The plausibility of long-wavelength stress correlation or stress magnitude as a mechanism for precursory seismicity: Results from two simple elastic models

Observations of accelerating seismic activity prior to large earthquakes in natural fault systems have raised hopes for intermediate-term eartquake forecasting. If this phenomena does exist, then what causes it to occur? Recent theoretical work suggests that the accelerating seismic release sequence is a symptom of increasing long-wavelength stress correlation in the fault region. A more traditional explanation, based on Reid's elastic rebound theory, argues that an accelerating sequence of seismic energy release could be a consequence of increasing stress in a fault system whose stress moment release is dominated by large events. Both of these theories are examined using two discrete models of seismicity: a Burridge-Knopoff block-slider model and an elastic continuum based model. Both models display an accelerating release of seismic energy prior to large simulated earthquakes. In both models there is a correlation between the rate of seismic energy release with the total root-mean-squared stress and the level of long-wavelength stress correlation. Furthermore, both models exhibit a systematic increase in the number of large events at high stress and high long-wavelength stress correlation levels. These results suggest that either explanation is plausible for the accelerating moment release in the models examined. A statistical model based on the Burridge-Knopoff block-slider is constructed which indicates that stress alone is sufficient to produce accelerating release of seismic energy with time prior to a large earthquake.

Effect of the toxic milk mutation (tx) on the function and intracellular localization of Wnd, the murine homologue of the Wilson copperATPase

Wilson disease is an autosomal recessive copper transport disorder resulting from defective biliary excretion of copper and subsequent hepatic copper accumulation and liver failure if not treated. The disease is caused by mutations in the ATP7B (WND) gene, which is expressed predominantly in the liver and encodes a copper-transporting P-type ATPase that is structurally and functionally similar to the Menkes protein (MNK), which is defective in the X-linked copper transport disorder Menkes disease. The toxic milk (tx) mouse has a clinical phenotype similar to Wilson disease patients and, recently, the tx mutation within the murine WND homologue (Wnd) of this mouse was identified, establishing it as an animal model for Wilson disease. In this study, cDNA constructs encoding the wild-type (Wnd-wt) and mutant (Wnd-tx) Wilson proteins (Wnd) were generated and expressed in Chinese hamster ovary (CHO) cells. The fx mutation disrupted the copper-induced relocalization of Wnd in CHO cells and abrogated Wnd-mediated copper resistance of transfected CHO cells. In addition, co-localization experiments demonstrated that while Wnd and MNK are located in the trans-Golgi network in basal copper conditions, with elevated copper, these proteins are sorted to different destinations within the same cell, Ultrastructural studies showed that with elevated copper levels, Wnd accumulated in large multivesicular structures resembling late endosomes that may represent a novel compartment for copper transport. The data presented provide further support for a relationship between copper transport activity and the copper-induced relocalization response of mammalian copper ATPases, and an explanation at a molecular level for the observed phenotype of fx mice.

Is bucindolol BEST? (A Key Paper Evaluation)

Carvedilol, a non-selective β-adrenoceptor blocker with ancillary properties, and metoprolol and bisoprolol, selective β1-blockers without ancillary properties, have been shown to reduce mortality and morbidity in heart failure. In the Beta-blocker Evaluation of Survival Trial (BEST), bucindolol, a non-selective β-adrenoceptor blocker with different ancillary properties to carvedilol, did not reduce overall survival in heart failure. Possible explanations for this include: more Blacks being included in the trial, bucindolol being more ‘sympatholytic’ than the other β-blockers and more advanced heart failure in BEST. Another possible explanation is that bucindolol is stimulating cardiac β2-adrenoceptors to counter the effects of inhibiting cardiac β1-adrenoceptors. Bucindolol is not the best treatment and carvedilol, metoprolol and bisoprolol should be preferred in heart failure.

A cluster of melioidosis cases from an endemic region is clonal and is linked to the water supply using molecular typing of Burkholderia pseudomallei isolates

Nine cases of melioidosis with four deaths occurred over a 28-month period in members of a small remote Aboriginal community in the top end of the Northern Territory of Australia. Typing by pulsed-field gel electrophoresis showed isolates of Burkholderia pseudomallei from six of the cases to be clonal and also identical to an isolate from the community water supply, but not to soil isolates. The clonality of the isolates found in this cluster contrasts with the marked genetic diversity of human and environmental isolates found in this region which is hyperendemic for B. pseudomallei. It is possible that the clonal bacteria persisted and were propagated in biofilm in the water supply system. While the exact mode of transmission to humans and the reasons for cessation of the outbreak remain uncertain, contamination of the unchlorinated community water supply is a likely explanation.

