1,061 research outputs found
The unusual UV continuum of quasar Ton 34 and the possibility of crystalline dust absorption
Luminous quasars are known to display a sharp steepening of the continuum
near 1100A. This spectral feature is not well fitted by current accretion disk
models, unless comptonization of the disk emission is invoked. Absorption by
carbon crystalline dust has been proposed to account for this feature. Ton 34
(z=1.928) exhibits the steepest far-UV decline (F_nu prop nu^{-5.3}) among the
183 quasar HST-FOS spectra analyzed by Telfer et al. It is an ideal object to
test the crystalline dust hypothesis as well as alternative interpretations of
the UV break. We reconstruct the UV spectral energy distribution of Ton 34 by
combining HST, IUE and Palomar spectra. The far-UV continuum shows a very deep
continuum trough, which is bounded by a steep far-UV rise. We fit the trough
assuming nanodiamond dust grains. Extinction by carbon crystalline dust
reproduces the deep absorption trough of Ton 34 reasonably well, but not the
observed steep rise in the extreme UV. We also study the possibility of an
intrinsic continuum rollover. The dust might be part of a high velocity outflow
(13000 km/s), which is observed in absorption in the lines of CIV, OVI, NV and
Ly_alpha.Comment: 7 figures, to appear in A&
Inflation and Relative Price Dispersion in Canada: An Empirical Assessment
The authors investigate empirically the relationship between different aspects of inflation and relative price dispersion in Canada using a Markov regime-switching Phillips curve. They examine three theories that explain movements in relative price dispersion: the signal extraction model, the extension of the signal extraction model, and the menu cost model. The authors show that expected inflation, which is captured by the menu cost model, is the aspect of inflation that is most closely associated with relative price dispersion. Furthermore, this result seems robust to different specifications. The authors, however, cannot completely discard inflation uncertainty (the signal extraction model), especially when using core inflation. They also observe a strong asymmetry regarding the impact of positive and negative unexpected inflation on relative price dispersion using total inflation, but this asymmetry is not observed for core inflation. This suggests that the strong asymmetry arises mainly from the presence of components typically associated with supply shocks, and not from the presence of downward nominal rigidities, as Aarstol (1999) proposes, following Ball and Mankiw (1992a,b).Inflation and prices
Dusty, Radiation Pressure Dominated Photoionization. II. Multi-Wavelength Emission Line Diagnostics for Narrow Line Regions
Seyfert narrow line region (NLR) emission line ratios are remarkably uniform,
displaying only ~0.5 dex variation between galaxies, and even less within an
individual object. Previous photoionization and shock models of this region
were unable to explain this observation without the introduction of arbitrary
assumptions or additional parameters. Dusty, radiation pressure dominated
photoionization models provide a simple physical mechanism which can reproduce
this spectral uniformity between different objects. In the first paper of this
series we described this model and its implementation in detail, as well as
presenting grids of model emission lines and examining the model structures.
Here we explore these models further, demonstrating their ability to reproduce
the observed Seyfert line ratios on standard line diagnostic diagrams in both
the optical and UV. We also investigate the effects that the variation of
metallicity, density and ionizing spectrum have upon both the new paradigm and
the standard photoionization models used hitherto. Along with the standard
diagnostic diagrams we provide several new diagnostic diagrams in the UV,
Optical and IR. These new diagrams can provide further tests of the dusty,
radiation pressure photoionization paradigm as well as being used as
diagnostics of the metallicity, density and ionizing spectrum of the emission
line clouds.Comment: Accepted by ApJS, full pdf including figures can be obtained at
http://www.mso.anu.edu.au/~bgroves/Papers/ApJS2.pd
Sequencing of Proteins Extracted from Stones
Proteins from urinary tract and gallbladder stones were extracted and characterized to determine the composition of the matrix and possibly unravel the role of the organic phase in stone formation. Proteins from crushed stones were extracted by electrodialysis and concentrated in the Amicon centricon cartridge or by lyophilization after dialysis against distilled water. Aliquots were first analyzed by isoelectric focusing in gel and if suitable subjected to two-dimensional (2D) electrophoresis. The most promising spots were harvested and the N-terminal amino acids sequenced, thus providing maximum information with minimum expenditure of material. The 2D separations and amino acid sequences of several protein extracts demonstrated similarities and differences in composition and achieved the identification or demonstration of previously and recently detected polypeptides
The Matrix of Urinary Tract Stones: Protein Composition, Antigenicity, and Ultrastructure
We have extracted proteins from urinary tract stones by electrodialysis and have developed antisera to the core and the shell of a renal stone. The protein composition varies between stones but is identical in the core and the shell of the same stone. One stone antigen is present in the urine of normal individuals and stone formers, as well as in cholesterol gallstone extracts. Electron microscopy of the core of a urate-calcium oxalate stone before and after demineralization reveals a fibrillar structure associated with mineral deposits, as well as aggregates of crystals
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