The optical module of the Baikal deep underwater neutrino telescope

A deep underwater Cherenkov telescope has been operating since 1993 in stages of growing size at 1.1 km depth in Lake Baikal. The key component of the telescope is the Optical Module (OM) which houses the highly sensitive phototube QUASAR-370. We describe design and parameters of the QUASAR-370, the layout of the optical module, the front-end electronics and the calibration procedures, and present selected results from the five-year operation underwater. Also, future developments with respect to a telescope consisting from several thousand OMs are discussed.Comment: 30 pages, 24 figure

Wavelength dependent negative and positive persistent photoconductivity in Sn d-doped GaAs structures

The photoconductivity of GaAs structures delta-doped by Sn has been investigated for wavelengths lambda= 650-1200 nm in the temperature interval T= 4.2-300 K. The electron densities and mobilities, before and after illumination, have been determined by magnetoresistance, Shubnikov-de Haas effect and Hall effect measurements, in high magnetic fields. For the heavily doped structures (n_H> 2x10^13 cm^-2) we observe under illumination by light with wavelengths larger than the band-gap wavelength of the host material (lambda= 815 nm at T= 4.2 K) first positive (PPPC) and then negative (NPPC) persistent photoconductivity. The NPPC is attributed to the ionisation of DX centres and PPPC is explained by the excitation of electrons from Cr impurity states in the substrate. For lambda< 815 nm in addition the excitation of electron over the band gap of GaAs contributes to the PPPC. For the lightly doped structures (n_H<= 2x10^13 cm^-2) the photoconductivity effect is always positive.Comment: 17 pages (includes 6 figures); Postscript file; Semicond. Sci. Technol. in prin

Safety and efficacy of a novel calcium sensitizer, levosimendan, in patients with left ventricular failure due to an acute myocardial infarction: A randomized, placebo-controlled, double-blind study (RUSSLAN)

Aims: To evaluate the safety and efficacy of levosimendan in patients with left ventricular failure complicating acute myocardial infarction. Methods and Results: Levosimendan at different doses (0·1-0·4 μg . kg-1 . min-1) or placebo were administered intravenously for 6 h to 504 patients in a randomised, placebo-controlled, double-blind study. The primary end-point was hypotension or myocardial ischaemia of clinical significance adjudicated by an independent Safety Committee. Secondary end-points included risk of death and worsening heart failure, symptoms of heart failure and all-cause mortality. The incidence of ischaemia and/or hypotension was similar in all treatment groups (P=0·319). A higher frequency of ischaemia and/or hypotension was only seen in the highest levosimendan dose group. Levosimendan-treated patients experienced lower risk of death and worsening heart failure than patients receiving placebo, during both the 6h infusion (2·0% vs 5·9%; P=0·033) and over 24 h (4·0% vs 8·8%; P=0·044). Mortality was lower with levosimendan compared with placebo at 14 days (11·7% vs 19·6%; hazard ratio 0·56 [95% CI 0·33-0·951; P=0·031) and the reduction was maintained at the 180-day retrospective follow-up (22·6% vs 31·4%; 0·67 [0·45-1·00], P=0·053). Conclusions: Levosimendan at doses 0·1-0·2 μg . kg-1 . min-1 did not induce hypotension or ischaemia and reduced the risk of worsening heart failure and death in patients with left ventricular failure complicating acute myocardial infarction. © 2002 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved