Drug diffusion from polymeric delivery devices: a problem with two moving boundaries

An existing model for solvent penetration and drug release from a spherically-shaped polymeric drug delivery device is revisited. The model has two moving boundaries, one that describes the interface between the glassy and rubbery states of polymer, and another that defines the interface between the polymer ball and the pool of solvent. The model is extended so that the nonlinear diffusion coefficient of drug explicitly depends on the concentration of solvent, and the resulting equations are solved numerically using a front-fixing transformation together with a finite difference spatial discretisation and the method of lines. We present evidence that our scheme is much more accurate than a previous scheme. Asymptotic results in the small-time limit are presented, which show how the use of a kinetic law as a boundary condition on the innermost moving boundary dictates qualitative behaviour, the scalings being very different to the similar moving boundary problem that arises from modelling the melting of an ice ball. The implication is that the model considered here exhibits what is referred to as ``non-Fickian'' or Case II diffusion which, together with the initially constant rate of drug release, has certain appeal from a pharmaceutical perspective

Applications of Transmission Electron Microscopy to Coal

Coal consists of a hydrocarbon matrix in which minerals are embedded. The hydrocarbon matter also contains impurities distributed as individual atoms. Thus, coal has phases similar to those in metallic or ceramic alloy systems; a matrix, included precipitates and atoms distributed individually in solid solution. Consequently, techniques of electron microscopy developed to examine metallic and ceramic alloy systems are directly applicable to coal. We report application of microanalytical techniques of electron microscopy to coal using examples of measurements for several coals. Identification and characterization of clays and sulfides is described. Use of x-ray emission spectroscopy for organic element measurement is emphasized

Bill Viola ou l’image sans représentation

Bill Viola affirme que l’ère de la vision optique est terminée et, malgré cela, ses œuvres donnent l’impression d’une parfaite évidence visuelle : ce paradoxe d’une image non destinée à la vue est le thème de cet article. La première thèse développée grâce à la comparaison de la production du vidéaste avec l’art figuratif et le théâtre est qu’elle a une autonomie esthétique spécifique qui se fonde sur l’élision préalable du seuil de la fiction. La deuxième thèse est que B. Viola propose à nouveau la conception de cet œil innocent dont on pensait qu’il n’existait pas, sous la forme d’un corps sincère dont l’existence reste encore à prouver. Il crée en effet des configurations audiovisuelles qui permettent, par la mise en avant de l’expressivité originaire de l’homme, de produire un effet persuasif, affirmatif même, sur le spectateur qu’il soit naïf ou sophistiqué tout en sollicitant son système nerveux. La troisième thèse est que dans toute sa production est à l’œuvre le même problème esthétique, à savoir le délitement de l’identité psychologique du spectateur qui fait l’expérience sur lui-même du véritable thème des vidéos : l’émotion. Ces images vont alors s’incorporer dans l’homme.Bill Viola claims that the era of optical vision is over and, despite this, his works give the impression of a perfect visual evidence. This article sets out to look at the paradox of an image which is not aimed to the sight. First, in comparing the work of this video-maker with figurative art and theatre, we can see that it partakes of a specific aesthetic autonomy grounded in the previous elision of the threshold of vision. Second, we can see that B. Viola offers once more the innocent eye which was believed not to exist, under the form of a sincere body whose existence remains to be proven. He indeed creates audio-visual configurations which allow by bringing forward the original expressivity of man, to produce a persuasive or even claiming effect on the viewer, be he naive or sophisticated in using his nervous system. Thirdly, the same aesthetic problem operates in his whole work: the deleting of psychological identity of the viewer experiencing within himself the theme of the video, this theme being emotion. Such images will then be incorporated within him

PhenDisco: phenotype discovery system for the database of genotypes and phenotypes.

