Economic growth and distribution of income: A growth model to fit Ghanaian data

Income distribution, economic growth, Development strategies,

Macro-micro feedback links of water management in South Africa : CGE analyses of selected policy regimes

The pressure on an already stressed water situation in South Africa is predicted to increase significantly under climate change, plans for large industrial expansion, observed rapid urbanization, and government programs to provide access to water to millions of previously excluded people. The present study employed a general equilibrium approach to examine the economy-wide impacts of selected macro and water related policy reforms on water use and allocation, rural livelihoods, and the economy at large. The analyses reveal that implicit crop-level water quotas reduce the amount of irrigated land allocated to higher-value horticultural crops and create higher shadow rents for production of lower-value, water-intensive field crops, such as sugarcane and fodder. Accordingly, liberalizing local water allocation in irrigation agriculture is found to work in favor of higher-value crops, and expand agricultural production and exports and farm employment. Allowing for water trade between irrigation and non-agricultural uses fueled by higher competition for water from industrial expansion and urbanization leads to greater water shadow prices for irrigation water with reduced income and employment benefits to rural households and higher gains for non-agricultural households. The analyses show difficult tradeoffs between general economic gains and higher water prices, making irrigation subsidies difficult to justify.Water Supply and Sanitation Governance and Institutions,Town Water Supply and Sanitation,Water Supply and Systems,Water and Industry,Water Conservation

Strategic policies and growth: An applied model of R&D-driven endogenous growth

Cataloged from PDF version of article.We introduce and explore a general equilibrium model with R&D-driven endogenous growth, whose antecedents are the models of Romer (1990) [Romer, P.M., 1990. Endogenous technological change. Journal of Political Economy, 98, S71-102] and Grossman and Helpman (1991) [Grossman, G.M., Helpman E., 1991. Innovation and Growth in the Global Economy, The MIT Press, Cambridge]. Utilizing evidence front recent econometric studies on sources of growth, the model also accounts explicitly for cross-border technological spillovers. The model is specified and calibrated to data from Japan, and is solved to obtain both the transitional and the steady-state equilibria. We explore the effects of selective trade and R&D promotion policies on long-run growth and social welfare. The model results suggest that while a strategic trade policy has little effect on re-allocating resources into domestic R&D activities, it can significantly affect the cross-border spillovers of technological knowledge, which, in turn, stimulates growth. We find that trade liberalization may cause the growth rate to fall and lead to a loss of social welfare in the long-run, although it improves welfare in the short-run. R&D promotion policies stimulate growth by inducing private agents to allocate more resources to domestic R&D, as well as to take greater advantage of global R&D spillovers. Here, we find significantly high growth effects together with sizable gains in social welfare at low incidence to tax payers. (C) 1999 Elsevier Science B.V. All rights reserved

Shape invariance approach to exact solutions of the Klein-Gordon equation

Using the shape invariance property we obtain exact solutions of the (1+1)dimensional Klein-Gordon equation for certain types of scalar and vector potentials. We also discuss the possibility of obtaining real energy spectrum with non-Hermitian interaction within this framework

Synaptic proteins promote calcium-triggered fast transition from point contact to full fusion.

The molecular underpinnings of synaptic vesicle fusion for fast neurotransmitter release are still unclear. Here, we used a single vesicle-vesicle system with reconstituted SNARE and synaptotagmin-1 proteoliposomes to decipher the temporal sequence of membrane states upon Ca(2+)-injection at 250-500 μM on a 100-ms timescale. Furthermore, detailed membrane morphologies were imaged with cryo-electron microscopy before and after Ca(2+)-injection. We discovered a heterogeneous network of immediate and delayed fusion pathways. Remarkably, all instances of Ca(2+)-triggered immediate fusion started from a membrane-membrane point-contact and proceeded to complete fusion without discernible hemifusion intermediates. In contrast, pathways that involved a stable hemifusion diaphragm only resulted in fusion after many seconds, if at all. When complexin was included, the Ca(2+)-triggered fusion network shifted towards the immediate pathway, effectively synchronizing fusion, especially at lower Ca(2+)-concentration. Synaptic proteins may have evolved to select this immediate pathway out of a heterogeneous network of possible membrane fusion pathways.DOI:http://dx.doi.org/10.7554/eLife.00109.001

Etude de la productivité et de la sensibilité de diverses variétés de tomate (Lycopersicon esculentum Mill) à la virose du jaunissement et de l’enroulement en cuillère des feuilles au Sénégal

