The Puzzling Frequencies of CEMP and NEMP Stars

We present the results of binary population simulations of carbon- and nitrogen-enhanced metal-poor (CEMP and NEMP) stars. We show that the observed paucity of very nitrogen-rich stars puts strong constraints on possible modifications of the initial mass function at low metallicity.Comment: 3 pages, contribution to "The Origin of the Elements Heavier than Iron" in honor of the 70th birthday of Roberto Gallino, Torino, Italy, September 200

Uniformity in association schemes and coherent configurations: cometric Q-antipodal schemes and linked systems

Inspired by some intriguing examples, we study uniform association schemes and uniform coherent configurations, including cometric Q-antipodal association schemes. After a review of imprimitivity, we show that an imprimitive association scheme is uniform if and only if it is dismantlable, and we cast these schemes in the broader context of certain --- uniform --- coherent configurations. We also give a third characterization of uniform schemes in terms of the Krein parameters, and derive information on the primitive idempotents of such a scheme. In the second half of the paper, we apply these results to cometric association schemes. We show that each such scheme is uniform if and only if it is Q-antipodal, and derive results on the parameters of the subschemes and dismantled schemes of cometric Q-antipodal schemes. We revisit the correspondence between uniform indecomposable three-class schemes and linked systems of symmetric designs, and show that these are cometric Q-antipodal. We obtain a characterization of cometric Q-antipodal four-class schemes in terms of only a few parameters, and show that any strongly regular graph with a ("non-exceptional") strongly regular decomposition gives rise to such a scheme. Hemisystems in generalized quadrangles provide interesting examples of such decompositions. We finish with a short discussion of five-class schemes as well as a list of all feasible parameter sets for cometric Q-antipodal four-class schemes with at most six fibres and fibre size at most 2000, and describe the known examples. Most of these examples are related to groups, codes, and geometries.Comment: 42 pages, 1 figure, 1 table. Published version, minor revisions, April 201

A Novel Protocol-Authentication Algorithm Ruling Out a Man-in-the-Middle Attack in Quantum Cryptography

In this work we review the security vulnerability of Quantum Cryptography with respect to "man-in-the-middle attacks" and the standard authentication methods applied to counteract these attacks. We further propose a modified authentication algorithm which features higher efficiency with respect to consumption of mutual secret bits.Comment: 4 pages, submitted to the International Journal of Quantum Information, Proceedings of the meeting "Foundations of Quantum Information", Camerino, April 200

Practical Quantum Key Distribution with Polarization-Entangled Photons

We present an entangled-state quantum cryptography system that operated for the first time in a real world application scenario. The full key generation protocol was performed in real time between two distributed embedded hardware devices, which were connected by 1.45 km of optical fiber, installed for this experiment in the Vienna sewage system. The generated quantum key was immediately handed over and used by a secure communication application.Comment: 5 pages, 3 figure

Extragalactic Planetary Nebulae: tracers of the chemical evolution of nearby galaxies

The study of the chemical composition of Planetary Nebulae in external galaxies is of paramount importance in the fields of stellar evolution and of the chemical enrichment history of galaxies. In the last years a number of spectroscopic studies with 6-8m-class telescopes have been devoted to this subject improving our knowledge of, among other, the time-evolution of the radial metallicity gradient in disk galaxies, the chemical evolution of dwarf galaxies, and the stellar evolution at low metallicity.Comment: 8 pages, 4 figures, Invited Review to IAU Symposium 283, "Planetary Nebulae: an Eye to the Future", Tenerife, 25-29 July 201

Probing nuclear skins and halos with elastic electron scattering

I investigate the elastic electron scattering off nuclei far from the stability line. The effects of the neutron and proton skins and halos on the differential cross sections are explored. Examples are given for the charge distribution in Sn isotopes and its relation to the neutron skin. The neutron halo in $^{11}$Li and the proton halo in $^{8}$B are also investigated. Particular interest is paid to the inverse scattering problem and its dependence on the experimental precision. These studies are of particular interest for the upcoming electron ion colliders at the GSI and RIKEN facilities.Comment: 27 pages, 9 figures, accepted for publication in J. Phys.

Identidade Social em Movimento: A Comunidade Japonesa na Grande Vitória (ES)

O presente trabalho objetivou identificar a identidade social de japoneses residentes na Grande Vitória (ES) a partir de falas sobre o próprio grupo e suas relações cotidianas, verificando-se também a existência de indícios de preconceito ou de tratamento discriminatório. Participaram da pesquisa 20 sujeitos, japoneses ou descendentes, de ambos os sexos, jovens e adultos. Os dados foram coletados através de entrevistas que exploraram os seguintes temas: namoro e conjugabilidade, padrões estéticos, preconceitos e estereótipo, identidade social e adaptação. Os resultados indicaram a existência de semelhanças e diferenças no que diz respeito à identidade do japonês capixaba, definida através de comparação com as características identitárias de japoneses de outros Estados. A principal semelhança identificada foi a flexibilidade de identidade social de nipo-brasileiro, que permite que em determinados momentos façam uso da identidade japonesa e, em outros momentos, da identidade brasileira, sempre procurando manter uma identidade social positiva. A principal diferenças que caracterizou os japoneses locais foi a apropriação de características atribuídas ao capixaba: ele é mais tranqüilo, mais fechado e mais normal. Foram encontrados também alguns indícios de discriminação e preconceito contra os japoneses locais. Tanto a receptividade quanto a adaptação ao contexto capixaba foram considerados boas, apesar de ainda indicarem um certo estranhamento por parte dos dois grupos, um em relação ao outro. Alguns fatores, como a imigração tardia para o Estado, o número reduzido de japoneses e uma comunidade japonesa economicamente homogênea, parecem afetar o tipo de relação estabelecido entre Capixabas e Japoneses e, conseqüentemente, a construção das identidades sociais