Correlated photon-pair generation in a periodically poled MgO doped stoichiometric lithium tantalate reverse proton exchanged waveguide

We demonstrate photon-pair generation in a reverse proton exchanged waveguide fabricated on a periodically poled magnesium doped stoichiometric lithium tantalate substrate. Detected pairs are generated via a cascaded second order nonlinear process where a pump laser at wavelength of 1.55 $\mu$m is first doubled in frequency by second harmonic generation and subsequently downconverted around the same spectral region. Pairs are detected at a rate of 42 per second with a coincidence to accidental ratio of 0.7. This cascaded pair generation process is similar to four-wave-mixing where two pump photons annihilate and create a correlated photon pair

Tail colour signals performance in blue tit nestlings

Indirect sexual selection arises when reproductive individuals choose their mates based on heritable ornaments that are genetically correlated to fitness. Evidence for genetic associations between ornamental colouration and fitness remains scarce. In this study, we investigate the quantitative genetic relationship between different aspects of tail structural colouration (brightness, hue and UV chroma) and performance (cell-mediated immunity, body mass and wing length) in blue tit (Cyanistes caeruleus) nestlings. In line with previous studies, we find low heritability for structural colouration and moderate heritability for performance measures. Multivariate animal models show positive genetic correlations between the three measures of performance, indicating quantitative genetic variation for overall performance, and tail brightness and UV chroma, two genetically independent colour measures, are genetically correlated with performance (positively and negatively, respectively). Our results suggest that mate choice based on independent aspects of tail colouration can have fitness payoffs in blue tits and provide support for the indirect benefits hypothesis. However, low heritability of tail structural colouration implies that indirect sexual selection on mate choice for this ornament will be a weak evolutionary force.Peer reviewe

Nanoantenna enhancement for telecom-wavelength superconducting single photon detectors

Superconducting nanowire single photon detectors are rapidly emerging as a key infrared photon-counting technology. Two front-side-coupled silver dipole nanoantennas, simulated to have resonances at 1480 and 1525 nm, were fabricated in a two-step process. An enhancement of 50 to 130% in the system detection efficiency was observed when illuminating the antennas. This offers a pathway to increasing absorption into superconducting nanowires, creating larger active areas, and achieving more efficient detection at longer wavelengths

Bayesian paternity analysis and mating patterns in a parasitic nematode, Trichostrongylus tenuis

Mating behaviour is a fundamental aspect of the evolutionary ecology of sexually reproducing species, but one that has been under-researched in parasitic nematodes. We analysed mating behaviour in the parasitic nematode Trichostrongylus tenuis by performing a paternity analysis in a population from a single red grouse host. Paternity of the 150 larval offspring of 25 mothers (sampled from one of the two host caeca) was assigned among 294 candidate fathers (sampled from both caeca). Each candidate father's probability of paternity of each offspring was estimated from 10-locus microsatellite genotypes. Seventy-six (51%) offspring were assigned a father with a probability of >0.8, and the estimated number of unsampled males was 136 (95% credible interval (CI) 77-219). The probability of a male from one caecum fathering an offspring in the other caecum was estimated as 0.024 (95% CI 0.003-0.077), indicating that the junction of the caeca is a strong barrier to dispersal. Levels of promiscuity (defined as the probability of two of an adult's offspring sharing only one parent) were high for both sexes. Variance in male reproductive success was moderately high, possibly because of a combination of random mating and high variance in post-copulatory reproductive success. These results provide the first data on individual mating behaviour among parasitic nematodes

Longitudinal Metagenomic Analysis of the Water and Soil from Gulf of Mexico Beaches Affected by the Deep Water Horizon Oil Spill

Estimates of 7x105 cubic meters of crude oil were released into the Gulf of Mexico as a consequence of the April 20th, 2010 Deep Water Horizon drilling rig explosion, leaving thousands of square miles of earth's surface covered in crude oil. Dispersants were used on large slicks and injected at the well head, resulting in oil being suspended throughout the water column. Starting in June 2010, oil reached hundreds of miles of Louisiana, Alabama, Mississippi, and Florida shoreline disturbing the ecological balance and economic stability of the region. While visible damages are evident in the wildlife populations and marine estuaries, the most significant affect may be on the most basic level of the ecosystems: the bacterial and plankton populations.We present results from high throughput DNA sequencing of close-to-shore water and beach soil samples before and during the appearance of oil in Louisiana and Mississippi. Sixteen samples were taken over a two month period at approximately two week intervals from Grand Isle, LA and Gulfport, MS and were sequenced using the Illumina GAIIx platform. Significant genomic-based population fluctuations were observed in the soil and water samples. These included large spikes in the human pathogen Vibrio cholera, a sharp increase in Rickettsiales sp., and decrease of Synechococus sp. in water samples. Analysis of the contiguous de-novo assembled DNAs (contigs) from the samples also suggested the loss of biodiversity in water samples by the time oil appeared at the shores in both locations. Our observations lead us to the conclusion that oil strongly influenced microbial population dynamics, had a striking impact on the phytoplankton and other flora present prior to the appearance of oil, and that the microbial community had not recovered to pre-spill conditions by the end of our observational period

