CROSS-LAYER DESIGN, OPTIMIZATION AND PROTOTYPING OF NoCs FOR THE NEXT GENERATION OF HOMOGENEOUS MANY-CORE SYSTEMS

This thesis provides a whole set of design methods to enable and manage the runtime heterogeneity of features-rich industry-ready Tile-Based Networkon- Chips at different abstraction layers (Architecture Design, Network Assembling, Testing of NoC, Runtime Operation). The key idea is to maintain the functionalities of the original layers, and to improve the performance of architectures by allowing, joint optimization and layer coordinations. In general purpose systems, we address the microarchitectural challenges by codesigning and co-optimizing feature-rich architectures. In application-specific NoCs, we emphasize the event notification, so that the platform is continuously under control. At the network assembly level, this thesis proposes a Hold Time Robustness technique, to tackle the hold time issue in synchronous NoCs. At the network architectural level, the choice of a suitable synchronization paradigm requires a boost of synthesis flow as well as the coexistence with the DVFS. On one hand this implies the coexistence of mesochronous synchronizers in the network with dual-clock FIFOs at network boundaries. On the other hand, dual-clock FIFOs may be placed across inter-switch links hence removing the need for mesochronous synchronizers. This thesis will study the implications of the above approaches both on the design flow and on the performance and power quality metrics of the network. Once the manycore system is composed together, the issue of testing it arises. This thesis takes on this challenge and engineers various testing infrastructures. At the upper abstraction layer, the thesis addresses the issue of managing the fully operational system and proposes a congestion management technique named HACS. Moreover, some of the ideas of this thesis will undergo an FPGA prototyping. Finally, we provide some features for emerging technology by characterizing the power consumption of Optical NoC Interfaces

Pseudomonads and symbiotic micro-organisms as biocontrol agents against fungal disease caused by

Experiments were undertaken to assess the antagonistic aptitude of Pseudomonas spp. alone or associated with mycorrhizal fungi on Pythium aphanidermaturm, the causal agent of seedlings dampingoffand stem rot of cowpea (Vigna unguiculata L. Walp). Evaluation was made using selected strains of pseudomonad (Pseudomonas fluorescens, P. putida and Pseudomonas sp.) isolated from V. unguiculata and Solanum tuberosum rhizospheric soils collected in three agroecological zones of Cameroon. Cultures were conducted on agar plates and in liquid media to evaluate the antagonistic capacity of those strains against Pythium aphanidermaturm and to evaluate their biocontrol activity in protecting cowpea plants. The results showed a direct inhibition of the pathogenic fungus by these bacteria. P. fluorescens used alone against Pythium aphanidermaturm, provided a reduction of the disease index from 3.44 to 1.06. When the arbuscular mycorrhizal fungi Glomus deserticola is associated to P. fluorescens, the disease index dropped to 0.13, confirming the synergistic effect of those beneficial micro-organisms

Occurrence and functioning of phosphate solubilizing microorganisms from oil palm tree (Elaeis guineensis) rhizosphere in Cameroon

Phosphorus replenishment, particularly in smallholder agriculture, remains a challenge as it is mainly fertilizer dependent. While the use of soluble mineral phosphate fertilizers is the obvious best means tocombat phosphate deficiency in Cameroon, their use is limited by their high cost and availability at farmer’s level. This study was aimed at maintaining the fertility of Cameroon soils by biological means,in order to improve agricultural production, using low inputs technology. Isolates were obtained from oil palm tree (Elaeis guineensis) root fragments and rhizospheric soils and their activity in mobilizingphosphate from insoluble sources was evaluated on agar plates and liquid culture media containing sparingly soluble phosphates. At the end of incubation time, it appeared that, phosphate solubilizationresulted from a combined effect of pH decrease of the media and organic acids production. Furthermore, each of the tested isolates was able to produce at least one of the most important organic acids such as citrate, malate and tartrate. Among the ten isolates tested, three were identified as Pseudomonas fluorescens and would be considered as potential biofertilizers

ANTIMICROBIAL AND ANTIDIARRHEAL EFFECTS OF FOUR CAMEROON MEDICINAL PLANTS: DICHROCEPHALA INTEGRIFOLIA, DIOSCOREA PREUSII, MELENIS MINUTIFLORA, AND TRICALYSIA OKELENSIS

