Low Abundance of King Eider Nests during Low Lemming Years in Northeast Greenland

Long-term surveys on Traill Island (Northeast Greenland) show that numbers of king eider (Somateria spectabilis) nests are correlated with high densities of collared lemming (Dicrostonyx groenlandicus). These observations match other zoological records from this region and agree with similar observations recorded elsewhere for arctic geese. Processes at work may be related to the fact that mammalian predators focus on lemmings when lemming numbers are high, but exert higher predation pressure on other prey at low lemming densities. Predators seem to increase their search effort during such low lemming years, thus increasing the likelihood that they will discover eider nests. This study highlights the importance of studying patterns at the community level in any attempt to interpret cyclic fluctuations in northern ecosystems.Une étude à long terme menée sur l'île de Traill (nord-est du Groenland) a mis en évidence que le nombre de nids d'eiders à tête grise (Somateria spectabilis) est corrélé à de fortes densités de lemming à collier (Dicrostonyx groenlandicus). Ces observations sont identiques à celles des autres relevés fauniques réalisés dans cette région et confortent des constats similaires sur le succès de reproduction des oies arctiques. Le déterminisme de ces phénomènes semble être lié au fait que les mammifères prédateurs se concentrent sur les lemmings lorsque ces derniers sont abondants, mais exercent une pression de prédation plus forte sur les autres espèces lorsque les lemmings se font plus rares. L'effort de recherche des prédateurs semble augmenter durant les années de creux, ce qui accroît la probabilité de découvrir les nids d'eiders. Cette étude souligne l'importance d'examiner les phénomènes dans l'ensemble de la communauté animale pour tenter d'expliquer les fluctuations cycliques dans les écosystèmes nordiques

Phase Structure of Z(3)-Polyakov-Loop Models

We study effective lattice actions describing the Polyakov loop dynamics originating from finite-temperature Yang-Mills theory. Starting with a strong-coupling expansion the effective action is obtained as a series of Z(3)-invariant operators involving higher and higher powers of the Polyakov loop, each with its own coupling. Truncating to a subclass with two couplings we perform a detailed analysis of the statistical mechanics involved. To this end we employ a modified mean field approximation and Monte Carlo simulations based on a novel cluster algorithm. We find excellent agreement of both approaches concerning the phase structure of the theories. The phase diagram exhibits both first and second order transitions between symmetric, ferromagnetic and anti-ferromagnetic phases with phase boundaries merging at three tricritical points. The critical exponents nu and gamma at the continuous transition between symmetric and anti-ferromagnetic phases are the same as for the 3-state Potts model.Comment: 20 pages, 22 figure

Genetic structure of the European hedgehog (Erinaceus europaeus) in Denmark

OBJECTIVES:Low genetic diversity can lead to reduced average fitness in a population or even extinction. Preserving genetic connectivity across fragmented landscapes is therefore vital to counteract the negative consequences of genetic drift and inbreeding. This study aimed to assess the genetic composition and consequently the conservation status of a nationwide sample of European hedgehogs (Erinaceus europaeus) in Denmark. METHODS:We applied an adaptation of the genotyping by sequencing (GBS) technique to 178 individuals from six geographically distinct populations. We used a Bayesian clustering method to subdivide individuals into genetically distinct populations. We estimated individual observed (iHO), observed (HO), and unbiased expected (uHE) heterozygosity, inbreeding coefficient (FIS), percentage of polymorphic loci (P%) and tested for deviations from Hardy-Weinberg equilibrium (HWE). We used linear models to test for potential anthropogenic effects on the genetic variability of hedgehogs with iHO, uHE, P% and FIS as response variables, and assessed the demographic history of the population. RESULTS:The Danish hedgehog population is composed of three genetic clusters. We found a mean P% of 54.44-94.71, a mean uHE of 0.126-0.318 and a mean HO of 0.124-0.293 in the six populations. The FIS was found to be significantly positive for three of the six populations. We detected a large heterogeneity of iHO values within populations, which can be due to inbreeding and/or fragmentation. FIS values decreased with increasing farmland density, but there was no significant association with human population or road density. CONCLUSIONS:We found a low level of genetic variability and evidence for genetic substructure and low effective population size, which are all consequences of habitat fragmentation. We failed to detect signs of a recent population bottleneck or population increase or decline. However, because the test only identifies recent changes in population size, we cannot reject the possibility of a longer-term decline in the Danish hedgehog population

International Guillain-Barré Syndrome Outcome Study (IGOS): protocol of a prospective observational cohort study on clinical and biological predictors of disease course and outcome in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an acute polyradiculoneuropathy with a highly variable clinical presentation, course, and outcome. The factors that determine the clinical variation of GBS are poorly understood which complicates the care and treatment of individual patients. The protocol of the ongoing International GBS Outcome Study (IGOS), a prospective, observational, multi-centre cohort study that aims to identify the clinical and biological determinants and predictors of disease onset, subtype, course and outcome of GBS is presented here. Patients fulfilling the diagnostic criteria for GBS, regardless of age, disease severity, variant forms, or treatment, can participate if included within two weeks after onset of weakness. Information about demography, preceding infections, clinical features, diagnostic findings, treatment, course and outcome is collected. In addition, cerebrospinal fluid and serial blood samples for serum and DNA is collected at standard time points. The original aim was to include at least 1000 patients with a follow-up of 1-3 years. Data are collected via a web-based data entry system and stored anonymously. IGOS started in May 2012 and by January 2017 included more than 1400 participants from 143 active centres in 19 countries across 5 continents. The IGOS data/biobank is available for research projects conducted by expertise groups focusing on specific topics including epidemiology, diagnostic criteria, clinimetrics, electrophysiology, antecedent events, antibodies, genetics, prognostic modelling, treatment effects and long-term outcome of GBS. The IGOS will help to standardize the international collection of data and biosamples for future research of GBS. ClinicalTrials.gov Identifier: NCT01582763

