1,106 research outputs found
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 Earthâs Upper Atmosphere
Nickel atoms are injected into the Earthâs 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 moleculeâ1 sâ1): k(Ni + O3, 293 K) = (6.5 ± 0.7) Ă 10â10; k(NiO + O3 â Ni + 2O2, 293 K) = (1.4 ± 0.5) Ă 10â10; k(NiO + O3 â NiO2 + O2, 293 K) = (2.5 ± 0.7) Ă 10â10; k(NiO + CO, 190â377 K) = (3.2 ± 0.6) Ă 10â11 (T/200)â0.19±0.05. For termolecular reactions (in cm6 moleculeâ2 sâ1, uncertainty ± Ï over the stated temperature range): log10(krec,0(Ni + O2 + N2, 190â455 K)) = â37.592 + 7.168log10(T) - 1.5650(log10(T))2, Ï = 11%; log10(krec,0(NiO + O2 + N2, 293â380 K)) = â41.0913 + 10.1064log10(T) â 2.2610(log10(T))2, Ï = 22%; and log10(krec,0(NiO + CO2 + N2, 191â375 K)) = â41.4265 + 10.9640log10(T) â 2.5287(log10(T))2, Ï = 15%. The faster recombination reaction NiO + H2O + N2, which is clearly in the falloff region over the experimental pressure range (3â10 Torr), is best described by log10(krec,0/cm6 moleculeâ2 sâ1) = â29.7651 + 5.2064log10(T) â 1.7118(log10(T))2, krec,â = 6.0 Ă 10â10 exp(â171/T) cm3 moleculeâ1 sâ1, broadening factor Fc = 0.84, Ï = 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 â white node or low â 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 â equestrian sport â 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
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