Outstanding intraindividual genetic diversity in fissiparous planarians (Dugesia, Platyhelminthes) with facultative sex.

Predicted genetic consequences of asexuality include high intraindividual genetic diversity (i.e., the Meselson effect) and accumulation of deleterious mutations (i.e., Muller’s Ratchet), among others. These consequences have been largely studied in parthenogenetic organisms, but studies on fissiparous species are scarce. Differing from parthenogens, fissiparous organisms inherit part of the soma of the progenitor, including somatic mutations. Thus, in the long term, fissiparous reproduction may also result in genetic mosaicism, besides the presence of the Meselson effect and Muller’s Ratchet. Dugesiidae planarians show outstanding regeneration capabilities, allowing them to naturally reproduce by fission, either strictly or combined with sex (facultative). Therefore, they are an ideal model to analyze the genetic footprint of fissiparous reproduction, both when it is alternated with sex and when it is the only mode of reproduction

Electron degeneracy and intrinsic magnetic properties of epitaxial Nb:SrTiO3_3 thin-films controlled by defects

We report thermoelectric power experiments in e-doped thin films of SrTiO$_3$ (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and non-linear Hall effect. Ab-initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this paper for tetragonally distorted e-doped STO thin films, is similarto that observed in LaAlO$_3$/STO interfaces and magnetic STO quantum wells.Comment: 5 pages, 5 figure

Thermodynamic conditions during growth determine the magnetic anisotropy in epitaxial thin-films of La0.7_{0.7}Sr0.3_{0.3}MnO3_{3}

The suitability of a particular material for use in magnetic devices is determined by the process of magnetization reversal/relaxation, which in turn depends on the magnetic anisotropy. Therefore, designing new ways to control magnetic anisotropy in technologically important materials is highly desirable. Here we show that magnetic anisotropy of epitaxial thin-films of half-metallic ferromagnet La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) is determined by the proximity to thermodynamic equilibrium conditions during growth. We performed a series of X-ray diffraction and ferromagnetic resonance (FMR) experiments in two different sets of samples: the first corresponds to LSMO thin-films deposited under tensile strain on (001) SrTiO$_{3}$ by Pulsed Laser Deposition (PLD; far from thermodynamic equilibrium); the second were deposited by a slow Chemical Solution Deposition (CSD) method, under quasi-equilibrium conditions. Thin films prepared by PLD show a in-plane cubic anisotropy with an overimposed uniaxial term. A large anisotropy constant perpendicular to the film plane was also observed in these films. However, the uniaxial anisotropy is completely suppressed in the CSD films. The out of plane anisotropy is also reduced, resulting in a much stronger in plane cubic anisotropy in the chemically synthesized films. This change is due to a different rotation pattern of MnO$_{6}$ octahedra to accomodate epitaxial strain, which depends not only on the amount of tensile stress imposed by the STO substrate, but also on the growth conditions. Our results demonstrate that the nature and magnitude of the magnetic anisotropy in LSMO can be tuned by the thermodynamic parameters during thin-film deposition.Comment: 6 pages, 8 Figure

Abundant dust found in intergalactic space

Galactic dust constitutes approximately half of the elements more massive than helium produced in stellar nucleosynthesis. Notwithstanding the formation of dust grains in the dense, cool atmospheres of late-type stars, there still remain huge uncertainties concerning the origin and fate of galactic stardust. In this paper, we identify the intergalactic medium (i.e. the region between gravitationally-bound galaxies) as a major sink for galactic dust. We discover a systematic shift in the colour of background galaxies viewed through the intergalactic medium of the nearby M81 group. This reddening coincides with atomic, neutral gas previously detected between the group members. The dust-to-HI mass ratio is high (1/20) compared to that of the solar neighborhood (1/120) suggesting that the dust originates from the centre of one or more of the galaxies in the group. Indeed, M82, which is known to be ejecting dust and gas in a starburst-driven superwind, is cited as the probable main source.Comment: 5 pages, 3 figures, 1 table. ApJ Letters in pres

On the Effects of Dissipative Turbulence on the Narrow Emission-Line Ratios in Seyfert Galaxies

