Long-run growth effects of taxation in a non-scale growth model with innovation

In previous studies, taxing income or consumption hinders long-run growth. Incorporating saving and leisure into the non-scale Schumpeterian model of [Journal of Political Economy 107 (1999) 715-730], we show that the usual growth effects of taxing consumption and labor income do not exist. (C) 2002 Elsevier Science B.V. All rights reserved.

Growth of a Bose-Einstein condensate: a detailed comparison of theory and experiment

We extend the earlier model of condensate growth of Davis et at (Davis M J, Gardiner C W and Ballagh R J 2000 Phys. Rev. A 62 063608) to include the effect of gravity in a magnetic trap. We carry out calculations to model the experiment reported by Kohl et al (Kohl M, Davis M J, Gardiner C W, Hansch T and Esslinger T 2001 Preprint cond-mat/0106642) who study the formation of a rubidium Bose-Einstein condensate for a range of evaporative cooling parameters. We find that, in the regime where our model is valid, the theoretical curves agree with all the experimental data with no fitting parameters. However, for the slowest cooling of the gas the theoretical curve deviates significantly from the experimental curves. It is possible that this discrepancy may be related to the formation of a quasicondensate.

Economic and environmental impacts of pollution control in a system of environment and economic interdependence

The importance of the rate of change of the pollution stock in determining the damage to the environment has been an issue of increasing concern in the literature. This paper uses a three-sector (economy, population and environment), non-linear, discrete time, calibrated model to examine pollution control. The model explicitly links economic growth to the health of the environment. The stock of natural resources is affected by the rate of pollution flows, through their impact on the regenerative capacity of the natural resource stock. This can shed useful insights into pollution control strategies, particularly in developing countries where environmental resources are crucial for production in many sectors of the economy. Simulation exercises suggested that, under plausible assumptions, it is possible to reverse undesirable transient dynamics through pollution control expenditure, but this is dependent upon the strategies used for control. The best strategy is to spend money fostering the development of production technologies that reduce pollution rather than spending money dealing with the effects of the pollution flow into the environment. (C) 2001 Elsevier Science Ltd. All rights reserved.

Constitutive expression of a phenylalanine ammonia-lyase gene from Stylosanthes humilis in transgenic tobacco leads to enhanced disease resistance but impaired plant growth

Transgenic tobacco plants expressing a phenylalanine ammonia-lyase cDNA (ShPAL), isolated from Stylosanthes humilis, under the control of the 35S promoter of the cauliflower mosaic virus were produced to test the effect of high level PAL expression on disease resistance. The transgenic plants showed up to eightfold PAL activity and were slowed in growth and flowering relative to non-transgenic controls which have segregated out the transgene. The expression of the ShPAL transgene and elevated PAL levels were correlated and stably inherited. In T-1 and T-2 tobacco plants with increased PAL activity, lesion expansion was significantly reduced by up to 55% on stems inoculated with the Oomycete pathogen Phytophthora parasitica pv. nicotianae, Lesion area was significantly reduced by up to 50% on leaves inoculated with the fungal pathogen Cercospora nicotianae. This study provides further evidence that PAL has a role in plant defence. (C) 2002 Elsevier Science Ltd. All rights reserved.

The effects of temperature on the growth, survival and biomass of different families of juvenile Penaeus japonicus Bate

Variation in the growth, survival and change in total biomass (termed biomass increase) of different families of juvenile Penaeus japonicus was investigated over a range of temperatures in controlled laboratory experiments. In the first experiment, the effects of temperature on six families of juveniles were examined over a broad range of temperatures (24 to 30 degreesC). In the second experiment, the effects of temperature on six more families of juveniles were examined over a narrower range of temperatures (27.5 to 31.2 degreesC). Over the broad temperature range, mean growth and biomass increase were highest at 27 degreesC and mean survival was highest at 24 degreesC. Mean growth was lowest at 24 degreesC, whilst survival and biomass increase were lowest at 30 degreesC. However, there was a significant interaction between family and temperature, with some families tolerating a broader range of temperatures than others. As a result, the ranking of families in relation to growth, survival and biomass increase changed at each temperature. This effect was more pronounced for survival than for growth. Over the narrower range, temperature significantly affected growth, survival and biomass increase, but there was no significant interaction between family and temperature. Growth, survival and biomass increase were significantly lower at 31.2 than at 27.5 and 29.2 degreesC. These results suggest that if grow-out conditions for P. japonicus vary by more than a few degrees, interactions between family and temperature could affect the efficiency of selection. The results also suggest that the family x temperature interaction may have a more pronounced effect on survival than on growth. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.

