Asylum legislation and asylum applications: a geographical analysis of Belgian asylum policy by country of origin (1992-2003)

In many European countries a traditional policy and legal response to an undesirable increase of asylum applications has been the change of asylum law and procedures. By making it more difficult to obtain asylum and refugee status, the attractiveness as a possible country of asylum is believed to diminish. In the period from 1992 to 2003 three major revisions of the Belgian asylum procedure were enacted. When speaking in absolute figures these changes resulted in a certain decrease in the number of asylum applications filed. However, upon a closer examination of the number of asylum applications per country of origin, the effects appeared to be quite differential. Hence, factors other than geographical ones, such as the location of the country of origin or distance, must be decisive for the effect of a change in legislation on the number of asylum claimants coming from one particular country. Nevertheless, it has been possible to distinguish seven clusters of countries of origin where similar developments in patterns of asylum applications and shifts therein, depending on changes in asylum law, can be seen

Detection of recombination in DNA multiple alignments with hidden markov models

CConventional phylogenetic tree estimation methods assume that all sites in a DNA multiple alignment have the same evolutionary history. This assumption is violated in data sets from certain bacteria and viruses due to recombination, a process that leads to the creation of mosaic sequences from different strains and, if undetected, causes systematic errors in phylogenetic tree estimation. In the current work, a hidden Markov model (HMM) is employed to detect recombination events in multiple alignments of DNA sequences. The emission probabilities in a given state are determined by the branching order (topology) and the branch lengths of the respective phylogenetic tree, while the transition probabilities depend on the global recombination probability. The present study improves on an earlier heuristic parameter optimization scheme and shows how the branch lengths and the recombination probability can be optimized in a maximum likelihood sense by applying the expectation maximization (EM) algorithm. The novel algorithm is tested on a synthetic benchmark problem and is found to clearly outperform the earlier heuristic approach. The paper concludes with an application of this scheme to a DNA sequence alignment of the argF gene from four Neisseria strains, where a likely recombination event is clearly detected

The parabolic Anderson model in a dynamic random environment: basic properties of the quenched Lyapunov exponent

In this paper we study the parabolic Anderson equation \partial u(x,t)/\partial t=\kappa\Delta u(x,t)+\xi(x,t)u(x,t), x\in\Z^d, t\geq 0, where the u-field and the \xi-field are \R-valued, \kappa \in [0,\infty) is the diffusion constant, and $\Delta$ is the discrete Laplacian. The initial condition u(x,0)=u_0(x), x\in\Z^d, is taken to be non-negative and bounded. The solution of the parabolic Anderson equation describes the evolution of a field of particles performing independent simple random walks with binary branching: particles jump at rate 2d\kappa, split into two at rate \xi\vee 0, and die at rate (-\xi)\vee 0. Our goal is to prove a number of basic properties of the solution u under assumptions on $\xi$ that are as weak as possible. Throughout the paper we assume that $\xi$ is stationary and ergodic under translations in space and time, is not constant and satisfies \E(|\xi(0,0)|)<\infty, where \E denotes expectation w.r.t. \xi. Under a mild assumption on the tails of the distribution of \xi, we show that the solution to the parabolic Anderson equation exists and is unique for all \kappa\in [0,\infty). Our main object of interest is the quenched Lyapunov exponent \lambda_0(\kappa)=\lim_{t\to\infty}\frac{1}{t}\log u(0,t). Under certain weak space-time mixing conditions on \xi, we show the following properties: (1)\lambda_0(\kappa) does not depend on the initial condition u_0; (2)\lambda_0(\kappa)<\infty for all \kappa\in [0,\infty); (3)\kappa \mapsto \lambda_0(\kappa) is continuous on [0,\infty) but not Lipschitz at 0. We further conjecture: (4)\lim_{\kappa\to\infty}[\lambda_p(\kappa)-\lambda_0(\kappa)]=0 for all p\in\N, where \lambda_p (\kappa)=\lim_{t\to\infty}\frac{1}{pt}\log\E([u(0,t)]^p) is the p-th annealed Lyapunov exponent. Finally, we prove that our weak space-time mixing conditions on \xi are satisfied for several classes of interacting particle systems.Comment: 50 pages. The comments of the referee are incorporated into the paper. A missing counting estimate was added in the proofs of Lemma 3.6 and Lemma 4.

