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Oxidation State of a Polyurethane Membrane after Plasma Etching
Matthew D. Moles,Colin A. Scotchford,Alastair Campbell Ritchie
Conference Papers in Science , 2014, DOI: 10.1155/2014/347979
Abstract: Low moduli cell culture substrates can be used to apply dynamic mechanical strain to cells, by surface deformation. Understanding the surface interaction with cells is critical to improving cell adhesion and normal growth. A medical grade polyurethane (PU), Chronoflex AL 80A, was modified by oxygen plasma etching and characterised by X-ray photoelectron spectroscopy. Etching resulted in increased cross-linking at the isocyanate bond and formation of new oxygen moieties. The model, derived from patent data and XPS data of the unetched PU, indicated that the additional oxygen was likely to be hydroxyl and carbonyl groups. Etched membranes enhanced protein adhesion, resulting in full surface coverage compared to unetched PU. The etched PU supported cell adhesion and spreading, while the unetched PU was not conducive to monolayer formation. 1. Introduction The human body comprises tissues with a range of elastic moduli. Improving the response of in vitro cell- and tissue-based investigations can be achieved by culturing cells upon a substrate with a modulus closer to that of living tissue, as opposed to tissue culture polystyrene that has a modulus an order of magnitude greater than smooth muscle, for example, [1]. In addition, dynamic modulation of the substrate can provide mechanical signals that drive differentiation or proliferation. Previously, a stable biocompatible polyurethane (PU), Chronoflex AL 80A (AdvanSource Biomaterials, Wilmington, MA), was tested as a low modulus candidate substrate for a bioreactor capable of subjecting cells to a dynamic mechanical environment [2]. PU was selected as it is more resilient [3] and has a better cell response than similar polymers [4]. It was shown that plasma etching is a key factor to the success of cell adhesion and normal cell growth: the wettability was found to be dependent on etching power and duration, while roughness was more affected by the duration [2]. Therefore the state of oxidation of the PU membrane has been examined, in order to understand the effects of plasma etching on protein and cell adhesion. 2. Method 2.1. Membrane Manufacture and Modification PU membranes were produced as described previously [2]. In brief, polyurethane membranes of thickness ?μm (mean ± standard deviation (SD)) were formed by solvent casting with tetrahydrofuran (10% w/w) and drying in a vacuum oven at 50°C. Surface modification was carried out by etching using an inductively coupled RF-source (13.56?MHz) plasma barrel etcher (Biorad PT7100). The sample chamber was evacuated to 8?Pa, purged with oxygen (grade 2
Cytocompatibility and Mechanical Properties of Short Phosphate Glass Fibre Reinforced Polylactic Acid (PLA) Composites: Effect of Coupling Agent Mediated Interface
Muhammad Sami Hasan,Ifty Ahmed,Andrew Parsons,Gavin Walker,Colin Scotchford
Journal of Functional Biomaterials , 2012, DOI: 10.3390/jfb3040706
Abstract: In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ? = 20 μm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent’s within medical implant devices.
Agency at Work: A Dynamic Interpretive Approach  [PDF]
Colin Campbell
Sociology Mind (SM) , 2012, DOI: 10.4236/sm.2012.24047
Abstract: Roy’s 1950s paper “Banana Time” is used as the basis for an exploration of the nature and relationship of agency and action. Roy’s activity in playing his “game of work” is shown to be a feature of individual conduct that, despite possessing subjective meaning, is largely neglected by contemporary sociologists, mainly because of its covert character. What an examination of this aspect of his conduct suggests is the need to revise the conventional observational approach to the definition of the unit act by recognising that there may well be an additional actor’s covert definition sitting within the accepted social definition and that it is therefore necessary to use the criterion of attentionality to identify the unit act. An analysis of Roy’s game of work also helps to shed light on the possible relationship between action and agency, revealing that while the power of agency enables individuals to act, it is also frequently necessary for individuals to act in order to maintain or restore their power of agency. Finally, a consideration of the function fulfilled by Roy’s game of work shows that a behaviourist-style stimulus-response analysis of conduct is not at odds either with voluntarism or the adoption of the actor’s standpoint. This is because Roy demonstrates how actors are themselves lay behaviourists, fully aware of how they need to manipulate stimuli in order to produce desired responses in themselves.
