Spins of the supermassive black hole in M87: new constraints from TeV observations

The rapid TeV $\gamma-$ray variability detected in the well-known nearby radio galaxy M87 implies an extremely compact emission region (5-10 Schwarzschild radii) near the horizon of the supermassive black hole in the galactic center. TeV photons are affected by dilution due to interaction with the radiation field of the advection-dominated accretion flow (ADAF) around the black hole, and can thus be used to probe the innermost regions around the black hole. We calculate the optical depth of the ADAF radiation field to the TeV photons and find it strongly depends on the spin of the black hole. We find that transparent radii of 10 TeV photons are of $5R_{\rm S}$ and $13R_{\rm S}$ for the maximally rotating and non-rotating black holes, respectively. With the observations, the calculated transparent radii strongly suggest the black hole is spinning fast in the galaxy. TeV photons could be used as a powerful diagnostic for estimating black hole spins in galaxies in the future.Comment: 4 pages, 4 figures. to appear in ApJ

Repression of histone H5 gene expression in chicken mature erythrocytes is correlated with reduced DNA-binding activities of transcription factors SP1 and GATA-1

AbstractDuring the final stages of erythroid maturation, the expression of the chicken histone H5 gene ceases. The histone H5 promoter has binding sites for Sp1 and UPE-binding protein. The 3' histone H5 enhancer has binding sites for Sp1, GATA-1 and NF1. Here, we show that the DNA-binding activities of transcription factors Sp1 and GATA-1 is reduced 5- to 10-fold in mature cells, while the activities of UPE-binding protein and NF1 remain the same in mature and immature erythrocytes. The reduced activities of Sp1 and GATA-1 may contribute to the inactivation of the histone H5 gene in mature erythrocytes

Blue Noise Sampling using an SPH-based Method

We propose a novel algorithm for blue noise sampling inspired by the Smoothed Particle Hydrodynamics (SPH) method. SPH is a well-known method in fluid simulation -- it computes particle distributions to minimize the internal pressure variance. We found that this results in sample points (i.e., particles) with a high quality blue-noise spectrum. Inspired by this, we tailor the SPH method for blue noise sampling. Our method achieves fast sampling in general dimensions for both surfaces and volumes. By varying a single parameter our method can generate a variety of blue noise samples with different distribution properties, ranging from Lloyd's relaxation to Capacity Constrained Voronoi Tessellations ({CCVT}). Our method is fast and supports adaptive sampling and multi-class sampling. We have also performed experimental studies of the SPH kernel and its influence on the distribution properties of samples. We demonstrate with examples that our method can generate a variety of controllable blue noise sample patterns, suitable for applications such as image stippling and re-meshing

The Additional Line Component within the Iron K\alpha Profile in MCG-6-30-15: Evidence for Blob Ejection?

The EPIC data of MCG -6-30-15 observed by XMM-Newton were analyzed for the complexities of the iron K-alpha line. Here we report that the additional line component (ALC) at 6.9 keV undoubtedly appears within the broad iron Kalpha; line profile at the high state, whereas it disappears at the low state. These state-dependent behaviors exclude several possible origins and suggest an origin of the ALC in matter being ejected from the vicinity of the black hole. At the low state, the newborn blob ejected from the accretion disk is so Thomson-thick that hard X-rays are blocked from ionizing the old blobs, leading to the disappearance of the ALC. When the blob becomes Thomson-thin as a result of expansion, the hard X-ray will penetrate it and ionize the old ones, emitting the ALC at the high state. The blob ejection is the key to switching the ALC on or off.Comment: 6 pages, 4 Figure

Evolutionary Consequences of Dusty Tori in Active Galactic Nuclei

Deep surveys of {\em Chandra} and {\em HST} (Hubble Space Telescope) show that active galactic nucleus (AGN) populations are changing with hard X-ray luminosities. This arises an interesting question whether the dusty torus is evolving with the central engines. We assemble a sample of 50 radio-quiet PG quasars to tackle this problem. The covering factors of the dusty tori can be estimated from the multiwavelength continuum. We find they are strongly correlated with the hard X-ray luminosity. Interestingly this correlation agrees with the fraction of type II AGNs discovered by {\em Chandra} and {\em HST}, implying strong evidence for that the AGN population changing results from the evolution of the tori. We also find that the frequencies of the dips around 1$\mu$m in the continuum correlate with the covering factors in the present sample, indicating the dip frequencies are adjusted by the covering factors. In the scenario of fueling black hole from the torus, the covering factor is a good and the dip frequency is a potential indicator of the torus evolution.Comment: 4 pages in emulateapj5.sty. Accepted by ApJ Letter

