Preoperative biliary drainage in hilar cholangiocarcinoma: Systematic review and meta-analysis.

BACKGROUND: The role of preoperative biliary drainage (PBD) for hilar cholangiocarcinoma (HCC) remains unclear. The aim of this meta-analysis is to investigate the role of PBD in the treatment of potentially resectable HCC. METHODS: All studies reporting outcomes on patients with PBD vs without PBD were included. A systematic literature search was performed in PubMed, Embase, and the Cochrane Library for studies published between 1980 and 2016. RESULTS: Initial search identified 667 articles. Only 9 studies met the inclusion criteria and were included in this analysis. No significant differences in mortality were observed between the two groups (RR = 0,935; 95% CI = 0,612 to 1429; p = 0,463). Overall morbidity was significantly higher in PBD group (RR = 1266; 95% CI = 1039 to 1543; p = 0,011). No significant differences in transfusion rate, hospital stay, anastomotic leaks, abdominal collections and operative time, were found. Wound infections were significantly higher in PBD group. CONCLUSIONS: PBD seems to be associated with higher postoperative morbidity and increases the risk of wound infections. Further prospective studies are needed to better define the impact of PBD in outcomes after surgery for hilar cholangiocarcinoma.

The power of relativistic jets is larger than the luminosity of their accretion disks.

Theoretical models for the production of relativistic jets from active galactic nuclei predict that jet power arises from the spin and mass of the central supermassive black hole, as well as from the magnetic field near the event horizon. The physical mechanism underlying the contribution from the magnetic field is the torque exerted on the rotating black hole by the field amplified by the accreting material. If the squared magnetic field is proportional to the accretion rate, then there will be a correlation between jet power and accretion luminosity. There is evidence for such a correlation, but inadequate knowledge of the accretion luminosity of the limited and inhomogeneous samples used prevented a firm conclusion. Here we report an analysis of archival observations of a sample of blazars (quasars whose jets point towards Earth) that overcomes previous limitations. We find a clear correlation between jet power, as measured through the γ-ray luminosity, and accretion luminosity, as measured by the broad emission lines, with the jet power dominating the disk luminosity, in agreement with numerical simulations. This implies that the magnetic field threading the black hole horizon reaches the maximum value sustainable by the accreting matter.

Fermi observations of high-energy gamma-ray emission from GRB 080916C.

Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

Compton-dragged Gamma-Ray Bursts Associated with Supernovae.

It is proposed that the gamma-ray photons that characterize the prompt emission of gamma-ray bursts are produced through the Compton-drag process, which is caused by the interaction of a relativistic fireball with a very dense soft photon bath. If gamma-ray bursts are indeed associated with supernovae, then the exploding star can provide enough soft photons for radiative drag to be effective. This model accounts for the basic properties of gamma-ray bursts, i.e., the overall energetics, the peak frequency of the spectrum, and the fast variability, with an efficiency that can exceed 50%. In this scenario, there is no need for particle acceleration in relativistic collisionless shocks. Furthermore, although the Poynting flux may be important in accelerating the outflow, no magnetic field is required in the gamma-ray production. The drag also naturally limits the relativistic expansion of the fireball to Gamma less, similar104.

Simultaneous X-Ray and TeV Observations of a Rapid Flare from Markarian 421.

Mrk 421 was observed for about 2 days with BeppoSAX in 1998 April as part of a worldwide multiwavelength campaign. A large, well-defined flare was observed in X-rays. The same flare was observed simultaneously at TeV energies by the Whipple Observatory gamma-ray telescope. These data provide (1) the first evidence that the X-ray and TeV intensities are well correlated on timescales of hours and (2) the first exactly simultaneous X-ray and TeV spectra. The results imply that the X-ray and TeV photons derive from the same region and from the same population of relativistic electrons. The physical parameters deduced from a homogeneous synchrotron self-Compton model for the spectral energy distribution yield electron cooling times close to the observed variability timescales.