1,721,048 research outputs found
Synthesis and properties of p-nitrophenylacetylene-phenylacetylene copolymers
No full textCopolymers of phenylacetylene (PA) and p-nitrophenylacetylene (pNPA) with various monomers ratios were prepared and characterized. The solubility of copolymers is dependent on the number of PA units in the chain. They show a good degree of stereoregularity and the (M) over bar(w)s are in the 10(3)-10(5) a.m.u. range, depending on the monomers and catalyst molar ratios. The soluble samples exhibit film-forming properties and the film-surface morphology may be varied by using different solvents. The copolymers give good electrical response to relative humidity variations
Evidence for different equilibrium regimes in poly(phenylacetylene)-iodine solutions by means of low-frequency electrical conductivity measurements
No full textThe electrical conductivity of poly( phenylacetylene)-iodine in tetrahydrofuran solutions has been measured at the frequency of 10 kHz, at different polymer concentrations in the presence of different amounts of iodine up to a concentration of 20 mg ml(-1). The data have been analysed in the light of current theories of polyelectrolyte solutions, considering the effect of counterions along the charged polymer chain. The dependence of the electrical conductivity on the iodine concentration suggests that the conduction mechanism is governed by different equilibria, resulting in two different charge-transfer complexes, PPA(+)I(5)(-) and PPA(+)I(3)(-); both of them can give rise to ion fluctuation
Differenti abitudini alimentari di Gambusia holbrooki Girard, 1859, in piccoli ecosistemi acquatici artificiali.
No full textGoing 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
Palladium and platinum dithiocarbamato compexes containing mono- and diamines.
No full textThe [M(DMDT)X](n) (M=Pd or Pt; DMDT=Me2NCS2-; X=Cl or Br) species have been reacted with various amines (Py, pyridine; Pra, n-propylamine; Cba, cyclobutylamine; Dap, 1,3-diaminopropane; En, ethylenediamine) in dichloromethane with the aim of obtaining mixed complexes of various stoichiometries. Along with the neutral complexes M(DMDT)(L)X (L=Py, Pra or Cba), the ionic species IM(DMDT)(L,)IX, [M(DMDT)(En)]X and [M(DMDT)(Dap)]X have been isolated, which have been characterised by IR and proton NMR spectroscopy. Thermogravimetric data suggest a particular behaviour for the palladium-Pra and palladium-Cba derivatives, with formation of low-stoichiometry intermediates of formula Pd-2(DMDT)(2)AmX2. The behaviour of the prepared complexes in various solvents has been described on the basis of the proton NMR spectra. All complexes have been tested for in vitro cytostatic activity against KB cells
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
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