Computation of the linear elastic properties of random porous materials with a wide variety of microstructure

A finite-element method is used to study the elastic properties of random three-dimensional porous materials with highly interconnected pores. We show that Young's modulus, E, is practically independent of Poisson's ratio of the solid phase, nu(s), over the entire solid fraction range, and Poisson's ratio, nu, becomes independent of nu(s) as the percolation threshold is approached. We represent this behaviour of nu in a flow diagram. This interesting but approximate behaviour is very similar to the exactly known behaviour in two-dimensional porous materials. In addition, the behaviour of nu versus nu(s) appears to imply that information in the dilute porosity limit can affect behaviour in the percolation threshold limit. We summarize the finite-element results in terms of simple structure-property relations, instead of tables of data, to make it easier to apply the computational results. Without using accurate numerical computations, one is limited to various effective medium theories and rigorous approximations like bounds and expansions. The accuracy of these equations is unknown for general porous media. To verify a particular theory it is important to check that it predicts both isotropic elastic moduli, i.e. prediction of Young's modulus alone is necessary but not sufficient. The subtleties of Poisson's ratio behaviour actually provide a very effective method for showing differences between the theories and demonstrating their ranges of validity. We find that for moderate- to high-porosity materials, none of the analytical theories is accurate and, at present, numerical techniques must be relied upon.

Disability focus groups: A strategy for including people with disability in parishes

This paper reports the findings of an exploratory qualitative study examining parish awareness of the need to include individuals with disability in genuine and meaningful ways. Based on the interviews of over thirty persons, including people with disability, parents, parish workers, volunteers and human service workers within church agencies in the Catholic Archdiocese of Brisbane, Australia, the authors devised a process for including individuals in parishes. This process, known as a Disability Focus Group, was then implemented in one parish as a pilot study. The outcomes of the pilot are discussed.

A compartmental model of hepatic disposition kinetics: 1. Model development and application to linear kinetics

The conventional convection-dispersion model is widely used to interrelate hepatic availability (F) and clearance (Cl) with the morphology and physiology of the liver and to predict effects such as changes in liver blood flow on F and Cl. The extension of this model to include nonlinear kinetics and zonal heterogeneity of the liver is not straightforward and requires numerical solution of partial differential equation, which is not available in standard nonlinear regression analysis software. In this paper, we describe an alternative compartmental model representation of hepatic disposition (including elimination). The model allows the use of standard software for data analysis and accurately describes the outflow concentration-time profile for a vascular marker after bolus injection into the liver. In an evaluation of a number of different compartmental models, the most accurate model required eight vascular compartments, two of them with back mixing. In addition, the model includes two adjacent secondary vascular compartments to describe the tail section of the concentration-time profile for a reference marker. The model has the added flexibility of being easy to modify to model various enzyme distributions and nonlinear elimination. Model predictions of F, MTT, CV2, and concentration-time profile as well as parameter estimates for experimental data of an eliminated solute (palmitate) are comparable to those for the extended convection-dispersion model.

Global job satisfaction and facet description: The moderating role of facet importance

Recent research support sLocke's (1976) model of facet satisfaction in which the range of affect of objectively defined facet descriptions is moderated by subjective evaluations of facet importance (McFarlin & Rice, 1992). This study examined the utility of Locke's moderated model of face t satisfaction for the prediction of organizationally important global measures of job satisfaction. A large dataset of two groups of workers allowed testing over different time periods and across a broad range of satisfaction measures. The hypothesis derived from Locke's model, that global satisfaction would represent a linear function of facet satisfaction (i.e., facet description x facet importance), was not supported. Instead, a simple (have-want) discrepancy model (operationalized as facet description) provided the most consistent set of predictors. The results suggests that workers, when providing global measures of job satisfaction, may use cognitive heuristics to reduce the complexity of facet description x importance calculations. The implications of these data for Locke's model and directions for future research are outlined.

Being attuned to intergroup differences in mergers: The role of aligned leaders for low-status groups

The present research focused on responses of low-status group members to a merger with a high-status group. A study was conducted (N = 153) in which the alignment of the leader for the merged group (ingroup vs. outgroup) and leader behavior (equality, outgroup favoritism, ingroup favoritism, complementarity) were manipulated. The authors predicted that the leader, by his or her behavior, would play an important role in defining the new relationship between premerger groups. Overall, low-status ingroup leaders were evaluated more positively than high-status outgroup leaders. Ingroup leaders were evaluated more favorably and were more likely to engender a common identity in the merged group than were outgroup leaders when leaders behaved in an ingroup-favoring or complementary fashion. In contrast, evaluations of ingroup and outgroup leaders did not differ when the leader stressed equality or was outgroup favoring. The findings demonstrate the important role leaders can play in accentuating or de-emphasizing premerger status differences.

The expression of conflict in computer-mediated and face-to-face groups

This study integrated the research streams of computer-mediated communication (CMC) and group conflict by comparing the expression of different types of conflict in CMC groups and face-to face (FTF) groups over time. The main aim of the study was to compare the cues-filtered-out approach against the social information processing theory A laboratory study was conducted with 39 groups (19 CMC and 20 FTF) in which members were required to work together over three sessions. The frequencies of task, process, and relationship conflict were analyzed. Findings supported the social information processing theory. There was more process and relationship conflict in CMC groups compared to FTF groups on Day 1. However, this difference disappeared on Days 2 and 3. There was no difference between CMC and FTF groups in the amount of task conflict expressed on any day.

