| 1. |
- Micheva, G., et al.
(författare)
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Deep multiband surface photometry on star forming galaxies : I. A sample of 24 blue compact galaxies
- 2012
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Ingår i: ArXiv e-prints.
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Tidskriftsartikel (refereegranskat)abstract
- [Abridged] We present deep optical and near-infrared UBVRIHKs imaging data for 24 blue compact galaxies (BCGs). The sample contains luminous dwarf and intermediate-mass BCGs which are predominantly metal-poor, although a few have near-solar metallicities. We have analyzed isophotal and elliptical integration surface brightness and color profiles, extremely deep (mu_B\lt29 mag arcsec\^$$-2$$) contour maps and RGB images for each galaxy in the sample. The colors are compared to different spectral evolutionary models. We detect extremely extended low surface brightness (LSB) components dominant beyond the Holmberg radius as well as optical bridges between companion galaxies at the mu_V~28th mag arcsec\^$$-2$$ isophotal level. The central surface brightness mu_0 and scale length h_r are derived from two radial ranges typically assumed to be dominated by the underlying host galaxy. We find that mu_0 and h_r of the BCGs host deviate from those of dwarf ellipticals (dE) and dwarf irregulars (dI) solely due to a strong burst contribution to the surface brightness profile almost down to the Holmberg radius. Structural parameters obtained from a fainter region, mu_B=26-28 mag arcsec\^$$-2$$, are consistent with those of true LSB galaxies for the starbursting BCGs in our sample, and with dEs and dIs for the BCGs with less vigorous star formation.
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| 2. |
- Hedborg, Fredrik, et al.
(författare)
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Differentiation in Neuroblastoma : Diffusion-Limited Hypoxia Induces Neuro-Endocrine Secretory Protein 55 and Other Markers of a Chromaffin Phenotype
- 2010
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:9, s. e12825-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Neuroblastoma is a childhood malignancy of sympathetic embryonal origin. A high potential for differentiation is a hallmark of neuroblastoma cells. We have previously presented data to suggest that in situ differentiation in tumors frequently proceeds along the chromaffin lineage and that decreased oxygen ( hypoxia) plays a role in this. Here we explore the utility of Neuro-Endocrine Secretory Protein 55 ( NESP55), a novel member of the chromogranin family, as a marker for this process. Methodology/Principal Findings: Immunohistochemical analyses and in situ hybridizations were performed on human fetal tissues, mouse xenografts of human neuroblastoma cell lines, and on specimens of human neuroblastoma/ganglioneuroma. Effects of anaerobic exposure on gene expression by cultured neuroblastoma cells was analyzed with quantitative real-time PCR. Fetal sympathetic nervous system expression of NESP55 was shown to be specific for chromaffin cell types. In experimental and clinical neuroblastoma NESP55 immunoreactivity was specific for regions of chronic hypoxia. NESP55 expression also correlated strikingly with morphological evidence of differentiation and with other chromaffin-specific patterns of gene expression, including IGF2 and HIF2 alpha. Anaerobic culture of five neuroblastoma cell lines resulted in an 18.9-fold mean up-regulation of NESP55. Conclusions/Significance: The data confirms that chronic tumor hypoxia is a key microenvironmental factor for neuroblastoma cell differentiation, causing induction of chromaffin features and NESP55 provides a reliable marker for this neuronal to neuroendocrine transition. The hypoxia-induced phenotype is the predominant form of differentiation in stroma-poor tumors, while in stroma-rich tumors the chromaffin phenotype coexists with ganglion cell-like differentiation. The findings provide new insights into the biological diversity which is a striking feature of this group of tumors.
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| 3. |
- Larsson, Josefin, et al.
(författare)
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X-ray illumination of the ejecta of supernova 1987A
- 2011
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 474:7352, s. 484-486
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Tidskriftsartikel (refereegranskat)abstract
- When a massive star explodes as a supernova, substantial amounts of radioactive elements-primarily (56)Ni, (57)Ni and (44)Ti-are produced(1). After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements(2). However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium(3). The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of (44)Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.
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