Power sector reform and goverance in west and central Africa

Thesis(Master) --KDI School:Master of Development Policy,2014masterpublishedTokam Bobino Franklin

Transdimensional inversion of receiver functions and surface wave dispersion

International audienceWe present a novel method for joint inversion of receiver functions and surface wave dispersion data, using a transdimensional Bayesian formulation. This class of algorithm treats the number of model parameters (e.g. number of layers) as an unknown in the problem. The dimension of the model space is variable and a Markov chain Monte Carlo (McMC) scheme is used to provide a parsimonious solution that fully quantifies the degree of knowledge one has about seismic structure (i.e constraints on the model, resolution, and trade-offs). The level of data noise (i.e. the covariance matrix of data errors) effectively controls the information recoverable from the data and here it naturally determines the complexity of the model (i.e. the number of model parameters). However, it is often difficult to quantify the data noise appropriately, particularly in the case of seismic waveform inversion where data errors are correlated. Here we address the issue of noise estimation using an extended Hierarchical Bayesian formulation, which allows both the variance and covariance of data noise to be treated as unknowns in the inversion. In this way it is possible to let the data infer the appropriate level of data fit. In the context of joint inversions, assessment of uncertainty for different data types becomes crucial in the evaluation of the misfit function. We show that the Hierarchical Bayes procedure is a powerful tool in this situation, because it is able to evaluate the level of information brought by different data types in the misfit, thus removing the arbitrary choice of weighting factors. After illustrating the method with synthetic tests, a real data application is shown where teleseismic receiver functions and ambient noise surface wave dispersion measurements from the WOMBAT array (South-East Australia) are jointly inverted to provide a probabilistic 1D model of shear-wave velocity beneath a given station

The African Landscape through Space and Time

It is generally accepted that Cenozoic epeirogeny of the African continent is moderated by convective circulation of the mantle. Nevertheless, the spatial and temporal evolution of Africa's “basin-and-swell” physiography is not well known. Here we show how continental drainage networks can be used to place broad constraints on the pattern of uplift through space and time. First, we assemble an inventory of 710 longitudinal river profiles that includes major tributaries of the 10 largest catchments. River profiles have been jointly inverted to determine the pattern of uplift rate as a function of space and time. Our inverse model assumes that shapes of river profiles are controlled by uplift rate history and modulated by erosional processes, which can be calibrated using independent geologic evidence (e.g., marine terraces, volcanism and thermochronologic data). Our results suggest that modern African topography started to develop ∼30 Myr ago when volcanic swells appeared in North and East Africa. During the last 15–20 Myr, subequatorial Africa was rapidly elevated, culminating in the appearance of three large swells that straddle southern and western coasts. Our results enable patterns of sedimentary flux at major deltas to be predicted and tested. We suggest that the evolution of drainage networks is dominated by rapid upstream advection of signals produced by a changing pattern of regional uplift. An important corollary is that, with careful independent calibration, these networks might act as useful tape recorders of otherwise inaccessible mantle processes. Finally, we note that there are substantial discrepancies between our results and published dynamic topographic predictions

Comparative Study on Load Monitoring Approaches

Without an appropriate monitoring system, the condition/state of electrical appliances/devices in operation in households cannot be fully assessed, resulting in uncontrolled expenses. The purpose of load monitoring techniques is to save electricity consumption. With proper controls, overconsumption of energy can be reduced and unwanted activity that can lead to unnecessary electricity consumption can be eliminated. To achieve this, two approaches are used. The first approach, which says that each device is monitored by means of individual meters or metering devices, is called intrusive load monitoring (ILM) and requires expensive deployment of metering devices for its use. In contrast to the first one, the second approach is non-intrusive load monitoring (NILM), which monitors electricity consumption without the need for any intrusion. In this configuration, the total energy consumed is disaggregated into the individual consumption of each load. With progress/advances in artificial intelligence, this approach is gaining interest with influences in other areas of research. Knowing that these developed techniques aim to encourage the occupants of dwellings to save energy by optimizing their electricity consumption, the paper presents a comparative study of these approaches, in order to highlight the strengths as well as the weaknesses of each of them. It is therefore a means of offering researchers the opportunity to make choices according to the orientations given to the research work

