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First example of cocrystals of polymorphic maleic hydrazide
No full textThe first cocrystals of polymorphic maleic hydrazide with 3-methyluracil have been studied by X-ray diffraction methods. They crystallize in the orthorhombic system, space group Pmcn, a = 6.440 ( 1) Angstrom, b = 6.974 ( 1) Angstrom, c = 22.829 ( 11) Angstrom, V = 1025.3 ( 5) Angstrom(3), Z = 4. The asymmetric unit contains one molecule of each compound. Planar ribbons of the ( 1: 1) molecular complex are obtained through the formation of O-H...O and O-H...N intermolecular hydrogen bonds, just forming a well-known R-2(2)(8) supramolecular synthon. Supramolecular assemblies are then formed by weak C-H...O and C-H...N hydrogen bonds through adjacent antiparallel ribbons
Solid-Phase Molecular Recognition of Cytosine Based on Proton-Transfer Reaction
No full textThe proton-transfer molecular adducts cytosine/isoorotic acid (1: 1) dihydrate (CytIsor) and cytosine/maleic hydrazide (2: 2) dihydrate (CytMal) have been studied by X-ray diffraction methods. CytIsor crystallizes in the orthorhombic system, space group Pbnb, a = 7.4859 4), b = 12.7977 (9), c = 26.4573 (16) angstrom, V = 2534.7 (3) angstrom(3). CytMal crystallizes in the triclinic system, space group P - 1, a = 6.7767 ( 9), b = 12.063 ( 2), c = 12.937 (3) angstrom, alpha = 78.58 (2), beta = 75.87 (2), gamma = 75.63 (1)degrees, V = 982.8 (3) angstrom(3). In both compounds protonation occurs at the N3 atom of the cytosine aminooxo tautomer as a result of the proton-transfer process from the acidic hydroxy groups of the counterions. In the crystal structure, both cocrystals are stabilized by a plethora of N-H center dot center dot center dot O, N-H center dot center dot center dot N and O-H center dot center dot center dot O hydrogen bonds. It is shown the ability of cytosine to form large organic assemblies, with the appropriate guest, due to solid-state recognition involving synthons based on hydrogen bonding between functional groups as sites of proton-transfer reactions
The Effect of Hydrogen Bonding on the Structures of Uracil and Some Methyl Derivatives Studied by Experiment and Theory.
No full textSynthesis and Structural Investigations of Novel Palladium(II) and Rhodium(I) Complexes Containing Chiral Ligands with a Stereogenic Sulfur Donor, Such As â-Amino Sulfoxides and C2-Symmetric Bis-Sulfoxides
No full textTwo kinds of new optically active chelating ligands bearing a chiral sulfinyl functionality,
namely the 3,4-bis-(p-tolylsulfinyl)hexanes 4 and the N-mono- and N,N-disubstituted â-ptolylsulfinyl
ethylamines 5 and 2, have been synthesized and their coordination chemistry
with Pd(II) and Rh(I) metals has been studied in detail. Complexes formed with ligands 4
featured a homocoordination between the two sulfur donors and the metal atom, in solution
as well as in the solid state, as demonstrated by X-ray diffraction of cis-dichloro[3,4-bis-(ptolylsulfinyl)
hexane]palladium(II) ((3R,4R,RS,RS)-7), in which the ligand shows a C2 symmetry.
Complexes formed with ligands 2 and 5 showed a heterocoordination of the metal by
the sulfur and the nitrogen donors, as confirmed by X-ray diffraction of cis-dichloro[N,Ndimethyl-
2-(p-tolylsulfinyl)ethylamine]palladium(II) ((R)-6). All nine complexes 6-11, displaying
a monomeric structure, have been synthesized and completely characterized in the
solid state (IR, MS-FAB) as well as in solution (1H and 13C NMR, alpha 25
D
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
Le lastre Campana e l’uso del colore su lastre architettoniche fittili nella tarda Repubblica e nella prima età imperiale. Archeologia e Archeometria
No full textLe Lastre Campana sono lastre architettoniche fittili prodotte in ambito urbano e suburbano tra l’inizio del I secolo a.C. e la fine del I sec. d.C. Ultima espressione della lunghissima tradizione artistica ed artigiana legata alla decorazione fittile dei templi italici, le lastre Campana se ne discostano non solo per l’ambito di utilizzo, edifici pubblici e privati non templari, ma anche per la varietà di temi e le vivaci policromie. Lo studio di questi materiali si è sempre fondato sulla sola analisi stilistica, cui fa eccezione la recente pubblicazione del Museo Kostner di Hannover, e, a fronte di una immensa quantità di frammenti rinvenuti in scavi o sparsi in tutti i principali musei europei, non ha finora riguardato il punto di vista tecnologico ed archeometrico. Difficile risulta anche desumere dalla documentazione fotografica, solitamente in bianco e nero, la presenza di colore e dei suoi ambiti di applicazione. Se infatti negli ultimi anni si è sviluppato un intenso filone di studio della policromia delle statue antiche, sulle lastre Campana non si è mai tentata l’identificazione dei pigmenti e lo studio delle tecniche utilizzate per l’applicazione degli stessi, anche se soggetti ad altrettanti pericoli conservativi. Il primo obbiettivo è stato quindi cercare di capire quali colori erano applicati e dove, con il supporto dei paralleli studi effettuati per materiali marmorei e architettonici e con il fondamentale aiuto di alcune tecniche analitiche non invasive e micro distruttive.
Dopo un’attenta osservazione al microscopio ottico, i colori sono stati classificati in relazione al loro Fattore di Riflessione Spettrale. Sono stati poi individuati gli elementi caratterizzanti la superficie dipinta con la fluorescenza X e quindi sono stati fatti dei micro prelievi per la diffrazione X per l’identificazione dei composti.
L’individuazione del blu egiziano è stata confermata utilizzando la tecnica della luminescenza indotta nel visibile
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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