Preliminary investigation of high power microwave plasmas for electrothermal thruster use

Results are reported from preliminary tests to evaluate the high power microwave electrothermal thruster (MET) concept, which employs a free-floating plasma discharge maintained by applied CW microwave power to heat a propellant gas flow. Stable plasmas have been created and maintained in helium (He), nitrogen (N2), and hydrogen (H2) as propellants in both the TM(sub 011) and TM(sub 012) modes at discharge pressures from 10 Pa to 69 kPa. Reproducible starting conditions of pressure and power have been documented for all the plasmas. Vortical inflow of the propellant gas was observed to cause the formation of on-axis 'spike' plasmas. The formation and unformation conditions of these plasmas were studied. Operation in the spike plasma condition enables maximum power absorption with minimum wall heating and offers maximum efficiency in heating the propellant gas. In the spike condition, plasmas of the three propellant gases were investigated in an open channel configuration to a maximum applied power level of 11.2 kW (in N2). Microwave power coupling efficiencies of over 90 percent were routinely obtained at absorbed power levels up to 2 kW. Magnetic nozzle effects were investigated with a superconducting solenoid Al magnet applying a high magnetic field to the plasmas in and exiting from the discharge tube

Improved LeRoy-Bernstein near-dissociation expansion formula. Tutorial application to photoassociation spectroscopy of long-range states

NDE (Near-dissociation expansion) including LeRoy-Bernstein formulas are improved by taking into account the multipole expansion coefficients and the non asymptotic part of the potential curve. Applying these new simple analytical formulas to photoassociation spectra of cold alkali atoms, we improve the determination of the asymptotic coefficient, reaching a 1% accuracy, for long-range relativistic potential curve of diatomic molecules.Comment: This article is part of Daniel Comparat's PhD thesis available at http://tel.ccsd.cnrs.fr

Heliocentric Escape and Lunar Impact from Near Rectilinear Halo Orbits

Spacecraft departing from the Gateway in a Near Rectilinear Halo Orbit (NRHO) experience gravitational forces from the Moon, the Earth, and the Sun, all of which can be simultaneously significant. These complex dynamics influence the post-separation risk of recontact with the Gateway and the eventual destinations of the departing spacecraft. The current investigation examines the flow of objects leaving NRHOs in the Bicircular Restricted Four-Body Problem, and results are applied to heliocentric escape and lunar impact trajectories in a higher-fidelity ephemeris model. Separation maneuver magnitude, direction, and location are correlated with risk of recontact with the Gateway and successful departure to various destinations

Creating Sustainable Neighborhood Design for Legacy Cities: A New Framework for Sustainability Assessment

Highly vacant neighborhoods present challenges for balancing social, environmental, and economic considerations for land reuse. Since the 1960’s, many post-Industrial cities such as Detroit have seen extreme population decline, creating severe economic loss and disinvestment in their communities. Strategies and opportunities for stabilization and revitalization, especially those that can be created and implemented by community groups, have become particularly important in these legacy (shrinking) cities. This report uses a case study site on the Lower East Side of Detroit to examine how the Community Development Advocates of Detroit (CDAD) Strategic Framework, a new land use and development framework for highly vacant cities, can be used to influence the Leadership in Energy and Environmental Design for Neighborhood Development (LEED-ND) criteria to allow it to better consider the social, economic, and environmental context of a legacy city. The land use typology described in CDAD’s Strategic Framework inform the criteria in the LEED-ND valuation tool measuring the sustainability of a neighborhood in order to create a new framework: Sustainable Neighborhood Development for Legacy Cities (SND-LC). SND-LC provides recommendations to further integrate social capital, social equity, and ecological considerations into the two frameworks through various planning and design techniques. Joan Nassauer’s concept of “cues to care” is instrumental for examining social capital in vacant neighborhoods and in identifying opportunities to grow social networks. Recommendations for land use reconsiderations call for the integration of social variables such as neighborhood cohesion and access to resources, as well as ecological variables such as stormwater and green space connectivity. Recommendations in SND-LC encourage retrofitting and illustrate how sustainability can be achieved through a more strategic use of vacant land areas rather than through compactness or new development. The new credit rating system applies the economic and social conditions of a legacy city to a new valuation system that can allow highly vacant neighborhoods across the country to achieve a sustainable neighborhood status.Master of Landscape ArchitectureMaster of ScienceNatural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/90939/1/Final OAP Completed Project 4.26.pd

Effect of Biodiversity Changes in Disease Risk: Exploring Disease Emergence in a Plant-Virus System