The Value of Using Unofficial Measurements of Rainfall: The Dublin Storm and Flood of June 1963  [PDF]
Colin Clark
Journal of Geoscience and Environment Protection (GEP) , 2019, DOI: 10.4236/gep.2019.72006
Abstract: Rainfall measurements are vital for the design of hydraulic structures, climate change studies, irrigation and land drainage works. The most important source of design rainfall data comes from convective storms. Accurate assessment of the storm rainfall requires a fairly dense network of raingauges. In 1963, such a storm took place over Dublin in Ireland. However, the existing raingauge network was insufficient to identify both the depth and pattern of rainfall. An appeal was made by Met Eireann for additional unofficial rainfall data. The result was remarkable in that the estimated maximum rainfall depth was found to be more than double the official value and that the resulting depth area analysis suggested a rainfall volume over a large area much bigger than the original isohyet map indicated. This result has huge implications for the estimation of maximum rainfall and dam safety assessment, especially in countries where the raingauge network has a low density. This paper first provides a description of the synoptic conditions that led to the storm, second an analysis of the rainfall data and how the unofficial measurements produced a very different depth area relationship; third, the social consequences of the resulting flood are described. Fourth, the storm is then placed in the context of other storms in the British Isles Finally the implications for rainfall measurement, gauge density and an example of how revised estimates of probable maximum precipitation (PMP) have been used to improve the safety and design standard of a flood detention dam are discussed.
Shifts in Circulating Concentrations of Glucose in Domesticated Mammals: Is There a Consistent Adaptation to Domestication?  [PDF]
Colin G. Scanes
Food and Nutrition Sciences (FNS) , 2014, DOI: 10.4236/fns.2014.517178
Abstract: There have been marked changes in amylase gene number during human evolution resulting in shifts in carbohydrate metabolism. This has been related to utilization of starch. Similarly, there are changes in enzymes related to carbohydrate metabolism in dogs. Again, this has been linked to improving starch utilization following domestication. It was questioned as circulating concentrations of glucose is a good indicator of putative differences in carbohydrate metabolism across domesticated animals. Domesticated bovids had lower (p < 0.001) circulating concentrations of glucose than wild species in their respective subfamilies. Circulating concentrations of glucose were consistently lower (p < 0.001) in domesticated animals compared to either closely related wild species or the mean for wild species in their subfamilies (or families where there is insufficient data available). It is suggested that shift to lower circulating concentrations of glucose in domesticated animals is related to greater starch intake following domestication in a manner akin to the shifts in carbohydrate metabolism and amylase gene number in human evolution.
Correction: A Challenge for the Development of Malaria Vaccines: Polymorphic Target Antigens
Colin Sutherland
PLOS Medicine , 2007, DOI: 10.1371/journal.pmed.0040175
A Challenge for the Development of Malaria Vaccines: Polymorphic Target Antigens
Colin Sutherland
PLOS Medicine , 2007, DOI: 10.1371/journal.pmed.0040116
Lightning Sensors for Observing, Tracking and Nowcasting Severe Weather
Colin Price
Sensors , 2008, DOI: 10.3390/s8010157
Abstract: Severe and extreme weather is a major natural hazard all over the world, oftenresulting in major natural disasters such as hail storms, tornados, wind storms, flash floods,forest fires and lightning damages. While precipitation, wind, hail, tornados, turbulence,etc. can only be observed at close distances, lightning activity in these damaging stormscan be monitored at all spatial scales, from local (using very high frequency [VHF]sensors), to regional (using very low frequency [VLF] sensors), and even global scales(using extremely low frequency [ELF] sensors). Using sensors that detect the radio wavesemitted by each lightning discharge, it is now possible to observe and track continuouslydistant thunderstorms using ground networks of sensors. In addition to the number oflightning discharges, these sensors can also provide information on lightningcharacteristics such as the ratio between intra-cloud and cloud-to-ground lightning, thepolarity of the lightning discharge, peak currents, charge removal, etc. It has been shownthat changes in some of these lightning characteristics during thunderstorms are oftenrelated to changes in the severity of the storms. In this paper different lightning observingsystems are described, and a few examples are provided showing how lightning may beused to monitor storm hazards around the globe, while also providing the possibility ofsupplying short term forecasts, called nowcasting.
