Calculation of three-dimensional compressible laminar and turbulent boundary flows. Three-dimensional compressible boundary layers of reacting gases over realistic configurations

A three-dimensional boundary-layer code was developed for particular application to realistic hypersonic aircraft. It is very general and can be applied to a wide variety of boundary-layer flows. Laminar, transitional, and fully turbulent flows of compressible, reacting gases are efficiently calculated by use of the code. A body-oriented orthogonal coordinate system is used for the calculation and the user has complete freedom in specifying the coordinate system within the restrictions that one coordinate must be normal to the surface and the three coordinates must be mutually orthogonal

A comparison of melatonin and α-lipoic acid in the induction of antioxidant defences in L6 rat skeletal muscle cells.

Aging is characterized by a progressive deterioration in physiological functions and metabolic processes. The loss of cells during aging in vital tissues and organs is related to several factors including oxidative stress and inflammation. Skeletal muscle degeneration is common in elderly people; in fact, this tissue is particularly vulnerable to oxidative stress since it requires large amounts of oxygen, and thus, oxidative damage is abundant and accumulates with increasing age. Melatonin (N-acetyl-5-methoxytryptamine) is a highly efficient scavenger of reactive oxygen species and it also exhibits beneficial anti-inflammatory and anti-aging effects. This study investigated the susceptibility of rat L6 skeletal muscle cells to an induced oxidative stress following their exposure to hydrogen peroxide (50 μM) and evaluating the potential protective effects of pre-treatment with melatonin (10 nM) compared to the known beneficial effect of alpha-lipoic acid (300 μM). Hydrogen peroxide-induced obvious oxidative stress; it increased the expression of tumour necrosis factor-alpha and in turn promoted nuclear factor kappa-B and overrode the endogenous defence mechanisms. Conversely, pre-treatment of the hydrogen peroxide-exposed cells to melatonin or alpha-lipoic acid increased endogenous antioxidant enzymes, including superoxide dismutase-2 and heme oxygenase-1; moreover, they ameliorated significantly oxidative stress damage and partially reduced alterations in the muscle cells, which are typical of aging. In conclusion, melatonin was equally effective as alpha-lipoic acid; it exhibited marked antioxidant and anti-aging effects at the level of skeletal muscle in vitro even when it was given in a much lower dose than alpha-lipoic acid

Stark shift and field ionization of arsenic donors in 28^{28}Si-SOI structures

We develop an efficient back gate for silicon-on-insulator (SOI) devices operating at cryogenic temperatures, and measure the quadratic hyperfine Stark shift parameter of arsenic donors in isotopically purified $^{28}$Si-SOI layers using such structures. The back gate is implemented using MeV ion implantation through the SOI layer forming a metallic electrode in the handle wafer, enabling large and uniform electric fields up to $\sim$ 2 V/$\mu$m to be applied across the SOI layer. Utilizing this structure we measure the Stark shift parameters of arsenic donors embedded in the $^{28}$Si SOI layer and find a contact hyperfine Stark parameter of $\eta_a=-1.9\pm0.2\times10^{-3} \mu$m$^2$/V$^2$. We also demonstrate electric-field driven dopant ionization in the SOI device layer, measured by electron spin resonance.Comment: 5 pages, 3 figure

Finite Temperature Effective Potential for Gauge Models in de Sitter Space

The one-loop effective potential for gauge models in static de Sitter space at finite temperatures is computed by means of the $\zeta$--function method. We found a simple relation which links the effective potentials of gauge and scalar fields at all temperatures. In the de Sitter invariant and zero-temperature states the potential for the scalar electrodynamics is explicitly obtained, and its properties in these two vacua are compared. In this theory the two states are shown to behave similarly in the regimes of very large and very small radii a of the background space. For the gauge symmetry broken in the flat limit ($a \to \infty$) there is a critical value of a for which the symmetry is restored in both quantum states. Moreover, the phase transitions which occur at large or at small a are of the first or of the second order, respectively, regardless the vacuum considered. The analytical and numerical analysis of the critical parameters of the above theory is performed. We also established a class of models for which the kind of phase transition occurring depends on the choice of the vacuum.Comment: 23 pages, LaTeX, 5 figure.ep

T1ρ and T2 relaxation times predict progression of knee osteoarthritis

SummaryObjectiveTo evaluate whether T2 and T1ρ relaxation times of knee cartilage determined with 3T magnetic resonance imaging (MRI) at baseline predict longitudinal progression of cartilage degenerative changes.MethodsQuantitative analysis of cartilage was performed using 3T MRI with both T2 and T1ρ mapping techniques in 55 subjects without evidence of severe osteoarthritis (OA) [Kellgren–Lawrence (KL) score of 0–3] at baseline. Morphological abnormalities of cartilage, menisci, ligaments and bone marrow were analyzed on sagittal fat-saturated intermediate-weighted fast spin echo (FSE) sequences. Progression of degenerative changes was analyzed over a period of 2 years. Progression was detected in 27 subjects while in 28 subjects no changes were found. Differences between T2 and T1ρ relaxation times in these two cohorts were compared using one-way analysis of variance (ANOVA) and t tests.ResultsBaseline T2 and T1ρ values were significantly higher in the progression cohort in all compartments (P < 0.05) except the lateral tibia (LT) for T2 and the medial tibia (MT) for T1ρ. Progression of cartilage degenerative disease was most pronounced at the medial femoral condyles and at the femoro-patellar joint; differences between the two cohorts for T2 and T1ρ were also most significant in these compartments.ConclusionsT2 and T1ρ measurements were significantly higher at baseline in individuals that showed progression of cartilage abnormalities over a period of 2 years and may therefore serve as potential predictors for progression of degenerative cartilage abnormalities in knee OA

Appointment scheduling with unscheduled arrivals and reprioritization

Inspired by the real life problem of a radiology department in a Dutch hospital, we study the problem of scheduling appointments, taking into account unscheduled arrivals and reprioritization. The radiology department offers CT diagnostics to both scheduled and unscheduled patients. Of these unscheduled patients, some must be seen immediately, while others may wait for some time. Herein a trade-off is sought between acceptable waiting times for appointment patients and unscheduled patients’ lateness. In this paper we use a discrete event simulation model to determine the performance of a given appointment schedule in terms of waiting time and lateness. Also we propose a constructive and local search heuristic that embeds this model and optimizes the schedule. For smaller instances, we verify the simulation model as well as compare our search heuristics’ performance with optimal schedules obtained using a Markov reward process. In addition we present computational results from the case study in the Dutch hospital. These results show that a considerable decrease of waiting time is possible for scheduled patients, while still treating unscheduled patients on time

Recent Decisions

Comments on recent decisions by William J. Harte, John A. Di Nardo, Donald A. Garrity, Nick J. Neiers, Arthur J. Perry, G. R. Blakey, Matthew T. Hogan, and John V. Reilly, Jr

Race and the Psychological Health of African Americans

This study examined an array of race-related factors pertaining to psychological well-being and distress among 300 African American participants. Findings obtained via structural equation modeling pointed to the importance of having positive implicit ingroup attitudes for psychological health and underscored the significance of Black cultural immersion, particularly in shaping implicit attitudes. Support was obtained for three models: ingroup identity as an antecedent to perceived prejudice, which, in turn, was negatively associated with psychological health; ingroup identity as a consequence of perceived prejudice with positive implications for psychological health; and ingroup identity as a moderator of perceived prejudice, with stronger identity providing a buffer from prejudice. Findings illustrate the consequential and complex role of racial variables in African Americans' psychological health