Mass properties survey of solar array technologies

An overview of the technologies, electrical performance, and mass characteristics of many of the presently available and the more advanced developmental space solar array technologies is presented. Qualitative trends and quantitative mass estimates as total array output power is increased from 1 kW to 5 kW at End of Life (EOL) from a single wing are shown. The array technologies are part of a database supporting an ongoing solar power subsystem model development for top level subsystem and technology analyses. The model is used to estimate the overall electrical and thermal performance of the complete subsystem, and then calculate the mass and volume of the array, batteries, power management, and thermal control elements as an initial sizing. The array types considered here include planar rigid panel designs, flexible and rigid fold-out planar arrays, and two concentrator designs, one with one critical axis and the other with two critical axes. Solar cell technologies of Si, GaAs, and InP were included in the analyses. Comparisons were made at the array level; hinges, booms, harnesses, support structures, power transfer, and launch retention mountings were included. It is important to note that the results presented are approximations, and in some cases revised or modified performance and mass estimates of specific designs

EU Enlargement and Immigration

This paper assesses the consequences of EU enlargement for East West migration. In the theoretical part, we identify several factors in addition to the reduction of moving costs by which EU membership influences migration. Specifically, EU accession affects income gaps. Moreover, if EU membership is refused, fear of future restrictions on immigration will lead to increased current migration. Additionally, casual evidence from the 1980s EU South enlargement is examined. Since then no increases in migration flows from Spain, Portugal and Greece were observed. We conclude that granting EU accession to Eastern European countries will not necessarily induce massive East-West migration flows

Multi-megawatt inverter/converter technology for space power applications

Large power conditioning mass reductions will be required to enable megawatt power systems envisioned by the Strategic Defense Initiative, the Air Force, and NASA. Phase 1 of a proposed two phase interagency program has been completed to develop an 0.1 kg/kW DC/DC converter technology base for these future space applications. Three contractors, Hughes, General Electric (GE), and Maxwell were Phase 1 contractors in a competitive program to develop a megawatt lightweight DC/DC converter. Researchers at NASA Lewis Research Center and the University of Wisconsin also investigated technology in topology and control. All three contractors, as well as the University of Wisconsin, concluded at the end of the Phase 1 study, which included some critical laboratory work, that 0.1-kg/kW megawatt DC/DC converters can be built. This is an order of magnitude lower specific weight than is presently available. A brief description of each of the concepts used to meet the ambitious goals of this program are presented

The urea connection. Intramolecular Diels-Alder reactions of ureas

Intramoleeular Diels-Alder reactions with a urea tether afford adducts in good yields, yet the analogous carbamates fail to cycliz

Synthesis of chelating bidentate isocyano and cyano ligands and their metal complexes

Molecular models indicate that they should chelate to metals with the donor groups at 90° with respect to each other. From reactions of the diisocyano ligand DiNC, the following complexes with chelating DiNC ligands have been isolated: Cr(CO),(DiNC), Mo(CO),(DiNC), W(CO),(DiNC), MII(CO)~(D~NC)B~, CpFe(CO)(DiNC)+, and CpFe(CS)(DiNC)+. The characterization of these complexes demonstrates that DiNC can function as a chelating ligand despite its formation of a 13-member chelate ring

EU enlargement and immigration

This paper assesses the consequences of EU enlargement for East West migration. In the theoretical part, we identify several factors in addition to the reduction of moving costs by which EU membership influences migration. Specifically, EU accession affects income gaps. Moreover, if EU membership is refused, fear of future restrictions on immigration will lead to increased current migration. Additionally, casual evidence from the 1980s EU South enlargement is examined. Since then no increases in migration flows from Spain, Portugal and Greece were observed. We conclude that granting EU accession to Eastern European countries will not necessarily induce massive East-West migration flows. --Europe,Migration,Uncertainty,Enlargement

Widespread Horizontal Genomic Exchange does not Erode Species Barriers among Sympatric Ducks

