Costs of adjustment to climate change

The present paper argues that the costs of climate change are primarily adjustment costs. The central result is that climate change will reduce welfare whenever it occurs more rapidly than the rate at which capital stocks (interpreted broadly to include natural resource stocks) would naturally adjust through market processes. The costs of climate change can be large even when lands are close to their climatic optimum, or evenly distributed both above and below that optimum.

Postural and respiratory activation of the trunk muscles changes with mode and speed of locomotion

Despite the importance of the deep intrinsic spinal muscles for trunk control, few studies have investigated their activity during human locomotion or how this may change with speed and mode of locomotion. Furthermore, it has not been determined whether the postural and respiratory functions, of which these muscles take part, can be coordinated when locomotor demands are increased. EMG recordings of abdominal and paraspinal muscles were made in seven healthy subjects using fine-wire and surface electrodes. Measurements were also made of respiration and gait parameters. Recordings were made for 10s as subjects walked on a treadmill at 1 and 2 ms(-1) and ran at 2, 3, 4 and 5 ms(-1). Unlike the superficial muscles, transversus abdominis was active tonically throughout the gait cycle with all tasks, except running at speeds of 3 ms(-1) and greater. All other muscles were recruited in a phasic manner. The relative duration of these bursts of activity was influenced by speed and/or mode of locomotion. Activity of all abdominal muscles, except rectus abdominis (RA), was modulated both for respiration and locomotor-related functions but this activity was affected by the speed and mode of locomotion. This study provides evidence that the deep abdominal muscles are controlled independently of the other trunk muscles. Furthermore, the pattern of recruitment of the trunk muscles and their respiratory and postural coordination is dependent on the speed and mode of locomotion. (C) 2003 Published by Elsevier B.V.

Optimal Paths and Costs of Adjustment in Dynamic DEA Models: With Application to Chilean Department Stores

In this paper we propose a range of dynamic data envelopment analysis (DEA) models which allow information on costs of adjustment to be incorporated into the DEA framework. We first specify a basic dynamic DEA model predicated on a number or simplifying assumptions. We then outline a number of extensions to this model to accommodate asymmetric adjustment costs, non-static output quantities, non-static input prices, and non-static costs of adjustment, technological change, quasi-fixed inputs and investment budget constraints. The new dynamic DEA models provide valuable extra information relative to the standard static DEA models-they identify an optimal path of adjustment for the input quantities, and provide a measure of the potential cost savings that result from recognising the costs of adjusting input quantities towards the optimal point. The new models are illustrated using data relating to a chain of 35 retail department stores in Chile. The empirical results illustrate the wealth of information that can be derived from these models, and clearly show that static models overstate potential cost savings when adjustment costs are non-zero.

Adjustment of chldren who have a sibling with Down syndrome: perspectives of mothers, fathers and children

Background A number of methodological weaknesses have contributed to our relatively poor understanding of the impact on children of having a brother or sister with a disability. These include a focus on poor adjustment, using multidiagnostic groups, inadequate matching, and a failure to consider the perspectives of children and parents together. Method This study compared the adjustment of 53 siblings of a child with Down syndrome with a comparison group of siblings of children who were developing typically. Children were matched on a case-by-case basis for gender, age and position in family. Families were matched for family size and father's occupation. The age range of the target siblings was 7-14 years. Data were gathered from mothers, fathers and siblings. Results There were no significant differences between the groups on adjustment measures. These included parent perceptions of externalizing and internalizing behaviours, parent perceptions of sibling competence, and sibling perceptions of their own competence and self-worth. Associations between measures of adjustment and child reports of their contribution to household functioning depended on sex rather than group membership. There was an association between parental reports of externalizing behaviour and sibling relationships with the brother/sister closest in age. Conclusions Having a brother or sister with Down syndrome does not inevitably lead to poor adjustment. Examination of within-family processes would appear to be more useful in identifying children at risk than merely group membership.

Predictors of cultural adjustment: Intergroup status relations and boundary permeability

We examined intergroup predictors of cultural adjustment among Asian international students in Australia. Sociostructural beliefs (status, legitimacy, and permeability) and initial adjustment were assessed (N = 113) at Time 1, and measures of adjustment were obtained (N = 80) at Time 2 eight weeks later. International students who perceived their cultural group to be relatively low in status experienced lower levels of psychological adjustment. Also, as expected, the effects of status were moderated by perceptions of both the permeability of intergroup boundaries and the legitimacy of the status differential. At high levels of legitimacy, perceptions of permeable group boundaries were associated with better psychological, sociocultural, and academic adjustment among international students perceiving their group to be low in status, but lower levels of adjustment among students who perceived their group to be high in status. At low levels of legitimacy, irrespective of group status position, perceived permeability was not related to adjustment.

