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University of Missouri, St. Louis

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2008

Articles 1 - 12 of 12

Full-Text Articles in Physical Sciences and Mathematics

Laser-Induced Photon-Branched Chain Reaction In A Chemically-Active Gas-Dispersed Medium, Thomas George, Renat Letfullin, Galen Duree Dec 2008

Laser-Induced Photon-Branched Chain Reaction In A Chemically-Active Gas-Dispersed Medium, Thomas George, Renat Letfullin, Galen Duree

Chemistry & Biochemistry Faculty Works

A promising avenue in the development of high-energy pulsed chemical HF/DF lasers and amplifiers is the utilization of a photon-branched chain reaction initiated in a two-phase active medium, that is, a medium containing a laser working gas and ultradispersed passivated metal particles. These particles are evaporated under the action of IR laser radiation which results in the appearance of free atoms, their diffusion into the gas, and the development of a photon-branching chain process, which involves photons as both reactants and products. The key obstacle here is the formation of a relatively large volume (in excess of 10^3 cm^3) of …

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Time-Resolved Au-Scale Jets Traced By Masers In The Iras 4a/B Regions Of Ngc 1333, Bruce Wilking, Kevin Marvel, Mark Claussen, Alwyn Wootten Sep 2008

Time-Resolved Au-Scale Jets Traced By Masers In The Iras 4a/B Regions Of Ngc 1333, Bruce Wilking, Kevin Marvel, Mark Claussen, Alwyn Wootten

Physics Faculty Works

We present results of VLBI observations of the water masers associated with IRAS 4A and IRAS 4B in the NGC 1333 star-forming region taken in four epochs over a two month period. Both objects have been classified as extremely young sources, and each source is known to be a multiple system. Using the Very Long Baseline Array, we detected 35 masers in epoch I, 40 masers in epoch II, 35 in epoch III, and 24 in epoch IV. Only one identified source in each system is associated with these masers. These data are used to calculate proper motions for the …

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A Simplex Model For Layered Niche Networks, Philip Fraundorf Jul 2008

A Simplex Model For Layered Niche Networks, Philip Fraundorf

Physics Faculty Works

No abstract provided.

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The Peculiar Volatile Composition Of Comet 8p/Tuttle: A Contact Binary Of Chemically Distinct Cometesimals?, Boncho Bonev, Michael Mumma, Yana Radeva, Michael Disanti, Erika Gibb, Geronimo Villanueva Jun 2008

The Peculiar Volatile Composition Of Comet 8p/Tuttle: A Contact Binary Of Chemically Distinct Cometesimals?, Boncho Bonev, Michael Mumma, Yana Radeva, Michael Disanti, Erika Gibb, Geronimo Villanueva

Physics Faculty Works

We report measurements of eight native (i.e., released directly from the comet nucleus) volatiles (H2O, HCN, CH4, C2H2, C2H6, CO, H2CO, and CH3OH) in comet 8P/Tuttle using NIRSPEC at Keck 2. Comet Tuttle reveals a truly unusual composition, distinct from that of any comet observed to date at infrared wavelengths. The prominent enrichment of methanol relative to water contrasts with the depletions of other molecules, especially C2H2, HCN, and H2CO. We suggest that the nucleus of 8P/Tuttle may contain two cometesimals characterized by distinct volatile composition. The relative abundances C2/CN, C2/OH, and CN/OH in 8P/Tuttle (measured at optical/near-UV wavelengths) differ …

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Diethyl 2-[(4-Nitro­Phen­Yl)(4-Phenyl-1,2,3-Selenadiazol-5-Yl)Meth­Yl]Malonate, A. Marx, S. Saravanan, S. Muthusubramanian, V. Manivannan, Nigam Rath Apr 2008

Diethyl 2-[(4-Nitro­Phen­Yl)(4-Phenyl-1,2,3-Selenadiazol-5-Yl)Meth­Yl]Malonate, A. Marx, S. Saravanan, S. Muthusubramanian, V. Manivannan, Nigam Rath

Chemistry & Biochemistry Faculty Works

In the title compound, C22H21N3O6Se, the heterocyclic ring makes dihedral angles of 50.03 (11) and 67.75 (11)°, respectively, with the benzene and phenyl rings. The terminal C atoms of the ester groups are disordered over two positions: the site occupancies for the C atoms are 0.62 (3)/0.38 (3) and 0.48 (3)/0.52 (3). In the crystal structure, weak intra- and inter­molecular C-H...O inter­actions are observed.

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Dioxidobis(2-Oxo-1,2-Dihydropyridin-3-Olato)­Molybdenum(Vi), Manoj Trivedi, Daya Pandey, Nigam Rath Apr 2008

Dioxidobis(2-Oxo-1,2-Dihydropyridin-3-Olato)­Molybdenum(Vi), Manoj Trivedi, Daya Pandey, Nigam Rath

Chemistry & Biochemistry Faculty Works

In the title compound, [Mo(C5H4NO2)2O2], the MoVI atom exhibits a distorted octa­hedral coordination geometry formed by two terminal oxo ligands and two monoanionic O,O-bidentate pyridinone ligands. The two terminal oxo ligands lie in a cis arrangement, the ketonic O atoms of the pyridinone ligands are coordinated trans to the oxo ligands and the deprotonated hydroxyl O atoms are located trans to each other. The crystal structure contains inter­molecular N-H...O hydrogen bonds, C-H...O contacts and face-to-face [pi]-[pi] stacking inter­actions with an inter­planar separation of 3.25 (1) Å.