Horizontal transmission of Shiga toxin-producing Escherichia coli within groups of dairy calves

To examine the dissemination of Shiga-toxigenic Escherichia coli (STEC) within cattle groups, dairy calves on two farms utilizing different calf-rearing practices were exposed to a traceable STEC strain. Test strain dissemination differed significantly between farms, with a higher prevalence being associated with group penning. Pen floors and calf hides may be the main environmental mechanisms of transmission. Dairy calf husbandry represents a control point for reducing on-farm STEC prevalence.

Adsorption of aromatic compounds by activated carbon: Effects of functional groups and molecular size

The adsorption of three aromatic compounds on to an untreated carbon was investigated. The solution pH was lowered in all experiments so that all the solutes were in their molecular forms. It was shown that the difference in the maximum adsorption of the solutes was mainly a result of the difference in the sizes of the molecules and their functional groups. Further-more, it was illustrated that the packing arrangement was most likely edge-to-face (sorbate-sorbent) with various tilt angles. On the other hand, the affinity and heterogeneity of the adsorption systems were apparently related to the pK(a) values of the solutes.

Spatial and temporal changes in multiple hormone groups during lateral bud release shortly following apex decapitation of chickpea (Cicer arietinum) seedlings

Although the co-ordination of promotive root-sourced cytokinin (CK) and inhibitory shoot apex-sourced auxin (IAA) is central to all current models on lateral bud dormancy release, control by those hormones alone has appeared inadequate in many studies. Thus it was hypothesized that the IAA : CK model is the central control but that it must be considered within the relevant timeframe leading to lateral bud release and against a backdrop of interactions with other hormone groups. Therefore, IAA and a wide survey of cytokinins (CKs), were examined along with abscisic acid (ABA) and polyamines (PAs) in released buds, tissue surrounding buds and xylem sap at 1 and 4 h after apex removal, when lateral buds of chickpea are known to break dormancy. Three potential lateral bud growth inhibitors, IAA, ABA and cis-zeatin 9-riboside (ZR), declined sharply in the released buds and xylem following decapitation. This is in contrast to potential dormancy breaking CKs like trans-ZR and trans-zeantin 9-riboside 5'phosphate (ZRMP), which represented the strongest correlative changes by increasing 3.5-fold in xylem sap and 22-fold in buds. PAs had not changed significantly in buds or other tissues after 4 h, so they were not directly involved in the breaking of bud dormancy. Results from the xylem and surrounding tissues indicated that bud CK increases resulted from a combination synthesis in the bud and selective loading of CK nucleotides into the xylem from the root.

A study of five cervicocephalic relocation tests in three different subject groups

Objective: To compare head relocation accuracy in traumatic ( whiplash), insidious onset neck pain patients and asymptomatic subjects when targeting a natural head posture (NHP) and complex predetermined positions. Design: A case-control study. Setting: University-based musculoskeletal research clinic. Participants: Sixty-three volunteers divided into three groups of similar gender and age: Group 1 (n=21) an asymptomatic group; group 2 (n=20) insidious onset neck pain; group 3 (n=22) a history of whiplash injury. Intervention: Five randomly ordered tests designed to detect relocation accuracy of the head. Outcome measures: A 3-Space Fastrak system measured the mean absolute relocation error of three trials of each relocation test. Results: A significant difference was found between groups in one of the tests targeting the NHP (p=0.001). Post-hoc pairwise comparisons revealed a significant difference (pless than or equal to0.05) between the asymptomatic group and each symptomatic group. The difference between the symptomatic groups just failed to reach significance (p=0.07). None of the other four tests revealed significant differences. Conclusion: The test of targeting the NHP indicates that relocation inaccuracy exists in patients with neck pain with a trend to suggest that the deficit may be greater in whiplash patients. Tests employing unfamiliar postures or more complex movement were not successful in differentiating subject groups.

Relations between high and low power groups: The importance of legitimacy

Using a social identity perspective, two experiments examined the effects of power and the legitimacy of power differentials on intergroup bias. In Experiment 1, 125 math-science students were led to believe that they had high or low representation in a university decision-making body relative to social-science students and that this power position was either legitimate or illegitimate. Power did not have an independent effect on bias; rather, members of both high and low power groups showed more bias when the power hierarchy was illegitimate than when it was legitimate. This effect was replicated in Experiment 2 (N =105). In addition, Experiment 2 showed that groups located within an unfair power hierarchy expected the superordinate power body to be more discriminatory than did those who had legitimately high or low power. The results are discussed in terms of their implications for group relations.

Segmenting the market of West Australian senior tourists using an artificial neural network

Measuring perceptions of customers can be a major problem for marketers of tourism and travel services. Much of the problem is to determine which attributes carry most weight in the purchasing decision. Older travellers weigh many travel features before making their travel decisions. This paper presents a descriptive analysis of neural network methodology and provides a research technique that assesses the weighting of different attributes and uses an unsupervised neural network model to describe a consumer-product relationship. The development of this rich class of models was inspired by the neural architecture of the human brain. These models mathematically emulate the neurophysical structure and decision making of the human brain, and, from a statistical perspective, are closely related to generalised linear models. Artificial neural networks or neural networks are, however, nonlinear and do not require the same restrictive assumptions about the relationship between the independent variables and dependent variables. Using neural networks is one way to determine what trade-offs older travellers make as they decide their travel plans. The sample of this study is from a syndicated data source of 200 valid cases from Western Australia. From senior groups, active learner, relaxed family body, careful participants and elementary vacation were identified and discussed. (C) 2003 Published by Elsevier Science Ltd.