The plasticisation effect of glycerol and water on the gelatinisation of wheat starch

In the extrusion manufacture of starch-based thermoplastics, such as biodegradable packaging materials, glycerol is an effective additive as a plasticiser, that is, to diminish the brittle nature of the product and provide the desired extent of flexibility. However, the addition of glycerol may also affect the gelatinisation behaviour of the starch-water mixture, and hence the required processing conditions for producing a homogeneously gelatinised starch-based material. The effect of glycerol on the gelatinisation of wheat starch was studied using differential scanning calorimetry (DSC). Mixtures of starch, water and glycerol were investigated with a water content ranging from 12 - 40% and a glycerol concentration up to 75%. Dependent on composition, the enthalpy of gelatinisation ranged from 1.7 - 12.6 J/g (on a dry starch basis), while the onset and peak temperatures varied from 54 to 86 degreesC and 60 to 90 degreesC, respectively. As expected, water acted as a plasticiser in that the onset temperature for gelatinisation (TO) decreased with increasing moisture content. Glycerol, however, increased To. It is shown that the T-0 of starch-glycerol-water mixtures may be predicted on the basis of the effective moisture content of the starch fraction of these mixtures resulting from the relative speed of moisture absorption by glycerol and starch, respectively. Moisture sorption kinetics of wheat starch and glycerol in 100% relative humidity were determined and used to predict the preferential water absorption by glycerol in starch-glycerol-water mixtures and hence the resulting T-0 of the system.

Locomotor performance of closely related Tropidurus species: relationships with physiological parameters and ecological divergence

Tropidurid lizards have colonized a variety of Brazilian open environments without remarkable morphological variation, despite ecological and structural differences among habitats used. This study focuses on two Tropidurus sister-species that, despite systematic proximity and similar morphology, exhibit great ecological divergence and a third ecologically generalist congeneric species providing an outgroup comparison. We quantified jumping capacity and sprint speed of each species on sand and rock to test whether ecological divergence was also accompanied by differences in locomotor performance. Relevant physiological traits possibly associated with locomotor performance metabolic scopes and fiber type composition, power output and activity of the enzymes citrate synthase, pyruvate kinase and lactate dehydrogenase of the iliofibularis muscle - were also compared among the three Tropidurus species. We found that the two sister-species exhibited remarkable differences in jumping performance, while Tropidurus oreadicus, the more distantly related species, exhibited intermediate values. Tropidurus psamonastes, a species endemic to sand dunes, exhibited high absolute sprint speeds on sand, jumped rarely and possessed a high proportion of glycolytic fibers and low activity of citrate synthase. The sister-species Tropidurus itambere, endemic to rocky outcrops, performed a large number of jumps and achieved lower absolute sprint speed than T. psamonastes. This study provides evidence of rapid divergence of locomotor parameters between sister-species that use different substrates, which is only partially explained by variation in physiological parameters of the iliofibularis muscle.

An investigation into effects of long-distance seed dispersal on organelle population genetic structure and colonization rate: a model analysis

A simulation-based modelling approach is used to examine the effects of stratified seed dispersal (representing the distribution of the majority of dispersal around the maternal parent and also rare long-distance dispersal) on the genetic structure of maternally inherited genomes and the colonization rate of expanding plant populations. The model is parameterized to approximate postglacial oak colonization in the UK, but is relevant to plant populations that exhibit stratified seed dispersal. The modelling approach considers the colonization of individual plants over a large area (three 500 km x 10 km rolled transects are used to approximate a 500 km x 300 km area). Our approach shows how the interaction of plant population dynamics with stratified dispersal can result in a spatially patchy haplotype structure. We show that while both colonization speeds and the resulting genetic structure are influenced by the characteristics of the dispersal kernel, they are robust to changes in the periodicity of long-distance events, provided the average number of long-distance dispersal events remains constant. We also consider the effects of additional physical and environmental mechanisms on plant colonization. Results show significant changes in genetic structure when the initial colonization of different haplotypes is staggered over time and when a barrier to colonization is introduced. Environmental influences on survivorship and fecundity affect both the genetic structure and the speed of colonization. The importance of these mechanisms in relation to the postglacial spread and genetic structure of oak in the UK is discussed.

