1,720,972 research outputs found
On Stein fillings of contact torus bundles
Get PDFWe consider a large family F of torus bundles over the circle, and we use recent work of Li--Mak to construct, on each Y in F, a Stein fillable contact structure C. We prove that (i) each Stein filling of (Y,C) has vanishing first Chern class and first Betti number, (ii) if Y in F is elliptic then all Stein fillings of (Y,C) are pairwise diffeomorphic and (iii) if Y in F is parabolic or hyperbolic then all Stein fillings of (Y,C) share the same Betti numbers and fall into finitely many diffeomorphism classes. Moreover, for infinitely many hyperbolic torus bundles Y in F we exhibit non-homotopy equivalent Stein fillings of (Y,C)
Melting of nanoporous-crystalline and co-crystalline solution cast films of poly(2,6-dimethyl-1,4-phenylene) oxide
No full textThe melting behavior of nanoporous-crystalline (NC) and co-crystalline (CC) PPO films is mainly studied by differential scanning calorimetry. For NC films, the dependence of melting behavior on α or β forms as well as on the chemical nature of the guest of precursor CC forms is explored. A relevant result of this contribution is that the use of PPO films with c//orientation also allows establishing melting temperatures of CC phases, being not accessible for other PPO samples. An additional relevant result is the achievement, by suitable annealing procedures on c//oriented CC films, of partially filled CC PPO films with melting temperature just below 300 °C, while NC PPO films always exhibit melting temperatures lower than 265 °C. The reported data, both on NC and CC films, also indicate that molecular volumes most suitable for guests of the α NC form of PPO are in the range 160–230 Å3
Isolated and aggregated carvacrol guest molecules in cocrystalline poly(2,6-dimethyl-1,4-phenylene)oxide films
No full textPoly(2,6-dimethyl-1,4-phenylene)oxide (PPO) is a high-performance commercial thermoplastic polymer that exhibits cocrystalline phases (CC) with many low molecular mass guest molecules as well as nanoporous crystalline (NC) phases. In this paper, preparation and characterization, mainly by WAXD and FTIR techniques, of PPO films exhibiting the CC phase with carvacrol (a relevant natural antimicrobial) are reported. The study shows that the relative intensities of two O–H out-of-plane deformation peaks (at 698 and 717 cm−1) of carvacrol are highly sensitive to its concentration in CC films. The reported data can be rationalized by assuming that 698 and 717 cm−1 peaks are due to isolated and hydrogen-bonded guest molecules, respectively, and by preferential inclusion of carvacrol in the cavities of the NC phase. Polarized FTIR spectra of axially stretched CC PPO/carvacrol films show that the guest peak at 717 cm−1 is not dichroic, while the guest peak at 698 cm−1 is markedly dichroic. This confirms that the O–H out-of-plane deformation peak at 698 cm−1 is due to isolated guest molecules, which are mainly enclosed in the cavities of the axially oriented CC phase
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
Rethinking access control and authentication for the Home Internet of Things (IoT)
No full textComputing is transitioning from single-user devices to the Internet of Things (IoT), in which multiple users with complex social relationships interact with a single device. Currently deployed techniques fail to provide usable access-control specification or authentication in such settings. In this paper, we begin reenvisioning access control and authentication for the home IoT. We propose that access control focus on IoT capabilities (i. e., certain actions that devices can perform), rather than on a per-device granularity. In a 425-participant online user study, we find stark differences in participants' desired access-control policies for different capabilities within a single device, as well as based on who is trying to use that capability. From these desired policies, we identify likely candidates for default policies. We also pinpoint necessary primitives for specifying more complex, yet desired, access-control policies. These primitives range from the time of day to the current location of users. Finally, we discuss the degree to which different authentication methods potentially support desired policies
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
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