The late stages of the evolution of intermediate-mass primordial stars: the effects of overshooting

We compute and analyze the evolution of primordial stars of masses at the ZAMS between 5 M_sun and 10 M_sun, with and without overshooting. Our main goals are to determine the nature of the remnants of massive intermediate-mass primordial stars and to check the influence of overshooting in their evolution. Our calculations cover stellar evolution from the main sequence phase until the formation of the degenerate cores and the thermally pulsing phase. We have obtained the values for the limiting masses of Population III progenitor stars leading to carbon-oxygen and oxygen-neon compact cores. Moreover, we have also obtained the limiting mass for which isolated primordial stars would lead to core-collapse supernovae after the end of the main central burning phases. Considering a moderate amount of overshooting the mass thresholds at the ZAMS for the formation of carbon-oxygen and oxygen-neon degenerate cores shifts to smaller values by about 2 M_sun. As a by-product of our calculations, we have also obtained the structure and composition profiles of the resulting compact remnants. Opposite to what happens with solar metallicity objects, the final fate of primordial stars is not straightforward determined from the mass of the compact cores at the end of carbon burning. Instead, the small mass-loss rates typically associated to stellar winds of low metallicity stars might allow the growth of the resulting degenerate cores up to the Chandrasekhar mass, on time scales one or two orders of magnitude shorter than the time required to loose the envelope. This would lead to the formation of supernovae for initial masses as small as about 5 M_sun

Memory and Executive Dysfunction Predict Complex Activities of Daily Living Impairment in Amnestic Multi-Domain Mild Cognitive Impairment

[EN]Background: Specific cognitive alterations could be one of the predictors that lead to the complex activities of daily living (CADL) impairment in mild cognitive impairment (MCI) and, hence, help to explain the continuum between MCI and dementia. Objective: We aimed to reevaluate the existing uncertainty regarding the impact of memory and executive functions on CADL in patients with MCI. Methods: Caregivers of 161 patients with amnestic multi-domain MCI and of 150 patients with incipient Alzheimer’s disease as well as 100 age-, sex-, and education-matched controls, completed the Interview for Deterioration in Daily Living Activities in Dementia, a suitable instrument for the description and discrimination of CADL. In addition, all patients and controls were assessed with a neuropsychological battery to measure explicit memory and executive functions performance. Results: Multiple regression analyses showed that in the group of patients with amnestic multi-domain MCI, 67.4% of the variability of the CADL impairment was explained by worse performance on executive functions tests (p < 0.0001) and 41.8% by different explicit memory components impairment (p < 0.0001). Further, in patients with incipient AD, 44.0% of the variability of CADL impairment was explained by worse performance on executive functions tests (p < 0.0001) and 39.9% by different explicit memory components worsening (p < 0.0001). Conclusions: Memory and executive functions alterations impact similarly on the CADL in both amnestic multi-domain MCI and incipient Alzheimer’s disease. Given the continuum that exists between both conditions, we conclude that CADL impairment may be an important early step in the evolution towards Alzheimer’s disease from amnestic multi-domain MCI

Demonstration of the event identification capabilities of the NEXT-White detector

In experiments searching for neutrinoless double-beta decay, the possibility of identifying the two emitted electrons is a powerful tool in rejecting background events and therefore improving the overall sensitivity of the experiment. In this paper we present the first measurement of the efficiency of a cut based on the different event signatures of double and single electron tracks, using the data of the NEXT-White detector, the first detector of the NEXT experiment operating underground. Using a 228Th calibration source to produce signal-like and background-like events with energies near 1.6 MeV, a signal efficiency of 71.6 ± 1.5 stat± 0.3 sys% for a background acceptance of 20.6 ± 0.4 stat± 0.3 sys% is found, in good agreement with Monte Carlo simulations. An extrapolation to the energy region of the neutrinoless double beta decay by means of Monte Carlo simulations is also carried out, and the results obtained show an improvement in background rejection over those obtained at lower energies. [Figure not available: see fulltext.

Design and Operation of Front-End Electronics for the HERA-B Muon Detector

We have implemented a cost-effective design for the readout electronics of both the anode wires and the cathode pads of large area proportional wire chambers for the HERA-B muon system based on the ASD-08 integrated circuit. To control and monitor the large number of readout channels, we have built a distributed control system based on Philips Semiconductors' I2C bus and microcontrollers. To date we have installed about 10800 channels of muon chambers and electronics. The average single channel noise occupancy is less than 10**-5, and the detectors have been operated with target interaction rates as high as 70 MHz

Strangelet search at RHIC

Two position sensitive Shower Maximum Detector (SMDs) for Zero-Degree Calorimeters (ZDCs) were installed by STAR before run 2004 at both upstream and downstream from the interaction point along the beam axis where particles with small rigidity are swept away by strong magnetic field. The ZDC-SMDs provides information about neutral energy deposition as a function of transverse position in ZDCs. We report the preliminary results of strangelet search from a triggered data-set sampling 100 million Au+Au collisions at top RHIC energy.Comment: Strange Quark Matter 2004 conference proceedin

