130 research outputs found
Starburst and cirrus models for submillimeter galaxies
We present radiative transfer models for submillimeter galaxies with
spectroscopic redshifts and mid-infrared spectroscopy from Spitzer/IRS and
analyze available Spitzer/MIPS 24, 70 and 160mu data. We use two types of
starburst models, a cirrus model and a model for the emission of an AGN torus
in order to investigate the nature of these objects. We find that for three of
the objects (25%) cirrus emission alone can account for the mid-infrared
spectrum and the MIPS and submillimeter data. For the remaining objects we find
that we need a combination of starburst and cirrus in order to fit
simultaneously the multi--wavelength data.
We find that the typical submillimeter galaxy has comparable luminosity in
the starburst (median L=10^12.5 Lo) and cirrus (median L=10^12.4 Lo)
components. This could arise if the galaxies have been forming stars
continuously for the last 250Myr with the star formation occurring in the last
5Myr being shrouded by high-optical-depth molecular cloud dust, whereas the
rest of the starlight is attenuated by diffuse dust or cirrus with an Av of
about 1mag.Comment: 9 pages, AA accepte
Carbon–Carbon Bond-Forming Reactions of α-Thioaryl Carbonyl Compounds for the Synthesis of Complex Heterocyclic Molecules
Strategies for the formation of carbon–carbon
bonds from
the α-thioaryl carbonyl products of substituted lactams are
described. Although direct functionalization is possible, a two step
process of oxidation and magnesium-sulfoxide exchange has proven optimal.
The oxidation step results in the formation of two diastereomers that
exhibit markedly different levels of stability toward elimination,
which is rationalized on the basis of quantum mechanical calculations
and X-ray crystallography. Treatment of the sulfoxide with <i>i</i>-PrMgCl results in the formation of a magnesium enolate
that will undergo an intramolecular Michael addition reaction to form
two new stereogenic centers. The relationship between the substitution
patterns of the sulfoxide substrate and the efficiency of the magnesium
exchange reaction are also described
Carbon–Carbon Bond-Forming Reactions of α-Thioaryl Carbonyl Compounds for the Synthesis of Complex Heterocyclic Molecules
Strategies for the formation of carbon–carbon
bonds from
the α-thioaryl carbonyl products of substituted lactams are
described. Although direct functionalization is possible, a two step
process of oxidation and magnesium-sulfoxide exchange has proven optimal.
The oxidation step results in the formation of two diastereomers that
exhibit markedly different levels of stability toward elimination,
which is rationalized on the basis of quantum mechanical calculations
and X-ray crystallography. Treatment of the sulfoxide with <i>i</i>-PrMgCl results in the formation of a magnesium enolate
that will undergo an intramolecular Michael addition reaction to form
two new stereogenic centers. The relationship between the substitution
patterns of the sulfoxide substrate and the efficiency of the magnesium
exchange reaction are also described
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