Physicochemical water quality of the Mfoundi River watershed at Yaoundé, Cameroon, and its relevance to the distribution of bacterial indicators of faecal contamination.

Water quality of the Mfoundi River and four of its tributaries was studied by assessing some physicochemical variables (temperature, pH, conductivity, chlorides, phosphates and nitrogen ammonia, dissolved oxygen and carbon dioxide, organic matter content and Biological Oxygen Demand) and their influence on the distribution of bacterial indicators of faecal contamination (total coliform, faecal coliform and faecal streptococci). For this, standard methods for the examination of physicochemical parameters in water were followed, and statistical analysis (Pearson correlations) used to establish any relationships between physicochemical and biological variables. Our results revealed that almost all of the examined physicochemical variables exceeded World Health Organization (WHO) guidelines for recreational water. This was in agreement with a previous microbiological study indicating that these waters were not safe for human use or primary contact according to water quality standards established by the WHO. Results of our correlation analysis suggested that physicochemical and biological variables interact in complicated ways reflecting the complex processes occurring in the natural environment. It was also concluded that pollution in the Mfoundi River watershed poses an increased risk of infection for users and there exists an urgent need to control dumping of wastewater into this watershed

Piezoelectric and optical setup to measure an electrical field: Application to the longitudinal near-field generated by a tapered coax

We propose a new setup to measure an electrical field in one direction. This setup is made of a piezoelectric sintered lead zinconate titanate film and an optical interferometric probe. We used this setup to investigate how the shape of the extremity of a coaxial cable influences the longitudinal electrical near-field generated by it. For this application, we designed our setup to have a spatial resolution of 100 um in the direction of the electrical field. Simulations and experiments are presented

Microwire Thermocouple Scanning Thermal Microscope (SThM) in Active Mode: Thermal Conductivity Measurement of Bulk Materials

International audienc

Generation of local magnetic field; application to VCSEL

International audienceIn this article, we report on the simulation and realization of a magnetic circuit allowing to apply an axial magnetic field higher than 1 T. The proposed electromagnet is used to investigate the influence of a magnetic field on the polarization behavior of a vertical-cavity-surface-emitting laser (VCSEL). A non-linear polarization behavior can be experimentally observed for currents as low as the threshold current, provided that the magnetic field is strong enough

Caractérisations physico-chimiques et électriques de films ferroélectriques synthétisés par voie hydrothermale

National audienc