KITD816V+ systemic mastocytosis associated with KITD816V+ acute erythroid leukaemia: first case report with molecular evidence for same progenitor cell derivation

Toll-like receptor (TLR)-9 recognizes CpG motifs in microbial DNA. TLR9 signalling stimulates innate antimicrobial immunity and modulates adaptive immune responses including autoimmunity against chromatin, e.g., in systemic lupus erythematosus (SLE). This review summarizes the available data for a role of TLR9 signalling in lupus and discusses the following questions that arise from these observations: 1) Is CpG-DNA/TLR9 interaction involved in infection-induced disease activity of lupus? 2) What are the risks of CpG motifs in vaccine adjuvants for lupus patients? 3) Is TLR9 signalling involved in the pathogenesis of lupus by recognizing self DNA

Mass accretion rate of the galactic black hole A0620-00 in its quiescent state

Our recent radio observation using the Giant Meter Radio Telescope (GMRT) of the galactic black hole transient A0620-00 at 1.280GHz revealed a micro-flare of a few milli-Jansky. Assuming an equipartition of magnetic energy and the gravitational potential energy of accreting matter, it is possible to estimate the upper limit of the accretion rate. Assuming a black hole mass of $10M_\odot$ residing at the center, we find this to be at the most ${\dot M} = (8.5 \pm 1.4) \times 10^{-11} M_\odot$ yr$^{-1}$. This is consistent with earlier estimates of accretion rates based on optical and X-ray observations.Comment: 3 pages 1 figur

The politics of representation in the politics of anti-racism

In this short response to Gavan Titley’s new book Racism and Media, I engage with his discussion of the politics of the representation in relation to his important concept of debatability. I underline two key contributions made by Titley in the chapter “The Politics of Representation in Postracial Media Culture”: (1) the limitations of an anti-racist politics based on media representation alone and (2) how the politics of representation and the commentary and debate that it generates has become commodified and transformed into media content itself. I end the piece by suggesting some new routes for media-based anti-racist interventions, targeted at the level of political economy of the cultural industries

Advection-Dominated Accretion and Black Hole Event Horizons

The defining characteristic of a black hole is that it possesses an event horizon through which matter and energy can fall in but from which nothing escapes. Soft X-ray transients (SXTs), a class of X-ray binaries, appear to confirm this fundamental property of black holes. SXTs that are thought to contain accreting black holes display a large variation of luminosity between their bright and faint states, while SXTs with accreting neutron stars have a smaller variation. This difference is predicted if the former stars have horizons and the latter have normal surfaces.Comment: 11 pages, including 2 tables and 2 figures. To appear in The Astrophysical Journal Letter

Anti-correlated Soft Lags in the Intermediate State of Black Hole Source GX 339-4

We report the few hundred second anti-correlated soft lags between soft and hard energy bands in the source GX 339-4 using RXTE observations. In one observation, anti-correlated soft lags were observed using the ISGRI/INTEGRAL hard energy band and the PCA/RXTE soft energy band light curves. The lags were observed when the source was in hard and soft intermediate states, i.e., in a steep power-law state.We found that the temporal and spectral properties were changed during the lag timescale. The anti-correlated soft lags are associated with spectral variability during which the geometry of the accretion disk is changed. The observed temporal and spectral variations are explained using the framework of truncated disk geometry. We found that during the lag timescale, the centroid frequency of quasi-periodic oscillation is decreased, the soft flux is decreased along with an increase in the hard flux, and the power-law index steepens together with a decrease in the disk normalization parameter. We argue that these changes could be explained if we assume that the hot corona condenses and forms a disk in the inner region of the accretion disk. The overall spectral and temporal changes support the truncated geometry of the accretion disk in the steep power-law state or in the intermediate state.Comment: published in ApJ, 9 pages, 8 figure

X-ray Nova XTE J1550-564: RXTE Spectral Observations

Excellent coverage of the 1998 outburst of the X-ray Nova XTE J1550-564 was provided by the Rossi X-ray Timing Explorer. XTE J1550-564 exhibited an intense (6.8 Crab) flare on 1998 September 19 (UT), making it the brightest new X-ray source observed with RXTE. We present a spectral analysis utilizing 60 Proportional Counter Array spectra from 2.5-20 keV spanning 71 days, and a nearly continuous All Sky Monitor light curve. The spectra were fit to a model including multicolor blackbody disk and power-law components. XTE J1550-564 is observed in the very high, high/soft, and intermediate canonical outburst states of Black Hole X-ray Novae.Comment: 14 pages including 1 table and 4 figures, Accepted to ApJ Letter

HST/STIS UV Spectroscopy of Two Quiescent X-ray Novae: A0620-00 and Centaurus X-4

In 1998 we made UV spectroscopic observations with HST/STIS of A0620-00 and Cen X-4, which are two X-ray novae (aka soft X-ray transients). These binary systems are similar in all respects except that the former contains a black hole and the latter contains a neutron star. A UV spectrum (1700-3100A) is presented for the quiescent state of each system in the context of previously published UV/optical and X-ray data. The non-stellar, continuum spectrum of black hole A0620-00 has a prominent UV/optical peak centered at about 3500A. In contrast the spectrum of neutron-star Cen X-4 lacks a peak and rises steadily with frequency over the entire UV/optical band. In the optical, the two systems are comparably luminous. However, black hole A0620-00 is about 6 times less luminous at 1700A, and about 40 times less luminous in the X-ray band. The broadband spectrum of A0620-00 is discussed in terms of the advection-dominated accretion flow model.Comment: 18 pages including 4 figures; tentatively scheduled for the March 10, 2000 issue of ApJ; minor revision