Guidance, Navigation and Control System of a Hopper Spacecraft Simulator

The space hopper simulator project drew its origin from a partnership with Penn State University to compete in the Google Lunar XPRIZE competition. Lehigh University is tasked with the exploring the guidance, navigation and control (GN&C) system of the hopper spacecraft. To simulate the dynamics and flight behavior of the concept, Earth-based multirotor flying platforms were developed with the end goal of executing the hopping maneuver.The overall project has been ongoing for more than 5 years and went through several major revisions to fix flaws discovered in the previous design. As older students graduate and new teams are form, knowledge and experience are lost in the process. Due to the time it take to relearn and redesign the simulators, the project progress only get as far as achieving radio controlled flight. The current and 3rd generation development team aims to change that by developing both the hardware and software using modular design.With modular design, the manufacturing, repair and modification process for the multirotor speed up significantly. The damaged component can be replaced with little effort. In addition to the hardware advantages, the software modules enable concurrent development of both a PID and a Fuzzy Logic based flight control system using similar avionics and software architecture. Since the flight operating system function by linking the various software modules, individual modules can easily be swapped to test different control laws, electronic devices, etc. The software modules are also capable of being reused in other applications, such as running the thrust test stand and logging data with the wireless ground station.In theory and simulation, the GN&C system is quite simple. The hopping guidance trajectory can be generated by a set of linear and trigonometric equations. The trajectory can be optimized by minimizing the total energy consumption at the end of the hopping maneuver. The navigational data can be collected from the GPS and localized for the cascade PID controllers to achieve the desired trajectory. In the ideal world, everything is simple and easy.In the real world, a range of problems arise during implementation. Factors such as time delay and noises significantly impact the performance of the control system, making stable aggressive tuning very difficult to achieve. In an attempt to improve the condition, a number of digital filters such as the moving average filter and the Kalman filter were explored. In addition, every sub-system was analyzed in depth to optimize for speed. This resulted in 3 major revisions in changing flight computer and programming languages.Even though the main topic of this research is the guidance, navigation and control system, the project quickly expanded into a systems engineering problem. Everything must work well together in order for the aircraft to achieve stable flight

An Autonomous Power Controller for the NASA Human Deep Space Gateway

Autonomous control of a spacecraft is an enabling technology that must be developed for deep space human exploration. NASA's current long term human space platform, the International Space Station which is in Low Earth Orbit, is in almost continuous communication with ground based mission control. This allows near real-time control of all the vehicle core systems, including power, to be controlled by the ground. As the focus shifts from Low Earth Orbit, communication time-lag and bandwidth limitations beyond geosynchronous orbit does not permit this type of ground based operation. This paper presents the ongoing work at NASA to develop an architecture for autonomous power control system and a vehicle manager which monitors, coordinates, and delegates all the onboard subsystems to enable autonomous control of the complete spacecraft

Autonomous Power Controller for the NASA Human Deep Space Gateway

Autonomous control of a spacecraft is an enabling technology that must be developed for deep space human exploration. NASA's current long term human space platform, the International Space Station which is in Low Earth Orbit, is in almost continuous communication with ground based mission control. This allows near real-time control of all the vehicle core systems, including power, to be controlled by the ground. As the focus shifts from Low Earth Orbit, communication time-lag and bandwidth limitations beyond geosynchronous orbit does not permit this type of ground based operation. This paper presents the ongoing work at NASA to develop an architecture for autonomous power control system and a vehicle manager which monitors, coordinates, and delegates all the onboard subsystems to enable autonomous control of the complete spacecraft

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

Spraints demonstrate small population size and reliance on fishponds for Eurasian otter (Lutra lutra) in Hong Kong

Abstract Lack of data on population sizes and resource requirements are major impediments to the effective conservation of rare species globally. The conservation of the Eurasian otter (Lutra lutra) in Hong Kong reflects many of these key challenges for elusive and difficult‐to‐study mammals. It is a rare carnivore that has narrowly escaped extirpation, now surviving within a human‐dominated environment. Using sign surveys and spraint analysis, we recorded only 40 fresh spraints from 246 otter signs locations, over 4 months of intensive sampling across 2 years. Records were restricted to the Mai Po wetlands, confirming this as the core area for Hong Kong's otter population. Molecular analysis and microsatellite genotyping identified a minimum of seven individuals, two pairs of which were likely related. The genetic and sign data together strongly indicate a small population. Fish dominated the otter diet, highlighting the importance of fishpond habitats as a premium foraging resource. Given the rapid changes surrounding the Mai Po area (especially the new Northern Metropolis Development Strategy), maintaining quality and connected habitats, in addition to sustaining commercial fishponds will be key to otter recovery and long‐term population viability in Hong Kong

Targeting calcium signaling by inositol trisphosphate receptors: A novel mechanism for the anti-asthmatic effects of Houttuynia cordata

Asthma is a chronic inflammatory disease characterized by airway hypersensitivity and remodeling. The current treatments provide only short-term benefits and may have undesirable side effects; thus, alternative or supplementary therapy is needed. Because intracellular calcium (Ca2+) signaling plays an essential role in regulating the contractility and remodeling of airway smooth muscle cells, the targeting of Ca2+ signaling is a potential therapeutic strategy for asthma. Houttuynia cordata is a traditional Chinese herb that is used to treat asthma due to its anti-allergic and anti-inflammatory properties. We hypothesized that H. cordata might modulate intracellular Ca2+ signaling and could help relieve asthmatic airway remodeling. We found that the mRNA and protein levels of inositol trisphosphate receptors (IP3Rs) were elevated in interleukin-stimulated primary human bronchial smooth muscle cells and a house dust mite–sensitized model of asthma. The upregulation of IP3R expression enhanced intracellular Ca2+ release upon stimulation and contributed to airway remodeling in asthma. Intriguingly, pretreatment with H. cordata essential oil rectified the disruption of Ca2+ signaling, mitigated asthma development, and prevented airway narrowing. Furthermore, our analysis suggested that houttuynin/2-undecanone could be the bioactive component in H. cordata essential oil because we found similar IP3R suppression in response to the commercially available derivative sodium houttuyfonate. An in silico analysis showed that houttuynin, which downregulates IP3R expression, binds to the IP3 binding domain of IP3R and may mediate a direct inhibitory effect. In summary, our findings suggest that H. cordata is a potential alternative treatment choice that may reduce asthma severity by targeting the dysregulation of Ca2+ signaling