Stable isotopes of oxygen and carbon compositions in the Neoproterozoic of South Gabon (Schisto-Calcaire Subgroup, Nyanga Basin): Are cap carbonates and lithoherms recording a particular destabilization event after the Marinoan glaciation?
Preat A.,Free University of Brussels |
Prian J.-P.,Bureau de Recherches Geologiques et Minieres |
Thieblemont D.,Bureau de Recherches Geologiques et Minieres |
Obame R.M.,University Des Science Et Technique Of Masuku |
Delpomdor F.,Free University of Brussels
Journal of African Earth Sciences | Year: 2011
Geologic evidence of tropical sea level glaciation in the Neoproterozoic remains a matter of debate in the Snowball Earth hypothesis. The Niari Tillite Formation and the cap carbonates record the late Neoproterozoic Marinoan glaciation in South Gabon. These cap carbonates are located at the base of the Schisto-Calcaire Subgroup a predominantly carbonate succession that rests with sharp contact on top of the Niari Tillite. Integrating sedimentological and stable isotope data, a consistent sequence of precipitation events is proposed, with strongly negative δ13C values pointing to a particular event in the cap carbonates (average δ13C value=-3.2‰ V-PDB) and in a further newly defined lithohermal unit (average δ13C value=-4.6‰ V-PDB). Subsequent shallow evaporitive platform carbonates display carbon and oxygen isotopic compositions indicative of relatively unaltered seawater values. Strongly negative δ18O values in the lithoherms and replacement of aragonite fans by equigranular calcite suggest flushing of meteoric water derived from glacial meltwater. © 2011 Elsevier Ltd.
Audran G.,Aix - Marseille University |
Bosco L.,Aix - Marseille University |
Nkolo P.,Aix - Marseille University |
Bikanga R.,University Des Science Et Technique Of Masuku |
And 4 more authors.
Organic and Biomolecular Chemistry | Year: 2016
In two recent articles (Org. Biomol. Chem., 2015 and 2016), we showed that changes in the phosphorus hyperfine coupling constant aP at position β in β-phosphorylated nitroxides can be dramatic. Such changes were applied to the titration of water in organic solvents and conversely of organic solvents in water. One of the molecules tested was a non-cyclic nitroxide meaning that a thorough investigation of the solvent effect on the EPR hyperfine coupling constant is timely due. In this article, we show that the aP of persistent non-cyclic β-phosphorylated nitroxides decrease with the normalized polarity Reichardt's constant EN T. The Koppel-Palm and Kalmet-Abboud-Taft relationships were applied to gain deeper insight into the effects influencing aN and aP: polarity/polarizability, hydrogen bond donor properties, and the structuredness of the cybotactic region. © The Royal Society of Chemistry 2016.
Ngomanda A.,British Petroleum |
Mavouroulou Q.M.,University Des Science Et Technique Of Masuku |
Obiang N.L.E.,British Petroleum |
Iponga D.M.,British Petroleum |
And 5 more authors.
Journal of Tropical Ecology | Year: 2012
Many tropical tree species have buttresses at the standard breast height (1.3m above ground) of diameter measurement, with a presumable role in improving nutrient acquisition or tree anchorage in the ground (Newbery et al. 2009, Richter 1984). Measuring the diameter using standard dendrometrical tools such as callipers or graduated tapes, which require that the cross-section of the trunk has a convex shape, is then impossible (Nogueira et al. 2006). The recommended method in this case is to measure the diameter above the buttress (DAB), thus possibly leading to biased estimates of the basal area (West 2009), of tree above-ground biomass (Dean & Roxburgh 2006, Dean et al. 2003) and of tree growth (Metcalf et al. 2009). As an alternative, one can measure the basal area at breast height of buttressed trees, using a method that can deal with the irregular non-convex shape of the cross-section of the stem such as the Picus calliper, photogrammetry or 3D laser scanning (Badia et al. 2003, Dean 2003, Newbery et al. 2009). © 2012 Cambridge University Press.
Padzys G.S.,University Des Science Et Technique Of Masuku |
Ondo J.P.,University Des Science Et Technique Of Masuku |
Omouenze L.P.,University Des Science Et Technique Of Masuku |
Zongo S.,University Des Science Et Technique Of Masuku
Ethnicity and Disease | Year: 2015
Objectives: Many researchers continue to believe that urbanization is a major contributor to diabetes. We seek to demonstrate that the social status associated with urbanization has an impact on the prevalence of diabetes in Libreville, Gabon in sub-Saharan Africa. Methods: Our study was conducted in Libreville, the capital of Gabon; the city has a population of 397,000. Our study analyzed data from the registries of patients hospitalized in 2013 in the main diabetes center in Libreville. Result: The results revealed that, for 2013, 798 patients were hospitalized with diabetes at a prevalence of .2%. We found differences (P<.05) between women (423) and men (375). Mean age for women was 52.02 years and 48.88 years for men. The number of existing cases hospitalized was significantly more than new cases. All levels of society were represented in our study: students (42); military (36); administratives (99); technicians (180); unemployed (295); and retired (146). The results showed that the unemployed (36%), particularly women (29.40%) are most affected by diabetes. Conclusion: Our results show the impact of social status on the increase of diabetes in Libreville. We found that urbanization, associated with insecurity especially in women, had an effect on the prevalence of diabetes in Libreville. These results indicate that, apart from the non-modifiable factors (age, race, ethnicity), insecurity is a modifiable factor that should be taken into account.