden joints are fully soldered. Intended for soldering connector pins in plated through holes in circuit boards. Molten solder flows into plated through holes, drawn by vacuum in manifold over circuit board. Differential-pressure process ensures solder wets entire through hole around connector pin.
Ensuring Fully Soldered Through Holes
NASA Technical Reports Server (NTRS)
Blow, Raymond K.
1987-01-01
Simple differential-pressure soldering method provides visual evidence that hidden joints are fully soldered. Intended for soldering connector pins in plated through holes in circuit boards. Molten solder flows into plated through holes, drawn by vacuum in manifold over circuit board. Differential-pressure process ensures solder wets entire through hole around connector pin.
Anisotropic inflation in Gauss-Bonnet gravity
Lahiri, Sayantani
2016-09-19
We study anisotropic inflation with Gauss-Bonnet correction in presence of a massless vector field. In this scenario, exact anisotropic power-law inflation is realized when the inflaton potential, gauge coupling function and the Gauss-Bonnet coupling are exponential functions. We show that anisotropy becomes proportional to two slow-roll parameters of the theory and hence gets enhanced in presence of quadratic curvature corrections. The stability analysis reveals that anisotropic power-law solutions remain stable over a substantially large parameter region.
Shaped beam scattering by an anisotropic particle
NASA Astrophysics Data System (ADS)
Chen, Zhenzhen; Zhang, Huayong; Huang, Zhixiang; Wu, Xianliang
2017-03-01
An exact semi-analytical solution to the electromagnetic scattering from an optically anisotropic particle illuminated by an arbitrarily shaped beam is proposed. The scattered fields and fields within the anisotropic particle are expanded in terms of spherical vector wave functions. The unknown expansion coefficients are determined by using the boundary conditions and the method of moments scheme. For incidence of a Gaussian beam, zero-order Bessel beam and Hertzian electric dipole radiation, numerical results of the normalized differential scattering cross section are given to a uniaxial, gyrotropic anisotropic spheroid and circular cylinder of finite length. The scattering properties are analyzed concisely.
Finite-volume scheme for anisotropic diffusion
Es, Bram van; Koren, Barry; Blank, Hugo J. de
2016-02-01
In this paper, we apply a special finite-volume scheme, limited to smooth temperature distributions and Cartesian grids, to test the importance of connectivity of the finite volumes. The area of application is nuclear fusion plasma with field line aligned temperature gradients and extreme anisotropy. We apply the scheme to the anisotropic heat-conduction equation, and compare its results with those of existing finite-volume schemes for anisotropic diffusion. Also, we introduce a general model adaptation of the steady diffusion equation for extremely anisotropic diffusion problems with closed field lines.
Anisotropic superfluidity in a dipolar Bose gas.
Ticknor, Christopher; Wilson, Ryan M; Bohn, John L
2011-02-11
We study the superfluid character of a dipolar Bose-Einstein condensate (DBEC) in a quasi-two dimensional geometry. We consider the dipole polarization to have some nonzero projection into the plane of the condensate so that the effective interaction is anisotropic in this plane, yielding an anisotropic dispersion relation. By performing direct numerical simulations of a probe moving through the DBEC, we observe the sudden onset of drag or creation of vortex-antivortex pairs at critical velocities that depend strongly on the direction of the probe's motion. This anisotropy emerges because of the anisotropic manifestation of a rotonlike mode in the system.
Anisotropic Superfluidity in a Dipolar Bose Gas
Ticknor, Christopher; Wilson, Ryan M.; Bohn, John L.
2011-02-11
We study the superfluid character of a dipolar Bose-Einstein condensate (DBEC) in a quasi-two dimensional geometry. We consider the dipole polarization to have some nonzero projection into the plane of the condensate so that the effective interaction is anisotropic in this plane, yielding an anisotropic dispersion relation. By performing direct numerical simulations of a probe moving through the DBEC, we observe the sudden onset of drag or creation of vortex-antivortex pairs at critical velocities that depend strongly on the direction of the probe's motion. This anisotropy emerges because of the anisotropic manifestation of a rotonlike mode in the system.
Riaud, Antoine; Thomas, Jean-Louis; Baudoin, Michael; Bou Matar, Olivier
2015-12-01
Despite their self-reconstruction properties in heterogeneous media, Bessel beams are known to degenerate when they are refracted from an isotropic to an anisotropic medium. In this paper, we study the converse situation wherein an anisotropic Bessel beam is refracted into an isotropic medium. It is shown that these anisotropic Bessel beams also degenerate, leading to confined vortical waves that may serve as localized particle trap for acoustical tweezers. The linear nature of this degeneration allows the three-dimensional control of this trap position by wavefront correction. Theory is confronted to experiments performed in the field of acoustics. A swirling surface acoustic wave is synthesized at the surface of a piezoelectric crystal by a microelectromechanical integrated system and radiated inside a miniature liquid vessel. The wavefront correction is operated with inverse filter technique. This work opens perspectives for contactless on-chip manipulation devices.
Dipolar matter-wave solitons in two-dimensional anisotropic discrete lattices
NASA Astrophysics Data System (ADS)
Chen, Huaiyu; Liu, Yan; Zhang, Qiang; Shi, Yuhan; Pang, Wei; Li, Yongyao
2016-05-01
We numerically demonstrate two-dimensional (2D) matter-wave solitons in the disk-shaped dipolar Bose-Einstein condensates (BECs) trapped in strongly anisotropic optical lattices (OLs) in a disk's plane. The considered OLs are square lattices which can be formed by interfering two pairs of plane waves with different intensities. The hopping rates of the condensates between two adjacent lattices in the orthogonal directions are different, which gives rise to a linearly anisotropic system. We find that when the polarized orientation of the dipoles is parallel to disk's plane with the same direction, the combined effects of the linearly anisotropy and the nonlocal nonlinear anisotropy strongly influence the formations, as well as the dynamics of the lattice solitons. Particularly, the isotropy-pattern solitons (IPSs) are found when these combined effects reach a balance. Motion, collision, and rotation of the IPSs are also studied in detail by means of systematic simulations. We further find that these IPSs can move freely in the 2D anisotropic discrete system, hence giving rise to an anisotropic effective mass. Four types of collisions between the IPSs are identified. By rotating an external magnetic field up to a critical angular velocity, the IPSs can still remain localized and play as a breather. Finally, the influences from the combined effects between the linear and the nonlocal nonlinear anisotropy with consideration of the contact and/or local nonlinearity are discussed too.
An optical apparatus for rotation and trapping
Gutiérrez-Medina, Braulio; Andreasson, Johan O. L.; Greenleaf, William J.; LaPorta, Arthur; Block, Steven M.
2010-01-01
We present details of the design, construction and testing of a single-beam optical tweezers apparatus capable of measuring and exerting torque, as well as force, on microfabricated, optically anisotropic particles (an ‘optical torque wrench’). The control of angular orientation is achieved by rotating the linear polarization of a trapping laser with an electro-optic modulator (EOM), which affords improved performance over previous designs. The torque imparted to the trapped particle is assessed by measuring the difference between left- and right-circular components of the transmitted light, and constant torque is maintained by feeding this difference signal back into a custom-designed electronic servo loop. The limited angular range of the EOM (±180°) is extended by rapidly reversing the polarization once a threshold angle is reached, enabling the torque clamp to function over unlimited, continuous rotations at high bandwidth. In addition, we developed particles suitable for rotation in this apparatus using microfabrication techniques. Altogether, the system allows for the simultaneous application of forces (~0.1–100 pN) and torques (~1–10,000 pN nm) in the study of biomolecules. As a proof of principle, we demonstrate how our instrument can be used to study the supercoiling of single DNA molecules. PMID:20627165
Low Earth orbit assessment of proton anisotropy using AP8 and AP9 trapped proton models.
Badavi, Francis F; Walker, Steven A; Santos Koos, Lindsey M
2015-04-01
The completion of the International Space Station (ISS) in 2011 has provided the space research community with an ideal evaluation and testing facility for future long duration human activities in space. Ionized and secondary neutral particles radiation measurements inside ISS form the ideal tool for validation of radiation environmental models, nuclear reaction cross sections and transport codes. Studies using thermo-luminescent detectors (TLD), tissue equivalent proportional counter (TPEC), and computer aided design (CAD) models of early ISS configurations confirmed that, as input, computational dosimetry at low Earth orbit (LEO) requires an environmental model with directional (anisotropic) capability to properly describe the exposure of trapped protons within ISS. At LEO, ISS encounters exposure from trapped electrons, protons and geomagnetically attenuated galactic cosmic rays (GCR). For short duration studies at LEO, one can ignore trapped electrons and ever present GCR exposure contributions during quiet times. However, within the trapped proton field, a challenge arises from properly estimating the amount of proton exposure acquired. There exist a number of models to define the intensity of trapped particles. Among the established trapped models are the historic AE8/AP8, dating back to the 1980s and the recently released AE9/AP9/SPM. Since at LEO electrons have minimal exposure contribution to ISS, this work ignores the AE8 and AE9 components of the models and couples a measurement derived anisotropic trapped proton formalism to omnidirectional output from the AP8 and AP9 models, allowing the assessment of the differences between the two proton models. The assessment is done at a target point within the ISS-11A configuration (circa 2003) crew quarter (CQ) of Russian Zvezda service module (SM), during its ascending and descending nodes passes through the south Atlantic anomaly (SAA). The anisotropic formalism incorporates the contributions of proton narrow
Low Earth orbit assessment of proton anisotropy using AP8 and AP9 trapped proton models
NASA Astrophysics Data System (ADS)
Badavi, Francis F.; Walker, Steven A.; Santos Koos, Lindsey M.
2015-04-01
The completion of the International Space Station (ISS) in 2011 has provided the space research community with an ideal evaluation and testing facility for future long duration human activities in space. Ionized and secondary neutral particles radiation measurements inside ISS form the ideal tool for validation of radiation environmental models, nuclear reaction cross sections and transport codes. Studies using thermo-luminescent detectors (TLD), tissue equivalent proportional counter (TPEC), and computer aided design (CAD) models of early ISS configurations confirmed that, as input, computational dosimetry at low Earth orbit (LEO) requires an environmental model with directional (anisotropic) capability to properly describe the exposure of trapped protons within ISS. At LEO, ISS encounters exposure from trapped electrons, protons and geomagnetically attenuated galactic cosmic rays (GCR). For short duration studies at LEO, one can ignore trapped electrons and ever present GCR exposure contributions during quiet times. However, within the trapped proton field, a challenge arises from properly estimating the amount of proton exposure acquired. There exist a number of models to define the intensity of trapped particles. Among the established trapped models are the historic AE8/AP8, dating back to the 1980s and the recently released AE9/AP9/SPM. Since at LEO electrons have minimal exposure contribution to ISS, this work ignores the AE8 and AE9 components of the models and couples a measurement derived anisotropic trapped proton formalism to omnidirectional output from the AP8 and AP9 models, allowing the assessment of the differences between the two proton models. The assessment is done at a target point within the ISS-11A configuration (circa 2003) crew quarter (CQ) of Russian Zvezda service module (SM), during its ascending and descending nodes passes through the south Atlantic anomaly (SAA). The anisotropic formalism incorporates the contributions of proton narrow
NASA Technical Reports Server (NTRS)
Oldham, Timothy R.
2003-01-01
We consider radiation-induced charge trapping in SiO2 dielectric layers, primarily from the point of view of CMOS devices. However, SiO2 insulators are used in many other ways, and the same defects occur in other contexts. The key studies, which determined the nature of the oxide charge traps, were done primarily on gate oxides in CMOS devices, because that was the main radiation problem in CMOS at one time. There are two major reviews of radiation-induced oxide charge trapping already in the literature, which discuss the subject in far greater detail than is possible here. The first of these was by McLean et al. in 1989, and the second, ten years later, was intended as an update, because of additional, new work that had been reported. Basically, the picture that has emerged is that ionizing radiation creates electron-hole pairs in the oxide, and the electrons have much higher mobility than the holes. Therefore, the electrons are swept out of the oxide very rapidly by any field that is present, leaving behind any holes that escape the initial recombination process. These holes then undergo a polaron hopping transport toward the Si/SiO2 interface (under positive bias). Near the interface, some fraction of them fall into deep, relatively stable, long-lived hole traps. The nature and annealing behavior of these hole traps is the main focus of this paper.
Negative refraction in anisotropic composites
NASA Astrophysics Data System (ADS)
Chui, S. T.
2004-03-01
Left-handed materials (LHM) are materials in which the direction of wave propagation S is opposite to the wave vector k . S <0 .[1,2,3] LHM exhibit nagative refraction. Experiments have been carried out on a medium consisting of arrays of metallic rings and wrires.[3] An example of a different class of anisotropic left-handed materials are metallic magnetic granular composites. Based on the effective medium approximation, we show that by incorporating metallic magnetic nanoparticles into an appropriate insulating matrix, it may be possible to prepare a composite medium of low eddy current loss which is left-handed for electromagnetic waves propagating in some special direction and polarization in a frequency region near the ferromagnetic resonance frequency.[4,5] This composite may be easier to make on an industrial scale. In addition, its physical properties may be easily tuned by rotating the magnetization locally. The physics involved seems to be different from the original argument.[1,2] In our argument[5], the imaginary part of the dielectric constant of the metal is much larger than the real part, opposite to the original argument. In anisotropic materials so that some of the susceptibilities are negative, the criterion for LHM may not be the same as that for negative refraction.[6] Ansiotropic materials exhibit a richer manifold of anomlous behaviour[6,7,8] and offers more flexibility in apllications.[8] More recently it was found that negative refraction can occur in anisotropic materials where all the susceptibilities are positive.[9] We found that the range of applicability of this effect is much larger than originally thought.[10] S. T. Chui was supported in part by the Office of Naval Research, by the Army Research Laboratory through the Center of Composite Materials at the University of Delaware, by DARPA and by the NSF. [1] J.B.Pendry, A.J.Holden, W.J.Stewart, and I.Youngs, Phys. Rev. Lett 76, 4773 (1996). [2] V.G.Veselago, Sov. Phys. Usp. 10, 509
Composite strings in (2+1)-dimensional anisotropic weakly coupled Yang-Mills theory
Orland, Peter
2008-01-15
The small-scale structure of a string connecting a pair of static sources is explored for the weakly coupled anisotropic SU(2) Yang-Mills theory in (2+1) dimensions. A crucial ingredient in the formulation of the string Hamiltonian is the phenomenon of color smearing of the string constituents. The quark-antiquark potential is determined. We close with some discussion of the standard, fully Lorentz-invariant Yang-Mills theory.
Anisotropic wettability on imprinted hierarchical structures.
Zhang, Fengxiang; Low, Hong Yee
2007-07-03
A series of two-level hierarchical structures on polystyrene (PS) and poly(methyl methacrylate) (PMMA) were fabricated using sequential nanoimprinting lithography (NIL). The hierarchical structures consist of micrometer and sub-micrometer scale grating imprinted with varying orientations. Through water contact angle measurements, these surface hierarchical structures showed a wide range of anisotropic wettabilities on PMMA and PS, with PMMA having an anisotropic wettability from 6 degrees to 54 degrees and PS having an anisotropic wettability from 8 degrees to 32 degrees. At the same time, the water contact angle of PMMA and PS can be tuned to nearly 120 degrees without modifying the surface chemistry. A tunable anisotropic wettability is beneficial for applications where controlling the direction of liquid flow is important, such as in microfluidic devices.
Fully depleted back illuminated CCD
Holland, Stephen Edward
2001-01-01
A backside illuminated charge coupled device (CCD) is formed of a relatively thick high resistivity photon sensitive silicon substrate, with frontside electronic circuitry, and an optically transparent backside ohmic contact for applying a backside voltage which is at least sufficient to substantially fully deplete the substrate. A greater bias voltage which overdepletes the substrate may also be applied. One way of applying the bias voltage to the substrate is by physically connecting the voltage source to the ohmic contact. An alternate way of applying the bias voltage to the substrate is to physically connect the voltage source to the frontside of the substrate, at a point outside the depletion region. Thus both frontside and backside contacts can be used for backside biasing to fully deplete the substrate. Also, high resistivity gaps around the CCD channels and electrically floating channel stop regions can be provided in the CCD array around the CCD channels. The CCD array forms an imaging sensor useful in astronomy.
Weilnau, C; Denz, C; Ahles, M; Stepken, A; Motzek, K; Kaiser, F
2001-11-01
We investigate the generation of higher-order optical vector solitons in two transverse dimensions in anisotropic nonlinear media consisting of an incoherent superposition of a Gaussian beam and a higher-order laser mode with a complex internal modal structure. We demonstrate both numerically and experimentally various examples of these stable self-trapped light structures and show that vortex modes carrying topological charge always decay into multiple-humped structures that remain self trapped during propagation. Furthermore, we demonstrate the mutual stabilization of a triple- and a double-humped transverse light structure leading to the formation of a two-dimensional vector soliton without a stabilizing fundamental Gaussian mode.
Fully synthetic taped insulation cables
Forsyth, Eric B.; Muller, Albert C.
1984-01-01
A high voltage oil-impregnated electrical cable with fully polymer taped insulation operable to 765 kV. Biaxially oriented, specially processed, polyethylene, polybutene or polypropylene tape with an embossed pattern is wound in multiple layers over a conductive core with a permeable screen around the insulation. Conventional oil which closely matches the dielectric constant of the tape is used, and the cable can be impregnated after field installation because of its excellent impregnation characteristics.
Fully automated urban traffic system
NASA Technical Reports Server (NTRS)
Dobrotin, B. M.; Hansen, G. R.; Peng, T. K. C.; Rennels, D. A.
1977-01-01
The replacement of the driver with an automatic system which could perform the functions of guiding and routing a vehicle with a human's capability of responding to changing traffic demands was discussed. The problem was divided into four technological areas; guidance, routing, computing, and communications. It was determined that the latter three areas being developed independent of any need for fully automated urban traffic. A guidance system that would meet system requirements was not being developed but was technically feasible.
Inflation in anisotropic scalar-tensor theories
NASA Technical Reports Server (NTRS)
Pimentel, Luis O.; Stein-Schabes, Jaime
1988-01-01
The existence of an inflationary phase in anisotropic Scalar-Tensor Theories is investigated by means of a conformal transformation that allows us to rewrite these theories as gravity minimally coupled to a scalar field with a nontrivial potential. The explicit form of the potential is then used and the No Hair Theorem concludes that there is an inflationary phase in all open or flat anisotropic spacetimes in these theories. Several examples are constructed where the effect becomes manifest.
Phase space analysis in anisotropic optical systems
NASA Technical Reports Server (NTRS)
Rivera, Ana Leonor; Chumakov, Sergey M.; Wolf, Kurt Bernardo
1995-01-01
From the minimal action principle follows the Hamilton equations of evolution for geometric optical rays in anisotropic media. As in classical mechanics of velocity-dependent potentials, the velocity and the canonical momentum are not parallel, but differ by an anisotropy vector potential, similar to that of linear electromagnetism. Descartes' well known diagram for refraction is generalized and a factorization theorem holds for interfaces between two anisotropic media.
On the anisotropic elastic properties of hydroxyapatite.
NASA Technical Reports Server (NTRS)
Katz, J. L.; Ukraincik, K.
1971-01-01
Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.
NASA Astrophysics Data System (ADS)
Geisler, Reinhard; Kurz, Thomas; Lauterborn, Werner
2000-07-01
A small, oscillating bubble in a liquid can be trapped in the antinode of an acoustic standing wave field. Bubble stability is required for the study of single bubble sonoluminescence (SBSL). The properties of the acoustic resonator are essential for the stable trapping of sonoluminescing bubbles. Resonators can be chosen according to the intended application: size and geometry can be varied in a wide range. In this work, the acoustic responses of different resonators were measured by means of holographic interferometry, hydrophones and a laser vibrometer. Also, high-speed photography was used to observe the bubble dynamics. Several single, stable sonoluminescent bubbles were trapped simultaneously within an acoustic resonator in the pressure antinodes of a higher harmonic mode (few bubble sonoluminescence, FBSL).
Thermoelectrically cooled water trap
Micheels, Ronald H.
2006-02-21
A water trap system based on a thermoelectric cooling device is employed to remove a major fraction of the water from air samples, prior to analysis of these samples for chemical composition, by a variety of analytical techniques where water vapor interferes with the measurement process. These analytical techniques include infrared spectroscopy, mass spectrometry, ion mobility spectrometry and gas chromatography. The thermoelectric system for trapping water present in air samples can substantially improve detection sensitivity in these analytical techniques when it is necessary to measure trace analytes with concentrations in the ppm (parts per million) or ppb (parts per billion) partial pressure range. The thermoelectric trap design is compact and amenable to use in a portable gas monitoring instrumentation.
The effect of an anisotropic pressure of thermal particles on resistive wall mode stability
Berkery, J. W. Sabbagh, S. A.; Betti, R.; Guazzotto, L.; Manickam, J.
2014-11-15
The effect of an anisotropic pressure of thermal particles on resistive wall mode stability in tokamak fusion plasmas is derived through kinetic theory and assessed through calculation with the MISK code [B. Hu et al., Phys. Plasmas 12, 0 57301 (2005)]. The fluid anisotropy is treated as a small perturbation on the plasma equilibrium and modeled with a bi-Maxwellian distribution function. A complete stability treatment without an assumption of high frequency mode rotation leads to anisotropic kinetic terms in the dispersion relation in addition to anisotropy corrections to the fluid terms. With the density and the average pressure kept constant, when thermal particles have a higher temperature perpendicular to the magnetic field than parallel, the fluid pressure-driven ballooning destabilization term is reduced. Additionally, the stabilizing kinetic effects of the trapped thermal ions can be enhanced. Together these two effects can lead to a modest increase in resistive wall mode stability.
Variable range hopping electric and thermoelectric transport in anisotropic black phosphorus
NASA Astrophysics Data System (ADS)
Liu, Huili; Sung Choe, Hwan; Chen, Yabin; Suh, Joonki; Ko, Changhyun; Tongay, Sefaattin; Wu, Junqiao
2017-09-01
Black phosphorus (BP) is a layered semiconductor with a high mobility of up to ˜1000 cm2 V-1 s-1 and a narrow bandgap of ˜0.3 eV, and shows potential applications in thermoelectrics. In stark contrast to most other layered materials, electrical and thermoelectric properties in the basal plane of BP are highly anisotropic. To elucidate the mechanism for such anisotropy, we fabricated BP nanoribbons (˜100 nm thick) along the armchair and zigzag directions, and measured the transport properties. It is found that both the electrical conductivity and Seebeck coefficient increase with temperature, a behavior contradictory to that of traditional semiconductors. The three-dimensional variable range hopping model is adopted to analyze this abnormal temperature dependency of electrical conductivity and Seebeck coefficient. The hopping transport of the BP nanoribbons, attributed to high density of trap states in the samples, provides a fundamental understanding of the anisotropic BP for potential thermoelectric applications.
Self-similarity criteria in anisotropic flows with viscosity stratification
NASA Astrophysics Data System (ADS)
Danaila, L.; Voivenel, L.; Varea, E.
2017-02-01
Variable-viscosity flows exhibit a faster trend towards a fully developed turbulent state since fluctuations are produced at a larger amount. A legitimate expectation is that self-similarity to be tenable earlier than in classical, single-viscosity flows. The question which begs to be answered is: which are the self-similarity criteria for variable-viscosity, density-matched, flows? The similarity assumption, i.e., all scales evolve in a similar fashion in space/time, is applied to the transport equation for one- and two-point statistics of anisotropic, variable-viscosity flows. It is shown that the similarity assumption is valid for regions of the flow where viscosity (mean values and the fluctuations root-mean-square) is uniform. In regions where viscosity gradients are important, such as the sheared region and jet boundaries, similarity is not tenable. Our claims are applicable to any decaying flow, isotropic or anisotropic. Support is provided by experimental data obtained in the near field region of a jet issuing into a more viscous environment. The viscosity ratio is 3.5.
Accurately simulating anisotropic thermal conduction on a moving mesh
NASA Astrophysics Data System (ADS)
Kannan, Rahul; Springel, Volker; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark
2016-05-01
We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretization stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the conductive heat transport in galaxy clusters, the evolution of supernova remnants, or the distribution of heat from black hole-driven jets into the intracluster medium.
Evaluation of a Rapid Anisotropic Model for ECG Simulation.
Pezzuto, Simone; Kal'avský, Peter; Potse, Mark; Prinzen, Frits W; Auricchio, Angelo; Krause, Rolf
2017-01-01
State-of-the-art cardiac electrophysiology models that are able to deliver physiologically motivated activation maps and electrocardiograms (ECGs) can only be solved on high-performance computing architectures. This makes it nearly impossible to adopt such models in clinical practice. ECG imaging tools typically rely on simplified models, but these neglect the anisotropic electric conductivity of the tissue in the forward problem. Moreover, their results are often confined to the heart-torso interface. We propose a forward model that fully accounts for the anisotropic tissue conductivity and produces the standard 12-lead ECG in a few seconds. The activation sequence is approximated with an eikonal model in the 3d myocardium, while the ECG is computed with the lead-field approach. Both solvers were implemented on graphics processing units and massively parallelized. We studied the numerical convergence and scalability of the approach. We also compared the method to the bidomain model in terms of ECGs and activation maps, using a simplified but physiologically motivated geometry and 6 patient-specific anatomies. The proposed methods provided a good approximation of activation maps and ECGs computed with a bidomain model, in only a few seconds. Both solvers scaled very well to high-end hardware. These methods are suitable for use in ECG imaging methods, and may soon become fast enough for use in interactive simulation tools.
Evaluation of a Rapid Anisotropic Model for ECG Simulation
Pezzuto, Simone; Kal'avský, Peter; Potse, Mark; Prinzen, Frits W.; Auricchio, Angelo; Krause, Rolf
2017-01-01
State-of-the-art cardiac electrophysiology models that are able to deliver physiologically motivated activation maps and electrocardiograms (ECGs) can only be solved on high-performance computing architectures. This makes it nearly impossible to adopt such models in clinical practice. ECG imaging tools typically rely on simplified models, but these neglect the anisotropic electric conductivity of the tissue in the forward problem. Moreover, their results are often confined to the heart-torso interface. We propose a forward model that fully accounts for the anisotropic tissue conductivity and produces the standard 12-lead ECG in a few seconds. The activation sequence is approximated with an eikonal model in the 3d myocardium, while the ECG is computed with the lead-field approach. Both solvers were implemented on graphics processing units and massively parallelized. We studied the numerical convergence and scalability of the approach. We also compared the method to the bidomain model in terms of ECGs and activation maps, using a simplified but physiologically motivated geometry and 6 patient-specific anatomies. The proposed methods provided a good approximation of activation maps and ECGs computed with a bidomain model, in only a few seconds. Both solvers scaled very well to high-end hardware. These methods are suitable for use in ECG imaging methods, and may soon become fast enough for use in interactive simulation tools. PMID:28512434
SAR Segmentation using Anisotropic Diffusion
NASA Astrophysics Data System (ADS)
Intajag, Sathit; Tipsuwanporn, Vittaya; Cheevasuwit, Fusak
Speckle effects are commonly observed in synthetic aperture radar (SAR) images. The human eye is capable of deriving meaningful information from SAR images; however, an automatic or semi-automatic processing algorithm has difficulty in distinguishing objects in the images because of noise effects present in those images. This paper presents a segmentation method for SAR images, which employs an anisotropic diffusion algorithm. In the proposed scheme, a SAR image is transformed into a logarithmic domain where the diffusion process is used to grow homogeneous regions in the noise environment until the regions reach some criteria for homogeneity; consequently, the segmented image in the logarithm domain is converted to the intensity domain by an exponential function. To grow homogeneous regions the adaptive diffusion method is introduced with a tensor technique in which tensor data are varied with the neighboring pixels. The diffusion algorithm will stop itself by a standard deviation divided by the mean, which is provided according to the homogeneity criteria. Results are shown on both synthetic and satellite SAR images. The evaluation of the proposed method employs the theoretical gain of equivalent numbers of looks (ENL).
Magnetospheric equilibrium with anisotropic pressure
Cheng, C.Z.
1991-07-01
Self-consistent magnetospheric equilibrium with anisotropic pressure is obtained by employing an iterative metric method for solving the inverse equilibrium equation in an optimal flux coordinate system. A method of determining plasma parallel and perpendicular pressures from either analytic particle distribution or particle distribution measured along the satellite's path is presented. The numerical results of axisymmetric magnetospheric equilibrium including the effects of finite beta, pressure anisotropy, and boundary conditions are presented for a bi-Maxwellian particle distribution. For the isotropic pressure cases, the finite beta effect produces an outward expansion of the constant magnetic flux surfaces in relation to the dipole field lines, and along the magnetic field the toroidal ring current is maximum at the magnetic equator. The effect of pressure anisotropy is found to further expand the flux surfaces outward. Along the magnetic field lines the westward ring current can be peak away from the equator due to an eastward current contribution resulting from pressure anisotropy. As pressure anisotropy increases, the peak westward current can become more singular. The outer boundary flux surface has significant effect on the magnetospheric equilibrium. For the outer flux boundary resembling dayside compressed flux surface due to solar wind pressure, the deformation of the magnetic field can be quite different from that for the outer flux boundary resembling the tail-like surface. 23 refs., 17 figs.
Spin precession in anisotropic media
NASA Astrophysics Data System (ADS)
Raes, B.; Cummings, A. W.; Bonell, F.; Costache, M. V.; Sierra, J. F.; Roche, S.; Valenzuela, S. O.
2017-02-01
We generalize the diffusive model for spin injection and detection in nonlocal spin structures to account for spin precession under an applied magnetic field in an anisotropic medium, for which the spin lifetime is not unique and depends on the spin orientation. We demonstrate that the spin precession (Hanle) line shape is strongly dependent on the degree of anisotropy and on the orientation of the magnetic field. In particular, we show that the anisotropy of the spin lifetime can be extracted from the measured spin signal, after dephasing in an oblique magnetic field, by using an analytical formula with a single fitting parameter. Alternatively, after identifying the fingerprints associated with the anisotropy, we propose a simple scaling of the Hanle line shapes at specific magnetic field orientations that results in a universal curve only in the isotropic case. The deviation from the universal curve can be used as a complementary means of quantifying the anisotropy by direct comparison with the solution of our generalized model. Finally, we applied our model to graphene devices and find that the spin relaxation for graphene on silicon oxide is isotropic within our experimental resolution.
SAW imaging in anisotropic media
NASA Astrophysics Data System (ADS)
Clark, M.; Sharples, S. D.; Somekh, M. G.
2000-05-01
We have developed a non-contact laser ultrasound SAW microscope operating at 82 MHz and harmonics thereof, which is capable of rapid image acquisition. Conventional acoustic microscopy is largely immune to the effects of aberration because of the very short acoustic path length that is imposed by the presence of the couplant. The couplant also limits the sensitivity of contacting acoustic microscopy. In laser ultrasound systems the absence of couplant means that longer path lengths are possible but the anisotropy and grain structure of the material can aberrate the passage of the acoustic wave limiting the performance of the system and producing acoustic speckle. We show that even weakly aberrating materials (e.g. aluminum) can produce significant speckle effects. We present experimental non-contacting imaging results on isotropic and textured anisotropic samples; together with simulated images. The results demonstrate that the speckle statistics of the experimental and simulated results agree well; thus demonstrating the cause of the speckle in the experimental images. We demonstrate how a wavefront sensor and adaptation of the optical excitation profile offers a solution to the problem of texture in non-contacting SAW imaging. Finally, we discuss how some material properties may be inferred from the speckle.
Ibrahim, Yehia M.; Smith, Richard D.
2016-01-26
An ion trap device is disclosed. The device includes a series of electrodes that define an ion flow path. A radio frequency (RF) field is applied to the series of electrodes such that each electrode is phase shifted approximately 180 degrees from an adjacent electrode. A DC voltage is superimposed with the RF field to create a DC gradient to drive ions in the direction of the gradient. A second RF field or DC voltage is applied to selectively trap and release the ions from the device. Further, the device may be gridless and utilized at high pressure.
Barlow, Stephan E.; Alexander, Michael L.; Follansbee, James C.
1997-01-01
An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity.
Barlow, S.E.; Alexander, M.L.; Follansbee, J.C.
1997-12-02
An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode is disclosed. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity. 4 figs.
The Reusable Astronomy Portal (TRAP)
NASA Astrophysics Data System (ADS)
Donaldson, T.; Rogers, A.; Wallace, G.
2012-09-01
The Reusable Astronomy Portal (TRAP) aims to provide a common platform for rapidly deploying Astronomy Archives to the web. TRAP is currently under development for both the VAO Data Discovery Portal and the MAST Multi-Mission Portal (Figure 1). TRAP consists of 2 major software packages: the TRAP Client and the TRAP Server. The TRAP framework allows developers to deploy the Server, connect to data resources, then focus on building custom tools for the Client. TRAP is built upon proven industry technologies including the Ext/JS JavaScript Component Library, Mono.NET Web Services, and JSON message based APIs. The multi-layered architecture of TRAP decouples each layer: Client, Service and Data Access, enabling each to evolve independently over time. Although currently deployed to provide astronomy science data access, the TRAP architecture is flexible enough to thrive in any distributed data environment.
A revolutionary graphitisation system: Fully automated, compact and simple
NASA Astrophysics Data System (ADS)
Wacker, L.; Němec, M.; Bourquin, J.
