1,720,964 research outputs found
Brushite/Hydroxyapatite Coatings obtained by galvanic deposition on 316L Stainless Steel
No full textHydroxyapatite (HA, Ca10(PO4)6(OH)2) is a basic calcium phosphate mineral with chemical composition similar to that of bones and teeth. Owing to this peculiarity HA is a biocompatible material of high medical interest. Unfortunately, it possesses poor mechanical properties, because is brittle, has a low fracture resistance and a poor wear resistance. For these reasons, in the last years the research was been focused on the use of HA as a coating of another biomaterial that acts as support. The best choice is that to use a substrate that must be bionert and mechanically stable, such as 316L stainless steel (316LSS). This is useful for biomedical implants, because of its excellent biocompatibility and good mechanical properties. However, since 316LSS is a bioinert material, it cannot form strong chemical bonds with bones. To improve the osteointegration, it is necessary to cover 316LSS substrates with hydroxyapatite layers. Thus, the use of bio-device based on HA coatings supported on 316LSS allows to exceed the two of principal disadvantages that these two materials present when are used individually: the brittleness of HA and the poor osteointegration of 316LSS. Many methods were developed to deposit HA on bio-inert substrate, including ion beam sputtering, sol–gel, electrophoretic deposition, pulsed laser deposition, plasma spraying and electrochemical deposition. Here, we propose a new fabrication process that permits to obtain brushite and brushite/hydroxyapatite, that is a very simple and low cost. Brushite is dicalcium phosphate dihydrate (BS, CaHPO4·2H2O) that, when placed in simulated body fluid (SBF, knowed as Hank’s solution), it converts into hydroxyapatite. In particular, brushite and brushite/hydroxyapatite coatings were deposited on 316LSS from a solution containing Ca(NO3)2·4H2O and NH4H2PO4 through a displacement reaction based on a galvanic contact between 316LSS and a sheet of zinc that acts as sacrificial anode. Driving force for the cementation reaction arises from the difference in the electrochemical standard potentials of 316LSS and Zn that were immersed in the electrolyte. This process allows to deposit Brushite/Hydroxyapatite coatings without power supply. Samples were obtained varying deposition time (24 hours, 72 h and 108 h) and temperature (6 °C, 25 °C and 50 °C). SEM, EDS, Raman and XRD were used to full characterized the coatings. SEM images showed that the morphology changes as the temperature increases passing by a spherical dispersed structure, for films obtained from a 6 °C and 25 °C, to a tetrahedral and more compact structure, in the case of the film obtained at 50 °C. Through EDS the chemical composition of coatings was identified, calculating the Ca/P ratio, to obtain the stoichiometry, and the Ca/Fe ratio, to estimate the degree of coverage of the substrate. The temperature increase allows to obtain a uniform coating with a Ca/P ratio close to the optimal value (1.67), and a very high value of Ca/Fe ratio that obviously implies the formation of a very thick coating on the substrate. By Raman spectroscopy and X-ray diffraction (XRD) the phases were identified and the characteristic peaks of BS and BS/HA were found. Besides, corrosion (open circuit potential, potentiodynamic polarization and impedence measurement) and biocompatibility (cytotoxicity assays with osteoblastic cell) test were performed. Here, we will show that galvanic deposition is an advantageous method because is able to produce BS and BS/HA coatings that enhance the corrosion and biological properties of the 316LSS substrate
Mass transfer and phenolic profile of strawberries upon refrigerated osmodehydration
No full textWhole strawberries were osmodehydrated at low temperature (5 degrees C) in a sucrose syrup (500 g/kg of solution) for different processing times (24, 48, 72, 96, and 120 h); after the treatment, water loss, solid gain, and weight reduction were recorded. Next, the osmodehydrated samples were frozen, and after a 5-month storage at - 18 degrees C they were analyzed for drip loss, titratable acidity, refractometric index, pH, and sensory acceptance. The phenolic profile of the samples was characterized by means of high performance liquid chromatography (HPLC). After thawing, osmodehydrated samples presented a high acceptability for consumers. In addition, they presented drip loss values that were inversely correlated with the processing time, with 120-h samples presenting negligible drip loss after thawing. The processing time influenced the final quality of strawberries, and samples treated for 24-48 h were very suitable for direct consumption after thawing, in substitution of fresh strawberries. The samples treated for 72 120 h also presented characteristics that may render them suitable for applications in the food industry
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
Environmental enrichment reverts the effects of continuous or intermittent perinatal alcohol exposure. Focus on alcohol vulnerability and affectivity in the offspring
No full textAlcohol consumption during perinatal periods is common, despite the warning of adverse effects on the foetal development. In female rats, the intermittent pattern of alcohol consumption is responsible for higher drinking levels and more profound disruption of maternal care than traditional continuous free-access paradigm, which can have persistent effects on the offspring. The environmental enrichment, a powerful form of experience-dependent plasticity that allows high cognitive, motor and sensory stimulations, is helpful for recovering from different neurological pathologies.
Thus, this study aimed at exploring the effects of environmental enrichment on alcohol vulnerability and affective behaviour in the offspring that was perinatally exposed to continuous or intermittent alcohol. Dams were given two-bottle choice to water and 20% alcohol with either continuous- or intermittent access (CA vs IA), along a 12-week period. They were alcohol-deprived during breeding and resumed alcohol self-administration from late gestation and throughout lactation. Alcohol-exposed offspring, reared in either standard- or enriched- conditions, were assessed for alcohol drinking behaviour in a free-choice paradigm and were also tested for the deprivation effect. Moreover, they were tested for behavioural reactivity in the open field; anxiety-like behaviour in the elevated plus maze and depressive-like behaviour in the forced swim test during the drinking paradigm.
Our results show that perinatal CA to alcohol did not increase alcohol-drinking behaviour with respect to controls. On the other hand, rats perinatally exposed to IA displayed a high vulnerability to alcohol, in terms of drinking behaviour and deprivation effect. The environmental enrichment was able to exert a protective role on alcohol vulnerability in perinatally IA exposed rats and controls, especially during relapse. Moreover, it was able to induce an increase in behavioural reactivity in the open field and a decrease in anxiety-like behaviour in the elevated plus maze, in both perinatally CA and IA exposed groups.
In conclusion, the pattern of alcohol consumption during pregnancy and lactation can influence long-term alcohol vulnerability in the offspring. Rearing conditions that promote high cognitive, motor and sensory stimulations improve resilience to alcohol abuse and affective tone, although they cannot be sufficient to full recovery from detrimental effects of perinatal alcohol exposure
Some chemical characteristics of amorfa fruticosa honey, a peculiar production of friuli venezia giulia (italy) region(poster)
No full textCaratterizzazione preliminare del miele di Amorpha frutticosa, prodotto in Friuli Venezia Giulia
No full textDispelling 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
- …
