1,721,679 research outputs found
Studies on homogeneous and immobilized metal carbonyl clusters on inorganic oxide
No full textA detailed investigation of the reaction between Os3(C))12 and Ru3(CO)12 with HOR (R = CH3, SiPh3), HOOCR (R = H, CH3) and 2,4-pentanedione was undertaken and the products of the form (μ-H)M3(CO)10(L) and [ M3(CO)10L^-] were characterized by i.r. and n.m.r. spectroscopies. The substitution of (μ-H)Os3(CO)10(O2CCH3) with phosphines is studied and the resulting cluster compounds (μ-H)Os3(CO)9(O2CCH3)(PPh3) isolated and characterized by i.r. and n.m.r. spectroscopies. Infrared and Raman spectroscopic studies of triosmium and triruthenium hydride carbonyl clusters were carried out to determine the hydrogen vibrational frequencies. The hydride modes of vibration in (μ-H)2M3(CO)10, (μ-H)2M3(CO)9(E), (E = S, PPh) and (μ-H) (μ-E')Os3(CO)10 (E' = OR, O2CR and acac) clusters were compared and the ability to identify particular co-ordination modes of hydrogen established. The immobilization of metal carbonyl clusters onto inorganic oxide and phosphine functionalized supports was investigated by i.r. and solid state magic angle spinning n.m.r. The triosmium and triruthenium carbonyls were shown to react with silica and alumina to form [(μ-H)M3(CO)10-O O-silica/alumina] or [(μ-H)M3(CO)10-O-silica/alumina] in mild conditions. The reaction of Os3(CO)11(L) and H20s3(CO)10(L) (L =PPh2(CH)2Si(OEt)3) with silica was shown to give intact supported species, while a surface attached cluster (μ-H)Os3(CO)9(L)break (O O-silica) is proposed to result in the case of (μ-H)_2Os_3(CO)9(L). The rhodium carbonyls Rh4(CO)_11(L) and Rh6(CO)15(L) were found to form initially [ Rh_4(CO)11(L')] and Rh6(CO)15(L') (L' = PPh_2(CH2)2Si-(OEt)3-x(OSi≡)x) which decompose on exposure to air to a common surface containing L'Rh(I)(O)2and Rh(I)(CO2)2. The direct interaction of Rh4(CO)12 and RH6(CO)16, at room temperature, with phosphinated silica was shown to result in initial formation of Rh (CO)12-x(L')x' x = 1,2 and complex surface, containing Rh6(CO)16-x(L')x x = 1, LRh(I)(CO)2, Rh(I)(CO)2 fragments and CO covered metallic rhodium. (D74035/87)</p
Simulation of fluorescence anisotropy experiments: Probing protein dynamics
Get PDFAbstractTime-resolved fluorescence anisotropy decay experiments on a protein-attached dye can probe local protein dynamics and steric restrictions, but are difficult to interpret at the structural level. Aiming at an atomistic description, we have carried out molecular dynamics simulations of such experiments. Our simulations describe an Alexa488 fluorescent dye maleimide derivative covalently attached via a single cysteine to the AB-loop of bacteriorhodopsin. Fluorescence anisotropy decay curves obtained from the simulations agree well with the measured ones. Three anisotropy decay components were resolved and assigned to: 1), the fast dynamics of the attached dye on the picosecond timescale; 2), the slower dynamics of the loop at the one nanosecond timescale; and 3), the overall tumbling of the molecule. For the biologically relevant 1-ns component we identified two processes from simulations, the motion of the flexible loop as well as slow conformational dynamics of the dye. These two processes are not separable by experiment alone. Furthermore, analysis of the correlation between the dye and the protein motion revealed which part and which motion of the protein is actually probed by the experiment. Finally, our simulations allowed us to test the usual and inevitable assumption underlying these types of spectroscopic measurements that the attached dye probe does not severely perturb the protein dynamics. For the case at hand, by comparison with a simulation of the dye-free protein, the perturbation was quantified and found to be small
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Critical Analysis of Chinese Lexicographical Discourse: A Case Study of -zhuyi : 主义 Entries in the Xiandai hanyu cidian 现代汉语词典
No full textThis paper adopts the theoretical framework of critical analysis of lexicographical discourse to carry out a diachronic analysis of the lexicographical treatment of selected -zhuyi -主义(-ism) entries in the 1973, 1996, and 2016 editions of the Xiandai hanyu cidian 现代汉语词典. The present research aims to investigate the ways in which a certain meaning is constructed in the definitions as a neutral core meaning of the selected headwords, by also detecting forms of evaluation in the definitions, as well as discussing changes in the successive definitions
Critical Analysis of Chinese Lexicographical Discourse: A Case Study of -zhuyi 主义 Entries in the Xiandai hanyu cidian 现代汉语词典
No full textThis paper adopts the theoretical framework of critical analysis of lexicographical discourse to carry out a diachronic analysis of the lexicographical treatment of selected -zhuyi -主义(-ism) entries in the 1973, 1996, and 2016 editions of the Xiandai hanyu cidian 现代汉语词典. The present research aims to investigate the ways in which a certain meaning is constructed in the definitions as a neutral core meaning of the selected headwords, by also detecting forms of evaluation in the definitions, as well as discussing changes in the successive definitions
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
- …
