Use of three-dimensional Gaussian interpolation in the projector/backprojector pair of iterative reconstruction for compensation of known rigid-body motion in SPECT

Due to the extended imaging times employed in single photon emission computed tomography (SPECT) and positron emission tomography (PET), patient motion during imaging is a common clinical occurrence. The fast and accurate correction of the three-dimensional (3-D) translational and rotational patient motion in iterative reconstruction is thus necessary to address this important cause of artifacts. We propose a method of incorporating 3-D Gaussian interpolation in the projector/backprojector pair to facilitate compensation for rigid-body motion in addition to attenuation and distance-dependent blurring. The method works as the interpolation step for moving the current emission voxel estimates and attenuation maps in the global coordinate system to the new patient location in the rotating coordinate system when calculating the expected projection. It also is employed for moving back the backprojection of the ratio of the measured projection to the expected projection and backprojection of the unit value (sensitivity factor) to the original location. MCAT simulations with known six-degree-of-freedom (6DOF) motion were employed to evaluate the accuracy of our method of motion compensation. We also tested the method with acquisitions of the data spectrum anthropomorphic phantom where motion during SPECT acquisition was measured using the Polaris IR motion tracking system. No motion artifacts were seen on the reconstructions with the motion compensation.     

Quantum mechanical aspects of transport in nanoelectronics

The authors discuss some of the effects quantum mechanics has on the performance of nanometer-scale devices. At low temperature, the confinement and the coherence of the electronic motion on the scale of the electron wavelength give rise to gross deviations from classical charge transport that describes the resistance found in large conventional devices. The authors examine three examples of the quantum mechanical nature of the resistance of a split-gate MODFET, that are not accounted for in conventional classical models of a FET, and yet may influence device speed, noise performance and device isolation. The authors consider the temperature and electric field ranges where quantum mechanical effects are manifested in the charge transport, and speculate about the conditions in which parasitic quantum mechanical effects might be found in a conventional device     

Soft-bit decoding of regular low-density parity-check codes

A novel representation, using soft-bit messages, of the belief propagation (BP) decoding algorithm for low-density parity-check codes is derived as an alternative to the log-likelihood-ratio (LLR)-based BP and min-sum decoding algorithms. A simple approximation is also presented. Simulation results demonstrate the functionality of the soft-bit decoding algorithm. Floating-point soft-bit and LLR BP decoding show equivalent performance; the approximation incurs 0.5-dB loss, comparable to min-sum performance loss over BP. Fixed-point results show similar performance to LLR BP decoding; the approximation converges to floating-point results with one less bit of precision.     

Comparison of thin epitaxial film silicon photovoltaics fabricated on monocrystalline and polycrystalline seed layers on glass

We fabricate thin epitaxial crystal silicon solar cells on display glass and fused silica substrates overcoated with a silicon seed layer. To confirm the quality of hot‐wire chemical vapor deposition epitaxy, we grow a 2‐µm‐thick absorber on a (100) monocrystalline Si layer transfer seed on display glass and achieve 6.5% efficiency with an open circuit voltage (V_OC) of 586 mV without light‐trapping features. This device enables the evaluation of seed layers on display glass. Using polycrystalline seeds formed from amorphous silicon by laser‐induced mixed phase solidification (MPS) and electron beam crystallization, we demonstrate 2.9%, 476 mV (MPS) and 4.1%, 551 mV (electron beam crystallization) solar cells. Grain boundaries likely limit the solar cell grown on the MPS seed layer, and we establish an upper bound for the grain boundary recombination velocity (S_GB) of 1.6x10⁴ cm/s. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of temperature and the role of chromium on the kinetics of sulfidation of 310 stainless steel

The sulfidation of 310 stainless steel was studied over the temperature range from 910 to 1285° K. By adjusting the ratio of hydrogen to hydrogen sulfide, variations in sulfur potential were obtained. The effect of temperature on sulfidation was determined at three different sulfur potentials: 39 N·m^–2, 1.4×10^–2 N·m^–2, and 1.5×10^–4 N·m^–2. All sulfide scales contained one or two surface layers in addition to a subscale. The second outer layer (OL-II), furthest from the alloy, contained primarily Fe-Ni-S. The first outer layer0 (OL-I), nearest the subscale, contained Fe-Cr-S. The subscale consisted of sulfide inclusions in the metal matrix. Two different phases were observed in OL-II depending on the temperature and sulfur potential. Below 1065°K OL-II is composed of a mixture of monosulfides of iron and nickel (Fe Ni)_1–xS and pentlandite (Fe_4.5Ni_4.5S₈) with the pentlandite phase exsolved as lamellae upon cooling. At temperatures higher than 1065°K only the pentlandite phase was formed, which melted above 1145°K at sulfur potentials greater than 10^–2 N·m^–2, yielding metal-rich iron-nickel-sulfur. Above 1145°K, and at sulfur potentials less than 10^–2 N·m^–2, OL-II ceased to exist (this temperature is termed transition temperature). Below the transition temperature, where OL-II exists, OL-I could be represented by the general composition (Fe, Cr)_1–xS. This phase on cooling transformed into an array of structures differing in FeCr ratio. These substructures, however, were not observed in quenched samples. Above the transition temperature OL-I changed to a chromium-rich sulfide composition and was associated with a sudden decrease in reaction rate. Subscale formation was found to be due to the dissociation of OL-I at the scale-metal interface, and the extent of subscale growth was found to depend on the temperature and the sulfur potential, as well as the composition of OL-I. At a given temperature and sulfur potential the weight-gain data obeyed the parabolic rate law after an initial transient period. The parabolic rate constants obtained at the sulfur potential of 39 N·m^–2 did not show a break when the logarithm of the rate constant was plotted as a function of the inverse of absolute temperature. Sulfidation carried out at a sulfur potential below 2 × 10^–2 N·m^–2, however, did show a break at 1145°K. This break was found to be associated with the changes which had occurred in the FeCr ratio of OL-I. Below the transition temperature the activation energy was found to be approximately 125 kJ · mole^–1. Above the transition temperature the rate of sulfidation decreased with temperature but depended on the FeCr ratio in the ironchromium-sulfide layers of the OL-I. A reaction mechanism consistent with the experimental results has been proposed in which the diffusion of cations through OL-I is the rate-controlling step. Below the transition temperature the diffusion of Fe and Ni through OL-I contributes to the scale formation, whereas above the transition temperature the diffusion of Cr through OL-I controls the scale formation. Existing literature on the Fe-Ni-S system is compared with the present results.     

