Genetic influence on ERP slow wave measures of working memory

Individual differences in the variance of event-related potential (ERP) slow wave (SW) measures were examined. SW was recorded at prefrontal and parietal sites during memory and sensory trials of a delayed-response task in 391 adolescent twin pairs. Familial resemblance was identified and there was a strong suggestion of genetic influence. A common genetic factor influencing memory and sensory SW was identified at the prefrontal site (accounting for an estimated 35%-37% of the reliable variance) and at the parietal site (51%-52% of the reliable variance). Remaining reliable variance was influenced by unique environmental factors. Measurement error accounted for 24% to 30% of the total variance of each variable. The results show genetic independence for recording site, but not trial type, and suggest that the genetic factors identified relate more directly to brain structures, as defined by the cognitive functions they support, than to the cognitive networks that link them.

Quantum slow motion

We investigate the center-of-mass motion of cold atoms in a standing amplitude modulated laser field. We use a simple model to explain the momentum distribution of the atoms after any distinct number of modulation cycles. The atoms starting near a classical phase-space resonance move slower than we would expect classically. We explain this by showing that for a wave packet on the classical resonances we can replace the complicated dynamics in the quantum Liouville equation in phase space by its classical dynamics with a modified potential.

Australia, the United States and a 'China growing strong': managing conflict avoidance

How to deal with a rising China constitutes one of the most seminal challenges facing the ANZUS alliance since its inception a half a century ago. Australia must reconcile its geography and economic interests in Asia with its post-war strategic and historic cultural orientation towards the United States. It must succeed in this policy task without alienating either Beijing or Washington in the process. The extent to which this is achieved will shape Australia's national security posture for decades to come. Three specific components of the 'Sino-American-Australian' triangle are assessed here: the future of Taiwan, the American development of a National Missile Defence (NMD), and the interplay between Sino-American power balancing and multilateral security politics. The policy stakes for Australia and for the continued viability of ANZUS are high in all three policy areas as a new US Administration takes office in early 2001. The article concludes that Australia's best interest is served by applying deliberate modes of decisionmaking in its own relations with both China and the US and by facilitating consistent and systematic dialogue and consultations with both of those great powers on key strategic issues.

The ecological basis of life history variation in marsupials

Our understanding of the diversity of mammalian life histories is based almost exclusively on eutherian mammals, in which the slow-fast continuum persists even after controlling for effects of body size and phylogeny. In this paper, we use modern comparative methods to test the extent to which this eutherian-based framework can be extrapolated to metatherian mammals. First, we examine the pattern of covariation among life history traits, and second, we test for correlations between variation in life history and variation in six candidate ecological variables: type of diet, extent of intraspecific competition, risk of juvenile mortality, diurnal pattern of activity, arboreality, and rainfall pattern. Even when controlling for body size and phylogeny, we observe a slow-fast continuum in metatherian mammals. Some parameters involved are different from those identified by studies of eutherians, but the underlying relationships among longevity, fecundity, and age at maturity persist. We also show that overall variation in a key life history variable, reproductive output (measured by annual reproductive rate and litter size), is significantly related to variation in type of diet, with a foliage-rich diet being associated with low fecundity. This is interesting because, although ecological correlations have been found within some eutherian subgroups, modern comparative approaches have failed to reveal robust ecological correlates of overall life history diversity in eutherians. Copyright ESA. All rights reserved.

Reconciling Globalisation and Technological Change: Growing Income Inequalities and Remedial Policies

From the mid-1970s through the 1980s and into the 1990s, wage inequality and skill differentials in earnings and employment increased sharply in OECD countries. After 1973 and especially in the 1980s, the US experienced a dismal real wage performance for the less skilled. Among the factors singled out by economists as possible major contributors to this development are economic globalisation processes and skill-biased technological change. Although these are most commonly considered as independent influences, after critically outlining views about these factors, this article argues that strong interdependence exists between them. The article then examines potential policy responses to this growing inequality.

Body size and latitudinal gradients in regional diversity of New World birds

Axe latitudinal gradients in regional diversity random or biased with respect to body size? Using data for the New World avifauna, I show that the slope of the increase in regional species richness from the Arctic to the equator is not independent of body size. The increase is steepest among small and medium-sized species, and shallowest among the largest species. This is reflected in latitudinal variation in the shape of frequency distributions of body sizes in regional subsets of the New World avifauna. Because species are added disproportionately in small and medium size classes towards low latitudes, distributions become less widely spread along the body size axis than expected from the number of species. These patterns suggest an interaction between the effects of latitude and body size on species richness, implying that mechanisms which vary with both latitude and body size may be important determinants of high tropical diversity in New World birds.

