On the masses of black-holes in radio-loud quasars

The central black-hole masses of a sample of radio-loud quasars are estimated by using the data of $H_{\beta}$ line-width and the optical continuum luminosity. The vast majority of the quasars in this sample have black-hole masses larger than $10^{8} M_{\odot}$, while a few quasars may contain relatively smaller black-holes. We found a significant anti-correlation between the radio-loudness and the central black-hole mass. It might imply that the jet formation is governed by the black-hole mass.Comment: 5 pages, two figures are added, accepted by MNRAS Letter

A strongly inhomogeneous superfluid in an iron-based superconductor

Among the mysteries surrounding unconventional, strongly correlated superconductors is the possibility of spatial variations in their superfluid density. We use atomic-resolution Josephson scanning tunneling microscopy to reveal a strongly inhomogeneous superfluid in the iron-based superconductor FeTe0.55Se0.45. By simultaneously measuring the topographic and electronic properties, we find that this inhomogeneity in the superfluid density is not caused by structural disorder or strong inter-pocket scattering, and does not correlate with variations in Cooper pair-breaking gap. Instead, we see a clear spatial correlation between superfluid density and quasiparticle strength, putting the iron-based superconductors on equal footing with the cuprates and demonstrating that locally, the quasiparticles are sharpest when the superconductivity is strongest. When repeated at different temperatures, our technique could further help elucidate what local and global mechanisms limit the critical temperature in unconventional superconductors

Why are some BL Lacs detected by \fermi, but others not ?

By cross-correlating an archival sample of 170 BL Lacs with 2 year \fermilat AGN sample, we have compiled a sample of 100 BL Lacs with \fermi detection (FBLs), and a sample of 70 non-\fermi BL Lacs (NFBLs). We compared various parameters of FBLs with those of NFBLs, including the redshift, the low frequency radio luminosity at 408 MHz ($L_{\rm 408MHz}$), the absolute magnitude of host galaxies ($M_{\rm host}$), the polarization fraction from NVSS survey ($P_{\rm NVSS}$), the observed arcsecond scale radio core flux at 5 GHz ($F_{\rm core}$) and jet Doppler factor; all the parameters are directly \textbf{measured} or derived from available data from literatures. We found that the Doppler factor is on average larger in FBLs than in NFBLs, and the $Fermi~ \gamma$-ray detection rate is higher in sources with higher Doppler factor. In contrast, there are no significant differences in terms of the intrinsic parameters of redshift, $L_{\rm 408MHz}$, $M_{\rm host}$ and $P_{\rm NVSS}$. FBLs seem to have a higher probability of exhibiting measurable proper motion. These results strongly indicate a higher beaming effect in FBLs compared to NFBLs. The radio core flux is found to be strongly correlated with $\gamma$-ray flux, which remains after excluding the common dependence of the Doppler factor. At the fixed Doppler factor, FBLs have systematically larger radio core flux than NFBLs, implying lower $\gamma$-ray emission in NFBLs since the radio and $\gamma$-ray flux are significantly correlated. Our results indicate that the Doppler factor is an important parameter of $\gamma$-ray detection, the non-detection of $\gamma$-ray emission in NFBLs is likely due to low beaming effect, and/or low intrinsic $\gamma$-ray flux, and the gamma-rays are likely produced co-spatially with the arcsecond-scale radio core radiation and mainly through the SSC process.Comment: 6 pages, 6 figures, accepted by A&

Cu nuclear magnetic resonance study of charge and spin stripe order in La1.875_{1.875}Ba0.125_{0.125}CuO4_4

We present a Cu nuclear magnetic/quadrupole resonance study of the charge stripe ordered phase of LBCO, with detection of previously unobserved ('wiped-out') signal. We show that spin-spin and spin-lattice relaxation rates are strongly enhanced in the charge ordered phase, explaining the apparent signal decrease in earlier investigations. The enhancement is caused by magnetic, rather than charge fluctuations, conclusively confirming the long-suspected assumption that spin fluctuations are responsible for the wipeout effect. Observation of the full Cu signal enables insight into the spin and charge dynamics of the stripe-ordered phase, and measurements in external magnetic fields provide information on the nature and suppression of spin fluctuations associated with charge order. We find glassy spin dynamics, in agreement with previous work, and incommensurate static charge order with charge modulation amplitude similar to other cuprate compounds, suggesting that the amplitude of charge stripes is universal in the cuprates.Comment: 7 pages, 5 figure

Cylindrical couette flow in the transition regime by the method of moments

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The moment method is employed to study the characteristics of cylindrical Couette gas flow under rarefied conditions. Computed velocity profiles from the linearised R13 and R26 moment equations are compared with direct simulation Monte Carlo data. It is found that the moment method can extend the macroscopic equations into the early transition regime, but the surface curvature narrows the validity range of the macroscopic models. The slip velocity on the inner and outer cylinder is not equal due to curvature effects and the torque acting on the cylinder wall decreases as the rarefaction becomes stronger