Couple distress after sudden infant or perinatal death: A 30-month follow up

Objective: To examine, using a 30-month prospective study, patterns of anxiety, depression and alcohol use in couples following stillbirth, neonatal death or sudden infant death syndrome. Methodology: One hundred and thirty-eight bereaved and 156 non-bereaved couples completed standardized interviews at 2, 8, 15 and 30 months post-loss. Results: At all interviews, bereaved couples were significantly more likely than non-bereaved couples to have at least one distressed partner. Rarely were both partners distressed in either group. For bereaved couples, 'mother only' distress declined from 21% to 10% during the study. 'Father only' distress ranged from 7% to 15%, peaking at 30 months. Bereaved mothers who were distressed at 2 months reported significantly lower marital satisfaction at 30 months. Conclusions: At the couple level, the experience of a baby's death is multifaceted. Gender differences are common and partners' needs may change over time. Early recognition of these differences may facilitate longer-term adjustment for both partners.

Adjusting for fat-free mass in metabolic studies

in a recent publication, Eriksson et al. [1] explored the relationship between size at birth and resting metabolic rate and body composition in adulthood in a cohort of over 300 men and women. They reported an unexpected finding that people of both sexes who had a low birth weight also had a higher metabolic activity per unit muscle tissue. This conclusion was drawn from an analysis where resting metabolic rate (expressed as kcal/kg fat-free mass) in adulthood was examined relative to the birth weight of the subject. One explanation that they suggested was that the apparent increased activity of muscle tissue resulted from an increased sympathetic drive associated with low birth weight. There may be a less physiological reason for the findings of Eriksson et al. Whilst the data are not given specifically in the text, it can be seen clearly from Fig. 1 in the paper that the mean fat-free mass measured in adulthood increased, in both sexes, from the lightest birth weight group to the heaviest birth weight group when the cohort were divided into tertiles based on birth weight. The crux of the issue is that in many - indeed most - cases, expressing resting energy expenditure as kcal/kg fat-free mass does not totally adjust for fat-free mass [2 - 5], and a bias is introduced so that those who have a higher fat-free mass will tend to have a lower resting energy expenditure when expressed per kg fat-free mass. This bias found when expressing many physiological parameters relative to body size, body weight or body composition has long been known [6], and should be carefully considered by appropriate adjustment and hence analysis.

Transforming the architect: Ownership form and archetype change

The adoption of the incorporated form of ownership in preference to partnership is linked to the shift to a more modem organizational archetype in professional firms. Yet existing empirical research offers insufficient insight into the organizational processes of this transformation in different professional arenas. Where ownership and control become separated, there is a clearer theoretical explanation of the implications for the way the firm is run. Where ownership and control remain inside, the firm, however, the consequences are not so clear and have not been well explored. Using survey and interview materials derived from a study of architecture practices, we examine the processes by which differences based on ownership emerge. Then, by drawing on Weberian theories, where they are concerned with professionalization as a project with material and social rewards, we specify more clearly the context for change in professional firms' archetypes. This, we conclude, provides a stronger basis for understanding the change trajectories of firms within professions and comparative organizational analysis between professions.

Resolving the puzzle of productive and destructive conflict in culturally heterogeneous workgroups: A communication accommodation theory approach

This study presents an investigation of the communicative behaviors and strategies employed in the stimulation and management of productive and destructive conflict in culturally heterogeneous workgroups. Using communication accommodation theory (CAT), we argue that the type and course of conflict in culturally heterogeneous workgroups is impacted by the communicative behaviors and strategies employed by group members during interactions. Analysis of data from participant observations, non-participant observations, semi-structured interviews, and self-report questionnaires support CA T-based predictions and provide fresh insights into the triggers and management strategies associated with conflict in culturally heterogeneous workgroups. In particular, results indicated that the more groups used discourse management Strategies, the more they experienced productive conflict. In addition, the use of explanation and checking of own and others' understanding was a major feature of productive conflict, while speech interruptions emerged as a strategy leading to potential destructive conflict. Groups where leaders emerged and assisted in reversing communication breakdowns were better able to manage their discourse, and achieved consensus On task processes. Contributions to the understanding of the triggers and the management of productive conflict in culturally heterogeneous workgroups are discussed.