Corpuscular model of two-beam interference and double-slit experiments with single photons

We introduce an event-based corpuscular simulation model that reproduces the wave mechanical results of single-photon double slit and two-beam interference experiments and (of a one-to-one copy of an experimental realization) of a single-photon interference experiment with a Fresnel biprism. The simulation comprises models that capture the essential features of the apparatuses used in the experiment, including the single-photon detectors recording individual detector clicks. We demonstrate that incorporating in the detector model, simple and minimalistic processes mimicking the memory and threshold behavior of single-photon detectors is sufficient to produce multipath interference patterns. These multipath interference patterns are built up by individual particles taking one single path to the detector where they arrive one-by-one. The particles in our model are not corpuscular in the standard, classical physics sense in that they are information carriers that exchange information with the apparatuses of the experimental set-up. The interference pattern is the final, collective outcome of the information exchanges of many particles with these apparatuses. The interference patterns are produced without making reference to the solution of a wave equation and without introducing signalling or non-local interactions between the particles or between different detection points on the detector screen.Comment: Accepted for publication in J. Phys. Soc. Jpn

Niobium diselenide superconducting photodetectors

We report the photoresponse of niobium diselenide (NbSe$_2$), a transition metal dichalcogenide (TMD) which exhibits superconducting properties down to a single layer. Devices are built by using micro-mechanically cleaved 2 to 10 layers and tested under current bias using nano-optical mapping in the 350mK-5K range, where they are found to be superconducting. The superconducting state can be broken by absorption of light, resulting in a voltage signal when the devices are current biased. The response found to be energy dependent making the devices useful for applications requiring energy resolution, such as bolometry, spectroscopy and infrared imaging.Comment: 6 pages, 6 figure

Variable strength of forest stand attributes and weather conditions on the questing activity of Ixodes ricinus ticks over years in managed forests

Given the ever-increasing human impact through land use and climate change on the environment, we crucially need to achieve a better understanding of those factors that influence the questing activity of ixodid ticks, a major disease-transmitting vector in temperate forests. We investigated variation in the relative questing nymph densities of Ixodes ricinus in differently managed forest types for three years (2008–2010) in SW Germany by drag sampling. We used a hierarchical Bayesian modeling approach to examine the relative effects of habitat and weather and to consider possible nested structures of habitat and climate forces. The questing activity of nymphs was considerably larger in young forest successional stages of thicket compared with pole wood and timber stages. Questing nymph density increased markedly with milder winter temperatures. Generally, the relative strength of the various environmental forces on questing nymph density differed across years. In particular, winter temperature had a negative effect on tick activity across sites in 2008 in contrast to the overall effect of temperature across years. Our results suggest that forest management practices have important impacts on questing nymph density. Variable weather conditions, however, might override the effects of forest management practices on the fluctuations and dynamics of tick populations and activity over years, in particular, the preceding winter temperatures. Therefore, robust predictions and the detection of possible interactions and nested structures of habitat and climate forces can only be quantified through the collection of long-term data. Such data are particularly important with regard to future scenarios of forest management and climate warming

Fertility, Living Arrangements, Care and Mobility

There are four main interconnecting themes around which the contributions in this book are based. This introductory chapter aims to establish the broad context for the chapters that follow by discussing each of the themes. It does so by setting these themes within the overarching demographic challenge of the twenty-first century – demographic ageing. Each chapter is introduced in the context of the specific theme to which it primarily relates and there is a summary of the data sets used by the contributors to illustrate the wide range of cross-sectional and longitudinal data analysed

Siblings, Stories and the Self: the sociological significance of young people’s sibling relationships

This article explores the significance of intra-generational ties with siblings to sociological understandings of the formation of social identity and sense of self in young people’s lives. Drawing on data from a qualitative study exploring young people’s sense of who they are and who they have the potential to become in the future, it is demonstrated that young people’s identities are often constructed in relation to how they are similar to or different from their sibling(s). Literature expounding the role of stories in the construction of the self is used to suggest that the comparing that is at the heart of the relational construction of sibling identities can occur through the telling and re-telling of family stories within the politics and power dynamics of existing relationships. The article concludes by suggesting that sibling relationships be conceptualized as part of a web of relationships in which young people are embedded