Reversible to Irreversible Flow Transition in Periodically Driven Vortices

We show that periodically driven superconducting vortices in the presence of quenched disorder exhibit a transition from reversible to irreversible flow under increasing vortex density or cycle period. This type of behavior has recently been observed for periodically sheared colloidal suspensions and we demonstrate that driven vortex systems exhibit remarkably similar behavior. We also provide evidence that the onset of irreversible behavior is a dynamical phase transition.Comment: 4 pages, 4 postscript figures. Version to appear in Physical Review Letter

Improved large-mode area endlessly single-mode photonic crystal fibers

We numerically study the possibilities for improved large-mode area endlessly single mode photonic crystal fibers for use in high-power delivery applications. By carefully choosing the optimal hole diameter we find that a triangular core formed by three missing neighboring air holes considerably improves the mode area and loss properties compared to the case with a core formed by one missing air hole. In a realized fiber we demonstrate an enhancement of the mode area by ~30 % without a corresponding increase in the attenuation.Comment: 3 pages including 3 eps-figures. Accepted for Optics Letter

Kinetic Study of Ni and NiO Reactions Pertinent to the Earth’s Upper Atmosphere

Nickel atoms are injected into the Earth’s mesosphere by meteoric ablation, producing a Ni layer between 70 and 105 km in altitude. The subsequent reactions of Ni and NiO with atmospherically relevant species were studied using the time-resolved pulsed laser photolysis-laser-induced fluorescence technique, combined with electronic structure calculations and RRKM theory where appropriate. Results for bimolecular reactions (in cm3 molecule–1 s–1): k(Ni + O3, 293 K) = (6.5 ± 0.7) × 10–10; k(NiO + O3 → Ni + 2O2, 293 K) = (1.4 ± 0.5) × 10–10; k(NiO + O3 → NiO2 + O2, 293 K) = (2.5 ± 0.7) × 10–10; k(NiO + CO, 190–377 K) = (3.2 ± 0.6) × 10–11 (T/200)−0.19±0.05. For termolecular reactions (in cm6 molecule–2 s–1, uncertainty ± σ over the stated temperature range): log10(krec,0(Ni + O2 + N2, 190–455 K)) = −37.592 + 7.168log10(T) - 1.5650(log10(T))2, σ = 11%; log10(krec,0(NiO + O2 + N2, 293–380 K)) = −41.0913 + 10.1064log10(T) – 2.2610(log10(T))2, σ = 22%; and log10(krec,0(NiO + CO2 + N2, 191–375 K)) = −41.4265 + 10.9640log10(T) – 2.5287(log10(T))2, σ = 15%. The faster recombination reaction NiO + H2O + N2, which is clearly in the falloff region over the experimental pressure range (3–10 Torr), is best described by log10(krec,0/cm6 molecule–2 s–1) = −29.7651 + 5.2064log10(T) – 1.7118(log10(T))2, krec,∞ = 6.0 × 10–10 exp(−171/T) cm3 molecule–1 s–1, broadening factor Fc = 0.84, σ = 16%. The implications of these results in the atmosphere are then discussed

Patterns of Interactions in Complex Social Networks Based on Coloured Motifs Analysis

Coloured network motifs are small subgraphs that enable to discover and interpret the patterns of interaction within the complex networks. The analysis of three-nodes motifs where the colour of the node reflects its high – white node or low – black node centrality in the social network is presented in the paper. The importance of the vertices is assessed by utilizing two measures: degree prestige and degree centrality. The distribution of motifs in these two cases is compared to mine the interconnection patterns between nodes. The analysis is performed on the social network derived from email communication

Patterns of subnet usage reveal distinct scales of regulation in the transcriptional regulatory network of Escherichia coli

The set of regulatory interactions between genes, mediated by transcription factors, forms a species' transcriptional regulatory network (TRN). By comparing this network with measured gene expression data one can identify functional properties of the TRN and gain general insight into transcriptional control. We define the subnet of a node as the subgraph consisting of all nodes topologically downstream of the node, including itself. Using a large set of microarray expression data of the bacterium Escherichia coli, we find that the gene expression in different subnets exhibits a structured pattern in response to environmental changes and genotypic mutation. Subnets with less changes in their expression pattern have a higher fraction of feed-forward loop motifs and a lower fraction of small RNA targets within them. Our study implies that the TRN consists of several scales of regulatory organization: 1) subnets with more varying gene expression controlled by both transcription factors and post-transcriptional RNA regulation, and 2) subnets with less varying gene expression having more feed-forward loops and less post-transcriptional RNA regulation.Comment: 14 pages, 8 figures, to be published in PLoS Computational Biolog

Long-term (25-year) survival after renal homotransplantation - The world experience