2010-04-01
A new graphitisation system, directly coupled to an elemental analyser, has been developed for convenient, fast and efficient sample preparations for radiocarbon measurement by means of accelerator mass spectrometry. We demonstrate an alternative to the cryogenic transport of CO 2 into the graphitisation reactors with liquid nitrogen, which is used by others. Instead, the CO 2 coming from an EA is absorbed on a single column filled with zeolite. The CO 2 can then be easily released by heating the zeolite trap and transferred to the reactor by gas expansion. The system is simple and fully automated for sample combustion and graphitisation.
Measurement of Trap Length for an Optical Trap
NASA Technical Reports Server (NTRS)
Wrbanek, Susan Y.
2009-01-01
The trap length along the beam axis for an optical trap formed with an upright, oil-immersion microscope was measured. The goals for this effort were twofold. It was deemed useful to understand the depth to which an optical trap can reach for purposes of developing a tool to assist in the fabrication of miniature devices. Additionally, it was desired to know whether the measured trap length favored one or the other of two competing theories to model an optical trap. The approach was to trap a microsphere of known size and mass and raise it from its initial trap position. The microsphere was then dropped by blocking the laser beam for a pre-determined amount of time. Dropping the microsphere in a free-fall mode from various heights relative to the coverslip provides an estimate of how the trapping length changes with depth in water in a sample chamber on a microscope slide. While it was not possible to measure the trap length with sufficient precision to support any particular theory of optical trap formation, it was possible to find regions where the presence of physical boundaries influenced optical traps, and determine that the trap length, for the apparatus studied, is between 6 and 7 m. These results allow more precise control using optical micromanipulation to assemble miniature devices by providing information about the distance over which an optical trap is effective.
NASA Astrophysics Data System (ADS)
Cuestas, Eloisa; Garagiola, Mariano; Pont, Federico M.; Osenda, Omar; Serra, Pablo
2017-07-01
The occupancies and entropic entanglement measures for the ground state of two particles in a two-dimensional harmonic anisotropic trap are studied. We implement a method to study the large interaction strength limit for different short- and long-range interaction potentials that allows to obtain the exact entanglement spectrum and several entropies. We show that for long-range interactions, the von Neumann, min-entropy and the family of Rényi entropies remain finite for the anisotropic traps and diverge logarithmically for the isotropic traps. In the short-range interaction case the entanglement measures diverge for any anisotropic parameter due to the divergence of uncertainty in the momentum since for short-range interactions the relative position width vanishes. We also show that when the reduced density matrix has finite support the Rényi entropies present a non-analytical behavior.
Hybrid quantum systems with trapped charged particles
NASA Astrophysics Data System (ADS)
Kotler, Shlomi; Simmonds, Raymond W.; Leibfried, Dietrich; Wineland, David J.
2017-02-01
as fast entangling gates, long coherence, and flexible topology that is fully electronic in nature. Realizing such a system, however, is technologically challenging because it requires accommodating both a trapping technology and superconducting circuitry in a compatible manner. We review some of the challenges involved, such as the required trap parameters, electron sources, electrical circuitry, and cooling schemes in order to promote further investigations towards the realization of such a hybrid system.
Lévy Flights due to Anisotropic Disorder in Graphene.
Gattenlöhner, S; Gornyi, I V; Ostrovsky, P M; Trauzettel, B; Mirlin, A D; Titov, M
2016-07-22
We study transport properties of graphene with anisotropically distributed on-site impurities (adatoms) that are randomly placed on every third line drawn along carbon bonds. We show that stripe states characterized by strongly suppressed backscattering are formed in this model in the direction of the lines. The system reveals Lévy-flight transport in the stripe direction such that the corresponding conductivity increases as the square root of the system length. Thus, adding this type of disorder to clean graphene near the Dirac point strongly enhances the conductivity, which is in stark contrast with a fully random distribution of on-site impurities, which leads to Anderson localization. The effect is demonstrated both by numerical simulations using the Kwant code and by an analytical theory based on the self-consistent T-matrix approximation.
Lévy Flights due to Anisotropic Disorder in Graphene
NASA Astrophysics Data System (ADS)
Gattenlöhner, S.; Gornyi, I. V.; Ostrovsky, P. M.; Trauzettel, B.; Mirlin, A. D.; Titov, M.
2016-07-01
We study transport properties of graphene with anisotropically distributed on-site impurities (adatoms) that are randomly placed on every third line drawn along carbon bonds. We show that stripe states characterized by strongly suppressed backscattering are formed in this model in the direction of the lines. The system reveals Lévy-flight transport in the stripe direction such that the corresponding conductivity increases as the square root of the system length. Thus, adding this type of disorder to clean graphene near the Dirac point strongly enhances the conductivity, which is in stark contrast with a fully random distribution of on-site impurities, which leads to Anderson localization. The effect is demonstrated both by numerical simulations using the Kwant code and by an analytical theory based on the self-consistent T -matrix approximation.
Engineering tool for trapped proton flux anisotropy evaluation.
Kruglanski, M
1996-11-01
At low altitudes, the high-energy trapped proton fluxes are strongly anisotropic. The proton flux is controlled by the density distribution of the Earth's atmosphere that induces a steep pitch-angle distribution and an East-West effect, the latter caused by the finite size of the proton gyration radius. We have developed a software package, ANISO, to evaluate averaged energy spectra of trapped proton unidirectional fluxes for a given spacecraft orbit and attitude by deducing the angular-dependent proton flux spectra from the AP-8 omnidirectional flux. Included in the model are both the Armstrong et al. (1990) model and a model based on the Badhwar and Konradi (1990) pitch-angle distribution.
Elliptical ion traps and trap arrays for quantum computation
NASA Astrophysics Data System (ADS)
Devoe, Ralph G.
1998-08-01
The properties of a rf quadrupole trap, the elliptical ion trap, are derived. Elliptical traps can confine large numbers of ions in the Lamb-Dicke regime due to a hitherto unrecognized mechanism unique to one-dimensional Coulomb crystals, implicit in the theories of Dubin and Schiffer. This follows from a linear crystal stability condition, which uniquely relates the crystal size to ellipticity, and a micromotion relation, which reveals a 1/5-root dependence on the number of trapped ions. Elliptical traps offer several advantages over linear traps in the Cirac-Zoller model of quantum computing, both for initial tests and as a potential method of creating a full-scale quantum computer. Numerical solutions of a one-electrode structure show that microscopic elliptical traps, each containing ~100 ions, can be constructed at a density of 100 traps/cm2, making possible arrays containing >106 ions in the Lamb-Dicke regime for precision spectroscopy or quantum computation.
Menou, Kristen
2013-09-01
Although tidally locked habitable planets orbiting nearby M-dwarf stars are among the best astronomical targets to search for extrasolar life, they may also be deficient in volatiles and water. Climate models for this class of planets show atmospheric transport of water from the dayside to the nightside, where it is precipitated as snow and trapped as ice. Since ice only slowly flows back to the dayside upon accumulation, the resulting hydrological cycle can trap a large amount of water in the form of nightside ice. Using ice sheet dynamical and thermodynamical constraints, I illustrate how planets with less than about a quarter the Earth's oceans could trap most of their surface water on the nightside. This would leave their dayside, where habitable conditions are met, potentially dry. The amount and distribution of residual liquid water on the dayside depend on a variety of geophysical factors, including the efficiency of rock weathering at regulating atmospheric CO{sub 2} as dayside ocean basins dry up. Water-trapped worlds with dry daysides may offer similar advantages as land planets for habitability, by contrast with worlds where more abundant water freely flows around the globe.
NASA Astrophysics Data System (ADS)
Menou, Kristen
2013-09-01
Although tidally locked habitable planets orbiting nearby M-dwarf stars are among the best astronomical targets to search for extrasolar life, they may also be deficient in volatiles and water. Climate models for this class of planets show atmospheric transport of water from the dayside to the nightside, where it is precipitated as snow and trapped as ice. Since ice only slowly flows back to the dayside upon accumulation, the resulting hydrological cycle can trap a large amount of water in the form of nightside ice. Using ice sheet dynamical and thermodynamical constraints, I illustrate how planets with less than about a quarter the Earth's oceans could trap most of their surface water on the nightside. This would leave their dayside, where habitable conditions are met, potentially dry. The amount and distribution of residual liquid water on the dayside depend on a variety of geophysical factors, including the efficiency of rock weathering at regulating atmospheric CO2 as dayside ocean basins dry up. Water-trapped worlds with dry daysides may offer similar advantages as land planets for habitability, by contrast with worlds where more abundant water freely flows around the globe.
Practical axial optical trapping
Mack, A. H.; Schlingman, D. J.; Regan, L.; Mochrie, S. G. J.
2012-01-01
We describe a new method for calibrating optical trapping measurements in which tension is applied in the direction of the laser beam to a molecule tethered between a surface and an optically trapped bead. Specifically, we present a generally-applicable procedure for converting from the measured scattering intensity and the measured stage displacement to applied tension and bead-coverslip separation, using measurements of the light intensity scattered from an untethered, trapped bead. Our calibration accounts for a number of effects, including aberrations and the interference of forward-reflected bead-scattered light with the trapping beam. To demonstrate the accuracy of our method, we show measurements of the DNA force-versus-extension relation using a range of laser intensities, and show that these measurements match the expected extensible wormlike-chain (WLC) behavior. Finally, we also demonstrate a force-clamp, in which the tension in a tether is held fixed while the extension varies as a result of molecular events. PMID:23126750
Ryan, Michael J.
1988-01-01
A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (the combination of a hot finger and thermocouple well) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more thermocouples for detecting condensate level and energy, while the cold finger contains a liquid with a lower boiling temperature than that of water. Vapor pressure from the liquid is used to do work such as displacing a piston or bellows in providing an indication of total energy (steam+condensate) of the system. Processing means coupled to and responsive to outputs from the thermocouple well hot and cold fingers subtracts the condensate energy as measured by the hot finger and thermocouple well from the total energy as measured by the cold finger to provide an indication of the presence of steam downstream from the trap indicating that the steam trap is malfunctioning.
ERIC Educational Resources Information Center
Goodman, Paul
The compulsory system of education is criticized on the grounds that it has become a regimented "universal trap" antithetical to democracy. In contrast to the Jeffersonian concept of education in the service of citizen initiative for the preservation of freedom, current compulsory education is a tool of industrialism and of a rigidly stratified…
ERIC Educational Resources Information Center
Rueckner, Wolfgang; And Others
1995-01-01
Describes a demonstration in which a ball is placed in an unstable position on a saddle shape. The ball becomes stable when it is rotated above some threshold angular velocity. The demonstration is a mechanical analog of confining a particle in a "Paul Trap". (DDR)
Vortex precession in trapped superfluids from effective field theory
NASA Astrophysics Data System (ADS)
Esposito, Angelo; Krichevsky, Rafael; Nicolis, Alberto
2017-09-01
We apply a recently developed effective string theory for vortex lines to the case of two-dimensional trapped superfluids. We do not assume a perturbative microscopic description for the superfluid, but only a gradient expansion for the long-distance hydrodynamical description and for the trapping potential. For any regular trapping potential, we compute the spatial dependence of the superfluid density and the orbital frequency and trajectory of an off-center vortex. Our results are fully relativistic and in the nonrelativistic limit reduce to known results based on the Gross-Pitaevskii model. In our formalism, the leading effect in the nonrelativistic limit arises from two simple Feynman diagrams in which the vortex interacts with the trapping potential through the exchange of hydrodynamical modes.
Rotational state detection of electrically trapped polyatomic molecules
NASA Astrophysics Data System (ADS)
Glöckner, Rosa; Prehn, Alexander; Rempe, Gerhard; Zeppenfeld, Martin
2015-05-01
Detecting the internal state of polar molecules is a substantial challenge when standard techniques such as resonance-enhanced multiphoton ionization or laser-induced fluorescense do not work. As this is the case for most polyatomic molecule species, in this paper we investigate an alternative based on state-selective removal of molecules from an electrically trapped ensemble. Specifically, we deplete molecules by driving rotational and/or vibrational transitions to untrapped states. Fully resolving the rotational state with this method can be a considerable challenge, as the frequency differences between various transitions are easily substantially less than the Stark broadening in an electric trap. However, by using a unique trap design that provides homogeneous fields in a large fraction of the trap volume, we successfully discriminate all rotational quantum numbers, including the rotational M-substate.
Phase slippage and self-trapping in a self-induced bosonic Josephson junction
Abad, M.; Guilleumas, M.; Mayol, R.; Pi, M.; Jezek, D. M.
2011-09-15
A dipolar condensate confined in a toroidal trap constitutes a self-induced Josephson junction when the dipoles are oriented perpendicularly to the trap symmetry axis and the s-wave scattering length is small enough. The ring-shaped double-well potential coming from the anisotropic character of the mean-field dipolar interaction is robust enough to sustain self-trapping dynamics, which takes place when the initial population imbalance between the two wells is large. We show that, in this system, the self-trapping regime is directly related to a vortex-induced phase-slip dynamics. A vortex and antivortex are spontaneously nucleated in the low-density regions before a minimum of the population imbalance is reached and then cross the toroidal section in opposite directions through the junctions. This vortex dynamics yields a phase slip between the two weakly linked condensates causing an inversion of the particle flux.
Borovikov, V. A.; Kalinin, S. V.; Khavin, Yu.; ...
2015-08-19
We derive the Green's functions for a three-dimensional semi-infinite fully anisotropic piezoelectric material using the plane wave theory method. The solution gives the complete set of electromechanical fields due to an arbitrarily oriented point force and a point electric charge applied to the boundary of the half-space. Moreover, the solution constitutes generalization of Boussinesq's and Cerruti's problems of elastic isotropy for the anisotropic piezoelectric materials. On the example of piezoceramics PZT-6B, the present results are compared with the previously obtained solution for the special case of transversely isotropic piezoelectric solid subjected to the same boundary condition.
Borovikov, V. A.; Kalinin, S. V.; Khavin, Yu.; Mirman, B.; Karapetian, E.
2015-08-19
We derive the Green's functions for a three-dimensional semi-infinite fully anisotropic piezoelectric material using the plane wave theory method. The solution gives the complete set of electromechanical fields due to an arbitrarily oriented point force and a point electric charge applied to the boundary of the half-space. Moreover, the solution constitutes generalization of Boussinesq's and Cerruti's problems of elastic isotropy for the anisotropic piezoelectric materials. On the example of piezoceramics PZT-6B, the present results are compared with the previously obtained solution for the special case of transversely isotropic piezoelectric solid subjected to the same boundary condition.
Plasmon resonance-based optical trapping of single and multiple Au nanoparticles.
Toussaint, K. C.; Liu, M.; Pelton, M.; Pesic, J.; Guffey, M.; Guyot-Sionnest, P.; Scherer, N. F.; Univ. of Chicago
2007-01-01
The plasmon resonance-based optical trapping (PREBOT) method is used to achieve stable trapping of metallic nanoparticles of different shapes and composition, including Au bipyramids and Au/Ag core/shell nanorods. In all cases the longitudinal plasmon mode of these anisotropic particles is used to enhance the gradient force of an optical trap, thereby increasing the strength of the trap potential. Specifically, the trapping laser is slightly detuned to the long-wavelength side of the longitudinal plasmon resonance where the sign of the real component of the polarizability leads to an attractive gradient force. A second (femtosecond pulsed) laser is used to excite two-photon fluorescence for detection of the trapped nanoparticles. Two-photon fluorescence time trajectories are recorded for up to 20 minutes for single and multiple particles in the trap. In the latter case, a stepwise increase reflects sequential loading of single Au bipyramids. The nonlinearity of the amplitude and noise with step number are interpreted as arising from interactions or enhanced local fields among the trapped particles and fluctuations in the arrangements thereof.
Anisotropic nanomaterials: structure, growth, assembly, and functions
Sajanlal, Panikkanvalappil R.; Sreeprasad, Theruvakkattil S.; Samal, Akshaya K.; Pradeep, Thalappil
2011-01-01
Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications. PMID:22110867
Anisotropic nanomaterials: structure, growth, assembly, and functions.
Sajanlal, Panikkanvalappil R; Sreeprasad, Theruvakkattil S; Samal, Akshaya K; Pradeep, Thalappil
2011-01-01
Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications.
Quasiparticle anisotropic hydrodynamics for central collisions
NASA Astrophysics Data System (ADS)
Alqahtani, Mubarak; Nopoush, Mohammad; Strickland, Michael
2017-03-01
We use quasiparticle anisotropic hydrodynamics to study an azimuthally symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state (EoS). We compare results obtained by using the quasiparticle method with the standard method of imposing the EoS in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio η /s . We find that the three methods agree well for small shear viscosity to entropy density ratio η /s , but differ at large η /s , with the standard anisotropic EoS method showing suppressed production at low transverse-momentum compared with the other two methods considered. Finally, we demonstrate explicitly that, when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative at large pT. Such behavior is not seen in either anisotropic hydrodynamics approach, irrespective of the value of η /s .
Matter sourced anisotropic stress for dark energy
NASA Astrophysics Data System (ADS)
Chang, Baorong; Lu, Jianbo; Xu, Lixin
2014-11-01
Usually a dark energy as a perfect fluid is characterized by the ratio of pressure to energy density (w =p /ρ ) and the ratio of their perturbations in its rest frame (cs2=δ p /δ ρ ). However, a dark energy would have other characteristics beyond its equation of state and the effective speed of sound. Here the extra property is the anisotropic stress sourced by matter as a simple extension to the perfect fluid model. At the background level, this anisotropic stress is zero with respect to the cosmological principle, but not at the first-order perturbation. We tested the viability of the existence of this kind of anisotropic stress by using the currently available cosmic observations through the geometrical and dynamical measurements. Using the Markov-chain Monte Carlo method, we found that the upper bounds on the anisotropic stress which enters into the summation of the Newtonian potentials should be of the order O (1 0-3)Δm . We did not find any strong evidence for the existence of this matter-sourced anisotropic stress, even in the 1 σ region.
Calibration of optical traps by dual trapping of one bead.
Dutov, Pavel; Schieber, Jay
2013-11-15
We introduce a method for optical trap calibration that is suitable for viscoelastic material. The method is designed for use on experimental setups with two optical tweezers and is based on pulling a trapped particle with one trap while holding it with the other. No piezo stage is needed, and only one optical trap must be movable with galvo mirrors, piezo mirrors, or acousto-optical deflectors. The method combines advantages of commonly known PSD-fitting and fast-sweeping methods, allowing calibration of a completely fixed trap in a fluid of unknown viscosity/viscoelasticity. A detailed method description, a theoretical derivation, and an experimental comparison to other methods are reported.
Liquid trap seals thermocouple leads
NASA Technical Reports Server (NTRS)
Ruppe, E. P.
1966-01-01
Liquid trap seals thermocouple leads coming out of a brazing retort that operates with a controlled atmosphere so that air cannot enter the retort and hydrogen cannot escape. The trap is fastened to a duct welded to the retort. Thermocouple leads are led out through the duct and trap, with the fluid forming a gastight seal between the atmosphere and the retort.
Fully integrated, fully automated generation of short tandem repeat profiles
2013-01-01
Background The generation of short tandem repeat profiles, also referred to as ‘DNA typing,’ is not currently performed outside the laboratory because the process requires highly skilled technical operators and a controlled laboratory environment and infrastructure with several specialized instruments. The goal of this work was to develop a fully integrated system for the automated generation of short tandem repeat profiles from buccal swab samples, to improve forensic laboratory process flow as well as to enable short tandem repeat profile generation to be performed in police stations and in field-forward military, intelligence, and homeland security settings. Results An integrated system was developed consisting of an injection-molded microfluidic BioChipSet cassette, a ruggedized instrument, and expert system software. For each of five buccal swabs, the system purifies DNA using guanidinium-based lysis and silica binding, amplifies 15 short tandem repeat loci and the amelogenin locus, electrophoretically separates the resulting amplicons, and generates a profile. No operator processing of the samples is required, and the time from swab insertion to profile generation is 84 minutes. All required reagents are contained within the BioChipSet cassette; these consist of a lyophilized polymerase chain reaction mix and liquids for purification and electrophoretic separation. Profiles obtained from fully automated runs demonstrate that the integrated system generates concordant short tandem repeat profiles. The system exhibits single-base resolution from 100 to greater than 500 bases, with inter-run precision with a standard deviation of ±0.05 - 0.10 bases for most alleles. The reagents are stable for at least 6 months at 22°C, and the instrument has been designed and tested to Military Standard 810F for shock and vibration ruggedization. A nontechnical user can operate the system within or outside the laboratory. Conclusions The integrated system represents the
Fully analogue photonic reservoir computer.
Duport, François; Smerieri, Anteo; Akrout, Akram; Haelterman, Marc; Massar, Serge
2016-03-03
Introduced a decade ago, reservoir computing is an efficient approach for signal processing. State of the art capabilities have already been demonstrated with both computer simulations and physical implementations. If photonic reservoir computing appears to be promising a solution for ultrafast nontrivial computing, all the implementations presented up to now require digital pre or post processing, which prevents them from exploiting their full potential, in particular in terms of processing speed. We address here the possibility to get rid simultaneously of both digital pre and post processing. The standalone fully analogue reservoir computer resulting from our endeavour is compared to previous experiments and only exhibits rather limited degradation of performances. Our experiment constitutes a proof of concept for standalone physical reservoir computers.
Fully analogue photonic reservoir computer
Duport, François; Smerieri, Anteo; Akrout, Akram; Haelterman, Marc; Massar, Serge
2016-01-01
Introduced a decade ago, reservoir computing is an efficient approach for signal processing. State of the art capabilities have already been demonstrated with both computer simulations and physical implementations. If photonic reservoir computing appears to be promising a solution for ultrafast nontrivial computing, all the implementations presented up to now require digital pre or post processing, which prevents them from exploiting their full potential, in particular in terms of processing speed. We address here the possibility to get rid simultaneously of both digital pre and post processing. The standalone fully analogue reservoir computer resulting from our endeavour is compared to previous experiments and only exhibits rather limited degradation of performances. Our experiment constitutes a proof of concept for standalone physical reservoir computers. PMID:26935166
Adaptive-Anisotropic Wavelet Collocation Method on general curvilinear coordinate systems
NASA Astrophysics Data System (ADS)
Brown-Dymkoski, Eric; Vasilyev, Oleg V.
2017-03-01
A new general framework for an Adaptive-Anisotropic Wavelet Collocation Method (A-AWCM) for the solution of partial differential equations is developed. This proposed framework addresses two major shortcomings of existing wavelet-based adaptive numerical methodologies, namely the reliance on a rectangular domain and the "curse of anisotropy", i.e. drastic over-resolution of sheet- and filament-like features arising from the inability of the wavelet refinement mechanism to distinguish highly correlated directional information in the solution. The A-AWCM addresses both of these challenges by incorporating coordinate transforms into the Adaptive Wavelet Collocation Method for the solution of PDEs. The resulting integrated framework leverages the advantages of both the curvilinear anisotropic meshes and wavelet-based adaptive refinement in a complimentary fashion, resulting in greatly reduced cost of resolution for anisotropic features. The proposed Adaptive-Anisotropic Wavelet Collocation Method retains the a priori error control of the solution and fully automated mesh refinement, while offering new abilities through the flexible mesh geometry, including body-fitting. The new A-AWCM is demonstrated for a variety of cases, including parabolic diffusion, acoustic scattering, and unsteady external flow.
Grundy, B.R.
1981-09-29
The radial cold trap comprises a housing having a plurality of mesh bands disposed therein. The mesh bands comprise concentrically arranged bands of mesh with the mesh specific surface area of each band increasing from the outermost mesh band to the innermost mesh band. An inlet nozzle is attached to the outside section of the housing while an outlet nozzle is attached to the inner portion of the housing so as to be concentrically connected to the innermost mesh band. An inlet baffle having orifices therein may be disposed around the outermost mesh band and within the housing for directing the flow of the fluid from the inlet nozzle to the outermost mesh band in a uniform manner. The flow of fluid passes through each consecutive mesh band and into the outlet nozzle. The circular pattern of the symmetrically arranged mesh packing allows for better utilization of the entire cold trap volume. 2 figs.
Grundy, Brian R.
1981-01-01
The radial cold trap comprises a housing having a plurality of mesh bands disposed therein. The mesh bands comprise concentrically arranged bands of mesh with the mesh specific surface area of each band increasing from the outermost mesh band to the innermost mesh band. An inlet nozzle is attached to the outside section of the housing while an outlet nozzle is attached to the inner portion of the housing so as to be concentrically connected to the innermost mesh band. An inlet baffle having orifices therein may be disposed around the outermost mesh band and within the housing for directing the flow of the fluid from the inlet nozzle to the outermost mesh band in a uniform manner. The flow of fluid passes through each consecutive mesh band and into the outlet nozzle. The circular pattern of the symmetrically arranged mesh packing allows for better utilization of the entire cold trap volume.
Hla, Saw Wai
2015-09-01
Engineering of supramolecular assemblies on surfaces is an emerging field of research impacting chemistry, electronics, and biology. Among supramolecular assemblies, metal-containing structures provide rich properties and enable robust nanostructured designs. In this issue of ACS Nano, Feng eta!, report that supramolecular assemblies can trap gold adatoms that maintain a charged state on a Au(111) surface. Such charged adatoms may offer additional degrees of freedom in designing novel supramolecular architectures for efficient catalysts, memory, and charge storage for medical applications.
Guon, Jerold
1976-04-13
A sintered filter trap is adapted for insertion in a gas stream of sodium vapor to condense and deposit sodium thereon. The filter is heated and operated above the melting temperature of sodium, resulting in a more efficient means to remove sodium particulates from the effluent inert gas emanating from the surface of a liquid sodium pool. Preferably the filter leaves are precoated with a natrophobic coating such as tetracosane.
Liu, Wenbin; Zhang, Jianfa; Zhu, Zhihong; Yuan, Xiaodong; Qin, Shiqiao
2016-01-01
In this paper, anisotropic graphene plasmonic structures are explored for light trapping and absorption enhancement in surrounding media. It is shown that electrically tunable and versatile spectral and polarization selectivity can be realized. Particularly, it is possible to control absorption of the incident light’s polarization component at a specific wavelength by varying the Fermi energy with suitable geometric designs. It may find applications for new types of infrared and THz photodetectors and will promote the research of other novel polarization devices.
Leith diffusion model for homogeneous anisotropic turbulence
NASA Astrophysics Data System (ADS)
Rubinstein, Robert; Clark, Timothy; Kurien, Susan
2016-11-01
A new spectral closure model for homogeneous anisotropic turbulence is proposed. The systematic development begins by closing the third-order correlation describing nonlinear interactions by an anisotropic generalization of the Leith diffusion model for isotropic turbulence. The correlation tensor is then decomposed into a tensorially isotropic part, or directional anisotropy, and a trace-free remainder, or polarization anisotropy. The directional and polarization components are then decomposed using irreducible representations of the SO(3) symmetry group. Under the ansatz that the decomposition is truncated at quadratic order, evolution equations are derived for the directional and polarization pieces of the correlation tensor. Numerical simulation of the model equations for a freely decaying anisotropic flow illustrate the non-trivial effects of spectral dependencies on the different return-to-isotropy rates of the directional and polarization contributions.
Leith diffusion model for homogeneous anisotropic turbulence
Rubinstein, Robert; Clark, Timothy T.; Kurien, Susan
2017-06-01
Here, a proposal for a spectral closure model for homogeneous anisotropic turbulence. The systematic development begins by closing the third-order correlation describing nonlinear interactions by an anisotropic generalization of the Leith diffusion model for isotropic turbulence. The correlation tensor is then decomposed into a tensorially isotropic part, or directional anisotropy, and a trace-free remainder, or polarization anisotropy. The directional and polarization components are then decomposed using irreducible representations of the SO(3) symmetry group. Under the ansatz that the decomposition is truncated at quadratic order, evolution equations are derived for the directional and polarization pieces of the correlation tensor. Here, numericalmore » simulation of the model equations for a freely decaying anisotropic flow illustrate the non-trivial effects of spectral dependencies on the different return-to-isotropy rates of the directional and polarization contributions.« less
Elliptical-anisotropic eikonal phase velocity tomography
NASA Astrophysics Data System (ADS)
de Ridder, S. A. L.; Biondi, B. L.; Nichols, D.
2015-02-01
We formulated an anisotropic eikonal tomography approach for phase velocities based on a two-dimensional elliptical-anisotropic wave equation. We can fit the parameters of the ellipse directly from measured first-order traveltime surface gradients and constrain these parameters to vary smoothly over space. The method is applied to Scholte waves in virtual seismic sources from stations in the Life of Field Seismic Ocean Bottom Cable array installed over the Ekofisk field. The fast directions of the azimuthally anisotropic Scholte wave velocities form a large circular pattern over the Ekofisk field. This pattern dominates the Scholte wave phase velocities at Ekofisk between 0.7 and 1.1 Hz. It results from the overburden stress state and from seafloor subsidence induced by decades of hydrocarbon extraction.
Generalized Fractional Derivative Anisotropic Viscoelastic Characterization
Hilton, Harry H.
2012-01-01
Isotropic linear and nonlinear fractional derivative constitutive relations are formulated and examined in terms of many parameter generalized Kelvin models and are analytically extended to cover general anisotropic homogeneous or non-homogeneous as well as functionally graded viscoelastic material behavior. Equivalent integral constitutive relations, which are computationally more powerful, are derived from fractional differential ones and the associated anisotropic temperature-moisture-degree-of-cure shift functions and reduced times are established. Approximate Fourier transform inversions for fractional derivative relations are formulated and their accuracy is evaluated. The efficacy of integer and fractional derivative constitutive relations is compared and the preferential use of either characterization in analyzing isotropic and anisotropic real materials must be examined on a case-by-case basis. Approximate protocols for curve fitting analytical fractional derivative results to experimental data are formulated and evaluated. PMID:28817038
Azimuthally Anisotropic 3D Velocity Continuation
Burnett, William; Fomel, Sergey
2011-01-01
We extend time-domain velocity continuation to the zero-offset 3D azimuthally anisotropic case. Velocity continuation describes how a seismic image changes given a change in migration velocity. This description turns out to be of a wave propagation process, in which images change along a velocity axis. In the anisotropic case, the velocity model is multiparameter. Therefore, anisotropic image propagation is multidimensional. We use a three-parameter slowness model, which is related to azimuthal variations in velocity, as well as their principal directions. This information is useful for fracture and reservoir characterization from seismic data. We provide synthetic diffraction imaging examples to illustratemore » the concept and potential applications of azimuthal velocity continuation and to analyze the impulse response of the 3D velocity continuation operator.« less
Elastic properties of spherically anisotropic piezoelectric composites
NASA Astrophysics Data System (ADS)
Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming
2010-09-01
Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed.
Gravitational stresses in anisotropic rock masses
Amadei, B.; Savage, W.Z.; Swolfs, H.S.
1987-01-01
This paper presents closed-form solutions for the stress field induced by gravity in anisotropic rock masses. These rocks are assumed to be laterally restrained and are modelled as a homogeneous, orthotropic or transversely isotropic, linearly elastic material. The analysis, constrained by the thermodynamic requirement that strain energy be positive definite, gives the following important result: inclusion of anisotropy broadens the range of permissible values of gravity-induced horizontal stresses. In fact, for some ranges of anisotropic rock properties, it is thermodynamically admissible for gravity-induced horizontal stresses to exceed the vertical stress component; this is not possible for the classical isotropic solution. Specific examples are presented to explore the nature of the gravity-induced stress field in anisotropic rocks and its dependence on the type, degree and orientation of anisotropy with respect to the horizontal ground surface. ?? 1987.
Magnetization of anisotropic Type II superconductors
Mints, R.G.
1989-04-10
Peculiarities of magnetization of anisotropic type II superconductors are of considerable interest in view of the discovery of high-T/sub c/ superconductors characterized by strongly asymmetric layered structure. Specifics of the penetration of magnetic flux into an anisotropic type II superconductor were discussed in the literature. This analysis gave the distribution of induction in an isolated vortex, its energy, and critical magnetic field H/sub c1/. However, the magnetization curve of anisotropic superconductors was not considered. This paper deals with the magnetic moment of uniaxial London superconductor in the interval H/sub c1/ /le/ H/sub 0/ << H/sub c2/, where H/sub 0/ is the external magnetic field strength.
Anisotropic Failure Modeling for HY-100 Steel
NASA Astrophysics Data System (ADS)
Harstad, E. N.; Maudlin, P. J.; McKirgan, J. B.
2004-07-01
HY-100 steel is a material that behaves isotropically in the elastic and plastic region and acts anisotropically in failure. Since HY-100 is a ductile metal, a more gradual failure process is observed as opposed to the nearly instantaneous failure in brittle materials. We extend our elasto-plastic-damage constitutive model by including of a decohesion model to describe material behavior between the onset of failure and fracture. We also develop an anisotropic failure surface to account for directionality in material failure. Both the anisotropic failure and decohesion models have been implemented into a finite element code, where the effects of these models are studied in a uniaxial stress simulations, a plate impact simulations, and a quasistatic notched round bar tensile test simulations.
Infrared properties of an anisotropically stirred fluid
NASA Technical Reports Server (NTRS)
Rubinstein, Robert; Barton, J. Michael
1987-01-01
A renormalization group is developed for the Navier-Stokes equations driven by an anisotropically correlated random stirring force. The stirring force generates homogeneous turbulence with a preferred direction. The force correlation is the sum of a small anisotropic perturbation and an isotropic correlation chosen, so that the fixed point of renormalization group has a k exp -5/3 energy spectrum. Fixed points for the anisotropic correlation are found near this isotropic fixed point. Two types of anisotropy are analyzed. when the additional stirring is in the plane perpendicular to the preferred direction, the renormalized viscosity is increased. When it is aligned with the preferred direction, the viscosity is decreased. A possible connection with the inverse energy cascade of two-dimensional turbulence is discussed.
