Lakowicz, J R; Cherek, H; Gryczynski, I; Joshi, N; Johnson, M L
1987-01-01
Enhanced resolution of rapid and complex anisotropy decays was obtained by measurement and analysis of data from progressively quenched samples. Collisional quenching by acrylamide was used to vary the mean decay time of indole or of the tryptophan fluorescence from melittin. Anisotropy decays were obtained from the frequency-response of the polarized emission at frequencies from 4 to 2,000 MHz. Quenching increases the fraction of the total emission, which occurs on the subnanosecond timescale, and thereby provides increased information on picosecond rotational motions or local motions in proteins. For monoexponential subnanosecond anisotropy decays, enhanced resolution is obtained by measurement of the most highly quenched samples. For complex anisotropy decays, such as those due to both local motions and overall protein rotational diffusion, superior resolution is obtained by simultaneous analysis of data from quenched and unquenched samples. We demonstrate that measurement of quenched samples greatly reduces the uncertainty of the 50-ps correlation time of indole in water at 20 degrees C, and allows resolution of the anisotropic rotation of indole with correlation times of 140 and 720 ps. The method was applied to melittin in the monomeric and tetrameric forms. With increased quenching, the anisotropy data showed decreasing contributions from overall protein rotation and increased contribution from picosecond tryptophan motions. The tryptophan residues in both the monomeric and the tetrameric forms of melittin displayed substantial local motions with correlation times near 0.16 and 0.06 ns, respectively. The amplitude of the local motion is twofold less in the tetramer. These highly resolved anisotropy decays should be valuable for comparison with molecular dynamics simulations of melittin. PMID:3593873
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.
NASA Astrophysics Data System (ADS)
Neirotti, Juan
2016-07-01
We consider the process of opinion formation in a society of interacting agents, where there is a set B of socially accepted rules. In this scenario, we observed that agents, represented by simple feed-forward, adaptive neural networks, may have a conservative attitude (mostly in agreement with B ) or liberal attitude (mostly in agreement with neighboring agents) depending on how much their opinions are influenced by their peers. The topology of the network representing the interaction of the society's members is determined by a graph, where the agents' properties are defined over the vertexes and the interagent interactions are defined over the bonds. The adaptability of the agents allows us to model the formation of opinions as an online learning process, where agents learn continuously as new information becomes available to the whole society (online learning). Through the application of statistical mechanics techniques we deduced a set of differential equations describing the dynamics of the system. We observed that by slowly varying the average peer influence in such a way that the agents attitude changes from conservative to liberal and back, the average social opinion develops a hysteresis cycle. Such hysteretic behavior disappears when the variance of the social influence distribution is large enough. In all the cases studied, the change from conservative to liberal behavior is characterized by the emergence of conservative clusters, i.e., a closed knitted set of society members that follow a leader who agrees with the social status quo when the rule B is challenged.
Neirotti, Juan
2016-07-01
We consider the process of opinion formation in a society of interacting agents, where there is a set B of socially accepted rules. In this scenario, we observed that agents, represented by simple feed-forward, adaptive neural networks, may have a conservative attitude (mostly in agreement with B) or liberal attitude (mostly in agreement with neighboring agents) depending on how much their opinions are influenced by their peers. The topology of the network representing the interaction of the society's members is determined by a graph, where the agents' properties are defined over the vertexes and the interagent interactions are defined over the bonds. The adaptability of the agents allows us to model the formation of opinions as an online learning process, where agents learn continuously as new information becomes available to the whole society (online learning). Through the application of statistical mechanics techniques we deduced a set of differential equations describing the dynamics of the system. We observed that by slowly varying the average peer influence in such a way that the agents attitude changes from conservative to liberal and back, the average social opinion develops a hysteresis cycle. Such hysteretic behavior disappears when the variance of the social influence distribution is large enough. In all the cases studied, the change from conservative to liberal behavior is characterized by the emergence of conservative clusters, i.e., a closed knitted set of society members that follow a leader who agrees with the social status quo when the rule B is challenged.
Mean flow and anisotropic cascades in decaying 2D turbulence
NASA Astrophysics Data System (ADS)
Liu, Chien-Chia; Cerbus, Rory; Gioia, Gustavo; Chakraborty, Pinaki
2015-11-01
Many large-scale atmospheric and oceanic flows are decaying 2D turbulent flows embedded in a non-uniform mean flow. Despite its importance for large-scale weather systems, the affect of non-uniform mean flows on decaying 2D turbulence remains unknown. In the absence of mean flow it is well known that decaying 2D turbulent flows exhibit the enstrophy cascade. More generally, for any 2D turbulent flow, all computational, experimental and field data amassed to date indicate that the spectrum of longitudinal and transverse velocity fluctuations correspond to the same cascade, signifying isotropy of cascades. Here we report experiments on decaying 2D turbulence in soap films with a non-uniform mean flow. We find that the flow transitions from the usual isotropic enstrophy cascade to a series of unusual and, to our knowledge, never before observed or predicted, anisotropic cascades where the longitudinal and transverse spectra are mutually independent. We discuss implications of our results for decaying geophysical turbulence.
2016-01-01
The fractional cell kill is a mathematical expression describing the rate at which a certain population of cells is reduced to a fraction of itself. We investigate the mathematical function that governs the rate at which a solid tumor is lysed by a cell population of cytotoxic lymphocytes. We do it in the context of enzyme kinetics, using geometrical and analytical arguments. We derive the equations governing the decay of a tumor in the limit in which it is plainly surrounded by immune cells. A cellular automaton is used to test such decay, confirming its validity. Finally, we introduce a modification in the fractional cell kill so that the expected dynamics is attained in the mentioned limit. We also discuss the potential of this new function for non-solid and solid tumors which are infiltrated with lymphocytes. PMID:27310010
An anisotropic universe due to dimension-changing vacuum decay
Scargill, James H.C.
2015-08-01
In this paper we consider the question of observational signatures of a false vacuum decay event in the early universe followed by a period of inflation; in particular, motivated by the string landscape, we consider decays in which the parent vacuum has a smaller number of large dimensions than the current vacuum, which leads to an anisotropic universe. We go beyond previous studies, and examine the effects on the CMB temperature and polarisation power spectra, due to both scalar and tensor modes, and consider not only late-time effects but also the full cosmological perturbation theory at early times. We find that whilst the scalar mode behaves as one would expect, and the effects of anisotropy at early times are sub-dominant to the late-time effects already studied, for the tensor modes in fact the the early-time effects grow with multipole and can become much larger than one would expect, even dominating over the late-time effects. Thus these effects should be included if one is looking for such a signal in the tensor modes.
Vortex Dynamics in Anisotropic Superconductors
NASA Astrophysics Data System (ADS)
Steel, David Gordon
Measurements of the ac screening response and resistance of superconducting Bi_2Sr _2CaCu_2O _8 (BSCCO) crystals have been used to probe the dynamics of the magnetic flux lines within the mixed state as a function of frequency, temperature, and applied dc field. For the particular range of temperature and magnetic field in which measurements were made, the systematic behavior of the observed dissipation peak in the screening response is consistent with electromagnetic skin size effects rather than a phase transition. According to microscopic theories of the interaction between the flux lines and a driving ac field, such a skin size effect is expected for the case when the vortex motion is diffusive in nature. However, diffusive motion is inconsistent with simple activation models that use a single value for the pinning energy (derived from direct measurement of the dc resistance). This contradiction suggests a distribution of pinning energies within the sample. Interlayer vortex decoupling has been directly observed as a function of temperature and applied magnetic field using electronic transport perpendicular to the layers in synthetic amorphous MoGe/Ge multilayer samples. Perpendicular transport has been shown to be a far more sensitive measure of the phase coupling between layers than in-plane properties. Below the decoupling temperature T_{D} the resistivity anisotropy collapses and striking nonlinearities appear in the perpendicular current-voltage behavior, which are not observed in parallel transport. A crossover in behavior is also observed at a field H _{x}, in accordance with theory. The data suggest the presence of a phase transition into a state with finite in-plane resistivity. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.).
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.
Energy decay laws in strongly anisotropic magnetohydrodynamic turbulence.
Bigot, Barbara; Galtier, Sébastien; Politano, Hélène
2008-02-22
We investigate the influence of a uniform magnetic field B(0)=B(0)e( parallel) on energy decay laws in incompressible magnetohydrodynamic (MHD) turbulence. The nonlinear transfer reduction along B(0) is included in a model that distinguishes parallel and perpendicular directions, following a phenomenology of Kraichnan. We predict a slowing down of the energy decay due to anisotropy in the limit of strong B(0), with distinct power laws for energy decay of shear- and pseudo-Alfvén waves. Numerical results from the kinetic equations of Alfvén wave turbulence recover these predictions, and MHD numerical results clearly tend to follow them in the lowest perpendicular planes.
Anisotropic decay of the energy spectrum in two-dimensional dense granular flows
NASA Astrophysics Data System (ADS)
Saitoh, Kuniyasu; Mizuno, Hideyuki
2017-07-01
We study anisotropic collective motions of two-dimensional granular particles under simple shear deformations. Employing molecular-dynamics simulations of large system sizes, we find that anisotropic fluidized bands develop in the system yielding under quasistatic deformations, where the spectrum of nonaffine velocities, which is associated with the energy spectrum for turbulent flows, exhibits a quadrupole structure. To explain theoretically the anisotropic spectrum, we derive hydrodynamic modes from a continuum model of dense granular materials, where we find that fluidized bands are caused by long-lived hydrodynamic fluctuations characterized by compressibility.
Finite-Temperature Entanglement Dynamics in an Anisotropic Two-Qubit Heisenberg Spin Chain
NASA Astrophysics Data System (ADS)
Chen, Tao; Shan, Chuanjia; Li, Jinxing; Liu, Tangkun; Huang, Yanxia; Li, Hong
2010-07-01
This paper investigates the entanglement dynamics of an anisotropic two-qubit Heisenberg spin chain in the presence of decoherence at finite temperature. The time evolution of the concurrence is studied for different initial Werner states. The influences of initial purity, finite temperature, spontaneous decay and Hamiltonian on the entanglement evolution are analyzed in detail. Our calculations show that the finite temperature restricts the evolution of the entanglement all the time when the Hamiltonian improves it and the spontaneous decay to the reservoirs can produce quantum entanglement with the anisotropy of spin-spin interaction. Finally, the steady-state concurrence which may remain non-zero for low temperature is also given.
Dynamic Scaling of Island-size Distribution on Anisotropic Surfaces
NASA Astrophysics Data System (ADS)
Li, Maozhi; Wang, E. G.; Liu, Banggui; Zhang, Zhenyu
2002-03-01
Dynamic scaling of island-size distribution on isotropic and anisotropic surfaces in submonolayer growth is systematically studied using kinetic Monte Carlo simulations. It is found that the island-size distribution in anisotropic submonolayer growth exhibits a general dynamic scaling behavior. An analytic expression is proposed for the scaling function, and is compared with the simulation results. This scaling function not only improves previous results for the isotropic growth (1), but also describes the scaling behavior of the island-size distribution in anisotropic submonolayer growth very well (2). 1. J. G. Amar and F. Family, Phys. Rev. Lett. 74, 2066 (1995). 2. M. Z. Li, E. G. Wang, B. G. Liu, and Z. Y. Zhang, Phys. Rev. Lett. (submitted).
Anisotropic Local Correlations and Dynamics in a Relaxor Ferroelectric
NASA Astrophysics Data System (ADS)
Takenaka, Hiroyuki; Grinberg, Ilya; Rappe, Andrew M.
2013-04-01
Relaxor ferroelectrics have been a focus of intense attention due to their anomalous properties, and understanding the structure and dynamics of relaxors has been one of the long-standing challenges in solid-state physics. We investigate the local structure and dynamics in 75%PbMg1/3Nb2/3O3-25%PbTiO3 using molecular dynamics simulations and the dynamic pair distribution function technique. We show that relaxor transitions can be described by local order parameters. The relaxor phase is characterized by the presence of highly anisotropic correlations between the local cation displacements that resemble the hydrogen bond network in water. This contradicts the current model of polar nanoregion inside a nonpolar matrix. We therefore suggest a new model of a homogeneous random network of anisotropically coupled dipoles.
Steep Decay of GRB X-Ray Flares: The Results of Anisotropic Synchrotron Radiation
NASA Astrophysics Data System (ADS)
Geng, Jin-Jun; Huang, Yong-Feng; Dai, Zi-Gao
2017-05-01
When an emitting spherical shell with a constant Lorentz factor turns off emission abruptly at some radii, its high-latitude emission would obey the relation of \\hat{α } (the temporal index) = 2+\\hat{β } (the spectral index). However, this relation is violated by the X-ray fares in some gamma-ray bursts (GRBs), whose \\hat{α } is much more steeper. We show that the synchrotron radiation should be anisotropic when the angular distribution of accelerated electrons has a preferable orientation, and this anisotropy would naturally lead to a steeper decay for the high-latitude emission if the intrinsic emission is limb-brightened. We use this simple toy model to reproduce the temporal and spectral evolution of X-ray flares. We show that our model can well interpret the steep decay of the X-ray flares in the three GRBs selected as an example. Recent simulations on particle acceleration may support the specific anisotropic distribution of the electrons adopted in our work. Reversely, confirmation of the anisotropy in the radiation would provide meaningful clues to the details of electron acceleration in the emitting region.
Colloidal aggregation and dynamics in anisotropic fluids
Mondiot, Frédéric; Botet, Robert; Snabre, Patrick; Mondain-Monval, Olivier; Loudet, Jean-Christophe
2014-01-01
We present experiments and numerical simulations to investigate the collective behavior of submicrometer-sized particles immersed in a nematic micellar solution. We use latex spheres with diameters ranging from 190 to 780 nm and study their aggregation properties due to the interplay of the various colloidal forces at work in the system. We found that the morphology of aggregates strongly depends on the particle size, with evidence for two distinct regimes: the biggest inclusions clump together within minutes into either compact clusters or V-like structures that are completely consistent with attractive elastic interactions. On the contrary, the smallest particles form chains elongated along the nematic axis, within comparable timescales. In this regime, Monte Carlo simulations, based on a modified diffusion-limited cluster aggregation model, strongly suggest that the anisotropic rotational Brownian motion of the clusters combined with short-range depletion interactions dominate the system coarsening; elastic interactions no longer prevail. The simulations reproduce the sharp transition between the two regimes on increasing the particle size. We provide reasonable estimates to interpret our data and propose a likely scenario for colloidal aggregation. These results emphasize the growing importance of the diffusion of species at suboptical-wavelength scales and raise a number of fundamental issues. PMID:24715727
Threedimensional dynamics of nuclear decay modes
NASA Astrophysics Data System (ADS)
Mirea, M.; Poenaru, D. N.; Greiner, W.
1994-03-01
We study nondissipative fission dynamics in a wide range of mass asymmetry, covering three groups of nuclear decay modes: cluster radioactivities; alpha-decay and cold fission. The WKB action integral is calculated by using the Werner-Wheeler inertia tensor and the deformation energy within Yukawa-plus-exponential model extended to binary systems with different charge densities. The optimum dynamical trajectory in a threedimensional deformation space (elongation, necking-in and mass-asymmetry) is determined by solving a nonlinear system of differential equations. This new method is illustrated for three decay modes of234U: α-decay, Mg-radioactivity and cold fission with100Zr as a light fragment.
Dynamics and Control of Articulated Anisotropic Timoshenko Beams
NASA Technical Reports Server (NTRS)
Balakrishnan, A. V.
1996-01-01
The paper illustrates the use of continuum models in control design for stabilizing flexible structures. A 6-DOF anisotropic Timoshenko beam with discrete nodes where lumped masses or actuators are located provides a sufficiently rich model to be of interest for mathematical theory as well as practical application. We develop concepts and tools to help answer engineering questions without having to resort to ad hoc heuristic ("physical") arguments or faith. In this sense the paper is more mathematically oriented than engineering papers and vice versa at the same time. For instance we make precise time-domain solutions using the theory of semigroups of operators rather than formal "inverse Laplace transforms." We show that the modes arise as eigenvalues of the generator of the semigroup, which are then related to the eigenvalues of the stiffness operator. With the feedback control, the modes are no longer orthogonal and the question naturally arises as to whether there is still a modal expansion. Here we prove that the eigenfunctions yield a biorthogonal Riesz basis and indicate the corresponding expansion. We prove mathematically that the number of eigenvalues is nonfinite, based on the theory of zeros of entire functions. We make precise the notion of asymptotic modes and indicate how to calculate them. Although limited by space, we do consider the root locus problem and show for instance that the damping at first increases as the control gain increases but starts to decrease at a critical value, and goes to zero as the gain increases without bound. The undamped oscillatory modes remain oscillatory and the rigid-body modes go over into deadbeat modes. The Timoshenko model dynamics are translated into a canonical wave equation in a Hilbert space. The solution is shown to require the use of an "energy" norm which is no more than the total energy: potential plus kinetic. We show that, under an appropriate extension of the notion of controllability, rate feedback with
Polaron dynamics in anisotropic Holstein-Peierls systems.
Ribeiro Junior, Luiz Antonio; Stafström, Sven
2017-02-01
Polaron dynamics in anisotropic organic molecular semiconductors is theoretically investigated and simulated in the framework of a semi-classical Holstein-Peierls model. Our computational protocol is presented and applied to studies of a two-dimensional molecular crystal. The intermolecular (Peierls) parameters for a particular crystal direction are systematically changed in order to study the effect of anisotropy in the system. The usefulness of this methodology is highlighted by studying the polaron dynamics on a picosecond timescale, which provides a microscopic insight into the influence of the interplay between different intramolecular parameters on the charge transport mechanism. Our results show that the polaron mobility is substantially reduced in going from an anisotropic to an isotropic relationship between the Peierls parameters for different directions in the crystal. Interestingly, the molecular charge distribution presents three different signatures corresponding to a one-dimensional polaron, a two-dimensional polaron, and an intermediate state for which the polaron localization depends on the degree of anisotropy. Importantly, the two-dimensional polaron, which is present in the essentially isotropic system, is immobile whereas the other two types of polarons are mobile. This, in order for polaron transport to occur in a two-dimensional molecular based system, this system has to be anisotropic.
Dynamic pressure-shear loading of materials using anisotropic crystals
NASA Astrophysics Data System (ADS)
Chhabildas, L. C.; Swegle, J. W.
1980-09-01
An experimental technique is described which uses anisotropic crystals to generate dynamic pressure-shear loading in materials. The coupled longitudinal and shear motion generated upon planar impact of the anisotropic crystal can be transmitted into a specimen bonded to the rear surface of the crystal, and monitored using velocity interferometer techniques. Test results using y-cut quartz generators and x-cut quartz and y-cut quartz samples indicate that shear stresses up to 0.35 GPa can be transmitted across epoxy-bonded interfaces. The technique has been successfully used to detect a 0.2 GPa shear wave in 6061-T6 aluminum at 0.7 GPa longitudinal stress. The shear wave velocity profiles have an accuracy of ±12%. The use of longer delay legs in the interferometer is suggested to improve the accuracy. Results obtained in this investigation are compared with numerical solutions obtained using the finite-difference wave propagation code TOODY.
Interacting Dark Fluid in Anisotropic Universe with Dynamical Deceleration Parameter
NASA Astrophysics Data System (ADS)
Adhav, K. S.; Bokey, V. D.; Bansod, A. S.; Munde, S. L.
2016-10-01
In this paper we have studied the anisotropic and homogeneous Bianchi Type-I and V universe filled with Interacting Dark Matter and Holographic Dark Energy. The solutions of field equations are obtained for both models under the assumption of linearly varying deceleration parameter which yields dynamical deceleration parameter. It has been observed that the anisotropy of expansion dies out very quickly (soon after inflation) in both models (B-I, B-V). The physical and geometrical parameters for the both models have been obtained and discussed in details.
Particle dynamics during the transition from isotropic to anisotropic turbulence
NASA Astrophysics Data System (ADS)
Lee, Chung-Min; Gylfason, Armann; Toschi, Federico
2016-11-01
Turbulent fluctuations play an important role on the dynamics of particles in turbulence, enhancing their dispersion and mixing. In recent years the statistical properties of particles in several statistically stationary turbulent flows have been the subject of many numerical and experimental studies. In many natural and industrial environments, however, one deals with turbulence in a transient state. As a prototype system, we investigate the transition from an isotropic to an anisotropic flow, namely looking at the influence of a developing mean flow on the dynamics of particles. We simulate, via direct numerical simulation, stationary homogeneous and isotropic turbulence and then suddenly impose a mean shear or strain. This allows us to quantify the effects of the mean flow on particle dynamics in these transient periods. Preliminary results on single particle properties, such as velocities and accelerations will be reported.
Imaging Anisotropic Nanoplasma Dynamics in Superfluid Helium Droplets
NASA Astrophysics Data System (ADS)
Bacellar, Camila; Chatterley, Adam; Lackner, Florian; Pemmaraju, Sri; Tanyag, Rico; Bernando, Charles; Verma, Deepak; O'Connell, Sean; Osipiv, Timur; Ray, Dipanwita; Ferguson, Kenneth; Gorkhover, Tais; Swiggers, Michele; Bucher, Maximilian; Vilesov, Andrey; Bostedt, Christoph; Gessner, Oliver
2016-05-01
The dynamics of strong-field induced nanoplasmas inside superfluid helium droplets are studied using single-shot, single-particle femtosecond time-resolved X-ray coherent diffractive imaging (CDI) at the Linac Coherent Light Source (LCLS). Intense (~ 1015 W/ cm2, ~ 50 fs) 800 nm laser pulses are employed to initiate nanoplasma formation in sub-micron (200 nm - 600 nm) sized helium droplets. The dynamics of the nanoplasma formation and subsequent droplet evolution are probed by x-rays pulses (~ 100 fs, 600 eV) that are delayed with respect to the near-infrared (NIR) pulses by 10's of femtoseconds to hundreds of picoseconds. Pump-probe time-delay dependent effects in the CDI patterns reveal distinct dynamics evolving on multiple timescales. Very fast (<100 fs) appearing features are possibly indicative of electronic dynamics, while slower (>= 1 ps) dynamics are likely associated with structural changes correlated to nuclear motion including droplet disintegration. In particular, the CDI images exhibit strong indications for anisotropic dynamics governed by the NIR polarization axis, providing previously inaccessible insight into the mechanisms of nanoplasma formation and evolution.
Parameter Tuning of Three-Flavor Dynamical Anisotropic Clover Action
Huey-Wen Lin; Robert G. Edwards; Balint Joo
2007-08-04
In this work, we perform parameter tuning with dynamical anisotropic clover lattices using the Schr\\"odinger functional and stout-smearing in the fermion field. We find that $\\xi_R/\\xi_0$ is relatively close to 1 in our parameter search, which allows us to fix $\\xi_0$ in our runs. We proposed to determine the gauge and fermion anisotropy in a Schr\\"odinger-background small box using Wilson loop ratios and PCAC masses. We demonstrate that these ideas are equivalent to but more efficient than the conventional meson dispersion approach. The spatial and temporal clover coefficients are fixed to the tree-level tadpole-improved clover values, and we demonstrate that they satisfy the nonperturbative condition determined by Schr\\"odinger functional method.
Strong anisotropic dynamics of ultra-confined water.
Kolesnikov, Alexander I; Anovitz, Lawrence M; Mamontov, Eugene; Podlesnyak, Andrey; Ehlers, Georg
2014-11-26
Dynamics of water confined in ∼5 Å diameter channels of beryl and cordierite single crystals were studied by using inelastic (INS) and quasielastic (QENS) neutron scattering. The INS spectra for both samples were similar and showed that there are no hydrogen bonds acting on water molecule, which experiences strong anisotropic potential, steep along the channels and very soft perpendicular to it. The high-resolution (3.4 μeV) QENS data revealed gradual freezing out of the water molecule dynamics for both minerals at temperatures below about 80 K when the scattering momentum transfer was parallel to the channels, but not when it was perpendicular to the channels. The QENS study with medium energy resolution (0.25 meV) of the beryl with the scattering momentum transfer along the channels showed gradual freezing out of water molecule dynamics at temperatures below about 200 K, whereas at higher temperatures the data could be described as 2-fold rotational jumps about the axis coinciding with the direction of the dipole moment (that is, perpendicular to the channels), with a residence time of 5.5 ps at 225 K. The energy resolution dependence of the apparent dynamics freezing temperature suggests gradual slowing down of the rotational jumps as the temperature is decreased, until the associated QENS broadening can no longer be detected, rather than actual freezing.
Anisotropic dynamics of dipolar liquids in narrow slit pores.
Froltsov, Vladimir A; Klapp, Sabine H L
2006-04-07
We report molecular dynamics simulation results for Stockmayer fluids confined to narrow slitlike pores with structureless, nonconducting walls. The translational and rotational dynamics of the dipolar particles have been investigated by calculating autocorrelation functions, diffusion coefficients, and relaxation times for various pore widths (five or less particle diameters) and directions parallel and perpendicular to the walls. The dynamic properties of the confined systems are compared to bulk properties, where corresponding bulk and pore states at the same temperature and chemical potential are determined in parallel grand canonical Monte Carlo simulations. We find that the dynamic behavior inside the pore depends on the distance from the walls and can be strongly anisotropic even in globally isotropic systems. This concerns especially the particles in the surface layers close to the walls, where the single particle and collective dipolar relaxation resemble that of true two-dimensional dipolar fluids with different in-plane and out-of-plane relaxations. On the other hand, bulklike relaxation is observed in the pore center of sufficiently wide pores.
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
Simulations of energetic particles interacting with nonlinear anisotropic dynamical turbulence
NASA Astrophysics Data System (ADS)
Heusen, M.; Shalchi, A.
2016-09-01
We investigate test-particle diffusion in dynamical turbulence based on a numerical approach presented before. For the turbulence we employ the nonlinear anisotropic dynamical turbulence model which takes into account wave propagation effects as well as damping effects. We compute numerically diffusion coefficients of energetic particles along and across the mean magnetic field. We focus on turbulence and particle parameters which should be relevant for the solar system and compare our findings with different interplanetary observations. We vary different parameters such as the dissipation range spectral index, the ratio of the turbulence bendover scales, and the magnetic field strength in order to explore the relevance of the different parameters. We show that the bendover scales as well as the magnetic field ratio have a strong influence on diffusion coefficients whereas the influence of the dissipation range spectral index is weak. The best agreement with solar wind observations can be found for equal bendover scales and a magnetic field ratio of δ B / B0 = 0.75.
Dhara, Soumen; Giri, Pk
2011-04-11
In this article, we report on the visible absorption, photoluminescence (PL), and fast PL decay dynamics from freestanding Si nanocrystals (NCs) that are anisotropically strained. Direct evidence of strain-induced dislocations is shown from high-resolution transmission electron microscopy images. Si NCs with sizes in the range of approximately 5-40 nm show size-dependent visible absorption in the range of 575-722 nm, while NCs of average size <10 nm exhibit strong PL emission at 580-585 nm. The PL decay shows an exponential decay in the nanosecond time scale. The Raman scattering studies show non-monotonic shift of the TO phonon modes as a function of size because of competing effect of strain and phonon confinement. Our studies rule out the influence of defects in the PL emission, and we propose that owing to the combined effect of strain and quantum confinement, the strained Si NCs exhibit direct band gap-like behavior.
Bose polarons: Dynamical decay and RF signatures
NASA Astrophysics Data System (ADS)
Corson, John; Bohn, John
2016-05-01
Interactions of a single impurity with a quantum many-body environment are known to alter the character of the impurity, thereby forming a ``quasiparticle''. The condensed matter tradition often identifies quasiparticles as poles of a Green function in the complex plane, a notion whose sophistication sometimes obscures the underlying physics. The problem of a single quantum impurity in a Bose condensate, or Bose polaron, is an illustrative example where the meaning of the impurity Green function, and hence the quasiparticle itself, becomes especially transparent. Using direct diagonalization in a truncated Hilbert space, we examine the dynamical evolution and quasiparticle decay of the repulsive Bose polaron. This approach also allows us to simulate RF spectroscopy across a Feshbach resonance and outside the linear regime, as well as account for motional and thermal effects in a harmonic trap.
Local structure in anisotropic systems determined by molecular dynamics simulation
NASA Astrophysics Data System (ADS)
Komolkin, Andrei V.; Maliniak, Arnold
In the present communication we describe the investigation of local structure using a new visualization technique. The approach is based on two-dimensional pair correlation functions derived from a molecular dynamics computer simulation. We have used this method to analyse a trajectory produced in a simulation of a nematic liquid crystal of 4-n-pentyl-4'-cyanobiphenyl (5CB) (Komolkin et al., 1994, J. chem. Phys., 101, 4103). The molecule is assumed to have cylindrical symmetry, and the liquid crystalline phase is treated as uniaxial. The pair correlation functions or cylindrical distribution functions (CDFs) are calculated in the molecular (m) and laboratory (l) frames, gm2(z1 2, d1 2) and g12(Z1 2, D1 2). Anisotropic molecular organization in the liquid crystal is reflected in laboratory frame CDFs. The molecular excluded volume is determined and the effect of the fast motion in the alkyl chain is observed. The intramolecular distributions are included in the CDFs and indicate the size of the motional amplitude in the chain. Absence of long range order was confirmed, a feature typical for a nematic liquid crystal.
Vortex-pair dynamics in anisotropic bistable media: a kinematic approach.
Hagberg, Aric; Meron, Ehud
2003-11-28
In isotropic bistable media, a vortex pair typically evolves into rotating spiral waves. In an anisotropic system, instead of spiral waves, the vortices can form wave fragments that propagate with a constant speed in a given direction determined by the system's anisotropy. The fragments may propagate invariably, shrink, or expand. We develop a kinematic approach for the study of vortex-pair dynamics in anisotropic bistable media and use it to capture the wave fragment dynamics.
Pn anisotropic tomography and dynamics under eastern Tibetan plateau
NASA Astrophysics Data System (ADS)
Lei, Jianshe; Li, Yuan; Xie, Furen; Teng, Jiwen; Zhang, Guangwei; Sun, Changqing; Zha, Xiaohui
2014-03-01
We present a new anisotropic tomographic model of the uppermost mantle around eastern Tibet using Pn traveltime data from a newly deployed temporary seismic array and recent observation bulletins of Chinese provincial networks. Our results are generally consistent with previous results but provide new insights into the dynamics of Tibetan plateau. Prominent high-velocity (high-V) anomalies are visible under Alashan block and Qaidam and Sichuan basins, which clearly outline their tectonic margins. A distinct high-V zone representing the double-sided subduction of Indo-Eurasian plates is imaged from Lhasa block to the south of Qaidam basin. A pronounced low-velocity (low-V) zone is observed from Songpan-Ganzi block to southern Chuan-Dian diamond block, suggesting the existence of hot material upwelling there. Crustal strong earthquakes frequently occurred around high-V anomalies or transition zones from high-V to low-V anomalies, suggesting that these earthquakes could be related to lateral heterogeneities in the mantle. The Pn fast direction approximately rotates around Eastern Himalayan Syntaxis, and it is tangential to the margins of Sichuan basin, suggesting that the mantle material flow of Tibetan plateau may have affected east China. In the Yunnan region to the south of 26°N, the Pn fast direction is different from SKS splitting results, indicating that the mantle lithosphere could be mechanically decoupled at certain depth below the uppermost mantle, which might be attributable to the subduction of Indian (or Burma) slab. Although the correlation between anisotropy and velocity is complicated, anisotropy strength could be associated with the pattern of velocity anomalies in the region.
NASA Astrophysics Data System (ADS)
Vijaykumar, Adithya; Ouldridge, Thomas E.; ten Wolde, Pieter Rein; Bolhuis, Peter G.
2017-03-01
The modeling of complex reaction-diffusion processes in, for instance, cellular biochemical networks or self-assembling soft matter can be tremendously sped up by employing a multiscale algorithm which combines the mesoscopic Green's Function Reaction Dynamics (GFRD) method with explicit stochastic Brownian, Langevin, or deterministic molecular dynamics to treat reactants at the microscopic scale [A. Vijaykumar, P. G. Bolhuis, and P. R. ten Wolde, J. Chem. Phys. 143, 214102 (2015)]. Here we extend this multiscale MD-GFRD approach to include the orientational dynamics that is crucial to describe the anisotropic interactions often prevalent in biomolecular systems. We present the novel algorithm focusing on Brownian dynamics only, although the methodology is generic. We illustrate the novel algorithm using a simple patchy particle model. After validation of the algorithm, we discuss its performance. The rotational Brownian dynamics MD-GFRD multiscale method will open up the possibility for large scale simulations of protein signalling networks.
Dynamics of anisotropic universe in f(G) gravity
NASA Astrophysics Data System (ADS)
Shamir, M. Farasat
2017-04-01
The main objective of this paper is to investigate anisotropic universe in f(G) gravity. Locally rotationally symmetric Bianchi type I cosmological model is considered for this purpose. First, some exact solutions with a well-known form of f(G) model are explored. In particular, two solutions are reported for the analysis. Secondly, we discuss the energy conditions for the model under consideration. The viability of the model is investigated via graphical analysis using the present day values of cosmological parameters. The strong energy condition is violated which shows that anisotropic universe in f(G) gravity supports the phenomenon of expansion of universe.
Burden, Conrad J; Oakley, Aaron J
2007-06-11
Molecular dynamics (MD) simulations using empirical force fields are popular for the study of proteins. In this work, we compare anisotropic atomic fluctuations in nanosecond-timescale MD simulations with those observed in an ultra-high-resolution crystal structure of crambin. In order to make our comparisons, we have developed a compact graphical technique for assessing agreement between spatial atomic distributions determined by MD simulations and observed anisotropic temperature factors.
Pn anisotropic tomography and mantle dynamics beneath China
NASA Astrophysics Data System (ADS)
Zhou, Zhigang; Lei, Jianshe
2016-08-01
We present a new high-resolution Pn anisotropic tomographic model of the uppermost mantle beneath China inferred from 52,061 Pn arrival-time data manually picked from seismograms recorded at provincial seismic stations in China and temporary stations in Tibet and the Tienshan orogenic belt. Significant features well correlated with surface geology are revealed and provide new insights into the deep dynamics beneath China. Prominent high Pn velocities are visible under the stable cratonic blocks (e.g., the Tarim, Junngar, and Sichuan basins, and the Ordos block), whereas remarkable low Pn velocities are observed in the tectonically active areas (e.g., Pamir, the Tienshan orogenic belt, central Tibet and the Qilian fold belt). A distinct N-S trending low Pn velocity zone around 86°E is revealed under the rift running from the Himalayan block through the Lhasa block to the Qiangtang block, which indicates the hot material upwelling due to the breaking-off of the subducting Indian slab. Two N-S trending low Pn velocity belts with an approximate N-S Pn fast direction along the faults around the Chuan-Dian diamond block suggest that these faults may serve as channels of mantle flow from Tibet. The fast Pn direction changes from N-S in the north across 27°N to E-W in the south, which may reflect different types of mantle deformation. The anisotropy in the south could be caused by the asthenospheric flow resulted from the eastward subduction of the Indian plate down to the mantle transition zone beneath the Burma arc. Across the Talas-Fergana fault in the Tienshan orogenic belt, an obvious difference in velocity and anisotropy is revealed. To the west, high Pn velocities and an arc-shaped fast Pn direction are observed, implying the Indo-Asian collision, whereas to the east low Pn velocities and a range-parallel Pn fast direction are imaged, reflecting the northward underthrusting of the Tarim lithosphere and the southward underthrusting of the Kazakh lithosphere. In
Density-dependent decay in HIV-1 dynamics.
Holte, Sarah E; Melvin, Ann J; Mullins, James I; Tobin, Nicole H; Frenkel, Lisa M
2006-03-01
The decay of HIV-1-infected cell populations after treatment with antiretroviral therapy has been measured using simple exponential decay models. These models are unlikely to be realistic over periods longer than a few months, however, because the population dynamics of HIV are complex. We considered an alternate model developed by Perelson and colleagues that extends the standard model for biphasic viral load decline and allows for nonlinear log decay of infected cell populations. Using data from 6 children on highly active antiretroviral therapy (HAART) and a single parameter in the new model, the assumption of log linear decay of infected cell populations is tested. Our analysis indicates that the short-lived and long-lived infected cell populations do not decay according to a simple exponential model. Furthermore, the resulting estimates of time to eradication of infected cell compartments are dramatically longer than those previously reported (eg, decades vs. years for long-lived infected cell populations and years vs. weeks for short-lived infected cell populations). Furthermore, estimates of the second-phase decay rates are significantly different than 0 for most children when obtained using the Perelson biphasic decay model. In contrast, this rate is not significantly different than 0 when the density-dependent decay model is used for parameter estimation and inference. Thus, the density-dependent decay model but not the simple exponential decay model is consistent with recent data showing that even under consistent HAART-mediated suppression of viral replication, decay rates of infected cell reservoirs decay little over several years. This suggests that conclusions about long-term viral dynamics of HIV infection based on simple exponential decay models should be carefully re-evaluated.
Nuclear dynamics during the resonant Auger decay of water molecules.
Eroms, Matthis; Vendrell, Oriol; Jungen, Martin; Meyer, Hans-Dieter; Cederbaum, Lorenz S
2009-04-21
The resonant Auger decay of water molecules is investigated. Here, the excitation process, the motion of the nuclei, and the decay of the resonantly excited state take place on the same (femtosecond) time scale. Therefore, a multistep picture is not suitable. Instead, the nuclear wave packet at each instant of time is a result of several competing and interfering contributions. The resonant Auger decay of water is simulated and its dynamics is studied in detail. An analysis of the final vibrational distribution is given. The multiconfiguration time-dependent Hartree method is used to study the intricate multidimensional dynamics. The potential energy surfaces have been calculated using a multireference configuration interaction method.
Dynamics of anisotropic power-law f( R) cosmology
NASA Astrophysics Data System (ADS)
Shamir, M. F.
2016-12-01
Modified theories of gravity have attracted much attention of the researchers in the recent years. In particular, the f( R) theory has been investigated extensively due to important f( R) gravity models in cosmological contexts. This paper is devoted to exploring an anisotropic universe in metric f( R) gravity. A locally rotationally symmetric Bianchi type I cosmological model is considered for this purpose. Exact solutions of modified field equations are obtained for a well-known f( R) gravity model. The energy conditions are also discussed for the model under consideration. The viability of the model is investigated via graphical analysis using the present-day values of cosmological parameters. The model satisfies null energy, weak energy, and dominant energy conditions for a particular range of the anisotropy parameter while the strong energy condition is violated, which shows that the anisotropic universe in f( R) gravity supports the crucial issue of accelerated expansion of the universe.
Dynamics of anisotropic power-law f(R) cosmology
Shamir, M. F.
2016-12-15
Modified theories of gravity have attracted much attention of the researchers in the recent years. In particular, the f(R) theory has been investigated extensively due to important f(R) gravity models in cosmological contexts. This paper is devoted to exploring an anisotropic universe in metric f(R) gravity. A locally rotationally symmetric Bianchi type I cosmological model is considered for this purpose. Exact solutions of modified field equations are obtained for a well-known f(R) gravity model. The energy conditions are also discussed for the model under consideration. The viability of the model is investigated via graphical analysis using the present-day values of cosmological parameters. The model satisfies null energy, weak energy, and dominant energy conditions for a particular range of the anisotropy parameter while the strong energy condition is violated, which shows that the anisotropic universe in f(R) gravity supports the crucial issue of accelerated expansion of the universe.
Dynamic regulation of mRNA decay during neural development.
Burow, Dana A; Umeh-Garcia, Maxine C; True, Marie B; Bakhaj, Crystal D; Ardell, David H; Cleary, Michael D
2015-04-21
Gene expression patterns are determined by rates of mRNA transcription and decay. While transcription is known to regulate many developmental processes, the role of mRNA decay is less extensively defined. A critical step toward defining the role of mRNA decay in neural development is to measure genome-wide mRNA decay rates in neural tissue. Such information should reveal the degree to which mRNA decay contributes to differential gene expression and provide a foundation for identifying regulatory mechanisms that affect neural mRNA decay. We developed a technique that allows genome-wide mRNA decay measurements in intact Drosophila embryos, across all tissues and specifically in the nervous system. Our approach revealed neural-specific decay kinetics, including stabilization of transcripts encoding regulators of axonogenesis and destabilization of transcripts encoding ribosomal proteins and histones. We also identified correlations between mRNA stability and physiologic properties of mRNAs; mRNAs that are predicted to be translated within axon growth cones or dendrites have long half-lives while mRNAs encoding transcription factors that regulate neurogenesis have short half-lives. A search for candidate cis-regulatory elements identified enrichment of the Pumilio recognition element (PRE) in mRNAs encoding regulators of neurogenesis. We found that decreased expression of the RNA-binding protein Pumilio stabilized predicted neural mRNA targets and that a PRE is necessary to trigger reporter-transcript decay in the nervous system. We found that differential mRNA decay contributes to the relative abundance of transcripts involved in cell-fate decisions, axonogenesis, and other critical events during Drosophila neural development. Neural-specific decay kinetics and the functional specificity of mRNA decay suggest the existence of a dynamic neurodevelopmental mRNA decay network. We found that Pumilio is one component of this network, revealing a novel function for this RNA
Dynamics of hadron strong production and decay
NASA Astrophysics Data System (ADS)
Burns, T. J.; Close, F. E.; Thomas, C. E.
2008-02-01
We generalize results of lattice QCD to determine the spin-dependent symmetries and factorization properties of meson production in Okubo-Zweig-Iizuka allowed processes. This explains some conjectures previously made in the literature about axial meson decays and gives predictions for exclusive decays of vector charmonia, including ways of establishing the structure of Y(4260) and Y(4325) from their S-wave decays. Factorization gives a selection rule which forbids e+e-→D*D2 near threshold with the tensor meson in helicity 2. The relations among amplitudes for double charmonia production e+e-→ψ+χ0,1,2 are expected to differ from the analogous relations among light flavor production such as e+e-→ωf0,1,2.
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.
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.
Controlling decay dynamics of quantum emitters with Plsmonic self assembly templates
NASA Astrophysics Data System (ADS)
Indukuri, S. R. K. Chaitanya; Basu, J. K.
2015-03-01
Controlling the emission of quantum dots by tailoring local density of states(LDOS) in self assembled plasmonic template. Using very small diameter gold (Au) spherical nanoantenna within a polymer tem plate randomly dispersed with quantum dots, we show how the photoluminescence intensity and lifetime anisotropy of these dots can be significantly enhanced through LDOS tuning. We also studied the effect of dispersion, wider range of geometric and spectral parameters bringing out the versatility of these functional plasmonic templates. We studied the effect of nano antenna distribution on radiative and non radiative decay rates in the templates. We demonstrated that the decay dynamics in the plasmonic templates can be controlled in a facile manner by changing the filling fraction of the Au nanoparticles. This polarization dependent anisotropic decay dynamics for the quantum emitters is determined by polarization dependent LDOS of the plasmonic templates as demonstrated by FDTD simulations. Our work provides a new method to achieve spontaneous emission intensity and anisotropy enhancement with nanoscale plasmon resonators for applications from controlled photon emitters to light harvesting. DST, India Nanomission.
Anisotropic alpha decay from oriented odd-mass isotopes of some light actinides
Berggren, T. )
1994-11-01
Half-lives and anisotropies in the [alpha] decay of [sup 205,207,209]Rn, [sup 219]Rn, [sup 221]Fr, [sup 227,229]Pa, and [sup 229]U have been calculated using the reaction-theoretical formalism proposed by Jackson and Rhoades-Brown and adapted for axially symmetric deformed nuclei by Berggren and Olanders. The possibility of octupole deformation has been taken into account. In addition, a variant of triaxial octupole deformation has been considered tentatively in the case of [sup 227]Pa and [sup 229]Pa.
NASA Astrophysics Data System (ADS)
Yoshida, Satoru; Takinoue, Masahiro; Iwase, Eiji; Onoe, Hiroaki
2016-08-01
This paper describes a system through which the self-assembly of anisotropic hydrogel microparticles is achieved, which also enables dynamic transformation of the assembled structures. Using a centrifuge-based microfluidic device, anisotropic hydrogel microparticles encapsulating superparamagnetic materials on one side are fabricated, which respond to a magnetic field. We successfully achieve dynamic assembly using these hydrogel microparticles and realize three different self-assembled structures (single and double pearl chain structures, and close-packed structures), which can be transformed to other structures dynamically via tuning of the precessional magnetic field. We believe that the developed system has potential application as an effective platform for a dynamic cell manipulation and cultivation system, in biomimetic autonomous microrobot organization, and that it can facilitate further understanding of the self-organization and complex systems observed in nature.
Dynamical Evolution of Anisotropic Response in Black Phosphorus under Ultrafast Photoexcitation.
Ge, Shaofeng; Li, Chaokai; Zhang, Zhiming; Zhang, Chenglong; Zhang, Yudao; Qiu, Jun; Wang, Qinsheng; Liu, Junku; Jia, Shuang; Feng, Ji; Sun, Dong
2015-07-08
Black phosphorus has recently emerged as a promising material for high-performance electronic and optoelectronic device for its high mobility, tunable mid-infrared bandgap, and anisotropic electronic properties. Dynamical evolution of photoexcited carriers and the induced transient change of electronic properties are critical for materials' high-field performance but remain to be explored for black phosphorus. In this work, we perform angle-resolved transient reflection spectroscopy to study the dynamical evolution of anisotropic properties of black phosphorus under photoexcitation. We find that the anisotropy of reflectivity is enhanced in the pump-induced quasi-equilibrium state, suggesting an extraordinary enhancement of the anisotropy in dynamical conductivity in hot carrier dominated regime. These results raise attractive possibilities of creating high-field, angle-sensitive electronic, optoelectronic, and remote sensing devices exploiting the dynamical electronic anisotropy with black phosphorus.
2011-01-01
In this article, we report on the visible absorption, photoluminescence (PL), and fast PL decay dynamics from freestanding Si nanocrystals (NCs) that are anisotropically strained. Direct evidence of strain-induced dislocations is shown from high-resolution transmission electron microscopy images. Si NCs with sizes in the range of approximately 5-40 nm show size-dependent visible absorption in the range of 575-722 nm, while NCs of average size <10 nm exhibit strong PL emission at 580-585 nm. The PL decay shows an exponential decay in the nanosecond time scale. The Raman scattering studies show non-monotonic shift of the TO phonon modes as a function of size because of competing effect of strain and phonon confinement. Our studies rule out the influence of defects in the PL emission, and we propose that owing to the combined effect of strain and quantum confinement, the strained Si NCs exhibit direct band gap-like behavior. PMID:21711845
An elementary singularity-free Rotational Brownian Dynamics algorithm for anisotropic particles
Ilie, Ioana M.; Briels, Wim J.; Otter, Wouter K. den
2015-03-21
Brownian Dynamics is the designated technique to simulate the collective dynamics of colloidal particles suspended in a solution, e.g., the self-assembly of patchy particles. Simulating the rotational dynamics of anisotropic particles by a first-order Langevin equation, however, gives rise to a number of complications, ranging from singularities when using a set of three rotational coordinates to subtle metric and drift corrections. Here, we derive and numerically validate a quaternion-based Rotational Brownian Dynamics algorithm that handles these complications in a simple and elegant way. The extension to hydrodynamic interactions is also discussed.
An elementary singularity-free Rotational Brownian Dynamics algorithm for anisotropic particles.
Ilie, Ioana M; Briels, Wim J; den Otter, Wouter K
2015-03-21
Brownian Dynamics is the designated technique to simulate the collective dynamics of colloidal particles suspended in a solution, e.g., the self-assembly of patchy particles. Simulating the rotational dynamics of anisotropic particles by a first-order Langevin equation, however, gives rise to a number of complications, ranging from singularities when using a set of three rotational coordinates to subtle metric and drift corrections. Here, we derive and numerically validate a quaternion-based Rotational Brownian Dynamics algorithm that handles these complications in a simple and elegant way. The extension to hydrodynamic interactions is also discussed.
Reheating dynamics affects non-perturbative decay of spectator fields
Enqvist, Kari; Lerner, Rose N.; Rusak, Stanislav E-mail: rose.lerner@helsinki.fi
2013-11-01
The behaviour of oscillating scalar spectator fields after inflation depends on the thermal background produced by inflaton decay. Resonant decay of the spectator is often blocked by large induced thermal masses. We account for the finite decay width of the inflaton and the protracted build-up of the thermal bath to determine the early evolution of a homogeneous spectator field σ coupled to the Higgs Boson Φ through the term g{sup 2}σ{sup 2}Φ{sup 2}, the only renormalisable coupling of a new scalar to the Standard Model. We find that for very large higgs-spectator coupling g∼>10{sup −3}, the resonance is not always blocked as was previously suggested. As a consequence, the oscillating spectator can decay quickly. For other parameter values, we find that although qualitative features of the thermal blocking still hold, the dynamics are altered compared to the instant decay case. These findings are important for curvaton models, where the oscillating field must be relatively long lived in order to produce the curvature perturbation. They are also relevant for other spectator fields, which must decay sufficiently early to avoid spoiling the predictions of baryogenesis and nucleosynthesis.
X-ray Birefringence Imaging of Materials with Anisotropic Molecular Dynamics.
Palmer, Benjamin A; Edwards-Gau, Gregory R; Kariuki, Benson M; Harris, Kenneth D M; Dolbnya, Igor P; Collins, Stephen P; Sutter, John P
2015-02-05
The X-ray birefringence imaging (XBI) technique, reported very recently, is a sensitive tool for spatially resolved mapping of the local orientational properties of anisotropic materials. In this paper, we report the first XBI measurements on materials that undergo anisotropic molecular dynamics. Using incident linearly polarized X-rays with energy close to the Br K-edge, the X-ray birefringence is dictated by the orientational properties of the C-Br bonds in the material. We focus on two materials (urea inclusion compounds containing 1,8-dibromooctane and 1,10-dibromodecane guest molecules) for which the reorientational dynamics of the brominated guest molecules (and hence the reorientational dynamics of the C-Br bonds) are already well characterized by other experimental techniques. The XBI results demonstrate clearly that, for the anisotropic molecular dynamics in these materials, the effective X-ray optic axis for the X-ray birefringence phenomenon is the time-averaged resultant of the orientational distribution of the C-Br bonds.
Vortex dynamics and decay of supercurrent in 2-D superconductors
Ping Ao
1992-11-01
The decay of supercurrent in a 2-d superconductor through the homogeneous quantum nucleation of vortex-antivortex pairs is formulated as a (2 + 1)-d scalar quantum electrodynamic problem. The calculation of the quantum decay rate can then be simplified to the usual single particle WKB calculation. The authors show explicitly that the homogeneous quantum nucleation of vortex-antivortex pairs is incompatible to the existence of the magnus force in the absence of dissipation, and pint out more complicated nucleation processes needed to be studied by the vortex dynamics method in such case. 9 refs.
Critical dynamics of the classical anisotropic BCC Heisenberg antiferromagnet.
NASA Astrophysics Data System (ADS)
Tsai, Shan-Ho; Bunker, Alex; Landau, D. P.
2001-03-01
Large-scale spin-dynamics simulations have been used to investigate the dynamic behavior of the classical Heisenberg antiferromagnet with single-site uniaxial anisotropy, in bcc lattices. Time evolutions of spin configurations were determined numerically from coupled equations of motion for individual spins using an algorithm implemented by Krech et al [1], which is based on fourth-order Suzuki-Trotter decompositions of exponential operators. The dynamic structure factor S(q,ω) was calculated from the space- and time-displaced spin-spin correlation function. Preliminary results for the transverse and the longitudinal components of S(q,ω) show that while the former is propagative, with a relatively short time scale, the latter is diffusive and its computation requires very long time integrations. Because of difficulties for experiments to probe the critical region, experimental data have not yet been able to distinguish between competing theories. While limited by finite lattice size and finite integration time, simulations offer the hope of shedding light on the differences between theories and experiment. [1] M. Krech, A. Bunker, D.P. Landau, Comput. Phys. Commun. 111, 1 (1998). Supported by NSF and SDSC
Dynamical manipulation of electromagnetic polarization using anisotropic meta-mirror
Cui, Jianhua; Huang, Cheng; Pan, Wenbo; Pu, Mingbo; Guo, Yinghui; Luo, Xiangang
2016-01-01
Polarization control of electromagnetic wave is very important in many fields. Here, we propose an active meta-mirror to dynamically manipulate electromagnetic polarization state at a broad band. This meta-mirror is composed of a double-layered metallic pattern backed by a metallic flat plate, and the active elements of PIN diodes are integrated into the meta-atom to control the reflection phase difference between two orthogonal polarization modes. Through switching the operating state of the PIN diodes, the meta-mirror is expected to achieve three polarization states which are left-handed, right-handed circular polarizations and linear polarization, respectively. We fabricated this active meta-mirror and validated its polarization conversion performance by measurement. The linearly polarized incident wave can be dynamically converted to right-handed or left-handed circular polarization in the frequency range between 3.4 and 8.8 GHz with the average loss of 1 dB. Furthermore, it also can keep its initial linear polarization state. PMID:27469028
Dynamical manipulation of electromagnetic polarization using anisotropic meta-mirror
NASA Astrophysics Data System (ADS)
Cui, Jianhua; Huang, Cheng; Pan, Wenbo; Pu, Mingbo; Guo, Yinghui; Luo, Xiangang
2016-07-01
Polarization control of electromagnetic wave is very important in many fields. Here, we propose an active meta-mirror to dynamically manipulate electromagnetic polarization state at a broad band. This meta-mirror is composed of a double-layered metallic pattern backed by a metallic flat plate, and the active elements of PIN diodes are integrated into the meta-atom to control the reflection phase difference between two orthogonal polarization modes. Through switching the operating state of the PIN diodes, the meta-mirror is expected to achieve three polarization states which are left-handed, right-handed circular polarizations and linear polarization, respectively. We fabricated this active meta-mirror and validated its polarization conversion performance by measurement. The linearly polarized incident wave can be dynamically converted to right-handed or left-handed circular polarization in the frequency range between 3.4 and 8.8 GHz with the average loss of 1 dB. Furthermore, it also can keep its initial linear polarization state.
Anisotropic sliding dynamics, peak effect, and metastability in stripe systems.
