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Growth Rate Increase (growth + rate_increase)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Output Taxation, Human Capital and Growth

THE MANCHESTER SCHOOL, Issue 2 2000
Rosa Capolupo
In this paper we investigate the long-run effects of government spending and taxation in an endogenous growth setting. The model is a variant of Barro's model (,Government Expenditure in a Simple Model of Endogenous Growth', Journal of Political Economy, Vol. 98, 1990, pp. S103,S125) and Lucas's model (,On the Mechanics of Economic Development', Journal of Monetary Economics, Vol. 22, 1988, pp. 3,42) in which human capital accumulation is driven by government spending on public education. To balance the budget the government levies a tax on output in two alternative specifications of the human capital accumulation equation. The results consolidate some recent findings that taxation, when it is used for productive purposes, may lead to faster growth. Growth rates increase with taxes up to a level around 60,70 per cent. [source]

An ecological law and its macroecological consequences as revealed by studies of relationships between host densities and parasite prevalence

ECOGRAPHY, Issue 3 2001
Per ArnebergArticle first published online: 30 JUN 200
Epidemiological models predict a positive relationship between host population density and abundance of macroparasites. Here I test these by a comparative study. I used data on communities of four groups of parasites inhabiting the gastrointestinal tract of mammals, nematodes of the orders Oxyurida, Ascarida, Enoplida and Spirurida, respectively. The data came from 44 mammalian species and represent examination of 16 886 individual hosts. I studied average prevalence of all nematodes within an order in a host species, a measure of community level abundance, and considered the potential confounding effects of host body weight, fecundity, age at maturity and diet. Host population density was positively correlated with parasite prevalence within the order Oxyurida, where all species have direct life cycles. Considering the effects of other variables did not change this. This supports the assumption that parasite transmission rate generally is a positive function of host population density. It also strengthens the hypothesis that host densities generally act as important determinants of species richness among directly transmitted parasites and suggests that negative influence of such parasites on host population growth rate increase with increasing host population density among host species. Within the other three nematode orders, where a substantial number of the species have indirect life cycles, no relationships between prevalence and host population density were seen. Again, considering the effects of other variables did not affect this conclusion. This suggests that host population density is a poor predictor of species richness of indirectly transmitted parasites and that effects of such parasites on host population dynamics do not scale with host densities among species of hosts. [source]

Growth-enhanced fish can be competitive in the wild

FUNCTIONAL ECOLOGY, Issue 5 2001
J. I. Johnsson
Summary 1,The widespread commercial interest in producing growth-enhanced organisms has raised concerns about ecological consequences, emphasizing the need to understand the costs and benefits associated with accelerated growth in nature. Here, sustained-release growth hormone (GH) implants were used to estimate the competitive ability of growth-enhanced fish in the wild. Growth rate, movements and survival over winter were compared between GH-implanted and control Brown Trout in a natural stream. The study was repeated over two consecutive years. 2,GH treatment had no effect on recapture rates, indicating that mortality rates did not differ between GH-treated and control fish. More GH-treated trout (63%) than control fish (41%) were recaptured within their 10 m section of release. Thus, GH-treated fish were more stationary than control fish over winter. 3,GH-treated fish grew about 20% faster than control fish. This was mainly because of a three-fold growth rate increase in GH-treated fish in late summer, whereas growth rates over winter did not differ significantly between treatment groups. These results were consistent over both replicate years. 4,This first study of growth-enhanced fish in the wild shows that they can survive well and therefore may out-compete normal fish with lower growth rates. Although selection against rapid growth may be more intense at other life-history stages and/or during periods of extreme climate conditions, our findings raise concerns that released or escaped growth-enhanced salmonids may compete successfully with resident fish. It is clear that the potential ecological risks associated with growth-enhanced fish should not be ignored. [source]

Gas-Phase and Surface Kinetics of Epitaxial Silicon Carbide Growth Involving Chlorine-Containing Species,

CHEMICAL VAPOR DEPOSITION, Issue 8-9 2006
A. Veneroni
Abstract A detailed chemical mechanism for the silicon carbide epitaxial growth using light hydrocarbons, silane, and either chlorosilanes and/or HCl as the chlorine source is presented. The mechanism involves 153,gas-phase and 76 surface reactions among 47,gas-phase and 9 surface species, respectively. A comparison with the performances of the standard process using silane-hydrocarbons is presented, and the observed growth rate increase and the disappearing of the homogeneous silicon droplets in gas phase is explained. [source]

Intraspecific variation in the strength of density dependence in aphid populations

ECOLOGICAL ENTOMOLOGY, Issue 5 2004
Anurag A. Agrawal
Abstract., 1. Experimental evidence is presented for positive, negative, and no density dependence from 32 independent density manipulations of milkweed aphids (Aphis nerii) in laboratory and field experiments. This substantial variation in intraspecific density dependence is associated with temperature and host-plant species. 2. It is reported that as population growth rate increases, density dependence becomes more strongly negative, suggesting that the monotonic definition of density dependence used in many common population models is appropriate for these aphids, and that population growth rate and carrying capacity are not directly proportional. 3. For populations that conform to these assumptions, population growth rate may be widely applicable as a predictor of the strength of density dependence. [source]