Population health, environment and economic development

This paper studies the role of income distribution and technology transfer in the process of economic development. A novel aspect of the model is that the composition of human capital as well as the level affect economic growth. Utilizing an overlapping-generations model in which income distribution changes endogenously, we present an economic explanation for why some countries could not start modern economic growth; why some countries took off but have apparently stopped growing after some time; and why some countries have successfully developed and continue to grow

Reconciling paleodistribution models and comparative phylogeography in the Wet Tropics rainforest land snail Gnarosophia bellendenkerensis (Brazier 1875)

Comparative phylogeography has proved useful for investigating biological responses to past climate change and is strongest when combined with extrinsic hypotheses derived from the fossil record or geology. However, the rarity of species with sufficient, spatially explicit fossil evidence restricts the application of this method. Here, we develop an alternative approach in which spatial models of predicted species distributions under serial paleoclimates are compared with a molecular phylogeography, in this case for a snail endemic to the rainforests of North Queensland, Australia. We also compare the phylogeography of the snail to those from several endemic vertebrates and use consilience across all of these approaches to enhance biogeographical inference for this rainforest fauna. The snail mtDNA phylogeography is consistent with predictions from paleoclimate modeling in relation to the location and size of climatic refugia through the late Pleistocene-Holocene and broad patterns of extinction and recolonization. There is general agreement between quantitative estimates of population expansion from sequence data (using likelihood and coalescent methods) vs. distributional modeling. The snail phylogeography represents a composite of both common and idiosyncratic patterns seen among vertebrates, reflecting the geographically finer scale of persistence and subdivision in the snail. In general, this multifaceted approach, combining spatially explicit paleoclimatological models and comparative phylogeography, provides a powerful approach to locating historical refugia and understanding species' responses to them.

Microevolution in island forms: the roles of drift and directional selection in morphological divergence of a passerine bird

Theory predicts that in small isolated populations random genetic drift can lead to phenotypic divergence; however this prediction has rarely been tested quantitatively in natural populations. Here we utilize natural repeated island colonization events by members of the avian species complex, Zosterops lateralis, to assess whether or not genetic drift alone is an adequate explanation for the observed patterns of microevolutionary divergence in morphology. Morphological and molecular genetic characteristics of island and mainland populations are compared to test three predictions of drift theory: (1) that the pattern of morphological change is idiosyncratic to each island; (2) that there is concordance between morphological and neutral genetic shifts across island populations; and (3) for populations whose time of colonization is known, that the rate of morphological change is sufficiently slow to be accounted for solely by genetic drift. Our results are not consistent with these predictions. First, the direction of size shifts was consistently towards larger size, suggesting the action of a nonrandom process. Second, patterns of morphological divergence among recently colonized populations showed little concordance with divergence in neutral genetic characters. Third, rate tests of morphological change showed that effective population sizes were not small enough for random processes alone to account for the magnitude of microevolutionary change. Altogether, these three lines of evidence suggest that drift alone is not an adequate explanation of morphological differentiation in recently colonized island Zosterops and therefore we suggest that the observed microevolutionary changes are largely a result of directional natural selection.

Interspecific variation in plumage colour among birds: species recognition or light environment?

The traditional explanation for interspecific plumage colour variation in birds is that colour differences between species are adaptations to minimize the risk of hybridization. Under this explanation, colour differences between closely related species of birds represent reproductive character displacement. An alternative explanation is that interspecific variation in plumage colour is an adaptive response to variation in light environments across habitats. Under this explanation, differences in colour between closely related species are a product of selection on signal efficiency. We use a comparative approach to examine these two hypotheses, testing the effects of sympatry and habitat use, respectively, on divergence in male plumage colour. Contrary to the prediction of the Species Isolation Hypothesis, we find no evidence that sympatric pairs of species are consistently more divergent in coloration than are allopatric pairs of species. However, in agreement with the Light Environment Hypothesis, we find significant associations between plumage coloration and habitat use. All of these results remain qualitatively unchanged irrespective of the statistical methodology used to compare reflectance spectra, the body regions used in the analyses, or the exclusion of areas of plumage not used in sexual displays. Our results suggest that, in general, interspecific variation in plumage colour among birds is more strongly influenced by the signalling environment than by the risk of hybridization.

