On the impact of dispersal asymmetry on metapopulation persistence

Metapopulation theory for a long time has assumed dispersal to be symmetric, i.e. patches are connected through migrants dispersing bi-directionally without a preferred direction. However, for natural populations symmetry is often broken, e.g. for species in the marine environment dispersing through the transport of pelagic larvae with ocean currents. The few recent studies of asymmetric dispersal concluded, that asymmetry has a distinct negative impact on the persistence of metapopulations. Detailed analysis however revealed, that these previous studies might have been unable to properly disentangle the effect of symmetry from other potentially confounding properties of dispersal patterns. We resolve this issue by systematically investigating the symmetry of dispersal patterns and its impact on metapopulation persistence. Our main analysis based on a metapopulation model equivalent to previous studies but now applied on regular dispersal patterns aims to isolate the effect of dispersal symmetry on metapopulation persistence. Our results suggest, that asymmetry in itself does not imply negative effects on metapopulation persistence. For this reason we recommend to investigate it in connection with other properties of dispersal instead of in isolation.Comment: 19 pages, 5 figure

Multiconfiguration Dirac-Hartree-Fock calculations of atomic electric dipole moments of 225^Ra, 199^Hg, and 171^Yb

The multiconfiguration Dirac-Hartree-Fock (MCDHF) method has been employed to calculate atomic electric dipole moments (EDM) of 225^Ra, 199^Hg, and 171^Yb. For the calculations of the matrix elements we extended the relativistic atomic structure package GRASP2K. The extension includes programs to evaluate matrix elements of (P, T)-odd e-N tensor-pseudotensor and pseudoscalar-scalar interactions, the atomic electric dipole interaction, the nuclear Schiff moment, and the interaction of the electron electric dipole moment with nuclear magnetic moments. The interelectronic interactions were accounted for through valence and core-valence electron correlation effects. The electron shell relaxation was included with separately optimised wave functions of opposite parities

Can eccentric training give a long-term effect on the extensibility of the musculotendinous complex? : a literature study

Background. Good flexibility is one of the basic conditions for optimum performance, regardless of the patient or athlete concerned. Traditional methods of increasing the extensibility of the musculo-tendinous complex show only short-term effect. Training with focus on the eccentric muscle contraction has shown potential to fill this gap. Purpose. To summarize the long-term effect of eccentric training on the extensibility of the musculo-tendinous complex as measured by angular joint mobility. Method. A literature review was conducted. Search was made in the databases PubMed and CINAHL. Seven studies were included. The quality of the studies was examined by SBU´s review template. Results. Of the seven included studies three showed significant increases in extensibility in the musculo-tendinous complex measured as the impact on the range of motion (ROM) and lasting longer than 24 hours. Four studies showed no increase or a slight decline of the ROM. Conclusion. Eccentric exercise performed to the end range of motion, lasting a longer time with medium to high training load indicates a long-term effect on the extensibility of the musculo-tendinous complex and thus an increase in angular joint movement. The mechanism behind the improvement is probably by addition of sarcomeres in series in the muscle cell.Bakgrund: God rörlighet är en av grundförutsättningarna för optimal funktion oberoende av vilken patientgrupp eller idrottsutövare det gäller. Traditionella metoder för att öka töjbarheten i muskel-senkomplexet har visat sig endast ha kortvarigt resultat. Träning med fokus på excentrisk muskelkontraktion har visat en potentiell möjlighet att fylla luckan. Syfte: Att sammanställa kunskap avseende excentrisk tränings långvariga effekt på muskel-senkomplexets töjbarhet mätt via angulär ledrörlighet. Metod: En litteraturstudie genomfördes. Litteratur söktes i databaserna PubMed och CINAHL. Sju studier inkluderades. De kvalitetsgranskades med SBUs granskningsmall. Resultat: Av de sju inkluderade studierna visade tre signifikanta ökningar av muskel-senkomplexets töjbarhet med en långvarig effekt på rörelseomfånget (ROM) i knäleden mätt efter minst 24 timmar. Fyra studier visade ingen ökning eller en liten minskning av rörelseomfånget. Konklusion: Excentrisk träning som utförs till rörelsebanans ytterläge, har pågått en längre tid och har medel till hög belastning indikerar en långvarig effekt på muskel-senkomplexets töjbarhet och därmed en ökning av angulär ledrörlighet. Bakomliggande mekanism är troligen ett ökat antal sarcomerer i muskelcellernas längsriktning

Estimating Social and Ethnic Inequality in School Surveys: Biases from Child Misreporting and Parent Nonresponse

We study the biases that arise in estimates of social inequalities in children’s cognitive ability test scores due to (i) children’s misreporting of socio-economic origin and (ii) parents’ nonresponse. Unlike most previous studies, we are able to draw on linked register data with high reliability and almost no missingness and thereby jointly consider the impact of measurement error and nonresponse. Using data on 14-year-olds (n = 18,716) from a new survey conducted in England, Germany, the Netherlands, and Sweden (Children of Immigrants Longitudinal Survey in Four European Countries), we find that child reports on parental occupation are well aligned with parents’ reports in all countries, but reports on parental education less so. This leads to underestimation of socio-economic disparities when child reports of education are used, but not occupation. Selective nonresponse among parents turns out to be a real problem, resulting in similar underestimation. We also investigate conditional estimates of immigrant–non-immigrant disparities, which are surprisingly little affected by measurement error or nonresponse in socio-economic control variables. We conclude that school-based surveys on teenagers are well advised to include questions on parental occupation, while the costs for carrying out parental questionnaires may outweigh the gains

