A discussion on 55 respirator cases in the recent poliomyelitis epidemic of 1956

No Abstrac

Rheological Methods and Their Application To Biological Systems

Pectin is a major component of the primary plant cell wall and is known to play an important role in many physiological processes. It also has has many uses in the food and biomedical industries as it is abundant, mechanochemically versatile and non-toxic. However, the relationship between its chemistry and mechanical properties is not fully understood. In this thesis, pectin in vitro and the pectin-rich outer cells of Arabidopsis seedlings are studied using an AFM methodology adapted from the animal rheology literature. The effects of the degree of methylation, and degree of blockiness on the viscoelastic properties of pectin are explored. Elastic and viscous properties of pectin are found to be negatively correlated with its degree of methylesterification, whilst elastic properties are positively correlated with its degree of blockiness. Mixed gels, composed of pectin with differing degrees of methylesterification are also investigated and their parameters are found to scale in accordance with their volume fraction. In vivo mechanical properties observed in the Arabidopsis hypocotyl are harder to disentangle, but a number of interesting differences between transverse and axial cell walls are observed. A modelling approach is taken, and although a model based on exponentially decaying terms is found to be adequate for the two material types studied, a fractional viscoelastic model is found to be far superior for pectin in vitro. Fractional viscoelasticity is the use of fractional differential equations for the modelling of viscoelastic phenomena. In addition to its aforementioned use for pectin, its utility is evidenced here by re-analysis of data gathered from the biomechanical literature. In spite of the apparently simple qualitative behaviours they exhibit, there are a number of unique challenges associated with the selection and fitting of fractional viscoelastic models due to their mathematical complexity. This complexity may, in part, explain why fractional viscoelasticity has seen limited use thus far, even though it captures many of the qualitative behaviours commonly observed in biomaterials. This observation led to the development of an open-source rheology analysis software package, RHEOS, which has many of the common fractional and non-fractional viscoelastic models built-in. The architecture, features and implementation specifics of RHEOS are discussed

Wupperthal : strategy for action : a case-study in co-operative rural development

This study documents an attempt to employ a direct-action strategy within the rural community of Wupperthal in order to combat rural stagnation and disintegration, to reduce poverty, and to promote development. The direct-action strategy employed was that of helping people to form themselves into co-operative enterprises, thus utilizing the concepts of participation and control in order to raise levels of responsibility, initiative and critical awareness. The study documents the difficulties experienced and analyses the causes of, and reasons for, the successes achieved, and the failures encountered. It also discusses some of the dangers of First World intervention in a Third World community. It ends by suggesting ways in which the co-operative direct-action strategy may be extended and improved in order to make it more efficacious in the long term

Discriminating dynamical from additive noise in the Van der Pol oscillator

We address the distinction between dynamical and additive noise in time series analysis by making a joint evaluation of both the statistical continuity of the series and the statistical differentiability of the reconstructed measure. Low levels of the latter and high levels of the former indicate the presence of dynamical noise only, while low values of the two are observed as soon as additive noise contaminates the signal. The method is presented through the example of the Van der Pol oscillator, but is expected to be of general validity for continuous-time systems.Comment: 12 pages (Elsevier LaTeX class), 4 EPS figures, submitted to Physica D (4 july 2001

Participation: Some Basic Considerations on the Theme Of Academe

published or submitted for publicatio