1,720,986 research outputs found
Liquids in confined geometry: How to connect changes in the structure factor to modifications of local order
No full textTemperature versus density effects in glassforming liquids and polymers: A scaling hypothesis and its consequences
No full textTemperature, density, and pressure dependence of relaxation times in supercooled liquids
No full textOrganic glass-forming liquids and the concept of fragility
Full text linkInternational audienceAn important category of glass-forming materials is organic; it includes molecular liquids, polymers, solutions, proteins that can be vitrified by cooling the liquid under standard conditions or after special thermal treatments. The range of applications is large from materials to life sciences and recently to electronics. To distinguish them from other systems described in this issue, some specific properties such as the range of their glass transition temperature (), their ability to vitrify and some rules of thumb to locate are presented. The most remarkable property of these liquids is how fast in temperature their viscosity or structural relaxation time increases as approaching . To characterize this behavior and rank the liquids of different strength, C.A. Angell introduced the concept of Fragility nearly 40 years ago. He proposed to classify liquids as fragile or strong in an Arrhenius plot with scaling (the strongest ones have never being observed in organic glasses, except for water under specific conditions). The value and the fragility of a given liquid can be changed by applying pressure, i.e. changing the density. One can then explore the properties of the supercooled/overcompressed liquid and the glass in a phase diagram. The line corresponds to an isochronic line, i.e. a line at constant relaxation time with different pairs of density-temperature. We observe that all data can be placed on master-curves that depend only on a single density-and species-dependent and T-independent effective interaction energy, (ρ). An isochoric fragility index is defined as an intrinsic property of a given liquid, that can help in rationalizing all the correlations between the glass properties below T g and the viscous slowing down just above from which they are made. Geometrical confinement of liquids is also a way to modify the dynamics of a liquid and the properties of a glass; it corresponds to a large number of situations encountered in nature. Another phase diagram (d= pore diameter) can be defined with a non-trivial pore size dependence of the glass transition, which is also strongly affected by surface interactions
Finite-size and surface effects on the glass transition of liquid toluene confined in cylindrical mesopores
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
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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