Substrate influence on the plasmonic response of clusters of spherical nanoparticles

The plasmonic response of nanoparticles is exploited in many subfields of science and engineering to enhance optical signals associated with probes of nanoscale and subnanoscale entities. We develop a numerical algorithm based on previous theoretical work that addresses the influence of a substrate on the plasmonic response of collections of nanoparticles of spherical shape. Our method is a real space approach within the quasi-static limit that can be applied to a wide range of structures. We illustrate the role of the substrate through numerical calculations that explore single nanospheres and nanosphere dimers fabricated from either a Drude model metal or from silver on dielectric substrates, and from dielectric spheres on silver substrates.Comment: 12 pages, 13 figure

Landscape Context Influences Nest Survival in a Midwest Grassland

Although the management and restoration of habitat is the key method to conserve species of interest, local habitat management often fails to elicit desired responses in populations. Landscape features beyond the local habitat scale affect the population dynamics of ring-necked pheasants (Phasianus colchicus), but the mechanism behind this response is unknown. One possibility is that nest survival, which is primarily reduced by nest predation, is regulating pheasant responses to the landscape. We investigated the extent to which land use affected nest survival by studying 202 artificial nests on 12 Conservation Reserve Program (CRP) fields in Nebraska, USA with varying surrounding land-use practices. After running a hierarchical analysis of competing models, we found that predicted nest survival increased as the amount of CRP, winter wheat, and pastureland surrounding a CRP field increased, whereas increasing fallow fields was correlated with decreased nest success. Our findings support theoretical and empirical evidence that nest predation rates are shaped by predator search efficacy. Changing the relative availability of nesting habitat that potentially holds alternative prey sources in our study affected nest survival rates, possibly by altering the search area of opportunistic nest predators. The similarities between the landscape relationships that predict nest survival and landscape predictors of pheasant abundance indicate that nest survival may potentially act as the mechanism shaping population dynamics within an ever changing farmland ecosystem. We recommend that managers consider the land use surrounding areas under consideration for habitat improvement to enhance conservation investments

Patch Size and Nest Density Influence Nest Survival

Nest predation is the primary cause of avian nest failure and therefore an important driver of avian population growth. Studies indicate that landscape context plays an important role in nest success, and although this is widely attributed to changes in nest predator communities, landscape context also influences nest density which affects predator search area and effort. Much debate remains as to whether specifically the size of a habitat patch or the density of nests has the greatest effect on nest predation rates. We explored the interactions between landscape context, predator efficiency, and nest survival. Northern bobwhite quail (Colinus virginianus) possess specific habitat requirements within a small home range and are a short-lived species that relies upon high reproductive performance, which make them the ideal system to test the extent to which landscape context affects nest predation rates. We investigated the extent to which the size of a grassland patch versus nest density affects nest survival by studying the predation rates of 617 artificial nests during two 23 day trials on 12 study sites in south central Nebraska. To examine the effects of patch size, we selected 6 study sites that were small patches of grassland (including pastures and Conservation Reserve Program fields) ranging in size from 40-60 ha and 6 study sites that were approximately 50 ha sections of larger contiguous grasslands. A high density of artificial nests were placed on half of the small and large patch study sites with the remaining sites having a low density of nests, for the second trial the nest density treatments were switched for each site

Landscape Context Influences Nest Survival in a Midwest Grassland

Although the management and restoration of habitat is the key method to conserve species of interest, local habitat management often fails to elicit desired responses in populations. Landscape features beyond the local habitat scale affect the population dynamics of ring-necked pheasants (Phasianus colchicus), but the mechanism behind this response is unknown. One possibility is that nest survival, which is primarily reduced by nest predation, is regulating pheasant responses to the landscape. We investigated the extent to which land use affected nest survival by studying 202 artificial nests on 12 Conservation Reserve Program (CRP) fields in Nebraska, USA with varying surrounding land-use practices. After running a hierarchical analysis of competing models, we found that predicted nest survival increased as the amount of CRP, winter wheat, and pastureland surrounding a CRP field increased, whereas increasing fallow fields was correlated with decreased nest success. Our findings support theoretical and empirical evidence that nest predation rates are shaped by predator search efficacy. Changing the relative availability of nesting habitat that potentially holds alternative prey sources in our study affected nest survival rates, possibly by altering the search area of opportunistic nest predators. The similarities between the landscape relationships that predict nest survival and landscape predictors of pheasant abundance indicate that nest survival may potentially act as the mechanism shaping population dynamics within an ever changing farmland ecosystem. We recommend that managers consider the land use surrounding areas under consideration for habitat improvement to enhance conservation investments

Distinguishing fractional and white noise in one and two dimensions

We discuss the link between uncorrelated noise and Hurst exponent for one and two-dimensional interfaces. We show that long range correlations cannot be observed using one-dimensional cuts through two-dimensional self-affine surfaces whose height distributions are characterized by a Hurst exponent lower than -1/2. In this domain, fractional and white noise are not distinguishable. A method analysing the correlations in two dimensions is necessary. For Hurst exponents larger than -1/2, a crossover regime leads to a systematic over estimate of the Hurst exponent.Comment: 3 pages RevTeX, 4 Postscript figure

Space Radiation Program Element Tissue Sharing Initiative

No abstract availabl

Space Radiation Program Element Tissue Sharing Initiative

Over the years, a large number of animal experiments have been conducted at the NASA Space Radiation Laboratory and other facilities under the support of the NASA Space Radiation Program Element (SRPE). Studies using rodents and other animal species to address the space radiation risks will remain a significant portion of the research portfolio of the Element. In order to maximize scientific return of the animal studies, SRPE is taking the initiative to promote tissue sharing among the scientists in the space radiation research community. This initiative is enthusiastically supported by the community members as voiced in the responses to a recent survey. For retrospective tissue samples, an online platform will be established for the PIs to post a list of the available samples, and to exchange information with the potential recipients. For future animal experiments, a tissue sharing policy is being developed by SRPE

Ghosts from the past: a review of fossil Hepialoidea (Lepidoptera)

We critically re-examine nine of the ten fossil specimens currently assigned to Hepialidae. Three fossils with impressions of wing veins and scales placed in the fossil genus Prohepialus Piton, 1940, and two mummified larvae that show apomorphic characters, have features that support placement in Hepialidae. The other four fossils that we evaluate, Prohepialus incertus Piton, 1940; Oiophassus nycterus Zhang, 1989; Protohepialus comstocki Pierce, 1945; and a fossil scale, lack definitive hepialid characters. One of these, Prohepialus incertus Piton, 1940, appears to represent a symphytan (Hymenoptera), and is excluded from Lepidoptera. The fossilized wings placed in Prohepialus by Jarzembowski display numerous features that indicate a proximate phylogenetic relationship to extant members of the hepialid genus Sthenopis Packard and related genera.Peer reviewe

Entropy of the Nordic electricity market: anomalous scaling, spikes, and mean-reversion

The electricity market is a very peculiar market due to the large variety of phenomena that can affect the spot price. However, this market still shows many typical features of other speculative (commodity) markets like, for instance, data clustering and mean reversion. We apply the diffusion entropy analysis (DEA) to the Nordic spot electricity market (Nord Pool). We study the waiting time statistics between consecutive spot price spikes and find it to show anomalous scaling characterized by a decaying power-law. The exponent observed in data follows a quite robust relationship with the one implied by the DEA analysis. We also in terms of the DEA revisit topics like clustering, mean-reversion and periodicities. We finally propose a GARCH inspired model but for the price itself. Models in the context of stochastic volatility processes appear under this scope to have a feasible description.Comment: 16 pages, 7 figure