Telecommunications and economic growth: an empirical analysis of sub-saharan Africa

We examine the effect on economic growth of mobile cellular phones in sub-Saharan Africa where a marked asymmetry is present between land-line penetration and mobile telecommunications expansion. This study extends previous ones along two important dimensions. First, we allow for the potential endogeneity between economic growth and telecommunications expansion by employing a special linear generalized method of moments (GMM) estimator. Second, we explicitly model for varying degrees of substitutability between mobile cellular and land-line telephony, so that greater expansion of mobile telecommunications can have a different impact whenever the level of land-line penetration differs. We find that mobile cellular phone expansion is an important determinant of the rate of economic growth in Sub-Saharan Africa. Moreover, we find that the contribution of mobile cellular phones to economic growth has been growing in importance in the region, and that the marginal impact of mobile telecommunication services is even greater wherever land-line phones are rare. Given the low cost of mobile telecommunications technology relative to other broad infrastructure projects, especially land-line infrastructure, we advocate that mobile telecommunication services be encouraged in the area.

Reforma regulatoria energética en Europa: impacto de los cambios de control corporativo sobre el valor de las empresas

El proceso de desregulación del sector eléctrico en la Unión Europea generó acciones estratégicas de parte de las empresas del sector que han llevado al reordenamiento de su mercado de energía eléctrica. Una serie de fusiones y adquisiciones ocurrieron a raíz de ese proceso. Este trabajo investiga cómo la consecuente ola de fusiones y adquisiciones que se dio en la primera década de este siglo ha afectado el valor en bolsa de las empresas compradoras y adquiridas. Para este propósito, haciendo uso de la metodología de los estudios de acontecimiento y con técnicas econométricas de MCO, GARCH y SURE se encontró que las fusiones y adquisiciones presentaron un efecto positivo estadísticamente significativo sobre el precio de cotización en bolsa para la empresa objeto de compra (u opada), lo cual es consistente con estudios previos.The deregulation process of the European power sector generated strategic moves by the power companies leading to a complete reordering of the European electric market that brought out an upsurge of mergers and acquisitions. This paper researches how the following wave of mergers and acquisitions that took place in the 2000 impacted the market value for the acquiring and selling companies that took part of it. With this objective and making use of the event study methodology, and OLS, GARCH, and SURE econometric techniques, we found that mergers and acquisitions had a positive and significant effect on the average market price in public stock exchanges for the companies that were target which is consistent with previous studies

System and Apparatus for Deploying a Satellite

A frictionless satellite constraint system is provided. The constraint system includes at least one clamp bar configured to restrain a satellite within the constraint system in an axial direction. The constraint system also includes a plurality of pins configured to restrain the satellite within the constraint system in a lateral direction

Growth of the tropical scallop, Euvola (Pecten) ziczac, in bottom and suspended culture in the Golfo de Cariaco, Venezuela

We compared the growth of the scallop Euuolu (Pecten) ziczuc (L.) in three situations which potentially could be used for commercial culture, in cages maintained in suspension, in cages on the bottom and in cages partly buried in a sediment bottom. The latter permitted the scallops to bury themselves as in their natural habitat. Throughout the 7-month study, growth, as measured by shell length and muscle mass, was by far superior for scallops in the partly buried cages. Possible explanations for this are ( 1) that the scallops are stressed by enclosures which prevent them from burying themselves and (2) that organic material at the sediment/water interface is an important food resource and E. ziczac has better access to this when it buries itself flush with the bottom. The timing of gonadal growth and spawning varied markedly among treatments. Some spawnings coincided with temperature increases but others did not. Differences between scallops in suspension compared to those in bottom treatments suggested that reproduction is as much controlled by conditions in the immediate environment of the scallops as by large-scale environmental factors. Survival was highest for the scallops maintained in partly buried cages

Effect of pesticides on integrated mite management in Washington State

The effect of pesticides used against codling moth, Cydia pomonella L., on integrated mite management was studied for three years in five or six commercial apple orchards in central Washington. Phytophagous and predatory mites were counted throughout the season in blocks ranging from 0.4-1.6 ha in size treated with four codling moth insecticides. In one year of the study (2006), five out of six orchards experienced elevated mite densities relative to the standard. In four orchards, novaluron caused a 3.0-16.9× increase in mite populations; acetamiprid caused a 2.6-3.4× increase, and thiacloprid caused a 1.7-13.8× increase. In the fifth orchard, the organophosphate standard had an extremely high mite population, in addition to all three experimental treatments. In 2005 and 2007, only one or two orchards had elevated mite levels in the novaluron, acetamiprid, and thiacloprid treatments. Additive effects of codling moth and thinning programs were evaluated in small plot research trials. Treatments with all three elements [1) codling moth insecticide; 2) calcium polysulfide; 3) carbaryl] produced the highest levels ofspider mites. Three sulfur-containing products (calcium polysulfide, ammonium thiosulfate, and dry flowable sulfur) were evaluated for their effect onGalandromus occidentalis (Nesbitt) and apple rust mite, Aculus schlechtendali (Nalepa). All three materials caused suppressed G. occidentalis numbers. Calcium polysulfide caused the greatest reduction in apple rust mite numbers, ammonium thiosulfate the least reduction, with dry flowable sulfur intermediate between the two. Additive effects of codling moth materials, carbaryl, and sulfur-containing products may be causing increased mite levels in Washington orchards

