This report presents the result of a study on radiation-induced color center densities in La-doped lead tungstate (PbWO 4 ) crystals. The creation and annihilation constants of radiation-induced color centers were determined by using transmittance data measured for a PbWO 4 sample before and during 60Co c-ray irradiation at a dose rate of 15 rad/h. Following a model of color center kinetics, th...

Nitrate reductase from mutant 305 o f Chlamydomonas reinhardii has been purified about 90-fold and biochemically characterized. The enzyme can use reduced flavins and viologens as electron donors to reduce nitrate but, unlike the nitrate reductase com plex from its parental wild strain, lacks NAD(P)H-nitrate reductase and NAD(P)H-cytochrom e c reductase activities, does not bind to Blue-Agarose...

The luminescence of complex ions like vanadate, niobate and tungstate is well known and has been studied intensively [1]. We have shown that edgeor face-sharing octahedra of this type are luminescent species with high quenching temperatures [2,3]. Examples are Mg4Nb20g and BasSrNb209 with Nb20g8_ anions and Ba3W20g with W2O96anions. These anions consist of face-sharing niobate and tungstate oct...

We report our recent work on obtaining on-chip lasers in crystalline double tungstate waveguides using focused-ion-beam (FIB) nanostructuring. Photonic cavity structures were defined by forming deeply etched Bragg gratings in KGdxLu1-x(WO4)2:Yb 3+ using FIB milling. The FIB milling procedure was optimized and gratings more than 4 μm in depth with an improved total sidewall angle of about 5 wer...

The barrel part of the CMS electromagnetic calorimeter consists of about 60000 Lead Tungstate (PWO) crystals and will be assembled in two Regional Centers, nearby Rome and at CERN. Two automatic machines have been designed to check the crystal quality before assembly. The main crystal characteristics are compared to a set of specifications included in the contract with the crystal producers. Th...

Further tests of lead tungstate crystal matrices made in high energy electron beams in 1996, using new crystals, new APDs and an improved test setup confirm that an energy resolution of better than 0.6% at 100 GeV can be obtained when the longitudinal uniformity of the struck crystal is adequate. Light loss measurements under low dose irradiation are reported. It is shown that there is no loss ...

An organism identified as Pseudomonas putida was isolated from an enrichment culture with 2-furoic acid as its sole source of carbon and energy. The organism contained a 2-furoyl-coenzyme A (CoA) synthetase to form 2-furoyl-CoA and a 2-furoyl-CoA dehydrogenase to form 5-hydroxy-2-furoyl-CoA as the first two enzymes involved in the degradation. Tungstate, the specific antagonist of molybdate, de...

BACKGROUND Microbial electrosynthesis (MES) and gas fermentation are bioenergy technologies in which a microbial catalyst reduces CO2 into organic carbon molecules with electrons from the cathode of a bioelectrochemical system or from gases such as H2. The acetogen Sporomusa ovata has the capacity of reducing CO2 into commodity chemicals by both gas fermentation and MES. Acetate is often the on...

The Electromagnetic Calorimeter of the CMS experiment, consisting of about 75000 Lead Tungstate scintillating crystals, aims at achieving an extreme precision in photon and electron energy measurement. Since the ultimate energy resolution will be affected by the crystal light yield and its uniformity along the crystal axis, systematic measurements of both these parameters are performed in the R...

A very good radiation resistance of Lead Tungstate crystals is mandatory for their use in the high precision electromagnetic calorimeter of the CMS experiment at LHC. Since the beginning of 1996 we have organised systematic investigations of the parameters influencing the radiation hardness of this crystal. Two classes of parameters have been particularly studied, the first one related to the c...