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Graham Baker

Publications and source records attributed to Graham Baker.

4 recordsLinked to original sources
PubMed2005

An anisotropic thermomechanical damage model for concrete at transient elevated temperatures.

The behaviour of concrete at elevated temperatures is important for an assessment of integrity (strength and durability) of structures exposed to a high-temperature environment, in applications such as fire exposure, smelting plants and nuclear installations. In modelling terms, a coupled thermomechanical analysis represents a generalization of the computational mechanics of fracture and damage. Here, we develop a fully coupled anisotropic thermomechanical damage model for concrete under high stress and transient temperature, with emphasis on the adherence of the model to the laws of thermodynamics. Specific analytical results are given, deduced from thermodynamics, of a novel interpretation on specific heat, evolution of entropy and the identification of the complete anisotropic, thermomechanical damage surface. The model is also shown to be stable in a computational sense, and to satisfy the laws of thermodynamics.

Journal Article↗
PubMed2005

Thermodynamics in solid mechanics: a commentary.

This commentary on thermodynamics in solid mechanics aims to provide an overview of the main concepts of thermodynamic processes as they apply to, and may be exploited for, studies in nonlinear solid mechanics. We give a descriptive commentary on the (physical) interpretation of these concepts, and relate these where appropriate to behaviour of solids under thermo-mechanical conditions. The motivation is firstly that students of solid mechanics have often had less exposure to thermodynamics than those in other branches of science and engineering, yet there is great value in analytical formulations of material behaviour derived from the principles of thermodynamics. It also sets the contributions in this Theme Issue in context. Along with the deliberately descriptive treatment of thermodynamics, we do outline the main mathematical statements that define the subject, knowing that full details are provided by the authors in their corresponding contributions to this issue. The commentary ends on a lighter note. In order to aid understanding and to stimulate discussion of thermodynamics in solid mechanics, we have invented a number of very basic and completely fictitious materials. These have strange and extreme behaviours that describe certain thermodynamics concepts, such as entropy, in isolation from the complexities of real material behaviour.

Journal Article↗
PubMed2003

The effect of nitric oxide on the permeability of nasal epithelial cells from healthy and asthmatic donors.

BACKGROUND: To see if the higher levels of nitric oxide expired by asthmatics compared to healthy subjects might be of significance to airway function, the effect of nitric oxide and its second messenger, guanosine 3', 5'- cyclic monophosphate (cGMP), on the permeability of human nasal epithelial cells was studied. MATERIAL/METHODS: Cells from healthy and asthmatic donors, collected by swab biopsy, were plated on agar gel before being impaled with a microelectrode to measure their intracellular potential and membrane resistance. RESULTS: Exposure of cells to 300 mM sodium nitroprusside, a nitric oxide donor, caused a profound fall in both parameters in cells from non-asthmatics but no change in cells from asthmatic subjects. A similar response was seen when cells were exposed to 0.9 mM of the permeable form of cGMP, 8-Br-cGMP. Selective inhibition of ion transport pathways in healthy cells indicated that nitric oxide produced changes in permeability consistent with secretion of anions by the cells. CONCLUSIONS: Since anion secretion is associated with fluid secretion in the intact epithelium, we suggest that nitric oxide mediates a protective mechanism to remove foreign material from the airway surface. The defective response to nitric oxide seen in asthmatic cells may contribute to the disease by compromising the removal of allergens from the airway.

Adult↗