On the origin of HE0107-5240, the most iron deficient star presently known

We show that the "puzzling" chemical composition observed in the extremely metal poor star HE0107-5240 may be naturally explained by the concurrent pollution of at least two supernovae. In the simplest possible model a supernova of quite low mass (~15 Msun), underwent a "normal" explosion and ejected ~0.06 Msun of 56Ni while a second one was massive enough (~35 Msun) to experience a strong fall back that locked in a compact remnant all the carbon-oxygen core. In a more general scenario, the pristine gas clouds were polluted by one or more supernovae of relatively low mass (less than ~25 Msun). The successive explosion of a quite massive star experiencing an extended fall back would have largely raised the abundances of the light elements in its close neighborhood.Comment: 10 pages; 3 figures; accepted for publication in the The Astrophysical Journal Letter

C/O white dwarfs of very low mass: 0.33-0.5 Mo

The standard lower limit for the mass of white dwarfs (WDs) with a C/O core is roughly 0.5 Mo. In the present work we investigated the possibility to form C/O WDs with mass as low as 0.33 Mo. Both the pre-WD and the cooling evolution of such nonstandard models will be described.Comment: Submitted to the "Proceedings of the 16th European White Dwarf Workshop" (to be published JPCS). 7 pages including 13 figure

On the Origin of the Early Solar System Radioactivities. Problems with the AGB and Massive Star Scenarios

Recent improvements in stellar models for intermediate-mass and massive stars are recalled, together with their expectations for the synthesis of radioactive nuclei of lifetime $\tau \lesssim 25$ Myr, in order to re-examine the origins of now extinct radioactivities, which were alive in the solar nebula. The Galactic inheritance broadly explains most of them, especially if $r$-process nuclei are produced by neutron star merging according to recent models. Instead, $^{26}$Al, $^{41}$Ca, $^{135}$Cs and possibly $^{60}$Fe require nucleosynthesis events close to the solar formation. We outline the persisting difficulties to account for these nuclei by Intermediate Mass Stars (2 $\lesssim$ M/M$_\odot \lesssim 7 - 8$). Models of their final stages now predict the ubiquitous formation of a $^{13}$C reservoir as a neutron capture source; hence, even in presence of $^{26}$Al production from Deep Mixing or Hot Bottom Burning, the ratio $^{26}$Al/$^{107}$Pd remains incompatible with measured data, with a large excess in $^{107}$Pd. This is shown for two recent approaches to Deep Mixing. Even a late contamination by a Massive Star meets problems. In fact, inhomogeneous addition of Supernova debris predicts non-measured excesses on stable isotopes. Revisions invoking specific low-mass supernovae and/or the sequential contamination of the pre-solar molecular cloud might be affected by similar problems, although our conclusions here are weakened by our schematic approach to the addition of SN ejecta. The limited parameter space remaining to be explored for solving this puzzle is discussed.Comment: Accepted for publication on Ap

Prevalência de parasitismo por Toxocara canis em cães e presença de ovos de Toxocara sp. no solo de localidades públicas da zona urbana do município de Londrina, Estado do Paraná, Brasil

Out of 158 dogs submitted to coprological examination or necropsy, 70 (44.30%) were found to be infected by Toxocara canis, the prevalence being higher among puppies with and up to 6 months of age. Out of 15 soil samples taken from public places atended by children, ova of Toxocara species were found in 60% indicating the possibility of transmission of toxocaral infection to humans through ova containing larvae.De um total de 158 cães examinados, através de exame parasitológico de fezes ou necropsia, 70 (44,30%) mostraram-se infectados por Toxocara canis, predominando a infecção nos animais com até 6 meses de idade. Através do exame de amostras de terra de localidades públicas utilizadas por crianças para diversão, demonstrou-se a presença de ovos de Toxocara sp. em 60% das amostras, evidenciando a possibilidade de ocorrer infecção humana, ingestão de ovos larvados do helminto

The centrosomal kinase NEK2 is a novel splicing factor kinase involved in cell survival

NEK2 is a serine/threonine kinase that promotes centrosome splitting and ensures correct chromosome segregation during the G2/M phase of the cell cycle, through phosphorylation of specific substrates. Aberrant expression and activity of NEK2 in cancer cells lead to dysregulation of the centrosome cycle and aneuploidy. Thus, a tight regulation of NEK2 function is needed during cell cycle progression. In this study, we found that NEK2 localizes in the nucleus of cancer cells derived from several tissues. In particular, NEK2 co-localizes in splicing speckles with SRSF1 and SRSF2. Moreover, NEK2 interacts with several splicing factors and phosphorylates some of them, including the oncogenic SRSF1 protein. Overexpression of NEK2 induces phosphorylation of endogenous SR proteins and affects the splicing activity of SRSF1 toward reporter minigenes and endogenous targets, independently of SRPK1. Conversely, knockdown of NEK2, like that of SRSF1, induces expression of pro-apoptotic variants from SRSF1-target genes and sensitizes cells to apoptosis. Our results identify NEK2 as a novel splicing factor kinase and suggest that part of its oncogenic activity may be ascribed to its ability to modulate alternative splicing, a key step in gene expression regulation that is frequently altered in cancer cells

