Observation and applications of single-electron charge signals in the XENON100 experiment

The XENON100 dark matter experiment uses liquid xenon in a time projection chamber (TPC) to measure xenon nuclear recoils resulting from the scattering of dark matter weakly interacting massive particles (WIMPs). In this paper, we report the observation of single-electron charge signals which are not related to WIMP interactions. These signals, which show the excellent sensitivity of the detector to small charge signals, are explained as being due to the photoionization of impurities in the liquid xenon and of the metal components inside the TPC. They are used as a unique calibration source to characterize the detector. We explain how we can infer crucial parameters for the XENON100 experiment: the secondary-scintillation gain, the extraction yield from the liquid to the gas phase and the electron drift velocity.

Measurement of the intrinsic electron neutrino component in the T2K neutrino beam with the ND280 detector

The T2K experiment has reported the first observation of the appearance of electron neutrinos in a muon neutrino beam. The main and irreducible background to the appearance signal comes from the presence in the neutrino beam of a small intrinsic component of electron neutrinos originating from muon and kaon decays. In T2K, this component is expected to represent 1.2% of the total neutrino flux. A measurement of this component using the near detector (ND280), located 280 m from the target, is presented. The charged current interactions of electron neutrinos are selected by combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeters of ND280. The measured ratio between the observed electron neutrino beam component and the prediction is 1.01±0.10 providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. Electron neutrinos coming from muons and kaons decay are also separately measured, resulting in a ratio with respect to the prediction of 0.68±0.30 and 1.10±0.14 , respectively.

Measurement of plasma electron density generated in an experiment of laser shock processing, utilizing the H­α­-line

In this work we have realized plasma diagnosis produced by Laser (LPP), by means of emission spectroscopy in a Laser Shock Processing (LSP). The LSP has been proposed as an alternative technology, competitive with classical surface treatments. The ionic species present in the plasma together with electron density and its temperature provide significant indicators of the degree of surface effect of the treated material. In order to analyze these indicators, we have realized spectroscopic studies of optical emission in the laser-generated plasmas in different situations. We have worked focusing on an aluminum sample (Al2024) in air and/or in LSP conditions (water flow) a Q-switched laser of Nd:YAG (λ = 1.06 μm, 10 ns of pulse duration, running at 10 Hz repetition rate). The pulse energy was set at 2,5 J per pulse. The electron density has been measured using, in every case, the Stark broadening of H Balmer α line (656.27 nm). In the case of the air, this measure has been contrasted with the value obtained with the line of 281.62 nm of Al II. Special attention has been paid to the self-absorption of the spectral lines used. The measures were realized with different delay times after the pulse of the laser (1–8 μs) and with a time window of 1 μs. In LSP the electron density obtained was between 1017 cm−3 for the shortest delays (4–6 μs), and 1016 cm−3 for the greatest delays (7,8 μs).

Understanding sickness presenteeism through the experience of immigrant workers in a context of economic crisis

Background: Previous economic recessions show that immigrant workers may experience longer periods of unemployment, a situation that may lead employees to presenteeism, the act of working in spite of a health problem. This study explored perceptions about the factors that lead to presenteeism in immigrant workers considering the context of economic crisis. Methods: Six focus group discussions were held (February 2012), with men and women from Colombia, Ecuador, and Morocco (n = 44) living in Spain and selected by theoretical sample. A qualitative content analysis was performed. Results: Four categories were identified as factors that influence the occurrence of presenteeism in a context of economic crisis: poor employment conditions, fear of unemployment, employer/employee relationship, and difficulties in finding temporary replacement workers. Furthermore, musculoskeletal, respiratory, and mental problems were related to presenteeism. Conclusions: It is important to develop strategies to protect workers from negative working conditions that are associated with deterioration of health.

