Extensive population synthesis of isolated neutron stars with field decay

We perform population synthesis studies of different types of neutron stars taking into account the magnetic field decay. For the first time, we confront our results with observations using {\it simultaneously} the Log N -- Log S distribution for nearby isolated neutron stars, the Log N -- Log L distribution for magnetars, and the distribution of radio pulsars in the $P$ -- $\dot P$ diagram. We find that our theoretical model is consistent with all sets of data if the initial magnetic field distribution function follows a log-normal law with $\sim 13.25$ and $\sigma_{\log B_0}\sim 0.6$. The typical scenario includes about 10% of neutron stars born as magnetars, significant magnetic field decay during the first million years of a NS life. Evolutionary links between different subclasses may exist, although robust conclusions are not yet possible. We apply the obtained field distribution and the model of decay to study long-term evolution of neuton stars till the stage of accretion from the interstellar medium. It is shown that though the subsonic propeller stage can be relatively long, initially highly magnetized neutron stars ($B_0 > \sim 10^{13}$ G) reach the accretion regime within the Galactic lifetime if their kick velocities are not too large. The fact that in previous studies made $>$10 years ago, such objects were not considered results in a slight increase of the Accretor fraction in comparison with earlier conclusions. Most of the neutron stars similar to the Magnificent seven are expected to become accreting from the interstellar medium after few billion years of their evolution. They are the main predecestors of accreting isolated neutron stars.Comment: 4 pages, conference "Astrophysics of Neutron Stars - 2010" in honor of M. Ali Alpar, Izmir, Turke

Z_2-gradings of Clifford algebras and multivector structures

Let Cl(V,g) be the real Clifford algebra associated to the real vector space V, endowed with a nondegenerate metric g. In this paper, we study the class of Z_2-gradings of Cl(V,g) which are somehow compatible with the multivector structure of the Grassmann algebra over V. A complete characterization for such Z_2-gradings is obtained by classifying all the even subalgebras coming from them. An expression relating such subalgebras to the usual even part of Cl(V,g) is also obtained. Finally, we employ this framework to define spinor spaces, and to parametrize all the possible signature changes on Cl(V,g) by Z_2-gradings of this algebra.Comment: 10 pages, LaTeX; v2 accepted for publication in J. Phys.

Revisión de los Gordiacea (Nematomorpha) de la colección de la Academia de Ciencias de California con descripción de una nueva especie

The Gordiacea of the California Academy of Sciences collection are studied. The specimens are included in the known species Gordius robustus Leidy, Pseudochordodes bedriagae (Camerano) and a new species, Neochordodes californensis n. sp. is proposed. Morphological, morphometric and geographical data are provided for these species.En este trabajo se estudian los Gordiacea de la colección de la California Academy of Sciences. Los ejemplares se incluyen en dos especies conocidas, Gordius robustus Leidy y Pseudochordodes bedriagae (Camerano), y una especie nueva: Neochordodes californensis n. sp. Se proporcionan datos morfológicos, morfométricos y geográficos para cada una de las especies

Multivariate analysis of Vitis subgenus Vitis seed morphology

We studied 142 grapevine seed samples belonging to 5 Vitis species, 92 cultivars of Vitis vinifera, 12 feral/wild populations and 4 hybrid rootstock cultivars. Eleven different characters from the seed and one allometric index have been used. Seeds show a wide range of variation in body dimensions, and in other parameters. Two largely differentiated clusters were obtained. Coincidences with previous seed classifications are discussed. Wild extra-European species have smaller seeds. The index breadth/length (STUMMER’s index) doesn’t allow to separate wild grapevines and cultivars. It defines, however, the “wild syndrome” values above 0.8 corresponding to wild extra-European Vitis species, occasionally used as rootstocks. Ferals/wild individuals tend to display smaller berries and plumper pips than their cultivated relatives therefore “looking wild”. The multivariate analysis place together ferals/wild and related cultivars in their respective clusters and does not discriminate a cluster of wild European grapevine.

Electronic structure of the Sr0.4Ca13.6Cu24O41Sr_{0.4}Ca_{13.6}Cu_{24}O_{41} incommensurate compound

We extracted, from strongly-correlated ab-initio calculations, a complete model for the chain subsystem of the $Sr_{0.4}Ca_{13.6}Cu_{24}O_{41}$ incommensurate compound. A second neighbor $t-J+V$ model has been determined as a function of the fourth crystallographic parameter $\tau$, for both low and room temperature crystallographic structures. The analysis of the obtained model shows the crucial importance of the structural modulations on the electronic structure through the on-site energies and the magnetic interactions. The structural distortions are characterized by their long range effect on the cited parameters that hinder the reliability of analyses such as BVS. One of the most striking results is the existence of antiferromagnetic nearest-neighbor interactions for metal-ligand-metal angles of $90^\circ$. A detailed analysis of the electron localization and spin arrangement is presented as a function of the chain to ladder hole transfer and of the temperature. The obtained spin arrangement is in agreement with antiferromagnetic correlations in the chain direction at low temperature

Balancing parallel assembly lines with disabled workers

[EN] In this paper, we study an assembly line balancing problem that occurs in sheltered worker centres for the disabled, where workers with very different characteristics are present. We are interested in the situation in which complete parallel assembly lines are allowed and name the resulting problem as parallel assembly line worker assignment and balancing problem (PALWABP). This approach enables many new possible worker-tasks assignments, what is beneficial in terms of both labour integration and productivity. We present a linear mixed-integer formulation and two heuristic solution methods: one is based on tabu search and the other is a biased random-key genetic algorithm (BRKGA). Computational results with a large set of instances recently proposed in the literature show the advantages of allowing such alternative line layouts.This research was supported by CAPES-Brazil and MEC-Spain (coordinated project CAPES DGU 258-12/PHB2011-0012-PC) and by FAPESP-Brazil. The authors thank Dr. Marcus Ritt, from Universidade Federal do Rio Grande do Sul (UFRGS - Brazil), for providing the optimal solutions for the serial ALWABP. The authors also thank three anonymous reviewers for their comments which have helped improve this paper.Araujo, FFB.; Costa, AM.; Miralles Insa, CJ. (2015). Balancing parallel assembly lines with disabled workers. European J of Industrial Engineering. 9(3):344-365. https://doi.org/10.1504/EJIE.2015.069343S3443659

Recombination dramatically speeds up evolution of finite populations

We study the role of recombination, as practiced by genetically-competent bacteria, in speeding up Darwinian evolution. This is done by adding a new process to a previously-studied Markov model of evolution on a smooth fitness landscape; this new process allows alleles to be exchanged with those in the surrounding medium. Our results, both numerical and analytic, indicate that for a wide range of intermediate population sizes, recombination dramatically speeds up the evolutionary advance