A continuum treatment of growth in biological tissue: The coupling of mass transport and mechanics

Growth (and resorption) of biological tissue is formulated in the continuum setting. The treatment is macroscopic, rather than cellular or sub-cellular. Certain assumptions that are central to classical continuum mechanics are revisited, the theory is reformulated, and consequences for balance laws and constitutive relations are deduced. The treatment incorporates multiple species. Sources and fluxes of mass, and terms for momentum and energy transfer between species are introduced to enhance the classical balance laws. The transported species include: (\romannumeral 1) a fluid phase, and (\romannumeral 2) the precursors and byproducts of the reactions that create and break down tissue. A notable feature is that the full extent of coupling between mass transport and mechanics emerges from the thermodynamics. Contributions to fluxes from the concentration gradient, chemical potential gradient, stress gradient, body force and inertia have not emerged in a unified fashion from previous formulations of the problem. The present work demonstrates these effects via a physically-consistent treatment. The presence of multiple, interacting species requires that the formulation be consistent with mixture theory. This requirement has far-reaching consequences. A preliminary numerical example is included to demonstrate some aspects of the coupled formulation.Comment: 29 pages, 11 figures, accepted for publication in Journal of the Mechanics and Physics of Solids. See journal for final versio

Biological remodelling: Stationary energy, configurational change, internal variables and dissipation

Remodelling is defined as an evolution of microstructure or variations in the configuration of the underlying manifold. The manner in which a biological tissue and its subsystems remodel their structure is treated in a continuum mechanical setting. While some examples of remodelling are conveniently modelled as evolution of the reference configuration (Case I), others are more suited to an internal variable description (Case II). In this paper we explore the applicability of stationary energy states to remodelled systems. A variational treatment is introduced by assuming that stationary energy states are attained by changes in microstructure via one of the two mechanisms--Cases I and II. An example is presented to illustrate each case. The example illustrating Case II is further studied in the context of the thermodynamic dissipation inequality.Comment: 24 pages, 4 figures. Replaced version has corrections to typos in equations, and the corresponding correct plot of the solution--all in Section

The Secrets of African Managerial Success

Summary Summary It has become customary to despair at the quality of African public sector management, and to attribute the problem to an inhospitable social and political context. Yet we can discover success stories even in the usual sector in which failure is most prevalent. By looking at these cases we can attempt to discover the ‘secret of success’ and thus some indications about how to deal with less successful cases. This article attempts to do this by looking at the life and career histories of four prominent Kenyan officials who were able to endow success on many enterprises that they led. It concludes that the way in which they were able to maintain the autonomy of their organisations was by establishing effective links with the political leadership; it explains how their commitment to good administration derived from and was reinforced by a strong sense of professional vocation; how their capacity to raise resources was reinforced by their ability to maintain the support of donor agencies; how they sought effective methods of balancing Africanisation against the need to retain expatriate staff; and how their willingness to take risks depended upon their ability to make a good living outside the state service if need be. Resumé Resumé Les Secrets du Succès du Management africain Il est devenu courant de désespérer de la qualité du management du secteur publique africain, et d'attribuer le problème à un contexte politique et social défavorable. Pourtant on peut trouver des succès même dans le secteur rural, où normalement l'échec est le plus fréquent. En analysant ces cas, nous pouvons essayer de découvrir les ‘secrets du succès’ et ainsi trouver quelques indications sur la manière de résoudre ceux qui ont moins réussi. Cet article se propose de présenter cette analyse en s'appuyant sur un exposé de la vie et la carrière de quatre important officiels du Kenya, qui ont mené au succès bien des projets qu'ils ont dirigés. Il analyse la manière dont ils ont réussi à maintenir l'autonomie de leurs organisations en établissant des liens efficaces avec les dirigeants politiques; aussi comment leur engagement pour une bonne administration provenait et était renforcée par un sentiment profond de vocation professionelle; comment leur aptitude à augmenter les resources a été renforcée par leur compétence dans le maintien de leur soutien Ils ont recherché des méthodes effectives pour équilibrer l'africanisation et le besoin de conserver le personnel étrange; Ils ont aussi recherché comment le fait qu'ils étaient disposés à prendre des risques dépendait de leur aptitude à gagner leur vie en dehors de leur fonction publique si cela était nécessaire

Impact Evaluation of Training Natural Leaders during a Community-Led Total Sanitation Intervention: A Cluster-Randomized Field Trial in Ghana

We used a cluster-randomized field trial to evaluate training natural leaders (NLs) as an addition to a community-led total sanitation (CLTS) intervention in Ghana. NLs are motivated community members who influence their peers’ behaviors during CLTS. The outcomes were latrine use and quality, which were assessed from surveys and direct observation. From October 2012, Plan International Ghana (Plan) implemented CLTS in 60 villages in three regions in Ghana. After 5 months, Plan trained eight NLs from a randomly selected half of the villages, then continued implementing CLTS in all villages for 12 more months. The NL training led to increased time spent on CLTS by community members, increased latrine construction, and a 19.9 percentage point reduction in open defecation (p < 0.001). The training had the largest impact in small, remote villages with low exposure to prior water and sanitation projects, and may be most effective in socially cohesive villages. For both interventions, latrines built during CLTS were less likely to be constructed of durable materials than pre-existing latrines, but were equally clean, and more often had handwashing materials. CLTS with NL training contributes to three parts of Goal 6 of the Sustainable Development Goals: eliminating open defecation, expanding capacity-building, and strengthening community participation

Primary pericardial malignant mesothelioma and response to radiation therapy

We report a case of a primary pericardial malignant mesothelioma. A 59-year-old male presented with episodic chest pain and dyspnea on exertion. Cardiac magnetic resonance imaging revealed a large mass in the pericardium attached to the right ventricle. Partial resection of the mass was undertaken revealing malignant mesothelioma, byphasic type. The patient was treated with chemotherapy intermittently over a period of 3 years, but his disease continued to progress. The patient was then treated with definitive radiation therapy to 64 Gy to the primary tumor using a six field 3D conformal technique. The patient remains free of progressive disease 86 months from the time of diagnosis and 50 months from the completion of his radiotherapy