1,720,967 research outputs found
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
Spectroscopic and calorimetric study on different gamma-irradiated poly-epsilon-caprolactone/hydroxyapatite (PCL/HA) composite biomaterials.
No full textDifferent studies haave underlined that gamma-irradiation, a common method for sterilization, can induce structural changes on biomaterials (cross-linking, changes in molecular weight and cristallinity) through the formation of aggressive radicals (OH, COO, O2).
Poly-epsilon-caprolactone/hydroxyapatite (PCL/HA) samples (synthesized at IMCB-CNR Napoli, Italy) with different composition (100%, 70%, 60%, 50% w/w of PCL) were irradiated in air or under nitrogen at doses of 10, 25 and 50 kGy (dose to water) with gamma-rays from a 60Co Nordion 220 Gammacell at a dose rate of 0.7 kGy/h. Irradiation does were chosen as recommended for sterilization of bone tissue for inactivation of bacteria. The samples were analyzed after each dose with Raman and FT-IR/ATR spectroscopies to study morphology through changes in area, width, intensity and position of bands associated to crystalline and amorphous phases of PCL and HA; spectroscopic data about cristallinity and relative PCL/HA ratios were confirmed by calorimetric methods (TG and DSC). We find out that both PCL and HA were affected by irradiation: amorphous content increased with irradiation, in particular in air. Relevant changes were observed in the IR spectra of HA in carbonate bands. Samples treated under nitrogen showed smaller changes because of the lower concentration of radicals originated from oxygen and water. This study helps to understand how composite biomaterials can react to gamma-sterilization and could be the starting point of further studies on the effect of different types of irradiation and radicals on biomaterials
Analisi spettroscopica e calorimetrica di biomateriali compositi a base di poli-epsilon-caprolattone/idrossiapatite trattati con raggi gamma.
No full textIl trattamento con radiazioni ionizzanti, raggi gamma ed elettroni accelerati è un metodo largamente applicato per la sterilizzazione di materiali biocompatibili. La formazione di radicali particolarmente aggressivi (es. OH, COO, O2) in seguito al trattamento con radiazioni ionizzanti può determinare cambiamenti strutturali nel biomateriale in particolare nella cristallinità. Il poli-epsilon-caprolattone/idrossiapatite (PCL/IA) è un biomateriale utilizzato nella ricostituzione dei tessuti ossei che necessita di sterilizzazione prima dell'impianto.
Campioni di PCL/IA di differente composizione (100%, 70%, 60%, 50% di PCL) sono stati trattati con radiazioni ionizzanti e successivamente analizzati mediante spettroscopia vibrazionale e calorimetria allo scopo di valutare le possibili alterazioni indotte nella loro composizione e struttura.
Gli irraggiamenti sono stati effettuati mediante raggi gamma da 60Co a differenti dosi (0, 10, 25, 50 kGy) (dose in acqua) in aria e in atmosfera inerte. Le dosi sono state scelte sulla base di quelle raccomandate per la sterilizzazione dei tessuti ossei.
L'analisi degli spettri Raman e IR ha evidenziato che sia la cristallinità che la composizione dei campioni non subiscono sensibili variazioni in seguito all'irraggiamento fino alla dose di 50 kGy; inoltre non si sono riscontrate differenze negli irraggiamenti effettuati in aria e in azoto.
L'unica alterazione del biomateriale, evidenziata mediante calorimetria, è la riduzione della lunghezza delle catene polimeriche, dovuta all'azione dei radicali formatisi nell'irraggiamento
Properties-morpholohy-processing relationships in the e-beam curing of epoxy resin-thermoplastic blends for advanced composite matrices
No full textDispelling 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
Effects of sterilisation by high-energy radiation on biomedical poly( -caprolactone)/hydroxyapatite (PCL/HA) composites.
No full textThe effects of a high energy sterilization treatment on poly-epsilon-caprolactone/carbonated hydroxyapatite composites have been investigated. Poly-epsilon-caprolactone is a biodegradable polymer used as long-term bioresorbable scaffold for bone tissue engineering and carbonated hydroxyapatite is a bioactive material able to promote bone growth. The composites were gamma-irradiated in air or under nitrogen atmosphere with doses ranging from 10 to 50 kGy (i.e. to a value higher than that recommended for sterilization). The effects of the irradiation treatment were evaluated by vibrational spectroscopy (IR and Raman spectroscopies) coupled to thermal analysis (Differential Scanning Calorimetry and Thermogravimetry) and Electron Paramagnetic Resonance spectroscopy. Irradiation with the doses required for sterilization induced acceptable structural changes and damaging effects: only a very slight fragmentation of the polymeric chains and some defects in the inorganic component were observed. Moreover, the radiation sensitivity of the composites proved almost the same under the two different atmospheres
Calorimetric and spectroscopic study on different gamma-irradiated poly-epsilon-caprolactone/hydroxyapatite (PCL/HA) composite biomaterials.
No full textPoly(epsilon-caprolactone) (PCL), an aliphatic polyester, has received much attention because of its possible application as both a biocompatible and a biodegradable material. For biomedical purposes, PCL-based products can be used as drug delivery systems to the human body or tissue engineering scaffold material. In the latter case the three dimensional synthetic scaffolds, implanted at the tissue defect site, provide a frame-work for cells to attach, proliferate and form extra cellular matrix. To enhance bone regeneration process, hydroxyapatite (HA), the main component of the inorganic phase of bone, is generally added to the polymer material.
Response of the organism to the implanted composite biomaterial depends on numerous factors, one of the most important is sterilisation. Different procedures can be utilised for sterilisation, among them high energy radiations present many benefits. In fact, because of excellent penetration characteristics of ionising radiations, radiation sterilisation eliminates problems associated with residual and ethylene oxide gas penetration, uniformity of sterilisation, etc. The doses for radiation sterilization for medical devices and health care products are established by procedures defined in standard ISO 11137. For tissue allografts, international tissue bank standard recommended 15 kGy* as a minimum dose for bacteria decontamination and 25 kGy as minimum dose for bacteria sterilization. These doses should be validated using procedures established by ISO 11137. Other international tissue banks recommended dose up to 35 kGy. However, high-energy radiation, in addition killing bacterial life, may also affect material properties and the interaction between the different phase of the material. This study was aimed at evaluating possible irradiation-induced effects on morphological and thermal properties of both inorganic and polymeric components of some PCL-HA composites. To this purpose PCL-HA samples with different PCL/HA ratios were exposed to gamma radiations. The sample irradiation was performed at 50 kGy, dose greater than the recommended sterilization dose range under N2 or air atmosphere. The samples were investigated by vibrational spectroscopy (IR and Raman spectroscopies) coupled to thermal analysis measurements (Differential Scanning Calorimetry and Thermogravimetry) which revealed to be highly sensible to structure variations
- …