A follow-up is provided for 64 patients treated with renal transplantation at the University of Colorado before 31 March 1964. The 25-year survival was 15/64 (23.4%) and 14 patients (22%) are still alive after 25 1/2 to 27 years. There are 9 other survivors in the world from this era, distributed in 4 American and 2 European centers. All of the 25-year survivors received their grafts from living related donors

Rapid recovery following short-term acoustic disturbance in two fish species

ArticleNoise from human activities is known to impact organisms in a variety of taxa, but most experimental studies on the behavioural effects of noise have focused on examining responses associated with the period of actual exposure. Unlike most pollutants, acoustic noise is generally short-lived, usually dissipating quickly after the source is turned off or leaves the area. In a series of experiments, we use established experimental paradigms to examine how fish behaviour and physiology are affected, both during short-term (2 min) exposure to playback of recordings of anthropogenic noise sources and in the immediate aftermath of noise exposure. We considered the anti-predator response and ventilation rate of juvenile European eels (Anguilla anguilla), and ventilation rate of juvenile European seabass (Dicentrarchus labrax). As previously found, additional-noise exposure decreased eel anti-predator responses, increased startle latency and increased ventilation rate relative to ambient-noise-exposed controls. Our results show for the first time that those effects quickly dissipated; eels showed rapid recovery of startle responses and startle latency, and rapid albeit incomplete recovery of ventilation rate in the 2 min after noise cessation. Seabass in both laboratory and open-water conditions showed an increased ventilation rate during playback of additional noise compared to ambient conditions. However, within 2 min of noise cessation, ventilation rate showed complete recovery to levels equivalent to ambient-exposed control individuals. Care should be taken in generalizing these rapid-recovery results, as individuals might have accrued other costs during noise exposure and other species might show different recovery times. Nonetheless, our results from two different fish species provide tentative cause for optimism concerning recovery following short-duration noise exposure, and suggest that considering periods following noise exposures could be important for mitigation and management decisions.DefraNER

'Dressage Is Full of Queens!' Masculinity, Sexuality and Equestrian Sport

Attitudes towards sexuality are changing and levels of cultural homophobia decreasing, yet there remain very few openly gay men within sport. As a proving ground for heteromasculinity, sport has traditionally been a hostile environment for gay men. This article is based on an ethnographic study within a sporting subworld in which gay men do appear to be accepted: equestrian sport. Drawing on inclusive masculinity theory, equestrian sport is shown to offer an unusually tolerant environment for gay men in which heterosexual men of all ages demonstrate low levels of homophobia. Inclusive masculinity theory is a useful framework for exploring the changing nature of masculinities and this study demonstrates that gay men are becoming increasingly visible and accepted within once unreceptive locales, such as sport and rural communities. However, this more tolerant attitude is purchased at the expense of a subordinated feminine Other, perpetuating the dominance of men within competitive sport. © The Author(s) 2012

Together, yet still not equal? Sex integration in equestrian sport

Sex segregation is a core organising principle of most modern sports and is a key element in the marginalisation and subordination of girls and women in sport and beyond. In this article I explore the only Olympic-level sport which is not organised around sex segregation – equestrian sport – in order to consider the implications of sex integration for female participants. I draw on a study conducted on elite riders that found that although sex integration in equestrian sport does not lead to female participants being excluded from high-level competition, men continue to perform disproportionately well. This suggests that although sex integration may be an important step towards breaking down gender hierarchies in sport, without accompanying wider changes in gender norms and expectations, sex integration alone will not be enough to achieve greater gender equality in equestrian sport

Subgraphs and network motifs in geometric networks

Many real-world networks describe systems in which interactions decay with the distance between nodes. Examples include systems constrained in real space such as transportation and communication networks, as well as systems constrained in abstract spaces such as multivariate biological or economic datasets and models of social networks. These networks often display network motifs: subgraphs that recur in the network much more often than in randomized networks. To understand the origin of the network motifs in these networks, it is important to study the subgraphs and network motifs that arise solely from geometric constraints. To address this, we analyze geometric network models, in which nodes are arranged on a lattice and edges are formed with a probability that decays with the distance between nodes. We present analytical solutions for the numbers of all 3 and 4-node subgraphs, in both directed and non-directed geometric networks. We also analyze geometric networks with arbitrary degree sequences, and models with a field that biases for directed edges in one direction. Scaling rules for scaling of subgraph numbers with system size, lattice dimension and interaction range are given. Several invariant measures are found, such as the ratio of feedback and feed-forward loops, which do not depend on system size, dimension or connectivity function. We find that network motifs in many real-world networks, including social networks and neuronal networks, are not captured solely by these geometric models. This is in line with recent evidence that biological network motifs were selected as basic circuit elements with defined information-processing functions.Comment: 9 pages, 6 figure