High Energy Variability Of Synchrotron-Self Compton Emitting Sources: Why One Zone Models Do Not Work And How We Can Fix It

With the anticipated launch of GLAST, the existing X-ray telescopes, and the enhanced capabilities of the new generation of TeV telescopes, developing tools for modeling the variability of high energy sources such as blazars is becoming a high priority. We point out the serious, innate problems one zone synchrotron-self Compton models have in simulating high energy variability. We then present the first steps toward a multi zone model where non-local, time delayed Synchrotron-self Compton electron energy losses are taken into account. By introducing only one additional parameter, the length of the system, our code can simulate variability properly at Compton dominated stages, a situation typical of flaring systems. As a first application, we were able to reproduce variability similar to that observed in the case of the puzzling `orphan' TeV flares that are not accompanied by a corresponding X-ray flare.Comment: to appear in the 1st GLAST symposium proceeding

Group II intron mobility occurs by target DNA-primed reverse transcription

AbstractMobile group II introns encode reverse transcriptases and insert site specifically into intronless alleles (homing). Here, in vitro experiments show that homing of the yeast mtDNA group II intron a12 occurs by reverse transcription at a double-strand break in the recipient DNA. A site-specific endonuclease cleaves the antisense strand of recipient DNA at position +10 of exon 3 and the sense strand at the intron insertion site. Reverse transcription of al2-containing pre-mRNA is primed by the antisense strand cleaved in exon 3 and results in cotransfer of the intron and flanking exon sequences. Remarkably, the DNA endonuclease that initiates homing requires both the a12 reverse transcriptase protein and a12 RNA. Parallels in their reverse transcription mechanisms raise the possibility that mobile group II introns were ancestors of nuclear non-long terminal repeat retrotransposons and telomerases

Bacterial group II introns in a deep-sea hydrothermal vent environment

Author Posting. © American Society for Microbiology, 2002. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Applied and Environmental Microbiology 68 (2002): 6392-6398, doi:10.1128/AEM.68.12.6392-6398.2002.Group II introns are catalytic RNAs and mobile retrotransposable elements known to be present in the genomes of some nonmarine bacteria and eukaryotic organelles. Here we report the discovery of group II introns in a bacterial mat sample collected from a deep-sea hydrothermal vent near 9°N on the East Pacific Rise. One of the introns was shown to self-splice in vitro. This is the first example of marine bacterial introns from molecular population structure studies of microorganisms that live in the proximity of hydrothermal vents. These types of mobile genetic elements may prove useful in improving our understanding of bacterial genome evolution and may serve as valuable markers in comparative studies of bacterial communities.This research was supported by a WHOI Townsend postdoctoral scholarship to M.P., by National Science Foundation grant OCE-9712233 to L.M., by NIH grant GM31480 and grant I-1211 from the Robert A. Welch Foundation to P.S.P., and by NASA Astrobiology Cooperative Agreement NCC2-1054 and continuing support from the Unger G. Vetlesen Foundation to M.L.S

A multi-zone model for simulating the high energy variability of TeV blazars

We present a time-dependent multi-zone code for simulating the variability of Synchrotron-Self Compton (SSC) sources. The code adopts a multi-zone pipe geometry for the emission region, appropriate for simulating emission from a standing or propagating shock in a collimated jet. Variations in the injection of relativistic electrons in the inlet propagate along the length of the pipe cooling radiatively. Our code for the first time takes into account the non-local, time-retarded nature of synchrotron self-Compton (SSC) losses that are thought to be dominant in TeV blazars. The observed synchrotron and SSC emission is followed self-consistently taking into account light travel time delays. At any given time, the emitting portion of the pipe depends on the frequency and the nature of the variation followed. Our simulation employs only one additional physical parameter relative to one-zone models, that of the pipe length and is computationally very efficient, using simplified expressions for the SSC processes. The code will be useful for observers modeling GLAST, TeV, and X-ray observations of SSC blazars.Comment: ApJ, accepte

A function for the mitochondrial chaperonin Hsp60 in the structure and transmission of mitochondrial DNA nucleoids in Saccharomyces cerevisiae

The yeast mitochondrial chaperonin Hsp60 has previously been implicated in mitochondrial DNA (mtDNA) transactions: it is found in mtDNA nucleoids associated with single-stranded DNA; it binds preferentially to the template strand of active mtDNA ori sequences in vitro; and wild-type (ρ+) mtDNA is unstable in hsp60 temperature-sensitive (ts) mutants grown at the permissive temperature. Here we show that the mtDNA instability is caused by a defect in mtDNA transmission to daughter cells. Using high resolution, fluorescence deconvolution microscopy, we observe a striking alteration in the morphology of mtDNA nucleoids in ρ+ cells of an hsp60-ts mutant that suggests a defect in nucleoid division. We show that ρ− petite mtDNA consisting of active ori repeats is uniquely unstable in the hsp60-ts mutant. This instability of ori ρ− mtDNA requires transcription from the canonical promoter within the ori element. Our data suggest that the nucleoid dynamics underlying mtDNA transmission are regulated by the interaction between Hsp60 and mtDNA ori sequences

3D Relativistic Magnetohydrodynamic Simulations of Magnetized Spine-Sheath Relativistic Jets

Numerical simulations of weakly magnetized and strongly magnetized relativistic jets embedded in a weakly magnetized and strongly magnetized stationary or weakly relativistic (v = c/2) sheath have been performed. A magnetic field parallel to the flow is used in these simulations performed by the new GRMHD numerical code RAISHIN used in its RMHD configuration. In the numerical simulations the Lorentz factor $\gamma = 2.5$ jet is precessed to break the initial equilibrium configuration. In the simulations sound speeds are $\lesssim c/\sqrt 3$ in the weakly magnetized simulations and $\lesssim 0.3c$ in the strongly magnetized simulations. The Alfven wave speed is $\lesssim 0.07c$ in the weakly magnetized simulations and $\lesssim 0.56c$ in the strongly magnetized simulations. The results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized relativistic magnetohydrodynamic (RMHD) equations capable of describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized relativistically moving sheath. The theoretical dispersion relation allows investigation of effects associated with maximum possible sound speeds, Alfven wave speeds near light speed and relativistic sheath speeds. The prediction of increased stability of the weakly magnetized system resulting from c/2 sheath speeds and the stabilization of the strongly magnetized system resulting from c/2 sheath speeds is verified by the numerical simulation results.Comment: 31 pages, 8 figures, accepted for publicatin in ApJ. A paper with high resolution figures available at http://gammaray.nsstc.nasa.gov/~mizuno/research_new.htm