Magnetic nanocomposites at microwave frequencies

Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small. Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table

Sexual selection and population divergence III : interspecific and intraspecific variation in mating signals

Funding: Orthopterists' Society, Natural Environment Research Council (Grant Number(s): NE/G00949X/1, NE/G014906/1, NE/L011255/1), ARC (Grant Number(s): DP180101708).A major challenge for studying the role of sexual selection in divergence and speciation is understanding the relative influence of different sexually selected signals on those processes in both intra‐ and interspecific contexts. Different signals may be more or less susceptible to co‐option for species identification depending on the balance of sexual and ecological selection acting upon them. To examine this, we tested three predictions to explain geographic variation in long‐ versus short‐range sexual signals across a 3,500 + km transect of two related Australian field cricket species (Teleogryllus spp.): (a) selection for species recognition, (b) environmental adaptation and (c) stochastic divergence. We measured male calling song and male and female cuticular hydrocarbons (CHCs) in offspring derived from wild populations, reared under common garden conditions. Song clearly differentiated the species, and no hybrids were observed suggesting that hybridization is rare or absent. Spatial variation in song was not predicted by geography, genetics or climatic factors in either species. In contrast, CHC divergence was strongly associated with an environmental gradient supporting the idea that the climatic environment selects more directly upon these chemical signals. In light of recently advocated models of diversification via ecological selection on secondary sexual traits, the different environmental associations we found for song and CHCs suggest that the impact of ecological selection on population divergence, and how that influences speciation, might be different for acoustic versus chemical signals.Publisher PDFPeer reviewe

Morphological traits can track coral reef responses to the Anthropocene

MD was supported by the John Templeton Foundation (60501) and JM was supported by the Australian Research Council (FT110100609) during the period this research was undertaken.1. Susceptibility to human-driven environmental changes is mediated by species traits. Therefore, identifying traits that predict organism performance, ecosystem function and response to changes in environmental conditions can help forecast how ecosystems are responding to the Anthropocene. 2. Morphology dictates how organisms interact with their environment and other organisms, partially determining the environmental and biological contexts in which they are successful. Morphology is important for autogenic ecosystem engineering organisms, such as reef-building corals, because it determines the shape of the structures they create and by extension the communities they support. 3. Here, we present six morphological traits that capture variation in volume compactness, surface complexity and top-heaviness. With support from the literature, we propose causal links between morphology and a performance–function–response framework. 4. To illustrate these concepts, we combine 3D scanning and coral survey data to predict morphological traits from in situ colonies. We present a case study that examines how assemblage-scale morphological traits have responded to two cyclones and the 2016 mass bleaching event—two phenomena predicted to increase in severity in the Anthropocene—and discuss how these changes may impact ecosystem function. 5. The morphological traits outlined here offer a generalised and hypothesis-driven approach to tracking how reefs respond to the Anthropocene. The ability to predict these traits from field data and the increasing use of photogrammetry makes them readily applicable across broad spatiotemporal scales.PostprintPeer reviewe

Afterglow upper limits for four short duration, hard spectrum gamma-ray bursts

We present interplanetary network localization, spectral, and time history information for four short-duration, hard spectrum gamma-ray bursts, GRB000607, 001025B, 001204, and 010119. All of these events were followed up with sensitive radio and optical observations (the first and only such bursts to be followed up in the radio to date), but no detections were made, demonstrating that the short bursts do not have anomalously intense afterglows. We discuss the upper limits, and show that the lack of observable counterparts is consistent both with the hypothesis that the afterglow behavior of the short bursts is like that of the long duration bursts, many of which similarly have no detectable afterglows, as well as with the hypothesis that the short bursts have no detectable afterglows at all. Small number statistics do not allow a clear choice between these alternatives, but given the present detection rates of various missions, we show that progress can be expected in the near future.Comment: 19 pages, 4 figures; Revised version, accepted by the Astrophysical Journa

Tensor calculus on noncommutative spaces

It is well known that for a given Poisson structure one has infinitely many star products related through the Kontsevich gauge transformations. These gauge transformations have an infinite functional dimension (i.e., correspond to an infinite number of degrees of freedom per point of the base manifold). We show that on a symplectic manifold this freedom may be almost completely eliminated if one extends the star product to all tensor fields in a covariant way and impose some natural conditions on the tensor algebra. The remaining ambiguity either correspond to constant renormalizations to the symplectic structure, or to maps between classically equivalent field theory actions. We also discuss how one can introduce the Riemannian metric in this approach and the consequences of our results for noncommutative gravity theories.Comment: 17p; v2: extended version, to appear in CQ

