Classical novae are thermonuclear explosions that occur on the surfaces of white dwarf stars in interacting binary systems (Bode & Evans 2008). It has long been thought that the luminosity of ...classical novae is powered by continued nuclear burning on the surface of the white dwarf after the initial runaway (Gallaher & Starrfield 1978). However, recent observations of GeV \(\gamma\)-rays from classical novae have hinted that shocks internal to the nova ejecta may dominate the nova emission. Shocks have also been suggested to power the luminosity of events as diverse as stellar mergers (Metzger & Pejcha 2017), supernovae (Moriya et al. 2018), and tidal disruption events (Roth et al. 2016), but observational confirmation has been lacking. Here we report simultaneous space-based optical and \(\gamma\)-ray observations of the 2018 nova V906 Carinae (ASASSN-18fv), revealing a remarkable series of distinct correlated flares in both bands. The optical and \(\gamma\)-ray flares occur simultaneously, implying a common origin in shocks. During the flares, the nova luminosity doubles, implying that the bulk of the luminosity is shock-powered. Furthermore, we detect concurrent but weak X-ray emission from deeply embedded shocks, confirming that the shock power does not appear in the X-ray band and supporting its emergence at longer wavelengths. Our data, spanning the spectrum from radio to \(\gamma\)-ray, provide direct evidence that shocks can power substantial luminosity in classical novae and other optical transients.
Expression of the Wilms' tumour suppressor gene, WT1, is tightly regulated during nephrogenesis, and loss of function of its gene product correlates with malignancy. By using luciferase reporter gene ...constructs containing DNA sequences from the first intron of the WT1 gene, we have identified an antisense WT1 promoter operational in the opposite direction relative to the 5' promoter. Transcription directed by the promoter is negatively regulated by upstream elements, but is activated by expression of WT1. This effect of WT1 is reciprocal to that observed on the 5' promoter, suggesting that antisense promoter activity is involved in WT1 gene regulation. By mimicking expression of the transcript regulated by the antisense promoter, we demonstrate that cellular levels of WT1 can be effectively down-regulated by antisense mRNA complementary to sequences in the first exon of WT1.
We compare common star-formation rate (SFR) indicators in the local Universe in the GAMA equatorial fields (around 160 sq. deg.), using ultraviolet (UV) photometry from GALEX, far-infrared (FIR) and ...sub-millimetre (sub-mm) photometry from H-ATLAS, and Halpha spectroscopy from the GAMA survey. With a high-quality sample of 745 galaxies (median redshift 0.08), we consider three SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope beta (SFRUV,corr), Halpha line luminosity corrected for dust using the Balmer decrement (BD) (SFRHalpha,corr), and the combination of UV and IR emission (SFRUV+IR). We demonstrate that SFRUV,corr can be reconciled with the other two tracers after applying attenuation corrections by calibrating IRX (i.e. the IR to UV luminosity ratio) and attenuation in the Halpha (derived from BD) against beta. However, beta on its own is very unlikely to be a reliable attenuation indicator. We find that attenuation correction factors depend on parameters such as stellar mass, z and dust temperature (Tdust), but not on Halpha equivalent width (EW) or Sersic index. Due to the large scatter in the IRX vs beta correlation, when compared to SFRUV+IR, the beta-corrected SFRUV,corr exhibits systematic deviations as a function of IRX, BD and Tdust.
Branching fraction and asymmetry measurements of charmless B + → K * + h + 1 h − 2 (where h 1 , 2 = K , π ) decays are presented, using a data sample of 232 × 10 6 Υ ( 4 S ) → B ¯¯¯ B decays ...collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. Using a maximum likelihood fit, the following branching fraction results were obtained: B ( B + → K * + K + K − ) = ( 36.2 ± 3.3 ± 3.6 ) × 10 − 6 and B ( B + → K * + π + π − ) = ( 75.3 ± 6.0 ± 8.1 ) × 10 − 6 . Upper limits were set for B ( B + → K * + π + K − ) < 11.8 × 10 − 6 and B ( B + → K * + K + π − ) < 6.1 × 10 − 6 at 90% confidence level. The charge asymmetries for the decays B + → K * + K + K − and B + → K * + π + π − were measured to be A K ∗ K K = 0.11 ± 0.08 ± 0.03 and A K ∗ π π = 0.07 ± 0.07 ± 0.04 , respectively. The first error quoted on branching fraction and asymmetry measurements is statistical and the second systematic.
We present an analysis of the mid-infrared WISE sources seen within the equatorial GAMA G12 field, located in the North Galactic Cap. Our motivation is to study and characterize the behavior of WISE ...source populations in anticipation of the deep multi-wavelength surveys that will define the next decade, with the principal science goal of mapping the 3D large scale structures and determining the global physical attributes of the host galaxies. In combination with cosmological redshifts, we identify galaxies from their WISE W1 3.4um resolved emission, and by performing a star-galaxy separation using apparent magnitude, colors and statistical modeling of star-counts. The resultant galaxy catalog has ~590,000 sources in 60 deg^2, reaching a W1 5-sigma depth of 31 uJy. At the faint end, where redshifts are not available, we employ a luminosity function analysis to show that approximately 27% of all WISE extragalactic sources to a limit of 17.5 mag (31 uJy) are at high redshift, z > 1. The spatial distribution is investigated using two-point correlation functions and a 3D source density characterization at 5 Mpc and 20 Mpc scales. For angular distributions, we find brighter and more massive sources are strongly clustered relative to fainter and lower mass source; likewise, based on WISE colors, spheroidal galaxies have the strongest clustering, while late-type disk galaxies have the lowest clustering amplitudes. Along the radial direction, the strongest clustering is in the largest redshift shell, while the weakest is in the nearest redshift shell, consistent with the stellar mass and morphological type dependency results. In three dimensions, we find a number of distinct groupings, often bridged by filaments and super-structures. Using special visualization tools, we map these structures, exploring how clustering may play a role with stellar mass and galaxy type.
Rearrangements of mitochondrial DNA (mtDNA) are a well-recognized cause of human disease; deletions are more frequent, but duplications are more readily transmitted to offspring. In theory, partial ...duplications of mtDNA can be resolved to partially deleted and wild-type (WT) molecules, via homologous recombination. Therefore, the yeast CCE1 gene, encoding a Holliday junction resolvase, was introduced into cells carrying partially duplicated or partially triplicated mtDNA. Some cell lines carrying the CCE1 gene had substantial amounts of WT mtDNA suggesting that the enzyme can mediate intramolecular recombination in human mitochondria. However, high levels of expression of CCE1 frequently led to mtDNA loss, and so it is necessary to strictly regulate the expression of CCE1 in human cells to ensure the selection and maintenance of WT mtDNA.
Femtomolar concentrations of hydrogen fluoride, a decomposition component of nerve agents, were detected using a SiO2 microcantilever. The microcantilever underwent bending due to the reaction of HF ...with SiO2. The microcantilever deflection increased as the concentration of HF increased. Other acids, such as HCl, had no effect on the deflection of the cantilever. The mechanism of reaction-induced bending and the correlation of microcantilever deflection with the HF concentration are discussed. The deflection in response to HF of a commercially available silicon cantilever was also studied, and its response was compared with that of the SiO2 cantilever. Much less bending amplitude and sensitivity were observed for the silicon cantilever.
Landmines are affecting the lives and livelihoods of millions of people around the world. A number of detection techniques, developed for use with impulse ground penetrating radar, are described, ...with emphasis on a Kalman filter based approach. Comparison of results from real data show that the Kalman filter algorithm provides the best detection performance, although its computational burden is also the highest.
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