Olson Reichhardt, C J; Reichhardt, C; Bishop, A R
2011-04-01
A variety of soft and hard condensed matter systems are known to form stripe patterns. Here we use numerical simulations to analyze how such stripe states depin and slide when interacting with a random substrate and with driving in different directions with respect to the orientation of the stripes. Depending on the strength and density of the substrate disorder, we find that there can be pronounced anisotropy in the transport produced by different dynamical flow phases. We also find a disorder-induced "peak effect" similar to that observed for superconducting vortex systems, which is marked by a transition from elastic depinning to a state where the stripe structure fragments or partially disorders at depinning. Under the sudden application of a driving force, we observe pronounced metastability effects similar to those found near the order-disorder transition associated with the peak effect regime for three-dimensional superconducting vortices. The characteristic transient time required for the system to reach a steady state diverges in the region where the flow changes from elastic to disordered. We also find that anisotropy of the flow persists in the presence of thermal disorder when thermally induced particle hopping along the stripes dominates. The thermal effects can wash out the effects of the quenched disorder, leading to a thermally induced stripe state. We map out the dynamical phase diagram for this system, and discuss how our results could be explored in electron liquid crystal systems, type-1.5 superconductors, and pattern-forming colloidal assemblies. ©2011 American Physical Society
Spatial-Temporal Imaging of Anisotropic Photocarrier Dynamics in Black Phosphorus
NASA Astrophysics Data System (ADS)
Liao, Bolin; Zhao, Huan; Najafi, Ebrahim; Yan, Xiaodong; Tian, He; Tice, Jesse; Minnich, Austin J.; Wang, Han; Zewail, Ahmed H.
2017-06-01
As an emerging single elemental layered material with a low symmetry in-plane crystal lattice, black phosphorus (BP) has attracted significant research interest owing to its unique electronic and optoelectronic properties, including its widely tunable bandgap, polarization dependent photoresponse and highly anisotropic in-plane charge transport. Despite extensive study of the steady-state charge transport in BP, there has not been direct characterization and visualization of the hot carriers dynamics in BP immediately after photoexcitation, which is crucial to understanding the performance of BP-based optoelectronic devices. Here we use the newly developed scanning ultrafast electron microscopy (SUEM) to directly visualize the motion of photo-excited hot carriers on the surface of BP in both space and time. We observe highly anisotropic in-plane diffusion of hot holes, with a 15-times higher diffusivity along the armchair (x-) direction than that along the zigzag (y-) direction. Our results provide direct evidence of anisotropic hot carrier transport in BP and demonstrate the capability of SUEM to resolve ultrafast hot carrier dynamics in layered two-dimensional materials.
Dynamic finite element implementation of nonlinear, anisotropic hyperelastic biological membranes.
Einstein, D R; Reinhall, P; Nicosia, M; Cochran, R P; Kunzelman, K
2003-02-01
We present a novel method for the implementation of hyperelastic finite strain, non-linear strain-energy functions for biological membranes in an explicit finite element environment. The technique is implemented in LS-DYNA but may also be implemented in any suitable non-linear explicit code. The constitutive equations are implemented on the foundation of a co-rotational uniformly reduced Hughes-Liu shell. This shell is based on an updated-Lagrangian formulation suitable for relating Cauchy stress to the rate-of-deformation, i.e. hypo-elasticity. To accommodate finite deformation hyper-elastic formulations, a co-rotational deformation gradient is assembled over time, resulting in a formulation suitable for pseudo-hyperelastic constitutive equations that are standard assumptions in biomechanics. Our method was validated by comparison with (1) an analytic solution to a spherically-symmetric dynamic membrane inflation problem, incorporating a Mooney-Rivlin hyperelastic equation and (2) with previously published finite element solutions to a non-linear transversely isotropic inflation problem. Finally, we implemented a transversely isotropic strain-energy function for mitral valve tissue. The method is simple and accurate and is believed to be generally useful for anyone who wishes to model biologic membranes with an experimentally driven strain-energy function.
Nonlinear dynamics and anisotropic structure of rotating sheared turbulence.
Salhi, A; Jacobitz, F G; Schneider, K; Cambon, C
2014-01-01
Homogeneous turbulence in rotating shear flows is studied by means of pseudospectral direct numerical simulation and analytical spectral linear theory (SLT). The ratio of the Coriolis parameter to shear rate is varied over a wide range by changing the rotation strength, while a constant moderate shear rate is used to enable significant contributions to the nonlinear interscale energy transfer and to the nonlinear intercomponental redistribution terms. In the destabilized and neutral cases, in the sense of kinetic energy evolution, nonlinearity cannot saturate the growth of the largest scales. It permits the smallest scale to stabilize by a scale-by-scale quasibalance between the nonlinear energy transfer and the dissipation spectrum. In the stabilized cases, the role of rotation is mainly nonlinear, and interacting inertial waves can affect almost all scales as in purely rotating flows. In order to isolate the nonlinear effect of rotation, the two-dimensional manifold with vanishing spanwise wave number is revisited and both two-component spectra and single-point two-dimensional energy components exhibit an important effect of rotation, whereas the SLT as well as the purely two-dimensional nonlinear analysis are unaffected by rotation as stated by the Proudman theorem. The other two-dimensional manifold with vanishing streamwise wave number is analyzed with similar tools because it is essential for any shear flow. Finally, the spectral approach is used to disentangle, in an analytical way, the linear and nonlinear terms in the dynamical equations.
Nonlinear dynamics and anisotropic structure of rotating sheared turbulence
NASA Astrophysics Data System (ADS)
Salhi, A.; Jacobitz, F. G.; Schneider, K.; Cambon, C.
2014-01-01
Homogeneous turbulence in rotating shear flows is studied by means of pseudospectral direct numerical simulation and analytical spectral linear theory (SLT). The ratio of the Coriolis parameter to shear rate is varied over a wide range by changing the rotation strength, while a constant moderate shear rate is used to enable significant contributions to the nonlinear interscale energy transfer and to the nonlinear intercomponental redistribution terms. In the destabilized and neutral cases, in the sense of kinetic energy evolution, nonlinearity cannot saturate the growth of the largest scales. It permits the smallest scale to stabilize by a scale-by-scale quasibalance between the nonlinear energy transfer and the dissipation spectrum. In the stabilized cases, the role of rotation is mainly nonlinear, and interacting inertial waves can affect almost all scales as in purely rotating flows. In order to isolate the nonlinear effect of rotation, the two-dimensional manifold with vanishing spanwise wave number is revisited and both two-component spectra and single-point two-dimensional energy components exhibit an important effect of rotation, whereas the SLT as well as the purely two-dimensional nonlinear analysis are unaffected by rotation as stated by the Proudman theorem. The other two-dimensional manifold with vanishing streamwise wave number is analyzed with similar tools because it is essential for any shear flow. Finally, the spectral approach is used to disentangle, in an analytical way, the linear and nonlinear terms in the dynamical equations.
Acharyya, Muktish
2004-02-01
A uniaxially (along the Z axis) anisotropic Heisenberg ferromagnet, in the presence of time-dependent (but uniform over space) magnetic field, is studied by Monte Carlo simulation. The time-dependent magnetic field was taken as elliptically polarized where the resultant field vector rotates in the X-Z plane. The system is cooled (in the presence of the elliptically polarized magnetic field) from high temperature. As the temperature decreases, it was found that in the low anisotropy limit the system undergoes three successive dynamical phase transitions. These three dynamic transitions were confirmed by studying the temperature variation of dynamic "specific heat." The temperature variation of dynamic specific heat shows three peaks indicating three dynamic transition points.
Formation and decay of the compound nucleus *220Th within the dynamical cluster-decay model
NASA Astrophysics Data System (ADS)
Hemdeep, Chopra, Sahila; Kaur, Arshdeep; Gupta, Raj K.
2017-01-01
Background: The radioactive *220Th compound nucleus (CN) is of interest since the evaporation residue (ER) cross sections are available for various entrance channels 16O+204Pb , 40Ar+180Hf , 48Ca+172Yb , and 82Se+138Ba at near barrier energies. Within the dynamical cluster-decay model (DCM), the radioactive CNs *215Fr, *242Pu, *246Bk, and *254Fm are studied where the main decay mode is fission, with very small predicted ER cross section. *220Th provides a first case with experimentally observed ER cross section instead of fission. Purpose: To look for the optimum "hot-compact" target-projectile (t-p) combinations for the synthesis of "cold"*. For best fitting of the measured ER cross sections, with quasifission (qf) content, if any, the fusion-fission (ff) component is predicted. The magic-shell structure and entrance channel mass-asymmetry effects are analyzed, and the behavior of CN formation and survival probabilities PCN and Psurv is studied. Methods: The quantum-mechanical fragmentation theory (QMFT) is used to predict the possible cold t-p combinations for synthesizing *220Th, and the QMFT-based DCM is used to analyze its decay channels for the experimentally studied entrance channels. The only parameter of the model, the neck length Δ R , varies smoothly with the excitation energy E* of CN and is used to best fit the ER data and predict qf and ff cross sections. Results: The hot-compact and "cold-elongated" fragmentation paths show dissimilar results, whose comparisons with measured fission yields result in t-p combinations, the cold reaction valleys. For the decay process, the fixed Δ R fit the measured ER cross section nicely, but not the individual decay-channel cross sections, which require the presence of qf effects, less so for asymmetric t-p combinations, and large (predicted) ff cross section. Conclusions: The calculated yields for hot-compact fragmentation path compared favorably with the observed asymmetric fission-mass distribution, resulting in
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.
Hou, Kai; Wang, Huiyi; Lin, Yunyin; Chen, Shaohua; Yang, Shengyuan; Cheng, Yanhua; Hsiao, Benjamin S; Zhu, Meifang
2016-10-14
Hydrogel microfibers have been considered as a potential biomaterial to spatiotemporally biomimic 1D native tissues such as nerves and muscles which are always assembled hierarchically and have anisotropic response to external stimuli. To produce facile hydrogel microfibers in a mathematical manner, a novel dynamic-crosslinking-spinning (DCS) method is demonstrated for direct fabrication of size-controllable fibers from poly(ethylene glycol diacrylate) oligomer in large scale, without microfluidic template and in a biofriendly environment. The diameter of fibers can be precisely controlled by adjusting the spinning parameters. Anisotropic swelling property is also dependent on inhomogeneous structure generated in spinning process. Comparing with bulk hydrogels, the resulting fibers exhibit superior rapid water adsorption property, which can be attributed to the large surface area/volume ratio of fiber. This novel DCS method is one-step technology suitable for large-scale production of anisotropic hydrogel fibers which has a promising application in the area such as biomaterials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Cosmological perturbations of axion with a dynamical decay constant
Kobayashi, Takeshi; Takahashi, Fuminobu
2016-08-25
A QCD axion with a time-dependent decay constant has been known to be able to accommodate high-scale inflation without producing topological defects or too large isocurvature perturbations on CMB scales. We point out that a dynamical decay constant also has the effect of enhancing the small-scale axion isocurvature perturbations. The enhanced axion perturbations can even exceed the periodicity of the axion potential, and thus lead to the formation of axionic domain walls. Unlike the well-studied axionic walls, the walls produced from the enhanced perturbations are not bounded by cosmic strings, and thus would overclose the universe independently of the number of degenerate vacua along the axion potential.
Pham, Thanh Tung; To, Quy Dong; Lauriat, Guy; Léonard, Céline
2013-05-01
In this paper we examine the anisotropic slip theory for gas flows based on tangential accommodation coefficients and compare it with molecular dynamics (MD) results. A special gas-wall boundary condition is employed within MD simulations to mimic the anisotropic gas-wall collision mechanism. Results from MD simulations with different surface orientations show good agreement with the slip quantification proposed in this work.
NASA Astrophysics Data System (ADS)
Franco, Luís F. M.; Castier, Marcelo; Economou, Ioannis G.
2016-08-01
Applying classical molecular dynamics simulations, we calculate the parallel self-diffusion coefficients of different fluids (methane, nitrogen, and carbon dioxide) confined between two { 10 1 ¯ 4 } calcite crystal planes. We have observed that the molecules close to the calcite surface diffuse differently in distinct directions. This anisotropic behavior of the self-diffusion coefficient is investigated for different temperatures and pore sizes. The ion arrangement in the calcite crystal and the strong interactions between the fluid particles and the calcite surface may explain the anisotropy in this transport property.
Franco, Luís F M; Castier, Marcelo; Economou, Ioannis G
2016-08-28
Applying classical molecular dynamics simulations, we calculate the parallel self-diffusion coefficients of different fluids (methane, nitrogen, and carbon dioxide) confined between two {101̄4} calcite crystal planes. We have observed that the molecules close to the calcite surface diffuse differently in distinct directions. This anisotropic behavior of the self-diffusion coefficient is investigated for different temperatures and pore sizes. The ion arrangement in the calcite crystal and the strong interactions between the fluid particles and the calcite surface may explain the anisotropy in this transport property.
The Exponential Decay Law, Bell's Inequality, and Nonlinear Dynamics
NASA Astrophysics Data System (ADS)
McHarris, Wm. C.
2002-10-01
What do the exponential decay law and Bell's inequality have in common? And with nonlinear dynamics? Simply that they both are among the puzzles at the heart of quantum mechanics, puzzles which can have parallel explanations in terms of chaos or nonlinear dynamics. The statistical nature of the exponential decay law, which at first glance is incompatible with the quantum mechanical concept of indistinguishabe particles, can be mocked up by the extreme sensitivity of chaotic systems to initial conditions. In accord with Ockham's Razor, iteration of a simple unimodal (e.g., quadratic) map in its chaotic region and keeping track of the number of iterations required for a trajectory starting from a point chosen at random within a small interval to escape into another small small interval reproduces the observed exponential behavior. Similarly, Bell's inequality derived using classical mechanics (with an underlying assumption of classical statistics) places an upper limit on numbers derived from measurements on entangled states, whereas quantum mechanics implies that this upper limit no longer holds. Experiments have shown the inequality to be violated, upholding quantum mechanics. However, nonlinear dynamics, with its correlated statistics, can yield results overlapping with the quantum mechanical predictions. Whether or not the experiments rule out "local realism" is thus a moot point. Nonlinear determinism just might exist within quantum mechanics.
Anisotropic magnetic field dependence of the magnetization dynamics in UPd2Al3
NASA Astrophysics Data System (ADS)
Hiess, A.; Blackburn, E.; Bernhoeft, N.; Lander, G. H.
2007-10-01
The magnetization dynamics of the magnetic superconductor UPd2Al3 has been investigated by inelastic neutron scattering in the normal and superconducting, antiferromagnetically ordered state under a magnetic field applied parallel to the hexagonal c axis. Within the available resolution, the dynamic response below 2.5meV is insensitive to the applied field on the scale of the field dependence reported by E. Blackburn [Phys. Rev. B 74, 024406 (2006)] in which the field was applied in the basal plane. Our results support that the previously reported field dependent quasielastic contribution is related to the dynamics of the rotation of the magnetic moment. The changes observed in the inelastic part of the excitation spectrum are consistent with those expected from spin-wave theory. Interestingly, the anisotropic field dependence of the normal-state response may be correlated with the superconducting properties of this material.
Wang, Ge; Sun, L. Z.
2006-01-01
Major heart diseases such as ischemia and hypertrophic myocardiopathy are accompanied with significant changes in the passive mechanical properties and active contractility of myocardium. Identification of these changes helps diagnose heart diseases, monitor therapy, and design surgery. A dynamic cardiac elastography (DCE) framework is developed to assess the anisotropic viscoelastic passive properties and active contractility of myocardial tissues, based on the chamber pressure and dynamic displacement measured with cardiac imaging techniques. A dynamic adjoint method is derived to enhance the numerical efficiency and stability of DCE. Model-based simulations are conducted using a numerical left ventricle (LV) phantom with an ischemic region. The passive material parameters of normal and ischemic tissues are identified during LV rapid/reduced filling and artery contraction, and those of active contractility are quantified during isovolumetric contraction and rapid/reduced ejection. It is found that quasistatic simplification in the previous cardiac elastography studies may yield inaccurate material parameters. PMID:23165032
Liu, Yi; Wang, Ge; Sun, L Z
2006-01-01
Major heart diseases such as ischemia and hypertrophic myocardiopathy are accompanied with significant changes in the passive mechanical properties and active contractility of myocardium. Identification of these changes helps diagnose heart diseases, monitor therapy, and design surgery. A dynamic cardiac elastography (DCE) framework is developed to assess the anisotropic viscoelastic passive properties and active contractility of myocardial tissues, based on the chamber pressure and dynamic displacement measured with cardiac imaging techniques. A dynamic adjoint method is derived to enhance the numerical efficiency and stability of DCE. Model-based simulations are conducted using a numerical left ventricle (LV) phantom with an ischemic region. The passive material parameters of normal and ischemic tissues are identified during LV rapid/reduced filling and artery contraction, and those of active contractility are quantified during isovolumetric contraction and rapid/reduced ejection. It is found that quasistatic simplification in the previous cardiac elastography studies may yield inaccurate material parameters.
An Energy Decaying Scheme for Nonlinear Dynamics of Shells
NASA Technical Reports Server (NTRS)
Bottasso, Carlo L.; Bauchau, Olivier A.; Choi, Jou-Young; Bushnell, Dennis M. (Technical Monitor)
2000-01-01
A novel integration scheme for nonlinear dynamics of geometrically exact shells is developed based on the inextensible director assumption. The new algorithm is designed so as to imply the strict decay of the system total mechanical energy at each time step, and consequently unconditional stability is achieved in the nonlinear regime. Furthermore, the scheme features tunable high frequency numerical damping and it is therefore stiffly accurate. The method is tested for a finite element spatial formulation of shells based on mixed interpolations of strain tensorial components and on a two-parameter representation of director rotations. The robustness of the, scheme is illustrated with the help of numerical examples.
The impact of exospheric neutral dynamics on ring current decay
NASA Astrophysics Data System (ADS)
Ilie, R.; Liemohn, M. W.; Skoug, R. M.; Funsten, H. O.; Gruntman, M.; Bailey, J. J.; Toth, G.
2015-12-01
The geocorona plays an important role in the energy budget of the Earth's inner magnetosphere since charge exchange of energetic ions with exospheric neutrals makes the exosphere act as an energy sink for ring current particles. Long-term ring current decay following a magnetic storm is mainly due to these electron transfer reactions, leading to the formation energetic neutral atoms (ENAs) that leave the ring current system on ballistic trajectories. The number of ENAs emitted from a given region of space depends on several factors, such as the energy and species of the energetic ion population in that region and the density of the neutral gas with which the ions undergo charge exchange. However, the density and structure of the exosphere are strongly dependent on changes in atmospheric temperature and density as well as charge exchange with the ions of plasmaspheric origin, which depletes the geocorona (by having a neutral removed from the system). Moreover, the radiation pressure exerted by solar far-ultraviolet photons pushes the geocoronal hydrogen away from the Earth in an anti-sunward direction to form a tail of neutral hydrogen. TWINS ENA images provide a direct measurement of these ENA losses and therefore insight into the dynamics of the ring current decay through interactions with the geocorona. We assess the influence of geocoronal neutrals on ring current formation and decay by analysis of the predicted ENA emissions using 6 different geocoronal models and simulations from the HEIDI ring current model during storm time. Comparison with TWINS ENA images shows that the location of the peak ENA enhancements is highly dependent on the distribution of geocoronal hydrogen density. We show that the neutral dynamics has a strong influence on the time evolution of the ring current populations as well as on the formation of energetic neutral atoms.
Role of quantum statistics in multi-particle decay dynamics
Marchewka, Avi; Granot, Er’el
2015-04-15
The role of quantum statistics in the decay dynamics of a multi-particle state, which is suddenly released from a confining potential, is investigated. For an initially confined double particle state, the exact dynamics is presented for both bosons and fermions. The time-evolution of the probability to measure two-particle is evaluated and some counterintuitive features are discussed. For instance, it is shown that although there is a higher chance of finding the two bosons (as oppose to fermions, and even distinguishable particles) at the initial trap region, there is a higher chance (higher than fermions) of finding them on two opposite sides of the trap as if the repulsion between bosons is higher than the repulsion between fermions. The results are demonstrated by numerical simulations and are calculated analytically in the short-time approximation. Furthermore, experimental validation is suggested.
NASA Astrophysics Data System (ADS)
Li, Ying; Kalia, Rajiv K.; Misawa, Masaaki; Nakano, Aiichiro; Nomura, Ken-Ichi; Shimamura, Kohei; Shimojo, Fuyuki; Vashishta, Priya
2016-05-01
At the nanoscale, chemistry can happen quite differently due to mechanical forces selectively breaking the chemical bonds of materials. The interaction between chemistry and mechanical forces can be classified as mechanochemistry. An example of archetypal mechanochemistry occurs at the nanoscale in anisotropic detonating of a broad class of layered energetic molecular crystals bonded by inter-layer van der Waals (vdW) interactions. Here, we introduce an ab initio study of the collision, in which quantum molecular dynamic simulations of binary collisions between energetic vdW crystallites, TATB molecules, reveal atomistic mechanisms of anisotropic shock sensitivity. The highly sensitive lateral collision was found to originate from the twisting and bending to breaking of nitro-groups mediated by strong intra-layer hydrogen bonds. This causes the closing of the electronic energy gap due to an inverse Jahn-Teller effect. On the other hand, the insensitive collisions normal to multilayers are accomplished by more delocalized molecular deformations mediated by inter-layer interactions. Our nano-collision studies provide a much needed atomistic understanding for the rational design of insensitive energetic nanomaterials and the detonation synthesis of novel nanomaterials.At the nanoscale, chemistry can happen quite differently due to mechanical forces selectively breaking the chemical bonds of materials. The interaction between chemistry and mechanical forces can be classified as mechanochemistry. An example of archetypal mechanochemistry occurs at the nanoscale in anisotropic detonating of a broad class of layered energetic molecular crystals bonded by inter-layer van der Waals (vdW) interactions. Here, we introduce an ab initio study of the collision, in which quantum molecular dynamic simulations of binary collisions between energetic vdW crystallites, TATB molecules, reveal atomistic mechanisms of anisotropic shock sensitivity. The highly sensitive lateral collision
Quantum phase transition and quench dynamics in the anisotropic Rabi model
NASA Astrophysics Data System (ADS)
Shen, Li-Tuo; Yang, Zhen-Biao; Wu, Huai-Zhi; Zheng, Shi-Biao
2017-01-01
We investigate the quantum phase transition (QPT) and quench dynamics in the anisotropic Rabi model when the ratio of the qubit transition frequency to the oscillator frequency approaches infinity. Based on the Schrieffer-Wolff transformation, we find an anti-Hermitian operator that maps the original Hamiltonian into a one-dimensional oscillator Hamiltonian within the spin-down subspace. We analytically derive the eigenenergy and eigenstate of the normal and superradiant phases and demonstrate that the system undergoes a second-order quantum phase transition at a critical border. The critical border is a straight line in a two-dimensional parameter space which essentially extends the dimensionality of QPT in the Rabi model. By combining the Kibble-Zurek mechanism and the adiabatic dynamics method, we find that the residual energy vanishes as the quench time tends to zero, which is a sharp contrast to the universal scaling where the residual energy diverges in the same limit.
Dynamical analysis of cylindrically symmetric anisotropic sources in f( R, T) gravity
NASA Astrophysics Data System (ADS)
Zubair, M.; Azmat, Hina; Noureen, Ifra
2017-03-01
In this paper, we have analyzed the stability of cylindrically symmetric collapsing object filled with locally anisotropic fluid in f( R, T) theory, where R is the scalar curvature and T is the trace of stress-energy tensor of matter. Modified field equations and dynamical equations are constructed in f( R, T) gravity. The evolution or collapse equation is derived from dynamical equations by performing a linear perturbation on them. The instability range is explored in both the Newtonian and the post-Newtonian regimes with the help of an adiabetic index, which defines the impact of the physical parameters on the instability range. Some conditions are imposed on the physical quantities to secure the stability of the gravitating sources.
NASA Astrophysics Data System (ADS)
Kotambkar, S.; Singh, G. P.; Kelkar, R.; Bishi, Binaya K.
2017-02-01
This paper deals with study of generalized Chaplygin gas model with dynamical gravitational and cosmological constants. In this paper a new set of exact solutions of Einstein field equations for spatially homogeneous and anisotropic Bianchi type I space-time have been obtained. The solutions of the Einstein’s field equations are obtained by considering (i) the power law relation between Hubble parameter H and scale factor R and (ii) scale factor of the form R = ‑1/t + t 2, t > 1. The assumptions lead to constant and variable deceleration parameter respectively. The physical and dynamical behaviors of the models have been discussed with the help of graphical representations. Also we have discussed the stability and physical acceptability of solutions for solution type-I and solution type-II.
Joiner, Wilsaan M.; Ajayi, Obafunso; Sing, Gary C.
2011-01-01
The ability to generalize learned motor actions to new contexts is a key feature of the motor system. For example, the ability to ride a bicycle or swing a racket is often first developed at lower speeds and later applied to faster velocities. A number of previous studies have examined the generalization of motor adaptation across movement directions and found that the learned adaptation decays in a pattern consistent with the existence of motor primitives that display narrow Gaussian tuning. However, few studies have examined the generalization of motor adaptation across movement speeds. Following adaptation to linear velocity-dependent dynamics during point-to-point reaching arm movements at one speed, we tested the ability of subjects to transfer this adaptation to short-duration higher-speed movements aimed at the same target. We found near-perfect linear extrapolation of the trained adaptation with respect to both the magnitude and the time course of the velocity profiles associated with the high-speed movements: a 69% increase in movement speed corresponded to a 74% extrapolation of the trained adaptation. The close match between the increase in movement speed and the corresponding increase in adaptation beyond what was trained indicates linear hypergeneralization. Computational modeling shows that this pattern of linear hypergeneralization across movement speeds is not compatible with previous models of adaptation in which motor primitives display isotropic Gaussian tuning of motor output around their preferred velocities. Instead, we show that this generalization pattern indicates that the primitives involved in the adaptation to viscous dynamics display anisotropic tuning in velocity space and encode the gain between motor output and motion state rather than motor output itself. PMID:20881197
Joiner, Wilsaan M; Ajayi, Obafunso; Sing, Gary C; Smith, Maurice A
2011-01-01
The ability to generalize learned motor actions to new contexts is a key feature of the motor system. For example, the ability to ride a bicycle or swing a racket is often first developed at lower speeds and later applied to faster velocities. A number of previous studies have examined the generalization of motor adaptation across movement directions and found that the learned adaptation decays in a pattern consistent with the existence of motor primitives that display narrow Gaussian tuning. However, few studies have examined the generalization of motor adaptation across movement speeds. Following adaptation to linear velocity-dependent dynamics during point-to-point reaching arm movements at one speed, we tested the ability of subjects to transfer this adaptation to short-duration higher-speed movements aimed at the same target. We found near-perfect linear extrapolation of the trained adaptation with respect to both the magnitude and the time course of the velocity profiles associated with the high-speed movements: a 69% increase in movement speed corresponded to a 74% extrapolation of the trained adaptation. The close match between the increase in movement speed and the corresponding increase in adaptation beyond what was trained indicates linear hypergeneralization. Computational modeling shows that this pattern of linear hypergeneralization across movement speeds is not compatible with previous models of adaptation in which motor primitives display isotropic Gaussian tuning of motor output around their preferred velocities. Instead, we show that this generalization pattern indicates that the primitives involved in the adaptation to viscous dynamics display anisotropic tuning in velocity space and encode the gain between motor output and motion state rather than motor output itself.
Telschow, Kenneth Louis; Deason, Vance Albert
2002-12-01
An important material property in the paper industry is the anisotropic stiffness distribution due to the fibrous microstructure of paper and to processing procedures. Ultrasonic methods offer a means of determining the stiffness of sheets of paper from the anisotropic propagation characteristics of elastic Lamb waves along the machine direction and the cross direction. That is, along and perpendicular to the direction of paper production. Currently, piezoelectric ultrasonic methods are employed in the industry to measure the elastic polar diagram of paper through multiple contacting measurements made in all directions. This paper describes a new approach utilizing the INEEL Laser Ultrasonic Camera to provide a complete image of the elastic waves traveling in all directions in the plane of the paper sheet. This approach is based on optical dynamic holographic methods that record the out of plane ultrasonic motion over the entire paper surface simultaneously without scanning. The full-field imaging technique offers great potential for increasing the speed of the measurement and it ultimately provides a substantial amount of information concerning local property variations and flaws in the paper. This report shows the success of the method and the manner in which it yields the elastic polar diagram for the paper from the dispersive flexural or antisymmetric Lamb wave.
The Anisotropic Dynamic Response of Ultrafast Shocked Single Crystal PETN and Beta-HMX
NASA Astrophysics Data System (ADS)
Zaug, Joseph; Armstrong, Michael; Crowhurst, Jonathan; Austin, Ryan; Ferranti, Louis; Fried, Laurence; Bastea, Sorin
2015-06-01
We report results from ultrafast shockwave experiments conducted on single crystal high explosives. Experimental results consist of 12 picosecond time-resolved dynamic response wave profile data, (ultrafast time-domain interferometry-TDI), which are used to validate calculations of anisotropic stress-strain behavior of shocked loaded energetic materials. In addition, here we present unreacted equations of state data from PETN and beta-HMX up to higher pressures than previously reported, which are used to extend the predictive confidence of hydrodynamic simulations. Our previous results derived from a 360 ps drive duration yielded anisotropic elastic wave response in single crystal beta-HMX ((110) and (010) impact planes). Here we provide results using a 3x longer drive duration to probe the plastic response regime of these materials. We compare our ultrafast time domain interferometry (TDI) results with previous gun platform results. Ultrafast time scale resolution TDI measurements further guide the development of continuum models aimed to study pore collapse and energy localization in shock-compressed crystals of beta-HMX. This work was performed under the auspices of the U.S. Department of Energy jointly by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
NASA Astrophysics Data System (ADS)
Wagner, M.; Wang, Y.; Husen, S.; Woessner, J.; Kissling, E. H.; Ouillon, G.; Giardini, D.; Sornette, D.
2010-12-01
Active fault zones are the causal locations of most earthquakes, which release tectonic stresses. Yet, identification and association of faults and earthquakes is not straightforward. On the one hand, many earthquakes occur on faults that are unknown. On the other hand, systematic biases and uncertainties in earthquake locations hamper the association of earthquakes and known faults. We tackle the problem of linking earthquakes to faults by relocating them in a non-linear probabilistic manner and by applying a three-dimensional optimal anisotropic dynamic clustering approach to the relocated events to map fault networks. Non-linear probabilistic earthquake location allows to compute probability density functions that provide the complete probabilistic solution to the earthquake hypocenter location problem, including improved information on location uncertainties. To improve absolute earthquake locations we use a newly developed combined controlled-source seismology and local earthquake tomography model, which allows the use of secondary phases, such as PmP. Dynamic clustering is a very general image processing technique that allows partitioning a set of data points. Our improved optimal anisotropic dynamic clustering technique accounts for uncertainties in earthquake locations by the use of probability density functions, as provided by non-linear probabilistic earthquake location. Hence, number and size of the reconstructed faults is controlled by earthquake location uncertainty. We apply our approach to seismicity in Switzerland to identify active faults in the region. Relocated earthquake catalogs and associated fault networks will be compared to already existing information on faults, such as geological and seismotectonic maps, to derive a more complete picture of active faulting in Switzerland.
Weak decays of heavy hadrons into dynamically generated resonances
Oset, Eulogio; Liang, Wei -Hong; Bayar, Melahat; ...
2016-01-28
In this study, we present a review of recent works on weak decay of heavy mesons and baryons with two mesons, or a meson and a baryon, interacting strongly in the final state. The aim is to learn about the interaction of hadrons and how some particular resonances are produced in the reactions. It is shown that these reactions have peculiar features and act as filters for some quantum numbers which allow to identify easily some resonances and learn about their nature. The combination of basic elements of the weak interaction with the framework of the chiral unitary approach allowmore » for an interpretation of results of many reactions and add a novel information to different aspects of the hadron interaction and the properties of dynamically generated resonances.« less
Weak decays of heavy hadrons into dynamically generated resonances
Oset, Eulogio; Liang, Wei -Hong; Bayar, Melahat; Xie, Ju -Jun; Dai, Lian Rong; Albaladejo, Miguel; Nielsen, Marina; Sekihara, Takayasu; Navarra, Fernando; Roca, Luis; Mai, Maxim; Nieves, Juan; Dias, Jorgivan Morais; Feijoo, Alberto; Magas, Volodymyr K.; Ramos, Angels; Miyahara, Kenta; Hyodo, Tetsuo; Jido, Daisuke; Doring, Michael; Molina, Raquel; Chen, Hua -Xing; Wang, En; Geng, Lisheng; Ikeno, Natsumi; Fernandez-Soler, Pedro; Sun, Zhi Feng
2016-01-28
In this study, we present a review of recent works on weak decay of heavy mesons and baryons with two mesons, or a meson and a baryon, interacting strongly in the final state. The aim is to learn about the interaction of hadrons and how some particular resonances are produced in the reactions. It is shown that these reactions have peculiar features and act as filters for some quantum numbers which allow to identify easily some resonances and learn about their nature. The combination of basic elements of the weak interaction with the framework of the chiral unitary approach allow for an interpretation of results of many reactions and add a novel information to different aspects of the hadron interaction and the properties of dynamically generated resonances.
ERIC Educational Resources Information Center
Fuson, Michael M.
2017-01-01
Laboratories studying the anisotropic rotational diffusion of bromobenzene using nuclear spin relaxation and molecular dynamics simulations are described. For many undergraduates, visualizing molecular motion is challenging. Undergraduates rarely encounter laboratories that directly assess molecular motion, and so the concept remains an…
Mixed models and reduction method for dynamic analysis of anisotropic shells
NASA Technical Reports Server (NTRS)
Noor, A. K.; Peters, J. M.
1985-01-01
A time-domain computational procedure is presented for predicting the dynamic response of laminated anisotropic shells. The two key elements of the procedure are: (1) use of mixed finite element models having independent interpolation (shape) functions for stress resultants and generalized displacements for the spatial discretization of the shell, with the stress resultants allowed to be discontinuous at interelement boundaries; and (2) use of a dynamic reduction method, with the global approximation vectors consisting of the static solution and an orthogonal set of Lanczos vectors. The dynamic reduction is accomplished by means of successive application of the finite element method and the classical Rayleigh-Ritz technique. The finite element method is first used to generate the global approximation vectors. Then the Rayleigh-Ritz technique is used to generate a reduced system of ordinary differential equations in the amplitudes of these modes. The temporal integration of the reduced differential equations is performed by using an explicit half-station central difference scheme (Leap-frog method). The effectiveness of the proposed procedure is demonstrated by means of a numerical example and its advantages over reduction methods used with the displacement formulation are discussed.
Mixed models and reduction method for dynamic analysis of anisotropic shells
NASA Technical Reports Server (NTRS)
Noor, A. K.; Peters, J. M.
1985-01-01
A time-domain computational procedure is presented for predicting the dynamic response of laminated anisotropic shells. The two key elements of the procedure are: (1) use of mixed finite element models having independent interpolation (shape) functions for stress resultants and generalized displacements for the spatial discretization of the shell, with the stress resultants allowed to be discontinuous at interelement boundaries; and (2) use of a dynamic reduction method, with the global approximation vectors consisting of the static solution and an orthogonal set of Lanczos vectors. The dynamic reduction is accomplished by means of successive application of the finite element method and the classical Rayleigh-Ritz technique. The finite element method is first used to generate the global approximation vectors. Then the Rayleigh-Ritz technique is used to generate a reduced system of ordinary differential equations in the amplitudes of these modes. The temporal integration of the reduced differential equations is performed by using an explicit half-station central difference scheme (Leap-frog method). The effectiveness of the proposed procedure is demonstrated by means of a numerical example and its advantages over reduction methods used with the displacement formulation are discussed.
NASA Astrophysics Data System (ADS)
Bertin, N.; Upadhyay, M. V.; Pradalier, C.; Capolungo, L.
2015-09-01
In this paper, we propose a novel full-field approach based on the fast Fourier transform (FFT) technique to compute mechanical fields in periodic discrete dislocation dynamics (DDD) simulations for anisotropic materials: the DDD-FFT approach. By coupling the FFT-based approach to the discrete continuous model, the present approach benefits from the high computational efficiency of the FFT algorithm, while allowing for a discrete representation of dislocation lines. It is demonstrated that the computational time associated with the new DDD-FFT approach is significantly lower than that of current DDD approaches when large number of dislocation segments are involved for isotropic and anisotropic elasticity, respectively. Furthermore, for fine Fourier grids, the treatment of anisotropic elasticity comes at a similar computational cost to that of isotropic simulation. Thus, the proposed approach paves the way towards achieving scale transition from DDD to mesoscale plasticity, especially due to the method’s ability to incorporate inhomogeneous elasticity.
Static and Dynamic Anisotropic Muduli of a Shale Sample from Southern Alberta, Canada
NASA Astrophysics Data System (ADS)
Melendez Martinez, J.; Schmitt, D. R.; Kofman, R. S.
2012-12-01
Recent interest in unconventional reservoirs broadly motivates our work in laboratory measurements of seismic anisotropy. Seismic anisotropy is the variation in speed of a wave as a function of its direction of propagation and particle polarization. When assuming an isotropic model of Earth during conventional seismic processing in areas with evidence of anisotropy a poor resolution images or erroneous localization of geological structures with strong dipping is produced. Ignoring anisotropy in unconventional reservoirs leads, for example, leads to erroneous estimation of horizontal stresses, wellbore stress as well as wellbore stability during hydraulic fracturing In this sense, laboratory measurements are an important tool to study seismic anisotropy since they provide information on the anisotropy intrinsic to the rock material itself. This is important to know as this contributes to the observed seismic anisotropy that is influenced by stress states and fractures. In this work, assuming a transversally isotropic medium (VTI), elastic anisotropic moduli of a dry shale from Southern Alberta are estimated as a function of confining pressure. Estimation of elastic constants and dynamic bulk moduli in a VTI medium involves recording P and S travel times by using pulse transmission method in a minimum of three different directions. These are often taken for the sake of convenience to be perpendicular (P0o and S0o), parallel (P90o and SH90o), and oblique (P45o and SH45o) to the layering of the material with the assumption that the perpendicular and parallel directions align with the principal anisotropic axes. The pulse transmission method involves generating and recording P and S ultrasonic waves traveling through a sample. Static Bulk moduli is estimated by measuring the volumetric deformation (strain) for a given confining pressure (stress) by using strain gauges directly bonded on the sample in two different directions: perpendicular to bedding and parallel to
Wang, Chi-Jen; Han, Yong; Walen, Holly; Russell, Selena M.; Thiel, Patricia A.; Evans, James W.
2013-10-01
Submonolayer homoepitaxial fcc (110) systems display behavior reflecting strong anisotropy at lower temperatures, including one-dimensional decay during Ostwald ripening of rectangular islands maintaining constant width in the (001) direction. To appropriately describe this behavior, we first develop a refined continuum Burton-Cabrera-Frank formalism, which accounts for a lack of equilibration of island shape and importantly also for inhibited incorporation of adatoms at almost-faceted (1¯10) island edges through effective kinetic coefficients. This formalism is shown to describe accurately the adatom diffusion fluxes between islands and thus island evolution for a complex experimental island configuration, as confirmed by matching results from realistic atomistic simulations for this configuration. This approach also elucidates basic dependencies of flux on island geometry and temperature. Second, a further refinement is presented incorporating separate terrace and edge adatom density fields either in a continuum setting or alternatively in a spatially discrete diffusion equation setting. The second approach allows more flexibility and accuracy in accounting for edge-diffusion kinetics including corner rounding, a lack of equilibration of the edge adatom density at (1¯10) island edges, and the effect of rare kinks on (1¯10) island edges. Finally and significantly, it suggests facile two-way corner rounding at the island periphery during island decay, contrasting the previous picture.
Dynamics of excimer formation and decay in supercritical krypton
Holroyd, Richard A.; Cook, Andrew R.; Preses, Jack M.
2009-12-14
New infrared absorbing species are identified in the pulse radiolysis of supercritical Kr at high pressures. The species are believed to be excimers. Their formation and decay rates have been time resolved using the Laser Electron Accelerator Facility. An initial species, formed in less than 1 ns, absorbs at several wavelengths between 790 and 1300 nm; The decay of this species is initially fast, followed by a slower component; the decay rate increases with pressure. As this initial species decays a second excimer is formed absorbing at 830, 890, and 990 nm. The growth and decay rates of this excimer are also pressure dependent. A third excimer, absorbing between 1000 and 1200 nm grows at a rate similar to that of the decay of the second species. The decay rate of the third species is also pressure dependent; the lifetime increases from 9.4 ns at 109 bar to 49 ns at 15 bar. A kinetic mechanism is proposed that satisfactorily reproduces the experimental results. The first species is identified as a higher energy gerade triplet state excimer and the second as the singlet gerade state.
Investigation of protein fluctuations via Anisotropic Network Model and Molecular Dynamics
NASA Astrophysics Data System (ADS)
Okan, Osman B.; Turgut, Deniz; Rammohan, Aravind; Garcia, Angel E.; Ozisik, Rahmi
2014-03-01
We use Anisotropic Network Model (ANM) and compare its protein fluctuation predictions against molecular dynamics (MD) simulations and experimental findings for 210 globular proteins. The ANM results are analyzed using bond orientational order (BOO) parameters. We show that BOO parameters could be reformulated as a sum of contact density and geometrical (distribution of contacts in space) components. This reformulation of BOO makes it possible to investigate the role of each individual component separately, and identify cut-off ranges where each component dominates protein fluctuations. Our results indicate that the widely accepted correlation between mean squared displacements (MSDs) and inverse contact density is valid for ANM within the cut-off range of 10-15 Å. We show that the two components of the BOO dominate protein fluctuations at different length scales: contact density at small length scales and geometric distribution of residues at length scales comparable to the protein size. It is also shown that the relationship between MSD and contact density is firmly rooted in BOO, and is rendered possible with a unique distribution of residues that nullifies the average geometric component's contribution to the BOO within the 10 -15 Å cut-off.__ The material is partially based upon work supported by NSF under Grant Nos. 1200270 and 1003574, and 1050966.
NASA Astrophysics Data System (ADS)
Rajasekaran, G.; Parashar, Avinash
2016-09-01
The mechanical properties of graphene sheet can be tailored with the help of topological defects. In this research article, the effects of Stone-Thrower-Wales (STW) defects on the mechanical properties of graphene sheet was investigated with the help of molecular dynamics based simulations. Authors has made an attempt to analyse the stress field developed in and around the vicinity of defect due to bond reorientation and further systematic evaluation has been carried out to study the effect of these stress fields against the applied axial compressive load. The results obtained with the pristine graphene were made to compare with the available open literature and the results were reported to be in good agreement with theoretical and experimental data. It was predicted that graphene with STW defect cannot able to bear compressive strength in zigzag direction, whereas on the other hand it was predicted that graphene sheet containing STW defect can bear higher compressive load in armchair direction, which shows an anisotropic response of STW defects in graphene. From the obtained results it can be observed that orientation of STW defects and the loading direction plays an important role to alter the strength of graphene under axial compression.
NASA Astrophysics Data System (ADS)
Chen, Ming-Wen; Li, Lin-Yan; Guo, Hui-Min
2017-08-01
The dynamics of nucleation and growth of a particle affected by anisotropic surface tension in the ternary alloy melt is studied. The uniformly valid asymptotic solution for temperature field, concentration field, and interface evolution of nucleation and particle growth is obtained by means of the multiple variable expansion method. The asymptotic solution reveals the critical radius of nucleation in the ternary alloy melt and an inward melting mechanism of the particle induced by the anisotropic effect of surface tension. The critical radius of nucleation is dependent on isotropic surface tension, temperature undercooling, and constitutional undercooling in the ternary alloy melt, and the solute diffusion melt decreases the critical radius of nucleation. Immediately after a nucleus forms in the initial stage of solidification, the anisotropic effect of surface tension makes some parts of its interface grow inward while some parts grow outward. Until the inward melting attains a certain distance (which is defined as "the melting depth"), these parts of interface start to grow outward with other parts. The interface of the particle evolves into an ear-like deformation, whose inner diameter may be less than two times the critical radius of nucleation within a short time in the initial stage of solidification. The solute diffusion in the ternary alloy melt decreases the effect of anisotropic surface tension on the interface deformation.
Decay dynamics of HIV-1 depend on the inhibited stages of the viral life cycle.
Sedaghat, Ahmad R; Dinoso, Jason B; Shen, Lin; Wilke, Claus O; Siliciano, Robert F
2008-03-25
The time to suppression of HIV-1 viremia to below the limit of detection of standard clinical assays is an important prognostic indicator for patients on highly active antiretroviral therapy (HAART). Recent clinical trials of the integrase inhibitor raltegravir have demonstrated more rapid viral decay than previously seen with reverse transcriptase (RT) or protease inhibitor-based regimens. Because of the therapeutic importance of drugs that target different steps in the virus life cycle, it is imperative to consider whether viral dynamics are affected by the stage of the viral life cycle at which an antiretroviral drug acts. We use a mathematical model to investigate the effects of various drug classes on the dynamics of HIV-1 decay and show that the stage at which a drug acts affects the dynamics of viral decay. We find that the drug class acting latest in the viral life cycle dictates the dynamics of HIV-1 decay. In general, we find that the later in the life cycle an inhibitor acts, the more rapid the decay in viremia, and we illustrate this by comparing the effect of RT and integrase inhibitors on viral dynamics. We conclude that the rapid decay observed in patients on integrase-inhibitor-containing regimens is not necessarily an indication of greater drug efficacy but rather an expected consequence of the fact that this drug acts later in the life cycle. We propose that clinically observed viral decay rates for HAART regimens should be evaluated in the context of the drug classes that are represented.
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.
Simulation of thermal decay and dynamic relaxation in ferromagnetic materials
NASA Astrophysics Data System (ADS)
Boerner, Eric David
2000-07-01
Thermal stability of magnetic recording is of great importance. This dissertation discusses the major theories and simulation techniques currently in use. Simulations using a Langevin approach are conducted to examine the thermal decay of ensembles of non-interacting particles with both coherent and non-coherent magnetization. This decay is compared to the simplified model of exponential decay. Understanding the magnetization relaxation process is of importance when trying to understand the reversal of the magnetization within materials. This process becomes increasingly important as data rates increase. Simulations will be conducted that do not assume a phenomenological damping. Instead, it will be seen how the relaxation process begins by dissipating energy to magnetostatic and exchange coupled excitations. A model incorporating damping to lattice vibrations by magnetostriction will also be presented. During the relaxation process energy flows from the magnetic system to the lattice. Results of simulations are compared to the damping obtained via a phenomenological approach.
Dynamical Model for the Decay of Hot and Rotating Compound Nuclei
Gupta, Raj K.; Singh, Dalip; Arun, Sham K.; Niyti; Kumar, Raj
2009-03-04
As an alternative to the well known Hauser-Feshbach analysis and statistical fission model, a dynamical collective clusterization model, called the dynamical cluster-decay model (DCM), is developed for the decay of hot and rotating compound nuclei (CN) formed in the low-energy heavy ion reactions. The model is a non-statistical description for the decay of a CN to light particles (LPs), intermediate mass fragments (IMFs), fusion-fission (FF) and quasi-fission (QF)(equivalently, capture) processes. The model considers all decay products as dynamical mass motions of preformed fragments or clusters through the interaction barrier, thereby including structure effects of the CN, and is applicable to CN from different mass regions.
NASA Astrophysics Data System (ADS)
Berezkin, Anatoly V.; Kudryavtsev, Yaroslav V.; Gorkunov, Maxim V.; Osipov, Mikhail A.
2017-04-01
Local distribution and orientation of anisotropic nanoparticles in microphase-separated symmetric diblock copolymers has been simulated using dissipative particle dynamics and analyzed with a molecular theory. It has been demonstrated that nanoparticles are characterized by a non-trivial orientational ordering in the lamellar phase due to their anisotropic interactions with isotropic monomer units. In the simulations, the maximum concentration and degree of ordering are attained for non-selective nanorods near the domain boundary. In this case, the nanorods have a certain tendency to align parallel to the interface in the boundary region and perpendicular to it inside the domains. Similar orientation ordering of nanoparticles located at the lamellar interface is predicted by the molecular theory which takes into account that the nanoparticles interact with monomer units via both isotropic and anisotropic potentials. Computer simulations enable one to study the effects of the nanorod concentration, length, stiffness, and selectivity of their interactions with the copolymer components on the phase stability and orientational order of nanoparticles. If the volume fraction of the nanorods is lower than 0.1, they have no effect on the copolymer transition from the disordered state into a lamellar microstructure. Increasing nanorod concentration or nanorod length results in clustering of the nanorods and eventually leads to a macrophase separation, whereas the copolymer preserves its lamellar morphology. Segregated nanorods of length close to the width of the diblock copolymer domains are stacked side by side into smectic layers that fill the domain space. Thus, spontaneous organization and orientation of nanorods leads to a spatial modulation of anisotropic composite properties which may be important for various applications.
Berezkin, Anatoly V; Kudryavtsev, Yaroslav V; Gorkunov, Maxim V; Osipov, Mikhail A
2017-04-14
Local distribution and orientation of anisotropic nanoparticles in microphase-separated symmetric diblock copolymers has been simulated using dissipative particle dynamics and analyzed with a molecular theory. It has been demonstrated that nanoparticles are characterized by a non-trivial orientational ordering in the lamellar phase due to their anisotropic interactions with isotropic monomer units. In the simulations, the maximum concentration and degree of ordering are attained for non-selective nanorods near the domain boundary. In this case, the nanorods have a certain tendency to align parallel to the interface in the boundary region and perpendicular to it inside the domains. Similar orientation ordering of nanoparticles located at the lamellar interface is predicted by the molecular theory which takes into account that the nanoparticles interact with monomer units via both isotropic and anisotropic potentials. Computer simulations enable one to study the effects of the nanorod concentration, length, stiffness, and selectivity of their interactions with the copolymer components on the phase stability and orientational order of nanoparticles. If the volume fraction of the nanorods is lower than 0.1, they have no effect on the copolymer transition from the disordered state into a lamellar microstructure. Increasing nanorod concentration or nanorod length results in clustering of the nanorods and eventually leads to a macrophase separation, whereas the copolymer preserves its lamellar morphology. Segregated nanorods of length close to the width of the diblock copolymer domains are stacked side by side into smectic layers that fill the domain space. Thus, spontaneous organization and orientation of nanorods leads to a spatial modulation of anisotropic composite properties which may be important for various applications.
Decay of aftershock density with distance does not indicate triggering by dynamic stress
Richards-Dinger, K.; Stein, R.S.; Toda, S.
2010-01-01
Resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard. Felzer and Brodsky examined the distance distribution of earthquakes occurring in the first five minutes after 2 ≤ M M M ≥ 2 aftershocks showed a uniform power-law decay with slope −1.35 out to 50 km from the mainshocks. From this they argued that the distance decay could be explained only by dynamic triggering. Here we propose an alternative explanation for the decay, and subject their hypothesis to a series of tests, none of which it passes. At distances more than 300 m from the 2 ≤ M< 3 mainshocks, the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards, indicating that the mainshocks have no effect at distances outside their static triggering range. Omori temporal decay, the fundamental signature of aftershocks, is absent at distances exceeding 10 km from the mainshocks. Finally, the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock, which violates causality. We argue that Felzer and Brodsky implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second, and that the first of two shocks in a creep- or intrusion-driven swarm triggers the second, when this need not be the case.
Cao, Gaolong; Sun, Shuaishuai; Li, Zhongwen; Tian, Huanfang; Yang, Huaixin; Li, Jianqi
2015-02-12
Recent advances in the four-dimensional ultrafast transmission electron microscope (4D-UTEM) with combined spatial and temporal resolutions have made it possible to directly visualize structural dynamics of materials at the atomic level. Herein, we report on our development on a 4D-UTEM which can be operated properly on either the photo-emission or the thermionic mode. We demonstrate its ability to obtain sequences of snapshots with high spatial and temporal resolutions in the study of lattice dynamics of the multi-walled carbon nanotubes (MWCNTs). This investigation provides an atomic level description of remarkable anisotropic lattice dynamics at the picosecond timescales. Moreover, our UTEM measurements clearly reveal that distinguishable lattice relaxations appear in intra-tubular sheets on an ultrafast timescale of a few picoseconds and after then an evident lattice expansion along the radial direction. These anisotropic behaviors in the MWCNTs are considered arising from the variety of chemical bonding, i.e. the weak van der Waals bonding between the tubular planes and the strong covalent sp(2)-hybridized bonds in the tubular sheets.
NASA Astrophysics Data System (ADS)
Cao, Gaolong; Sun, Shuaishuai; Li, Zhongwen; Tian, Huanfang; Yang, Huaixin; Li, Jianqi
2015-02-01
Recent advances in the four-dimensional ultrafast transmission electron microscope (4D-UTEM) with combined spatial and temporal resolutions have made it possible to directly visualize structural dynamics of materials at the atomic level. Herein, we report on our development on a 4D-UTEM which can be operated properly on either the photo-emission or the thermionic mode. We demonstrate its ability to obtain sequences of snapshots with high spatial and temporal resolutions in the study of lattice dynamics of the multi-walled carbon nanotubes (MWCNTs). This investigation provides an atomic level description of remarkable anisotropic lattice dynamics at the picosecond timescales. Moreover, our UTEM measurements clearly reveal that distinguishable lattice relaxations appear in intra-tubular sheets on an ultrafast timescale of a few picoseconds and after then an evident lattice expansion along the radial direction. These anisotropic behaviors in the MWCNTs are considered arising from the variety of chemical bonding, i.e. the weak van der Waals bonding between the tubular planes and the strong covalent sp2-hybridized bonds in the tubular sheets.
NASA Astrophysics Data System (ADS)
Zeisner, J.; Brockmann, M.; Zimmermann, S.; Weiße, A.; Thede, M.; Ressouche, E.; Povarov, K. Yu.; Zheludev, A.; Klümper, A.; Büchner, B.; Kataev, V.; Göhmann, F.