The database of genotypes and phenotypes (dbGaP) developed by the National Center for Biotechnology Information (NCBI) is a resource that contains information on various genome-wide association studies (GWAS) and is currently available via NCBI's dbGaP Entrez interface. The database is an important resource, providing GWAS data that can be used for new exploratory research or cross-study validation by authorized users. However, finding studies relevant to a particular phenotype of interest is challenging, as phenotype information is presented in a non-standardized way. To address this issue, we developed PhenDisco (phenotype discoverer), a new information retrieval system for dbGaP. PhenDisco consists of two main components: (1) text processing tools that standardize phenotype variables and study metadata, and (2) information retrieval tools that support queries from users and return ranked results. In a preliminary comparison involving 18 search scenarios, PhenDisco showed promising performance for both unranked and ranked search comparisons with dbGaP's search engine Entrez. The system can be accessed at http://pfindr.net

‘Question Moments’: A Rolling Programme of Question Opportunities in Classroom Science

This article has been made available through the Brunel Open Access Publishing Fund.This naturalistic study integrates specific 'question moments' into lesson plans to increase pupils' classroom interactions. A range of teaching tools has explored students' ideas through opportunities to ask and write questions. Their oral and written outcomes provide data on individual and group misunderstandings. Changes to the schedule of lessons were introduced to discuss these questions and solve disparities. Flexible lesson planning over fourteen lessons across a four-week period of highschool chemistry accommodated students' contributions and increased student participation, promoted inquiring and individualised teaching, with each teaching strategy feeding forward into the next

The presentation, diagnosis and management of non-traumatic wrist pain: an evaluation of current practice in secondary care in the UK NHS

AbstractObjectivesThe study aims were to assess the burden of non-traumatic wrist pain in terms of numbers of referrals to secondary care, and to characterise how patients present, are diagnosed and are managed in secondary care in the United Kingdom National Health Service.MethodsTen consecutive patients presenting with non-traumatic wrist pain were identified retrospectively at each of 16 participating hospitals and data was extracted for twelve months following the initial referral.ResultsThe 160 patients consisted of 100 females and 60 males with a median age of 49, accounting for approximately 13% of all new hand/wrist referrals. The dominant wrist was affected in 60% of cases and the mean symptom duration was 13.3 months. Diagnoses were grouped into: osteoarthritis (OA) (31%), tendinopathy (13%), ganglion (14%), ulnar sided pain (17%) and other (25%). The OA group was significantly older than other groups, while other groups contained a predominance of females.The non-surgical interventions in decreasing frequency of usage were: steroid injections (39%), physiotherapy (32%), splint (31%) and analgesics (12%). Of those who underwent surgery, all patients had previously received non-surgical treatment, however 42% had undergone only one non-surgical intervention.ConclusionNon-traumatic wrist pain represents a significant burden to secondary care both in terms of new patient referrals and in terms of investigation, follow up and treatment. Those presenting with osteoarthritis are more likely to be older and male, while those presenting with other diagnoses are more likely to be younger and female

Contextual influences on health worker motivation in district hospitals in Kenya

<p>Abstract</p> <p>Background</p> <p>Organizational factors are considered to be an important influence on health workers' uptake of interventions that improve their practices. These are additionally influenced by factors operating at individual and broader health system levels. We sought to explore contextual influences on worker motivation, a factor that may modify the effect of an intervention aimed at changing clinical practices in Kenyan hospitals.</p> <p>Methods</p> <p>Franco LM, et al's (Health sector reform and public sector health worker motivation: a conceptual framework. Soc Sci Med. 2002, 54: 1255–66) model of motivational influences was used to frame the study Qualitative methods including individual in-depth interviews, small-group interviews and focus group discussions were used to gather data from 185 health workers during one-week visits to each of eight district hospitals. Data were collected prior to a planned intervention aiming to implement new practice guidelines and improve quality of care. Additionally, on-site observations of routine health worker behaviour in the study sites were used to inform analyses.</p> <p>Results</p> <p>Study settings are likely to have important influences on worker motivation. Effective management at hospital level may create an enabling working environment modifying the impact of resource shortfalls. Supportive leadership may foster good working relationships between cadres, improve motivation through provision of local incentives and appropriately handle workers' expectations in terms of promotions, performance appraisal processes, and good communication. Such organisational attributes may counteract de-motivating factors at a national level, such as poor schemes of service, and enhance personally motivating factors such as the desire to maintain professional standards.</p> <p>Conclusion</p> <p>Motivation is likely to influence powerfully any attempts to change or improve health worker and hospital practices. Some factors influencing motivation may themselves be influenced by the processes chosen to implement change.</p