A high pressure xenon gas time projection chamber with electroluminescent amplification (EL HPGXe TPC) searching for the neutrinoless double beta (0νββ) decay offers: excellent energy resolution 1, 2 ...(0.5 − 0.7% FWHM at the Qββ), by amplifying the ionization signal with electroluminescent light, and tracking capabilities 3, as demonstrated by the NEXT collaboration using two kg-scale prototypes. The NEXT collaboration is building an EL HPGXe TPC capable of holding 100 kg (NEXT-100) of xenon isotopically enriched in 136Xe. The installation and commissioning of the NEXT-100 detector at the Laboratorio Subterráneo de Canfranc (LSC) is planned for 2018. The current estimated background level for the NEXT-100 detector is of 4 × 10−4 counts/keV-kg-yr or less in the energy region of interest 4. Assuming an energy resolution of 0.75% FWHM at the Qνββ and a 0νββ signal efficiency of about 28%, this gives an expected sensitivity (at 90% CL) to the 0νββ decay half life of T 1 / 2 0 ν > 6.0 × 10 25 yr for an exposure of 275 kg yr. A first phase of the NEXT experiment, called NEW, is currently being commissioned at the LSC. The NEW detector is a scale 1:2 in size (1:10 in mass) of the NEXT-100 detector using the same materials and photosensors and will be used to perform a characterization of the 0νββ backgrounds and a measurement of the standard double beta decay with neutrinos (2ν ββ). An 8 sigma significance for the 2νββ signal in the NEW detector has been estimated for a 100-day run.
This study explores the differences in sickness absence trends in women according to reproductive age group and medical diagnoses.
Data were obtained from two administrative registries: the ...Continuous Working Life Sample and the Catalonian Institute of Medical Evaluations from 2012 to 2014, containing 47,879 female employees. Incidence rates and incidence risk ratios derived from Poisson and negative binomial models were calculated to compare sickness absence trends among reproductive age groups based on Catalonian birthrates: early-reproductive (25-34 years old), middle-reproductive (35-44) and late-reproductive (45-54), according to diagnostic groups, selected diseases, type of contract, occupational category, and country of origin.
Younger women show a higher incidence of overall sickness absence compared to late-reproductive-aged women. Incidence risk ratios of sickness absence decreased significantly from early-reproductive to late-reproductive age for low back pain, hemorrhage in early pregnancy, nausea and vomiting, and abdominal and pelvic pain.
The higher incidence of sickness absence due to pregnancy-related health conditions in early-reproductive women compared to other reproductive age groups, may explain the sickness absence differences by age in women. Proper management of sickness absence related to pregnancy should be a goal to reduce the sickness absence gap between younger and older women.
Within the framework of xenon-based double beta decay experiments, we propose the possibility to improve the background rejection of an electroluminescent Time Projection Chamber (EL TPC) by reducing ...the diffusion of the drifting electrons while keeping nearly intact the energy resolution of a pure xenon EL TPC. Based on state-of-the-art microscopic simulations, a substantial addition of helium, around 10 or 15 %, may reduce drastically the transverse diffusion down to 2.5 mm/m from the 10.5 mm/m of pure xenon. The longitudinal diffusion remains around 4 mm/m. Light production studies have been performed as well. They show that the relative variation in energy resolution introduced by such a change does not exceed a few percent, which leaves the energy resolution practically unchanged. The technical caveats of using photomultipliers close to an helium atmosphere are also discussed in detail.
We have studied the relative stability of narrow-finite length Carbon nanotubes and nanostrips as a function of their length. We find that the critical radius (∼2
Å) for tube stability is independent ...of the length of the tubes and equals the critical radius of infinite length tubes. The independence of the critical radius on chirality is also established. We have also investigated the thermal stability of short nanotubes and nanostrips by performing extensive molecular dynamics simulations. The strips exhibit a higher thermal stability than the tubes even in those cases when they are structurally less stable. The thermal decomposition temperature (∼1000
K) of the tubes comes out in good agreement with the experiments.
In silica (SiO
2
) and in most silicates, atomic associations exist with composition SiO
4
and a structure with four O atoms in tetrahedral coordination around the Si atom. A similar feature is ...observed in germania (GeO
2
) and some solids containing Ge instead of Si, although the number of phases containing GeO
4
tetrahedra is smaller. In contrast, and in spite of the fact that C is in the same column of the periodic table as Si and Ge, CO
2
is a molecular solid, and crystalline and amorphous phases of CO
2
showing CO
4
tetrahedra are only obtained under extremely high pressures. We have investigated the relation between free SiO
4
, GeO
4
and CO
4
clusters and the tetrahedral associations found in the solids mentioned above. The lowest energy structure of those three free clusters is planar, but they have near-tetrahedral and distorted-tetrahedral isomers. The promotion energy from the planar structure to the distorted tetrahedral is low in SiO
4
, large in CO
4
, and intermediate in GeO
4
. This correlates with the facility to form tetrahedral associations in the solids.
A
bstract
The
Neutrino Experiment with a Xenon TPC
(NEXT) searches for the neutrinoless double-beta (0
νββ
) decay of
136
Xe using high-pressure xenon gas TPCs with electroluminescent amplification. ...A scaled-up version of this technology with about 1 tonne of enriched xenon could reach in less than 5 years of operation a sensitivity to the half-life of 0
νββ
decay better than 10
27
years, improving the current limits by at least one order of magnitude. This prediction is based on a well-understood background model dominated by radiogenic sources. The detector concept presented here represents a first step on a compelling path towards sensitivity to the parameter space defined by the inverted ordering of neutrino masses, and beyond.
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