The effect of biodiversity on the ability of parasites to infect their host and cause disease (i.e. disease risk) is a major question in pathology, which is central to understand the emergence of infectious diseases, and to develop strategies for their management. Two hypotheses, which can be considered as extremes of a continuum, relate biodiversity to disease risk: One states that biodiversity is positively correlated with disease risk (Amplification Effect), and the second predicts a negative correlation between biodiversity and disease risk (Dilution Effect). Which of them applies better to different host-parasite systems is still a source of debate, due to limited experimental or empirical data. This is especially the case for viral diseases of plants. To address this subject, we have monitored for three years the prevalence of several viruses, and virus-associated symptoms, in populations of wild pepper (chiltepin) under different levels of human management. For each population, we also measured the habitat species diversity, host plant genetic diversity and host plant density. Results indicate that disease and infection risk increased with the level of human management, which was associated with decreased species diversity and host genetic diversity, and with increased host plant density. Importantly, species diversity of the habitat was the primary predictor of disease risk for wild chiltepin populations. This changed in managed populations where host genetic diversity was the primary predictor. Host density was generally a poorer predictor of disease and infection risk. These results support the dilution effect hypothesis, and underline the relevance of different ecological factors in determining disease/infection risk in host plant populations under different levels of anthropic influence. These results are relevant for managing plant diseases and for establishing conservation policies for endangered plant species

Nueva esterasa tolerante a los solventes orgánicos aislada por metagenómica: ideas sobre la clasificación de las esterasas/lipasas

In order to isolate novel organic solvent-tolerant (OST) lipases, a metagenomic library was built using DNA derived from a temperate forest soil sample. A two-step activity-based screening allowed the isolation of a lipolytic clone active in the presence of organic solvents. Sequencing of the plasmid pRBest recovered from the positive clone revealed the presence of a putative lipase/esterase encoding gene. The deduced amino acid sequence (RBest1) contains the conserved lipolytic enzyme signature and is related to the previously described OST lipase from Lysinibacillus sphaericus 205y, which is the sole studied prokaryotic enzyme belonging to the 4.4 / hydrolase subgroup (abH04.04). Both in vivo and in vitro studies of the substrate specificity of RBest1, using triacylglycerols or nitrophenyl-esters, respectively, revealed that the enzyme is highly specific for butyrate (C4) compounds, behaving as an esterase rather than a lipase. The RBest1 esterase was purified and biochemically characterized. The optimal esterase activity was observed at pH 6.5 and at temperatures ranging from 38 to 45 °C. Enzymatic activity, determined by hydrolysis of p nitrophenyl esters, was found to be affected by the presence of different miscible and non-miscible organic solvents, and salts. Noteworthy, RBest1 remains significantly active at high ionic strength. These findings suggest that RBest1 possesses the ability of OST enzymes to molecular adaptation in the presence of organic compounds and resistance of halophilic proteins.Con el fin de aislar nuevas variantes de lipasas tolerantes a solventes orgánicos (OST), se construyó una librería metagenómica a partir de ADN obtenido de una muestra de suelo de bosque templado. A través de un monitoreo en dos etapas, basado en la detección de actividades, se aisló un clon con actividad lipolítica en presencia de solventes orgánicos. La secuenciación del plásmido pRBest recuperado del clon positivo reveló la presencia de un gen codificante de una hipotética lipasa/esterasa. La secuencia deducida de amino ácidos (RBest1) contiene los motivos conservados de enzimas lipolíticas y está relacionada con la lipasa OST previamente descrita de Lysinibacillus sphaericus 205y, que es la única enzima procariota estudiada perteneciente al subgrupo 4.4 de α/β hidrolasas (abH4.04). Estudios in vivo e in vitro sobre la especificidad de sustratos de RBest1, utilizando triacil-gliceroles o p-nitrofenil-ésteres, respectivamente, revelaron que la enzima es altamente específica para compuestos butíricos (C4 ), comportándose como una esterasa y no como una lipasa. La esterasa RBest1 fue purificada y caracterizada bioquímicamente. La actividad óptima de esterasa fue observada a pH 6,5 y las temperaturas óptimas fueron entre 38 y 45 °C. Se estableció que la actividad enzimática, determinada por hidrólisis de p-nitrofenil ésteres, es afectada en presencia de diferentes solventes orgánicos miscibles y no miscibles, y también sales. Notoriamente, RBest1 permanece significativamente activa a elevadas fuerzas iónicas. Estos hallazgos sugieren que RBest1 posee la capacidad de las enzimas OST de la adaptación molecular en presencia de compuestos orgánicos, así como la resistencia de las proteínas halófilasFil: Berlemont, Renaud. Universite de Liege; BélgicaFil: Spee, Olivier. Universite de Liege; BélgicaFil: Delsaute, Maud. Universite de Liege; BélgicaFil: Lara, Yannick. Universite de Liege; BélgicaFil: Schuldes, Jörg. Universitat of Gottingen; AlemaniaFil: Simon, Carola. Universitat of Gottingen; AlemaniaFil: Power, Pablo. Universite de Liege; Bélgica. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Daniel, Rolf. Universitat of Gottingen; AlemaniaFil: Galleni, Moreno. Universite de Liege; Bélgic

