A GATE-based Monte Carlo simulation of a dual-layer pixelized gadolinium oxyorthosilicate (GSO) detector performance and response for micro PET scanner

The purpose of this study was to simulate the GSO detector of a micro PET using GATE simulation platform. The performance and responses of the simulated GSO detector assembly were evaluated by comparing the simulated data to the experimental and XCOM data to validate the simulation platform and procedure. Based on NEMA NU-4 2008 protocols, the performance of GSO detector in terms of sensitivity was simulated and compared to the experimental data. Similarly, the GSO detector response to photons interaction was simulated and compared against the XCOM data for absorbed intensity ratio in the GSO detector and survived intensity ratio in Pb blocks. Results showed that simulated and experimental sensitivities agreed well with R2 of 0.995 and two overlapping bands at 95% confidence. An agreement with R2 of 0.972 and 0.973 as well as with overlapping bands at 95% confidence was obtained in simulated and XCOM data for absorbed and survived intensity ratio in the GSO detector and Pb blocks, respectively. The observed agreements demonstrate the accuracy of the simulation method to mimic the behaviour of the GSO detector. The validated GATE algorithm for micro PET scanner is therefore recommended for simulation and optimisation of collimator design in further studies. Keywords: GATE simulation, Experimental data, XCOM data, GSO detector, micro PET. &nbsp

Review of the Imaging Performance and the Current Status of the Cascade Gamma-Rays Coincidence Imagers

Various studies that have investigated the detection of gamma coincidence events have revealed that design factors and image reconstruction approaches dictate the spatial resolution, coincidence efficiency, and levels of statistical noise of the detection system. In the case of imaging, cascade gamma-ray coincidence (CGC) imagers coupled with collimated detectors offer promising values for both spatial resolution and coincidence efficiency. However, to date, no CGC imager with single or multiple collimated detectors has reported a performance level beyond 6.7 mm spatial resolution (FWHM) and 6.0 ×1ncidence efficiency. Given the recent developments and the current interests in high resolution and localization of an individual decaying nucleus, there is a need for CGC imagers with higher performance in terms of spatial resolution and efficiency. Therefore, deploying a CGC imager coupled with multiple collimated detectors may prove to be of value in nuclear imaging and probably in clinical application

Adverse impact of banana Xanthomonas Wilt on farmers’ livelihoods in Eastern and Central Africa

Banana is a key crop in the livelihoods of many people in the Great Lakes region of East and Central Africa. For more than a decade now, the crop has been threatened by Banana Xanthomonas Wilt (BXW) which has spread throughout the region but at different rates. The disease attacks all banana cultivars and can cause up to 100% yield losses at farm level if effective control measures are not put in place. However, limited information on impact of BXW at regional level is available to guide interventions. Thus, this study assessed the impact of BXW on farmers’ livelihoods in Kagera basin of Tanzania, Burundi and Rwanda. A total of 436 households (Tanzania 120, Burundi 208 and Rwanda 108) mostly from major banana-producing and BXW-affected districts were sampled and interviewed in a household survey. Thirty-three to seventy-five of the total banana mats per farm in the three countries were infected with BXW. Banana production losses caused by BXW were valued at US$10.2 million and US$ 2.95 million in Tanzania and Rwanda, respectively, banana sales by farmers dropped by 35% while bunch prices unpredictably doubled. Since banana is a key component of these farming communities, the banana production losses resulted in significant reduction in household food security and incomes. To cope with these challenges, most households are diversifying into other food crops such as maize, cassava and sweet potatoes. This poses a number of socio-economic and biological implications that require further investigation

Rice value chain analysis in Tanzania: Identification of constraints, opportunities and upgrading strategies