Objective: In order to verify the antidiarrheal activities of Dichrocephala integrifolia, Dioscorea preusii, Melenis minutiflora, Tricalysia okelensis, the in vitro antimicrobial effect on Salmonella typhi, Escherichia coli, Shigella dysenteriae A1 and Candida albicans, and the in vivo antidiarrheal activities on the intestine transit of the hydroethanol (v/v) plants extracts were studied. Methods: The antimicrobial effect of the extracts was assayed in vitro by the disc diffusion and the agar dilution methods. For in vivo study, male and female mice received per os castor oil and one hour later different doses of the extracts. Results: In vitro, D. integrifolia, D. preusii, M. minutiflora, and T. okelensis extract showed concentration-dependent activity against all the tested microbial strains with the inhibition zone ranged from 08 to 24 mm. D. integrifolia 0.5 mg/mL showed the lowest MIC on Candida albicans. The M. minutiflora and D. integrifolia MIC was 3 mg/mL on Escherichia coli and Shigella dysenteriae A1. In vivo, D. integrifolia, D. preusii, T. okelensis extract at 50 and 100 mg/kg bw and M. minutiflora 75 and 150 mg/kg bw significantly (P< 0.01) inhibited the intestinal charcoal transit. D. integrifolia 100 mg/kg bw exhibited the highest inhibition rate, 70%. Conclusion: These results suggest that D. integrifolia, D. preusii, M. minutiflora and T. okelensis extracts possesses antimicrobial and antidiarrheal properties, could be effective for diarrhea treating, and could thus justify their use in traditional medicine to treat diarrhea. D. integrifolia could have the most efficiency antimicrobial properties

Niveau d'infestation des arbres fruitiers des groupements végétaux par Phragmanthera capitata (Sprengel) S. Balle (Loranthaceae) dans la région littorale du Cameroun

Au Cameroun, Phragmanthera capitata parasite de nombreuses essences ligneuses sauvages et cultivées, et est responsable de la réduction de leur rendement. L’optique de cette étude est de justifier le comportement de cette Loranthaceae ubiquiste dans les groupements végétaux homogènes et hétérogènes des sites retenus du littoral camerounais. Les groupements végétaux homogènes sont des plantations agricolesconstituées de Hevea brasiliensis et appartenant à la société Hévéa du Cameroun (Hévécam) située à Nyétté. Les groupements végétaux hétérogènes appartiennent à quatre sites de la région de Douala : un verger à Makondo et une plantation agricole paysanne à Cola acuminata à Penja, deux jardins de cases (Logbessou et axe routier aéroport-Bonanjo). Sur chaque arbre hôte ont été notés: le diamètre du tronc à 1,30 m du sol, les différentes espèces de Loranthaceae reconnues et le nombre de touffes comptées. Dans les groupements végétaux hétérogènes, 16 espèces hôtes réparties dans 12 genres et 10 familles sont parasitées par P. capitata. Cette dernière est la plus fréquente et la plus abondante de toutes les Loranthaceae et sa dissémination est facilitée par des facteurs d’origine anthropique. Il est indispensable et urgent de mettre en place un programme de recherche de lutte ciblée pour les plantes fruitières et ornementales

Selected Rhizosphere Bacteria Help Tomato Plants Cope with Combined Phosphorus and Salt Stresses

Plants are often challenged by multiple abiotic stresses simultaneously. The inoculation of beneficial bacteria is known to enhance plant growth under these stresses, such as phosphorus starvation or salt stress. Here, for the first time, we assessed the efficiency of selected beneficial bacterial strains in improving tomato plant growth to better cope with double stresses in salty and P-deficient soil conditions. Six strains of Arthrobacter and Bacillus with different reservoirs of plant growth-promoting traits were tested in vitro for their abilities to tolerate 2–16% (w/v) NaCl concentrations, and shown to retain their motility and phosphate-solubilizing capacity under salt stress conditions. Whether these selected bacteria promote tomato plant growth under combined P and salt stresses was investigated in greenhouse experiments. Bacterial isolates from Cameroonian soils mobilized P from different phosphate sources in shaking culture under both non-saline and saline conditions. They also enhanced plant growth in P-deficient and salt-affected soils by 47–115%, and their PGP effect was even increased in higher salt stress conditions. The results provide valuable information for prospective production of effective bio-fertilizers based on the combined application of local rock phosphate and halotolerant phosphate-solubilizing bacteria. This constitutes a promising strategy to improve plant growth in P-deficient and salt-affected soils.Peer Reviewe

In vitro evaluation of the antimicrobial properties of Mallotus oppositifolium decoction leaf extracts and fractions