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4-(4-Chlorophenyl)-5-[1-(4-Chlorophenyl)-2-Methyl-2-Nitropropyl]-1,2,3-Selenadiazole, A. Marx, S. Saravanan, S. Muthusubramanian, V. Manivannan, Nigam Rath Feb 2008

4-(4-Chlorophenyl)-5-[1-(4-Chlorophenyl)-2-Methyl-2-Nitropropyl]-1,2,3-Selenadiazole, A. Marx, S. Saravanan, S. Muthusubramanian, V. Manivannan, Nigam Rath

Chemistry & Biochemistry Faculty Works

In the title compound, C18H15Cl2N3O2Se, the selenadiazole ring makes dihedral angles of 49.87 (3) and 55.70 (3)° with the two benzene rings. The dihedral angle between the two benzene rings is 11.90 (5)°. In the crystal structure, intra­molecular C-H...O and C-H...Se inter­actions and inter­molecular C-H...O, C-H...Cl and C-H...N inter­actions are observed.

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Critically Evaluated Thermochemical Properties Of Polycyclic Aromatic Hydrocarbons, María Roux, Manuel Temprado, James Chickos, Yatsuhisa Nagano Jan 2008

Critically Evaluated Thermochemical Properties Of Polycyclic Aromatic Hydrocarbons, María Roux, Manuel Temprado, James Chickos, Yatsuhisa Nagano

Chemistry & Biochemistry Faculty Works

No abstract provided.

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Thermal Roots Of Correlation-Based Complexity, Philip Fraundorf Jan 2008

Thermal Roots Of Correlation-Based Complexity, Philip Fraundorf

Physics Faculty Works

Bayesian maxent lets one integrate thermal physics and information theory points of view in the quantitative study of complex systems. Since net surprisal (a free energy analog for measuring “departures from expected”) allows one to place second law constraints on mutual information (a multimoment measure of correlations), it makes a quantitative case for the role of reversible thermalization in the natural history of invention, and suggests multiscale strategies to monitor standing crop as well. It prompts one to track evolved complexity starting from live astrophysically observed processes, rather than only from evidence of past events. Various gradients and boundaries that …

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Assessment Of The Influence Factos On In Vitro Testing Of Nasal Sprays Using Box-Behnken Experimental Design, Keith Stine, Changning Guo, John Kauffman, William Doub Jan 2008

Assessment Of The Influence Factos On In Vitro Testing Of Nasal Sprays Using Box-Behnken Experimental Design, Keith Stine, Changning Guo, John Kauffman, William Doub

Chemistry & Biochemistry Faculty Works

The purpose of the research was to investigate the influences of actuation parameters and formulation physical properties on nasal spray delivery performance using design of experiment (DOE) methodology. A 3-level, 4-factor Box-Behnken design with a total of 27 experimental runs was used in this study. Nine simulated aqueous formulations with different viscosities and surface tensions were prepared using carboxymethylcellulose sodium (CMC, gelling agent) and Tween80 (surfactant) each at three concentration levels. Four factors, actuation stroke length, actuation velocity, concentration of gelling agent, and concentration of surfactant were investigated for their influences on measured responses of shot weight, spray pattern, plume …

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Modeling The Physical Properties Of A Homologous Series On The Melting Temperatures And Densities Of N-Alkanes And Their Simple Alkyl-Derivatives, Antun Rubčić, Jasna Rubčić, James Chickos Jan 2008

Modeling The Physical Properties Of A Homologous Series On The Melting Temperatures And Densities Of N-Alkanes And Their Simple Alkyl-Derivatives, Antun Rubčić, Jasna Rubčić, James Chickos

Chemistry & Biochemistry Faculty Works

No abstract provided.

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The Dynamic Evolutionary History Of The Bananaquit (Coereba Flaveola) In The Caribbean Revealed By A Multigene Analysis, Eva Bellemain, Eldredge Bermingham, Robert Ricklefs Jan 2008

The Dynamic Evolutionary History Of The Bananaquit (Coereba Flaveola) In The Caribbean Revealed By A Multigene Analysis, Eva Bellemain, Eldredge Bermingham, Robert Ricklefs

Biology Department Faculty Works

BackgroundThe bananaquit (Coereba flaveola) is a small nectivorous and frugivorous emberizine bird (order Passeriformes) that is an abundant resident throughout the Caribbean region. We used multi-gene analyses to investigate the evolutionary history of this species throughout its distribution in the West Indies and in South and Middle America. We sequenced six mitochondrial genes (3744 base pairs) and three nuclear genes (2049 base pairs) for forty-four bananaquits and three outgroup species. We infer the ancestral area of the present-day bananaquit populations, report on the species' phylogenetic, biogeographic and evolutionary history, and propose scenarios for its diversification and range expansion.ResultsPhylogenetic concordance between …

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