The importance of rice ( Oryza sativa L.) as a food and cash crop in Eastern Africa, is increasing, but its value chain is becoming complex. In 2012/13, rice value chain analysis was conducted in rice farming systems of Lake, Eastern and Southern-Highlands zones of Tanzania. A sample of 240 producers, 60 traders and 30 processors was involved in the study. The aim of this study was to enhance rice actors with knowledge of the rice value chain, and identify feasible upgrading strategies. The study results revealed that rice was staple crop for more than 50% of the communities in Kilombero, Kyela and Mvomero districts; and less than 30% in Rorya, Mbarali and Maswa districts. It was also an important cash crop (79 - 100%) in all districts. About 44 and 61% of the total crop area cultivated per household, in lowland rainfed and irrigated ecosystems, respectively were under rice cultivation. SARO 5 was the only improved variety widely grown by 27% of farmers out of 32 varieties. Rice yield ranged from 1.5 to 4.3 t ha-1 and varied greatly by ecosystem and variety. About 61-93% of farmers sold their rice paddy to collectors, used non-standard measurements. Farmers profits ranged from US $206.63 to 994.85 per hectare. Producer\u2019s share of selling rice ranged from 34 to 40This implies that upgrading strategies are required that can increase producers\u2019 market share and improve competitiveness of rice value chain.L\u2019importance du riz ( Oryza sativa L.) comme produit de consummation et et d\u2019echanges commerciaux en Afrique de l\u2019Est va grandissante, mais la chaine de valeur du riz de plus en plus complexe. En 2012/13 l\u2019analyse de la chaine de valeur du riz a ete conduite dans les systemes de culture de riz dans la zone lacustre de l\u2019Est et Sud de la Tanzannie. L\u2019etude s\u2019est servid\u2019un echantillon de 240 producteurs, 60 commercants et 30 transformateurs de riz. L\u2019objectif de l\u2019etude etait de doter les acteurs du riz de connaissances et informations sur la chaine de valeur et identifier des strategies possibles de modernization. L\u2019etude a revele que le riz est un produit vivrier de grande consommation pour plus de 50des districts de Kilombero, Kyela et Mvomero et moins de 30districts de Rorya, Mbarali et Maswa. Le riz est aussi une culture de rente (79 - 100Environ 44 et 61par chaque menage est plantee en riz. Sur 32 varietes, SARO 5 etait la seule variete amelioree largement cultivee par 27rendement en grain du riz variait de 1,5 t ha-1 to 4,3 t ha-1 ceci en fonction de l\u2019ecosysteme et de la variete. Environ 61 \u2013 93des producteurs vendent leur riz paddy a des collectionneurs qui utilisent des outils de mesure non conventionnels. Les benefices des paysans varient de 206,63$ a 994.85 $ par hectare. La part des producteurs varient de 34 a 40%. Ceci indique que des strategies de modernisation sont necessaires et pourrait accroitre le revenue des producteurs mais aussi ameliorer la competitivite de la filiere

Inventaire Floristique des Mauvaises Herbes dans une Caféiculture en Pure dans le Territoire de Kabare, DR Congo

Objectif: Cette étude avait pour objectif d’identifier les mauvaises herbes dans une caféiculture en pure, tout en précisant le degré d’infestation de chacune d’elles afin de planifier une lutte intégrée pour améliorer la production du café.Méthodologie et résultats: La méthode utilisée dans cette étude est la méthode phytosociologique de Braun Blanquet ; où trois plantations ont été enquêtées en réalisant cinq aires minimales de 35 à 90 m2 Ainsi, Une aire minimale de 20m2 à 80m2 a été déterminée suivant l’homogénéité de la végétation adventice. C’est ainsi que, 5 aires minimales par plantation ont été enquêtées avec un total de 15 aires minimales et 8 relevés par aire avec un total de 120 relevés enquêtés Il a été trouvé que la famille des asteraceae représente 35.29% et que Bidens pilosa et Galisonga ciliata sont les espèces les plus représentées et présentant un degré d’infestation élevé (adventices majeures dans les caféicultures) par rapport aux autres espèces.Conclusion et Application des résultats: Cette étude a révélé que la plupart d'espèces caractéristiques des champs de caféier en pure sont des asteraceae (Galinsoga ciliata, Bidens pilosa, Botriocline longipes, etc.) et des poaceae (Digitaria vestida, Setaria barbata, etc.). En plus, Ageratum conyzoidens, Achyranthes asper, Oxalis corymbosa, Crassophalum bumbese, Lactus spp., Cyperus distans, Commelina diffusa, Drymaria cordata, Sida acuta, Galinsoga ciliata et Bidens pilosa sont des espèces nuisibles dans les caféicultures. Ainsi, les résultats de cette étude pourraient être utilisés par les malherbologues afin de mettre en place une lutte focalisée et intégrée contre l’ensemble des mauvaises herbes qui peuvent avoir un impact négatif sur la culture du café et/ou son rendement.Mots clés: Inventaire, Mauvaises herbes, Caféier, asteraceae, gestion des mauvaises herbesEnglish AbstractObjective: The floristic inventory of weeds in this study aims to identify weeds in a pure coffee plantation, while specifying the degree of infestation of each of them in order to plan an integrated fight to improve the production of coffee.Methodology and results: The method used for this study is the phytosociological method of Braun Blanquet; where 5 minimum areas of 20 to 80 sqm were analysed in three large coffee farms. In each minimum area 8 quadrats were investigated. The Asteraceae has been found at 35.29% and Bidens pilosa and Galisonga ciliata are most represented species with a high degree of infestation.Conclusion and application and results: This study revealed that most characteristic species of pure coffee fields are Asteraceae (Galinsoga ciliata, Bidens pilosa, Botriocline longipes, etc.) and Poaceae (Digitaria vestida, Setaria barbata, etc.). In addition, Ageratum conyzoidens, Achyranthes asper, Oxalis corymbosa, Crassophalum bumbese, Lactus spp. Cyperus distans, Commelina diffusa, Drymaria cordata. Aida acuta. Galinsoga ciliata and Bidens pilosa are harmful species in coffee growing. Thus, the results of this study could be used by weed scientists to put in place a focused and integrated fight against all weeds that can have a negative impact on the coffee culture and / or its yield.Keywords: Inventory, Weeds, Coffee, Asteraceae, weed managemen