Mapping intertidal habitats and an evaluation of their conservation status in Queensland, Australia

The goal of biodiversity conservation has been described as the conservation of diversity at three levels: ecosystem, species and genetic diversity. Developing a representative system of marine protected areas (MPAs) is considered an effective way to achieve this goal in the marine environment. In the absence of detailed information relating to biological distributions there has been increasing use of biodiversity surrogates to determine MPA priorities at regional levels. The development of biodiversity surrogates at fine scales (i.e. habitats) will have an increasingly important role in the identification of sites that will contribute to a representative system of MPAs. This is because it will increase the likelihood that the system will adequately achieve biodiversity objectives by ensuring protection of a greater range of habitats and species. This article provides an explanation of an intertidal shoreline habitat surrogate used to describe 24,216km of Queensland's coastline. The protective status of intertidal habitats was evaluated to assist with designing a representative system of intertidal MPAs. (C) 2002 Elsevier Science Ltd. All rights reserved.

Control of dimethylsulfoxide reductase expression in Rhodobacter capsulatus: the role of carbon metabolites and the response regulators DorR and RegA

Regulation of the expression of dimethylsulfoxide (DMSO) reductase was investigated in the purple phototrophic bacterium Rhodobacter capsulatus. Under phototrophic, anaerobic conditions with malate as carbon source, DMSO caused an approximately 150-fold induction of DMSO reductase activity. The response regulator DorR was required for DMSO-dependent induction and also appeared to slightly repress DMSO reductase expression in the absence of substrate. Likewise, when pyruvate replaced malate as carbon source there was an induction of DMSO reductase activity in cells grown at low light intensity (16 W m(-2)) and again this induction was dependent on DorR. The level of DMSO reductase activity in aerobically grown cells was elevated when pyruvate replaced malate as carbon source. One possible explanation for this is that acetyl phosphate, produced from pyruvate, may activate expression of DMSO reductase by direct phosphorylation of DorR, leading to low levels of induction of dor gene expression in the absence of DMSO. A mutant lacking the global response regulator of photosynthesis gene expression, RegA, exhibited high levels of DMSO reductase in the absence of DMSO, when grown phototrophically with malate as carbon source. This suggests that phosphorylated RegA acts as a repressor of dor operon expression under these conditions. It has been proposed elsewhere that RegA-dependent expression is negatively regulated by the cytochrome cbb(3) oxidase. A cco mutant lacking cytochrome cbb(3) exhibited significantly higher levels of Phi[dorA::lacZ] activity in the presence of DMSO compared to wild-type cells and this is consistent with the above model. Pyruvate restored DMSO reductase expression in the regA mutant to the same pattern as found in wild-type cells. These data suggest that R. capsulatus contains a regulator of DMSO respiration that is distinct from DorR and RegA, is activated in the presence of pyruvate, and acts as a negative regulator of DMSO reductase expression.

Social structure in migrating humpback whales (Megaptera novaeangliae)

Although largely solitary, humpback whales exhibit a number of behaviours where individuals co-operate with one another, for example during bubble net feeding. Such cases could be due to reciprocal altruism brought on by exceptional circumstances, for example the presence of abundant shoaling fish. An alternative explanation is that these behaviours have evolved through kin selection. With little restriction to either communication or movement, diffuse groups of relatives could maintain some form of social organization without the need to travel in tight-nit units. To try to distinguish between these hypotheses, we took advantage of the fact that migrating humpback whales often swim together in small groups. If kin selection is important in humpback whale biology, these groups should be enriched for relatives. Consequently, we analysed biopsy samples from 57 groups of humpback whales migrating off Eastern Australia in 1992. A total of 142 whales were screened for eight microsatellite markers. Mitochondrial DNA sequences (371 bp) were also used to verify and assist kinship identification. Our data add support to the notion that mothers travel with their offspring for the first year of the calf's life. However, beyond the presence of mother-calf/yearling pairs, no obvious relatedness pattern was found among whales sampled either in the same pod or on the same day. Levels of relatedness did not vary between migratory phases (towards or away from the breeding ground), nor between the two sexes considered either overall or in the north or south migrations separately. These findings suggest that, if any social organization does exist, it is formed transiently when needed rather than being a constant feature of the population, and hence is more likely based on reciprocal altruism than kin selection.