Current status of MCNP6 as a simulation tool useful for space and accelerator applications

For the past several years, a major effort has been undertaken at Los Alamos National Laboratory (LANL) to develop the transport code MCNP6, the latest LANL Monte-Carlo transport code representing a merger and improvement of MCNP5 and MCNPX. We emphasize a description of the latest developments of MCNP6 at higher energies to improve its reliability in calculating rare-isotope production, high-energy cumulative particle production, and a gamut of reactions important for space-radiation shielding, cosmic-ray propagation, and accelerator applications. We present several examples of validation and verification of MCNP6 compared to a wide variety of intermediate- and high-energy experimental data on reactions induced by photons, mesons, nucleons, and nuclei at energies from tens of MeV to about 1 TeV/nucleon, and compare to results from other modern simulation tools.Comment: 4 pages, 3 figures, Proc. 11th Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2012), St. Petersburg, FL, May 28 - June 3, 201

High-temperature oxidation of nickel-based alloys and estimation of the adhesion strength of resulting oxide layers

The kinetics of isothermal oxidation (1100°C) of commercial nickel-based alloys with different content of sulfur (0.22–3.2 wt ppm) is studied. The adhesion strength in a metal/oxide system is estimated as a function of sulfur content and duration of high-temperature exposure. The scratch-test technique is proposed to quantitatively estimate the work of adhesion of resulting oxide films. It is found that the film microstructure is composed of an inner α-Al2O3 layer and an outer NiAl2O4 spinel layer, which are separated by discrete inclusions of TiO2. Residual stresses in the oxide film are experimentally determined by X-ray diffraction. spinel layer, which are separated by discrete inclusions of TiO2. Residual stresses in the oxide film are experimentally determined by X-ray diffractio

Bearing restoration by grinding

A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed

Evolving localizations in reaction-diffusion cellular automata

We consider hexagonal cellular automata with immediate cell neighbourhood and three cell-states. Every cell calculates its next state depending on the integral representation of states in its neighbourhood, i.e. how many neighbours are in each one state. We employ evolutionary algorithms to breed local transition functions that support mobile localizations (gliders), and characterize sets of the functions selected in terms of quasi-chemical systems. Analysis of the set of functions evolved allows to speculate that mobile localizations are likely to emerge in the quasi-chemical systems with limited diffusion of one reagent, a small number of molecules is required for amplification of travelling localizations, and reactions leading to stationary localizations involve relatively equal amount of quasi-chemical species. Techniques developed can be applied in cascading signals in nature-inspired spatially extended computing devices, and phenomenological studies and classification of non-linear discrete systems.Comment: Accepted for publication in Int. J. Modern Physics

Rapid-sequence MRI for long-term surveillance for paraganglioma and phaeochromocytoma in patients with succinate dehydrogenase (SDHx) mutations

INTRODUCTION: Patients with SDHx mutations need long-term radiological surveillance for the development of paragangliomas and phaeochromocytomas, but no longitudinal data exist. We assessed the performance of rapid-sequence non-contrast magnetic resonance imaging (MRI) in the long-term monitoring of patients with SDHx mutations. METHODS: Retrospective study between 2005-2015 at a University Hospital and regional endocrine genetics referral center. Clinical and imaging data of forty-seven patients with SDHx mutations [SDHB (36), SDHC (6), SDHD (5)] who had surveillance for detection of paragangliomas by rapid-sequence non-contrast MRI (base of skull to pubic symphysis) were collected. RESULTS: Twelve index cases (9 SDHB, 1 SDHC, 2 SDHD) and 35 mutation-positive relatives were monitored for a mean of 6.4 years (range 3.1 to 10.0 years). Mean age at the end of the study: SDHB 46.9+/-17.6 years; SDHC 42.3+/-24.4 years; SDHD 54.9 +/- 10.6 years. Excluding imaging at initial diagnosis of index cases forty-three patients underwent 116 rapid-sequence MRI scans: 83 scans were negative and 31 scans were positive for a sPGL/HNPGL in 13 patients. Most patients had multiple scans [n=number of patients (number of rapid-sequence MRI scans during screening)]; n=9 (2), n=20 (3), n=6 (4), n=1 (6). Nine patients (3 index) were diagnosed with new paragangliomas during surveillance and non-operated tumour size was monitored in 9 patients. There were two false positive scans (1.6%). Scans were repeated every 27 +/- 9 months. CONCLUSIONS: Biannual rapid-sequence non-contrast MRI is effective to monitor patients with SDHx mutations for detection of new tumours and monitoring of known tumours

Exploring psychosocial predictors of STI testing in University students

Peer reviewedPublisher PD

Bioimpedance of soft tissue under compression

In this paper compression-dependent bioimpedance measurements of porcine spleen tissue are presented. Using a Cole–Cole model, nonlinear compositional changes in extracellular and intracellular makeup; related to a loss of fluid from the tissue, are identified during compression. Bioimpedance measurements were made using a custom tetrapolar probe and bioimpedance circuitry. As the tissue is increasingly compressed up to 50%, both intracellular and extracellular resistances increase while bulk membrane capacitance decreases. Increasing compression to 80% results in an increase in intracellular resistance and bulk membrane capacitance while extracellular resistance decreases. Tissues compressed incrementally to 80% show a decreased extracellular resistance of 32%, an increased intracellular resistance of 107%, and an increased bulk membrane capacitance of 64% compared to their uncompressed values. Intracellular resistance exhibits double asymptotic curves when plotted against the peak tissue pressure during compression, possibly indicating two distinct phases of mechanical change in the tissue during compression. Based on these findings, differing theories as to what is happening at a cellular level during high tissue compression are discussed, including the possibility of cell rupture and mass exudation of cellular material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98622/1/0967-3334_33_6_1095.pd

The Voluntary Adjustment of Railroad Obligations

Automatic memory management techniques eliminate many programming errors that are both hard to find and to correct. However, these techniques are not yet used in embedded systems with hard realtime applications. The reason is that current methods for automatic memory management have a number of drawbacks. The two major ones are: (1) not being able to always guarantee short real-time deadlines and (2) using large amounts of extra memory. Memory is usually a scarce resource in embedded applications. In this paper we present a new technique, Real-Time Reference Counting (RTRC) that overcomes the current problems and makes automatic memory management attractive also for hard real-time applications. The main contribution of RTRC is that often all memory can be used to store live objects. This should be compared to a memory overhead of about 500% for garbage collectors based on copying techniques and about 50% for garbage collectors based on mark-and-sweep techniques