Interacting roles of myofibroblasts, apoptosis and fibrogenic growth factors in the pathogenesis of renal tubulo-interstitial fibrosis

The interrelationship between myofibroblasts and fibrogenic growth factors in the pathogenesis of renal fibrosis is poorly defined. A temporal and spatial analysis of myofibroblasts, their proliferation and death, and presence of transforming growth factor-beta1 (TGF-beta1) and platelet-derived growth factor-B (PDGF-B) was carried out in an established rodent model in which chronic renal scarring and fibrosis occurs after healed renal papillary necrosis (RPN), similar to that seen with analgesic nephropathy. Treated and control groups (N = 6 and 4, respectively) were compared at 2, 4, 8 and 12 weeks. A positive relationship was found between presence of tubulo-interstitial myofibroblasts and development of fibrosis. Apoptotic myofibroblasts were identified in the interstitium and their incidence peaked 2 weeks after treatment. Levels of interstitial cell apoptosis and fibrosis were negatively correlated over time (r = -0.57, p < 0.01 ), suggesting that as apoptosis progressively failed to limit myofibroblast numbers, fibrosis increased. In comparison with the diminishing apoptosis in the interstitium, the tubular epithelium had progressively increasing levels of apoptosis over time, indicative of developing atrophy of nephrons. TGF-beta1 protein expression had a close spatial and temporal association with fibrosis and myofibroblasts, whilst PDGF-B appeared to have a closer link with populations of other chronic inflammatory cells such as infiltrating lymphocytes. Peritubular myofibroblasts were often seen near apoptotic cells in the tubular epithelium, suggestive of a paracrine toxic effect of factor/s secreted by the myofibroblasts. In vitro , TGF-beta1 was found to be toxic to renal tubular epithelial cells. These findings suggest an interaction between myofibroblasts, their deletion by apoptosis, and the presence of the fibrogenic growth factor TGF-beta1 in renal fibrosis, whereby apoptotic deletion of myofibroblasts could act as a controlling factor in progression of fibrosis.

Convergent maternal care strategies in ungulates and macropods

Mammals show extensive interspecific variation in the form of maternal care. Among ungulates, there is a dichotomy between species in which offspring follow the mother (following strategy) versus species in which offspring remain concealed (hiding strategy). Here we reveal that the same dichotomy exists among macropods (kangaroos, wallabies and allies). We test three traditional adaptive explanations and one new life history hypothesis. and find very similar patterns among both ungulates and macropods. The three traditional explanations that we tested were that a ''following'' strategy is associated with (1) open habitat, (2) large mothers, and (3) gregariousness. Our new life-history hypothesis is that a following strategy'' is associated with delayed weaning, and thus with the slow end of the slow-fast mammalian life-history continuum, because offspring devote resources to locomotion rather than rapid growth. Our comparative test strongly supports the habitat structure hypothesis and provides some support for this new delayed weaning hypothesis for both ungulates and macropods. We propose that sedentary young in closed habitats benefit energetically by having milk brought to them. In open habitats, predation pressure will select against hiding. Followers will suffer slower growth to independence. Taken together, therefore, our results provide the first quantitative evidence that macropods and ungulates are convergent with respect to interspecific variation in maternal care strategy. In both clades, differences between species in the form of parental care are due to a similar interaction between habitat, social behavior, and life history.

Investigations of growth processes in Y-Ba-Cu-O materials by microstructural examination of quenched samples

Y-Ba-Cu-O samples with additions of Y2O3 and CeO2 were quenched during seeded isothermal melt processing and examined by optical microscopy and scanning electron microscopy. Large YBa2Cu3O7-y (Y123) particles in the starting powder were found to form a distinct type of melt during heating, which was unaffected by the Y2O3 or CeO2 additives. This type of melt later formed regions with a low concentration of Y2BaCuO5 (Y211) particles in the Y123 matrix. The maximum growth rate of Y123 that could be sustained in the sample was found to be lower in the melt formed from large Y123 particles, and this may lead to growth accidents and subgrains in some samples.