We present a photoionization model study of the effects of micro-turbulence and dissipative heating on emission lines for number and column densities, elemental abundances, and ionizations typical for the narrow emission line regions (NLRs) of Seyfert galaxies. Earlier studies of NLR spectra generally found good agreement between the observations and the model predictions for most strong emission lines, such as [O III] $\lambda$5007, [O II] $\lambda$3727, [N II] $\lambda$6583, [Ne III] $\lambda$3869, and the H and He recombination lines. Nevertheless, the strengths of lines from species with ionization potentials greater than that of He$^{+}$(54.4 eV), e.g. N$^{+4}$ and Ne$^{+4}$, were often under-predicted. Among the explanations suggested for these discrepancies were (selectively) enhanced elemental abundances and contributions from shock heated gas. Interestingly, the NLR lines have widths of several 100 km s$^{-1}$, well in excess of the thermal broadening. If this is due to micro-turbulence, and the turbulence dissipates within the emission-line gas, the gas can be heated in excess of that due to photoionization. We show that the combined effects of turbulence and dissipative heating can strongly enhance N V $\lambda$1240 (relative to He II $\lambda$1640), while the heating alone can boost the strength of [Ne V] $\lambda$3426. We suggest that this effect is present in the NLR, particularly within $\sim$ 100 pc of the central engine. Finally, since micro-turbulence would make clouds robust against instabilities generated during acceleration, it is not likely to be a coincidence that the radially outflowing emission-line gas is turbulent.Comment: 29 oages, including 10 figures. Accepted for publication in the Astrophysical Journa

Tratamiento médico de la estenosis arterial intracraneal. ¿Es el mismo en prevención primaria que en secundaria?

In this study we review the risk factors associated with the formation and progression of an atheroma plaque, the mechanism involved in cerebral ischemia secondary to intracranial atheromatosis and possible medical treatment in primary and secondary prevention. DEVELOPMENT: Medical treatment of intracranial stenoses (ICS) is aimed at stopping the progression of the atheroma plaque and at preventing recurrences in the case of symptomatic stenoses. It is based on the control of vascular risk factors, the use of statins and antithrombotic therapy (antiplatelet or anticoagulation drugs). Although antiplatelet agents have not proved to be beneficial in the primary prevention of stroke, they are recommended in patients with ICS in order to lower the risk of heart attack associated with this pathology. The use of antiplatelet drugs in the secondary prevention of ischemic stroke secondary to an ICS is based on clinical trials which have shown that antiaggregation prevents non-cardioembolic strokes. Nevertheless, several retrospective studies have observed that oral anticoagulation is better than antiaggregation with aspirin. Two prospective clinical trials are currently being conducted which will, in the next few years, help to determine what the first choice medical treatment is for this group of patients. CONCLUSIONS: Medical treatment of ICS patients must include the control of vascular risk factors and the use of statins. New studies are needed to be able to establish the first choice antithrombotic drug in secondary prevention

The X-ray Properties of the Nearby Star-Forming Galaxy IC 342: The XMM-Newton View

We present the X-ray properties of IC342 using XMM-Newton. Thirty-five sources are detected coincident with the disk of IC342 (more than tripling the number known), of which ~31 are likely to be intrinsic to IC342. This population shows a range of spectral properties and has an X-ray luminosity function slope and infrared luminosity comparable to that of starburst galaxies such as M82 and the Antennae, while its relative lack of extended X-ray emission is similar to the properties of quiescent spirals. We do detect long-term variability between this observation and the 1991 ROSAT and 1993/2000 ASCA observations for five sources. Notably, the second most luminous source IC342 X-2 is is found to be in its the lowest luminosity state observed for X-2 to date, although the slope of the spectrum is intermediate between the previously observed low/hard and high/soft states. IC342 X-1, on the other hand, is found to be in an identical state to that observed in 2000 with ASCA. Assuming X-1 is in an anomalous very high (VH) state, then either (1) X-1 has remained in this state between 2000 and 2002, and is therefore the longest duration VH-state binary ever observed, or (2) it was simply caught in a VH state by chance in both the 2000 ASCA and 2002 XMM-Newton observations. We have also confirmed the ROSAT HRI result that the nucleus of IC342 is made up of both point-like and extended emission. The relative fluxes of the two spectral components suggest that the nucleus is complex, with a soft extended component contributing approximately half of the total luminosity. (Abridged)Comment: AJ in press (December 2003), 9 pages, 7 figures, 2 tables, emulateapj.cls use