Present day Nd isotopic composition of seawater and sediment leaches from the Pacific sector of the Southern Ocean

ABSTRACT FINAL ID: PP11B-1785 The Southern Ocean plays a key role in the climate evolution of Earth’s history, nevertheless its biggest region, the Pacific sector, has been poorly investigated in comparison to other regions in many paleoceanographic aspects. Some of them will try to be explained by the SOPATRA Project (SOuth PAcific TRAnsects). One of those aspects is radiogenic isotope compositions. Hereby we present the first εNd data extracted from Fe-Mn hydroxide coatings of bulk sediments from the Pacific sector of the Southern Ocean. These surface sediments results, scattered along a longitudinal transect of about 10,000 miles, collected from cruise SO213 from middle Chile to New Zealand (between 36°S and 45°S), represent a reliable overview of the present day Nd isotopic composition of the ambient water masses in this region, and will provide useful information for the interpretation of later downcore studies of this water mass tracer. Multiple analysis were carried out to confirm the reliability of the data as well as the validity of the applied leaching method: 1) Measurements of the present day radiogenic Nd bottom water signatures were compared to the Nd isotope compositions of the leachates in order to verify their seawater origin. 2) The leachates’ 87Sr/86Sr isotope ratios were monitored to confirm the holocenic origin of the samples. 3) Radiogenic Nd and Sr compositions of the detrital fraction of the sediment were measured after total dissolution of the same set of samples in order to exclude detrital contamination of leachates. 4) Two different leaching procedures were tested. Preliminary results show εNd values between -4 and -6, corresponding the lowest values to central south Pacific, which could represent the imprint of the circumpolar deep water moving northward. These findings are in agreement with other authors who extracted bottom water Nd isotope compositions from manganese nodules

Reconstructing the South Pacific upper water conditions during the Late Quaternary

PP11B-1780: The Antarctic Circumpolar Current system (ACCs) is the most important current system in the Southern Ocean, characterized by strong zonal variations in specific surface water properties, variations used to classify regions whose edges are defined by fronts. The past changes in the strength and latitudinal position of the ACC frontal system are supposed to play a major role on the global oceanic circulation and thus the Earth’s climate through their impact on atmospheric CO2 contents by changes in water stratification conditions, Therefore the study of variability in the surface characteristics of the ACCs provides crucial information to understand and to reconstruct the global climate evolution. The dynamics of the upper-ocean vertical structure, primarily defined by vertical changes in salinity and temperature from the mixed layer down to the seasonal and permanent thermocline, can be tracked using the differences in stable oxygen isotopes (__18O) and Mg/Ca-based temperatures (_T) recorded in the test of planktic foraminifera. Only Mg/Ca thermometry coupled with _18O can guarantee a common source of signal, averaging the same environmental conditions (season and spatial habitat), where, the combined measurements of Mg/Ca and _18O allow to extract the _18O record of past upper ocean water, and accordingly salinity variations In this study we present paired measurements of Mg/Ca and stable oxygen isotopes of shallow-living and deeper-living planktic foraminifera preserved in core top and downcore samples from the South Pacific (36° to 45° S) retrieved during the SOPATRA cruise (South Pacific Paleoceanographic Transect) Chile-New Zealand. The total Mg/Ca values preserved in the foraminiferal calcite from 31 core top samples ranged from ~2 to 1.3 mmol/mol, allowing estimate SSTs between 16° and 12° C. Additionally, to evaluate the reliability of the Mg/Ca signal paleothermometry for long term reconstruction we determined the effect of calcite saturation state (_CO32-) into on foraminiferal Mg/Ca concentration in the different selected species. In order to track the upper water column dynamics and strength of the ACC during the last ~200 kyr, we will test our calibration on downcore records gravity cores SO213-59-2 and SO213-60-2 retrieved from the northern border of the Subantarctic Zone (SAZ) of the East Pacific Rise