2017-07-01
We compare theoretical results for electron spin resonance (ESR) properties of the Heisenberg-Ising Hamiltonian with ESR experiments on the quasi-one-dimensional magnet Cu (py) 2Br2 (CPB). Our measurements were performed over a wide frequency and temperature range giving insight into the spin dynamics, spin structure, and magnetic anisotropy of this compound. By analyzing the angular dependence of ESR parameters (resonance shift and linewidth) at room temperature, we show that the two weakly coupled inequivalent spin-chain types inside the compound are well described by Heisenberg-Ising chains with their magnetic anisotropy axes perpendicular to the chain direction and almost perpendicular to each other. We further determine the full g tensor from these data. In addition, the angular dependence of the linewidth at high temperatures gives us access to the exponent of the algebraic decay of a dynamical correlation function of the isotropic Heisenberg chain. From the temperature dependence of static susceptibilities, we extract the strength of the exchange coupling (J /kB=52.0 K ) and the anisotropy parameter (δ ≈-0.02 ) of the model Hamiltonian. An independent compatible value of δ is obtained by comparing the exact prediction for the resonance shift at low temperatures with high-frequency ESR data recorded at 4 K . The spin structure in the ordered state implied by the two (almost) perpendicular anisotropy axes is in accordance with the propagation vector determined from neutron scattering experiments. In addition to undoped samples, we study the impact of partial substitution of Br by Cl ions on spin dynamics. From the dependence of the ESR linewidth on the doping level, we infer an effective decoupling of the anisotropic component J δ from the isotropic exchange J in these systems.
Qi, Wenpeng; Chen, Jige; Yang, Junwei; Lei, Xiaoling; Song, Bo; Fang, Haiping
2013-07-03
The dynamics and structure of the hydrogen-bond network in confined water are of importance in understanding biological and chemical processes. Recently, terahertz (THz) time domain spectroscopy was widely applied for studying the kinetics of molecules and the hydrogen-bond network in water. However, the characteristics of the THz spectroscopy varying with respect to the confinement and the mechanism underlying the variation are still unclear. Here, on the basis of molecular dynamics simulations, the relationship between the anisotropic dielectric relaxation and the structure of the water confined in a carbon nanotube (CNT) was investigated. The results show that there are two preferred hydrogen-bond orientations of the confined water in the nanotube: (1) parallel to the CNT axis and (2) perpendicular to the CNT axis, which are clearly different. Moreover, the response of the orientations to the increment of the CNT diameters is opposite, leading to the opposite variations of the dielectric relaxation times along the two directions. The anisotropy in the relaxation time can be presented by the anisotropic dielectric permittivity which is able to be observed through THz spectroscopy. The anormal behaviors above are attributed to the special structure of the water close to the nanotube wall due to the confinement and hydrophobicity of CNT. These studies contribute an important step in understanding the THz experiments of water in nanoscales, and designing a chamber for specific chemical and biological reactions by controlling the diameters and materials of the nanotube.
Activated barrier crossing dynamics in the non-radiative decay of NADH and NADPH
NASA Astrophysics Data System (ADS)
Blacker, Thomas S.; Marsh, Richard J.; Duchen, Michael R.; Bain, Angus J.
2013-08-01
In live tissue, alterations in metabolism induce changes in the fluorescence decay of the biological coenzyme NAD(P)H, the mechanism of which is not well understood. In this work, the fluorescence and anisotropy decay dynamics of NADH and NADPH were investigated as a function of viscosity in a range of water-glycerol solutions. The viscosity dependence of the non-radiative decay is well described by Kramers and Kramers-Hubbard models of activated barrier crossing over a wide viscosity range. Our combined lifetime and anisotropy analysis indicates common mechanisms of non-radiative relaxation in the two emitting states (conformations) of both molecules. The low frequencies associated with barrier crossing suggest that non-radiative decay is mediated by small scale motion (e.g. puckering) of the nicotinamide ring. Variations in the fluorescence lifetimes of NADH and NADPH when bound to different enzymes may therefore be attributed to differing levels of conformational restriction upon binding.
NASA Astrophysics Data System (ADS)
Pal, Mandira; Banerjee, Chitram; Chandel, Shubham; Bag, Ankan; Majumder, Shovan K.; Ghosh, Nirmalya
2016-12-01
Spin orbit interaction and the resulting Spin Hall effect of light are under recent intensive investigations because of their fundamental nature and potential applications. Here, we report an interesting manifestation of spin Hall effect of light and demonstrate its tunability in an inhomogeneous anisotropic medium exhibiting spatially varying retardance level. In our system, the beam shift occurs only for one circular polarization mode keeping the other orthogonal mode unaffected, which is shown to arise due to the combined spatial gradients of the geometric phase and the dynamical phase of light. The constituent two orthogonal circular polarization modes of an input linearly polarized light evolve in different trajectories, eventually manifesting as a large and tunable spin separation. The spin dependent beam shift and the demonstrated principle of simultaneously tailoring space-varying geometric and dynamical phase of light for achieving its tunability (of both magnitude and direction), may provide an attractive route towards development of spin-optical devices.
Pal, Mandira; Banerjee, Chitram; Chandel, Shubham; Bag, Ankan; Majumder, Shovan K; Ghosh, Nirmalya
2016-12-22
Spin orbit interaction and the resulting Spin Hall effect of light are under recent intensive investigations because of their fundamental nature and potential applications. Here, we report an interesting manifestation of spin Hall effect of light and demonstrate its tunability in an inhomogeneous anisotropic medium exhibiting spatially varying retardance level. In our system, the beam shift occurs only for one circular polarization mode keeping the other orthogonal mode unaffected, which is shown to arise due to the combined spatial gradients of the geometric phase and the dynamical phase of light. The constituent two orthogonal circular polarization modes of an input linearly polarized light evolve in different trajectories, eventually manifesting as a large and tunable spin separation. The spin dependent beam shift and the demonstrated principle of simultaneously tailoring space-varying geometric and dynamical phase of light for achieving its tunability (of both magnitude and direction), may provide an attractive route towards development of spin-optical devices.
Pal, Mandira; Banerjee, Chitram; Chandel, Shubham; Bag, Ankan; Majumder, Shovan K.; Ghosh, Nirmalya
2016-01-01
Spin orbit interaction and the resulting Spin Hall effect of light are under recent intensive investigations because of their fundamental nature and potential applications. Here, we report an interesting manifestation of spin Hall effect of light and demonstrate its tunability in an inhomogeneous anisotropic medium exhibiting spatially varying retardance level. In our system, the beam shift occurs only for one circular polarization mode keeping the other orthogonal mode unaffected, which is shown to arise due to the combined spatial gradients of the geometric phase and the dynamical phase of light. The constituent two orthogonal circular polarization modes of an input linearly polarized light evolve in different trajectories, eventually manifesting as a large and tunable spin separation. The spin dependent beam shift and the demonstrated principle of simultaneously tailoring space-varying geometric and dynamical phase of light for achieving its tunability (of both magnitude and direction), may provide an attractive route towards development of spin-optical devices. PMID:28004825
Martinez, Angel; Smalyukh, Ivan I
2015-02-23
Oscillatory and excitable systems commonly exhibit formation of dynamic non-equilibrium patterns. For example, rotating spiral patterns are observed in biological, chemical, and physical systems ranging from organization of slime mold cells to Belousov-Zhabotinsky reactions, and to crystal growth from nuclei with screw dislocations. Here we describe spontaneous formation of spiral waves and a large variety of other dynamic patterns in anisotropic soft matter driven by low-intensity light. The unstructured ambient or microscope light illumination of thin liquid crystal films in contact with a self-assembled azobenzene monolayer causes spontaneous formation, rich spatial organization, and dynamics of twisted domains and topological solitons accompanied by the dynamic patterning of azobenzene group orientations within the monolayer. Linearly polarized incident light interacts with the twisted liquid crystalline domains, mimicking their dynamics and yielding patterns in the polarization state of transmitted light, which can be transformed to similar dynamic patterns in its intensity and interference color. This shows that the delicate light-soft-matter interaction can yield complex self-patterning of both. We uncover underpinning physical mechanisms and discuss potential uses.
Martinez, Angel; Smalyukh, Ivan I.
2015-02-12
Oscillatory and excitable systems very commonly exhibit formation of dynamic non-equilibrium patterns. For example, rotating spiral patterns are observed in biological, chemical, and physical systems ranging from organization of slime mold cells to Belousov-Zhabotinsky reactions, and to crystal growth from nuclei with screw dislocations. Here we describe spontaneous formation of spiral waves and a large variety of other dynamic patterns in anisotropic soft matter driven by low-intensity light. The unstructured ambient or microscope light illumination of thin liquid crystal films in contact with a self-assembled azobenzene monolayer causes spontaneous formation, rich spatial organization, and dynamics of twisted domains and topologicalmore » solitons accompanied by the dynamic patterning of azobenzene group orientations within the monolayer. Linearly polarized incident light interacts with the twisted liquid crystalline domains, mimicking their dynamics and yielding patterns in the polarization state of transmitted light, which can be transformed to similar dynamic patterns in its intensity and interference color. This shows that the delicate light-soft-matter interaction can yield complex self-patterning of both. Finally, we uncover underpinning physical mechanisms and discuss potential uses.« less
Martinez, Angel; Smalyukh, Ivan I.
2015-02-12
Oscillatory and excitable systems very commonly exhibit formation of dynamic non-equilibrium patterns. For example, rotating spiral patterns are observed in biological, chemical, and physical systems ranging from organization of slime mold cells to Belousov-Zhabotinsky reactions, and to crystal growth from nuclei with screw dislocations. Here we describe spontaneous formation of spiral waves and a large variety of other dynamic patterns in anisotropic soft matter driven by low-intensity light. The unstructured ambient or microscope light illumination of thin liquid crystal films in contact with a self-assembled azobenzene monolayer causes spontaneous formation, rich spatial organization, and dynamics of twisted domains and topological solitons accompanied by the dynamic patterning of azobenzene group orientations within the monolayer. Linearly polarized incident light interacts with the twisted liquid crystalline domains, mimicking their dynamics and yielding patterns in the polarization state of transmitted light, which can be transformed to similar dynamic patterns in its intensity and interference color. This shows that the delicate light-soft-matter interaction can yield complex self-patterning of both. Finally, we uncover underpinning physical mechanisms and discuss potential uses.
Decay of surface nanostructures via long-time-scale dynamics
Voter, A.F.; Stanciu, N.
1998-11-01
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have developed a new approach for extending the time scale of molecular dynamics simulations. For infrequent-event systems, the category that includes most diffusive events in the solid phase, this hyperdynamics method can extend the simulation time by a few orders of magnitude compared to direct molecular dynamics. The trajectory is run on a potential surface that has been biased to raise the energy in the potential basins without affecting the transition state region. The method is described and applied to surface and bulk diffusion processes, achieving microsecond and millisecond simulation times. The authors have also developed a new parallel computing method that is efficient for small system sizes. The combination of the hyperdynamics with this parallel replica dynamics looks promising as a general materials simulation tool.
Spectroscopy and decay dynamics of several methyl-and fluorine-substituted benzene radical cations
Bondybey, V.E.; Vaughn, C.; Miller, T.A.; English, J.H.; Shiley, R.H.
1981-01-01
Spectra of several fluorobenzene cation radicals containing 1-3 methyl substituents were observed in solid Ne matrix and analyzed. Comparisons between these compounds and other fluorobenzenes studied previously as well as comparisons between the B?? state lifetimes in the gas phase and in the matrix are used to gain a deeper insight into the B?? state decay dynamics. ?? 1981 American Chemical Society.
Dynamic surface acoustic response to a thermal expansion source on an anisotropic half space.
Zhao, Peng; Zhao, Ji-Cheng; Weaver, Richard
2013-05-01
The surface displacement response to a distributed thermal expansion source is solved using the reciprocity principle. By convolving the strain Green's function with the thermal stress field created by an ultrafast laser illumination, the complete surface displacement on an anisotropic half space induced by laser absorption is calculated in the time domain. This solution applies to the near field surface displacement due to pulse laser absorption. The solution is validated by performing ultrafast laser pump-probe measurements and showing very good agreement between the measured time-dependent probe beam deflection and the computed surface displacement.
Constrained Analysis of Fluorescence Anisotropy Decay:Application to Experimental Protein Dynamics
Feinstein, Efraim; Deikus, Gintaras; Rusinova, Elena; Rachofsky, Edward L.; Ross, J. B. Alexander; Laws, William R.
2003-01-01
Hydrodynamic properties as well as structural dynamics of proteins can be investigated by the well-established experimental method of fluorescence anisotropy decay. Successful use of this method depends on determination of the correct kinetic model, the extent of cross-correlation between parameters in the fitting function, and differences between the timescales of the depolarizing motions and the fluorophore's fluorescence lifetime. We have tested the utility of an independently measured steady-state anisotropy value as a constraint during data analysis to reduce parameter cross correlation and to increase the timescales over which anisotropy decay parameters can be recovered accurately for two calcium-binding proteins. Mutant rat F102W parvalbumin was used as a model system because its single tryptophan residue exhibits monoexponential fluorescence intensity and anisotropy decay kinetics. Cod parvalbumin, a protein with a single tryptophan residue that exhibits multiexponential fluorescence decay kinetics, was also examined as a more complex model. Anisotropy decays were measured for both proteins as a function of solution viscosity to vary hydrodynamic parameters. The use of the steady-state anisotropy as a constraint significantly improved the precision and accuracy of recovered parameters for both proteins, particularly for viscosities at which the protein's rotational correlation time was much longer than the fluorescence lifetime. Thus, basic hydrodynamic properties of larger biomolecules can now be determined with more precision and accuracy by fluorescence anisotropy decay. PMID:12524313
Microbial community dynamics alleviate stoichiometric constraints during litter decay
Kaiser, Christina; Franklin, Oskar; Dieckmann, Ulf; Richter, Andreas
2014-01-01
Under the current paradigm, organic matter decomposition and nutrient cycling rates are a function of the imbalance between substrate and microbial biomass stoichiometry. Challenging this view, we demonstrate that in an individual-based model, microbial community dynamics alter relative C and N limitation during litter decomposition, leading to a system behaviour not predictable from stoichiometric theory alone. Rather, the dynamics of interacting functional groups lead to an adaptation at the community level, which accelerates nitrogen recycling in litter with high initial C : N ratios and thus alleviates microbial N limitation. This mechanism allows microbial decomposers to overcome large imbalances between resource and biomass stoichiometry without the need to decrease carbon use efficiency (CUE), which is in contrast to predictions of traditional stoichiometric mass balance equations. We conclude that identifying and implementing microbial community-driven mechanisms in biogeochemical models are necessary for accurately predicting terrestrial C fluxes in response to changing environmental conditions. PMID:24628731
Wetzel, David J.; Malone, Marvin A.; Haasch, Richard T.; Meng, Yifei; Vieker, Henning; Hahn, Nathan; Golzhauser, Armin; Zuo, Jian-Min; Zavadil, Kevin R.; Gewirth, Andrew A.; Nuzzo, Ralph G.
2015-08-10
Rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, though little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. Finally, the passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.
Wetzel, David J; Malone, Marvin A; Haasch, Richard T; Meng, Yifei; Vieker, Henning; Hahn, Nathan T; Gölzhäuser, Armin; Zuo, Jian-Min; Zavadil, Kevin R; Gewirth, Andrew A; Nuzzo, Ralph G
2015-08-26
Although rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. The passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.
Marcela Zalamea; Grizelle Gonzalez; Chien-Lu Ping; Gary Michaelson
2007-01-01
Decaying wood is an important structural and functional component of forests: it contributes to generate habitat diversity, acts as either sink or source of nutrients, and plays a preponderant role in soil formation. Thus, decaying wood might likely have measurable effects on chemical properties of the underlying soil.We hypothesized that decaying wood would have a...
NASA Astrophysics Data System (ADS)
Stepanov, Serguei; Hernández, Eliseo; Plata, Marcos
2005-06-01
We report on observations of transient two-wave mixing (TWM) of orthogonally polarized waves counterpropagating through an Er-doped single-mode optical fiber. Experiments were performed in a 2-m-long moderately birefringent (with beat length ~2 cm) Er-doped fiber without optical pumping at the laser wavelength 1549 nm. The transient TWM signal observed for crossed linear polarizations of the recording waves oriented along two orthogonal birefringence axes of the fiber (i.e., for the interference pattern with spatially modulated state of light polarization only) proved to be approximately half of that observed for parallel polarizations. Direct measurements of the transient polarization hole-burning effect (i.e., that observed for fast switching of the input light linear polarization between two orthogonal orientations of the doped fiber birefringence axes) allow us to attribute formation of the corresponding anisotropic dynamic grating to this effect.
NASA Astrophysics Data System (ADS)
Zheng, Zijian; Wang, Zixuan; Wang, Lu; Liu, Jun; Wu, Youping; Zhang, Liqun
2016-07-01
Although a large number of studies have been performed to study the dispersion behavior of spherical nanoparticles (NPs) in the polymer matrix, little effort has been directed to anisotropic NPs via simulation, which is convenient for controlling the physical parameters compared to experiment. In this work we adopt molecular dynamics simulation to study polymer nanocomposites filled with anisotropic NPs such as graphene and carbon nanotubes (CNTs). We investigate the effects of the grafting position, grafting density, the length and flexibility of the grafted chains on the dispersion of graphene and CNTs. In particular, we find that when the grafting position is located on the surface center of the graphene or the middle of the CNT, the dispersion state is the best, leading to the greatest stress-strain behavior. Meanwhile, the mechanical property can be further strengthened by introducing chemical couplings in the interfacial region, by chemically tethering the grafted chains to the matrix chains. To monitor the processing effect, we exert a dynamic periodic shear deformation in the x direction with its gradient in the y direction. Polymer chains are found to align in the x direction, graphene sheets align in the xoz plane and CNTs orientate in the z direction. We study the effects of the shear amplitude, the shear frequency, polymer-NP interaction strength and volume fraction of NPs on the stress-strain behavior. We also observe that the relaxation process following the shear deformation deteriorates the mechanical performance, resulting from the disorientation of polymer chains and NPs. In general, this work could provide valuable guidance in manipulating the distribution and alignment of graphene and CNTs in the polymer matrix.
Impact of nuclear dynamics on interatomic Coulombic decay in a He dimer
Sisourat, Nicolas; Kryzhevoi, Nikolai V.; Cederbaum, Lorenz S.; Kolorenc, Premysl; Scheit, Simona
2010-11-15
After simultaneous ionization and excitation of one helium atom within the giant weakly bound helium dimer, the excited ion can relax via interatomic Coulombic decay (ICD) and the excess energy is transferred to ionize the neighboring helium atom. We showed [Sisourat et al. Nature Phys. 6, 508 (2010)] that the distributions of the kinetic energy released by the two ions reflect the nodal structures of the ICD-involved vibrational wave functions. We also demonstrated that energy transfer via ICD between the two helium atoms can take place over more than 14 A. We report here a more detailed analysis of the ICD process and of the impact of the nuclear dynamics on the electronic decay. Nonadiabatic effects during the ICD process and the accuracy of the potential energy curve of helium dimer and of the computed decay rates are also investigated.
Visualization of anisotropic-isotropic phase transformation dynamics in battery electrode particles
Wang, Jiajun; Karen Chen-Wiegart, Yu-chen; Eng, Christopher; Shen, Qun; Wang, Jun
2016-08-12
Anisotropy, or alternatively, isotropy of phase transformations extensively exist in a number of solid-state materials, with performance depending on the three-dimensional transformation features. Fundamental insights into internal chemical phase evolution allow manipulating materials with desired functionalities, and can be developed via real-time multi-dimensional imaging methods. In this paper, we report a five-dimensional imaging method to track phase transformation as a function of charging time in individual lithium iron phosphate battery cathode particles during delithiation. The electrochemically driven phase transformation is initially anisotropic with a preferred boundary migration direction, but becomes isotropic as delithiation proceeds further. We also observe the expected two-phase coexistence throughout the entire charging process. Finally, we expect this five-dimensional imaging method to be broadly applicable to problems in energy, materials, environmental and life sciences.
Visualization of anisotropic-isotropic phase transformation dynamics in battery electrode particles
Wang, Jiajun; Karen Chen-Wiegart, Yu-chen; Eng, Christopher; Shen, Qun; Wang, Jun
2016-01-01
Anisotropy, or alternatively, isotropy of phase transformations extensively exist in a number of solid-state materials, with performance depending on the three-dimensional transformation features. Fundamental insights into internal chemical phase evolution allow manipulating materials with desired functionalities, and can be developed via real-time multi-dimensional imaging methods. Here, we report a five-dimensional imaging method to track phase transformation as a function of charging time in individual lithium iron phosphate battery cathode particles during delithiation. The electrochemically driven phase transformation is initially anisotropic with a preferred boundary migration direction, but becomes isotropic as delithiation proceeds further. We also observe the expected two-phase coexistence throughout the entire charging process. We expect this five-dimensional imaging method to be broadly applicable to problems in energy, materials, environmental and life sciences. PMID:27516044
Entanglement production due to quench dynamics of an anisotropic XY chain in a transverse field
NASA Astrophysics Data System (ADS)
Sengupta, K.; Sen, Diptiman
2009-09-01
We compute concurrence and negativity as measures of two-spin entanglement generated by a power-law quench (characterized by a rate τ-1 and an exponent α ) which takes an anisotropic XY chain in a transverse field through a quantum critical point (QCP). We show that only spins separated by an even number of lattice spacings get entangled in such a process. Moreover, there is a critical rate of quench, τc-1 , above which no two-spin entanglement is generated; the entire entanglement is multipartite. The ratio of the entanglements between consecutive even neighbors can be tuned by changing the quench rate. We also show that for large τ , the concurrence (negativity) scales as α/τ (α/τ) , and we relate this scaling behavior to defect production by the quench through a QCP.
Dynamics of a Flat Multidimensional Anisotropic Universe in the Gauss-Bonnet Gravity
NASA Astrophysics Data System (ADS)
Toporensky, Alexey; Kirnos, Ilya; Pavluchenko, Sergyey
We consider a flat anisotropic metric in (4+1)- and (5+1)-dimensional space-time in Gauss-Bonnet gravity. In the present presentation we are interesting in the behavior mostly in the vicinity of the cosmological singularity, which allows us to take into account only corrections of the highest possible order. In our case it is the Gauss-Bonnet contribution, so we neglect Einstein terms. In the absence of matter sources this problem have been studied in Ref. 1,2, in the present presentation we take matter into account. The full Einstein - Gauss-Bonnet system shows a complicated behavior even in the vacuum case3,4 and we leave investigation of such system with matter for a future work.
Gorelikov, G. A.; Fridman, Yu. A.
2013-07-15
The spectra of coupled magnetoelastic waves in a semi-infinite strongly anisotropic easy-plane ferromagnet with a rigidly fixed face are analyzed for two variants of fixation (in the basal plane and perpendicularly to it). The phase states of the system are determined. Differences in the phase diagrams and elementary excitation spectra depending on the choice of the sample fixation plane are considered. When rotational invariance is taken into account, the nonreciprocity effect for the velocities of sound in a crystal appears. It is shown that the velocity of sound in the sample considerably depends on the symmetry of the imposed mechanical boundary conditions. The phase diagrams of the system under investigation are presented.
Visualization of anisotropic-isotropic phase transformation dynamics in battery electrode particles
Wang, Jiajun; Karen Chen-Wiegart, Yu-chen; Eng, Christopher; ...
2016-08-12
Anisotropy, or alternatively, isotropy of phase transformations extensively exist in a number of solid-state materials, with performance depending on the three-dimensional transformation features. Fundamental insights into internal chemical phase evolution allow manipulating materials with desired functionalities, and can be developed via real-time multi-dimensional imaging methods. In this paper, we report a five-dimensional imaging method to track phase transformation as a function of charging time in individual lithium iron phosphate battery cathode particles during delithiation. The electrochemically driven phase transformation is initially anisotropic with a preferred boundary migration direction, but becomes isotropic as delithiation proceeds further. We also observe the expectedmore » two-phase coexistence throughout the entire charging process. Finally, we expect this five-dimensional imaging method to be broadly applicable to problems in energy, materials, environmental and life sciences.« less
Wetzel, David J.; Malone, Marvin A.; Haasch, Richard T.; ...
2015-08-10
Rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, though little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pitmore » densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. Finally, the passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.« less
Chun, Chan Lan; Peller, Julie R.; Shively, Dawn; Byappanahalli, Muruleedhara N.; Whitman, Richard L.; Staley, Christopher; Zhang, Qian; Ishii, Satoshi; Sadowsky, Michael J.
2017-01-01
Cladophora mats that accumulate and decompose along shorelines of the Great Lakes create potential threats to the health of humans and wildlife. The decaying algae create a low oxygen and redox potential environment favoring growth and persistence of anaerobic microbial populations, including Clostridium botulinum, the causal agent of botulism in humans, birds, and other wildlife. In addition to the diverse population of microbes, a dynamic chemical environment is generated, which involves production of numerous organic and inorganic substances, many of which are believed to be toxic to the sand and aquatic biotic communities. In this study, we used 16S-rDNA-based-amplicon sequencing and microfluidic-based quantitative PCR approaches to characterize the bacterial community structure and the abundances of human pathogens associated with Cladophora at different stages (up to 90 days) of algal decay in laboratory microcosms. Oxygen levels were largely depleted after a few hours of incubation. As Cladophora decayed, the algal microbial biodiversity decreased within 24 h, and the mat transitioned from an aerobic to anaerobic environment. There were increasing abundances of enteric and pathogenic bacteria during decomposition of Cladophora, including Acinetobacter, Enterobacter, Kluyvera, Cedecea, and others. In contrast, there were no or very few sequences (< 0.07%) assigned to such groups in fresh Cladophora samples. Principal coordinate analysis indicated that the bacterial community structure was dynamic and changed significantly with decay time. Knowledge of microbial communities and chemical composition of decaying algal mats is critical to our further understanding of the role that Cladophora plays in a beach ecosystem's structure and function, including the algal role in trophic interactions. Based on these findings, public and environmental health concerns should be considered when decaying Cladophora mats accumulate Great Lakes shorelines.
Chun, Chan Lan; Peller, Julie R; Shively, Dawn; Byappanahalli, Muruleedhara N; Whitman, Richard L; Staley, Christopher; Zhang, Qian; Ishii, Satoshi; Sadowsky, Michael J
2017-01-01
Cladophora mats that accumulate and decompose along shorelines of the Great Lakes create potential threats to the health of humans and wildlife. The decaying algae create a low oxygen and redox potential environment favoring growth and persistence of anaerobic microbial populations, including Clostridium botulinum, the causal agent of botulism in humans, birds, and other wildlife. In addition to the diverse population of microbes, a dynamic chemical environment is generated, which involves production of numerous organic and inorganic substances, many of which are believed to be toxic to the sand and aquatic biotic communities. In this study, we used 16S-rDNA-based-amplicon sequencing and microfluidic-based quantitative PCR approaches to characterize the bacterial community structure and the abundances of human pathogens associated with Cladophora at different stages (up to 90days) of algal decay in laboratory microcosms. Oxygen levels were largely depleted after a few hours of incubation. As Cladophora decayed, the algal microbial biodiversity decreased within 24h, and the mat transitioned from an aerobic to anaerobic environment. There were increasing abundances of enteric and pathogenic bacteria during decomposition of Cladophora, including Acinetobacter, Enterobacter, Kluyvera, Cedecea, and others. In contrast, there were no or very few sequences (<0.07%) assigned to such groups in fresh Cladophora samples. Principal coordinate analysis indicated that the bacterial community structure was dynamic and changed significantly with decay time. Knowledge of microbial communities and chemical composition of decaying algal mats is critical to our further understanding of the role that Cladophora plays in a beach ecosystem's structure and function, including the algal role in trophic interactions. Based on these findings, public and environmental health concerns should be considered when decaying Cladophora mats accumulate Great Lakes shorelines.
Decay and nutrient dynamics of coarse woody debris in the Qinling Mountains, China
Yuan, Jie; Hou, Lin; Wei, Xin; Shang, Zhengchun; Cheng, Fei; Zhang, Shuoxin
2017-01-01
As an ecological unit, coarse woody debris (CWD) plays an essential role in productivity, nutrient cycling, carbon sequestration, community regeneration and biodiversity. However, thus far, the information on quantification the decomposition and nutrient content of CWD in forest ecosystems remains considerably limited. In this study, we conducted a long-term (1996–2013) study on decay and nutrient dynamics of CWD for evaluating accurately the ecological value of CWD on the Huoditang Experimental Forest Farm in the Qinling Mountains, China. The results demonstrated that there was a strong correlation between forest biomass and CWD mass. The single exponential decay model well fit the CWD density loss at this site, and as the CWD decomposed, the CWD density decreased significantly. Annual temperature and precipitation were all significantly correlated with the annual mass decay rate. The K contents and the C/N ratio of the CWD decreased as the CWD decayed, but the C, N, P, Ca and Mg contents increased. We observed a significant CWD decay effect on the soil C, N and Mg contents, especially the soil C content. The soil N, P, K, Ca and Mg contents exhibited large fluctuations, but the variation had no obvious regularity and changed with different decay times. The results showed that CWD was a critical component of nutrient cycling in forest ecosystems. Further research is needed to determine the effect of diameter, plant tissue components, secondary wood compounds, and decomposer organisms on the CWD decay rates in the Qinling Mountains, which will be beneficial to clarifying the role of CWD in carbon cycles of forest ecosystems. PMID:28384317
Decay and nutrient dynamics of coarse woody debris in the Qinling Mountains, China.
Yuan, Jie; Hou, Lin; Wei, Xin; Shang, Zhengchun; Cheng, Fei; Zhang, Shuoxin
2017-01-01
As an ecological unit, coarse woody debris (CWD) plays an essential role in productivity, nutrient cycling, carbon sequestration, community regeneration and biodiversity. However, thus far, the information on quantification the decomposition and nutrient content of CWD in forest ecosystems remains considerably limited. In this study, we conducted a long-term (1996-2013) study on decay and nutrient dynamics of CWD for evaluating accurately the ecological value of CWD on the Huoditang Experimental Forest Farm in the Qinling Mountains, China. The results demonstrated that there was a strong correlation between forest biomass and CWD mass. The single exponential decay model well fit the CWD density loss at this site, and as the CWD decomposed, the CWD density decreased significantly. Annual temperature and precipitation were all significantly correlated with the annual mass decay rate. The K contents and the C/N ratio of the CWD decreased as the CWD decayed, but the C, N, P, Ca and Mg contents increased. We observed a significant CWD decay effect on the soil C, N and Mg contents, especially the soil C content. The soil N, P, K, Ca and Mg contents exhibited large fluctuations, but the variation had no obvious regularity and changed with different decay times. The results showed that CWD was a critical component of nutrient cycling in forest ecosystems. Further research is needed to determine the effect of diameter, plant tissue components, secondary wood compounds, and decomposer organisms on the CWD decay rates in the Qinling Mountains, which will be beneficial to clarifying the role of CWD in carbon cycles of forest ecosystems.
Dynamical Decay of a Massive Multiple System in Orion KL?
NASA Astrophysics Data System (ADS)
Gómez, Laura; RodrÍguez, Luis F.; Loinard, Laurent; Lizano, Susana; Poveda, Arcadio; Allen, Christine
2005-12-01
We present absolute astrometry of 35 radio sources in the Orion Trapezium and Becklin-Neugebauer/Kleinman-Low (BN/KL) regions, obtained from Very Large Array archival observations collected over a period of 15 years. By averaging the results for all the sources, we estimate the mean absolute proper motion of Orion to be-in Galactic coordinates-μlcosb=+2.1+/-0.2 mas yr-1, μb=-0.1+/-0.2 mas yr-1. These values agree remarkably well with those expected from the differential rotation of the Milky Way. Subtraction of this mean motion from the individual measurements allows us to register all proper motions to the rest frame of the Orion Nebula and to identify radio sources with large residual velocities. In the KL region, we find three sources in this situation: the BN object, the radio source I, and the radio counterpart of the infrared source n. All three objects appear to be moving away from a common point where they must all have been located about 500 years ago. This suggests that all three sources were originally part of a multiple massive stellar system that recently disintegrated as a result of a close dynamical interaction.
Detecting the dynamical state of the atmosphere from the orbital decay of the ODERACS spheres
NASA Technical Reports Server (NTRS)
Tan, Arjun
1996-01-01
The orbital decay curve of a satellite having constant cross-sectional area and in circular orbit can furnish valuable information regarding the dynamical state of the atmosphere. It is shown that a rectilinear decay curve having constant downward slope (zero curvature) should indicate that the atmosphere was undergoing compression during that period. A decay curve having concavity upwards (positive curvature) will strongly indicate that the atmosphere was in a contracting phase. A decay curve with downward concavity (negative curvature) may indicate an expanding, a stationary or a contracting atmosphere. This theory, when applied to the orbital decay of the Orbital Debris Radar Calibration Spheres (ODERACS) satellites, indicates that during the period from Day 90 through Day 240 in the year 1994, the atmosphere was very definitely in a compression mode. During this period, ODERACS Sphere 1 faced nearly constant densities while Sphere 6 actually encountered progressively smaller air densities as they descended. The atmospheric scale height as calculated from the orbital data of Spheres 1 and 6 diminished steadily during the same period. It is shown that Spheres 1 and 6 descended faster and slower respectively, than the level of constant air density equal to 5 x 10 kg/m . During a brief period from Day 240 through Day 290, the atmosphere reversed to a strongly expanding mode. Thereafter, the atmosphere reverted back to a compression mode from Day 290 through Day 390, 1994.
Choudhary, Ashu; Chandra, Amalendu
2016-02-17
The anisotropic structure and dynamics of the hydration shell of a benzene solute in liquid water have been investigated by means of ab initio molecular dynamics simulations using the BLYP (Becke-Lee-Yang-Parr) and dispersion corrected BLYP-D functionals. The main focus has been to look at the influence of π-hydrogen-bonding and hydrophobic interactions on the distance and angle resolved various structural and dynamic properties of solvation shell. The structure of hydration shell water molecules around benzene is found to be highly anisotropic as revealed by the radial distribution functions of different conical regions and joint radial/angular distribution functions. The benzene-water dimer potential energy curves are calculated for a variety of orientations of water along the axial and equatorial directions for both BLYP and BLYP-D functionals. The simulation results of the hydration shell structure of benzene, particularly the axial and equatorial benzene-water RDFs are discussed based on the differences in the benzene-water potential energies for different orientations and functionals. The inter-particle distance/angle correlations show an enhanced water structure in the solvation shell of benzene compared to that between the solvation shell and bulk and also between the bulk molecules. On average, a single πH-bond is found to be formed between water and benzene in the 45° axial conical region of the solvation shell. The πH-bonded water molecules are found to have faster translational dynamics and also found to follow a fast jump mechanism of reorientation to change their hydrogen bonded partners. The presence of π-hydrogen-bonded water makes the overall dynamics of the axial region faster than that of the equatorial region where the water molecules are hydrophobically solvated and hydrogen bonded to other water molecules.
Flow Decay: A Novel Spirometric Index to Quantify Dynamic Airway Resistance.
Oh, Anita; Morris, Tessa A; Yoshii, Isaac T; Morris, Timothy A
2017-07-01
Dynamic airway resistance from obstructive disease causes a concavity in the mid-expiratory portion of the spirometric flow-volume loop. We developed a simple model to measure the exponential decay in air flow during forced exhalation to quantify the extent of dynamic airway obstruction and facilitate the detection of obstructive airway diseases clinically. We calculated flow decay as the slope of volume versus ln(1/flow) in mid-exhalation. We derived the normal range in a derivation group of healthy volunteers in whom spirometry had been performed repeatedly. We validated the derived upper limit of normal (mean + 2 × SD) by using it to distinguish a separate group of healthy subjects (n = 25) from subjects with independently diagnosed reversible airway obstruction (n = 31) and subjects with obstruction, hyperinflation, and air trapping (n = 62). In the derivation group (n = 7), the mean ± SD flow decay was 0.588 ± 0.107 L(-1) (upper limit of normal = 0.802 L(-1)). Flow decay in 23 of 25 healthy subjects in the validation group was below the upper limit of normal. In contrast, it was above the upper limit of normal in 29 of 31 subjects with reversible airway obstruction (sensitivity 94%, 95% CI 79-99%; specificity 92%, 95% CI 74-99%) and in 59 of 62 of subjects with obstruction, hyperinflation, and air trapping (sensitivity 92%, 95% CI 74-99%; specificity 95%, 95% CI 86-99%). Flow decay distinguished subjects with obstructive lung defects from healthy subjects. It is a straightforward representation of spirometry data that provides a reproducible index to quantify dynamic airway obstruction. Copyright © 2017 by Daedalus Enterprises.
Eslami, Hossein; Mohammadzadeh, Laila; Mehdipour, Nargess
2012-03-14
While polymers are known as thermal insulators, recent studies show that stretched single chains of polymers have a very high thermal conductivity. In this work, our new simulation scheme for simulation of heat flow in nanoconfined fluids [H. Eslami, L. Mohammadzadeh, and N. Mehdipour, J. Chem. Phys. 135, 064703 (2011)] is employed to study the effect of chain ordering (stretching) on the rate of heat transfer in polyamide-6,6 nanoconfined between graphene surfaces. Our results for the heat flow in the parallel direction (the plane of surfaces) show that the coefficient of thermal conductivity depends on the intersurface distance and is much higher than that of the bulk polymer. A comparison of results in this work with our former findings on the heat flow in the perpendicular direction, with the coefficient of heat conductivity less than the bulk sample, reveal that well-organized polymer layers between the confining surfaces show an anisotropic heat conduction; the heat conduction in the direction parallel to the surfaces is much higher than that in the perpendicular direction. The origin of such anisotropy in nanometric heat flow is shown to be the dramatic anisotropy in chain conformations (chain stretching) beside the confining surfaces. The results indicate that the coefficients of heat conductivity in both directions, normal and parallel to the surfaces, depend on the degree of polymer layering between the surfaces and the pore width.
Dynamical Cluster-decay Model (DCM) applied to 9Li+208Pb reaction
NASA Astrophysics Data System (ADS)
Kaur, Arshdeep; Hemdeep; Kaushal, Pooja; Behera, Bivash R.; Gupta, Raj K.
2017-10-01
The decay mechanism of 217At* formed in 9Li+208Pb reaction is studied within the dynamical cluster-decay model (DCM) at various center-of-mass energies. The aim is to see the behavior of a light neutron-rich radioactive beam on a doubly-magic target nucleus for the (total) fusion cross section σfus and the individual decay channel cross sections. Experimentally, only the isotopic yield of heavy mass residues 211-214At * [equivalently, the light-particles (LPs) evaporation residue cross sections σxn for x = 3- 6 neutrons emission] are measured, with the fusion-fission (ff) component σff taken zero. For a fixed neck-length parameter ΔR, the only parameter in the DCM, we are able to fit σfus =∑x=16σxn almost exactly for 9Li on 208Pb at all E c . m .'s. However, the observed individual decay channels (3n-6n) are very poorly fitted, with unobserved channels (1n, 2n) and σff strongly over-estimated. Different ΔR values, meaning thereby different reaction time scales, are required to fit individually both the observed and unobserved evaporation residue channels (1n-6n) and σff, but then the compound nucleus (CN) contribution σCN is very small (< 1%), and the non-compound nucleus (nCN) decay cross section σnCN contributes the most towards total σfus (=σCN +σnCN). Thus, the 9Li induced reaction on doubly-magic 208Pb is more of a quasi-fission-like nCN decay, which is further analyzed in terms of the statistical CN formation probability PCN and CN survival probability Psurv. For the reaction under study, PCN < < 1 and Psurv → 1, in particular at above barrier energies.
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.
Molecular dynamics study on the failure modes of aluminium under decaying shock loading
NASA Astrophysics Data System (ADS)
Shao, Jian-Li; Wang, Pei; He, An-Min; Duan, Su-Qing; Qin, Cheng-Sen
2013-04-01
We have investigated the failure modes of single crystal aluminium under decaying shock loading by using molecular dynamics simulations. The microstructure evolution during the failure is presented in terms of the central symmetry parameter, and the corresponding pressure and temperature profiles are calculated and discussed. These results explain the failure morphology and mechanical properties under dynamic tension and especially the difference between solid and melted states. In addition, the fracture strength of aluminium is analyzed from surface velocity within acoustic approximation and virial theorem.
NASA Astrophysics Data System (ADS)
Gale, Charles; Jeon, Sangyong; Schenke, Björn; Tribedy, Prithwish; Venugopalan, Raju
2013-01-01
Anisotropic flow coefficients v1-v5 in heavy ion collisions are computed by combining a classical Yang-Mills description of the early time Glasma flow with the subsequent relativistic viscous hydrodynamic evolution of matter through the quark-gluon plasma and hadron gas phases. The Glasma dynamics, as realized in the impact parameter dependent Glasma (IP-Glasma) model, takes into account event-by-event geometric fluctuations in nucleon positions and intrinsic subnucleon scale color charge fluctuations; the preequilibrium flow of matter is then matched to the music algorithm describing viscous hydrodynamic flow and particle production at freeze-out. The IP-Glasma+MUSIC model describes well both transverse momentum dependent and integrated vn data measured at the Large Hadron Collider and the Relativistic Heavy Ion Collider. The model also reproduces the event-by-event distributions of v2, v3 and v4 measured by the ATLAS Collaboration. The implications of our results for better understanding of the dynamics of the Glasma and for the extraction of transport properties of the quark-gluon plasma are outlined.
Greene, George W; Zappone, Bruno; Söderman, Olle; Topgaard, Daniel; Rata, Gabriel; Zeng, Hongbo; Israelachvili, Jacob N
2010-04-01
A compression cell designed to fit inside an NMR spectrometer was used to investigate the in situ mechanical strain response, structural changes to the internal pore structure, and the diffusion and flow of interstitial water in full-thickness cartilage samples as it was deforming dynamically under a constant compressive load (pressure). We distinguish between the hydrostatic pressure acting on the interstitial fluid and the pore pressure acting on the cartilage fibril network. Our results show that properties related to the pore matrix microstructure such as diffusion and hydraulic conductivity are strongly influenced by the hydrostatic pressure in the interstitial fluid of the dynamically deforming cartilage which differ significantly from the properties measured under static i.e. equilibrium loading conditions (when the hydrostatic pressure has relaxed back to zero). The magnitude of the hydrostatic fluid pressure also appears to affect the way cartilage's pore matrix changes during deformation with implications for the diffusion and flow-driven fluid transport through the deforming pore matrix. We also show strong evidence for a highly anisotropic pore structure and deformational dynamics that allows cartilage to deform without significantly altering the axial porosity of the matrix even at very large strains. The insensitivity of the axial porosity to compressive strain may be playing a critical function in directing the flow of pressurized interstitial fluid in the compressed cartilage to the surface, to support the load, and provide a protective interfacial fluid film that 'weeps' out from the deforming tissue and thereby enhances the (elasto)hydrodynamic efficacy of sliding joints. Our results appear to show a close synergy between the structure of cartilage and both the hydrodynamic and boundary lubrication mechanisms. Copyright 2010 Elsevier Ltd. All rights reserved.
Non-Abelian dynamics in the resonant decay of the Higgs after inflation
Enqvist, Kari; Nurmi, Sami; Rusak, Stanislav E-mail: sami.nurmi@helsinki.fi
2014-10-01
We study the resonant decay of the Higgs condensate into weak gauge bosons after inflation and estimate the corrections arising from the non-Abelian self-interactions of the gauge fields. We find that non-Abelian interaction terms induce an effective mass which tends to shut down the resonance. For the broad resonance relevant for the Standard Model Higgs the produced gauge particles backreact on the dynamics of the Higgs condensate before the non-Abelian terms grow large. The non-Abelian terms can however significantly affect the final stages of the resonance after the backreaction. In the narrow resonance regime, which may be important for extensions of the Standard Model, the non-Abelian terms affect already the linear stage and terminate the resonance before the Higgs condensate is affected by the backreaction of decay products.
Duhamel, Jean
2014-03-11
The aim of this review is to introduce the reader first to the mathematical complexity associated with the analysis of fluorescence decays acquired with solutions of macromolecules labeled with a fluorophore and its quencher that are capable of interacting with each other via photophysical processes within the macromolecular volume, second to the experimental and mathematical approaches that have been proposed over the years to handle this mathematical complexity, and third to the information that one can expect to retrieve with respect to the internal dynamics of such fluorescently labeled macromolecules. In my view, the ideal fluorophore-quencher pair to use in studying the internal dynamics of fluorescently labeled macromolecules would involve a long-lived fluorophore, a fluorophore and a quencher that do not undergo energy migration, and a photophysical process that results in a change in fluorophore emission upon contact between the excited fluorophore and quencher. Pyrene, with its ability to form an excimer on contact between excited-state and ground-state species, happens to possess all of these properties. Although the concepts described in this review apply to any fluorophore and quencher pair sharing pyrene's exceptional photophysical properties, this review focuses on the study of pyrene-labeled macromolecules that have been characterized in great detail over the past 40 years and presents the main models that are being used today to analyze the fluorescence decays of pyrene-labeled macromolecules reliably. These models are based on Birks' scheme, the DMD model, the fluorescence blob model, and the model free analysis. The review also provides a step-by-step protocol that should enable the noneducated user to achieve a successful decay analysis exempt of artifacts. Finally, some examples of studies of pyrene-labeled macromolecules are also presented to illustrate the different types of information that can be retrieved from these fluorescence decay
Fusion-Fission Dynamics of Super-Heavy Element Formation and Decay
Zagrebaev, V.I.
2004-04-12
The paper is focused on reaction dynamics of super-heavy nucleus formation and decay at beam energies near the Coulomb barrier. The aim is to review the things we have learned from recent experiments on fusion-fission reactions leading to the formation of compound nuclei with Z {>=} 102 and from their extensive theoretical analysis. Main attention is paid to the dynamics of formation of very heavy compound nuclei taking place in strong competition with the process of fast fission (quasi-fission). The choice of collective degrees of freedom playing a principal role, finding the multi-dimensional driving potential and the corresponding dynamic equation regulating the whole process are discussed. Theoretical predictions are made for synthesis of SH nuclei up to Z=120 in the asymmetric 'hot' fusion reactions basing on use of the heavy transactinide targets.
Daish, C; Blanchard, R; Gulati, K; Losic, D; Findlay, D; Harvie, D J E; Pivonka, P
2017-06-01
In this paper, a comprehensive framework is proposed to estimate the anisotropic permeability matrix in trabecular bone specimens based on micro-computed tomography (microCT) imaging combined with pore-scale fluid dynamics simulations. Two essential steps in the proposed methodology are the selection of (i) a representative volume element (RVE) for calculation of trabecular bone permeability and (ii) a converged mesh for accurate calculation of pore fluid flow properties. Accurate estimates of trabecular bone porosities are obtained using a microCT image resolution of approximately 10 μm. We show that a trabecular bone RVE in the order of 2 × 2 × 2 mm(3) is most suitable. Mesh convergence studies show that accurate fluid flow properties are obtained for a mesh size above 125,000 elements. Volume averaging of the pore-scale fluid flow properties allows calculation of the apparent permeability matrix of trabecular bone specimens. For the four specimens chosen, our numerical results show that the so obtained permeability coefficients are in excellent agreement with previously reported experimental data for both human and bovine trabecular bone samples. We also identified that bone samples taken from long bones generally exhibit a larger permeability in the longitudinal direction. The fact that all coefficients of the permeability matrix were different from zero indicates that bone samples are generally not harvested in the principal flow directions. The full permeability matrix was diagonalized by calculating the eigenvalues, while the eigenvectors showed how strongly the bone sample's orientations deviated from the principal flow directions. Porosity values of the four bone specimens range from 0.83 to 0.86, with a low standard deviation of ± 0.016, principal permeability values range from 0.22 to 1.45 ⋅ 10( -8) m(2), with a high standard deviation of ± 0.33. Also, the anisotropic ratio ranged from 0.27 to 0.83, with high standard deviation. These
A Dynamic/Anisotropic Low Earth Orbit (LEO) Ionizing Radiation Model
NASA Technical Reports Server (NTRS)
Badavi, Francis F.; West, Katie J.; Nealy, John E.; Wilson, John W.; Abrahms, Briana L.; Luetke, Nathan J.
2006-01-01
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 ionizing 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 6 degree of freedom (DOF) description of ISS trajectory and orientation.
NASA Astrophysics Data System (ADS)
Bunker, Alex; Landau, D. P.; Chen, Kun
1996-03-01
Using Monte Carlo and spin-dynamics techniques^1 we studied the dynamic behavior of the body-centered cubic classical Heisenberg antiferromagnet with single site anisotropy. In order that we may directly compare our results to experiment we have set the single site anisotropy term to match the degree of anisotropy found^2 in MnF_2. Through the determination and analysis of the form of the neutron scattering function S(q,ω) at and below T_c, we have found the dispersion curves for different temperatures and studied the critical dynamics. We have compared our results to simulations^1 for the isotropic case and experiment^2 on MnF_2. Research supported in part by the NSF ^**current address: Solid State Division, Oak Ridge National Laboratory ^1 K. Chen, D. P. Landau, Phys. Rev. B \\underline49, 3266, (1994) ^2 J. Als-Nielsen in Phase Transitions and Critical Phenomena, ed. C. Domb, M. S. Green, (Academic Press, 1976)
Effects of dynamical masses of gluons and quarks on hadronic B decays
Zanetti, C. M.; Natale, A. A.
2010-11-12
We study hadronic annihilation decays of B mesons within the perturbative QCD at collinear approximation. The regulation of endpoint divergences is performed with the help of an infrared finite gluon propagator characterized by a non-perturbative dynamical gluon mass. The divergences at twist-3 are regulated by a dynamical quark mass. Our results fit quite well the existent data of B{sup 0}{yields}D{sub s}{sup -}K{sup +} and B{sup 0}{yields}D{sub s}{sup -*}K{sup +} for the expected range of dynamical gluon masses. We also make predictions for the rare decays B{sup 0}{yields}K{sup -}K{sup +}, B{sub s}{sup 0}{yields}{pi}{sup -}{pi}{sup +}, {pi}{sup 0}{pi}{sup 0}, B{sup +}{yields}D{sub s}{sup (*)+}K-bar{sup 0}, B{sup 0}{yields}D{sub s}{sup {+-}(*)}K{sup {+-}} and B{sub s}{sup 0}{yields}D{sup {+-}(*)}{pi}{sup {+-}}, D{sup 0}{pi}{sup 0}.
The formation of close binary systems by dynamical interactions and orbital decay
NASA Astrophysics Data System (ADS)
Bate, Matthew R.; Bonnell, Ian A.; Bromm, Volker
2002-11-01
We present results from the first hydrodynamical star formation calculation to demonstrate that close binary stellar systems (separations <~ 10 au) need not be formed directly by fragmentation. Instead, a high frequency of close binaries can be produced through a combination of dynamical interactions in unstable multiple systems and the orbital decay of initially wider binaries. Orbital decay may occur as a result of gas accretion and/or the interaction of a binary with its circumbinary disc. These three mechanisms avoid the problems associated with the fragmentation of optically thick gas to form close systems directly. They also result in a preference for close binaries to have roughly equal-mass components because dynamical exchange interactions and the accretion of gas with high specific angular momentum drive mass ratios towards unity. Furthermore, because of the importance of dynamical interactions, we find that stars with greater masses ought to have a higher frequency of close companions, and that many close binaries ought to have wide companions. These properties are in good agreement with the results of observational surveys.
Dynamical picture for the formation and decay of the exotic XYZ mesons.
Brodsky, Stanley J; Hwang, Dae Sung; Lebed, Richard F
2014-09-12
We present a new dynamical picture that identifies the formation of the exotic c[over ¯]c-containing states XYZ with the confinement-induced hadronization of a rapidly separating pair of a compact diquark and antidiquark. This picture combines the advantages of diquark-based models, which can accommodate much of the known XYZ spectrum, with the experimental fact that such states are both relatively narrow and are produced promptly. It also naturally explains the preference of some of the exotic states to decay to ψ(2S), rather than J/ψ, in terms of a simple wave-function overlap effect.
Optical excitation and decay dynamics of ytterbium atoms embedded in a solid neon matrix.
Xu, C.-Y.; Hu, S.-M.; Singh, J.; Bailey, K.; Lu, Z.-T.; Mueller, P.; O'Connor, T. P.; Welp, U.
2011-09-01
Neutral ytterbium atoms embedded in solid neon qualitatively retain the structure of free atoms. Despite the atom-solid interaction, the 6s6p {sup 3}P{sub 0} level is found to remain metastable with its lifetimes determined to be in the range of ten to hundreds of seconds. The atomic population can be almost completely transferred between the ground level and the metastable level via optical excitation and spontaneous decay. The dynamics of this process is examined and is used to explicitly demonstrate that the transition broadening mechanism is homogeneous.
Optical Excitation and Decay Dynamics of Ytterbium Atoms Embedded in a Solid Neon Matrix
Xu, C.-Y.; Lu, Z.-T.; Hu, S.-M.; Singh, J.; Bailey, K.; Mueller, P.; O'Connor, T. P.; Welp, U.
2011-08-26
Neutral ytterbium atoms embedded in solid neon qualitatively retain the structure of free atoms. Despite the atom-solid interaction, the 6s6p {sup 3}P{sub 0} level is found to remain metastable with its lifetimes determined to be in the range of ten to hundreds of seconds. The atomic population can be almost completely transferred between the ground level and the metastable level via optical excitation and spontaneous decay. The dynamics of this process is examined and is used to explicitly demonstrate that the transition broadening mechanism is homogeneous.
Dynamic properties of bicellar lipid mixtures observed by rheometry and quadrupole echo decay.