Efficacy of different treatment regimes against setariosis (Setaria tundra, Nematoda: Filarioidea) and associated peritonitis in reindeer

<p>Abstract</p> <p>Background</p> <p>When a severe peritonitis outbreak in semi-domesticated reindeer was noticed in 2003 in Finland, the concerned industry urged immediate preventive actions in order to avoid detrimental effects of <it>S. tundra </it>and further economical losses. A research programme was swiftly initiated to study <it>S. tundra </it>and its impact on the health and wellbeing of reindeer.</p> <p>Methods</p> <p>The ultimate aim of this study was to test the efficacy of different treatment regimes against <it>S. tundra </it>and associated peritonitis in reindeer. The timing of the trials was planned to be compatible with the annual rhythm of the reindeer management; (1) the treatment of calves in midsummer, during routine calf ear marking, with ivermectin injection prophylaxis and deltamethrin pour-on solution as a repellent against insect vectors, (2) the treatment of infected calves in early autumn with ivermectin injection, and (3) ivermectin treatment of breeding reindeer in winter. The results were assessed using the post mortem inspection data and <it>S. tundra </it>detection. Finally, to evaluate on the population level the influence of the annual (late autumn-winter) ivermectin treatment of breeding reindeer on the transmission dynamics of <it>S. tundra</it>, a questionnaire survey was conducted.</p> <p>Results</p> <p>In autumn, ivermectin treatment was efficient against peritonitis and in midsummer had a slight negative impact on the degree of peritonitis and positive on the fat layer, but deltamethrin had none. Ivermectin was efficient against adult <it>S. tundra </it>and its smf. All the reindeer herding cooperatives answered the questionnaire and it appeared that antiparasitic treatment of reindeer population was intense during the study period, when 64–90% of the animals were treated. In the southern part of the Finnish reindeer husbandry area, oral administration of ivermectin was commonly used.</p> <p>Conclusion</p> <p>Autumn, and to a lesser degree summer, treatment of reindeer calves with injectable ivermectin resulted in decreased severity of peritonitis and perihepatitis in reindeer calves due to setariosis. In the case of necessity for animal welfare reasons, treatment during early autumn round ups should be considered. On the population level, massive and routinely applied antiparasitic treatments can improve the health of breeding reindeer and decrease the mortality and the number of carriers but during the outbreak could not prevent its movement and expansion to the North.</p

Enhanced light extraction from InGaN/GaN quantum wells with silver gratings

We demonstrate that an extraction enhancement by a factor of 2.8 can be obtained for a GaN quantum well structure using metallic nanostructures, compared to a flat semiconductor. The InGaN/GaN quantum well is inserted into a dielectric waveguide, naturally formed in the structure, and a silver grating is deposited on the surface and covered with a polymer film. The polymer layer greatly improves the extraction compared to a single metallic grating. The comparison of the experiments with simulations gives strong indications on the key role of weakly guided modes in the polymer layer diffracted by the grating.Peer reviewe

Antidepressant treatment among social workers, human service professionals, and non-human service professionals : A multi-cohort study in Finland, Sweden and Denmark

Background: Social workers have an elevated risk for mental disorders, but little is known about their antidepressant treatment. Aims: To examine any and long-term antidepressant treatment among social workers in Finland, Sweden and Denmark. Methods: We linked records from drug prescription registers to three prospective cohorts: the Finnish Public Sector study, years 2006-2011, and nation-wide cohorts in Sweden and Denmark, years 2006-2014, including a total of 1.5 million employees in (1) social work, (2) other social and health care professions, (3) education and (4) office work. We used Cox proportional hazards models to estimate hazard ratios for any and long-term (>6 months) antidepressant treatment among social workers compared to the three reference occupational groups and carried out meta-analyses. Results: During follow-up, 25% of social workers had any prescriptions for antidepressants (19-24% reference occupations) and 20% for long-term treatment (14-19% reference occupations). The pooled effects for any and long-term treatment showed that probabilities were 10% higher in social workers compared to other health and social care professionals and 30% higher compared to education and non-human service professionals. Probabilities for any treatment in the three countries were relatively similar, but for long-term treatment social workers in Finland had a greater risk compared with other human service professions. Limitations: There were differences between the cohorts in the availability of data. Specific diagnoses for the antidepressant treatment were not known neither adherence to treatment. Conclusion: Social workers have a higher risk for any and long-term antidepressant treatment than other human and non-human service professionals.Peer reviewe