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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
HyFlex EDM: caratteristiche superficiali e resistenza alla fatica ciclica di innovativi strumenti rotanti NiTi prodotti per elettroerosione
No full textINTRODUZIONE
Gli strumenti endodontici in Controlled Memory Wire hanno mostrato flessibilità e comportamenti meccanici superiori alle leghe NiTi convenzionali. Gli HyFlex EDM (Colténe/Whaledent, Switzerland) sono prodotti con un innovativo processo di fabbricazione per elettroerosione (electro discharge machining-EDM) mediante scariche elettriche generate da un elettrodo in prossimità dello strumento.
OBIETTIVI
Esaminare la morfologia super ciale e la microstruttura interna di prototipi HyFlex EDM nuovi e usati in vitro e testare la loro resistenza in fatica ciclica.
MATERIALI E METODI
Quindici prototipi HyFlex EDM sono stati utilizzati per la strumentazione in vitro di 10 canali curvi. La morfologia di super cie e la microstruttura interna di strumenti nuovi e usati sono state indagate con un Microscopio Elet- tronico a Scansione (ESEM-EVO50 EP, Carl Zeiss, Germany) con Spettroscopia EDS e con un microscopio ottico metallogra co (Leica DMI5000 M, Germany). Altri 30 HyFlex EDM e 20 HyFlex CM sono stati testati in fatica ciclica in un canale arti ciale con angolo di curvatura di 70°. I dati ottenuti sono stati validati con il test di Kruskal-Wallis e glistrumenti fratturati sono stati sottoposti ad analisi frattogra ca con ESEM.
RISULTATI E DISCUSSIONE
Le indagini all’ESEM hanno rivelato una speci ca struttura irregolare caratterizzata da una super cie con mor- fologia a “cratere”. Non sono state evidenziate alterazioni super ciali nei prototipi utilizzati. Tutti gli strumenti, dopo diversi utilizzi, hanno preservato il loro peculiare aspetto crateriforme e non hanno mostrato appiattimento dell’angolo di taglio delle lame. Non si è veri cata nessuna frattura. L‘analisi metallogra ca sulla sezione trasver- sale degli strumenti ha mostrato la presenza di una microstruttura uniforme con un’omogenea fase martensitica. I test di fatica ciclica hanno evidenziato una resistenza superiore degli HyFlex EDM rispetto agli HyFlex CM, pari a circa il 700% quando strumenti di stessa conicità e diametro in punta sono stati esaminati. Gli HyFlex EDM hanno dimostrato un a dabile comportamento in vitro quando sottoposti a strumentazione di canali molto curvi. La caratteristica principale di tali strumenti è la super cie crateriforme che ben si conserva dopo ripetuti utilizzi. Gli strumenti di diametro minore sono apparsi quelli maggiormente stressati. La resistenza in fatica ciclica di stru- menti della stessa lega sembra essere notevolmente aumentata dal di erente processo di produzione.
Se da una parte l’implantologia o re al clinico un’opzione terapeutica altamente predicibile, in particolar modo nella sostituzione degli elementi naturali mancanti o irrecuperabili, dall’altra la terapia endodontica e restaura- tiva deve rappresentare la prima strada da percorrere in ogni piano di trattamento interdisciplinare.
OBIETTIVI
Il mantenimento dell’elemento naturale è oggi possibile in virtù di strumenti sempre più a dabili e di tecniche sempre più conservative sia in ambito endodontico che in ambito restaurativo. La letteratura scienti ca riporta percentuali di successo paragonabili tra trattamento endodontico e trattamento implantare. Pertanto la scelta conservativa o estrattiva-implantare non deve dipendere da particolari attitudini del clinico, ma dalla gestione del caso con la tecnica migliore in termini di costi-bene ci.
MATERIALI E METODI
Vengono presentati e discussi casi clinici complessi gestiti con approccio interdiciplinare. Vengono descritti gli aspetti diagnostici che hanno indotto il clinico all’opzione estrattiva ed alla sostituzione con un impianto osteo-integrato. Vengono riportati casi di elementi gravemente compromessi, recuperati attraverso ritrattamenti endodontici e terapie restaurative adesive. La presentazione di follow-up a distanza testimonia la correttezza dell’opzione terapeutica scelta.
RISULTATI E DISCUSSIONE
Il mantenimento dell’elemento naturale, con il ripristino di forma, funzione ed estetica, rappresenta la prima scelta per il clinico. In presenza di tessuti parodontali sani e sostanza dentale sana residua su ciente, tutti gli elementi dentali che si possano inserire in un piano di trattamento interdisciplinare devono poter essere preser- vati. Il successo a lungo termine in casi complessi dipenderà dal rispetto e dalla minuziosa applicazione di pro- tocolli operativi codi cati, dall’utilizzo di uno strumentario adeguato (ingrandimento, illuminazione dedicata e sistemi ad ultrasuoni in primis) e dal fattore operatore, aspetto, quest’ultimo, che non deve essere sottovalutato
HyFlex EDM rotary Ni-Ti prototypes: the effect of an innovative machining technology on Ni-Ti wear
No full textAim. HyFlex EDM files were recently introduced pre- senting an innovative electro discharge machining (EDM) process of fabrication. The aim of this study was to evalua- te the surface and microstructural alterations of new and in vitro used HyFlex EDM Ni-Ti rotary prototypes.
