1,720,977 research outputs found
Multivariate Calibration of ToF-SIMS and XPS Data from Plasma-Treated Polypropylene Thin Films
No full textThe multivariate analysis techniques of principal components analysis (PCA), principal component
regression (PCR), and partial least squares regression (PLSR) were used to calibrate time-of-flight
secondary ion mass spectrometry (ToF-SIMS) data against X-ray photoelectron spectroscopy (XPS) data
obtained from plasma-treated polypropylene. This establishes correlations between quantitative
information obtained from XPS with the molecular information indicated by ToF-SIMS, allowing
the relative concentration of CO functional
groups and C:O atomic concentration ratio on
the surfaces of plasma-treated polypropylene to
be predicted from ToF-SIMS data alone. A fourfactor
prediction model was constructed, and was
deemed as adequate to predict the concentrations
of the surface CO functional groups, and of the
C:O atomic ratio with root mean square error of
prediction (RMSEP) values of 0.445 and 0.671 at%,
respectively
Clinical potential of plasma-functionalized graphene oxide ultrathin sheets for bone and blood vessel regeneration: Insights from cellular and animal models
Get PDFGraphene and graphene oxide (GO), due to their unique chemical and physical properties, possess biochemical characteristics that can trigger intercellular signals promoting tissue regeneration. Clinical applications of thin GO-derived sheets have inspired the development of various tissue regeneration and repair approaches. In this study, we demonstrate that ultrathin sheets of plasma-functionalized and reduced GO, with the oxygen content ranging from 3.2 % to 22 % and the nitrogen content from 0 % to 8.3 %, retain their essential mechanical and molecular integrity, and exhibit robust potential for regenerating bone tissue and blood vessels across multiple cellular and animal models. Initially, we observed the growth of blood vessels and bone tissue in vitro using these functionalized GO sheets on human adipose-derived mesenchymal stem cells and umbilical vein endothelial cells. Remarkably, our study indicates a 2.5-fold increase in mineralization and two-fold increase in tubule formation even in media lacking osteogenic and angiogenic supplements. Subsequently, we observed the initiation, conduction, and formation of bone and blood vessels in a rat tibial osteotomy model, evident from a marked 4-fold increase in the volume of low radio-opacity bone tissue and a significant elevation in connectivity density, all without the use of stem cells or growth factors. Finally, we validated these findings in a mouse critical-size calvarial defect model (33 % higher healing rate) and a rat skin lesion model (up to 2.5-fold increase in the number of blood vessels, and 35 % increase in blood vessels diameter). This study elucidates the pro-osteogenic and pro-angiogenic properties of both pristine and plasma-treated GO ultrathin films. These properties suggest their significant potential for clinical applications, and as valuable biomaterials for investigating fundamental aspects of bone and blood vessel regeneration
Ultra-thin polymer coating for promoting neural cells integration with neural implants
No full textHuman neuroblastoma (SH-SY5Y) cells were used to demonstrate biocompatibility ( including control over direction of neurites) for multilayer thin polymer coatings with neural cells. The ultra-thin (<20 nm) coatings were synthesised using plasma deposition process with (CH4, C2H2 and O2) gasses as precursors. The aim is to use these thin films to add bio-selectivity to orthopaedic and neurological implants such as cervical disc and interbody replacement, in addition to providing other qualities such as degradation resistance and permeation barrier. X-ray photo electron spectroscopy and contact angle measurements were used to provide surface molecular and surface energy information, respectively. The thin coatings’ functionality remained intact despite robust sterilisation process. The coatings showed no toxicity effects on neural cells growth and spreading after 6 days. Neural cells responded favourably (cell growth and spreading) to thinner (<6 nm) coatings that are rich in oxygen. Closer inspection revealed that neurites grow denser on surfaces with C=O functional groups and reacted negatively to the increase in C-O functional groups on the surface. Best neurite-like differentiation towards neural-like cells were observed on surfaces that were plasma deposited using C2H2 gas (with or without oxygen). Plasma treatment using CH4 produced thin coatings with lowest surface energy that repelled neurites cells (very low cell density). Hence, the latter treatment is useful for cases where cells/bio-coatings inhibition is desired
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
Hybrid graphene oxide/amorphous carbon coatings and their effect on the viability and toxicity of different cell types
No full textHerein, we explored the possibility to develop hybrid graphene oxide/amorphous carbon (GO/a-C) coatings with
different oxidation degree and analysed the influence of surface oxygen composition on biocompatibility.
GO/a-C films were obtained by plasma treatment of GO-coated PEEK substrates using different relative
amounts of methane and oxygen as gaseous precursors. The chemical surface composition of the coatings, including
oxygen abundance and nature of the oxygen-containing groups, was analysed by X-ray photoelectron
spectroscopy, and cell response to the sample materials was assessed by viability and cytotoxicity assays on two
different cell types, including human osteoblasts (hFOB) and human gingiva fibroblasts (hGF).
The cells presented partially decreased viability on plasma-treated samples respect to the untreated PEEK
substrate, but no significant evidence of cell toxicity was shown, with LDH release largely below 20% for all the
materials. A distinct cell-specific cytotoxicity response was observed. No significant effects were registered on
hGF cells, suggesting that hGF cells were not sensitive to the different oxygen surface content of the coatings. On
the other side, hFOB showed relatively higher toxicity when cultured on the samples with high surface oxygen
concentration. Human osteoblasts cell toxicity increased considerably with increasing content of carbonyl and
carboxyl groups on the surface, suggesting that these functional groups had an important role in inducing
oxidative stress in hFOB cells
Dispelling 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
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