247 research outputs found
The case for increasing returns I: "The Hicksian Getaway" and "The Hirshleifer Rescue"
The case for increasing returns is accepted by most heterodox economists. Yet allegiance to decreasing returns in orthodox circles still endures directly and in the form of substitution assumptions. In forty short years from 1928 to 1968, beliefs shifted from Pigou calling rising cost âinadmissibleâ to Alchian deeming decreasing returns âa universally valid lawâ until Kaldor revived the case for increasing returns in the 1970s. How did these shifts of view occur? After dapham opened the door and Pigou defined the orthodox stand, the 1930s debates swept through imperfect competition and many other issues into Keynesian disequilibrium theory. In 1939, âThe Hicksian Getawayâ opened an Age of Denial leading to equilibrium theories based on substitution; then during the 1960s a second challenge to rising cost based on learning and technical change was defeated by âThe Hirshleifer Bescueâ of decreasing returns and thus substitution in neoclassical theory. Why economists\u27 substitution assumptions still hold sway is the focus of this study. First, the paper reviews âThe Hicksian Getawayâ in its context and with respect to equilibrium models. Second, the paper analyzes and disproves âThe Hirshleifer Bescueâ as an invalid argument based on a non-sequitur and thus simply asserted. Third, the case for increasing returns is developed into a theory of planning horizons supporting a generalized complementarity in economics. Some methodological implications are explored at the end
The case for increasing returns I: "The Hicksian Getaway" and "The Hirshleifer Rescue"
The case for increasing returns is accepted by most heterodox economists. Yet allegiance to decreasing returns in orthodox circles still endures directly and in the form of substitution assumptions. In forty short years from 1928 to 1968, beliefs shifted from Pigou calling rising cost âinadmissibleâ to Alchian deeming decreasing returns âa universally valid lawâ until Kaldor revived the case for increasing returns in the 1970s. How did these shifts of view occur? After dapham opened the door and Pigou defined the orthodox stand, the 1930s debates swept through imperfect competition and many other issues into Keynesian disequilibrium theory. In 1939, âThe Hicksian Getawayâ opened an Age of Denial leading to equilibrium theories based on substitution; then during the 1960s a second challenge to rising cost based on learning and technical change was defeated by âThe Hirshleifer Bescueâ of decreasing returns and thus substitution in neoclassical theory. Why economists\u27 substitution assumptions still hold sway is the focus of this study. First, the paper reviews âThe Hicksian Getawayâ in its context and with respect to equilibrium models. Second, the paper analyzes and disproves âThe Hirshleifer Bescueâ as an invalid argument based on a non-sequitur and thus simply asserted. Third, the case for increasing returns is developed into a theory of planning horizons supporting a generalized complementarity in economics. Some methodological implications are explored at the end
Trematominae and Artedidraconinae: contrasted mitogenome evolution for two Antarctic radiations
Cellular respiration has been widely studied in Antarctic teleost fishes because of their peculiar adaptations to an extreme environment. In parallel mitochondrial sequence markers have become highly popular for molecular systematics. However, there are few whole mitochondrial genome sequences published, and none available for some of the subfamilies. Here, we present two large mitogenome datasets including most species and multiple sequences for many species of two subfamilies, Trematominae and Artedidraconinae (Duhamel et al. 2014). These include two highly diverse but very different adaptative radiations, with contrasting divergence dates, morphological polymorphism, and habitat dominance. The sampling is based on a well identified, extensive collection resulting from the 2008 CEAMARC survey and the subsequent REVOLTA surveys in Terre AdĂŠlie (IPEV), already DNA barcoded and sequenced in previous studies. The mitogenome sequences for these two subfamilies differ in composition, gene order, and relative divergence of mitochondrial