Flynn, Alanna; Ducey, Michael; Yethiraj, Anand; Morrow, Michael R
2012-02-07
In bicellar dispersions of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), the transition from isotropic reorientation to partial orientational order, on warming, is known to coincide with a sharp increase in viscosity. In this work, cone-and-plate rheometry, (2)H NMR spectroscopy, and quadrupole echo decay observations have been used to obtain new insights into the dynamics of phases observed in bicellar DMPC/DHPC mixtures. Samples with 25% of the DMPC component deuterated were used to correlate rheological measurements with phase behavior observed by (2)H NMR spectroscopy. Mixtures containing only normal DMPC (DMPC/DHPC) or only chain perdeuterated DMPC (DMPC-d(54)/DHPC) were used to refine rheology and quadrupole echo decay measurements respectively. The viscosity peaked at 4-9 Pa·s, just above the isotropic-to-nematic transition, and then dropped as samples were warmed through the nematic-to-lamellar transition. Quadrupole echo decay times above the nematic-to-lamellar transition were significantly longer than typically observed in the liquid crystalline phase of saturated lipid multilamellar vesicles. This may indicate a damping of slow bilayer undulations resulting from the coupling of opposite bilayer surfaces by DHPC-lined pores.
NASA Astrophysics Data System (ADS)
Jeppesen, Claus; Flyvbjerg, Henrik; Mouritsen, Ole G.
1989-11-01
Monte Carlo computer-simulation techniques are used to elucidate the equilibrium phase behavior as well as the late-stage ordering dynamics of some two-dimensional models with ground-state ordering of a high degeneracy Q. The models are Q-state Potts models with anisotropic grain-boundary potential on triangular lattices-essentially clock models, except that the potential is not a cosine, but a sine function of the angle between neighboring grain orientations. For not too small Q, these models display two thermally driven phase transitions, one which takes the system from a low-temperature Potts-ordered phase to an intermediate phase which lacks conventional long-range order, and another transition which takes the system to the high-temperature disordered phase. The linear nature of the sine potential used makes it a marginal case in the sense that it favors neither hard domain boundaries, like the standard Potts models do, nor a wetting of the boundaries, as the standard clock models do. Thermal fluctuations nevertheless cause wetting to occur for not too small temperatures. Specifically, we have studied models with Q=12 and 48. The models are quenched from infinity to zero as well as finite temperatures within the two low-temperature phases. The order parameter is a nonconserved quantity during these quenches. The nonequilibrium ordering process subsequent to the quench is studied as a function of time by calculating the interfacial energy, ΔE, associated with the entire grain-boundary network. The time evolution of this quantity is shown to obey the growth law, ΔE(t)~t-n, over an extended time range at late times. It is found that the zero-temperature dynamics is characterized by a special exponent value which for the Q=48 model is n~=0.25 in accordance with earlier work. However, for quenches to finite temperatures in the Potts-ordered phase there is a distinct crossover to the classical Lifshitz-Allen-Cahn exponent value, n=(1/2, for both values of Q. This
NASA Astrophysics Data System (ADS)
Shogin, Dmitry; Amund Amundsen, Per
2016-10-01
We test the physical relevance of the full and the truncated versions of the Israel-Stewart (IS) theory of irreversible thermodynamics in a cosmological setting. Using a dynamical systems method, we determine the asymptotic future of plane symmetric Bianchi type I spacetimes with a viscous mathematical fluid, keeping track of the magnitude of the relative dissipative fluxes, which determines the applicability of the IS theory. We consider the situations where the dissipative mechanisms of shear and bulk viscosity are involved separately and simultaneously. It is demonstrated that the only case in the given model when the fluid asymptotically approaches local thermal equilibrium, and the underlying assumptions of the IS theory are therefore not violated, is that of a dissipative fluid with vanishing bulk viscosity. The truncated IS equations for shear viscosity are found to produce solutions which manifest pathological dynamical features and, in addition, to be strongly sensitive to the choice of initial conditions. Since these features are observed already in the case of an oversimplified mathematical fluid model, we have no reason to assume that the truncation of the IS transport equations will produce relevant results for physically more realistic fluids. The possible role of bulk and shear viscosity in cosmological evolution is also discussed.
Cross, T.A.; Lee, K.C.; Ketchem, R.R.; Hu, W.; Lazo, N.D.; Huo, S.
1994-12-01
To understand the details of macromolecular function, high-resolution structural and dynamic detail is essential. The polypeptide fold of the gramicidin channel has been effectively modeled for the past 20 years, yet the functional changes in conductance and channel lifetime associated with amino acid substitutions cannot be predicted. To accomplish this goal, high-resolution electrostatic modeling and the precise orientation of all dipoles are required. Furthermore, an enhanced knowledge of the complex molecular environment of this membrane-bound peptide is needed. An aqueous environment is relatively uniform and achiral. The membrane environment is very heterogenous and chiral. A knowledge of the interactions, specific and nonspecific, between peptide and lipid will aid in developing a better understanding of this environment. To accomplish this goal, it is necessary to study the peptide in an extended lipid bilayer, rather than in a vesicular or micellar form. These latter environments are likely to possess increased dynamics, increased water penetration, and distorted interactions between the polypeptide and membrane surface. To perform NMR studies on bilayer bound peptides, solid state NMR methods are required, and for specific site information, isotopic labels are incorporated using solid phase peptide synthesis.
Anisotropic stokes drag and dynamic lift on cylindrical colloids in a nematic liquid crystal.
Rovner, Joel B; Lapointe, Clayton P; Reich, Daniel H; Leheny, Robert L
2010-11-26
We have measured the Stokes drag on magnetic nanowires suspended in the nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB). The effective drag viscosity for wires moving perpendicular to the nematic director differs from that for motion parallel to the director by factors of 0.88 to 2.4, depending on the orientation of the wires and their surface anchoring. When the force on the wires is applied at an oblique angle to the director, the wires move at an angle to the force, demonstrating the existence of a lift force on particles moving in a nematic. This dynamic lift is significantly larger for wires with homeotropic anchoring than with longitudinal anchoring in the experiments, suggesting the lift force as a mechanism for sorting particles according to their surface properties.
Anisotropic dynamics of a spin-orbit-coupled Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Martone, Giovanni I.; Li, Yun; Pitaevskii, Lev P.; Stringari, Sandro
2012-12-01
By calculating the density response function we identify the excitation spectrum of a Bose-Einstein condensate with equal Rashba and Dresselhaus spin-orbit coupling. We find that the velocity of sound along the direction of spin-orbit coupling is deeply quenched and vanishes when one approaches the second-order phase transition between the plane-wave and the zero momentum quantum phases. We also point out the emergence of a roton minimum in the excitation spectrum for small values of the Raman coupling, providing the onset of the transition to the stripe phase. Our findings point out the occurrence of a strong anisotropy in the dynamic behavior of the gas. A hydrodynamic description accounting for the collective oscillations in both uniform and harmonically trapped gases is also derived.
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
Selective decay and dynamic alignment in the MHD turbulence: The role of the rugged invariants
NASA Astrophysics Data System (ADS)
Telloni, Daniele; Perri, Silvia; Carbone, Vincenzo; Bruno, Roberto
2016-03-01
In the evolving MagnetoHydroDynamic (MHD) turbulence a key role is played by the relaxation processes, which drive a magnetized fluid towards self-organized, stable configurations, like a force-free state (resulting from a selective decay) or a dynamic alignment (anti-alignment) between the plasma flow velocity and magnetic field. The evolution of the three MHD rugged invariants, namely of the magnetic helicity Hm, the cross-helicity Hc and the total energy E, is of particular importance in interpreting the asymptotic solutions of the MHD decay. It is thus prominent to investigate the magnetic and cross-helicity content carried by the solar wind and by magnetic structures advected by the flowing plasma, and particularly their radial evolution throughout the inner heliosphere, in order to offer a rather complete picture of the phenomenological aspect of the relaxation phenomena occurring in the solar wind turbulence. The results presented in this paper show that within some solar wind streams, the ideal MHD decays towards a state with maximal cross-helicity, where the magnetic and velocity fluctuations are (anti-)aligned with a high correlation degree. The maximal magnetic helicity state, say the force-free configuration, is instead observed in interplanetary flux ropes, a particular class of magnetic objects advected by the solar wind. However, it is worth noting that in some peculiar flux ropes, the competitive action of both rugged invariants drives the MHD configuration of these structures to intermediate states, where both the magnetic and cross-helicity significantly deviate from zero, without, however, reaching a maximum value.
NASA Astrophysics Data System (ADS)
Anovitz, Lawrence M.; Mamontov, Eugene; ben Ishai, Paul; Kolesnikov, Alexander I.
2013-11-01
The properties of fluids can be significantly altered by the geometry of their confining environments. While there has been significant work on the properties of such confined fluids, the properties of fluids under ultraconfinement, environments where, at least in one plane, the dimensions of the confining environment are similar to that of the confined molecule, have not been investigated. This paper investigates the dynamic properties of water in beryl (Be3Al2Si6O18), the structure of which contains approximately 5-Å-diam channels parallel to the c axis. Three techniques, inelastic neutron scattering, quasielastic neutron scattering, and dielectric spectroscopy, have been used to quantify these properties over a dynamic range covering approximately 16 orders of magnitude. Because beryl can be obtained in large single crystals we were able to quantify directional variations, perpendicular and parallel to the channel directions, in the dynamics of the confined fluid. These are significantly anisotropic and, somewhat counterintuitively, show that vibrations parallel to the c-axis channels are significantly more hindered than those perpendicular to the channels. The effective potential for vibrations in the c direction is harder than the potential in directions perpendicular to it. There is evidence of single-file diffusion of water molecules along the channels at higher temperatures, but below 150 K this diffusion is strongly suppressed. No such suppression, however, has been observed in the channel-perpendicular direction. Inelastic neutron scattering spectra include an intramolecular stretching O-H peak at ˜465 meV. As this is nearly coincident with that known for free water molecules and approximately 30 meV higher than that in liquid water or ice, this suggests that there is no hydrogen bonding constraining vibrations between the channel water and the beryl structure. However, dielectric spectroscopic measurements at higher temperatures and lower frequencies
Anovitz, Lawrence M; Mamontov, Eugene; ben Ishai, Paul; Kolesnikov, Alexander I
2013-11-01
The properties of fluids can be significantly altered by the geometry of their confining environments. While there has been significant work on the properties of such confined fluids, the properties of fluids under ultraconfinement, environments where, at least in one plane, the dimensions of the confining environment are similar to that of the confined molecule, have not been investigated. This paper investigates the dynamic properties of water in beryl (Be(3)Al(2)Si(6)O(18)), the structure of which contains approximately 5-Å-diam channels parallel to the c axis. Three techniques, inelastic neutron scattering, quasielastic neutron scattering, and dielectric spectroscopy, have been used to quantify these properties over a dynamic range covering approximately 16 orders of magnitude. Because beryl can be obtained in large single crystals we were able to quantify directional variations, perpendicular and parallel to the channel directions, in the dynamics of the confined fluid. These are significantly anisotropic and, somewhat counterintuitively, show that vibrations parallel to the c-axis channels are significantly more hindered than those perpendicular to the channels. The effective potential for vibrations in the c direction is harder than the potential in directions perpendicular to it. There is evidence of single-file diffusion of water molecules along the channels at higher temperatures, but below 150 K this diffusion is strongly suppressed. No such suppression, however, has been observed in the channel-perpendicular direction. Inelastic neutron scattering spectra include an intramolecular stretching O-H peak at ~465 meV. As this is nearly coincident with that known for free water molecules and approximately 30 meV higher than that in liquid water or ice, this suggests that there is no hydrogen bonding constraining vibrations between the channel water and the beryl structure. However, dielectric spectroscopic measurements at higher temperatures and lower
Decay of aftershock density with distance indicates triggering by dynamic stress
Felzer, K.R.; Brodsky, E.E.
2006-01-01
The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults. ?? 2006 Nature Publishing Group.
Decay of aftershock density with distance indicates triggering by dynamic stress.
Felzer, K R; Brodsky, E E
2006-06-08
The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults.
Spin dynamics of paramagnetic centers with anisotropic g tensor and spin of ½
Maryasov, Alexander G.
2012-01-01
The influence of g tensor anisotropy on spin dynamics of paramagnetic centers having real or effective spin of 1/2 is studied. The g anisotropy affects both the excitation and the detection of EPR signals, producing noticeable differences between conventional continuous-wave (cw) EPR and pulsed EPR spectra. The magnitudes and directions of the spin and magnetic moment vectors are generally not proportional to each other, but are related to each other through the g tensor. The equilibrium magnetic moment direction is generally parallel to neither the magnetic field nor the spin quantization axis due to the g anisotropy. After excitation with short microwave pulses, the spin vector precesses around its quantization axis, in a plane that is generally not perpendicular to the applied magnetic field. Paradoxically, the magnetic moment vector precesses around its equilibrium direction in a plane exactly perpendicular to the external magnetic field. In the general case, the oscillating part of the magnetic moment is elliptically polarized and the direction of precession is determined by the sign of the g tensor determinant (g tensor signature). Conventional pulsed and cw EPR spectrometers do not allow determination of the g tensor signature or the ellipticity of the magnetic moment trajectory. It is generally impossible to set a uniform spin turning angle for simple pulses in an unoriented or ‘powder’ sample when g tensor anisotropy is significant. PMID:22743542
NASA Astrophysics Data System (ADS)
Alexander, C. S.; Key, C. T.; Schumacher, S. C.
2014-05-01
Recently there has been renewed interest in the dynamic response of composite materials; specifically low density epoxy matrix binders strengthened with continuous reinforcing fibers. This is in part due to the widespread use of carbon fiber composites in military, commercial, industrial, and aerospace applications. The design community requires better understanding of these materials in order to make full use of their unique properties. Planar impact testing was performed resulting in pressures up to 15 GPa on a unidirectional carbon fiber - epoxy composite, engineered to have high uniformity and low porosity. Results illustrate the anisotropic nature of the response under shock loading. Along the fiber direction, a two-wave structure similar to typical elastic-plastic response is observed, however, when shocked transverse to the fibers, only a single bulk shock wave is detected. At higher pressures, the epoxy matrix dissociates resulting in a loss of anisotropy. Greater understanding of the mechanisms responsible for the observed response has been achieved through numerical modeling of the system at the micromechanical level using the CTH hydrocode. From the simulation results it is evident that the observed two-wave structure in the longitudinal fiber direction is the result of a fast moving elastic precursor wave traveling in the carbon fibers ahead of the bulk response in the epoxy resin. Similarly, in the transverse direction, results show a collapse of the resin component consistent with the experimental observation of a single shock wave traveling at speeds associated with bulk carbon. Experimental and simulation results will be discussed and used to show where additional mechanisms, not fully described by the currently used models, are present.
Mohammadi, Maziar; Larson, Eric D; Liu, Jun; Larson, Ronald G
2015-01-14
Brownian dynamics simulations are performed to study the binding kinetics in the dilute-sphere limit by considering interactions of two spheres under shear flow across the entire range of Peclet numbers, spanning both perikinetic (diffusion-controlled) and orthokinetic (flow-controlled) coagulation regimes. The dilute regime is attained by carrying out two-sphere simulations in periodic boxes of different sizes and aspect ratios and extrapolating toward the infinite box limit. Effects of particle type (Janus and isotropic particles), shear rate, hydrodynamic interactions, and inter-particle potential are explored. We find that rectangular boxes with appropriate aspect ratios overcome a particle "shadow effect" that cannot be overcome with cubic boxes unless huge boxes are used. With rectangular boxes, we obtain converged binding kinetics for the whole Peclet number range, while cubic boxes of increasing size allow converged results only in the absence of flow. We consider the effect of binding both in a secondary minimum controlled by a combination of electrostatic repulsion and depletion attraction, as well as in a primary minimum governed by induced-dipole attraction. Results are computed using both realistic interaction potentials and by replacing the potential with a simple cutoff gap distance at which binding is deemed to occur. Results agree with several existing reports including Smoluchowski predictions in the zero- and infinite-shear-rate limits, and high-Pe perturbation results of Feke and Schowalter [J. Fluid Mech. 133, 17-35 (1983)] at Peclet numbers (Pe) above 100. Finally, we compute binding times for anisotropic Janus particles which have both repulsive and attractive faces, for a wide range of Pe number.
Droplet impact dynamics for two liquids impinging on anisotropic superhydrophobic surfaces
NASA Astrophysics Data System (ADS)
Pearson, John T.; Maynes, Daniel; Webb, Brent W.
2012-09-01
Droplet impingement experiments were performed on grooved hydrophobic surfaces with cavity fractions of 0, 80, and 93 % using droplets of water and a 50 %/50 % water/glycerol mixture. The influence of liquid viscosity, cavity fraction, and spreading direction, relative to the surface grooves, is explored qualitatively and quantitatively. The maximum droplet spread diameter, velocity of the rebounding jet, and the time delay between droplet impact and jet emission were characterized for Weber numbers, We, based on droplet impact speed and diameter, up to 500. The unequal shear stresses and contact angles influence the maximum spread diameters in the two primary spread directions. At We > 100, the ratio of the spread diameter along the direction of the grooves to the spread diameter perpendicular to the grooves increases above unity with increasing We. The maximum droplet spread diameter is compared to recent predictive models, and the data reveal differing behavior for the two fluids considered. The results also reveal the existence of very high relative jet velocities in the range 5 ≤ We ≤ 15 for water droplets, while such jets were not observed for the more viscous mixture. Further, in the range 115 ≤ We ≤ 265, the water/glycerol jet formation dynamics are radically different from the water behavior. Most evident is the existence of two-pronged jets, which arise from the anisotropy of the surface and the unequal shear stresses and contact angles that prevail on the surfaces. It is these influences that give rise to differences in the maximum spread diameters in the two primary spread directions. Similar two-pronged jet emission was observed for water over the very narrow range of We from 91 to 96. The issuing jet velocities were also observed to increase with increasing cavity fraction for both fluids and over the entire range of We explored. Lastly, the elapsed time between droplet impact and jet emission decreased with increasing cavity fraction.
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.
Inverse boundary value problem for anisotropic heat operators
NASA Astrophysics Data System (ADS)
Kim, Kyoungsun; Nakamura, Gen
2011-04-01
As a mathematical model of thermography, a reconstruction scheme called the dynamical probe method is given for identifying unknown separated inclusions inside a known anisotropic heat conductor. The heat conductivities of inclusions can be also anisotropic. The measured data is the so called Neumann to Dirichlet map which is a mathematical idealization of many measurements consisting of injecting heat flux and measuring the corresponding heat distribution on the part of the boundary of the known heat conductor by infrared camera for any fixed time interval. This idealization becomes relevant if we have for instance the cooling boundary condition on the other part of the boundary. This is due to the exponential decay of temperature in time which enables to conduct many measurements in a short time.
Barbosa, Jorge G.; Brown, Julia M.; Donelan, Ryan P.; Eaglesham, James B.; Eggleston, Erin M.; LaBarre, Brenna A.
2012-01-01
Aquatic viruses play important roles in the biogeochemistry and ecology of lacustrine ecosystems; however, their composition, dynamics, and interactions with viruses of terrestrial origin are less extensively studied. We used a viral shotgun metagenomic approach to elucidate candidate autochthonous (i.e., produced within the lake) and allochthonous (i.e., washed in from other habitats) viral genotypes for a comparative study of their dynamics in lake waters. Based on shotgun metagenomes prepared from catchment soil and freshwater samples from two contrasting lakes (Cayuga Lake and Fayetteville Green Lake), we selected two putatively autochthonous viral genotypes (phycodnaviruses likely infecting algae and cyanomyoviruses likely infecting picocyanobacteria) and two putatively allochthonous viral genotypes (geminiviruses likely infecting terrestrial plants and circoviruses infecting unknown hosts but common in soil libraries) for analysis by genotype-specific quantitative PCR (TaqMan) applied to DNAs from viruses in the viral size fraction of lake plankton, i.e., 0.2 μm > virus > 0.02 μm. The abundance of autochthonous genotypes largely reflected expected host abundance, while the abundance of allochthonous genotypes corresponded with rainfall and storm events in the respective catchments, suggesting that viruses with these genotypes may have been transported to the lake in runoff. The decay rates of allochthonous and autochthonous genotypes, assessed in incubations where all potential hosts were killed, were generally lower (0.13 to 1.50% h−1) than those reported for marine virioplankton but similar to those for freshwater virioplankton. Both allochthonous and autochthonous viral genotypes were detected at higher concentrations in subsurface sediments than at the water-sediment interface. Our data indicate that putatively allochthonous viruses are present in lake plankton and sediments, where their temporal dynamics reflect active transport to the lake during
Hewson, Ian; Barbosa, Jorge G; Brown, Julia M; Donelan, Ryan P; Eaglesham, James B; Eggleston, Erin M; LaBarre, Brenna A
2012-09-01
Aquatic viruses play important roles in the biogeochemistry and ecology of lacustrine ecosystems; however, their composition, dynamics, and interactions with viruses of terrestrial origin are less extensively studied. We used a viral shotgun metagenomic approach to elucidate candidate autochthonous (i.e., produced within the lake) and allochthonous (i.e., washed in from other habitats) viral genotypes for a comparative study of their dynamics in lake waters. Based on shotgun metagenomes prepared from catchment soil and freshwater samples from two contrasting lakes (Cayuga Lake and Fayetteville Green Lake), we selected two putatively autochthonous viral genotypes (phycodnaviruses likely infecting algae and cyanomyoviruses likely infecting picocyanobacteria) and two putatively allochthonous viral genotypes (geminiviruses likely infecting terrestrial plants and circoviruses infecting unknown hosts but common in soil libraries) for analysis by genotype-specific quantitative PCR (TaqMan) applied to DNAs from viruses in the viral size fraction of lake plankton, i.e., 0.2 μm > virus > 0.02 μm. The abundance of autochthonous genotypes largely reflected expected host abundance, while the abundance of allochthonous genotypes corresponded with rainfall and storm events in the respective catchments, suggesting that viruses with these genotypes may have been transported to the lake in runoff. The decay rates of allochthonous and autochthonous genotypes, assessed in incubations where all potential hosts were killed, were generally lower (0.13 to 1.50% h(-1)) than those reported for marine virioplankton but similar to those for freshwater virioplankton. Both allochthonous and autochthonous viral genotypes were detected at higher concentrations in subsurface sediments than at the water-sediment interface. Our data indicate that putatively allochthonous viruses are present in lake plankton and sediments, where their temporal dynamics reflect active transport to the lake during
Morishita, Yoshihiro; Kuroiwa, Atsushi; Suzuki, Takayuki
2015-05-01
Tissue-level characterization of deformation dynamics is crucial for understanding organ morphogenetic mechanisms, especially the interhierarchical links among molecular activities, cellular behaviors and tissue/organ morphogenetic processes. Limb development is a well-studied topic in vertebrate organogenesis. Nevertheless, there is still little understanding of tissue-level deformation relative to molecular and cellular dynamics. This is mainly because live recording of detailed cell behaviors in whole tissues is technically difficult. To overcome this limitation, by applying a recently developed Bayesian approach, we here constructed tissue deformation maps for chick limb development with high precision, based on snapshot lineage tracing using dye injection. The precision of the constructed maps was validated with a clear statistical criterion. From the geometrical analysis of the map, we identified three characteristic tissue growth modes in the limb and showed that they are consistent with local growth factor activity and cell cycle length. In particular, we report that SHH signaling activity changes dynamically with developmental stage and strongly correlates with the dynamic shift in the tissue growth mode. We also found anisotropic tissue deformation along the proximal-distal axis. Morphogenetic simulation and experimental studies suggested that this directional tissue elongation, and not local growth, has the greatest impact on limb shaping. This result was supported by the novel finding that anisotropic tissue elongation along the proximal-distal axis occurs independently of cell proliferation. Our study marks a pivotal point for multi-scale system understanding in vertebrate development. © 2015. Published by The Company of Biologists Ltd.
Makwana, K. D. Cattaneo, F.; Zhdankin, V.; Li, H.; Daughton, W.
2015-04-15
Simulations of decaying magnetohydrodynamic (MHD) turbulence are performed with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k{sub ⊥}{sup −1.3}. The kinetic code shows a spectral slope of k{sub ⊥}{sup −1.5} for smaller simulation domain, and k{sub ⊥}{sup −1.3} for larger domain. We estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. This work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.
Dynamics of biomolecules: assignment of local motions by fluorescence anisotropy decay.
Bialik, C N; Wolf, B; Rachofsky, E L; Ross, J B; Laws, W R
1998-01-01
Many biological systems have multiple fluorophores that experience multiple depolarizing motions, requiring multiple lifetimes and correlation times to define the fluorescence intensity and anisotropy decays, respectively. To simplify analyses, an assumption often made is that all fluorophores experience all depolarizing motions. However, this assumption usually is invalid, because each lifetime is not necessarily associated with each correlation time. To help establish the correct associations and recover accurate kinetic parameters, a general kinetic scheme that can examine all possible associations is presented. Using synthetic data sets, the ability of the scheme to discriminate among all nine association models possible for two lifetimes and two correlation times has been evaluated. Correct determination of the association model, and accurate recovery of the decay parameters, required the global analysis of related data sets. This general kinetic scheme was then used for global analyses of liver alcohol dehydrogenase anisotropy data sets. The results indicate that only one of the two tryptophan residues in each subunit is depolarized by process(es) independent of the enzyme's rotations. By applying the proper kinetic scheme and appropriate analysis procedures to time-resolved fluorescence anisotropy data, it is therefore possible to examine the dynamics of specific portions of a macromolecule in solution. PMID:9788952
Is the physical decay correction of the (18)F-FDG input function in dynamic PET imaging justified?
Laffon, Eric; Barret, Olivier; Marthan, Roger; Ducassou, Dominique
2009-06-01
In this theoretic note, the rationale for the physical decay correction of the (18)F-FDG input function in dynamic PET is investigated, using the Patlak equation as an example. The Patlak equation conventionally obtained when correcting the (18)F-FDG input function and correcting the tissue activity measurement for (18)F physical decay can also be derived from a 2-compartment analysis that does not conceptually involve any physical decay correction of the (18)F-FDG input function but accounts only for the physical decay of the trapped tracer. We demonstrate that exactly the same equation can be derived from the 2 conceptual approaches, and hence each approach yields the correct uptake rate of the tracer. No advantage in (18)F-FDG dynamic PET can be expected from using the concept of uncorrected data rather than that of decay-corrected data. Nevertheless, conceptually, we show that correcting the (18)F-FDG input function for radioactive decay cannot be justified and that this correction is not compatible with the calculation of patient radiation dose.
Role of Aggregates in the Luminescence Decay Dynamics of Conjugated Polymers.
Chakraborty, Rajarshi; Rothberg, Lewis J
2016-02-04
Fluorescence quantum yields of conjugated polymer films are systematically lower than their counterparts in dilute solution. Films also exhibit a long "temporal tail" in their fluorescence decay dynamics not present in solution. We study the spectroscopy, excitation wavelength dependence, temperature dependence, and electric field quenching of the temporal tail of the photoluminescence in MEH-PPV on a nanosecond time scale to elucidate the relationship between those observations. We conclude that the tail represents emission from H-like aggregated regions in the polymer. Using a simple model of the photophysics, we estimate the formation yield of the aggregates responsible for the tail emission to be <20% so that they cannot account for the large reduction in fluorescence observed in densely packed films relative to that in solution.
Full-dimensional control of the radiationless decay in pyrazine using the dynamic Stark effect
NASA Astrophysics Data System (ADS)
Saab, Mohamad; Sala, Matthieu; Lasorne, Benjamin; Gatti, Fabien; Guérin, Stéphane
2014-10-01
We present a full quantum-mechanical study of the laser control of the radiationless decay between the B3u(nπ*) and B2u(ππ*) states of pyrazine using the dynamic Stark effect. In contrast to our previous study [Sala et al., J. Chem. Phys. 140, 194309 (2014)], where a four-dimensional model was used, all the 24 degrees of freedom are now included in order to test the robustness of the strategy of control. Using a vibronic coupling Hamiltonian model in a diabatic representation, the multi-layer version of the multi-configuration time-dependent Hartree method is exploited to propagate the corresponding wave packets. We still observe a trapping of the wavepacket on the B2u(ππ*) potential energy surface due to the Stark effect for a longer time than the "non-resonant field-free" B2u(ππ*) lifetime.
Significance of decay mechanism into continuum in dynamical Wannier-Stark ladder
Nemoto, Yuya; Maeshima, Nobuya; Hino, Ken-ichi
2013-12-04
We examine the resonance structure of photodressed electron states of laser-driven Wannier-Stark ladder, namely, dynamic Wannier-Stark ladder, in terms of the excess density of states (DOS) closely related to a lifetime of the state of concern. It is revealed that the resonance structure in the strong laser-field region shows clear dependence on the ratio, η, of a Bloch-frequency to a laser frequency. As the laser strength increases, for η = 1, the excess DOS becomes involved with a lot of newly-growing resonance peaks. This result would be understood from the viewpoint of a Fano-like decay-mechanism caused by a multichannel continuum effect, in marked contrast to the cases of larger η’s; for η = 3, the excess DOS just is found to show a pronounced red-shift of a single dominant peak caused by a single-channel continuum effect.
NASA Astrophysics Data System (ADS)
Alexander, C.
2013-06-01
Recently there has been renewed interest in the dynamic response of composite materials; specifically low density epoxy resin binders strengthened with continuous reinforcing fibers. This is in part due to the widespread use of carbon fiber composites in military, commercial, industrial, and aerospace applications. The design community requires better understanding of these materials in order to make full use of their unique properties. Experimental testing has been performed on a unidirectional carbon fiber - epoxy composite, engineered to have high uniformity and low porosity. Planar impact testing was performed at the Shock Thermodynamics Applied Research (STAR) facility at Sandia National Labs resulting in pressures up to 15 GPa in the composite material. Results illustrate the anisotropic nature of the response under shock loading. Along the fiber direction, a two-wave structure similar to typical elastic-plastic response is observed, however, when shocked transverse to the fibers, only a single bulk shock wave is detected. The two-wave structure persists when impact occurs at angles up to 45 degrees off the fiber direction. At higher pressures, the epoxy matrix dissociates resulting in a loss of anisotropy. Details of the experimental configurations and results will be presented and discussed. Greater understanding of the mechanisms responsible for the observed response has been achieved through the use of numerical modeling of the system at the micromechanical level using the CTH hydrocode. From the simulation results it is evident that the observed two-wave structure in the longitudinal fiber direction is the result of a fast moving elastic precursor wave traveling in the carbon fibers ahead of the bulk response in the epoxy resin. Similarly, in the transverse direction, results show a collapse of the resin component consistent with the experimental observation of a single shock wave traveling at speeds associated with bulk carbon. These results will be
Yandell, Margaret A.; King, Sarah B.; Neumark, Daniel M.
2014-05-14
Decay dynamics of nascent dipole bound states of acetonitrile and nitromethane are examined using time-resolved photoelectron imaging of iodide-acetonitrile (I{sup −}·CH{sub 3}CN) and iodide-nitromethane (I{sup −}·CH{sub 3}NO{sub 2}) complexes. Dipole-bound anions are created by UV-initiated electron transfer to the molecule of interest from the associated iodide ion at energies just below the vertical detachment energy of the halide-molecule complex. The acetonitrile anion is observed to decay biexponentially with time constants in the range of 4–900 ps. In contrast, the dipole bound state of nitromethane decays rapidly over 400 fs to form the valence bound anion. The nitromethane valence anion species then decays biexponentially with time constants of 2 ps and 1200 ps. The biexponential decay dynamics in acetonitrile are interpreted as iodine atom loss and autodetachment from the excited dipole-bound anion, followed by slower autodetachment of the relaxed metastable ion, while the dynamics of the nitromethane system suggest that a dipole-bound anion to valence anion transition proceeds via intramolecular vibrational energy redistribution to nitro group modes in the vicinity of the iodine atom.
Groch, M W
1998-01-01
When a parent radionuclide decays to its daughter radionuclide by means of alpha, beta, or isomeric transition, the decay follows an exponential form, which is characterized by the decay constant lambda. The decay constant represents the probability per unit time that a single radioatom will decay. The decay equation can be used to provide a useful expression for radionuclide decay, the half-life, the time when 50% of the radioatoms present will have decayed. Radiotracer half-life has direct implications in nuclear imaging, radiation therapy, and radiation safety because radionuclide half-life affects the ability to evaluate tracer kinetics and create appropriate nuclear images and also affects organ, tumor, and whole-body radiation dose. The number of radioatoms present in a sample is equal to the activity, defined as the number of transitions per unit time, divided by the decay constant; the mass of radioatoms present in a sample can be calculated to determine the specific activity (activity per unit mass). The dynamic relationship between the number of parent and daughter atoms present over time may lead to radioactive equilibrium, which takes two forms--secular and transient--and has direct relevance to generator-produced radionuclides.
Water dynamics in conifer logs in early stages of decay in the Pacific Northwest, U.S.A
Jay M. Sexton; Mark E. Harmon
2009-01-01
Water dynamics in decaying conifer logs of four species (Abies amabilis [Pacific silver fir], Pseudotsuga menziesii [Douglas-fir], Thuja plicata [western red cedar], and Tsuga heterophylla [western hemlock]) were studied in the Coast Range of Oregon. Measurements were made of...
The πd Decay of the 3F3 Diproton in the Faddeev πNN Dynamics
NASA Astrophysics Data System (ADS)
Araki, M.; Koike, Y.; Ueda, T.
1980-06-01
The πd decay branching ratio of the 3F3 diproton in the Faddeev πNN dynamics is of order 0.1%. This is in a qualitative agreement with the result of phenomenological partial-wave analysis by Kamo and Watari.
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.
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.
Dynamic decay of a single vortex into vortex-antivortex pairs
Lendínez, Sergi; Jain, Shikha; Novosad, Valentyn Fradin, Frank Y.; Pearson, John E.; Tejada, Javier; Bader, Samuel D.
2014-05-07
A variety of metastable states, including vortices, antivortices, and their combinations, is typical for magnetically soft, thin films and patterned structures. The physics of individual spin vortices in patterned structures has been rather extensively explored. In contrast, there are few studies of the vortex–antivortex–vortex (v-av-v) system, in part because the configuration is rather challenging to obtain experimentally. We demonstrate herein how a recently proposed resonant-spin-ordering technique can be used to induce the dynamic decay of a single vortex into v-av states in elongated elements. The approach is based on first driving the system from the linear regime of constant vortex gyrations to the non-linear regime of vortex-core reversals at a fixed excitation frequency, and then subsequently reducing the excitation field back to the linear regime. This procedure stabilizes the system into a v-av-v state that is completely decoupled from the initialization excitation frequency. The newly acquired state is stable in remanence. The dynamic response of this system is expected to demonstrate a number of collective modes, depending on the combination of the vortex core polarities, and/or the excitation field direction, and, hence, is of interest for future studies.
Dynamic Decay of a Single Vortex into Vortex-Antivortex Pairs.
Lendinez, Sergi; Jain, Shikha; Novosad, Valentyn; Fradin, Frank Y.; Pearson, John E.; Tejada, J; Bader, Samuel D.
2014-05-07
A variety of metastable states, including vortices, antivortices, and their combinations, is typical for magnetically soft, thin films and patterned structures. The physics of individual spin vortices in patterned structures has been rather extensively explored. In contrast, there are few studies of the vortex–antivortex–vortex (v-av-v) system, in part because the configuration is rather challenging to obtain experimentally. We demonstrate herein how a recently proposed resonant-spin-ordering technique can be used to induce the dynamic decay of a single vortex into v-av states in elongated elements. The approach is based on first driving the system from the linear regime of constant vortex gyrations to the non-linear regime of vortex-core reversals at a fixed excitation frequency, and then subsequently reducing the excitation field back to the linear regime. This procedure stabilizes the system into a v-av-v state that is completely decoupled from the initialization excitation frequency. The newly acquired state is stable in remanence. The dynamic response of this system is expected to demonstrate a number of collective modes, depending on the combination of the vortex core polarities, and/or the excitation field direction, and, hence, is of interest for future studies.
Makwana, K. D.; Zhdankin, V.; Li, H.; Daughton, W.; Cattaneo, F.
2015-04-10
We performed simulations of decaying magnetohydrodynamic (MHD) turbulence with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k-1.3⊥k⊥-1.3. The kinetic code shows a spectral slope of k-1.5⊥k⊥-1.5 for smaller simulation domain, and k-1.3⊥k⊥-1.3 for larger domain. We then estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. Finally, this work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.
Makwana, K. D.; Zhdankin, V.; Li, H.; ...
2015-04-10
We performed simulations of decaying magnetohydrodynamic (MHD) turbulence with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k-1.3⊥k⊥-1.3. The kinetic code shows a spectral slope of k-1.5⊥k⊥-1.5 for smallermore » simulation domain, and k-1.3⊥k⊥-1.3 for larger domain. We then estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. Finally, this work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.« less
Bicknese, S; Rossi, M; Thevenin, B; Shohet, S B; Verkman, A S
1995-08-22
Time-resolved anisotropy was utilized to detect nanosecond segmental motions of the band 3 intramembrane domain. Band 3 at lysine 430 was fluorescently labeled in ghost membranes by fluorescein or eosin maleimide treatment of intact human erythrocytes followed by hypotonic lysis. Single lifetimes for fluorescein (3.8-4.1 ns) and eosin (3.2-3.4 ns) were observed. Phase-modulation measurement of anisotropy decay indicated a segmental motion model, r(t) = exp(-t/tau 1c)[r infinity + (ro-r infinity) exp(-t/tau 2c)], defined by rotational correlation times corresponding to band 3 segmental motion (tau 1c, 30-70 ns) and rapid fluorescein motion in its binding pocket (tau 2c, 200-400 ps), and a residual anisotropy (r infinity, 0.23-0.28) describing hindered fluorescein motion. In PBS at pH 7.4, tau 1c, tau 2c, and r infinity were 44 ns, 307 ps, and 0.24, respectively, predicting a steady-state anisotropy of 0.24, in agreement with the measured value of 0.23. Factors that might influence band 3 structure/dynamics were examined. Whereas pH (range 5-10) had little effect on r(t), [NaCl] addition (0-150 mM) remarkably decreased tau 1c from 68 to 44 ns. The decrease in tau 1c correlated with solution ionic strength, and did not depend on osmolality (studied by mannitol addition), or specific anion interactions (comparing Cl, Br, F, SO4, citrate). The ionic strength effect was not observed in fluorescein-labeled carbonic anhydrase and trypsin-cleaved band 3, suggesting a specific effect on intact band 3. Anisotropy decay was relatively insensitive to external lectin or internal 2,3-DPG binding, but was sensitive to temperature, membrane fluidity, urea denaturation, fluid-phase viscosity, and aldehyde fixation.(ABSTRACT TRUNCATED AT 250 WORDS)
Study of decay dynamics and C P asymmetry in D+→KL0e+νe decay
NASA Astrophysics Data System (ADS)
Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Bai, J. Z.; Ferroli, R. Baldini; Ban, Y.; Bennett, D. W.; Bennett, J. V.; Bertani, M.; Bettoni, D.; Bian, J. M.; Bianchi, F.; Boger, E.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, H. Y.; Chen, J. C.; Chen, M. L.; Chen, S.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Cibinetto, G.; Dai, H. L.; Dai, J. P.; Dbeyssi, A.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Duan, P. F.; Fan, J. Z.; Fang, J.; Fang, S. S.; Fang, X.; Fang, Y.; Fava, L.; Feldbauer, F.; Felici, G.; Feng, C. Q.; Fioravanti, E.; Fritsch, M.; Fu, C. D.; Gao, Q.; Gao, X. L.; Gao, X. Y.; Gao, Y.; Gao, Z.; Garzia, I.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, R. P.; Guo, Y.; Guo, Y. P.; Haddadi, Z.; Hafner, A.; Han, S.; Hao, X. Q.; Harris, F. A.; He, K. L.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Hu, Y.; Huang, G. M.; Huang, G. S.; Huang, J. S.; Huang, X. T.; Huang, Y.; Hussain, T.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. W.; Jiang, X. S.; Jiang, X. Y.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Johansson, T.; Julin, A.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Ke, B. C.; Kiese, P.; Kliemt, R.; Kloss, B.; Kolcu, O. B.; Kopf, B.; Kornicer, M.; Kuehn, W.; Kupsc, A.; Lange, J. S.; Lara, M.; Larin, P.; Leng, C.; Li, C.; Li, Cheng; Li, D. M.; Li, F.; Li, F. Y.; Li, G.; Li, H. B.; Li, H. J.; Li, J. C.; Li, Jin; Li, K.; Li, K.; Li, Lei; Li, P. R.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. M.; Li, X. N.; Li, X. Q.; Li, Z. B.; Liang, H.; Liang, J. J.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B. J.; Liu, C. X.; Liu, D.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. B.; Liu, J. P.; Liu, J. Y.; Liu, K.; Liu, K. Y.; Liu, L. D.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqing; Loehner, H.; Lou, X. C.; Lu, H. J.; Lu, J. G.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lyu, X. R.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, M. M.; Ma, Q. M.; Ma, T.; Ma, X. N.; Ma, X. Y.; Maas, F. E.; Maggiora, M.; Mao, Y. J.; Mao, Z. P.; Marcello, S.; Messchendorp, J. G.; Min, J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Morales, C. Morales; Moriya, K.; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, S. L.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pan, Y.; Patteri, P.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Pettersson, J.; Ping, J. L.; Ping, R. G.; Poling, R.; Prasad, V.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, N.; Qin, X. S.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ripka, M.; Rong, G.; Rosner, Ch.; Ruan, X. D.; Sarantsev, A.; Savrié, M.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, P. X.; Shen, X. Y.; Sheng, H. Y.; Shi, M.; Song, W. M.; Song, X. Y.; Sosio, S.; Spataro, S.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. H.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Tiemens, M.; Ullrich, M.; Uman, I.; Varner, G. S.; Wang, B.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, S. G.; Wang, W.; Wang, W. P.; Wang, X. F.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Wang, Z. Y.; Weber, T.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, L. J.; Wu, Z.; Xia, L.; Xia, L. G.; Xia, Y.; Xiao, D.; Xiao, H.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, J. J.; Xu, L.; Xu, Q. J.; Xu, X. P.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. J.; Yang, H. X.; Yang, L.; Yang, Y.; Yang, Y. X.; Ye, M.; Ye, M. H.; Yin, J. H.; Yu, B. X.; Yu, C. X.; Yu, J. S.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Yuncu, A.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zeng, Z.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, K.; Zhang, L.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. N.; Zhang, Y. H.; Zhang, Y. T.; Zhang, Yu; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. W.; Zhao, S. J.; Zhao, T. C.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, W. J.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, K.; Zhu, K. J.; Zhu, S.; Zhu, S. H.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zotti, L.; Zou, B. S.; Zou, J. H.; Besiii Collaboration
2015-12-01
Using 2.92 fb-1 of electron-positron annihilation data collected at √{s }=3.773 GeV with the BESIII detector, we obtain the first measurements of the absolute branching fraction B (D+→KL0e+νe)=(4.481 ±0.027 (stat)±0.103 (sys))% and the C P asymmetry ACP D+→KL0 e+νe =(-0.59 ±0.60 (stat)±1.48 (sys))% . From the D+→KL0e+νe differential decay rate distribution, the product of the hadronic form factor and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element, f+K(0 )|Vc s| , is determined to be 0.728 ±0.006 (stat)±0.011 (sys) . Using |Vc s| from the SM constrained fit with the measured f+K(0 )|Vc s|, f+K(0 )=0.748 ±0.007 (stat)±0.012 (sys) is obtained, and utilizing the unquenched Lattice QCD (LQCD) calculation for f+K(0 ), |Vc s|=0.975 ±0.008 (stat)±0.015 (sys)±0.025 (LQCD ) .
NASA Astrophysics Data System (ADS)
Fernandes, Brian; Hegde, Manu; Stanish, Paul C.; Mišković, Zoran L.; Radovanovic, Pavle V.
2017-09-01
We developed a comprehensive theoretical model describing the photoluminescence decay dynamics at short and long time scales based on the donor-acceptor defect interactions in γ-Ga2O3 nanocrystals, and quantitatively determined the importance of exclusion distance and spatial distribution of defects. We allowed for donors and acceptors to be adjacent to each other or separated by different exclusion distances. The optimal exclusion distance was found to be comparable to the donor Bohr radius and have a strong effect on the photoluminescence decay curve at short times. The importance of the exclusion distance at short time scales was confirmed by Monte Carlo simulations.
Cui, Fengchao; Liu, Lunyang; Sun, Zhaoyan; Chen, Jizhong; Li, Yunqi
2016-01-01
Gay-Berne (GB) potential is regarded as an accurate model in the simulation of anisotropic particles, especially for liquid crystal (LC) mesogens. However, its computational complexity leads to an extremely time-consuming process for large systems. Here, we developed a GPU-accelerated molecular dynamics (MD) simulation with coarse-grained GB potential implemented in GALAMOST package to investigate the LC phase transitions for mesogens in small molecules, main-chain or side-chain polymers. For identical mesogens in three different molecules, on cooling from fully isotropic melts, the small molecules form a single-domain smectic-B phase, while the main-chain LC polymers prefer a single-domain nematic phase as a result of connective restraints in neighboring mesogens. The phase transition of side-chain LC polymers undergoes a two-step process: nucleation of nematic islands and formation of multi-domain nematic texture. The particular behavior originates in the fact that the rotational orientation of the mesogenes is hindered by the polymer backbones. Both the global distribution and the local orientation of mesogens are critical for the phase transition of anisotropic particles. Furthermore, compared with the MD simulation in LAMMPS, our GPU-accelerated code is about 4 times faster than the GPU version of LAMMPS and at least 200 times faster than the CPU version of LAMMPS. This study clearly shows that GPU-accelerated MD simulation with GB potential in GALAMOST can efficiently handle systems with anisotropic particles and interactions, and accurately explore phase differences originated from molecular structures. PMID:26986851
Chen, Wenduo; Zhu, Youliang; Cui, Fengchao; Liu, Lunyang; Sun, Zhaoyan; Chen, Jizhong; Li, Yunqi
2016-01-01
Gay-Berne (GB) potential is regarded as an accurate model in the simulation of anisotropic particles, especially for liquid crystal (LC) mesogens. However, its computational complexity leads to an extremely time-consuming process for large systems. Here, we developed a GPU-accelerated molecular dynamics (MD) simulation with coarse-grained GB potential implemented in GALAMOST package to investigate the LC phase transitions for mesogens in small molecules, main-chain or side-chain polymers. For identical mesogens in three different molecules, on cooling from fully isotropic melts, the small molecules form a single-domain smectic-B phase, while the main-chain LC polymers prefer a single-domain nematic phase as a result of connective restraints in neighboring mesogens. The phase transition of side-chain LC polymers undergoes a two-step process: nucleation of nematic islands and formation of multi-domain nematic texture. The particular behavior originates in the fact that the rotational orientation of the mesogenes is hindered by the polymer backbones. Both the global distribution and the local orientation of mesogens are critical for the phase transition of anisotropic particles. Furthermore, compared with the MD simulation in LAMMPS, our GPU-accelerated code is about 4 times faster than the GPU version of LAMMPS and at least 200 times faster than the CPU version of LAMMPS. This study clearly shows that GPU-accelerated MD simulation with GB potential in GALAMOST can efficiently handle systems with anisotropic particles and interactions, and accurately explore phase differences originated from molecular structures.
Anisotropic superconductivity and vortex dynamics in magnetially coupled F/S and F/S/F hybrids.
Karapetrov, G.; Belkin, A.; Iavarone, M.; Fedor, J.; Novosad, V.; Milosevic, M. V.; Peeters, F. M.
2011-01-01
Magnetically coupled superconductor-ferromagnet hybrids offer advanced routes for nanoscale control of superconductivity. Magnetotransport characteristics and scanning tunneling microscopy images of vortex structures in superconductor-ferromagnet hybrids reveal rich superconducting phase diagrams. Focusing on a particular combination of a ferromagnet with a well-ordered periodic magnetic domain structure with alternating out-of-plane component of magnetization, and a small coherence length superconductor, we find directed nucleation of superconductivity above the domain wall boundaries. We show that near the superconductor-normal state phase boundary the superconductivity is localized in narrow mesoscopic channels. In order to explore the Abrikosov flux line ordering in F/S hybrids, we use a combination of scanning tunneling microscopy and Ginzburg-Landau simulations. The magnetic stripe domain structure induces periodic local magnetic induction in the superconductor, creating a series of pinning-anti-pinning channels for externally added magnetic flux quanta. Such laterally confined Abrikosov vortices form quasi-1D arrays (chains). The transitions between multichain states occur through propagation of kinks at the intermediate fields. At high fields we show that the system becomes nonlinear due to a change in both the number of vortices and the confining potential. In F/S/F hybrids we demonstrate the evolution of the anisotropic conductivity in the superconductor that is magnetically coupled with two adjacent ferromagnetic layers. Stripe magnetic domain structures in both F-layers are aligned under each other, resulting in a directional superconducting order parameter in the superconducting layer. The conductance anisotropy strongly depends on the period of the magnetic domains and the strength of the local magnetization. The anisotropic conductivity of up to three orders of magnitude can be achieved with a spatial critical temperature modulation of 5% of T{sub c
C S2 decay dynamics investigated by two-color femtosecond laser pulses
NASA Astrophysics Data System (ADS)
Liu, Hongping; Zhang, Jianyang; Yin, Shuhui; Wang, Li; Lou, Nanquan
2004-10-01
The Rydberg-state decay dynamics of carbon disulfide (CS2) has been investigated by (2+1') resonance-enhanced multiphoton ionization with the pump-probe technique (pump wavelength 266nm and probe wavelength 400nm ) on our homebuilt femtosecond laser system. The CS2 is pumped into Rydberg state 6sσg by two 266-nm photons, corresponding to the excitation energy 9.4eV , and then ionized by temporally delayed 400-nm pulse. The CS2 ion yield dependence on the time delay determines the excited-state lifetime to be 409±6fs for C32S32S and 441±7fs for C32S34S , respectively, at 265nm pump and the isotopically averaged lifetime 1034±31fs at 267.5nm pump. The wavelength dependence of the lifetime may be due to the effect of electron spin on the potential energy surface—namely, separately subjected to two different mechanisms: internal conversion and intersystem crossing interaction.
Laser control of the radiationless decay in pyrazine using the dynamic Stark effect.
Sala, Matthieu; Saab, Mohamad; Lasorne, Benjamin; Gatti, Fabien; Guérin, Stéphane
2014-05-21
The laser control of the radiationless decay between the B(3u)(nπ*) and B(2u)(ππ*) states of pyrazine using the dynamic Stark effect has been investigated. A vibronic coupling model Hamiltonian in diabatic representation, including potential energy, transition dipole, and static polarizability surfaces as a function of the four most important vibrational modes of the molecule has been parametrized using multi-reference electronic structure calculations. The interaction of the molecule with a strong non-resonant laser pulse has been analyzed in terms of dressed potential energy surfaces. Because of the large polarizability difference between the vibronically coupled B(3u)(nπ*) and B(2u)(ππ*) states, the Stark effect induced by the non-resonant laser pulse shifts the conical intersection away from the Franck-Condon region. We have shown, by solving the time-dependent Schrödinger equation for the molecule interacting with a relatively weak pump pulse driving the electronic excitation from the ground state to the B(2u)(ππ*) state, and a strong non-resonant control pulse, that this control mechanism can be used to trap the wavepacket on the B(2u)(ππ*) potential energy surface for a much longer time than the natural B(2u)(ππ*) lifetime.
Laser control of the radiationless decay in pyrazine using the dynamic Stark effect
NASA Astrophysics Data System (ADS)
Sala, Matthieu; Saab, Mohamad; Lasorne, Benjamin; Gatti, Fabien; Guérin, Stéphane
2014-05-01
The laser control of the radiationless decay between the B3u(nπ*) and B2u(ππ*) states of pyrazine using the dynamic Stark effect has been investigated. A vibronic coupling model Hamiltonian in diabatic representation, including potential energy, transition dipole, and static polarizability surfaces as a function of the four most important vibrational modes of the molecule has been parametrized using multi-reference electronic structure calculations. The interaction of the molecule with a strong non-resonant laser pulse has been analyzed in terms of dressed potential energy surfaces. Because of the large polarizability difference between the vibronically coupled B3u(nπ*) and B2u(ππ*) states, the Stark effect induced by the non-resonant laser pulse shifts the conical intersection away from the Franck-Condon region. We have shown, by solving the time-dependent Schrödinger equation for the molecule interacting with a relatively weak pump pulse driving the electronic excitation from the ground state to the B2u(ππ*) state, and a strong non-resonant control pulse, that this control mechanism can be used to trap the wavepacket on the B2u(ππ*) potential energy surface for a much longer time than the natural B2u(ππ*) lifetime.
Laser control of the radiationless decay in pyrazine using the dynamic Stark effect
Sala, Matthieu Guérin, Stéphane; Saab, Mohamad; Lasorne, Benjamin; Gatti, Fabien
2014-05-21
The laser control of the radiationless decay between the B{sub 3u}(nπ*) and B{sub 2u}(ππ*) states of pyrazine using the dynamic Stark effect has been investigated. A vibronic coupling model Hamiltonian in diabatic representation, including potential energy, transition dipole, and static polarizability surfaces as a function of the four most important vibrational modes of the molecule has been parametrized using multi-reference electronic structure calculations. The interaction of the molecule with a strong non-resonant laser pulse has been analyzed in terms of dressed potential energy surfaces. Because of the large polarizability difference between the vibronically coupled B{sub 3u}(nπ*) and B{sub 2u}(ππ*) states, the Stark effect induced by the non-resonant laser pulse shifts the conical intersection away from the Franck-Condon region. We have shown, by solving the time-dependent Schrödinger equation for the molecule interacting with a relatively weak pump pulse driving the electronic excitation from the ground state to the B{sub 2u}(ππ*) state, and a strong non-resonant control pulse, that this control mechanism can be used to trap the wavepacket on the B{sub 2u}(ππ*) potential energy surface for a much longer time than the natural B{sub 2u}(ππ*) lifetime.
Full-dimensional control of the radiationless decay in pyrazine using the dynamic Stark effect
Saab, Mohamad Lasorne, Benjamin Gatti, Fabien; Sala, Matthieu; Guérin, Stéphane
2014-10-07
We present a full quantum-mechanical study of the laser control of the radiationless decay between the B{sub 3u}(nπ{sup *}) and B{sub 2u}(ππ{sup *}) states of pyrazine using the dynamic Stark effect. In contrast to our previous study [Sala et al., J. Chem. Phys. 140, 194309 (2014)], where a four-dimensional model was used, all the 24 degrees of freedom are now included in order to test the robustness of the strategy of control. Using a vibronic coupling Hamiltonian model in a diabatic representation, the multi-layer version of the multi-configuration time-dependent Hartree method is exploited to propagate the corresponding wave packets. We still observe a trapping of the wavepacket on the B{sub 2u}(ππ{sup *}) potential energy surface due to the Stark effect for a longer time than the “non-resonant field-free” B{sub 2u}(ππ{sup *}) lifetime.
