Hybridization gap and anisotropic far-infrared optical conductivity of URu2Si2

We performed far-infrared optical spectroscopy measurements on the heavy fermion compound URu 2 Si 2 as a function of temperature. The light's electric-field was applied along the a-axis or the c-axis of the tetragonal structure. We show that in addition to a pronounced anisotropy, the optical conductivity exhibits for both axis a partial suppression of spectral weight around 12 meV and below 30 K. We attribute these observations to a change in the bandstructure below 30 K. However, since these changes have no noticeable impact on the entropy nor on the DC transport properties, we suggest that this is a crossover phenomenon rather than a thermodynamic phase transition.Comment: To be published in Physical Review

bif1, a new BMP signaling inhibitor, regulates embryonic hematopoiesis in the zebrafish.

Hematopoiesis maintains the entire blood system, and dysregulation of this process can lead to malignancies (leukemia), immunodeficiencies or red blood cell diseases (anemia, polycythemia vera). We took advantage of the zebrafish model that shares most of the genetic program involved in hematopoiesis with mammals to characterize a new gene of unknown function, si:ch73-299h12.2, which is expressed in the erythroid lineage during primitive, definitive and adult hematopoiesis. This gene, required during primitive and definitive erythropoiesis, encodes a C2H2 zinc-finger protein that inhibits BMP signaling. We therefore named this gene blood-inducing factor 1 and BMP inhibitory factor 1 (bif1). We identified a bif1 ortholog in Sinocyclocheilus rhinocerous, another fish, and in the mouse genome. Both genes also inhibit BMP signaling when overexpressed in zebrafish. In conclusion, we have deorphanized a new zebrafish gene of unknown function: bif1 codes for a zinc-finger protein that inhibits BMP signaling and also regulates primitive erythropoiesis and definitive hematopoiesis

Hydraulic interactions between fractures and bedding planes in a carbonate aquifer studied by means of experimentally induced water-table fluctuations (Coaraze experimental site, southeastern France)

International audienceIn aquifers with variable permeability, the water exchanges between high and low permeability regions are controlled by the hydraulic head gradient. Past studies have addressed this problem mainly considering steadystate hydraulic conditions. To study such exchanges during water-table fluctuations, a spring was equipped with a water-gate that creates 10-meter artificial fluctuations of the water table. The water exchanges are discussed with respect to hydrochemical and pressure measurements in the groundwater. With successive water-table fluctuations the mineralization and pH decrease, but the bicarbonate content increases in response to carbon dioxide dissolution . At this scale of single fractures and surroundings, the hydrochemistry allows water flows from low or high permeability discontinuities to be discriminated. During hydraulic head fluctuations, the waters from low and high permeability discontinuities become mixed. During water-table rise, the low-permeability matrix contributed to the refilling of the permeable faults and to the mixing of the waters. Dynamic flows in the opposite direction to the hydraulic gradient can expel mineralized water, pushing it towards permeable discontinuities. This mechanism could be the cause of the peak in the mineralisation recorded in some karst springs at the start of flood events

A New Tool Preliminary Assessment on Temporal-Comorbidity Adjusted Risk of Emergency Readmission (T-CARER)

Patients’ comorbidities, operations and complications can be associated with reduced long-term survival probability and increased healthcare utilisation. The aim of this research was to produce an adjusted case-mix model of comorbidity risk and develop a user-friendly toolkit to encourage public adaptation and incremental development.It has been shown in healthcare research that demographics, temporal dimensions, length-of-stay and time between admissions, can noticeably improve the statistical measures related to comorbidities. The proposed model incorporates temporal aspects, medical procedures, demographics, and admission details, as well as diagnoses.The research resulted in the development of Temporal-Comorbidity Adjusted Risk of Emergency Readmission (T-CARER) model using routinely collected hospital data

Test engineering education in Europe: the EuNICE-Test project

The paper deals with a European experience of education in industrial test of ICs and SoCs using remote testing facilities. The project addresses the problem of the shortage in microelectronics engineers aware with the new challenge of testing mixed-signal SoCs far multimedia/telecom market. It aims at providing test training facilities at a European scale in both initial and continuing education contexts. This is done by allowing the academic and industrial partners of the consortium to train engineers using the common test resources center (CRTC) hosted by LIRMM (Laboratoire d'Informatique, de Robotique et de Microelectronique de Montpellier, France). CRTC test tools include up-to-date/high-tech testers that are fully representative of real industrial testers as used on production testfloors. At the end of the project, it is aimed at reaching a cruising speed of about 16 trainees per year per center. Each trainee will have attend at least one one-week training using the remote test facilities of CRTC

Mesoscopic rings with Spin-Orbit interactions

A didactic description of charge and spin equilibrium currents on mesoscopic rings in the presence of Spin-Orbit interaction is presented. Emphasis is made on the non trivial construction of the correct Hamiltonian in polar coordinates, the calculation of eigenvalues and eigenfunctions and the symmetries of the ground state properties. Spin currents are derived following an intuitive definition and then a more thorough derivation is built upon the canonical Lagrangian formulation that emphasizes the SU(2) gauge structure of the transport problem of spin 1/2 fermions in spin-orbit active media. The quantization conditions that follow from the constraint of single-valued Pauli spinors are also discussed. The targeted students are those of a graduate Condensed Matter Physics course

Diffusion over a saddle with a Langevin equation

The diffusion problem over a saddle is studied using a multi-dimensional Langevin equation. An analytical solution is derived for a quadratic potential and the probability to pass over the barrier deduced. A very simple solution is given for the one dimension problem and a general scheme is shown for higher dimensions.Comment: 13 pages, use revTeX, to appear in Phys. Rev. E6

Dynamic ferromagnetic proximity effect in photoexcited semiconductors

The spin dynamics of photoexcited carriers in semiconductors in contact with a ferromagnet is treated theoretically and compared with time-dependent Faraday rotation experiments. The long time response of the system is found to be governed by the first tens of picoseconds in which the excited plasma interacts strongly with the intrinsic interface between semiconductor and ferromagnet in spite of the existence of a Schottky barrier in equilibrium

Potentials for hyper-Kahler metrics with torsion

We prove that locally any hyper-K\"ahler metric with torsion admits an HKT potential.Comment: 9 page

Synergistic prostaglandin E synthesis by myeloid and endothelial cells promotes fetal hematopoietic stem cell expansion in vertebrates

During development, hematopoietic stem cells (HSCs) are produced from the hemogenic endothelium and will expand in a transient hematopoietic niche. Prostaglandin E2 (PGE2) is essential during vertebrate development and HSC specification, but its precise source in the embryo remains elusive. Here, we show that in the zebrafish embryo, PGE2 synthesis genes are expressed by distinct stromal cell populations, myeloid (neutrophils, macrophages), and endothelial cells of the caudal hematopoietic tissue. Ablation of myeloid cells, which produce the PGE2 precursor prostaglandin H2 (PGH2), results in loss of HSCs in the caudal hematopoietic tissue, which could be rescued by exogeneous PGE2 or PGH2 supplementation. Endothelial cells contribute by expressing the PGH2 import transporter slco2b1 and ptges3, the enzyme converting PGH2 into PGE2. Of note, differential niche cell expression of PGE2 biosynthesis enzymes is also observed in the mouse fetal liver. Taken altogether, our data suggest that the triad composed of neutrophils, macrophages, and endothelial cells sequentially and synergistically contributes to blood stem cell expansion during vertebrate development