1,178 research outputs found
Driven activation versus thermal activation
Activated dynamics in a glassy system undergoing steady shear deformation is
studied by numerical simulations. Our results show that the external driving
force has a strong influence on the barrier crossing rate, even though the
reaction coordinate is only weakly coupled to the nonequilibrium system. This
"driven activation" can be quantified by introducing in the Arrhenius
expression an effective temperature, which is close to the one determined from
the fluctuation-dissipation relation. This conclusion is supported by
analytical results for a simplified model system.Comment: 5 pages, 3 figure
Importance of depletion interactions for structure and dynamics of ferrofluids
Abstract.: The influence of attractive depletion forces on the structure and dynamics of ferrofluids is studied by computer simulations. In the presence of a magnetic field, we find that sufficiently strong depletion forces lead to an assembly of particle chains into columnar structures with hexagonal ordering inside the columns. In a planar shear flow, this ordering is destroyed, leading to strong shear thinning behavior. A pronounced anisotropy of the shear viscosity is observed. The viscosity is found to be largest when the magnetic field is oriented in the gradient direction of the flo
Ideal contribution to the macroscopic quasiequilibrium entropy of anisotropic fluids
The Landau-de Gennes free energy plays a central role in the macroscopic theory of anisotropic fluids. Here, the ideal, entropic contribution to this free energy—that is always present in these systems, irrespectively of the detailed form of interactions or applied fields—is derived within the quasiequilibrium ensemble and successfully tested. An explicit and compact form of the macroscopic, ideal entropy is derived. This entropy is nonpolynomial in the order parameter, diverging logarithmically near the fully oriented state and therefore restricting the order parameter to physical admissible values. As an application, it is shown that the isotropic-nematic transition within the Maier-Saupe model is described in a simple and very accurate manner
Tagged particle in a sheared suspension: effective temperature determines density distribution in a slowly varying external potential beyond linear response
We consider a sheared colloidal suspension under the influence of an external
potential that varies slowly in space in the plane perpendicular to the flow
and acts on one selected (tagged) particle of the suspension. Using a
Chapman-Enskog type expansion we derive a steady state equation for the tagged
particle density distribution. We show that for potentials varying along one
direction only, the tagged particle distribution is the same as the equilibrium
distribution with the temperature equal to the effective temperature obtained
from the violation of the Einstein relation between the self-diffusion and
tagged particle mobility coefficients. We thus prove the usefulness of this
effective temperature for the description of the tagged particle behavior
beyond the realm of linear response. We illustrate our theoretical predictions
with Brownian dynamics computer simulations.Comment: Accepted for publication in Europhys. Let
Shear-induced anisotropic decay of correlations in hard-sphere colloidal glasses
Spatial correlations of microscopic fluctuations are investigated via
real-space experiments and computer simulations of colloidal glasses under
steady shear. It is shown that while the distribution of one-particle
fluctuations is always isotropic regardless of the relative importance of shear
as compared to thermal fluctuations, their spatial correlations show a marked
sensitivity to the competition between shear-induced and thermally activated
relaxation. Correlations are isotropic in the thermally dominated regime, but
develop strong anisotropy as shear dominates the dynamics of microscopic
fluctuations. We discuss the relevance of this observation for a better
understanding of flow heterogeneity in sheared amorphous solids.Comment: 6 pages, 4 figure
Keragaman Genetik Anakan Shorea Leprosula Berdasarkan Penanda Mikrosatelit
Genetic diversity value of offspring might indicate a reproductive success in a forest. Aim in this study was to access genetic diversity values of offspring of Shorea leprosula from different forest types. Leaf samples were collected from six population i.e. a plantation from Carita, and five natural forests from Gunung Bunga A and B, SBK, ITCI and Gunung Lumut. Using four microsatellite markers, the results showed that SBK population maintained high value of genetic diversity. Values of expected heterozygosity (HE) ranged between 0.717 (Carita) and 0.836 (SBK). Values of coefficient inbreeding (F) were insignificant deviated from Hardy-Weinberg Equilibrium, but the value was significant in SBK population. PCA analysis demonstrated a cluster among Gunung Bunga A, SBK, ITCI, and Gunung Lumut. Amova showed that different province significantly contributed 1% to the value of genetic diversity of S. leprosula
Amidoschwarz10B in der forensischen Spurenuntersuchung: Vergleichende Untersuchungen an forensischem Spurenmaterial