SensibleSleep: A Bayesian Model for Learning Sleep Patterns from Smartphone Events

We propose a Bayesian model for extracting sleep patterns from smartphone events. Our method is able to identify individuals' daily sleep periods and their evolution over time, and provides an estimation of the probability of sleep and wake transitions. The model is fitted to more than 400 participants from two different datasets, and we verify the results against ground truth from dedicated armband sleep trackers. We show that the model is able to produce reliable sleep estimates with an accuracy of 0.89, both at the individual and at the collective level. Moreover the Bayesian model is able to quantify uncertainty and encode prior knowledge about sleep patterns. Compared with existing smartphone-based systems, our method requires only screen on/off events, and is therefore much less intrusive in terms of privacy and more battery-efficient

Træk af svinets udvikling - historisk set.

Tamsvinenes vilde forfædre fandtes over store dele af Europa og Asien. I Danmark kendes domesticerede svin fra stenalderen. De kan være opstået ved indførsel fra Asien eller tæmning af lokale vildsvin eller en krydsning af indførte lokale svin med vildsvin. I hvert fald er de ældste danske tamsvin primitive

How to select networks of marine protected areas for multiple species with different dispersal strategies

Aim: To develop and test theory based on connectivity to identify optimal networks of marine protected areas (MPAs) that protect multiple species with a range of dispersal strategies. Location: The eastern North Sea in the Atlantic Ocean. Methods: Theory of finding optimal MPA network is based on eigenvalue perturbation theory applied to population connectivity. Previous theory is here extended to the persistence of multiple species by solving a maximization problem with constraints, which identifies an optimal consensus network of MPAs. The theory is applied to two test cases within a 120,000 km2 area in the North Sea where connectivity was estimated with a biophysical model. In a realistic case, the theory is applied to the protection of rocky-reef habitats, where the biophysical model is parameterized with realistic dispersal traits for key species. Theoretical predictions of optimal networks were validated with a simple metapopulation model. Persistence of optimal consensus MPA networks is compared to randomly selected networks as well as to the existing MPA network. Results: Despite few overlapping MPA sites for the optimal networks based on single dispersal strategies, the consensus network for multiple dispersal strategies performed well for 3 of 4 contrasting strategies even without user-defined constraints. In the test with five realistic dispersal strategies, representing a community on threatened rocky reefs, the consensus network performed equally well compared to solutions for single species. Different dispersal strategies were also protected jointly across the MPA network (93% of sites), in contrast to simulations of the existing MPA network (2% of sites). Consensus networks based on connectivity were significantly more efficient compared to existing MPAs. Main conclusions: Our findings suggest that the new theoretic framework can identify a consensus MPA network that protects a whole community containing species with multiple dispersal strategies

Physical and numerical modeling of the role of hydrodynamic processes on adult-larval interactions of a suspension-feeding bivalve

The importance of hydrodynamic processes for adult-larval interactions in the cockle, Cerastoderma edule, was examined through physical and numerical modeling. A set of physical experiments in a flow-tank using adult cockles and larval mimics showed that the settlement of particles was affected by adult cockles. Settlement was reduced by 20% in an area of 2.5 cm2 surrounding the siphons, and the most marked decrease occurred near the inhalant siphon. On a larger spatial scale downstream of the siphons, settlement was more heterogeneous compared to surfaces without cockles. The experimental results near individual cockles were compared with numerical models of settlement dynamics in conditions with no horizontal flow. The models suggest that the vertical position of the siphon orifice determines whether any small-scale reduction in larval settlement should be expected near suspension-feeding benthic invertebrates. The results are compared qualitatively and quantitatively with previous observations of small-scale patterns (≈1 cm) around individual C. edule and with observations of larger-scale (1-10 m) differences among patches with varying densities of cockles. These comparisons indicate that passive hydrodynamic processes can explain patterns around individual cockles, whereas a combination of active and passive processes are necessary to explain differences among patches. Such hydrodynamic modification of larval behavior has previously been reported to greatly increase rates of mortality for settling bivalve larvae

Instantaneous Flow Structures and Opportunities for Larval Settlement: Barnacle Larvae Swim to Settle

Water flow affects settlement of marine larvae on several scales. At the smallest scale local flow regime may control the probability of adhesion to the substrate. Our aim was to mechanistically understand the transition from suspended to attached larvae in turbulent flow. Recently it was proposed that opportunities for larval settlement in turbulent boundary layers depend on time windows with suitable instantaneous flow properties. In flume flow we characterized the proportion of suitable time windows in a series of flow velocities with focus on the near-bed flow. The change in the proportion of potential settling windows with increasing free-stream velocities was compared to the proportion of temporary attachment of barnacle cypris larvae at different flow velocities. We found large instantaneous flow variations in the near-bed flow where cyprid attachment took place. The probability of temporary attachment in cyprids declined with local flow speed and this response was compatible with a settling window lasting at least 0.1 s with a maximum local flow speed of 1.9–2.4 cm s-1. Cyprids swam against the near-bed flow (negative rheotaxis) and the swimming speed (1.8 cm s-1) was close to the critical speed that permitted temporary attachment. We conclude that temporary attachment in barnacle cyprids requires upstream swimming to maintain a fixed position relative to the substrate for at least 0.1 s. This behaviour may explain the ability of barnacles to recruit to high-flow environments and give cyprids flexibility in the pre-settlement choice of substrates based on flow regime