The desktop genome
Colin Semple
Genome Biology , 2001, DOI: 10.1186/gb-2000-2-1-reports2001
Abstract: And now the caveats. Genscan can detect most (perhaps between 70 and 90%), but not all, of the genes present in human genomic sequences, and by no means all novel genes show significant similarity to previously known sequences. This means that the set of confirmed genes in Ensembl is necessarily a conservative one. This problem may be further exacerbated by the quality of the sequence submitted. Ensembl uses the Human genome project working draft sequence assemblies (or 'golden path') produced at the University of California at Santa Cruz, which are known to contain many gaps and misassemblies. The golden path appears to be particularly unreliable in regions where it is composed of many small genomic sequence fragments from recently sequenced bacterial artificial chromosomes (BAC) clones. Many of these fragments are assembled in the wrong order and/or orientation. Such misassemblies will be a further source of errors and omissions in Ensembl. Although Genscan can detect the presence of most genes, it is substantially less successful in predicting their correct exonic structures (as with other ab initio gene predictions). This means that many, if not most, of the gene structures in Ensembl will be incorrect, or 'partial' predictions in Ensembl parlance.In spite of these difficulties Ensembl remains a useful tool for the cautious biologist. It should detect the presence of most genes in a given fragment of genomic sequence and indicate their location in the genome on the basis of the best mapping data available. In addition it has a stab at predicting gene structures that should be accurate if the gene in question has a close homolog which is already known. Most aspects of the analysis Ensembl carries out are the subject of active research, so improvements in performance, as a result of the inclusion of new sequence data and algorithms, will be ongoing. Having secured major funding earlier this year, the database promises to become the most important source of annotat
The family way
Colin Semple
Genome Biology , 2000, DOI: 10.1186/gb-2000-1-2-reports2044
Abstract: Since its inception in 1996, Pfam has aimed to be a comprehensive database of protein families defined by the presence of shared domains. The database is partitioned into two sections: Pfam-A contains accurate multiple alignments that are curated manually, whereas Pfam-B is generated automatically by clustering and aligning protein sequences not already covered by Pfam-A. Pfam-A families have permanent accession numbers and contain functional annotation and cross-references to other protein domain and motif databases, whereas Pfam-B families are regenerated at each release and are less well annotated. Each domain in Pfam is represented by a position-specific scoring model or profile; the particular type of statistical model used to derive such profiles in Pfam is the hidden Markov model (HMM). Pfam consists of a library of HMMs that can be used as sensitive tools to find new members of the domains represented. It is reported that Pfam HMMs match around two thirds of proteins in SWISSPROT and TrEMBL, and that for complete genomes Pfam currently matches up to half of the proteins discovered. It is possible to browse Pfam online or to perform a search with a protein or DNA sequence of interest. Once a Pfam domain has been identified, information relating to its physical structure, typical position (for example, carboxy-terminal), functional annotation and species distribution can be retrieved.The site is well documented with links to related literature and software as well as other profile search sites. It is possible to bookmark individual Pfam domain pages.Pfam is updated erratically every few months from the protein sequences deposited in SWISSPROT and TrEMBL.A single Pfam search can often be as sensitive as a detailed trawl through the databases with BLAST or FASTA, and can therefore save a lot of time in characterizing proteins with no strong similarities to known sequences. In addition, the HMM software on which Pfam is based is licensed under the Gnu Public Lice
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