5,721 research outputs found
Mean-field dynamical density functional theory
We examine the out-of-equilibrium dynamical evolution of density profiles of
ultrasoft particles under time-varying external confining potentials in three
spatial dimensions. The theoretical formalism employed is the dynamical density
functional theory (DDFT) of Marini Bettolo Marconi and Tarazona [J. Chem. Phys.
{\bf 110}, 8032 (1999)], supplied by an equilibrium excess free energy
functional that is essentially exact. We complement our theoretical analysis by
carrying out extensive Brownian Dynamics simulations. We find excellent
agreement between theory and simulations for the whole time evolution of
density profiles, demonstrating thereby the validity of the DDFT when an
accurate equilibrium free energy functional is employed.Comment: 8 pagers, 4 figure
Heritability of testosterone levels in 12-year-old twins and its relation to pubertal development
The aim of this study was to estimate the heritability of variation in testosterone levels in 12-year-old children, and to explore the overlap in genetic and environmental influences on circulating testosterone levels and androgen dependent pubertal development. Midday salivary testosterone samples were collected on two consecutive days in a sample of 183 unselected twin pairs. Androgen induced pubertal development was assessed using self report Tanner scales of pubic hair development (boys and girls) and genital development (boys). A significant contribution of genetic effects to the variance in testosterone levels was found.
Heritability was approximately 50% in both boys and girls. The remaining proportion of the variance in testosterone levels could be explained by non-shared environmental influences. The relatively high correlation between testosterone levels of opposite sex dizygotic twins suggests that sex differences in genes influencing variation in testosterone levels have not yet developed in pre- and early puberty. Variance in pubertal development was explained by a large genetic component, moderate shared environmental influences, and a small non-shared environmental effect. Testosterone levels correlated moderately (r = .31) with pubertal development; the covariance between testosterone levels and pubertal development was entirely accounted for by genetic influences
Biomimetic direction of arrival estimation for resolving front-back confusions in hearing aids
Sound sources at the same angle in front or behind a two-microphone array (e.g., bilateral hearing aids) produce the same time delay and two estimates for the direction of arrival: A front-back confusion. The auditory system can resolve this issue using head movements. To resolve front-back confusion for hearing-aid algorithms, head movement was measured using an inertial sensor. Successive time-delay estimates between the microphones are shifted clockwise and counterclockwise by the head movement between estimates and aggregated in two histograms. The histogram with the largest peak after multiple estimates predicted the correct hemifield for the source, eliminating the front-back confusions
Dynamical density functional theory for dense atomic liquids
Starting from Newton's equations of motion, we derive a dynamical density
functional theory (DDFT) applicable to atomic liquids. The theory has the
feature that it requires as input the Helmholtz free energy functional from
equilibrium density functional theory. This means that, given a reliable
equilibrium free energy functional, the correct equilibrium fluid density
profile is guaranteed. We show that when the isothermal compressibility is
small, the DDFT generates the correct value for the speed of sound in a dense
liquid. We also interpret the theory as a dynamical equation for a coarse
grained fluid density and show that the theory can be used (making further
approximations) to derive the standard mode coupling theory that is used to
describe the glass transition. The present theory should provide a useful
starting point for describing the dynamics of inhomogeneous atomic fluids.Comment: 14 pages, accepted for publication in J. Phys.: Condens. Matte
Criticality and phase separation in a two-dimensional binary colloidal fluid induced by the solvent critical behavior
We present an experimental and theoretical study of the phase behavior of a
binary mixture of colloids with opposite adsorption preferences in a critical
solvent. As a result of the attractive and repulsive critical Casimir forces,
the critical fluctuations of the solvent lead to a further critical point in
the colloidal system, i.e. to a critical colloidal-liquid--colloidal-liquid
demixing phase transition which is controlled by the solvent temperature. Our
experimental findings are in good agreement with calculations based on a simple
approximation for the free energy of the system.Comment: 5 pages, 5 figures, to be published in Europhysics Letter
Generation of defects and disorder from deeply quenching a liquid to form a solid
We show how deeply quenching a liquid to temperatures where it is linearly
unstable and the crystal is the equilibrium phase often produces crystalline
structures with defects and disorder. As the solid phase advances into the
liquid phase, the modulations in the density distribution created behind the
advancing solidification front do not necessarily have a wavelength that is the
same as the equilibrium crystal lattice spacing. This is because in a deep
enough quench the front propagation is governed by linear processes, but the
crystal lattice spacing is determined by nonlinear terms. The wavelength
mismatch can result in significant disorder behind the front that may or may
not persist in the latter stage dynamics. We support these observations by
presenting results from dynamical density functional theory calculations for
simple one- and two-component two-dimensional systems of soft core particles.Comment: 25 pages, 11 figure
Crop Residue Harvest Economics: An Iowa and North Dakota Case Study
Rigorous economic analyses are crucial for the successful launch of lignocellulosic bioenergy facilities in 2014 and beyond. Our objectives are to (1) introduce readers to a query tool developed to use data downloaded from the Agricultural Research Service (ARS) REAPnet for constructing enterprise budgets and (2) demonstrate the use of the query tool with REAPnet data from two field research sites (Ames, IA, and Mandan, ND) for evaluating short-term economic performance of various biofuel feedstock production strategies. Our results for both sites showed that short-term (\u3c3 years) impacts on grain profitability were lower at lower average annual crop residue removal rates. However, it will be important to monitor longer term changes to see if grain profitability declines over time and if biomass harvest degrades soil resources. Analyses for Iowa showed short-term breakeven field-edge biomass prices of 42Mg−1 among the most efficient strategies, while results for North Dakota showed breakeven prices of 73 Mg−1. We suggest that development of the data query tool is important because it helps illustrate several different soil and crop management strategies that could be used to provide sustainable feedstock supplies
Quasicrystal formation in binary soft matter mixtures
Using a strategy that may be applied in theory or in experiments, we identify the regime in which a model binary soft matter mixture forms quasicrystals. The system is described using classical density functional theory combined with integral equation theory. Quasicrystal formation requires particle ordering with two characteristic length scales in certain particular ratios. How the length scales are related to the form of the pair interactions is reasonably well understood for one-component systems, but less is known for mixtures. In our model mixture of big and small colloids confined to an interface, the two length scales stem from the range of the interactions between pairs of big particles and from the cross big-small interactions, respectively. The small-small length scale is not significant. Our strategy for finding quasicrystals involves tuning locations of maxima in the dispersion relation, or equivalently in the liquid state partial static structure factors
Mode-coupling theory and the fluctuation-dissipation theorem for nonlinear Langevin equations with multiplicative noise
In this letter, we develop a mode-coupling theory for a class of nonlinear
Langevin equations with multiplicative noise using a field theoretic formalism.
These equations are simplified models of realistic colloidal suspensions. We
prove that the derived equations are consistent with the
fluctuation-dissipation theorem. We also discuss the generalization of the
result given here to real fluids, and the possible description of supercooled
fluids in the aging regime. We demonstrate that the standard idealized
mode-coupling theory is not consistent with the FDT in a strict field theoretic
sense.Comment: 14 pages, to appear in J. Phys.
P-glycoprotein and metallothionein expression and resistance to chemotherapy in osteosarcoma.
The expression of the drug resistance (DR) mediators P-glycoprotein (P-gp) and the metallothioneins (MT) was assessed immunohistochemically in biopsy material from patients with high-grade malignant osteosarcoma (OS). No significant difference was found in survival rate between expressors of both P-gp and MT and non-expressors. Thus, it was concluded that lack of expression of these two drug resistance-related proteins does not appear to confer any advantage in terms of patient survival in osteosarcoma
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