8- by 6-Foot Supersonic Wind Tunnel Compressor Inspected

The NASA Glenn Research Center's 8- by 6-Foot Supersonic Wind Tunnel (8 6 SWT) is NASA's only transonic propulsion wind tunnel. The test section speed range is between Mach 0.25 and 2.0. The 9- by 15-Foot Low-Speed Wind Tunnel (9 15 LWST), which has a speed range from 0 to 175 mph, is housed in the return leg of the 8 6 SWT and uses the same compressor. The 8 6 SWT uses a large, seven-stage axial flow compressor to drive the air through the tunnel. The compressor is 17 ft in diameter and is rated at 1600 m3 (56,600 ft3) of air/sec. It is driven by three electric motors with a combined horsepower of 87,000. A close examination of this compressor was performed in 2001, the first time since February of 1966

Optimality in superselective surface binding by multivalent DNA nanostars

Weak multivalent interactions govern a large variety of biological processes like cell-cell adhesion and virus-host interactions. These systems distinguish sharply between surfaces based on receptor density, known as superselectivity. Earlier experimental and theoretical work provided insights into the control of selectivity: Weak interactions and a high number of ligands facilitate superselectivity. Present experimental studies typically involve tens or hundreds of interactions, resulting in a high entropic contribution leading to high selectivities. However, if, and if so how, systems with few ligands, such as multi-domain proteins and virus binding to a membrane, show superselective behavior is an open question. Here, we address this question with a multivalent experimental model system based on star shaped branched DNA nanostructures (DNA nanostars) with each branch featuring a single stranded overhang that binds to complementary receptors on a target surface. Each DNA nanostar possesses a fluorophore, to directly visualize DNA nanostar surface adsorption by total internal reflection fluorescence microscopy (TIRFM). We observe that DNA nanostars can bind superselectively to surfaces and bind optimally at a valency of three. We quantitatively explain this optimum by extending the current theory with interactions between DNA nanostar binding sites (ligands). Our results add to the understanding of multivalent interactions, by identifying microscopic mechanisms that lead to optimal selectivity, and providing quantitative values for the relevant parameters. These findings inspire additional design rules which improve future work on selective targeting in directed drug delivery.Comment: 14 pages, 4 figure

Sicheres und einfaches Data Sharing mit SowiDataNet: dokumentieren - veröffentlichen - nachnutzen

SowiDataNet ist eine im Aufbau befindliche Forschungsdateninfrastruktur für die Sozial- und Wirtschaftswissenschaften. Zentraler Baustein ist die Entwicklung eines web-basierten Forschungsdatenrepositoriums, welches es Forscherinnen erlaubt, ihre Daten sicher und dauerhaft zu dokumentieren, zu publizieren und mit anderen Forschern zu teilen. Die Entwicklung dieses neuen Services orientiert sich am konkreten Bedarf der Fachcommunity, was sich u.a. in der Durchführung einer detaillierten Anforderungsanalyse widerspiegelt. Ein spezieller Fokus liegt zudem auf der flexiblen Einbindung des Repositoriums in die praktischen Workflows des institutionellen Forschungsdatenmanagements

Modeling of Neuronal Growth In Vitro: Comparison of Simulation Tools NETMORPH and CX3D

We simulate the growth of neuronal networks using the two recently published tools, NETMORPH and CX3D. The goals of the work are (1) to examine and compare the simulation tools, (2) to construct a model of growth of neocortical cultures, and (3) to characterize the changes in network connectivity during growth, using standard graph theoretic methods. Parameters for the neocortical culture are chosen after consulting both the experimental and the computational work presented in the literature. The first (three) weeks in culture are known to be a time of development of extensive dendritic and axonal arbors and establishment of synaptic connections between the neurons. We simulate the growth of networks from day 1 to day 21. It is shown that for the properly selected parameters, the simulators can reproduce the experimentally obtained connectivity. The selected graph theoretic methods can capture the structural changes during growth.Peer reviewe

