1,720,991 research outputs found
Stereochemical analysis of cobalt(III) complexes with tridentate imino- and amino-oxime ligands.
No full textStereochemical features of the disulfoxides 1,3-bis(n-propylsulfinyl)propane (BPSP) and 1,2-bis(methylsulfinyl)ethane (BMSE), and their copper(II) complexes. Crystal and molecular structure of meso-BPSP, [trans-Cu(meso-BPSP)(2)(H2O)(2)](ClO4)(2), trans-Cu(meso-BMSE)(2)(ClO4)(2), and trans-Cu(rac-BMSE)(2)(ClO4)(2)
No full textDiastereomeric meso and rac forms of 1,3-bis(n-propylsulfinyl)propane (BPSP) and 1,2-bis(methylsulfinyl)ethane (BMSE) have been separated and treated with CU(ClO4)(2) to obtain [trans-Cu(meso-BPSP)(2)(H2O)(2)](ClO4)(2) (2) trans-Cu(meso-BMSE)(2)(ClO4)(2) (3) and trans-Cu(rac-BMSE)(2)(ClO4)(2) (4). The configurational assignment to BPSP has been performed by single crystal X-ray analysis, showing that the alpha (m.p. 139.0-139.9 degreesC) and beta (m.p. 107.0-107.6 degreesC) forms correspond to the meso and rac isomers. respectively. Enthalpies of fusion, determined by differential scanning calorimetry techniques, are 34.3 (meso-BMSE), 22.2 (rac-BMSE), 40.6 (meso-BPSP), and 35.1 kJ mol(-1) (rac-BPSP). Single crystals, acceptable for X-ray diffraction studies, were grown by the hanging-drop method of vapor diffusion and micro-seeding techniques. The crystal structure of meso-BPSP.(1) is characterized by an anti conformation of the propane bridge. The two sulfinyl bonds (av. S-O bond distance, 1.487(4) Angstrom) are nearly parallel. In fact, the S --> O vectors form an angle of 2.3 degrees and the pseudo-torsion angle O-S . . .S-O is of 2.2 degrees. Crystals belong to the C2/c space group, with a = 32.285(11), b = 5.315(5), c = 15.232(7) Angstrom, beta = 109.98(3)degrees. The structure was refined to R = 0.092. Crystal data for the copper complexes are space group P2/n, a = 13.914(7), b = 7.834(4), c = 14.805(11) Angstrom, beta = 96.61(5)degrees for 2; space group P2(1)/c, a = 7.348(7), b = 17.892(4), c = 8.620(2) Angstrom, beta = 113.06(2)degrees for 3; space group P2(1)/a, a = 8.343(3), b = 12.337(6), c = 9.390(3) Angstrom, beta = 97.35(3)degrees for 4. The structures were refined to R = 0.066, 0.062, and 0.097 for 2, 3, and 4, respectively. The crystal structures of the meso Cu(II) complexes 2 and 3 are characterized by linear chains of copper atoms, bridged by two disulfoxide molecules acting as bis-monodentate O-ligands. In the rac complex 4, BMSE acts again as a mu (2)-O,O ligand, but forms layers with a net structure containing four copper atoms per mesh, and each layer contains sulfur atoms with both R and S chirality. In the copper complexes the mean S-O bond length is of 1.520(3) Angstrom, confirming the already observed increase in comparison to free sulfoxides. (C) 2001 Elsevier Science BN. All rights reserved
A molecular mechanics force field for alkylcobaloximes, a model of vitamin B-12 coenzyme. Implications of steric and electronic factors in the Co-C bond cleavage
No full textEffects of long term feeding diets differing in protein source and pre-slaughter starvation on biometry, qualitative traits and liver IGF-I expression in large rainbow trout
Full text linkThe effects of feeding two complete extruded diets differing in protein source (fish meal-FM vs. vegetable proteins-VP) over 30 weeks and subsequent 30 days of starvation on biometry, fillet composition and liver IGF-I mRNNA were studied in large rainbow trout. At the end of the feeding period, the dietary protein source little affected major biometry traits, dressing out yields and overall adiposity (P>0.05) but fish given the VP diet resulted in higher content of PUFA n-6 fatty acids in muscle (0.46 vs. 0.22 g/100g fillet, P<0.05). Regardless of the previous diet, 30 days of starvation resulted in increased carcass yield (P<0.05), in a slight reduction in adiposity (P>0.05) and of all fatty acids in fillet (P<0.05), except DHA. Liver IGF-I mRNNA content was little affected by the test diet and starvation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Steric properties of sulfoxide ligands. Synthesis and crystal-structure of mer-[RuCl3(Ph(2)SO)3]
No full textNew geometrical and linkage isomers of the Ru(II) precursor cis,cis,trans-RuCl2(dmso-S)2(dmso-O)(CO): a spectroscopic and structural investigation
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