Biochemical Reactions Instigating Vision – Parameter Sensitivity Analysis

The purpose of this work is to investigate the sensitivity of parameters involved in a cascade of biochemical reactions occurring in photoreceptor cells in the retina of the eye. This cascade constitutes the first stage of the elaborate process of vision, by which light captured in a photoreceptor generates an electrical signal. It is this signal that travels to the brain enabling vision. Sensitivity on parameters was performed on an ODE model of the biochemical cascade using two methods. One method used SimLab, a statistical sensitivity analysis program. We found that there are at most five important parameters out of the sixteen that affect the production of activated phosphodiesterase (PDE* ) and the photoreceptor (electrical current) response (RR ). Another method performed was to vary each of the sixteen parameters separately over a range and observe the effect on PDE* ; this method also produced five most influential parameters essential to the production of PDE* . While the parameter rankings differed from one method to the other, the five parameters found using partial differential analysis of our ODE model agree with the parameters obtained via SimLab. The second aspect of our problem involved looking at the effect of the variations of parameters on the time at which PDE* and RR attain their maximum values. Only three of the parameters highly affecting variations of PDE* were also found to influence the time-of-peak values

Parasitological prevalence of bovine trypanosomosis in the Faro and Deo division valley of the Adamaoua plateau, Cameroon

A cross sectional survey to determine the distribution and prevalence of trypanosomosis was conducted in the Faro and Deo division valley, on the Adamaoua Plateau in Cameroon. A total of 334 adult cattle from 5 sedentary herds were examined in 5 villages. Dark field buffy coat method, as well as stained thin blood film examination and packed cell volume (PCV) evaluation were the diagnostic techniques used. The overall prevalence of bovine trypanosomosis in the area was 23%. Among the positive animals, 44 (57.1%), 26 (33.8%), 5 (6.5%) and 2 (2.6%) were due to Trypanosoma congolense, Trypanosoma brucei, Trypanosoma vivax and mixed infection (T. congolense and T. brucei) respectively. The mean PCV of the positive and negative animals ranged between 21.1-27% and 28.2-30.1% respectively. The mean PCV of negative animals (29.1±0.7%) was significantly higher than the mean PCV of positive animals (24.2±2.5%) (P< 0.005). In view of the high risk of trypanosomosis, in the area, an integrated intervention approach to which combines the strategic application of appropriate tsetse fly control methods to reduce host fly contact and chemotherapy and chemoprophylaxis against trypanosomosis is recommended.© 2009 International Formulae Group. All rights reserved.Key words: Adamaoua, Cameroon, Cattle, Prevalence, Trypanosomosis, Tsetse

Composition, Structure And Diversity of The Vegetation of The Manda National Park (MNP) in The Moyen-Chari Province of Chad

The present work was initiated in order to evaluate the composition, structure and diversity of the flora of the Manda National Park (MNP) to contribute to its sustainable management. The survey area is a square plot of 1m x 1m and a semi plot of 10m x 10m respectively for grassy savannah and shrub savannah and a rectangular plot of 50m x 20m for woodland and tree savannah. The diameter at breast height and total height of all woody individuals were measured. The floristic inventory resulted in a total of 12885 individuals belonging to 102 species, 81 genera and 34 families. The tree savannah (78 species, 59 genera and 26 families) and woodland (65 species, 54 genera and 24 families) are richer in taxonomic groups than the shrub savannah (38 species, 32 genera and 16 families) and the grassy savannah (19 species, 18 genera and 8 families) The average density of the park and its Shannon index are respectively 1956 ind/ha and 2.82 bits. For these plant formations, their density and Shannon index are highest in the tree savannah (3507 ind/ha and 3.11 bits) and lowest in the shrub savannah (1133 ind/ha and 2.03 bits). The Piélou index for each of the plant formations is low (0.19 to 0.25), indicating a poor equi- distribution of individuals between the different species for the plant formations. In the woodland, the diametrical and vertical distributions are bell-shaped and skewed to the right, centered on young individuals. In contrast, in the Tree and Shrub Savannahs the distributions are in the shape of an inverted "J", characteristic of a formation dominated by juvenile individuals. These results lead to the conclusion that the Manda Park has a good species diversity and is under anthropic pressure due to the destruction of its vegetation cover

