533 resultados para Obserwatorium Astronomiczne UAM


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Reproduction of the original in the Henry E. Huntington Library.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Caracterizacin sociodemogrfica y satisfaccin con la formacin recibida, las competencias y con los recursos institucionales ofrecidos por la UAM a los graduados de los programas de pregrado y posgrado.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers Au+Au collisions at <radical><radicand>s(NN)</radicand></radical>=62.4 and 200 GeV, and Cu+Cu collisions at <radical><radicand>s(NN)</radicand></radical>=22.5,62.4, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for nondynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon p+p data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. A comparison of the data with a model where hadrons are independently emitted from a number of hadron clusters suggests that the mean number of hadrons per cluster is small in heavy ion collisions.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We present a new analysis of J/psi production yields in deuteron-gold collisions at root s(NN) =200 GeV using data taken from the PHENIX experiment in 2003 and previously published in S. S. Adler [Phys. Rev. Lett 96, 012304 (2006)]. The high statistics proton-proton J/psi data taken in 2005 are used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors (R(dAu)). A suppression of J/psi in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial-state low-x gluons in the gold nucleus. The measured nuclear modification factors are compared to theoretical calculations of nuclear shadowing to which a J/psi (or precursor) breakup cross section is added. Breakup cross sections of sigma(breakup)=2.8(-1.4)(+1.7) (2.2(-1.5)(+1.6)) mb are obtained by fitting these calculations to the data using two different models of nuclear shadowing. These breakup cross-section values are consistent within large uncertainties with the 4.2 +/- 0.5 mb determined at lower collision energies. Projecting this range of cold nuclear matter effects to copper-copper and gold-gold collisions reveals that the current constraints are not sufficient to firmly quantify the additional hot nuclear matter effect.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We present transverse momentum (p(T)) spectra of charged hadrons measured in deuteron-gold and nucleon-gold collisions at root s(NN)=200 GeV for four centrality classes. Nucleon-gold collisions were selected by tagging events in which a spectator nucleon was observed in one of two forward rapidity detectors. The spectra and yields were investigated as a function of the number of binary nucleon-nucleon collisions, nu, suffered by deuteron nucleons. A comparison of charged particle yields to those in p+p collisions show that yield per nucleon-nucleon collision saturates with nu for high momentum particles. We also present the charged hadron to neutral pion ratios as a function of p(T).

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Time-resolved Z-scan measurements were performed in a Nd(3+)-doped Sr(0.61)Ba(0.39)Nb(2)O(6) laser crystal through ferroelectric phase transition. Both the differences in electronic polarizability (Delta alpha(p)) and cross section (Delta sigma) of the neodymium ions have been found to be strongly modified in the surroundings of the transition temperature. This observed unusual behavior is concluded to be caused by the remarkable influence that the structural changes associated to the ferro-to-paraelectric phase transition has on the 4f -> 5d transition probabilities. The maximum polarizability change value Delta alpha(p)=1.2x10(-25) cm(3) obtained at room temperature is the largest ever measured for a Nd(3+)-doped transparent material.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The temperature and compositional dependences of thermo- optical properties of neodymium doped yttrium aluminum garnet (YAG) crystals and fine grain ceramics have been systematically investigated by means of time- resolved thermal lens spectrometry. We have found that Nd:YAG ceramics show a reduced thermal diffusivity compared to Nd:YAG single crystals in the complete temperature range investigated (80-300 K). The analysis of the time- resolved luminescent properties of Nd(3+) has revealed that the reduction in the phonon mean free path taking place in Nd:YAG ceramics cannot be associated with an increment in the density of lattice defects, indicating that phonon scattering at grain boundaries is the origin of the observed reduction in the thermal diffusivity of Nd: YAG ceramics. Finally, our results showed the ability of the time- resolved thermal lens to determine and optimize the thermo- optical properties of Nd: YAG ceramic based lasers. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2975335]

Relevância:

10.00% 10.00%

Publicador:

Resumo:

De acuerdo con la informacin aportada por el Instituto Nacional de Evaluacin (2012), Espaa ha participado en las ediciones de 1990, 2006 y 2011 de PIRLS y en las ediciones de 1995 y de 2011 de TIMSS. Por otra parte, en el ao 2009, nuestro pas particip por primera vez en el Estudio Internacional de Civismo y Ciudadana (Instituto de Evaluacin, 2010). Finalmente, Espaa participa en el Programa para la Evaluacin Internacional de los Alumnos (PISA). Por otra parte, junto a estas evaluaciones internacionales, tanto a nivel estatal como autonmico, se han implementado otras pruebas externas. Esta tendencia se ha visto reafirmada y ampliada por la nueva Ley Orgnica para la Mejora de la Calidad Educativa (LOMCE), aspecto que ser analizado en esta comunicacin. La proliferacin de estas prcticas puede ser analizada desde diversas perspectivas. En esta comunicacin se realiza una aproximacin sustentada en numerosos escritos recientes (Prez y Soto, 2011, Perrenoud, 2008; Stake, 2006), que advierten sobre los impactos de los sistemas de evaluacin en las prcticas de enseanza. Por otra parte, desde esta aproximacin crtica, se sostiene que las evidencias sobre lo que stas aportan para la mejora de la educacin no parecen ser tan abundantes.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dissertao apresentada Escola Superior de Educao de Lisboa para obteno do grau de Mestre em Ensino Especial ramo de Problemas de Cognio e Multideficincia

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dissertao apresentada Escola Superior de Educao de Lisboa para obteno de grau de mestre em Educao Especial

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dissertao apresentada Escola Superior de Educao de Lisboa para obteno do grau de Mestre em Educao Especial ramo de Problemas de Cognio e Multideficincia