In order to verify the in vitro antimicrobial properties of Mallotus oppositifolium (Euphorbiaceae), the qualitative phytochemical screening and the antimicrobial activities on Shigella dysenteriae A2, Salmonella typhi, Escherichia coli, Enterococcus faecalis, Staphyllococcus aureus and Candida albicans strains of the aqueous decoction (DEMO) hexane (HEMO) and methanol (MEMO) fractions of leaves were assessed. The screening was performed using colorimetric methods. The antimicrobial activity was carried out using disc diffusion assays. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by the dilution methods. The screening revealed the presence of metabolites such as alkaloids, flavonoids, phenolic compounds, tannins, saponins, lipids, carbohydrates, mucilages, proteins, triterpens and steroids. DEMO, HEMO, MEMO showed a concentration-dependent activity against Shigella dysenteriae A2 and Salmonella typhi, with inhibition zone ranging from 9.44±0.44 to 19.00±0.24 mm, 8.94±0.05 to 20.03±0.17 mm and 8.13±0.17 to 16.76±0.11 mm respectively. The MIC showed ranges from 0.25 to 1.00 mg.mL-1, 0.20 to 0.50 mg.mL-1 and 1.00 to 3.00 mg.mL-1, while the MBC ranged from 1.00 to 5.00 mg.mL-1, 0.50 to 1.00 and 3.00 to 10.00 mg.mL-1 respectively. The leaves decoction and fractions activity on the two strains showed promising activities to justify the use of the plant against diarrhoea in folk medicine.Keywords: Folk medicine, phytochemical analysis, Mallotus oppositifolium diarrhea, antimicrobial

Influence of nitrogen sources and plant growth-promoting rhizobacteria Inoculation on growth, crude fiber and nutrient uptake in squash (cucurbita moschata duchesne ex poir.) plants

Plant growth promoting rhizobacteria (PGPR, B) have immense potential application in sustainable agriculture as ecofriendly biofertilizers and biopesticides. In this study, the effects of three nitrogen (N) sources (NO3-, NH4+ and NO3NH4) and PGPR on growth, crude fiber and nutrient uptake were investigated in squash plants. Some growth parameters [root dry weight (RDW), shoot dry weight (SDW), total plant dry weight (PDW), number of leaves (NL), shoot length (SL), stem diameter (SD) and number of ramifications (NR)], crude fiber (cellulose content) and nutrient uptake (N, P, K, Ca, Mg, Na, Fe, Cu, Mn and Zn) were determined. Application of NO3-, NH4+ or NO3NH4 singly or in combination with PGPR inoculation led to a significant increase in RDW, SDW, PDW, NL, SL, SD and NR. Na, Cu and Zn contents, on the contrary, decreased in inoculated treated plants while no significant differences were recorded in cellulose contents (CE) of leaves except in plants fed with NO3-. The leaf CE content ranged from 12.58 to 13.67%. The plants supplied with NO3+B, NH4+B and NO3NH4+B showed significantly higher plant biomass and accumulation of N, P, K and Mn concentrations in leaves compared to all other treatments. These results suggest that specific combinations of PGPR with NO3-, NH4+ or NO3NH4 fertilizers can be considered as efficient alternative biofertilizers to improve significantly the squash growth and nutrient uptake

Biodiversity of the phosphate solubilizing microorganisms (PSMs) population from the rice rhizosphere soils of the two agro-ecological zones of Cameroon

The plant rhizosphere microorganisms having the phosphate solubilizing capacity can convert the insoluble soil organic and inorganic phosphates into a soluble form and make the phosphorus (P) available to the plant. With the objective of evaluating the phosphate solubilizing microorganism populations under the rice rhizosphere, soils samples were collected in three locations of two agro ecological zones of Cameroon and analyzed for their PSMs diversity. Isolation of microorganisms was made on non selective nutrient agar plates and the phosphate solubilizing activity of isolates was tested on National Botanical Research Institute’s Phosphate growth medium (NBRIP) amended with sparingly soluble rock phosphates of different origins. The morphological description of isolates allowed evaluating the phosphate solubilizing microorganism’s diversity under the rice rhizospheric soil. The most probable number of PSMs ranged between 22 and 53% with an average of 48%, 52.80% and 22.44% for Nkolbisson, Nyokon and Santchou respectively. The 65 isolates obtained from all locations were distributed in four diverse groups. The index of solubilization ranged between 2.70 and 7.24 depending on isolate. From a total of 65 isolates obtained from the three sampling sites, 46 were phosphate solubilizing isolates among which: 20 were of low solubilization, 16 of medium and 10 of high solubilization. This is the first work reporting phosphate solubilizing microorganisms on rice rhizosphere in Cameroon. However, the selection of phosphate solubilizing microorganisms as possible inoculation tools for phosphate-deficient soils should focus on the integral interpretation of laboratory assays, greenhouse experiments as well as field trials.© 2015 International Formulae Group. All rights reserved.Keywords: Diversity, index of solubilization, isolates, rice, rock phosphate