1,720,961 research outputs found
Collagen-based 3D printed poly (glycerol sebacate) composite scaffold with biomimicking mechanical properties for enhanced cartilage defect repair
No full textCartilage defect repair with optimal efficiency remains a significant challenge due to the limited self-repair capability of native tissues. The development of bioactive scaffolds with biomimicking mechanical properties and degradation rates matched with cartilage regeneration while simultaneously driving chondrogenesis, plays a crucial role in enhancing cartilage defect repair. To this end, a novel composite scaffold with hierarchical porosity was manufactured by incorporating a pro-chondrogenic collagen type I/II-hyaluronic acid (CI/II-HyA) matrix to a 3D-printed poly(glycerol sebacate) (PGS) framework. Based on the mechanical enforcement of PGS framework, the composite scaffold exhibited a compressive modulus of 167.0 kPa, similar to that of native cartilage, as well as excellent fatigue resistance, similar to that of native joint tissue. In vitro degradation tests demonstrated that the composite scaffold maintained structural, mass, and mechanical stability during the initial cartilage regeneration period of 4 weeks, while degraded linearly over time. In vitro biological tests with rat-derived mesenchymal stem cell (MSC) revealed that, the composite scaffold displayed increased cell loading efficiency and improved overall cell viability due to the incorporation of CI/II-HyA matrix. Additionally, it also sustained an effective and high-quality MSC chondrogenesis and abundant de-novo cartilage-like matrix deposition up to day 28. Overall, the biomimetic composite scaffold with sufficient mechanical support, matched degradation rate with cartilage regeneration, and effective chondrogenesis stimulation shows great potential to be an ideal candidate for enhancing cartilage defect repair
Magnesium-based supports for stem cell therapy of vascular disease
Full text linkMagnesium (Mg) is a widely used material in industrial applications due its low weight, ductility and good mechanical properties. For clinical applications such as non-permanent implants Mg is considered as a good option because it is biodegradable and its degradation products are not harmful for the human body. Moreover, Mg is essential element in the biology of mammals. However, Mg is chemically reactive and hydrogen gas is released as part of the oxidation i.e. degradation. Pockets of hydrogen gas may develop at implant sites and cause unwanted tissue necrosis. Fortunately, the degradation rate can be altered by physico-chemical modification of the material and may alleviate adverse biological responses. A successful procedure is plasma electrolytic oxidation (PEO) technique, which generates as a surface layer of MgO/Mg(OH)2 in a controlled way. Thus the degradation rate of the Mg can be carefully tuned and reduced. An additional advantage of PEO is that properly designed topographical surfaces can be produced that improve adhesion and function of e.g. therapeutic stem cells. The aims of this work was firstly to use PEO to modify the surface of c.p Mg (chemically pure Mg) in order to improve its degradation considering using this support to deliver therapeutic cells that augment healing of vascular lesions. A second major aim was to set off the development of therapeutic devices that synchronize the degradation of the material with the progress of the tissue healing in particular after balloon catheterization of atherosclerotic arteries and placing magnesium-based stents. This thesis contains in the different chapters a complete study of modified magnesium from both a material and a biological perspective. This work started with the production, optimization and characterization of the material. After that, a biological validation was performed based on in vitro and ex vivo assays, performed under static and dynamic conditions with different cell types related to blood vessels (arteries) including endothelial cells, smooth muscle cells, macrophages and fibroblasts. Additionally, cell-material interaction and therapeutically effect of adipose tissue-derived stromal/stem cells cultured on the surfaces was studied. This work yielded prototype coatings that reduce the degradation rate of the material, while improving biocompatibility, in particular under hemodynamic conditions. The complexity to develop the idea to a final product is large and requires further investment in time and investigation to achieve the final goal of a biofunctional, biodegradable cardiovascular stent, for which we made the first pioneering steps. We conclude that modification c.p Mg implants by PEO technique is promising for cardiovascular devices that support the healing of the vascular lesion by delivering of stem cells
Magnesium-based supports for stem cell therapy of vascular disease
Full text linkMagnesium (Mg) is a widely used material in industrial applications due its low weight, ductility and good mechanical properties. For clinical applications such as non-permanent implants Mg is considered as a good option because it is biodegradable and its degradation products are not harmful for the human body. Moreover, Mg is essential element in the biology of mammals. However, Mg is chemically reactive and hydrogen gas is released as part of the oxidation i.e. degradation. Pockets of hydrogen gas may develop at implant sites and cause unwanted tissue necrosis. Fortunately, the degradation rate can be altered by physico-chemical modification of the material and may alleviate adverse biological responses. A successful procedure is plasma electrolytic oxidation (PEO) technique, which generates as a surface layer of MgO/Mg(OH)2 in a controlled way. Thus the degradation rate of the Mg can be carefully tuned and reduced. An additional advantage of PEO is that properly designed topographical surfaces can be produced that improve adhesion and function of e.g. therapeutic stem cells. The aims of this work was firstly to use PEO to modify the surface of c.p Mg (chemically pure Mg) in order to improve its degradation considering using this support to deliver therapeutic cells that augment healing of vascular lesions. A second major aim was to set off the development of therapeutic devices that synchronize the degradation of the material with the progress of the tissue healing in particular after balloon catheterization of atherosclerotic arteries and placing magnesium-based stents. This thesis contains in the different chapters a complete study of modified magnesium from both a material and a biological perspective. This work started with the production, optimization and characterization of the material. After that, a biological validation was performed based on in vitro and ex vivo assays, performed under static and dynamic conditions with different cell types related to blood vessels (arteries) including endothelial cells, smooth muscle cells, macrophages and fibroblasts. Additionally, cell-material interaction and therapeutically effect of adipose tissue-derived stromal/stem cells cultured on the surfaces was studied. This work yielded prototype coatings that reduce the degradation rate of the material, while improving biocompatibility, in particular under hemodynamic conditions. The complexity to develop the idea to a final product is large and requires further investment in time and investigation to achieve the final goal of a biofunctional, biodegradable cardiovascular stent, for which we made the first pioneering steps. We conclude that modification c.p Mg implants by PEO technique is promising for cardiovascular devices that support the healing of the vascular lesion by delivering of stem cells
