1,721,089 research outputs found
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
Microtensile bond strength and interfacial properties of self-etching and self-adhesive resin cements used to lute composite onlays under different seating forces
No full textPurpose: To evaluate strength and morphology of the interface created on enamel and dentin by Panavia F 2.0 (P, Kuraray), RelyX Unicem (RU, 3M ESPE), and Maxeem (M, Sybron-Kerr), applied under two standardized clinically realistic seating pressures. Materials and Methods: Composite overlays (Paradigm MZ100, 3M ESPE) were luted on flat enamel or dentin surfaces of 48 extracted molars. During the initial 5-min self-curing period, a pressure of either 20 or 40 g/mm2 was maintained on the overlay. Curing was completed by light irradiation from the top of the overlay for 20 s. Microtensile sticks and specimens for SCM observations were obtained from the luted teeth. Bond strength data from enamel and dentin (MPa) were analyzed with separate two-way ANOVAs in order to assess the effect of cement type, luting pressure, and their interactions. Tukey's test was used for post-hoc comparisons (α = 0.05), Results: The bond strengths (MPa) to dentin were: P 20 g/mm2 7.5 ± 3.7, 40 g/mm2 10.9 ± 4.5; RU 20 g/mm2 6.8 ± 2.6, 40 g/mm2 14.5 ± 5.3; M 20 g/mm2 4.1 ± 1.8, 40 g/mm2 5.2 ± 1.6. The bond strengths (MPa) to enamel were: P 20 g/mm2 25.2 ± 9.0, 40 g/mm2 30.7 ± 8.6; RU 20 g/mm2 10.7 ± 4.9, 40 g/mm2 11.1 ± 5; M 20 g/mm2 7.3 ± 3.1, 40 g/mm2 7.9 ± 3.2. Cement type, luting pressure, and the interaction of these two factors had significant influences on dentin bond strength, with RU and P outperforming M. RU and P significantly benefited from the increase in luting pressure. In enamel, the type of cement was a significant factor for adhesion, with P yielding the highest and M the lowest strength. The measured bond strengths corresponded with the morphological results. Conclusion: Interfacial strength and adaptation of self-etching and self-adhesive dual-curing cements are enhanced if a seating force greater than finger pressure is maintained throughout the initial self-curing period
Post-surface conditioning improves interfacial adhesion in post/core restorations
No full textOBJECTIVES:
To verify the influence of different etching procedures of the post-surface on microtensile bond strength values between fiber posts and composite core materials.
METHODS:
60 DT Light Posts were divided into 10 subgroups using five different chemical surface treatments and two composite materials to build-up the abutment. Chemical surface treatments including etching with potassium permanganate; treatment with 10% hydrogen peroxide; treatment with 21% sodium ethoxide; etching with potassium permanganate and 10 vol.% HCl; silanization (control group) were performed on the post's surface. The build-up was performed using (A) Core Paste XP (Dent Mat) and (B) Unifil Flow (GC). Two samples of each group were randomly selected to investigate the morphologic aspect of the post/core interface with a scanning electron microscope (SEM). The remaining specimens were cut so as to obtain microtensile sticks that were loaded in tension at a cross-head speed of 1mm/min until failure. The statistical analysis was performed using two-way ANOVA and the Tukey's test for post-hoc comparisons (alpha=0.05).
RESULTS:
SEM examination showed an interpenetrating adhesion network between the treated fiber post-surface and the composite material in all the groups tested. The results achieved with potassium permanganate had a significant influence on microtensile interfacial bond strength values with both the tested materials. Post-superficial treatments enhanced the bond strength particularly of Core Paste XP.
SIGNIFICANCE:
Etching procedures showed a similar effect on the post-surface and enhanced the adhesion of composite core build-ups as a result of micromechanical and chemical retention
Sealing properties of one-step root-filling fibre post-obturators vs. two-step delayed fibre post-placement
No full textOBJECTIVES:
The sealing properties of a one-step obturation post-placement technique consisting of Resilon-capped fibre post-obturators were compared with a two-step technique based on initial Resilon root filling following by 24h-delayed fibre post-placement.
