Universities Space Research Association

About: Universities Space Research Association is a nonprofit organization based out in Columbia, Maryland, United States. It is known for research contribution in the topics: Gamma-ray burst & Galaxy. The organization has 1921 authors who have published 5412 publications receiving 255681 citations. The organization is also known as: USRA.

Bisphosphonates as a supplement to exercise to protect bone during long-duration spaceflight

Abstract: We report the results of alendronate ingestion plus exercise in preventing the declines in bone mass and strength and elevated levels of urinary calcium and bone resorption in astronauts during 55 months of spaceflight This investigation was an international collaboration between NASA and the JAXA space agencies to investigate the potential value of antiresorptive agents to mitigate the well-established bone changes associated with long-duration spaceflight We report the results from seven International Space Station (ISS) astronauts who spent a mean of 55 months on the ISS and who took an oral dose of 70 mg of alendronate weekly starting 3 weeks before flight and continuing throughout the mission All crewmembers had available for exercise a treadmill, cycle ergometer, and a resistance exercise device Our assessment included densitometry of multiple bone regions using X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) and assays of biomarkers of bone metabolism In addition to pre- and post-flight measurements, we compared our results to 18 astronauts who flew ISS missions and who exercised using an early model resistance exercise device, called the interim resistance exercise device, and to 11 ISS astronauts who exercised using the newer advanced resistance exercise device (ARED) Our findings indicate that the ARED provided significant attenuation of bone loss compared with the older device although post-flight decreases in the femur neck and hip remained The combination of the ARED and bisphosphonate attenuated the expected decline in essentially all indices of altered bone physiology during spaceflight including: DXA-determined losses in bone mineral density of the spine, hip, and pelvis, QCT-determined compartmental losses in trabecular and cortical bone mass in the hip, calculated measures of fall and stance computed bone strength of the hip, elevated levels of bone resorption markers, and urinary excretion of calcium The combination of exercise plus an antiresoptive drug may be useful for protecting bone health during long-duration spaceflight

Changing Arctic Snow Cover: A Review of Recent Developments and Assessment of Future Needs for Observations, Modelling, and Impacts

Abstract: Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.

Satellite-Based Assessment of Rainfall-Triggered Landslide Hazard for Situational Awareness

Abstract: Determining the time, location, and severity of natural disaster impacts is fundamental to formulating mitigation strategies, appropriate and timely responses, and robust recovery plans. A Landslide Hazard Assessment for Situational Awareness (LHASA) model was developed to indicate potential landslide activity in near real-time. LHASA combines satellite-based precipitation estimates with a landslide susceptibility map derived from information on slope, geology, road networks, fault zones, and forest loss. Precipitation data from the Global Precipitation Measurement (GPM) mission are used to identify rainfall conditions from the past seven days. When rainfall is considered to be extreme and susceptibility values are moderate to very high, a nowcast is issued to indicate the times and places where landslides are more probable. When LHASA nowcasts were evaluated with a Global Landslide Catalog, the probability of detection (POD) ranged from 8 to 60%, depending on the evaluation period, precipitation product used, and the size of the spatial and temporal window considered around each landslide point. Applications of the LHASA system are also discussed, including how LHASA is used to estimate long-term trends in potential landslide activity at a nearly global scale and how it can be used as a tool to support disaster risk assessment. LHASA is intended to provide situational awareness of landslide hazards in near real-time, providing a flexible, open source framework that can be adapted to other spatial and temporal scales based on data availability.

Gamma-Ray Spectral States of Galactic Black Hole Candidates

Abstract: OSSE has observed seven transient black hole candidates: GRO J0422+32, GX339-4, GRS 1716-249, GRS 1009-45, 4U 1543-47, GRO J1655-40, and GRS 1915+105. Two gamma-ray spectral states are evident and, based on a limited number of contemporaneous X-ray and gamma-ray observations, these states appear to be correlated with X-ray states. The former three objects show hard spectra below 100 keV (photon number indices Gamma < 2) that are exponentially cut off with folding energy ~100 keV, a spectral form that is consistent with thermal Comptonization. This "breaking gamma-ray state" is the high-energy extension of the X-ray low, hard state. In this state, the majority of the luminosity is above the X-ray band, carried by photons of energy ~100 keV. The latter four objects exhibit a "power-law gamma-ray state" with a relatively soft spectral index (Gamma ~ 2.5-3) and no evidence for a spectral break. For GRO J1655-40, the lower limit on the break energy is 690 keV. GRS 1716-249 exhibits both spectral states, with the power-law state having significantly lower gamma-ray luminosity. The power-law gamma-ray state is associated with the presence of a strong ultrasoft X-ray excess (kT ~ 1 keV), the signature of the X-ray high, soft (or perhaps very high) state. The physical process responsible for the unbroken power law is not well understood, although the spectra are consistent with bulk-motion Comptonization in the convergent accretion flow.