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

Spatial structure and habitat variation in a grasshopper hybrid zone

A hybrid zone between the grasshoppers Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) in northern Spain has been analyzed for variation in morphology and ecology. These species are readily distinguished by the number of stridulatory pegs on the hind femur. Both sexes are fully winged and inhabit disturbed habitats throughout the study area. We develop a maximum-likelihood approach to fitting a two-dimensional cline to geographical variation in quantitative traits and for estimating associations of population mean with local habitat. This method reveals a cline in peg number approximately 30 km south of the Picos de Europa Mountains that shows substantial deviations in population mean compared with the expectations of simple tension zone models. The inclusion of variation in local vegetation in the model explains a significant proportion of the residual variation in peg number, indicating that habitat-genotype associations contribute to the observed spatial pattern. However, this association is weak, and a number of populations continue to show strong deviations in mean even after habitat is included in the final model. These outliers may be the result of long-distance colonization of sites distant from the cline center or may be due to a patchy pattern of initial contact during postglacial expansion. As well as contrasting with the smooth hybrid zones described for Chorthippus parallelus, this situation also contrasts with the mosaic hybrid zones observed in Gryllus crickets and in parts of the hybrid zone between Bombina toad species, where habitat-genotype associations account for substantial amounts of among-site variation.

Shear stress and sediment transport calculations for swash zone modelling

It is shown that the observed difference in sediment transporting efficiency by the swash uprush, compared with the downrush, could be mainly due to greater bed shear stress for a given velocity in the more abruptly accelerated uprush. The bed shear stress generated by an arbitrary free stream velocity time series is modelled in terms of usual wave boundary layer models plus a phase lead (phi(tau) of the bed shear stress compared with the free stream velocity at the peak frequency. With this approach, the total transport amounts in uprush and downrush can be modelled satisfactorily with the same sediment transport formula, without the need for different uprush and downrush coefficients. While the adaptation of sediment transport formulae from steady flow can thus lead to the right total amounts of sediment moved by this method, the timing of the instantaneous sediment transport rates are probably not accurately modelled due to the highly unsteady nature of the swash and the presence of pre-suspended sediment in the uprush. Nevertheless, the proposed method is a useful intermediate step before we have a complete understanding of sediment transport under very rapid accelerations and of the relative contribution of pre-suspended sediment to the onshore sediment transport in swash zones. (C) 2002 Published by Elsevier Science B.V.

Lamproites from Gaussberg, Antarctica: Possible transition zone melts of Archaean subducted sediments

Petrogenetic models for the origin of lamproites are evaluated using new major element, trace element, and Sr, Nd, and Pb isotope data for Holocene lamproites from the Gaussberg volcano in the East Antarctic Shield. Gaussberg lamproites exhibit very unusual Pb isotope compositions (Pb-206/Pb-204 = 17.44-17.55 and Pb-207/Pb-204 = 15.56-15.63), which in common Pb isotope space plot above mantle evolution lines and to the left of the meteorite isochron. Combined with very unradiogenic Nd, such compositions are shown to be inconsistent with an origin by melting of sub-continental lithospheric mantle. Instead, a model is proposed in which late Archaean continent-derived sediment is subducted as K-hollandite and other ultra-high-pressure phases and sequestered in the Transition Zone (or lower mantle) where it is effectively isolated for 2-3 Gyr. The high Pb-207/Pb-204 ratio is thus inherited from ancient continent-derived sediment, and the relatively low Pb-206/Pb-204 ratio is the result of a single stage of U/Pb fractionation by subduction-related U loss during slab dehydration. Sr and Nd isotope ratios, and trace element characteristics (e.g. Nb/Ta ratios) are consistent with sediment subduction and dehydration-related fractionation. Similar models that use variable time of isolation of subducted sediment can be derived for all lamproites. Our interpretation of lamproite sources has important implications for ocean island basalt petrogenesis as well as the preservation of geochemically anomalous reservoirs in the mantle.

Ductile fabrics in the zone of active oblique convergence near the Alpine Fault, New Zealand: identifying the neotectonic overprint

The mid-crustal Alpine Schist in central Southern Alps, New Zealand has been exhumed during the past similar to3 m.y. on the hanging wall of the oblique-slip Alpine Fault. These rocks underwent ductile deformation during their passage through the similar to 150-km-wide Pacific-Australia plate boundary zone. Likely to be Cretaceous in age, peak metamorphism predates the largely Pliocene and younger oblique convergence that continues to uplift the Southern Alps today. Late Cenozoic ductile deformation constructively reinforced a pre-existing fabric that was well oriented to accommodate a dextral-transpressive overprint. Quartz microstructures below a recently exhumed brittle-ductile transition zone reflect a late Cenozoic increment of ductile strain that was distributed across deeper levels of the Pacific Plate. Deformation was transpressive, including a dextral-normal shear component that bends and rotates a delaminated panel of Pacific Plate crust onto the oblique footwall ramp of the Alpine Fault. Progressive ductile shear in mylonites at the base of the Pacific Plate overprints earlier fabrics in a dextral-reverse sense, a deformation that accompanies translation of the schists up the Alpine Fault. Ductile shear along that structure affects not only the 12-km-thick section of Alpine mylonites, but is distributed across several kilometres of overlying nonmylonitic rocks. (C) 2001 Elsevier Science Ltd. All rights reserved.

Which aspects of socio-economic status are related to health in mid-aged and older women?

