JCB • VOLUME 171 • NUMBER 4 • 2005 582 A Sisyphean helicase ome helicases continually bang their heads against the wall, if a new report from Sua Myong, Taekjip Ha (University of Illinois, UrbanaChampaign, IL), and colleagues is any indication. The Rep helicase, the group finds, repeatedly motors along a track of DNA, hits an obstacle, and returns to square one. Not all helicases can unwind DNA...

We present a high-order accurate boundary-based solver for three-dimensional (3D) frequency-domain scattering from a doubly-periodic grating of smooth axisymmetric sound-hard or transmission obstacles. We build the one-obstacle solution operator using separation into P azimuthal modes via the FFT, the method of fundamental solutions (with N proxy points lying on a curve), and dense direct least...

We uncover anisotropic permeability in microfluidic deterministic lateral displacement (DLD) arrays. A DLD array can achieve high-resolution bimodal size-based separation of microparticles, including bioparticles, such as cells. For an application with a given separation size, correct device operation requires that the flow remains at a fixed angle to the obstacle array. We demonstrate via expe...

In this article, a new collision-avoidance scheme is proposed for autonomous land vehicle (ALV) navigation in indoor corridors. The goal is to conduct indoor collisionfree navigation of a three-wheel ALV among static obstacles with no a priori position information as well as moving obstacles with unknown trajectories. Based on the predicted positions of obstacles, a local collision-free path is...

We have studied the diffusion of tracer proteins in highly concentrated random-coil polymer and globular protein solutions imitating the crowded conditions encountered in cellular environments. Using fluorescence correlation spectroscopy, we measured the anomalous diffusion exponent alpha characterizing the dependence of the mean-square displacement of the tracer proteins on time, r(2)(t) appro...

The deep quench obstacle problem models phase separation at low temperatures. During phase separation, domains of high and low concentration are formed, then coarsen or grow in average size. Of interest is the time dependence of the dominant length scales of the system. Relying on recent results by Novick-Cohen & Shishkov [16], we demonstrate upper bounds for coarsening for the deep quench obst...

Abstract We prove an existence result for obstacle problems related to convection-diffusion parabolic equations with singular coefficients in the convective term. Our operator is not coercive, function time-dependent irregular, and lower-order term belong a borderline mixed Lebesgue-Marcinkiewicz space.

Are colors objective or subjective? Are they properties, processes, or events of the physical world or, instead, of the perceiving subject? This question has been debated at least since the time of Galileo and remains unsettled to this day. Evidence from computational and psychophysical studies of vision has not decided the issue, with both objectivists and subjectivists claiming that the evide...

GOLDMAN, SUSAN R., and VARNHAGEN, CONNIE K. Comprehension of Stories with No-Obstacle and Obstacle Endings. CHILD DEVELOPMENT, 1983, 54, 980-992. Comprehension of stories with and without obstacles to goal attainment was examined. 16 secondand fifth-grade students and 16 adults listened to and read single-episode stories in which (1) the protagonist met the episode goal (no-obstacle ending) and...