Correlations in STAR: interferometry and event structure

STAR observes a complex picture of RHIC collisions where correlation effects of different origins -- initial state geometry, semi-hard scattering, hadronization, as well as final state interactions such as quantum intensity interference -- coexist. Presenting the measurements of flow, mini-jet deformation, modified hadronization, and the Hanbury Brown and Twiss effect, we trace the history of the system from the initial to the final state. The resulting picture is discussed in the context of identifying the relevant degrees of freedom and the likely equilibration mechanism.Comment: 8 pages, 6 figures, plenary talk at the 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma, to appear in Journal of Physics G (http://www.iop.org

Azimuthal anisotropy and correlations at large transverse momenta in p+p and Au+Au collisions at sqrt[sNN] = 200 GeV

Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for Au+Au collisions at sqrt[sNN]=200 GeV. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in Au+Au collisions to those in p+p at the same energy. The elliptic anisotropy v2 is found to reach its maximum at pt~3 GeV/c, then decrease slowly and remain significant up to pt ~ 7-10 GeV/c. Stronger suppression is found in the back-to-back high-pt particle correlations for particles emitted out of plane compared to those emitted in plane. The centrality dependence of v2 at intermediate pt is compared to simple models based on jet quenching

Neutral Kaon Interferometry in Au+Au collisions at sqrt(s_NN) = 200 GeV

We present the first statistically meaningful results from two-K0s interferometry in heavy-ion collisions. A model that takes the effect of the strong interaction into account has been used to fit the measured correlation function. The effects of single and coupled channel were explored. At the mean transverse mass m_T = 1.07 GeV, we obtain the values R = 4.09 +/- 0.46 (stat.) +/- 0.31 (sys) fm and lambda = 0.92 +/- 0.23 (stat) +/- 0.13 (sys), where R and lambda are the invariant radius and chaoticity parameters respectively. The results are qualitatively consistent with m_T systematics established with pions in a scenario characterized by a strong collective flow.Comment: 11 pages, 10 figure

Sympherobius barberi (Banks, 1903) (Neuroptera: Hemerobiidae): morfología, presas y rango de distribución en México y América

Los hemeróbidos tienen una distribución cosmopolita y destacan por sus hábitos entomófagos sobre insectos pequeños de cuerpo blando. En México, la especie Sympherobius barberi (Banks, 1903) se registra en Baja California, Estado de México Guanajuato, y Morelos. El interés sobre su potencial uso comercial como agente de control biológico en el país motivó la revisión de esta especie. Tanto en publicaciones científicas como en bases de datos y colecciones biológicas, se documentan los caracteres taxonómicos requeridos para determinar esta especie y se propone sustituir la taxonomía básica basada en patrones de manchas alares. Además, se reporta nueva información sobre presas y plantas hospederas: Brevicoryne brassicae (Linnaeus, 1758) en Brassica spp.; Dactylopius confusus (Cockerell, 1893) en varias especies del género Opuntia y Nopalea cochenillifera; Dactylopius opuntiae (Cockerell, 1896) sobre Opuntia ficus-indica; Phenacoccus solenopsis Tinsley, 1898 en algodón; Planococcus ficus Signoret, 1875 en vid; y larvas de Plutella xylostella (Linnaeus, 1758) en brócoli.Brown lacewings have a cosmopolitan distribution and stand out for their entomophagous habits on small, soft-bodied prey. In Mexico, the species Sympherobius barberi (Banks, 1903) is recorded from Baja California, Estado de Mexico, Guanajuato, and Morelos. Interest in its potential commercial use as a biological control agent in the country motivated the review of this species. Both in scientific publications and in databases and biological collections, the taxonomic characters required to determine this species are documented, proposing to replace the basic taxonomy based on wing spot patterns. In addition, new information on prey and host plants is recorded: Brevicoryne brassicae (Linnaeus, 1758) in Brassica spp.; Dactylopius confusus (Cockerell, 1893) in various species of Opuntia y Nopalea cochenillifera; Dactylopius opuntiae in Opuntia ficus-indica; Phenacoccus solenopsis Tinsley, 1898 in cotton; Planococcus ficus Signoret, 1875 in grapevine; and larvae of Plutella xylostella (Linnaeus, 1758) in broccoli

Hopping conduction and persistent photoconductivity in Cu2ZnSnS4 thin films

The temperature dependence of electrical conductivity and the photoconductivity of polycrystalline Cu2ZnSnS4 were investigated. It was found that at high temperatures the electrical conductivity was dominated by band conduction and nearest-neighbour hopping. However, at lower temperatures, both Mott variable-range hopping (VRH) and Efros–Shklovskii VRH were observed. The analysis of electrical transport showed high doping levels and a large compensation ratio, demonstrating large degree of disorder in Cu2ZnSnS4. Photoconductivity studies showed the presence of a persistent photoconductivity effect with decay time increasing with temperature, due to the presence of random local potential fluctuations in the Cu2ZnSnS4 thin film. These random local potential fluctuations cannot be attributed to grain boundaries but to the large disorder in Cu2ZnSnS4