NASA Astrophysics Data System (ADS)
Zhao, Li; Zhou, Pan-Wang; Zhao, Guang-Jiu
2016-07-01
The trans-urocanic acid, a UV chromophore in the epidermis of human skin, was found to exhibit a wavelength dependent isomerization property. The isomerization quantum yield to cis-urocanic is greatest when being excited to the S1 state, whereas exciting the molecule to the S2 state causes almost no isomerization. The comparative photochemical behavior of the trans-urocanic on the S1 and S2 states continues to be the subject of intense research effort. This study is concerned with the unique photo-behavior of this interesting molecule on the S2 state. Combining the on-the-fly surface hopping dynamics simulations and static electronic structure calculations, three decay channels were observed following excitation to the S2 state. An overwhelming majority of the molecules decay to the S1 state through a planar or pucker characterized minimum energy conical intersection (MECI), and then decay to the ground state along a relaxation coordinate driven by a pucker deformation of the ring. A very small fraction of molecules decay to the S1 state by a MECI characterized by a twisting motion around the CC double bond, which continues to drive the molecule to deactivate to the ground state. The latter channel is related with the photoisomerization process, whereas the former one will only generate the original trans-form products. The present work provides a novel S2 state decay mechanism of this molecule, which offers useful information to explain the wavelength dependent isomerization behavior.
Molecular Assessment of litter decay dynamics across old and young forest sites
NASA Astrophysics Data System (ADS)
Filley, T. R.; Crow, S.; Gamblin, D.; McCormick, M.; Whigham, D.; Taylor, D. L.
2006-12-01
The response of soil organic matter pools to changes in litter input, land cover, and ýinvertebrate activity is a research area of intensive study given the proposed impacts that ýrising CO2 and surface temperatures may have on forest productivity and distribution of ýinvasive species. In a mixed deciduous forest at the Smithsonian Environmental ýResearch Center litter amendment plots were established in old (120-150 y) and young ýý(50-70 y) forests. In May 2004, six plots were amended with locally collected ýLirodendron tulipifera wood (chipped) and leaves. At the same time, leaf and wood litter ýbag decomposition experiments on the sites were also started. Changes in the ýconcentration and composition of biopolymers, e.g. lignin and cutin/suberin, after ýapproximately four months of decay were tracked by alkaline CuO extraction. Resultant ýleaf and wood litter in the surface amendments was distinct between age groupings. ýYoung sites exhibited the greatest change in chemical character showing increased lignin ýand decreased cutin/suberin resulting in a cutin-poor residue. Minor changes to ýbiopolymer character were observed in older sites with residues exhibiting small but ýopposite trends to the young sites. In contrast, the litter bag studies exhibited little to no ývariation in chemistry with age of stand; although, generally leaf litter showed the ýgreatest age-related effect. These patterns in litter decay are consistent with both ýmicrobial activity and relative biomass of invasive earthworms; young forests exhibit ýrelatively higher activity of both phenol oxidase and B-glucosidase in the soil (0-5 cm) ýplots and greater biomass and relative abundance invasive earthworms. These results are ýimportant as they show how stand age and the presence of invertebrate species may have ýimportant controls on the impact that many global change drivers may have on forest soil ýand carbon exchange dynamics.ý
Yao, Zi-Shuo; Wu, Shu-Qi; Kitagawa, Yasutaka; Su, Sheng-Qun; Huang, You-Gui; Li, Guo-Ling; Ni, Zhong-Hai; Nojiri, Hiroyuki; Shiota, Yoshihito; Yoshizawa, Kazunari; Kang, Soonchul; Kanegawa, Shinji; Sato, Osamu
2017-01-16
Atypically anisotropic and large changes in magnetic susceptibility, along with a change in crystalline shape, were observed in a Co(II) complex at near room temperature. This was achieved by combining oxalate molecules, acting as rotor, and a Co(II) ion with unquenched orbital angular momentum. A thermally controlled 90° rotation of the oxalate counter anion triggered a symmetry-breaking ferroelastic phase transition, accompanied by contraction-expansion behavior (ca. 4.5 %) along the long axis of a rod-like single crystal. The molecular rotation induced a minute variation in the coordination geometry around the Co(II) ion, resulting in an abrupt decrease and a remarkable increase in magnetic susceptibility along the direction perpendicular and parallel to the long axis of the crystal, respectively. Theoretical calculations suggested that such an unusual anisotropic change in magnetic susceptibility was due to a substantial reorientation of magnetic anisotropy induced by slight disruption in the ideal D3 coordination environment of the complex cation.
Dynamical Calculation of Θ+ Mass and Decay width in the Quark Model
NASA Astrophysics Data System (ADS)
Rostampour, M.; Saadat, H.; Farahani, H.
2012-08-01
In this paper we study the mass splitting and the decay width of pentaquark (Θ+) at the ground states in the framework of flux tube, quark delocalization and color screening model. We consider the pentaquark as diquark-triquark configuration and obtained closer values of mass splitting and the decay width of Θ+ to the experimental data.
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.
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 and long-range vortex interactions in two-dimensional dipolar Bose gases.
Mulkerin, B C; van Bijnen, R M W; O'Dell, D H J; Martin, A M; Parker, N G
2013-10-25
We perform a theoretical study into how dipole-dipole interactions modify the properties of superfluid vortices within the context of a two-dimensional atomic Bose gas of co-oriented dipoles. The reduced density at a vortex acts like a giant antidipole, changing the density profile and generating an effective dipolar potential centred at the vortex core whose most slowly decaying terms go as 1/ρ(2) and ln(ρ)/ρ(3). These effects modify the vortex-vortex interaction which, in particular, becomes anisotropic for dipoles polarized in the plane. Striking modifications to vortex-vortex dynamics are demonstrated, i.e., anisotropic corotation dynamics and the suppression of vortex annihilation.
Anisotropic and Long-Range Vortex Interactions in Two-Dimensional Dipolar Bose Gases
NASA Astrophysics Data System (ADS)
Mulkerin, B. C.; van Bijnen, R. M. W.; O'Dell, D. H. J.; Martin, A. M.; Parker, N. G.
2013-10-01
We perform a theoretical study into how dipole-dipole interactions modify the properties of superfluid vortices within the context of a two-dimensional atomic Bose gas of co-oriented dipoles. The reduced density at a vortex acts like a giant antidipole, changing the density profile and generating an effective dipolar potential centred at the vortex core whose most slowly decaying terms go as 1/ρ2 and ln(ρ)/ρ3. These effects modify the vortex-vortex interaction which, in particular, becomes anisotropic for dipoles polarized in the plane. Striking modifications to vortex-vortex dynamics are demonstrated, i.e., anisotropic corotation dynamics and the suppression of vortex annihilation.
NASA Astrophysics Data System (ADS)
Guillemin, R.; Sheinerman, S.; Bomme, C.; Journel, L.; Marin, T.; Marchenko, T.; Kushawaha, R. K.; Trcera, N.; Piancastelli, M. N.; Simon, M.
2012-07-01
Argon 1s photoionization followed by multiple Auger decays is investigated both experimentally, by means of photoelectron-ion coincidences, and theoretically. A strong influence of the different Auger decays on the photoelectron spectra is observed through postcollision interaction which shifts the maximum of the energy distribution and distorts the spectral shape. A good agreement between the calculated and measured spectra for selected Arn+ ions (n=1-5) allows one to estimate the widths (lifetimes) of the intermediate states for each specific decay pathway.
Collective Clusterization in Nuclei and Excited Compound Systems: The Dynamical Cluster-Decay Model
NASA Astrophysics Data System (ADS)
Gupta, Raj K.
Clustering is a general feature of light, N = Z, α-like stable nuclei for both the ground and (intrinsic) excited states. This phenomenon is observed in spontaneous decays of heavy radioactive nuclei, and seems to play an important role in the decay of excited compound systems formed in heavy ion reactions. It is also shown to be present in exotic light-halo, super-heavy and super-superheavy nuclei.
Spectral imbalance in the inertial range dynamics of decaying rotating turbulence
NASA Astrophysics Data System (ADS)
Valente, P. C.; Dallas, V.
2017-02-01
Direct numerical simulations of homogeneous decaying turbulence with background rotation show the existence of a systematic and significant imbalance between the non-linear energy cascade to small scales and its dissipation. By starting the decay from a statistically stationary and weakly rotating turbulent state, where the dissipation and the energy flux are approximately equal, the data show a growing imbalance between the two until a maximum is reached when the dissipation is about twice the energy flux. This dichotomy of behaviors during decay is reminiscent of the nonequilibrium and the equilibrium regions previously reported for nonrotating turbulence [Valente and Vassilicos, Phys. Rev. Lett. 108, 214503 (2012), 10.1103/PhysRevLett.108.214503]. Note, however, that for decaying rotating turbulence the classical scaling of the dissipation rate ɛ ∝u'3/L (where u' and L are the root mean square fluctuating velocity and the integral length scale, respectively) does not appear to hold during decay, which may be attributed to the effect of the background rotation on the energy cascade. On the other hand, the maximum energy flux holds the scaling Πmax∝u'3/L in the initial stage of the decay until the maximum imbalance is reached.
NASA Astrophysics Data System (ADS)
Cheng, Hao-Chung; Hsieh, Min-Hsiu; Tomamichel, Marco
2017-09-01
In this work, we extend the theory of quantum Markov processes on a single quantum state to a broader theory that covers Markovian evolution of an ensemble of quantum states, which generalizes Lindblad's formulation of quantum dynamical semigroups. Our results establish the equivalence between an exponential decrease of the matrix Φ -entropies and the Φ -Sobolev inequalities, which allows us to characterize the dynamical evolution of a quantum ensemble to its equilibrium. In particular, we study the convergence rates of two special semigroups, namely, the depolarizing channel and the phase-damping channel. In the former, since there exists a unique equilibrium state, we show that the matrix Φ -entropy of the resulting quantum ensemble decays exponentially as time goes on. Consequently, we obtain a stronger notion of monotonicity of the Holevo quantity—the Holevo quantity of the quantum ensemble decays exponentially in time and the convergence rate is determined by the modified log-Sobolev inequalities. However, in the latter, the matrix Φ -entropy of the quantum ensemble that undergoes the phase-damping Markovian evolution generally will not decay exponentially. There is no classical analogy for these different equilibrium situations. Finally, we also study a statistical mixing of Markov semigroups on matrix-valued functions. We can explicitly calculate the convergence rate of a Markovian jump process defined on Boolean hypercubes and provide upper bounds to the mixing time.
2015-01-01
Transition metal doped semiconductor nanocrystals (d-dots) possess fundamentally different emission properties upon photo- or electroexcitation, which render them as unique emitters for special applications. However, in comparison with intrinsic semiconductor nanocrystals, the potential of d-dots has been barely realized, because many of their unique emission properties mostly rely on precise control of their photoluminescence (PL) decay dynamics. Results in this work revealed that it would be possible to obtain bright d-dots with nearly single-exponential PL decay dynamics. By tuning the number of Mn2+ ions per dot from ∼500 to 20 in Mn2+ doped ZnSe nanocrystals (Mn:ZnSe d-dots), the single-exponential PL decay lifetime was continuously tuned from ∼50 to 1000 μs. A synthetic scheme was further developed for uniform and epitaxial growth of thick ZnS shell, ∼7 monolayers. The resulting Mn:ZnSe/ZnS core/shell d-dots were found to be essential for necessary environmental durability of the PL properties, both steady-state and transient ones, for the d-dot emitters. These characteristics combined with intense absorption and high PL quantum yields (70 ± 5%) enabled greatly simplified schemes for various applications of PL lifetime multiplexing using Mn:ZnSe/ZnS core/shell d-dots. PMID:27163024
NASA Astrophysics Data System (ADS)
Kaur, Arshdeep; Chopra, Sahila; Gupta, Raj K.
2014-08-01
The compound nucleus (CN) fusion/formation probability PCN is defined and its detailed variations with the CN excitation energy E*, center-of-mass energy Ec .m., fissility parameter χ, CN mass number ACN, and Coulomb interaction parameter Z1Z2 are studied for the first time within the dynamical cluster-decay model (DCM). The model is a nonstatistical description of the decay of a CN to all possible processes. The (total) fusion cross section σfusion is the sum of the CN and noncompound nucleus (nCN) decay cross sections, each calculated as the dynamical fragmentation process. The CN cross section σCN is constituted of evaporation residues and fusion-fission, including intermediate-mass fragments, each calculated for all contributing decay fragments (A1, A2) in terms of their formation and barrier penetration probabilities P0 and P. The nCN cross section σnCN is determined as the quasi-fission (qf) process, where P0=1 and P is calculated for the entrance-channel nuclei. The DCM, with effects of deformations and orientations of nuclei included in it, is used to study the PCN for about a dozen "hot" fusion reactions forming a CN of mass number A ˜100 to superheavy nuclei and for various different nuclear interaction potentials. Interesting results are that PCN=1 for complete fusion, but PCN<1 or PCN≪1 due to the nCN contribution, depending strongly on different parameters of the entrance-channel reaction but found to be independent of the nuclear interaction potentials used.
Towards a Dynamical Understanding of the Non-D Dmacr Decay of ψ(3770)
NASA Astrophysics Data System (ADS)
Zhang, Yuan-Jiang; Li, Gang; Zhao, Qiang
2009-05-01
We investigate the ψ(3770) non-D Dmacr decays into VP, where V and P denote vector and pseudoscalar mesons, respectively, via Okubo-Zweig-Iizuka-rule-evading intermediate meson rescatterings in an effective Lagrangian theory. By identifying the leading meson loop transitions and constraining the model parameters with the available experimental data for ψ(3770)→J/ψη, ϕη, and ρπ, we succeed in making a quantitative prediction for all ψ(3770)→VP with BRVP from 0.41% to 0.64%. It indicates that the Okubo-Zweig-Iizuka-rule-evading long-range interactions play a role in ψ(3770) strong decays, and could be a key towards a full understanding of the mysterious ψ(3770) non-D Dmacr decay mechanism.
Cheng, Kwan H; Aijmo, Jacob; Ma, Lun; Yao, Mingzhen; Zhang, Xing; Como, John; Hope-Weeks, Louisa J; Huang, Juyang; Chen, Wei
2008-10-22
We have studied the luminescence decay and trace biomaterials detection potential of two surface-functionalized nanoparticles, poly(ethylene glycol) bis(carboxymethyl) ether-coated LaF(3):Ce,Tb (~20 nm) and thioglycolic acid-coated ZnS/Mn (~5 nm). Upon UV excitation, these nanoparticles emitted fluorescence peaking at 540 and 597 nm, respectively, in solution. Fluorescence imaging revealed that these nanoparticles targeted the trace biomaterials from fingerprints that were deposited on various nonporous solid substrates. Highly ordered, microscopic sweat pores within the friction ridges of the fingerprints were labeled with good spatial resolutions by the nanoparticles on aluminum and polymethylpentene substrates, but not on glass or quartz. In solution, these nanoparticles exhibited multicomponent fluorescence decays of resolved lifetimes ranging from nano-to microseconds and of average lifetimes of ~24 and 130 micros for the coated LaF(3):Ce,Tb and ZnS:Mn, respectively. The long microsecond-decay components are associated with the emitters at or near the nanocrystal core surface that are sensitive to the size, surface-functionalization, and solvent exposure of the nanoparticles. When the nanoparticles were bound to the surface of a solid substrate and in the dried state, a decrease in the microsecond decay lifetimes was observed, indicative of a change in the coating environment of the nanocrystal surface upon binding and solvent removal. The average decay lifetimes for the surface-bound ZnS:Mn in the dried state were ~60, 30, and 11 micros on quartz, aluminum, and polymethylpentene, respectively. These values were still 2 orders of magnitude longer than the typical fluorescence decay background of most substrates (e.g., ~0.36 micros for polymethylpentene) in trace forensic evidence detections. We conclude that coated ZnS: Mn nanoparticles hold great promise as a nontoxic labeling agent for ultrasensitive, time-gated, trace evidence detections in nanoforensic
Cheng, Kwan H.; Aijmo, Jacob; Ma, Lun; Yao, Mingzhen; Zhang, Xing; Como, John; Hope-Weeks, Louisa J.; Huang, Juyang; Chen, Wei
2009-01-01
We have studied the luminescence decay and trace biomaterials detection potential of two surface-functionalized nanoparticles, poly(ethylene glycol) bis(carboxymethyl) ether-coated LaF3:Ce,Tb (~20 nm) and thioglycolic acid-coated ZnS/Mn (~5 nm). Upon UV excitation, these nanoparticles emitted fluorescence peaking at 540 and 597 nm, respectively, in solution. Fluorescence imaging revealed that these nanoparticles targeted the trace biomaterials from fingerprints that were deposited on various nonporous solid substrates. Highly ordered, microscopic sweat pores within the friction ridges of the fingerprints were labeled with good spatial resolutions by the nanoparticles on aluminum and polymethylpentene substrates, but not on glass or quartz. In solution, these nanoparticles exhibited multicomponent fluorescence decays of resolved lifetimes ranging from nano-to microseconds and of average lifetimes of ~24 and 130 µs for the coated LaF3:Ce,Tb and ZnS:Mn, respectively. The long microsecond-decay components are associated with the emitters at or near the nanocrystal core surface that are sensitive to the size, surface-functionalization, and solvent exposure of the nanoparticles. When the nanoparticles were bound to the surface of a solid substrate and in the dried state, a decrease in the microsecond decay lifetimes was observed, indicative of a change in the coating environment of the nanocrystal surface upon binding and solvent removal. The average decay lifetimes for the surface-bound ZnS:Mn in the dried state were ~60, 30, and 11 µs on quartz, aluminum, and polymethylpentene, respectively. These values were still 2 orders of magnitude longer than the typical fluorescence decay background of most substrates (e.g., ~0.36 µs for polymethylpentene) in trace forensic evidence detections. We conclude that coated ZnS: Mn nanoparticles hold great promise as a nontoxic labeling agent for ultrasensitive, time-gated, trace evidence detections in nanoforensic applications
NASA Astrophysics Data System (ADS)
Kumar, Raj; Sandhu, Kirandeep; Sharma, Manoj K.; Gupta, Raj K.
2013-05-01
The decay of the Z=115 superheavy nuclear system, formed in the 243Am+48Ca reaction, is studied by using the dynamical cluster-decay model. The calculated excitation functions of 2n-, 3n-, and 4n-evaporation channels, for the excitation energy range ECN*=31-47 MeV, are compared with the recent experimental data. The deformation effects are included up to β2, within the hot optimum orientation approach, and a comparative analysis of spherical versus static and dynamic deformations is investigated explicitly for the 2n-evaporation residue, as only 2n decay responds to spherical fragments. The 3n and 4n decay cross sections could be fitted only after the inclusion of deformation effects. The variation of preformation probability, barrier penetrability, and barrier modification is investigated in order to extract a better picture of the dynamics involved in the reaction under consideration. It is observed that, for the 3n-evaporation channel, the barrier modification at ECN*=36.15 MeV is the smallest and hence supports the experimental observation of maximum cross section (8.5 pb) at this energy. The role of isospin (N/Z ratio) is also investigated for the decay of various isotopes of Z=115 formed in 48Ca+241,243,245Am reactions. Furthermore, the evaporation cross sections of 2n, 3n, and 4n channels are also estimated at the Bass barrier by interpolating the neck-length parameters fixed in reference to available data at above-barrier energies. Finally, the α-decay chains are analyzed by using the preformed cluster model. It is shown that the present data of α-decay half-lives support “hot” optimum orientations of nuclei, rather than the usual “cold” ones, within a constant empirical factor in penetrability.
Anisotropic. cap alpha. -emission of on-line separated isotopes
Wouters, J.; Vandeplassche, D.; van Walle, E.; Severijns, N.; Van Haverbeke, J.; Vanneste, L.
1987-12-10
The technical realization of particle detection at very low temperatures (4K) has made it possible to study for the first time the anisotropic ..cap alpha..-decay of oriented nuclei which have been produced, separated and implanted on line. The measured ..cap alpha..-angular distributions reveal surprising new results on nuclear aspects as well as in solid state physics. The nuclear structure information from these data questions the older ..cap alpha..-decay theoretical interpretation and urges for a reaxamination of the earliest work on anisotropic ..cap alpha..-decay.
Spin noise in the anisotropic central spin model
NASA Astrophysics Data System (ADS)
Hackmann, Johannes; Anders, Frithjof B.
2014-01-01
Spin-noise measurements can serve as a direct probe for the microscopic decoherence mechanism of an electronic spin in semiconductor quantum dots (QDs). We have calculated the spin-noise spectrum in the anisotropic central spin model using a Chebyshev expansion technique which exactly accounts for the dynamics up to an arbitrary long but fixed time in a finite-size system. In the isotropic case, describing QD charge with a single electron, the short-time dynamics is in good agreement with quasistatic approximations for the thermodynamic limit. The spin-noise spectrum, however, shows strong deviations at low frequencies with a power-law behavior of ω-3/4 corresponding to a t-1/4 decay at intermediate and long times. In the Ising limit, applicable to QDs with heavy-hole spins, the spin-noise spectrum exhibits a threshold behavior of (ω-ωL)-1/2 above the Larmor frequency ωL=gμBB. In the generic anisotropic central spin model we have found a crossover from a Gaussian type of spin-noise spectrum to a more Ising-type spectrum with increasing anisotropy in a finite magnetic field. In order to make contact with experiments, we present ensemble averaged spin-noise spectra for QD ensembles charged with single electrons or holes. The Gaussian-type noise spectrum evolves to a more Lorentzian shape spectrum with increasing spread of characteristic time scales and g factors of the individual QDs.
Flux decay during thermonuclear X-ray bursts analysed with the dynamic power-law index method
NASA Astrophysics Data System (ADS)
Kuuttila, J.; Kajava, J. J. E.; Nättilä, J.; Motta, S. E.; Sánchez-Fernández, C.; Kuulkers, E.; Cumming, A.; Poutanen, J.
2017-08-01
The cooling of type-I X-ray bursts can be used to probe the nuclear burning conditions in neutron star envelopes. The flux decay of the bursts has been traditionally modelled with an exponential, even if theoretical considerations predict power-law-like decays. We have analysed a total of 540 type-I X-ray bursts from five low-mass X-ray binaries observed with the Rossi X-ray Timing Explorer. We grouped the bursts according to the source spectral state during which they were observed (hard or soft), flagging those bursts that showed signs of photospheric radius expansion (PRE). The decay phase of all the bursts were then fitted with a dynamic power-law index method. This method provides a new way of probing the chemical composition of the accreted material. Our results show that in the hydrogen-rich sources the power-law decay index is variable during the burst tails and that simple cooling models qualitatively describe the cooling of presumably helium-rich sources 4U 1728-34 and 3A 1820-303. The cooling in the hydrogen-rich sources 4U 1608-52, 4U 1636-536, and GS 1826-24, instead, is clearly different and depends on the spectral states and whether PRE occurred or not. Especially the hard state bursts behave differently than the models predict, exhibiting a peculiar rise in the cooling index at low burst fluxes, which suggests that the cooling in the tail is much faster than expected. Our results indicate that the drivers of the bursting behaviour are not only the accretion rate and chemical composition of the accreted material, but also the cooling that is somehow linked to the spectral states. The latter suggests that the properties of the burning layers deep in the neutron star envelope might be impacted differently depending on the spectral state.
(3 +1 )D Quasiparticle Anisotropic Hydrodynamics for Ultrarelativistic Heavy-Ion Collisions
NASA Astrophysics Data System (ADS)
Alqahtani, Mubarak; Nopoush, Mohammad; Ryblewski, Radoslaw; Strickland, Michael
2017-07-01
We present the first comparisons of experimental data with phenomenological results from (3 +1 )D quasiparticle anisotropic hydrodynamics (aHydroQP). We compare particle spectra, average transverse momentum, and elliptic flow. The dynamical equations used for the hydrodynamic stage utilize aHydroQP, which naturally includes both shear and bulk viscous effects. The (3 +1 )D aHydroQP evolution obtained is self-consistently converted to hadrons using anisotropic Cooper-Frye freeze-out. Hadron production and decays are modeled using a customized version of therminator 2. In this first study, we utilized smooth Glauber-type initial conditions and a single effective freeze-out temperature TFO=130 MeV with all hadronic species in full chemical equilibrium. With this rather simple setup, we find a very good description of many heavy-ion observables.
Yamada, Tomoko; Uchino, Takashi
2005-08-22
The time-resolved photoluminescence (PL) decays are measured for transparent amorphous silica prepared from solid-phase sintering of nanometer-sized silica particles, which has recently been shown to exhibit a unique white PL emission under ultraviolet excitation [T. Uchino and T. Yamada, Appl. Phys. Lett. 85, 1164 (2004)]. Unlike usual PL processes observed in normal silica glass, it is shown that the present PL results from trapping-controlled migration of photoexcited carriers and their radiative recombination.
NASA Astrophysics Data System (ADS)
Yamada, Tomoko; Uchino, Takashi
2005-08-01
The time-resolved photoluminescence (PL) decays are measured for transparent amorphous silica prepared from solid-phase sintering of nanometer-sized silica particles, which has recently been shown to exhibit a unique white PL emission under ultraviolet excitation [T. Uchino and T. Yamada, Appl. Phys. Lett. 85, 1164 (2004)]. Unlike usual PL processes observed in normal silica glass, it is shown that the present PL results from trapping-controlled migration of photoexcited carriers and their radiative recombination.
New Evidence for the Dynamical Decay of a Multiple System in the Orion Kleinmann-Low Nebula
NASA Astrophysics Data System (ADS)
Luhman, K. L.; Robberto, M.; Tan, J. C.; Andersen, M.; Giulia Ubeira Gabellini, M.; Manara, C. F.; Platais, I.; Ubeda, L.
2017-03-01
We have measured astrometry for members of the Orion Nebula Cluster with images obtained in 2015 with the Wide Field Camera 3 on board the Hubble Space Telescope. By comparing those data to previous measurements with the Near-Infrared Camera and Multi-Object Spectrometer on Hubble in 1998, we have discovered that a star in the Kleinmann-Low Nebula, source x from Lonsdale et al., is moving with an unusually high proper motion of 29 mas yr-1, which corresponds to 55 km s-1 at the distance of Orion. Previous radio observations have found that three other stars in the Kleinmann-Low Nebula (the Becklin-Neugebauer object and sources I and n) have high proper motions (5-14 mas yr-1) and were near a single location ˜540 years ago, and thus may have been members of a multiple system that dynamically decayed. The proper motion of source x is consistent with ejection from that same location 540 years ago, which provides strong evidence that the dynamical decay did occur and that the runaway star BN originated in the Kleinmann-Low Nebula rather than the nearby Trapezium cluster. However, our constraint on the motion of source n is significantly smaller than the most recent radio measurement, which indicates that it did not participate in the event that ejected the other three stars. Based on observations made with the NASA/ESA Hubble Space Telescope and the NASA Infrared Telescope Facility.
Andersen, Olaf; Vesenjak, Matej; Fiedler, Thomas; Jehring, Ulrike; Krstulović-Opara, Lovre
2016-01-01
Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted. PMID:28773522
Severin, Jonathan; Jund, Philippe
2017-02-07
In this work, we aim to study the thermal properties of materials using classical molecular dynamics simulations and specialized numerical methods. We focus primarily on the thermal conductivity κ using non-equilibrium molecular dynamics (NEMD) to study the response of a crystalline solid, namely hematite (α-Fe2O3), to an imposed heat flux as is the case in real life applications. We present a methodology for the calculation of κ as well as an adapted potential for hematite. Taking into account the size of the simulation box, we show that not only the longitudinal size (in the direction of the heat flux) but also the transverse size plays a role in the determination of κ and should be converged properly in order to have reliable results. Moreover we propose a comparison of thermal conductivity calculations in two different crystallographic directions to highlight the spatial anisotropy and we investigate the non-linear temperature behavior typically observed in NEMD methods.
NASA Astrophysics Data System (ADS)
Severin, Jonathan; Jund, Philippe
2017-02-01
In this work, we aim to study the thermal properties of materials using classical molecular dynamics simulations and specialized numerical methods. We focus primarily on the thermal conductivity κ using non-equilibrium molecular dynamics (NEMD) to study the response of a crystalline solid, namely hematite (α -Fe2O3 ), to an imposed heat flux as is the case in real life applications. We present a methodology for the calculation of κ as well as an adapted potential for hematite. Taking into account the size of the simulation box, we show that not only the longitudinal size (in the direction of the heat flux) but also the transverse size plays a role in the determination of κ and should be converged properly in order to have reliable results. Moreover we propose a comparison of thermal conductivity calculations in two different crystallographic directions to highlight the spatial anisotropy and we investigate the non-linear temperature behavior typically observed in NEMD methods.
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
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.
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.
Decay dynamics of the unbound 25O and 26O nuclei
NASA Astrophysics Data System (ADS)
Hagino, K.; Sagawa, H.
2016-03-01
We study the ground and excited resonance states of 26O with a three-body model of 24O+n +n taking into account the coupling to the continuum. To this end, we use the new experimental data for the invariant mass spectroscopy of the unbound 25O and 26O nuclei, and present an update of three-body model calculations for the two-neutron decay of the 26O nucleus. With the new model inputs determined with the ground-state decay of 26O, we discuss the dineutron correlations and a halo nature of this nucleus, as well as the structure of the excited states. For the energy of the 2+ state, we achieve an excellent agreement with the experimental data with this calculation. We show that the 2+ state consists predominantly of the (d3/2) 2 configuration, for which the pairing interaction between the valence neutrons slightly decreases its energy from the unperturbed one. We also discuss the structure of excited 0+ states of the 26O nucleus. In particular, we show the existence of an excited 0+ state at 3.38 MeV, which is mainly composed of the (f7/2) 2 configuration.
Ultrafast Excited-State Decays in [Re(CO)3(N,N)(L)](n+): Nonadiabatic Quantum Dynamics.
Fumanal, Maria; Gindensperger, Etienne; Daniel, Chantal
2017-03-14
The ultrafast luminescent decay of [Re(CO)3(phen)(im)](+), representative of Re(I) carbonyl α-diimine photosensitizers, is investigated by means of wavepacket propagations based on the multiconfiguration time-dependent Hartree (MCTDH) method. On the basis of electronic structure data obtained at the time-dependent density functional theory (TD-DFT) level, the luminescence decay is simulated by solving a 14 electronic states multimode problem including both vibronic and spin-orbit coupling (SOC) up to 15 vibrational modes. A careful analysis of the results provides the key features of the mechanism of the intersystem crossing (ISC) in this complex. The intermediate state, detected by means of fs - ps time-resolved spectroscopies, is assigned to the T3 state corresponding to the triplet intraligand ((3)IL) transition localized on the phen ligand. By switching off/on SOC and vibronic coupling in the model it is shown that efficient population transfer occurs from the optically active metal-to-ligand-charge-transfer1,3MLCT states to T3 and to the lowest long-lived phosphorescent (3)MLCT (T1) state. The early ultrafast SOC-driven decay followed by a T3/T1 equilibration controlled by vibronic coupling underlies the photoluminescent properties of [Re(CO)3(phen)(im)](+). The impact of the axial and N,N ligands on the photophysics of this class of Re(I) complexes is further rationalized on the basis of their calculated optical properties. The relative position of the (3)IL and upper (3)MLCT states with respect to the optically active singlet state is influenced by the N,N ligand and affects the relaxation dynamics.
NASA Astrophysics Data System (ADS)
Zhou, Hai-Chao; Wei, Shu-Dong; Zeng, Qi; Zhang, Li-Hua; Tam, Nora Fung-yee; Lin, Yi-Ming
2010-03-01
Avicennia marina is a typical mangrove species in the subtropical coastlines of China. The main objective of this study was to assess nutrient and caloric dynamics in A. marina leaves at different developmental and decay stages. Decomposition studies using litter bags suggested that the time required for the loss of half of the initial dry weight ( t50) was 19 days. The extracts of A. marina leaves contained non-tannin phenolics and tannin phenolics (hydrolysable tannin), but no condensed tannin. Non-tannin phenolics and tannin phenolics contents did not differ significantly from each other at various developmental stages, but decreased rapidly during leaf decomposition. Avicennia marina leaves had high N levels, and both N and P concentrations decreased significantly during senescence. During decomposition, N concentration of the leaf litter increased gradually but the phosphorus concentration showed a decrease in the first week, and both N and P remained the same towards the end of the experiment. The gross caloric value (GCV) of mature leaves was significantly higher than those of young and senescent leaves, while ash-free caloric value (AFCV) did not change significantly during leaf development and senescence. During leaf decomposition, both GCV and AFCV increased gradually and remained the same at late stages. In subtropical Zhangjiang River Estuary, high N levels and lack of condensed tannins in A. marina leaves were responsible for the fast rate of decay. Non-tannin phenolics and tannin phenolics had no great effect on rate of decay. Nitrogen resorption during leaf senescence, and high litter decomposition followed by nitrogen immobilization are the important nutrient conservation strategy for A. marina.
NASA Astrophysics Data System (ADS)
Bikram Singh, Bir; Kaur, Mandeep; Sharma, Manoj K.; Gupta, Raj K.
2014-12-01
The study of the decay of 32S* and 31P* compound systems formed in 20Ne+12C and 19F+12C reactions, respectively, is further extended on the basis of collective clusterization process within the dynamical cluster model (DCM) of Gupta and collaborators, with the effects of deformations and orientations included, at an excitation energy E*CN=60 MeV. In the present study, we have investigated the effects of deformations and orientations on the target, i.e., 12C like yield, denoted C-yield (σC), which contains fusion-fission (FF) decay cross-section, σFF, from compound nucleus process and deep inelastic orbiting (DIO) cross-section, σD1O, from non-compound nucleus process. As observed in one of our earlier study for 32S* system there is a competition between FF and DIO, while, for 31P* there is a contribution of FF cross-section only, in the total C-yield. The comparative analysis of C-Yield for the considerations of spherical and oriented nuclei, shows similar results with the only difference of the values of neck length parameter (ΔR), which are more for the later case. The calculated cross-sections ac show good agreement with experimental data for both the considerations.
Dissociation dynamics: Measurements of decay fractions of metastable ammonia cluster ions
Wei, S.; Tzeng, W.B.; Castleman, A.W. Jr. )
1990-08-15
The decay fractions of metastable ammonia cluster ions which undergo unimolecular (evaporative) dissociation in a time window of 1--40 {mu}s were measured by using a reflection time-of-flight mass spectrometer. Corrections concerning instrumental artifacts and ion trajectory of parents and daughters are made to imporve the precision of the measurements. The data are used to derive the Gspann parameter and heat capacity of clusters as described in evaporative ensemble model of metastable dissociation. Using the dissociation fractions measured in the present studies, in conjunction with kinetic energy release values previously measured in our laboratory, we apply Klots' evaporative ensemble model to obtain binding energies of ammonia cluster ions (NH{sub 3}){sub {ital n}}H{sup +}, 4{le}{ital n}{le}17. The deduced binding energy values are found to be in very good agreement with both thermochemical data and Engelking's modified statistical theory.
Phenomenological approach to describe oscillatory growth or decay in different dynamical systems
NASA Astrophysics Data System (ADS)
Biswas, Dibyendu; Poria, Swarup; Patra, Sankar Narayan
2016-12-01
The approach of the phenomenological universalities of growth is considered to describe the behaviour of a system showing an oscillatory growth. Two phenomenological classes are proposed to consider the oscillatory behaviour of a system. One of them is showing oscillatory nature with constant amplitude and the other represents oscillatory nature with a change in amplitude. The term responsible for decay (or growth) in amplitude in the proposed class is also been identified. The variations in the nature of oscillation with the dependent parameters are studied in this communication. In this connection, the variation of a specific growth rate is also been considered. The significance of the presence and the absence of each term involved in the phenomenological description are also taken into consideration. These proposed classes might be useful for the experimentalists to extract a characteristic feature from the data set and to develop a suitable model consistent with their data set.
Solvent-modified ultrafast decay dynamics in conjugated polymer/dye labeled single stranded DNA
NASA Astrophysics Data System (ADS)
Kim, Inhong; Kang, Mijeong; Woo, Han Young; Oh, Jin-Woo; Kyhm, Kwangseuk
2015-07-01
We have investigated that organic solvent (DMSO, dimethyl sulfoxide) modifies energy transfer efficiency between conjugated polymers (donors) and fluorescein-labeled single stranded DNAs (acceptors). In a mixture of buffer and organic solvent, fluorescence of the acceptors is significantly enhanced compared to that of pure water solution. This result can be attributed to change of the donor-acceptor environment such as decreased hydrophobicity of polymers, screening effect of organic solvent molecules, resulting in an enhanced energy transfer efficiency. Time-resolved fluorescence decay of the donors and the acceptors was modelled by considering the competition between the energy harvesting Foerster resonance energy transfer and the energy-wasting quenching. This enables to quantity that the Foerster distance (R0 = 43.3 Å) and resonance energy transfer efficiency (EFRET = 58.7 %) of pure buffer solution become R0 = 38.6 Å and EFRET = 48.0 % when 80% DMSO/buffer mixture is added.
NASA Astrophysics Data System (ADS)
Sahmani, S.; Fattahi, A. M.
2017-06-01
Based upon an interlocking hexagonal arrangement of carbon atoms, it is possible to have a mechanically stable three-dimensional (3D) carbon structure including metallicity which provides a wide range of applications. In the present study, a novel calibrated size-dependent plate model using nonlocal continuum theory of elasticity with an exponential distribution of the shear deformation is constructed to anticipate accurately the nonlinear instability response of biaxially loaded 3D metallic carbon nanosheets. Explicit expressions for the size-dependent equilibrium curves are proposed via a two-stepped perturbation technique. After that, the critical biaxial buckling loads obtained by the developed nonlocal plate model are matched with those evaluated by some molecular dynamics (MD) simulations of biaxial instability of square 3D metallic carbon nanosheets to catch the proper value of nonlocal parameter. It is indicated that by using the proposed calibrated nonlocal plate model, the error in prediction of the biaxial instability behavior of 3D metallic carbon nanosheets reduces significantly.
NASA Astrophysics Data System (ADS)
Namekata, Daisuke; Umemura, Masayuki
2016-07-01
We explore the gas dynamics near the dust sublimation radius of active galactic nucleus (AGN). For the purpose, we perform axisymmetric radiation hydrodynamic simulations of a dusty gas disc of radius ≈1 pc around a supermassive black hole of mass 107 M⊙ taking into account (1) anisotropic radiation of accretion disc, (2) X-ray heating by corona, (3) radiative transfer of infrared (IR) photons re-emitted by dust, (4) frequency dependence of direct and IR radiations, and (5) separate temperatures for gas and dust. As a result, we find that for Eddington ratio ≈0.77, a nearly neutral, dense ({≈ } 10^{6-8}cm^{-3}), geometrically thin (h/r < 0.06) disc forms with a high-velocity (≈200 ˜ 3000 km s-1) dusty outflow launched from the disc surface. The disc temperature is determined by the balance between X-ray heating and various cooling, and the disc is almost supported by thermal pressure. Contrary to Krolik (2007), the radiation pressure by IR photons is not effective to thicken the disc, but rather compresses it. Thus, it seems difficult for a radiation-supported, geometrically thick, obscuring torus to form near the dust sublimation radius as far as the Eddington ratio is high (˜1). The mass outflow rate is 0.05-0.1M_{⊙} yr^{-1} and the column density of the outflow is NH ≲ 1021 cm-2. To explain observed type-II AGN fraction, it is required that outflow gas is extended to larger radii (r ≳ 10 pc) or that a denser dusty wind is launched from smaller radii (r ˜ 104 Rg).
NASA Astrophysics Data System (ADS)
Young-Gonzales, Amanda R.; Samanta, Subarna; Richert, Ranko
2015-09-01
For glycerol and three monohydroxy alcohols, we have measured the non-linear dielectric effects resulting from the application and removal of a high dc bias electric field. The field effects are detected by virtue of a small amplitude harmonic field, from which time resolved changes in the dielectric loss are derived. The changes in permittivity are dominated by modifications of the time constants (rather than amplitudes) which display two contributions: a heating-like decrease of relaxation times that originates from the time dependent field when the bias is switched on and off and a slowing down of the dynamics resulting from the field induced reduction of configurational entropy. As observed for the electro-optical Kerr effect, the rise of the entropy change is slower than its decay, a feature that we rationalize on the basis of the quadratic dependence of the entropy change on polarization. For glycerol, the observed steady state level of the field induced shift of the glass transition temperature (+84 mK) matches the expectation based on the entropy change and its impact on dynamics via the Adam-Gibbs relation (+88 mK). For the alcohols, these non-linear effects rise and decay on the time scales of the prominent dielectric Debye process, underscoring the relation of these features to polarization anisotropy, opposed to mechanical or enthalpy relaxation which are orders of magnitude faster in these systems. A model is discussed which captures the observed magnitudes as well as time dependences in a near quantitative fashion. It is demonstrated that the high bias field modifies the response of polarization to the ac field, including a temporary change in the low field susceptibility.
Young-Gonzales, Amanda R; Samanta, Subarna; Richert, Ranko
2015-09-14
For glycerol and three monohydroxy alcohols, we have measured the non-linear dielectric effects resulting from the application and removal of a high dc bias electric field. The field effects are detected by virtue of a small amplitude harmonic field, from which time resolved changes in the dielectric loss are derived. The changes in permittivity are dominated by modifications of the time constants (rather than amplitudes) which display two contributions: a heating-like decrease of relaxation times that originates from the time dependent field when the bias is switched on and off and a slowing down of the dynamics resulting from the field induced reduction of configurational entropy. As observed for the electro-optical Kerr effect, the rise of the entropy change is slower than its decay, a feature that we rationalize on the basis of the quadratic dependence of the entropy change on polarization. For glycerol, the observed steady state level of the field induced shift of the glass transition temperature (+84 mK) matches the expectation based on the entropy change and its impact on dynamics via the Adam-Gibbs relation (+88 mK). For the alcohols, these non-linear effects rise and decay on the time scales of the prominent dielectric Debye process, underscoring the relation of these features to polarization anisotropy, opposed to mechanical or enthalpy relaxation which are orders of magnitude faster in these systems. A model is discussed which captures the observed magnitudes as well as time dependences in a near quantitative fashion. It is demonstrated that the high bias field modifies the response of polarization to the ac field, including a temporary change in the low field susceptibility.
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.
NASA Astrophysics Data System (ADS)
Cottaar, Sanne; Lekic, Vedran
2017-04-01
the core-mantle boundary. It is still unclear if these represent anomalies that float, sink, or rise. Recent studies of anisotropy in the lowermost mantle seem to correlate with anisotropy being present in the anomalously fast regions, this can give an additional constraining on the dynamics and/or composition in these regions.
Power-law decay exponents: A dynamical criterion for predicting thermalization
NASA Astrophysics Data System (ADS)
Távora, Marco; Torres-Herrera, E. J.; Santos, Lea F.
2017-01-01
From the analysis of the relaxation process of isolated lattice many-body quantum systems quenched far from equilibrium, we deduce a criterion for predicting when they are certain to thermalize. It is based on the algebraic behavior ∝t-γ of the survival probability at long times. We show that the value of the power-law exponent γ depends on the shape and filling of the weighted energy distribution of the initial state. Two scenarios are explored in detail: γ ≥2 and γ <1 . Exponents γ ≥2 imply that the energy distribution of the initial state is ergodically filled and the eigenstates are uncorrelated, so thermalization is guaranteed to happen. In this case, the power-law behavior is caused by bounds in the energy spectrum. Decays with γ <1 emerge when the energy eigenstates are correlated and signal lack of ergodicity. They are typical of systems undergoing localization due to strong onsite disorder and are found also in clean integrable systems.
Li, Ming-Juan; Liu, Ming-Xia; Zhao, Yan-Ying; Pei, Ke-Mei; Wang, Hui-Gang; Zheng, Xuming; Fang, Wei Hai
2013-10-03
The resonance Raman spectroscopic study of the excited state structural dynamics of 1,3-dimethyluracil (DMU), 5-bromo-1,3-dimethyluracil (5BrDMU), uracil, and thymine in water and acetonitrile were reported. Density functional theory calculations were carried out to help elucidate the ultraviolet electronic transitions associated with the A-, and B-band absorptions and the vibrational assignments of the resonance Raman spectra. The effect of the methylation at N1, N3 and C5 sites of pyrimidine ring on the structural dynamics of uracils in different solvents were explored on the basis of the resonance Raman intensity patterns. The relative resonance Raman intensities of DMU and 5BrDMU are computed at the B3LYP-TD level. Huge discrepancies between the experimental resonance Raman intensities and the B3LYP-TD predicted ones were observed. The underlying mechanism was briefly discussed. The decay channel through the S1((1)nπ*)/S2((1)ππ*) conical intersection and the S1((1)nπ*)/T1((3)ππ*) intersystem crossing were revealed by using the CASSCF(8,7)/6-31G(d) level of theory calculations.
McGuire, R G
2000-11-01
ABSTRACT Coating formulations of shellac, sucrose ester, and cellulose were tested that support populations of bacterial and yeast antagonists of postharvest Penicillium decay of grapefruit. Surface populations of Pseudomonas syringae, P. fluorescens, and P. putida were stable between 10(3) and 10(4) CFU/cm(2) on shellacked fruit over 4 months at 13 degrees C, but numbers of the yeast Candida oleophila rose steadily from 2.35 x 10(3) to nearly 10(5). Through the first 15 days of cold storage, surface populations of P. syringae and C. oleophila were greater when applied to fruit within the pH 7.2 shellac than when applied by dipping fruit into an antagonist suspension and drying the fruit prior to shellacking; numbers were generally equivalent thereafter. Within wounds of shellacked fruit, populations of P. syringae were equal regardless of the method of application and increased from 10(4) to more than 1.2 x 10(7) CFU within 2 weeks. In contrast, numbers of C. oleophila in wounds over the first 2 weeks of storage were greater in fruit dipped and coated with shellac than when the antagonist was incorporated in this material; populations stabilized at approximately 6 x 10(6) CFU after 2 weeks. Incorporation of P. syringae and C. oleophila into ester and cellulose coatings, however, initially fostered greater numbers of both antagonists in wounds ( approximately 10(6) CFU) than did the preliminary dip application, and significant population differences persisted for several weeks. In cold storage, although application method did not affect the efficacy of P. syringae, C. oleophila was more efficacious after 3 and 4 months when applied in the shellac than when applied by a preliminary immersion and subsequent drying of fruit prior to shellacking.
Shilton, A; Harrison, J
2003-01-01
CFD mathematical modelling offers the potential to predict the actual flow pattern in a pond rather than generalising its mixing and mass transport as either an ideal flow reactor or, in the case of the non-ideal flow reactor, as a single dispersion number. However, perhaps the greatest benefit that CFD offers over the previous approaches is its ability to directly account for physical influences on the pond hydraulics such as the addition of baffles for example. In addition to solving the equations of fluid flow, CFD modelling also allows incorporation of other equations. The next logical development is, therefore, the integration of a reaction model within its solution domain. This potential has been recognised by several researchers, but to date no such work has been published. The primary aim of this paper was to present a CFD model of a field pond that incorporates the first order decay equation for coliforms. Experimental monitoring of the field pond gave an average effluent concentration of 3,710 f.c./100 mL, while the CFD model predicted 4,600 f.c./100 mL. Considering the pond provides an order of magnitude decrease in faecal coliform concentration, the integrated CFD model has clearly predicted the treatment efficiency very well. The secondary aim of this paper was to demonstrate the potential application of this technique. A typical pond was designed and modelled along with two variations incorporating two baffles and six baffles respectively. As is typically found in pond systems, the standard design suffered from severe short-circuiting with the model predicting a value of 6.2 x 10(6) f.c./100 mL at the outlet. The simulations of the baffled designs illustrate how treatment efficiency was improved by reducing the short-circuiting through the pond. The model predicted values of 6.0 x 10(3) f.c./100 mL for the 2-baffle design and 5.7 x 10(2) f.c./100 mL for the 6-baffle design.
NASA Astrophysics Data System (ADS)
Six, A.; Bocheux, A.; Charra, F.; Mathevet, F.; Kreher, D.; Attias, A.-J.
2017-01-01
Here we report the synthesis and characterization of a series of new phenylene-vinylene tectons. The study by scanning tunneling microscopy of their supramolecular self-assembly at the interface between a phenyloctane solution and highly oriented pyrolytic graphite demonstrates that variation of concentration and length of alkyl chains led to the formation of different networks, a compact one and a nanoporous one, with a fine control of the lattice parameters. The study of guest-host properties of the nanoporous network revealed a selectivity toward guest compounds according to their shape and size. Moreover, the statistical analysis of pore-to-pore guest dynamics evidences an anisotropic diffusion process.
NASA Astrophysics Data System (ADS)
Singh, Birbikram; Sharma, Manoj K.; Gupta, Raj K.
2008-05-01
The decay of the Bk246* nucleus, formed in entrance channel reactions B11+U235 and N14+Th232 at different incident energies, is studied by using the dynamical cluster-decay model (DCM) extended to include the deformations and orientations of nuclei. The main decay mode here is fission. The other (weaker) decay channels are the light particles evaporation (A⩽4) and intermediate mass fragments (5⩽A⩽20). All decay products are calculated as emissions of preformed clusters through the interaction barriers. The calculated fission cross sections σfiss, taken as a sum of the energetically favored symmetric and near symmetric fragments (ACN/2±7 and A=106-110 plus complementary fragments) show an excellent agreement with experimental data at all experimental incident c.m. energies for both reactions, except for the top three energies in the case of the B11+U235 reaction. The disagreement between the DCM calculations and data at higher incident c.m. energies for the B11+U235 entrance channel is associated with the presence of additional effects of noncompound, quasifission (qf) components, in contradiction with the measured anisotropy effects which indicate the other entrance channel N14+Th232 to contain the noncompound nucleus contribution. The prediction of two fission windows, the symmetric fission (SF) and near symmetric or heavy mass fragments (HMFs), suggests the presence of a fine structure of fission fragments, which also need an experimental verification. The only parameter of the model is the neck length parameter ▵R whose value is shown to depend strongly on limiting angular momentum, which in turn depends on the use of sticking or nonsticking moment of inertia for angular momentum effects.
Singh, BirBikram; Sharma, Manoj K.; Gupta, Raj K.
2008-05-15
The decay of the {sup 246}Bk* nucleus, formed in entrance channel reactions {sup 11}B+{sup 235}U and {sup 14}N+{sup 232}Th at different incident energies, is studied by using the dynamical cluster-decay model (DCM) extended to include the deformations and orientations of nuclei. The main decay mode here is fission. The other (weaker) decay channels are the light particles evaporation (A{<=}4) and intermediate mass fragments (5{<=}A{<=}20). All decay products are calculated as emissions of preformed clusters through the interaction barriers. The calculated fission cross sections {sigma}{sub fiss}, taken as a sum of the energetically favored symmetric and near symmetric fragments (A{sub CN}/2{+-}7 and A=106-110 plus complementary fragments) show an excellent agreement with experimental data at all experimental incident c.m. energies for both reactions, except for the top three energies in the case of the {sup 11}B+{sup 235}U reaction. The disagreement between the DCM calculations and data at higher incident c.m. energies for the {sup 11}B+{sup 235}U entrance channel is associated with the presence of additional effects of noncompound, quasifission (qf) components, in contradiction with the measured anisotropy effects which indicate the other entrance channel {sup 14}N+{sup 232}Th to contain the noncompound nucleus contribution. The prediction of two fission windows, the symmetric fission (SF) and near symmetric or heavy mass fragments (HMFs), suggests the presence of a fine structure of fission fragments, which also need an experimental verification. The only parameter of the model is the neck length parameter {delta}R whose value is shown to depend strongly on limiting angular momentum, which in turn depends on the use of sticking or nonsticking moment of inertia for angular momentum effects.
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.
PAHs in decaying Quercus ilex leaf litter: mutual effects on litter decomposition and PAH dynamics.
De Nicola, F; Baldantoni, D; Alfani, A
2014-11-01
The investigation of the relationships between litter decomposition and polycyclic aromatic hydrocarbons (PAHs) is important to shed light not only on the effects of these pollutants on fundamental ecosystem processes, such as litter decomposition, but also on the degradation of these pollutants by soil microbial community. This allows to understand the effect of atmospheric PAH contamination on soil PAH content via litterfall. At this aim, we studied mass and PAH dynamics of Quercus ilex leaf litters collected from urban, industrial and remote sites, incubated in mesocosms under controlled conditions for 361d. The results highlighted a litter decomposition rate of leaves sampled in urban>industrial>remote sites; the faster decomposition of litter of the urban site is also related to the low C/N ratio of the leaves. The PAHs showed concentrations at the beginning of the incubation of 887, 650 and 143 ng g(-1)d.w., respectively in leaf litters from urban, industrial and remote sites. The PAHs in litter decreased along the time, with the same trend observed for mass litter, showing the highest decrease at 361 d for the urban leaf litter. Anyway, PAH dynamics in all the litters exhibited two phases of loss, separated by a PAH increase observed at 246 d and mainly linked to benzo[e]pyrene.
Lepton flavor non-universality in B decays from dynamical Yukawas
NASA Astrophysics Data System (ADS)
Crivellin, Andreas; Fuentes-Martín, Javier; Greljo, Admir; Isidori, Gino
2017-03-01
The basic features of quark and lepton mass matrices can be successfully explained by natural minima of a generic potential with dynamical Yukawa fields invariant under the [ SU (3) ] 5 × O (3) flavor symmetry. If this symmetry is gauged, in order to avoid potentially dangerous Goldstone bosons, and small perturbations are added to exactly fit the observed pattern of fermion masses, the spectrum of massive flavor gauge bosons can naturally explain the hints for new physics in b → sℓ+ℓ- transitions, including RK. In particular, the desired pattern of the Standard Model Yukawa couplings is compatible with a gauged U (1) q in the quark sector, and U (1) μ - τ in the lepton sector spontaneously broken around the TeV scale. In order to explain the aforementioned experimental hints, the corresponding neutral gauge bosons are required to mix, yielding to potentially observable signals in dimuon resonance searches at the LHC.