METHODS:
Thirty root segments were shaped to size 40, 0.04 taper and filled with: (1) InnoEndo obturators; (2) Resilon/24h-delayed FibreKor post-cementation. Obturator, root filling and post-cementation procedures were performed using InnoEndo bonding agent/dual-cured root canal sealer. Fluid flow rate through the filled roots was evaluated at 10psi using a computerised fluid filtration model before root resection and after 3 and 9mm apical resections. Fluid flow data were analysed using two-way repeated measures ANOVA and Tukey test to examine the effects of root-filling post-placement techniques and root resection lengths on fluid leakage from the filled canals (alpha=0.05).
RESULTS:
A significantly greater amount of fluid leakage was observed with the one-step technique when compared with two-step technique. No difference in fluid leakage was observed among intact canals and canals resected at different lengths for both materials.
CONCLUSIONS:
The seal of root canals achieved with the one-step obturator is less effective than separate Resilon root fillings followed by a 24-h delay prior to the fibre post-placement. Incomplete setting of the sealer and restricted relief of polymerisation shrinkage stresses may be responsible for the inferior seal of the one-step root-filling/post-restoration technique
Noninvasive pit and fissure sealing: microtensile bond strength to intact bovine enamel of different pit and fissure sealants in a simplified fissure model
No full textPurpose: To measure the microtensile bond strength of different pit and fissure sealants in a simplified fissure model.
Materials and Methods: Twenty extracted bovine mandibular permanent incisors were randomly divided into 4 groups for treatment: G1: 35% phosphoric acid/Clinpro Sealant; G2: 35% phosphoric acid/Delton; G3: Non-Rinse Conditioner/Dyract Seal; G4: 20% polyacrylic acid/Fuji IILC. Each tooth was sectioned into 6 pieces (4 x 6 mm) of buccal enamel. SEM examination was used to confirm the presence of aprismatic enamel on each tooth. Using a spacer, two pieces of etched enamel were secured to a glass slide at a mean distance of 0.6 +/- 0.1 mm. The space between enamel substrates was then etched/conditioned and sealed with different materials according to the tested groups. By serially cutting each double-bonded sample, multiple beam-shaped specimens about 0.8mm(2) in cross section were obtained and tested in tension (0.5 mm/min) until failure occurred at either one of the two stressed interfaces. Failure modes were classified by stereomicroscopy.
Results: G1 and G2 showed statistically higher bond strengths than G3 and G4. G4 demonstrated the significantly lowest bond strength. Failures were mostly adhesive in G1, G2, G3, and mainly cohesive/mixed in G4.
Conclusion: According to this model, resin-based materials (Clinpro Sealant, Delton) showed better microtensile bond strength than compomer (Dyract Seal) or resin-modified glass ionomer (Fuji IILC)
Water uptake of bonding systems applied on root dentin surfaces: a SEM and confocal microscopic study
No full textObjectives. Dentin adhesives have been proposed as desensitizing agents to seat exposed root dentin surfaces. Simplified 'one-step' dentin adhesives are highly permeable to water. The authors hypothesized that a tactic acid challenge may increase permeability of simplified adhesives and may induce fast degradation of bonding. This phenomenon adversely affects their durability as tong term desensitizing agents. The aim of this in vitro study was to evaluate the ability of four dentin adhesives to seat root dentin surfaces that were exposed to water and tactic acid challenges. Methods. Four commercially-available dentin adhesives were applied with a small sponge to the root dentin of extracted human molars as de-sensitizing agents. Impression replicas of the adhesive-covered root dentin were fabricated after water immersion, as a control, and after tactic acid challenge. The replicas were examined with SEM for quantitative comparison of fluid droplet formation on the surfaces. The bonded specimens were also examined using reflected tight confocal microscopy. Results. Replicas of water droplets were observed on the adhesive surfaces, by SEM which corresponded with direct confocal. observation of blisters and voids from the surface of the bonded specimens. There were significantly more water droplets from samples that were subjected to tactic acid challenge than water only immersion. Significance. Although the dentin adhesives examined were able to cover exposed root dentin, they all exhibited fluid transudation through the polymerized adhesives. Dentin adhesives were also susceptible to surface degradation after tactic acid challenge. As simplified self-etch adhesives were highly water permeable and exhibited the most extensive surface damage, they may not be the best adhesives to be used for tong-term dentin desensitization. These preliminary in vitro findings warrant validation in vivo. (c) 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved
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