1,720,992 research outputs found
Structural analysis of polymeric scaffolds by Micro-CT
No full textThe use of porous structures as tissue engineering scaffolds imposes demands on structural parameters such as porosity, pore size and interconnectivity. For the structural analysis of porous scaffolds, micro-computed tomography (μCT) is an ideal tool. μCT is a 3D X-ray imaging method that has several advantages over scanning electron microscopy (SEM) and other conventional characterisation techniques:\ud
\ud
• visualisation in 3D\ud
• quantitative results\ud
• non-destructiveness\ud
• minimal sample preparatio
Fabrication of osteochondral scaffolds with stereolithography
No full textThe osteochondral defect is a classical model for a multiple-tissue problem[1]. Tissue engineering of either bone or cartilage imposes different demands on a scaffold concerning porosity, pore size and interconnectivity. Furthermore, local release of tissue-specific growth factors necessitates a tailored architecture. For the fabrication of an osteochondral scaffold with region specific architecture, an advanced technique is required. Stereolithography is a rapid prototyping technique that allows for the creation of such 3D polymer objects with well-defined architecture. Its working principle is the partial irradiation of a resin, causing a liquid-solid transition. By irradiating this resin by a computer-driven light source, a solid 3D object is constructed layer by layer. To make biodegradable polymers applicable in stereolithography, low-molecular weight polymers have to be functionalised with double bonds to enable photo-initiated crosslinking
Properties of porous structures prepared by stereolithography using a polylactide resin
Full text linkRapid prototyping techniques such as stereolithography allow for\ud
building designed tissue engineering scaffolds with high accuracy. In this work, a stereolithography\ud
resin based on poly(D,L-lactide) was developed. Biodegradable scaffolds with varying porosity were\ud
built from this resin. The scaffolds were analysed by μCT-scanning and compression testing. The\ud
porous structures showed excellent mechanical properties in the range of trabecular bone
Development of a PDLLA-based stereolithography resin for making tissue engineering scaffolds
No full textThe use of porous structures as tissue engineering scaffolds imposes high demands on the pore architecture. Stereolithography is a rapid prototyping method based on photo-polymerisation, that can be utilised to make 3D constructs with high spatial control. In this study, biodegradable resins were developed that can find application in stereolithography. Poly(D,L-lactide) (PDLLA) oligomers were synthesised and functionalised with methacrylate end-groups. By mixing the resulting macromers with a diluent, photo-initiator and inhibitor, lowviscosity resins were obtained that were photocrosslinked to yield stiff and strong degradable poly(lactide) networks. Also, porous scaffolds were fabricated on a stereolithography apparatus (SLA) from a nondegradable resin
Designed tissue engineering scaffolds prepared by stereolithography
No full textFor the fabrication of tissue engineering scaffolds, the\ud
intended tissue formation process imposes requirements\ud
on the architecture. The chosen porosity often is a tradeoff\ud
between volume and surface area accessible to cells,\ud
and mechanical properties of the construct.\ud
Interconnectivity of the pores is essential for cell\ud
migration through the scaffold and for mass transport.\ud
Conventional techniques such as salt leaching often\ud
result in heterogeneous structures and do not allow for a\ud
precise control of the architecture. Stereolithography is\ud
a rapid prototyping method that can be utilised to make\ud
3D constructs with high spatial control by radical photopolymerisation.\ud
In this study, a regular structure based on cyclic\ud
repetition of cell units were designed through CAD\ud
modelling.. One of these structures was built on a\ud
stereolithography apparatus (SLA). Furthermore, a\ud
polylactide-based resin was developed that can be\ud
applied in stereolithography. Polylactide has proven\ud
before to be a well-performing polymer in bone tissue\ud
engineering. The final objective in this study is to build\ud
newly designed PDLLA scaffolds with a precise SLA\ud
fabrication technique to study the effect of scaffold\ud
architecture on mechanical and biological properties
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
Properties of porous poly(trimethylene carbonate) structures for controlled release applications using high CO2
No full textVariations 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
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