Getting connected : competition and diffusion in African mobile telecommunications markets

The author studies the determinants of the diffusion of mobile telecommunications in Africa in a fixed effects model. He uses data from 1987-2000 on 41 African countries that have adopted cellular telecommunications technologies. He finds that competition is the driving force behind the mobile telecommunications explosion in Africa. Duopoly and triopoly markets grow significantly faster than monopoly markets, although growth does not appear to differ between the first two markets. Evidence of preemptive behavior is found in competitive sequential entries into the market, but the major effect of competition on diffusion occurs after the actual year of entry. The introduction of digital technology has a positive and significant effect on the diffusion of mobile phones. The presence of an incumbent-owned cellular operator has a negative effect on the diffusion of mobiles, suggesting an abuse of a dominant position by the incumbent fixed-line operator. However, privatization of the incumbent fixed-line cellular operator accelerates mobile growth and mitigates that negative effect.Trade Finance and Investment,Economic Theory&Research,Environmental Economics&Policies,ICT Policy and Strategies,Health Economics&Finance,Economic Theory&Research,ICT Policy and Strategies,Environmental Economics&Policies,Governance Indicators,Health Economics&Finance

Assessment of the Toxicity of Legacy and Next-Generation Perfluoroalkyl Substances (PFAS) in Early-Life Stages of Freshwater and Marine Fish

Per- and polyfluoroalkyl substances (PFASs) are a group of synthetic surfactants that have utilized for several decades in a wide range of industrial and manufacturing applications. Owing to their high chemical stability, PFAS are widespread and persistent in the environment, and have been shown to be bioaccumulative in diverse organisms including plants, wildlife, and humans. Exposure to PFASs has been linked to a range of documented toxic and/or adverse effects in relation to human and animal health. The potential environmental health and ecotoxicity of next-generation PFAS remain unclear. In the present study, toxicity, and bioconcentration potential, of several perfluoroether carboxylic acids (PFECA), as emerging pollutants of concern, in early life stages of marine (Mahi-Mahi and Olive Flounder) and freshwater fish (zebrafish) was assessed. Toxicity including lethality, behavioral and developmental effects of PFECA, and the legacy PFAS, perfluorooctanoic acid (PFOA), was assessed in embryonic stages of zebrafish, alongside high-resolution magic angle spin nuclear magnetic resonance (HRMAS NMR) metabolomics techniques to elucidate metabolic pathways affected by PFAS. These studies identified acute embryotoxicity (i.e., lethality), as well behavioral and developmental effects, in the nominal micromolar range for all PFAS tested, which was correlated with fluoroalkyl chain length (and relative lipophilicity, i.e., log P), and suggested quantitatively comparable toxicity for next-generation (i.e, PFECA) and legacy (i.e., PFOA) variants. Metabolomic studies indicated targeting of liver, and specifically mitochondria, and associated metabolic pathways. Subsequently, toxicity assays were developed and applied to early life stages of mahi-mahi to assess toxicity of PFECA and PFOA. Mahi-mahi embryos were significantly more sensitive to PFAS with lethal concentrations extending into the environmentally relevant (e.g., parts-per-billion) concentration range. Finally, bioconcentration of PFECA and PFOA were comparatively assessed in embryos of zebrafish and flounder. These studies measured bioconcentration factors (BCF) ranging from 83 to 226-fold and 22 to 329-fold bioconcentration (relative to measured concentration in water) in embryos of zebrafish and flounder, respectively, with BCF values significantly correlated with fluoroalkyl chain length and log P values, in both cases. These findings raise concerns regarding PFECA as environmental toxicants, and specifically, as next generation replacements to legacy PFAS

Spatial Epidemiology of Birth Defects in the United States and the State of Utah Using Geographic Information Systems and Spatial Statistics