markers, with strong, taxon-specific biases like very high C contents in some regions. The gene order change provides a synapomorphy for the subfamily Trematominae and an interesting development in teleost mitogenomes. The complete Artedidraconinae mitogenomes provide a much higher amount of variable sites (approx*30), while previous sequence datasets were plagued by low informativeness (Lecointre et al. 2011). As already established on single mitochondrial genes, intraspecific variability is lower than interspecific variability within each subfamily, however interspecific variability in Artedidraconinae is lower or similar to intraspecific variability in Trematominae. This expanded dataset confirms the unusual evolution of the mitochondrial coded sequences involved in the cellular respiration in Antarctic Nototheniidae, as well as the usefulness of complete mitochondrial genomes for their systematics. The two level multiplexing (Timmermans et al. 2010) and next generation sequencing of long PCR amplicons (following Hinsinger et al. 2015) is efficient to obtain large mitogenomic datasets representative of both inter- and intraspecific variability, key to the understanding of mitochondrial evolution and a step closer to resolving the relationships among these taxa.RECTO (Refugia and Ecosystem Tolerance in the Southern Ocean, BR/154/A1/RECTO
A call for using natural compounds in the development of new antimalarial treatments â an introduction
Natural compounds, mostly from plants, have been the mainstay of traditional medicine for thousands of years. They have also been the source of lead compounds for modern medicine, but the extent of mining of natural compounds for such leads decreased during the second half of the 20th century. The advantage of natural compounds for the development of drugs derives from their innate affinity for biological receptors. Natural compounds have provided the best anti-malarials known to date. Recent surveys have identified many extracts of various organisms (mostly plants) as having antiplasmodial activity. Huge libraries of fractionated natural compounds have been screened with impressive hit rates. Importantly, many cases are known where the crude biological extract is more efficient pharmacologically than the most active purified compound from this extract. This could be due to synergism with other compounds present in the extract, that as such have no pharmacological activity. Indeed, such compounds are best screened by cell-based assay where all potential targets in the cell are probed and possible synergies identified. Traditional medicine uses crude extracts. These have often been shown to provide many concoctions that deal better with the overall disease condition than with the causative agent itself. Traditional medicines are used by ~80 % of Africans as a first response to ailment. Many of the traditional medicines have demonstrable anti-plasmodial activities. It is suggested that rigorous evaluation of traditional medicines involving controlled clinical trials in parallel with agronomical development for more reproducible levels of active compounds could improve the availability of drugs at an acceptable cost and a source of income in malaria endemic countries
Forced Convection Heat Transfer from a Finite-Height Cylinder
[EN] This paper presents a large eddy simulation of forced convection heat transfer in
the flow around a surface-mounted finite-height circular cylinder. The study was carried out
for a cylinder with height-to-diameter ratio of 2.5, a Reynolds number based on the cylinder
diameter of 44 000 and a Prandtl number of 1. Only the surface of the cylinder is heated
while the bottom wall and the inflow are kept at a lower fixed temperature. The approach
flow boundary layer had a thickness of about 10% of the cylinder height. Local and averaged
heat transfer coefficients are presented. The heat transfer coefficient is strongly affected
by the free-end of the cylinder. As a result of the flow over the top being downwashed
behind the cylinder, a vortex-shedding process does not occur in the upper part, leading
to a lower value of the local heat transfer coefficient in that region. In the lower region,
vortex-shedding takes place leading to higher values of the local heat transfer coefficient.