Risk Link to the Volcanic Activity of the Mt. Cameroon in Cameroon

The Mt. Cameroon is a large volcanic horst belonging to the majure tectonic line (Cameroon volcanic line). The geographical morphology of the mountain is controlled by regional tectonics. The Mt. Cameroon is consisted of precambrian metamorphic basement covered with Cretaceous to recent sediments distributed mainly in the Douala and Riodel Rey basin. The oldest lava could be of upper Miocene age. The Mt. Cameroon has erupted six times in the 20th century. The 1982 eruption took place inside the crater of an ancient cone. The lavas are picrites (with forsteritic olivine phenocrysts), alkali basalts (with salitic augite phenocrysts), hawaiites (with labrador-bytownite plagioclase phenocrysts) and mugearites (with scarce kaersutite phenocrysts and microlitic phlogopite or nosean). According to Deruelle et al.(1987), the Mt. Cameroon lava series is typically alkaline with no tholeiitic or transitional trend. Risk related to volcanism is actual for the human constructions especially along the axis of the horst. The severe volcanic risk has been limited to explosion, lava flows and lahar. It is possibility that explosion, laver flow and earthquarke take place anywhere on the volcanic mountain. Nevertheless, these explosions are most likely to occur in the delimited sector which is shown in a map presented in this paper. Even if we could divert the course of the lava flows to certain safer direction, flows caused by sudden earthquarke and explosion may cause serious damages

Supported polysilsesquioxane membrane and production thereof

Membranes of the invention comprise a hybrid silica film on a organic polymer support. The silica comprises organic bridging groups bound to two or more silicon atoms, in particular at least 1 of said organic bridging groups per 10 silicon atoms. The membranes can be produced by dry chemistry processes, in particular plasma-enhanced vapour deposition of bridged silane precursors, or by wet chemistry involving hydrolysis of the bridged silane precursors. The membranes are inexpensive and efficient for separation of small molecules and filtration processes

Mantle sources and magma evolution beneath the Cameroon Volcanic Line: Geochemistry of mafic rocks from the Bamenda Mountains (NW Cameroon)

International audienceWe report the mineralogy, geochemistry and geochronology of the mafic rocks from the Bamenda Mountains, part of the Cameroon Volcanic Line (CVL), in order to discuss the origin and evolution of the magmas in this part of the CVL. Mafic rocks in the Bamenda Mountains are basanites, basalts, hawaiites and mugearites with an alkaline affinity. K-Ar ages have been obtained on 10 samples and range from 17.6 Myr to present. Trace element and isotopic compositions (Sr-Nd-Pb) show that some samples among the oldest are slightly contaminated by a crustal component with high La/Nb and 87Sr/86Sr ratios and low Pb isotopic ratios. The mafic rocks strongly resemble OIB in their trace element compositions. Some samples possess a positive Sr and Eu anomaly which cannot be explained by a process of plagioclase accumulation. These anomalies are also observed in some pyroxenites found as xenoliths in the Adamawa volcanic province further north. Furthermore, non-contaminated samples have high Pb isotopic ratios and point towards an HIMU component similar to the St. Helena mantle plume. We propose that the Bamenda mafic magmas with positive Sr and Eu anomalies were formed by hybridization of asthenospheric melts with melts formed by the partial melting of pyroxenites. Samples without these anomalies result from the hybridization of the same asthenopheric melts with melts coming from the metasomatized, amphibole-bearing, lithospheric mantle

Cardiomyopathie Du Postpartum: A propos de cinq cas au Gabon.

Nous rapportons une analyse rétrospective de cinq cas de cardiomyopathie du postpartum traités en l’espace d’un an à l’hôpital d’instruction des armées Omar BONGO ONDIMBA de Libreville. Les patientes étaient âgées de moins de 32 ans et deux avaient une prééclampsie sévère. L’insuffisance cardiaque congestive avec oedème aigue du poumon, étaient le maître symptôme.La radiographie du thorax montrait toujours une cardiomégalie avec des signes de congestion pulmonaire. L’échocardiographie montrait un diamètre télédiastolique ventriculaire gauche de plus de 58 mm et une fraction de raccourcissement inférieure ou égale à 18%. Le traitement comportait, outre le repos au lit, la restriction hydrosodée, un digitalique, un diurétique et uninhibiteur de l’enzyme de conversion. Trois des patients ont guéri et chez deux persistait une altération échocardiographique de la fonction ventriculaire gauche. Les principaux problèmes posés par la cardiomyopathie du postpartum sont soulevés