Oral clefts are the most common form of birth defects in the United States (US) and the State of Utah has among the highest prevalence of oral clefts in the nation. The overall objective of this dissertation was to examine the spatial distribution of oral clefts and their linkage with a broad range of demographic, behavioral, social, economic, and environmental risk factors through the application of Geographic Information Systems (GIS) and spatial statistics. Using innovative linked micromaps plots, we investigated the geographic patterns of oral clefts occurrence from 1998 to 2002 and their relationships with maternal smoking rates and proportion of American Indians and Alaskan Natives (AIAN) at large scales across the US. The findings indicated higher oral clefts occurrence in the southwest and the midwest and lower occurrence in the east. Furthermore, these spatial patterns were significantly related to the smoking rates and AIAN. Then at the small area level, hierarchical Bayesian models were built to examine the spatial variation in oral clefts risk in the State of Utah from 1995 to 2004 and to assess association with mothers using tobacco, mothers consuming alcohol during pregnancy, and the proportion of mothers with no high school diploma. Next, multi-scalar spatial clustering and cluster techniques were used to test the hypothesis whether there was spatial clustering of oral clefts anywhere in the State of Utah and whether there were statistically significant local clusters with elevated oral cleft cases. Results generally revealed modest spatial variation in oral clefts risk in the State of Utah, with no pronounced spatial clustering, indicating environmental exposures are unlikely plausible cause of oral clefts. However, a few notable areas within Tri-County Local Health District, Provo/Brigham Young University, and North Orem had a tendency toward elevated oral clefts cases. Investigation of the maternal characteristics of these potential clusters supports the hypotheses that maternal smoking, lower education level, and family history are possible causes of oral clefts. Throughout this dissertation, we demonstrated how birth defects data collected by state and local surveillance systems coupled with GIS and spatial statistics methods can be useful in exploratory etiologic research of birth defects

Telecommunications reform in Malawi

In 1998 the Government of Malawi decided to reform its telecommunications sector. Although the reform was ambitious in some ways, it was modest when compared with the most ambitious reforms adopted elsewhere in Sub-Saharan Africa. The two main accomplishments were splitting the incumbent fixed line monopoly, the Malawi Post and Telecommunications Corporation, into two companies-Malawi Telecommunications Limited (MTL) and Malawi Post Corporation (MPC)-and issuing two new cellular licenses to two new private entrants. In addition, the Government also established a new regulator which was separate from, but heavily dependent on, the Ministry of Information and liberalized entry in value-added and Internet services. However, the Government had neither privatized the fixed-line telecommunications operator nor introduced competition in fixed-line services by the end of 2002. Clarke, Gebreab, and Mgombelo discuss sector performance before reform, details of the reform, the political motivation for reform, and events in the five years following the reform. The reform yielded mixed results. Although cellular penetration and Internet use expanded dramatically following reform, prices increased, especially for cellular calls, and fixed-line penetration remains low by regional standards.Public Sector Economics&Finance,Rural Communications,Telecommunications Infrastructure,ICT Policy and Strategies,Knowledge Economy,ICT Policy and Strategies,Rural Communications,Education for the Knowledge Economy,Knowledge Economy,Public Sector Economics&Finance

Telecommunications reform in Uganda

The paper documents the case of Uganda's telecommunications reform. Uganda is one of only two countries in Africa that decided to privatize telecommunications in a competitive framework by selling a second national operator license. The authors find that Uganda did not sacrifice significant sales proceeds by choosing competition, but instead gained tremendously in both the speed and scale of investment from its early focus on competition.Knowledge Economy,ICT Policy and Strategies,Environmental Economics&Policies,Economic Theory&Research,Decentralization,ICT Policy and Strategies,Economic Theory&Research,Environmental Economics&Policies,Public Sector Economics&Finance,Education for the Knowledge Economy

Interfacing of battery with a medium voltage DC-DC converter using MATLAB/Simulink

Master of ScienceDepartment of Electrical and Computer EngineeringSanjoy DasNoel SchulzElectrical power, although convenient form of energy to distribute and use, cannot easily be stored in large quantities economically. Most electrical power generated by utility plants is consumed simultaneously in real time. However, in some cases, energy storage systems become crucial when power generated from sources does not fulfill peak power load demand in a power system or energy storage systems are needed as backup. Due to these reasons, various technologies such as batteries, ultracapacitors (UC), superconducting magnetic energy storage (SEMS) and flywheels are beneficial options for energy storage systems. Shipboard power systems must use one or more energy storage systems in order to backup the existing power system if locally generated power is unavailable. This will lessen the effect of voltage sags on power quality, and improve system reliability. This report mainly focuses on the design of a Boost DC-DC converter and the integration of that converter with a previously designed battery storage model, as well as the effect of varying loads at the end of the converter

How does Poisson kriging compare to the popular BYM model for mapping disease risks?