Prevalência de parasitismo por Toxocara canis em cães e presença de ovos de Toxocara sp. no solo de localidades públicas da zona urbana do município de Londrina, Estado do Paraná, Brasil

Out of 158 dogs submitted to coprological examination or necropsy, 70 (44.30%) were found to be infected by Toxocara canis, the prevalence being higher among puppies with and up to 6 months of age. Out of 15 soil samples taken from public places atended by children, ova of Toxocara species were found in 60% indicating the possibility of transmission of toxocaral infection to humans through ova containing larvae.De um total de 158 cães examinados, através de exame parasitológico de fezes ou necropsia, 70 (44,30%) mostraram-se infectados por Toxocara canis, predominando a infecção nos animais com até 6 meses de idade. Através do exame de amostras de terra de localidades públicas utilizadas por crianças para diversão, demonstrou-se a presença de ovos de Toxocara sp. em 60% das amostras, evidenciando a possibilidade de ocorrer infecção humana, ingestão de ovos larvados do helminto

TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies

In the course of the TOPoS (Turn Off Primordial Stars) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. We here present our analysis of six CEMP stars. Calcium and carbon are the only elements that can be measured in all six stars. The range is -5.0<=[Ca/H]< -2.1 and 7.12<=A(C)<=8.65. For star SDSS J1742+2531 we were able to detect three FeI lines from which we deduced [Fe/H]=-4.80, from four CaII lines we derived [Ca/H]=-4.56, and from synthesis of the G-band we derived A(C)=7.26. For SDSS J1035+0641 we were not able to detect any iron lines, yet we could place a robust (3sigma) upper limit of [Fe/H]< -5.0 and measure the Ca abundance, with [Ca/H]=-5.0, and carbon, A(C)=6.90. No lithium is detected in the spectrum of SDSS J1742+2531 or SDSS J1035+0641, which implies a robust upper limit of A(Li)<1.8 for both stars. Our measured carbon abundances confirm the bimodal distribution of carbon in CEMP stars, identifying a high-carbon band and a low-carbon band. We propose an interpretation of this bimodality according to which the stars on the high-carbon band are the result of mass transfer from an AGB companion, while the stars on the low-carbon band are genuine fossil records of a gas cloud that has also been enriched by a faint supernova (SN) providing carbon and the lighter elements. (Abridged)Comment: to be published on A&

Diminuição da força muscular em Rattus norvegicus experimentalmente infectados por Toxocara canis

Roedores são reconhecidos como hospedeiros paratênicos de Toxocara canis. Um dos mecanismos de transmissão desse ascarídeo para cães, seus hospedeiros habituais, consiste na predação de hospedeiros paratênicos, que albergam larvas de terceiro estágio em seus órgãos e tecidos, entre os quais músculos estriados. No presente trabalho estudou-se se a infecção por larvas de Toxocara canis provoca alterações na força muscular de exemplares de Rattus norvegicus experimentalmente infectados. Cinqüenta Rattus norvegicus foram divididos em três grupos: G1, com 20 ratos infectados com 300 ovos de Toxocara canis; G2, com 20 ratos infectados com 2.000 ovos do ascarídeo e G3, com 10 ratos sem infecção. Dez e 30 dias após a infecção determinou-se a força muscular nas patas dianteiras dos roedores; ao mesmo tempo, avaliou-se seu peso corporal. Não foram observadas diferenças no peso dos animais dos três grupos; contudo, verificou-se decréscimo na força muscular dos ratos infectados com 2.000 ovos após o 30º dia de infecção.The muscular strength of experimental infected Rattus norvegicus with 3rd. stage Toxocara canis larvae was investigated. Fifty Wistar rats, divided in three groups (G1 - 20 rats infected by 300 eggs of T. canis; G2 - 20 rats infected by 2,000 eggs of T. canis and G3 - 10 rats without infection) had been used. Ten and 30 days after infection the muscular strength in the fore-feet of the rats was checked; at the same time, the body weight was determined. No significative differences in the body weight were noted among the infected and control rats in both occasions. Otherwise, an impairment on the muscular strength was observed in rats infected with T. canis 30 days after inoculation