The concurrent validity and test-retest reliability of a visuospatial working memory task

To determine whether the visuospatial n-back working memory task is a reliable and valid measure of cognitive processes believed to underlie intelligence, this study compared the reaction times and accuracy of perforniance of 70 participants, with performance on the Multidimensional Aptitude Battery (MAB). Testing was conducted over two sessions separated by 1 week. Participants completed the MAB during the second test session. Moderate testretest reliability for percentage accuracy scores was found across the four levels of the n-back task, whilst reaction times were highly reliable. Furthermore, participants' performance on the MAB was negatively correlated with accuracy of performance at the easier levels of the n-back task and positively correlated with accuracy of performance at the harder task levels. These findings confirm previous research examining the cognitive basis of intelligence, and suggest that intelligence is the product of faster speed of information processing, as well as superior working memory capacity. (C) 2004 Elsevier Inc. All rights reserved.

A new equation for macroscopic description of capillary rise in porous media

Capillary rise in porous media is frequently modeled using the Washburn equation. Recent accurate measurements of advancing fronts clearly illustrate its failure to describe the phenomenon in the long term. The observed underprediction of the position of the front is due to the neglect of dynamic saturation gradients implicit in the formulation of the Washburn equation. We consider an approximate solution of the governing macroscopic equation, which retains these gradients, and derive new analytical formulae for the position of the advancing front, its speed of propagation, and the cumulative uptake. The new solution properly describes the capillary rise in the long term, while the Washburn equation may be recovered as a special case. (C) 2004 Elsevier Inc. All rights reserved.

Equity market linkage and multinational trade accords: The case of NAFTA

This paper examines the impact of multinational trade accords on the degree of stock market linkage using NAFTA as a case study. Besides liberalizing trade among the U.S., Canada and Mexico, NAFTA has also sought to strengthen linkage among stock markets of these countries. If successful, this could lessen the appeal of asset diversification across the North American region and promote a higher degree of market efficiency. We assess the possible impact of NAFTA on market linkage using cross-correlations, multivariate price cointegrating systems, speed of convergence, and generalized variance decompositions of unexpected stock returns. The evidence proves robust and consistently indicates intensified equity market linkage since the NAFTA accord. The results also suggest that interdependent goods markets in the region are a primary reason behind the stronger equity market linkage observed in the post-NAFTA period. (c) 2005 Elsevier Ltd. All rights reserved.

Influence of charge size distribution on net-power draw of tumbling mill based on DEM modelling

Modelling and optimization of the power draw of large SAG/AG mills is important due to the large power draw which modern mills require (5-10 MW). The cost of grinding is the single biggest cost within the entire process of mineral extraction. Traditionally, modelling of the mill power draw has been done using empirical models. Although these models are reliable, they cannot model mills and operating conditions which are not within the model database boundaries. Also, due to its static nature, the impact of the changing conditions within the mill on the power draw cannot be determined using such models. Despite advances in computing power, discrete element method (DEM) modelling of large mills with many thousands of particles could be a time consuming task. The speed of computation is determined principally by two parameters: number of particles involved and material properties. The computational time step is determined by the size of the smallest particle present in the model and material properties (stiffness). In the case of small particles, the computational time step will be short, whilst in the case of large particles; the computation time step will be larger. Hence, from the point of view of time required for modelling (which usually corresponds to time required for 3-4 mill revolutions), it will be advantageous that the smallest particles in the model are not unnecessarily too small. The objective of this work is to compare the net power draw of the mill whose charge is characterised by different size distributions, while preserving the constant mass of the charge and mill speed. (C) 2004 Elsevier Ltd. All rights reserved.

On the estimation and comparison of short-rate models using the generalised method of moments

Subsequent to the influential paper of [Chan, K.C., Karolyi, G.A., Longstaff, F.A., Sanders, A.B., 1992. An empirical comparison of alternative models of the short-term interest rate. Journal of Finance 47, 1209-1227], the generalised method of moments (GMM) has been a popular technique for estimation and inference relating to continuous-time models of the short-term interest rate. GMM has been widely employed to estimate model parameters and to assess the goodness-of-fit of competing short-rate specifications. The current paper conducts a series of simulation experiments to document the bias and precision of GMM estimates of short-rate parameters, as well as the size and power of [Hansen, L.P., 1982. Large sample properties of generalised method of moments estimators. Econometrica 50, 1029-1054], J-test of over-identifying restrictions. While the J-test appears to have appropriate size and good power in sample sizes commonly encountered in the short-rate literature, GMM estimates of the speed of mean reversion are shown to be severely biased. Consequently, it is dangerous to draw strong conclusions about the strength of mean reversion using GMM. In contrast, the parameter capturing the levels effect, which is important in differentiating between competing short-rate specifications, is estimated with little bias. (c) 2006 Elsevier B.V. All rights reserved.