The circumferentially averaged heat transfer coefficient is 20 % higher near the ground than
near the top of the cylinder. The spreading and dilution of the mean temperature field in the
wake of the cylinder are also discussed.The simulation was carried out using the supercomputing facilities of the Steinbuch Centre for Computing (SCC) of the Karlsruhe Institute of Technology. MGV has been partially supported by grant TRA2012-37714 of the Spanish Ministry of Economy and Competitiveness.GarcĂa Villalba, M.; Palau-Salvador, G.; Rodi, W. (2014). Forced Convection Heat Transfer from a Finite-Height Cylinder. Flow, Turbulence and Combustion. 93(1):171-187. https://doi.org/10.1007/s10494-014-9543-7S171187931Ames, F., Dvorak, L.: Turbulent transport in pin fin arrays: experimental data and predictions. J. Turbomach. 128(1), 71â81 (2006)Armstrong, J., Winstanley, D.: A review of staggered array pin fin heat transfer for turbine cooling applications. J. Turbomach. 110, 94 (1988)Breuer, M., Rodi, W.: Large eddy simulation of complex turbulent flows of practical interest. In: Hirschel, E. (ed.) 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Mammalian Comparative Sequence Analysis of the Agrp Locus
Agouti-related protein encodes a neuropeptide that stimulates food intake. Agrp expression in the brain is restricted to neurons in the arcuate nucleus of the hypothalamus and is elevated by states of negative energy balance. The molecular mechanisms underlying Agrp regulation, however, remain poorly defined. Using a combination of transgenic and comparative sequence analysis, we have previously identified a 760 bp conserved region upstream of Agrp which contains STAT binding elements that participate in Agrp transcriptional regulation. In this study, we attempt to improve the specificity for detecting conserved elements in this region by comparing genomic sequences from 10 mammalian species. Our analysis reveals a symmetrical organization of conserved sequences upstream of Agrp, which cluster into two inverted repeat elements. Conserved sequences within these elements suggest a role for homeodomain proteins in the regulation of Agrp and provide additional targets for functional evaluation
Climate Change and Trophic Response of the Antarctic Bottom Fauna
BACKGROUND: As Earth warms, temperate and subpolar marine species will increasingly shift their geographic ranges poleward. The endemic shelf fauna of Antarctica is especially vulnerable to climate-mediated biological invasions because cold temperatures currently exclude the durophagous (shell-breaking) predators that structure shallow-benthic communities elsewhere. METHODOLOGY/PRINCIPAL FINDINGS: We used the Eocene fossil record from Seymour Island, Antarctic Peninsula, to project specifically how global warming will reorganize the nearshore benthos of Antarctica. A long-term cooling trend, which began with a sharp temperature drop approximately 41 Ma (million years ago), eliminated durophagous predators-teleosts (modern bony fish), decapod crustaceans (crabs and lobsters) and almost all neoselachian elasmobranchs (modern sharks and rays)-from Antarctic nearshore waters after the Eocene. Even prior to those extinctions, durophagous predators became less active as coastal sea temperatures declined from 41 Ma to the end of the Eocene, approximately 33.5 Ma. In response, dense populations of suspension-feeding ophiuroids and crinoids abruptly appeared. Dense aggregations of brachiopods transcended the cooling event with no apparent change in predation pressure, nor were there changes in the frequency of shell-drilling predation on venerid bivalves. CONCLUSIONS/SIGNIFICANCE: Rapid warming in the Southern Ocean is now removing the physiological barriers to shell-breaking predators, and crabs are returning to the Antarctic Peninsula. Over the coming decades to centuries, we predict a rapid reversal of the Eocene trends. Increasing predation will reduce or eliminate extant dense populations of suspension-feeding echinoderms from nearshore habitats along the Peninsula while brachiopods will continue to form large populations, and the intensity of shell-drilling predation on infaunal bivalves will not change appreciably. In time the ecological effects of global warming could spread to other portions of the Antarctic coast. The differential responses of faunal components will reduce the endemic character of Antarctic subtidal communities, homogenizing them with nearshore communities at lower latitudes
Analysis of sequence variations in the suppressor of cytokine signaling (SOCS)-3 gene in extremely obese children and adolescents
BACKGROUND: The suppressor of cytokine signaling (SOCS)-3 is a negative feedback regulator of cytokine signaling and also influences leptin signaling. We investigated association of variations in the coding sequence and promoter region of SOCS3 with extreme obesity in German children and adolescents. METHODS: An initial screen for sequence variations in 181 extremely obese children and adolescents and 188 healthy underweight adults revealed two previously reported single nucleotide polymorphisms (SNPs) in the SOCS3 5' region: -1044 C>A (numbering refers to bases upstream of ATG in exon 2) within a predicted STAT3 binding element and -920 C>A (rs12953258, for numbering, see above). RESULTS: We did not detect significant differences in allele or genotype frequencies for any of these SNPs between the analysed study groups (all nominal p > 0.2). In addition, we performed a pedigree transmission disequilibrium test (PDT) for the SNP -1044 C>A in families comprising 703 obese children and adolescents, 281 of their obese siblings and both biological parents. The PDT revealed no transmission disequilibrium (nominal p > 0.05). CONCLUSION: In conclusion, our data do not suggest evidence for a major role of the respective SNPs in SOCS3 in the pathogenesis of extreme obesity in our study groups
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