Large-eddy simulation of dust-uplift by a haboob density current

Cold pool outflows have been shown from both observations and convection-permitting models to be a dominant source of dust emissions (“haboobs”) in the summertime Sahel and Sahara, and to cause dust uplift over deserts across the world. In this paper Met Office Large Eddy Model (LEM) simulations, which resolve the turbulence within the cold-pools much better than previous studies of haboobs with convection-permitting models, are used to investigate the winds that uplift dust in cold pools, and the resultant dust transport. In order to simulate the cold pool outflow, an idealized cooling is added in the model during the first 2 h of 5.7 h run time. Given the short duration of the runs, dust is treated as a passive tracer. Dust uplift largely occurs in the “head” of the density current, consistent with the few existing observations. In the modeled density current dust is largely restricted to the lowest, coldest and well mixed layers of the cold pool outflow (below around 400 m), except above the “head” of the cold pool where some dust reaches 2.5 km. This rapid transport to above 2 km will contribute to long atmospheric lifetimes of large dust particles from haboobs. Decreasing the model horizontal grid-spacing from 1.0 km to 100 m resolves more turbulence, locally increasing winds, increasing mixing and reducing the propagation speed of the density current. Total accumulated dust uplift is approximately twice as large in 1.0 km runs compared with 100 m runs, suggesting that for studying haboobs in convection-permitting runs the representation of turbulence and mixing is significant. Simulations with surface sensible heat fluxes representative of those from a desert region during daytime show that increasing surface fluxes slows the density current due to increased mixing, but increase dust uplift rates, due to increased downward transport of momentum to the surface

Effects of dredge deposits on seagrasses : an integrative model for Laguna Madre : concluding report. Volume I, Executive Summary.

Interagency Coordination Team, U.S. Army Corps of Engineers, Galveston District, The University of Texas Marine Science Institute, Texas A&M University Department of Oceanography, Texas Parks and Wildlife DepartmentThis report presents the results of an interdisciplinary collaborative effort to develop an integrative model for seagrass productivity in Laguna Madre. One of the major components of this integrative model is the Laguna Madre Seagrass Model (LMSM) which was designed to interface with other component models described in this report, including carbon and nitrogen allocation, sediment diagenesis, and spectral irradiance and radiative transfer. Linkage with hydrodynamic and sediment transport models provided a potentially valuable management tool to assess the effects of maintenance dredging and resuspension of dredged material deposits on seagrasses of Laguna Madre.Texas A&M University and the U.S. Army Corps of Engineers (Galveston District) 96-PL-03Marine Scienc

Allotetraploidization in Brachypodium May Have Led to the Dominance of One Parent’s Metabolome in Germinating Seeds

Seed germination is a complex process during which a mature seed resumes metabolic activity to prepare for seedling growth. In this study, we performed a comparative metabolomic analysis of the embryo and endosperm using the community standard lines of three annual Brachypodium species, i.e., B. distachyon (Bd) and B. stacei (Bs) and their natural allotetraploid B. hybridum (BdBs) that has wider ecological range than the other two species. We explored how far the metabolomic impact of allotetraploidization would be observable as over-lapping changes at 4, 12, and 24 h after imbibition (HAI) with water when germination was initiated. Metabolic changes during germination were more prominent in Brachypodium embryos than in the endosperm. The embryo and endosperm metabolomes of Bs and BdBs were similar, and those of Bd were distinctive. The Bs and BdBs embryos showed increased levels of sugars and the tricarboxylic acid cycle compared to Bd, which could have been indicative of better nutrient mobilization from the endosperm. Bs and BdBs also showed higher oxalate levels that could aid nutrient transfer through altered cellular events. In Brachypodium endosperm, the thick cell wall, in addition to starch, has been suggested to be a source of nutrients to the embryo. Metabolites indicative of sugar metabolism in the endosperm of all three species were not prominent, suggesting that mobilization mostly occurred prior to 4 HAI. Hydroxycinnamic and monolignol changes in Bs and BdBs were consistent with cell wall remodeling that arose following the release of nutrients to the respective embryos. Amino acid changes in both the embryo and endosperm were broadly consistent across the species. Taking our data together, the formation of BdBs may have maintained much of the Bs metabolome in both the embryo and endosperm during the early stages of germination. In the embryo, this conserved Bs metabolome appeared to include an elevated sugar metabolism that played a vital role in germination. If these observations are confirmed in the future with more Brachypodium accessions, it would substantiate the dominance of the Bs metabolome in BdBs allotetraploidization and the use of metabolomics to suggest important adaptive changes