Hyperelastic cloaking theory: Transformation elasticity with pre-stressed solids

Transformation elasticity, by analogy with transformation acoustics and optics, converts material domains without altering wave properties, thereby enabling cloaking and related effects. By noting the similarity between transformation elasticity and the theory of incremental motion superimposed on finite pre-strain it is shown that the constitutive parameters of transformation elasticity correspond to the density and moduli of small-on-large theory. The formal equivalence indicates that transformation elasticity can be achieved by selecting a particular finite (hyperelastic) strain energy function, which for isotropic elasticity is semilinear strain energy. The associated elastic transformation is restricted by the requirement of statically equilibrated pre-stress. This constraint can be cast as \tr {\mathbf F} = constant, where $\mathbf{F}$ is the deformation gradient, subject to symmetry constraints, and its consequences are explored both analytically and through numerical examples of cloaking of anti-plane and in-plane wave motion.Comment: 20 pages, 5 figure

Public institutions under idiosyncratic uncertainty

Analysis of public institutions must be robust to the uncertainties facing agents within them, and the varying ways in which individuals cope with these uncertainties. This dissertation uses formal theoretical models to analyze the subjective and idiosyncratic nature with which most citizens face risk and uncertainty. This dissertation focuses on how different public institutions perform in specific settings based on the possibilities that agents may err in either their assessment of possible outcomes or the relevant choices and payoffs that are available. In the first chapter, I show that allowing for voter beliefs to feature ex-post error changes the incentives for candidates to set policy platforms, reducing the incentives for candidate convergence even with purely electorally-motivated candidates. Therefore, even if voters are on-average correct about political platforms and behavior, the distribution of imprecision will still change the incentives of political actors competing for their votes. This reopens consideration of how American political polarization may be driven by changes in the ways in which voters form beliefs about politicians, even as the distribution of political preferences may have remained unchanged. In the second chapter, co-authored with Keith N. Hylton, we determine that the incentives for potential litigants depend fundamentally upon the specific setting in which courts make determinations. We show that courts, facing only the facts concerning this particular decision, and not all the facts necessary to determine the global optimum, will be more likely to create incentives for socially excessive (i.e., defensive) care. In the final chapter, I modify a model of strategic communication to consider situations under which groups may be able to manipulate legislators who are uncertain which topics are most salient to said groups. Such uncertainty changes the incentives of interest groups, providing a new avenue of exploration for why different ideological groups take on different issues. I find that they must weigh the ability to “hide” their salient issue within a bundle of others with the possibility that taking on too many will cause the receiver to ignore their advice entirely

The Common Shrew (Sorex araneus): A neglected host of tick-borne infections?

Although the importance of rodents as reservoirs for a number of tick-borne infections is well established, comparatively little is known about the potential role of shrews, despite them occupying similar habitats. To address this, blood and tick samples were collected from common shrews (Sorex araneus) and field voles (Microtus agrestis), a known reservoir of various tick-borne infections, from sites located within a plantation forest in northern England over a 2-year period. Of 647 blood samples collected from shrews, 121 (18.7%) showed evidence of infection with Anaplasma phagocytophilum and 196 (30.3%) with Babesia microti. By comparison, of 1505 blood samples from field voles, 96 (6.4%) were positive for A. phagocytophilum and 458 (30.4%) for Ba. microti. Both species were infested with the ticks Ixodes ricinus and Ixodes trianguliceps, although they had different burdens: on average, shrews carried almost six times as many I. trianguliceps larvae, more than twice as many I. ricinus larvae, and over twice as many nymphs (both tick species combined). The finding that the nymphs collected from shrews were almost exclusively I. trianguliceps highlights that this species is the key vector of these infections in this small mammal community. These findings suggest that common shrews are a reservoir of tick-borne infections and that the role of shrews in the ecology and epidemiology of tick-borne infections elsewhere needs to be comprehensively investigated

An application of adaptive techniques in the control of a class of manufacturing processes

The application of adaptive, steady-state control to batch type manufacturing processes is addressed. An empirical modeling technique based on steepest ascent is developed and the performance of an optimal control system is compared with that of an adaptive control system

Neo-Hookean fiber composites undergoing finite out-of-plane shear deformations

The response of a neo-Hookean fiber composite undergoing finite out-of-plane shear deformation is examined. To this end an explicit close form solution for the out-of-plane shear response of a cylindrical composite element is introduced. We find that the overall response of the cylindrical composite element can be characterized by a fictitious homogeneous neo-Hookean material. Accordingly, this macroscopic response is identical to the response of a composite cylinder assemblage. The expression for the effective shear modulus of the composite cylinder assemblage is identical to the corresponding expression in the limit of small deformation elasticity, and hence also to the expression for the Hashin-Shtrikman bounds on the out-of-plane shear modulus

Salinity Action Plan : wetland vegetation monitoring, 1997/1998

This report represents the vegetation component of a project designed to provide on-going monitoring of wetland salinity and biological resources in wetlands of the agricultural zone of south-west Western Australia. Maintenance of wetland biological diversity in the agricultural zone is one of the major objectives of the Salinity Action Plan. Due to their low position in the landscape, wetlands are the habitat most affected by salinisation..

Synthesis and photolytic evaluation of a nitroindoline-caged glycine with a side chain of high negative charge for use in neuroscience

A photolabile precursor of the neuroinhibitory amino acid glycine has been synthesised with two phosphate groups attached to the indoline nucleus at a 4-alkoxy substituent. In common with the photochemical properties of other 1-acyl-7-nitroindolines, this releases glycine on a sub-is time scale upon irradiation with near-UV light. The synthetic route previously developed for the preparation of the GABA analogue required some modifications because of the greater hydrolytic sensitivity of the glycine compound. The phosphorylation method used here could be beneficial to the synthesis of other nitroindoline-caged amino acids, especially the related caged GABA derivative. Glycine released by laser photolysis on spinal cord neurons generated fast-rising responses and the pharmacological properties of the reagent are such that it is useful for physiological experiments

Towards a radiocarbon calibration for oxygen isotope stage 3 using New Zealand kauri (Agathis australis)

It is well known that radiocarbon years do not directly equate to calendar time. As a result, considerable effort has been devoted to generating a decadally resolved calibration curve for the Holocene and latter part of the last termination. A calibration curve that can be unambiguously attributed to changes in atmospheric ¹⁴C content has not, however, been generated beyond 26 kyr cal BP, despite the urgent need to rigorously test climatic, environmental, and archaeological models. Here, we discuss the potential of New Zealand kauri (Agathis australis) to define the structure of the ¹⁴C calibration curve using annually resolved tree rings and thereby provide an absolute measure of atmospheric ¹⁴C. We report bidecadally sampled ¹⁴C measurements obtained from a floating 1050-yr chronology, demonstrating repeatable ¹⁴C measurements near the present limits of the dating method. The results indicate that considerable scope exists for a high-resolution ¹⁴C calibration curve back through OIS-3 using subfossil wood from this source

Salinity Action Plan : wetland vegetation monitoring, 1998/1999

This report represents the vegetation component of a project designed to provide on-going monitoring of wetland salinity and biological resources in wetlands of the agricultural zone of south-west Western Australia. Maintenance of wetland biological diversity in the agricultural zone is one of the major objectives of the Salinity Action Plan. Due to their low position in the landscape, wetlands are the habitat most affected by salinisation..