Willingness to Pay for Rural Landscape Improvements: Combining Mixed Logit and Random-Effects Models

This paper reports the findings from a discrete-choice experiment designed to estimate the economic benefits associated with rural landscape improvements in Ireland. Using a mixed logit model, the panel nature of the dataset is exploited to retrieve willingness-to-pay values for every individual in the sample. This departs from customary approaches in which the willingness-to-pay estimates are normally expressed as measures of central tendency of an a priori distribution. Random-effects models for panel data are subsequently used to identify the determinants of the individual-specific willingness-to-pay estimates. In comparison with the standard methods used to incorporate individual-specific variables into the analysis of discrete-choice experiments, the analytical approach outlined in this paper is shown to add considerable explanatory power to the welfare estimates.

CoMFA and homology-based models of the glycine binding site of N-methyl-D-aspartate receptor

Homology modeling was used to build 3D models of the N-methyl-D-aspartate (NMDA) receptor glycine binding site on the basis of an X-ray structure of the water-soluble AMPA-sensitive receptor. The docking of agonists and antagonists to these models was used to reveal binding modes of ligands and to explain known structure-activity relationships. Two types of quantitative models, 3D-QSAR/CoMFA and a regression model based on docking energies, were built for antagonists (derivatives of 4-hydroxy-2-quinolone, quinoxaline-2,3-dione, and related compounds). The CoMFA steric and electrostatic maps were superimposed on the homology-based model, and a close correspondence was marked. The derived computational models have permitted the evaluation of the structural features crucial for high glycine binding site affinity and are important for the design of new ligands.

Multi-ionization of helium and lithium using the independent electron and independent event models with intrinsic CDW

Cross sections for the multi-ionization of He and Li are presented for impact energies in the range of 50 to 1000 keV/amu. These are calculated using the eikonal initial state approximation to represent the input and exit channels of the active electrons. The ionization process is simulated in a variety of ways, most notably an attempt to account for the effects of electron correlation via the inclusion of a continuum density of states (CDS) term. Inadequacies, of the CDW formulation at small impact parameters, and of the models themselves, are discussed and conclusions are drawn on what repercussions this has for the cross sections calculated.

Sexual cannibalism and mate choice

Sexual cannibalism, where a female kills and consumes a courting male, represents an extreme form of sexual conflict and has been proposed as a mechanism of mate choice. We evaluate the evidence for mate choice through premating sexual cannibalism via mate rejection, other indirect mechanisms of mate 'choice' and choice in postmating sexual cannibalism. We highlight a paucity of investigations, particularly of field studies, and note gaps in our knowledge. There is empirical support for the size-dependent sexual cannibalism predicted by mate choice through premating sexual cannibalism. This may represent mate choice operating on absolute male size but it could be a by-product of female foraging behaviour and greater vulnerability of relatively smaller males. Thus, indirect mate choice is as plausible an explanation of size-dependent sexual cannibalism as is direct mate choice based on discrimination of male traits. Direct female choice, mediated through premating sexual cannibalism, has yet to be demonstrated. We suggest a framework for distinguishing direct and indirect choice and note an absence of information on which to test it. There is evidence for sequential mate choice in postmating sexual cannibalism, but the nature or basis of the female's discriminatory behaviour remains unclear. Costs and long-term fitness benefits of the putative mate choice have been largely ignored. Reversed sexual cannibalism, in which the male eats the female, presumably occurs when the gain from food is high and potential gain from mating low and probably has little to do with mate choice. (c) 2005 The Association for the Study of Animal Behaviour Published by Elsevier Ltd. All rights reserved.

Coordination and movement pathology: models of structure and function

Here we consider the role of abstract models in advancing our understanding of movement pathology. Models of movement coordination and control provide the frameworks necessary for the design and interpretation of studies of acquired and developmental disorders. These models do not however provide the resolution necessary to reveal the nature of the functional impairments that characterise specific movement pathologies. In addition, they do not provide a mapping between the structural bases of various pathologies and the associated disorders of movement. Current and prospective approaches to the study and treatment of movement disorders are discussed. It is argued that the appreciation of structure-function relationships, to which these approaches give rise, represents a challenge to current models of interlimb coordination, and a stimulus for their continued development. (C) 2002 Elsevier Science B.V. All rights reserved.

Building and testing age models for radiocarbon dates in Lateglacial and Early Holocene sediments

The growing importance of understanding past abrupt climate variability at a regional and global scale has led to the realisation that independent chronologies of past environmental change need to be compared between various archives. This has in turn led to attempts at significant improvements in the required precision at which records can be dated. Radiocarbon dating is still the most prominent method for dating organic material from terrestrial and marine archives, and as such many of the recent developments in improving precision have been aimed at this technique. These include: (1) selection of the most suitable datable fractions within a record, (2) the development of better calibration curves, and (3) more precise age modelling techniques. While much attention has been focussed oil the first two items, testing the possibilities of the relatively new age modelling approaches has not received much attention. Here, we test the potential for methods designed to significantly improve precision in radiocarbon-based age models, wiggle match dating and various forms of Bayesian analyses. We demonstrate that while all of the methods can perform very well, in some scenarios, caution must be taken when applying them. It appears that an integrated approach is required in real life dating situations where more than one model is applied, with strict error calculation, and with the integration of radiocarbon data with sedimentological analyses of site formation processes. (C) 2007 Elsevier Ltd. All rights reserved.

Automated mixed dimensional modelling from 2D and 3D CAD models

The motivation for this paper is to present procedures for automatically creating idealised finite element models from the 3D CAD solid geometry of a component. The procedures produce an accurate and efficient analysis model with little effort on the part of the user. The technique is applicable to thin walled components with local complex features and automatically creates analysis models where 3D elements representing the complex regions in the component are embedded in an efficient shell mesh representing the mid-faces of the thin sheet regions. As the resulting models contain elements of more than one dimension, they are referred to as mixed dimensional models. Although these models are computationally more expensive than some of the idealisation techniques currently employed in industry, they do allow the structural behaviour of the model to be analysed more accurately, which is essential if appropriate design decisions are to be made. Also, using these procedures, analysis models can be created automatically whereas the current idealisation techniques are mostly manual, have long preparation times, and are based on engineering judgement. In the paper the idealisation approach is first applied to 2D models that are used to approximate axisymmetric components for analysis. For these models 2D elements representing the complex regions are embedded in a 1D mesh representing the midline of the cross section of the thin sheet regions. Also discussed is the coupling, which is necessary to link the elements of different dimensionality together. Analysis results from a 3D mixed dimensional model created using the techniques in this paper are compared to those from a stiffened shell model and a 3D solid model to demonstrate the improved accuracy of the new approach. At the end of the paper a quantitative analysis of the reduction in computational cost due to shell meshing thin sheet regions demonstrates that the reduction in degrees of freedom is proportional to the square of the aspect ratio of the region, and for long slender solids, the reduction can be proportional to the aspect ratio of the region if appropriate meshing algorithms are used.