The bulk Lorentz factors of Fermi-LAT GRBs

The Lorentz factor (LF) of gamma-ray burst (GRB) ejecta may be constrained by observations of high-energy (HE) spectral attenuation. The recent Fermi-LAT observations of prompt GeV emission from several bright GRBs have leaded to conclusions of unexpectedly large LFs, $\Gamma>10^3$. Here we revisit this problem with two main concerns. (1) With one-zone assumption where all photons are assumed to be generated in the same region (radius) and time, we {\em self-consistently} calculate the $\gamma\gamma$ optical depth by adopting a target photon spectrum with HE cutoff. We find that this might be important when the GRB LF is below a few hundreds. (2) Recent Fermi-LAT observations suggest that the bulk MeV-range and HE (\ga100 MeV) emission may arise from different regions. We then consider a two-zone case where HE emission is generated in much larger radii than that of the MeV-range emission. We find that the HE emission may be mainly attenuated by MeV-range emission and that the attenuated HE spectrum does not show an exponential spectral cutoff but a slight steepening. This suggests that there may be no abrupt cutoff due to $\gamma\gamma$ attenuation if relaxing the one-zone assumption. By studying the spectra of three bright Fermi-LAT GRBs 080916C, 090510 and 090902B, we show that a bulk LF of\textbf{ $\Gamma\sim600$ }can be consistent with observations in the two-zone case. Even lower LFs can be obtained in the multi-zone case.Comment: 8 pages, a schematic figure added, the other 5 figures updated, ApJ, in pres

A text-based approach to the ImageCLEF 2010 photo annotation task

The challenges of searching the increasingly large collections of digital images which are appearing in many places mean that automated annotation of images is becoming an important task. We describe our participation in the ImageCLEF 2010 Visual Concept Detection and Annotation Task. Our approach used only the textual features (Flickr user tags and EXIF information) to perform the automatic annotation. Our approach was to explore the use of different techniques to improve the results of textual annotation. We identify the drawbacks of our approach and how these might be addressed and optimized in further work

Failure to detect Xenotropic murine leukaemia virus-related virus in Chinese patients with chronic fatigue syndrome

<p>Abstract</p> <p>Background</p> <p>Recent controversy has surrounded the question of whether xenotropic murine leukaemia virus-related virus (XMRV) contributes to the pathogenesis of chronic fatigue syndrome (CFS). To investigate the question in a Chinese population, 65 CFS patients and 85 blood donor controls were enrolled and multiplex real-time PCR or reverse transcriptase PCR (RT-PCR) was developed to analyze the XMRV infection status of the study participants. The assay was standardized by constructing plasmid DNAs and armored RNAs as XMRV standards and competitive internal controls (CICs), respectively.</p> <p>Results</p> <p>The sensitivities of the multiplex real-time PCR and RT-PCR assays were 20 copies/reaction and 10 IU/ml, respectively, with 100% specificity. The within-run precision coefficient of variation (CV) ranged from 1.76% to 2.80% and 1.70% to 2.59%, while the between-run CV ranged from 1.07% to 2.56% and 1.06% to 2.74%. XMRV was not detected in the 65 CFS patients and 65 normal individuals out of 85 controls.</p> <p>Conclusions</p> <p>This study failed to show XMRV in peripheral blood mononuclear cells (PBMCs) and plasma of Chinese patients with CFS. The absence of XMRV nucleic acids does not support an association between XMRV infection and the development of CFS in Chinese.</p

Prevalence of human herpesvirus 8 infection in systemic lupus erythematosus

<p>Abstract</p> <p>Background</p> <p>For decades, scientists have tried to understand the environmental factors involved in the development of systemic lupus erythematosus (SLE), in which viral infections was included. Previous studies have identified Epstein-Barr virus (EBV) to incite SLE. Human herpesvirus 8 (HHV-8), another member of the gammaherpesvirus family, shares a lot in common with EBV. The characteristics of HHV-8 make it a well-suited candidate to trigger SLE.</p> <p>Results</p> <p>In the present study, serum samples from patients (n = 108) with diagnosed SLE and matched controls (n = 122) were collected, and the prevalence of HHV-8 was compared by a virus-specific nested PCR and a whole virus enzyme-linked immunoassay (EIA). There was significant difference in the prevalence of HHV-8 DNA between SLE patients and healthy controls (11 of 107 vs 1 of 122, <it>p </it>= 0.001); significant difference was also found in the detection of HHV-8 antibodies (19 of 107 vs 2 of 122, <it>p </it>< 0.001).</p> <p>We also detected the antibodies to Epstein-Barr virus viral capsid antigen (EBV-VCA) and Epstein-Barr nuclear antigen-1 (EBNA-1). Both patients and controls showed high seroprevalence with no significant difference (106 of 107 vs 119 of 122, <it>p </it>= 0.625).</p> <p>Conclusion</p> <p>Our finding indicated that there might be an association between HHV-8 and the development of SLE.</p