Antibiofilm Synergistic Activity of Streptomycin in Combination with Thymol-Loaded Poly (Lactic-co-glycolic Acid) Nanoparticles against Klebsiella pneumoniae Isolates

Background. Thymol is an important component of essential oils found in the oil of thyme, is extracted mainly from Thymus vulgaris, and was shown to act synergistically with streptomycin against Klebsiella pneumoniae biofilms. Additionally, thymol could be encapsulated into poly (lactic-co-glycolic acid) (PLGA) nanoparticles to overcome issues related to its low water solubility and high volatility. The present study aimed to investigate the antibiofilm activity of thymol-loaded PLGA nanoparticles (Thy-NPs) alone and in combination with streptomycin against biofilms of K. pneumoniae isolates. Methods. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The antibiofilm activities were determined by the safranin dye assay. The synergistic effect of Thy-NPs with streptomycin was assessed by the checkerboard method. The kinetic study of the biofilm biomass and time-kill assay were further performed. Results. Thy-NPs exhibited the highest antibacterial activity against K. pneumoniae isolates, with MIC values ranging from 1 to 8 µg/mL. Additionally, Thy-NPs showed the highest antibiofilm activity against K. pneumoniae isolates with minimal biofilm inhibitory concentration (MBIC) and minimal biofilm eradication concentration (MBEC) values ranging from 16 to 64 µg/mL and from 32 to 128 µg/Ml, respectively. The combination treatment combining Thy-NPs with streptomycin showed a synergistic effect against the inhibition of biofilm formation and eradication of biofilms of K. pneumoniae isolates with fractional inhibitory concentration index values ranging from 0.13 to 0.28. In addition, the MBIC and MBEC values of streptomycin against K. pneumoniae isolates were dramatically reduced (up to 128-fold) in combination with Thy-NPs, suggesting that Thy-NPs would enhance the antibiofilm activity of streptomycin. The biomass and time-kill kinetics analysis confirmed the observed synergistic interactions and showed the bactericidal activity of streptomycin in combination with Thy-NPs. Conclusions. Our results indicate that the synergistic bactericidal effect between streptomycin and Thy-NPs could be a promising approach in the control of biofilm-associated infections caused by K. pneumoniae.</p

Structure of the Crust beneath Cameroon, West Africa, from the Joint Inversion of Rayleigh Wave Group Velocities and Receiver Functions

The Cameroon Volcanic Line (CVL) is a major geologic feature that cuts across Cameroon from the south west to the north east. It is a unique volcanic lineament which has both an oceanic and a continental sector and consists of a chain of Tertiary to Recent, generally alkaline volcanoes stretching from the Atlantic island of Pagalu to the interior of the African continent. The oceanic sector includes the islands of Bioko (formerly Fernando Po) and Sao Tome and Principe while the continental sector includes the Etinde, Cameroon, Manengouba, Bamboutos, Oku and Mandara mountains, as well as the Adamawa and Biu Plateaus. In addition to the CVL, three other major tectonic features characterize the region: the Benue Trough located northwest of the CVL, the Central African Shear Zone (CASZ), trending N70 degrees E, roughly parallel to the CVL, and the Congo Craton in southern Cameroon. The origin of the CVL is still the subject of considerable debate, with both plume and non-plume models invoked by many authors (e.g., Deruelle et al., 2007; Ngako et al, 2006; Ritsema and Allen, 2003; Burke, 2001; Ebinger and Sleep, 1998; Lee et al, 1994; Dorbath et al., 1986; Fairhead and Binks, 1991; King and Ritsema, 2000; Reusch et al., 2010). Crustal structure beneath Cameroon has been investigated previously using active (Stuart et al, 1985) and passive (Dorbath et al., 1986; Tabod, 1991; Tabod et al, 1992; Plomerova et al, 1993) source seismic data, revealing a crust about 33 km thick at the south-western end of the continental portion of the CVL (Tabod, 1991) and the Adamawa Plateau, and thinner crust (23 km thick) beneath the Garoua Rift in the north (Stuart et al, 1985) (Figure 1). Estimates of crustal thickness obtained using gravity data show similar variations between the Garoua rift, Adamawa Plateau, and southern part of the CVL (Poudjom et al., 1995; Nnange et al., 2000). In this study, we investigate further crustal structure beneath the CVL and the adjacent regions in Cameroon using 1-D shear wave velocity models obtained from the joint inversion of Rayleigh wave group velocities and P-receiver functions for 32 broadband seismic stations. From the 1-D shear wave velocity models, we obtain new insights into the composition and structure of the crust and upper mantle across Cameroon. After briefly reviewing the geological framework of Cameroon, we describe the data and the joint inversion method, and then interpret variations in crustal structure found beneath Cameroon in terms of the tectonic history of the region

