Ames Arc Jets in Support for Planetary Defense

Poster showing overview of the Arc Jet Complex, Past use for testing TPS materials for hypersonic entry, possible uses for planetary defense and understanding ablation of meteors at entry

NASA Ames Arc Jets and Range, Capabilities for Planetary Entry

NASA is pursuing innovative technologies and concepts as part of America's Vision for Space Exploration. The rapidly emerging field of nanotechnology has led to new concepts for multipurpose shields to prevent catastrophic loss of vehicles and crew against the triple threats of aeroheating during atmospheric entry, radiation (Solar and galactic cosmic rays) and Micrometorid/Orbital Debris (MMOD) strikes. One proposed concept is the Thermal Radiation Impact Protection System (TRIPS) using carbon nanotubes, hydrogenated carbon nanotubes, and ceramic coatings as a multi-use TPS. The Thermophysics Facilities Branch of the Space Technology Division at NASA Ames Research Center provides testing services for the development and validation of the present and future concepts being developed by NASA and national and International research firms. The Branch operates two key facilities - the Range Complex and the Arc Jets. The Ranges include both the Ames Vertical Gun Range (AVGR) and the Hypervelocity Free Flight (HFF) gas guns best suited for MMOD investigations. Test coupons can be installed in the AVGR or HFF and subjected to particle impacts from glass or metal particles from micron to _ inch (6.35-mm) diameters and at velocities from 5 to 8 kilometers per second. The facility can record high-speed data on film and provide damage assessment for analysis by the Principle Investigator or Ames personnel. Damaged articles can be installed in the Arc Jet facility for further testing to quantify the effects of damage on the heat shield s performance upon entry into atmospheric environments

Perturbation propagation in random and evolved Boolean networks

We investigate the propagation of perturbations in Boolean networks by evaluating the Derrida plot and modifications of it. We show that even small Random Boolean Networks agree well with the predictions of the annealed approximation, but non-random networks show a very different behaviour. We focus on networks that were evolved for high dynamical robustness. The most important conclusion is that the simple distinction between frozen, critical and chaotic networks is no longer useful, since such evolved networks can display properties of all three types of networks. Furthermore, we evaluate a simplified empirical network and show how its specific state space properties are reflected in the modified Derrida plots.Comment: 10 pages, 8 figure

The phase diagram of random threshold networks

Threshold networks are used as models for neural or gene regulatory networks. They show a rich dynamical behaviour with a transition between a frozen and a chaotic phase. We investigate the phase diagram of randomly connected threshold networks with real-valued thresholds h and a fixed number of inputs per node. The nodes are updated according to the same rules as in a model of the cell-cycle network of Saccharomyces cereviseae [PNAS 101, 4781 (2004)]. Using the annealed approximation, we derive expressions for the time evolution of the proportion of nodes in the "on" and "off" state, and for the sensitivity $\lambda$. The results are compared with simulations of quenched networks. We find that for integer values of h the simulations show marked deviations from the annealed approximation even for large networks. This can be attributed to the particular choice of the updating rule.Comment: 8 pages, 6 figure

Response of Boolean networks to perturbations

We evaluate the probability that a Boolean network returns to an attractor after perturbing h nodes. We find that the return probability as function of h can display a variety of different behaviours, which yields insights into the state-space structure. In addition to performing computer simulations, we derive analytical results for several types of Boolean networks, in particular for Random Boolean Networks. We also apply our method to networks that have been evolved for robustness to small perturbations, and to a biological example

Cooccurrence of prey species alters the impact of predators on prey performance through multiple mechanisms

When prey are differentially affected by intra and interspecific competition, the cooccurrence of multiple prey species alters the per capita availability of food for a particular prey species which could alter how prey respond to the threat of predation, and hence the overall�effect of predators. We conducted an experiment to examine the extent to which the nonconsumptive and overall effect of predatory water bugs on snail and tadpole traits (performance and morphology) depended on whether tadpoles and snails cooccurred. Tadpoles and snails differed in their relative susceptibility to intraspecific and interspecific competition, and predators affected both prey species via consumptive and nonconsumptive mechanisms. Furthermore, the overall effect of predators often depended on whether another prey species was present. The reasoning for why the overall effect of predators depended on whether prey species cooccurred, however, differed for each of the response variables. Predators affected snail body growth via nonconsumptive mechanisms, but the change in the overall effect of predators on snail body growth was attributable to how snails responded to competition in the absence of predators, rather than a change in how snails responded to the threat of predation. Predators did not affect tadpole body growth via nonconsumptive mechanisms, but the greater vulnerability of competitively superior prey (snails) to predators increased the strength of consumptive mechanisms (and hence the overall effect) through which predators affected tadpole growth. Predators affected tadpole morphology via nonconsumptive mechanisms, but the greater propensity for predators to kill competitively superior prey (snails) enhanced the ability of tadpoles to alter their morphology in response to the threat of predation by creating an environment where tadpoles had a higher per capita supply of food available to invest in the development of morphological defenses. Our work indicates that the mechanisms through which predators affect prey depends on the other members of the community

Perkutane Klappenintervention der Trikuspidalklappeninsuffizienz: Relevanz für die nachhaltige Lebensqualität von Patienten

Einleitung Die Trikuspidalklappeninsuffizienz (TI) ist eine hochprävalente kardiologische Erkrankung und zieht tiefgreifende Einschränkungen in der Alltagskompetenz und Lebensqualität betroffener Patienten nach sich. Seit einigen Jahren erfolgt zu ihrer Therapie nun die Anwendung perkutaner Interventionen, welche die Therapie auch nicht chirurgisch operabler Patienten ermöglicht, welche zuvor lediglich medikamentös behandelt werden konnten. Der langfristige Einfluss perkutaner Therapien auf die Lebensqualität und Alltagskompetenz der Patienten ist noch nicht ausreichend erforscht und soll in dieser Arbeit untersucht werden. Methoden Zur Identifizierung der vielfältigen Einschränkungen im Alltag und der Lebensqualität erfolgte die Datenerhebung mittels Fragebögen. Des Weiteren erfolgten unter anderem Tests zur Untersuchung der körperlichen Belastbarkeit, transthorakale Echokardiographien (TTE), Laboruntersuchungen, sowie Elektrokardiographien. Die Untersuchungen erfolgten sowohl vor der Intervention, nach vier bis sechs Wochen und nach zwölf Monaten. Ergebnisse Nach zwölf Monaten zeigten sich in der TTE-Kontrolle anhaltend gute Ergebnisse der Intervention mit deutlich reduziertem TI-Grad (p≤0,001). Ebenso zeigten sich die Lebensqualität, gemessen am MLWHFQ Score (p≤0,001) und die NYHA-Klasse (p≤0,001) gebessert. Sowohl die Alltagskompetenz (p=0,059), als auch die kognitiven Fähigkeiten (p=0,025) zeigten sich nach zwölf Monaten gebessert, während diese Parameter nach vier bis sechs Wochen keinen signifikanten Unterschied zeigten. Die periinterventionelle Mortalität verblieb mit 2,2% niedrig. Diskussion Die perkutane Trikuspidalklappenintervention erwies sich als effektive, sowie sichere, mit wenigen unerwünschten Ereignissen assoziierte Methode zur TI-Reduktion. Des Weiteren trug sie effektiv zur anhaltenden Verbesserung der klinischen Symptomatik der betroffenen Patienten bei