Chemical and mineralogical characterization and ceramic suitability of raw feldspathic materials from Dschang (Cameroon)

The chemical and mineralogical characterization of raw feldspathic materials from Dschang (Cameroon) was realized by means of X-ray diffraction, differential thermal analyses, optical and scanning electron microscopies, and analytical techniques. It was found that these materials consist of albite (43 ± 3 wt.%), microcline (41 and 26 wt.%), quartz (14.5 ± 1.5 wt.%), plagioclase (oligoclase type) (6 and 12 wt.%) and a minor content of biotite. The amount of fluxing oxides is about 12 wt.% and those of pigments are quasi-null. The ceramic suitability of these materials was assessed in the light of the obtained chemical data and physical characteristics (fusibility, viscosity, colour). The results showed that these raw materials are convenient, as fluxing compounds, for manufacturing white ceramic.KEY WORDS: Raw feldspathic materials, Mineralogy, Chemical composition, Ceramic suitability, Cameroon   Bull. Chem. Soc. Ethiop. 2010, 24(1), 39-46

Influence de la complémentation et de la prophylaxie sur la viabilité des ovins Foulbé au Nord-Cameroun

Quatre lots de 60 agnelles âgées de 3 à 5 mois (lot CP : complémentation, vaccination contre la peste des petits ruminants, vermifugation et déparasitage externe; lot C : complémentation sans prophylaxie ni traitement; lot P : prophylaxie et traitement sans complémentation; lot T : témoin) ont été constitués en avril 1993 en vue d'étudier l'effet de la complémentation alimentaire et des traitements sanitaires sur leur viabilité. La complémentation consistait en 200 g de tourteau de coton par tête et par jour et un complément minéral sous forme de pierre à lécher. Les traitements sanitaires consistaient en deux déparasitages internes en début et en fin des pluies et un déparasitage externe chaque fois que l'on notait la présence des tiques sur les agnelles. Les animaux ont fait l'objet d'un suivi clinique et de notation d'état corporel sur une année. Le jetage, les boiteries et les diarrhées ont représenté les principaux signes cliniques observés (respectivement 50,9, 15,2 et 13,0 %). Les quotients annuels de mortalité ont été de 16,7, 37,3, 31,7 et 52,5 % respectivement pour les lots CP, C, P et T. La complémentation et la prophylaxie ont permis une réduction très sensible de la mortalité (p < 0,05). La mortalité a considérablement augmenté avec le retour des pluies. Les infestations par des parasites gastro-intestinaux et la sous-alimentation ont été les principaux facteurs favorisant la mortalité. Cette stratégie de complémentation protéique et de prophylaxie peut être encouragée pour réduire les fortes mortalités, principal facteur limitant lé productivité des élevages ovins au Nord-Cameroun

Deep Neural Networks for Energy and Position Reconstruction in EXO-200

We apply deep neural networks (DNN) to data from the EXO-200 experiment. In the studied cases, the DNN is able to reconstruct the relevant parameters - total energy and position - directly from raw digitized waveforms, with minimal exceptions. For the first time, the developed algorithms are evaluated on real detector calibration data. The accuracy of reconstruction either reaches or exceeds what was achieved by the conventional approaches developed by EXO-200 over the course of the experiment. Most existing DNN approaches to event reconstruction and classification in particle physics are trained on Monte Carlo simulated events. Such algorithms are inherently limited by the accuracy of the simulation. We describe a unique approach that, in an experiment such as EXO-200, allows to successfully perform certain reconstruction and analysis tasks by training the network on waveforms from experimental data, either reducing or eliminating the reliance on the Monte Carlo.Comment: Accepted version. 33 pages, 28 figure

Measurement of the Spectral Shape of the beta-decay of 137Xe to the Ground State of 137Cs in EXO-200 and Comparison with Theory

We report on a comparison between the theoretically predicted and experimentally measured spectra of the first-forbidden non-unique $\beta$-decay transition ^{137}\textrm{Xe}(7/2^-)\to\,^{137}\textrm{Cs}(7/2^+). The experimental data were acquired by the EXO-200 experiment during a deployment of an AmBe neutron source. The ultra-low background environment of EXO-200, together with dedicated source deployment and analysis procedures, allowed for collection of a pure sample of the decays, with an estimated signal-to-background ratio of more than 99-to-1 in the energy range from 1075 to 4175 keV. In addition to providing a rare and accurate measurement of the first-forbidden non-unique $\beta$-decay shape, this work constitutes a novel test of the calculated electron spectral shapes in the context of the reactor antineutrino anomaly and spectral bump.Comment: Version as accepted by PR

Search for nucleon decays with EXO-200

A search for instability of nucleons bound in $^{136}$Xe nuclei is reported with 223 kg$\cdot$yr exposure of $^{136}$Xe in the EXO-200 experiment. Lifetime limits of 3.3$\times 10^{23}$ and 1.9$\times 10^{23}$ yrs are established for nucleon decay to $^{133}$Sb and $^{133}$Te, respectively. These are the most stringent to date, exceeding the prior decay limits by a factor of 9 and 7, respectively