971 resultados para MILKY SPOTS
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Clinically important mutant p53 proteins may be tumorigenic through a dominant-negative mechanism or due to a gain-of-function. Examples for both hypotheses have been described; however, it remains unclear to what extent they apply to TP53 mutations in general. Here it is shown that the mutational spectrum of dominant-negative p53 mutants selected in a novel yeast assay correlates tightly with p53 mutations in cancer. Two classes of dominant-negative mutations are described; the more dominant one affects codons that are essential for the stabilization of the DNA-binding surface of the p53 core domain and for the direct interaction of p53 with its DNA binding sites. These results predict that the vast majority of TP53 mutations leading to cancer do so in a dominant-negative fashion.
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El objetivo principal de este artículo es señalar los valores sociales presentes en los spots de bebidas emitidos por televisión, en España, durante el año 2006. Se estudian los valores sociales que transmiten los anuncios al margen de su función comercial. En total, se han analizado 191 spots; para los que se detallan los valores atribuidos al producto y al consumidor. La salud, la juventud, la importancia de las relaciones sociales o de construirse una personalidad genuina son algunos de los principales valores e ideales transmitidos a través de los spots sometidos a estudio.
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The center of our Galaxy hosts a supermassive black hole, Sagittarius (Sgr) A∗. Young, massive stars within 0.5 pc of Sgr A∗ are evidence of an episode of intense star formation near the black hole a few million years ago, which might have left behind a young neutron star traveling deep into Sgr A∗’s gravitational potential. On 2013 April 25, a short X-ray burst was observed from the direction of the Galactic center. With a series of observations with the Chandra and the Swift satellites, we pinpoint the associated magnetar at an angular distance of 2.4±0.3 arcsec from Sgr A∗, and refine the source spin period and its derivative (P = 3.7635537(2) s and ˙ P = 6.61(4) × 10−12 s s−1), confirmed by quasi simultaneous radio observations performed with the Green Bank Telescope and Parkes Radio Telescope, which also constrain a dispersion measure of DM = 1750 ± 50 pc cm−3, the highest ever observed for a radio pulsar. We have found that this X-ray source is a young magnetar at ≈0.07–2 pc from Sgr A∗. Simulations of its possible motion around Sgr A∗ show that it is likely (∼90% probability) in a bound orbit around the black hole. The radiation front produced by the past activity from the magnetar passing through the molecular clouds surrounding the Galactic center region might be responsible for a large fraction of the light echoes observed in the Fe fluorescence features.
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Aims. We study the optical and near-infrared colour excesses produced by circumstellar emission in a sample of Be/X-ray binaries. Our main goals are exploring whether previously published relations, valid for isolated Be stars, are applicable to Be/X-ray binaries and computing the distance to these systems after correcting for the effects of the circumstellar contamination. Methods. Simultaneous UBVRI photometry and spectra in the 3500−7000 Å spectral range were obtained for 11 optical counterparts to Be/X-ray binaries in the LMC, 5 in the SMC and 12 in the Milky Way. As a measure of the amount of circumstellar emission we used the Hα equivalent width corrected for photospheric absorption. Results. We find a linear relationship between the strength of the Hα emission line and the component of E(B − V) originating from the circumstellar disk. This relationship is valid for stars with emission lines weaker than EW ≈ −15 Å. Beyond this point, the circumstellar contribution to E(B − V) saturates at a value ≈0.17 mag. A similar relationship is found for the (V − I) near infrared colour excess, albeit with a steeper slope and saturation level. The circumstellar excess in (B − V) is found to be about five times higher for Be/X-ray binaries than for isolated Be stars with the same equivalent width EW(Hα), implying significant differences in the physical properties of their circumstellar envelopes. The distance to Be/X-ray binaries (with non-shell Be star companions) can only be correctly estimated by taking into account the excess emission in the V band produced by free-free and free-bound transitions in the circumstellar envelope. We provide a simple method to determine the distances that includes this effect.
