On Using Commercial Off-the-Shelf (COTS) Electronic Products in Space

NASA's Johnson Space Center (JSC) has utilized COTS products in its programs since the early 1990's. Recently it has become evident that, of all failure modes possible, radiation will probably dominate; sometimes to the point of driving system architecture. It is now imperative that radiation susceptibility be addressed when writing the system requirements. Susceptibility assessment, e.g. testing, must begin early in the design phase to establish performance and continue through the hardware qualification program to prove satisfaction of the original requirements(s). Examples of requirements, testing, and architecture versus failure rate will be given

Tracking Systems to Support the Common Lunar Lander (CLL)

A discussion of the tracking system for Artemis (the Common Lunar Lander) is presented. Among the topics presented are the following: major drivers for system definition, results of vendor survey, baseline system properties, program considerations, and mission phases requiring tracking

Minimizing epicormic branch formation on Louisiana leading commercial bottomland red oaks

The goal of this study was to isolate biological, natural, and silvicultural factors that encourage the production of epicormic branches on bottomland red oak saw-timber trees and to use this information to help landowners and forest managers reduce epicormic branches in stands dominated by bottomland red oaks. Quercus nigra, Q. pagoda, Q. phellos, and Q. texana, the most common commercial bottomland red oaks in Louisiana, were evaluated in this study. Both qualitative and quantitative variables were assessed in this study. The following attributes were collected from each sample tree and primary competitor: site class, basal area, crown class DBH, presence or absence of epicormic branches, soil series, flooding regime, total tree height, height to base of live crown, live crown ratio, localized disturbance, and distance to nearest competitor. A total of 768 trees were evaluated, of which 384 trees displayed epicormic branching and 384 were without epicormic branches. Sample trees of all four species were equally distributed across four crown classes (dominant, co-dominant, intermediate, and suppressed). Equal numbers of all four oak species were collected to maintain homogeneity within the dataset. Logistic and Poisson regressions were used to analyze the data. An á level of 0.1 was considered effective for significance in this exploratory research. Logistic regression analysis yielded three variables significant in relation to the probability of epicormic branch occurrence. Variables significantly affecting the probability of epicormic branch production were total height of the sample tree, distance from the sample tree to the primary competitor, and crown class of the nearest primary competitor. The Poisson regression analysis was used to evaluate the number of epicormic branches a tree might produce. In this analysis dbh of the sample tree, crown class of the primary competitor, disturbance, flooding regime, and live crown ratio of sample trees were significant in relation to the number of epicormic branches produced. Tree, site, and environmental characteristics isolated as being important to epicormic branch production produced a means for evaluating the potential development of epicormic branches. These factors in concert provide the forester or land manager with a simple means of enhancing bottomland red oak value. The driving mechanism for sudden appearance of epicormic branches seems to be related to reduced tree vigor as affected by competition (or relative vigor based on relative height to competitors) and site stress factors. Taller trees with less competition from similar sized trees have a reduced probability of epicormic branches. Or stated in another way, trees with close competitors or nearly equal height are more likely to produce epicormic branches. Dominant trees have a reduced likelihood of developing epicormic branches if other stress factors are not at play. Intermediate and suppressed crown class trees should be removed during early thinnings of red oaks stands to avoid or reduce epicormic branch production. In concert, factors reducing competition and decreasing tree vigor tend to reduce the probability of epicormic branch production on bottomland red oaks

Initial Hardware Development Schedule

The hardware development schedule for the Common Lunar Lander's (CLLs) tracking system is presented. Among the topics covered are the following: historical perspective, solution options, industry contacts, and the rationale for selection

A Monte Carlo Model for LET Spectra of 200 MeV Protons Used for Microelectronic Testing

The direct ionization Linear Energy Transfer (LET) for 200 MeV protons in silicon is much smaller than that for higher charged particles since LET increases as the square of the ion charge. However, occasionally the proton interacts with the silicon nuclei and produces a shower of fragments and a recoiling nucleus. When this happens, the LET produced is much greater than the direct ionization LET. Testing the single event effect susceptibility of components using energetic (200 MeV) protons is often the only viable option for system level testing commercial-off-the-shelf (COTS) avionics that have not been designed for space environments. However, the question of how a system tested with protons will perform in a heavy ion environment arises. Here the concern is not only with prediction of on-orbit upset rate, but also about possibility of on-orbit failures that were not observed during proton testing

