Full-field optical measurement of curvatures in ultra-thin-film–substrate systems in the range of geometrically nonlinear deformations

This article describes coherent gradient sensing (CGS) as an optical, full-field, real-time, nonintrusive, and noncontact technique for the measurement of curvatures and nonuniform curvature changes in film-substrate systems. The technique is applied to the study of curvature fields in thin Al films (6 mum) deposited on thin circular silicon wafers (105 mum) of "large" in-plane dimensions (50.8 mm in diameter) subjected to thermal loading histories. The loading and geometry is such that the system experiences deformations that are clearly within the nonlinear range. The discussion is focused on investigating the limits of the range of the linear relationship between the thermally induced mismatch strain and the substrate curvature, on the degree to which the substrate curvature becomes spatially nonuniform in the range of geometrically nonlinear deformation, and finally, on the bifurcation of deformation mode from axial symmetry to asymmetry with increasing mismatch strain. Results obtained on the basis of both simple models and more-detailed finite-element simulations are compared with the full-field CGS measurements with the purpose of validating the analytical and numerical models

Multiple Polymorphic Loci for Molecular Typing of Strains of Mycobacterium leprae

The need for molecular tools for the differentiation of isolates of Mycobacterium leprae, the organism that causes leprosy, is urgent in view of the continuing high levels of new case detection, despite years of aggressive chemotherapy and the consequent reduction in the prevalence of leprosy. The slow onset of leprosy and the reliance on physical examination for detection of disease have restricted the epidemiological tracking necessary to understand and control transmission. Two genetic loci in several isolates of M. leprae have previously been demonstrated to contain variable-number tandem repeats (VNTRs). On the basis of these reports and the availability of the full genome sequence, multiple-locus VNTR analysis for strain typing has been undertaken. A panel of 11 short tandem repeat (STR) loci with repeat units of 1, 2, 3, 6, 12, 18, 21, and 27 bp from four clinical isolates of M. leprae propagated in armadillo hosts were screened by PCR. Fragment length polymorphisms were detected at 9 of the 11 loci by agarose gel electrophoresis. Sequencing of representative DNA products confirmed the presence of VNTRs between isolates. The application of nine new polymorphic STRs in conjunction with automated methods for electrophoresis and size determination allows greater discrimination between isolates of M. leprae and enhances the potential of this technique to track the transmission of leprosy