Leith diffusion model for homogeneous anisotropic turbulence
Rubinstein, Robert; Clark, Timothy T.; Kurien, Susan
2016-07-19
Here, a proposal for a spectral closure model for homogeneous anisotropic turbulence. The systematic development begins by closing the third-order correlation describing nonlinear interactions by an anisotropic generalization of the Leith diffusion model for isotropic turbulence. The correlation tensor is then decomposed into a tensorially isotropic part, or directional anisotropy, and a trace-free remainder, or polarization anisotropy. The directional and polarization components are then decomposed using irreducible representations of the SO(3) symmetry group. Under the ansatz that the decomposition is truncated at quadratic order, evolution equations are derived for the directional and polarization pieces of the correlation tensor. Here, numerical simulation of the model equations for a freely decaying anisotropic flow illustrate the non-trivial effects of spectral dependencies on the different return-to-isotropy rates of the directional and polarization contributions.
Isotropic versus anisotropic modeling of photorefractive solitons.
Belić, M R; Vujić, D; Stepken, A; Kaiser, F; Calvo, G F; Agulló-López, F; Carrascosa, M
2002-06-01
The question of the isotropic versus anisotropic modeling of incoherent spatial screening solitons in photorefractive crystals is addressed by a careful theoretical and numerical analysis. Isotropic, or local, models allow for an extended spiraling of two interacting scalar solitons, and for a prolonged propagation of vortex vector solitons, whereas anisotropic, nonlocal, models prevent such phenomena. In the context of Kukhtarev's material equations, the difference in behavior is traced to the continuity equation for the current density. We further show that neither an indefinite spiraling of two solitons nor stable propagation of vortex vector solitons is generally possible in both isotropic and anisotropic models. Such systems do not conserve angular momentum, even in the case of an isotropic change in the index of refraction.
Forming Limits for Anisotropic Sheet Metals
NASA Astrophysics Data System (ADS)
Kim, Youngsuk; Kim, Chul; Lee, Sangryong; Won, Sungyeun; Hwang, Sangmoo
Most failures of ductile materials in metal forming processes occurred due to material damage evolution-void nucleation, growth and coalescence. In this paper, modified version of Gurson-Tvergaard's yield function in conjunction with the Hosford's non-quadratic anisotropic yield criterion is studied to clarify the plastic deformation characteristic of voided anisotropic sheet metals. The void growth of an anisotropic sheet under biaxial tensile loading and damage effect of void growth on forming limits of sheet metals are investigated. Also the characteristic length defining the neck geometry is introduced in M-K model to incorporate the effect of triaxial stress in necked region on forming limits. The forming limits theoretically predicted are compared with some experimental data. Satisfactory agreement was obtained between the predictions and experimental data.
Anisotropic Hanle line shape via magnetothermoelectric phenomena
NASA Astrophysics Data System (ADS)
Das, K. S.; Dejene, F. K.; van Wees, B. J.; Vera-Marun, I. J.
2016-11-01
We observe anisotropic Hanle line shape with unequal in-plane and out-of-plane nonlocal signals for spin precession measurements carried out on lateral metallic spin valves with transparent interfaces. The conventional interpretation for this anisotropy corresponds to unequal spin relaxation times for in-plane and out-of-plane spin orientations as for the case of two-dimensional materials like graphene, but it is unexpected in a polycrystalline metallic channel. Systematic measurements as a function of temperature and channel length, combined with both analytical and numerical thermoelectric transport models, demonstrate that the anisotropy in the Hanle line shape is magnetothermal in origin, caused by the anisotropic modulation of the Peltier and Seebeck coefficients of the ferromagnetic electrodes. Our results call for the consideration of such magnetothermoelectric effects in the study of anisotropic spin relaxation.
NASA Astrophysics Data System (ADS)
Rusconi, Roberto; Guasto, Jeffrey S.; Stocker, Roman
2012-11-01
Bacteria are ubiquitously exposed to flow, both in natural environments and artificial devices (e.g., catheters), where confining surfaces create non-uniform shear. While the effects of shear on passive particles are well understood, little is known about the consequences of shear on motile bacteria. We exposed bacteria having different motility strategies (e.g., run-and-tumble, run-and-reverse) to microfluidic Poiseuille flows and quantified the swimming kinematics and cell distribution in the channel using video-microscopy. We discovered that the coupling of motility and a spatially varying shear results in a dramatic trapping of motile cells in high-shear regions, and conversely a strong depletion in the low-shear portion of the channel. We demonstrate experimentally that this trapping process is robust across species such as Bacillus subtilis and Pseudomonas aeruginosa, and can have far-reaching consequences on bacterial transport, by (i) counteracting bacterial chemotactic responses; and (ii) enhancing surface attachment and thus biofilm formation by trapping cells near walls. More generally, this work shows that-despite the low Reynolds number-the coupling of flow and self-propulsion can be nonlinear and not simply a superposition of the two effects.
Modeling Geodynamic Mobility of Anisotropic Lithosphere
NASA Astrophysics Data System (ADS)
Perry-Houts, J.; Karlstrom, L.
2016-12-01
The lithosphere is often idealized as a linear, or plastic layer overlying a Newtonian half-space. This approach has led to many insights into lithospheric foundering that include Rayligh-Taylor drips, slab-style delaminations, and small scale convection in the asthenosphere. More recent work has begun to quantify the effect of anisotropic lithosphere viscosity on these same phenomena. Anisotropic viscosity may come about due to stratigraphic deposition in the upper crust, dike/sill emplacement in the mid crust, or volcanic underplating at the Moho related to arcs or plumes. Anisotropic viscosity is also observed in the mantle, due to preferential orientation of olivine grains during flow. Here we extend the work of Lev & Hager (2008) on modeling anisotropic lithospheric foundering to investigate the effects of anisotropic regions which vary in size, magnitude, and orientation. We have extended Aspect, a modern geodynamic finite element code with a large developer and user base, to model exotic constitutive laws with an arbitrary fourth order tensor in place of the viscosity term. We further implement a material model to represent a transverse isotropic medium, such as is expected in a layered, or fractured lithosphere. We have validated our implementation against previous results, and analytic solutions, reproducing the result that horizontally oriented anisotropy tends to inhibit drips, and produce longer-wavelength instabilities. We expect that increased lateral extent of anisotropic regions will exaggerate this effect, to a limit at which the effect will plateau. Varying lithosphere thickness, and mantle anisotropy anisotropy may produce similar behavior. The implications of this effect are significant to lithospheric foundering beneath arcs and hotspots, possibly influencing the recycling of eclogite, production of silicic magmas, and dynamic topography.
Foam front propagation in anisotropic oil reservoirs.
Grassia, P; Torres-Ulloa, C; Berres, S; Mas-Hernández, E; Shokri, N
2016-04-01
The pressure-driven growth model is considered, describing the motion of a foam front through an oil reservoir during foam improved oil recovery, foam being formed as gas advances into an initially liquid-filled reservoir. In the model, the foam front is represented by a set of so-called "material points" that track the advance of gas into the liquid-filled region. According to the model, the shape of the foam front is prone to develop concave sharply curved concavities, where the orientation of the front changes rapidly over a small spatial distance: these are referred to as "concave corners". These concave corners need to be propagated differently from the material points on the foam front itself. Typically the corner must move faster than those material points, otherwise spurious numerical artifacts develop in the computed shape of the front. A propagation rule or "speed up" rule is derived for the concave corners, which is shown to be sensitive to the level of anisotropy in the permeability of the reservoir and also sensitive to the orientation of the corners themselves. In particular if a corner in an anisotropic reservoir were to be propagated according to an isotropic speed up rule, this might not be sufficient to suppress spurious numerical artifacts, at least for certain orientations of the corner. On the other hand, systems that are both heterogeneous and anisotropic tend to be well behaved numerically, regardless of whether one uses the isotropic or anisotropic speed up rule for corners. This comes about because, in the heterogeneous and anisotropic case, the orientation of the corner is such that the "correct" anisotropic speed is just very slightly less than the "incorrect" isotropic one. The anisotropic rule does however manage to keep the corner very slightly sharper than the isotropic rule does.
The family of anisotropically scaled equatorial waves
NASA Astrophysics Data System (ADS)
RamíRez GutiéRrez, Enver; da Silva Dias, Pedro Leite; Raupp, Carlos; Bonatti, Jose Paulo
2011-04-01
In the present work we introduce the family of anisotropic equatorial waves. This family corresponds to equatorial waves at intermediate states between the shallow water and the long wave approximation model. The new family is obtained by using anisotropic time/space scalings on the linearized, unforced and inviscid shallow water model. It is shown that the anisotropic equatorial waves tend to the solutions of the long wave model in one extreme and to the shallow water model solutions in the other extreme of the parameter dependency. Thus, the problem associated with the completeness of the long wave model solutions can be asymptotically addressed. The anisotropic dispersion relation is computed and, in addition to the typical dependency on the equivalent depth, meridional quantum number and zonal wavenumber, it also depends on the anisotropy between both zonal to meridional space and velocity scales as well as the fast to slow time scales ratio. For magnitudes of the scales compatible with those of the tropical region, both mixed Rossby-gravity and inertio-gravity waves are shifted to a moderately higher frequency and, consequently, not filtered out. This draws attention to the fact that, for completeness of the long wave like solutions, it is necessary to include both the anisotropic mixed Rossby-gravity and inertio-gravity waves. Furthermore, the connection of slow and fast manifolds (distinguishing feature of equatorial dynamics) is preserved, though modified for the equatorial anisotropy parameters used δ ∈ < 1]. New possibilities of horizontal and vertical scale nonlinear interactions are allowed. Thus, the anisotropic shallow water model is of fundamental importance for understanding multiscale atmosphere and ocean dynamics in the tropics.
An Anisotropic Multiphysics Model for Intervertebral Disk
Gao, Xin; Zhu, Qiaoqiao; Gu, Weiyong
2016-01-01
Intervertebral disk (IVD) is the largest avascular structure in human body, consisting of three types of charged hydrated soft tissues. Its mechanical behavior is nonlinear and anisotropic, due mainly to nonlinear interactions among different constituents within tissues. In this study, a more realistic anisotropic multiphysics model was developed based on the continuum mixture theory and employed to characterize the couplings of multiple physical fields in the IVD. Numerical simulations demonstrate that this model is capable of systematically predicting the mechanical and electrochemical signals within the disk under various loading conditions, which is essential in understanding the mechanobiology of IVD. PMID:27099402
Evolution of multidimensional flat anisotropic cosmological models
Beloborodov, A. ); Demianski, M. Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw International Center for Relativistic Astrophysics , Universita di Roma I, La Sapienza, Rome ); Ivanov, P.; Polnarev, A.G. )
1993-07-15
We study the dynamics of a flat multidimensional anisotropic cosmological model filled with an anisotropic fluidlike medium. By an appropriate choice of variables, the dynamical equations reduce to a two-dimensional dynamical system. We present a detailed analysis of the time evolution of this system and the conditions of the existence of spacetime singularities. We investigate the conditions under which violent, exponential, and power-law inflation is possible. We show that dimensional reduction cannot proceed by anti-inflation (rapid contraction of internal space). Our model indicates that it is very difficult to achieve dimensional reduction by classical means.
Inverse moments equilibria for helical anisotropic systems
NASA Astrophysics Data System (ADS)
Cooper, W. A.; Hirshman, S. P.; Depassier, M. C.
1987-11-01
An energy functional is devised for magnetic confinement schemes that have anisotropic plasma pressure. The minimization of this energy functional is demonstrated to reproduce components of the magnetohydrodynamic (MHD) force balance relation in systems with helical symmetry. An iterative steepest descent procedure is applied to the Fourier moments of the inverse magnetic flux coordinates to minimize the total energy and thus generate anisotropic pressure MHD equilibria. Applications to straight ELMO Snaky Torus (NTIS Document No. DE-84002406) configurations that have a magnetic well on the outermost flux surfaces have been obtained.
On cracking of charged anisotropic polytropes
NASA Astrophysics Data System (ADS)
Azam, M.; Mardan, S. A.
2017-01-01
Recently in [1], the role of electromagnetic field on the cracking of spherical polytropes has been investigated without perturbing charge parameter explicitly. In this study, we have examined the occurrence of cracking of anisotropic spherical polytropes through perturbing parameters like anisotropic pressure, energy density and charge. We consider two different types of polytropes in this study. We discuss the occurrence of cracking in two different ways (i) by perturbing polytropic constant, anisotropy and charge parameter (ii) by perturbing polytropic index, anisotropy and charge parameter for each case. We conclude that cracking appears for a wide range of parameters in both cases. Also, our results are reduced to [2] in the absence of charge.
Raman Tensor Formalism for Optically Anisotropic Crystals.
Kranert, Christian; Sturm, Chris; Schmidt-Grund, Rüdiger; Grundmann, Marius
2016-03-25
We present a formalism for calculating the Raman scattering intensity dependent on the polarization configuration for optically anisotropic crystals. It can be applied to crystals of arbitrary orientation and crystal symmetry measured in normal incidence backscattering geometry. The classical Raman tensor formalism cannot be used for optically anisotropic materials due to birefringence causing the polarization within the crystal to be depth dependent. We show that in the limit of averaging over a sufficiently large scattering depth, the observed Raman intensities converge and can be described by an effective Raman tensor given here. Full agreement with experimental results for uniaxial and biaxial crystals is demonstrated.
Optical Activity of Anisotropic Achiral Surfaces
Verbiest, T.; Kauranen, M.; Van Rompaey, Y.; Persoons, A. |
1996-08-01
Anisotropic achiral surfaces respond differently to left- and right-hand circularly polarized light. This occurs when the orientation of the surface with respect to an otherwise achiral experimental setup makes the total geometry chiral. Such optical activity is demonstrated in second-harmonic generation from an anisotropic thin molecular film. The circular-difference response reverses sign as the handedness of the geometry is reversed and vanishes when the setup possesses a mirror plane. The results are explained within the electric-dipole-allowed second-order surface nonlinearity. {copyright} {ital 1996 The American Physical Society.}
Directional wetting in anisotropic inverse opals.
Phillips, Katherine R; Vogel, Nicolas; Burgess, Ian B; Perry, Carole C; Aizenberg, Joanna
2014-07-01
Porous materials display interesting transport phenomena due to restricted motion of fluids within the nano- to microscale voids. Here, we investigate how liquid wetting in highly ordered inverse opals is affected by anisotropy in pore geometry. We compare samples with different degrees of pore asphericity and find different wetting patterns depending on the pore shape. Highly anisotropic structures are infiltrated more easily than their isotropic counterparts. Further, the wetting of anisotropic inverse opals is directional, with liquids filling from the side more easily. This effect is supported by percolation simulations as well as direct observations of wetting using time-resolved optical microscopy.
Anisotropic superconductors in tilted magnetic fields
Vlasko-Vlasov, V. K.; Glatz, A.; Koshelev, A. E.; Welp, U.; Kwok, W. K.
2015-06-01
We present images of magnetic flux structures in a single crystal of YBa2Cu3O7-d during remagnetization by fields tilted from the basal plane of the crystal. Depending on the magnitude and angle of the applied field we observe anisotropic flux penetration along and across the in-plane field component and emergence of vortex instabilities resulting in modulated flux distributions. We associate the observed patterns with flux cutting effects and with tilted vortex structures intrinsic for layered superconductors. Time dependent Ginzburg-Landau simulations show preferential vortex motion across the c-axis and reveal the flux structure evolution in anisotropic superconductors under tilted magnetic fields.
Differential matrix formalism for depolarizing anisotropic media.
Ossikovski, Razvigor
2011-06-15
Azzam's differential matrix formalism [J. Opt. Soc. Am. 68, 1756 (1978)], originally developed for longitudinally inhomogeneous anisotropic nondepolarizing media, is extended to include depolarizing media. The generalization is physically interpreted in terms of means and uncertainties of the elementary optical properties of the medium, as well as of three anisotropy absorption parameters introduced to describe the depolarization. The formalism results in a particularly simple mathematical procedure for the retrieval of the elementary properties of a generally depolarizing anisotropic medium, assumed to be globally homogeneous, from its experimental Mueller matrix. The approach is illustrated on literature data and the conditions of its validity are identified and discussed.
Magnetic trap for thulium atoms
Sukachev, D D; Sokolov, A V; Chebakov, K A; Akimov, A V; Kolachevskii, N N; Sorokin, Vadim N
2011-08-31
For the first time ultra-cold thulium atoms were trapped in a magnetic quadrupole trap with a small field gradient (20 Gs cm{sup -1}). The atoms were loaded from a cloud containing 4x10{sup 5} atoms that were preliminarily cooled in a magneto-optical trap to the sub-Doppler temperature of 80 {mu}K. As many as 4x10{sup 4} atoms were trapped in the magnetic trap at the temperature of 40 {mu}K. By the character of trap population decay the lifetime of atoms was determined (0.5 s) and an upper estimate was obtained for the rate constant of inelastic binary collisions for spin-polarised thulium atoms in the ground state (g{sub in} < 10{sup -11}cm{sup 3} s{sup -1}). (magnetic traps)
Measurement of Lamellipodial Protrusion by Optical Trapping
NASA Astrophysics Data System (ADS)
Sakai, Ken'ichi; Kohmoto, Sogo; Nobezawa, Daisuke; Ikeda, Sho-ichi; Miyata, Hidetake
2015-02-01
Lamellipodial protrusion is a fundamental step in cell locomotion. This important process is driven by actin polymerization, but its physical aspect has not yet been fully investigated. We previously studied the lamellipodial protrusion of Swiss 3T3 fibroblast cells at 33 ms temporal resolution and 10 nm accuracy by probing the motion of the cell edge with a 1 µm bead held in an optical trap. In that study, we found a transient mode of protrusion and analyzed the time variation of the protrusion velocity. In this study, we analyzed the power spectra of the fluctuations of a trap-held bead during the protrusion and found cell-specific fluctuations. The maximal amplitude of the fluctuations was 23 nm, which was estimated from the power of the fluctuations accumulated over 1.9 and 7.6 Hz. This value was significantly larger than that of the fluctuations of the trap-held bead that is not in contact with the cell edge (14 nm). The amplitude of the fluctuation of the probing bead showed a positive correlation with the cell edge velocity, suggesting that the cell-specific fluctuations play an important role in the lamellipodial protrusion.
Fully Employing Software Inspections Data
NASA Technical Reports Server (NTRS)
Shull, Forrest; Feldmann, Raimund L.; Seaman, Carolyn; Regardie, Myrna; Godfrey, Sally
2009-01-01
Software inspections provide a proven approach to quality assurance for software products of all kinds, including requirements, design, code, test plans, among others. Common to all inspections is the aim of finding and fixing defects as early as possible, and thereby providing cost savings by minimizing the amount of rework necessary later in the lifecycle. Measurement data, such as the number and type of found defects and the effort spent by the inspection team, provide not only direct feedback about the software product to the project team but are also valuable for process improvement activities. In this paper, we discuss NASA's use of software inspections and the rich set of data that has resulted. In particular, we present results from analysis of inspection data that illustrate the benefits of fully utilizing that data for process improvement at several levels. Examining such data across multiple inspections or projects allows team members to monitor and trigger cross project improvements. Such improvements may focus on the software development processes of the whole organization as well as improvements to the applied inspection process itself.
Models of collapsing and expanding anisotropic gravitating source in f( R, T) theory of gravity
NASA Astrophysics Data System (ADS)
Abbas, G.; Ahmed, Riaz
2017-07-01
In this paper, we have formulated the exact solutions of the non-static anisotropic gravitating source in f( R, T) gravity which may lead to expansion and collapse. By assuming there to be no thermal conduction in gravitating source, we have determined parametric solutions in f( R, T) gravity with a non-static spherical geometry filled using an anisotropic fluid. We have examined the ranges of the parameters for which the expansion scalar becomes negative and positive, leading to collapse and expansion, respectively. Further, using the definition of the mass function, the conditions for the trapped surface have been explored, and it has been investigated that there exists a single horizon in this case. The impact of the coupling parameter λ has been discussed in detail in both cases. For the various values of the coupling parameter λ , we have plotted the energy density, anisotropic pressure and anisotropy parameter in the cases of collapse and expansion. The physical significance of the graphs has been explained in detail.
NASA Astrophysics Data System (ADS)
Crowgey, Benjamin Reid
Rectangular waveguide methods are appealing for measuring isotropic and anisotropic materials because of high signal strength due to field confinement, and the ability to control the polarization of the applied electric field. As a stepping stone to developing methods for characterizing materials with fully-populated anisotropic tensor characteristics, techniques are presented in this dissertation to characterize isotropic, biaxially anisotropic, and gyromagnetic materials. Two characterization techniques are investigated for each material, and thus six different techniques are described. Additionally, a waveguide standard is introduced which may be used to validate the measurement of the permittivity and permeability of materials at microwave frequencies. The first characterization method examined is the Nicolson-Ross-Weir (NRW) technique for the extraction of isotropic parameters of a sample completely filling the cross-section of a rectangular waveguide. A second technique is proposed for the characterization of an isotropic conductor-backed sample filling the cross-section of a waveguide. If the sample is conductor-backed, and occupies the entire cross-section, a transmission measurement is not available, and thus a method must be found for providing two sufficiently different reflection measurements.The technique proposed here is to place a waveguide iris in front of the sample, exposing the sample to a spectrum of evanescent modes. By measuring the reflection coefficient with and without an iris, the necessary two data may be obtained to determine the material parameters. A mode-matching approach is used to determine the theoretical response of a sample placed behind the waveguide iris. This response is used in a root-searching algorithm to determine permittivity and permeability by comparing to measurements of the reflection coefficient. For the characterization of biaxially anisotropic materials, the first method considers an extension of the NRW technique
An Engineered Anisotropic Nanofilm with Unidirectional Wetting Properties
2010-01-01
ARTICLES PUBLISHED ONLINE: 10 OCTOBER 2010 | DOI: 10.1038/NMAT2864 An engineered anisotropic nanofilm with unidirectional wetting properties Niranjan...body3. Engineering synthetic materials with such anisotropic adhesive properties has led to advances in digitalmicrofluidic devices5,6 andmedicine7,8...The anisotropic wetting properties of existing engineered surfaces are derived either from spatial gradients (for example, temperature, surface
Stable Trapping of Multielectron Helium Bubbles in a Paul Trap
NASA Astrophysics Data System (ADS)
Joseph, E. M.; Vadakkumbatt, V.; Pal, A.; Ghosh, A.
2016-11-01
In a recent experiment, we have used a linear Paul trap to store and study multielectron bubbles (MEBs) in liquid helium. MEBs have a charge-to-mass ratio (between 10^{-4} and 10^{-2} C/kg) which is several orders of magnitude smaller than ions (between 10^6 and 10^8 C/kg) studied in traditional ion traps. In addition, MEBs experience significant drag force while moving through the liquid. As a result, the experimental parameters for stable trapping of MEBs, such as magnitude and frequency of the applied electric fields, are very different from those used in typical ion trap experiments. The purpose of this paper is to model the motion of MEBs inside a linear Paul trap in liquid helium, determine the range of working parameters of the trap, and compare the results with experiments.
Dynamics of vortex dipoles in anisotropic Bose-Einstein condensates
Goodman, Roy H.; Kevrekidis, P. G.; Carretero-González, R.
2015-04-14
We study the motion of a vortex dipole in a Bose-Einstein condensate confined to an anisotropic trap. We focus on a system of ODEs describing the vortices' motion, which is in turn a reduced model of the Gross-Pitaevskii equation describing the condensate's motion. Using a sequence of canonical changes of variables, we reduce the dimension and simplify the equations of motion. In this study, we uncover two interesting regimes. Near a family of periodic orbits known as guiding centers, we find that the dynamics is essentially that of a pendulum coupled to a linear oscillator, leading to stochastic reversals in the overall direction of rotation of the dipole. Near the separatrix orbit in the isotropic system, we find other families of periodic, quasi-periodic, and chaotic trajectories. In a neighborhood of the guiding center orbits, we derive an explicit iterated map that simplifies the problem further. Numerical calculations are used to illustrate the phenomena discovered through the analysis. Using the results from the reduced system, we are able to construct complex periodic orbits in the original, PDE, mean-field model for Bose-Einstein condensates, which corroborates the phenomenology observed in the reduced dynamical equations.
Dynamics of vortex dipoles in anisotropic Bose-Einstein condensates
Goodman, Roy H.; Kevrekidis, P. G.; Carretero-González, R.
2015-04-14
We study the motion of a vortex dipole in a Bose-Einstein condensate confined to an anisotropic trap. We focus on a system of ODEs describing the vortices' motion, which is in turn a reduced model of the Gross-Pitaevskii equation describing the condensate's motion. Using a sequence of canonical changes of variables, we reduce the dimension and simplify the equations of motion. In this study, we uncover two interesting regimes. Near a family of periodic orbits known as guiding centers, we find that the dynamics is essentially that of a pendulum coupled to a linear oscillator, leading to stochastic reversals inmore » the overall direction of rotation of the dipole. Near the separatrix orbit in the isotropic system, we find other families of periodic, quasi-periodic, and chaotic trajectories. In a neighborhood of the guiding center orbits, we derive an explicit iterated map that simplifies the problem further. Numerical calculations are used to illustrate the phenomena discovered through the analysis. Using the results from the reduced system, we are able to construct complex periodic orbits in the original, PDE, mean-field model for Bose-Einstein condensates, which corroborates the phenomenology observed in the reduced dynamical equations.« less
Data-driven imaging in anisotropic media
Volker, Arno; Hunter, Alan
2012-05-17
Anisotropic materials are being used increasingly in high performance industrial applications, particularly in the aeronautical and nuclear industries. Some important examples of these materials are composites, single-crystal and heavy-grained metals. Ultrasonic array imaging in these materials requires exact knowledge of the anisotropic material properties. Without this information, the images can be adversely affected, causing a reduction in defect detection and characterization performance. The imaging operation can be formulated in two consecutive and reciprocal focusing steps, i.e., focusing the sources and then focusing the receivers. Applying just one of these focusing steps yields an interesting intermediate domain. The resulting common focus point gather (CFP-gather) can be interpreted to determine the propagation operator. After focusing the sources, the observed travel-time in the CFP-gather describes the propagation from the focus point to the receivers. If the correct propagation operator is used, the measured travel-times should be the same as the time-reversed focusing operator due to reciprocity. This makes it possible to iteratively update the focusing operator using the data only and allows the material to be imaged without explicit knowledge of the anisotropic material parameters. Furthermore, the determined propagation operator can also be used to invert for the anisotropic medium parameters. This paper details the proposed technique and demonstrates its use on simulated array data from a specimen of Inconel single-crystal alloy commonly used in the aeronautical and nuclear industries.
Thermal D mesons from anisotropic lattice QCD
NASA Astrophysics Data System (ADS)
Kelly, Aoife; Skullerud, Jon-Ivar
2017-03-01
We present results for correlators and spectral functions of open charm mesons using 2+1 flavours of clover fermions on anisotropic lattices. The D mesons are found to dissociate close to the deconfinement crossover temperature Tc. Our preliminary results suggest a shift in the thermal D meson mass below Tc. Mesons containing strange quarks exhibit smaller thermal modifications than those containing light quarks.
Casimir interactions for anisotropic magnetodielectric metamaterials
Da Rosa, Felipe S; Dalvit, Diego A; Milonni, Peter W
2008-01-01
We extend our previous work on the generalization of the Casimir-Lifshitz theory to treat anisotropic magnetodielectric media, focusing on the forces between metals and magnetodielectric metamaterials and on the possibility of inferring magnetic effects by measurements of these forces.
Purpose-Built Anisotropic Metal Oxide Nanomaterials
2001-01-01
Proceedings Volume 635. Anisotropic Nanoparticles - Synthesis , Characterization and Applications To order the complete compilation report, use...for instance, to the oxidation of sedimentary organic matter [11]. In its various allotropic forms, iron oxides and oxyhydroxides represent important...16-18] and photocatalysts [19], for magnetic storage devices, cathodes for primary and secondary batteries [20], chemical flame suppressant [21] and
Wave propagation in anisotropic layered composites
NASA Astrophysics Data System (ADS)
Braga, Arthur Martins Barbosa
1990-08-01
The propagation of harmonic waves in laminated anisotropic composites is investigated. The analysis is carried out within the framework of the linear theory of elasticity. Two basic geometries are considered, namely, layered half-spaces and infinite laminated plates. The method employed in the description of the wave motion in the anisotropic composites is based on Stroh's sextic matrix formalism for anisotropic elasticity. An extension of this formalism to periodic media, in conjunction with Floquet's theorem, is applied when the layers are disposed periodically. The 'in vacuo' free motions of laminated composites are investigated. Particular attention is paid to Rayleigh and Rayleigh-Lamb wave propagation in layered media. The dynamic interaction of laminated composites with a surrounding acoustic fluid is also investigated. The concept of surface impedance tensor is introduced. It is shown that, for harmonic motions, this rank-two tensor completely characterizes the solid surface in contact with the fluid. An algorithm for the numerical computation of the surface impedance tensor of anisotropic layered composites is presented. This algorithm is numerically stable for a wide range of frequencies. Special attention is paid to the subsonic Sholte-Gogoladze-like wave, which propagates unattenuated along the planar fluid/solid interface.
Vibrations and stresses in layered anisotropic cylinders
NASA Technical Reports Server (NTRS)
Mulholland, G. P.; Gupta, B. P.
1976-01-01
An equation describing the radial displacement in a k layered anisotropic cylinder was obtained. The cylinders are initially unstressed but are subjected to either a time dependent normal stress or a displacement at the external boundaries of the laminate. The solution is obtained by utilizing the Vodicka orthogonalization technique. Numerical examples are given to illustrate the procedure.
THEORY OF COMPTON SCATTERING BY ANISOTROPIC ELECTRONS
Poutanen, Juri; Vurm, Indrek E-mail: indrek.vurm@oulu.f
2010-08-15
Compton scattering plays an important role in various astrophysical objects such as accreting black holes and neutron stars, pulsars, relativistic jets, and clusters of galaxies, as well as the early universe. In most of the calculations, it is assumed that the electrons have isotropic angular distribution in some frame. However, there are situations where the anisotropy may be significant due to the bulk motions, or where there is anisotropic cooling by synchrotron radiation or an anisotropic source of seed soft photons. Here we develop an analytical theory of Compton scattering by anisotropic distribution of electrons that can significantly simplify the calculations. Assuming that the electron angular distribution can be represented by a second-order polynomial over the cosine of some angle (dipole and quadrupole anisotropies), we integrate the exact Klein-Nishina cross section over the angles. Exact analytical and approximate formulae valid for any photon and electron energies are derived for the redistribution functions describing Compton scattering of photons with arbitrary angular distribution by anisotropic electrons. The analytical expressions for the corresponding photon scattering cross section on such electrons, as well as the mean energy of scattered photons, its dispersion, and radiation pressure force are also derived. We apply the developed formalism to the accurate calculations of the thermal and kinematic Sunyaev-Zeldovich effects for arbitrary electron distributions.
Anisotropic MHD model and some solutions
Kuznetsov, V. D.; Dzhalilov, N. S.
2010-09-15
MHD waves and instabilities in a collisionless anisotropic-pressure plasma are analyzed in an anisotropic MHD model based on the 16-moment approximation, and the results are found to agree well with those obtained in the low-frequency limit of the kinetic model. It is shown that accounting for heat fluxes leads to an asymmetry in the phase velocities of the wave modes with respect to the heat flux direction and also to a strong interaction between the modes, especially between the backward ones (those that propagate in a direction opposite to that of the heat flux). A correct description of the mirror instability is given. The resonant interaction of three backward modes-fast acoustic, fast magnetosonic, and slow acoustic-under the conditions for the onset of the classical firehose instability triggers a new type of instability the growth rate of which is faster than the maximum growth rate of the conventional firehose instability. The results prove that, in contrast to the familiar Chew-Goldberger-Low approximate model, the anisotropic MHD approach provides a correct description of the large-scale dynamics of collisionless anisotropic plasmas (such as solar corona, solar wind, and ionospheric and magnetospheric plasmas).
An anisotropic thermomechanical damage model for concrete at transient elevated temperatures.
Baker, Graham; de Borst, René
2005-11-15
The behaviour of concrete at elevated temperatures is important for an assessment of integrity (strength and durability) of structures exposed to a high-temperature environment, in applications such as fire exposure, smelting plants and nuclear installations. In modelling terms, a coupled thermomechanical analysis represents a generalization of the computational mechanics of fracture and damage. Here, we develop a fully coupled anisotropic thermomechanical damage model for concrete under high stress and transient temperature, with emphasis on the adherence of the model to the laws of thermodynamics. Specific analytical results are given, deduced from thermodynamics, of a novel interpretation on specific heat, evolution of entropy and the identification of the complete anisotropic, thermomechanical damage surface. The model is also shown to be stable in a computational sense, and to satisfy the laws of thermodynamics.
Gabor-based anisotropic diffusion for speckle noise reduction in medical ultrasonography.
