The Goddard Version of the Schubart-stumpff N-body Program

Goddard version of Schubart-Stumpff N-Body program for computation of solar system orbit

Student Attitudes Regarding Active Learning In Health Professions Microbiology Course

While many active learning strategies are evidence-based, it is unclear as to which methods are preferred by most students. In the present study students in an undergraduate health professions microbiology course were assigned four projects (“types” 1 – 4) that included elements of active learning and that required students to apply microbiological concepts to health care or public health. A type 1 project involved the student consulting professional journals, textbooks and/or websites and preparing an informative brochure on an infectious disease suitable for reading by the lay public. A type 2 project involved the student shadowing a health care professional. A type 3 project involved the student performing a community service. A type 4 project involved the student designing and conducting an original lab research study. A survey was used to assess student attitudes about doing these projects. I report that while some students preferred particular project types, no project type was preferred by a majority of students. In addition, students ranked all four project types highly and considered them all to have equal educational value and relevance to course content. These results suggest that instructors should avoid using a “one size fits all” active learning approach. Students value the use of diverse pedagogical approches that engage their learning in different ways and that connect course concepts to real-world applications.

Solvent Replacement for Hydrochlorofluorocarbon-225 for Cleaning Oxygen System Components

This Technical Memorandum is the result of a 2-year project funded by the Defense Logistics Agency-Aviation, Hazardous Minimization and Green Products Branch, to identify and test two candidate solvents to replace hydrochlorofluorocarbon-225 (HCFC-225) for cleaning oxygen systems. The solvents were also compared to a second solvent composed predominantly of perfluorobutyl iodide (PFBI), which had received limited approval by the United States Air Force (USAF) for hand wipe cleaning of components for aviators breathing oxygen systems. The tests performed for this study were based on those reported in AFRL-ML-WP-TR-2003-4040, The Wipe Solvent Program, the test program used to qualify Ikon Solvent P for USAF applications.The study was completed in August 2014, prior to the completion of a more extensive study funded by the NASA Rocket Propulsion Test (RPT) program. The results of the RPT project are reported in NASA/TP-2015-18207, Replacement of Hydrochlorofluorocarbon225 Solvent for Cleaning and Verification Sampling of NASA Propulsion Oxygen Systems Hardware, Ground Support Equipment, and Associated Test Systems. The test methods used in this study for nonvolatile residue (NVR) background, materials compatibility, and cleaning effectiveness were different than those used for the RPT project; a smaller set of materials and contaminants were tested. The tests for this study were complementary to and provided supplementary information for the down-selection process during the course of the test program reported in NASA/TP-2015-218207

Replacement of Hydrochlorofluorocarbon (HCFC) -225 Solvent for Cleaning and Verification Sampling of NASA Propulsion Oxygen Systems Hardware, Ground Support Equipment, and Associated Test Systems

Since the 1990's, when the Class I Ozone Depleting Substance (ODS) chlorofluorocarbon-113 (CFC-113) was banned, NASA's rocket propulsion test facilities at Marshall Space Flight Center (MSFC) and Stennis Space Center (SSC) have relied upon hydrochlorofluorocarbon-225 (HCFC-225) to safely clean and verify the cleanliness of large scale propulsion oxygen systems. Effective January 1, 2015, the production, import, export, and new use of HCFC-225, a Class II ODS, was prohibited by the Clean Air Act. In 2012 through 2014, leveraging resources from both the NASA Rocket Propulsion Test Program and the Defense Logistics Agency - Aviation Hazardous Minimization and Green Products Branch, test labs at MSFC, SSC, and Johnson Space Center's White Sands Test Facility (WSTF) collaborated to seek out, test, and qualify a replacement for HCFC-225 that is both an effective cleaner and safe for use with oxygen systems. Candidate solvents were selected and a test plan was developed following the guidelines of ASTM G127, Standard Guide for the Selection of Cleaning Agents for Oxygen Systems. Solvents were evaluated for materials compatibility, oxygen compatibility, cleaning effectiveness, and suitability for use in cleanliness verification and field cleaning operations. Two solvents were determined to be acceptable for cleaning oxygen systems and one was chosen for implementation at NASA's rocket propulsion test facilities. The test program and results are summarized. This project also demonstrated the benefits of cross-agency collaboration in a time of limited resources

Results of the Test Program for Replacement of AK-225G Solvent for Cleaning NASA Propulsion Oxygen Systems