Formation and decay of tetrazane derivatives--a Car-Parrinello molecular dynamics study.
Nonnenberg, Christel; Frank, Irmgard
2008-08-14
The complications during flight 510 of the Ariane Project were ascribed to problems in the upper stage engine that employs the bipropellant monomethylhydrazine (MMH) and nitrogen tetroxide (NTO). This has led to the question what conditions or reactions possibly cause an uncontrolled behaviour in the combustion process of MMH/NTO. We use first-principles molecular dynamics to investigate the reactions of the hypergolic mixture in different chemical situations. It was possible to observe the ultrafast redox reaction between the reactants on the timescale of an unconstrained simulation. We show that electrostatic attraction is crucial for the understanding of this reaction. Besides a cold reaction preceding the ignition, a reaction path leading to the highly reactive compound dimethyltetrazane could be identified.
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.
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.
Calcium-Dependent Calcium Decay Explains STDP in a Dynamic Model of Hippocampal Synapses
Standage, Dominic; Trappenberg, Thomas; Blohm, Gunnar
2014-01-01
It is widely accepted that the direction and magnitude of synaptic plasticity depends on post-synaptic calcium flux, where high levels of calcium lead to long-term potentiation and moderate levels lead to long-term depression. At synapses onto neurons in region CA1 of the hippocampus (and many other synapses), NMDA receptors provide the relevant source of calcium. In this regard, post-synaptic calcium captures the coincidence of pre- and post-synaptic activity, due to the blockage of these receptors at low voltage. Previous studies show that under spike timing dependent plasticity (STDP) protocols, potentiation at CA1 synapses requires post-synaptic bursting and an inter-pairing frequency in the range of the hippocampal theta rhythm. We hypothesize that these requirements reflect the saturation of the mechanisms of calcium extrusion from the post-synaptic spine. We test this hypothesis with a minimal model of NMDA receptor-dependent plasticity, simulating slow extrusion with a calcium-dependent calcium time constant. In simulations of STDP experiments, the model accounts for latency-dependent depression with either post-synaptic bursting or theta-frequency pairing (or neither) and accounts for latency-dependent potentiation when both of these requirements are met. The model makes testable predictions for STDP experiments and our simple implementation is tractable at the network level, demonstrating associative learning in a biophysical network model with realistic synaptic dynamics. PMID:24465987
NASA Astrophysics Data System (ADS)
Pflamm-Altenburg, J.; Kroupa, P.
2006-11-01
The Orion Nebula cluster (ONC) appears to be unusual on two grounds: the observed constellation of the OB stars of the entire ONC and its Trapezium at its centre implies a time-scale problem given the age of the Trapezium, and an initial mass function (IMF) problem for the whole OB star population in the ONC. Given the estimated crossing time of the Trapezium, it ought to have totally dynamically decayed by now. Furthermore, by combining the lower limit of the ONC mass with a standard IMF it emerges that the ONC should have formed at least about 40 stars heavier than 5 Msolar while only 10 are observed. Using the N-body experiments we (i) confirm the expected instability of the Trapezium and (ii) show that beginning with a compact OB-star configuration of about 40 stars both the number of observed OB stars after 1 Myr within 1 pc radius and a compact trapezium configuration can be reproduced. These two empirical constraints thus support our estimate of 40 initial OB stars in the cluster. Interestingly, a more-evolved version of the ONC resembles the Upper Scorpius OB association. The N-body experiments are performed with the new C-code CATENA by integrating the equations of motion using the chain-multiple-regularization method. In addition, we present a new numerical formulation of the IMF.
NASA Astrophysics Data System (ADS)
Hobara, S.; Osono, T.; Noro, K.; Hirota, M.; Benner, R. H.
2011-12-01
There is still much to be revealed about carbon (C) and nitrogen (N) dynamics in terrestrial soil systems. The objectives of this study were to identify molecular changes in composition during plant litter decomposition and gain insights about microbial contributions to C and N dynamics in decaying litter. Litter bag experiments with three plant species, Miscanthus sinensis, Pinus densiflora and Quercus crispula, were conducted for three years, and the concentrations of C, N, amino acids and amino sugars were determined at various times during the experiments. Mass loss (AFDW) ranged from 66-90% for the plant tissues. The weight %C remained fairly constant, whereas the weight %N increased throughout the study indicating N immobilization was occurring. The percentages of C as amino acids and amino sugars also increased throughout the study suggesting these biomolecules were largely of microbial origin. The increasing yields of amino acids and amino sugars were inversely related to overall C loss from the litter material. As microorganisms degraded the plant litter they left behind molecular signatures that were useful predictors of the extent of overall degradation. The C/N ratio of litter decreased throughout the study and was inversely related to galactosamine yields. The glucosamine/galactosamine (GlcN/GalN) ratio gradually declined to values near 2 by the end of the study. Galactoasamine is more abundant in bacteria than fungi, and the declining GlcN/GalN ratio suggest the relative contributions of bacterial to litter C and N increased relative to contributions from fungi. A cluster analysis of 0- and 36-month litters based on amino acid and amino sugar composition showed that 0-month litters of three plant species were separated from 36-month litters, suggesting common diagenetic pathways during decomposition irrespective of plant species. The microbial decomposers contribute to N immobilization and their contributions to the C and N content of litter increases
Shet, Anita; Nagaraja, Pradeep
2016-01-01
Background: Despite the high prevalence of HIV-1 subtype C (HIV-1C) worldwide, information on HIV-1C viral dynamics and response to antiretroviral therapy (ART) is limited. We sought to measure viral load decay dynamics during treatment and estimate the within-host basic reproductive ratio, R0, and the critical efficacy, εc, for successful treatment of HIV-1C infection. Methods: Individuals initiated on first-line ART in India and monitored for 6 months of treatment were considered. Viral load, CD4+ count, and adherence data were collected at baseline, 4, 12, 16 and 24 weeks after ART initiation. Drug resistance genotyping was performed at baseline. R0 and εc were estimated using a mathematical model. Results: Among 257 patients with complete data, mean baseline viral load was 5.7 log10 copies per milliliter and median CD4+ count was 165 cells per cubic millimeter. Primary drug resistance was present in 3.1% at baseline. At 6 months, 87.5% had undetectable viral load, indicating excellent response to ART despite high baseline viremia. After excluding those with transmitted resistance, suboptimal adherence and viral rebound, data from 112 patients were analyzed using a mathematical model. We estimated the median R0 to be 5.3. The corresponding εc was ∼0.8. Conclusions: These estimates of R0 and εc are smaller than current estimates for HIV-1B, suggesting that HIV-1C exhibits lower in vivo fitness compared with HIV-1B, which allows successful treatment despite high baseline viral loads. The lower fitness, and potentially lower virulence, together with high viral loads may underlie the heightened transmission potential of HIV-1C and its growing global spread. PMID:27273158
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
NASA Astrophysics Data System (ADS)
Sterzik, Michael F.; Durisen, Richard H.
1998-11-01
We investigate the dynamic decay of nonhierarchical few-body systems, with an emphasis on applications to young stellar multiples formed by fragmenting cloud collapse. A chain regularization scheme is used to integrate orbits for 300 or more crossing times in order to guarantee that most systems are fully decayed. In this paper, we consider cases where the number N of point-mass stars is three, four, or five; and we explore effects of the stellar mass spectrum on the outcome in the low angular momentum limit. A novel classification scheme is introduced to identify the remnant decay products, including singles, binaries, and bound hierarchical multiples. The ensemble of final system configurations is then analysed to determine mass and escape speed distributions, and to characterize properties of the binary and triple stars formed during the decay. Some statistical features of the endstates can be understood analytically using well-known principles of few-body dynamics. Our results suggest observable signatures in and around star forming regions which would be expected if multiply fragmenting collapse is a common mode of star formation.
Kumar, Raj; Gupta, Raj K.
2009-03-15
Application of the preformed clusters based dynamical cluster-decay model (DCM) is made to the recent data on decay of the compound systems {sup 118,122}Ba* at a relatively low bombarding energy of 5.5 MeV/A. The same model has been applied earlier to the intermediate mass fragment (IMF) data of {sup 116}Ba*, observed at medium and higher incident energies. For the heavier {sup 118,122}Ba* systems, however, a complete mass fragmentation spectrum is observed experimentally. Except for a small narrow region of heavier mass fragments (8{<=}Z{sub L}{<=}15), the DCM gives an overall reasonable description of the observed data on both the intermediate mass fragments and the fusion-fission cross-sections, whereas the statistical model calculations based on BUSCO and GEMINI codes describe the intermediate mass fragment data and the heavier mass fragment and fusion-fission data, respectively. Within the DCM (with preformation factor P{sub 0}=1), the possibility of non-compound-nucleus decay contributing to the region 8{<=}Z{sub L}{<=}15 of heavier mass fragments is also explored. All three models use the maximum angular momentum l{sub max} as a fitting parameter, which in the DCM is fixed via a neck-length parameter for the penetrability P{yields}1.
Conformal anisotropic mechanics and the Horava dispersion relation
Romero, Juan M.; Cuesta, Vladimir; Garcia, J. Antonio; Vergara, J. David
2010-03-15
In this paper we implement scale anisotropic transformations between space and time in classical mechanics. The resulting system is consistent with the dispersion relation of Horava gravity [P. Horava, Phys. Rev. D 79, 084008 (2009)]. Also, we show that our model is a generalization of the conformal mechanics of Alfaro, Fubini, and Furlan. For an arbitrary dynamical exponent we construct the dynamical symmetries that correspond to the Schroedinger algebra. Furthermore, we obtain the Boltzmann distribution for a gas of free particles compatible with anisotropic scaling transformations and compare our result with the corresponding thermodynamics of the recent anisotropic black branes proposed in the literature.
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.
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.
Pommé, S; Stroh, H; Altzitzoglou, T; Paepen, J; Van Ammel, R; Kossert, K; Nähle, O; Keightley, J D; Ferreira, K M; Verheyen, L; Bruggeman, M
2017-09-07
Some authors have raised doubt about the invariability of decay constants, which would invalidate the exponential-decay law and the foundation on which the common measurement system for radioactivity is based. Claims were made about a new interaction - the fifth force - by which neutrinos could affect decay constants, thus predicting changes in decay rates in correlation with the variations of the solar neutrino flux. Their argument is based on the observation of permille-sized annual modulations in particular decay rate measurements, as well as transient oscillations at frequencies near 11 year(-1) and 12.7 year(-1) which they speculatively associate with dynamics of the solar interior. In this work, 12 data sets of precise long-term decay rate measurements have been investigated for the presence of systematic modulations at frequencies between 0.08 and 20 year(-1). Besides small annual effects, no common oscillations could be observed among α, β(-), β(+) or EC decaying nuclides. The amplitudes of fitted oscillations to residuals from exponential decay do not exceed 3 times their standard uncertainty, which varies from 0.00023 % to 0.023 %. This contradicts the assertion that 'neutrino-induced' beta decay provides information about the deep solar interior. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.
Zhu, Chaoyuan; Jasper, Ahren W; Truhlar, Donald G
2005-07-01
Electronic energy flow in an isolated molecular system involves coupling between the electronic and nuclear subsystems, and the coupled system evolves to a statistical mixture of pure states. In semiclassical theories, nuclear motion is treated using classical mechanics, and electronic motion is treated as an open quantal system coupled to a "bath" of nuclear coordinates. We have previously shown how this can be simulated by a time-dependent Schrödinger equation with coherent switching and decay of mixing, where the decay of mixing terms model the dissipative effect of the environment on the electronic subdynamics (i.e., on the reduced dynamics of the electronic subsystem). In the present paper we reformulate the problem as a Liouville-von Neumann equation of motion (i.e., we propagate the reduced density matrix of the electronic subsystem), and we introduce the assumption of first-order linear decay. We specifically examine the cases of equal relaxation times for both longitudinal (i.e., population) decay and transverse decay (i.e., dephasing) and of longitudinal relaxation only, yielding the linear decay of mixing (LDM) and the population-driven decay of mixing (PDDM) schemes, respectively. Because we do not generally know the basis in which coherence decays, that is, the pointer basis, we judge the semiclassical methods in part by their ability to give good results in both the adiabatic and diabatic bases. The accuracy in the prediction of physical observables is shown to be robust not only with respect to basis but also with respect to the way in which demixing is incorporated into the master equation for the density matrix. The success of the PDDM scheme is particularly interesting because it incorporates the least amount of decoherence (i.e., the PDDM scheme is the most similar of the methods discussed to the fully coherent semiclassical Ehrenfest method). For both the new and previous decay of mixing schemes, four kinds of decoherent state switching
Alfalah, S.; Deeb, O.; Belz, S.; Leibscher, M.; Manz, J.; Zilberg, S.
2009-03-28
In this study, we investigate the photoinduced nonadiabatic dynamics of para- and ortho-fulvene by a combination of quantum chemical ab initio calculations and quantum dynamical simulations. We explore the competition between two different pathways, the photoisomerization and radiationless decay via a conical intersection (CI) at planar configuration. For this purpose, we extend a previous two-dimensional model which included the molecular torsion and the antisymmetric stretch as a coupling mode [Grohmann et al., Chem. Phys. 338, 252 (2007)] to a three-dimensional model, taking into account also the symmetric stretch as additional vibrational mode. Quantum dynamical simulations show that upon excitation with a single short laser pulse, the mode selective motion along the symmetric stretch drives the system to the CI, followed by radiationless decay before photoisomerization of fulvene can take place, thus confirming previous semiclassical calculations [Bearpark et al., J. Am. Chem. Soc. 118, 5253 (1996)]. Moreover, we show that the competition between photoisomerization and radiationless decay at a planar geometry depends on the nonadiabatic coupling strength.
NASA Astrophysics Data System (ADS)
Hansel, C. M.; Buchwald, C.; Diaz, J. M.; Dyhrman, S.; Van Mooy, B. A. S.
2014-12-01
Reactive oxygen species (ROS) are key players in the biogeochemistry of the ocean, where they serve a critical role in the cycling of carbon and metals. Research in the past decade has introduced phytoplankton and, most recently, heterotrophic bacteria as significant sources of ROS, including superoxide, within both photic and aphotic regions of the ocean. ROS are both beneficial and detrimental to life. For instance, superoxide is a vital inter- and intra-cellular signaling molecule, yet at high concentrations it induces lipid peroxidation and initiates programmed cell death (PCD). In fact, superoxide has been implicated in PCD in the nitrogen-fixing diazotroph Trichodesmium, presumably leading to the demise of blooms within oligotrophic marine systems. Here, we explore the rates of superoxide production and decay by natural Trichodesmium populations obtained from various surface waters in the Sargasso Sea. We investigate also the role of light and colony density and morphology (puff v. raft) on superoxide fluxes. We find that Trichodesmium colonies produce extracellular superoxide at extremely high rates in the dark that are on par with those of the toxic raphidophyte Chattonella. The rates of superoxide production, however, rapidly decline with increasing cell density pointing to a role for superoxide in cell signaling in these organisms. We also find extremely rapid extracellular superoxide degradation by Trichodesmium. Together, this likely reflects a need for these organisms to maintain ROS at levels that will support signaling but below the threshold level that triggers PCD or oxidative damage. We also show differences in the effect of light on superoxide fluxes as a function of Trichodesmium colony morphology, suggesting differences in either colony physiology or associated bacterial symbionts. These findings point to complex physiological, ecological, and physical influences on ROS dynamics in phytoplankton that require further exploration.
Radioactive decay is the emission of energy in the form of ionizing radiation. Example decay chains illustrate how radioactive atoms can go through many transformations as they become stable and no longer radioactive.
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
Li, Xiying; Mao, Liqun; Ma, Xuehu
2013-01-29
Textured silicon surfaces decorated by square arrays of pillars with adjustable pitch were fabricated. The wetting behavior, especially for direction-dependent water contact angles on textured silicon surfaces after silanization, was investigated by incorporating the contact line fraction into a modified Wenzel model. Also, the effect of geometrical parameters on the anisotropic wetting behavior of water was examined with respect to water droplet impact on the textured surface. Moreover, the maximum spreading factor was studied theoretically in terms of energy conservation, allowing for surface topography and viscous friction of the liquid flowing among the arrays of the posts. Theoretical models were found to be in good agreement with experimental data.
You call it a cavity. Your dentist calls it tooth decay or dental caries. They're all names for a hole in your tooth. The cause of tooth decay is plaque, a sticky substance in your mouth made up mostly of germs. Tooth decay starts in the outer layer, called the enamel. Without ...
Alex L. Shigo
1989-01-01
Trunk decays are major causes of low quality wood-wood with little or no economic value. As a forest practitioner you should be able to recognize trees at high risk for decay and remove them if timber production is your primary objective. Remember, however, that decayed trees often develop into den trees or nesting sites and provide essential habitat for wildlife....
Kanevce, Ana; Kuciauskas, Darius; Levi, Dean H.; Johnston, Steven W.; Allende Motz, Alyssa M.
2015-07-28
We use two-dimensional numerical simulations to analyze high spatial resolution time-resolved spectroscopy data. This analysis is applied to two-photon excitation time-resolved photoluminescence (2PE-TRPL) but is broadly applicable to all microscopic time-resolved techniques. By solving time-dependent drift-diffusion equations, we gain insight into carrier dynamics and transport characteristics. Accurate understanding of measurement results establishes the limits and potential of the measurement and enhances its value as a characterization method. Diffusion of carriers outside of the collection volume can have a significant impact on the measured decay but can also provide an estimate of carrier mobility as well as lifetime. In addition to material parameters, the experimental conditions, such as spot size and injection level, can impact the measurement results. Although small spot size provides better resolution, it also increases the impact of diffusion on the decay; if the spot size is much smaller than the diffusion length, it impacts the entire decay. By reproducing experimental 2PE-TRPL decays, the simulations determine the bulk carrier lifetime from the data. The analysis is applied to single-crystal and heteroepitaxial CdTe, material important for solar cells, but it is also applicable to other semiconductors where carrier diffusion from the excitation volume could affect experimental measurements.
NASA Astrophysics Data System (ADS)
Kanevce, Ana; Kuciauskas, Darius; Levi, Dean H.; Allende Motz, Alyssa M.; Johnston, Steven W.
2015-07-01
We use two-dimensional numerical simulations to analyze high spatial resolution time-resolved spectroscopy data. This analysis is applied to two-photon excitation time-resolved photoluminescence (2PE-TRPL) but is broadly applicable to all microscopic time-resolved techniques. By solving time-dependent drift-diffusion equations, we gain insight into carrier dynamics and transport characteristics. Accurate understanding of measurement results establishes the limits and potential of the measurement and enhances its value as a characterization method. Diffusion of carriers outside of the collection volume can have a significant impact on the measured decay but can also provide an estimate of carrier mobility as well as lifetime. In addition to material parameters, the experimental conditions, such as spot size and injection level, can impact the measurement results. Although small spot size provides better resolution, it also increases the impact of diffusion on the decay; if the spot size is much smaller than the diffusion length, it impacts the entire decay. By reproducing experimental 2PE-TRPL decays, the simulations determine the bulk carrier lifetime from the data. The analysis is applied to single-crystal and heteroepitaxial CdTe, material important for solar cells, but it is also applicable to other semiconductors where carrier diffusion from the excitation volume could affect experimental measurements.
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.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Miyazaki, Tetsuo; Morikawa, Akiyuki; Kumagai, Jun; Ikehata, Masateru; Koana, Takao; Kikuchi, Shoshi
2002-09-01
Long-lived radicals produced by γ-irradiation or vital activity in plants, animals, cells, and protein (albumin) solution were studied by electron spin resonance spectroscopy. Long-lived radicals produced by vital activity exist in biological systems, such as plants, animals, and cells, in the range of 0.1-20 nmol g -1. Since vital organs keep the radicals at a constant concentration, the radicals are probably related to life conservation. Long-lived radicals are also produced by γ-irradiation of cells or protein solution. The radicals decay after death of living things or after γ-irradiation. We found that the decay dynamics in all biological systems can be expressed by the same kinetic equation of an inhomogeneous reaction.
Gauden, Magdalena; Pezzella, Alessandro; Panzella, Lucia; Napolitano, Alessandra; d'Ischia, Marco; Sundström, Villy
2009-09-17
As part of a program designed to elucidate the excited state properties of key eumelanin building blocks, we report herein a study of 5,6-dihydroxyindole (DHI) in phosphate buffer at pH 3 and pH 7 using femtosecond transient absorption spectroscopy. The transient absorption changes following excitation at 266 nm were used to directly monitor relaxation of the excited states. It was found that the initially generated excited state of DHI, exhibiting two main absorption bands at approximately 450 and approximately 550 nm, decays with a time constant of 5-10 ps to the equilibrated singlet excited state characterized by a very similar spectrum. This latter state then decays to the ground state and the triplet state with a characteristic time of approximately 140-180 ps. Concomitant with the singlet excited state decay of DHI, spectral features characteristic of the DHI cation radical (band at approximately 575 nm) and the triplet state (band at 440-450 nm) are detected. These species do not decay further since geminate recombination of the solvated electron and the DHI radical cation, as well as deprotonation of the cation to form the neutral semiquinone radical, occur on a time scale longer than that covered by the present experiments. These results offer novel insights into the mechanisms of nonradiative decay of eumelanin building blocks of possible relevance to the putative photoprotective and phototoxic roles of these biopolymers.
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 Nanomechanics of Boron Nitride Nanotubes: Nanostructured "Skin" Effect
NASA Technical Reports Server (NTRS)
Srivastava, Deepak; Menon, Madhu; Cho, KyeongJae
2000-01-01
The stiffness and plasticity of boron nitride nanotubes are investigated using generalized tight-binding molecular dynamics and ab-initio total energy methods. Due to boron-nitride BN bond buckling effects, compressed zigzag BN nanotubes are found to undergo novel anisotropic strain release followed by anisotropic plastic buckling. The strain is preferentially released towards N atoms in the rotated BN bonds. The tubes buckle anisotropically towards only one end when uniaxially compressed from both. A "skin-effect" model of smart nanocomposite materials is proposed which will localize the structural damage towards the 'skin' or surface side of the material.
Hydrodynamic cavitation in Stokes flow of anisotropic fluids
NASA Astrophysics Data System (ADS)
Stieger, Tillmann; Agha, Hakam; Schoen, Martin; Mazza, Marco G.; Sengupta, Anupam
2017-05-01
Cavitation, the nucleation of vapour in liquids, is ubiquitous in fluid dynamics, and is often implicated in a myriad of industrial and biomedical applications. Although extensively studied in isotropic liquids, corresponding investigations in anisotropic liquids are largely lacking. Here, by combining liquid crystal microfluidic experiments, nonequilibrium molecular dynamics simulations and theoretical arguments, we report flow-induced cavitation in an anisotropic fluid. The cavitation domain nucleates due to sudden pressure drop upon flow past a cylindrical obstacle within a microchannel. For an anisotropic fluid, the inception and growth of the cavitation domain ensued in the Stokes regime, while no cavitation was observed in isotropic liquids flowing under similar hydrodynamic parameters. Using simulations we identify a critical value of the Reynolds number for cavitation inception that scales inversely with the order parameter of the fluid. Strikingly, the critical Reynolds number for anisotropic fluids can be 50% lower than that of isotropic fluids.
Nonequilibrium current-carrying steady states in the anisotropic X Y spin chain
NASA Astrophysics Data System (ADS)
Lancaster, Jarrett L.
2016-05-01
Out-of-equilibrium behavior is explored in the one-dimensional anisotropic X Y model. Initially preparing the system in the isotropic X X model with a linearly varying magnetic field to create a domain-wall magnetization profile, dynamics is generated by rapidly changing the exchange interaction anisotropy and external magnetic field. Relaxation to a nonequilibrium steady state is studied analytically at the critical transverse Ising point, where correlation functions may be computed in closed form. For arbitrary values of anisotropy and external field, an effective generalized Gibbs' ensemble is shown to accurately describe observables in the long-time limit. Additionally, we find spatial oscillations in the exponentially decaying, transverse spin-spin correlation functions with wavelength set by the magnetization jump across the initial domain wall. This wavelength depends only weakly on anisotropy and magnetic field in contrast to the current, which is highly dependent on these parameters.
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.
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).
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.
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.
Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Tisserand, V.; Zghiche, A.; Grauges, E.; Palano, A.; Pappagallo, M.; Pompili, A.; Chen, J.C.; Qi, N.D.; Rong, G.; Wang, P.; Zhu, Y.S.; Eigen, G.; Ofte, I.; Stugu, B. /Bergen U. /LBL, Berkeley /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /Bristol U. /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /Ferrara U. /INFN, Ferrara /Frascati /Genoa U. /INFN, Genoa /Harvard U. /Heidelberg U. /Imperial Coll., London /Iowa U. /Iowa State U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT, LNS /McGill U. /Milan U. /INFN, Milan /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /Naples U. /INFN, Naples /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /Padua U. /INFN, Padua /Paris U., VI-VII /Pennsylvania U. /Perugia U. /INFN, Perugia /Pisa U. /INFN, Pisa /Prairie View A-M /Princeton U. /Rome U. /INFN, Rome /Rostock U. /Rutherford /DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Stony Brook /Tennessee U. /Texas U. /Texas U., Dallas /Turin U. /INFN, Turin /Trieste U. /INFN, Trieste /Valencia U., IFIC /Vanderbilt U. /Victoria U. /Warwick U. /Wisconsin U., Madison /Yale U.
2005-07-06
With a sample of 232 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector, we study the decay B{sup +} {yields} p{bar p}K{sup +} excluding charmonium decays to p{bar p}. We measure a branching fraction {Beta}(B{sup +} {yields} p{bar p}K{sup +}) = (6.7 {+-} 0.5 {+-} 0.4) x 10{sup -6}. An enhancement at low p{bar p} mass is observed and the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this B decay. We search for a pentaquark candidate {Theta}*{sup ++} decaying into pK{sup +} in the mass range 1.43 to 2.00 GeV/c{sup 2} and set limits on {Beta}(B{sup +} {yields} {Theta}*{sup ++} {bar p}) x {Beta}({Theta}*{sup ++} {yields} pK{sup +}) at the 10{sup -7} level.
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.
Shear-free anisotropic cosmological models in {f (R)} gravity
NASA Astrophysics Data System (ADS)
Abebe, Amare; Momeni, Davood; Myrzakulov, Ratbay
2016-04-01
We study a class of shear-free, homogeneous but anisotropic cosmological models with imperfect matter sources in the context of f( R) gravity. We show that the anisotropic stresses are related to the electric part of the Weyl tensor in such a way that they balance each other. We also show that within the class of orthogonal f( R) models, small perturbations of shear are damped, and that the electric part of the Weyl tensor and the anisotropic stress tensor decay with the expansion as well as the heat flux of the curvature fluid. Specializing in locally rotationally symmetric spacetimes in orthonormal frames, we examine the late-time behaviour of the de Sitter universe in f( R) gravity. For the Starobinsky model of f( R), we study the evolutionary behavior of the Universe by numerically integrating the Friedmann equation, where the initial conditions for the expansion, acceleration and jerk parameters are taken from observational data.
NASA Astrophysics Data System (ADS)
Roscioli, Jerome D.; Ghosh, Soumen; Bishop, Michael M.; Lafountain, Amy M.; Frank, Harry A.; Beck, Warren F.
Transient grating spectroscopy was used to study the dynamics of nonradiative decay of the S1 (21Ag-) state in ß-carotene and peridinin after optical preparation of the S2) state. The kinetics of the recovery of the absorption and dispersion components of the third-order signal exhibit significantly different time constants. For β-carotene in benzonitrile, the absorption and dispersion recovery time constants are 11.6 and 10.2 ps. For peridinin in methanol, the time constants are 9.9 and 7.4 ps. These results indicate that the initial product of the decay of the S1 state is a conformationally displaced structure. The decay rate for the S1 state and the conformational relaxation rate are both slowed in peridinin as the polarity of the solvent decreases; in ethyl acetate, the conformational relaxation time constant is 45 ps, which rules out a dominant contribution from vibrational cooling. These results indicate that the S1 state develops intramolecular charge transfer character owing to distortions along torsional and out-of-plane coordinates, with a pyramidal structure favored as the most stable conformation. Recovery of the photoselected ground state conformation involves a reverse charge-transfer event followed by relaxation to a planar structure. Work supported by Photosynthetic Systems Program of the U.S. Department of Energy under Grant DE-SC0010847.
NASA Astrophysics Data System (ADS)
Amaro, Mariana; Kubiak-Ossowska, Karina; Birch, David J. S.; Rolinski, Olaf J.
2013-03-01
The development of Alzheimer’s disease is associated with the aggregation of the beta-amyloid peptides Aβ1-40 and Aβ1-42. It is believed that the small oligomers formed during the early stages of the aggregation are neurotoxic and involved in the process of neurodegeneration. In this paper we use fluorescence decay measurements of beta-amyloid intrinsic fluorophore tyrosine (Tyr) and molecular dynamics (MD) simulations to study the early stages of oligomer formation for the Aβ1-40 and Aβ1-42 peptides in vitro. We demonstrate that the lifetime distributions of the amyloid fluorescence decay efficiently describe changes in the complex Tyr photophysics during the peptide aggregation and highlight the differences in aggregation performance of the two amyloids. Tyr fluorescence decay is found to be a more sensitive sensor of Aβ1-40 aggregation than Aβ1-42 aggregation. The MD simulation of the peptide aggregation is compared with the experimental data and supports a four-rotamer model of Tyr.
Kumbhakar, Manoj; Mukherjee, Tulsi; Pal, Haridas
2005-01-01
The fluorescence anisotropy decay dynamics of the fluorescent probe Coumarin-153 (C153) have been investigated in two neutral micelles, Triton-X-100 (TX-100) and Brij-35 (BJ-35), at different temperatures and analyzed on the basis of the well-known two-step model. Because steady-state fluorescence spectra of the above probe do not show any noticeable changes with respect to temperature, for either of the studied micelles, suggests a similar polarity in the microenvironment around the probe at all the temperatures studied. The anisotropy results indicated that, for both the micelles, the fluidity inside the Palisade layer increases with temperature. However, the temperature effect on the anisotropy decay is relatively more pronounced in TX-100 than in BJ-35. It is inferred that the temperature effect on the anisotropy decay in the BJ-35 micelle is mainly due to the thermal effect on the microviscosity in the micellar phase. In the case of TX-100, the results indicate that, along with the above thermal effect, an additional effect is observed due to the increased size and hydration of the micelle with temperature, with the result being that the fluorescence anisotropy decay in TX-100 is more sensitive to temperature than in BJ-35. In the TX-100 micelle, our studies show that with an increase in temperature, even though the micellar size increases substantially, the distance of the probe from the micellar core does not increase that significantly. Thus, with increasing temperature, the probe undergoes a relative migration toward the micellar core to avoid the increased hydration in the micellar Palisade layer.
NASA Astrophysics Data System (ADS)
Sahrai, M.; Boroojerdi, V. Tahmoorian Askari
2017-06-01
Time evolution of the entanglement between a four-level atom near the band edge of a photonic crystal and its spontaneous emission field is investigated. It is shown that the quantum entropy has a faster oscillator behavior as the upper levels move further into the band gap. Entanglement oscillations can be controlled by the intensity and the detuning of the coupling field. An enhanced entanglement is achieved in the presence of quantum interference resulting from the two possible decay channels. In addition, the atom-photon entanglement will be influenced noticeably by the reservoir coupling constant, intensity of coupling field, and the detuning.
NASA Astrophysics Data System (ADS)
Coto, Pedro B.; Serrano-Andrés, Luis; Gustavsson, Thomas; Fujiwara, Takashige; Lim, Edward C.
2010-06-01
4-(Dimethylamino)benzonitrile (DMABN) is a paradigm molecule system that exhibits dual fluorescence and intramolecular charge transfer (ICT) in polar solvents. Although numbers of different experimental and theoretical methods have been carried out to date for elucidating the basic mechanism of its energy relaxation, there are still some crucial problems that remain unanswered. The time-resolved transient absorption and time-resolved fluorescence upconversion will be presented, as combined with ab initio CASPT2//CASSCF calculations, which indicate that a more complex mechanism may be suggested in the ICT reaction in a polar environment. A scheme of ultrafast branching relaxation followed by two-fold decay is proposed in which, whereas the fully twisted ICT (TICT) state is responsible for the transient absorption, a distinct partially twisted ICT (pTICT) structure is for the fluorescent ICT state, both displaying clearly different decay rates.
Avraamova, O G; Kulazhenko, T V; Gabitova, K F
2016-01-01
The paper presents the assessment of tooth decay prevalence in clinically homogenous groups of children receiving long-term preventive program (PP) in school dental facilities. Five-years PP were introduced in clinical practice in 2 Moscow schools. Preventive treatment was performed by dental hygienist. The results show that systematic preventive treatment in school dental offices starting from elementary school allows reducing dental caries incidence 46-53% and stabilize the incidence of caries complications. It should be mentioned though that analysis of individualized outcomes proves heterogeneity of study results despite of equal conditions of PP. Potentially significant hence is early diagnostics and treatment of initial caries forms as demineralization foci, especially in children with intensive tooth decay. Optimization of pediatric dentist and dental hygienist activity in school dental facilities is the main factor of caries prevention efficiency.
NASA Technical Reports Server (NTRS)
Schiestel, R.
1987-01-01
The CTR numerical data base generated by direct simulation of homogeneous anisotropic turbulence was used to calculate all of the terms in the spectral balance equations for the turbulent Reynolds stresses. The aim in not only to test the main closure assumptions used in the split-spectrum models, but also to try to devise improved hypotheses deduced from the statistical information. Numerical simulations of turbulent flows provide a large amount of data, a thought provoking wealth of information. The main advantage of this type of comparison is that a great variety of flows can be considered, and this is necessary to test closure hypotheses. Moreover various initial conditions can be introduced in the calculation, even if they are not experimentally feasible. All the terms in the spectral equations can be calculated. The limited Reynolds numbers of the simulations and the statistical noise caused by a small sample, particularly at the large scales, causes some difficulty in the interpretation of the results, but the method of approach proved to be a powerful tool for testing and improving spectral closures.
NASA Astrophysics Data System (ADS)
Niyti; Gupta, Raj K.; Hess, Peter Otto
2015-06-01
The dynamical cluster-decay model (DCM), with deformation and orientation effects included, is used to calculate the fusion evaporation residue cross-sections σxn for x = 1, 2, 3 and 4 neutrons emission in a fusion reaction 206Pb + 48Ca → 254No* at various 48Ca-beam energies Elab = 212.7- 242.5 MeV (equivalently, E* = 19.8- 43.9 MeV). Considering the higher multipole deformations up to hexadecapole deformation β4i and the sticking moment-of-inertia IS, the DCM with pocket formula for nuclear proximity potential is shown to give a good description of the measured individual light-particle (here neutrons) decay channels for configurations of "hot, compact" orientations θci, within one parameter fitting of the neck-length ΔR. A check on some of the variables involved in DCM shows that (i) spherical configurations give nearly the same result as above for deformed and oriented ones; (ii) the non-sticking moment-of-inertia INS gives unphysical results; and (iii) configurations of "cold, elongated" orientations do not fit the data at all. Furthermore, for the four different isotopes of 204,206,207,208Pb-based reactions, the dependence of, say, the 2n-emission yield σ2n on the isotopic composition of the compound nucleus is also studied within the DCM for "hot" fusion process. Of all the four Pb-isotopes and three excitation energies E* considered, at each E*, the ΔR is largest for compound system 256No*, followed by 255No*, 254No* and smallest for 252No*, which means to suggest that the neutrons emission occur earliest for 256No*, then for 255No*, 254No* and finally by 252No*, in complete agreement with experimental data according to which compound system 256No* has the highest cross-section and 252No* the lowest with 255No* and 254No* lying in between. This result is related to the double magicity of both the target (208Pb) and projectile (48Ca) nuclei, as well as to the experimentally known result of projectile with a larger number of neutrons (here the target
Mao, Ying-Bo; Liu, Yao-Qian; Chen, Dian-Yang; Chen, Fang-Yan; Fang, Xin; Hong, Gao-Jie; Wang, Ling-Jian; Wang, Jia-Wei; Chen, Xiao-Ya
2017-01-09
Immunity deteriorates with age in animals but comparatively little is known about the temporal regulation of plant resistance to herbivores. The phytohormone jasmonate (JA) is a key regulator of plant insect defense. Here, we show that the JA response decays progressively in Arabidopsis. We show that this decay is regulated by the miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) group of proteins, which can interact with JA ZIM-domain (JAZ) proteins, including JAZ3. As SPL9 levels gradually increase, JAZ3 accumulates and the JA response is attenuated. We provide evidence that this pathway contributes to insect resistance in young plants. Interestingly however, despite the decay in JA response, older plants are still comparatively more resistant to both the lepidopteran generalist Helicoverpa armigera and the specialist Plutella xylostella, along with increased accumulation of glucosinolates. We propose a model whereby constitutive accumulation of defense compounds plays a role in compensating for age-related JA-response attenuation during plant maturation.
Mao, Ying-Bo; Liu, Yao-Qian; Chen, Dian-Yang; Chen, Fang-Yan; Fang, Xin; Hong, Gao-Jie; Wang, Ling-Jian; Wang, Jia-Wei; Chen, Xiao-Ya
2017-01-01
Immunity deteriorates with age in animals but comparatively little is known about the temporal regulation of plant resistance to herbivores. The phytohormone jasmonate (JA) is a key regulator of plant insect defense. Here, we show that the JA response decays progressively in Arabidopsis. We show that this decay is regulated by the miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) group of proteins, which can interact with JA ZIM-domain (JAZ) proteins, including JAZ3. As SPL9 levels gradually increase, JAZ3 accumulates and the JA response is attenuated. We provide evidence that this pathway contributes to insect resistance in young plants. Interestingly however, despite the decay in JA response, older plants are still comparatively more resistant to both the lepidopteran generalist Helicoverpa armigera and the specialist Plutella xylostella, along with increased accumulation of glucosinolates. We propose a model whereby constitutive accumulation of defense compounds plays a role in compensating for age-related JA-response attenuation during plant maturation. PMID:28067238
Anisotropic Turbulence and Protostellar Feedback in Molecular Clouds
NASA Astrophysics Data System (ADS)
Hansen, Charles Edward
I investigate the decay and regeneration of turbulence in molecular clouds and the resulting star formation in those clouds in the presence of protostellar feedback. Studies of turbulence generally only consider isotropic turbulence, while the turbulence in molecular clouds may be anisotropic. I perform a series of simulations of anisotropic turbulence and measure its decay rate. I find that anisotropic turbulence decays slower than isotropic turbulence. When I break the velocity dispersion into isotropic and anisotropic components, I find the decay time is the crossing time of the isotropic component, which can be much slower than the total velocity dispersion. As part of this study, I present a measure of anisotropy that can be calculated in observations of molecular clouds. I also investigate the effects of compression on turbulence. This is motivated by the need to replenish turbulent energy. Using a series of simulations of contracting turbulence, I find that turbulence behaves as a monatomic ideal gas under isotropic compression. I also find that compression in a single direction imparts energy to that direction, but does not transfer that energy to the other two directions. Finally, I perform a series of high resolution star formation simulations with adaptive mesh refinement (AMR) including hydrodynamics, gravity, radiation, protostellar outflows and protostellar luminosity. The simulations provide a self-consistent story of star formation, all while matching observations. The matched observations include the masses of both stars and prestellar cores, the clustering of cores and the luminosity function of protostars. In this story of star formation, cores form on the Jeans length of the host cloud. Each core forms a central star or binary, but also fragments repeatedly down 0.05 M⊙ stars. The stellar radiation prevents fragmentation below this mass scale, but is not important on larger scales. The protostellar outflows eject 2/3 of the incoming mass
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.
Prolonging entanglement dynamics near periodic plasmonic nanostructures
NASA Astrophysics Data System (ADS)
Iliopoulos, Nikos; Terzis, Andreas F.; Yannopapas, Vassilios; Paspalakis, Emmanuel
2017-08-01
We study the dynamics of two initially entangled qubits, where each one interacts locally and independently of the other, with a plasmonic nanostructure. By considering two different cases for the qubits, two identical two-level systems and two identical V-type quantum systems, where one two-level transition plays the role of the qubit while the third level acts as an "umbrella level", we study the corresponding entanglement dynamics for several pure and mixed initial states. As the plasmonic nanostructure we take a two-dimensional lattice of metal-coated dielectric nanoparticles. The presence of this nanostructure leads to highly suppressed spontaneous emission rates of the individual quantum systems, as well as to highly anisotropic spontaneous decay rates for orthogonal dipole matrix elements due to the anisotropic Purcell effect, leading to quantum interference in spontaneous emission. Both of the effects can be used for significantly prolonging the time evolution of entanglement for several system parameters.
Weibel Instability Driven by Spatially Anisotropic Density Structures
NASA Astrophysics Data System (ADS)
Tomita, Sara; Ohira, Yutaka
2016-07-01
Observations of afterglows of gamma-ray bursts (GRBs) suggest that post-shock magnetic fields are strongly amplified to about 100 times the shock-compressed value. The Weibel instability appears to play an important role in generating the magnetic field. However, recent simulations of collisionless shocks in homogeneous plasmas show that the magnetic field generated by the Weibel instability rapidly decays. There must be some density fluctuations in interstellar and circumstellar media. The density fluctuations are anisotropically compressed in the downstream region of relativistic shocks. In this paper, we study the Weibel instability in electron-positron plasmas with spatially anisotropic density distributions by means of two-dimensional particle-in-cell simulations. We find that large magnetic fields are maintained for a longer time by the Weibel instability driven by spatially anisotropic density structure. Particles anisotropically escape from the high density region, so that a temperature anisotropy is generated and the Weibel instability becomes unstable. Our simulation results suggest that the Weibel instability driven by an anisotropic density structure can generate sufficiently large magnetic fields and they can cover sufficiently large regions to explain the afterglow emission of GRBs.
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 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.
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.
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 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.
Uprety, Priyanka; Patel, Kunjal; Karalius, Brad; Ziemniak, Carrie; Chen, Ya Hui; Brummel, Sean S; Siminski, Suzanne; Van Dyke, Russell B; Seage, George R; Persaud, Deborah
2017-06-01
Early antiretroviral therapy (ART) limits proviral reservoirs, a goal for human immunodeficiency virus type 1 (HIV-1) remission strategies. Whether this is an immediate or long-term effect of virologic suppression (VS) in perinatal infection is unknown. We quantified HIV-1 DNA longitudinally for up to 14 years in peripheral blood mononuclear cells (PBMCs) among 61 perinatally HIV-1-infected youths in the Pediatric HIV/AIDS Cohort Study who achieved VS at different ages. Participants in group 1 (n = 13) were <1 year of age and in group 2 (n = 48) from 1 through 5 years of age at VS. Piecewise linear mixed-effects regression models assessed the effect of age at VS on HIV-1 DNA trajectories during VS. In the first 2 years following VS, HIV-1 DNA levels decreased by -0.25 (95% confidence interval [CI], -.36 to -.13) log10 copies/million PBMCs per year and was faster with early VS by age 1 year compared with after age 1 (-0.50 and -0.15 log10 copies/million PBMCs per year, respectively). Between years 2 and 14 from VS, HIV-1 DNA decayed by -0.05 (95% CI, -.06 to -.03) log10 copies/million PBMCs per year and was no longer significantly different between groups. The estimated mean half-life of HIV-1 DNA from VS was 15.9 years and was shorter for group 1 compared to group 2 at 5.9 years and 18.8 years, respectively (P = .09). Adjusting for CD4 cell counts had no effect on decay estimates. Early effective, long-term ART initiated from infancy leads to decay of HIV-1-infected cells to exceedingly low concentrations desired for HIV-1 remission strategies.
Hibbs, Ryan E; Johnson, David A; Shi, Jianxin; Hansen, Scott B; Taylor, Palmer
2005-12-20
The three-fingered alpha-neurotoxins have played a pivotal role in elucidating the structure and function of the muscle-type and neuronal alpha7 nicotinic acetylcholine receptors (nAChRs). To advance our understanding of the alpha-neurotoxin-nAChR interaction, we examined the flexibility of alpha-neurotoxin bound to the acetylcholine-binding protein (AChBP), which shares structural similarity and sequence identities with the extracellular domain of nAChRs. Because the crystal structure of five alpha-cobratoxin molecules bound to AChBP shows the toxins projecting radially like propeller "blades" from the perimeter of the donut-shaped AChBP, the toxin molecules should increase the frictional resistance and thereby alter the hydrodynamic properties of the complex. alpha-Bungarotoxin binding had little effect on the frictional coefficients of AChBP measured by analytical ultracentrifugation, suggesting that the bound toxins are flexible. To support this conclusion, we measured the anisotropy decay of four site-specifically labeled alpha-cobratoxins (conjugated at positions Lys(23), Lys(35), Lys(49), and Lys(69)) bound to AChBP and free in solution and compared their anisotropy decay properties with fluorescently labeled cysteine mutants of AChBP. The results indicated that the core of the toxin molecule is relatively flexible when bound to AChBP. When hydrodynamic and anisotropy decay analyses are taken together, they establish that only one face of the second loop of the alpha-neurotoxin is immobilized significantly by its binding. The results indicate that bound alpha-neurotoxin is not rigidly oriented on the surface of AChBP but rather exhibits segmental motion by virtue of flexibility in its fingerlike structure.
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.
NASA Astrophysics Data System (ADS)
Xie, Xiaoping; Zhao, Xiaohu; Fang, Youtong; Cao, Zhitong; He, Guoguang
2011-04-01
The upper and lower bounds of the linear variance decay (LVD) dimension density are analytically deduced using multivariate series with uncorrelated and perfectly correlated component series. Then, the normalized LVD dimension density ( δ) is introduced. In order to measure the complexity of a scalar series with δ, a pseudo-multivariate series was constructed from the scalar time series using time-delay embedding. Thus, δ is used to characterize the complexity of the pseudo-multivariate series. The results from the model systems and fMRI data of anxiety subjects reveal that this method can be used to analyze short and noisy time series.
Hoppe, Björn; Krger, Krüger; Kahl, Tiemo; Arnstadt, Tobias; Buscot, François; Bauhus, Jürgen; Wubet, Tesfaye
2015-04-08
Deadwood is an important biodiversity hotspot in forest ecosystems. While saproxylic insects and wood-inhabiting fungi have been studied extensively, little is known about deadwood-inhabiting bacteria. The study we present is among the first to compare bacterial diversity and community structure of deadwood under field conditions. We therefore compared deadwood logs of two temperate forest tree species Fagus sylvatica and Picea abies using 16S rDNA pyrosequencing to identify changes in bacterial diversity and community structure at different stages of decay in forest plots under different management regimes. Alphaproteobacteria, Acidobacteria and Actinobacteria were the dominant taxonomic groups in both tree species. There were no differences in bacterial OTU richness between deadwood of Fagus sylvatica and Picea abies. Bacteria from the order Rhizobiales became more abundant during the intermediate and advanced stages of decay, accounting for up to 25% of the entire bacterial community in such logs. The most dominant OTU was taxonomically assigned to the genus Methylovirgula, which was recently described in a woodblock experiment of Fagus sylvatica. Besides tree species we were able to demonstrate that deadwood physico-chemical properties, in particular remaining mass, relative wood moisture, pH, and C/N ratio serve as drivers of community composition of deadwood-inhabiting bacteria.
Anisotropic Landau-Lifshitz-Gilbert models of dissipation in qubits
NASA Astrophysics Data System (ADS)
Crowley, Philip J. D.; Green, A. G.
2016-12-01
We derive a microscopic model for dissipative dynamics in a system of mutually interacting qubits coupled to a thermal bath that generalizes the dissipative model of Landau-Lifshitz-Gilbert to the case of anisotropic bath couplings. We show that the dissipation acts to bias the quantum trajectories towards a reduced phase space. This model applies to a system of superconducting flux qubits whose coupling to the environment is necessarily anisotropic. We study the model in the context of the D-Wave computing device and show that the form of environmental coupling in this case produces dynamics that are closely related to several models proposed on phenomenological grounds.
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.
NASA Astrophysics Data System (ADS)
Beck, Warren F.; Homoelle, Bradley J.; Diffey, William M.
1998-03-01
We have employed two third-order femtosecond spectroscopic methods, stimulated-photon-echo peak-shift (3PEPS) and transient-grating (TG) spectroscopy, to characterize solvation dynamics at physiological temperatures in phycobiliprotein systems, the α subunit of C-phycocyanin and allophycocyanin in the trimeric aggregation state. Both systems exhibit a biphasic solvation response: an inertial phase, arising from librational motions of the amino acids or included water molecules in the chromophore-binding site, contributes a 80--100-fs component to the 3PEPS profile and appears as a rapidly-damped 72-cm-1 modulation of the TG signal; the diffusive phase, arising from collective protein-matrix motions, exhibits a component in the TG signal and 3PEPS profile on the 5--20-ps and longer time scales. The 3PEPS profile observed with allophycocyanin exhibits additional fast decay components, with time constants of 56 fs and 220 fs, that report the additional contributions to electronic dephasing that arise from interexciton-state radiationless decay and vibrational relaxation in the lower exciton state, respectively. These results, taken along with those of previous transient hole-burning experiments, show that the exciton states in allophycocyanin are imperfectly correlated.
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.
Weber, Valéry; Laino, Teodoro; Pozdneev, Alexander; Fedulova, Irina; Curioni, Alessandro
2015-07-14
In this paper, we present a novel, highly efficient, and massively parallel implementation of the sparse matrix-matrix multiplication algorithm inspired by the midpoint method that is suitable for matrices with decay. Compared with the state of the art in sparse matrix-matrix multiplications, the new algorithm heavily exploits data locality, yielding better performance and scalability, approaching a perfect linear scaling up to a process box size equal to a characteristic length that is intrinsic to the matrices. Moreover, the method is able to scale linearly with system size reaching constant time with proportional resources, also regarding memory consumption. We demonstrate how the proposed method can be effectively used for the construction of the density matrix in electronic structure theory, such as Hartree-Fock, density functional theory, and semiempirical Hamiltonians. We present the details of the implementation together with a performance analysis up to 185,193 processes, employing a Hamiltonian matrix generated from a semiempirical NDDO scheme.
Hewitt, Joshua T; Concepcion, Javier J; Damrauer, Niels H
2013-08-28
Photophysics of the MLCT excited-state of [Ru(bpy)(tpy)(OH2)](2+) (1) and [Ru(bpy)(tpy)(OD2)](2+) (2) (bpy = 2,2'-bipyridine and tpy = 2,2':6',2″-terpyridine) have been investigated in room-temperature H2O and D2O using ultrafast transient pump-probe spectroscopy. An inverse isotope effect is observed in the ground-state recovery for the two complexes. These data indicate control of excited-state lifetime via a pre-equilibrium between the (3)MLCT state that initiates H-bond dynamics with the solvent and the (3)MC state that serves as the principal pathway for nonradiative decay.
NASA Astrophysics Data System (ADS)
Zhang, Teng-Shuo; Xue, Jia-Dan; Zheng, Xuming; Xie, Bin-Bin; Fang, Wei-Hai
2017-03-01
The excited-state structural dynamics and the decay mechanism of 2(1H)-pyridinone (NHP) after excitation to the S4(21π π* ) light-absorbing state were studied using resonance Raman spectroscopy and complete-active space self-consistent field (CASSCF) calculations. The B-band absorption cross-section and the corresponding absolute resonance Raman cross-sections were simulated using a simple model based on time-dependent wave-packet theory. The geometric structures of the singlet electronic excited states and their curve-crossing points were optimized at the CASSCF level of theory. The obtained short-time structural dynamics in easy-to-visualize internal coordinates were then compared with the CASSCF-predicted structural-parameter changes of S4(21π π* ) /S3 (21nπ* ) -MIN , S4(21π π* ) /S1 (11nπ* ) -MIN , and S4(21π π* ) -MIN . Our results indicate that the initial population of NHP in the S4 state bifurcates in or near the Franck-Condon region, leading to two predominant (S4S3-MIN and S4S1-MIN) internal conversion pathways. The lowest-lying S2(11π π* ) excited state is finally formed via subsequent internal conversions S3(21nπ* ) /S2 (11π π* ) -MIN and S1(11nπ* ) /S2 (11π π* ) -MIN. The enol-keto tautomeric mechanism does not seem to play a role. The decay mechanism in the singlet realm is proposed.
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.
Vacuum self similar anisotropic cosmologies in F( R)-gravity
NASA Astrophysics Data System (ADS)
Apostolopoulos, Pantelis S.
2017-04-01
The implications from the existence of a proper Homothetic Vector Field on the dynamics of vacuum anisotropic models in F( R) gravitational theory are studied. The fact that every Spatially Homogeneous vacuum model is equivalent, formally, with a "flux"-free anisotropic fluid model in standard gravity and the induced power-law form of the functional F( R) due to self-similarity enable us to close the system of equations. We found some new exact anisotropic solutions that arise as fixed points in the associated dynamical system. The non-existence of Kasner-like (Bianchi type I) solutions in proper F( R)-gravity (i.e. R≠ 0) strengthens the belief that curvature corrections will prevent the shear influence into the past thus permitting an isotropic singularity. We also discuss certain issues regarding the lack of vacuum models of type III, IV, VIIh in comparison with the corresponding results in standard gravity.
Anisotropic light scattering of individual sickle red blood cells
NASA Astrophysics Data System (ADS)
Kim, Youngchan; Higgins, John M.; Dasari, Ramachandra R.; Suresh, Subra; Park, YongKeun
2012-04-01
We present the anisotropic light scattering of individual red blood cells (RBCs) from a patient with sickle cell disease (SCD). To measure light scattering spectra along two independent axes of elongated-shaped sickle RBCs with arbitrary orientation, we introduce the anisotropic Fourier transform light scattering (aFTLS) technique and measured both the static and dynamic anisotropic light scattering. We observed strong anisotropy in light scattering patterns of elongated-shaped sickle RBCs along its major axes using static aFTLS. Dynamic aFTLS analysis reveals the significantly altered biophysical properties in individual sickle RBCs. These results provide evidence that effective viscosity and elasticity of sickle RBCs are significantly different from those of the healthy RBCs.
