Resistance of superconducting nanowires connected to normal metal leads

We study experimentally the low temperature resistance of superconducting nanowires connected to normal metal reservoirs. We find that a substantial fraction of the nanowires is resistive, down to the lowest temperature measured, indicative of an intrinsic boundary resistance due to the Andreev-conversion of normal current to supercurrent. The results are successfully analyzed in terms of the kinetic equations for diffusive superconductors

Toxicity of statins on rat skeletal muscle mitochondria

Abstract.: We investigated mitochondrial toxicity of four lipophilic stains (cerivastatin, fluvastatin, atorvastatin, simvastatin) and one hydrophilic statin (pravastatin). In L6 cells (rat skeletal muscle cell line), the four lipophilic statins (100μmol/l) induced death in 27-49% of the cells. Pravastatin was not toxic up to 1mmol/l. Cerivastatin, fluvastatin and atorvastatin (100μmol/l) decreased the mitochondrial membrane potential by 49-65%, whereas simvastatin and pravastatin were less toxic. In isolated rat skeletal muscle mitochondria, all statins, except pravastatin, decreased glutamate-driven state 3 respiration and respiratory control ratio. Beta-oxidation was decreased by 88-96% in the presence of 100μmol/l of the lipophilic statins, but only at higher concentrations by pravastatin. Mitochondrial swelling, cytochrome c release and DNA fragmentation was induced in L6 cells by the four lipophilic statins, but not by pravastatin. Lipophilic statins impair the function of skeletal muscle mitochondria, whereas the hydrophilic pravastatin is significantly less toxi

Hepatic effects of Cimicifuga racemosa extract in vivo and in vitro

Abstract.: Extracts of Cimicifuga racemosa are used frequently for menopausal complaints. Cimicifuga is well tolerated but can occasionally cause liver injury. To assess hepatotoxicity of cimicifuga in more detail, ethanolic C. racemosa extract was administered orally to rats, and liver sections were analyzed by electron microscopy. Tests for cytotoxicity, mitochondrial toxicity and apoptosis/necrosis were performed using HepG2 cells. Mitochondrial toxicity was studied using isolated rat liver mitochondria. Microvesicular steatosis was found in rats treated with > 500 μg/kg body weight cimicifuga extract. In vitro, cytotoxicity was apparent at concentrations ≥ 75 μg/mL, and mitochondrial β-oxidation was impaired at concentrations ≥ 10 μg/mL. The mitochondrial membrane potential was decreased at concentrations ≥ 100 μg/mL, and oxidative phosphorylation was impaired at concentrations ≥ 300 μg/mL. The mechanism of cell death was predominantly apoptosis. C. racemosa exerts toxicity in vivo and in vitro, eventually resulting in apoptotic cell death. The results are compatible with idiosyncratic hepatotoxicity as observed in patients treated with cimicifuga extract

Methotrexate area under the curve is an important outcome predictor in patients with primary CNS lymphoma: A pharmacokinetic–pharmacodynamic analysis from the IELSG no. 20 trial

This analysis was initiated to define the predictive value of the area under the curve of high-dose methotrexate (AUC(HD-MTX)) in patients with primary central nervous system lymphoma (PCNSL).; We included 55 patients with PCNSL and available pharmacokinetic (PK) data from the International Extranodal Lymphoma Study Group (IELSG) no. 20 trial, randomised to HD-MTX (n=30) or HD-MTX and high-dose cytarabine (HD-AraC) (n=25). Individual AUC(HD-MTX) from population PK analysis was tested on drug toxicity and clinical outcome using multivariate logistic regression analysis and Cox hazards modelling.; AUC(HD-MTX), the IELSG score and treatment group were significant predictors for treatment response (complete or partial) in the adjusted model. The AUC(HD-MTX) did not predict toxicity, with the exception of liver toxicity and neutropaenia. A high AUC(HD-MTX) was associated with better event-free survival (EFS) (P=0.01) and overall survival (OAS) (P=0.02). Both the AUC(HD-MTX) and the IELSG score were significant predictors of EFS and OAS in the adjusted model, with a hazard ratio of 0.82 and 0.73, respectively, per 100 micromol l(-1) h(-1) increase in AUC(HD-MTX).; Individualised dosing of HD-MTX might have the potential to improve clinical outcome in patients with PCNSL, even when administered concurrently with HD-AraC. In the future, this could be carried out by using first-cycle PK modelling with determination of potential dose adaptations for later cycles using Bayesian analysis

