259 research outputs found

    Search for double beta decay of 136^{136}Ce and 138^{138}Ce with HPGe gamma detector

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    Search for double β\beta decay of 136^{136}Ce and 138^{138}Ce was realized with 732 g of deeply purified cerium oxide sample measured over 1900 h with the help of an ultra-low background HPGe γ\gamma detector with a volume of 465 cm3^3 at the STELLA facility of the Gran Sasso National Laboratories of the INFN (Italy). New improved half-life limits on double beta processes in the cerium isotopes were set at the level of limT1/210171018\lim T_{1/2}\sim 10^{17}-10^{18}~yr; many of them are even two orders of magnitude larger than the best previous results.Comment: 21 pages, 6 figures, 3 tables; version accepted for publication on Nucl. Phys.

    Faecal carriage of extended-spectrum beta-lactamase-producing Enterobacteriaceae in healthy volunteers and hospitalized patients in Ouagadougou, Burkina Faso: prevalence, resistance profile, and associated risk factors

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    Background: Extended spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) are a serious challenge to patients’ treatment. The aim of this study is to determine the prevalence of ESBL-PE, investigate the associated resistance, and analyze the associated risk factors for acquisition of ESBL-PE.Methodology: A cross-sectional study was conducted on healthy volunteers and inpatients. After obtaining informed consent, rectal swabs were collected from each participant for isolation of Enterobacteriaceae on Hektoen enteric agar containing 4µg/L cefotaxime. The Enterobacteriaceae isolates were identified using biochemical tests and ESBL production was confirmed by the double-disc synergy test of amoxicillin and clavulanic acid. Antibiotic susceptibility test of each isolate was done by the disc diffusion method and interpreted using the recommendations of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) clinical  breakpoints version 5.0.Results: During the study period, prevalence of faecal ESBL-PE among the study participants was 54.5% (103/189); 53.5% among healthy volunteers and 55.7% among inpatients (p=0.87). The major ESBL-PE isolates was Escherichia coli (71%) followed by Klebsiella pneumoniae (16%). The isolates in hospitalized patients were resistant to norfloxacin (84.2%), cotrimoxazole (89.5%), and gentamicin (7.0%). The isolates from healthy volunteers were resistant to norfloxacin (86.2%), cotrimoxazole (82.8%), and gentamicin (1.7%).Gender, age, and previous antibiotic use were not significantly associated with carriage of ESBL-PE (p=0.51).Conclusion: The high prevalence of ESBL-PE in this study is worrying. There is an urgent need to develop measures to monitor and limit the spread of these multidrug-resistant organisms in healthcare facilities and the community in Burkina Faso. Keywords: faecal carriage, ESBL-PE, healthy volunteers, inpatients, Burkina Fas

    Radioactive contamination of ZnWO4 crystal scintillators

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    The radioactive contamination of ZnWO4 crystal scintillators has been measured deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN in Italy with a total exposure 3197 kg x h. Monte Carlo simulation, time-amplitude and pulse-shape analyses of the data have been applied to estimate the radioactive contamination of the ZnWO4 samples. One of the ZnWO4 crystals has also been tested by ultra-low background gamma spectrometry. The radioactive contaminations of the ZnWO4 samples do not exceed 0.002 -- 0.8 mBq/kg (depending on the radionuclide), the total alpha activity is in the range: 0.2 - 2 mBq/kg. Particular radioactivity, beta active 65Zn and alpha active 180W, has been detected. The effect of the re-crystallization on the radiopurity of the ZnWO4 crystal has been studied. The radioactive contamination of samples of the ceramic details of the set-ups used in the crystals growth has been checked by low background gamma spectrometry. A project scheme on further improvement of the radiopurity level of the ZnWO4 crystal scintillators is briefly addressed.Comment: 15 pages, 8 figures, 6 tables, submitted for publicatio

    ZnO-based scintillating bolometers: New prospects to study double beta decay of 64^{64}Zn

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    The first detailed study on the performance of a ZnO-based cryogenic scintillating bolometer as a detector to search for rare processes in zinc isotopes was performed. A 7.2 g ZnO low-temperature detector, containing more than 80\% of zinc in its mass, exhibits good energy resolution of baseline noise 1.0--2.7 keV FWHM at various working temperatures resulting in a low-energy threshold for the experiment, 2.0--6.0 keV. The light yield for β\beta/γ\gamma events was measured as 1.5(3) keV/MeV, while it varies for α\alpha particles in the range of 0.2--3.0 keV/MeV. The detector demonstrate an effective identification of the β\beta/γ\gamma events from α\alpha events using time-properties of only heat signals. %(namely, Rise time parameter). The radiopurity of the ZnO crystal was evaluated using the Inductively Coupled Plasma Mass Spectrometry, an ultra-low-background High Purity Ge γ\gamma-spectrometer, and bolometric measurements. Only limits were set at the level of O\mathcal{O}(1--100) mBq/kg on activities of \Nuc{K}{40}, \Nuc{Cs}{137} and daughter nuclides from the U/Th natural decay chains. The total internal α\alpha-activity was calculated to be 22(2) mBq/kg, with a major contribution caused by 6(1) mBq/kg of \Nuc{Th}{232} and 12(2) mBq/kg of \Nuc{U}{234}. Limits on double beta decay (DBD) processes in \Nuc{Zn}{64} and \Nuc{Zn}{70} isotopes were set on the level of O(1017\mathcal{O}(10^{17}--1018)10^{18}) yr for various decay modes profiting from 271 h of acquired background data in the above-ground lab. This study shows a good potential for ZnO-based scintillating bolometers to search for DBD processes of Zn isotopes, especially in \Nuc{Zn}{64}, with the most prominent spectral features at \sim10--20 keV, like the two neutrino double electron capture. A 10 kg-scale experiment can reach the experimental sensitivity at the level of O(1024)\mathcal{O}(10^{24}) yr.Comment: Prepared for submission to JINST; 27 pages, 9 figures, and 7 table

    First Results from the AMoRE-Pilot neutrinoless double beta decay experiment

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    The Advanced Molybdenum-based Rare process Experiment (AMoRE) aims to search for neutrinoless double beta decay (0νββ\nu\beta\beta) of 100^{100}Mo with \sim100 kg of 100^{100}Mo-enriched molybdenum embedded in cryogenic detectors with a dual heat and light readout. At the current, pilot stage of the AMoRE project we employ six calcium molybdate crystals with a total mass of 1.9 kg, produced from 48^{48}Ca-depleted calcium and 100^{100}Mo-enriched molybdenum (48depl^{48\textrm{depl}}Ca100^{100}MoO4_4). The simultaneous detection of heat(phonon) and scintillation (photon) signals is realized with high resolution metallic magnetic calorimeter sensors that operate at milli-Kelvin temperatures. This stage of the project is carried out in the Yangyang underground laboratory at a depth of 700 m. We report first results from the AMoRE-Pilot 0νββ0\nu\beta\beta search with a 111 kg\cdotd live exposure of 48depl^{48\textrm{depl}}Ca100^{100}MoO4_4 crystals. No evidence for 0νββ0\nu\beta\beta decay of 100^{100}Mo is found, and a upper limit is set for the half-life of 0νββ\nu\beta\beta of 100^{100}Mo of T1/20ν>9.5×1022T^{0\nu}_{1/2} > 9.5\times10^{22} y at 90% C.L.. This limit corresponds to an effective Majorana neutrino mass limit in the range mββ(1.22.1)\langle m_{\beta\beta}\rangle\le(1.2-2.1) eV
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