Extraction of Water from Martian Regolith Simulant via Open Reactor Concept

To demonstrate proof of concept water extraction from simulated Martian regolith, an open reactor design is presented along with experimental results. The open reactor concept avoids sealing surfaces and complex moving parts. In an abrasive environment like the Martian surface, those reactor elements would be difficult to maintain and present a high probability of failure. A general lunar geotechnical simulant was modified by adding borax decahydrate (Na2B4O710H2O) (BDH) to mimic the ~ 3 percent water content of hydrated salts in near surface soils on Mars. A rotating bucket wheel excavated the regolith from a source bin and deposited the material onto an inclined copper tray, which was fitted with heaters and a simple vibration system. The combination of vibration, tilt angle and heat was used to separate and expose as much regolith surface area as possible to liberate the water contained in the hydrated minerals, thereby increasing the efficiency of the system. The experiment was conducted in a vacuum system capable of maintaining a Martian like atmosphere. Evolved water vapor was directed to a condensing system using the ambient atmosphere as a sweep gas. The water vapor was condensed and measured. Processed simulant was captured in a collection bin and weighed in real time. The efficiency of the system was determined by comparing pre- and post-processing soil mass along with the volume of water captured

Mars Surface Mobility Leading to Sustainable Exploration

A Mars rocket-propelled hopper concept was evaluated for feasibility through analysis and experiments. The approach set forth in this paper is to combine the use of in-situ resources in a new Mars mobility concept that will greatly enhance the science return while providing the first opportunity towards reducing the risk of incorporating ISRU into the critical path for the highly coveted, but currently unaffordable, sample return mission. Experimental tests were performed on a high-pressure, self-throttling gaseous oxygen/methane propulsion system to simulate a two-burn-with-coast hop profile. Analysis of the trajectory, production plant requirements, and vehicle mass indicates that a small hopper vehicle could hop 2 km every 30 days with an initial mass of less than 60 kg. A larger vehicle can hop 15 km every 30 to 60 days with an initial mass of 300 to 430 kg

Evidence for a Monomeric Structure of Nonribosomal Peptide Synthetases

AbstractNonribosomal peptide synthetases (NRPS) are multimodular biocatalysts that bacteria and fungi use to assemble many complex peptides with broad biological activities. The same modular enzymatic assembly line principles are found in fatty acid synthases (FAS), polyketide synthases (PKS), and most recently in hybrid NRPS/PKS multienzymes. FAS as well as PKS are known to function as homodimeric enzyme complexes, raising the question of whether NRPS may also act as homodimers. To test this hypothesis, biophysical methods (size exclusion chromatography, analytical equilibrium ultracentrifugation, and chemical crosslinking) and biochemical methods (two-affinity-tag-system and complementation studies with enzymes being inactivated in different catalytic domains) were applied to NRPS subunits from the gramicidin S (GrsA-ATE), tyrocidine (TycB1-CAT and TycB2-3-AT.CATE), and enterobactin (EntF-CATTe) biosynthetic systems. These methods had revealed the dimeric structure of FAS and PKS previously, but all three NRPS systems investigated are functionally active as monomers

