1,720,992 research outputs found
Effect of areal chain density on the location of polymer-modified gold nanoparticles in a block copolymer template
No full textA strategy for controlling the location of gold nanoparticles within block copolymer domains through varying the surface coverage of gold nanoparticles by end-attached polymer ligands is described. Gold nanoparticles coated by short thiol end functional polystyrene homopolymers (PS-SH) (M-n = 3.4 kg/mol) are incorporated into a poly(styrene-b-2-vinylpyridine) diblock copolymer template (PS-b-P2VP) (M-n = 196 kg/mol), the P2VP block of which has a more favorable interaction with a bare gold particle surface than does the PS block. The areal chain density of the PS-SH ligands on gold particles is varied by changing the mole ratio of PS-SH chains to gold atoms. It is found that the areal density of PS chains on the gold particles is critical to controlling their location in block copolymer templates. PS-coated gold nanoparticles with PS chain areal density higher than 1.6 chains/nm(2) are dispersed in PS domains of PS-b-P2VP while they are segregated along the interface between PS and P2VP domains of PS-b-P2VP for PS chain areal density < 1.3 chains/nm(2). Even at extremely low grafting densities of polymer ligands, gold nanoparticles can be stabilized in solution, and self- assembly of these nanoparticles can be controlled within the block copolymer template
Surface active block copolymers: Biofouling resistant coatings from chemically modified polymers
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Interfacial Roughening Induced by the Reaction of End-Functionalized Polymers at a PS/P2VP Interface: Quantitative Analysis by DSIMS
No full textThe reaction of end-functionalized polymer chains at the melt interface between the immiscible polymers, polystyrene (PS) and poly(2-vinylpyridine) (P2VP), has been investigated experimentally. Diblock copolymers were formed at the interface by the reaction of amine end-functionalized deuterated PS with anhydride end-functionalized P2VP. The normalized interfacial excess (ξ = z*PS/Rg,PS) of the deuterium-labeled block copolymer was determined using dynamic secondary ion mass spectrometry (DSIMS). As ξ increases, the interfacial tension decreases to zero, at which point the interface becomes unstable, inducing interfacial roughening by hydrodynamic flow of the homopolymers. Roughening was detected using scanning force microscopy (SFM) after removing the polystyrene with a selective solvent. Evidence of the interfacial instability was also observed by cross-sectional transmission electron microscopy (TEM). The length scale of the corrugation was around 15 nm, which was comparable to the diameter of diblock copolymer emulsified droplets found near the interface. For a short symmetric block copolymer (PS (4K)−P2VP (4K)), we observed that the interfacial roughening takes place above ξ = 0.9, in good agreement with the predictions of self-consistent mean-field theory.We acknowledge the support of the UCSB Materials Research Lab. (NSF-DMR-MRSEC Grant DMR00-80034). The skillful help of Dr. Tom Mates and Dr. Krystyna Brzezinska of this facility as well as useful discussions with Dr. Ryan Hayward and Dr. Seung-Heon Lee is greatly appreciated
- …
