Emblemata: The emblem books of Andrea Alciato

A study of the life and works of the legal scholar and humanist, Andrea Alciato (1492-1550), the originator of the emblem book. The nature of the emblem is elucidated and placed in its historical, intellectual and artistic contexts, with special attention paid to the many and varied published manifestations of Alciato???s emblems from 1531 to 1621.published or submitted for publicationnot peer reviewe

Derivation of a tangent function using an integrated circuit four-quadrant multiplier

A tangent function generator is provided which utilizes input signals proportionate to the sine and cosine of a given angle. The equipment accomplishes a trigonometric manipulation which forms an output signal substantially independent of the input reference voltage but proportional to the tangent of the angle. The device uses a multiplier and operational amplifier

The torquing of circumnuclear accretion disks by stars and the evolution of massive black holes

An accreting massive black hole (MBH) in a galactic nucleus is surrounded by a dense stellar cluster. We analyze and simulate numerically the evolution of a thin accretion disk due to its internal viscous torques, due to the frame-dragging torques of a spinning MBH (the Bardeen-Petterson effect) and due to the orbit-averaged gravitational torques by the stars (Resonant Relaxation). We show that the evolution of the MBH mass accretion rate, the MBH spin growth rate, and the covering fraction of the disk relative to the central ionizing continuum source, are all strongly coupled to the stochastic fluctuations of the stellar potential via the warps that the stellar torques excite in the disk. These lead to fluctuations by factors of up to a few in these quantities over a wide range of timescales, with most of the power on timescales >~(M_bh/M_d)P(R_d), where M_bh and M_d are the masses of the MBH and disk, and P is the orbital period at the disk's mass-weighted mean radius R_d. The response of the disk is stronger the lighter it is and the more centrally concentrated the stellar cusp. As proof of concept, we simulate the evolution of the low-mass maser disk in NGC4258, and show that its observed O(10 deg) warp can be driven by the stellar torques. We also show that the frame-dragging of a massive AGN disk couples the stochastic stellar torques to the MBH spin and can excite a jitter of a few degrees in its direction relative to that of the disk's outer regions.Comment: ApJ, in press. Updated to reflect published version, including high order viscosity terms, improved variability analysi

The spectral appearance of comets from 5 to 20 micrometers: A survey of the data

Based on the concept of comets as being conglomerates of rocks and ices, it is expected that they reflect these components in their emission spectra. Silicate materials (rocks) are common in many astronomical environments and show prominent features at about 10 and 18 micrometers. Carbon should be abundant, but is much more difficult to detect spectroscopically since it has no strong features (except for the hydrogenated form). Ices are present in comets, but they are difficult to detect since they are volatile enough to dissipate when the comet is bright enough to be easily observed in the IR, with present equipment. There are other materials present in comets, but the ones listed above should be the most common and thus dominate the thermal IR spectrum. Most of the IR observations made on comets between 5 and 20 micrometers are summarized. They fall into three broad categories: (1) filter photometry; (2) circular variable filter wheel spectroscopy; and (3) spectra obtained with multidetector grating spectrometers

Constraining the Milky Way's Hot Gas Halo with OVII and OVII Emission Lines

The Milky Way hosts a hot ($\approx 2 \times 10^6$ K), diffuse, gaseous halo based on detections of z = 0 OVII and OVIII absorption lines in quasar spectra and emission lines in blank-sky spectra. Here we improve constraints on the structure of the hot gas halo by fitting a radial model to a much larger sample of OVII and OVIII emission line measurements from XMM-Newton EPIC-MOS spectra compared to previous studies ($\approx$ 650 sightlines). We assume a modified $\beta$-model for the halo density distribution and a constant-density Local Bubble from which we calculate emission to compare with the observations. We find an acceptable fit to the OVIII emission line observations with $\chi^{2}_{red}$ (dof) = 1.08 (644) for best-fit parameters of $n_o r_c^{3\beta} = 1.35 \pm 0.24$ cm$^{-3}$ kpc$^{3\beta}$ and $\beta = 0.50 \pm 0.03$ for the hot gas halo and negligible Local Bubble contribution. The OVII observations yield an unacceptable $\chi^{2}_{red}$ (dof) = 4.69 (645) for similar best-fit parameters, which is likely due to temperature or density variations in the Local Bubble. The OVIII fitting results imply hot gas masses of $M$(< 50 kpc) = $3.8_{-0.3}^{+0.3} \times 10^{9} M_{\odot}$ and $M$(< 250 kpc) = $4.3_{-0.8}^{+0.9} \times 10^{10} M_{\odot}$, accounting for $\lesssim$ 50% of the Milky Way's missing baryons. We also explore our results in the context of optical depth effects in the halo gas, the halo gas cooling properties, temperature and entropy gradients in the halo gas, and the gas metallicity distribution. The combination of absorption and emission line analyses implies a sub-solar gas metallicity that decreases with radius, but that also must be $\geq 0.3 Z_{\odot}$ to be consistent with the pulsar dispersion measure toward the LMC.Comment: 26 pages, 13 figures, Accepted to Ap