A methodology for selective removal of orbital debris

Earth-orbiting objects, large enough to be tracked, were surveyed for possible systematic debris removal. Based upon the statistical collision studies of others, it was determined that objects in orbits approximately 1000 km above the Earth's surface are at greatest collisional risk. Russian C-1B boosters were identified as the most important target of opportunity for debris removal. Currently, more than 100 in tact boosters are orbiting the Earth with apogees between 950 km and 1050 km. Using data provided by Energia USA, specific information on the C-1B booster, in terms of rendezvous and capture strategies, was discussed

Low Gravity Guidance System for Airborne Microgravity Research

Microgravity research techniques have been established to achieve a greater understanding of the role of gravity in the fundamentals of a variety of physical phenomena and material processing. One technique in use at the NASA Lewis Research Center involves flying Keplarian trajectories with a modified Lear Jet and DC-9 aircraft to achieve a highly accurate Microgravity environment by neutralizing accelerations in all three axis of the aircraft. The Low Gravity Guidance System (LGGS) assists the pilot and copilot in flying the trajectories by displaying the aircraft acceleration data in a graphical display format. The Low Gravity Guidance System is a microprocessor based system that acquires and displays the aircraft acceleration information. This information is presented using an electroluminescent display mounted over the pilot's instrument panel. The pilot can select the Microgravity range that is required for a given research event. This paper describes the characteristics, design, calibration and testing of the Low Gravity Guidance System Phase 3, significant lessons from earlier systems and the developmental work on future systems

Piloted Evaluation of an Integrated Methodology for Propulsion and Airframe Control Design

An integrated methodology for propulsion and airframe control has been developed and evaluated for a Short Take-Off Vertical Landing (STOVL) aircraft using a fixed base flight simulator at NASA Lewis Research Center. For this evaluation the flight simulator is configured for transition flight using a STOVL aircraft model, a full nonlinear turbofan engine model, simulated cockpit and displays, and pilot effectors. The paper provides a brief description of the simulation models, the flight simulation environment, the displays and symbology, the integrated control design, and the piloted tasks used for control design evaluation. In the simulation, the pilots successfully completed typical transition phase tasks such as combined constant deceleration with flight path tracking, and constant acceleration wave-off maneuvers. The pilot comments of the integrated system performance and the display symbology are discussed and analyzed to identify potential areas of improvement

The Costs of Carnivory

Mammalian carnivores fall into two broad dietary groups: smaller carnivores (<20 kg) that feed on very small prey (invertebrates and small vertebrates) and larger carnivores (>20 kg) that specialize in feeding on large vertebrates. We develop a model that predicts the mass-related energy budgets and limits of carnivore size within these groups. We show that the transition from small to large prey can be predicted by the maximization of net energy gain; larger carnivores achieve a higher net gain rate by concentrating on large prey. However, because it requires more energy to pursue and subdue large prey, this leads to a 2-fold step increase in energy expenditure, as well as increased intake. Across all species, energy expenditure and intake both follow a three-fourths scaling with body mass. However, when each dietary group is considered individually they both display a shallower scaling. This suggests that carnivores at the upper limits of each group are constrained by intake and adopt energy conserving strategies to counter this. Given predictions of expenditure and estimates of intake, we predict a maximum carnivore mass of approximately a ton, consistent with the largest extinct species. Our approach provides a framework for understanding carnivore energetics, size, and extinction dynamics

Cardiovascular and gastrointestinal outcomes in clopidogrel users on proton pump inhibitors: results of a large Dutch cohort study.

Contains fulltext : 88128.pdf (publisher's version ) (Closed access)OBJECTIVES: Recent studies have raised concerns on the clinical effectiveness of clopidogrel when taken in combination with proton pump inhibitors (PPIs), demonstrating an increase in the occurrence of cardiovascular events. In this study, the association between the co-administration of a PPI and clopidogrel and the occurrence of cardiovascular and gastrointestinal (GI) events in a large cohort in the Netherlands was investigated. METHODS: A retrospective study was conducted using data from 4 million individuals. New clopidogrel users were identified between January 2006 and December 2007 and followed over time. The Kaplan-Meier method and Cox proportional hazard regression [corrected]analysis were used to calculate the risk of cardiovascular and GI outcomes in clopidogrel patients with or without PPI use. RESULTS: A total of 18,139 new clopidogrel users were identified; 5,734 subjects (32%) used PPIs concurrently. Patients on PPIs were significantly older, used more co-medications and suffered from more comorbidities. Use of clopidogrel and PPIs was associated with an increased risk of myocardial infarction (hazard ratio (HR) 1.93, 95% confidence interval (CI) 1.40-2.65), unstable angina pectoris (HR 1.79, 95% CI 1.60-2.03), and the composite endpoint (HR 1.75, 95% CI 1.58-1.94) compared with clopidogrel users without PPIs. PPI users also had an increased risk of GI events compared with non-PPI users (HR 4.76, 95% CI 1.18-19.17). CONCLUSIONS: New clopidogrel users on PPIs are at an increased risk of cardiovascular and GI complications compared with those who are not using a PPI. The inferior cardiovascular profile of clopidogrel users on PPIs and the occurrence of channeling bias may be important factors underlying this observation.1 november 201

OBSERVATIONAL LIMITS ON COMPANIONS TO G29-38

Recent interset in the variable (DAV) white dwarf G29-38 has been stirred by a tentative report of a radial velocity variation that may be due to an unseen companion. Earlier evidence for a brown dwarf in the system has come from an observed infrared excess in the star's spectrum. For asteroseismological reasons, we have accumulated more than five seasons of high-speed photometric data on the star. By measuring the phase of an isolated, stable frequency in the power spectrum, we show the measured variation is not due (at least in its entirety) to an orbital companion. Because any orbital radial velocity variation must result in a systematic phase variation, the data we present can be used to place stringent limits on the types of companions the system may contain

Evaluating training for a simulated team in complex whole procedure simulations in the endovascular suite

Introduction: Simulators supporting the development of technical skills for complex procedures are gaining prominence. Safe performance of complex procedures requires effective team interactions. Our research group creates ‘whole’ procedure simulations to produce the psychological fidelity of clinical settings. Recruitment of real interventional team (IT) members has proved challenging. Actors as a simulated team are expensive. We hypothesised that medical students and trainees in a vascular unit could authentically portray members of the endovascular suite for carotid stenting. Methods: This paper describes the evaluation of a training programme for a simulated IT. Participants rated the extent to which programmes objectives were met and realism of simulations. Researchers’ field notes provided insight into strengths and weaknesses of the programme. Results: Seven members from the vascular unit undertook training. Learning objectives were largely met. Nineteen simulations with 13 interventionalists were performed. Realism levels were at least moderate. Simulated IT members reported increased understanding of teamwork and roles in the endovascular suite. Discussion: A simulated IT proved feasible. Authentic psychological fidelity complemented the physical fidelity of the simulated suite. Although there were areas for development in training, this approach might contribute considerably to interventionalist training and increase knowledge and skills of vascular trainees and medical students