through-plane concomitant field phase accrual, for a phantom (squares no correction, triangles corrected) and human brain (circles no correction, diamonds corrected). Dephasing from concomitant gradient fields leads to error in ADC that increases with distance from isocenter (zS = 10cm-superior; zS = 0cm-inferior). FIG 1. Diffusion gradient timing for StejskalTanner (ST; insensitive to concomit...

Randy K. Dumas,1 Thomas Gredig,2,3 Chang-Peng Li,2,* Ivan K. Schuller,2 and Kai Liu1,† 1Department of Physics, University of California, Davis, California 95616, USA 2Department of Physics, University of California–San Diego, La Jolla, California 92093, USA 3Department of Physics and Astronomy, California State University, Long Beach, California 90840, USA Received 18 December 2008; revised man...

Purpose: Wedged beam are often used in clinical radiotherapy to compensate missing tissues and dose gradients. The Elekta Precise linear accelerator supports an internal motorized wedge, which is a single large, physical wedge on a motorized carriage. In this study, the dosimetric performance of Elekta precise three dimensional treatment planning system (3DTPS) is evaluated by comparing the cal...

Most existing flow visualization techniques focus on the analysis and visualization of the vector field that describes the flow. In this paper, we employ a rather different approach by performing tensor field analysis and visualization on the gradient of the vector field, which can provide additional and complementary information to the direct analysis of the vector field. Our techniques focus ...

We propose a novel parameter, namely, the skewness, or asymmetry, of the shape of a receptive field to characterize two properties of hippocampal place fields. First, a majority of hippocampal receptive fields on linear tracks are negatively skewed, such that during a single pass the firing rate is low as the rat enters the field but high as it exits. Second, while the place fields are symmetri...

Theories of sequence learning based on temporally asymmetric, Hebbian long-term potentiation predict that during route learning the spatial firing distributions of hippocampal neurons should enlarge in a direction opposite to the animal's movement. On a route AB, increased synaptic drive from cells representing A would cause cells representing B to fire earlier and more robustly. These effects ...

Modeling studies have shown that recurrent interactions within neural networks are capable of self-sustaining non-uniform activity profiles. These patterns are thought to be the neural basis of working memory. However, the lack of robustness challenge this view as already small deviations from the assumed interaction symmetry destroy the attractor state. Here we analyze attractor states of a ne...

Initially inspired by biological motors, new types of nanodevice have been proposed for controlling the motion of nanoparticles. Structures incorporating spatially asymmetric potential profiles (ratchet substrates) have been realized experimentally to manipulate vortices in superconductors, particles in asymmetric silicon pores, as well as charged particles through artificial pores and arrays o...

Asymmetric nanocomposite particle pairs of polystyrene and silica were prepared via one-step miniemulsion polymerization for the first time. The transmission electron microscopy images showed that these nanocomposite particle pairs were monodisperse and highly asymmetric in morphology. The key to obtaining the asymmetric nanocomposite particle pairs was the combination of miniemulsion polymeriz...

It is argued that string theory predicts unified field theory rather than general relativity coupled to matter fields. In unified field theory all the objects are geometrical, for strings the Kalb-Ramond matter field is identical to the asymmetric part of the metric except that the fields contribute to different sides of the field equations. The dilaton is related to the object of non-metricity.