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.

Fatal monensin toxicity in a dog after chewing a bovine intra-ruminal slow-release device

A 20kg, 10-month-old male Kelpie developed a rapid onset of profound paresis progressing to flaccid paralysis and dyspnoea, followed by death about 36 hours after chewing on a partly discharged anti-bloat capsule from a dead cow. Intoxication by monensin in the capsule was considered the cause of death. No Lodes holocyclus were found on the dog. Evidence of muscle damage was seen in clinical biochemistry assays of plasma, but consent for necropsy was not obtained. The median lethal dose for Beagle dogs of the material contained in anti-bloat capsules is 0.5-1.0g. As this represents a serious toxicity risk if dogs chew these devises, the manufacturer includes a warning on potential dog toxicity in product literature.

Zeolite/rock phosphate - a novel slow release phosphorus fertiliser for potted plant production

A glasshouse study was undertaken to determine if the zeolite mineral clinoptilolite from an Australian deposit in combination with rock phosphate (RP) could significantly enhance the uptake of P by sunflowers. The zeolite/RP combination was intended to act as an exchange-fertiliser, with Ca2+ exchanging onto the zeolite in response to plant uptake of nutrient cations (NH4+ or K) enhancing the dissolution of the RP. A reactive RP (Sechura) and a relatively non-reactive RP (Duchess) were examined. Zeolite was used in Ca2+-, K+- and NH4+-saturated forms at ratios of 3.5:1 and 7:1 with RP; Ca2+-zeolite was considered the control, with exchange-induced dissolution possible from K+-and NH4+-zeolite, The zeolite/RP mixture was applied as a vertical band adjacent to the sunflower seedling. In addition, N was supplied as urea in an effort to determine if RP dissolution resulted from H+ release by nitrification. Phosphorus supply from the zeolite/RP system was compared with an available P source (KH2PO4). The experiment clearly demonstrated greatly enhanced plant uptake of P from RP when applied in combination with NH4-zeolite, though the P uptake was lower than that from the soluble P source. The zeolite/RP interaction was much more effective with the reactive R-P than the non-reactive material, Within the NH4+-zeolite/RP band, root proliferation was greatly increased, as would be expected in an exchange-fertiliser system. The K+-zeolite system did not produce a significantly greater yield than the Ca2+-zeolite control, probably because adequate K+ supply from the basal application reduced uptake within the zeolite/RP band, thus reducing the extent of exchange-induced dissolution. Nevertheless, increased root proliferation within the band was observed, implying that exchange-induced dissolution may also be possible from this system. The zeolite/RP system offers the considerable advantage of P release in response to plant demand and is unique in this regard. (C) 2002 Elsevier Science B.V. All rights reserved.

Growing Atriplex and Maireana species in saline sodic and waterlogged soils

Utilization of salt affected wasteland by growing forage shrubs has enormous economic and environmental implication for developing countries like Pakistan, where approximately 6.3 million ha of the land is salt affected. Considering the importance of Atriplex and Maireana species, research has been conducted using their different species on the salt affected soils of Faisalabad. Most of Atriplex and Maireana species survived under the environmental conditions of Faisalabad and gave the good yield in the form of forage. Some of these species are woody and can be used for fuel purposes. Sixteen genotypes of Atriplex and Maireana were tested for their tolerance to waterlogging in order to identify halophytic fodder shrubs suitable for growth on secondary salt-affected and waterlogged farmland. The physiological and morphological responses of the species tested were typical of species with a generally poor tolerance to waterlogging. Despite this, some species (e.g., A. amnicola) were surprisingly resistant, surviving up to five months of waterlogging at moderate salinity and high evapotranspirational demand. The most resistant species, A amnicola maintained higher transpiration rates, leaf water potentials and shoot extension rates than most other species during five weeks of waterlogging, and a return to control levels more quickly than other species after plots were drained. Although little morphological adaptation to waterlogged conditions was detected, a shallow and extensive lateral root system and the formation of many short aerenchymatous adventitious roots from procumbent branches appeared to advantage A. amnicola in an environment highly heterogeneous in salinity and low in oxygen concentration. Waterlogging quickly killed shallow fibrous rooted species, although the procumbent branches of some individuals survived as clones if they developed adventitious roots.