<p>Abstract</p> <p>Background</p> <p>Geostatistical techniques are now available to account for spatially varying population sizes and spatial patterns in the mapping of disease rates. At first glance, Poisson kriging represents an attractive alternative to increasingly popular Bayesian spatial models in that: 1) it is easier to implement and less CPU intensive, and 2) it accounts for the size and shape of geographical units, avoiding the limitations of conditional auto-regressive (CAR) models commonly used in Bayesian algorithms while allowing for the creation of isopleth risk maps. Both approaches, however, have never been compared in simulation studies, and there is a need to better understand their merits in terms of accuracy and precision of disease risk estimates.</p> <p>Results</p> <p>Besag, York and Mollie's (BYM) model and Poisson kriging (point and area-to-area implementations) were applied to age-adjusted lung and cervix cancer mortality rates recorded for white females in two contrasted county geographies: 1) state of Indiana that consists of 92 counties of fairly similar size and shape, and 2) four states in the Western US (Arizona, California, Nevada and Utah) forming a set of 118 counties that are vastly different geographical units. The spatial support (i.e. point versus area) has a much smaller impact on the results than the statistical methodology (i.e. geostatistical versus Bayesian models). Differences between methods are particularly pronounced in the Western US dataset: BYM model yields smoother risk surface and prediction variance that changes mainly as a function of the predicted risk, while the Poisson kriging variance increases in large sparsely populated counties. Simulation studies showed that the geostatistical approach yields smaller prediction errors, more precise and accurate probability intervals, and allows a better discrimination between counties with high and low mortality risks. The benefit of area-to-area Poisson kriging increases as the county geography becomes more heterogeneous and when data beyond the adjacent counties are used in the estimation. The trade-off cost for the easier implementation of point Poisson kriging is slightly larger kriging variances, which reduces the precision of the model of uncertainty.</p> <p>Conclusion</p> <p>Bayesian spatial models are increasingly used by public health officials to map mortality risk from observed rates, a preliminary step towards the identification of areas of excess. More attention should however be paid to the spatial and distributional assumptions underlying the popular BYM model. Poisson kriging offers more flexibility in modeling the spatial structure of the risk and generates less smoothing, reducing the likelihood of missing areas of high risk.</p

Editorial: Antiretroviral therapy program in Ethiopia benefits from virology treatment monitoring

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Eritrea’s Self-reliance policy and the Road to Sustainable Food and Water Security

Eritrea's models of self-reliance policy and its collective of governance strategy are exceptional which is not experienced in other African countries. The government strongly argues that development cannot be achieved through aid but can be attained through trade and investment from development partners (GebreMichael 2016). As a new country when Eritrea achieved its independence in 1991, the government received a war-torn country with poor or nonexistent public service. All development programs started from scratch. However, in the past two decades, the government established substantial funds to build a network of dams throughout the country to reduce the dependence of rainfed agricultural activities and practice modern agricultural techniques that can increase agricultural productivity and adopt a mechanism that can overcome the effect of climate change. To attain the desired food and water security in the past 30 years the government built 785 big and small dams (Ministry of Information 2021). It is very hard for the Eritrean government to purchase the desired amount and type of food on need because of the sanctions so the only option of the government is to produce it through the implementing of the Self-reliance model and the collective governance model that engages different institutions in the process. Doing that a considerable progress has been attained on the reduction of poverty and increasing the agricultural productivity that ensured food and nutrition security. It is hard to achieve both food and nutrition security with the existence of food supply gaps that does not cause hunger. A report obtained from the Ministry of Finance and National Development (2021) indicated that “although comprehensive end data are unavailable the proportions of poor people and those suffering from food insecurity in the country are believed to have declined subsequently since independence 1991” (Ministry of Finance and National Development 2021:48