FACT - Threshold prediction for higher duty cycle and improved scheduling

The First G-APD Cherenkov telescope (FACT) is the first telescope using silicon photon detectors (G-APD aka. SiPM). The use of Silicon devices promise a higher photon detection efficiency, more robustness and higher precision than photo-multiplier tubes. Being operated during different light-conditions, the threshold settings of a Cherenkov telescope have to be adapted to feature the lowest possible threshold but also an efficient suppression of triggers from night-sky background photons. Usually this threshold is set either by experience or a mini-ratescan. Since the measured current through the sensors is directly correlated with the noise level, the current can be used to set the best threshold at any time. Due to the correlation between the physical threshold and the final energy threshold, the current can also be used as a measure for the energy threshold of any observation. This presentation introduces a method which uses the properties of the moon and the source position to predict the currents and the corresponding energy threshold for every upcoming observation allowing to adapt the observation schedule accordingly

FACT - Long-term stability and observations during strong Moon light

The First G-APD Cherenkov Telescope (FACT) is the first Cherenkov telescope equipped with a camera made of silicon photon detectors (G-APD aka. SiPM). Since October 2011, it is regularly taking data on the Canary Island of La Palma. G-APDs are ideal detectors for Cherenkov telescopes as they are robust and stable. Furthermore, the insensitivity of G-APDs towards strong ambient light allows to conduct observations during bright Moon and twilight. This gain in observation time is essential for the long-term monitoring of bright TeV blazars. During the commissioning phase, hundreds of hours of data (including data from the the Crab Nebula) were taken in order to understand the performance and sensitivity of the instrument. The data cover a wide range of observation conditions including different weather conditions, different zenith angles and different light conditions (ranging from dark night to direct full Moon). We use a new parmetrisation of the Moon light background to enhance our scheduling and to monitor the atmosphere. With the data from 1.5 years, the long-term stability and the performance of the camera during Moon light is studied and compared to that achieved with photomultiplier tubes so far.Comment: 3 pages, 3 figures, FACT Contribution to the 33rd International Cosmic Ray Conference (ICRC), Rio de Janeir

FACT - Long-term Monitoring of Bright TeV-Blazars

Since October 2011, the First G-APD Cherenkov Telescope (FACT) is operated successfully on the Canary Island of La Palma. Apart from the proof of principle for the use of G-APDs in Cherenkov telescopes, the major goal of the project is the dedicated long-term monitoring of a small sample of bright TeV blazars. The unique properties of G-APDs permit stable observations also during strong moon light. Thus a superior sampling density is provided on time scales at which the blazar variability amplitudes are expected to be largest, as exemplified by the spectacular variations of Mrk 501 observed in June 2012. While still in commissioning, FACT monitored bright blazars like Mrk 421 and Mrk 501 during the past 1.5 years so far. Preliminary results including the Mrk 501 flare from June 2012 will be presented.Comment: 4 pages, 4 figures, presented at the 33rd ICRC (2013

FACT - How stable are the silicon photon detectors?

The First G-APD Cherenkov telescope (FACT) is the first telescope using silicon photon detectors (G-APD aka. SiPM). The use of Silicon devices promise a higher photon detection efficiency, more robustness and higher precision than photo-multiplier tubes. Since the properties of G-APDs depend on auxiliary parameters like temperature, a feedback system adapting the applied voltage accordingly is mandatory. In this presentation, the feedback system, developed and in operation for FACT, is presented. Using the extraction of a single photon-equivalent (pe) spectrum as a reference, it can be proven that the sensors can be operated with very high precision. The extraction of the single-pe, its spectrum up to 10\,pe, its properties and their precision, as well as their long-term behavior during operation are discussed. As a by product a single pulse template is obtained. It is shown that with the presented method, an additional external calibration device can be omitted. The presented method is essential for the application of G-APDs in future projects in Cherenkov astronomy and is supposed to result in a more stable and precise operation than possible with photo-multiplier tubes

FACT -- the First Cherenkov Telescope using a G-APD Camera for TeV Gamma-ray Astronomy (HEAD 2010)

Geiger-mode Avalanche Photodiodes (G-APD) bear the potential to significantly improve the sensitivity of Imaging Air Cherenkov Telescopes (IACT). We are currently building the First G-APD Cherenkov Telescope (FACT) by refurbishing an old IACT with a mirror area of 9.5 square meters and construct a new, fine pixelized camera using novel G-APDs. The main goal is to evaluate the performance of a complete system by observing very high energy gamma-rays from the Crab Nebula. This is an important field test to check the feasibility of G-APD-based cameras to replace at some time the PMT-based cameras of planned future IACTs like AGIS and CTA. In this article, we present the basic design of such a camera as well as some important details to be taken into account.Comment: Poster shown at HEAD 2010, Big Island, Hawaii, March 1-4, 201