815 research outputs found
Shell-model half-lives for r-process waiting point nuclei including first-forbidden contributions
We have performed large-scale shell-model calculations of the half-lives and
neutron-branching probabilities of the r-process waiting point nuclei at the
magic neutron numbers N=50, 82, and 126. The calculations include contributions
from allowed Gamow-Teller and first-forbidden transitions. We find good
agreement with the measured half-lives for the N=50 nuclei with charge numbers
Z=28-32 and for the N=82 nuclei 129Ag and 130Cd. The contribution of forbidden
transitions reduce the half-lives of the N=126 waiting point nuclei
significantly, while they have only a small effect on the half-lives of the
N=50 and 82 r-process nuclei.Comment: 14 pages, 17 figures, submitted to Phys. Rev.
Catálogo de los micromamĂferos (Rodentia, Eulipotyphla, Chiroptera) del Cuaternario Superior IbĂ©rico del Museu de Geologia de Barcelona, Spain
The present catalogue represents an attempt to list Middle–Upper Pleistocene and Holocene micromammal material deposited in the Museu de Geologia de Barcelona, coming from 12 Iberian Peninsula localities (ten from Catalonia, one from Castilla y León and one from Andalucia). It permits to observe changes in species geographical distribution as Iberomys cabrerae, Microtus oeconomus, Hystrix cristata or Citellus sp. with regard to their present location. By this way, we can observe the existence during the Middle–Upper Pleistocene of some today extinct species such as Pliomys lenki or Allocricetus bursae.
Key words: Middle-Upper Pleistocene, Holocene, Micromammals, Palaeobiogeography, Museo de Geologia de Barcelona, Spain.En este trabajo se presenta una lista del material de micromamĂferos del Pleistoceno Medio-Superior y Holoceno depositado en el Museo de GeologĂa de Barcelona, perteneciente a 12 yacimientos de la PenĂnsula IbĂ©rica (diez de Cataluña, uno de Castilla y LeĂłn y uno de AndalucĂa). Este listado nos permite observar cambios en la distribuciĂłn de especies como Iberomys cabrerae, Microtus oeconomus, Hystrix cristata o Citellus sp. respecto a su actual situaciĂłn geográfica. AsĂ mismo, nos permite vislumbrar la existencia durante el Pleistoceno Medio–Superior de algunas especies actualmente extintas, como Pliomys lenki y Allocricetus bursae.
Palabras clave: Pleistoceno Medio-Superior, Holoceno, MicromamĂferos, PaleobiogeografĂa, Museu de Geologia de Barcelona, España
Design tool to predict the open-hole failure strength of composite laminates subjected to in-plane loads
A design tool based on Whitney-Nuismer model is proposed to predict the failure strength of open-hole composite plates subjected to in-plane loads, both tensile and compressive. One of the limitations of this model is the use of characteristic distances, which have to be estimated, and which are mostly considered constant material properties. In this work, it is demonstrated that these characteristic distances are a function of the plate geometry and are not a material property. Different analytical expressions are proposed to estimate the characteristic distances by using the results of only three experimental tests. This approach enables an accurate and fast estimation of the failure strength when the parameters of the plate are modified without using numerical simulations that require a longer time to be carried out.The authors are indebted for the financial support of this work to the Ministry of Economy and Finance of Spain (project DPI2013-42240-R).Publicad
Loss of Melanopsin-Expressing Ganglion Cell Subtypes and Dendritic Degeneration in the Aging Human Retina
In mammals, melanopsin-expressing retinal ganglion cells (mRGCs) are, among other things, involved in several non-image-forming visual functions, including light entrainment of circadian rhythms. Considering the profound impact of aging on visual function and ophthalmic diseases, here we evaluate changes in mRGCs throughout the life span in humans. In 24 post-mortem retinas from anonymous human donors aged 10–81 years, we assessed the distribution, number and morphology of mRGCs by immunostaining vertical retinal sections and whole-mount retinas with antibodies against melanopsin. Human retinas showed melanopsin immunoreactivity in the cell body, axon and dendrites of a subset of ganglion cells at all ages tested. Nearly half of the mRGCs (51%) were located within the ganglion cell layer (GCL), and stratified in the outer (M1, 12%) or inner (M2, 16%) margin of the inner plexiform layer (IPL) or in both plexuses (M3, 23%). M1 and M2 cells conformed fairly irregular mosaics, while M3 cell distribution was slightly more regular. The rest of the mRGCs were more regularly arranged in the inner nuclear layer (INL) and stratified in the outer margin of the IPL (M1d, 49%). The quantity of each cell type decrease after age 70, when the total number of mRGCs was 31% lower than in donors aged 30–50 years. Moreover, in retinas with an age greater than 50 years, mRGCs evidenced a decrease in the dendritic area that was both progressive and age-dependent, as well as fewer branch points and terminal neurite tips per cell and a smaller Sholl area. After 70 years of age, the distribution profile of the mRGCs was closer to a random pattern than was observed in younger retinas. We conclude that advanced age is associated with a loss in density and dendritic arborization of the mRGCs in human retinas, possibly accounting for the more frequent occurrence of circadian rhythm disorders in elderly persons.This research was supported by grants from the Spanish Ministry of Economy and Competitiveness (MINECO-FEDER BFU2015-67139-R), Instituto de Salud Carlos III (RETICS-FEDER RD16/0008/0016) and Generalitat Valenciana (PROMETEO/2016/158)
Los Batanes (Biescas, Spain), a roost site for horseshoe bats in the Pyrenees during the late Pleistocene
