1,720,974 research outputs found
Polymeric micelles for cutaneous delivery of resveratrol
No full textPurpose: The efficacy of resveratrol (RES) in preventing skin aging and protecting epidermis from damages induced by UVA and UVB has been recently demonstrated (Soeur et al., 2015). Considering the low skin penetration of UV rays, the design of delivery systems able to promote the RES localization into the epidermis resulted of interest to guarantee skin protection. The present study aimed to evaluate the feasibility of poloxamer micelles for enhancing the RES penetration in the upper skin layers.
Methods: 0.1% w/v RES-loaded polymeric micelles were prepared using solvent diffusion method (acetone solution/water: 1/10 v/v). Poloxamer 118 (P118) and 407 (P407) were selected as excipients because of their high solubility in water, other than the different molecular weight and HLB value. To study the impact of polymer composition on the physical properties and stability of RES-loaded polymeric micelles, different formulations were prepared using different concentrations of polymers (0.1-1.0% w/v), as single polymer or 1:1 mixture. The resulting nanosystems were characterized in terms of particle size, ζ-potential and apparent solubility of RES in water. Their physical stability was also checked over 1 month at room temperature. Release studies through artificial membrane (i.e., Cuprophan®) and in vitro permeation studies through full-thickness porcine ear skin were performed over 24 h by using Franz cells.
Results: Poloxamers can auto-assemble in nano-micelles when RES was added to the formulation. The size of micelles ranged from 30 to 300 nm, as function of their compositions; ζ-potential was almost neutral for all formulations. In micellar systems containing P407, the RES apparent solubility significantly increased (1.05±0.7 mg/mL) with respect to a saturated solution (0.04±0.00 mg/mL). Similar results were observed with P118, but it had a lower solubilizing efficiency (0.36±0.33 mg/mL). The release study suggested that micelles could act as nano-reservoir systems for RES. Indeed, the RES amount diffused through Cuprophan® membrane within 8h (<5%) was six-time lower for polymeric micelles in comparison to the control solution (≈30%). Among micellar systems, the diffused RES amounts increased in the order: P407 < P118/P407 (1:1) ≈ P118. In vitro permeation study demonstrated that the RES permeation through full-thickness porcine skin was negligible for all tested formulations and the RES retention in the deep epidermal and dermal layers resulted lower than 1% of total RES loaded. Nevertheless, the stripping technique revealed that micellar formulations were more efficient in promoting the penetration and retention of RES than control (p < 0.01) in the upper epidermal layers. Interestingly, micelles made of P188 and P407 (1:1) could enhance the permeation of RES in the lower epidermal layers more than other micellar systems and control (p < 0.05).
Conclusions: Poloxamers can auto-assemble in presence of RES to form micellar systems, enhancing significantly its apparent solubility in water. Micelles made of P188 and P407 resulted promising nanocarriers for enhancing the skin partition of RES and its localization in the upper skin layers.
References
Soeur J et al. Skin resistance to oxidative stress induced by resveratrol: From Nrf2 activation to GSH biosynthesis. Free Radical Biology and Medicine 2015, 78, 213-223
Water status, growth and calcium nutrition of apple trees in relation of bitter pit
No full textThree different water status conditions (full watered, mild deficit and high deficit) were applied to cultivar 'Granny Smith' apple trees growing in pots during two periods of 4 weeks (last phase of fruit growth by cell division and middle phase of fruit growth by cell enlargement). In the first period, water deficit strongly reduced shoot, leaf and fruit growth, increased the calcium content in leaves and reduced the appearance of bitter pit in fruits. When applied in the second period, water deficit reduced leaf weight and fruit growth, increased the calcium content in leaves and reduced the appearance of bitter pit in fruits. Leaf sap osmolarity was lowered by the water deficit condition. These results are discussed with regard to patterns of diurnal water status in the differently watered trees
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
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