A Refined Higher-Order Hybrid Stress Quadrilateral Element for Free Vibration and Buckling Analyses of Reissner-Mindlin Plates

This paper is devoted to develop a new 8-node higher-order hybrid stress element (QH8) for free vibration and buckling analysis based on the Mindlin/Reissner plate theory. In particular, a simple explicit expression of a refine method with an adjustable constant is introduced to improve the accuracy of the analysis. A combined mass matrix for natural frequency analysis and a combined geometric stiffness matrix for buckling analysis are obtained using the refined method. It is noted that numerical examples are presented to show the validity and efficiency of the present element for free vibration and buckling analysis of plates. Furthermore, satisfactory accuracy for thin and moderately thick plates is obtained and it is free from shear locking for thin plate analysis and can pass the nonzero shear stress patch test

A Comparative analysis of economic cost of podoconiosos and leprosy on affected households in Northwest region of Cameroon

Leprosy and podoconiosis (podo) are neglected tropical diseases that cause severe disfigurement and disability, and may lead to catastrophic health expenditure and hinder economic development of affected persons and households. This study compared economic costs of both diseases on affected households with unaffected neighboring households in the Northwest Region (N.W.R.) of Cameroon. A matched comparative cross-sectional design was used enrolling 170 households (43 podo case households, 41 podo control households, 43 leprosy case households, and 43 leprosy control households) from three health districts in the N.W.R. Direct treatment costs for podo averaged 142 United State dollar (USD), compared with zero for leprosy (P < 0.001). This was also reflected in the proportion of annual household income consumed (0.4 versus 0.0, respectively, P < 0.001). Both diseases caused considerable reductions in working days (leprosy 115 versus podo 135 days. P for comparison < 0.001). The average household income was considerably lower in podo-affected households than unaffected households (410 versus 913 USD, P = 0.01), whereas income of leprosy-affected households was comparable to unaffected households (329 versus 399 USD, P = 0.23). Both leprosy and podo cause financial burdens on affected households, but those on podo-affected families are much greater. These burdens occur through direct treatment costs and reduced ability to work. Improved access to public health interventions for podo including prevention, morbidity management and disability prevention are likely to result in economic returns to affected families. In Cameroon, one approach to this would be through subsidized health insurance for these economically vulnerable households

Perceptions of consent, permission structures and approaches to the community: a rapid ethical assessment performed in North West Cameroon

BACKGROUND Understanding local contextual factors is important when conducting international collaborative studies in low-income country settings. Rapid ethical assessment (a brief qualitative intervention designed to map the ethical terrain of a research setting prior to recruitment of participants), has been used in a range of research-naïve settings. We used rapid ethical assessment to explore ethical issues and challenges associated with approaching communities and gaining informed consent in North West Cameroon. METHODS This qualitative study was carried out in two health districts in the North West Region of Cameroon between February and April 2012. Eleven focus group discussions (with a total of 107 participants) were carried out among adult community members, while 72 in-depth interviews included health workers, non-government organisation staff and local community leaders. Data were collected in English and pidgin, translated where necessary into English, transcribed and coded following themes. RESULTS Many community members had some understanding of informed consent, probably through exposure to agricultural research in the past. Participants described a centralised permission-giving structure in their communities, though there was evidence of some subversion of these structures by the educated young and by women. Several acceptable routes for approaching the communities were outlined, all including the health centre and the Fon (traditional leader). The importance of time spent in sensitizing the community and explaining information was stressed. CONCLUSIONS Respondents held relatively sophisticated understanding of consent and were able to outline the structures of permission-giving in the community. Although the structures are unique to these communities, the role of certain trusted groups is common to several other communities in Kenya and Ethiopia explored using similar techniques. The information gained through Rapid Ethical Assessment will form an important guide for future studies in North West Cameroon

High-performance geometric nonlinear analysis with the unsymmetric 4-node, 8-DOF plane element US-ATFQ4

A recent unsymmetric 4-node, 8-DOF plane element US-ATFQ4, which exhibits excellent precision and distortion-resistance for linear elastic problems, is extended to geometric nonlinear analysis. Since the original linear element US-ATFQ4 contains the analytical solutions for plane pure bending, how to modify such formulae into incremental forms for nonlinear applications and design an appropriate updated algorithm become the key of the whole job. First, the analytical trial functions should be updated at each iterative step in the framework of updated Lagrangian formulation that takes the configuration at the beginning of an incremental step as the reference configuration during that step. Second, an appropriate stress update algorithm in which the Cauchy stresses are updated by the Hughes-Winget method is adopted to estimate current stress fields. Numerical examples show that the new nonlinear element US-ATFQ4 also possesses amazing performance for geometric nonlinear analysis, no matter whether regular or distorted meshes are used. It again demonstrates the advantages of the unsymmetric finite element method with analytical trial functions

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Refined nine-parameter triangular thin plate bending element by using refined direct stiffness method

Based on a new generalized variational principle, a refined direct stiffness method (RDSM) which can be directly used to improve non-conforming elements is proposed. The formulation is similar to that of the direct stiffness method (DSM), but the constraint condition of interelement continuity is satisfied in an average sense and as a result convergence and high accuracy are insured. The well-known BCIZ nine- parameter triangular thin plate bending element is refined by the RDSM to yield a new nine-parameter thin plate bending element RT9. Numerical examples are presented to show that the present model passes the patch test and possesses high accuracy.link_to_subscribed_fulltex

Isoparametric hybrid hexahedral elements for three dimensional stress analysis

Based on a new functional in which displacements, strains and stresses are taken as independent variables, a set of three 8-node hexahedral hybrid elements is developed. The adoption of separated stress and displacement variables proves to be effective in improving the accuracy of the elements. The new elements are all capable of yielding converging results, and they all possess the properties of having no zero energy deformation modes and of being coordinate invariant. From the numerical example of a beam under bending it is concluded that exact solutions can be obtained for right prism elements, while good results are still attainable for severely distorted elements. The relationship between the new hybrid elements and the conventional displacement elements is also explored in this paper.link_to_subscribed_fulltex