Zhang, Qi; Han, Hong; Ji, Chunhong; Yu, Jinhua; Wang, Yuanyuan; Wang, Wenping
2014-06-01
In ultrasound (US), optical coherence tomography, synthetic aperture radar, and other coherent imaging systems, images are corrupted by multiplicative speckle noise that obscures image interpretation. An anisotropic diffusion (AD) method based on the Gabor transform, named Gabor-based anisotropic diffusion (GAD), is presented to suppress speckle in medical ultrasonography. First, an edge detector using the Gabor transform is proposed to capture directionality of tissue edges and discriminate edges from noise. Then the edge detector is embedded into the partial differential equation of AD to guide the diffusion process and iteratively denoise images. To enhance GAD's adaptability, parameters controlling diffusion are determined from a fully formed speckle region that is automatically detected. We evaluate the GAD on synthetic US images simulated with three models and clinical images acquired in vivo. Compared with seven existing speckle reduction methods, the GAD is superior to other methods in terms of noise reduction and detail preservation.
Lu, Z.-T.; Bailey, K.; Chen, C.-Y.; Du, X.; Li, Y.-M.; O'Connor, T. P.; Young, L.
2000-05-25
A new method of ultrasensitive trace-isotope analysis has been developed based upon the technique of laser manipulation of neutral atoms. It has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. The atom counts are free of contamination from other isotopes, elements,or molecules. The method is applicable to other trace-isotopes that can be efficiently captured with a magneto-optical trap, and has a broad range of potential applications.
Quantifying the Nonlinear, Anisotropic Material Response of Spinal Ligaments
NASA Astrophysics Data System (ADS)
Robertson, Daniel J.
Spinal ligaments may be a significant source of chronic back pain, yet they are often disregarded by the clinical community due to a lack of information with regards to their material response, and innervation characteristics. The purpose of this dissertation was to characterize the material response of spinal ligaments and to review their innervation characteristics. Review of relevant literature revealed that all of the major spinal ligaments are innervated. They cause painful sensations when irritated and provide reflexive control of the deep spinal musculature. As such, including the neurologic implications of iatrogenic ligament damage in the evaluation of surgical procedures aimed at relieving back pain will likely result in more effective long-term solutions. The material response of spinal ligaments has not previously been fully quantified due to limitations associated with standard soft tissue testing techniques. The present work presents and validates a novel testing methodology capable of overcoming these limitations. In particular, the anisotropic, inhomogeneous material constitutive properties of the human supraspinous ligament are quantified and methods for determining the response of the other spinal ligaments are presented. In addition, a method for determining the anisotropic, inhomogeneous pre-strain distribution of the spinal ligaments is presented. The multi-axial pre-strain distributions of the human anterior longitudinal ligament, ligamentum flavum and supraspinous ligament were determined using this methodology. Results from this work clearly demonstrate that spinal ligaments are not uniaxial structures, and that finite element models which account for pre-strain and incorporate ligament's complex material properties may provide increased fidelity to the in vivo condition.
Anisotropic adsorption and distribution of immobilized carboxyl on nanodiamond
NASA Astrophysics Data System (ADS)
Lai, Lin; Barnard, Amanda S.
2014-11-01
Stable and predictable functionalization of nanodiamond with carboxyl is an important first step in loading these materials with therapeutic agents, and the conjugation with proteins, cytochrome, antigen, and DNA. By creating a map of the adsorption strength of COOH, OH, O and H with atomic level resolution across the entire surface of an experimentally realistic nanodiamond, we have shown how the distribution is highly anisotropic, and depends on surface reconstructions, facet orientation, and ultimately the shape. This provides useful insights into how the structure of nanodiamond impacts the formation of COOH surface monolayers, and suggests that efforts to separate nanodiamonds by shape would be highly beneficial in the development of drug delivery vehicles targeted to specific treatment regimes.Stable and predictable functionalization of nanodiamond with carboxyl is an important first step in loading these materials with therapeutic agents, and the conjugation with proteins, cytochrome, antigen, and DNA. By creating a map of the adsorption strength of COOH, OH, O and H with atomic level resolution across the entire surface of an experimentally realistic nanodiamond, we have shown how the distribution is highly anisotropic, and depends on surface reconstructions, facet orientation, and ultimately the shape. This provides useful insights into how the structure of nanodiamond impacts the formation of COOH surface monolayers, and suggests that efforts to separate nanodiamonds by shape would be highly beneficial in the development of drug delivery vehicles targeted to specific treatment regimes. Electronic supplementary information (ESI) available: Coordinates of the fully replaced diamond nanoparticle used in this study (in standard xyz format), and images of all of the relaxed ND-COOH binding configurations. See DOI: 10.1039/c4nr05363j
Anisotropic Tuning of Graphite Thermal Conductivity by Lithium Intercalation.
Qian, Xin; Gu, Xiaokun; Dresselhaus, Mildred S; Yang, Ronggui
2016-11-17
Understanding thermal transport in lithium intercalated layered materials is not only important for managing heat generation and dissipation in lithium ion batteries but also the understanding potentially provides a novel way to design materials with reversibly tunable thermal conductivity. In this work, the thermal conductivity of lithium-graphite intercalation compounds (LixC6) is calculated using molecular dynamics simulations as a function of the amount of lithium intercalated. We found that intercalation of lithium has an anisotropic effect on tuning the thermal conductivity: the thermal conductivity in the basal plane decreases monotonically from 1232 W/m·K of pristine graphite to 444 W/m·K of the fully lithiated LiC6, while the thermal conductivity along the c-axis decreases first from 6.5 W/m·K for graphite to 1.3 W/m·K for LiC18 and then increases to 5.0 W/m·K for LiC6 as the lithium composition increases. More importantly, we provide the very first atomic-scale insight into the effect of lithium intercalation on the spectral phonon properties of graphite. The intercalated lithium ions are found to suppress the phonon lifetime and to reduce the group velocity of phonons parallel to the basal plane but significantly to increase the phonon group velocity along the c-axis, which anisotropically tunes the thermal conductivity of lithiated graphite compounds. This work could shed some light on the search for tunable thermal conductivity materials and might have strong impacts on the thermal management of lithium ion batteries.
Observation of Cold Collisions between Trapped Ions and Trapped Atoms
NASA Astrophysics Data System (ADS)
Grier, Andrew T.; Cetina, Marko; Oručević, Fedja; Vuletić, Vladan
2009-06-01
We study cold collisions between trapped ions and trapped atoms in the semiclassical (Langevin) regime. Using Yb+ ions confined in a Paul trap and Yb atoms in a magneto-optical trap, we investigate charge-exchange collisions of several isotopes over three decades of collision energies down to 3μeV (kB×35mK). The minimum measured rate coefficient of 6×10-10cm3s-1 is in good agreement with that derived from a Langevin model for an atomic polarizability of 143 a.u.
Anisotropic Tomography of Portugal (West Iberia) from ambient seismic noise
NASA Astrophysics Data System (ADS)
Silveira, Graça; Stutzmann, Éléonore; Schimmel, Martin; Dias, Nuno; Kiselev, Sergey; Custódio, Susana; Dundar, Suleyman
2016-04-01
Located on the western Iberian Peninsula, Portugal constitutes a key area for accretionary terrane and basin research, providing the best opportunity to probe a crustal formation shaped by the Paleozoic Variscan orogeny followed by the Mesozoic-Cenozoic extensions. The geology of Portugal documents a protracted history from Paleozoic basement formation to the Mesozoic opening of the North Atlantic Ocean. The inheritance of such complex geologic history is yet to be fully determined, playing an important role in the current geodynamic framework influencing, for example, the observed regional seismicity. The physical properties of its crust have largely remained undetermined so far, with unevenly distributed knowledge on the spatial distributions of a detailed crustal structure. Also, the deep seismic reflection/refraction surveys conducted in Western Iberia do not provide a clear picture of the regional characteristics of the crust. Using Seismic Broad Band observations from a dense temporary deployment, conducted between 2010 and 2012 in the scope of the WILAS project and covering the entire Portuguese mainland, we computed a 3D anisotropic model from ambient seismic noise. The dispersion measurements were computed for each station pair using empirical Green's functions generated by cross-correlating one-day-length seismic ambient-noise records. After dispersion analysis, group velocity measurements were regionalized to obtain 2D anisotropic tomographic images. Afterwards, the dispersion curves, extracted from each cell of the 2D group velocity maps, were inverted as a function of depth to obtain a 3D shear wave anisotropic model, using a bayesian approach. A simulated annealing method, in which the number of splines that describes the model, is adapted within the inversion. The models are jointly interpreted with the models gathered from Ps receiver functions as well as with the regional seismicity, enabling to obtain a more detailed picture of the crustal
The trap line as a measure of small mammal populations
Stickel, L.F.
1948-01-01
SUMMARY: The value of a line of traps as a measure of relative abundance of small mammals was studied by field trials on Peromyscus leucopus populations. Comparisons were made between the numbers of mice captured by a line of live traps and the numbers captured in intensive live trapping of a larger area surrounding the line. Trials were made in bottomland woods where mice were numerous and in upland woods where mice were less common. It was found that wood mice living in upland woods had significantly larger cruising ranges than those living in bottomland woods. Consequently, a line of traps in the bottomlands captured mice from a smaller surrounding territory than in the uplands. Therefore, comparisons of relative size of the mouse population in these two areas on the basis of line-trapping showed an erroneously large number for the upland woods. As a result of these trials and the studies of other workers, it is concluded that lines of traps are not fully reliable means of measuring relative abundance of small mammals.
Nanofriction in cold ion traps.
Benassi, A; Vanossi, A; Tosatti, E
2011-01-01
Sliding friction between crystal lattices and the physics of cold ion traps are so far non-overlapping fields. Two sliding lattices may either stick and show static friction or slip with dynamic friction; cold ions are known to form static chains, helices or clusters, depending on the trapping conditions. Here we show, based on simulations, that much could be learnt about friction by sliding, through, for example, an electric field, the trapped ion chains over a corrugated potential. Unlike infinite chains, in which the theoretically predicted Aubry transition to free sliding may take place, trapped chains are always pinned. Yet, a properly defined static friction still vanishes Aubry-like at a symmetric-asymmetric structural transition, found for decreasing corrugation in both straight and zig-zag trapped chains. Dynamic friction is also accessible in ringdown oscillations of the ion trap. Long theorized static and dynamic one-dimensional friction phenomena could thus become accessible in future cold ion tribology.
Lionnet, Timothée; Allemand, Jean-François; Revyakin, Andrey; Strick, Terence R; Saleh, Omar A; Bensimon, David; Croquette, Vincent
2012-01-01
In recent years, techniques have been developed to study and manipulate single molecules of DNA and other biopolymers. In one such technique, the magnetic trap, a single DNA molecule is bound at one end to a glass surface and at the other to a magnetic microbead. Small magnets, whose position and rotation can be controlled, pull on and rotate the microbead. This provides a simple method to stretch and twist the molecule. The system allows one to apply and measure forces ranging from 10(-3) to >100 picoNewtons (pN). In contrast to other techniques, the force measurement is absolute and does not require calibration of the sensor. This protocol describes a procedure for building and using a magnetic trap. It gives a method for constructing a microchamber suitable for magnetic tweezers studies, including antibody coating and passivation. It also describes a series of simple steps to achieve end-labeling of DNA anchoring fragments. One anchoring fragment is biotin-labeled and the other is labeled with digoxigenin. The anchoring fragments are then digested and ligated to a central DNA region containing the sequence of interest. The biotinylated DNA is adsorbed onto streptavidin-coated magnetic beads, and the DNA-bead mixture attaches specifically to the antidigoxigenin-coated surface of the microchamber.
NASA Astrophysics Data System (ADS)
Braun, Dieter
2011-03-01
The hallmark of living matter is the replication of genetic molecules and their active storage against diffusion. We have argued in the past that thermal convection can host the million-fold accumulation even of single nucleotides and at the same time trigger exponential replication. Accumulation is driven by thermophoresis and convection in elongated chambers, replication by the inherent temperature cycling in convection. Optothermal pumping [2,3] allows to implement the thermal trap efficiently in a toroidal or linear geometry. Based on this method, we were in a position to combine accumulation and replication of DNA in the same chamber. As we are missing a solid chemistry of prebiotic replication, we used as a proxy reaction for to replication the polymerase chain reaction. Convective flow both drives the DNA replicating polymerase chain reaction (PCR) while concurrent thermophoresis accumulates the replicated 143 base pair DNA in bulk solution. The time constant for accumulation is 92 s while DNA is doubled every 50 s. The length of the amplified DNA is checked with thermophoresis. Finite element simulations confirm the findings. The experiments explore conditions in pores of hydrothermal rock which can serve as a model environment for the origin of life and has prospects towards the first autonomous evolution, hosting the Darwin process by molecular selection using the thermophoretic trap. On the other side, the implemented continuous evolution will be able to breed well specified DNA or RNA molecules in the future.
Magnetically induced anisotropic orientation of graphene oxide locked by in situ hydrogelation.
Wu, Linlin; Ohtani, Masataka; Takata, Masaki; Saeki, Akinori; Seki, Shu; Ishida, Yasuhiro; Aida, Takuzo
2014-05-27
A general method to prepare polymer gels containing anisotropically oriented graphene oxide (GO) or reduced graphene oxide (RGO) was developed, by using the magnetically induced orientation of GO. Under a magnetic field, an aqueous dispersion of GO was gelated by in situ cross-linking polymerization of an acryl monomer and a cross-linker. In the resultant hydrogel, the orientation of GO was retained even in the absence of the magnetic field, because the gel network trapped GO via noncovalent interactions and efficiently suppressed the structural relaxation of GO. The locked structure enabled quantitative investigation on the magnetic orientation of GO using 2D small-angle X-ray scattering, which revealed that GO nanosheets orient parallel to the magnetic field with an order parameter of up to 0.80. Systematic studies with varying gelation conditions indicate that the present method can afford a wide range of GO-hybridized anisotropic materials, in terms of GO alignment direction, sample shape, and GO concentration. Also by virtue of the locked structure, the orientation of GO in the hydrogel was well preserved throughout the in situ chemical reduction of GO, yielding an RGO-hybridized anisotropic hydrogel, as well as the conversion of the hydrogel into organo- and ionogels through the replacement of the internal water with solvents. As a preliminary demonstration of the present method for practical application, a polymer-composite film containing RGO oriented vertical to the film surface was prepared, and its anisotropically enhanced electroconductivity along the orientation direction of RGO was confirmed by the flash-photolysis time-resolved microwave conductivity measurement.
Trapped-electron runaway effect
NASA Astrophysics Data System (ADS)
Nilsson, E.; Decker, J.; Fisch, N. J.; Peysson, Y.
2015-08-01
In a tokamak, trapped electrons subject to a strong electric field cannot run away immediately, because their parallel velocity does not increase over a bounce period. However, they do pinch toward the tokamak center. As they pinch toward the center, the trapping cone becomes more narrow, so eventually they can be detrapped and run away. When they run away, trapped electrons will have a very different signature from circulating electrons subject to the Dreicer mechanism. The characteristics of what are called trapped-electron runaways are identified and quantified, including their distinguishable perpendicular velocity spectrum and radial extent.
DNA Separation Using Photoelectrophoretic Traps
Braiman, Avital; Thundat, Thomas George; Rudakov, Fedor M
2011-01-01
In our recent publications we presented a design that allows formation of highly localized and optically controlled electrophoretic traps. 1,2 We demonstrated that electrophoretic traps can be utilized for biomolecule photoconcentration, optically directed transport, and separation by size. 1,2 In the current publication we suggest a hybrid design for biomolecule separation which implements electrophoretic traps in tandem with well-established electrophoretic techniques. We perform Monte Carlo simulations that demonstrate that the resolution of well-established electrophoretic techniques can be greatly enhanced by introducing photoelectrophoretic traps.
Optical traps with geometric aberrations
Roichman, Yael; Waldron, Alex; Gardel, Emily; Grier, David G
2006-05-20
We assess the influence of geometric aberrations on the in-plane performance of optical traps by studying the dynamics of trapped colloidal spheres in deliberately distorted holographic optical tweezers. The lateral stiffness of the traps turns out to be insensitive to moderate amounts of coma, astigmatism, and spherical aberration. Moreover holographic aberration correction enables us to compensate inherent shortcomings in the optical train, thereby adaptively improving its performance. We also demonstrate the effects of geometric aberrations on the intensity profiles of optical vortices, whose readily measured deformations suggest a method for rapidly estimating and correcting geometric aberrations in holographic trapping systems.
Benner, W. Henry
1999-01-01
The design and operation of a new type of charged-particle trap provides simultaneous measurements of mass, charge, and velocity of large electrospray ions. The trap consists of a detector tube mounted between two sets of center-bored trapping plates. Voltages applied to the trapping plates define symmetrically-opposing potential valleys which guide axially-injected ions to cycle back and forth through the charge-detection tube. A low noise charge-sensitive amplifier, connected to the tube, reproduces the image charge of individual ions as they pass through the detector tube. Ion mass is calculated from measurement of ion charge and velocity following each passage through the detector.
Ability of TiO_{2}(110) Surface to Be Fully Hydroxylated and Fully Reduced
Wang, Zhitao; Garcia, Juan C.; Deskins, N. A.; Lyubinetsky, Igor
2015-08-06
Many TiO_{2} applications (e.g., in heterogeneous catalysis) involve contact with ambient atmosphere and/or water. The resulting hydroxylation can significantly alter its surface properties. While behavior of single, isolated OH species on the model metal oxide surface of rutile TiO_{2}(110) is relatively well understood, much less is known regarding highly-hydroxylated surfaces and/or whether TiO_{2}(110) could be fully-hydroxylated under ultra-high vacuum conditions. Here we report in situ formation of a well-ordered, fully-hydroxylated TiO_{2}(110)-(1 x 1) surface using an enhanced photochemical approach, key parts of which are pre-dosing of water and multi-step dissociative adsorption and subsequent photolysis of the carboxylic (trimethyl acetic) acid. Combining scanning tunneling microscopy, ultra-violet photoelectron spectroscopy and density functional theory results, we show that the attained “super OH” surface is also fully-reduced, as a result of the photochemical trapping of electrons at the OH groups.
Elliptical silicon arrays with anisotropic optical and wetting properties.
Wang, Tieqiang; Li, Xiao; Zhang, Junhu; Wang, Xianzhe; Zhang, Xuemin; Zhang, Xun; Zhu, Difu; Hao, Yudong; Ren, Zhiyu; Yang, Bai
2010-08-17
We demonstrate a facile etching method to fabricate silicon elliptical pillar arrays (Si-EPAs) with unique anisotropic optical and wetting characters using polystyrene elliptical hemisphere arrays (EHAs) as mask. The EHAs were fabricated via a modified micromolding method. By varying the experimental conditions in the fabrication process, the morphology of the resulting microstructures can be controlled exactly. Because of the anisotropic morphology of the elliptical pillar, the Si-EPA shows unique anisotropic properties, such as anisotropic surface reflection and anisotropic wetting property. Additionally, through oblique evaporation deposition of Au and selective chemical modification to turn the elliptical pillars into "Janus" elliptical pillars, the "Janus" Si-EPA shows more peculiar anisotropic properties owing to the further increased asymmetry. We believe that the Si-EPAs will have potential applications in anisotropic optical and electronic devices.
Traps and seals II. Stratigraphic/capillary traps
Foster, N.H.; Beaumont, E.A.
1988-01-01
This text is a reprint belonging to a series of reprint volumes which in turn are part of the Treatise of Petroleum Geology. This volume contains papers that describe different stratigraphically controlled trap types, the preservation of porosity, and the importance of capillarity in trapping hydrocarbons.
50 CFR 697.19 - Trap limits and trap tag requirements for vessels fishing with lobster traps.
Code of Federal Regulations, 2014 CFR
2014-10-01
... vessels fishing with lobster traps. 697.19 Section 697.19 Wildlife and Fisheries FISHERY CONSERVATION AND... requirements for vessels fishing with lobster traps. (a) Area 1 trap limits. The Area 1 trap limit is 800 traps. Federally permitted lobster fishing vessels shall not fish with, deploy in, possess in, or haul back...
Oligonucleotide-Functionalized Anisotropic Gold Nanoparticles
NASA Astrophysics Data System (ADS)
Jones, Matthew Robert
In this thesis, we describe the properties of oligonucleotide-functionalized gold colloids under the unique set of conditions where the particles are geometrically anisotropic and have nanometer-scale dimensions. While nearly two decades of previous work elucidated numerous unexpected and emergent phenomena arising from the combination of inorganic nanoparticles with surface-bound DNA strands, virtually nothing was known about how these properties are altered when the shape of the nanoparticle core is chosen to be non-spherical. In particular, we are interested in understanding, and ultimately controlling, the ways in which these DNA-conjugated anisotropic nanostructures interact when their attraction is governed by programmable DNA hybridization events. Chapter 1 introduces the field of DNA-based materials assembly by discussing how nanoscale building blocks which present rigid, directional interactions can be thought of as possessing artificial versions of the familiar chemical principles of "bonds" and "valency". In chapter 2 we explore the fundamental interparticle binding thermodynamics of DNA-functionalized spherical and anisotropic nanoparticles, which reveals enormous preferences for collective ligand interactions occurring between flat surfaces over those that occur between curved surfaces. Using these insights, chapter 3 demonstrates that when syntheses produce mixtures of different nanoparticle shapes, the tailorable nature of DNA-mediated interparticle association can be used to selectively crystallize and purify the desired anisotropic nanostructure products, leaving spherical impurity particles behind. Chapter 4 leverages the principle that the flat facets of anisotropic particles generate directional DNA-based hybridization interactions to assemble a variety of tailorable nanoparticle superlattices whose symmetry and dimensionality are a direct consequence of the shape of the nanoparticle building block used in their construction. Chapter 5 explores
Xie, Longtao; Zhang, Chuanzeng; Sladek, Jan; Sladek, Vladimir
2016-01-01
Novel unified analytical displacement and stress fundamental solutions as well as the higher order derivatives of the displacement fundamental solutions for three-dimensional, generally anisotropic and linear elastic materials are presented in this paper. Adequate integral expressions for the displacement and stress fundamental solutions as well as the higher order derivatives of the displacement fundamental solutions are evaluated analytically by using the Cauchy residue theorem. The resulting explicit displacement fundamental solutions and their first and second derivatives are recast into convenient analytical forms which are valid for non-degenerate, partially degenerate, fully degenerate and nearly degenerate cases. The correctness and the accuracy of the novel unified and closed-form three-dimensional anisotropic fundamental solutions are verified by using some available analytical expressions for both transversely isotropic (non-degenerate or partially degenerate) and isotropic (fully degenerate) linear elastic materials. PMID:27118881
Xie, Longtao; Zhang, Chuanzeng; Sladek, Jan; Sladek, Vladimir
2016-02-01
Novel unified analytical displacement and stress fundamental solutions as well as the higher order derivatives of the displacement fundamental solutions for three-dimensional, generally anisotropic and linear elastic materials are presented in this paper. Adequate integral expressions for the displacement and stress fundamental solutions as well as the higher order derivatives of the displacement fundamental solutions are evaluated analytically by using the Cauchy residue theorem. The resulting explicit displacement fundamental solutions and their first and second derivatives are recast into convenient analytical forms which are valid for non-degenerate, partially degenerate, fully degenerate and nearly degenerate cases. The correctness and the accuracy of the novel unified and closed-form three-dimensional anisotropic fundamental solutions are verified by using some available analytical expressions for both transversely isotropic (non-degenerate or partially degenerate) and isotropic (fully degenerate) linear elastic materials.
Anisotropic electronic states in the fractional quantum Hall regime
NASA Astrophysics Data System (ADS)
Ciftja, Orion
2017-05-01
Recent experiments indicate the presence of new anisotropic fractional quantum Hall states at regimes not anticipated before. These experiments raise many fundamental questions regarding the inner nature of the electronic system that leads to such anisotropic states. Interplay between electron mass anisotropy and electron-electron correlation effects in a magnetic field can create a rich variety of possibilities. Several anisotropic electronic states ranging from anisotropic quantum Hall liquids to anisotropic Wigner solids may stabilize due to such effects. The electron mass anisotropy in a two-dimensional electron gas effectively leads to an anisotropic Coulomb interaction potential between electrons. An anisotropic interaction potential may strongly influence the stability of various quantum phases that are close in energy since the overall stability of an electronic system is very sensitive to local order. As a result there is a possibility that various anisotropic electronic phases may emerge even in the lowest Landau level in regimes where one would not expect them. In this work we study the state with filling factor 1/6 in the lowest Landau level, a state which is very close to the critical filling factor where the liquid-solid transition takes place. We investigate whether an anisotropic Coulomb interaction potential is able to stabilize an anisotropic electronic liquid state at this filling factor. We describe such an anisotropic state by means of a liquid crystalline wave function with broken rotational symmetry which can be adiabatically connected to the actual wave function for the corresponding isotropic phase. We perform quantum Monte Carlo simulations in a disk geometry to study the properties of the anisotropic electronic liquid state under consideration. The findings indicate stability of liquid crystalline order in presence of an anisotropic Coulomb interaction potential. The results are consistent with the existence of an anisotropic electronic
Particle directionality and trapped proton fluences on LDEF
NASA Technical Reports Server (NTRS)
Nefedov, N.; Csige, I.; Benton, E. V.; Frank, A. L.; Frigo, L. A.; Benton, E. R.
1996-01-01
Directionality of incident space radiation is a significant factor in spacecraft shielding and astronaut dosimetry in low Earth orbit (LEO). Particle directionality of GCR and trapped protons were measured on LDEF with plastic nuclear track detectors (PNTD) from the P0006 west-side experiment. This experiment consisted of a thick detector stack and is described more fully in a companion article (Benton et al., 1996). The anisotropy of the trapped protons produced maximum intensity for protons arriving from the west. The fluences of the eastward directed trapped protons have been measured by selection of the particles on the basis of range in the PNTDs. The measured fluences are compared with the model calculations of Armstrong and Colborn (1993).
Solar Cell light trapping beyond the ray optic limit.
Callahan, Dennis M; Munday, Jeremy N; Atwater, Harry A
2012-01-11
In 1982, Yablonovitch proposed a thermodynamic limit on light trapping within homogeneous semiconductor slabs, which implied a minimum thickness needed to fully absorb the solar spectrum. However, this limit is valid for geometrical optics but not for a new generation of subwavelength solar absorbers such as ultrathin or inhomogeneously structured cells, wire-based cells, photonic crystal-based cells, and plasmonic cells. Here we show that the key to exceeding the conventional ray optic or so-called ergodic light trapping limit is in designing an elevated local density of optical states (LDOS) for the absorber. Moreover, for any semiconductor we show that it is always possible to exceed the ray optic light trapping limit and use these principles to design a number of new solar absorbers with the key feature of having an elevated LDOS within the absorbing region of the device, opening new avenues for solar cell design and cost reduction.
Nonlinear static and dynamic analysis of beam structures using fully intrinsic equations
NASA Astrophysics Data System (ADS)
Sotoudeh, Zahra
2011-07-01
Beams are structural members with one dimension much larger than the other two. Examples of beams include propeller blades, helicopter rotor blades, and high aspect-ratio aircraft wings in aerospace engineering; shafts and wind turbine blades in mechanical engineering; towers, highways and bridges in civil engineering; and DNA modeling in biomedical engineering. Beam analysis includes two sets of equations: a generally linear two-dimensional problem over the cross-sectional plane and a nonlinear, global one-dimensional analysis. This research work deals with a relatively new set of equations for one-dimensional beam analysis, namely the so-called fully intrinsic equations. Fully intrinsic equations comprise a set of geometrically exact, nonlinear, first-order partial differential equations that is suitable for analyzing initially curved and twisted anisotropic beams. A fully intrinsic formulation is devoid of displacement and rotation variables, making it especially attractive because of the absence of singularities, infinite-degree nonlinearities, and other undesirable features associated with finite rotation variables. In spite of the advantages of these equations, using them with certain boundary conditions presents significant challenges. This research work will take a broad look at these challenges of modeling various boundary conditions when using the fully intrinsic equations. Hopefully it will clear the path for wider and easier use of the fully intrinsic equations in future research. This work also includes application of fully intrinsic equations in structural analysis of joined-wing aircraft, different rotor blade configuration and LCO analysis of HALE aircraft.
Segmented trapped vortex cavity
NASA Technical Reports Server (NTRS)
Grammel, Jr., Leonard Paul (Inventor); Pennekamp, David Lance (Inventor); Winslow, Jr., Ralph Henry (Inventor)
2010-01-01
An annular trapped vortex cavity assembly segment comprising includes a cavity forward wall, a cavity aft wall, and a cavity radially outer wall there between defining a cavity segment therein. A cavity opening extends between the forward and aft walls at a radially inner end of the assembly segment. Radially spaced apart pluralities of air injection first and second holes extend through the forward and aft walls respectively. The segment may include first and second expansion joint features at distal first and second ends respectively of the segment. The segment may include a forward subcomponent including the cavity forward wall attached to an aft subcomponent including the cavity aft wall. The forward and aft subcomponents include forward and aft portions of the cavity radially outer wall respectively. A ring of the segments may be circumferentially disposed about an axis to form an annular segmented vortex cavity assembly.
NASA Technical Reports Server (NTRS)
Brantley, L. W., Jr. (Inventor)
1976-01-01
An apparatus is described for trapping solar energy for heating a fluid that could be subsequently used in turbines and similar devices. The apparatus includes an elongated vertical light pipe having an open end through which the visible spectrum of electromagnetic radiation from the sun passes to strike a tubular absorber. The light pipe has a coated interior surface of a low absorptivity and a high reflectivity at the visible wavelengths and a high absorptivity/emissivity ratio at infrared wavelengths. The tubular absorber has a coating on the surface for absorbing visible wavelengths to heat the fluid passing through. Infrared wave lengths are radiated from the tubular absorber back into the light pipe for heating fluid passing through a tubular coil wound around it.
Development of an Anisotropic Thermal Transport Material
2014-01-13
interfacial trapping method . Boron nitride was exfoliated for the first time in large quantities. Boron nitride, unlike graphite , is electrically...composites and include the use of a self-assembling solvent mixture and an interfacial trapping method . Boron nitride was exfoliated for the first time in...the material. The methods developed in the work supported by this grant allow for the use of un-oxidized and un-damaged graphene for thermal
Fully scalable implementation of a volume coupling scheme for the modeling of multiscale materials
NASA Astrophysics Data System (ADS)
Schlittler, Thiago Milanetto; Cottereau, Régis
2017-07-01
We present in this paper a new implementation of a multi-scale, multi-model coupling algorithm, with a proposed parallelization scheme for the construction of the coupling terms between the models. This allows one to study such problems with a fully scalable algorithm on large computer clusters, even when the models and/or the coupling have a high number of degrees of freedom. As an application example, we will consider a system composed by an homogeneous, macroscopic Elastic model and an anisotropic polycrystalline material model, with a volume coupling based on the Arlequin framework.
Anisotropic singularities in modified gravity models
NASA Astrophysics Data System (ADS)
Figueiró, Michele Ferraz; Saa, Alberto
2009-09-01
We show that the common singularities present in generic modified gravity models governed by actions of the type S=∫d4x-gf(R,ϕ,X), with X=-(1)/(2)gab∂aϕ∂bϕ, are essentially the same anisotropic instabilities associated to the hypersurface F(ϕ)=0 in the case of a nonminimal coupling of the type F(ϕ)R, enlightening the physical origin of such singularities that typically arise in rather complex and cumbersome inhomogeneous perturbation analyses. We show, moreover, that such anisotropic instabilities typically give rise to dynamically unavoidable singularities, precluding completely the possibility of having physically viable models for which the hypersurface (∂f)/(∂R)=0 is attained. Some examples are explicitly discussed.
Birefringent light propagation on anisotropic cosmological backgrounds
NASA Astrophysics Data System (ADS)
Asenjo, Felipe A.; Hojman, Sergio A.
2017-08-01
Exact electromagnetic wave solutions to Maxwell equations on anisotropic Bianchi I cosmological spacetime backgrounds are studied. The waves evolving on Bianchi I spacetimes exhibit birefringence (associated with linear polarization) and dispersion. The particular case of a vacuum-dominated anisotropic Universe, which reproduces a Friedmann-Robertson-Walker Universe (for late times)—while, for earlier times, it matches a Kasner Universe—is studied. The electromagnetic waves do not, in general, follow null geodesics. This produces a modification of the cosmological redshift, which is then dependent on light polarization, its dispersion, and its non-null geodesic behavior. New results presented here may help to tackle some issues related to the "horizon" problem.
Rainbow metric from quantum gravity: Anisotropic cosmology
NASA Astrophysics Data System (ADS)
Assanioussi, Mehdi; Dapor, Andrea
2017-03-01
In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformation parameter β in the modified dispersion relation of the modes, hence, inducing an isotropic deformation despite the general starting considerations. We then ensure the recovery of the dispersion relation realized in the isotropic case, studied in [M. Assanioussi, A. Dapor, and J. Lewandowski, Phys. Lett. B 751, 302 (2015), 10.1016/j.physletb.2015.10.043], when some proper symmetry constraints are imposed, and we estimate the value of the deformation parameter for this case in loop quantum cosmology context.
Method of caustics for anisotropic materials
NASA Astrophysics Data System (ADS)
Rossmanith, H. P.
1991-12-01
During the past 25 years the optical method of caustics has matured to a very powerful tool for application in fracture mechanics for the determination of stress intensity factors or the J- integral, in contact mechanics for the determination of contact forces, etc. The technique is applicable to two-dimensional static or dynamic problems and works for any kind of stress- strain relationship. The method displays its full power when employed in conjunction with interactive numerical data reduction and evaluation procedures. Recently, the industrial application of high strength-low weight composite materials has boomed. Application of the method of caustics to anisotropic materials requires the development of the theoretical background. This contribution focuses on the theoretical development of the method of caustics and its applicability to anisotropic materials.