Generalized polarizabilities and the chiral structure of the nucleon

We discuss the virtual Compton scattering reaction $e^-p\to e^-p\gamma$ at low energies. We present results for the generalized polarizabilities of the nucleon obtained in heavy baryon chiral perturbation theory at $O(p^3)$.Comment: 5 pages, LaTex file, 1 postscript figure, uses ``espcrc1.sty'', talk given by S. Scherer at the 15th International Conference on Few Body Problems in Physics, Groningen, The Netherlands, 22-26 July 1997, to appear in the proceedings (Nucl. Phys. A

Stochastic modelling of reaction-diffusion processes: algorithms for bimolecular reactions

Several stochastic simulation algorithms (SSAs) have been recently proposed for modelling reaction-diffusion processes in cellular and molecular biology. In this paper, two commonly used SSAs are studied. The first SSA is an on-lattice model described by the reaction-diffusion master equation. The second SSA is an off-lattice model based on the simulation of Brownian motion of individual molecules and their reactive collisions. In both cases, it is shown that the commonly used implementation of bimolecular reactions (i.e. the reactions of the form A + B -> C, or A + A -> C) might lead to incorrect results. Improvements of both SSAs are suggested which overcome the difficulties highlighted. In particular, a formula is presented for the smallest possible compartment size (lattice spacing) which can be correctly implemented in the first model. This implementation uses a new formula for the rate of bimolecular reactions per compartment (lattice site).Comment: 33 pages, submitted to Physical Biolog

Steps in the bacterial flagellar motor

The bacterial flagellar motor is a highly efficient rotary machine used by many bacteria to propel themselves. It has recently been shown that at low speeds its rotation proceeds in steps [Sowa et al. (2005) Nature 437, 916--919]. Here we propose a simple physical model that accounts for this stepping behavior as a random walk in a tilted corrugated potential that combines torque and contact forces. We argue that the absolute angular position of the rotor is crucial for understanding step properties, and show this hypothesis to be consistent with the available data, in particular the observation that backward steps are smaller on average than forward steps. Our model also predicts a sublinear torque-speed relationship at low torque, and a peak in rotor diffusion as a function of torque

Improving rigid fiberoptic intubation: a comparison of the Bonfils Intubating Fiberscope™ with a novel modification

<p>Abstract</p> <p>Background</p> <p>The Bonfils intubating fiberscope has a limited upward tip angle of 40° and requires retromolar entry into the hypopharynx. These factors may make its use less desirable when managing the difficult airway because most anesthesia providers are well versed in midline oral intubation rather than the lateral retromolar approach. The <it>Center for Advanced Technology and Telemedicine </it>at the University of Nebraska Medical Center has developed a novel fiberscope with a more anterior 60° curve to allow for easier midline insertion and intubation. The objective of this work was to evaluate the novel fiberscope, in comparison to the Bonfils intubating fiberscope, in terms of use and function in difficult airway intubation.</p> <p>Methods</p> <p>Twenty-two anesthesia providers participated in simulated intubations of a difficult airway mannequin to compare the Bonfils intubating fiberscope with the novel curved Boedeker intubating fiberscope. The intubations were assessed based upon the following variables: recorded Cormack Lehane airway scores, requests for cricoid pressure, time to intubation, number of intubation attempts and success or failure of the procedure.</p> <p>Results</p> <p>Participants using the Bonfils fiberscope recorded an average Cormack Lehane (CL) airway score of 1.67 ± 1.02 (median = 1); with the novel fiberscope, the recorded average airway grade improved to 1.18 ± 0.50 (median = 1). The difference in airway scores was not statistically significant (p = 0.34; Fishers Exact Test comparing CL grades 1&2 vs. 3&4). There was, however, a statistically significant difference in intubation success rates between the two devices. With the Bonfils fiberscope, 68% (15/22) of participants were successful in intubation compared to a 100% success rate in intubation with the novel fiberscope (22/22) (p = 0.008). After the intubation trial, the majority of participants (95%) indicated a preference for the novel fiberscope (n = 20).</p> <p>Conclusions</p> <p>With this data, we can infer that the novel fiberscope curvature appears to improve or maintain the quality of an intubation attempt (airway score, cricoid pressure requirement, intubation time, number of attempts, placement success). The data indicate that the novel fiberscope offers a superior intubation experience to currently available best practices. The instrument was well received and would be welcomed by most study participants should the device become clinically available in the future.</p