Adsorption of benzene on graphitized thermal carbon black: Reduction of the quadrupole moment in the adsorbed phase

The performance of intermolecular potential models on the adsorption of benzene on graphitized thermal carbon black at various temperatures is investigated. Two models contain only dispersive sites, whereas the other two models account explicitly for the dispersive and electrostatic sites. Using numerous data in the literature on benzene adsorption on graphitized thermal carbon black at various temperatures, we have found that the effect of surface mediation on interaction between adsorbed benzene molecules must be accounted for to describe correctly the adsorption isotherm as well as the isosteric heat. Among the two models with partial charges tested, the WSKS model of Wick et at. I that has only six dispersive sites and three discrete partial charges is better than the very expensive all-atom model of Jorgensen and Severance.(2) Adsorbed benzene molecules on graphitized thermal carbon black have a complex orientation with respect to distance from the surface and also with respect to loading. At low loadings, they adopt the parallel configuration relative to the graphene surface, whereas at higher loadings (still less than monolayer coverage) some molecules adopt a slant orientation to maximize the fluid-fluid interaction. For loadings in the multilayer region, the orientation of molecules in the first layer is influenced by the presence of molecules in the second layer. The data that are used in this article come from the work of Isirikyan and Kiselev,(3) Pierotti and Smallwood,(4) Pierce and Ewing,(5) Belyakova, Kiselev, and Kovaleva,(6) and Carrott et al.(7)

Iron speciation and magnetic susceptibility in bottom sediments of the Black Sea, Core SMG91-903

12 cores of Late Pleistocene - Holocene deposits were studied. They were collected by gravity cores on the continental slope and in the deep-water part of the Black Sea within the Adler-Tuapse polygon. In four of them in New Euxinian deposits at the base of a packet of hydrotroilite laminae paleomagnetic anomalies likely resulting from the Gothenburg magnetic excursion occur. Comparison with results of similar studies in the western Black Sea, where the Gothenburg magnetic excursion was previously found, let to validate stratigraphic synchronism of the hydrotroilite horizon in the eastern and western parts of the Black Sea and to confirm the authors' views about peculiarities of paleogeographical development of the Black Sea basin in the Late Pleistocene - Holocene.

The storage and dissipation of magnetic energy in the quiet sun corona determined from SDO/HMI magnetograms

In recent years, higher cadence, higher resolution observations have revealed the quiet-Sun photosphere to be complex and rapidly evolving. Since magnetic fields anchored in the photosphere extend up into the solar corona, it is expected that the small-scale coronal magnetic field exhibits similar complexity. For the first time, the quiet-Sun coronal magnetic field is continuously evolved through a series of non-potential, quasi-static equilibria, deduced from magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, where the photospheric boundary condition which drives the coronal evolution exactly reproduces the observed magnetograms. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. We find that the free magnetic energy built up and stored within the field is sufficient to explain small-scale, impulsive events such as nanoflares. On comparing with coronal images of the same region, the energy storage and dissipation visually reproduces many of the observed features. The results indicate that the complex small-scale magnetic evolution of a large number of magnetic features is a key element in explaining the nature of the solar corona.

Effects of gamma and electron beam irradiation in the antioxidante potential of methanolic extracts and infusions of Arenaria Montana L

Irradiation is a methodology qualified for dry ingredients preservation or decontamination and can be performed using various radiation sources and energy levels in accordance with the objectives to be achieved [1]. Electron beam irradiation is used mainly for food products with low density, while gamma irradiation is mainly used for large volumes [2]. Arenaria Montana L. has a high antioxidant potential and richness in bioactive phytochemicals. It is used in Portuguese traditional medicine, acting therapeutically as an anti-inflammatory and diuretic plant [3]. The aim of this work was to evaluate the effects of gamma and electron beam irradiation at different doses (I and 10 kGy) in the antioxidant activity of A. montana. Free radicals scavenging activity, reducing power and lipid peroxidation inhibition properties of its methanolic extracts and infusions were evaluated. Through a global analysis, it was concluded that the antioxidant activity proved to be higher in methanolic extracts in comparison with the infusions, where it decreased with increasing irradiation dose regardless of the technology used (gamma or electron beam). For methanolic extracts, electron beam resulted in increased antioxidant activity while gamma irradiation caused a decrease in these extracts. Thus, the antioxidant potential is variable depending not only on the type of radiation and the dose applied, but also on the solvent used in the preparation of the extracts (methanol or water).

Magnetic interactions in the oxide systems LaNi1-xMxO3 (M = Cr, Fe, or Co)

Magnetic susceptibilities of several members of the series of oxides of the general formula LaNi1-xMxO3 (M = Cr, Fe, or Co) are reported. The oxides show evidence for interesting ferrimagnetic (Cr and Co) and antiferromagnetic (Fe) interactions.