Nonorthogonal polarisation eigenstates in anisotropic cavities
Mamaev, Yu A; Khandokhin, Pavel A
2011-06-30
The Jones matrix method is used to analyse the polarisation eigenmodes of a solid-state laser with an anisotropic Fabry - Perot cavity containing amplitude and phase anisotropic elements. The results demonstrate that, when the axes of these elements do not coincide, the eigenpolarisations become elliptical and nonorthogonal. The ellipticities and azimuths of the polarisation modes and the magnitude and phase of the nonorthogonality parameter are determined as functions of polariser angle at different relationships between the amplitude and phase anisotropies, and the effect is shown to be strongest at a polariser angle of 45{sup 0}. There is critical phase anisotropy, dependent on amplitude anisotropy, at which the magnitude of the nonorthogonality parameter and ellipticity of the polarisation modes approach unity. (resonators)
Fluctuations in a Primordial Anisotropic ERA
NASA Astrophysics Data System (ADS)
Novello, Mário; de Freitas, Luciane R.
The primordial Universe is treated in terms of a nonperfect fluid configuration endowed with an anisotropic expansion. The deGennes-Landau mechanism of phase transition acts as a very efficient process to provide the elimination of the previous anisotropy and to set the universe in the current isotropic FRW stage. The entropy produced, as a consequence of the phase transition, depends on the strength of the previous shear. We suggest the hypothesis that the germinal perturbations that will grow into the observed system of galaxies occurring in the anisotropic era. We present a model to deal with this idea that provides a power spectrum of fluctuations of the form δ 2k ˜ 1/(a +bk2). We compare this prediction of our model to the current knowledge on the galaxy formation process.
Anisotropic stellar models admitting conformal motion
NASA Astrophysics Data System (ADS)
Banerjee, Ayan; Banerjee, Sumita; Hansraj, Sudan; Ovgun, Ali
2017-04-01
We address the problem of finding static and spherically symmetric anisotropic compact stars in general relativity that admit conformal motions. The study is framed in the language of f( R) gravity theory in order to expose opportunity for further study in the more general theory. Exact solutions of compact stars are found under the assumption that spherically symmetric spacetimes admit conformal motion with anisotropic matter distribution in nature. In this work, two cases have been studied for the existence of such solutions: first, we consider the model given by f(R)=R and then f(R)=aR+b . Finally, specific characteristics and physical properties have been explored analytically along with graphical representations for conformally symmetric compact stars in f( R) gravity.
Anisotropic properties of tracheal smooth muscle tissue.
Sarma, P A; Pidaparti, R M; Meiss, R A
2003-04-01
The anisotropic (directional-dependent) properties of contracting tracheal smooth muscle tissue are estimated from a computational model based on the experimental data of length-dependent stiffness. The area changes are obtained at different muscle lengths from experiments in which stimulated muscle undergoes unrestricted shortening. Then, through an interative process, the anisotropic properties are estimated by matching the area changes obtained from the finite element analysis to those derived from the experiments. The results obtained indicate that the anisotropy ratio (longitudinal stiffness to transverse stiffness) is about 4 when the smooth muscle undergoes 70% strain shortening, indicating that the transverse stiffness reduces as the longitudinal stiffness increases. It was found through a sensitivity analysis from the simulation model that the longitudinal stiffness and the in-plane shear modulus are not very sensitive as compared to major Poisson's ratio to the area changes of the muscle tissue. Copyright 2003 Wiley Periodicals, Inc.
Optical sharper focusing in an anisotropic crystal.
Wang, Sicong; Xie, Xiangsheng; Gu, Min; Zhou, Jianying
2015-06-01
Optical super-resolution technique through tight focusing is a widely used technique to image material samples with anisotropic optical properties. The knowledge of the field distribution of a tightly focused beam in anisotropic media is both scientifically interesting and technologically important. In this paper, the optical properties of a uniaxial crystal with the optic axis perpendicular to the interface under a tight focusing configuration are studied with rigorous theoretical and numerical analysis. The significant effect of the Poynting vector on the focal position introduces an obvious displacement of the focal spot formed by the extraordinary waves (e-ray). Moreover, a sharper focus with a lateral size of 0.22λ is obtained as a result of the effective separation of the ordinary waves (o-ray) and the e-ray. It provides a new tool to fabricate optical structures with higher resolutions than that in an isotropic medium through the far-field method.
Performance comparison of fundamental anisotropic diffusion algorithms
NASA Astrophysics Data System (ADS)
Bayraktar, Bulent; Analoui, Mostafa
2004-05-01
Anisotropic diffusion (AD), first introduced by Perona and Malik (PM), provides image enhancement a strong benefit as it favors intra-region over inter-region smoothing. Early updates on the original PM algorithm focused on the cures for its drawbacks. Later some authors provided their own versions of AD techniques with a wide variety of applications. We surveyed the pros and cons of many fundamental AD techniques. To put our purpose into perspective, we compared the performances of fundamental AD algorithms to simple traditional filters and to more sophisticated tools such as wavelets. Visual inspection and two mathematical criteria are used for performance comparison: Signal-to-noise ratio (SNR) and universal image quality index (UIQI). We believe that a good overview of its simplicity and power will show the rightful reason of so much interest in anisotropic diffusion since its introduction.
Nonminimal coupling in anisotropic teleparallel inflation
NASA Astrophysics Data System (ADS)
Abedi, Habib; Wright, Matthew; Abbassi, Amir M.
2017-03-01
We study an anisotropic inflationary scenario in teleparallel gravity. We consider a model where the inflaton is nonminimally coupled both to torsion and a vector field, which can lead to anisotropic inflation. In the weak-coupling limit, our results coincide with the results obtained in the general relativistic framework. However, in the strong-coupling regime of the Jordan frame, we show that the anisotropy shear to expansion ratio is a constant, and can be much larger than the slow-roll parameter. Applying a conformal transformation we then work in the Einstein frame, which in teleparallel gravity introduces a different form of coupling between the inflaton and torsion. In this frame we show that in the strong coupling regime the anisotropy shear to expansion ratio is a different constant, that can be made suitably small.
Anisotropic hydrodynamic function of dense confined colloids
NASA Astrophysics Data System (ADS)
Nygârd, Kim; Buitenhuis, Johan; Kagias, Matias; Jefimovs, Konstantins; Zontone, Federico; Chushkin, Yuriy
2017-06-01
Dense colloidal dispersions exhibit complex wave-vector-dependent diffusion, which is controlled by both direct particle interactions and indirect nonadditive hydrodynamic interactions mediated by the solvent. In bulk the hydrodynamic interactions are probed routinely, but in confined geometries their studies have been hitherto hindered by additional complications due to confining walls. Here we solve this issue by combining high-energy x-ray photon correlation spectroscopy and small-angle x-ray-scattering experiments on colloid-filled microfluidic channels to yield the confined fluid's hydrodynamic function in the short-time limit. Most importantly, we find the confined fluid to exhibit a strongly anisotropic hydrodynamic function, similar to its anisotropic structure factor. This observation is important in order to guide future theoretical research.
Wireless energy transfer between anisotropic metamaterials shells
Díaz-Rubio, Ana; Carbonell, Jorge; Sánchez-Dehesa, José
2014-06-15
The behavior of strongly coupled Radial Photonic Crystals shells is investigated as a potential alternative to transfer electromagnetic energy wirelessly. These sub-wavelength resonant microstructures, which are based on anisotropic metamaterials, can produce efficient coupling phenomena due to their high quality factor. A configuration of selected constitutive parameters (permittivity and permeability) is analyzed in terms of its resonant characteristics. The coupling to loss ratio between two coupled resonators is calculated as a function of distance, the maximum (in excess of 300) is obtained when the shells are separated by three times their radius. Under practical conditions an 83% of maximum power transfer has been also estimated. -- Highlights: •Anisotropic metamaterial shells exhibit high quality factors and sub-wavelength size. •Exchange of electromagnetic energy between shells with high efficiency is analyzed. •Strong coupling is supported with high wireless transfer efficiency. •End-to-end energy transfer efficiencies higher than 83% can be predicted.
The Impact of Anisotropic Error Correlation Modelling
NASA Technical Reports Server (NTRS)
Swinbank, R.; Riishojgaard, L. P.; Menard, R.
1999-01-01
Most data assimilation systems assume isotropic forecast error correlations, but results from two dimensional Kalman Filter experiments indicate that the correlations can be far from isotropic. In this paper we use a simple two-dimensional data assimilation system, which analyses trace chemical species such as ozone, to assess different approaches to modelling the error correlations. We compare assimilation results using isotropic correlations with results obtained using different approaches to modelling anisotropic correlations: first, using correlations based on the concentrations of the trace chemicals, and secondly using an advective correlation model. We show that these relatively cheap ways of modelling anisotropic correlations give objectively better results than using isotropic correlations. We discuss the possible extension of these approaches to a full 3-D meteorological data assimilation system.
Modeling anisotropic magnetoresistance in layered antiferromagnets
NASA Astrophysics Data System (ADS)
Santos, D. L. R.; Pinheiro, F. A.; Velev, J.; Chshiev, M.; Castro, J. d.'Albuquerque e.; Lacroix, C.
2017-06-01
We have investigated the electronic transport and the anisotropic magnetoresistance in systems consisting of pairs of antiferromagnetically aligned layers separated by a non-magnetic layer, across which an antiferromagnetic coupling between the double layers is established. Calculations have been performed within the framework of the tight-binding model, taking into account the exchange coupling within the ferromagnetic layers and the Rashba spin-orbit interaction. Conductivities have been evaluated in the ballistic regime, based on Kubo formula. We have systematically studied the dependence of the conductivity and of the anisotropic magnetoresistance on several material and structural parameters, such as the orientation of the magnetic moments relative to the crystalline axis, band filling, out-of-plane hopping and spin-orbit parameter.
Cosmological signatures of anisotropic spatial curvature
Pereira, Thiago S.; Marugán, Guillermo A. Mena; Carneiro, Saulo E-mail: mena@iem.cfmac.csic.es
2015-07-01
If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature.
Thermodynamics of soft anisotropic contact lines.
Rey, Alejandro D
2004-08-01
Contact lines arising from the intersection of interfaces between liquids and nematic liquid crystals are representative models of soft anisotropic contact lines. This paper presents the thermodynamics of soft anisotropic contact lines and the derivation of the one dimensional (1D) Gibbs-Duhem adsorption equation. Consistency between the 1D Gibbs-Duhem equation and the classical equations of lineal nematostatics is shown. Using a phase space that takes into account thermodynamics, liquid crystalline order, and geometric variables, the generalized nematic line Gibbs-Duhem equation reveals the presence of couplings between curvature, torsion, adsorption, temperature, and average molecular orientation. Merging the thermodynamic analysis with nematostatics results in a model for contact line shape and orientation selection. The ability of an adsorbed solute to orient the director and to bend and twist the contact line is predicted. The thermodynamic origin of preferred orientation at a straight contact line is established.
Observation of an Anisotropic Wigner Crystal
NASA Astrophysics Data System (ADS)
Liu, Yang; Hasdemir, S.; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.
2016-09-01
We report a new correlated phase of two-dimensional charged carriers in high magnetic fields, manifested by an anisotropic insulating behavior at low temperatures. It appears in a large range of low Landau level fillings 1 /3 ≲ν ≲2 /3 in hole systems confined to wide GaAs quantum wells when the sample is tilted in magnetic field to an intermediate angle. The parallel field component (B∥) leads to a crossing of the lowest two Landau levels, and an elongated hole wave function in the direction of B∥. Under these conditions, the in-plane resistance exhibits an insulating behavior, with the resistance along B∥ about 10 times smaller than the resistance perpendicular to B∥. We interpret this anisotropic insulating phase as a two-component, striped Wigner crystal.
Quantum computing with trapped ions
Hughes, R.J.
1998-01-01
The significance of quantum computation for cryptography is discussed. Following a brief survey of the requirements for quantum computational hardware, an overview of the ion trap quantum computation project at Los Alamos is presented. The physical limitations to quantum computation with trapped ions are analyzed and an assessment of the computational potential of the technology is made.
Mass trapping for Anastrepha suspensa
USDA-ARS?s Scientific Manuscript database
Mass trapping has been found to be highly effective for control of pest fruit flies when populations are low and a highly effective lure is available for the target species. Successful population control through mass trapping is an indicator that attract-and-kill bait stations may be equally succes...
The ALPHA antihydrogen trapping apparatus
NASA Astrophysics Data System (ADS)
Amole, C.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Butler, E.; Capra, A.; Carpenter, P. T.; Cesar, C. L.; Chapman, S.; Charlton, M.; Deller, A.; Eriksson, S.; Escallier, J.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Gutierrez, A.; Hangst, J. S.; Hardy, W. N.; Hayano, R. S.; Hayden, M. E.; Humphries, A. J.; Hurt, J. L.; Hydomako, R.; Isaac, C. A.; Jenkins, M. J.; Jonsell, S.; Jørgensen, L. V.; Kerrigan, S. J.; Kurchaninov, L.; Madsen, N.; Marone, A.; McKenna, J. T. K.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Parker, B.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Seddon, D.; Seif El Nasr, S.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; Thornhill, J.; Wells, D.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.
2014-01-01
The ALPHA collaboration, based at CERN, has recently succeeded in confining cold antihydrogen atoms in a magnetic minimum neutral atom trap and has performed the first study of a resonant transition of the anti-atoms. The ALPHA apparatus will be described herein, with emphasis on the structural aspects, diagnostic methods and techniques that have enabled antihydrogen trapping and experimentation to be achieved.
Electrostatic trapping of ammonia molecules
Bethlem; Berden; Crompvoets; Jongma; van Roij AJ; Meijer
2000-08-03
The ability to cool and slow atoms with light for subsequent trapping allows investigations of the properties and interactions of the trapped atoms in unprecedented detail. By contrast, the complex structure of molecules prohibits this type of manipulation, but magnetic trapping of calcium hydride molecules thermalized in ultra-cold buffer gas and optical trapping of caesium dimers generated from ultra-cold caesium atoms have been reported. However, these methods depend on the target molecules being paramagnetic or able to form through the association of atoms amenable to laser cooling, respectively, thus restricting the range of species that can be studied. Here we describe the slowing of an adiabatically cooled beam of deuterated ammonia molecules by time-varying inhomogeneous electric fields and subsequent loading into an electrostatic trap. We are able to trap state-selected ammonia molecules with a density of 10(6) cm(-3) in a volume of 0.25 cm3 at temperatures below 0.35 K. We observe pronounced density oscillations caused by the rapid switching of the electric fields during loading of the trap. Our findings illustrate that polar molecules can be efficiently cooled and trapped, thus providing an opportunity to study collisions and collective quantum effects in a wide range of ultra-cold molecular systems.
Nontoxic Antifreeze for Insect Traps
USDA-ARS?s Scientific Manuscript database
Propylene glycol in water is a safe and effective alternative to ethylene glycol as a capture liquid in insect traps (pitfalls, flight intercepts, pan traps). Propylene glycol formulations are readily available because it is the primary (95%) ingredient in certain automotive antifreeze formulations...
Globally linked vortex clusters in trapped wave fields.
Crasovan, Lucian-Cornel; Molina-Terriza, Gabriel; Torres, Juan P; Torner, Lluis; Pérez-García, Víctor M; Mihalache, Dumitru
2002-09-01
We put forward the existence of a rich variety of fully stationary vortex structures, termed H clusters, made of an increasing number of vortices nested in paraxial wave fields confined by trapping potentials. However, we show that the constituent vortices are globally linked, rather than products of independent vortices. Also, they always feature a monopolar global wave front and exist in nonlinear systems, such as the Bose-Einstein condensates. Clusters with multipolar global wave fronts are nonstationary or, at best, flipping.
Symmetry analysis for anisotropic field theories
Parra, Lorena; Vergara, J. David
2012-08-24
The purpose of this paper is to study with the help of Noether's theorem the symmetries of anisotropic actions for arbitrary fields which generally depend on higher order spatial derivatives, and to find the corresponding current densities and the Noether charges. We study in particular scale invariance and consider the cases of higher derivative extensions of the scalar field, electrodynamics and Chern-Simons theory.
Continuous Observability for the Anisotropic Maxwell System
Eller, Matthias M.
2007-03-15
A boundary observability inequality for the homogeneous Maxwell system with variable, anisotropic coefficients is proved. The result implies uniqueness for an ill-posed Cauchy problem for Maxwell's system. Both results are so far known only in the special case of isotropic coefficients, i.e., when Maxwell's system reduces to a vector wave equation. Here the analysis has been carried out for the first-order system directly without references to the wave equation.
Slotted Antenna with Anisotropic Magnetic Loading
2016-07-26
10 SLOTTED ANTENNA WITH ANISOTROPIC MAGNETIC LOADING STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured...therefor. CROSS REFERENCE TO OTHER PATENT APPLICATIONS [0002] None. BACKGROUND OF THE INVENTION (1) Field of the Invention [0003] The present invention ...of the VSWR curve, and modest bandwidth in each passband. SUMMARY OF THE INVENTION [0006] It is a first object of the present invention to provide
Anisotropic cosmological solutions in massive vector theories
NASA Astrophysics Data System (ADS)
Heisenberg, Lavinia; Kase, Ryotaro; Tsujikawa, Shinji
2016-11-01
In beyond-generalized Proca theories including the extension to theories higher than second order, we study the role of a spatial component v of a massive vector field on the anisotropic cosmological background. We show that, as in the case of the isotropic cosmological background, there is no additional ghostly degrees of freedom associated with the Ostrogradski instability. In second-order generalized Proca theories we find the existence of anisotropic solutions on which the ratio between the anisotropic expansion rate Σ and the isotropic expansion rate H remains nearly constant in the radiation-dominated epoch. In the regime where Σ/H is constant, the spatial vector component v works as a dark radiation with the equation of state close to 1/3. During the matter era, the ratio Σ/H decreases with the decrease of v. As long as the conditions |Σ| ll H and v2 ll phi2 are satisfied around the onset of late-time cosmic acceleration, where phi is the temporal vector component, we find that the solutions approach the isotropic de Sitter fixed point (Σ = 0 = v) in accordance with the cosmic no-hair conjecture. In the presence of v and Σ the early evolution of the dark energy equation of state wDE in the radiation era is different from that in the isotropic case, but the approach to the isotropic value wDE(iso) typically occurs at redshifts z much larger than 1. Thus, apart from the existence of dark radiation, the anisotropic cosmological dynamics at low redshifts is similar to that in isotropic generalized Proca theories. In beyond-generalized Proca theories the only consistent solution to avoid the divergence of a determinant of the dynamical system corresponds to v = 0, so Σ always decreases in time.
Probabilistic Anisotropic Failure Criteria for Composite Materials.
1987-12-01
worksheets were based on Microsoft Excel software. 55 55 ’. 2.’ ..’. -.. ’-,’€’.’’.’ :2.,2..’..’.2.’.’.,’.." ... .2...analytically described the failure cri - terion and probabilistic failure states of a anisotropic composite in a combined stress state. Strength...APPENDIX F RELIABILITY/FAILURE FUNCTION WORKSHEET ........... 76 APPENDIX G PERCENTILE STRENGTH WORKSHEET ....................... 80 LIST OF
Anisotropic Thermal Conductivity of Exfoliated Black Phosphorus.
Jang, Hyejin; Wood, Joshua D; Ryder, Christopher R; Hersam, Mark C; Cahill, David G
2015-12-22
The anisotropic thermal conductivity of passivated black phosphorus (BP), a reactive two-dimensional material with strong in-plane anisotropy, is ascertained. The room-temperature thermal conductivity for three crystalline axes of exfoliated BP is measured by time-domain thermo-reflectance. The thermal conductivity along the zigzag direction is ≈2.5 times higher than that of the armchair direction.
Observational signatures of anisotropic inflationary models
Ohashi, Junko; Tsujikawa, Shinji; Soda, Jiro E-mail: jiro@phys.sci.kobe-u.ac.jp
2013-12-01
We study observational signatures of two classes of anisotropic inflationary models in which an inflaton field couples to (i) a vector kinetic term F{sub μν}F{sup μν} and (ii) a two-form kinetic term H{sub μνλ}H{sup μνλ}. We compute the corrections from the anisotropic sources to the power spectrum of gravitational waves as well as the two-point cross correlation between scalar and tensor perturbations. The signs of the anisotropic parameter g{sub *} are different depending on the vector and the two-form models, but the statistical anisotropies generally lead to a suppressed tensor-to-scalar ratio r and a smaller scalar spectral index n{sub s} in both models. In the light of the recent Planck bounds of n{sub s} and r, we place observational constraints on several different inflaton potentials such as those in chaotic and natural inflation in the presence of anisotropic interactions. In the two-form model we also find that there is no cross correlation between scalar and tensor perturbations, while in the vector model the cross correlation does not vanish. The non-linear estimator f{sub NL} of scalar non-Gaussianities in the two-form model is generally smaller than that in the vector model for the same orders of |g{sub *}|, so that the former is easier to be compatible with observational bounds of non-Gaussianities than the latter.
Anisotropic conducting films for electromagnetic radiation applications
Cavallo, Francesca; Lagally, Max G.; Rojas-Delgado, Richard
2015-06-16
Electronic devices for the generation of electromagnetic radiation are provided. Also provided are methods for using the devices to generate electromagnetic radiation. The radiation sources include an anisotropic electrically conducting thin film that is characterized by a periodically varying charge carrier mobility in the plane of the film. The periodic variation in carrier mobility gives rise to a spatially varying electric field, which produces electromagnetic radiation as charged particles pass through the film.
A viscoplastic theory for anisotropic materials
NASA Technical Reports Server (NTRS)
Nouailhas, D.; Freed, A. D.
1992-01-01
The purpose of this work is the development of a unified, cyclic, viscoplastic model for anisotropic materials. The first part of the paper presents the foundations of the model in the framework of thermodynamics with internal variables. The second part considers the particular case of cubic symmetry, and addresses the cyclic behavior of a nickel-base single-crystal superalloy, CMSX-2, at high temperature (950 C).
Multidimensional reaction rate theory with anisotropic diffusion.
Berezhkovskii, Alexander M; Szabo, Attila; Greives, Nicholas; Zhou, Huan-Xiang
2014-11-28
An analytical expression is derived for the rate constant that describes diffusive transitions between two deep wells of a multidimensional potential. The expression, in contrast to the Kramers-Langer formula for the rate constant, is valid even when the diffusion is highly anisotropic. Our approach is based on a variational principle for the reactive flux and uses a trial function for the splitting probability or commitor. The theoretical result is validated by Brownian dynamics simulations.
Perspectives of anisotropic flow measurements at NICA
NASA Astrophysics Data System (ADS)
Korotkikh, V. L.; Lokhtin, I. P.; Malinina, L. V.; Petrushanko, S. V.; Snigirev, A. M.
2016-08-01
High-accuracy and high-luminosity measurements of anisotropic flow for various hadron types over full NICA energy range will provide important constraints on the early dynamics of heavy-ion reactions under the conditions where a first-order quark-hadron phase transition may occur. The statistical reach for elliptic flow measurements at NICA is estimated with HYDJET++ heavy-ion event generator.
Effect of inflation on anisotropic cosmologies
Jensen, L.G.; Stein-Schabes, J.A.
1986-03-01
The effects of anisotropic cosmologies on inflation are studied. By properly formulating the field equations it is possible to show that any model that undergoes sufficient inflation will become isotropic on scales greater than the horizon today. Furthermore, we shall show that it takes a very long time for anisotropies to become visible in the observable part of the Universe. It is interesting to note that the time scale will be independent of the Bianchi Model and of the initial anisotropy. 6 refs.
Nanocarpets for Trapping Microscopic Particles
NASA Technical Reports Server (NTRS)
Noca, Flavio; Chen, Fei; Hunt, Brian; Bronikowski, Michael; Hoenk, Michael; Kowalczyk, Robert; Choi, Daniel
2004-01-01
Nanocarpets that is, carpets of carbon nanotubes are undergoing development as means of trapping microscopic particles for scientific analysis. Examples of such particles include inorganic particles, pollen, bacteria, and spores. Nanocarpets can be characterized as scaled-down versions of ordinary macroscopic floor carpets, which trap dust and other particulate matter, albeit not purposefully. Nanocarpets can also be characterized as mimicking both the structure and the particle-trapping behavior of ciliated lung epithelia, the carbon nanotubes being analogous to cilia. Carbon nanotubes can easily be chemically functionalized for selective trapping of specific particles of interest. One could, alternatively, use such other three-dimensionally-structured materials as aerogels and activated carbon for the purposeful trapping of microscopic particles. However, nanocarpets offer important advantages over these alternative materials: (1) Nanocarpets are amenable to nonintrusive probing by optical means; and (2) Nanocarpets offer greater surface-to-volume ratios.
ARTc: Anisotropic reflectivity and transmissivity calculator
NASA Astrophysics Data System (ADS)
Malehmir, Reza; Schmitt, Douglas R.
2016-08-01
While seismic anisotropy is known to exist within the Earth's crust and even deeper, isotropic or even highly symmetric elastic anisotropic assumptions for seismic imaging is an over-simplification which may create artifacts in the image, target mis-positioning and hence flawed interpretation. In this paper, we have developed the ARTc algorithm to solve reflectivity, transmissivity as well as velocity and particle polarization in the most general case of elastic anisotropy. This algorithm is able to provide reflectivity solution from the boundary between two anisotropic slabs with arbitrary symmetry and orientation up to triclinic. To achieve this, the algorithm solves full elastic wave equation to find polarization, slowness and amplitude of all six wave-modes generated from the incident plane-wave and welded interface. In the first step to calculate the reflectivity, the algorithm solves properties of the incident wave such as particle polarization and slowness. After calculation of the direction of generated waves, the algorithm solves their respective slowness and particle polarization. With this information, the algorithm then solves a system of equations incorporating the imposed boundary conditions to arrive at the scattered wave amplitudes, and thus reflectivity and transmissivity. Reflectivity results as well as slowness and polarization are then tested in complex computational anisotropic models to ensure their accuracy and reliability. ARTc is coded in MATLAB ® and bundled with an interactive GUI and bash script to run on single or multi-processor computers.
Active Damping Using Distributed Anisotropic Actuators
NASA Technical Reports Server (NTRS)
Schiller, Noah H.; Cabell, Randolph H.; Quinones, Juan D.; Wier, Nathan C.
2010-01-01
A helicopter structure experiences substantial high-frequency mechanical excitation from powertrain components such as gearboxes and drive shafts. The resulting structure-borne vibration excites the windows which then radiate sound into the passenger cabin. In many cases the radiated sound power can be reduced by adding damping. This can be accomplished using passive or active approaches. Passive treatments such as constrained layer damping tend to reduce window transparency. Therefore this paper focuses on an active approach utilizing compact decentralized control units distributed around the perimeter of the window. Each control unit consists of a triangularly shaped piezoelectric actuator, a miniature accelerometer, and analog electronics. Earlier work has shown that this type of system can increase damping up to approximately 1 kHz. However at higher frequencies the mismatch between the distributed actuator and the point sensor caused control spillover. This paper describes new anisotropic actuators that can be used to improve the bandwidth of the control system. The anisotropic actuators are composed of piezoelectric material sandwiched between interdigitated electrodes, which enables the application of the electric field in a preferred in-plane direction. When shaped correctly the anisotropic actuators outperform traditional isotropic actuators by reducing the mismatch between the distributed actuator and point sensor at high frequencies. Testing performed on a Plexiglas panel, representative of a helicopter window, shows that the control units can increase damping at low frequencies. However high frequency performance was still limited due to the flexible boundary conditions present on the test structure.
Anisotropic hydrodynamics for conformal Gubser flow
NASA Astrophysics Data System (ADS)
Strickland, Michael; Nopoush, Mohammad; Ryblewski, Radoslaw
2016-12-01
In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3)q symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.
Anisotropic impedance surfaces for enhanced antenna isolation
NASA Astrophysics Data System (ADS)
Miragliotta, Joseph A.; Shrekenhamer, David; Sievenpiper, Daniel F.
2015-09-01
Anisotropic impedance surfaces, which include metasurfaces and high impedance surfaces (HIS), can be designed to control the amplitude and propagation direction of surface electromagnetic waves and are an effective means to enhance the isolation between antennas that share a common ground plane. To date, the majority of metastructures that have been designed for antenna isolation have relied on an isotropic distribution of unit cells that possess a stop band that inhibits the propagation of surface waves between neighboring antennas. A less common approach to isolation has been through the design of a metasurface that enables the re-direction of surface waves away from the location of the antenna structure, which effectively limits the coupling. In this paper, we discuss results from our computational investigation associated with improving antenna isolation through the use of an anisotropic metastructure. Simulated results associated with the isolation performance of two simple, but similar, anisotropic structures are compared to the corresponding results from a broadband magnetic radar absorbing materials (magRAM).
Shock capturing by anisotropic diffusion oscillation reduction
NASA Astrophysics Data System (ADS)
Wei, G. W.
2002-04-01
This paper introduces an anisotropic diffusion oscillation reduction (ADOR) scheme for shock wave computations. The connection is made between digital image processing, in particular, image edge detection, and numerical shock capturing. Indeed, numerical shock capturing can be formulated on the lines of iterative digital edge detection. Various anisotropic diffusion and super diffusion operators originated from image edge detection are proposed for the treatment of hyperbolic conservation laws and near-hyperbolic hydrodynamic equations of change. The similarity between anisotropic diffusion and artificial viscosity is discussed. Physical origins and mathematical properties of the artificial viscosity are analyzed from the point of view of kinetic theory. A form of pressure tensor is derived from the first principles of the quantum mechanics. Quantum kinetic theory is utilized to arrive at macroscopic transport equations from the microscopic theory. Macroscopic symmetry is used to simplify pressure tensor expressions. The latter provides a basis for the design of artificial viscosity. The ADOR approach is validated by using (inviscid) Burgers' equation, the gas tube problems, the incompressible Navier-Stokes equation and the Euler equation. Both standard central difference schemes and a discrete singular convolution algorithm are utilized to illustrate the approach. Results are compared with those of third-order upwind scheme and essentially non-oscillatory (ENO) scheme.
Monotonic solution of heterogeneous anisotropic diffusion problems
NASA Astrophysics Data System (ADS)
Aricò, Costanza; Tucciarelli, Tullio
2013-11-01
Anisotropic problems arise in various areas of science and engineering, for example groundwater transport and petroleum reservoir simulations. The pure diffusive anisotropic time-dependent transport problem is solved on a finite number of nodes, that are selected inside and on the boundary of the given domain, along with possible internal boundaries connecting some of the nodes. An unstructured triangular mesh, that attains the Generalized Anisotropic Delaunay condition for all the triangle sides, is automatically generated by properly connecting all the nodes, starting from an arbitrary initial one. The control volume of each node is the closed polygon given by the union of the midpoint of each side with the “anisotropic” circumcentre of each final triangle. A structure of the flux across the control volume sides similar to the standard Galerkin Finite Element scheme is derived. A special treatment of the flux computation, mainly based on edge swaps of the initial mesh triangles, is proposed in order to obtain a stiffness M-matrix system that guarantees the monotonicity of the solution. The proposed scheme is tested using several literature tests and the results are compared with analytical solutions, as well as with the results of other algorithms, in terms of convergence order. Computational costs are also investigated.
Anisotropic representations for superresolution of hyperspectral data
NASA Astrophysics Data System (ADS)
Bosch, Edward H.; Czaja, Wojciech; Murphy, James M.; Weinberg, Daniel
2015-05-01
We develop a method for superresolution based on anisotropic harmonic analysis. Our ambition is to efficiently increase the resolution of an image without blurring or introducing artifacts, and without integrating additional information, such as sub-pixel shifts of the same image at lower resolutions or multimodal images of the same scene. The approach developed in this article is based on analysis of the directional features present in the image that is to be superesolved. The harmonic analytic technique of shearlets is implemented in order to efficiently capture the directional information present in the image, which is then used to provide smooth, accurate images at higher resolutions. Our algorithm is compared to both a recent anisotropic technique based on frame theory and circulant matrices,1 as well as to the standard superresolution method of bicubic interpolation. We evaluate our algorithm on synthetic test images, as well as a hyperspectral image. Our results indicate the superior performance of anisotropic methods, when compared to standard bicubic interpolation.
Waveguide structures in anisotropic nonlinear crystals
NASA Astrophysics Data System (ADS)
Li, Da; Hong, Pengda; Meissner, Helmuth E.
2017-02-01
We report on the design and manufacturing parameters of waveguiding structures of anisotropic nonlinear crystals that are employed for harmonic conversions, using Adhesive-Free Bonding (AFB®). This technology enables a full range of predetermined refractive index differences that are essential for the design of single mode or low-mode propagation with high efficiency in anisotropic nonlinear crystals which in turn results in compact frequency conversion systems. Examples of nonlinear optical waveguides include periodically bonded walk-off corrected nonlinear optical waveguides and periodically poled waveguide components, such as lithium triborate (LBO), beta barium borate (β-BBO), lithium niobate (LN), potassium titanyl phosphate (KTP), zinc germanium phosphide (ZGP) and silver selenogallate (AGSE). Simulation of planar LN waveguide shows that when the electric field vector E lies in the k-c plane, the power flow is directed precisely along the propagation direction, demonstrating waveguiding effect in the planar waveguide. Employment of anisotropic nonlinear optical waveguides, for example in combination with AFB® crystalline fiber waveguides (CFW), provides access to the design of a number of novel high power and high efficiency light sources spanning the range of wavelengths from deep ultraviolet (as short as 200 nm) to mid-infrared (as long as about 18 μm). To our knowledge, the technique is the only generally applicable one because most often there are no compatible cladding crystals available to nonlinear optical cores, especially not with an engineer-able refractive index difference and large mode area.
