UBVRI observations of the flickering of RS Ophiuchi at Quiescence

We report observations of the flickering variability of the recurrent nova RS Oph at quiescence on the basis of simultaneous observations in 5 bands (UBVRI). RS Oph has flickering source with (U-B)_0=-0.62 \pm 0.07, (B-V)_0=0.15 \pm 0.10, (V-R)_0=0.25 \pm 0.05. We find for the flickering source a temperature T_fl = 9500 \pm 500 K, and luminosity L_fl = 50 - 150 L_sun (using a distance of d=1.6kpc). We also find that on a (U-B) vs (B-V) diagram the flickering of the symbiotic stars differs from that of the cataclysmic variables. The possible source of the flickering is discussed. The data are available upon request from the authors and on the web www.astro.bas.bg/~rz/RSOph.UBVRI.2010.MNRAS.tar.gz.Comment: 7 pages, MNRAS (accepted

Changes in the red giant and dusty environment of the recurrent nova RS Ophiuchi following the 2006 eruption

We present near-infrared spectroscopy of the recurrent nova RS Ophiuchi (RS Oph) obtained on several occasions after its latest outburst in 2006 February. The 1–5 μm spectra are dominated by the red giant, but the H i, He i and coronal lines present during the eruption are present in all our observations. From the fits of the computed infrared spectral energy distributions to the observed fluxes, we find Teff= 4200 ± 200 K for the red giant. The first overtone CO bands at 2.3 μm, formed in the atmosphere of the red giant, are variable. The spectra clearly exhibit an infrared excess due to dust emission longward of 5 μm; we estimate an effective temperature for the emitting dust shell of 500 K, and find that the dust emission is also variable, being beyond the limit of detection in 2007. Most likely, the secondary star in RS Oph is intrinsically variable

Circumstellar Na I and Ca II lines of type Ia supernovae in symbiotic scenario

Formation of circumstellar lines of Na I and Ca II in type Ia supernovae is studied for the case, when supernova explodes in a binary system with a red giant. The model suggests a spherically-symmetric wind and takes into account ionization and heating of the wind by X-rays from the shock wave and by gamma-quanta of ^{56}Ni radioactive decay. For the wind density typical of the red giant the expected optical depth of the wind in Na I lines turnes out too low (\tau<0.001}) to detect the absorption. For the same wind densities the predicted optical depth of Ca II 3934 \AA is sufficient for the detection (\tau>0.1). I conclude that the absorption lines detected in SN 2006X cannot form in the red giant wind; they are rather related to clouds at distances larger than the dust evaporation radius (r>10^{17} cm). From the absence in SN 2006X of Ca II absorption lines not related with the similar Na I components I derive the upper limit of the mass loss rate by the wind with velocity u: \dot{M}<10^{-8}(u/10 km/s) M_{\odot} yr^{-1}.Comment: 10 pages, 6 figures, Astronomy Letters (accepted

The Unseen Population of F to K-type Companions to Hot Subdwarf Stars

We present a method to select hot subdwarf stars with A to M-type companions using photometric selection criteria. We cover a wide range in wavelength by combining GALEX ultraviolet data, optical photometry from the SDSS and the Carlsberg Meridian telescope, near-infrared data from 2MASS and UKIDSS. We construct two complimentary samples, one by matching GALEX, CMC and 2MASS, as well as a smaller, but deeper, sample using GALEX, SDSS and UKIDSS. In both cases, a large number of composite subdwarf plus main-sequence star candidates were found. We fit their spectral energy distributions with a composite model in order to estimate the subdwarf and companion star effective temperatures along with the distance to each system. The distribution of subdwarf effective temperature was found to primarily lie in the 20,000 - 30,000 K regime, but we also find cooler subdwarf candidates, making up ~5-10 per cent. The most prevalent companion spectral types were seen to be main-sequence stars between F0 and K0, while subdwarfs with M-type companions appear much rarer. This is clear observational confirmation that a very efficient first stable Roche-lobe overflow channel appears to produce a large number of subdwarfs with F to K-type companions. Our samples thus support the importance of binary evolution for subdwarf formation.Comment: 30 pages, 10 figures, 11 tables. Accepted for publication in MNRA

An asymmetric shock wave in the 2006 outburst of the recurrent nova RS Ophiuchi

Nova outbursts take place in binary star systems comprising a white dwarf and either a low-mass Sun-like star or, as in the case of the recurrent nova RS Ophiuchi, a red giant. Although the cause of these outbursts is known to be thermonuclear explosion of matter transferred from the companion onto the surface of the white dwarf, models of the previous (1985) outburst of RS Ophiuchi failed to adequately fit the X-ray evolution and there was controversy over a single-epoch high-resolution radio image, which suggested that the remnant was bipolar rather than spherical as modelled. Here we report the detection of spatially resolved structure in RS Ophiuchi from two weeks after its 12 February 2006 outburst. We track an expanding shock wave as it sweeps through the red giant wind, producing a remnant similar to that of a type II supernova but evolving over months rather than millennia. As in supernova remnants, the radio emission is non-thermal (synchrotron emission), but asymmetries and multiple emission components clearly demonstrate that contrary to the assumptions of spherical symmetry in models of the 1985 explosion, the ejection is jet-like, collimated by the central binary whose orientation on the sky can be determined from these observations.Comment: 10 pages, 4 figures, accepted by Natur

Improved blood tests for cancer screening: general or specific?

