1,720,963 research outputs found
Ion-Implanted Amorphous Titania Nanotube Arrays - Tailoring Morphology, Chemical Composition and Electrical Conductivity for Advanced Biomedical Implants
No full textTitania nanotubes arrays represent a highly biocompatible material with an enormous surface area. Their tunable surface characteristics, especially tube diameters, enable the long-term culture of sensitive adult mammalian tissues ex vivo. Cultured murine brain slices survive for up to 14 days without showing significant degenerative effects. In fact, histomorphology and physiology of the tissues remain intact, as the native structure of the tissue is not destroyed, and physiological niches are preserved. However, increasing the conductivity of the intrinsically insulating arrays might benefit the culture of electrically excitable tissues. Moreover, conductive titania nanotube arrays might pave the way toward manufacturing advanced brain electrodes that ensure long-term neuronal tissue adhesion and stimulation. The presented thesis describes the effects of carbon ion implantation in amorphous titania nanotubes, which is carried out at room temperature to retain the amorphous structure. Since carbon is already present in the chemical composition of the pristine structures, low-energy, low-fluence carbon implantation seems advantageous for preserving the unique surface topography and biocompatibility. This thesis covers experimental, analytical, and theoretical approaches to investigate implantation-related phenomena and material characteristics within five subprojects. In detail, the research is guided by the interplay of sputtering and readsorption, amorphization and crystallization, viscous material flow and thermal spikes. The first subproject addresses morphological and compositional changes that arise from carbon implantation. Experimental observations and ab-initio-based thermodynamic considerations are combined to describe the local compositional patterning. The second subproject explores pore shrinking that occurs upon implantation in an experimental, analytical and theoretical manner. Defect-induced effects are reproduced using molecular dynamics calculations. Related to irradiation-induced viscous material flow upon implantation, surface relaxation and smoothing is quantified in the third subproject. In the fourth subproject, the increase in conductivity is analyzed both locally and globally, and the depth-dependent stoichiometry is determined. In the fifth subproject, laminin protein adsorption is assessed and the overall biocompatibility is evaluated with glial cells and neurons.
In conclusion, this thesis reveals manifold phenomena arising from carbon ion implantation of amorphous titania nanotubes, creating a comprehensive understanding of the underlying physics. Physical and chemical characteristics are evaluated to lay a foundation for further applications in the biomedical field.Titandioxid-Nanoröhren-Arrays stellen ein sehr biokompatibles Material mit einer enormen Oberfläche dar. Die justierbaren Oberflächeneigenschaften ermöglichen die Langzeitkultur empfindlicher adulter Gewebe ex vivo. So können murine Hirnschnitte in Dünnschnittkultur bis zu 14 Tage in ihrer Histomorphologie und Physiologie erhalten werden. Die native Struktur des Gewebes wird dabei nicht zerstört; physiologische Nischen bleiben erhalten. Eine Erhöhung der Leitfähigkeit der grundsätzlich isolierenden Arrays könnte die Kultur elektrisch erregbarer Gewebe begünstigen und die Herstellung fortschrittlicher Hirnelektroden ermöglichen, die eine langfristige Adhäsion und Stimulation von neuronalen Geweben bieten. Die vorliegende Arbeit beschreibt die Auswirkungen der Kohlenstoffimplantation in Titandioxid-Nanoröhren. Durch Implantation von Ionen mit niedriger Energie und geringer Fluenz sollen die amorphe Phase und die einzigartige Oberflächentopographie beibehalten werden. In fünf Teilprojekten werden experimentelle, analytische und theoretische Ansätze verfolgt, um implantationsbezogene Phänomene und Materialeigenschaften zu erforschen. Dabei wird das Zusammenspiel von Sputtern und Readsorption, Amorphisierung und Kristallisation, viskosem Materialfluss und thermischen Spikes betrachtet. Das erste Teilprojekt befasst sich mit Veränderungen der Morphologie und der chemischen Zusammensetzung. Experimentelle Beobachtungen und ab-initio-basierte thermodynamische Betrachtungen werden kombiniert, um die lokale Bildung von Strukturen mit unterschiedlichen stöchiometrischen Verhältnissen zu beschreiben. Das zweite Teilprojekt behandelt auf experimenteller, analytischer und theoretischer Ebene das Schrumpfen der Poren, das bei der Implantation auftritt. Defektinduzierte Effekte werden durch Molekulardynamik-Berechnungen nachvollzogen. Es ergibt sich ein bestrahlungsinduzierter viskoser Materialfluss, der die im dritten Teilprojekt beschriebene Oberflächenentspannung und -glättung bedingt. Das vierte Teilprojekt widmet sich der Erhöhung der Leitfähigkeit, welche lokal und global analysiert wird. Zusätzlich wird tiefenabhängig die Stöchiometrie untersucht. Im fünften Teilprojekt wird die Adsorption des Proteins Laminin evaluiert und die Biokompatibilität durch Zelltests mit Gliazellen und Neuronen eingeschätzt. Letztendlich ergibt sich ein umfassendes Bild der physikalischen Zusammenhänge und Materialeigenschaften, die aus der Kohlenstoffimplantation in amorphe Titandioxid-Nanoröhren resultieren. Damit wird der Weg zur weiteren Nutzung in der Biomedizin geebnet