What can ecosystems learn? Expanding evolutionary ecology with learning theory

Background: The structure and organisation of ecological interactions within an ecosystem is modified by the evolution and coevolution of the individual species it contains. Understanding how historical conditions have shaped this architecture is vital for understanding system responses to change at scales from the microbial upwards. However, in the absence of a group selection process, the collective behaviours and ecosystem functions exhibited by the whole community cannot be organised or adapted in a Darwinian sense. A long-standing open question thus persists: Are there alternative organising principles that enable us to understand and predict how the coevolution of the component species creates and maintains complex collective behaviours exhibited by the ecosystem as a whole?Results: Here we answer this question by incorporating principles from connectionist learning, a previously unrelated discipline already using well-developed theories on how emergent behaviours arise in simple networks. Specifically, we show conditions where natural selection on ecological interactions is functionally equivalent to a simple type of connectionist learning, ‘unsupervised learning’, well-known in neural-network models of cognitive systems to produce many non-trivial collective behaviours. Accordingly, we find that a community can self-organise in a well-defined and non-trivial sense without selection at the community level; its organisation can be conditioned by past experience in the same sense as connectionist learning models habituate to stimuli. This conditioning drives the community to form a distributed ecological memory of multiple past states, causing the community to: a) converge to these states from any random initial composition; b) accurately restore historical compositions from small fragments; c) recover a state composition following disturbance; and d) to correctly classify ambiguous initial compositions according to their similarity to learned compositions. We examine how the formation of alternative stable states alters the community’s response to changing environmental forcing, and we identify conditions under which the ecosystem exhibits hysteresis with potential for catastrophic regime shifts.Conclusions: This work highlights the potential of connectionist theory to expand our understanding of evo-eco dynamics and collective ecological behaviours. Within this framework we find that, despite not being a Darwinian unit, ecological communities can behave like connectionist learning systems, creating internal conditions that habituate to past environmental conditions and actively recalling those conditions.Theoretical ecology, Communityassembly, Network structures, Ecological memory, Associative learning, Regime shifts, Community matrix*Correspondence

Rendering an Account: An Open-State Archive in Postgraduate Supervision

The paper begins with a brief account of the transformation of research degree studies under the pressures of global capitalism and neo-liberal governmentality. A parallel transformation is occurring in the conduct of research through the use of information and communication technologies. Yet the potential of ICTs to shape practices of surveillance or to produce new student-supervisor relations and enhance the processes of developing the dissertation has received almost no critical attention. As doctoral supervisor and student, we then describe the features and uses of a web-based open state archive of the student's work-in-progress, developed by the student and accessible to his supervisor. Our intention was to encourage more open conversations between data and theorising, student and supervisor, and ultimately between the student and professional community. However, we recognise that relations of accountability, as these have developed within a contemporary "audit revolution" (Power, 1994, 1997) in universities, create particular "lines of visibility" (Munro, 1996). Thus while the open-state archive may help to redefine in less managerial terms notions of quality, transparency, flexibility and accountability, it might also make possible greater supervisory surveillance. How should we think about the panoptical potential of this archive? We argue that the diverse kinds of interactional patterns and pedagogical intervention it encourages help to create shifting subjectivities. Moreover, the archive itself is multiple, in bringing together an array of diverse materials that can be read in various ways, by following multiple paths. It therefore constitutes a collage, which we identify as a mode of cognition and of accounting distinct from but related to argument and narrative. As a more "open" text (Iser, 1978) it has an indeterminacy which may render it less open to abuse for the technologies of managerial accountability

Heritability of Individual Psychotic Experiences Captured by Common Genetic Variants in a Community Sample of Adolescents.

Occurrence of psychotic experiences is common amongst adolescents in the general population. Twin studies suggest that a third to a half of variance in adolescent psychotic experiences is explained by genetic influences. Here we test the extent to which common genetic variants account for some of the twin-based heritability. Psychotic experiences were assessed with the Specific Psychotic Experiences Questionnaire in a community sample of 2152 16-year-olds. Self-reported measures of Paranoia, Hallucinations, Cognitive Disorganization, Grandiosity, Anhedonia, and Parent-rated Negative Symptoms were obtained. Estimates of SNP heritability were derived and compared to the twin heritability estimates from the same sample. Three approaches to genome-wide restricted maximum likelihood (GREML) analyses were compared: (1) standard GREML performed on full genome-wide data; (2) GREML stratified by minor allele frequency (MAF); and (3) GREML performed on pruned data. The standard GREML revealed a significant SNP heritability of 20 % for Anhedonia (SE = 0.12; p < 0.046) and an estimate of 19 % for Cognitive Disorganization, which was close to significant (SE = 0.13; p < 0.059). Grandiosity and Paranoia showed modest SNP heritability estimates (17 %; SE = 0.13 and 14 %; SE = 0.13, respectively, both n.s.), and zero estimates were found for Hallucinations and Negative Symptoms. The estimates for Anhedonia, Cognitive Disorganization and Grandiosity accounted for approximately half the previously reported twin heritability. SNP heritability estimates from the MAF-stratified approach were mostly consistent with the standard estimates and offered additional information about the distribution of heritability across the MAF range of the SNPs. In contrast, the estimates derived from the pruned data were for the most part not consistent with the other two approaches. It is likely that the difference seen in the pruned estimates was driven by the loss of tagged causal variants, an issue fundamental to this approach. The current results suggest that common genetic variants play a role in the etiology of some adolescent psychotic experiences, however further research on larger samples is desired and the use of MAF-stratified approach recommended