Disease-modifying therapy prescription patterns in people with multiple sclerosis by age

BACKGROUND: Disease-modifying therapies (DMTs) for multiple sclerosis (MS) are approved for their ability to reduce disease activity, namely clinical relapses and signal changes on magnetic resonance imaging (MRI). Disease activity appears age dependent. Thus, the greatest benefit would be expected in younger people with MS (PwMS) whereas benefits in the elderly are uncertain. METHODS: Real-world data were obtained from PwMS from the North American Research Committee on Multiple Sclerosis (NARCOMS) registry and the US Department of Veterans Affairs Multiple Sclerosis Surveillance Registry (MSSR). RESULTS: 6948 PwMS were surveyed from NARCOMS, and the MSSR had 1719 participants. In younger adult PwMS 40-years old or less, 183 (61.4%) in NARCOMS and 179 (70.5%) in the MSSR were prescribed DMTs. Among PwMS over age 60, 1575 (40.1%) in NARCOMS and 239 (36.3%) in the MSSR were prescribed DMTs. More PwMS in the age group of 31-40 ( CONCLUSION: These findings suggest that DMTs are under-utilized in the younger population and continue to be commonly prescribed in the elderly. Broader access may explain the higher prescription rate of DMTs in US veterans

A retrospective claims analysis of combination therapy in the treatment of adult attention-deficit/hyperactivity disorder (ADHD)

<p>Abstract</p> <p>Background</p> <p>Combination therapy in managing psychiatric disorders is not uncommon. While combination therapy has been documented for depression and schizophrenia, little is known about combination therapy practices in managing attention-deficit/hyperactivity disorder (ADHD). This study seeks to quantify the combination use of ADHD medications and to understand predictors of combination therapy.</p> <p>Methods</p> <p>Prescription dispensing events were drawn from a U.S. national claims database including over 80 managed-care plans. Patients studied were age 18 or over with at least 1 medical claim with a diagnosis of ADHD (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] code 314.0), a pharmacy claim for ADHD medication during the study period July2003 to June2004, and continuous enrollment 6 months prior to and throughout the study period. Dispensing events were grouped into 6 categories: atomoxetine (ATX), long-acting stimulants (LAS), intermediate-acting stimulants (IAS), short-acting stimulants (SAS), bupropion (BUP), and Alpha-2 Adrenergic Agonists (A2A). Events were assigned to calendar months, and months with combined use from multiple categories within patient were identified. Predictors of combination therapy for LAS and for ATX were modeled for patients covered by commercial plans using logistic regression in a generalized estimating equations framework to adjust for within-patient correlation between months of observation. Factors included age, gender, presence of the hyperactive component of ADHD, prior diagnoses for psychiatric disorders, claims history of recent psychiatric visit, insurance plan type, and geographic region.</p> <p>Results</p> <p>There were 18,609 patients identified representing a total of 11,886 months of therapy with ATX; 40,949 months with LAS; 13,622 months with IAS; 38,141 months with SAS; 22,087 months with BUP; and 1,916 months with A2A. Combination therapy was present in 19.7% of continuing months (months after the first month of therapy) for ATX, 21.0% for LAS, 27.4% for IAS, 23.1% for SAS, 36.9% for BUP, and 53.0% for A2A.</p> <p>For patients receiving LAS, being age 25–44 or age 45 and older versus being 18–24 years old, seeing a psychiatrist, having comorbid depression, or having point-of-service coverage versus a Health Maintenance Organization (HMO) resulted in odds ratios significantly greater than 1, representing increased likelihood for combination therapy in managing adult ADHD.</p> <p>For patients receiving ATX, being age 25–44 or age 45 and older versus being 18–24 years old, seeing a psychiatrist, having a hyperactive component to ADHD, or having comorbid depression resulted in odds ratios significantly greater than 1, representing increased likelihood for combination therapy in managing adult ADHD.</p> <p>Conclusion</p> <p>ATX and LAS are the most likely drugs to be used as monotherapy. Factors predicting combination use were similar for months in which ATX was used and for months in which LAS was used except that a hyperactive component to ADHD predicted increased combination use for ATX but not for LAS.</p