Diagnosis of cancer at an early stage leads to improved survival. However, most current blood tests detect single biomarkers that are of limited suitability for screening, and existing screening programmes look only for cancers of one particular type. A new approach is needed. Recent developments suggest the possibility of blood-based screening for multiple tumour types. It may be feasible to develop a high-sensitivity general screen for cancer using multiple proteins and nucleic acids present in the blood of cancer patients, based on the biological characteristics of cancer. Positive samples in the general screen would be submitted automatically for secondary screening using tests to help define the likelihood of cancer and provide some indication of its type. Only those at high risk would be referred for further clinical assessment to permit early treatment and mitigate potential overdiagnosis. While the assays required for each step exist, they have not been used in this way. Recent experience of screening for breast, cervical and ovarian cancers suggest that there is likely to be widespread acceptance of such a strategy

Gene Profiling of Mta1 Identifies Novel Gene Targets and Functions

BACKGROUND: Metastasis-associated protein 1 (MTA1), a master dual co-regulatory protein is found to be an integral part of NuRD (Nucleosome Remodeling and Histone Deacetylation) complex, which has indispensable transcriptional regulatory functions via histone deacetylation and chromatin remodeling. Emerging literature establishes MTA1 to be a valid DNA-damage responsive protein with a significant role in maintaining the optimum DNA-repair activity in mammalian cells exposed to genotoxic stress. This DNA-damage responsive function of MTA1 was reported to be a P53-dependent and independent function. Here, we investigate the influence of P53 on gene regulation function of Mta1 to identify novel gene targets and functions of Mta1. METHODS: Gene expression analysis was performed on five different mouse embryonic fibroblasts (MEFs) samples (i) the Mta1 wild type, (ii) Mta1 knock out (iii) Mta1 knock out in which Mta1 was reintroduced (iv) P53 knock out (v) P53 knock out in which Mta1 was over expressed using Affymetrix Mouse Exon 1.0 ST arrays. Further Hierarchical Clustering, Gene Ontology analysis with GO terms satisfying corrected p-value<0.1, and the Ingenuity Pathway Analysis were performed. Finally, RT-qPCR was carried out on selective candidate genes. SIGNIFICANCE/CONCLUSION: This study represents a complete genome wide screen for possible target genes of a coregulator, Mta1. The comparative gene profiling of Mta1 wild type, Mta1 knockout and Mta1 re-expression in the Mta1 knockout conditions define "bona fide" Mta1 target genes. Further extensive analyses of the data highlights the influence of P53 on Mta1 gene regulation. In the presence of P53 majority of the genes regulated by Mta1 are related to inflammatory and anti-microbial responses whereas in the absence of P53 the predominant target genes are involved in cancer signaling. Thus, the presented data emphasizes the known functions of Mta1 and serves as a rich resource which could help us identify novel Mta1 functions

An integrative approach to identifying cancer chemoresistance-associated pathways

<p>Abstract</p> <p>Background</p> <p>Resistance to chemotherapy severely limits the effectiveness of chemotherapy drugs in treating cancer. Still, the mechanisms and critical pathways that contribute to chemotherapy resistance are relatively unknown. This study elucidates the chemoresistance-associated pathways retrieved from the integrated biological interaction networks and identifies signature genes relevant for chemotherapy resistance.</p> <p>Methods</p> <p>An integrated network was constructed by collecting multiple metabolic interactions from public databases and the k-shortest path algorithm was implemented to identify chemoresistant related pathways. The identified pathways were then scored using differential expression values from microarray data in chemosensitive and chemoresistant ovarian and lung cancers. Finally, another pathway database, Reactome, was used to evaluate the significance of genes within each filtered pathway based on topological characteristics.</p> <p>Results</p> <p>By this method, we discovered pathways specific to chemoresistance. Many of these pathways were consistent with or supported by known involvement in chemotherapy. Experimental results also indicated that integration of pathway structure information with gene differential expression analysis can identify dissimilar modes of gene reactions between chemosensitivity and chemoresistance. Several identified pathways can increase the development of chemotherapeutic resistance and the predicted signature genes are involved in drug resistant during chemotherapy. In particular, we observed that some genes were key factors for joining two or more metabolic pathways and passing down signals, which may be potential key targets for treatment.</p> <p>Conclusions</p> <p>This study is expected to identify targets for chemoresistant issues and highlights the interconnectivity of chemoresistant mechanisms. The experimental results not only offer insights into the mode of biological action of drug resistance but also provide information on potential key targets (new biological hypothesis) for further drug-development efforts.</p