Anisotropic and Hierarchical Porosity in Multifunctional Ceramics
NASA Astrophysics Data System (ADS)
Lichtner, Aaron Zev
The performance of multifunctional porous ceramics is often hindered by the seemingly contradictory effects of porosity on both mechanical and non-structural properties and yet a sufficient body of knowledge linking microstructure to these properties does not exist. Using a combination of tailored anisotropic and hierarchical materials, these disparate effects may be reconciled. In this project, a systematic investigation of the processing, characterization and properties of anisotropic and isotropic hierarchically porous ceramics was conducted. The system chosen was a composite ceramic intended as the cathode for a solid oxide fuel cell (SOFC). Comprehensive processing investigations led to the development of approaches to make hierarchical, anisotropic porous microstructures using directional freeze-casting of well dispersed slurries. The effect of all the important processing parameters was investigated. This resulted in an ability to tailor and control the important microstructural features including the scale of the microstructure, the macropore size and total porosity. Comparable isotropic porous ceramics were also processed using fugitive pore formers. A suite of characterization techniques including x-ray tomography and 3-D sectional scanning electron micrographs (FIB-SEM) was used to characterize and quantify the green and partially sintered microstructures. The effect of sintering temperature on the microstructure was quantified and discrete element simulations (DEM) were used to explain the experimental observations. Finally, the comprehensive mechanical properties, at room temperature, were investigated, experimentally and using DEM, for the different microstructures.
Longitudinal fluctuations and decorrelation of anisotropic flow
NASA Astrophysics Data System (ADS)
Pang, Long-Gang; Petersen, Hannah; Qin, Guang-You; Roy, Victor; Wang, Xin-Nian
2016-12-01
We investigate the decorrelation of 2nd and 3rd order anisotropic flow for charged particles in two different pseudo rapidity (η) windows by varying the pseudo rapidity gap, in an event-by-event (3+1)D ideal hydrodynamic model, with fluctuating initial conditions from A Multi-Phase Transport (AMPT) model. We visualize the parton distribution at initial state for Pb+Pb collisions at LHC and Au+Au collisions at RHIC, and demonstrate the longitudinal fluctuations originating from the asymmetry between forward and backward going participants, the fluctuations of the string length and the fluctuations due to finite number of partons at different beam energies. The decorrelation of anisotropic flow of final hadrons with large η gaps is found to originate from the spatial decorrelation along the longitudinal direction in the AMPT initial conditions through hydrodynamic evolution. The agreement between our results and recent CMS data in most centralities suggests that the string-like mechanism of initial parton production in AMPT model captures the initial longitudinal fluctuation that is responsible for the measured decorrelation of anisotropic flow in Pb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest RHIC energy show stronger longitudinal decorrelation than at LHC, indicating larger longitudinal fluctuations at lower beam energies.
Anisotropic halo model: implementation and numerical results
NASA Astrophysics Data System (ADS)
Sgró, Mario A.; Paz, Dante J.; Merchán, Manuel
2013-07-01
In the present work, we extend the classic halo model for the large-scale matter distribution including a triaxial model for the halo profiles and their alignments. In particular, we derive general expressions for the halo-matter cross-correlation function. In addition, by numerical integration, we obtain instances of the cross-correlation function depending on the directions given by halo shape axes. These functions are called anisotropic cross-correlations. With the aim of comparing our theoretical results with the simulations, we compute averaged anisotropic correlations in cones with their symmetry axis along each shape direction of the centre halo. From these comparisons we characterize and quantify the alignment of dark matter haloes on the Λcold dark matter context by means of the presented anisotropic halo model. Since our model requires multidimensional integral computation we implement a Monte Carlo method on GPU hardware which allows us to increase the precision of the results and it improves the performance of the computation.
Anisotropic Self-Assembly of Nanoparticle Amphiphiles
NASA Astrophysics Data System (ADS)
Kumar, Sanat
2009-03-01
It is easy to understand the self-assembly of particles having anisotropic shapes or interactions, such as Co nanoparticles or proteins, into highly extended structures. However, there is no experimentally established strategy for creating anisotropic structures from common spherical nanoparticles. We demonstrate that spherical nanoparticles, uniformly grafted with macromolecules, robustly self-assemble into a range of anisotropic superstructures when they are dispersed in the corresponding homopolymer matrix. This phenomenon is driven by the microphase separation between the inorganic nanoparticles and the (organic) polymeric chains grafted to their surfaces in a fashion similar to block copolymers. This microphase separation driven particle self-assembly provides a unique means of controlling the global nanoparticle dispersion state in polymer nanocomposites. The relationship between the state of particle dispersion and nanocomposite properties can thus be critically examined, and in particular we focus on the mechanical reinforcement afforded when particles are added to polymers. Grafted nanoparticles are thus versatile building blocks for creating tunable and functional particle superstructures with significant practical applications. With Pinar Akcora, Hongjun Liu, Yu Li, Brian Benicewicz, Linda Schadler, Thanos Panagiotopoulos, Jack Douglas, P. Thiyagarajan and Ralph Colby.
Anisotropic materials appearance analysis using ellipsoidal mirror
NASA Astrophysics Data System (ADS)
Filip, Jiří; Vávra, Radomír.
2015-03-01
Many real-world materials exhibit significant changes in appearance when rotated along a surface normal. The presence of this behavior is often referred to as visual anisotropy. Anisotropic appearance of spatially homogeneous materials is commonly characterized by a four-dimensional BRDF. Unfortunately, due to simplicity most past research has been devoted to three dimensional isotropic BRDFs. In this paper, we introduce an innovative, fast, and inexpensive image-based approach to detect the extent of anisotropy, its main axes and width of corresponding anisotropic highlights. The method does not rely on any moving parts and uses only an off-the-shelf ellipsoidal reflector with a compact camera. We analyze our findings with a material microgeometry scan, and present how results correspond to the microstructure of individual threads in a particular fabric. We show that knowledge of a material's anisotropic behavior can be effectively used in order to design a material-dependent sampling pattern so as the material's BRDF could be measured much more precisely in the same amount of time using a common gonioreflectometer.
Efficient Anisotropic Filtering of Diffusion Tensor Images
Xu, Qing; Anderson, Adam W.; Gore, John C.; Ding, Zhaohua
2009-01-01
To improve the accuracy of structural and architectural characterization of living tissue with diffusion tensor imaging, an efficient smoothing algorithm is presented for reducing noise in diffusion tensor images. The algorithm is based on anisotropic diffusion filtering, which allows both image detail preservation and noise reduction. However, traditional numerical schemes for anisotropic filtering have the drawback of inefficiency and inaccuracy due to their poor stability and first order time accuracy. To address this, an unconditionally stable and second order time accuracy semi-implicit Craig-Sneyd scheme is adapted in our anisotropic filtering. By using large step size, unconditional stability allows this scheme to take much fewer iterations and thus less computation time than the explicit scheme to achieve a certain degree of smoothing. Second order time accuracy makes the algorithm reduce noise more effectively than a first order scheme with the same total iteration time. Both the efficiency and effectiveness are quantitatively evaluated based on synthetic and in vivo human brain diffusion tensor images, and these tests demonstrate that our algorithm is an efficient and effective tool for denoising diffusion tensor images. PMID:20061113
Haywood, Rachel; Volkov, Arsen; Andrady, Carima; Sayer, Robert
2012-03-01
The in vitro star system used for sunscreen UVA-testing is not an absolute measure of skin protection being a ratio of the total integrated UVA/UVB absorption. The in vivo persistent-pigment-darkening method requires human volunteers. We investigated the use of the ESR-detectable DMPO protein radical-adduct in solar-simulator-irradiated skin substitutes for sunscreen testing. Sunscreens SPF rated 20+ with UVA protection, reduced this adduct by 40-65% when applied at 2 mg/cm(2). SPF 15 Organic UVA-UVB (BMDBM-OMC) and TiO(2)-UVB filters and a novel UVA-TiO(2) filter reduced it by 21, 31 and 70% respectively. Conventional broad-spectrum sunscreens do not fully protect against protein radical-damage in skin due to possible visible-light contributions to damage or UVA-filter degradation. Anisotropic spectra of DMPO-trapped oxygen-centred radicals, proposed intermediates of lipid-oxidation, were detected in irradiated sunscreen and DMPO. Sunscreen protection might be improved by the consideration of visible-light protection and the design of filters to minimise radical leakage and lipid-oxidation.
Selby, R D; Gage, S H; Whalon, M E
2014-04-01
Incorporating camera systems into insect traps potentially benefits insect phenology modeling, nonlethal insect monitoring, and research into the automated identification of traps counts. Cameras originally for monitoring mammals were instead adapted to monitor the entrance to pyramid traps designed to capture the plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae). Using released curculios, two new trap designs (v.I and v.II) were field-tested alongside conventional pyramid traps at one site in autumn 2010 and at four sites in autumn 2012. The traps were evaluated on the basis of battery power, ease-of-maintenance, adaptability, required-user-skills, cost (including labor), and accuracy-of-results. The v.II design fully surpassed expectations, except that some trapped curculios were not photographed. In 2012, 13 of the 24 traps recorded every curculio entering the traps during the 18-d study period, and in traps where some curculios were not photographed, over 90% of the omissions could be explained by component failure or external interference with the motion sensor. Significantly more curculios entered the camera traps between 1800 and 0000 hours. When compared with conventional pyramid traps, the v.I traps collected a similar number of curculios. Two observed but not significant trends were that the v.I traps collected twice as many plum curculios as the v.II traps, while at the same time the v.II traps collected more than twice as many photos per plum curculio as the v.I traps. The research demonstrates that low-cost, precise monitoring of field insect populations is feasible without requiring extensive technical expertise.
Fully localized two-dimensional embedded solitons
Yang Jianke
2010-11-15
We report the prediction of fully localized two-dimensional embedded solitons. These solitons are obtained in a quasi-one-dimensional waveguide array which is periodic along one spatial direction and localized along the orthogonal direction. Under appropriate nonlinearity, these solitons are found to exist inside the Bloch bands (continuous spectrum) of the waveguide and thus are embedded solitons. These embedded solitons are fully localized along both spatial directions. In addition, they are fully stable under perturbations.
Fully alloyed metal nanorods with highly tunable properties.
Albrecht, Wiebke; van der Hoeven, Jessi E S; Deng, Tian-Song; de Jongh, Petra E; van Blaaderen, Alfons
2017-02-23
Alloyed metal nanorods offer a unique combination of enhanced plasmonic and photothermal properties with a wide variety in optical and catalytic properties as a function of the alloy composition. Here, we show that fully alloyed anisotropic nanoparticles can be obtained with complete retention of the particle shape via thermal treatment at surprisingly low temperatures. By coating Au-Ag, Au-Pd and Au-Pt core-shell nanorods with a protective mesoporous silica shell the transformation of the rods to a more stable spherical shape was successfully prevented during alloying. For the Au-Ag core-shell NRs the chemical stability was drastically increased after alloying, and from Mie-Gans and finite-difference time-domain (FDTD) calculations it followed that alloyed AuAg rods also exhibit much better plasmonic properties than their spherical counterparts. Finally, the generality of our method is demonstrated by alloying Au-Pd and Au-Pt core-shell NRs, whereby the AuPd and AuPt alloyed NRs showed a surprisingly high increase in thermal stability of several hundred degrees compared with monometallic silica coated Au NRs.
Superfluid transition of homogeneous and trapped two-dimensional Bose gases.
Holzmann, Markus; Baym, Gordon; Blaizot, Jean-Paul; Laloë, Franck
2007-01-30
Current experiments on atomic gases in highly anisotropic traps present the opportunity to study in detail the low temperature phases of two-dimensional inhomogeneous systems. Although, in an ideal gas, the trapping potential favors Bose-Einstein condensation at finite temperature, interactions tend to destabilize the condensate, leading to a superfluid Kosterlitz-Thouless-Berezinskii phase with a finite superfluid mass density but no long-range order, as in homogeneous fluids. The transition in homogeneous systems is conveniently described in terms of dissociation of topological defects (vortex-antivortex pairs). However, trapped two-dimensional gases are more directly approached by generalizing the microscopic theory of the homogeneous gas. In this paper, we first derive, via a diagrammatic expansion, the scaling structure near the phase transition in a homogeneous system, and then study the effects of a trapping potential in the local density approximation. We find that a weakly interacting trapped gas undergoes a Kosterlitz-Thouless-Berezinskii transition from the normal state at a temperature slightly below the Bose-Einstein transition temperature of the ideal gas. The characteristic finite superfluid mass density of a homogeneous system just below the transition becomes strongly suppressed in a trapped gas.
Textured silicon nitride: processing and anisotropic properties
Zhu, Xinwen; Sakka, Yoshio
2008-01-01
Textured silicon nitride (Si3N4) has been intensively studied over the past 15 years because of its use for achieving its superthermal and mechanical properties. In this review we present the fundamental aspects of the processing and anisotropic properties of textured Si3N4, with emphasis on the anisotropic and abnormal grain growth of β-Si3N4, texture structure and texture analysis, processing methods and anisotropic properties. On the basis of the texturing mechanisms, the processing methods described in this article have been classified into two types: hot-working (HW) and templated grain growth (TGG). The HW method includes the hot-pressing, hot-forging and sinter-forging techniques, and the TGG method includes the cold-pressing, extrusion, tape-casting and strong magnetic field alignment techniques for β-Si3N4 seed crystals. Each processing technique is thoroughly discussed in terms of theoretical models and experimental data, including the texturing mechanisms and the factors affecting texture development. Also, methods of synthesizing the rodlike β-Si3N4 single crystals are presented. Various anisotropic properties of textured Si3N4 and their origins are thoroughly described and discussed, such as hardness, elastic modulus, bending strength, fracture toughness, fracture energy, creep behavior, tribological and wear behavior, erosion behavior, contact damage behavior and thermal conductivity. Models are analyzed to determine the thermal anisotropy by considering the intrinsic thermal anisotropy, degree of orientation and various microstructure factors. Textured porous Si3N4 with a unique microstructure composed of oriented elongated β-Si3N4 and anisotropic pores is also described for the first time, with emphasis on its unique mechanical and thermal-mechanical properties. Moreover, as an important related material, textured α-Sialon is also reviewed, because the presence of elongated α-Sialon grains allows the production of textured α-Sialon using the
Textured silicon nitride: processing and anisotropic properties.
Zhu, Xinwen; Sakka, Yoshio
2008-07-01
Textured silicon nitride (Si3N4) has been intensively studied over the past 15 years because of its use for achieving its superthermal and mechanical properties. In this review we present the fundamental aspects of the processing and anisotropic properties of textured Si3N4, with emphasis on the anisotropic and abnormal grain growth of β-Si3N4, texture structure and texture analysis, processing methods and anisotropic properties. On the basis of the texturing mechanisms, the processing methods described in this article have been classified into two types: hot-working (HW) and templated grain growth (TGG). The HW method includes the hot-pressing, hot-forging and sinter-forging techniques, and the TGG method includes the cold-pressing, extrusion, tape-casting and strong magnetic field alignment techniques for β-Si3N4 seed crystals. Each processing technique is thoroughly discussed in terms of theoretical models and experimental data, including the texturing mechanisms and the factors affecting texture development. Also, methods of synthesizing the rodlike β-Si3N4 single crystals are presented. Various anisotropic properties of textured Si3N4 and their origins are thoroughly described and discussed, such as hardness, elastic modulus, bending strength, fracture toughness, fracture energy, creep behavior, tribological and wear behavior, erosion behavior, contact damage behavior and thermal conductivity. Models are analyzed to determine the thermal anisotropy by considering the intrinsic thermal anisotropy, degree of orientation and various microstructure factors. Textured porous Si3N4 with a unique microstructure composed of oriented elongated β-Si3N4 and anisotropic pores is also described for the first time, with emphasis on its unique mechanical and thermal-mechanical properties. Moreover, as an important related material, textured α-Sialon is also reviewed, because the presence of elongated α-Sialon grains allows the production of textured α-Sialon using the
Huo, R; Agapiou, A; Bocos-Bintintan, V; Brown, L J; Burns, C; Creaser, C S; Devenport, N A; Gao-Lau, B; Guallar-Hoyas, C; Hildebrand, L; Malkar, A; Martin, H J; Moll, V H; Patel, P; Ratiu, A; Reynolds, J C; Sielemann, S; Slodzynski, R; Statheropoulos, M; Turner, M A; Vautz, W; Wright, V E; Thomas, C L P
2011-12-01
This experiment observed the evolution of metabolite plumes from a human trapped in a simulation of a collapsed building. Ten participants took it in turns over five days to lie in a simulation of a collapsed building and eight of them completed the 6 h protocol while their breath, sweat and skin metabolites were passed through a simulation of a collapsed glass-clad reinforced-concrete building. Safety, welfare and environmental parameters were monitored continuously, and active adsorbent sampling for thermal desorption GC-MS, on-line and embedded CO, CO(2) and O(2) monitoring, aspirating ion mobility spectrometry with integrated semiconductor gas sensors, direct injection GC-ion mobility spectrometry, active sampling thermal desorption GC-differential mobility spectrometry and a prototype remote early detection system for survivor location were used to monitor the evolution of the metabolite plumes that were generated. Oxygen levels within the void simulator were allowed to fall no lower than 19.1% (v). Concurrent levels of carbon dioxide built up to an average level of 1.6% (v) in the breathing zone of the participants. Temperature, humidity, carbon dioxide levels and the physiological measurements were consistent with a reproducible methodology that enabled the metabolite plumes to be sampled and characterized from the different parts of the experiment. Welfare and safety data were satisfactory with pulse rates, blood pressures and oxygenation, all within levels consistent with healthy adults. Up to 12 in-test welfare assessments per participant and a six-week follow-up Stanford Acute Stress Response Questionnaire indicated that the researchers and participants did not experience any adverse effects from their involvement in the study. Preliminary observations confirmed that CO(2), NH(3) and acetone were effective markers for trapped humans, although interactions with water absorbed in building debris needed further study. An unexpected observation from the NH(3
NASA Astrophysics Data System (ADS)
Lecoanet, Daniel; Parrish, Ian; Quataert, Eliot
2012-11-01
We study the effects of anisotropic thermal conduction along magnetic field lines on an accelerated contact discontinuity in a weakly collisional plasma. Anisotropic conduction can result in doubly-diffusive instabilities, including the magnetothermal instability (MTI) and the heat flux driven buoyancy instability (HBI). We run fully non-linear numerical simulations of a contact discontinuity with anisotropic conduction. The non-linear evolution can be described as a superposition of three physical effects: temperature diffusion due to vertical conduction, the Rayleigh-Taylor instability (RTI) and the HBI. In simulations with RTI-stable contact discontinuities, the temperature discontinuity spreads due to vertical heat conduction. The HBI slows this temperature diffusion by reorienting initially vertical magnetic field lines to a more horizontal geometry, eventually stopping vertical temperature diffusion. In simulations with RTI-unstable contact discontinuities, the dynamics are initially governed by temperature diffusion, but the RTI becomes increasingly important at late times. These results could be important in various astrophysical contexts including supernova remnants, solar prominences and cold fronts in galaxy clusters. DL is supported by the Hertz Foundation and NSF Grant DGE 1106400; IP & EQ are supported in part by NASA Grant ATP09-0125, NSF-DOE Grant PHY-0812811, and by the David and Lucille Packard Foundation.
Berryman, J.G.
2009-11-20
Poroelastic analysis usually progresses from assumed knowledge of dry or drained porous media to the predicted behavior of fluid-saturated and undrained porous media. Unfortunately, the experimental situation is often incompatible with these assumptions, especially when field data (from hydrological or oil/gas reservoirs) are involved. The present work considers several different experimental scenarios typified by one in which a set of undrained poroelastic (stiffness) constants has been measured using either ultrasound or seismic wave analysis, while some or all of the dry or drained constants are normally unknown. Drained constants for such a poroelastic system can be deduced for isotropic systems from available data if a complete set of undrained compliance data for the principal stresses are available - together with a few other commonly measured quantities such as porosity, fluid bulk modulus, and grain bulk modulus. Similar results are also developed here for anisotropic systems having up to orthotropic symmetry if the system is granular (i.e., composed of solid grains assembled into a solid matrix, either by a cementation process or by applied stress) and the grains are known to be elastically homogeneous. Finally, the analysis is also fully developed for anisotropic systems with nonhomogeneous (more than one mineral type), but still isotropic, grains - as well as for uniform collections of anisotropic grains as long as their axes of symmetry are either perfectly aligned or perfectly random.
NASA Astrophysics Data System (ADS)
Chen, Hao-Wei; Huang, Chih-Ling; Lo, Yu-Lung; Chang, You-Ren
2017-03-01
The optical properties of biological tissues under stretching are investigated using a full-field ellipsometry technique based on a differential Mueller matrix formalism. Traditional photoelastic-based formalism for extracting the linear birefringence (LB) properties of stretched anisotropic optical samples ignores the effects of the other optical properties of the sample. By contrast, in the formalism proposed in this study, the LB, linear dichroism (LD), circular birefringence (CB), circular dichroism (CD), and depolarization (Dep) properties are fully decoupled. Simulations are performed to evaluate the performance of the two formalisms in extracting the LB properties of optically anisotropic samples with different degrees of Dep, CB, LD, and CD. The practical feasibility of the proposed all-parameter decoupled formalism is then demonstrated using chicken breast muscle tissue. In general, the results show that both formalisms provide a reliable LB measurement performance for healthy chicken breast tissue under stretching. However, while the LB-only formalism has good robustness toward scattering, its measurement performance is seriously degraded for samples with high CB. Thus, of the two formalisms, the proposed all-parameter decoupled formalism provides a more effective approach for examining the anisotropic properties of biological tissues under stretching.
Reconstruction of three-dimensional anisotropic structure from small-angle scattering experiments
NASA Astrophysics Data System (ADS)
Huang, Guan-Rong; Wang, Yangyang; Wu, Bin; Wang, Zhe; Do, Changwoo; Smith, Gregory S.; Bras, Wim; Porcar, Lionel; Falus, Péter; Chen, Wei-Ren
2017-08-01
When subjected to flow, the structures of many soft-matter systems become anisotropic due to the symmetry breaking of the spatial arrangements of constituent particles at the microscopic level. At present, it is common practice to use various small-angle scattering techniques to explore flow-induced microstructural distortion. However, there has not been a thorough discussion in the literature on how a three-dimensional anisotropic structure can be faithfully reconstructed from two-dimensional small-angle scattering spectra. In this work, we address this issue rigorously from a mathematical perspective by using real spherical harmonic expansion analysis. We first show that, except for cases in which mechanical perturbation is sufficiently small, the existing small-angle scattering techniques generally do not provide complete information on structural distortion. This limitation is caused by the linear dependence of certain real spherical harmonic basis vectors on the flow-vorticity and flow-velocity gradient planes in the Couette shear cell. To circumvent the constraint imposed by this geometry, an alternative approach is proposed in which a parallel sliding plate shear cell is used with a central rotary axis along the flow direction. From the calculation of rotation of the reference frame, we demonstrate the feasibility of this experimental implementation for a fully resolved three-dimensional anisotropic structure via a case study of sheared polymers.
FDTD modeling of anisotropic nonlinear optical phenomena in silicon waveguides.
Dissanayake, Chethiya M; Premaratne, Malin; Rukhlenko, Ivan D; Agrawal, Govind P
2010-09-27
A deep insight into the inherent anisotropic optical properties of silicon is required to improve the performance of silicon-waveguide-based photonic devices. It may also lead to novel device concepts and substantially extend the capabilities of silicon photonics in the future. In this paper, for the first time to the best of our knowledge, we present a three-dimensional finite-difference time-domain (FDTD) method for modeling optical phenomena in silicon waveguides, which takes into account fully the anisotropy of the third-order electronic and Raman susceptibilities. We show that, under certain realistic conditions that prevent generation of the longitudinal optical field inside the waveguide, this model is considerably simplified and can be represented by a computationally efficient algorithm, suitable for numerical analysis of complex polarization effects. To demonstrate the versatility of our model, we study polarization dependence for several nonlinear effects, including self-phase modulation, cross-phase modulation, and stimulated Raman scattering. Our FDTD model provides a basis for a full-blown numerical simulator that is restricted neither by the single-mode assumption nor by the slowly varying envelope approximation.
First Attempts at Antihydrogen Trapping in ALPHA
Andresen, G. B.; Bowe, P. D.; Hangst, J. S.; Bertsche, W.; Butler, E.; Charlton, M.; Humphries, A. J.; Jenkins, M. J.; Joergensen, L. V.; Madsen, N.; Werf, D. P. van der; Bray, C. C.; Chapman, S.; Fajans, J.; Povilus, A.; Wurtele, J. S.; Cesar, C. L.; Lambo, R.; Silveira, D. M.; Fujiwara, M. C.
2008-08-08
The ALPHA apparatus is designed to produce and trap antihydrogen atoms. The device comprises a multifunction Penning trap and a superconducting, neutral atom trap having a minimum-B configuration. The atom trap features an octupole magnet for transverse confinement and solenoidal mirror coils for longitudinal confinement. The magnetic trap employs a fast shutdown system to maximize the probability of detecting the annihilation of released antihydrogen. In this article we describe the first attempts to observe antihydrogen trapping.
First Attempts at Antihydrogen Trapping in ALPHA
NASA Astrophysics Data System (ADS)
Andresen, G. B.; Bertsche, W.; Bowe, P. D.; Bray, C. C.; Butler, E.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Fujiwara, M. C.; Funakoshi, R.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayano, R. S.; Hayden, M. E.; Humphries, A. J.; Hydomako, R.; Jenkins, M. J.; Jørgensen, L. V.; Kurchaninov, L.; Lambo, R.; Madsen, N.; Nolan, P.; Olchanski, K.; Olin, A.; Page, R. D.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; El Nasr, S. Seif; Silveira, D. M.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.
2008-08-01
The ALPHA apparatus is designed to produce and trap antihydrogen atoms. The device comprises a multifunction Penning trap and a superconducting, neutral atom trap having a minimum-B configuration. The atom trap features an octupole magnet for transverse confinement and solenoidal mirror coils for longitudinal confinement. The magnetic trap employs a fast shutdown system to maximize the probability of detecting the annihilation of released antihydrogen. In this article we describe the first attempts to observe antihydrogen trapping.
Silverman, Jules; Sorenson, Clyde E; Waldvogel, Michael G
2006-10-01
Argentine ant, Linepithema humile (Mayr), management is constrained, in large part, by polydomy where nestmates are distributed extensively across urban landscapes, particularly within mulch. Management with trap-mulching is a novel approach derived from trap-cropping where ants are repelled from a broad domain of nest sites to smaller defined areas, which are subsequently treated with insecticide. This concept was field-tested with mulch surrounding ornamental trees replaced with a narrow band of pine (Pinus spp.) needle mulch (trap) within a much larger patch of repellent aromatic cedar (Juniperus spp.) mulch. After ants reestablished around the trees, the pine needle mulch band was treated with 0.06% fipronil (Termidor). Poor results were obtained when the trap extended from the tree trunk to the edge of the mulched area. When the trap was applied as a circular band around the tree trunk reductions in the number of foraging ants were recorded through 14 d compared with an untreated mulch control, but not for longer periods. Reductions in the number of ant nests within mulch were no different between the trap mulch and any of the other treatments. We conclude that trap-mulching offers limited benefits, and that successful management of Argentine ants will require implementation of complementary or perhaps alternative strategies.
Large scale anisotropic bias from primordial non-Gaussianity
Baghram, Shant; Firouzjahi, Hassan; Namjoo, Mohammad Hossein E-mail: mh.namjoo@ipm.ir
2013-08-01
In this work we study the large scale structure bias in models of anisotropic inflation. We use the Peak Background Splitting method in Excursion Set Theory to find the scale-dependent bias. We show that the amplitude of the bias is modified by a direction-dependent factor. In the specific anisotropic inflation model which we study, the scale-dependent bias vanishes at leading order when the long wavelength mode in squeezed limit is aligned with the anisotropic direction in the sky. We also extend the scale-dependent bias formulation to the general situations with primordial anisotropy. We find some selection rules indicating that some specific parts of a generic anisotropic bispectrum is picked up by the bias parameter. We argue that the anisotropic bias is mainly sourced by the angle between the anisotropic direction and the long wavelength mode in the squeezed limit.
Influence of anisotropic white matter modeling on EEG source localization.
Cuartas-Morales, E; Cardenas-Pena, D; Castellanos-Dominguez, G
2014-01-01
We study the influence of the anisotropic white matter within the ElectroEncephaloGraphy source localization problem. To this end, we consider three cases of the anisotropic white matter modeled in two concrete cases: by fixed or variable ratio. We extract information about highly anisotropic areas of the white matter from real Diffusion Weighted Imaging data. To validate the compared anisotropic models, we introduce the localization dipole and orientation errors. Obtained results show that the white matter model with a fixed anisotropic ratio leads to values of dipole localization error close to 1cm and may be enough in those cases avoiding localized analysis of neural brain activity. In contrast, modeling based on the anisotropic variable rate assumption becomes important in tasks regarding analysis and localization of deep sources neighboring the white matter tissue.
Design and Synthesis of Microscale Opto-Magnetic Trapping Handles
NASA Astrophysics Data System (ADS)
Lawson, Joseph L.
Opto-Magnetic Trapping (OMT) is a novel micromanipulation technology capable of translating particles with nanometer precision and producing forces on the order of pico-Newtons. OMT combines the benefits of optical trapping (OT) to manipulate handle particles in translational directions and magnetic trapping (MT) to provide rotational control. This combined manipulation technology shows promise for applications ranging from novel single molecule force spectroscopy to advanced manufacturing of smart micro or nano structures. Successful OMT requires handles containing material properties amenable to both OT and MT individually. Since these material properties are traditionally exclusive, novel anisotropic handles must be synthesized to accommodate both micromanipulation technologies. This body of research advances the state of the art in micromanipulation technology by addressing the fundamental material incompatibility issues associated with OMT. Novel micro-scale "patchy" handle particles were fabricated using a glancing angle deposition (GLAD) process. Due to their composite design combining dielectric and ferromagnetic materials, these particles successfully demonstrated OMT manipulation. These particles, along with the developed GLAD fabrication process, improve upon the current state of the art by enabling the robust synthesis of a wider range of particle sizes. Furthermore, the magnetic moments of these particles can be more accurately controlled over a wider range including producing magnetic moments grater than is capable with current techniques. A thorough numerical simulation was also conducted to identify the variation of OT performance of these patchy particles with respect to standard dielectric-only OT handles. While variations in trapping location do exist, they were found to be within an acceptable range for OMT applications and are still capable of manipulation with nanometer precision.
Grooved organogel surfaces towards anisotropic sliding of water droplets.
Zhang, Pengchao; Liu, Hongliang; Meng, Jingxin; Yang, Gao; Liu, Xueli; Wang, Shutao; Jiang, Lei
2014-05-21
Periodic micro-grooved organogel surfaces can easily realize the anisotropic sliding of water droplets attributing to the formed slippery water/oil/solid interface. Different from the existing anisotropic surfaces, this novel surface provides a versatile candidate for the anisotropic sliding of water droplets and might present a promising way for the easy manipulation of liquid droplets for water collection, liquid-directional transportation, and microfluidics.
Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps.
Hong, Seokjun; Lee, Minjae; Kwon, Yeong-Dae; Cho, Dong-Il Dan; Kim, Taehyun
2017-08-17
Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 µm-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 ((174)Yb(+)) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 ((171)Yb(+)) and to the manipulation of qubits.
NASA Astrophysics Data System (ADS)
Barbosa Murillo, Paula Andrea Carolina
The Vaca Muerta Formation (VM) is considered the fourth largest shale oil play in the world with an estimated 27 billion barrels of recoverable oil. The VM, as other unconventional reservoirs, contains layers with substantial velocity anisotropy. Former studies performed an isotropic characterization of the VM. Fernandez-Concheso M. (2015) worked on post and pre-stack seismic inversions to supply a tool to characterize the VM. Bishop (2015) developed a mechanical stratigraphy for the VM to evaluate its influence in the success of stimulation jobs. This study involves sequence stratigraphic analysis as a basis for estimating anisotropic elastic moduli, which can help improve geomechanical models to be built for the VM. Basin floor and slope environments were identified for the VM with unique characteristics. Rock-physics modeling is used to explain the log response of the VM in terms of rock properties. Anisotropy analysis is utilized to describe the VM as a VTI (transverse isotropic with a vertical symmetry axis) model. Parasequences were implemented to group and interpolate well log and core data. Linear relationships were observed between the stiffness coefficients measured on cores. Parameters of those relations (per parasequence) were used to compute stiffness coefficients where not enough data were available. The VTI model was fully described and anisotropic Young's modulus and Poisson's ratio were estimated. I found that acoustic impedance may be used to predict the Total organic content (TOC). TOC influences the hydrocarbon pore volume. A methodology is proposed to calculate the anisotropic elastic moduli. The spatial variations of anisotropic elastic moduli impacts the response of the VM under hydraulic fracturing which should be considered in the design of well-related operations. In summary, this research provides tools for locating sweet spots and optimization of well drilling and stimulations operations, which should help unlock this huge resource.
Optimal illusion and invisibility of multilayered anisotropic cylinders and spheres.