A population-based study was conducted to validate gender- and age-specific indexes of socio-economic status (SES) and to investigate the associations between these indexes and a range of health outcomes in 2 age cohorts of women. Data from 11,637 women aged 45 to 50 and 9,5 10 women aged 70 to 75 were analyzed. Confirmatory factor analysis produced four domains of SES among the mid-aged cohort (employment, family unit, education, and migration) and four domains among the older cohort (family unit, income, education, and migration). Overall, the results supported the factor structures derived from another population-based study (Australian Bureau of Statistics, 1995), reinforcing the argument that SES domains differ across age groups. In general, the findings also supported the hypotheses that women with low SES would have poorer health outcomes than higher SES women, and that the magnitude of these effects would differ according to the specific SES domain and by age group, with fewer and smaller differences observed among older women. The main exception was that in the older cohort, the education domain was significantly associated with specific health conditions. Results suggest that relations between SES and health are highly complex and vary by age, SES domain, and the health outcome under study.

Practical and economic advantages of choice feeding systems for laying poultry

Poultry can be managed under different feeding systems, depending on the husbandry skills and the feed available. These systems include the following: (1) a complete dry feed offered as a mash ad libitum; (2) the same feed offered as pellets or crumbles ad libitum; (3) a complete feed with added whole grain; (4) a complete wet feed given once or twice a day; (5) a complete feed offered on a restricted basis; (6) choice feeding. Of all these, an interesting alternative to offering complete diets is choice feeding which can be applied on both a small or large commercial scale. Under choice feeding or free-choice feeding birds are usually offered a choice between three types of feedstuffs: (a) an energy source (e.g. maize, rice bran, sorghum or wheat); (b) a protein source (e.g. soyabean meal, meat meal, fish meal or coconut meal) plus vitamins and minerals and (c), in the case of laying hens, calcium in granular form (i.e. oyster-shell grit). This system differs from the modern commercial practice of offering a complete diet comprising energy and protein sources, ground and mixed together. Under the complete diet system, birds are mainly only able to exercise their appetite for energy. When the environmental temperature varies, the birds either over- or under-consume protein and calcium. The basic principle behind practising choice feeding with laying hens is that individual hens are able to select from the various feed ingredients on offer and compose their own diet, according to their actual needs and production capacity. A choice-feeding system is of particular importance to small poultry producers in developing countries, such as Indonesia, because it can substantially reduce the cost of feed. The system is flexible and can be constructed in such a way that the various needs of a flock of different breeds, including village chickens, under different climates can be met. The system also offers a more effective way to use home-produced grain, such as maize, and by-products, such as rice bran, in developing countries. Because oyster-shell grit is readily available in developing countries at lower cost than limestone, the use of cheaper oyster-shell grit can further benefit small-holders in these countries. These benefits apart, simpler equipment suffices when designing and building a feed mixer on the farm, and transport costs are lower. If whole (unground) grain is used, the intake of which is accompanied by increased efficiency of feed utilisation, the costs of grinding, mixing and many of the handling procedures associated with mash and pellet preparation are eliminated. The choice feedstuffs can all be offered in the current feed distribution systems, either by mixing the ingredients first or by using a bulk bin divided into three compartments.

Impact of osteoarthritis on individuals and society: how much disability? Social consequences and health economic implications

Osteoarthritis is a major cause of disability in both the developed and developing world. With the population aging, the prevalence of osteoarthritis is increasing and its consequences are impacting significantly on society. This is one of the reasons why osteoarthritis has been adopted as a major focus (along with osteoporosis, rheumatoid arthritis, back pain, and musculoskeletal trauma) by the global initiative-the Decade of Bone and Joint Disease. Adequate studies on the costs of osteoarthritis are urgently required so that cogent arguments can be made to governments to appropriately fund prevention and treatment programs for this condition. Its recognition as a major cause of disability, particularly in the aging population, should increase community focus on this important condition. (C) 2002 Lippincott Williams Wilkins, Inc.

Koala mortality on roads in south-east Queensland: the koala speed-zone trial

In 1995, the Queensland Parks and Wildlife Service, the Queensland Department of Main Roads and Redland Shire Council initiated the Koala Speed Zone Trial in the Koala Coast, south-east Queensland. The aim of the trial was to assess the effect of differential speed signs on the number of koalas ( Phascolarctos cinereus) hit by vehicles in the Koala Coast from 1995 to 1999. On the basis of information collected by the Queensland Parks and Wildlife Service 1407 koalas were hit by vehicles in the Koala Coast during the five-year study ( mean 281 koalas per year, range 251 - 315). Monitoring of vehicle speeds by the Queensland Department of Main Roads suggested that there was no significant reduction in vehicle speed during the trial period from August to December. Consequently, there was no evidence to suggest that a reduction in the number of koalas hit by vehicles occurred during the trial. Approximately 70% of koalas were hit on arterial and sub-arterial roads and approximately 83% did not survive. The location of each koala hit was recorded and the signed speed limit of the road was noted. Most koalas that were hit by vehicles were young healthy males. Pooling of data on koala collisions and road speed limits suggested that the proportion of koalas that survived being hit by vehicles was slightly higher on roads with lower speed limits. However, vehicle speed was not the only factor that affected the number of koalas hit by vehicles. It is suggested that habitat destruction, koala density and traffic volume also contribute to road-associated koala mortality in the Koala Coast.