The search for neutrinoless double β decay probes lepton number conservation with high sensitivity and investigates the neutrino nature and mass scale. Experiments presently in preparation will cover ...the quasi-degeneracy region of the neutrino mass pattern. Probing the inverted hierarchy region requires improved sensitivities and next-generation experiments, based either on large expansions of the present searches or on new ideas. We examine here a novel technology relying on ZnMoO4 scintillating bolometers, which can provide an experiment with background close to zero in the ton × year exposure scale. The promising performance of a pilot detector is presented, both in terms of energy resolution and background control. A preliminary study of the sensitivities of future experiments shows that the inverted hierarchy region is within the reach of the technique here proposed. A realistic phased approach program towards a next-generation search is presented and briefly discussed.
The scintillation crystal bismuth germanate (BGO) is widely used in many applications. The unique technique developed in the Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia, allows ...routine production of top quality large-sized BGO crystals. One of the important properties of a scintillation crystal is its radiation hardness. The intensive study of the radiation hardness of BGO crystals has been carried out by the collaboration of the Institutes of Siberian Branch of the Russian Academy of Science, Novosibirsk. The influence of the raw material purity and growth procedure on radiation hardness has been studied. The final tests of the crystal radiation hardness were performed by irradiating it with gamma rays from the radioactive source. The degradation of a light output of the best crystals is less than 10% after irradiation with doses of 10-100 krad expected in astrophysics experiments at a satellite. Based on the results of this study, the radiation hard BGO crystals for the "INTEGRAL" and "ASTRO-H" satellite missions have been made. A selfrecovery of the crystal light output is clearly seen. The time scale of the self recovery strongly depends on a dose of irradiation. It is days for 1 krad irradiation, weeks - for a 10 krad dose and a much longer period is required for 100 krad irradiation. All the crystals irradiated with a dose of 100 krad completely recover after annealing. The study reveals that there will be no essential degradation if this dose will be integrated over years of operation.
The global heat transfer in a crystallization setup has been optimized to develop a strategy of control over a three-zone heater in the BGO Czochralski process, in order to provide invariable thermal ...conditions near the solid–liquid interface in the stage of a constant-diameter crystal growth. The functional related to the exactness of the heat balance condition at the crystallization front, i.e., the Stefan problem, was chosen as the target function. The optimization yielded unexpected results. The temperature of the lower heater should be lowered, relative to that of the middle heater, with increasing crystal length, whereas the temperature of the upper heater is to be raised. These recommendations were incorporated into a dynamic model of the oxide Czochralski process with a weighing control and into the control loop of the temperature regulators of a crystallization setup. A comparison of results of the time-dependent simulation with the real growth process confirmed that the new control strategy minimizes the deviation of the solid–liquid interface from the prescribed one, significantly decreases variations of interface shape during the process, and enables growth of high-quality crystals.
► Colorless single crystals of ZnMoO4 were grown for the first time. ► Two emission bands were observed and ascribed to the self-trapped excitons. ► TSL peak at 65K is ascribed to the thermal release ...of self-trapped holes. ► Origin of the threshold in TSL excitation spectrum is explained.
ZnMoO4 single crystals of high optical quality were grown using low temperature gradient Czochralski technique and their luminescence properties were studied. At low temperatures two overlapping luminescence bands with the maxima 1.93eV and 2.45eV were detected at Eex>3.9eV. The bands are attributed to the radiative recombination of self-trapped excitons of MoO42- parentage. High-intensity non-elementary peak of thermostimulated luminescence (TSL) observed at 65K is due to the thermal release of self-trapped holes. The threshold of TSL excitation spectrum at 6.2eV exceeds the bandgap value by 1.9eV and corresponds to electronic transitions from the valence band to the upper subband of the conduction band.
Spectral polarization characteristics of short-length fiber Bragg gratings UV-written in a highly-birefringent spun-fiber have been investigated. Based on the analysis of the characteristics the ...technique for measuring the built-in linear phase birefringence as well as the spin period in this fiber type has been suggested. In this method the birefringence dispersion is excluded and therefore the built-in linear phase birefringence can be measured with an improved accuracy.
Aging is accompanied by the triggering of numerous pathophysiological events, which include inflammation, cellular senescence and the development of the
senescence-associated secretory phenotype
...(SASP), altered glucose tolerance, and insulin resistance (IR). Neuroinflammation significantly contributes to the development of brain IR due to the activation of the multiprotein oligomeric complex, NLRP3 inflammasome. The aim of the present study was to explore the impairment of the mechanisms underlying insulin signaling and metabolic inflammation in the brain of aging C57BL/6 mice. We found that aging in these mice is accompanied by an increase both in the number of senescent cells in brain slices, as well as neuron–astrocyte co-culture, and in the expression of phosphorylated protein kinases PKR and IKKβ, metaflammasome components. Another metaflammasome component, whose expression increased in the hippocampus during aging, was IKKβ. We demonstrated that constitutive IKKβ activation is related with cell senescence and aging, as well as overactivation of the NLRP3 inflammasome and increased lactate production in aging mice. Changes in NLRP3 expression in the brain are reflected in changes in complex behaviors. Here, we documented the impairment of contextual memory, but not the acquisition process and cued memory, in aging mice. Nevertheless, aging in mice did not led to a change in the expression of insulin receptors, insulin receptor substrate 1 (IRS1phospho-S312), suggesting that during physiological aging, without signs of neurodegeneration (e.g., reactive astrogliosis), insulin signaling is not yet impaired, but the manifestations of metabolic inflammation are already observed. Thus, modulation of the activity of PKR and IKKβ metaflammasome components may represent a new pathogenetically substantiated strategy for managing the mechanisms of metabolic inflammation and SASP development in the brain, aimed at improving age-related cognitive dysfunctions.
The change in surface conductivity under the influence of hydrogen fluoride (HF) gas on quartz is experimentally studied. It is shown that the surface conductivity of quartz changes by a factor of ...more than 10
8
during the reaction. Possible heterogeneous chemical processes determining the observed experimental results are considered.
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