Zhang, Lin; Shi, Yan; Liang, Chang-Hong
2016-10-03
In this paper, full-wave electromagnetic scattering theory is employed to investigate illusion and invisibility of inhomogeneous anisotropic cylinders and spheres. With the use of a shell designed according to Mie series theory for multiple piecewise anisotropic layers, radar cross section (RCS) of the coated inhomogeneous anisotropic object can be dramatically reduced or disguised as another object in the long-wavelength limit. With the suitable adjustment of the anisotropy parameters of the shell, optimal illusion and invisibility characteristics of the coated inhomogeneous anisotropic object can be achieved. Details of theoretical analysis and numerical examples are presented to validate the proposed methodology.
Retrieval procedure of effective conductivity for plasmonic resonant anisotropic metasurface
NASA Astrophysics Data System (ADS)
Yermakov, O. Y.; Porubaev, F.; Bogdanov, A. A.; Samusev, A. K.; Iorsh, I. V.
2017-09-01
In this work we introduce the effective surface conductivity retrieval procedure in order to describe the properties of plasmonic resonant anisotropic metasurface consisting of plasmonic elliptical nanodisks.
Stability conditions for the Bianchi type II anisotropically inflating universes
Kao, W.F.; Lin, Ing-Chen E-mail: g9522528@oz.nthu.edu.tw
2009-01-15
Stability conditions for a class of anisotropically inflating solutions in the Bianchi type II background space are shown explicitly in this paper. These inflating solutions were known to break the cosmic no-hair theorem such that they do not approach the de Sitter universe at large times. It can be shown that unstable modes of the anisotropic perturbations always exist for this class of expanding solutions. As a result, we show that these set of anisotropically expanding solutions are unstable against anisotropic perturbations in the Bianchi type II space.
Mechanism of DNA Trapping in Nanoporous Structures during Asymmetric Pulsed-Field Electrophoresis
NASA Astrophysics Data System (ADS)
Zhou, Ya; Harrison, D. Jed
2014-03-01
DNA molecules (>100kbp) are trapped in separation sieves when high electric fields are applied in pulsed field electrophoresis, seriously limiting the speed of separation. Using crystalline particle arrays, to generate interstitial pores for molecular sieving, allows higher electric fields than in gels, (e.g 40 vs 5 V/cm), however trapping still limits the field strength. Using reverse pulses, which release DNA from being fully-stretched, allows higher fields (140 V/cm). We investigate the trapping mechanism of individual DNA molecules in ordered nanoporous structures. Two prerequisites for trapping are revealed by the dynamics of single trapped DNA, hernia formation and fully-stretched U/J shapes. Fully stretched DNA has longer unhooking times than expected by simple models. We propose a dielectrophoretic (DEP) force reduces the mobility of segments at the apex of the U or J, where field gradients are highest, based on simulations. A modified model for unhooking time is obtained after the DEP force is introduced. The new model explains the unhooking time data by predicting an infinite trapping time when the ratio of arm length differences (of the U or J) to molecule length Δx / L < β . β is a DEP parameter that is found to strongly increase with electric field. The work was supported by grant from Natural Sciences and Engineering Research Council of Canada (NSERC) and the National Institute for Nanotechnology (NINT).
Innovation: the classic traps.
Kanter, Rosabeth Moss
2006-11-01
these traps.
Hydrodynamic enhanced dielectrophoretic particle trapping
Miles, Robin R.
2003-12-09
Hydrodynamic enhanced dielectrophoretic particle trapping carried out by introducing a side stream into the main stream to squeeze the fluid containing particles close to the electrodes producing the dielelectrophoretic forces. The region of most effective or the strongest forces in the manipulating fields of the electrodes producing the dielectrophoretic forces is close to the electrodes, within 100 .mu.m from the electrodes. The particle trapping arrangement uses a series of electrodes with an AC field placed between pairs of electrodes, which causes trapping of particles along the edges of the electrodes. By forcing an incoming flow stream containing cells and DNA, for example, close to the electrodes using another flow stream improves the efficiency of the DNA trapping.
Mini ion trap mass spectrometer
Dietrich, D.D.; Keville, R.F.
1995-09-19
An ion trap is described which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10{sup 9} and commercial mass spectrometers requiring 10{sup 4} ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products. 10 figs.
Mini ion trap mass spectrometer
Dietrich, Daniel D.; Keville, Robert F.
1995-01-01
An ion trap which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10.sup.9 and commercial mass spectrometers requiring 10.sup.4 ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products.
The earth's trapped radiation belts
NASA Technical Reports Server (NTRS)
Noll, R. B.; Mcelroy, M. B.
1975-01-01
The near-earth charged particle environment is discussed in terms of spacecraft design criteria. Models are presented of the trapped radiation belts and based on in-situ data obtained from spacecraft.
Acoustic trapping of active matter
NASA Astrophysics Data System (ADS)
Takatori, Sho C.; de Dier, Raf; Vermant, Jan; Brady, John F.
2016-03-01
Confinement of living microorganisms and self-propelled particles by an external trap provides a means of analysing the motion and behaviour of active systems. Developing a tweezer with a trapping radius large compared with the swimmers' size and run length has been an experimental challenge, as standard optical traps are too weak. Here we report the novel use of an acoustic tweezer to confine self-propelled particles in two dimensions over distances large compared with the swimmers' run length. We develop a near-harmonic trap to demonstrate the crossover from weak confinement, where the probability density is Boltzmann-like, to strong confinement, where the density is peaked along the perimeter. At high concentrations the swimmers crystallize into a close-packed structure, which subsequently `explodes' as a travelling wave when the tweezer is turned off. The swimmers' confined motion provides a measurement of the swim pressure, a unique mechanical pressure exerted by self-propelled bodies.
Unconventional trapping of ultracold neutrons
NASA Astrophysics Data System (ADS)
Malik, S. S.; Sarkisov, D.; Steyerl, A.; Brenner, Th.; Butterworth, J.; Geltenbort, P.; Hino, M.; Okumura, K.; Utsuro, M.
1999-09-01
In unconventional storage experiments we filled ultracold neutrons (UCN) into a Fomblin-grease coated trap and then immediately removed the UCN from the storage volume by an absorber, until their residual density in the trap was measured to be negligible. When subsequently the absorber was withdrawn a significant number of UCN of higher energies emerged from the trap. Their appearance cannot be attributed to heating or cooling of residual UCN. Further experiments were performed to investigate the origin of these UCN which we call `late UCN'. We noticed that application of a magnetic field gradient at the trap wall as well as a replacement of Fomblin grease on the surface by Fomblin oil gave rise to small but measurable alterations of storage behavior. These phenomena are consistent with the hypothesis of temporary adhesion of a few UCN to a rough wall.
Weakly interacting Bose-Einstein condensates in temperature-dependent generic traps
NASA Astrophysics Data System (ADS)
Castellanos, E.; Briscese, F.; Grether, M.; de Llano, M.
2015-04-01
We study the shift Δ T c in the condensation temperature of an atomic Bose-Einstein condensate trapped in a temperature-dependent three-dimensional generic potential. With no assumptions other than the mean-field approach and the semiclassical approximation, it is shown that the inclusion of a T-dependent trap improves upon the pure semiclassical result giving better agreement between the predicted Δ T c value and its experimental value. However, despite this improvement, the effect of a T-dependent trap is not sufficient to fully reduce the discrepancy between theoretical prediction and data.
NASA Astrophysics Data System (ADS)
Rosa, Barbara L. T.; Marçal, Lucas A. B.; Ribeiro Andrade, Rodrigo; Dornellas Pinto, Luciana; Rodrigues, Wagner N.; Lustoza Souza, Patrícia; Pamplona Pires, Mauricio; Wagner Nunes, Ricardo; Malachias, Angelo
2017-07-01
In this work we attempt to directly observe anisotropic partial relaxation of epitaxial InAs islands using transmission electron microscopy (TEM) and synchrotron x-ray diffraction on a 15 nm thick InAs:GaAs nanomembrane. We show that under such conditions TEM provides improved real-space statistics, allowing the observation of partial relaxation processes that were not previously detected by other techniques or by usual TEM cross section images. Besides the fully coherent and fully relaxed islands that are known to exist above previously established critical thickness, we prove the existence of partially relaxed islands, where incomplete 60° half-loop misfit dislocations lead to a lattice relaxation along one of the <110> directions, keeping a strained lattice in the perpendicular direction. Although individual defects cannot be directly observed, their implications to the resulting island registry are identified and discussed within the frame of half-loops propagations.
Rosa, Barbara L T; Marçal, Lucas A B; Andrade, Rodrigo Ribeiro; Pinto, Luciana Dornellas; Rodrigues, Wagner N; Souza, Patrícia Lustoza; Pires, Mauricio Pamplona; Nunes, Ricardo Wagner; Malachias, Angelo
2017-07-28
In this work we attempt to directly observe anisotropic partial relaxation of epitaxial InAs islands using transmission electron microscopy (TEM) and synchrotron x-ray diffraction on a 15 nm thick InAs:GaAs nanomembrane. We show that under such conditions TEM provides improved real-space statistics, allowing the observation of partial relaxation processes that were not previously detected by other techniques or by usual TEM cross section images. Besides the fully coherent and fully relaxed islands that are known to exist above previously established critical thickness, we prove the existence of partially relaxed islands, where incomplete 60° half-loop misfit dislocations lead to a lattice relaxation along one of the 〈110〉 directions, keeping a strained lattice in the perpendicular direction. Although individual defects cannot be directly observed, their implications to the resulting island registry are identified and discussed within the frame of half-loops propagations.
Ionic Conductivity of Water-Soluble Fully Conjugated Heterocyclic Aromatic Polyelectrolytes
NASA Astrophysics Data System (ADS)
Bai, S. J.; Chen, Y. S.; Sun, J. P.; Dang, T. D.; Arnold, F. E.
2002-03-01
Fully conjugated poly[(1,7-dihydrobenzo[1,2-d:4,5-d']diimidazole-2,6-diyl)- 2-(2-sulfo)-p-phenylene], sPBI, has a para-catenated backbone. This rod-like polymer displays superior thermal and solvent stabilities. The stabilities hamper its processing for critical applications. Chemical derivative of the sPBI was achieved using pendants of propane-sulfonated Li^+ ionomer for a water-soluble polyelectrolyte, sPBI-PS(Li^+). sPBI-PS(Li^+) aqueous solutions were cast into freestanding films. Room-temperature direct current conductivity parallel to the film surface σ _|| was as high as 9.7 x 10-5 S/cm. Constant-voltage measurements indicated that σ _|| was mainly ionic. sPBI-PS(Li^+) doped with Li salts showed a σ _|| of 3 ~8 mS/cm. X-ray scattering revealed that the cast films were in-plane isotropic but out-of-the plane anisotropic with the rigid-rod backbone lying in the plane of the films. The anisotropic structure caused the conductivity transverse to the film surface was 10-3 ~ 10-4 to that of σ _||. Benzene-1,3,5-tricarboxylic acid with functional groups was added in the polycondensation reaction leading to heteroaromatic copolymer with fully conjugated but acticulated backbone. Cast films of the articulated copolymer had three-dimensionally isotropic σ as high as 3 mS/cm.
Computation of Large Anisotropic Seismic Heterogeneities (CLASH)
NASA Astrophysics Data System (ADS)
Beucler, Éric; Montagner, Jean-Paul
2006-05-01
A general tomographic technique is designed in order (i) to operate in anisotropic media; (ii) to account for the uneven seismic sampling and (iii) to handle massive data sets in a reasonable computing time. One modus operandi to compute a 3-D body wave velocity model relies on surface wave phase velocity measurements. An intermediate step, shared by other approaches, consists in translating, for each period of a given mode branch, the phase velocities integrated along ray paths into local velocity perturbations. To this end, we develop a method, which accounts for the azimuthal anisotropy in its comprehensive form. The weakly non-linear forward problem allows to use a conjugate gradient optimization. The Earth's surface is regularly discretized and the partial derivatives are assigned to the individual grid points. Possible lack of lateral resolution, due to the inescapable uneven ray path coverage, is taken into account through the a priori covariances on parameters with laterally variable correlation lengths. This method allows to efficiently separate the 2ψ and the 4ψ anisotropic effects from the isotropic perturbations. Fundamental mode and overtone phase velocity maps, derived with real Rayleigh wave data sets, are presented and compared with previous maps. The isotropic models concur well with the results of Trampert & Woodhouse. Large 4ψ heterogeneities are located in the tectonically active regions and over the continental lithospheres such as North America, Antarctica or Australia. At various periods, a significant 4ψ signature is correlated with the Hawaii hotspot track. Finally, concurring with the conclusions of Trampert & Woodhouse, our phase velocity maps show that Rayleigh wave data sets do need both 2ψ and 4ψ anisotropic terms.
Starkov, Pavel; Moore, Jared T; Duquette, Douglas C; Stoltz, Brian M; Marek, Ilan
2017-07-19
We report a divergent and modular protocol for the preparation of acyclic molecular frameworks containing newly created quaternary carbon stereocenters. Central to this approach is a sequence composed of a (1) regioselective and -retentive preparation of allyloxycarbonyl-trapped fully substituted stereodefined amide enolates and of a (2) enantioselective palladium-catalyzed decarboxylative allylic alkylation reaction using a novel bisphosphine ligand.
Cui, Linyan; Xue, Bindang; Zhou, Fugen
2015-11-16
Theoretical and experimental investigations have shown that the atmospheric turbulence exhibits both anisotropic and non-Kolmogorov properties. In this work, two theoretical atmosphere refractive-index fluctuations spectral models are derived for optical waves propagating through anisotropic non-Kolmogorov atmospheric turbulence. They consider simultaneously the finite turbulence inner and outer scales and the asymmetric property of turbulence eddies in the orthogonal xy-plane throughout the path. Two anisotropy factors which parameterize the asymmetry of turbulence eddies in both horizontal and vertical directions are introduced in the orthogonal xy-plane, so that the circular symmetry assumption of turbulence eddies in the xy-plane is no longer required. Deviations from the classic 11/3 power law behavior in the spectrum model are also allowed by assuming power law value variations between 3 and 4. Based on the derived anisotropic spectral model and the Rytov approximation theory, expressions for the variance of angle of arrival (AOA) fluctuations are derived for optical plane and spherical waves propagating through weak anisotropic non-Kolmogorov turbulence. Calculations are performed to analyze the derived spectral models and the variance of AOA fluctuations.
Simulation study of overtaking of ion-acoustic solitons in the fully kinetic regime
NASA Astrophysics Data System (ADS)
Hosseini Jenab, S. M.; Spanier, F.
2017-03-01
The overtaking collisions of ion-acoustic solitons in the presence of trapping effects of electrons are studied based on a fully kinetic simulation approach. The method is able to provide all the kinetic details of the process alongside the fluid-level quantities self consistently. Solitons are produced naturally by utilizing the chain formation phenomenon, and then are arranged in a new simulation box to test the different scenarios of overtaking collisions. Three achievements are reported here. First, simulations prove the long-time life span of the ion-acoustic solitons in the presence of trapping effect of electrons (kinetic effects), which serves as the benchmark of the simulation code. Second, their stability against overtaking mutual collisions is established by creating collisions between solitons with different number and shapes of trapped electrons, i.e., different trapping parameter. Finally, details of solitons during collisions for both ions and electrons are provided on both fluid and kinetic levels. These results show that on the kinetic level, trapped electron population accompanying each of the solitons are exchanged between the solitons during the collision. Furthermore, the behavior of electron holes accompanying solitons contradicts the theory about the electron holes interaction developed based on kinetic theory. They also show behaviors much different from other electron holes witnessed in processes such as nonlinear Landau damping (Bernstein-Greene-Kruskal -BGK- modes) or beam-plasma interaction (like two-beam instability).
Generalised model for anisotropic compact stars
NASA Astrophysics Data System (ADS)
Maurya, S. K.; Gupta, Y. K.; Ray, Saibal; Deb, Debabrata
2016-12-01
In the present investigation an exact generalised model for anisotropic compact stars of embedding class 1 is sought with a general relativistic background. The generic solutions are verified by exploring different physical aspects, viz. energy conditions, mass-radius relation, stability of the models, in connection to their validity. It is observed that the model presented here for compact stars is compatible with all these physical tests and thus physically acceptable as far as the compact star candidates RXJ 1856-37, SAX J 1808.4-3658 ( SS1) and SAX J 1808.4-3658 ( SS2) are concerned.
Chromo-natural model in anisotropic background
Maleknejad, Azadeh; Erfani, Encieh E-mail: eerfani@ipm.ir
2014-03-01
In this work we study the chromo-natural inflation model in the anisotropic setup. Initiating inflation from Bianchi type-I cosmology, we analyze the system thoroughly during the slow-roll inflation, from both analytical and numerical points of view. We show that the isotropic FRW inflation is an attractor of the system. In other words, anisotropies are damped within few e-folds and the chromo-natural model respects the cosmic no-hair conjecture. Furthermore, we demonstrate that in the slow-roll limit, the anisotropies in both chromo-natural and gauge-flation models share the same dynamics.
Local thermodynamics of a magnetized, anisotropic plasma
Hazeltine, R. D.; Mahajan, S. M.; Morrison, P. J.
2013-02-15
An expression for the internal energy of a fluid element in a weakly coupled, magnetized, anisotropic plasma is derived from first principles. The result is a function of entropy, particle density and magnetic field, and as such plays the role of a thermodynamic potential: it determines in principle all thermodynamic properties of the fluid element. In particular it provides equations of state for the magnetized plasma. The derivation uses familiar fluid equations, a few elements of kinetic theory, the MHD version of Faraday's law, and certain familiar stability and regularity conditions.
Anisotropic thermal expansion of strontium barium niobate
NASA Astrophysics Data System (ADS)
Qadri, Syed B.; Bellotti, Jeffrey A.; Garzarella, Anthony; Wu, Dong Ho
2005-06-01
Strontium barium niobate is a tungsten-bronze ferroelectric crystal having a tetragonal unit cell. Low-temperature x-ray diffraction studies were performed on a single crystal of Sr0.75Ba0.25Nb2O6 to determine the thermal expansivity along the a- and c-axes. Negative thermal expansion was observed along the c direction while a positive thermal expansion was measured along the a axis. The anisotropic thermal expansion behavior is explained as arising due to the geometry of the crystal structure.
Superscattering pattern shaping for radially anisotropic nanowires
NASA Astrophysics Data System (ADS)
Liu, Wei
2017-08-01
We achieve efficient shaping of superscattering by radially anisotropic nanowires relying on resonant multipolar interferences. It is shown that the radial anisotropy of refractive index can be employed to resonantly overlap electric and magnetic multipoles of various orders, and as a result, effective superscattering with different engineered angular patterns can be obtained. We further demonstrate that such superscattering shaping relying on unusual radial anisotropy parameters can be directly realized with isotropic multilayered nanowires, which may shed new light on much fundamental research and various applications related to scattering particles.
Anisotropic Tribological Properties of Silicon Carbide
NASA Technical Reports Server (NTRS)
Miyoshi, K.; Buckley, D. H.
1980-01-01
The anisotropic friction, deformation and fracture behavior of single crystal silicon carbide surfaces were investigated in two categories. The categories were called adhesive and abrasive wear processes, respectively. In the adhesive wear process, the adhesion, friction and wear of silicon carbide were markedly dependent on crystallographic orientation. The force to reestablish the shearing fracture of adhesive bond at the interface between silicon carbide and metal was the lowest in the preferred orientation of silicon carbide slip system. The fracturing of silicon carbide occurred near the adhesive bond to metal and it was due to primary cleavages of both prismatic (10(-1)0) and basal (0001) planes.
Creating an anisotropic plasma resistivity with waves
Fisch, N.J.; Boozer, A.H.
1980-05-01
An anisotropic plasma resistivity may be created by preferential heating of electrons traveling in one direction. This can result in a steady-state toroidal current in a tokamak even in the absence of net wave momentum. In fact, at high wave phase velocities, the current associated with the change in resistivity is greater than that associated with net momentum input. An immediate implication is that other waves, such as electron cyclotron waves, may be competitive with lower-hybrid waves as a means for generating current. An analytical expression is derived for the current generated per power dissipated which agrees remarkably well with numerical calculations.
Watertight Anisotropic Surface Meshing Using Quadrilateral Patches
NASA Technical Reports Server (NTRS)
Haimes, Robert; Aftosmis, Michael J.
2004-01-01
This paper presents a simple technique for generating anisotropic surface triangulations using unstructured quadrilaterals when the CAD entity can be mapped to a logical rectangle. Watertightness and geometric quality measures are maintained and are consistent with the CAPRI default tessellator. These triangulations can match user specified criteria for chord-height tolerance, neighbor triangle dihedral angle, and maximum triangle side length. This discrete representation has hooks back to the owning geometry and therefore can be used in conjunction with these entities to allow for easy enhancement or modification of the tessellation suitable for grid generation or other downstream applications.
Multidimensional Gravitational Model with Anisotropic Pressure
NASA Astrophysics Data System (ADS)
Grigorieva, O. A.; Sharov, G. S.
2013-08-01
We consider the gravitational model with additional spatial dimensions and anisotropic pressure which is nonzero only in these dimensions. Cosmological solutions of the Einstein equations in this model include accelerated expansion of the universe at late stage of its evolution and dynamical compactification of extra dimensions. This model describes observational data for Type Ia supernovae on the level or better than the ΛCDM model. We analyze two equations of state resulting in different predictions for further evolution, but in both variants the acceleration epoch is finite.
Laminated anisotropic reinforced plastic plates and shells
NASA Technical Reports Server (NTRS)
Korolev, V. I.
1981-01-01
Basic technical theories and engineering calculation equations for anisotropic plates and shells made of rigid reinforced plastics, mainly laminated fiberglass, are presented and discussed. Solutions are given for many problems of design of structural plates and shells, including curved sections and tanks, as well as two chapters on selection of the optimum materials, are given. Accounting for interlayer shearing and transverse separation, which are new engineering properties, are discussed. Application of the results obtained to thin three ply plates and shells wth a light elastic filler is presented and discussed.
Staggered Fermion Thermodynamics using Anisotropic Lattices
NASA Astrophysics Data System (ADS)
Levkova, L.
2003-05-01
Numerical simulations of full QCD on anisotropic lattices provide a convenient way to study QCD thermodynamics with fixed physics scales and reduced lattice spacing errors. We report results from calculations with 2-flavors of dynamical fermions where all bare parameters and hence the physics scales are kept constant while the temperature is changed in small steps by varying only the number of the time slices. The results from a series of zero-temperature scale setting simulations are used to determine the Karsch coefficients and the equation of state at finite temperatures.
Multichannel image regularization using anisotropic geodesic filtering
Grazzini, Jacopo A
2010-01-01
This paper extends a recent image-dependent regularization approach introduced in aiming at edge-preserving smoothing. For that purpose, geodesic distances equipped with a Riemannian metric need to be estimated in local neighbourhoods. By deriving an appropriate metric from the gradient structure tensor, the associated geodesic paths are constrained to follow salient features in images. Following, we design a generalized anisotropic geodesic filter; incorporating not only a measure of the edge strength, like in the original method, but also further directional information about the image structures. The proposed filter is particularly efficient at smoothing heterogeneous areas while preserving relevant structures in multichannel images.
Tunable anisotropic thermal conduction in graphane nanoribbons
NASA Astrophysics Data System (ADS)
Li, Dengfeng; Xu, Yong; Chen, Xiaobin; Li, Bolin; Duan, Wenhui
2014-04-01
Graphane and graphene are both two-dimensional materials but of different bonding configurations, which can result in distinct thermal conduction properties. We simulate thermal conduction in graphane nanoribbons (GANRs) using the nonequilibrium Green's function method. We find anisotropic thermal conduction in GANRs, with zigzag GANRs giving higher thermal conductance than armchair ones. Compared to the graphene counterparts, GANRs show lower ballistic thermal conductance and stronger thermal conductance anisotropy. Furthermore, hydrogen vacancies of GANRs considerably suppress thermal conduction, accompanied by enhanced thermal conductance anisotropy. The tunable thermal conduction, realized by controlling the ribbon width, edge shape, and hydrogen vacancy concentration of GANRs, could be useful for thermal management and thermoelectric applications.
Anisotropic fiber alignment in composite structures
Graham, Alan L.; Mondy, Lisa A.; Guell, David C.
1993-01-01
High strength material composite structures are formed with oriented fibers to provide controlled anisotropic fibers. Fibers suspended in non-dilute concentrations (e.g., up to 20 volume percent for fibers having an aspect ratio of 20) in a selected medium are oriented by moving an axially spaced array of elements in the direction of desired fiber alignment. The array elements are generally perpendicular to the desired orientation. The suspension medium may also include sphere-like particles where the resulting material is a ceramic.
Anisotropic bond percolation in two dimensions
NASA Astrophysics Data System (ADS)
Arovas, D.; Bhatt, R. N.; Shapiro, B.
1983-08-01
A new single-parameter renormalization-group equation is formulated for anisotropic bond percolation in two dimensions using a position-space renormalization approach. The new equation yields the exact critical line px+py=1 within both the Migdal-Kadanoff decimation and cell renormalization schemes. For large anisotropy, however, an additional critical line appears leading to a spurious divergence in the correlation-length critical exponent. An alternative scheme, which does not preserve the exact critical surface, but yields a correlation-length exponent relatively independent of anisotropy, is also examined.
Temperature and polarization patterns in anisotropic cosmologies
Sung, Rockhee; Coles, Peter E-mail: Peter.Coles@astro.cf.ac.uk
2011-06-01
We study the coherent temperature and polarization patterns produced in homogeneous but anisotropic cosmological models. We show results for all Bianchi types with a Friedman-Robertson-Walker limit (i.e. Types I, V, VII{sub 0}, VII{sub h} and IX) to illustrate the range of possible behaviour. We discuss the role of spatial curvature, shear and rotation in the geodesic equations for each model and establish some basic results concerning the symmetries of the patterns produced. We also give examples of the time-evolution of these patterns in terms of the Stokes parameters I, Q and U.
Anisotropic elasticity of experimental colloidal Wigner crystals.
Russell, Emily R; Spaepen, Frans; Weitz, David A
2015-03-01
Colloidal particles interacting via a long-range repulsion can, in contrast to hard-sphere systems, exhibit crystalline ordering at low volume fraction. Here we experimentally investigate the structure and properties of such "colloidal Wigner crystals." We find a body-centered-cubic crystalline phase at volume fractions of ϕ≳15%, which exhibits large fluctuations of individual particles from their average positions. We determine the three independent crystalline elastic constants and find that these crystals are very compliant and highly anisotropic.
Simulation of Anisotropic Rock Damage for Geologic Fracturing
NASA Astrophysics Data System (ADS)
Busetti, S.; Xu, H.; Arson, C. F.
2014-12-01
A continuum damage model for differential stress-induced anisotropic crack formation and stiffness degradation is used to study geologic fracturing in rocks. The finite element-based model solves for deformation in the quasi-linear elastic domain and determines the six component damage tensor at each deformation increment. The model permits an isotropic or anisotropic intact or pre-damaged reference state, and the elasticity tensor evolves depending on the stress path. The damage variable, similar to Oda's fabric tensor, grows when the surface energy dissipated by three-dimensional opened cracks exceeds a threshold defined at the appropriate scale of the representative elementary volume (REV). At the laboratory or wellbore scale (<1m) brittle continuum damage reflects microcracking, grain boundary separation, grain crushing, or fine delamination, such as in shale. At outcrop (1m-100m), seismic (10m-1000m), and tectonic (>1000m) scales the damaged REV reflects early natural fracturing (background or tectonic fracturing) or shear strain localization (fault process zone, fault-tip damage, etc.). The numerical model was recently benchmarked against triaxial stress-strain data from laboratory rock mechanics tests. However, the utility of the model to predict geologic fabric such as natural fracturing in hydrocarbon reservoirs was not fully explored. To test the ability of the model to predict geological fracturing, finite element simulations (Abaqus) of common geologic scenarios with known fracture patterns (borehole pressurization, folding, faulting) are simulated and the modeled damage tensor is compared against physical fracture observations. Simulated damage anisotropy is similar to that derived using fractured rock-mass upscaling techniques for pre-determined fracture patterns. This suggests that if model parameters are constrained with local data (e.g., lab, wellbore, or reservoir domain), forward modeling could be used to predict mechanical fabric at the relevant
Science, conservation, and camera traps
Nichols, James D.; Karanth, K. Ullas; O'Connel, Allan F.; O'Connell, Allan F.; Nichols, James D.; Karanth, K. Ullas
2011-01-01
Biologists commonly perceive camera traps as a new tool that enables them to enter the hitherto secret world of wild animals. Camera traps are being used in a wide range of studies dealing with animal ecology, behavior, and conservation. Our intention in this volume is not to simply present the various uses of camera traps, but to focus on their use in the conduct of science and conservation. In this chapter, we provide an overview of these two broad classes of endeavor and sketch the manner in which camera traps are likely to be able to contribute to them. Our main point here is that neither photographs of individual animals, nor detection history data, nor parameter estimates generated from detection histories are the ultimate objective of a camera trap study directed at either science or management. Instead, the ultimate objectives are best viewed as either gaining an understanding of how ecological systems work (science) or trying to make wise decisions that move systems from less desirable to more desirable states (conservation, management). Therefore, we briefly describe here basic approaches to science and management, emphasizing the role of field data and associated analyses in these processes. We provide examples of ways in which camera trap data can inform science and management.
Trapping ions and atoms optically
NASA Astrophysics Data System (ADS)
Schaetz, Tobias
2017-05-01
Isolating neutral and charged particles from the environment is essential in precision experiments. For decades, this has been achieved by trapping ions with radio-frequency (RF) fields and neutral particles with optical fields. Recently, the trapping of ions by interaction with light has been demonstrated. This might permit the advantages of optical trapping and ions to be combined. For example, we would benefit from superimposing optical traps to investigate ensembles of ions and atoms in the absence of any RF fields and from the versatile and scalable trapping geometries featured by optical lattices. In particular, ions provide individual addressability, and electronic and motional degrees of freedom that can be coherently controlled and detected via high-fidelity, state-dependent operations. Their long-range Coulomb interaction is significantly larger compared to those of neutral atoms and molecules. This enables ultra-cold interaction and the chemistry of trapped ions and atoms to be studied, as well as providing a novel platform for higher-dimensional experimental quantum simulations. The aim of this topical review is to present the current state of the art and to discuss the current challenges and prospects of the emerging field.
Federal Register 2010, 2011, 2012, 2013, 2014
2011-06-21
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Fully Depleted Charge-Coupled Devices
Holland, Stephen E.
2006-05-15
We have developed fully depleted, back-illuminated CCDs thatbuild upon earlier research and development efforts directed towardstechnology development of silicon-strip detectors used inhigh-energy-physics experiments. The CCDs are fabricated on the same typeof high-resistivity, float-zone-refined silicon that is used for stripdetectors. The use of high-resistivity substrates allows for thickdepletion regions, on the order of 200-300 um, with corresponding highdetection efficiency for near-infrared andsoft x-ray photons. We comparethe fully depleted CCD to thep-i-n diode upon which it is based, anddescribe the use of fully depleted CCDs in astronomical and x-ray imagingapplications.
Control of anisotropic interactions with microwaves in ultracold NaK molecules
NASA Astrophysics Data System (ADS)
Yan, Zoe; Loh, Huanqian; Park, Jee Woo; Will, Sebastian; Zwierlein, Martin
2016-05-01
Ultracold polar molecules offer long range anisotropic interactions, which can provide access to novel phases of condensed matter physics. The recent creation of fermionic NaK polar molecules in the ground hyperfine-rovibronic state, which is chemically stable, demonstrates an important step towards the study of new dipolar physics. To engineer dipolar interactions between molecules with large electric dipole moments, one can apply microwaves to mix the lowest and first excited rotational states. Hyperfine interaction in the first excited rotational state mixes nuclear spin and rotation, leading to states with rich character, which we map out by performing microwave spectroscopy. The admixed hyperfine character serves as a tool to engineer wide ranges of ``magic'' trap polarization angles, at which the lowest and first excited rotational states have matching polarizabilities. Finally, we demonstrate that we can access large dipole moments by coherently dressing the molecules with microwaves.
Anomalous anisotropic exciton temperature dependence in rutile TiO2
NASA Astrophysics Data System (ADS)
Baldini, Edoardo; Dominguez, Adriel; Chiodo, Letizia; Sheveleva, Evgeniia; Yazdi-Rizi, Meghdad; Bernhard, Christian; Rubio, Angel; Chergui, Majed
2017-07-01
Elucidating the details of electron-phonon coupling in semiconductors and insulators is a topic of pivotal interest, as it governs the transport mechanisms and is responsible for various phenomena such as spectral-weight transfers to phonon sidebands and self-trapping. Here, we investigate the influence of the electron-phonon interaction on the excitonic peaks of rutile TiO2, revealing a strong anisotropic polarization dependence with increasing temperature, namely, an anomalous blue shift for light polarized along the a axis and a conventional red shift for light polarized along the c axis. By employing many-body perturbation theory, we identify two terms in the electron-phonon interaction Hamiltonian that contribute to the anomalous blue shift of the a -axis exciton. Our approach paves the way to a complete ab initio treatment of the electron-phonon interaction and of its influence on the optical spectra of polar materials.
