Products from NASA's In-Space Propulsion Technology Program Applicable to Low-Cost Planetary Missions

Since September 2001 NASA s In-Space Propulsion Technology (ISPT) program has been developing technologies for lowering the cost of planetary science missions. Recently completed is the high-temperature Advanced Material Bipropellant Rocket (AMBR) engine providing higher performance for lower cost. Two other cost saving technologies nearing completion are the NEXT ion thruster and the Aerocapture technology project. Also under development are several technologies for low cost sample return missions. These include a low cost Hall effect thruster (HIVHAC) which will be completed in 2011, light weight propellant tanks, and a Multi-Mission Earth Entry Vehicle (MMEEV). This paper will discuss the status of the technology development, the cost savings or performance benefits, and applicability of these in-space propulsion technologies to NASA s future Discovery, and New Frontiers missions, as well as their relevance for sample return missions

‘It Takes Two Hands to Clap’: How Gaddi Shepherds in the Indian Himalayas Negotiate Access to Grazing

This article examines the effects of state intervention on the workings of informal institutions that coordinate the communal use and management of natural resources. Specifically it focuses on the case of the nomadic Gaddi shepherds and official attempts to regulate their access to grazing pastures in the Indian Himalayas. It is often predicted that the increased presence of the modern state critically undermines locally appropriate and community-based resource management arrangements. Drawing on the work of Pauline Peters and Francis Cleaver, I identify key instances of socially embedded ‘common’ management institutions and explain the evolution of these arrangements through dynamic interactions between individuals, communities and the agents of the state. Through describing the ‘living space’ of Gaddi shepherds across the annual cycle of nomadic migration with their flocks I explore the ways in which they have been able to creatively reinterpret external interventions, and suggest how contemporary arrangements for accessing pasture at different moments of the annual cycle involve complex combinations of the formal and the informal, the ‘traditional’ and the ‘modern’

Maximum likelihood estimation in hidden Markov models with inhomogeneous noise

We consider parameter estimation in finite hidden state space Markov models with time-dependent inhomogeneous noise, where the inhomogeneity vanishes sufficiently fast. Based on the concept of asymptotic mean stationary processes we prove that the maximum likelihood and a quasi-maximum likelihood estimator (QMLE) are strongly consistent. The computation of the QMLE ignores the inhomogeneity, hence, is much simpler and robust. The theory is motivated by an example from biophysics and applied to a Poisson- and linear Gaussian model.Comment: 31 pages, 6 figures, Accepted for publication in ESAIM Probab. Sta

Cycle-life of Li-ion Capacitors: Factors Influencing Aging

A comprehensive study of the factors influencing the cycle life of Li-ion capacitors (LiCs) at different stages of aging is essential for a promising LiC energy management system. This digest explicitly studies the factors influencing the initial stage of aging of LiCs. The commercially available Musashi LiC cells are chosen to perform cyclic aging experiments under different test conditions, including temperature, C-rate, and cycle depth. The results demonstrate the impact of the test conditions on LiC aging. A notable observation is that depth-of-discharge also significantly affects the initial aging stage. Finally, the Arrhenius equation has been applied to the test results and qualitatively analyzed the cell degradation mechanism

Enabling LVRT Compliance of Electrolyzer Systems Using Energy Storage Technologies

This paper presents a comprehensive techno-economic analysis of different energy storage systems (ESSs) in providing low-voltage ride-through (LVRT) support for power electronics-based electrolyzer systems. A framework for analyzing the performance of a grid-integrated electrolyzer-ESS system is developed, taking into account realistic scenarios and accurate models. The system components consist of a 500 kW alkaline electrolyzer module integrated with a medium-voltage grid and three different commercially available ESSs based on Li-ion battery, Li-ion capacitor, and supercapacitor technology, respectively. The performance of these ESSs is extensively studied for three LVRT profiles, with a primary focus on the upcoming Danish grid code. In order to perform simulation studies, the system is implemented on the MATLAB®/Simulink®-PLECS® platform. The results demonstrate that all three energy storage technologies are capable of supporting the electrolyzer systems during low-voltage abnormalities in the distribution grid. The study also reveals that the supercapacitor-based technology seems to be more appropriate, from a techno-economic perspective, for fault ride-through (FRT) compliance

Differences Between Randomized Clinical Trial Participants and Real-World Empagliflozin Users and the Changes in Their Glycated Hemoglobin Levels

Importance: Use of the sodium-glucose cotransporter 2 inhibitor empagliflozin has increased substantially since 2015. Little is known about characteristics of real-world patients who use empagliflozin or about empagliflozin's effectiveness in reducing glycated hemoglobin (HbA1c) levels in routine clinical care. Objectives: To characterize real-world initiators of empagliflozin, to examine the proportion of initiators who would have been eligible for participation in phase 3 randomized clinical trials (RCTs) of empagliflozin, and to assess changes in HbA1c levels after empagliflozin initiation. Design, Setting, and Participants: This cross-sectional study used linked population-based medical databases containing complete information on redeemed prescriptions, laboratory tests, and diagnoses for all residents in Northern Denmark. A total of 7034 residents of Denmark who filled a first-time empagliflozin prescription from January 2014 to December 2018 were included. Data analysis was performed in August 2019. Exposure: Empagliflozin initiation. Main Outcomes and Measures: Proportion of real-world users ineligible for RCT inclusion and absolute reduction in HbA1c level 6 months after empagliflozin initiation. Results: Of 7034 first-time empagliflozin initiators (median [interquartile range] age, 61.50 [53.30-69.38] years; 4475 [63.6%] men), 3878 (55.1%) would have been ineligible for phase 3 RCT participation; frequent reasons were concurrent use of specific glucose-lowering drugs (1955 initiators [27.8%]), baseline HbA1c level outside the eligibility range (1772 [25.2%]), or presence of comorbidities (1067 initiators [15.3%]). Initiation of empagliflozin was associated with a mean HbA1c reduction of -0.91% (95% CI, -0.94% to -0.87%) after 6 months, similar to phase 3 RCT results. Real-world empagliflozin initiators who would have been eligible for RCT participation experienced slightly lower mean HbA1c reductions (-0.78%; 95% CI, -0.82% to -0.74%) compared with patients who would have been ineligible (-1.01%; 95% CI, -1.07% to -0.95%). Ineligible initiators had higher median (interquartile range) baseline HbA1c values than eligible initiators (8.5% [7.4% to 10.1%] vs 8.2% [7.6% to 9.8%]). Conclusions and Relevance: In this cross-sectional study, more than half of empagliflozin initiators exhibited clinical characteristics that would have led to ineligibility for the RCTs leading to the drug's approval. While the findings suggest that the efficacy of empagliflozin in reducing HbA1c levels translates into real-world effectiveness, further studies should examine clinical outcome effectiveness and drug safety in routine clinical care.</p