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Context. It has been suggested that the compact open cluster VdBH 222 is a young massive distant object. Aims. We set out to characterise VdBH 222 using a comprehensive set of multi-wavelength observations. Methods. We obtained multi-band optical (UBVR) and near-infrared (JHKS) photometry of the cluster field, as well as multi-object and long-slit optical spectroscopy for a large sample of stars in the field. We applied classical photometric analysis, as well as more sophisticated methods using the CHORIZOS code, to determine the reddening to the cluster. We then plotted dereddened HR diagrams and determined cluster parameters via isochrone fitting. Results. We have identified a large population of luminous supergiants confirmed as cluster members via radial velocity measurements. We find nine red supergiants (plus one other candidate) and two yellow supergiants. We also identify a large population of OB stars. Ten of them are bright enough to be blue supergiants. The cluster lies behind ≈7.5 mag of extinction for the preferred value of RV = 2.9. Isochrone fitting allows for a narrow range of ages between 12 and 16 Ma. The cluster radial velocity is compatible with distances of ~6 and ~10 kpc. The shorter distance is inconsistent with the age range and Galactic structure. The longer distance implies an age ≈ 12 Ma and a location not far from the position where some Galactic models place the far end of the Galactic bar. Conclusions. VdBH 222 is a young massive cluster with a likely mass >20 000 M⊙. Its population of massive evolved stars is comparable to that of large associations, such as Per OB1. Its location in the inner Galaxy, presumably close to the end of the Galactic bar, adds to the increasing evidence for vigorous star formation in the inner regions of the Milky Way.
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We study the relationship between age, metallicity, and α-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra from the Gaia-ESO large stellar survey. We explore the limitations of the observed dataset, i.e. the accuracy of stellar parameters and the selection effects that are caused by the photometric target preselection. We find that the colour and magnitude cuts in the survey suppress old metal-rich stars and young metal-poor stars. This suppression may be as high as 97% in some regions of the age-metallicity relationship. The dataset consists of 144 stars with a wide range of ages from 0.5 Gyr to 13.5 Gyr, Galactocentric distances from 6 kpcto 9.5 kpc, and vertical distances from the plane 0 < |Z| < 1.5 kpc. On this basis, we find that i) the observed age-metallicity relation is nearly flat in the range of ages between 0 Gyr and 8 Gyr; ii) at ages older than 9 Gyr, we see a decrease in [Fe/H] and a clear absence of metal-rich stars; this cannot be explained by the survey selection functions; iii) there is a significant scatter of [Fe/H] at any age; and iv) [Mg/Fe] increases with age, but the dispersion of [Mg/Fe] at ages >9 Gyr is not as small as advocated by some other studies. In agreement with earlier work, we find that radial abundance gradients change as a function of vertical distance from the plane. The [Mg/Fe] gradient steepens and becomes negative. In addition, we show that the inner disk is not only more α-rich compared to the outer disk, but also older, as traced independently by the ages and Mg abundances of stars.
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Eleven-page notebook containing John Winthrop's handwritten observations and calculations. Titled by Winthrop "Observations of 'Spots' on ye Sun with ye Naked Eye," this is the first known record of his scientific observations and records what he saw while examining the sun "with an 8 foot telescope from 6 a.m. til sun set" on the Boston Commons and concluding with "a considerable aurora borealis" that night (April 20, 1739). It has been speculated that his reference to the aurora borealis in these observations may indicate that he recognized the interrelation of the aurora borealis and sun spots, a concept which was not definitively established until the mid-nineteenth century.
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As the leadership of the European Union hands over the baton to a new management this autumn, will the winds of change blow also through the cobwebs of the EU’s enlargement agenda? Jean-Claude Juncker – the incoming President of the European Commission – has already promised to put the gearbox of further EU widening in neutral for the next five years of his mandate, and has designated the Austrian Johannes Hahn as Commissioner for the re-baptised portfolio of now European Neighbourhood Policy and Enlargement Negotiations, instructing him to focus on the Union’s political and economic ties with Southern and Eastern Europe, and in particular with the Balkans. Such an approach in the field of enlargement – once crowned the jewel of EU foreign policy – has all the appeal of a damp rag but does not necessarily depart from the festina lente strategy of the recent past. Inside the Union, political appetite and public support for expansion have been fizzling since Bulgaria and Romania joined in 2007, and were then severely curbed in the context of the on-going crisis by growing fears of importing organised crime and migrants from the Balkans. Juncker’s logic of consolidation sounds depressingly similar to what it supposedly replaces and incidentally, it also fits neatly with the unambitious and inward-looking mantra favoured at present in discussions at all levels on the future of European integration, more generally. With the 28-member block determined to catch its breath in the immediate time period, and given that even the forerunner countries in the Balkans – that is, Montenegro and Serbia – will realistically need more than five years to complete their accession talks, what priorities should guide Commissioner Hahn, soon to be Directorate-General for Neighbourhood and Enlargement Negotiations – when they get down to business on 1 November?
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Includes bibliographical references
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Mode of access: Internet.
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"A catalogue of the animals of British North America: Zoological": p. 189-190; "Ornithological": p. 190-196.
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"A catalogue of the animals of British North America": p. [189]-196.
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Mode of access: Internet.
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Mode of access: Internet.
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Maps on end-papers.