Los Batanes C4 is a cave-site in the Spanish Pyrenees, the minimum sediment calendar age was determined to be 15, 234 ± 223 cal BP by radiocarbon dating. The cave opens on the northern bank of an eastern tributary of the River Gállego, at an altitude of 1025 m. The small vertebrates recorded are mainly bats, in order of abundance Rhinolophus euryale, R. ferrumequinum, Myotis sp. and Miniopterus schreibersii. The association suggests that at the time of the accumulation the climate was reasonably similar to the current climate; we situate it within a period of local retreat of the ice-cover in the Gállego Valley during the Lateglacial. This is the highest record of these species of Rhinolophus in the Iberian Quaternary, showing that the R. euryale altitudinal range was similar to its extant range during the favourable periods of the Lateglacial. This could indicate that this taxon was relatively quick in spreading into higher regions whenever climate conditions allowed it
Electron transport measurements in liquid xenon with Xenoscope, a large-scale DARWIN demonstrator
The DARWIN observatory is a proposed next-generation experiment with 40 tonnes of liquid xenon as an active target in a time projection chamber. To study challenges related to the construction and operation of a multi-tonne scale detector, we have designed and constructed a vertical, full-scale demonstrator for the DARWIN experiment at the University of Zurich. Here, we present the first results from a several-months run with 343kg of xenon and electron drift lifetime and transport measurements with a 53cm tall purity monitor immersed in the cryogenic liquid. After 88days of continuous purification, the electron lifetime reached a value of (664±23)μs. We measured the drift velocity of electrons for electric fields in the range (25–75) V/cm, and found values consistent with previous measurements. We also calculated the longitudinal diffusion constant of the electron cloud in the same field range, and compared with previous data, as well as with predictions from an empirical model
Electron transport measurements in liquid xenon with Xenoscope, a large-scale DARWIN demonstrator
The DARWIN observatory is a proposed next-generation experiment with 40 tonnes of liquid xenon as an active target in a time projection chamber. To study challenges related to the construction and operation of a multi-tonne scale detector, we have designed and constructed a vertical, full-scale demonstrator for the DARWIN experiment at the University of Zurich. Here, we present the first results from a several-months run with of xenon and electron drift lifetime and transport measurements with a tall purity monitor immersed in the cryogenic liquid. After of continuous purification, the electron lifetime reached a value of (664\,\pm \,23)\,\upmu \hbox {s}. We measured the drift velocity of electrons for electric fields in the range (25–75) V/cm, and found values consistent with previous measurements. We also calculated the longitudinal diffusion constant of the electron cloud in the same field range, and compared with previous data, as well as with predictions from an empirical model
Empirical Installation of Linear Algebra Shared-Memory Subroutines for Auto-Tuning
The final publication is available at Springer via http://dx.doi.org/10.1007/s10766-013-0249-6The introduction of auto-tuning techniques in linear algebra shared-memory routines is analyzed. Information obtained in the installation of the routines is used at running time to take some decisions to reduce the total execution time. The study is carried out with routines at different levels (matrix multiplication, LU and Cholesky factorizations and linear systems symmetric or general routines) and with calls to routines in the LAPACK and PLASMA libraries with multithread implementations. Medium NUMA and large cc-NUMA systems are used in the experiments. This variety of routines, libraries and systems allows us to obtain general conclusions about the methodology to use for linear algebra shared-memory routines auto-tuning. Satisfactory execution times are obtained with the proposed methodology.Partially supported by Fundacion Seneca, Consejeria de Educacion de la Region de Murcia, 08763/PI/08, PROMETEO/2009/013 from Generalitat Valenciana, the Spanish Ministry of Education and Science through TIN2012-38341-C04-03, and the High-Performance Computing Network on Parallel Heterogeneus Architectures (CAPAP-H). The authors gratefully acknowledge the computer resources and assistance provided by the Supercomputing Centre of the Scientific Park Foundation of Murcia and by the Centre de Supercomputacio de Catalunya.Cámara, J.; Cuenca, J.; GimĂ©nez, D.; GarcĂa, LP.; Vidal Maciá, AM. (2014). Empirical Installation of Linear Algebra Shared-Memory Subroutines for Auto-Tuning. 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Electric field effects on magnetotransport properties of multiferroic Py/YMnO3/Pt heterostructures
We report on the exchange bias between antiferromagnetic and ferroelectric
hexagonal YMnO3 epitaxial thin films sandwiched between a metallic electrode
(Pt) and a soft ferromagnetic layer (Py). Anisotropic magnetoresistance
measurements are performed to monitor the presence of an exchange bias field.
When the heteroestructure is biased by an electric field, it turns out that the
exchange bias field is suppressed. We discuss the dependence of the observed
effect on the amplitude and polarity of the electric field. Particular
attention is devoted to the role of current leakage across the ferroelectric
layer.Comment: Accepted for publication in Philosophical Magazine Letters (Special
issue on multiferroics
Bloqueantes adrenérgicos y funcionalismo tiroideo
La participaciĂłn del sistema adrenĂ©rgico en las manifestaciones clĂnicas del hipertiroidismo, ha sido señalada por diÂversos autores (GOETSCHE, 1918; PRIESTLY y cols., 1931; ROSENÂBLUM y cols., 1933; SAWYER y BROWN, 1935; McDONAL y cols., 1935; BARKER y cols., 1936; SCHNECKLOTH y cols., 1953; BREWSTER, 1956; WURTMAN y cols., 1963; GOLDSTEIN y KILLIP, 1965; HARRISON, 1967; MORI, 1968; WADA, 1968). La primera sugerencia se debe a GOETSCHE (1918 ). Este autor observĂł que los efectos cardĂacos de la adrenalina, en pacientes hipertiroideos, estaban aumentados, mientras que, en otros procesos que cursan con taquicardia -ansiedad- el aumento era menor..
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