1,721,042 research outputs found
The interaction of the polyphenylacetylene surface with biological environments studied by XPS, RAIRS and biological tests.
No full textAbstract
A pi-conjugated polymer, polyphenylacetylene or PPA, has been tested for its possible applications as biosensor or biomaterial. Protein adsorption was investigated by incubating PPA films in solutions of bovine serum albumin (BSA) dissolved in phosphate buffer (PBS) having increasing protein concentration. Investigations on the PPA films were carried out by means of two surface analysis techniques, X-ray photoelectron spectroscopy (XPS) and reflection-absorption infrared spectroscopy (RAIRS). Desorption of BSA from the PPA surface was also investigated. Finally, the cytototoxicity of the PPA surface was checked by measuring viability and proliferation of lymphoma macrophages and SAOS osteoblasts grown in the presence of the polymer
H2S gas interaction with Pt(II)-containing polymetallaynes of selected chain length: An XPS and EXAFS study
No full textThe interaction between gaseous H2S and the surface of several metal-containing oligomers, investigated by emission and absorption spectroscopies, is presented and discussed. The polymetallayne trans-{Cl-[Pt(PBu3)(2)(C C-C6H4-C6H4-C C)](9)Pt(PBu3)(2)Cl} and related model molecules, i.e. the binuclear transition metal dialkynyl bridged Pt(II) square planar complex trans,trans-[ClPt(PBu3)(2)(C C-C6H4-C6H4 Pt(PBu3)(2)CI], the tetranuclear linear oligomer trans-[Cl-[Pt(PBu3)(2)(C C-C6H4-C6H4-C C)](3)Pt(PBu3)(2)Cl}, the tetranuclear cyclic oligomer cis- [Pt(PBu3)(2)(C C - C6H4-C6H4 -C C)](4), were exposed to hydrogen sulfide and then investigated by X-ray photoelectron (XPS) and X-ray absorption (XAS) spectroscopies, in order to shed light on the gas/polymer interaction associated to the sensing properties of these materials. XPS measurements evidenced the presence of S in the polymetallayne samples exposed to H2S, and the measured S2p binding energy values correlate with H2S adsorbed by means of sulfur atoms chemically bonded to metal atoms, owing to the formation of sulfur-containing adducts. XAS data analysis suggested a squarepyramidal geometry around the transition metal with H2S in the apical position for the pentacoordinated platinum units
The reaction between Pt- and Pd-cis di-chloro complexes and 4,4'-diethynylbiphenyl: synthesis and characterization of a zig-zag metal/poly-yne polymer
No full textThe synthesis of poly-yne polymers containing transition metals inserted in the main chain has been attempted by reacting a dialkyne molecule, 4,4'-diethynylbiphenyl (or DEBP), with [PtCl2(dppe)] and [PdCl2(dppe)], the platinum- and palladium-cis square-planar dichlorine complexes containing diphenylphosphine ethane (dppe) as bidentate ligand. The aim of this work was to obtain organometallic polymers ([Pt(dppe)DEBP](n) and [Pd(dppe)DEBP](n), respectively) having an all-cis 'zigzag' structure, by formation of a sigma -acetylide bond between the transition metal complexes and the dialkyne molecule. When [PtCl2(dppe)] was reacted with DEBP, the formation of a chlorine-terminated [Pt(dppe)DEBP], oligomer was evidenced in the reaction involving the Pd(II) complex, on the other hand, [PdCl2(dppe)] seems to catalyse the polymerisation of DEBP via opening of the triple bond, producing a poly-DEBP polymer containing Pd(II) atoms inserted in the main chain
The interface between aluminium and a rod-like organometallic Pd-containing polymer film investigated by XPS
No full textX-ray photoelectron spectroscopy was used to study the formation of the interface between vapour-deposited Al and the organometallic polymer [-Pd(PBu3)(2)-C=-C-C6H4-C6H4-C=C-](n) (Pd-DEBP), for Al coverage up to 50 Angstrom. Core level analysis reveals that aluminium reacts primarily with the palladium atoms in the polymer chain by charge transfer from Al towards Pd. Al reacts and tends to diffuse some distance into the polymer film before agglomerating into metallic islands, There is no apparent interaction between Al and the organic moiety of the polymer. The C 1s shake-up structure remains unmodified over the whole range of Al coverage, and no appearance of carbide-like C Is signal has been detected. Subsequently to the Al-Pd interaction, aluminium seems to interact with an oxygenated species in different sites where phosphorus is present
The interface formation between thin films of conjugated polymers and evaporated metals investigated by X-ray photoemission spectroscopy
No full text
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
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