Experimental Quantum Communication without a Shared Reference Frame

We present an experimental realization of a robust quantum communication scheme [Phys. Rev. Lett. 93, 220501 (2004)] using pairs of photons entangled in polarization and time. Our method overcomes errors due to collective rotation of the polarization modes (e.g., birefringence in optical fiber or misalignment), is insensitive to the phase's fluctuation of the interferometer, and does not require any shared reference frame including time reference, except the need to label different photons. The practical robustness of the scheme is further shown by implementing a variation of the Bennett-Brassard 1984 quantum key distribution protocol over 1 km optical fiber.Comment: 4 pages, 4 figure

The Accretion Rates and Spectral Energy Distributions of BL Lacertae Objects

We investigate the relationship between accretion rates and the spectral energy distributions (SEDs) of BL Lac objects, using a sample of objects for which published information on the host galaxies, emission-line luminosities, and peak frequencies and luminosities of their SEDs are available. The sample is composed of 43 BL Lac objects which have a relatively continuous distribution of peak frequencies. Under the assumption that the observed emission lines are photoionized by the central accretion disk, we use the line luminosities to estimate the accretion luminosities and hence accretion rates. We find that low frequency-peaked BL Lac objects (LBLs) span a wide range of accretion rates, whereas high frequency-peaked BL Lac objects (HBLs) cover a more restricted range of lower values. There appears to be a continuous distribution of accretion rates between the two subclasses of BL Lac objects. We find that the peak frequency of the SED, \pknu, correlates with the accretion rate, approximately with the form \pknu\propto \Lambda^{-3} in HBLs and \pknu \propto \Lambda^{-0.25} in LBLs, where $\Lambda \equiv L_{\rm lines}/c^2$. The peak luminosity of the SED is also correlated with $\Lambda$. These results suggest that the accretion rate influences the shape of the SED in BL Lac objects. They also support models which couple the jet and the accretion disk. We present a physical scenario to account for the empirical trends.Comment: 6 pages in emulateapj.sty, 3 figures 1 table. The Astrophysical Journal (in press

Phosphorylated serine 28 of histone H3 is associated with destabilized nucleosomes in transcribed chromatin

Histone modifications and variants have key roles in the activation and silencing of genes. Phosphorylation of histone H3 at serine 10 and serine 28 is involved in transcriptional activation of genes responding to stress or mitogen-stimulated signaling pathways. The distribution of H3-modified isoforms in G0 phase chicken erythrocyte chromatin was investigated. H3 phosphorylated at serine 28 was found highly enriched in the active/competent gene fractions, as was H3 di- and trimethylated at lysine 4. The H3 variant H3.3 in this chromatin fraction was preferentially phosphorylated at serine 28. Conversely, H3 phosphorylated at serine 10 was present in all chromatin fractions, while H3 dimethylated at lysine 9 was associated with the chromatin-containing repressed genes. H3 phosphorylated at serine 28 was located at the promoter region of the transcriptionally active, but not competent, histone H5 and β-globin genes. We provide evidence that H3.3 phosphorylated at serine 28 was present in labile nucleosomes. We propose that destabilized nucleosomes containing H3.3 phosphorylated at serine 28 aid in the dynamic disassembly–assembly of nucleosomes in active promoters

Effect of gauge boson mass on the phase structure of QED3_{3}

Dynamical chiral symmetry breaking (DCSB) in QED$_{3}$ with finite gauge boson mass is studied in the framework of the rainbow approximation of Dyson-Schwinger equations. By adopting a simple gauge boson propagator ansatz at finite temperature, we first numerically solve the Dyson-Schwinger equation for the fermion self-energy to determine the chiral phase diagram of QED$_3$ with finite gauge boson mass at finite chemical potential and finite temperature, then we study the effect of the finite gauge mass on the phase diagram of QED$_3$. It is found that the gauge boson mass $m_{a}$ suppresses the occurrence of DCSB. The area of the region in the chiral phase diagram corresponding to DCSB phase decreases as the gauge boson mass $m_{a}$ increases. In particular, chiral symmetry gets restored when $m_{a}$ is above a certain critical value. In this paper, we use DCSB to describe the antiferromagnetic order and use the gauge boson mass to describe the superconducting order. Our results give qualitatively a physical picture on the competition and coexistence between antiferromagnetic order and superconducting orders in high temperature cuprate superconductors.Comment: 10 pages, 2 figure