This paper discusses the mobile phone boom in Africa and examines the potential impacts of mobiles on the socio-economic development process in African countries. Drawing on data from case studies, the paper explains that mobile phones may not just help create new jobs and new sources of revenue to the state but can also contribute to economic growth by widening markets, creating better information flow, lowering transaction costs, and becoming substitute for costly transportation that is lacking in rural Africa. On the social front, the paper contends that the mobile phone can help create unique personal identities and status symbols for some users. The technology also facilitates the democratic process as groups can use the enhanced communication tools for political and community action thereby reducing the reliance on conventional and often government controlled media. The paper discusses these and other ways by which mobile phones can influence conditions in Africa to induce changes that promote economic and social development. The paper concludes with suggestions that can strengthen ICT adoption in African countries.
Supercapacitors or electrochemical capacitors are receiving greater interest because of their high-power density, long life, and low maintenance. We have synthesized CuS nanoparticles and graphene oxide (CuS–GO) nanocomposites for supercapacitor applications because of their low cost and excellent electrochemical properties. The phase purity of each material was determined using powder XRD studies. The bandgap was determined by UV-visible spectrophotometric studies. Scanning electron microscope and transmission electron microscope images revealed the nano-scale morphology of the synthesized particles. All the electrochemical measurements were conducted in a standard three-electrode configuration, using a platinum wire as the counter electrode and Hg/HgO as the reference electrode. CuS and its composites with graphene oxide on nickel foam were used as working electrodes. All the electrochemical measurements were performed in 3M KOH solution. The CuS–GO nanocomposite electrode showed a specific capacitance of 250 F/g, 225 F/g, 182 F/g, 166 F/g, 161 F/g, and 158 F/g at a current density of 0.5 A/g, 1 A/g, 5 A/g, 10 A/g, 15 A/g, and 20 A/g, respectively. CuS–GO electrodes showed a specific capacitance retention of 70% after 5000 charge–discharge cycles at a current density of 5 A/g.
The direct current (dc) electrical conductivity of the conducting polymer Versicon TM blended in poly(vinyl chloride) (PVC) was measured from 25 K to 310 K. The data were fitted to various electrical transport models, and the best fit was found with the fluctuation-induced tunneling model, suggesting that tunneling dominates in the mode of electron transport at low temperatures. The parameters, T 1 and T 0 from the fluctuation-induced tunneling model, were found to be 625 K and 129 K, respectively. The interparticle distance was estimated to be about 13Å. At higher temperatures, the plot of the log of resistivity versus the reciprocal of the temperature was linear, indicating that thermally activated hopping dominated the mode of electrical transport at these temperatures. The results support earlier findings that Versicon TM forms continuous aggregates in blends. The results also support growing evidence in the literature that these types of aggregate formation tend to strongly influence the mode of electrical transport in composites.Versicon TM , a product of Allied Signal Inc., is a polyaniline doped with an organic sulfonic acid. 1 When Versicon TM is dispersed in poly(vinyl chloride) (PVC) and other thermoplastics, it is reported to have a tendency to aggregate spontaneously to form conducting pathways throughout the system. The Versicon TM particles are spherical and range in size from 20 to 100 mm, but can be broken down into submicron particles in blends. 1 Work done in our laboratory confirmed that even pressed pellets of Versicon TM behaved like they consisted of aggregates of spherical particles. 2 Versicon TM in blends such as PVC is reported to be useful for electrical shielding and other specific applications such as for loadings in conductive paints. 1 This study is to explore the mode of electrical transport in Versicon TM in blends with highly resistive media such as PVC.Blends of 10%, 20%, and 30% Versicon TM in PVC were supplied by Americhem in the form of grains about two millimeters in size. The samples were heat pressed at about 200 ± C. Only the 30% Versicon TM blend was used in our measurements since the 20% and 10% samples were practically insulators. A sample of the 30% Versicon TM blend was cut into a parallelepiped (14.6 3 2.1 3 1.0 mm) for the resistivity measurements. The four lead method was used in the I-V measurements. Silver paint was used to attach leads to the sample. The data acquisition system consisted of Keithley Model 196 Digital Multimeter, a Keithley a) Author to whom all correspondence should be addressed.Model 220 Current Source, a Keithley Model 705 Scanner to allow the sample circuits and a test circuit to be opened and closed, a Lake Shore Cryotronics Model 330 Autotuning Temperature Controller which sets and reads the temperature at the sample site, and a CTI-Cryogenices 22C/350C Cryodyne © closed cycle helium refrigerator from Janis Research. An IEEE 488 interface from Capital Equipment Corporation enabled these devices to be controlled and the data to be collecte...
ClassroomIn this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. "Classroom" is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learning science.
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