Methods. The surface and microstructural characteristi- cs of 15 new HyFlex EDM instruments were analyzed by ESEM equipped with energy dispersive x-ray spectropho- tometry (EDS) and optical metallographic imaging. Instru- ments were subjected to instrumentation tests on severely curved root canals (ranging between 50° and 70°) of ex- tracted multi-rooted teeth. Once that canal patency was verified with a #10 K-file, the working length was determi- ned by subtracting 1mm. HyFlex EDM files were used with a 16:1 reduction handpiece X-Smart (Dentsply Maillefer, Baillagues, Switzerland) following the manufacture’s direc- tion, at 500 rpm and 2.5Ncm, with slightly apical pressure and pecking motion. The operative sequence was: 25/12 at 2/3 of the WL, 10/05 and 25/08 at WL. Irrigation was per- formed at every change of instrument, with a total amount of3mlof5%NaOCland3mlof10%EDTA(Ogna,Mug- giò, Italy). Each instrument was used in 10 curved canals, washed in an ultrasonic bath containing detergent for 10 min and then autoclaved at 134°C. Surface and microstruc- tural characterizations were repeated on used instruments at same points and with same angulations to compare the pre- and postoperative micrographs, in order to verify the appearance of fractures, unwinding, microcracks, blade di- sruption and tip deformation.
Results. Surface and microstructural characteriza- tion of new instruments revealed the typical features of a NiTi ED-Machined alloy with an irregular and “craters-like” surface. High magnification microgra- phs disclosed a non-uniform structure were pits, po- res and voids caused the peculiar aspect of a “rough- spark-machined” surface. No fractures were registered during instrumentation of curved canals. Surface and microstructural characterization of used files revealed no wear and no degradation of the 25.12 and 25.08 files. The tip segment was confirmed as the most me- chanically stressed portion of 10.05 prototypes. All the instruments, after several uses, well-preserved the “craters-like” irregular surface without cutting edge al- terations. The metallographic inspection on the cross section of brand new HyFlex EDM files showed an homogeneous martensitic phase. The microstructure appeared uniform from the surface to the bulk, and no microcracks or defect were identified, even at high optical magnification (1000X).
Conclusion. Unaltered spark-machined surface and low microstructural degradation are the main features of recently introduced HyFlex EDM. Caution would be re- commended regarding reuse of small HyFlex EDM files. Instruments exhibited a safe in vitro use in presence of severely curved canals
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
Retreatment of Experimental Carrier-Based Obturators with the Remover NiTi Instrument: Evaluation of Apical Extrusion and Effects of New Kinematics
Full text linkThe objective of this study is to evaluate the retreatment time and weight of apically extruded debris yielded by two different kinematics during the removal of different root canal filling materials. Forty straight single-rooted extracted teeth were instrumented with HyFlex CM files and obturated with two different techniques: 25.04 HyFlex experimental carrier-based obturators (Coltène/Whaledent, Altstätten, Switzerland) (group 1) or 25.04 single gutta-percha cones (Roeko Coltène/Whaledent, Altstätten, Switzerland) (group 2) and Guttaflow Bioseal as the sealer. Samples were divided into four subgroups (n = 10) according to the used kinematics for the removal of root canal filling materials: continuous rotation (A) or retreatment motion (B) with a Remover and HyFlex EDM Nickel-Titanium instruments activated with a CanalPro Jeni micromotor (Coltène/Whaledent, Altstätten, Switzerland). Time for retreatment was digitally recorded, and debris extruded from the apex was collected in Eppendorf tubes and weighted with an analytical balance. Data on retreatment time and apical extrusion were statistically analyzed with the Kruskal-Wallis test (p<0.05). Working length was achieved in all the retreated samples. The removal of root filling material resulted significantly faster with the Jeni mode (p<0.001), and the difference was significant for the removal of both filling materials (p<0.05). No significant differences on debris extrusion between single cone and experimental obturators groups were noted (p>0.05), and no significant differences between kinematics (continuous rotation vs. Jeni motion) were observed (p>0.05). All the tested retreatment strategies lead to an extrusion of material from the apex, and the weight of apically extruded debris was similar. The use of the innovative CanalPro Jeni kinematics accelerates the time for the removal of root filling materials
Evaluation of the root filling quality with experimental carrier-based obturators: a CLSM and FEG-SEM analysis
Full text linkThis study evaluated tubule penetration of GuttaFlow Bioseal with cold single cone or carrier-based technique, under confocal laser scanning microscopy (CLSM). Twenty straight single-rooted teeth were instrumented with Hyflex CM and divided in two groups (n = 10) according to the obturation method: single cold gutta-percha cones; experimental carrier-based obturators. GuttaFlow Bioseal, labelled with Rhodamine B dye, was used as sealer in both groups. Teeth transversally sectioned were observed under CLSM. Percentage of sealer penetration and integrity of sealer layer perimeter were measured. Surface and microstructural characteristics of obturators and gutta-percha cones were compared by FEG-SEM and EDX analysis. No significant differences were found between groups for each examined parameter. Significant differences (P < 0.05) were reported mainly within groups. Integrity was similar among and within groups. FEG-SEM/EDX analysis of obturators revealed the presence of Ba and Zn. Carrier-based obturation technique associated with GuttaFlow Bioseal does not seem to affect sealer penetration into dentinal tubules
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
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