Since the 1990's, when the Class I Ozone Depleting Substance chlorofluorocarbon-113 was banned, NASA's propulsion test facilities at Marshall Space Flight Center and Stennis Space Center have relied upon the solvent Asahiklin AK-225 (hydrochlorofluorocarbon-225ca/cb or HCFC-225ca/cb) and, more recently AK-225G (the single isomer form, HCFC-225cb) to safely clean and verify the cleanliness of large scale propulsion oxygen systems. Effective January 1, 2015, the production, import, export, and new use of Class II Ozone Depleting Substances, including AK-225G, was prohibited in the United States by the Clean Air Act. In 2012 through 2014, NASA test labs at MSFC, SSC, and Johnson Space Center's White Sands Test Facility collaborated to seek out, test, and qualify a solvent replacement for AK-225G that is both an effective cleaner and safe for use with oxygen systems. This paper summarizes the tests performed, results, and lessons learned

Seasonal Resource Selection by Introduced Mountain Goats in the Southwest Greater Yellowstone Area

Mountain ungulates, although regarded as iconic and charismatic wildlife species, are the least studied and understood large mammals in the Greater Yellowstone Area (GYA). Mountain goats (Oreamnos americanus) are considered non-native in the GYA according to reviews of archeological, paleontological, and historical records, and have been steadily expanding their range since their initial introduction in the 1940s.  Because of the general propensity of mountain goats to inhabit high elevation, mountainous terrain, there is significant potential for range overlap with native bighorn sheep (Ovis canadensis) and the possibility that competition and disease transfer will be detrimental to sympatric bighorn populations.  I will broadly discuss mountain goat seasonal resource selection modeled from 15 (11 females and 4 males) allopatric mountain goats representing the sole established population in the southwest GYA.  These efforts produce the first spatial predictions of seasonal habitat use by mountain goats in the GYA using GPS data, and provide regional managers with important insights regarding the current and future distribution of mountain goats.  Of particular interest are areas where mountain goats are in the early stages of colonization, such as Grand Teton National Park.  Building seasonal resource selection models for mountain goats in the GYA is the first step needed to better understand their biological needs, ecological role, and potential to negatively impact native communities and species

Ecological Effects of Fear: How Spatiotemporal Heterogeneity in Predation Risk Influences Mule Deer Access to Forage in a Sky‐Island System

Forage availability and predation risk interact to affect habitat use of ungulates across many biomes. Within sky‐island habitats of the Mojave Desert, increased availability of diverse forage and cover may provide ungulates with unique opportunities to extend nutrient uptake and/or to mitigate predation risk. We addressed whether habitat use and foraging patterns of female mule deer (Odocoileus hemionus) responded to normalized difference vegetation index (NDVI), NDVI rate of change (green‐up), or the occurrence of cougars (Puma concolor). Female mule deer used available green‐up primarily in spring, although growing vegetation was available during other seasons. Mule deer and cougar shared similar habitat all year, and our models indicated cougars had a consistent, negative effect on mule deer access to growing vegetation, particularly in summer when cougar occurrence became concentrated at higher elevations. A seemingly late parturition date coincided with diminishing NDVI during the lactation period. Sky‐island populations, rarely studied, provide the opportunity to determine how mule deer respond to growing foliage along steep elevation and vegetation gradients when trapped with their predators and seasonally limited by aridity. Our findings indicate that fear of predation may restrict access to the forage resources found in sky islands

Electric Field Mapping System With Nanosecond Temporal Rosolution

The electric field dependence of the absorption coefficient in semi‐insulating GaAs at the absorption edge was measured in a high‐voltage pulsed experiment. Pulse duration was kept below 50 ns in order to avoid thermal effects. A GaAs laser diode was used as a probe light source with wavelength varied from 902 to 911 nm. For fields up to 40 kV/cm the absorption coefficient increased from 3 to 17 cm−1 at 902 nm, with smaller absolute increases evident at the longer wavelengths. Calculation from theory was consistent with this behavior. The spatial variation of the electric field was also recorded with a CCD camera. This method was used as a diagnostic technique to study the field distribution during the switching cycle of a high‐power photoconductive switch. The described system could be used as a simple electric field probe with temporal resolution of 100 ps, or as a field mapping system with spatial resolution approaching 1 μm

A Geophysical Atlas for Interpretation of Satellite-derived Data

A compilation of maps of global geophysical and geological data plotted on a common scale and projection is presented. The maps include satellite gravity, magnetic, seismic, volcanic, tectonic activity, and mantle velocity anomaly data. The Bibliographic references for all maps are included