1,720,981 research outputs found
Polyamide nanocapsules and nano-emulsions containing Parsol MCX and Parsol 1789: in vitro release, ex vivo skin penetration and photo-stability studies
No full textPurpose: To prepare polyamide nanocapsules for skin photo-protection, encapsulating α-tocopherol, Parsol® MCX (ethylhexyl methoxycinnamate) and/or Parsol® 1789 (butyl methoxydibenzoylmethane). Methods: Nanocapsules were obtained by combining spontaneous emulsification and interfacial polycondensation reaction between sebacoyl chloride and diethylenetriamine. Nanoemulsions used as control were obtained by the same process without monomers. The influence of carrier on release rate was studied in vitro with a membrane-free model. Epidermal penetration of encapsulated sunscreens was ex vivo evaluated using Franz diffusion cells. Ability of encapsulated sunscreens to improve photo-stability was verified by comparing percentage of degradation after UV radiation exposure. Results: Sunscreen-containing nanocapsules (260-400 nm) were successfully prepared; yield of encapsulation was >98%. Parsol® MCX and Parsol® 1789 encapsulation led to decreased release rate by up to 60%in comparison with nano-emulsion and allowed minimum penetration through pig ear epidermis. Presence of polyamide shell protected encapsulated sunscreen filters from photo-degradation without affecting their activity. Conclusions: Encapsulation of Parsol® MCX and Parsol® 1789 into oil-core of polyamide nanocapsules allowed protection from photo-degradation, controlled release from nanocapsules, and limited penetration through pig ear epidermis. © Springer Science+Business Media, LLC 2011
Tamoxifen loaded auto-assembled nanoparticles for oral delivery: cytotoxicity and peremeability studies
No full textThe purpose of this study was to characterise and study on cell cultures chitosan/lecithin nanoparticles loaded with tamoxifen (TAM-NCL). The mucoadhesion and the permeation through excised rat intestinal mucosa of the nanoparticles was also investigated
TAM-NCL were prepared by injection of methanol solution of lecithin and TAM in a chitosan solution. Cytotoxicity was investigated by MTT test using CaCo-2 and MCF-7 cells at different times and using different concentrations of TAM-NCL. The permeation studies through rat intestinal mucosa were performed in ex-vivo experiments using the Ussing chambers.
The TAM-NCL cytotoxicity experiments towards MCF-7 cells showed that only after 24 or 48 h cells viability was reduced. This is in accordance with previous drug release data in which the release of TAM from nanoparticles occurred only when enzymes degraded nanoparticle components.
Concerning the permeation trough the intestinal wall, nanoparticles slightly increased tamoxifen permeation compared to a control suspension of tamoxifen. However using enzymes able to degrade specifically the components of the nanoparticles (i.e. lipase contained in pancreatin) the tamoxifen flux trough the intestinal mucosa increased significantly. This increase was negated if a dialysis membrane is interposed as a barrier separating the nanoparticles from the mucosal surface. The permeation experiments on rat intestinal tissue showed then that mucoadhesion and enzymatic degradation of nanocarriers are required to increase the drug flux through the rat intestinal mucosa when chitosan/lecithin nanoparticles are employed as drug delivery system
PEGylation and preliminary biocompatibility evaluation of magnetite-silica nanocomposites obtained by high energy ball milling
No full textHigh energy ball milling (HEBM) has been used for the first time to prepare PEGylated magnetite-silica (Fe3O4-SiO2) nanocomposites intended to be used for biological purposes. Surface amine groups were introduced by a silanization reaction involving 3-aminopropyl triethoxysilane (APTS) followed by PEGylation to yield long-term stable and stealth nanocomposites of 200nm in diameter. The efficient coverage by PEG chains was shown by isothermal titration calorimetry (ITC) where PEGylated nanocomposites did not interact with BSA compared to non-PEGylated counterparts which led to a significant change in enthalpy. By cell viability (MTT) assays and cell morphology investigations, it was evidenced that PEGylated Fe3O4-SiO2 nanocomposites did not provide any appreciable cytotoxicity on J774 macrophage and MCF-7 breast cancer cell lines. Furthermore, noticeable internalization was evidenced by J774 cells with PEGylated Fe3O4-SiO2 nanocomposites in contrast to MCF-7 cells, in good agreement with the respective tendency of each cell line for endocytosis. © 2010 Elsevier B.V
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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