326,021 research outputs found
Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction
No full textWe examine the radial entropy distribution and its scaling using 31 nearby galaxy clusters from the representative XMM-Newton cluster structure survey (REXCESS), a sample in the temperature range 2-9 keV selected in X-ray luminosity only, with no bias toward any particular morphological type. The entropy profiles are robustly measured at least out to R1000 in all systems and out to R500 in thirteen systems. Compared to theoretical expectations from non-radiative cosmological simulations, the observed distributions show a radial and mass-dependent excess entropy, such that the excess is greater and extends to larger radii in lower mass systems. At R500, the mass dependence and entropy excess are both negligible within the large observational and theoretical uncertainties. Mirroring this behaviour, the scaling of gas entropy is shallower than self-similar in the inner regions, but steepens with radius, becoming consistent with self-similar at R500. There is a large dispersion in scaled entropy in the inner regions, apparently linked to the presence of cool cores and dynamical activity; at larger radii the dispersion decreases by approximately a factor of two to 30 per cent, and the dichotomy between subsamples disappears. There are two peaks in the distribution of both inner slope and, after parameterising the profiles with a power law plus constant model, in central entropy K0. However, we are unable to distinguish between a bimodal or a left-skewed distribution of K0 with the present data. The distribution of outer slopes is unimodal with a median value of 0.98, and there is a clear correlation of outer slope with temperature. Renormalising the dimensionless entropy profiles by the gas mass fraction profile fgas (<R), leads to a remarkable reduction in the scatter, implying that gas mass fraction variations with radius and mass are the cause of the observed entropy structural and scaling properties. The results are consistent with the picture of a cluster population in which entropy modification is centrally concentrated and extends to larger radii at lower mass, leading to both a radial and a mass-dependence in the gas mass fraction, but which is increasingly self-similar at large radius. The observed normalisation, however, would suggest entropy modification at least up to R1000, and even beyond, in all but the most massive systems. We discuss a tentative scenario to explain the observed behaviour of the entropy and gas mass fraction in the REXCESS sample, in which a combination of extra heating and merger mixing maintains an elevated central entropy level in the majority of the population, and a smaller fraction of systems is able to develop a cool core. <br/
Organoclay modification by insertion of hyperbranched aromatic polyamides
No full textHyperbranched (HB) aromatic polyamides (aramids) synthesized from A2 (p-phenylenediamine) + B3 (trimesic acid) reactants have been intercalated into three organically-modified montmorillonite-type clays (OMMT), namely Cloisite 30B®, Dellite 43B® and Dellite 72T®. Solution intercalation has been applied for the preparation of the OMMT/HB aramid pair. The presence of HB aramid has been found to increase the interlayer distances of some silicate layers and to reduce those of others. This phenomenon has been explained by the broad polydispersity of the HB aramid leading to a complex mixture of macromolecules which can interact with the organic compatibilizer of the clay in different ways and thus affect the arrangement of it inside the galleries. Purthermore, the swelling of the layered silicate in the solvent used has been found to be a key parameter, which strongly biases polymer intercalation. TGA measurements have evidenced the active role of clay in the degradation process of HB aramid and the higher thermal stability of clay/HB aramid systems, as compared to the pristine organoclays. Finally, the Cloisite 30B®/HB aramid system has been used as masterbatch to produce polyamide 6 (PA6)-based nanocomposites. WAXD and TEM characterization have evidenced the possibility to obtain fully exfoliated nanocomposites
Antistatic epoxy coatings with carbon nanotubes obtained by cationic photopolymerization
No full text
NMR Studies on a Hyperbranched Aromatic Polyamide from A2 and B3 Monomers: Structure and Interactions with Lithium Salts
No full textDiffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
La Turquie que l’on voit, par L. de Launay, membre de l’Institut. Paris, Hachette
No full textS. La Turquie que l’on voit, par L. de Launay, membre de l’Institut. Paris, Hachette. In: La revue pédagogique, tome 63, Juillet-Décembre 1913. p. 597
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
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