Chemical and Physical Sensing by Organic Field‐Effect Transistors and Related Devices

Organic semiconductor films are susceptible to noncovalent interactions, trapping and doping, photoexcitation, and dimensional deformation. While these effects can be detrimental to the performance of conventional circuits, they can be harnessed, especially in field‐effect architectures, to detect chemical and physical stimuli. This Review summarizes recent advances in the use of organic electronic materials for the detection of environmental chemicals, pressure, and light. The material features that are responsible for the transduction of the input signals to electronic information are discussed in detail.     

Reversal bending fatigue test system for investigating vibration integrity of spent nuclear fuel during transportation

Transportation packages for spent nuclear fuel (SNF) must meet safety requirements under normal and accident conditions as specified by federal regulations. During transportation, SNF experiences unique conditions and challenges to cladding integrity due to the vibrational and impact loading during road or rail shipment. Oak Ridge National Laboratory (ORNL) has been developing testing capabilities that can be used to improve the understanding of the impacts on SNF integrity due to vibration loading, especially for high burn-up SNF in normal transportation operation conditions. This information can be used to meet the nuclear industry and U.S. Nuclear Regulatory Commission needs in the area of safety and security of SNF storage and transportation operations. The ORNL developed test system can perform reversal bending fatigue testing to evaluate both the static and dynamic mechanical response of SNF rods under simulated loads. The testing apparatus is also designed to meet the challenges of hot cell operation, including remote installation and detachment of the SNF test specimen, in situ test specimen deformation measurement, and implementation of a driving system suitable for use in a hot cell. The system contains a U frame set-up equipped with uniquely designed grip rigs to protect the SNF rod sample and to ensure valid test results, and uses three specially designed linear variable differential transformers to obtain the in situ curvature measurement. A variety of surrogate test rods have been used to develop and calibrate the test system as well as in performing a series of systematic cyclic fatigue tests. The surrogate rods include stainless steel (SS) cladding, SS cladding with cast epoxy and SS cladding with alumina pellet inserts simulating fuel pellets. Testing to date has shown that the interface bonding between the SS cladding and the alumina pellets has a significant impact on the bending response of the test rods as well as their fatigue strength. The failure behaviours observed from tested surrogate rods provide a fundamental understanding of the underlying failure mechanisms of the SNF surrogate rod under vibration, which has not been achieved previously. The newly developed device is scheduled to be installed in the hot cell in summer 2013 to test high burn-up SNF.     

Robotics‐based telepresence using multi‐modal interaction for individuals with visual impairments

Although many assistive devices have been developed and utilized to aid in daily living, the most general assistive means for individuals with visual impairments are the walking cane and guide dogs. These assistive means are effective in assisting the user in navigating within an environment; however, the navigation space is limited to the proximal environment of the user. Thus, in this paper, we discuss a method to increase the range of accessibility to a remote environment through robotic embodiment that enables teleoperation and teleperception through multi‐modal feedback. In order to transform remote spatial information into a non‐visual modality, we present a framework for utilizing an RGB‐D‐based depth camera, a mobile robot, and a haptic interface for 3D haptic rendering to accomplish the goal of haptic exploration of a remote environment. Experiments with three different control methods for robot interaction are designed for users with and without visual impairments. Several hypothesis are built to study the correlation between control/feedback modality and performance in telerobotic operations. Results show that users performed best when combining semi‐autonomous navigation with 3D haptic exploration and also rated their experience with our system as fairly good. Copyright © 2014 John Wiley & Sons, Ltd.     

Does devoutness delay death? Psychological investment in religion and its association with longevity in the Terman sample.

Religious people tend to live slightly longer lives (M. E. McCullough, W. T. Hoyt, D. B. Larson, H. G. Koenig, & C. E. Thoresen, 2000). On the basis of the principle of social investment (J. Lodi-Smith & B. W. Roberts, 2007), the authors sought to clarify this phenomenon with a study of religion and longevity that (a) incorporated measures of psychological religious commitment; (b) considered religious change over the life course; and (c) examined 19 measures of personality traits, social ties, health behaviors, and mental and physical health that might help to explain the religion–longevity association. Discrete-time survival growth mixture models revealed that women (but not men) with the lowest degrees of religiousness through adulthood had shorter lives than did women who were more religious. Survival differences were largely attributable to cross-sectional and prospective between-class differences in personality traits, social ties, health behaviors, and mental and physical health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)