High-voltage-compatible, fully depleted CCDs
Holland, Stephen E.; Bebek, Chris J.; Dawson, Kyle S.; Emes, JohnE.; Fabricius, Max H.; Fairfield, Jessaym A.; Groom, Don E.; Karcher, A.; Kolbe, William F.; Palaio, Nick P.; Roe, Natalie A.; Wang, Guobin
2006-05-15
We describe charge-coupled device (CCD) developmentactivities at the Lawrence Berkeley National Laboratory (LBNL).Back-illuminated CCDs fabricated on 200-300 mu m thick, fully depleted,high-resistivity silicon substrates are produced in partnership with acommercial CCD foundry.The CCDs are fully depleted by the application ofa substrate bias voltage. Spatial resolution considerations requireoperation of thick, fully depleted CCDs at high substrate bias voltages.We have developed CCDs that are compatible with substrate bias voltagesof at least 200V. This improves spatial resolution for a given thickness,and allows for full depletion of thicker CCDs than previously considered.We have demonstrated full depletion of 650-675 mu m thick CCDs, withpotential applications in direct x-ray detection. In this work we discussthe issues related to high-voltage operation of fully depleted CCDs, aswell as experimental results on high-voltage-compatible CCDs.
Improvements on a Reliable Oak Seed Trap
Carl N. Phillips; Marianne K. Burke; Thomas B. Hunnicutt
1995-01-01
The need for seed trap longevity, capture of heavy seed, and protection from predation in several forest types for long-term studies of seed production prompted seed trap design improvements. Critical improvements were achieved by painting the trap with a latex exterior gloss house paint, raising traps above water lines in areas tbat flooded, and enclosing the seed...
An effective box trap for capturing lynx
Jay A. Kolbe; John R. Squires; Thomas W. Parker
2003-01-01
We designed a box trap for capturing lynx (Lynx lynx) that is lightweight, safe, effective, and less expensive than many commercial models. It can be constructed in approximately 3-4 hours from readily available materials. We used this trap to capture 40 lynx 89 times (96% of lynx entering traps) and observed no trapping related injuries. We compare our box...
50 CFR 31.16 - Trapping program.
Code of Federal Regulations, 2011 CFR
2011-10-01
... Disposal § 31.16 Trapping program. Except as hereafter noted, persons trapping animals on wildlife refuge areas where trapping has been authorized shall secure and comply with the provisions of a Federal permit... 50 Wildlife and Fisheries 8 2011-10-01 2011-10-01 false Trapping program. 31.16 Section 31.16...
Effects of oxide traps, interface traps, and border traps'' on metal-oxide-semiconductor devices
Fleetwood, D.M.; Winokur, P.S.; Reber, R.A. Jr.; Meisenheimer, T.L.; Schwank, J.R.; Shaneyfelt, M.R.; Riewe, L.C. )
1993-05-15
We have identified several features of the 1/[ital f] noise and radiation response of metal-oxide-semiconductor (MOS) devices that are difficult to explain with standard defect models. To address this issue, and in response to ambiguities in the literature, we have developed a revised nomenclature for defects in MOS devices that clearly distinguishes the language used to describe the physical location of defects from that used to describe their electrical response. In this nomenclature, oxide traps'' are simply defects in the SiO[sub 2] layer of the MOS structure, and interface traps'' are defects at the Si/SiO[sub 2] interface. Nothing is presumed about how either type of defect communicates with the underlying Si. Electrically, fixed states'' are defined as trap levels that do not communicate with the Si on the time scale of the measurements, but switching states'' can exchange charge with the Si. Fixed states presumably are oxide traps in most types of measurements, but switching states can either be interface traps or near-interfacial oxide traps that can communicate with the Si, i.e., border traps'' [D. M. Fleetwood, IEEE Trans. Nucl. Sci. [bold NS]-[bold 39], 269 (1992)]. The effective density of border traps depends on the time scale and bias conditions of the measurements. We show the revised nomenclature can provide focus to discussions of the buildup and annealing of radiation-induced charge in non-radiation-hardened MOS transistors, and to changes in the 1/[ital f] noise of MOS devices through irradiation and elevated-temperature annealing.
Building an anisotropic meniscus with zonal variations.
Higashioka, Michael M; Chen, Justin A; Hu, Jerry C; Athanasiou, Kyriacos A
2014-01-01
Toward addressing the difficult problems of knee meniscus regeneration, a self-assembling process has been used to re-create the native morphology and matrix properties. A significant problem in such attempts is the recapitulation of the distinct zones of the meniscus, the inner, more cartilaginous and the outer, more fibrocartilaginous zones. In this study, an anisotropic and zonally variant meniscus was produced by self-assembly of the inner meniscus (100% chondrocytes) followed by cell seeding the outer meniscus (coculture of chondrocytes and meniscus cells). After 4 weeks in culture, the engineered, inner meniscus exhibited a 42% increase in both instantaneous and relaxation moduli and a 62% increase in GAG/DW, as compared to the outer meniscus. In contrast, the circumferential tensile modulus and collagen/DW of the outer zone was 101% and 129% higher, respectively, than the values measured for the inner zone. Furthermore, there was no difference in the radial tensile modulus between the control and zonal engineered menisci, suggesting that the inner and outer zones of the engineered zonal menisci successfully integrated. These data demonstrate that not only can biomechanical and biochemical properties be engineered to differ by the zone, but they can also recapitulate the anisotropic behavior of the knee meniscus.
Dynamic Smagorinsky model on anisotropic grids
NASA Technical Reports Server (NTRS)
Scotti, A.; Meneveau, C.; Fatica, M.
1996-01-01
Large Eddy Simulation (LES) of complex-geometry flows often involves highly anisotropic meshes. To examine the performance of the dynamic Smagorinsky model in a controlled fashion on such grids, simulations of forced isotropic turbulence are performed using highly anisotropic discretizations. The resulting model coefficients are compared with a theoretical prediction (Scotti et al., 1993). Two extreme cases are considered: pancake-like grids, for which two directions are poorly resolved compared to the third, and pencil-like grids, where one direction is poorly resolved when compared to the other two. For pancake-like grids the dynamic model yields the results expected from the theory (increasing coefficient with increasing aspect ratio), whereas for pencil-like grids the dynamic model does not agree with the theoretical prediction (with detrimental effects only on smallest resolved scales). A possible explanation of the departure is attempted, and it is shown that the problem may be circumvented by using an isotropic test-filter at larger scales. Overall, all models considered give good large-scale results, confirming the general robustness of the dynamic and eddy-viscosity models. But in all cases, the predictions were poor for scales smaller than that of the worst resolved direction.
New formulation of leading order anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Tinti, Leonardo
2015-05-01
Anisotropic hydrodynamics is a reorganization of the relativistic hydrodynamics expansion, with the leading order already containing substantial momentum-space anisotropies. The latter are a cause of concern in the traditional viscous hydrodynamics, since large momentum anisotropies generated in ultrarelativistic heavy-ion collisions are not consistent with the hypothesis of small deviations from an isotropic background, i.e., from the local equilibrium distribution. We discuss the leading order of the expansion, presenting a new formulation for the (1+1)- dimensional case, namely, for the longitudinally boost invariant and cylindrically symmetric flow. This new approach is consistent with the well established framework of Israel and Stewart in the close to equilibrium limit (where we expect viscous hydrodynamics to work well). If we consider the (0+1)-dimensional case, that is, transversally homogeneous and longitudinally boost invariant flow, the new form of anisotropic hydrodynamics leads to better agreement with known solutions of the Boltzmann equation than the previous formulations, especially when we consider massive particles.
Radial stability of anisotropic strange quark stars
NASA Astrophysics Data System (ADS)
Arbañil, José D. V.; Malheiro, M.
2016-11-01
The influence of the anisotropy in the equilibrium and stability of strange stars is investigated through the numerical solution of the hydrostatic equilibrium equation and the radial oscillation equation, both modified from their original version to include this effect. The strange matter inside the quark stars is described by the MIT bag model equation of state. For the anisotropy two different kinds of local anisotropic σ = pt-pr are considered, where pt and pr are respectively the tangential and the radial pressure: one that is null at the star's surface defined by pr(R) = 0, and one that is nonnull at the surface, namely, σs = 0 and σs ≠ 0. In the case σs = 0, the maximum mass value and the zero frequency of oscillation are found at the same central energy density, indicating that the maximum mass marks the onset of the instability. For the case σs ≠ 0, we show that the maximum mass point and the zero frequency of oscillation coincide in the same central energy density value only in a sequence of equilibrium configurations with the same value of σs. Thus, the stability star regions are determined always by the condition dM/dρc > 0 only when the tangential pressure is maintained fixed at the star surface's pt(R). These results are also quite important to analyze the stability of other anisotropic compact objects such as neutron stars, boson stars and gravastars.
Gravothermal catastrophe in anisotropic spherical systems
NASA Astrophysics Data System (ADS)
Magliocchetti, Manuela; Pucacco, Giuseppe; Vesperini, Enrico
1998-11-01
In this paper we investigate the gravothermal instability of spherical stellar systems endowed with a radially anisotropic velocity distribution. We focus our attention on the effects of anisotropy on the conditions for the onset of instability and in particular we study the dependence of the spatial structure of critical models on the amount of anisotropy present in a system. The investigation has been carried out by the method of linear series which has already been used in the past to study the gravothermal instability of isotropic systems._ We consider models described by King, Wilson and Woolley-Dickens distribution functions. In the case of King and Woolley-Dickens models, our results show that, for quite a wide range of the amount of anisotropy in the system, the critical value of the concentration of the system (defined as the ratio of the tidal to the King core radius of the system) is approximately constant and equal to the corresponding value for isotropic systems. Only for very anisotropic systems does the critical value of the concentration start to change and it decreases significantly as the anisotropy increases and penetrates the inner parts of the system. For Wilson models the decrease of the concentration of critical models is preceded by an intermediate regime in which critical concentration increases, reaches a maximum and then starts to decrease. The critical value of the central potential always decreases as the anisotropy increases.
Anisotropic polyvinyl alcohol hydrogel for cardiovascular applications.
Millon, L E; Mohammadi, H; Wan, W K
2006-11-01
Polyvinyl alcohol (PVA) is a hydrophilic polymer with various characteristics desired for biomedical applications and can be transformed into a solid hydrogel by physical crosslinking, using a low-temperature thermal cycling process. As with most polymeric materials, the mechanical properties of the resultant PVA are isotropic, as oppose to most soft tissues, which are anisotropic. The objective of this research is to develop a PVA-based hydrogel that not only mimics the nonlinear mechanical properties displayed by cardiovascular tissues, but also their anisotropic behavior. By applying a controlled strain to the PVA samples, while undergoing low-temperature thermal cycling, we were able to create oriented mechanical properties in PVA hydrogels. The oriented stress-strain properties of porcine aorta were matched simultaneously by a PVA hydrogel prepared (10% PVA, cycle 3, 75% initial strain). This novel technique allows the controlled introduction of anisotropy to PVA hydrogel, and gives a broad range of control of its mechanical properties, for specific medical device applications. (c) 2006 Wiley Periodicals, Inc.
Shear waves in acoustic anisotropic media
Grechka, Vladimir; Zhang, Linbin; Rector, James W.
2003-01-02
Acoustic transversely isotropic (TI) media are defined by artificially setting the shear-wave velocity in the direction of symmetry axis, VS0, to zero. Contrary to conventional wisdom that equating VS0 = 0 eliminates shear waves, we demonstrate their presence and examine their properties. Specifically, we show that SV-waves generally have finite nonzero phase and group velocities in acoustic TI media. In fact, these waves have been observed in full waveform modeling, but apparently they were not understood and labeled as numerical artifacts. Acoustic TI media are characterized by extreme, in some sense infinite strength of anisotropy. It makes the following unusual wave phenomena possible: (1) there are propagation directions, where the SV-ray is orthogonal to the corresponding wavefront normal, (2) the SV-wave whose ray propagates along the symmetry axis is polarized parallel to the P-wave propagating in the same direction, (3) P-wave singularities, that is, directions where P- and SV -wave phase velocities coincide might exist in acoustic TI media. We also briefly discuss some aspects of wave propagation in low-symmetry acoustic anisotropic models. Extreme anisotropy in those media creates bizarre phase- and group-velocity surfaces that might bring intellectual delight to an anisotropic guru.
Finite-difference schemes for anisotropic diffusion
Es, Bram van; Koren, Barry; Blank, Hugo J. de
2014-09-01
In fusion plasmas diffusion tensors are extremely anisotropic due to the high temperature and large magnetic field strength. This causes diffusion, heat conduction, and viscous momentum loss, to effectively be aligned with the magnetic field lines. This alignment leads to different values for the respective diffusive coefficients in the magnetic field direction and in the perpendicular direction, to the extent that heat diffusion coefficients can be up to 10{sup 12} times larger in the parallel direction than in the perpendicular direction. This anisotropy puts stringent requirements on the numerical methods used to approximate the MHD-equations since any misalignment of the grid may cause the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. Currently the common approach is to apply magnetic field-aligned coordinates, an approach that automatically takes care of the directionality of the diffusive coefficients. This approach runs into problems at x-points and at points where there is magnetic re-connection, since this causes local non-alignment. It is therefore useful to consider numerical schemes that are tolerant to the misalignment of the grid with the magnetic field lines, both to improve existing methods and to help open the possibility of applying regular non-aligned grids. To investigate this, in this paper several discretization schemes are developed and applied to the anisotropic heat diffusion equation on a non-aligned grid.
Anisotropic hydraulic permeability in compressed articular cartilage.
Reynaud, Boris; Quinn, Thomas M
2006-01-01
The extent to which articular cartilage hydraulic permeability is anisotropic is largely unknown, despite its importance for understanding mechanisms of joint lubrication, load bearing, transport phenomena, and mechanotransduction. We developed and applied new techniques for the direct measurement of hydraulic permeability within statically compressed adult bovine cartilage explant disks, dissected such that disk axes were perpendicular to the articular surface. Applied pressure gradients were kept small to minimize flow-induced matrix compaction, and fluid outflows were measured by observation of a meniscus in a glass capillary under a microscope. Explant disk geometry under radially unconfined axial compression was measured by direct microscopic observation. Pressure, flow, and geometry data were input to a finite element model where hydraulic permeabilities in the disk axial and radial directions were determined. At less than 10% static compression, near free-swelling conditions, hydraulic permeability was nearly isotropic, with values corresponding to those of previous studies. With increasing static compression, hydraulic permeability decreased, but the radially directed permeability decreased more dramatically than the axially directed permeability such that strong anisotropy (a 10-fold difference between axial and radial directions) in the hydraulic permeability tensor was evident for static compression of 20-40%. Results correspond well with predictions of a previous microstructurally-based model for effects of tissue mechanical deformations on glycosaminoglycan architecture and cartilage hydraulic permeability. Findings inform understanding of structure-function relationships in cartilage matrix, and suggest several biomechanical roles for compression-induced anisotropic hydraulic permeability in articular cartilage.
Sheet Metal Formability Analysis for Anisotropic Materials
NASA Astrophysics Data System (ADS)
Stoughton, Thomas B.; Yoon, Jeong Whan
2004-06-01
Sheet metal formability is conventionally assessed in a two dimensional plot of principal strains or stresses in comparison to a forming limit curve. This method implicitly assumes that the forming limit is isotropic in the plane of the sheet, an assumption that is intrinsically inconsistent with the use of material models that are anisotropic. Since the trend today is to utilize models with full anisotropy in order to more accurately capture the physics of material behavior, the issue of anisotropy of forming limits must also be addressed. The challenge is that the forming limit is no longer defined by a curve but requires the definition of a surface in strain or stress space, and therefore it is no longer appropriate to view these limits with the convenience of the conventional two dimensional diagrams. Furthermore, recent developments in the characterization of sheet forming limits under nonproportional loading suggest that is advantageous to view forming limit behavior in terms of stresses rather than strains, a view that is adopted in this paper. A solution to the challenge of assessing formability for an anisotropic material is proposed and illustrated using an analysis of the 2-Stage Forming Benchmark highlighted in the Numisheet '99 Conference.
Anisotropic swelling behavior of the cornea.
Matsuura, Toyoaki; Ikeda, Hitoe; Idota, Naokazu; Motokawa, Ryuhei; Hara, Yoshiaki; Annaka, Masahiko
2009-12-24
The phase equilibrium property and structural and dynamical properties of pig cornea were studied by macroscopic observation of swelling behavior, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) under various conditions. It was found that the corneal gel collapses into a compact state isotropically or anisotropically depending on the external conditions. The corneal gel collapses uniformly into a compact state at a temperature above 55 degrees C because of the denaturation of collagen, whereas it collapses along an axis parallel to the optic axis with increasing NaCl concentration. Anisotropic deswelling was also observed during desiccation. SAXS measurements revealed that the periodicity of the collagen fiber of the cornea does not change even at higher NaCl concentration, which indicates that hydration and dehydration resulting from changes in salt concentration simply cause swelling and deswelling of the glycosaminoglycan (GAG), which is located between the regular two-dimensional lattices of collagen fibers, which obliges the change in thickness. From observations of the dynamics of light scattered by the corneal gel, intensity autocorrelation functions that revealed two independent diffusion coefficients were obtained. Divergent behavior in the measured total scattered light intensities and diffusion coefficients with varying temperature was observed. That is, a slowing of the dynamic modes accompanied by increased "static" scattered intensities was observed. This is indicative of the occurrence of a phase transition as a function of temperature.
Anisotropic diffusion phantoms based on microcapillaries
NASA Astrophysics Data System (ADS)
Vellmer, Sebastian; Edelhoff, Daniel; Suter, Dieter; Maximov, Ivan I.
2017-06-01
Diffusion MRI is an efficient and widely used technique for the investigation of tissue structure and organisation in vivo. Multiple phenomenological and biophysical diffusion models are intensively exploited for the analysis of the diffusion experiments. However, the verification of the applied diffusion models remains challenging. In order to provide a ;gold standard; and to assess the accuracy of the derived parameters and the limitations of the diffusion models, anisotropic diffusion phantoms with well known architecture are demanded. In the present work we built four anisotropic diffusion phantoms consisting of hollow microcapillaries with very small inner diameters of 5, 10 and 20 μ m and outer diameters of 90 and 150 μ m. For testing the suitability of these phantoms, we performed diffusion measurements on all of them and evaluated the resulting data with a set of popular diffusion models, such as diffusion tensor and diffusion kurtosis imaging, a two compartment model with intra- and extra-capillary water spaces using bi-exponential fitting, and time-dependent diffusion coefficients in Mitra's limit. The perspectives and limitations of these diffusion phantoms are presented and discussed.
Automated fully-stressed design with NASTRAN
NASA Technical Reports Server (NTRS)
Wallerstein, D. V.; Haggenmacher, G. W.
1976-01-01
An automated strength sizing capability is described. The technique determines the distribution of material among the elements of a structural model. The sizing is based on either a fully stressed design or a scaled feasible fully stressed design. Results obtained from the application of the strength sizing to the structural sizing of a composite material wing box using material strength allowables are presented. These results demonstrate the rapid convergence of the structural sizes to a usable design.
Progress in Fully Automated Abdominal CT Interpretation
Summers, Ronald M.
2016-01-01
OBJECTIVE Automated analysis of abdominal CT has advanced markedly over just the last few years. Fully automated assessment of organs, lymph nodes, adipose tissue, muscle, bowel, spine, and tumors are some examples where tremendous progress has been made. Computer-aided detection of lesions has also improved dramatically. CONCLUSION This article reviews the progress and provides insights into what is in store in the near future for automated analysis for abdominal CT, ultimately leading to fully automated interpretation. PMID:27101207
Universal collisional activation ion trap mass spectrometry
McLuckey, S.A.; Goeringer, D.E.; Glish, G.L.
1993-04-27
A universal collisional activation ion trap comprises an ion trapping means containing a bath gas and having connected thereto a noise signal generator. A method of operating a universal collisional activation ion trap comprises the steps of: providing an ion trapping means; introducing into the ion trapping means a bath gas; and, generating a noise signal within the ion trapping means; introducing into the ion trapping means a substance that, when acted upon by the noise signal, undergoes collisional activation to form product ions.
Universal collisional activation ion trap mass spectrometry
McLuckey, Scott A.; Goeringer, Douglas E.; Glish, Gary L.
1993-01-01
A universal collisional activation ion trap comprises an ion trapping means containing a bath gas and having connected thereto a noise signal generator. A method of operating a universal collisional activation ion trap comprises the steps of: providing an ion trapping means; introducing into the ion trapping means a bath gas; and, generating a noise signal within the ion trapping means; introducing into the ion trapping means a substance that, when acted upon by the noise signal, undergoes collisional activation to form product ions.
Microinstrument gradient-force optical trap.
Collins, S D; Baskin, R J; Howitt, D G
1999-10-01
A micromachined fiber-optic trap is presented. The trap consists of four single-mode, 1064-nm optical intersection. The beam fibers mounted in a micromachined silicon and glass housing. Micromachining provides the necessary precision to align the four optical fibers so that the outputs have a common intersection forms a strong three-dimensional gradient-force trap with trapping forces comparable with that of optical tweezers. Characterization of the multibeam fiber trap is illustrated for capture of polystyrene microspheres, computer simulations of the trap stiffness, and experimental determination of the trapping forces.
Anisotropic superfluidity in a dipolar Bose gas
Ticknor, Christopher; Wilson, Ryan M; Bohn, John L
2010-11-04
so that the in-plane interaction is anisotropic. By induding repulsive contact interactions to ensure a stable system, we perform direct numeric simulations of an obstacle moving through the system in directions parallel and perpendicular to the tilt of the dipoles. We observe a distinct anisotropic superfluid response in these cases, both for dissipation into quasipartides and topological excitations (vortices), in the form of an anisotropic critical velocity that is larger in the direction of the dipole tilt than in the perpendicular direction. Interestingly, we find that, while the roton displays an anisotropic character, the speed of sound in the systrm is isotropic. Thus, we characterize the DBEC as an fmisotropic superfluid while illuminating the crucial role that the roton plays in this anisotropic behavior.
Anisotropic artificial substrates for microwave applications
NASA Astrophysics Data System (ADS)
Shahvarpour, Attieh
The perfect electromagnetic conductor (PEMC) boundary is a novel fundamental electromagnetic concept. It is a generalized description of the electromagnetic boundary conditions including the perfect electric conductor (PEC) and the perfect magnetic conductor (PMC) and due to its fundamental properties, it has the potential of enabling several electromagnetic applications. However, the PEMC boundaries concept had remained at the theoretical level and has not been practically realized. Therefore, motivated by the importance of this electromagnetic fundamental concept and its potential applications, the first contribution of this thesis is focused on the practical implementation of the PEMC boundaries by exploiting Faraday rotation principle and ground reflection in the ferrite materials which are intrinsically anisotropic. As a result, this thesis reports the first practical approach for the realization of PEMC boundaries. A generalized scattering matrix (GSM) is used for the analysis of the grounded-ferrite PEMC boundaries structure. As an application of the PEMC boundaries, a transverse electromagnetic (TEM) waveguide is experimentally demonstrated using grounded ferrite PMC (as particular case of the PEMC boundaries) side walls. Perfect electromagnetic conductor boundaries may find applications in various types of sensors, reflectors, polarization convertors and polarization-based radio frequency identifiers. Leaky-wave antennas perform as high directivity and frequency beam scanning antennas and as a result they enable applications in radar, point-to-point communications and MIMO systems. The second contribution of this thesis is introducing and analysing a novel broadband and highly directive two-dimensional leaky-wave antenna. This antenna operates differently in the lower and higher frequency ranges. Toward its lower frequencies, it allows full-space conical-beam scanning while at higher frequencies, it provides fixed-beam radiation (at a designable angle
Effect of bait in live trapping Peromyscus
Stickel, L.F.
1948-01-01
SUMMARY: Evidence from live trapping tests indicated that Peromyscus leucopus did not leave their home ranges because of the attraction of trap bait in nearby areas. A trap line down the center of a heavily live-trapped area caught as many mice before the area trapping as afterward. Thus, there was reason to believe that the area trapping did not serve to pre-bait the mice. Two unbaited lines of live traps caught an equal number of Peromyscus. When one line was baited with rolled oats and peanut butter the efficiency of the traps was improved to the extent that the baited line captured more than twice as many mice as the unbaited line. It is concluded that for the species and habitat tested it is safe to make population calculations based on the assumption that the animals remain within their home ranges and do not tend to move into the trapped area because of the attraction of the trap bait.
Live trapping of hawks and owls
Stewart, R.E.; Cope, J.B.; Robbins, C.S.
1945-01-01
1. Hawks of six species (80 individuals) and owls of five species (37 individuals) were trapped for banding from November 1, 1943, to. May 26,1944. 2. In general, pole traps proved better than hand-operated traps or automatic traps using live bait. 3. Verbail pole traps proved very efficient, and were much more humane than padded steel traps because they rarely injured a captured bird. 4: Unbaited Verbail traps took a variety of raptors, in rough proportion to their local abundance, although slightly more of beneficial species were caught than of harmful types. 5. Hawks and owls were retrapped more readily in Verbail traps than in other types tried. 6. The number of song birds caught in Verbail traps was negligible. 7. Crows and vultures were not taken in Verbail traps, but possibly could be caught with bait.
Holographic Wilson loops in anisotropic quark-gluon plasma.
NASA Astrophysics Data System (ADS)
Ageev, Dmitry
2016-10-01
The nonequilibrium properties of the anisotropic quark-gluon plasma are condidered from the holographic viewpoint. Lifshitz-like solution is considered as a holographic dual of anisotropic QGP. The black brane formation in such background is considered as a thermalization in dual theory. As a probe of thermalization we consider rectangular spatial Wilson loops with different orientation.
Method for anisotropic etching in the manufacture of semiconductor devices
Koontz, Steven L.; Cross, Jon B.
1993-01-01
Hydrocarbon polymer coatings used in microelectronic manufacturing processes are anisotropically etched by atomic oxygen beams (translational energies of 0.2-20 eV, preferably 1-10 eV). Etching with hyperthermal (kinetic energy>1 eV) oxygen atom species obtains highly anisotropic etching with sharp boundaries between etched and mask-protected areas.
Anisotropic microporous supports impregnated with polymeric ion-exchange materials
Friesen, Dwayne; Babcock, Walter C.; Tuttle, Mark
1985-05-07
Novel ion-exchange media are disclosed, the media comprising polymeric anisotropic microporous supports containing polymeric ion-exchange or ion-complexing materials. The supports are anisotropic, having small exterior pores and larger interior pores, and are preferably in the form of beads, fibers and sheets.
Anisotropic microporous supports impregnated with polymeric ion-exchange materials
Friesen, D.; Babcock, W.C.; Tuttle, M.
1985-05-07
Novel ion-exchange media are disclosed, the media comprising polymeric anisotropic microporous supports containing polymeric ion-exchange or ion-complexing materials. The supports are anisotropic, having small exterior pores and larger interior pores, and are preferably in the form of beads, fibers and sheets. 5 figs.
Optical isotropy at terahertz frequencies using anisotropic metamaterials
NASA Astrophysics Data System (ADS)
Lee, In-Sung; Sohn, Ik-Bu; Kang, Chul; Kee, Chul-Sik; Yang, Jin-Kyu; Lee, Joong Wook
2016-07-01
We demonstrate optically isotropic filters in the terahertz (THz) frequency range using structurally anisotropic metamaterials. The proposed metamaterials with two-dimensional arrangements of anisotropic H-shaped apertures show polarization-independent transmission due to the combined effects of the dipole resonances of resonators and antennas. Our results may offer the potential for the design and realization of versatile THz devices and systems.
Behavioral analysis of anisotropic diffusion in image processing.
You, Y L; Xu, W; Tannenbaum, A; Kaveh, M
1996-01-01
In this paper, we analyze the behavior of the anisotropic diffusion model of Perona and Malik (1990). The main idea is to express the anisotropic diffusion equation as coming from a certain optimization problem, so its behavior can be analyzed based on the shape of the corresponding energy surface. We show that anisotropic diffusion is the steepest descent method for solving an energy minimization problem. It is demonstrated that an anisotropic diffusion is well posed when there exists a unique global minimum for the energy functional and that the ill posedness of a certain anisotropic diffusion is caused by the fact that its energy functional has an infinite number of global minima that are dense in the image space. We give a sufficient condition for an anisotropic diffusion to be well posed and a sufficient and necessary condition for it to be ill posed due to the dense global minima. The mechanism of smoothing and edge enhancement of anisotropic diffusion is illustrated through a particular orthogonal decomposition of the diffusion operator into two parts: one that diffuses tangentially to the edges and therefore acts as an anisotropic smoothing operator, and the other that flows normally to the edges and thus acts as an enhancement operator.
Symmetric periodic solutions of the anisotropic Manev problem
NASA Astrophysics Data System (ADS)
Santoprete, Manuele
2002-06-01
We consider the Manev potential in an anisotropic space, i.e., such that the force acts differently in each direction. Using a generalization of the Poincaré continuation method we study the existence of periodic solutions for weak anisotropy. In particular we find that the symmetric periodic orbits of the Manev system are perturbed to periodic orbits in the anisotropic problem.
Method for anisotropic etching in the manufacture of semiconductor devices
NASA Technical Reports Server (NTRS)
Koontz, Steven L. (Inventor); Cross, Jon B. (Inventor)
1993-01-01
Hydrocarbon polymer coatings used in microelectronic manufacturing processes are anisotropically etched by hyperthermal atomic oxygen beams (translational energies of 0.2 to 20 eV, preferably 1 to 10 eV). Etching with hyperthermal oxygen atom species obtains highly anisotropic etching with sharp boundaries between etched and mask protected areas.
Sengupta, Kishore; Abdel-Hamid, Tarek K; Van Wassenhove, Luk N
2008-02-01
When companies put seasoned managers in charge of important projects, they don't expect missed deadlines, budget overruns, and rampant defects. However, that's what researchers found when they tested hundreds of experienced project managers with computer games that simulated software development projects. The study, conducted by two professors from Insead and one from Naval Postgraduate School, strongly suggests that veterans in complex environments suffer a breakdown in the learning process. The research reveals three reasons for the breakdowns: Time lags between causes and effects make it difficult to see how they're connected; fallible estimates color the chain of decisions that determine a project's outcome; and a bias toward the initial goals prevents managers from setting revised, more appropriate, targets when project circumstances change. Sticking to an initial low budget goal after a project grew in scope, for instance, led subjects to ignore quality assurance, which led to soaring defect rates--and costs. Companies can take practical steps to fix the learning cycle. They can provide feedback that shows the relationships between important variables in the environment. Such feedback might reveal, say, the 20-day ramp-up that a new quality assurance team needs before becoming fully effective. Tools that apply formal models to calculate such things as the effect of turnover on team productivity also help. Setting goals for behavior, instead of targets for performance, is critical as well. Finally, firms can create project "flight simulators" that mimic actual learning environments but don't let complexity overwhelm trainees. Managers can continue learning only if they get decision support tailored to the challenges they face. Firms would do well to focus more on training people higher up in the organization and stop leaving them to fend for themselves.
Anisotropic conductivity imaging with MREIT using equipotential projection algorithm.
Değirmenci, Evren; Eyüboğlu, B Murat
2007-12-21
Magnetic resonance electrical impedance tomography (MREIT) combines magnetic flux or current density measurements obtained by magnetic resonance imaging (MRI) and surface potential measurements to reconstruct images of true conductivity with high spatial resolution. Most of the biological tissues have anisotropic conductivity; therefore, anisotropy should be taken into account in conductivity image reconstruction. Almost all of the MREIT reconstruction algorithms proposed to date assume isotropic conductivity distribution. In this study, a novel MREIT image reconstruction algorithm is proposed to image anisotropic conductivity. Relative anisotropic conductivity values are reconstructed iteratively, using only current density measurements without any potential measurement. In order to obtain true conductivity values, only either one potential or conductivity measurement is sufficient to determine a scaling factor. The proposed technique is evaluated on simulated data for isotropic and anisotropic conductivity distributions, with and without measurement noise. Simulation results show that the images of both anisotropic and isotropic conductivity distributions can be reconstructed successfully.
Neutron Trapping using a Magneto-Gravitational Trap
NASA Astrophysics Data System (ADS)
Liu, Chen-Yu
2014-03-01
Eighty years after Chadwick discovered the neutron, physicists today still cannot agree on how long the neutron lives. Measurements of the neutron lifetime have achieved the 0.1% level of precision (~ 1 s). However, results from several recent experiments are up to 7 s lower than the (pre-2010) particle data group (PDG) value. Experiments using the trap technique yield lifetime results lower than those using the beam technique. The PDG urges the community to resolve this discrepancy, now 6.5 sigma. Measuring the absolute neutron lifetime is difficult because of several limitations: the low energy of the neutron decay products, the inability to track slow neutrons, and the fact that the neutron lifetime is long (880.1 +/- 1.1 s). Slow neutrons are susceptible to many loss mechanisms other than beta-decay, such as upscattering and absorption on material surfaces. Often, these interactions act on time scales comparable to the neutron beta-decay, making the extraction of the beta-decay lifetime particularly challenging. We will revisit this measurement by trapping ultracold neutrons (UCN) in a hybrid magnetic-gravitational trap. The trap consists of a Halbach array of permanent magnets, which can levitate UCN up to 50 neV. These neutrons are also confined vertically up to 0.5 m by gravity. Such a trap minimizes the chance of neutron interactions with material walls. In addition, the open-top geometry allows room to implement novel schemes to detect neutrons and decay particles in-situ. The UCN τ experiment aims to reduce the uncertainty of the neutron lifetime measurement to below 1 second. In this talk, I will report results of our first attempt to trap UCN in 2013 and discuss plans to quantify systematic effects. The work is supported by NSF grant PHY-1306942.