1,721,006 research outputs found
ToF-SIMS of hydrogels
No full textData storage of 3 ToF-SIMS depth profiles of frozen-hydrated hydrogels as required by the EPSRC data deposit requiremen
Modelling of N-carboxy anhydride copolymerisations for improved sequence control of poly(amino acid)s in bioengineering applications
Full text linkSynthetically manufactured poly(amino acid)s have been exploited in a variety of bioengineering applications including antimicrobial surfaces and cell culture substrates because of their ability to display functionality linked to secondary structure formation. This functionality is closely connected to the sequence of the amino acids in the poly(amino acid) chains. N-carboxy anhydride (NCA) polymerisation is an attractive route to manufacture poly(amino acid)s but it lacks sequence control. Furthermore, experimental sequence analysis of poly(amino acid)s is challenging. Computational methods are an attractive alternative to obtain sequence related information but few computational copolymerisation models exist for this purpose and none have been designed for NCA polymerisations
Data for surface-controlled spatially heterogeneous physical properties of a supramolecular gel with homogeneous chemical composition
No full textData related to the research article entitled 'Surface-controlled spatially heterogeneous physical properties of a supramolecular gel with homogeneous chemical composition '
Plasma polymer gradients : developing a tool for the screening of biological responses to surfaces
Full text linkControlling the interaction of cells with a material surface is of major interest in the field of biomedical material science. Plasma polymers are an attractive way to modify the surface chemistry of a material because this technique is versatile and can be applied to a wide range of different surfaces. The aim of the present work is to prepare a new chemical gradient tool using plasma polymerisation and assess its ability to provoke position dependent cell-surface interactions. A novel diffusion based approach is used to develop gradients from hydrophobic hexane (ppHex) to more hydrophilic allylamine (ppAAm) plasma polymers. The surface of the gradient and that of uniform control samples is characterised using WCA, XPS, ToF-SIMS and AFM. This data shows that the most distinct gradient was found in the wettability profile which can be controlled by changing the size of the opening through which diffusion of depositing species from the plasma occurs. The mechanism of the gradient formation is studied with channels of well defined cross sections. The deposition rate obtained on these samples shows a sharp drop off in the amount of ppHex deposited from the plasma starting 2 mm in advance of the opening. An estimation of the sheath dimensions indicates that this corresponds to the sheath thickness. It is suggested that plasma deposition through small openings such as pores depends on the relative dimensions of the sheath and the pore cross section. Inside the channels, oligomer formation is observed in the gas phase, presumably following a nucleophilic addition reaction mechanism. To study the stability of these plasma polymer surfaces in physiological conditions, surface analysis is also carried out on samples exposed to aqueous solutions. Some changes in the topography of the plasma polymer films are found. Most notably, uniform samples of ppHex deposited on top of ppAAm show the formation of blisters that are not observed on other samples. It is argued that these blisters are the result of water penetrating through the top ppHex layer and interacting with the more hydrophilic ppAAm or glass substrate. 3T3 fibroblasts cultured on the gradients show a gradual increase in cell density. This cell density gradient can be related linearly to the wettability gradient on the surface with non-linear relationships being observed with other surface parameters such as the ppHex thickness. The cell number on uniform ppAAm is much greater than on the ppAAm side of the gradient. Data from experiments with non-proliferating 3T3 fibroblasts indicates that the differences between the gradient and uniform ppAAm as well as the cell density increase along the gradient have their origin in a different number of cells adhered to the surface within the first 24 hours of cell culture. The adsorption of albumin and fibronectin on the plasma polymers demonstrate that displacement of the former by the latter takes place on the surface when adsorbed competitively. However, this displacement does not occur in different extents along the gradient surface, suggesting that protein displacement can not explain the increase in cell density towards the ppAAm end of the gradient.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Modelling of N-carboxy anhydride copolymerisations for improved sequence control of poly(amino acid)s in bioengineering applications
Full text linkSynthetically manufactured poly(amino acid)s have been exploited in a variety of bioengineering applications including antimicrobial surfaces and cell culture substrates because of their ability to display functionality linked to secondary structure formation. This functionality is closely connected to the sequence of the amino acids in the poly(amino acid) chains. N-carboxy anhydride (NCA) polymerisation is an attractive route to manufacture poly(amino acid)s but it lacks sequence control. Furthermore, experimental sequence analysis of poly(amino acid)s is challenging. Computational methods are an attractive alternative to obtain sequence related information but few computational copolymerisation models exist for this purpose and none have been designed for NCA polymerisations
Plasma polymer gradients : developing a tool for the screening of biological responses to surfaces
No full textControlling the interaction of cells with a material surface is of major interest in the field of biomedical material science. Plasma polymers are an attractive way to modify the surface chemistry of a material because this technique is versatile and can be applied to a wide range of different surfaces. The aim of the present work is to prepare a new chemical gradient tool using plasma polymerisation and assess its ability to provoke position dependent cell-surface interactions. A novel diffusion based approach is used to develop gradients from hydrophobic hexane (ppHex) to more hydrophilic allylamine (ppAAm) plasma polymers. The surface of the gradient and that of uniform control samples is characterised using WCA, XPS, ToF-SIMS and AFM. This data shows that the most distinct gradient was found in the wettability profile which can be controlled by changing the size of the opening through which diffusion of depositing species from the plasma occurs.
The mechanism of the gradient formation is studied with channels of well defined cross sections. The deposition rate obtained on these samples shows a sharp drop off in the amount of ppHex deposited from the plasma starting 2 mm in advance of the opening. An estimation of the sheath dimensions indicates that this corresponds to the sheath thickness. It is suggested that plasma deposition through small openings such as pores depends on the relative dimensions of the sheath and the pore cross section. Inside the channels, oligomer formation is observed in the gas phase, presumably following a nucleophilic addition reaction mechanism.
To study the stability of these plasma polymer surfaces in physiological conditions, surface analysis is also carried out on samples exposed to aqueous solutions. Some changes in the topography of the plasma polymer films are found. Most notably, uniform samples of ppHex deposited on top of ppAAm show the formation of blisters that are not observed on other samples. It is argued that these blisters are the result of water penetrating through the top ppHex layer and interacting with the more hydrophilic ppAAm or glass substrate.
3T3 fibroblasts cultured on the gradients show a gradual increase in cell density. This cell density gradient can be related linearly to the wettability gradient on the surface with non-linear relationships being observed with other surface parameters such as the ppHex thickness. The cell number on uniform ppAAm is much greater than on the ppAAm side of the gradient. Data from experiments with non-proliferating 3T3 fibroblasts indicates that the differences between the gradient and uniform ppAAm as well as the cell density increase along the gradient have their origin in a different number of cells adhered to the surface within the first 24 hours of cell culture.
The adsorption of albumin and fibronectin on the plasma polymers demonstrate that displacement of the former by the latter takes place on the surface when adsorbed competitively. However, this displacement does not occur in different extents along the gradient surface, suggesting that protein displacement can not explain the increase in cell density towards the ppAAm end of the gradient
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
Surface-directed modulation of supramolecular gel properties
No full textSupramolecular materials are widely studied and used for a variety of applications; in most applications, these materials are in contact with surfaces of other materials. Whilst much focus has been placed on elucidating factors that affect supramolecular material properties, the influence of the material surface on gel formation is poorly characterised. Here, we demonstrate that surface properties directly affect the fibre architecture and mechanical properties of self-assembled cytidine based gel films
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