Zusammenfassung: Blutspuren gehören zu den aussagekräftigsten Spuren in der forensischen Fallanalyse. Einerseits kann die Beurteilung von Aussehen, Menge, Form und Verteilung an Tatorten Hinweise auf den Tathergang geben. Andererseits lassen sich heute auch aus kleinsten Blutmengen zumeist vollständige DNA-Profile erstellen, die dann ebenfalls eine Rekonstruktion des Tatablaufs und über die molekulargenetische DNA-Analyse Aussagen zur Tatbeteiligung von Personen ermöglichen. In der vorgestellten Studie wurden Vollblutproben auf unterschiedliche Spurenträger aufgebracht und mithilfe des Hexagon OBTI® auf das Vorhandensein von Blut hin untersucht. Nach Inkubation mit 2 verschiedenen Zubereitungen von Amidoschwarz10B konnte gezeigt werden, dass dessen Einsatz zu starken Beeinträchtigungen bzw. falsch-negativen Ergebnissen des OBTI führen kann. Ein negativer Einfluss von Amidoschwarz10B auf das Probenmaterial war hingegen bei den nachfolgend durchgeführten DNA-Analysen nicht festzustelle
Fluctuation relations and coarse-graining
We consider the application of fluctuation relations to the dynamics of
coarse-grained systems, as might arise in a hypothetical experiment in which a
system is monitored with a low-resolution measuring apparatus. We analyze a
stochastic, Markovian jump process with a specific structure that lends itself
naturally to coarse-graining. A perturbative analysis yields a reduced
stochastic jump process that approximates the coarse-grained dynamics of the
original system. This leads to a non-trivial fluctuation relation that is
approximately satisfied by the coarse-grained dynamics. We illustrate our
results by computing the large deviations of a particular stochastic jump
process. Our results highlight the possibility that observed deviations from
fluctuation relations might be due to the presence of unobserved degrees of
freedom.Comment: 19 pages, 6 figures, very minor change
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Diffusion-jump model for the combined Brownian and Neel relaxation dynamics of ferrofluids in the presence of external fields and flow
Relaxation of suspended magnetic nanoparticles occurs via Brownian rotational diffusion of the particle as well as internal magnetization dynamics. The latter is often modeled by the stochastic Landau-Lifshitz equation, but its numerical treatment becomes prohibitively expensive in many practical applications due to a time-scale separation between fast, Larmor-type precession and slow, barrier-crossing dynamics. Here, a diffusion-jump model is proposed to take advantage of the time-scale separation and to approximate barrier-crossings as thermally activated jump processes that occur alongside rotational diffusion. The predictions of our diffusion-jump model are compared to reference results obtained by solving the stochastic Landau-Lifshitz equation coupled to rotational Brownian motion. Good agreement is found in the regime of high energy barriers where Neel relaxation can be considered a thermally activated rare event. While many works in the field have neglected N\'eel relaxation altogether, our approach opens the possibility to efficiently include Neel relaxation also into interacting many-particle models
Karakteristik Pembungaan Dan Sistem Perkawinan Nyamplung (Calophyllum Inophyllum) Pada Hutan Tanaman Di Watusipat, Gunung Kidul
Flowering are influenced by internal factors, such as genetic and phytohormone, and environment factors, such as sunlight and nutrition intake. The flowering characteristics influence fruiting and genetic diversity seedlings through mating systems. This study aims to assess flowering and fruiting characteristics and to determine pattern of mating system of a Calophyllum inophyllum plantation at Watusipat, Gunung Kidul. Flowering and fruiting were observed at 4 locations, 3 parts of crown, and 4 main directions to know the effects of sunlight, nutrition intake and phytohormone in the flowering process. Mating system was assessed by comparing genetic diversity values between parent trees and offsprings. The values of genetic diversity were analyzed using 5 RAPD primers with 17 polymorphic loci. Analysis of variant showed that the locations, crown parts, directions and interaction between a location and direction significantly affected to differences number of flowers and fruits. Values of genetic diversity (h) of parent trees ranged between 0.1471 and 0.3056. The values increased at almost overall offsprings; it ranged between 0.2864 and 0.3750. Values of genetic distance (Da) between parent trees were high and very high (0.197 – 0.364), but the values was decreased between parent trees and their offspring, even between offspring populations. A dendrogram showed two main clusters; first cluster consisted parent trees at up edge with rare trees and second cluster consisted sub cluster parent trees at up edge; sub cluster parent trees at down middle; and sub cluster parent trees at down edge and overall offsprings. Flowering/ fruiting characteristics and pattern of mating systems of C. inophyllum were briefly discussed
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