La taeniose/ cysticercose à

La présente étude a été conduite d'août 1999 à avril 2000 et avait pour objectif de déterminer la prévalence de la taeniose due à Taenia solium dans Bafou et Bamendou, deux groupements villageois de la Menoua (Ouest-Cameroun). Quatre (0,13 %) sur 3 109 échantillons de matières fécales humaines ont été trouvés positifs pour des oeufs de Taenia spp. par la technique de la flottaison. Trois des quatre vers expulsés étaient des T. solium et un était T. saginata. Deux cas de cysticercose étaient présents dans une des familles où vivait un porteur de T. solium.En plus, des enquêtes coprologique et sérologique pour la taeniose et la cysticercose à T. solium ont été faites chez un groupe à risque constitué de bouchers et/ou langueyeurs (n = 137). Les résultats ont été comparés à ceux d'un groupe témoin (n = 198). Aucun porteur de Taenia n'a été détecté par l'examen microscopique. Les prévalences de la cysticercose dans les deux groupes ont été respectivement 3,6 et 4,5 %

La taeniose/ cysticercose à Taenia solium dans la Menoua (Ouest-Cameroun)

La présente étude a été conduite d'août 1999 à avril 2000 et avait pour objectif de déterminer la prévalence de la taeniose due à Taenia solium dans Bafou et Bamendou, deux groupements villageois de la Menoua (Ouest-Cameroun). Quatre (0,13 %) sur 3 109 échantillons de matières fécales humaines ont été trouvés positifs pour des oeufs de Taenia spp. par la technique de la flottaison. Trois des quatre vers expulsés étaient des T. solium et un était T. saginata. Deux cas de cysticercose étaient présents dans une des familles où vivait un porteur de T. solium.En plus, des enquêtes coprologique et sérologique pour la taeniose et la cysticercose à T. solium ont été faites chez un groupe à risque constitué de bouchers et/ou langueyeurs (n = 137). Les résultats ont été comparés à ceux d'un groupe témoin (n = 198). Aucun porteur de Taenia n'a été détecté par l'examen microscopique. Les prévalences de la cysticercose dans les deux groupes ont été respectivement 3,6 et 4,5 %

La taeniose/cysticercose Taenia solium dans la Menoua (Ouest-Cameroun)

The present study was carried out between August 1999 and April 2000 with the objective of determining the prevalence of Taenia solium taeniasis in two village communities of Bafou and Bamendou in the Menoua division (West Cameroon). Four (0.13%) out of 3,109 faecal samples were positive for Taenia spp. eggs using the flotation technique. Three of the four worms expelled were T. solium whereas the other one was T. saginata. Two cases of cysticercosis were diagnosed in one of the families with a T. solium carrier. Furthermore, coprological and serological investigations for T. solium taeniasis and cysticercosis were carried out among butchers and/or tongue inspectors (n = 137) of the city of Dschang. The results were compared with those of a control group (n = 198). Taenia spp. eggs were not detected by microscopic examination. The prevalence of cysticercosis in the two groups was relatively similar (3.6 and 4.5% respectively)