We present results from monitoring the multi-waveband flux, linear polarization, and parsec-scale structure of the quasar PKS 1510−089, concentrating on -2eight major γ-ray flares that occurred during the interval 2009.0-2009.5. The γ-ray peaks were essentially simultaneous with maxima at optical wavelengths, although the flux ratio of the two wavebands varied by an order of magnitude. The optical polarization vector rotated by 720 • during a 5-day period encompassing six of these flares. This culminated in a very bright, ∼ 1 day, optical and γ-ray flare as a bright knot of emission passed through the highest-intensity, stationary feature (the "core") seen in 43 GHz Very Long Baseline Array images. The knot continued to propagate down the jet at an apparent speed of 22c and emit strongly at γ-ray energies as a months-long X-ray/radio outburst intensified. We interpret these events as the result of the knot following a spiral path through a mainly toroidal magnetic field pattern in the acceleration and collimation zone of the jet, after which it passes through a standing shock in the 43 GHz core and then continues downstream. In this picture, the rapid γ-ray flares result from scattering of infrared seed photons from a relatively slow sheath of the jet as well as from optical synchrotron radiation in the faster spine. The 2006-2009.7 radio and X-ray flux variations are correlated at very high significance; we conclude that the X-rays are mainly from inverse Compton scattering of infrared seed photons by 20-40 MeV electrons.

We have carried out first-principles molecular dynamics simulations of silica liquid over a wide range of pressure ͑from 0 to ϳ 150 GPa͒ and temperature ͑3000-6000 K͒ within density functional theory and the pseudopotential approximation. Our results show that the liquid structure is highly sensitive to compression: the average Si-O coordination number increases from 4 at zero pressure initially slowly on compression and then more rapidly after 30% compression, reaching 6.5 at 150 GPa. At low compression, nearly all Si-O coordination environments are fourfold and relatively undistorted, whereas at high compression several coordination types ͑five-, six-, and sevenfold͒ coexist and the polyhedra are significantly distorted. The heat capacity and Grüneisen parameter show little variation with compression within the low-pressure regime and vary rapidly with compression in the high-pressure regime. Results are successfully fitted to the Mie-Grüneisen equation of state and show no evidence of spinodal instability or a temperature of maximum density. The behavior of the self-diffusion coefficient is consistent with a crossover from strong to fragile liquid behavior with increasing temperature and increasing pressure. Both Si and O self-diffusion coefficients vary anomalously at 4000 K-they initially increase with pressure and then decrease upon further compression. This anomalous behavior is absent at higher temperatures.

The structural, dynamical, and electronic properties of liquid MgO have been investigated over a wide range of pressure ͑0 to ϳ 240 GPa͒ and temperature ͑3000-10 000 K͒ using first-principles molecular dynamics ͑FPMD͒ within the framework of density-functional theory and the pseudopotential approximation. Our results show that the liquid structure is highly sensitive to compression: the Mg-O coordination number increases from 5 at zero pressure to 7 at high pressure. The Grüneisen parameter and heat capacity are found to increase upon twofold compression by 40% and 20%, respectively. The dynamical behavior of the liquid phase is characterized by the diffusion coefficient, which is found to decrease with increasing pressure and to increase with increasing temperature in a way that can be accurately characterized by an Arrhenius relationship with activation energy and volume of 0.85 eV and 1.3 Å 3 , respectively. The calculated electronic density of states show that the electronic structure of the liquid phase differs substantially from that of the crystalline phase: the liquid has no band gap and a density of states at the Fermi level increases with increasing volume and temperature.

BackgroundInfection control remains a key challenge for Tuberculosis (TB) control program with an increased risk of TB transmission among health care workers (HCWs), especially in settings with inadequate TB infection control measures. Poor knowledge among HCWs and inadequate infection control practices may lead to the increased risk of nosocomial TB transmission.MethodsAn institution-based cross-sectional survey was conducted in 28 health facilities providing TB services in the Kathmandu Valley, Nepal. A total of 190 HCWs were assessed for the knowledge, attitudes and practices on TB infection control using a structured questionnaire.ResultsThe level of knowledge on TB infection control among almost half (45.8%) of the HCWs was poor, and was much poorer among administration and lower level staff. The knowledge level was significantly associated with educational status, and TB training and/or orientation received. The majority (73.2%) of HCWs had positive attitude towards TB infection control. Sixty-five percent of HCWs were found to be concerned about being infected with TB. Use of respirators among the HCWs was limited and triage of TB suspects was also lacking.ConclusionsOverall knowledge and practices of HCWs on TB infection control were not satisfactory. Effective infection control measures including regular skill-based training and/or orientation for all categories of HCWs can improve infection control practices in health facilities.

We have measured peak apparent speeds of 25.6 ± 7.0 c, 25.6 ± 4.4 c, and 28.2 ± 6.6 c in the jets of 0235+164, 0827+243, and 1406−076, respectively, based on six epochs of high-sensitivity VLBA observations at 22 and 43 GHz during 2002 and 2003 (H 0 =71 km s −1 Mpc −1 , Ω m = 0.27, and Ω Λ = 0.73). These blazars had been identified as potentially having apparent speeds exceeding 40 c in an earlier VLBA survey of EGRET blazars by Jorstad et al. We therefore confirm (with high confidence in 0827+243, and lower confidence in 0235+164 and 1406−076) the presence of highly relativistic pattern speeds in these three jets, although not at the > 40 c levels reported by Jorstad et al. The lower limit to the bulk Lorentz factor implied by the observed apparent speeds is Γ >∼ 25−30 in these three sources, if the pattern speeds are equal to or slower than the bulk flow speed. 4 The > 40 c apparent speed reported by J01 for 0827+243 was actually due to an incorrect redshift for the source. The speed of 40.2 ± 7.6 c reported by J01 for 0827+243 (using our cosmological model) is actually 22.7 ± 4.3 c once the correct redshift is used.