Leadership: Past, present, and future

In this introductory chapter, the editors of the present volume provide readers with the background necessary to understand the chapters that follow. They first acquaint readers with the concept of leadership and why leadership is necessary. Then, the editors briefly trace the history of leadership research and examine its major schools, most of which are reviewed in this book. Their historical overview is also necessary as an organizing framework because chapter authors frequently refer to elements of the history of leadership research. Next, the editors discuss emerging issues in leadership research and how findings are being consolidated. Finally, they provide an overview of the book and a summary of each chapter

Status of Outer Planet Global Reference Atmospheric Model (GRAM) Upgrades

The inability to test planetary spacecraft in the flight environment prior to a mission requires engineers to rely on ground-based testing and models of the vehicle and expected environments. One of the most widely used engineering models of the atmosphere is the Global Reference Atmospheric Model (GRAM) developed and maintained by the NASA Marshall Space Flight Center (MSFC). The NASA Science Mission Directorate (SMD) has provided funding support to upgrade the GRAMs

Evaluation of Common Probe Trajectories at Multiple Solar System Destinations

No abstract availabl

Aerocapture Guidance and Performance at Mars for High-Mass Systems

The objective of this study is to understand the performance associated with using the aerocapture maneuver to slow high-mass systems from an Earth-approach trajectory into orbit around Mars. This work is done in conjunction with the Mars Entry Descent and Landing Systems Analysis (EDL-SA) task to explore candidate technologies necessary for development in order to land large-scale payloads on the surface of Mars. Among the technologies considered include hypersonic inflatable aerodynamic decelerators (HIADs) and rigid mid-lift to drag (L/D) aeroshells. Nominal aerocapture trajectories were developed for the mid-L/D aeroshell and two sizes of HIADs, and Monte Carlo analysis was completed to understand sensitivities to dispersions. Additionally, a study was completed in order to determine the size of the larger of the two HIADs which would maintain design constraints on peak heat rate and diameter. Results show that each of the three aeroshell designs studied is a viable option for landing high-mass payloads as none of the three exceed performance requirements

Correlated defects, metal-insulator transition, and magnetic order in ferromagnetic semiconductors

The effect of disorder on transport and magnetization in ferromagnetic III-V semiconductors, in particular (Ga,Mn)As, is studied theoretically. We show that Coulomb-induced correlations of the defect positions are crucial for the transport and magnetic properties of these highly compensated materials. We employ Monte Carlo simulations to obtain the correlated defect distributions. Exact diagonalization gives reasonable results for the spectrum of valence-band holes and the metal-insulator transition only for correlated disorder. Finally, we show that the mean-field magnetization also depends crucially on defect correlations.Comment: 4 pages RevTeX4, 5 figures include

Impact of nutritional vitamin D supplementation on parathyroid hormone and 25-hydroxyvitamin D levels in non-dialysis chronic kidney disease : a meta-analysis

Background. Secondary hyperparathyroidism (SHPT) is a common and major complication in chronic kidney disease (CKD), reflecting the increase of parathyroid hormone (PTH) in response to reduced vitamin D signalling and hypocalcaemia. This meta-analysis evaluated the impact of nutritional vitamin D (NVD) (cholecalciferol or ergocalciferol) on SHPT-related biomarkers. Methods. A systematic literature search was performed in PubMed to identify relevant randomized control trials to be included in the meta-analysis. Fixed- and random-effects models were used to pool study-level results. Effects were studied within NVD study arms and relative to control groups (placebo/no treatment); the former in order to identify the effect of actively altering biomarkers levels. Results. Reductions in PTH from supplementation with NVD were small when observed within the NVD study arms (pooled reduction: 10.5 pg/mL) and larger when compared with placebo/no treatment (pooled reduction: 49.7 pg/mL). NVD supplementation increased levels of 25-hydroxyvitamin D [25(OH)D] in both analyses (increase within NVD study arm: 20.6 ng/mL, increase versus placebo/no treatment: 26.9 ng/mL). While small and statistically non-significant changes in phosphate and fibroblast growth factor 23 were observed, NVD supplementation caused calcium levels to increase when compared with placebo/no treatment (increase: 0.23 mg/dL). Conclusions. Our results suggest that supplementation with NVD can be used to increase 25(OH)D to a certain extent, while the potential of NVD to actively reduce PTH in non-dialysis-CKD patients with SHPT is limited

Mars Global Reference Atmospheric Model (Mars-GRAM) Upgrades

The inability to test planetary spacecraft in the flight environment prior to a mission requires engineers to rely on ground-based testing and models of the vehicle and expected environments. One of the most widely used engineering models of the Martian atmosphere is the Mars Global Reference Atmospheric Model (Mars-GRAM) developed and maintained by the NASA Marshall Space Flight Center (MSFC). The NASA Science Mission Directorate (SMD) has provided funding support to upgrade the planetary GRAMs in Fiscal Year 2018 and 2019. This poster summarizes the upgrades that have been made to Mars-GRAM, the release status of Mars-GRAM, the new GRAMs that are under development, and future Mars-GRAM upgrade plans

Search for Free Decay of Negative Pions in Water and Light Materials

We report on a search for the free decay component of pi- stopped in water and light materials. A non-zero value of this would be an indication of anomalous nu_e contamination to the nu_e and nu_mu_bar production at stopped-pion neutrino facilities. No free decay component of pi- was observed in water, Beryllium, and Aluminum, for which upper limits were established at 8.2E-4, 3.2E-3, and 7.7E-3, respectively

Overview of the NASA Entry, Descent and Landing Systems Analysis Study

NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to make in order to successfully land large payloads at Mars for both robotic and human-scale missions. This paper summarizes the approach and top-level results from Year 1 of the Study, which focused on landing 10-50 mt on Mars, but also included a trade study of the best advanced parachute design for increasing the landed payloads within the EDL architecture of the Mars Science Laboratory (MSL) mission