The Cockayne Syndrome Natural History (CoSyNH) study:clinical findings in 102 individuals and recommendations for care

Purpose: Cockayne syndrome (CS) is a rare, autosomal-recessive disorder characterized by microcephaly, impaired postnatal growth, and premature pathological aging. It has historically been considered a DNA repair disorder; fibroblasts from classic patients often exhibit impaired transcription-coupled nucleotide excision repair. Previous studies have largely been restricted to case reports and small series, and no guidelines for care have been established. Methods: One hundred two study participants were identified through a network of collaborating clinicians and the Amy and Friends CS support groups. Families with a diagnosis of CS could also self-recruit. Comprehensive clinical information for analysis was obtained directly from families and their clinicians. Results and Conclusion: We present the most complete evaluation of Cockayne syndrome to date, including detailed information on the prevalence and onset of clinical features, achievement of neurodevelopmental milestones, and patient management. We confirm that the most valuable prognostic factor in CS is the presence of early cataracts. Using this evidence, we have created simple guidelines for the care of individuals with CS. We aim to assist clinicians in the recognition, diagnosis, and management of this condition and to enable families to understand what problems they may encounter as CS progresses

A two-dimensional thermoelastic rough surface contact model

By taking into account steady-state heat transfer and surface distortion due to thermal and elastic deformations, a two-dimensional thermoelastic model is developed for rough surface asperity contact, where the thermal influence function connecting the thermal deformation and the contact pressure is derived based on the Dundurs' theorem. The model has been shown to be accurate at low as well as high frictional heating conditions by comparison with published results. As an application of this model, the contact problem of a cylinder on a random rough surface is studied in detail. © 2004 by ASME.link_to_subscribed_fulltex

Thermal distortion of an anisotropic elastic half-plane and its application in contact problems including frictional heating

The thermal surface distortion of an anisotropic elastic half-plane is studied using the extended version of Stroh's formalism. In general, the curvature of the surface depends both on the local heat flux into the half-plane and the local temperature variation along the surface. However if the material is orthotropic, the curvature of the surface depends only on the local heat flux into the half-plane. As a direct application, the two-dimensional thermoelastic contact problem of an indenter sliding against an orthotropic half-plane is considered Two cases, where the indenter has either a flat or a parabolic profile, are studied in detail. Comparisons with other available results in the literature show that the present method is correct and accurate. Copyright © 2006 by ASME.link_to_subscribed_fulltex

Thermal distortion of an anisotropic elastic half-plane and its application in contact problems including frictional heating

The thermal surface distortion of an anisotropic elastic half-plane is studied using the extended version of Stroh's formalism. In general, the curvature of the surface depends both on the local heat flux into the half-plane and the local temperature variation along the surface. However, if the material is orthotropic, the curvature of the surface depends only on the local heat flux into the half-plane. As a direct application, the two-dimensional thermoelastic contact problem of an indenter sliding against an orthotropic half-plane is considered. Two cases, where the indenter has either a flat or a parabolic profile, are studied in detail. Comparisons with other available results in the literature show that the present method is correct and accurate. Copyright © 2004 by ASME.link_to_subscribed_fulltex

A rough surface contact model for general anisotropic materials

A method for solving the two-dimensional (2-D) isothermal rough surface contact problem of general anisotropic materials with friction is presented. By using Stroh's formalism, the surface displacements of an elastic half-space due to uniform distributions of traction over a strip are derived from the surface Green's function. The surface displacement and subsurface stresses of the anisotropic half-space due to the distributed contact pressure may then be calculated by superposition. The real contact area and the contact pressure are determined via an iteration scheme using the conjugate gradient method. © 2004 by ASME.link_to_subscribed_fulltex

Indentation of an anisotropic half-space by a heated flat punch

The two-dimensional thermoelastic contact problem of an anisotropic half-space indented by a heated rigid flat punch is studied using the extended version of Stroh's formalism. Two cases, where the contact interface is nonslip and frictionless, have been considered. In the first case, the contact is perfect throughout the punch face. In the second case, separation is assumed to occur at the edges of the punch.link_to_subscribed_fulltex

Thermoelastic problems for the anisotropic elastic half-plane

By applying the extended version of Stroh's formalism, the two-dimensional thermoelastic problem for a semi-infinite anisotropic elastic half-plane is formulated. The steady-state heat transfer condition is assumed and the technique of analytical continuation is employed; the formulation leads to the Hilbert problem, which can be solved in closed form. The general solutions due to different kinds of thermal and mechanical boundary conditions are obtained. The results show that unlike the two-dimensional thermoelastic problem for an isotropic media, where a simply-connected elastic body in a state of plane strain or plane stress remains stress free if the temperature distribution is harmonic and the boundaries are free of traction, the stress within the semi-infinite anisotropic media will generally not equal zero even if the boundary is free of traction. © 2004 by ASME.link_to_subscribed_fulltex

The stress and displacement fields produced in a semi-infinite solid by a uniform heat source over a rectangular area on the surface

An important problem in thermo-mechanical contacts is the determination of the stress and displacement fields caused by heat flow. Heat flow may come from a difference in temperature between the contacting solids, or from frictional heating at the sliding interface. Generally, the distribution of heat flow in a contact area is unknown. In many cases, however, it is approximately uniform or one may divide the contact area into small parts, and in each part the heat flow may be treated as approximately uniform. This work provides closed-form solutions of the stress and displacement fields in a semi-infinite solid caused by uniform steady-state heat flow over a rectangular area on the surface. The material is assumed to be homogeneous and isotropic.link_to_subscribed_fulltex

Indentation of an orthotropic half-space by a rigid ellipsoidal indenter

Anisotropic materials represent a unique class of materials, including crystals, wood, thin-films, and composites. Existing work in the literature has provided the engineering community with an in-depth understanding of isotropic contact mechanics, and the methodologies for solving isotropic contact problems have been fully developed. Anisotropic material systems, however, are more complex and their analysis is less fully-developed in the literature. Presented here is the analysis of indentation by a rigid ellipsoidal indenter against an orthotropic half-space, with the surface of the half-space parallel to two of the axes of material symmetry, derived from stress equilibrium. A numerical method has been used to solve for the contact parameters (contact dimensions and normal approach) for both orthotropic and transversely isotropic material systems.link_to_subscribed_fulltex