NASA Technology Area 07: Human Exploration Destination Systems Roadmap

This paper gives an overview of the National Aeronautics and Space Administration (NASA) Office of Chief Technologist (OCT) led Space Technology Roadmap definition efforts. This paper will given an executive summary of the technology area 07 (TA07) Human Exploration Destination Systems (HEDS). These are draft roadmaps being reviewed and updated by the National Research Council. Deep-space human exploration missions will require many game changing technologies to enable safe missions, become more independent, and enable intelligent autonomous operations and take advantage of the local resources to become self-sufficient thereby meeting the goal of sustained human presence in space. Taking advantage of in-situ resources enhances and enables revolutionary robotic and human missions beyond the traditional mission architectures and launch vehicle capabilities. Mobility systems will include in-space flying, surface roving, and Extra-vehicular Activity/Extravehicular Robotics (EVA/EVR) mobility. These push missions will take advantage of sustainability and supportability technologies that will allow mission independence to conduct human mission operations either on or near the Earth, in deep space, in the vicinity of Mars, or on the Martian surface while opening up commercialization opportunities in low Earth orbit (LEO) for research, industrial development, academia, and entertainment space industries. The Human Exploration Destination Systems (HEDS) Technology Area (TA) 7 Team has been chartered by the Office of the Chief Technologist (OCT) to strategically roadmap technology investments that will enable sustained human exploration and support NASA s missions and goals for at least the next 25 years. HEDS technologies will enable a sustained human presence for exploring destinations such as remote sites on Earth and beyond including, but not limited to, LaGrange points, low Earth orbit (LEO), high Earth orbit (HEO), geosynchronous orbit (GEO), the Moon, near-Earth objects (NEOs), which > 95% are asteroidal bodies, Phobos, Deimos, Mars, and beyond. The HEDS technology roadmap will strategically guide NASA and other U.S. Government agency technology investments that will result in capabilities enabling human exploration missions to diverse destinations generating high returns on investments

System Modeling of Lunar Oxygen Production: Mass and Power Requirements

A systems analysis tool for estimating the mass and power requirements for a lunar oxygen production facility is introduced. The individual modeling components involve the chemical processing and cryogenic storage subsystems needed to process a beneficiated regolith stream into liquid oxygen via ilmenite reduction. The power can be supplied from one of six different fission reactor-converter systems. A baseline system analysis, capable of producing 15 metric tons of oxygen per annum, is presented. The influence of reactor-converter choice was seen to have a small but measurable impact on the system configuration and performance. Finally, the mission concept of operations can have a substantial impact upon individual component size and power requirements

Mars ISRU for Production of Mission Critical Consumables - Options, Recent Studies, and Current State of the Art

In 1978, a ground breaking paper titled, "Feasibility of Rocket Propellant Production on Mars" by Ash, Dowler, and Varsi discussed how ascent propellants could be manufactured on the Mars surface from carbon dioxide collected from the atmosphere to reduce launch mass. Since then, the concept of making mission critical consumables such as propellants, fuel cell reactants, and life support consumables from local resources, commonly known as In-Situ Resource Utilization (ISRU), for robotic and human missions to Mars has been studied many times. In the late 1990's, NASA initiated a series of Mars Human Design Reference Missions (DRMs), the first of which was released in 1997. These studies primarily focused on evaluating the impact of making propellants on Mars for crew ascent to Mars orbit, but creating large caches of life support consumables (water & oxygen) as a backup for regenerative life support systems for long-duration surface stays (>500 days) was also considered in Mars DRM 3.0. Until science data from the Mars Odyssey orbiter and subsequent robotic missions revealed that water may be widely accessable across the surface of Mars, prior Mars ISRU studies were limited to processing Mars atmospheric resources (carbon dioxide, nitrogen, argon, oxygen, and water vapor). In December 2007, NASA completed the Mars Human Design Reference Architecture (DRA) 5.0 study which considered water on Mars as a potential resource for the first time in a human mission architecture. While knowledge of both water resources on Mars and the hardware required to excavate and extract the water were very preliminary, the study concluded that a significant reduction in mass and significant enhancements to the mission architecture were possible if Mars water resources were utilized. Two subsequent Mars ISRU studies aimed at reexamining ISRU technologies, processing options, and advancements in the state-of-the-art since 2007 and to better understand the volume and packaging associated with Mars ISRU systems further substantiated the preliminary results from the Mars DRA 5.0 study. This paper will provide an overview of Mars ISRU consumable production options, the analyses, results, and conclusions from the Mars DRA 5.0 (2007), Mars Collaborative (2013), and Mars ISRU Payload for the Supersonic Retro Propulsion (2014) mission studies, and the current state-of-the-art of Mars ISRU technologies and systems. The paper will also briefly discuss the mission architectural implications associated with Mars resource and ISRU processing options