Geo-Electric and Hydrogeochemical Mapping of Quaternary Deposits at Orerokpe in the Western Niger Delta

Resistivity surveys have been utilized to delineate the sand horizons and possible water bearing zones in the shallow Quaternary deposits that mask the Benin Formation that underlies the Sombreiro-Warri DeltaicPlain at Orerokpe in the western Niger Delta. Fifteen dug wells and shallow boreholes were sampled for water quality analysis. The results show that from the surface to about 70m, there are four layers of water bearing sands that are separated in places by discontinuous clay horizons. Depth to water level ranges from 3.5m to 5.5m. Ground water flow is from northeast to southwest towards the Warri River. Ground water which is used here for domestic purposes without treatment is soft and it is shown that the most important factor contributing to groundwater chemistry is weathering of the aquifer matrix. The order of preponderance of the cations is Na+ > K+ > Ca2+> Mg2+ and HCO3- > SO4 2-> Cl- for the anions; trends that are not only a departure from normal pristine conditions, but also basically different from those observed in nearby Warri and indicative of possible contamination. The relativelylow calcium and magnesium content is identified as a potential health problem if water constitutes the main source of ingestion of these ions. The results reinforce the complex geological nature and geochemical conditions that exist in the Quaternary superficial deposits of the Niger Delta environment

Resident phenotypically modulated vascular smooth muscle cells in healthy human arteries.

Vascular interstitial cells (VICs) are non-contractile cells with filopodia previously described in healthy blood vessels of rodents and their function remains unknown. The objective of this study was to identify VICs in human arteries and to ascertain their role. VICs were identified in the wall of human gastro-omental arteries using transmission electron microscopy. Isolated VICs showed ability to form new and elongate existing filopodia and actively change body shape. Most importantly sprouting VICs were also observed in cell dispersal. RT-PCR performed on separately collected contractile vascular smooth muscle cells (VSMCs) and VICs showed that both cell types expressed the gene for smooth muscle myosin heavy chain (SM-MHC). Immunofluorescent labelling showed that both VSMCs and VICs had similar fluorescence for SM-MHC and αSM-actin, VICs, however, had significantly lower fluorescence for smoothelin, myosin light chain kinase, h-calponin and SM22α. It was also found that VICs do not have cytoskeleton as rigid as in contractile VSMCs. VICs express number of VSMC-specific proteins and display features of phenotypically modulated VSMCs with increased migratory abilities. VICs, therefore represent resident phenotypically modulated VSMCs that are present in human arteries under normal physiological conditions

Thermal analysis of a multi-layer microchannel heat sink for cooling concentrator photovoltaic (CPV) cells

This is the final version of the article. Available from AIP Publishing via the DOI in this record.Concentrator Photovoltaic (CPV) technology is increasingly being considered as an alternative option for solar electricity generation. However, increasing the light concentration ratio could decrease the system output power due to the increase in the temperature of the cells. The performance of a multi-layer microchannel heat sink configuration was evaluated using numerical analysis. In this analysis, three dimensional incompressible laminar steady flow model was solved numerically. An electrical and thermal solar cell model was coupled for solar cell temperature and efficiency calculations. Thermal resistance, solar cell temperature and pumping power were used for the system efficiency evaluation. An increase in the number of microchannel layers exhibited the best overall performance in terms of the thermal resistance, solar cell temperature uniformity and pressure drop. The channel height and width has no effect on the solar cell maximum temperature. However, increasing channel height leads to a reduction in the pressure drop and hence less fluid pumping power.The PhD scholarship of Idris Al Siyabi is founded by the ministry of higher education at the sultanate of Oman through the national program of postgraduate scholarships

Security, Local Community, and the Democratic Political Culture in Africa

In this study, the idea of the local African community as a social structure ensuring the security of its members is presented. An understanding of the concept of security is first briefly discussed, followed by the meaning of the concept of the local African community. The chapter also makes an a priori distinction between what one can call “moderate” and “radical” types of communal life and two case studies exemplifying them are presented. The chapter aims to analyze the trade off, in terms of provision of security, including economic security, by local communities, for the shaping of a democratic political culture in Sub-Saharan Africa. Most importantly, however, this chapter also highlights the rationality that underpins the seemingly low-quality democratic political activities of members of local African communities