Ion-Implanted Amorphous Titania Nanotube Arrays - Tailoring Morphology, Chemical Composition and Electrical Conductivity for Advanced Biomedical Implants
No full textTitania nanotubes arrays represent a highly biocompatible material with an enormous surface area. Their tunable surface characteristics, especially tube diameters, enable the long-term culture of sensitive adult mammalian tissues ex vivo. Cultured murine brain slices survive for up to 14 days without showing significant degenerative effects. In fact, histomorphology and physiology of the tissues remain intact, as the native structure of the tissue is not destroyed, and physiological niches are preserved. However, increasing the conductivity of the intrinsically insulating arrays might benefit the culture of electrically excitable tissues. Moreover, conductive titania nanotube arrays might pave the way toward manufacturing advanced brain electrodes that ensure long-term neuronal tissue adhesion and stimulation. The presented thesis describes the effects of carbon ion implantation in amorphous titania nanotubes, which is carried out at room temperature to retain the amorphous structure. Since carbon is already present in the chemical composition of the pristine structures, low-energy, low-fluence carbon implantation seems advantageous for preserving the unique surface topography and biocompatibility. This thesis covers experimental, analytical, and theoretical approaches to investigate implantation-related phenomena and material characteristics within five subprojects. In detail, the research is guided by the interplay of sputtering and readsorption, amorphization and crystallization, viscous material flow and thermal spikes. The first subproject addresses morphological and compositional changes that arise from carbon implantation. Experimental observations and ab-initio-based thermodynamic considerations are combined to describe the local compositional patterning. The second subproject explores pore shrinking that occurs upon implantation in an experimental, analytical and theoretical manner. Defect-induced effects are reproduced using molecular dynamics calculations. Related to irradiation-induced viscous material flow upon implantation, surface relaxation and smoothing is quantified in the third subproject. In the fourth subproject, the increase in conductivity is analyzed both locally and globally, and the depth-dependent stoichiometry is determined. In the fifth subproject, laminin protein adsorption is assessed and the overall biocompatibility is evaluated with glial cells and neurons.
In conclusion, this thesis reveals manifold phenomena arising from carbon ion implantation of amorphous titania nanotubes, creating a comprehensive understanding of the underlying physics. Physical and chemical characteristics are evaluated to lay a foundation for further applications in the biomedical field.Titandioxid-Nanoröhren-Arrays stellen ein sehr biokompatibles Material mit einer enormen Oberfläche dar. Die justierbaren Oberflächeneigenschaften ermöglichen die Langzeitkultur empfindlicher adulter Gewebe ex vivo. So können murine Hirnschnitte in Dünnschnittkultur bis zu 14 Tage in ihrer Histomorphologie und Physiologie erhalten werden. Die native Struktur des Gewebes wird dabei nicht zerstört; physiologische Nischen bleiben erhalten. Eine Erhöhung der Leitfähigkeit der grundsätzlich isolierenden Arrays könnte die Kultur elektrisch erregbarer Gewebe begünstigen und die Herstellung fortschrittlicher Hirnelektroden ermöglichen, die eine langfristige Adhäsion und Stimulation von neuronalen Geweben bieten. Die vorliegende Arbeit beschreibt die Auswirkungen der Kohlenstoffimplantation in Titandioxid-Nanoröhren. Durch Implantation von Ionen mit niedriger Energie und geringer Fluenz sollen die amorphe Phase und die einzigartige Oberflächentopographie beibehalten werden. In fünf Teilprojekten werden experimentelle, analytische und theoretische Ansätze verfolgt, um implantationsbezogene Phänomene und Materialeigenschaften zu erforschen. Dabei wird das Zusammenspiel von Sputtern und Readsorption, Amorphisierung und Kristallisation, viskosem Materialfluss und thermischen Spikes betrachtet. Das erste Teilprojekt befasst sich mit Veränderungen der Morphologie und der chemischen Zusammensetzung. Experimentelle Beobachtungen und ab-initio-basierte thermodynamische Betrachtungen werden kombiniert, um die lokale Bildung von Strukturen mit unterschiedlichen stöchiometrischen Verhältnissen zu beschreiben. Das zweite Teilprojekt behandelt auf experimenteller, analytischer und theoretischer Ebene das Schrumpfen der Poren, das bei der Implantation auftritt. Defektinduzierte Effekte werden durch Molekulardynamik-Berechnungen nachvollzogen. Es ergibt sich ein bestrahlungsinduzierter viskoser Materialfluss, der die im dritten Teilprojekt beschriebene Oberflächenentspannung und -glättung bedingt. Das vierte Teilprojekt widmet sich der Erhöhung der Leitfähigkeit, welche lokal und global analysiert wird. Zusätzlich wird tiefenabhängig die Stöchiometrie untersucht. Im fünften Teilprojekt wird die Adsorption des Proteins Laminin evaluiert und die Biokompatibilität durch Zelltests mit Gliazellen und Neuronen eingeschätzt. Letztendlich ergibt sich ein umfassendes Bild der physikalischen Zusammenhänge und Materialeigenschaften, die aus der Kohlenstoffimplantation in amorphe Titandioxid-Nanoröhren resultieren. Damit wird der Weg zur weiteren Nutzung in der Biomedizin geebnet
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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