2,172 research outputs found
Quenching of lamellar ordering in an n-alkane embedded in nanopores
We present an X-ray diffraction study of the normale alkane nonadecane
C_{19}H_{40} embedded in nanoporous Vycor glass. The confined molecular crystal
accomplishes a close-packed structure by alignment of the rod-like molecules
parallel to the pore axis while sacrificing one basic principle known from the
bulk state, i.e. the lamellar ordering of the molecules. Despite this disorder,
the phase transitions observed in the confined solid mimic the phase behavior
of the 3D unconfined crystal, though enriched by the appearance of a true
rotator phase known only from longer alkane chains.Comment: 7 pages, 3 figure
Criminal Cases Gone Paperless : Hanging With the Wrong Crowd
This article explores issues concerning electronic discovery (e-discovery), its association with ESI, and how it impacts criminal litigation
Male infertility due to germ cell apoptosis in mice lacking the thiamin carrier, Tht1. A new insight into the critical role of thiamin in spermatogenesis.
A mouse model of thiamin-responsive megaloblastic anemia (diabetes mellitus, deafness, megaloblastic anemia) lacking functional Slc19a2 has been generated and unexpectedly found to have a male-specific sterility phenotype. We describe here the characterization of the testis-specific effects of absence of the high-affinity thiamin transporter, Tht1. Null males were found to have hypoplastic testes secondary to germ cell depletion. Morphologic and expression analysis revealed that under conditions of standard thiamin intake, tissues affected in the syndrome (pancreatic beta-cell, hematopoietic cells, auditory nerve) maintained normal function but pachytene stage spermatocytes underwent apoptosis. Under conditions of thiamin challenge, the apoptotic cell loss extended to earlier stages of germ cells but spared Sertoli cells and Leydig cells. Injection of high-dose thiamin was effective in reversing the spermatogenic failure, suggesting that the absence of the thiamin carrier could be overcome by diffusion-mediated transport at supranormal thiamin concentrations. These observations demonstrated that male germ cells, particularly those with high thiamin transporter expression beyond the blood-testis barrier, were more susceptible to apoptosis triggered by intracellular thiamin deficiency than any other tissue type. The findings described here highlight an unexpected and critical role for thiamin transport and metabolism in spermatogenesis
Liquid-liquid coexistence in the phase diagram of a fluid confined in fractal porous materials
Multicanonical ensemble sampling simulations have been performed to calculate
the phase diagram of a Lennard-Jones fluid embedded in a fractal random matrix
generated through diffusion limited cluster aggregation. The study of the
system at increasing size and constant porosity shows that the results are
independent from the matrix realization but not from the size effects. A
gas-liquid transition shifted with respect to bulk is found. On growing the
size of the system on the high density side of the gas-liquid coexistence curve
it appears a second coexistence region between two liquid phases. These two
phases are characterized by a different behaviour of the local density inside
the interconnected porous structure at the same temperature and chemical
potential.Comment: 5 pages, 4 figures. To be published in Europhys. Letter
Recovering piecewise smooth functions from nonuniform Fourier measurements
In this paper, we consider the problem of reconstructing piecewise smooth
functions to high accuracy from nonuniform samples of their Fourier transform.
We use the framework of nonuniform generalized sampling (NUGS) to do this, and
to ensure high accuracy we employ reconstruction spaces consisting of splines
or (piecewise) polynomials. We analyze the relation between the dimension of
the reconstruction space and the bandwidth of the nonuniform samples, and show
that it is linear for splines and piecewise polynomials of fixed degree, and
quadratic for piecewise polynomials of varying degree
Soft disks in a narrow channel
The pressure components of "soft" disks in a two dimensional narrow channel
are analyzed in the dilute gas regime using the Mayer cluster expansion and
molecular dynamics. Channels with either periodic or reflecting boundaries are
considered. It is found that when the two-body potential, u(r), is singular at
some distance r_0, the dependence of the pressure components on the channel
width exhibits a singularity at one or more channel widths which are simply
related to r_0. In channels with periodic boundary conditions and for
potentials which are discontinuous at r_0, the transverse and longitudinal
pressure components exhibit a 1/2 and 3/2 singularity, respectively. Continuous
potentials with a power law singularity result in weaker singularities of the
pressure components. In channels with reflecting boundary conditions the
singularities are found to be weaker than those corresponding to periodic
boundaries
Forced Imbibition - a Tool for Determining Laplace Pressure, Drag Force and Slip Length in Capillary Filling Experiments
When a very thin capillary is inserted into a liquid, the liquid is sucked
into it: this imbibition process is controlled by a balance of capillary and
drag forces, which are hard to quantify experimentally, in particularly
considering flow on the nanoscale. By computer experiments using a generic
coarse-grained model, it is shown that an analysis of imbibition forced by a
controllable external pressure quantifies relevant physical parameter such as
the Laplace pressure, Darcy's permeability, effective pore radius, effective
viscosity, dynamic contact angle and slip length of the fluid flowing into the
pore. In determining all these parameters independently, the consistency of our
analysis of such forced imbibition processes is demonstrated.Comment: 4 pages, 5 figure
An exact minimum variance filter for a class of discrete time systems with random parameter perturbations
An exact, closed-form minimum variance filter is designed for a class of discrete time uncertain systems which allows for both multiplicative and additive noise sources. The multiplicative noise model includes a popular class of models (Cox-Ingersoll-Ross type models) in econometrics. The parameters of the system under consideration which describe the state transition are assumed to be subject to stochastic uncertainties. The problem addressed is the design of a filter that minimizes the trace of the estimation error variance. Sensitivity of the new filter to the size of parameter uncertainty, in terms of the variance of parameter perturbations, is also considered. We refer to the new filter as the 'perturbed Kalman filter' (PKF) since it reduces to the traditional (or unperturbed) Kalman filter as the size of stochastic perturbation approaches zero. We also consider a related approximate filtering heuristic for univariate time series and we refer to filter based on this heuristic as approximate perturbed Kalman filter (APKF). We test the performance of our new filters on three simulated numerical examples and compare the results with unperturbed Kalman filter that ignores the uncertainty in the transition equation. Through numerical examples, PKF and APKF are shown to outperform the traditional (or unperturbed) Kalman filter in terms of the size of the estimation error when stochastic uncertainties are present, even when the size of stochastic uncertainty is inaccurately identified
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