Background: The study of speciation and maintenance of species barriers is at the core of evolutionary biology.During speciation the genome of one population becomes separated from other populations of the same species,which may lead to genomic incompatibility with time. This separation is complete when no fertile offspring isproduced from inter-population matings, which is the basis of the biological species concept. Birds, in particularducks, are recognised as a challenging and illustrative group of higher vertebrates for speciation studies. There aremany sympatric and ecologically similar duck species, among which fertile hybrids occur relatively frequently innature, yet these species remain distinct.Results: We show that the degree of shared single nucleotide polymorphisms (SNPs) between five species ofdabbling ducks (genus Anas) is an order of magnitude higher than that previously reported between any pair ofeukaryotic species with comparable evolutionary distances. We demonstrate that hybridisation has led to sustainedexchange of genetic material between duck species on an evolutionary time scale without disintegrating speciesboundaries. Even though behavioural, genetic and ecological factors uphold species boundaries in ducks, wedetect opposing forces allowing for viable interspecific hybrids, with long-term evolutionary implications. Based onthe superspecies concept we here introduce the novel term “supra-population” to explain the persistence of SNPsidentical by descent within the studied ducks despite their history as distinct species dating back millions of years.Conclusions: By reviewing evidence from speciation theory, palaeogeography and palaeontology we propose afundamentally new model of speciation to accommodate our genetic findings in dabbling ducks. This model, weargue, may also shed light on longstanding unresolved general speciation and hybridisation patterns in higherorganisms, e.g. in other bird groups with unusually high hybridisation rates. Observed parallels to horizontal genetransfer in bacteria facilitate the understanding of why ducks have been such an evolutionarily successful group ofanimals. There is large evolutionary potential in the ability to exchange genes among species and the resultingdramatic increase of effective population size to counter selective constraints

Evolution and Connectivity in the World-Wide Migration System of the Mallard: Inferences from Mitochondrial DNA

Background: Main waterfowl migration systems are well understood through ringing activities. However, inmallards (Anas platyrhynchos) ringing studies suggest deviations from general migratory trends and traditions inwaterfowl. Furthermore, surprisingly little is known about the population genetic structure of mallards, andstudying it may yield insight into the spread of diseases such as Avian Influenza, and in management andconservation of wetlands. The study of evolution of genetic diversity and subsequent partitioning thereof duringthe last glaciation adds to ongoing discussions on the general evolution of waterfowl populations and flywayevolution. Hypothesised mallard flyways are tested explicitly by analysing mitochondrial mallard DNA from thewhole northern hemisphere.Results: Phylogenetic analyses confirm two mitochondrial mallard clades. Genetic differentiation within Eurasia andNorth-America is low, on a continental scale, but large differences occur between these two land masses (FST =0.51). Half the genetic variance lies within sampling locations, and a negligible portion between currentlyrecognised waterfowl flyways, within Eurasia and North-America. Analysis of molecular variance (AMOVA) atcontinent scale, incorporating sampling localities as smallest units, also shows the absence of population structureon the flyway level. Finally, demographic modelling by coalescence simulation proposes a split between Eurasiaand North-America 43,000 to 74,000 years ago and strong population growth (~100fold) since then and littlemigration (not statistically different from zero).Conclusions: Based on this first complete assessment of the mallard’s world-wide population genetic structure weconfirm that no more than two mtDNA clades exist. Clade A is characteristic for Eurasia, and clade B for North-America although some representatives of clade A are also found in North-America. We explain this pattern byevaluating competing hypotheses and conclude that a complex mix of historical, recent and anthropogenic factorsshaped the current mallard populations. We refute population classification based on flyways proposed byornithologists and managers, because they seem to have little biological meaning. Our results have implications forwetland management and conservation, with special regard to the release of farmed mallards for hunting, as wellas for the possible transmission of Avian Influenza by mallards due to migration

A tailored-fit model evaluation strategy for better decisions about structural equation models

Abstract Proper measurement of technology knowledge and social change enables managers to advance strategies in technology management. Structural equation modeling is the ideal method in Technological Forecasting and Social Change (TFSC) and other leading journals to assess the measurement quality of the relevant decision variables and understand how they are related. However, a myriad of indicators are now available to judge how suitable these measurements are (i.e., how well they fit). Despite a consensus that fit indicators are highly context-dependent and no "one-fits-all approach" emerges, a more contingent perspective is surprisingly missing. To fill this gap, we advocate for a "tailored-fit model evaluation strategy" that is specific to the situation at hand to exploit the particular strengths of fit indicators. Motivated by a synthesis of structural equation modeling in TFSC, our simulation study finds that three critical distinctions regarding (a) model novelty, (b) focus on measurement or structural models, and (c) sample size are vital. The proposed strategy demonstrates that, in many contexts, only a few indicators are recommended to avoid artificially inflated Type I/II errors. We provide a decision tree to reach more accurate decisions in model evaluation in order to better theorize and forecast technological and social challenges