Proximity effect in planar TiN-Silicon junctions

We measured the low temperature subgap resistance of titanium nitride (superconductor, Tc=4.6K)/highly doped silicon (degenerated semiconductor) SIN junctions, where I stands for the Schottky barrier. At low energies, the subgap conductance is enhanced due to coherent backscattering of the electrons towards the interface by disorder in the silicon (''reflectionless tunneling''). This Zero Bias Anomaly (ZBA) is destroyed by the temperature or the magnetic field above 250mK or 0.04T respectively. The overall differential resistance behavior (vs temperature and voltage) is compared to existing theories and values for the depairing rate and the barrier transmittance are extracted. Such an analysis leads us to introduce an effective temperature for the electrons and to discuss heat dissipation through the SIN interface.Comment: 23 pages, 6 figures, added references and minor corrections. Accepted to Journal of Low Temperature Physic

Doubled Full Shot Noise in Quantum Coherent Superconductor - Semiconductor Junctions

We performed low temperature shot noise measurements in Superconductor (TiN) - strongly disordered normal metal (heavily doped Si) weakly transparent junctions. We show that the conductance has a maximum due to coherent multiple reflections at low energy and that shot noise is then twice the Poisson noise (S=4eI). The shot noise changes to the normal value (S=2eI) due to a large quasiparticle contribution.Comment: published in Physical Review Letter

Modulation of hippocampal acetylcholine release - a potent central action of interleukin-2

The potential of the T-cell growth factor interleukin-2 (IL-2) to modulate the release of ACh from rat hippocampus was studied in vitro, as a means to investigate the possible functional significance of this cytokine in the CNS. Hippocampal slices were superfused with Krebs' buffer medium, and endogenous ACh released into the superfusate was measured using a radioenzymatic assay. Recombinant human IL-2 present during a stimulation with 25 mM KCl altered, in a concentration-dependent manner, the evoked transmitter release. At a concentration of 15 U/ml (< or = 1 nM), IL-2 inhibited ACh release by more than 50% of the control level (evoked ACh release from the untreated contralateral hemispheres). Inhibition was observed within 20 min of tissue exposure to IL-2 and lasted for up to 1 hr. The inhibitory effect of IL-2 was reversible since transient tissue exposure to IL-2 did not affect subsequent evoked ACh release. IL-2 at this concentration also significantly decreased evoked ACh in frontal cortical slices, but was ineffective in the parietal cortex and striatum, revealing that IL-2 selectively modulates the release of ACh from certain, but not all, cholinergic nerve terminals in the CNS. At very low concentrations (1.5 mU/ml, < or = 0.1 pM), IL-2 transiently increased hippocampal evoked ACh release, resulting in a biphasic dose-response profile with no significant effect observed at 0.015 mU/ml (< or = 1 fM). Other cytokines (IL-1 alpha, IL-3, IL-5, IL-6, interferon alpha), tested in hippocampal slice incubations, failed to modulate ACh release

3D sensors for the HL-LHC

In order to increase its discovery potential, the Large Hadron Collider (LHC) accelerator will be upgraded in the next decade. The high luminosity LHC (HL-LHC) period demands new sensor technologies to cope with increasing radiation fluences and particle rates. The ATLAS experiment will replace the entire inner tracking detector with a completely new silicon-only system. 3D pixel sensors are promising candidates for the innermost layers of the Pixel detector due to their excellent radiation hardness at low operation voltages and low power dissipation at moderate temperatures. Recent developments of 3D sensors for the HL-LHC are presented.Comment: 8 pages, 5 figures, International Workshops on Radiation Imaging Detectors 201

Silicon-based three-dimensional microstructures for radiation dosimetry in hadrontherapy

In this work, we propose a solid-state-detector for use in radiation microdosimetry. This device improves the performance of existing dosimeters using customized 3D-cylindrical microstructures etched inside silicon. The microdosimeter consists of an array of micro-sensors that have 3D-cylindrical electrodes of 15 μm diameter and a depth of 5 μm within a silicon membrane, resulting in a well-defined micrometric radiation sensitive volume. These microdetectors have been characterized using an 241Am source to assess their performance as radiation detectors in a high-LET environment. This letter demonstrates the capability of this microdetector to be used to measure dose and LET in hadrontherapy centers for treatment plan verification as part of their patient-specific quality control program

Characterization of the first true coaxial 18-fold segmented n-type prototype detector for the GERDA project

The first true coaxial 18-fold segmented n-type HPGe prototype detector produced by Canberra-France for the GERDA neutrinoless double beta-decay project was tested both at Canberra-France and at the Max-Planck-Institut fuer Physik in Munich. The main characteristics of the detector are given and measurements concerning detector properties are described. A novel method to establish contacts between the crystal and a Kapton cable is presented.Comment: 21 pages, 16 Figures, to be submitted to NIM

Toward a New Kind of Asteroseismic Grid Fitting

Recent developments in instrumentation (e.g., in particular the Kepler and CoRoT satellites) provide a new opportunity to improve the models of stellar pulsations. Surface layers, rotation, and magnetic fields imprint erratic frequency shifts, trends, and other non-random behavior in the frequency spectra. As our observational uncertainties become smaller, these are increasingly important and difficult to deal with using standard fitting techniques. To improve the models, new ways to compare their predictions with observations need to be conceived. In this paper we present a completely probabilistic (Bayesian) approach to asteroseismic model fitting. It allows for varying degrees of prior mode identification, corrections for the discrete nature of the grid, and most importantly implements a treatment of systematic errors, such as the "surface effects." It removes the need to apply semi- empirical corrections to the observations prior to fitting them to the models and results in a consistent set of probabilities with which the model physics can be probed and compared. As an example, we show a detailed asteroseismic analysis of the Sun. We find a most probable solar age, including a 35 +- 5 million year pre-main sequence phase, of 4.591 billion years, and initial element mass fractions of X_0 = 0.72, Y_0 = 0.264, Z_0 = 0.016, consistent with recent asteroseismic and non-asteroseismic studies.Comment: 15 pages, 5 figures, accepted for publication in The Astrophysical Journal; v2 contains minor changes made in the proofs (updated references & corrected typos