NASA Astrophysics Data System (ADS)
Kundin, Julia; Ajmal Choudhary, Muhammad
2017-07-01
In this article, we present the recent advances in the development of the anisotropic phase-field crystal (APFC) model. These advances are important in basic researches for multiferroic and thermoelectric materials with anisotropic crystal lattices and in thin-film applications. We start by providing a general description of the model derived in our previous studies based on the crystal symmetry and the microscopic dynamical density functional theory for anisotropic interactions and show that there exist only two possible degrees of freedom for the anisotropic lattices which are described by two independent parameters. New findings concerning the applications of the APFC model for the estimation of the elastic modules of anisotropic systems including sheared and stretched lattices as well as for the investigation of the heterogeneous thin film growth are described. The simulation results demonstrate the strong dependency of the misfit dislocation formation during the film growth on the anisotropy and reveal the asymmetric behavior in the cases of positive and negative misfits. We also present the development of the amplitude representation for the full APFC model of two orientation variants and show the relationship between the wave vectors and the base angles of the anisotropic lattices.
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.
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.
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.
Magnetization dynamics down to a zero field in dilute (Cd,Mn)Te quantum wells.
Goryca, M; Ferrand, D; Kossacki, P; Nawrocki, M; Pacuski, W; Maślana, W; Gaj, J A; Tatarenko, S; Cibert, J; Wojtowicz, T; Karczewski, G
2009-01-30
The evolution of the magnetization in (Cd,Mn)Te quantum wells after a short pulse of magnetic field was determined from the giant Zeeman shift of spectroscopic lines. The dynamics in the absence of a static magnetic field was found to be up to 3 orders of magnitude faster than that at 1 T. Hyperfine interaction and strain are mainly responsible for the fast decay. The influence of a hole gas is clearly visible: at zero field anisotropic holes stabilize the system of Mn ions, while in a magnetic field of 1 T they are known to speed up the decay by opening an additional relaxation channel.
Wang, Qi; He, Deyan
2017-04-11
A time-decay resistive switching memory using a 3D vertical Pt/Ta2O5-x/W device architecture is demonstrated, in which horizontal W electrodes were fabricated, and vertical Pt electrodes was formed at the sidewall after oxide was deposited. Unlike conventional resistive switching, which usually form a conductive filament connect two electrodes, a weak conductive filament was formed from bottom electrode W to near top electrode Pt. The memory can be recovered with a time scale when the electrical stimulation is removed. However, different decay behaviors were observed in one decay curve, including rapid decay and slow decay processes. This can be a good simulation of different stages of forgetting. By a combination of the current decay fitting and the conductive analysis, the rapid decay and slow decay processes correspond to ion diffusion and electron detrapping, respectively.
Gim, Y.; Sethi, A.; Zhao, Q.; ...
2016-01-11
A major focus of experimental interest in Sr2IrO4 has been to clarify how the magnetic excitations of this strongly spin-orbit coupled system differ from the predictions of an isotropic 2D spin-1/2 Heisenberg model and to explore the extent to which strong spin-orbit coupling affects the magnetic properties of iridates. Here, we present a high-resolution inelastic light (Raman) scattering study of the low energy magnetic excitation spectrum of Sr2IrO4 and doped Eu-doped Sr2IrO4 as functions of both temperature and applied magnetic field. We show that the high-field (H > 1.5 T) in-plane spin dynamics of Sr2IrO4 are isotropic and governed bymore » the interplay between the applied field and the small in-plane ferromagnetic spin components induced by the Dzyaloshinskii-Moriya interaction. However, the spin dynamics of Sr2IrO4 at lower fields (H < 1.5 T) exhibit important effects associated with interlayer coupling and in-plane anisotropy, including a spin-flop transition at Hc in Sr2IrO4 that occurs either discontinuously or via a continuous rotation of the spins, depending upon the in-plane orientation of the applied field. Furthermore, these results show that in-plane anisotropy and interlayer coupling effects play important roles in the low-field magnetic and dynamical properties of Sr2IrO4.« less
NASA Astrophysics Data System (ADS)
Hanna, Athiya Mahmud; Vendrell, Oriol; Ourmazd, Abbas; Santra, Robin
2017-04-01
By theoretical calculation, we demonstrate the possibility to control and partially suppress the Coulomb explosion of N2 molecules after core-level photoionization by an x-ray laser and subsequent Auger decay. This is achieved by means of a femtosecond infrared laser pulse interacting with the N22 + dication produced by the x-ray pulse. Suppression of molecular fragmentation requires few-femtosecond IR pulses interacting with the system either during or shortly after the arrival of the x-ray pulse. The IR pulse suppresses fragmentation mostly by optically coupling the electronic routes to ultrafast molecular dissociation with electronic channels able to support long-lived vibrational resonances. The effect is strongly dependent on the orientation of the molecule with respect to the polarization axis of the IR field. Our calculations are motivated by x-ray pump-IR probe experiments performed at an x-ray free-electron laser [J. M. Glownia et al., Opt. Express 18, 17620 (2010), 10.1364/OE.18.017620], where only enhancement of N22 + fragmentation as a function of the pump-probe delay time was reported. The opposite effect reported here becomes apparent when the various electronic channels are considered separately. In practice, this corresponds to a coincident measurement of the energy of the ejected Auger electron.
NASA Astrophysics Data System (ADS)
Auty, A. R.; Jones, A. C.; Phillips, D.
1986-03-01
Fluorescence excitation spectra of supersonic jet-cooled carbazole (C) and N-ethylcarbazole (EC) are reported together with those of their homocyclic analogues fluorene (F) and 9-ethylfluorene (EF). Fluorescence spectra of C and EC have been measured following excitation at energies up to ≈ 1300 cm -1 above the S 1 origin and reveal that the onset of intramolecular vibrational redistribution occurs at around 900 cm -1 for both molecules, with redistribution being more extensive in the ethylated molecule. In C and EC, a number of modes are active in vibronically coupling the S 1 and S 2 states and Duschinsky mixing of these modes is apparent in the spectra. The fluorescence lifetimes of both C and EC show a slowly decreasing trend with increasing excitation energy in the range 0-1500 cm -1 excess vibrational energy; vibrational redistribution does not appear to enhance the rate of non-radiative decay in either molecule. Comparison of lifetime values under supersonic jet conditions with solution phase results indicates that solvation produces a considerable increase in the rate of intersystem crossing in these molecules.
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.
NASA Astrophysics Data System (ADS)
Phanindra, V. Eswara; Das, Sarmistha; Kumar, K. Santhosh; Agarwal, Piyush; Rana, Rakesh; Rana, D. S.
2017-02-01
The interplay of charge, spin, and lattice correlations strongly influence the insulator-metal (I-M) transition and magnetic ordering in rare earth nickelates. In this context, we explored the low-energy charge dynamics in structurally modulated PrNi O3 (PNO) thin films to unravel the complexity of ground state across I-M transition using terahertz (THz) spectroscopy. The THz optical constants of compressive film on LaAl O3 (100) substrate and the tensile films on NdGa O3 (100), (001), (110), and (111) substrates with varying orthorhombic distortion exhibit remarkably distinct features as a function of frequency and temperature. The THz conductivity of compressive film sans any I-M transition follows the Drude model. In contrast, the tensile strained films exhibit non-Drude THz conductivity, a giant positive dielectric permittivity, and negative imaginary conductivity, all of which can be explained by the Drude-Smith model. This rich variety of low-energy dynamics manifests as a function of temperature, strain, and crystal orientation. Such distinct THz spectral features, as induced by a subtle variation in strain while crossing over from tensile to compressive strain and with varying degree of orthorhombicity coupled with oxygen vacancies, reveal a novel facet of structure-property relationship of PNO.
Paul G. Scowcroft
1997-01-01
The structure and functioning of Acacia koa-Metrosideros polymorpha forests between 1200 and 1800 m elevation on the island of Hawaii are being threatened by Passiflora mollissima, an aggressive introduced liana from South America. This study was done to evaluate the short-term decomposition dynamics of...
High-order anisotropic diffraction in photoreflective crystals
Temple, D.A.; Warde, C.
1988-08-01
High-order anisotropic diffraction and anisotropic self-diffraction in barium titanate (BaTiO/sub 3/), strontium barium niobate (Sr/sub x/Ba/sub 1-//sub x/Nb/sub 2/O/sub 6/, or SBN), and barium strontium potassium sodium niobate (Ba/sub 2//sub -//sub x/Sr/sub x/K/sub 1-//sub y/Na/sub y/Nb/sub 5/O/sub 15/, or BSKNN) have been observed: up to fourth order in BaTiO/sub 3/ and SBN and up to fifth order in BSKNN. It is shown that the scattered beams arising from anisotropic self-diffraction are composed of multiple orders. To model anisotropic diffraction, high-order terms have been included in Kukhtarev's solution of the transport equations for diffusion-dominated transport. Light-induced grating decay rates and diffraction efficiencies were measured as a function of grating vector and modulation index for the first three orders in BaTiO/sub 3/ and were found to be in good agreement with the model.
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.
Guo, Jianchang; Han, Kee Sung; Mahurin, Shannon Mark; Baker, Gary A; Hillesheim, Patrick C; Dai, Sheng; Hagaman, Edward {Ed} W; Shaw, Robert W
2012-01-01
NMR spectroscopy and time-resolved fluorescence anisotropy decay (TRFAD) are two of the most commonly used methods to study solute-solvent interactions. However, only a few studies have been reported to date using a combined NMR and TRFAD approach to systematically investigate the overall picture of diffusional and rotational dynamics of both the solute and solvent. In this paper, we combined NMR and TRFAD to probe fluorescent rhodamine dyes in a pyrrolidinium-based room temperature ionic liquid (RTIL), an emergent environmentally-friendly solvent type used in several energy-related applications. A specific interaction of the R6G cation and [Tf2N]- anion was identified, resulting in near-stick boundary condition rotation of R6G in this RTIL. The diffusional rates of the R6G solute and [C4mpyr][Tf2N] solvent derived from 1H NMR suggest the rates are proportional to their corresponding hydrodynamic radii. The 1H and 13C NMR studies of self-rotational dynamics of [C4mpyr][Tf2N] showed that the self-rotational correlation time of [C4mpyr]+ is 47 2 ps at 300 K. At the same temperature, we find that the correlation time for N-CH3 rotation in [C4mpyr]+ is 77 2 ps, comparable to overall molecular reorientation. This slow motion is attributed to properties of the cation structure.
Carbonniere, Philippe; Pouchan, Claude; Improta, Roberto
2015-05-07
We report a study of intramolecular vibrational distribution (IVR) occurring in the electronic ground state of uracil (S0) in the gas phase, following photoexcitation in the lowest energy bright excited state (Sπ) and decay through the ethylene-like Sπ/S0 Conical Intersection (CI-0π). To this aim we have performed 20 independent ab initio molecular dynamics simulations starting from CI-0π (ten of them with 1 eV kinetic energy randomly distributed over the different molecular degrees of freedom) and 10 starting from the ground state minimum (Franck-Condon, FC, point), with the excess kinetic energy equal to the energy gap between CI-0π and the FC point. The simulations, exploiting PBE0/6-31G(d) calculations, were performed over an overall period of 10 ps. A thorough statistical analysis of the variation of the geometrical parameters of uracil during the simulation time and of the distribution of the kinetic energy among the different vibrational degrees of freedom provides a consistent picture of the IVR process. In the first 0-200 fs the structural dynamics involve mainly the recovery of the average planarity. In the 200-600 fs time range, a substantial activation of CO and NH degrees of freedom is observed. After 500-600 fs most of the geometrical parameters reach average values similar to those found after 10 ps, though the system cannot be considered to be in equilibrium yet.
NASA Astrophysics Data System (ADS)
Pazzaglia, F. J.; Zeitler, P. K.; McKeon, R. E.; Idleman, B. D.; Berti, C.
2010-12-01
The Appalachian Mountains in the eastern United States are constructed on a lithosphere that was assembled and modified during a long period of Paleozoic collisional tectonics, and then thinned by erosion and stretching with the opening of the Atlantic Ocean. Geologic, geomorphic, and geophysical data describe the long term erosion, persistence of mountainous topography, and coupling between surface and tectonic, isostatic, or eperiogenic processes of this ancient, decaying orogen. There are several key observables that must be reconciled to explain Appalachian post-orogenic (post-Triassic) evolution. These include subsidence of the former metamorphic core of the range and topographic inversion of the foreland, a long-term record of unsteady erosion preserved in the sediments of the Atlantic margin shelf-slope basins, the steepening of the longitudinal profiles of Atlantic slope rivers forming a zone of bedrock rapids as they approach the Atlantic, river knickpoints in the foreland with a common elevation that have no apparent relation to rock-type or structure, and evidence that the divide between Atlantic slope and Ohio drainages is not a static feature. The long term rate of Appalachian rock uplift (base level fall) and erosion is ~20-30 m/my., a result consistent with AHe thermochronology and the average sediment flux to the BCT, but misleading in terms of the unsteadiness demonstrated by river incision, growth of the Atlantic slope drainage, and short-term sediment flux to the BCT. This unsteadiness is likely influenced by several factors including climate change, sediment storage in the landscape and the Coastal Plain, and eustasy; however, we propose that the most important factor has been unsteady rock uplift as the result of a lithospheric flexural response to surface loads and sub-lithospheric mantle flow driven by the foundering Farallon slab.
Structural relaxation in dense liquids composed of anisotropic particles.
Shen, Tianqi; Schreck, Carl; Chakraborty, Bulbul; Freed, Denise E; O'Hern, Corey S
2012-10-01
We perform extensive molecular dynamics simulations of dense liquids composed of bidisperse dimer- and ellipse-shaped particles in two dimensions that interact via purely repulsive contact forces. We measure the structural relaxation times obtained from the long-time α decay of the self part of the intermediate scattering function for the translational and rotational degrees of freedom (DOF) as a function of packing fraction φ, temperature T, and aspect ratio α. We are able to collapse the packing-fraction and temperature-dependent structural relaxation times for disks, and dimers and ellipses over a wide range of α, onto a universal scaling function F(±)(|φ-φ(0)|,T,α), which is similar to that employed in previous studies of dense liquids composed of purely repulsive spherical particles in three dimensions. F(±) for both the translational and rotational DOF are characterized by the α-dependent scaling exponents μ and δ and packing fraction φ(0)(α) that signals the crossover in the scaling form F(±) from hard-particle dynamics to super-Arrhenius behavior for each aspect ratio. We find that the fragility of structural relaxation at φ(0), m(φ(0)), decreases monotonically with increasing aspect ratio for both ellipses and dimers. For α>α(p), where α(p) is the location of the peak in the packing fraction φ(J) at jamming onset, the rotational DOF are strongly coupled to the translational DOF, and the dynamic scaling exponents and φ(0) are similar for the rotational and translational DOF. For 1<α<α(p), the translational DOF become frozen at higher temperatures than the rotational DOF, and φ(0) for the rotational degrees of freedom increases above φ(J). Moreover, the results for the slow dynamics of dense liquids composed of dimer- and ellipse-shaped particles are qualitatively the same, despite the fact that zero-temperature static packings of dimers are isostatic, while static packings of ellipses are hypostatic. Thus, zero-temperature contact
Wenska, Grazyna; Taras-Goślińska, Katarzyna; Łukaszewicz, Adam; Burdziński, Gotard; Koput, Jacek; Maciejewski, Andrzej
2011-08-01
The absorption, phosphorescence and phosphorescence excitation spectra, phosphorescence quantum yields, and T(1) excited state lifetimes of four 4-thiouracil derivatives were measured for the first time in chemically inert and very weakly interacting perfluoro-1,3-dimethylcyclohexane at room temperature. The set of the 4-thiouracil derivatives comprises 1-propyl-4-thiouracil (PTU) and the related compounds having a methyl substituent at the position α to the thiocarbonyl group, namely 1-propyl-4-thiothymine (PTT), 1,3-dimethyl-4-thiouracil (DMTU), and 1-methyl-3-trideuteriomethyl-4-thiouracil ([D(3)]DMTU). Quantitative information on the intramolecular decay of the T(1) excited state of the four 4-thiouracil derivatives is presented, and the mechanism and dynamics of this process are discussed. In the absence of self quenching and solvent induced deactivation, the T(1) decay of the four 4-thiouracil derivatives was dominated by intramolecular nonradiative processes (NR). The values of the rate constant k(NR) in DMTU and [D(3)]DMTU are about 4 times larger than that in PTT and about 3 times larger than that in PTU. The reasons for the enhanced nonradiative rate constant in DMTU are discussed. It is concluded that the faster rate of the nonradiative processes in DMTU is related to a larger contribution from mixing of the T(2) (nπ*) state into the lowest energy T(1) (ππ*) state, as compared to the analogous coupling in PTU and PTT. This conclusion is supported by ab initio calculations performed at the EOM-CC2/aug-cc-pVDZ level of theory. The energy spacing between the T(2) (nπ*) and T(1) (ππ*) states is estimated to be about 500, 1100, and 2000 cm(-1) for DMTU, PTU, and PTT, respectively. Among the three compounds in question, the predicted energy spacing is thus the smallest for DMTU. This journal is © The Royal Society of Chemistry and Owner Societies 2011
Anisotropic deformations of spatially open cosmology in massive gravity theory
NASA Astrophysics Data System (ADS)
Mazuet, Charles; Mukohyama, Shinji; Volkov, Mikhail S.
2017-04-01
We combine analytical and numerical methods to study anisotropic deformations of the spatially open homogeneous and isotropic cosmology in the ghost free massive gravity theory with flat reference metric. We find that if the initial perturbations are not too strong then the physical metric relaxes back to the isotropic de Sitter state. However, the dumping of the anisotropies is achieved at the expense of exciting the Stueckelberg fields in such a way that the reference metric changes and does not share anymore with the physical metric the same rotational and translational symmetries. As a result, the universe evolves towards a fixed point which does not coincide with the original solution, but for which the physical metric is still de Sitter. If the initial perturbation is strong, then its evolution generically leads to a singular anisotropic state or, for some parameter values, to a decay into flat spacetime. We also present an infinite dimensional family of new homogeneous and isotropic cosmologies in the theory.
Wavefunction of anisotropic inflationary universes with no-boundary conditions
NASA Astrophysics Data System (ADS)
Bramberger, Sebastian F.; Farnsworth, Shane; Lehners, Jean-Luc
2017-04-01
We study the emergence of anisotropic (Bianchi IX) inflationary universes with no-boundary conditions in the path integral approach to quantum gravity. In contrast to previous work, we find no evidence for any limit to how large the anisotropies can become, although for increasing anisotropies the shape of the instantons becomes significantly different from Hawking's original no-boundary instanton. In all cases an inflationary phase is reached, with the anisotropies decaying away. Larger anisotropies are associated with a much larger imaginary part of the action, implying that the highly anisotropic branches of the wavefunction are heavily suppressed. Interestingly, the presence of anisotropies causes the wavefunction to become classical much more slowly than for isotropic inflationary universes. We derive the associated scaling of the WKB classicality conditions both numerically and analytically.
Ellis, Jamie P; Culviner, Peter H; Cavagnero, Silvia
2009-01-01
We still know very little about how proteins achieve their native three-dimensional structure in vitro and in the cell. Folding studies as proteins emerge from the mega Dalton-sized ribosome pose special challenges due to the large size and complicated nature of the ribosome-nascent chain complex. This work introduces a combination of three-component analysis of fluorescence depolarization decays (including the presence of two local motions) and in-cone analysis of diffusive local dynamics to investigate the spatial constraints experienced by a protein emerging from the ribosomal tunnel. We focus on E. coli ribosomes and an all-α-helical nascent globin in the presence and absence of the cotranslationally active chaperones DnaK and trigger factor. The data provide insights on the dynamic nature and structural plasticity of ribosome-nascent chain complexes. We find that the sub-ns motions of the N-terminal fluorophore, reporting on the globin dynamics in the vicinity of the N terminus, are highly constrained both inside and outside the ribosomal tunnel, resulting in high-order parameters (>0.85) and small cone semiangles (<30°). The shorter globin chains buried inside the tunnel are less spatially constrained than those of a reference sequence from a natively unfolded protein, suggesting either that the two nascent chain sequences have a different secondary structure and therefore sample different regions of the tunnel or that the tunnel undergoes local structural adjustments to accommodate the globin sequence. Longer globins emerging out of the ribosomal tunnel are also found to have highly spatially constrained slow (ns) motions. There are no observable spectroscopic changes in the absence of bound chaperones. PMID:19569194
Ge, Ni-Na; Wei, Yong-Kai; Song, Zhen-Fei; Chen, Xiang-Rong; Ji, Guang-Fu; Zhao, Feng; Wei, Dong-Qing
2014-07-24
Molecular dynamics simulations in conjunction with multiscale shock technique (MSST) are performed to study the initial chemical processes and the anisotropy of shock sensitivity of the condensed-phase HMX under shock loadings applied along the a, b, and c lattice vectors. A self-consistent charge density-functional tight-binding (SCC-DFTB) method was employed. Our results show that there is a difference between lattice vector a (or c) and lattice vector b in the response to a shock wave velocity of 11 km/s, which is investigated through reaction temperature and relative sliding rate between adjacent slipping planes. The response along lattice vectors a and c are similar to each other, whose reaction temperature is up to 7000 K, but quite different along lattice vector b, whose reaction temperature is only up to 4000 K. When compared with shock wave propagation along the lattice vectors a (18 Å/ps) and c (21 Å/ps), the relative sliding rate between adjacent slipping planes along lattice vector b is only 0.2 Å/ps. Thus, the small relative sliding rate between adjacent slipping planes results in the temperature and energy under shock loading increasing at a slower rate, which is the main reason leading to less sensitivity under shock wave compression along lattice vector b. In addition, the C-H bond dissociation is the primary pathway for HMX decomposition in early stages under high shock loading from various directions. Compared with the observation for shock velocities V(imp) = 10 and 11 km/s, the homolytic cleavage of N-NO2 bond was obviously suppressed with increasing pressure.
Bhattacharyya, Swarnendu Domcke, Wolfgang; Dai, Zuyang
2015-11-21
A diabatic three-sheeted six-dimensional potential-energy surface has been constructed for the ground state and the lowest excited state of the PH{sub 3}{sup +} cation. Coupling terms of Jahn-Teller and pseudo-Jahn-Teller origin up to eighth order had to be included to describe the pronounced anharmonicity of the surface due to multiple conical intersections. The parameters of the diabatic Hamiltonian have been optimized by fitting the eigenvalues of the potential-energy matrix to ab initio data calculated at the CASSCF/MRCI level employing the correlation-consistent triple-ζ basis. The theoretical photoelectron spectrum of phosphine and the non-adiabatic nuclear dynamics of the phosphine cation have been computed by propagating nuclear wave packets with the multiconfiguration time-dependent Hartree method. The theoretical photoelectron bands obtained by Fourier transformation of the autocorrelation function agree well with the experimental results. It is shown that the ultrafast non-radiative decay dynamics of the first excited state of PH{sub 3}{sup +} is dominated by the exceptionally strong Jahn-Teller coupling of the asymmetric bending vibrational mode together with a hyperline of conical intersections with the electronic ground state induced by the umbrella mode. Time-dependent population probabilities have been computed for the three adiabatic electronic states. The non-adiabatic Jahn-Teller dynamics within the excited state takes place within ≈5 fs. Almost 80% of the excited-state population decay to the ground state within about 10 fs. The wave packets become highly complex and delocalized after 20 fs and no further significant transfer of electronic population seems to occur up to 100 fs propagation time.
Particle decay in inflationary cosmology
Boyanovsky, D.; Vega, H.J. de
2004-09-15
We investigate the relaxation and decay of a particle during inflation by implementing the dynamical renormalization group. This investigation allows us to give a meaningful definition for the decay rate in an expanding universe. As a prelude to a more general scenario, the method is applied here to study the decay of a particle in de Sitter inflation via a trilinear coupling to massless conformally coupled particles, both for wavelengths much larger and much smaller than the Hubble radius. For superhorizon modes we find that the decay is of the form {eta}{sup {gamma}{sub 1}} with {eta} being conformal time and we give an explicit expression for {gamma}{sub 1} to leading order in the coupling which has a noteworthy interpretation in terms of the Hawking temperature of de Sitter space-time. We show that if the mass M of the decaying field is <
Particle decay in inflationary cosmology
NASA Astrophysics Data System (ADS)
Boyanovsky, D.; de Vega, H. J.
2004-09-01
We investigate the relaxation and decay of a particle during inflation by implementing the dynamical renormalization group. This investigation allows us to give a meaningful definition for the decay rate in an expanding universe. As a prelude to a more general scenario, the method is applied here to study the decay of a particle in de Sitter inflation via a trilinear coupling to massless conformally coupled particles, both for wavelengths much larger and much smaller than the Hubble radius. For superhorizon modes we find that the decay is of the form ηΓ1 with η being conformal time and we give an explicit expression for Γ1 to leading order in the coupling which has a noteworthy interpretation in terms of the Hawking temperature of de Sitter space-time. We show that if the mass M of the decaying field is ≪H then the decay rate during inflation is enhanced over the Minkowski space-time result by a factor 2H/πM. For wavelengths much smaller than the Hubble radius we find that the decay law is e with C(η) the scale factor and α determined by the strength of the trilinear coupling. In all cases we find a substantial enhancement in the decay law as compared to Minkowski space-time. These results suggest potential implications for the spectrum of scalar density fluctuations as well as non-Gaussianities.
Anisotropic spin dephasing of impurity-bound electron spins in ZnO
Lee, Jieun; Sih, Vanessa; Venugopal, Aneesh
2015-01-05
We investigate the electron spin dynamics of n-type c-axis oriented bulk zinc oxide (ZnO) by using time-resolved Kerr rotation and resonant spin amplification measurements. Calculating resonant spin amplification using an anisotropic spin dephasing model reveals that there are two species involved in the spin dynamics, which we attribute to conduction and impurity-bound electron spins, respectively. We find that the impurity-bound electron spin dephasing mechanism is strongly anisotropic due to anisotropic exchange interactions. The identification of the two spin species and their dephasing mechanisms is further supported by the temperature, power, and wavelength dependence of the spin coherence measurements.
Self-force on dislocation segments in anisotropic crystals.
Fitzgerald, S P; Aubry, S
2010-07-28
A dislocation segment in a crystal experiences a 'self-force', by virtue of the orientation dependence of its elastic energy. If the crystal is elastically isotropic, this force is manifested as a couple acting to rotate the segment toward the lower energy of the pure screw orientation (i.e. acting to align the dislocation line with its Burgers vector). If the crystal is anisotropic, there are additional contributions to the couple, arising from the more complex energy landscape of the lattice itself. These effects can strongly influence the dynamic evolution of dislocation networks, and via their governing role in dislocation multiplication phenomena, control plastic flow in metals. In this paper we develop a model for dislocation self-forces in a general anisotropic crystal, and briefly consider the technologically important example of α-iron, which becomes increasingly anisotropic as the temperature approaches that of the α-γ phase transition at 912 °C.
NASA Astrophysics Data System (ADS)
Germaschewski, K.; Grauer, R.; Bergé, L.; Mezentsev, V. K.; Juul Rasmussen, J.
2001-05-01
The self-focusing and splitting mechanisms of waves governed by the cubic nonlinear Schrödinger equation with anisotropic dispersion are investigated numerically by means of an adaptive mesh refinement code. Wave-packets having a power far above the self-focusing threshold undergo a transversal compression and are shown to split into two symmetric peaks. These peaks can sequentially decay into smaller-scale structures developing near the front edge of a shock, as long as their individual power remains above threshold, until the final dispersion of the wave. Their phase and amplitude dynamics are detailed and compared with those characterizing collapsing objects with no anisotropic dispersion. Their ability to mutually coalesce is also analyzed and modeled from the interaction of Gaussian components. Next, bunch-type and snake-type instabilities, which result from periodic modulations driven by even and odd localized modes, are studied. The influence of the initial wave amplitude, the amplitude and wavenumber of the perturbations on the interplay of snake and bunch patterns are finally discussed.
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).
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.
NASA Astrophysics Data System (ADS)
Bel, Lennaert; De Bruyn, Kristof; Fleischer, Robert; Mulder, Mick; Tuning, Niels
2015-07-01
The decays B {/d 0} → D {/d -} D {/d +} and B {/s 0} → D {/s -} D {/s +} probe the CP-violating mixing phases ϕ d and ϕ s , respectively. The theoretical uncertainty of the corresponding determinations is limited by contributions from penguin topologies, which can be included with the help of the U-spin symmetry of the strong interaction. We analyse the currently available data for B {/d, s 0} → D {/d, s -} D {/d, s +} decays and those with similar dynamics to constrain the involved non-perturbative parameters. Using further information from semileptonic B {/d 0} → D {/d -} ℓ + ν ℓ decays, we perform a test of the factorisation approximation and take non-factorisable SU(3)-breaking corrections into account. The branching ratios of the B {/d 0} → D {/d -} D {/d +}, B {/s 0} → D {/s -} D {/d +} and B {/s 0} → D {/s -} D {/s +}, B {/d 0} → D {/d -} D {/s +} decays show an interesting pattern which can be accommodated through significantly enhanced exchange and penguin annihilation topologies. This feature is also supported by data for the B {/s 0} → D {/d -} D {/d +} channel. Moreover, there are indications of potentially enhanced penguin contributions in the B {/d 0} → D {/d -} D {/d +} and B {/s 0} → D {/s -} D {/s +} decays, which would make it mandatory to control these effects in the future measurements of ϕ d and ϕ s . We discuss scenarios for high-precision measurements in the era of Belle II and the LHCb upgrade.
Boulesbaa, Abdelaziz; Borguet, Eric
2014-02-06
The dephasing dynamics of a vibrational coherence may reveal the interactions of chemical functional groups with their environment. To investigate this process at a surface, we employ free induction decay sum frequency generation (FID-SFG) to measure the time that it takes for free OH stretch oscillators at the charged (pH ≈ 13, KOH) interface of alumina/water (Al2O3/H2O) to lose their collective coherence. By employing noncollinear optical parametric amplification (NOPA) technology and nonlinear vibrational spectroscopy, we showed that the single free OH peak actually corresponds to two distinct oscillators oriented opposite to each other and measured the total dephasing time, T2, of the free OH stretch modes at the Al2O3/H2O interface with a sub-40 fs temporal resolution. Our results suggested that the free OH oscillators associated with interfacial water dephase on the time scale of 89.4 ± 6.9 fs, whereas the homogeneous dephasing of interfacial alumina hydroxyls is an order of magnitude slower.
Creasy, W R; Farrar, J M
1983-01-01
The title reaction has been studied at collision energies of 0.83 and 2.41 eV. Direct reaction dynamics have been observed at both energies and an increasingly high fraction of the total energy appears in product translation as the collision energy increases. This result is consistent with the concept of induced repulsive energy release, which becomes more effective as trajectories sample the corner of the potential energy surface. At the higher collision energy, the protonated acetone cation undergoes two unimolecular decay channels: C-C bond cleavage to CH/sub 3/CO/sup +/ and CH/sub 4/, and C-O bond cleavagto C/sub 3/H/sub 5//sup +/ (presumably to allyl cation) and H/sub 2/O. The CH/sub 3/CO/sup +/ channel, endothermic relative to ground state protonated acetone cations by 0.74 eV, appears to liberate 0.4 eV in relative product translation while the C/sub 3/H/sub 5//sup +/ channel, endothermic by 2.17 eV, liberates only 0.07 eV in relative translation. These results are discussed in terms of the location on the reaction coordinate and magnitudes of potential energy barriers to 1,3-hydrogen atoms shifts which must precede the bond cleavage processes.
Sampaio, Ana; Sampaio, José Paulo; Leão, Cecília
2007-06-01
Here we report on the results of a survey of the yeast populations occurring on submerged leaves (alder, eucalyptus and oak) in a natural mountain stream, during different phases of their decomposition and through two consecutive years. Leaf litter mass loss, total yeast counts, Shannon-Weiner index (H'), yeast community structure and physiologic abilities were analyzed to evaluate the dynamics of yeast communities during decay. Seventy-two yeast taxa were recorded, and in all litter types, species of basidiomycetous affinity predominated over ascomycetous ones. Discriminant analysis of presence/absence data (yeast species) showed significant differences both among substrate types (P<0.0026) and with decomposition time (P<0.0001). Carbon and nitrogen source utilization by yeast strains also varied with the substrate (P<0.0001) and decomposition time (P<0.0001). Further conclusions were that: (1) all litter types have in common ubiquitous yeast species, such as Cryptococcus albidus, Debaryomyces hansenii and Rhodotorula glutinis, among the common 20 yeast species; (2) only a few species were dominant, and most species were rare, being recorded once or twice throughout decomposition; and (3) the order of yeast appearance, and their substrate assimilation patterns, strongly suggest a succession phenomenon. Finally, explanations for the distribution patterns and variations in yeast communities are discussed.
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
NASA Astrophysics Data System (ADS)
Chopra, Sahila; Hemdeep, Gupta, Raj K.
2017-04-01
Within the framework of the dynamical cluster-decay model (DCM), we have studied the nuclear system with Z =122 and mass number A = 306 formed via two "hot" fusion reactions 58Fe+248Cm and 64Ni+242Pu . The up-to-date measured data are available only for the first reaction, and for fusion-fission cross section σff and quasifission cross section σqf, only at one compound nucleus (CN) excitation energy E*=33 MeV . In this study, we have included the deformation effects up to quadrupole deformations β2 i and with "optimum" orientations θiopt . for coplanar (Φ =00 ) configurations. The only parameter of the model is the neck-length parameter Δ R whose value, for the nuclear proximity potential used here, remains within its range of validity (˜2 fm ). Using the best fitted Δ R 's to the observed data for σff, calculated for mass region A /2 ±20 , and σqf for the incoming channel of Fe-induced reaction at E*=33 MeV , we have extended the DCM calculations to the other Ni-induced reaction, and to E*'s in the energy range 25-68 MeV. The interesting result is that the predicted evaporation residue cross section σER for 1-4 neutrons is largest for 4n decay at E*=45 MeV , having the value σER≡σ4 n˜10-5 pb for both reactions, and that the Δ R 's for the three processes (ER, ff, and qf) are different, i.e., they belong to different time scales where ff occurs first, then qf and the ER at the end. Other results of interest are the predictions of the magic N =82 136Xe fragment in the ff region of mass A /2 ±20 , and the doubly magic 208Pb in the qf region, in near close agreement with observed data (the observed fission fragment is of mass 132, instead of the predicted mass 136). The role of the weakly bound neutron-rich intermediate mass fragments and of the nucleus in the neighborhood of deformed magic Z = 108 are also indicated in the DCM calculations, which need experimental verification. For the predicted σER, the largest value of CN fusion probability PCN
NASA Astrophysics Data System (ADS)
Kar, Susmita; Dash, P. C.; Priyadarsini, M.; Naimuddin, Sk.; Barik, N.
2013-11-01
We study the exclusive nonleptonic Bc→VV decays, within the factorization approximation, in the framework of the relativistic independent quark model, based on a confining potential in the scalar-vector harmonic form. The weak form factors are extracted from the overlap integral of meson wave functions derived in the relativistic independent quark model. The predicted branching ratios for different Bc-meson decays are obtained in a wide range, from a tiny value of O(10-6) for Bc→D*D(s)* to a large value of 24.32% for Bc→Bs*ρ-, in general agreement with other dynamical-quark-model predictions. The decay modes Bc→Bs*ρ- and Bc→B*ρ- with high branching ratios of 24.32% and 1.73%, respectively, obtained in this model should be detectable at the LHC and Tevatron in the near future. The b→c, u induced decays are predicted predominantly in the longitudinal mode, whereas the c¯→s¯, d¯ induced decays are obtained in a slightly higher transverse mode. The CP-odd fractions (R⊥) for different decay modes are predicted and those for color-favored Bc→D*D*, D*Ds* decays indicate significant CP violation in this sector.
Quantum Decay of the 'False Vacuum' and Pair Creation of Soliton Domain Walls
Miller, John H. Jr.
2011-03-28
Quantum decay of metastable states ('false vacua') has been proposed as a mechanism for bubble nucleation of new universes and phase transitions in the early universe. Experiments indicate the occurrence of false vacuum decay, within a region bounded by soliton domain walls that nucleate via quantum tunneling, in a highly anisotropic condensed matter system. This phenomenon provides a compelling example of false vacuum decay in the laboratory.
The TT, TB, EB and BB correlations in anisotropic inflation
Chen, Xingang; Emami, Razieh; Firouzjahi, Hassan; Wang, Yi E-mail: emami@ipm.ir E-mail: yw366@cam.ac.uk
2014-08-01
The ongoing and future experiments will measure the B-mode from different sky coverage and frequency bands, with the potential to reveal non-trivial features in polarization map. In this work we study the TT, TB, EB and BB correlations associated with the B-mode polarization of CMB map in models of charged anisotropic inflation. The model contains a chaotic-type large field complex inflaton which is charged under the U(1) gauge field. We calculate the statistical anisotropies generated in the power spectra of the curvature perturbation, the tensor perturbation and their cross-correlation. It is shown that the asymmetry in tensor power spectrum is a very sensitive probe of the gauge coupling. While the level of statistical anisotropy in temperature power spectrum can be small and satisfy the observational bounds, the interactions from the gauge coupling can induce large directional dependence in tensor modes. This will leave interesting anisotropic fingerprints in various correlations involving the B-mode polarization such as the TB cross-correlation which may be detected in upcoming Planck polarization data. In addition, the TT correlation receives an anisotropic contribution from the tensor sector which naturally decays after l ∼> 100. We expect that the mechanism of using tensor sector to induce asymmetry at low l to be generic which can also be applied to address other low l CMB anomalies.
NASA Astrophysics Data System (ADS)
Chopra, Sahila; Kaur, Arshdeep; Hemdeep, Gupta, Raj K.
2016-04-01
The product PCNPsurv of compound nucleus (CN) fusion probability PCN and survival probability Psurv is calculated to determine the reduced evaporation residue cross section σER/σfusion , denoted σERreduced, with (total) fusion cross section σfusion given as a sum of CN-formation cross section σCN and non-CN cross section σnCN for each reaction, where σCN is the sum of evaporation residue cross section σER and fusion-fission cross section σff and σnCN, if not measured, is estimated empirically as the difference between measured and calculated σfusion. Our calculations of PCN and Psurv, based on the dynamical cluster-decay model, were successfully made for some 17 "hot" fusion reactions, forming different CN of mass numbers ACN˜100 -300 , with deformations of nuclei up to hexadecapole deformations and "compact" orientations for both coplanar (Φc=0∘ ) and noncoplanar (Φc≠0∘ ) configurations, using various different nuclear interaction potentials. Interesting variations of σERreduced with CN excitation energy E*, fissility parameter χ , CN mass ACN, and Coulomb parameter Z1Z2 show that, independent of entrance channel, different isotopes of CN, and nuclear interaction potentials used, the dominant quantity in the product is Psurv, which classifies all the studied CN into three groups of weakly fissioning, radioactive, and strongly fissioning superheavy nuclei, with relative magnitudes of σERreduced˜1 , ˜10-6 , and ˜10-11 , which, like for PCN, get further grouped in two dependencies of (i) weakly fissioning and strongly fissioning superheavy nuclei decreasing with increasing E* and (ii) radioactive nuclei increasing with increasing E*.
NASA Astrophysics Data System (ADS)
Sandell, A.; Libuda, J.; Brüauthwiler, P. A.; Andersson, S.; Bäautumer, M.; Maxwell, A. J.; M&; Artensson, N.; Freund, H.-J.
1997-03-01
Two alternative methods to experimentally monitor the development of a CO-adsorption system that gradually changes from molecular to metallic are presented: firstly by adsorption of CO on Pd islands of increasing size deposited under UHV conditions, and secondly by growth of a Pd carbonyl-like species, formed by Pd deposition in CO atmosphere. The change in screening dynamics as a function of the number of metal atoms was investigated, using x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and core-hole-decay techniques. For CO adsorbed on UHV-deposited islands, the electronic properties of the whole CO-Pd complex is strongly dependent on island size and CO coverage: large amounts of CO result in a reduced screening ability, and small effects characteristic of molecular systems can be detected even for islands containing about 100 Pd atoms. If about half of the CO overlayer is desorbed, the CO-Pd complex exhibits a relaxation upon core ionization that is nearly as efficient as for metallic systems, even for the smallest islands (of the order of 10 Pd atoms). The growth of the carbonyl-like compound proceeds via formation of Pd-Pd bonds and has a relatively well-defined local structure. It is demonstrated that the properties of this compound approach those of an extended system for increasing coverages, and it may therefore also serve as an important link between a carbonyl and CO adsorbed on a metallic surface. A brief discussion is also given in which the results are discussed in terms of electronic properties of the thin alumina film versus bulk alumina and the applicability of the former to the construction of model catalysts.
Turbulent Output-Based Anisotropic Adaptation
NASA Technical Reports Server (NTRS)
Park, Michael A.; Carlson, Jan-Renee
2010-01-01
Controlling discretization error is a remaining challenge for computational fluid dynamics simulation. Grid adaptation is applied to reduce estimated discretization error in drag or pressure integral output functions. To enable application to high O(10(exp 7)) Reynolds number turbulent flows, a hybrid approach is utilized that freezes the near-wall boundary layer grids and adapts the grid away from the no slip boundaries. The hybrid approach is not applicable to problems with under resolved initial boundary layer grids, but is a powerful technique for problems with important off-body anisotropic features. Supersonic nozzle plume, turbulent flat plate, and shock-boundary layer interaction examples are presented with comparisons to experimental measurements of pressure and velocity. Adapted grids are produced that resolve off-body features in locations that are not known a priori.
Analytical approach to relaxation dynamics of condensed Bose gases
Escobedo, Miguel; Pezzotti, Federica; Valle, Manuel
2011-04-15
Research Highlights: > Time evolution of perturbations from equilibrium in a condensed Bose gas is studied. > Just below the critical temperature the perturbations vanish algebraically. > Anisotropic perturbations are unstable. > At very low temperature perturbations decay exponentially. - Abstract: The temporal evolution of a perturbation of the equilibrium distribution of a condensed Bose gas is investigated using the kinetic equation which describes collision between condensate and noncondensate atoms. The dynamics is studied in the low momentum limit where an analytical treatment is feasible. Explicit results are given for the behavior at large times in different temperature regimes.
NASA Technical Reports Server (NTRS)
Oden, J. Tinsley; Fly, Gerald W.; Mahadevan, L.
1987-01-01
A hybrid stress finite element method is developed for accurate stress and vibration analysis of problems in linear anisotropic elasticity. A modified form of the Hellinger-Reissner principle is formulated for dynamic analysis and an algorithm for the determination of the anisotropic elastic and compliance constants from experimental data is developed. These schemes were implemented in a finite element program for static and dynamic analysis of linear anisotropic two dimensional elasticity problems. Specific numerical examples are considered to verify the accuracy of the hybrid stress approach and compare it with that of the standard displacement method, especially for highly anisotropic materials. It is that the hybrid stress approach gives much better results than the displacement method. Preliminary work on extensions of this method to three dimensional elasticity is discussed, and the stress shape functions necessary for this extension are included.
NASA Astrophysics Data System (ADS)
Chopra, Sahila; Kaur, Arshdeep; Gupta, Raj K.
2015-03-01
After a successful attempt to define and determine recently the compound nucleus (CN) fusion/ formation probability PCN within the dynamical cluster-decay model (DCM), we introduce and estimate here for the first time the survival probability Psurv of CN against fission, again within the DCM. Calculated as the dynamical fragmentation process, Psurv is defined as the ratio of the evaporation residue (ER) cross section σER and the sum of σER and fusion-fission (ff) cross section σff, the CN formation cross section σCN, where each contributing fragmentation cross section is determined in terms of its formation and barrier penetration probabilities P0 and P . In DCM, the deformations up to hexadecapole and "compact" orientations for both in-plane (coplanar) and out-of-plane (noncoplanar) configurations are allowed. Some 16 "hot" fusion reactions, forming a CN of mass number ACN˜100 to superheavy nuclei, are analyzed for various different nuclear interaction potentials, and the variation of Psurv on CN excitation energy E*, fissility parameter χ , CN mass ACN, and Coulomb parameter Z1Z2 is investigated. Interesting results are that three groups, namely, weakly fissioning, radioactive, and strongly fissioning superheavy nuclei, are identified with Psurv, respectively, ˜1 ,˜10-6 , and ˜10-10 . For the weakly fissioning group (100
Luth, Vera G.; /SLAC
2012-10-02
The following is an overview of the measurements of the CKM matrix elements |V{sub cb}| and |V{sub ub}| that are based on detailed studies of semileptonic B decays by the BABAR and Belle Collaborations and major advances in QCD calculations. In addition, a new and improved measurement of the ratios R(D{sup (*)}) = {Beta}({bar B} {yields} D{sup (*)}{tau}{sup -}{bar {nu}}{sub {tau}})/{Beta}({bar B} {yields} D{sup (*)}{ell}{sup -}{bar {nu}}{sub {ell}}) is presented. Here D{sup (*)} refers to a D or a D* meson and {ell} is either e or {mu}. The results, R(D) = 0.440 {+-} 0.058 {+-} 0.042 and R(D*) = 0.332 {+-} 0.024 {+-} 0.018, exceed the Standard Model expectations by 2.0{sigma} and 2.7{sigma}, respectively. Taken together, they disagree with these expectations at the 3.4{sigma} level. The excess of events cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.
Switch isotropic/anisotropic wettability via dual-scale rods
NASA Astrophysics Data System (ADS)
He, Yang; Jiang, Chengyu; Wang, Shengkun; Ma, Zhibo; Yuan, Weizheng
2014-10-01
It is the first time to demonstrate the comparison of isotropic/anisotropic wettability between dual-scale micro-nano-rods and single-scale micro-rods. Inspired by the natural structures of rice leaf, a series of micro-nano-rods and micro-rods with different geometric parameters were fabricated using micro-fabrication technology. Experimental measured apparent contact angles and advancing and receding contact angles from orthogonal orientations were characterized. The difference of contact angles from orthogonal orientation on dual-scale rods was much smaller than those on single-scale rods in both static and dynamic situation. It indicated that the dual-scale micro-nano-rods showed isotropic wettability, while single-scale micro-rods showed anisotropic wettability. The switch of isotropic/anisotropic wettability could be illustrated by different wetting state and contact line moving. It offers a facial way to switch isotropic/anisotropic wettability of the surface via dual-scale or single-scale structure.
Theoretical studies of anisotropic energy transport in TATB crystals
NASA Astrophysics Data System (ADS)
Kroonblawd, Matthew; Sewell, Thomas
2015-06-01
Anisotropic thermal transport properties were determined theoretically for single crystals of the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using molecular dynamics. TATB exhibits a graphitic-like layered packing structure with a two-dimensional hydrogen-bonding network within, but not between, the molecule-thick layers that comprise the crystal. Anisotropic thermal conductivity coefficients were determined for initially defect-free and defective TATB crystals at various temperatures and pressures, and direction-dependent relaxation of idealized hot spots was studied. The room temperature, atmospheric pressure thermal conductivity for TATB is predicted to be generally greater and more anisotropic than the thermal conductivities of other molecular explosives; conduction within the layers is at least 68% greater than conduction between them. The phonon mean free path length is predicted to be less than 1 nm. Decreases in thermal conductivity induced by molecular vacancy defects are also anisotropic and exhibit a linear dependence on defect density. Results from the hot-spot relaxation simulations were compared with and fit to an analytical solution for the one-dimensional continuum heat equation by treating the thermal diffusivity as a parameter. Validity of the continuum heat equation predictions for TATB is assessed for length scales below 20 nm.
Anisotropic 2D Materials for Tunable Hyperbolic Plasmonics.
Nemilentsau, Andrei; Low, Tony; Hanson, George
2016-02-12
Motivated by the recent emergence of a new class of anisotropic 2D materials, we examine their electromagnetic modes and demonstrate that a broad class of the materials can host highly directional hyperbolic plasmons. Their propagation direction can be manipulated on the spot by gate doping, enabling hyperbolic beam reflection, refraction, and bending. The realization of these natural 2D hyperbolic media opens up a new avenue in dynamic control of hyperbolic plasmons not possible in the 3D version.
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.
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.
NASA Astrophysics Data System (ADS)
Skrypnyk, T.
2017-08-01
We study the problem of separation of variables for classical integrable Hamiltonian systems governed by non-skew-symmetric non-dynamical so(3)\\otimes so(3) -valued elliptic r-matrices with spectral parameters. We consider several examples of such models, and perform separation of variables for classical anisotropic one- and two-spin Gaudin-type models in an external magnetic field, and for Jaynes-Cummings-Dicke-type models without the rotating wave approximation.
Hernandez, R.; Miller, W.H.; Moore, C.B. ); Polik, W.F. )
1993-07-15
A previously developed random matrix/transition state theory (RM/TST) model for the probability distribution of state-specific unimolecular decay rates has been generalized to incorporate total angular momentum conservation and other dynamical symmetries. The model is made into a predictive theory by using a semiclassical method to determine the transmission probabilities of a nonseparable rovibrational Hamiltonian at the transition state. The overall theory gives a good description of the state-specific rates for the D[sub 2]CO[r arrow]D[sub 2]+CO unimolecular decay; in particular, it describes the dependence of the distribution of rates on total angular momentum [ital J]. Comparison of the experimental values with results of the RM/TST theory suggests that there is mixing among the rovibrational states.
Gupta, Raj K.; Kumar, Rajesh; Singh, Dalip; Balasubramaniam, M.; Beck, C.
2005-01-01
The dynamical cluster-decay model (DCM) is developed further for the decay of hot and rotating compound nuclei (China) formed in light heavy-ion reactions. The model is worked out in terms of only one parameter, namely the neck-length parameter, which is related to the total kinetic energy TKE(T) or effective Q value Q{sub eff}(T) at temperature T of the hot CN and is defined in terms of the CN binding energy and ground-state binding energies of the emitted fragments. The emission of both the light particles (LP), with A{<=}4,Z{<=}2, as well as the complex intermediate mass fragments (IMF), with 42, is considered as the dynamical collective mass motion of preformed clusters through the barrier. Within the same dynamical model treatment, the LPs are shown to have different characteristics compared to those of the IMFs. The systematic variations of the LP emission cross section {sigma}{sub LP} and IMF emission cross section {sigma}{sub IMF} calculated from the present DCM match exactly the statistical fission model predictions. A nonstatistical dynamical description is developed for the first time for emission of light particles from hot and rotating CN. The model is applied to the decay of {sup 56}Ni* formed in the {sup 32}S+{sup 24}Mg reaction at two incident energies E{sub c.m.}=51.6 and 60.5 MeV. Both the IMFs and average TKE{sup lowbar} spectra are found to compare resonably well with the experimental data, favoring asymmetric mass distributions. The LPs' emission cross section is shown to depend strongly on the type of emitted particles and their multiplicities.
Marciano, W.J.
1983-01-01
Topics include minimal SU(5) predictions, gauge boson mediated proton decay, uncertainties in tau/sub p/, Higgs scalar effects, proton decay via Higgs scalars, supersymmetric SU(5), dimension 5 operators and proton decay, and Higgs scalars and proton decay. (WHK)
NASA Astrophysics Data System (ADS)
Singh, BirBikram; Kaur, Mandeep; Sharma, Manoj K.; Gupta, Raj K.
2015-01-01
The target-like C-yield in the decay of compound systems 32S* and 31P* formed in 20Ne+12C and 19F+12C reactions at E*CN=60 MeV, is studied for the contribution of fusion-fission (ff) decay cross section σff and the deep inelastic (DI) orbiting σorb from the compound nucleus (CN) and non-compound nucleus nCN processes, respectively. The calculations are performed using the collective clusterization of fragments within the dynamical cluster-decay model (DCM) of Gupta and collaborators. Besides studying the competition between ff and DI orbiting phenomenon in the C-yield of these systems, we exclusively investigate the preformation and barrier penetration probabilities P0 and P as a function of angular momentum ℓ values which subsequently affects the contributions of σff and σorb. For calculating the contribution of σff in the C-yield, we have added the contributions from all the minimized intermediate mass fragments (IMFs) for Z=6 in the calculated fragmentation potentials for 32S* (IMFs 11,12,13C are minimized) and for 31P* (IMFs 12,13C are minimized), while calculating subsequently, P0 and the P for these IMFs. The distribution of preformed clusters/fragments as a function of fragment mass visibly explore the nuclear structure effects for the C-yield in decay of these compound systems, wherein, it is shown to be more favoured in the decay of 31P* in comparison to 32S* decay. The contribution of σorb to the C-yield is calculated from P at different allowed ℓ-values (upto ℓmax and also P≤1) of the outgoing fragments (same as that in the entrance channel, i.e., P0=1). Though preliminary but useful results indicates the competition between the CN and nCN process in the C-yield for the compound system 32S* only while the decay of 31P* is of pure CN origin, as observed in the experimental study. The calculations are in good comparison with the available experimental data.
Modifying Moveout-Based Anisotropic Spreading Correction for Borehole Seismic Data
NASA Astrophysics Data System (ADS)
Tamimi, N.
2015-12-01
The higher signal-to-noise ratio of borehole seismic data compared to surface seismic data makes them suitable for amplitude-related analyses and reflection seismic imaging. However, sometimes removing undesirable effects from the amplitude information is necessary. Energy decay due to wavefront spreading (called geometrical spreading) is one of the effects that should be removed before amplitude analysis and imaging in exploration seismic, and it needs special considerations, where the subsurface medium is highly anisotropic. One of the successful surface seismic techniques to compensate for energy decay or amplitude distortion due to geometrical spreading is MASC (Moveout-Based Anisotropic Spreading Correction). However, this technique cannot be used for borehole seismic data easily and needs some modifications. Here, we modified this valuable technique for borehole seismic and applied it to a real field case study. The results show that the modified MASC technique can be applied to borehole seismic data easily with minimum subsurface velocity information.
Solutions to higher-order anisotropic parabolic equations in unbounded domains
NASA Astrophysics Data System (ADS)
Kozhevnikova, L. M.; Leont'ev, A. A.
