23,091 research outputs found
Stability of the Zagreb Carnegie-Mellon-Berkeley model
In ref. [1] we have used the Zagreb realization of Carnegie-Melon-Berkeley
coupled-channel, unitary model as a tool for extracting pole positions from the
world collection of partial wave data, with the aim of eliminating model
dependence in pole-search procedures. In order that the method is sensible, we
in this paper discuss the stability of the method with respect to the strong
variation of different model ingredients. We show that the Zagreb CMB procedure
is very stable with strong variation of the model assumptions, and that it can
reliably predict the pole positions of the fitted partial wave amplitudes.Comment: 25 pages, 12 figures, 19 table
Phosphine-Catalyzed Annulations of Azomethine Imines: Allene-Dependent [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] Pathways
In this paper we describe the phosphine-catalyzed [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] annulations of azomethine imines and allenoates. These processes mark the first use of azomethine imines in nucleophilic phosphine catalysis, producing dinitrogen-fused heterocycles, including tetrahydropyrazolo-pyrazolones, -pyridazinones, -diazepinones, and -diazocinones. Counting the two different reaction modes in the [3 + 3] cyclizations, there are five distinct reaction pathways—the choice of which depends on the structure and chemical properties of the allenoate. All reactions are operationally simple and proceed smoothly under mild reaction conditions, affording a broad range of 1,2-dinitrogen-containing heterocycles in moderate to excellent yields. A zwitterionic intermediate formed from a phosphine and two molecules of ethyl 2,3-butadienoate acted as a 1,5-dipole in the annulations of azomethine imines, leading to the [3 + 2 + 3] tetrahydropyrazolo-diazocinone products. The incorporation of two molecules of an allenoate into an eight-membered-ring product represents a new application of this versatile class of molecules in nucleophilic phosphine catalysis. The salient features of this protocol—the facile access to a diverse range of nitrogen-containing heterocycles and the simple preparation of azomethine imine substrates—suggest that it might find extensive applications in heterocycle synthesis
Toward a Multicultural Mid-Tudor England
Through close-readings of Mary Tudor's royal entry, the anonymous interlude Wealth and Health, and John Christopherson's Exhortation alongside anecdotes of popular resistance to Mary Tudor's antiimmigrant proclamations, this article shows that rather than a strong identification with the monarch or some sense of Englishness, Londoners more closely identified with their multicultural metropolitan community for religious and economic reasons
Thurgood Marshall: Tax Lawyer
During his twenty-four years on the Supreme Court, Justice Thurgood Marshall wrote better opinions on the law of federal income taxation than any of his fellow Justices. This is, of course, a subjective appraisal which others may dispute. Nevertheless, from two decades of teaching federal income taxation, I am convinced of the quality of Marshall\u27s work
Shock tube measurements of growth constants in the branched chain formaldehyde-carbon monoxide-oxygen system
Exponential free radical growth constants were measured for formaldehyde carbon monoxide-oxygen systems by monitoring the growth of oxygen atom concentration as manifested by CO flame band emission. Data were obtained over the temperature range of 1200 to 2000 K. The data were analyzed using a formaldehyde oxidation mechanism involving 12 elementary reaction steps. The computed growth constants are roughly in accord with experimental values, but are much more temperature dependent. The data was also analyzed assuming formaldehyde is rapidly decomposed to carbon monoxide and hydrogen. Growth constants computed for the resulting carbon monoxide hydrogen oxygen mixtures have a temperature dependence similar to experiments; however, for most mixtures, the computed growth constants were larger than experimental values
Optical photometry of the UCM Lists I and II. II-B band surface photometry and morphological discussion
We present Johnson B surface photometry for the UCM Survey galaxies.
One-dimensional bulge-disk decomposition is attempted, discussing on fitting
functions and computational procedures. The results from this decomposition,
jointly with concentration indices and an asymmetry coefficient, are employed
to study the morphological properties of these galaxies. We also compare our
results with the previous morphological classification established using Gunn r
imaging data and with other samples of galaxies. No major statistical
differences in morphology are found between red and blue data, although some
characteristics such as size and luminosity concentration vary. We find a
correlation between luminosity and size. Several parameters are used to
segregate the objects according to their morphological type.Comment: 19 pages, 20 PostScript figures, accepted for publication in A&A,
also available via anonymous ftp at
ftp://cutrex.fis.ucm.es/pub/OUT/pag/PAPERS/AA0
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