651 research outputs found
Highly Sensitive Measurements of 222Rn Diffusion and Emanation
No full textHighly sensitive techniques for determination of the 222Rn emanation from solids and diffusion through different membranes are presented. 222Rn and its daughters are measured via the alpha decays in special proportional counters at the absolute sensitivity of ~30 µBq. Radon diffusion can be measured at the level of ~10-13 cm2/s. Several samples were examined, e.g. stainless steel, teflon, various gaskets (emanation and diffusion measurements) and tanks. A combination of measurements of the 222Rn diffusion and emanation of thin nylon foils (used in the Borexino experiment) allowed the determination of 226Ra in the materials of interest at the level of ~10-12 g/g 238U-equivalent
Low background techniques applied in the BOREXINO experiment
No full textThe BOREXINO detector, located in the Gran Sasso National Laboratory in Italy, has been designed for real-time spectroscopy of low-energy solar neutrinos. Within the experiment several novel background reduction and assay techniques have been established. In many cases they are still the most sensitive world-wide. Developed methods and apparatus provided tools for a strict quality control program during the construction phase of the BOREXINO detector, which was the key to meet the background requirements. Achievement of extremely low background rate opened the possibility to probe in realtime almost entire spectrum of the solar neutrinos
The role of G-CSF in mature neutrophil function is not related to GM-CSF-type cell priming
No full textAbstract
Because of uncertainties regarding the comparability of granulocyte-macrophage and granulocyte colony-stimulating factors with regard to their effects on mature neutrophils (PMNs), we compared the actions of the two cytokines on reactive oxidant production and granular secretion by these cells. We found that chemiluminescence (CL) stimulated by formylmethionyl-leucylphenylalanine (fMLP) was not influenced by G-CSF (0.1–100 ng/ml), whereas GM-CSF priming (10 ng/ml) caused a nearly twofold increase in this PMN response. Moreover, the reactivity of PMNs treated with GM-CSF and G-CSF in combination was not different from that of PMNs treated with GM-CSF alone. GM-CSF (10 ng/ml) increased the rate of O2- production by 79%, caused a fivefold increase in fMLF-induced myeloperoxidase (MPO) secretion, and strongly enhanced CD11b expression. In contrast, G-CSF (50 ng/ml) only slightly increased O2- production (by 15%), and MPO secretion and CD11b expression remained unchanged. Both cytokines together gave results similar to those obtained with GM-CSF alone. In the presence of platelets (which by themselves enhanced PMN reactivity), the differences in the effects of the two cytokines persisted. We conclude that the priming effect of G-CSF on mature PMNs is negligible compared with that of GM-CSF. Our results are in conflict with previous reports of much more pronounced G-CSF effects but in accord with recent work showing the failure of this cytokine to induce a range of effects produced by GM-CSF. We therefore suggest that the primary role of G-CSF in mature PMN function is still unclear but may be related to the control of PMN distribution in view of the mobilizing and marginating effects of the cytokine in viva J. Leukoc. Biol. 55: 612–616; 1994.</jats:p
226Ra in the nylon scintillator vessel as a background source in the Solar Neutrino Experiment BOREXINO
No full textPauli postulated the existence of neutrino in the year 1931. This new particle has been introduced in order to solve the problem of energy and momentum loss in nuclear b decay. It has been proposed as a massless and chargeless particle traveling at the speed of light. Cowan and Reines observed neutrino first time in 1956 and since that time its study plays a great role in elementary particle physics and astrophysics. The most important source of these particles seems to be the Sun. It produces constantly a high flux (1010 n/cm2/s) of low energy (up to 18 MeV) neutrinos in thermonuclear reactions taking place in its center. Neutrinos and energy production in the Sun describes in details the Standard Solar Model (SSM). Up to now, five different collaborations have reported detection of solar neutrinos. The main result that they came to is the record of a flux of two to free times lower than expected according to the SSM. The discrepancy between the theoretical end experimental results is known as the Solar Neutrino Problem (SNP). Presently a few new projects aiming detection of solar neutrinos are under development or construction. They are characterized by real time and high statistics data taking, low energy thresholds and ability to distinguish different types of neutrino interactions (e.g. via charged or neutral current). These detectors are called “second generation detectors” – experiments run up to date exemplify the “first generation” detectors. One of the new projects is being realized by the BOREXINO collaboration in the Laboratori Nazionali del Gran Sasso (LNGS) of the Instituto Nazionale di Fisica Nucleare (INFN). BOREXINO is a 300-ton unsegmented liquid scintillator detector, which aims to measure mono-energetic 7Be neutrinos in real time through elastic neutrinoelectron scattering. Expected signal according to the SSM vary between 9 and 53 events per day depending on the neutrino oscillation scenario. Very low counting rate requires very low background of the detector. For this reason ultra-low levels of 238U, 232Th, 40K, 222Rn, 14C and other radioactive isotopes are requested in construction materials and in the scintillator. Background from cosmic rays is reduced by a 3500 m w.e. shield of dolomite rock over the laboratory. The possibility to achieve project’s specifications of radiopurity for a full-scale detector has been shown with the small prototype called Counting Test Facility
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