Experimental infection of reindeer with bovine viral diarrhea virus

Two 8-month reindeer (Rangifer tarandus) and a 1-month-old Hereford-Holstein calf (Bos taurus) were inoculated intranasally with the Singer (cytopathogenic) strain of bovine viral diarrhea (BVD) virus. Clinical signs in reindeer included loose stools containing blood and mucus, and transient laminitis or coronitis. Signs in the calf were limited to bloody mucus in the stool and lesions in the nasal mucosa. Antibody titers to BVD virus in the reindeer were intermittent, and titers in the calf persisted from days 14 to 63 post-inoculation (PI). Viremia was detected on PI day 4 in one reindeer, days 3-7 in the other, and days 2-7 in the calf. Bovine viral diarrhea virus was isolated from the lung of the calf at necropsy (PI day 63)

Larkin-Ovchinnikov-Fulde-Ferrell state in quasi-one-dimensional superconductors

The properties of a quasi-one-dimensional (quasi-1D) superconductor with {\it an open Fermi surface} are expected to be unusual in a magnetic field. On the one hand, the quasi-1D structure of the Fermi surface strongly favors the formation of a non-uniform state (Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state) in the presence of a magnetic field acting on the electron spins. On the other hand, a magnetic field acting on an open Fermi surface induces a dimensional crossover by confining the electronic wave-functions wave-functions along the chains of highest conductivity, which results in a divergence of the orbital critical field and in a stabilization at low temperature of a cascade of superconducting phases separated by first order transistions. In this paper, we study the phase diagram as a function of the anisotropy. We discuss in details the experimental situation in the quasi-1D organic conductors of the Bechgaard salts family and argue that they appear as good candidates for the observation of the LOFF state, provided that their anisotropy is large enough. Recent experiments on the organic quasi-1D superconductor (TMTSF)$_2$ClO$_4$ are in agreement with the results obtained in this paper and could be interpreted as a signature of a high-field superconducting phase. We also point out the possibility to observe a LOFF state in some quasi-2D organic superconductors.Comment: 24 pages+17 figures (upon request), RevTex, ORSAY-LPS-24109

Recoil Polarization for Delta Excitation in Pion Electroproduction

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q^2=1.0 (GeV/c)^2, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re(S1+/M1+)=-(6.84+/-0.15)% and Re(E1+/M1+)=-(2.91+/-0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and sp truncation.Comment: 5 pages, 2 figures, for PR

Active Brownian Particles. From Individual to Collective Stochastic Dynamics

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte

The Discovery and Mass Measurement of a New Ultra-Short-Period Planet: K2-131b

FWN – Publicaties zonder aanstelling Universiteit LeidenStars and planetary system

Characterization of genetic diversity in the nematode pristionchus pacificus from population-scale resequencing data

The hermaphroditic nematode Pristionchus pacificus is an established model system for comparative studies with Caenorhabditis elegans in developmental biology, ecology and population genetics. In this study, we present whole genome sequencing data of 104 P. pacificus strains and the draft assembly of the obligate outcrossing sister species Pristionchus exspectatus. We characterize genetic diversity within P. pacificus and investigate the population genetic processes shaping this diversity. P. pacificus is ten times more diverse than C. elegans and exhibits substantial population structure that allows us to probe its evolution on multiple time scales. Consistent with reduced effective recombination in this self-fertilizing species, we find haplotype blocks that span several megabases. Using the P. exspectatus genome as outgroup, we polarized variation in P. pacificus and found a site frequency spectrum (SFS) that decays more rapidly than expected in neutral models. The SFS at putatively neutral sites is U-shaped, which is a characteristic feature of pervasive linked selection. Based on the additional findings i) that the majority of non-synonymous variation is eliminated over time scales on the order of the separation between clades, ii) that diversity is reduced in gene rich regions, and iii) that highly differentiated clades show very similar patterns of diversity, we conclude that purifying selection on many mutations with weak effects is a major force shaping genetic diversity in P. pacificus