2014-01-01
The paper is devoted to a certain class of doubly nonlinear higher-order anisotropic parabolic equations. Using Galerkin approximations it is proved that the first mixed problem with homogeneous Dirichlet boundary condition has a strong solution in the cylinder D=(0,\\infty)\\times\\Omega, where \\Omega\\subset R^n, n\\geq 3, is an unbounded domain. When the initial function has compact support the highest possible rate of decay of this solution as t\\to \\infty is found. An upper estimate characterizing the decay of the solution is established, which is close to the lower estimate if the domain is sufficiently 'narrow'. The same authors have previously obtained results of this type for second order anisotropic parabolic equations. Bibliography: 29 titles.
Solutions to higher-order anisotropic parabolic equations in unbounded domains
Kozhevnikova, L M; Leont'ev, A A
2014-01-31
The paper is devoted to a certain class of doubly nonlinear higher-order anisotropic parabolic equations. Using Galerkin approximations it is proved that the first mixed problem with homogeneous Dirichlet boundary condition has a strong solution in the cylinder D=(0,∞)×Ω, where Ω⊂R{sup n}, n≥3, is an unbounded domain. When the initial function has compact support the highest possible rate of decay of this solution as t→∞ is found. An upper estimate characterizing the decay of the solution is established, which is close to the lower estimate if the domain is sufficiently 'narrow'. The same authors have previously obtained results of this type for second order anisotropic parabolic equations. Bibliography: 29 titles.
Anisotropic thermal conduction with magnetic fields in galaxy clusters
NASA Astrophysics Data System (ADS)
Arth, Alexander; Dolag, Klaus; Beck, Alexander; Petkova, Margarita; Lesch, Harald
2015-08-01
Magnetic fields play an important role for the propagation and diffusion of charged particles, which are responsible for thermal conduction. In this poster, we present an implementation of thermal conduction including the anisotropic effects of magnetic fields for smoothed particle hydrodynamics (SPH). The anisotropic thermal conduction is mainly proceeding parallel to magnetic fields and suppressed perpendicular to the fields. We derive the SPH formalism for the anisotropic heat transport and solve the corresponding equation with an implicit conjugate gradient scheme. We discuss several issues of unphysical heat transport in the cases of extreme ansiotropies or unmagnetized regions and present possible numerical workarounds. We implement our algorithm into the cosmological simulation code GADGET and study its behaviour in several test cases. In general, we reproduce the analytical solutions of our idealised test problems, and obtain good results in cosmological simulations of galaxy cluster formations. Within galaxy clusters, the anisotropic conduction produces a net heat transport similar to an isotropic Spitzer conduction model with low efficiency. In contrast to isotropic conduction our new formalism allows small-scale structure in the temperature distribution to remain stable, because of their decoupling caused by magnetic field lines. Compared to observations, strong isotropic conduction leads to an oversmoothed temperature distribution within clusters, while the results obtained with anisotropic thermal conduction reproduce the observed temperature fluctuations well. A proper treatment of heat transport is crucial especially in the outskirts of clusters and also in high density regions. It's connection to the local dynamical state of the cluster also might contribute to the observed bimodal distribution of cool core and non cool core clusters. Our new scheme significantly advances the modelling of thermal conduction in numerical simulations and overall gives
Charmless B decays involving baryons
NASA Astrophysics Data System (ADS)
Gronau, Michael; Rosner, Jonathan L.
1988-02-01
Predictions are made for the fraction of B-meson decays involving specific final states of NN¯+nπ (n>=0), as functions of (a) decay dynamics, (b) models for multipion production, (c) the isospin of the final state, and (d) the ratio ||Vbu/Vbc|| of Kobayashi-Maskawa matrix elements. From recent observations of B+-->pp¯π+(+c.c.) and B0-->pp¯π+π- by the ARGUS Collaboration, it is concluded that ||Vbu/Vbc||>~0.08, similar to the ARGUS Collaboration's own estimate of 0.07. However, a more likely value for this ratio is near its present experimental upper limit. Predictions are made for further final states in NN¯+nπ and in other charmless B decays. We also comment briefly on prospects for observing CP violation in B-->NN¯+nπ.
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.
NASA Astrophysics Data System (ADS)
Munzarova, Helena; Plomerova, Jaroslava; Kissling, Edi
2015-04-01
Considering only isotropic wave propagation and neglecting anisotropy in teleseismic tomography studies is a simplification obviously incongruous with current understanding of the mantle-lithosphere plate dynamics. Furthermore, in solely isotropic high-resolution tomography results, potentially significant artefacts (i.e., amplitude and/or geometry distortions of 3D velocity heterogeneities) may result from such neglect. Therefore, we have undertaken to develop a code for anisotropic teleseismic tomography (AniTomo), which will allow us to invert the relative P-wave travel time residuals simultaneously for coupled isotropic-anisotropic P-wave velocity models of the upper mantle. To accomplish that, we have modified frequently-used isotropic teleseismic tomography code Telinv (e.g., Weiland et al., JGR, 1995; Lippitsch, JGR, 2003; Karousova et al., GJI, 2013). Apart from isotropic velocity heterogeneities, a weak hexagonal anisotropy is assumed as well to be responsible for the observed P-wave travel-time residuals. Moreover, no limitations to orientation of the symmetry axis are prescribed in the code. We allow a search for anisotropy oriented generally in 3D, which represents a unique approach among recent trials that otherwise incorporate only azimuthal anisotopy into the body-wave tomography. The presented code for retrieving anisotropy in 3D thus enables its direct applications to datasets from tectonically diverse regions. In this contribution, we outline the theoretical background of the AniTomo anisotropic tomography code. We parameterize the mantle lithosphere and asthenosphere with an orthogonal grid of nodes with various values of isotropic velocities, as well as of strength and orientation of anisotropy in 3D, which is defined by azimuth and inclination of either fast or slow symmetry axis of the hexagonal approximation of the media. Careful testing of the new code on synthetics, concentrating on code functionality, strength and weaknesses, is a
Predicting signatures of anisotropic resonance energy transfer in dye-functionalized nanoparticles.
Gil, Gabriel; Corni, Stefano; Delgado, Alain; Bertoni, Andrea; Goldoni, Guido
2016-11-13
Resonance energy transfer (RET) is an inherently anisotropic process. Even the simplest, well-known Förster theory, based on the transition dipole-dipole coupling, implicitly incorporates the anisotropic character of RET. In this theoretical work, we study possible signatures of the fundamental anisotropic character of RET in hybrid nanomaterials composed of a semiconductor nanoparticle (NP) decorated with molecular dyes. In particular, by means of a realistic kinetic model, we show that the analysis of the dye photoluminescence difference for orthogonal input polarizations reveals the anisotropic character of the dye-NP RET which arises from the intrinsic anisotropy of the NP lattice. In a prototypical core/shell wurtzite CdSe/ZnS NP functionalized with cyanine dyes (Cy3B), this difference is predicted to be as large as 75% and it is strongly dependent in amplitude and sign on the dye-NP distance. We account for all the possible RET processes within the system, together with competing decay pathways in the separate segments. In addition, we show that the anisotropic signature of RET is persistent up to a large number of dyes per NP.
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.
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.
On anisotropic versions of three-dimensional pentamode metamaterials
NASA Astrophysics Data System (ADS)
Kadic, Muamer; Bückmann, Tiemo; Schittny, Robert; Wegener, Martin
2013-02-01
Pentamode materials are artificial solids with elastic properties that approximate those of isotropic liquids. The corresponding three-dimensional mechanical metamaterials or ‘meta-liquids’ have recently been fabricated. In contrast to normal liquids, anisotropic meta-liquids are also possible—a prerequisite for realizing many of the envisioned transformation-elastodynamics architectures. Here, we study several possibilities theoretically for introducing intentional anisotropy into three-dimensional pentamode metamaterials. In static continuum mechanics, the transition from anti-auxetic pentamode materials to auxetics is possible. Near this transition, in the dynamic case, approximately uniaxial versions of pentamode metamaterials deliver anisotropic longitudinal-wave phase velocities different by nearly a factor of 10 for realistically accessible microstructure parameters.
A crossover in anisotropic nanomechanochemistry of van der Waals crystals
Shimamura, Kohei; Misawa, Masaaki; Li, Ying; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Shimojo, Fuyuki
2015-12-07
In nanoscale mechanochemistry, mechanical forces selectively break covalent bonds to essentially control chemical reactions. An archetype is anisotropic detonation of layered energetic molecular crystals bonded by van der Waals (vdW) interactions. Here, quantum molecular dynamics simulations reveal a crossover of anisotropic nanomechanochemistry of vdW crystal. Within 10{sup −13} s from the passage of shock front, lateral collision produces NO{sub 2} via twisting and bending of nitro-groups and the resulting inverse Jahn-Teller effect, which is mediated by strong intra-layer hydrogen bonds. Subsequently, as we transition from heterogeneous to homogeneous mechanochemical regimes around 10{sup −12} s, shock normal to multilayers becomes more reactive, producing H{sub 2}O assisted by inter-layer N-N bond formation. These time-resolved results provide much needed atomistic understanding of nanomechanochemistry that underlies a wider range of technologies.
Driven Anisotropic Diffusion at Boundaries: Noise Rectification and Particle Sorting
NASA Astrophysics Data System (ADS)
Bo, Stefano; Eichhorn, Ralf
2017-08-01
We study the diffusive dynamics of a Brownian particle in the proximity of a flat surface under nonequilibrium conditions, which are created by an anisotropic thermal environment with different temperatures being active along distinct spatial directions. By presenting the exact time-dependent solution of the Fokker-Planck equation for this problem, we demonstrate that the interplay between anisotropic diffusion and hard-core interaction with the plain wall rectifies the thermal fluctuations and induces directed particle transport parallel to the surface, without any deterministic forces being applied in that direction. Based on current micromanipulation technologies, we suggest a concrete experimental setup to observe this novel noise-induced transport mechanism. We furthermore show that it is sensitive to particle characteristics, such that this setup can be used for sorting particles of different sizes.
Kushner, Sidney R
2007-04-01
This chapter discusses several topics relating to the mechanisms of mRNA decay. These topics include the following: important physical properties of mRNA molecules that can alter their stability; methods for determining mRNA half-lives; the genetics and biochemistry of proteins and enzymes involved in mRNA decay; posttranscriptional modification of mRNAs; the cellular location of the mRNA decay apparatus; regulation of mRNA decay; the relationships among mRNA decay, tRNA maturation, and ribosomal RNA processing; and biochemical models for mRNA decay. Escherichia coli has multiple pathways for ensuring the effective decay of mRNAs and mRNA decay is closely linked to the cell's overall RNA metabolism. Finally, the chapter highlights important unanswered questions regarding both the mechanism and importance of mRNA decay.
QCD in heavy quark production and decay
Wiss, J.
1997-06-01
The author discusses how QCD is used to understand the physics of heavy quark production and decay dynamics. His discussion of production dynamics primarily concentrates on charm photoproduction data which are compared to perturbative QCD calculations which incorporate fragmentation effects. He begins his discussion of heavy quark decay by reviewing data on charm and beauty lifetimes. Present data on fully leptonic and semileptonic charm decay are then reviewed. Measurements of the hadronic weak current form factors are compared to the nonperturbative QCD-based predictions of Lattice Gauge Theories. He next discusses polarization phenomena present in charmed baryon decay. Heavy Quark Effective Theory predicts that the daughter baryon will recoil from the charmed parent with nearly 100% left-handed polarization, which is in excellent agreement with present data. He concludes by discussing nonleptonic charm decay which is traditionally analyzed in a factorization framework applicable to two-body and quasi-two-body nonleptonic decays. This discussion emphasizes the important role of final state interactions in influencing both the observed decay width of various two-body final states as well as modifying the interference between interfering resonance channels which contribute to specific multibody decays. 50 refs., 77 figs.
Microscopic description of the anisotropy in alpha decay
Delion, D.S. ); Insolia, A. ); Liotta, R.J. )
1994-06-01
A microscopic description of alpha decay of odd mass nuclei is given for axially deformed nuclei. Realistic mean field+pairing residual interaction in a very large single particle basis is used. Systematics for At and Rn isotopes, as well as for [sup 221]Fr, are given. A pronounced anisotropic emission of alpha particles at low temperatures is predicted as a function of deformation for the At and Rn isotopes. This shows that alpha decay is an excellent tool to probe intrinsic deformations in nuclei.
Decay of oscillating universes
NASA Astrophysics Data System (ADS)
Mithani, Audrey Todhunter
2016-08-01
It has been suggested by Ellis et al that the universe could be eternal in the past, without beginning. In their model, the "emergent universe'' exists forever in the past, in an "eternal'' phase before inflation begins. We will show that in general, such an "eternal'' phase is not possible, because of an instability due to quantum tunneling. One candidate model, the "simple harmonic universe'' has been shown by Graham et al to be perturbatively stable; we find that it is unstable with respect to quantum tunneling. We also investigate the stability of a distinct oscillating model in loop quantum cosmology with respect to small perturbations and to quantum collapse. We find that the model has perturbatively stable and unstable solutions, with both types of solutions occupying significant regions of the parameter space. All solutions are unstable with respect to collapse by quantum tunneling to zero size. In addition, we investigate the effect of vacuum corrections, due to the trace anomaly and the Casimir effect, on the stability of an oscillating universe with respect to decay by tunneling to the singularity. We find that these corrections do not generally stabilize an oscillating universe. Finally, we determine the decay rate of the oscillating universe. Although the wave function of the universe lacks explicit time dependence in canonical quantum cosmology, time evolution may be present implicitly through the semiclassical superspace variables, which themselves depend on time in classical dynamics. Here, we apply this approach to the simple harmonic universe, by extending the model to include a massless, minimally coupled scalar field φ which has little effect on the dynamics but can play the role of a "clock''.
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.
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.
A TDPAC study of static and dynamic magnetic behaviour.
Webb, T A; Ryan, D H
2013-07-31
The a-FexHf100-x system is used to explore the application of TDPAC (the time differential perturbed γ-γ angular correlation technique) to non-trivial anisotropic magnetic relaxation. The effect of fluctuations in this system is primarily to cause a decay of the zero-frequency component, which is characterized by the phenomenological decay rate λ. The zero-field magnetic phase diagram, constructed from both static and dynamic features of the data, and the temperature dependence of λ are both fully consistent with the physics of partial bond frustration. The results demonstrate that the magnetic fluctuations are meaningfully characterized by simple spectrum features, and are not obscured by large static fields or severe disorder.
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.
ANISOTROPY LENGTHENS THE DECAY TIME OF TURBULENCE IN MOLECULAR CLOUDS
Hansen, Charles E.; McKee, Christopher F.; Klein, Richard I.
2011-09-01
The decay of isothermal turbulence with velocity anisotropy is investigated using computational simulations and synthetic observations. We decompose the turbulence into isotropic and anisotropic components with total velocity dispersions {sigma}{sub iso} and {sigma}{sub ani}, respectively. We find that the decay rate of the turbulence depends on the crossing time of the isotropic component only. A cloud of size L with significant anisotropy in its turbulence has a dissipation time, t{sub diss} = L/(2{sigma}{sub iso}). This translates into turbulent energy decay rates on the cloud scale that can be much lower for anisotropic turbulence than for isotropic turbulence. To help future observations determine whether observed molecular clouds have the level of anisotropy required to maintain the observed level of turbulence over their lifetimes, we performed a principal component analysis on our simulated clouds. Even with projection effects washing out the anisotropic signal, there is a measurable difference in the axis-constrained principal component analysis performed in directions parallel and perpendicular to the direction of maximum velocity dispersion. When this relative difference, {psi}, is 0.1, there is enough anisotropy for the dissipation time to triple the expected isotropic value. We provide a fit for converting {psi} into an estimate for the dissipation time, t{sub diss}.
Bloch equations for anisotropic paramagnetic centers with spin of 1/2.
Maryasov, Alexander G; Bowman, Michael K
2013-08-01
The Bloch equations are an invaluable tool in magnetic resonance for describing the dynamics of isotropic spin systems. However, when the Bloch equations are reformulated for anisotropic spin systems, much of their utility is lost because the spin evolution they describe is not physically observable. A set of Bloch-like equations are derived for these anisotropic systems in terms of the magnetic moment which is the physical property measured in magnetic resonance and other experiments. The equations describe the dynamics of the magnetic moment including relaxation and only contain parameters that are experimentally measurable.
Hamiltonian of mean force and a damped harmonic oscillator in an anisotropic medium
NASA Astrophysics Data System (ADS)
Jafari, Marjan; Kheirandish, Fardin
2017-01-01
The quantum dynamics of a damped harmonic oscillator is investigated in the presence of an anisotropic heat bath. The medium is modeled by a continuum of three dimensional harmonic oscillators and anisotropic coupling is treated by introducing tensor coupling functions. Starting from a classical Lagrangian, the total system is quantized in the framework of the canonical quantization. Following the Fano technique, the Hamiltonian of the system is diagonalized in terms of creation and annihilation operators that are linear combinations of the basic dynamical variables. Using the diagonalized Hamiltonian, the mean force internal energy, free energy and entropy of the damped oscillator are calculated.
Theory of triplon dynamics in the quantum magnet BiCu2PO6
NASA Astrophysics Data System (ADS)
Hwang, Kyusung; Kim, Yong Baek
2016-06-01
We provide a theory of triplon dynamics in the valence bond solid ground state of the coupled spin ladders modeled for BiCu2PO6 . Utilizing the recent high-quality neutron scattering data [K. W. Plumb et al., Nat. Phys. 12, 224 (2016), 10.1038/nphys3566] as guides and a theory of interacting triplons via the bond operator formulation, we determine a minimal spin Hamiltonian for this system. It is shown that the splitting of the low-energy triplon modes and the peculiar magnetic field dependence of the triplon dispersions can be explained by including substantial Dzyaloshinskii-Moriya and symmetric anisotropic spin interactions. Taking into account the interactions between triplons and the decay of the triplons to the two-triplon continuum via anisotropic spin interactions, we provide a theoretical picture that can be used to understand the main features of the recent neutron scattering experimental data.
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.
Hosseini, Eghbal A.; Nguyen, Katrina P.; Joiner, Wilsaan M.
2017-01-01
Motor adaptation paradigms provide a quantitative method to study short-term modification of motor commands. Despite the growing understanding of the role motion states (e.g., velocity) play in this form of motor learning, there is little information on the relative stability of memories based on these movement characteristics, especially in comparison to the initial adaptation. Here, we trained subjects to make reaching movements perturbed by force patterns dependent upon either limb position or velocity. Following training, subjects were exposed to a series of error-clamp trials to measure the temporal characteristics of the feedforward motor output during the decay of learning. The compensatory force patterns were largely based on the perturbation kinematic (e.g., velocity), but also showed a small contribution from the other motion kinematic (e.g., position). However, the velocity contribution in response to the position-based perturbation decayed at a slower rate than the position contribution to velocity-based training, suggesting a difference in stability. Next, we modified a previous model of motor adaptation to reflect this difference and simulated the behavior for different learning goals. We were interested in the stability of learning when the perturbations were based on different combinations of limb position or velocity that subsequently resulted in biased amounts of motion-based learning. We trained additional subjects on these combined motion-state perturbations and confirmed the predictions of the model. Specifically, we show that (1) there is a significant separation between the observed gain-space trajectories for the learning and decay of adaptation and (2) for combined motion-state perturbations, the gain associated to changes in limb position decayed at a faster rate than the velocity-dependent gain, even when the position-dependent gain at the end of training was significantly greater. Collectively, these results suggest that the state
Hosseini, Eghbal A; Nguyen, Katrina P; Joiner, Wilsaan M
2017-05-01
Motor adaptation paradigms provide a quantitative method to study short-term modification of motor commands. Despite the growing understanding of the role motion states (e.g., velocity) play in this form of motor learning, there is little information on the relative stability of memories based on these movement characteristics, especially in comparison to the initial adaptation. Here, we trained subjects to make reaching movements perturbed by force patterns dependent upon either limb position or velocity. Following training, subjects were exposed to a series of error-clamp trials to measure the temporal characteristics of the feedforward motor output during the decay of learning. The compensatory force patterns were largely based on the perturbation kinematic (e.g., velocity), but also showed a small contribution from the other motion kinematic (e.g., position). However, the velocity contribution in response to the position-based perturbation decayed at a slower rate than the position contribution to velocity-based training, suggesting a difference in stability. Next, we modified a previous model of motor adaptation to reflect this difference and simulated the behavior for different learning goals. We were interested in the stability of learning when the perturbations were based on different combinations of limb position or velocity that subsequently resulted in biased amounts of motion-based learning. We trained additional subjects on these combined motion-state perturbations and confirmed the predictions of the model. Specifically, we show that (1) there is a significant separation between the observed gain-space trajectories for the learning and decay of adaptation and (2) for combined motion-state perturbations, the gain associated to changes in limb position decayed at a faster rate than the velocity-dependent gain, even when the position-dependent gain at the end of training was significantly greater. Collectively, these results suggest that the state
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
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.
Modeling the decay of energy containing eddies: A source of solar wind heating
NASA Technical Reports Server (NTRS)
Hossain, M.; Gray, P. C.; Pontius, D. H.; Matthaeus, W. H.; Oughton, S.
1995-01-01
To understand the solar wind heating and acceleration mechanisms one needs to understand the decay of energy containing eddies. With this goal in mind, attempts have been made to extend the fluid dynamic phenomenology of large scale quasi-equilibrium to the case of magnetohydrodynamics. Matthaeus et al. have proposed a model for the inhomogeneous transport and decay of five mean variables, namely, two mean square Elsasser variables z(exp 2) (sub +/-) their correlation lengths, and the difference between the kinetic and magnetic energies. We test the validity of this model in the simplified case of homogeneous turbulence simulated in a periodic box. We propose a class of models and show that they may fit the simulation satisfactorily. Analytic solutions of this class of model reveal their inherent properties and demonstrate the difficulties associated with finite cross helicity. It is noted that adjustments are required to make the simplest models, which are based upon isotropic turbulence, scale properly with respect to the strength of the mean magnetic field. This can be interpreted as due to anisotropic turbulence, which can be modelled by simple parameterization in the phenomenology.
Modeling the decay of energy containing eddies: A source of solar wind heating
NASA Technical Reports Server (NTRS)
Hossain, M.; Gray, P. C.; Pontius, D. H.; Matthaeus, W. H.; Oughton, S.
1995-01-01
To understand the solar wind heating and acceleration mechanisms one needs to understand the decay of energy containing eddies. With this goal in mind, attempts have been made to extend the fluid dynamic phenomenology of large scale quasi-equilibrium to the case of magnetohydrodynamics. Matthaeus et al. have proposed a model for the inhomogeneous transport and decay of five mean variables, namely, two mean square Elsasser variables z(exp 2) (sub +/-) their correlation lengths, and the difference between the kinetic and magnetic energies. We test the validity of this model in the simplified case of homogeneous turbulence simulated in a periodic box. We propose a class of models and show that they may fit the simulation satisfactorily. Analytic solutions of this class of model reveal their inherent properties and demonstrate the difficulties associated with finite cross helicity. It is noted that adjustments are required to make the simplest models, which are based upon isotropic turbulence, scale properly with respect to the strength of the mean magnetic field. This can be interpreted as due to anisotropic turbulence, which can be modelled by simple parameterization in the phenomenology.
NASA Astrophysics Data System (ADS)
Chistov, R.
2016-02-01
In this talk the decays of B-mesons into baryons are discussed. Large mass of B-meson makes possible the decays of the type B → baryon (+mesons). Experimental observations and measurements of these decays at B-factories Belle and BaBar have stimulate the development of theoretical models in this field. We briefly review the experimental results together with the current theoretical models which describe baryonic B decays.
Sun, Chung-Huan J; Connelly, Kerrin; Nogueira, Raul G; Glenn, Brenda A; Zimmermann, Susan; Anda, Kim; Camp, Deborah; Gaunt, Susan; Pallard, Herma; Eckenroth, Michele; Frankel, Michael R; Belagaje, Samir R; Anderson, Aaron M; Nahab, Fadi; Yepes, Manuel; Gupta, Rishi
2015-01-01
Pretreatment Alberta Stroke Program Early CT Scores (ASPECTS) is associated with clinical outcomes. The rate of decline between subsequent images, however, may be more predictive of outcomes as it integrates time and physiology. A cohort of patients transferred from six primary stroke centers and treated with intra-arterial therapy (IAT) was retrospectively studied. Absolute ASPECTS decay was defined as ((ASPECTS First CT-ASPECTS Second CT)/hours elapsed between images). A logistic regression model was performed to determine if the rate of ASPECTS decay predicted good outcomes at 90 days (modified Rankin Scale score of 0-2). 106 patients with a mean age of 66±14 years and a median National Institutes of Health Stroke Scale score of 19 (IQR 15-23) were analyzed. Median time between initial CT at the outside hospital to repeat CT at our facility was 2.7 h (IQR 2.0-3.6). Patients with good outcomes had lower rates of absolute ASPECTS decay compared with those who did not (0.14±0.23 score/h vs 0.49±0.39 score/h; p<0.001). In multivariable modeling, the absolute rate of ASPECTS decay (OR 0.043; 95% CI 0.004 to 0.471; p=0.01) was a stronger predictor of good patient outcome than static pretreatment ASPECTS obtained before IAT (OR 0.64; 95% CI 0.38 to 1.04; p=0.075). In practical terms, every 1 unit increase in ASPECTS decline per hour correlates with a 23-fold lower probability of a good outcome. Patients with faster rates of ASPECTS decay during inter-facility transfers are associated with worse clinical outcomes. This value may reflect the rate of physiological infarct expansion and thus serve as a tool in patient selection for IAT. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
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 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.
Adaptive time-step with anisotropic meshing for incompressible flows
NASA Astrophysics Data System (ADS)
Coupez, T.; Jannoun, G.; Nassif, N.; Nguyen, H. C.; Digonnet, H.; Hachem, E.
2013-05-01
This paper presents a method of combining anisotropic mesh adaptation and adaptive time-stepping for Computational Fluid Dynamics (CFD). First, we recall important features of the anisotropic meshing approach using a posteriori estimates relying on the length distribution tensor approach and the associated edge based error analysis. Then we extend the proposed technique to contain adaptive time advancing based on a newly developed time error estimator. The objective of this paper is to show that the combination of time and space anisotropic adaptations with highly stretched elements can be used to compute high Reynolds number flows within reasonable computational and storage costs. In particular, it will be shown that boundary layers, flow detachments and all vortices are well captured automatically by the mesh. The time-step is controlled by the interpolation error and preserves the accuracy of the mesh adapted solution. A Variational MultiScale (VMS) method is employed for the discretization of the Navier-Stokes equations. Numerical solutions of some benchmark problems demonstrate the applicability of the proposed space-time error estimator. An important feature of the proposed method is its conceptual and computational simplicity as it only requires from the user a number of nodes according to which the mesh and the time-steps are automatically adapted.
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
Zonal flows in tokamaks with anisotropic pressure
Ren, Haijun
2014-04-15
Zonal flows (ZFs) in a tokamak plasma with anisotropic pressure are investigated. The dynamics of perpendicular and parallel pressures are determined by the Chew-Goldberger-Low double equations and low-β condition is adopted, where β is the ratio of plasma pressure to the magnetic field pressure. The dispersion relation is analytically derived and illustrates two branches of ZFs. The low frequency zonal flow (LFZF) branch becomes unstable when χ, the ratio of the perpendicular pressure to the parallel one, is greater than a threshold value χ{sub c}, which is about 3.8. In the stable region, its frequency increases first and then decreases with increasing χ. For χ = 1, the frequency of LFZF agrees well with the experimental observation. For the instability, the growth rate of LFZF increases with χ. The geodesic acoustic mode branch is shown to be always stable with a frequency increasing with χ. The safety factor is shown to diminish the frequencies of both branches or the growth rate of LFZF.
P wave anisotropic tomography of the Alps
NASA Astrophysics Data System (ADS)
Hua, Yuanyuan; Zhao, Dapeng; Xu, Yixian
2017-06-01
The first tomographic images of P wave azimuthal and radial anisotropies in the crust and upper mantle beneath the Alps are determined by joint inversions of arrival time data of local earthquakes and teleseismic events. Our results show the south dipping European plate with a high-velocity (high-V) anomaly beneath the western central Alps and the north dipping Adriatic plate with a high-V anomaly beneath the Eastern Alps, indicating that the subduction polarity changes along the strike of the Alps. The P wave azimuthal anisotropy is characterized by mountain chain-parallel fast-velocity directions (FVDs) in the western central Alps and NE-SW FVDs in the Eastern Alps, which may be caused by mantle flow induced by the slab subductions. Our results reveal a negative radial anisotropy (i.e., Vph < Vpv) within the subducting slabs and a positive radial anisotropy (i.e., Vph > Vpv) in the low-velocity mantle wedge, which may reflect the subvertical plate subduction and its induced mantle flow. The results of anisotropic tomography provide important new information on the complex mantle structure and dynamics of the Alps and adjacent regions.
Zonal flows in tokamaks with anisotropic pressure
NASA Astrophysics Data System (ADS)
Ren, Haijun
2014-04-01
Zonal flows (ZFs) in a tokamak plasma with anisotropic pressure are investigated. The dynamics of perpendicular and parallel pressures are determined by the Chew-Goldberger-Low double equations and low-β condition is adopted, where β is the ratio of plasma pressure to the magnetic field pressure. The dispersion relation is analytically derived and illustrates two branches of ZFs. The low frequency zonal flow (LFZF) branch becomes unstable when χ, the ratio of the perpendicular pressure to the parallel one, is greater than a threshold value χc, which is about 3.8. In the stable region, its frequency increases first and then decreases with increasing χ. For χ = 1, the frequency of LFZF agrees well with the experimental observation. For the instability, the growth rate of LFZF increases with χ. The geodesic acoustic mode branch is shown to be always stable with a frequency increasing with χ. The safety factor is shown to diminish the frequencies of both branches or the growth rate of LFZF.
Decay of correlation for random intermittent maps
NASA Astrophysics Data System (ADS)
Bahsoun, Wael; Bose, Christopher; Duan, Yuejiao
2014-07-01
We study a class of random transformations built over finitely many intermittent maps sharing a common indifferent fixed point. Using a Young-tower technique, we show that the map with the fastest relaxation rate dominates the asymptotics. In particular, we prove that the rate of correlation decay for the annealed dynamics of the random map is the same as the sharp rate of correlation decay for the map with the fastest relaxation rate.
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.
Low-frequency isotropic and anisotropic Raman spectra of aromatic liquids.
Heisler, Ismael A; Meech, Stephen R
2010-05-07
The Raman spectra below 300 wavenumbers of six different aromatic molecular liquids have been measured with a time and polarization resolved optical Kerr effect technique. The isotropic and anisotropic contributions were determined to yield the complete third order response, and thus a more detailed description of the microscopic liquid dynamics. The anisotropic contributions accurately reproduced previously published results. Both the isotropic and anisotropic Raman spectral densities shift toward lower frequencies with decreasing molecular weights. The first moment of the isotropic spectral densities scales linearly with the inverse square root of the molecular weight, which is consistent with interaction-induced dynamics in these liquids being driven mainly by motions with a translational character. Also, the isotropic spectral densities could be fit to a single Bucaro-Litovitz function. The exponent delta of this function increases monotonically with the inverse square root of the molecular weight. A possible physical origin of this behavior is discussed.
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.
Sancho, Pedro; Plaja, Luis
2011-06-15
T. Tanabe et al. [Phys. Rev. A 82, 040101(R) (2010)] have experimentally demonstrated that the emission properties of unstable atoms in entangled and product states are different. The authors define an apparent decay time as a fitting parameter which falls below the lifetime of the single atom for entangled pairs. We argue that their results about coincidence time spectra are correct, but those concerning lifetimes cannot be considered conclusive because they assume the emission of photons by the two atoms to be independent processes, a doubtful hypothesis for entangled states. We suggest an improved evaluation of the lifetimes based on a rigorous approach, which demands some modifications of the experimental procedure.
Quantum interference in a single anisotropic quantum dot near hyperbolic metamaterials.
Sun, Lu; Jiang, Chun
2016-04-04
We theoretically demonstrate an anisotropic quantum vacuum created by a judiciously designed hyperbolic metamaterial. An electric dipole located nearby shows strong orientation dependence in the decay rate. With a proper arrangement of the ellipsoid-shaped CdSe/ZnSe quantum dot relative to the Ag/TiO_{2} metamaterial, the anisotropies of quantum vacuum and quantum dot are harnessed to achieve an extraordinary quantum interference between radiative decay channels of orthogonal transitions. The ratio between cross damping term and spontaneous decay rate, Γ_{ij}/Γ_{ii}, which never exceeds unity in previously reported works reaches 1.04 in our numerical results. The corresponding evolution of excited state population in quantum dot is also dramatically modified.
Ferroelectric control of anisotropic damping in multiferroic tunnel junctions
NASA Astrophysics Data System (ADS)
Wang, Yan; Zhang, Ning; Berakdar, Jamal; Jia, Chenglong
2015-10-01
The magnetoelectric effect on nonlocal magnetization dynamics is theoretically investigated in normal-metal/ferroelectric-insulator/ferromagnetic tunnel junctions. In addition to the Rashba spin-orbit interaction (SOI) originating from loss of parity symmetry at the interfaces, the topology of interfacial spiral spins triggered by ferroelectric polarization acts with an effective SOI that is electrically controllable. These spin-dependent interactions result in an anisotropic Gilbert damping with C2 v symmetry. The findings are of a direct relevance for the utilization of composite multiferroics for devices that rely on electrically controlled magnetic switching.
Barkhausen avalanches in anisotropic ferromagnets with 180 degrees domain walls
Tadic; Nowak
2000-04-01
We show that Barkhausen noise in two-dimensional disordered ferromagnets with extended domain walls is characterized by the avalanche size exponent tau(s)=1.54 at low disorder. With increasing disorder the characteristic domain size is reduced relative to the system size due to nucleation of new domains and a dynamic phase transition occurs to the scaling behavior with tau(s)=1.30. The exponents decrease at finite driving rate. The results agree with recently observed behavior in amorphous Metglas and Fe-Co-B ribbons when the applied anisotropic stress is varied.
Bottomonia suppression in an anisotropic quark-gluon plasma
NASA Astrophysics Data System (ADS)
Ryblewski, Radoslaw
2017-03-01
A brief review of recent studies on suppression of bottomonia in an anisotropic quark-gluon plasma created in heavy-ion collisions at the LHC is presented. A reasonable agreement between the model predictions for the inclusive RAA suppression factor and the preliminary CMS experimental data is found. The values of the shear viscosity to the entropy density ratio extracted from the comparison with the data lie between one and two times the gauge/gravity duality lower bound. These values agree very well with the fluid dynamical fits to the light hadron correlation data and confirm that the quark-gluon plasma is a nearly-perfect fluid.
Two-flavor QCD thermodynamics using anisotropic lattices
NASA Astrophysics Data System (ADS)
Levkova, Ludmila; Manke, Thomas; Mawhinney, Robert
2006-04-01
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 two flavors of dynamical staggered fermions, where all bare parameters and the renormalized anisotropy are kept constant and the temperature is changed in small steps by varying only the number of time slices. Including results from zero-temperature scale-setting simulations, which determine the Karsch coefficients, allows for the calculation of the equation of state at finite temperatures.
Anisotropic Scale Invariance Investigation of Drainage Areas Via Remotely Sensed Data
NASA Astrophysics Data System (ADS)
Beaulieu, A.; Gaonac'h, H.; Lovejoy, S.
Spatial and temporal scale invariance investigation is now widespread in geophysical fields and reveals in most cases the existence of scaling or multiscaling behaviour over a large range of scales. However, not much attention is being paid to the anisotropy present in the analyzed geological and geophysical fields while self-similarity is as- sumed most of the time. Theory and models omitting such anisotropy do not take appropriately in consideration the anisotropic dynamics of these natural processes. However, anisotropy is a common characteristics of geophysical dynamics present in the oceans, atmosphere and earth interior and surface. It often implies differential strat- ification and rotation when describing the texture and morphology of the phenomenon scale by scale. In order to account for scaling anisotropy, the formalism of generalized scale invariance (GSI) was developed. Investigation of remotely sensed images (Land- sat, Aster and ERS-1) over drainage areas such as in Ethiopia is conducted to assess the importance of anisotropic scale invariance between eroded (highly anisotropic) and non-eroded (nearly isotropic) areas. The various spectral regions covered by these different satellite images reveal distinct anisotropic intrinsic characteristics of the re- gions (topography, chemical composition, structural features) which need to be ana- lyzed scale by scale. Multifractal parameters are reconsidered in this new anisotropic framework.
Controlling Structural Anisotropy of Anisotropic 2D Layers in Pseudo-1D/2D Material Heterojunctions.
Chen, Bin; Wu, Kedi; Suslu, Aslihan; Yang, Sijie; Cai, Hui; Yano, Aliya; Soignard, Emmanuel; Aoki, Toshihiro; March, Katia; Shen, Yuxia; Tongay, Sefaattin
2017-07-10
Chemical vapor deposition and growth dynamics of highly anisotropic 2D lateral heterojunctions between pseudo-1D ReS2 and isotropic WS2 monolayers are reported for the first time. Constituent ReS2 and WS2 layers have vastly different atomic structure, crystallizing in anisotropic 1T' and isotropic 2H phases, respectively. Through high-resolution scanning transmission electron microscopy, electron energy loss spectroscopy, and angle-resolved Raman spectroscopy, this study is able to provide the very first atomic look at intimate interfaces between these dissimilar 2D materials. Surprisingly, the results reveal that ReS2 lateral heterojunctions to WS2 produce well-oriented (highly anisotropic) Re-chains perpendicular to WS2 edges. When vertically stacked, Re-chains orient themselves along the WS2 zigzag direction, and consequently, Re-chains exhibit six-fold rotation, resulting in loss of macroscopic scale anisotropy. The degree of anisotropy of ReS2 on WS2 largely depends on the domain size, and decreases for increasing domain size due to randomization of Re-chains and formation of ReS2 subdomains. Present work establishes the growth dynamics of atomic junctions between novel anisotropic/isotropic 2D materials, and overall results mark the very first demonstration of control over anisotropy direction, which is a significant leap forward for large-scale nanomanufacturing of anisotropic systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Albright, B. J.; Yin, L.; Bowers, K. J.; ...
2016-03-04
Two- and three-dimensional particle-in-cell simulations of stimulated Brillouin scattering(SBS) in laser speckle geometry have been analyzed to evaluate the relative importance of competing nonlinear processes in the evolution and saturation of SBS. It is found that ion-trapping-induced wavefront bowing and breakup of ion acoustic waves(IAW) and the associated side-loss of trapped ions dominate electron-trapping-induced IAW wavefront bowing and breakup, as well as the two-ion-wave decay instability over a range of ZTe/Ti conditions and incident laser intensities. In the simulations, the latter instability does not govern the nonlinear saturation of SBS; however, evidence of two-ion-wave decay is seen, appearing as amore » modulation of the ion acoustic wavefronts. This modulation is periodic in the laser polarization plane, anti-symmetric across the speckle axis, and of a wavenumber matching that of the incident laser pulse. Furthermore, a simple analytic model is provided for how spatial “imprinting” from a high frequency inhomogeneity (in this case, the density modulation from the laser) in an unstable system with continuum eigenmodes can selectively amplify modes with wavenumbers that match that of the inhomogeneity.« less
NASA Astrophysics Data System (ADS)
Liu, Jing; Sun, Yang; Qi, Jinyi; Marcu, Laura
2012-02-01
We report a novel method for estimating fluorescence impulse response function (fIRF) from noise-corrupted time-domain fluorescence measurements of biological tissue. This method is based on the use of high-order Laguerre basis functions and a constrained least-squares approach that addresses the problem of overfitting due to increased model complexity. The new method was extensively evaluated on fluorescence data from simulation, fluorescent standard dyes, ex vivo tissue samples of atherosclerotic plaques and in vivo oral carcinoma. Current results demonstrate that this method allows for rapid and accurate deconvolution of multiple channel fluorescence decays without adaptively adjusting the Laguerre scale parameter. The appropriate choice of the scale parameter is essential for accurate estimation of the fIRF. The method described here is anticipated to play an important role in the development of computational techniques for real-time analysis of time-resolved fluorescence data from biological tissues and to support the advancement of fluorescence lifetime instrumentation for biomedical diagnostics by providing a means for on-line robust analysis of fluorescence decay.
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
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.
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.
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
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.
Study of dynamics of D0→K-e+νe and D0→π-e+νe decays
NASA Astrophysics Data System (ADS)
Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Bai, J. Z.; Ferroli, R. Baldini; Ban, Y.; Bennett, D. W.; Bennett, J. V.; Bertani, M.; Bettoni, D.; Bian, J. M.; Bianchi, F.; Boger, E.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, H. Y.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Cibinetto, G.; Dai, H. L.; Dai, J. P.; Dbeyssi, A.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Duan, P. F.; Eren, E. E.; Fan, J. Z.; Fang, J.; Fang, S. S.; Fang, X.; Fang, Y.; Fava, L.; Feldbauer, F.; Felici, G.; Feng, C. Q.; Fioravanti, E.; Fritsch, M.; Fu, C. D.; Gao, Q.; Gao, X. Y.; Gao, Y.; Gao, Z.; Garzia, I.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y.; Guo, Y. P.; Haddadi, Z.; Hafner, A.; Han, S.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, X. Q.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Hu, Y.; Huang, G. M.; Huang, G. S.; Huang, J. S.; Huang, X. T.; Huang, Y.; Hussain, T.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. L.; Jiang, L. W.; Jiang, X. S.; Jiang, X. Y.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Johansson, T.; Julin, A.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Ke, B. C.; Kiese, P.; Kliemt, R.; Kloss, B.; Kolcu, O. B.; Kopf, B.; Kornicer, M.; Kuehn, W.; Kupsc, A.; Lange, J. S.; Lara, M.; Larin, P.; Leng, C.; Li, C.; Li, Cheng; Li, D. M.; Li, F.; Li, F. Y.; Li, G.; Li, H. B.; Li, J. C.; Li, Jin; Li, K.; Li, K.; Li, Lei; Li, P. R.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. M.; Li, X. N.; Li, X. Q.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. B.; Liu, J. P.; Liu, J. Y.; Liu, K.; Liu, K. Y.; Liu, L. D.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqing; Loehner, H.; Lou, X. C.; Lu, H. J.; Lu, J. G.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lyu, X. R.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, Q. M.; Ma, T.; Ma, X. N.; Ma, X. Y.; Maas, F. E.; Maggiora, M.; Mao, Y. J.; Mao, Z. P.; Marcello, S.; Messchendorp, J. G.; Min, J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Morales, C. Morales; Moriya, K.; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, S. L.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Patteri, P.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Pettersson, J.; Ping, J. L.; Ping, R. G.; Poling, R.; Prasad, V.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, N.; Qin, X. S.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ripka, M.; Rong, G.; Rosner, Ch.; Ruan, X. D.; Santoro, V.; Sarantsev, A.; Savrié, M.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, P. X.; Shen, X. Y.; Sheng, H. Y.; Song, W. M.; Song, X. Y.; Sosio, S.; Spataro, S.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Tiemens, M.; Ullrich, M.; Uman, I.; Varner, G. S.; Wang, B.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, S. G.; Wang, W.; Wang, X. F.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Weber, T.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, Z.; Xia, L. G.; Xia, Y.; Xiao, D.; Xiao, H.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, L.; Xu, Q. J.; Xu, X. P.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. J.; Yang, H. X.; Yang, L.; Yang, Y.; Yang, Y. X.; Ye, M.; Ye, M. H.; Yin, J. H.; Yu, B. X.; Yu, C. X.; Yu, J. S.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Yuncu, A.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, K.; Zhang, L.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. N.; Zhang, Y. H.; Zhang, Y. T.; Zhang, Yu; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. W.; Zhao, S. J.; Zhao, T. C.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, W. J.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, K.; Zhu, K. J.; Zhu, S.; Zhu, S. H.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zotti, L.; Zou, B. S.; Zou, J. H.; Besiii Collaboration
2015-10-01
In an analysis of a 2.92 fb-1 data sample taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions B (D0→K-e+νe)=(3.505 ±0.014 ±0.033 )% and B (D0→π-e+νe)=(0.295 ±0.004 ±0.003 )% . From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the Cabibbo-Kobayashi- Maskawa (CKM) matrix element f+K(0 )|Vc s|=0.7172 ±0.0025 ±0.0035 and f+π(0 )|Vc d|=0.1435 ±0.0018 ±0.0009 . Combining these products with the values of |Vc s (d )| from the SM constraint fit, we extract the hadronic form factors f+K(0 )=0.7368 ±0.0026 ±0.0036 and f+π(0 )=0.6372 ±0.0080 ±0.0044 , and their ratio f+π(0 )/f+K(0 )=0.8649 ±0.0112 ±0.0073 . These form factors and their ratio are used to test unquenched lattice QCD calculations of the form factors and a light cone sum rule (LCSR) calculation of their ratio. The measured value of f+K (π )(0 )|Vc s (d )| and the lattice QCD value for f+K (π )(0 ) are used to extract values of the CKM matrix elements of |Vc s|=0.9601 ±0.0033 ±0.0047 ±0.0239 and |Vc d|=0.2155 ±0.0027 ±0.0014 ±0.0094 , where the third errors are due to the uncertainties in lattice QCD calculations of the form factors. Using the LCSR value for f+π(0 )/f+K(0 ) , we determine the ratio |Vc d|/|Vc s|=0.238 ±0.004 ±0.002 ±0.011 , where the third error is from the uncertainty in the LCSR normalization. In addition, we measure form factor parameters for three different theoretical models that describe the weak hadronic charged currents for these two semileptonic decays. All of these measurements are the most precise to date.
Scaling analysis of the anisotropic nonlocal Kardar-Parisi-Zhang equation
NASA Astrophysics Data System (ADS)
Tang, Gang; Ma, Benkun
2002-07-01
The scaling behaviors of the anisotropic nonlocal Kardar-Parisi-Zhang equation are studied by the scaling analysis method introduced by Hentschel and Family. The scaling exponents in both the weak- and strong-coupling regions are obtained, respectively. The scaling exponents in weak-coupling region can well match the results of the dynamic renormalization-group analysis.
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.
Numerical simulation of the dynamics of a liquid crystal in the case of plane strain using GPUs
Sadovskaya, O. V.
2014-11-12
Parallel computational algorithm is worked out for numerical implementation of two-dimensional dynamic model of a liquid crystal, which takes into account the mutual influence of three physical effects – transfer of acoustic energy due to translational motion, viscoelastic rotation of the particles under the action of tangential stresses, anisotropic thermal expansion and compression. The algorithm is based on the Godunov gap decay method, the Ivanov scheme with controlled dissipation of energy and the splitting method with respect to spatial variables. The CUDA technology for computer systems with graphic accelerators is used. Results of computations demonstrating the efficiency of proposed method and algorithm are represented.
Numerical simulation of the dynamics of a liquid crystal in the case of plane strain using GPUs
NASA Astrophysics Data System (ADS)
Sadovskaya, O. V.
2014-11-01
Parallel computational algorithm is worked out for numerical implementation of two-dimensional dynamic model of a liquid crystal, which takes into account the mutual influence of three physical effects - transfer of acoustic energy due to translational motion, viscoelastic rotation of the particles under the action of tangential stresses, anisotropic thermal expansion and compression. The algorithm is based on the Godunov gap decay method, the Ivanov scheme with controlled dissipation of energy and the splitting method with respect to spatial variables. The CUDA technology for computer systems with graphic accelerators is used. Results of computations demonstrating the efficiency of proposed method and algorithm are represented.
Rist, J.; Miteva, T.; Gaire, B.; Sann, H.; Trinter, F.; Keiling, M.; Gehrken, N.; Moradmand, A.; Berry, B.; Zohrabi, M.; Kunitski, M.; Ben-Itzhak, I.; Belkacem, A.; Weber, T.; Landers, A. L.; Schöffler, M.; Williams, J. B.; Kolorenč, P.; Gokhberg, K.; Jahnke, T.; Dörner, R.
2016-09-15
In this paper we present a comprehensive and detailed study of Interatomic Coulombic Decay (ICD) occurring after irradiating argon dimers with XUV-synchrotron radiation. A manifold of different decay channels is observed and the corresponding initial and final states are assigned. Additionally, the effect of nuclear dynamics on the ICD electron spectrum is examined for one specific decay channel. The internuclear distance-dependent width Γ(R) of the decay is obtained from the measured kinetic energy release distribution of the ions employing a classical nuclear dynamics model.
Lohmann, B.; Langer, B.; Snell, G.; Canton, S.; Berrah, N.; Kleiman, U.; Becker, U.; Martins, M.
2005-02-01
Spin-resolved measurements of the Ar{sup *}(2p{sub 1/2,3/2}{sup -1}4s{sub 1/2}){sub J=1} resonantly excited L{sub 2,3}M{sub 2,3}M{sub 2,3} Auger decay have been performed. The low resolution Auger spectrum, which due to cancellation between different multiplet components should exhibit virtually zero dynamic spin polarization, reveals an unexpected nonvanishing polarization effect. Calculations within a relativistic distorted wave approximation explain this effect as configuration-interaction (CI) induced. The CI generates experimentally unresolved fine structure components with low and high total angular momentum, giving rise to asymmetric cases where the high J part of certain multiplets is suppressed by internal selection rules for diagram lines. In this case, only the low J components survive with no partner for spin-polarization cancellation.
NASA Astrophysics Data System (ADS)
Giubega, L. E.
2016-12-01
Precise measurements on rare radiative B decays are performed with the LHCb experiment at LHC. The LHCb results regarding the ratio of branching fractions for two radiative decays, B 0 → K *0 γ and B s → ϕ γ, the direct CP asymmetry in B 0 → K *0 γ decay channel and the observation of the photon polarization in the B ± → K ±π∓π± γ decay, are included. The first two measurements were performed in 1 fb-1 of pp collisions data and the third one in 3 fb-1 of data, respectively.
Decay constants of the pion and its excitations on the lattice.
Mastropas, Ekaterina V.; Richards, David G.
2014-07-01
We present a calculation using lattice QCD of the ratios of decay constants of the excited states of the pion, to that of the pion ground state, at three values of the pion mass between 400 and 700 MeV, using an anisotropic clover fermion action with three flavors of quarks. We find that the decay constant of the first excitation, and more notably of the second, is suppressed with respect to that of the ground-state pion, but that the suppression shows little dependence on the quark mass. The strong suppression of the decay constant of the second excited state is consistent with its interpretation as a predominantly hybrid state.
29Si NMR spin-echo decay in YbRh2Si2
NASA Astrophysics Data System (ADS)
Kambe, S.; Sakai, H.; Tokunaga, Y.; Hattori, T.; Lapertot, G.; Matsuda, T. D.; Knebel, G.; Flouquet, J.; Walstedt, R. E.
2016-02-01
29Si nuclear magnetic resonance (NMR) has been measured in a 29Si-enriched single crystal sample of YbRh2Si2. The spin-echo decay for applied field H ∥, ⊥ the c-axes has been measured at 100 K. A clear spin-echo decay oscillation is observed for both cases, possibly reflecting the Ruderman-Kittel (RK) interaction. Since the observed oscillation frequency depends on the direction of applied magnetic field, anisotropic RK coupling and pseudo-dipolar (PD) interactions may not be negligible in this compound. The origin of spin-echo decay oscillations is discussed.
PIV anisotropic denoising using uncertainty quantification
NASA Astrophysics Data System (ADS)
Wieneke, B.
2017-08-01
Recently, progress has been made to reliably compute uncertainty estimates for each velocity vector in planar flow fields measured with 2D-or stereo-PIV. This information can be used for a post-processing denoising scheme to reduce errors by a spatial averaging scheme preserving true flow fluctuations. Starting with a 5 × 5 vector kernel, a second-order 2D-polynomial function is fitted to the flow field. Vectors just outside will be included in the filter kernel if they lie within the uncertainty band around the fitted function. Repeating this procedure, vectors are added in all directions until the true flow field can no longer be approximated by the second-order polynomial function. The center vector is then replaced by the value of the fitted function. The final shape and size of the filter kernel automatically adjusts to local flow gradients in an optimal way preserving true velocity fluctuations above the noise level. This anisotropic denoising scheme is validated first on synthetic vector fields varying spatial wavelengths of the flow field and noise levels relative to the fluctuation amplitude. For wavelengths larger than 5-7 times the spatial resolution, a noise reduction factor of 2-4 is achieved significantly increasing the velocity dynamic range. For large noise levels above 50% of the flow fluctuation, the denoising scheme can no longer distinguish between true flow fluctuations and noise. Finally, it is shown that the procedure performs well for typical experimental PIV vector fields. It provides an effective alternative to more complicated adaptive PIV algorithms optimizing interrogation window sizes and shapes based on seeding density, local flow gradients, and other criteria.
Temperature and magnetic-field dependence of radiative decay in colloidal germanium quantum dots.
Robel, István; Shabaev, Andrew; Lee, Doh C; Schaller, Richard D; Pietryga, Jeffrey M; Crooker, Scott A; L Efros, Alexander; Klimov, Victor I
2015-04-08
We conduct spectroscopic and theoretical studies of photoluminescence (PL) from Ge quantum dots (QDs) fabricated via colloidal synthesis. The dynamics of late-time PL exhibit a pronounced dependence on temperature and applied magnetic field, which can be explained by radiative decay involving two closely spaced, slowly emitting exciton states. In 3.5 nm QDs, these states are separated by ∼1 meV and are characterized by ∼82 μs and ∼18 μs lifetimes. By using a four-band formalism, we calculate the fine structure of the indirect band-edge exciton arising from the electron-hole exchange interaction and the Coulomb interaction of the Γ-point hole with the anisotropic charge density of the L-point electron. The calculations suggest that the observed PL dynamics can be explained by phonon-assisted recombination of excitons thermally distributed between the lower-energy "dark" state with the momentum projection J = ± 2 and a higher energy "bright" state with J = ± 1. A fairly small difference between lifetimes of these states is due to their mixing induced by the exchange term unique to crystals with a highly symmetric cubic lattice such as Ge.