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Tunnel field effect transistor (TFET) with lateral oxidation
A vertical-mode tunnel field-effect transistor (TFET) is provided with an oxide region that may be laterally positioned relative to a source region. The oxide region operates to reduce a tunneling effect in a tunnel region underlying a drain region, during an OFF-state of the TFET. The reduction in tunneling effect results in a reduction or elimination of a flow of OFF-state leakage current between the source region and the drain region. The TFET may have components made from group III-V compound materials.Board of Regents, University of Texas Syste
Convolutional Framework for Accelerated Magnetic Resonance Imaging
Magnetic Resonance Imaging (MRI) is a noninvasive imaging technique that
provides exquisite soft-tissue contrast without using ionizing radiation. The
clinical application of MRI may be limited by long data acquisition times;
therefore, MR image reconstruction from highly undersampled k-space data has
been an active area of research. Many works exploit rank deficiency in a Hankel
data matrix to recover unobserved k-space samples; the resulting problem is
non-convex, so the choice of numerical algorithm can significantly affect
performance, computation, and memory. We present a simple, scalable approach
called Convolutional Framework (CF). We demonstrate the feasibility and
versatility of CF using measured data from 2D, 3D, and dynamic applications.Comment: IEEE ISBI 2020, International Symposium on Biomedical Imagin
Excitonic energy transfer in light-harvesting complexes in purple bacteria
Two distinct approaches, the Frenkel-Dirac time-dependent variation and the
Haken-Strobl model, are adopted to study energy transfer dynamics in
single-ring and double-ring light-harvesting systems in purple bacteria. It is
found that inclusion of long-range dipolar interactions in the two methods
results in significant increases in intra- or inter-ring exciton transfer
efficiency. The dependence of exciton transfer efficiency on trapping positions
on single rings of LH2 (B850) and LH1 is similar to that in toy models with
nearest-neighbor coupling only. However, owing to the symmetry breaking caused
by the dimerization of BChls and dipolar couplings, such dependence has been
largely suppressed. In the studies of coupled-ring systems, both methods reveal
interesting role of dipolar interaction in increasing energy transfer
efficiency by introducing multiple intra/inter-ring transfer paths.
Importantly, the time scale (~4ps) of inter-ring exciton transfer obtained from
polaron dynamics is in good agreement with previous studies. In a double-ring
LH2 system, dipole-induced symmetry breaking leads to global minima and local
minima of the average trapping time when there is a finite value of non-zero
dephasing rate, suggesting that environment plays a role in preserving quantum
coherent energy transfer. In contrast, dephasing comes into play only when the
perfect cylindrical symmetry in the hypothetic system is broken. This study has
revealed that dipolar interaction between chromophores may play an important
part in the high energy transfer efficiency in the LH2 system and many other
natural photosynthetic systems.Comment: 14 pages 9 figure
Solving the Direction Field for Discrete Agent Motion
Models for pedestrian dynamics are often based on microscopic approaches
allowing for individual agent navigation. To reach a given destination, the
agent has to consider environmental obstacles. We propose a direction field
calculated on a regular grid with a Moore neighborhood, where obstacles are
represented by occupied cells. Our developed algorithm exactly reproduces the
shortest path with regard to the Euclidean metric.Comment: 8 pages, 4 figure
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