Origin of translocation barriers for polyelectrolyte chains

For single-file translocations of a charged macromolecule through a narrow pore, the crucial step of arrival of an end at the pore suffers from free energy barriers, arising from changes in intrachain electrostatic interaction, distribution of ionic clouds and solvent molecules, and conformational entropy of the chain. All contributing factors to the barrier in the initial stage of translocation are evaluated by using the self-consistent field theory for the polyelectrolyte and the coupled Poisson-Boltzmann description for ions, without radial symmetry. The barrier is found to be essentially entropic, due to conformational changes. For moderate and high salt concentrations, the barriers for the polyelectrolyte chain are quantitatively equivalent to that of uncharged self-avoiding walks. Electrostatic effects are shown to increase the free energy barriers, but only slightly. The degree of ionization, electrostatic interaction strength, decreasing salt concentration and the solvent quality all result in increases in the barrier.Comment: J.Chem. Phys. 131, 21 (2009) - to be appeare

Randomly forced DNA

We study the effect of random forces on a double stranded DNA in unzipping the two strands, analogous to the problem of an adsorbed polymer under a random force. The ground state develops bubbles of various lengths as the random force fluctuation is increased. The unzipping phase diagram is shown to be drastically different from the pure case.Comment: 4 figures, Published Versio

Nuclear Waste and Native America: The MRS Siting Exercise

Drs. Gowda & Easterling provide cross-cultural perspectives on issues of risk perception, equity and policy as they affect nuclear waste storage on Native American sites

A Deep Pyramid Deformable Part Model for Face Detection

We present a face detection algorithm based on Deformable Part Models and deep pyramidal features. The proposed method called DP2MFD is able to detect faces of various sizes and poses in unconstrained conditions. It reduces the gap in training and testing of DPM on deep features by adding a normalization layer to the deep convolutional neural network (CNN). Extensive experiments on four publicly available unconstrained face detection datasets show that our method is able to capture the meaningful structure of faces and performs significantly better than many competitive face detection algorithms

Hysteresis and nonequilibrium work theorem for DNA unzipping

We study by using Monte Carlo simulations the hysteresis in unzipping and rezipping of a double stranded DNA (dsDNA) by pulling its strands in opposite directions in the fixed force ensemble. The force is increased, at a constant rate from an initial value $g_0$ to some maximum value $g_m$ that lies above the phase boundary and then decreased back again to $g_{0}$. We observed hysteresis during a complete cycle of unzipping and rezipping. We obtained probability distributions of work performed over a cycle of unzipping and rezipping for various pulling rates. The mean of the distribution is found to be close (the difference being within 10%, except for very fast pulling) to the area of the hysteresis loop. We extract the equilibrium force versus separation isotherm by using the work theorem on repeated non-equilibrium force measurements. Our method is capable of reproducing the equilibrium and the non-equilibrium force-separation isotherms for the spontaneous rezipping of dsDNA.Comment: 8 figures, Final version to appear in Physical Review

Poisson Brackets of Normal-Ordered Wilson Loops

We formulate Yang-Mills theory in terms of the large-N limit, viewed as a classical limit, of gauge-invariant dynamical variables, which are closely related to Wilson loops, via deformation quantization. We obtain a Poisson algebra of these dynamical variables corresponding to normal-ordered quantum (at a finite value of $\hbar$) operators. Comparing with a Poisson algebra one of us introduced in the past for Weyl-ordered quantum operators, we find, using ideas closly related to topological graph theory, that these two Poisson algebras are, roughly speaking, the same. More precisely speaking, there exists an invertible Poisson morphism between them.Comment: 34 pages, 4 eps figures, LaTeX2.09; citations adde

Strong interrelationship between anomalous electric-field induced lattice strain along non-polar direction and domain reorientation in pseudorhombohedral piezoelectric ceramic BiScO3-PbTiO3

The lattice strain and domain switching behaviour was investigated as a function of cyclic field and grain orientation for a pseudorhombohedral composition of the high Curie point piezoelectric system xBiScO3 - (1-x)PbTiO3 (x = 0.40) by in-situ electric field diffraction technique with high energy synchrotron x-rays. Along the field direction, the system exhibts five time large strain along 100 as compared to the 111 direction. A one-to-one correspondence between the 200 lattice strain and the 111 domain switching suggests a strong correlation between the two phenomena.Comment: 11 pages, 7 figure