Tool pre-tensions covers prior to lacing

In securing a bulky object in a storage compartment, a cinching or tightening tool is used to draw two opposing cover halves together at a predetermined tension to permit quick lacing to retain the stored object. This tool is also useful in fabrication industries to draw components together during assembly or treating

On the Nature of X-ray Surface Brightness Fluctuations in M87

X-ray images of galaxy clusters and gas-rich elliptical galaxies show a wealth of small-scale features which reflect fluctuations in density and/or temperature of the intra-cluster medium. In this paper we study these fluctuations in M87/Virgo, to establish whether sound waves/shocks, bubbles or uplifted cold gas dominate the structure. We exploit the strong dependence of the emissivity on density and temperature in different energy bands to distinguish between these processes. Using simulations we demonstrate that our analysis recovers the leading type of fluctuation even in the presence of projection effects and temperature gradients. We confirm the isobaric nature of cool filaments of gas entrained by buoyantly rising bubbles, extending to 7' to the east and south-west, and the adiabatic nature of the weak shocks at 40" and 3' from the center. For features of 5--10 kpc, we show that the central 4'x 4' region is dominated by cool structures in pressure equilibrium with the ambient hotter gas while up to 30 percent of the variance in this region can be ascribed to adiabatic fluctuations. The remaining part of the central 14'x14' region, excluding the arms and shocks described above, is dominated by apparently isothermal fluctuations (bubbles) with a possible admixture (at the level of about 30 percent) of adiabatic (sound waves) and by isobaric structures. Larger features, of about 30 kpc, show a stronger contribution from isobaric fluctuations. The results broadly agree with an AGN feedback model mediated by bubbles of relativistic plasma.Comment: 16 pages, submitted to Ap

From Cycle Rooted Spanning Forests to the Critical Ising Model: an Explicit Construction

Fisher established an explicit correspondence between the 2-dimensional Ising model defined on a graph $G$ and the dimer model defined on a decorated version \GD of this graph \cite{Fisher}. In this paper we explicitly relate the dimer model associated to the critical Ising model and critical cycle rooted spanning forests (CRSFs). This relation is established through characteristic polynomials, whose definition only depends on the respective fundamental domains, and which encode the combinatorics of the model. We first show a matrix-tree type theorem establishing that the dimer characteristic polynomial counts CRSFs of the decorated fundamental domain \GD_1. Our main result consists in explicitly constructing CRSFs of \GD_1 counted by the dimer characteristic polynomial, from CRSFs of $G_1$ where edges are assigned Kenyon's critical weight function \cite{Kenyon3}; thus proving a relation on the level of configurations between two well known 2-dimensional critical models.Comment: 51 pages, 24 figures. To appear, Comm. Math. Phys. Revised version: title has changed. The terminology `correspondence' has been changed to that of `explicit construction' and `mapping

Communications technology satellite output-tube design and development

The design and development of a 200-watt-output, traveling-wave tube (TWT) for the Communications Technology Satellite (CTS) is discussed, with emphasis on the design evolution during the manufacturing phase of the development program. Possible further improvements to the tube design are identified

The Disturbed 17 keV Cluster Associated with the Radio Galaxy 3C 438

We present results from a {\em Chandra} observation of the cluster gas associated with the FR II radio galaxy 3C 438. This radio galaxy is embedded within a massive cluster with gas temperature $\sim$17 keV and bolometric luminosity of 6$\times10^{45}$ ergs s$^{-1}$. It is unclear if this high temperature represents the gravitational mass of the cluster, or if this is an already high ($\sim$ 11 keV) temperature cluster that has been heated transiently. We detect a surface brightness discontinuity in the gas that extends $\sim$600 kpc through the cluster. The radio galaxy 3C 438 is too small ($\sim$110 kpc across) and too weak to have created this large disturbance in the gas. The discontinuity must be the result of either an extremely powerful nuclear outburst or the major merger of two massive clusters. If the observed features are the result of a nuclear outburst, it must be from an earlier epoch of unusually energetic nuclear activity. However, the energy required ($\sim10^{63}$ ergs) to move the gas on the observed spatial scales strongly supports the merger hypothesis. In either scenario, this is one of the most extreme events in the local Universe.Comment: 13 pages, 4 figures, 1 table - accepted for publication in the Astrophysical Journal Letter

Tracing the Evolution of Active Galactic Nuclei Host Galaxies Over The Last 9 Gyr of Cosmic Time

We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 \u3c z \u3c 1.4 within the Sloan Digital Sky Survey, Boötes, and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared, and radio wavelengths. Supermassive black holes undergoing radiatively efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution

The infall of the Virgo elliptical galaxy M60 toward M87 and the gaseous structures produced by Kelvin-Helmholtz instabilities

We present Chandra observations of hot gas structures, characteristic of gas stripping during infall, in the Virgo cluster elliptical galaxy M60 (NGC4649) located 1 Mpc east of M87. 0.5−2 keV Chandra X-ray images show a sharp leading edge in the surface brightness 12.4±0.1 kpc north and west of the galaxy center in the direction of M87 characteristic of a merger cold front due to M60's motion through the Virgo ICM. We measured a temperature of 1.00±0.02 keV for abundance 0.5Z⊙ inside the edge and 1.37+0.35−0.19 keV for abundance 0.1Z⊙ in the Virgo ICM free stream region. We find that the observed jump in surface brightness yields a density ratio of 6.44+1.04−0.67 between gas inside the edge and in the cluster free stream region. If the edge is a cold front due solely to the infall of M60 in the direction of M87, we find a pressure ratio of 4.7+1.7−1.4 and Mach number 1.7±0.3. For 1.37 keV Virgo gas we find a total infall velocity for M60 of 1030±180 kms−1. We calculate the motion in the plane of the sky to be 1012+183−192 km−1 implying an inclination angle ξ=11±3 degrees. Surface brightness profiles show the presence of a faint diffuse gaseous tail. We identify filamentary, gaseous wing structures caused by the galaxy's motion through the ICM. The structure and dimensions of these wings are consistent with simulations of Kelvin-Helmholtz instabilities as expected if the gas stripping is close to inviscid