Clustering of activated CD8 T cells around Malaria-infected hepatocytes is rapid and is driven by antigen-specific cells

Malaria, a disease caused by parasites of the Plasmodium genus, begins when Plasmodium-infected mosquitoes inject malaria sporozoites while searching for blood. Sporozoites migrate from the skin via blood to the liver, infect hepatocytes, and form liver stages which in mice 48 h later escape into blood and cause clinical malaria. Vaccine-induced activated or memory CD8 T cells are capable of locating and eliminating all liver stages in 48 h, thus preventing the blood-stage disease. However, the rules of how CD8 T cells are able to locate all liver stages within a relatively short time period remains poorly understood. We recently reported formation of clusters consisting of variable numbers of activated CD8 T cells around Plasmodium yoelii (Py)-infected hepatocytes. Using a combination of experimental data and mathematical models we now provide additional insights into mechanisms of formation of these clusters. First, we show that a model in which cluster formation is driven exclusively by T-cell-extrinsic factors, such as variability in “attractiveness” of different liver stages, cannot explain distribution of cluster sizes in different experimental conditions. In contrast, the model in which cluster formation is driven by the positive feedback loop (i.e., larger clusters attract more CD8 T cells) can accurately explain the available data. Second, while both Py-specific CD8 T cells and T cells of irrelevant specificity (non-specific CD8 T cells) are attracted to the clusters, we found no evidence that non-specific CD8 T cells play a role in cluster formation. Third and finally, mathematical modeling suggested that formation of clusters occurs rapidly, within few hours after adoptive transfer of CD8 T cells, thus illustrating high efficiency of CD8 T cells in locating their targets in complex peripheral organs, such as the liver. Taken together, our analysis provides novel insights into and attempts to discriminate between alternative mechanisms driving the formation of clusters of antigen-specific CD8 T cells in the liver

Hartree-Fock ground state of the two-dimensional electron gas with Rashba spin-orbit interaction

We search for the uniform Hartree-Fock ground state of the two-dimensional electron gas formed in semiconductor heterostructures including the Rashba spin-orbit interaction. We identify two competing quantum phases: a ferromagnetic one with partial spin polarization in the perpendicular direction and a paramagnetic one with in-plane spin. We present a phase diagram in terms of the relative strengths of the Rashba to the Coulomb interaction and the electron density. We compare our theoretical description with existing experimental results obtained in GaAs-AlGaAs heterostructures.Comment: 5 pages, 2 figure

Efficacité d’extraits de feuilles de neem Azadirachta indica (Sapindale) sur Plutella xylostella (Lepidoptera : Plutellidae), Hellula undalis (Lepidoptera : Pyralidae) et Lipaphis erysimi (Hemiptera : Aphididae) du chou Brassica oleracea (Brassicaceae) da

Cette étude vise à évaluer l’efficacité d’extrait hydroéthanolique de feuilles de Azadirachta indica dans la lutte contre Plutella xylostella, Hellula undalis et Lipaphis erysimi, insectes ravageurs du chou dans une approche champ école paysan en milieu maraîcher au sud du Togo. L’efficacité de l’extrait hydroéthanolique a été comparée à celle d’un insecticide de synthèse (Cydim Super) et à celles d’un extrait aqueux de feuilles de A. indica et de deux pratiques paysannes. Les parcelles de chou ont été disposées en blocs complets randomisés et équilibrés. Les traitements à base d’extraits de feuilles de A. indica ont significativement réduit les populations de P. xylostella et de H. undalis par rapport à l’insecticide de synthèse et une pratique paysanne. Par contre, l’insecticide de synthèse a mieux contrôlé L. erysimi. Les rendements moyens en pommes de chou commercialisables sont compris entre 4,68 ± 1,63 t/ha pour le témoin, et 17,38 ± 0,98 t/ha pour les parcelles traitées avec l’extrait hydroéthanolique. Cet extrait a donné le double ou le triple du rendement des autres traitements. L’extrait hydroéthanolique peut être utilisé dans la gestion intégrée de P. xylostella, H. undalis et de L. erysimi sur le chou.Mots clés : Azadirachta indica, insectes ravageurs, chou, Togo