Magnesium-based supports for stem cell therapy of vascular disease
Full text linkMagnesium (Mg) is a widely used material in industrial applications due its low weight, ductility and good mechanical properties. For clinical applications such as non-permanent implants Mg is considered as a good option because it is biodegradable and its degradation products are not harmful for the human body. Moreover, Mg is essential element in the biology of mammals. However, Mg is chemically reactive and hydrogen gas is released as part of the oxidation i.e. degradation. Pockets of hydrogen gas may develop at implant sites and cause unwanted tissue necrosis. Fortunately, the degradation rate can be altered by physico-chemical modification of the material and may alleviate adverse biological responses. A successful procedure is plasma electrolytic oxidation (PEO) technique, which generates as a surface layer of MgO/Mg(OH)2 in a controlled way. Thus the degradation rate of the Mg can be carefully tuned and reduced. An additional advantage of PEO is that properly designed topographical surfaces can be produced that improve adhesion and function of e.g. therapeutic stem cells. The aims of this work was firstly to use PEO to modify the surface of c.p Mg (chemically pure Mg) in order to improve its degradation considering using this support to deliver therapeutic cells that augment healing of vascular lesions. A second major aim was to set off the development of therapeutic devices that synchronize the degradation of the material with the progress of the tissue healing in particular after balloon catheterization of atherosclerotic arteries and placing magnesium-based stents. This thesis contains in the different chapters a complete study of modified magnesium from both a material and a biological perspective. This work started with the production, optimization and characterization of the material. After that, a biological validation was performed based on in vitro and ex vivo assays, performed under static and dynamic conditions with different cell types related to blood vessels (arteries) including endothelial cells, smooth muscle cells, macrophages and fibroblasts. Additionally, cell-material interaction and therapeutically effect of adipose tissue-derived stromal/stem cells cultured on the surfaces was studied. This work yielded prototype coatings that reduce the degradation rate of the material, while improving biocompatibility, in particular under hemodynamic conditions. The complexity to develop the idea to a final product is large and requires further investment in time and investigation to achieve the final goal of a biofunctional, biodegradable cardiovascular stent, for which we made the first pioneering steps. We conclude that modification c.p Mg implants by PEO technique is promising for cardiovascular devices that support the healing of the vascular lesion by delivering of stem cells
Magnesium-based supports for stem cell therapy of vascular disease
Full text linkMagnesium (Mg) is a widely used material in industrial applications due its low weight, ductility and good mechanical properties. For clinical applications such as non-permanent implants Mg is considered as a good option because it is biodegradable and its degradation products are not harmful for the human body. Moreover, Mg is essential element in the biology of mammals. However, Mg is chemically reactive and hydrogen gas is released as part of the oxidation i.e. degradation. Pockets of hydrogen gas may develop at implant sites and cause unwanted tissue necrosis. Fortunately, the degradation rate can be altered by physico-chemical modification of the material and may alleviate adverse biological responses. A successful procedure is plasma electrolytic oxidation (PEO) technique, which generates as a surface layer of MgO/Mg(OH)2 in a controlled way. Thus the degradation rate of the Mg can be carefully tuned and reduced. An additional advantage of PEO is that properly designed topographical surfaces can be produced that improve adhesion and function of e.g. therapeutic stem cells. The aims of this work was firstly to use PEO to modify the surface of c.p Mg (chemically pure Mg) in order to improve its degradation considering using this support to deliver therapeutic cells that augment healing of vascular lesions. A second major aim was to set off the development of therapeutic devices that synchronize the degradation of the material with the progress of the tissue healing in particular after balloon catheterization of atherosclerotic arteries and placing magnesium-based stents. This thesis contains in the different chapters a complete study of modified magnesium from both a material and a biological perspective. This work started with the production, optimization and characterization of the material. After that, a biological validation was performed based on in vitro and ex vivo assays, performed under static and dynamic conditions with different cell types related to blood vessels (arteries) including endothelial cells, smooth muscle cells, macrophages and fibroblasts. Additionally, cell-material interaction and therapeutically effect of adipose tissue-derived stromal/stem cells cultured on the surfaces was studied. This work yielded prototype coatings that reduce the degradation rate of the material, while improving biocompatibility, in particular under hemodynamic conditions. The complexity to develop the idea to a final product is large and requires further investment in time and investigation to achieve the final goal of a biofunctional, biodegradable cardiovascular stent, for which we made the first pioneering steps. We conclude that modification c.p Mg implants by PEO technique is promising for cardiovascular devices that support the healing of the vascular lesion by delivering of stem cells
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
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