Après l’oignon, la tomate est le plus important légume au Sénégal. Elle est très sensible au virus Tomato Yellow Leaf Curl (TYLCV). Quatorze variétés de tomate ont été testées pour évaluer leur productivité et leur résistance au TYLC à différents stades phénologiques (floraison, fructification et maturité) dans un dispositif en blocs complets randomisés comptant trois répétitions. Les résultats ont montré que le nombre de fruits/grappe a varié entre les variétés. La masse unitaire des fruits était plus élevée pour Bybal, Roma VF et Lety F1. La longueur des fruits de Thoriya et Lety F1 était plus importante. Roma VF et Bybal ont présenté les plus gros fruits. TY75 et Ponchita ont produit les rendements en fruits consommables les plus élevés. Roma VF et Lety F1 ont produit les rendements non consommables les plus élevés. Globalement, TY75 et Roma VF ont été plus productives. Une résistance au virus a été observée chez douze variétés et une forte sensibilité chez deux autres (Roma VF et Xina). Ces résultats pourraient intéresser les sélectionneurs, les firmes semencières et les agriculteurs dans leur choix de variétés de tomate à cultiver.Mots clés : Tomate, Lycopersicon esculentum, TYLCV, Sénéga

Technical note: On uncertainties in plant water isotopic composition following extraction by cryogenic vacuum distillation

Recent studies have challenged the interpretation of plant water isotopes obtained through cryogenic vacuum distillation (CVD) based on observations of a large 2H fractionation. These studies have hypothesized the existence of an H-atom exchange between water and organic tissue during CVD extraction with the magnitude of H exchange related to relative water content of the sample; however, clear evidence is lacking. Here, we systematically tested the uncertainties in the isotopic composition of CVD-extracted water by conducting a series of incubation and rehydration experiments using isotopically depleted water, water at natural isotope abundance, woody materials with exchangeable H, and organic materials without exchangeable H (cellulose triacetate and caffeine). We show that the offsets between hydrogen and oxygen isotope ratios and expected reference values (Δ2H and Δ18O) have inversely proportional relationships with the absolute amount of water being extracted, i.e. the lower the water amount, the higher the Δ2H and Δ18O. However, neither Δ2H nor Δ18O values, were related to sample relative water content. The Δ2H pattern was more pronounced for materials with exchangeable H atoms than with non-exchangeable H atoms. This is caused by the combined effect of H exchange during the incubation of materials in water and isotopic enrichments during evaporation and sublimation that depend on absolute water amount. The H exchange during CVD extraction itself was negligible. Despite these technical issues, we observed that the water amount-dependent patterns were much less pronounced for samples at natural isotope abundance and particularly low when sufficiently high amounts of water were extracted (&gt;600 µL). Our study provides new insights into the mechanisms causing isotope fractionation during CVD extraction of water. The methodological uncertainties can be controlled if large samples of natural isotope abundance are used in ecohydrological studies.</p

Complications urologiques de la chirurgie pelvienne au CHU Aristide Le Dantec de Dakar

Objectifs: Déterminer les interventions chirurgicales du petit bassin pourvoyeuses de complications uro-logiques, recenser les différentes lésions et décrire leur prise en charge au CHU Aristide Le Dantec de Dakar. Matériels et méthodes: Nous avons mené une étude rétrospective sur huit ans incluant les dossiers de patients ayant eu une ou des complications urologiques au décours d’une intervention chirurgicale pelvienne. Les critères étudiés étaient les suivants: l’âge, le type de complication, le délai du diagnostic, l’acte opératoire causal et les modalités évolutives après la prise en charge finale. Résultats: Nous avons colligé vingt-neuf cas. L’âge moyen était de 34,2 ans +/- 8,5 ans. Le sexe masculine représentait 3% (1 cas). Le délai moyen du diagnostic était de sept semaines et dans huit cas le diagnostic lésionnel a été pose en per opératoire. Les principales causes de complications urologiques étaient la césarienne (37,%) et l’hystérectomie (34,%). Les sections complètes de l’uretère et les fistules vésico-vaginales représentaient 51,72% des complications (15 cas). Les suites de la chirurgie réparatrice ont été simples dans 82,75% (n=24) et nous avons noté deux décès. Conclusion: Les lésions les plus fréquentes étaient la section urétérale et la fistule vésico-vaginale survenant surtout lors de la chirurgie gynécologique.Objectives:To determine the pelvic surgical operations resulting in urological injuries, to assess the different types of injuries and describe their management in the University Hospital Aristide Le Dantec of Dakar. Material and methods:We did a retrospective study covering a period of eight years, reviewing the files of all patients who had urological injuries after pelvic surgery. The parameters studied were: age, the type of injury, the timing of diagnosis, the intervention responsible for the injury, the outcome after treatment. Results: Twenty nine cases of urological injuries were diagnosed. The average age of our patients was 34,2 years +/-8,5 years; there was only one male patient. The average time to diagnosis was about seven weeks, and in 8 patients the diagnosis of injury was possible immediately. Caesarian section and hysterectomy were the predominant procedures responsible for injuries (37,93% and 34,48%, respectively). Section of ureter and vesicovaginal fistula represented 51,72% of all injuries (15 cases). The Results of reconstructive surgery where favorable in 82,75%(n = 24), two patients died after surgery of the complication. Conclusion: The most frequent injuries were section of ureter and vesicovaginal fistula, often caused by gynecologic surgery