The Role of Multiplicity in Disk Evolution and Planet Formation

The past decade has seen a revolution in our understanding of protoplanetary disk evolution and planet formation in single star systems. However, the majority of solar-type stars form in binary systems, so the impact of binary companions on protoplanetary disks is an important element in our understanding of planet formation. We have compiled a combined multiplicity/disk census of Taurus-Auriga, plus a restricted sample of close binaries in other regions, in order to explore the role of multiplicity in disk evolution. Our results imply that the tidal influence of a close (<40 AU) binary companion significantly hastens the process of protoplanetary disk dispersal, as ~2/3 of all close binaries promptly disperse their disks within <1 Myr after formation. However, prompt disk dispersal only occurs for a small fraction of wide binaries and single stars, with ~80%-90% retaining their disks for at least ~2--3 Myr (but rarely for more than ~5 Myr). Our new constraints on the disk clearing timescale have significant implications for giant planet formation; most single stars have 3--5 Myr within which to form giant planets, whereas most close binary systems would have to form giant planets within <1 Myr. If core accretion is the primary mode for giant planet formation, then gas giants in close binaries should be rare. Conversely, since almost all single stars have a similar period of time within which to form gas giants, their relative rarity in RV surveys indicates either that the giant planet formation timescale is very well-matched to the disk dispersal timescale or that features beyond the disk lifetime set the likelihood of giant planet formation.Comment: Accepted to ApJ; 15 pages, 3 figures, 3 tables in emulateapj forma

Fundamental building blocks of nanoporous networks from ultra-small-angle x-ray scattering (USAXS) and small-angle x-ray scattering (SAXS) experiments

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on October 27, 2011).Thesis advisor: Dr. Peter Pfeifer.Vita.Ph. D. University of Missouri--Columbia 2010.A new method of structural analysis that measures the nominal dimensions of pores using ultra-small-angle x-ray scattering (USAXS) and small-angle x-ray scattering (SAXS) data is presented. The characterization technique developed is applied to highly porous carbons that are used for reversible methane and hydrogen storage based on physisorption. Data is analyzed and fit under the primary working assumption that there is only one size and shape of pore and that the number of pores present in the sample is accounted for by the sample porosity, [phi]. The procedure presented in this study is not restricted to the analysis of carbonaceous materials. It is applicable to any porous material in which the nanopore is the fundamental building block. The advantage of our technique in comparison to methods currently used to measure the size and shape of nanopores, is that in addition to a width, at least one additional characteristic length is determinedIncludes bibliographical reference

Synthesis of novel 6-deoxyanthracyclines

An extremely direct route to the 6-deoxyanthracycline skeleton is described. The initial route to quinone 10 failed due to an unexpected complication in the Ago demethylation step. However, starting from 2-bromo- 1,4-dimethoxynaphthalene, furan 17 could be prepared in two steps. Furan 17 was then converted into anthraquinone 19 in five steps. The eight-step route proceeds in 9% overall yield

Diels-Alder reactions using in situ generated quinones

High-yield syntheses of Diels-Alder adducts involving dienes and unstable quinones can be effected by generating the quinone in the presence of the diene with silver oxide