Anticorrelation between Ion Acceleration and Nonlinear Coherent Structures from Laser-Underdense Plasma Interaction

In laser-plasma experiments, we observed that ion acceleration from the Coulomb explosion of the plasma channel bored by the laser, is prevented when multiple plasma instabilities such as filamentation and hosing, and nonlinear coherent structures (vortices/post-solitons) appear in the wake of an ultrashort laser pulse. The tailoring of the longitudinal plasma density ramp allows us to control the onset of these insabilities. We deduced that the laser pulse is depleted into these structures in our conditions, when a plasma at about 10% of the critical density exhibits a gradient on the order of 250 {\mu}m (gaussian fit), thus hindering the acceleration. A promising experimental setup with a long pulse is demonstrated enabling the excitation of an isolated coherent structure for polarimetric measurements and, in further perspectives, parametric studies of ion plasma acceleration efficiency.Comment: 4 pages, 5 figure

Initial Data Identication in Space Dependent Conservation Laws and Hamilton-Jacobi Equations

Consider a Conservation Law and a Hamilton-Jacobi equation with a ux/Hamiltonian depending also on the space variable. We characterize rst the attainable set of the two equations and, second, the set of initial data evolving at a prescribed time into a prescribed prole. An explicit example then shows the deep dierences between the cases of x-independent and x-dependent uxes/Hamiltonians

Soil salinity and acidity : spatial variabil[it]y and effects on rice production in West Africa's mangrove zone

In the mangrove environment of West Africa, high spatial and temporal variability of soil constraints (salinity and acidity) to rice production is a problem for the transfer and adoption of new agronomic techniques, for land use planning, and for soil and water management. Recently, several National and International Agricultural Centers have initiated research programs to characterize environments where their newly developed technologies have to be applied. However, the mangrove agro- ecosystems in West Africa have not been characterized in a detailed way. Most of the soils in this environment are potential or actual saline acid sulfate soils. The spatial and temporal variability of soil salinity and acidity in these coastal lowlands results from complex interactions between climate, coastal morphology, river hydrology, vegetation, landform and tidal flooding. Diagnosing the occurrence of both potential and actual acid sulfate soils is the first step in land use planning for such areas. But to cope with the intricacies of these soils, understanding the processes of soil salinization and acidification at different scales should be formalized to properly characterize mangrove environments.The main objectives of this thesis were: 1) to give a comprehensive characterization framework for the West African mangrove environments with emphasis on the possibilities of and constraints for rice cultivation; 2) to determine the various causal factors for soil salinization and acidification; 3) to test whether temporal variability of soil chemistry is sufficient to provide a time window of minimum stress during the rice growing period; 4) to relate the response of rice to improved agronomic practices in specific environments and to provide a means to characterize specific rice growing locations, and 5) to test rice varietal responses to saline and acid sods under different agronomic practices and to relate yields and yield components to the nutrient contents in leaves, in order to diagnose physiological disorders.First, a multi-scale approach was developed involving a range from Macro to Micro level based on the pre-conditions of acid sulfate soil formation. The main factors for classification are climate and coastal morphology at Macro scale; hydrology, physiography and vegetation complexes at Meso level; and topography (catena), vegetation species, tidal flooding and sedimentation rate at Micro level. Information from previous process-based studies on acid sulfate soil formation and data from secondary sources were used. Different environments were then distinguished and their characteristics were summarized by ecological zone. Constraints to rice production and potentials for agricultural development were matched with environmental conservation issues.To determine the significance of the causal factors developed in the multiple scale approach, 12 sites were selected along 4 river basins in West Africa, vz. from north to south the Gambia, the Casamance (Senegal), the Geba (Guinea Bissau) and the Great Scarcies (Sierra Leone). Along each river basin 3 sites were selected based on distance from the river mouth. Within a site a strip of land perpendicular to the river was selected for intensive grid sampling (40 by 20 m). Soil samples were taken at each grid node during the dry season of 1991. The relation between causal factors and soil salinization and acidification was determined at Macro and Meso levels by nested ANOVA and yielded a classification of the study area in main ecoregions and sub-environments within watershed. At a detailed scale, geostatistics were applied and zones within catena were defined in terms of their main soil characteristics. A nested statistical approach and geostatistics were used complementarily to disentangle the complexity of the causes of soil salinization and acidification.Temporal variability was studied by monitoring soil solution chemistry at each main landscape unit within the catena. Since the production of rice critically depends on the lowering of salinity and acidity by natural flooding during rainy season, time windows during which soil limitations are minimal were defined and matched with rice varietal duration.The response of rice to different improvement techniques were tested by means of a network of trials in the 1991 and 1992 rainy seasons. The residual effects of lime and phosphate rock (applied in 1991) during 1992 was also evaluated. Lime dressing (2 t ha -1) was found effective whenever dissolved Ca and Mg in the soil were low, and had a clear residual effect in the year after application. Application of phosphate rock did not seem to be effective in general. For iron toxicity, the molar fraction of Fe and (Ca + Mg) in soil solution and in flag leaves were found to be more relevant for diagnosing physiological disorders than the absolute Fe content in the soil solution and in rice flag leaves at panicle initiation.In the 1993 rainy season, rice varietal behavior under different improvement techniques within the main soil limitations in the mangrove environment was tested. Differences in yield and yield components and element contents in flag leaves at panicle initiation were observed between varieties in saline and less saline acid soils. Multiple correlation between rice yields, yield components, element contents in flag leaves at panicle initiation was found to be an effective diagnostic tool for assessing physiological disorders.The approach used in this study provides a logical framework to describe mangrove environments. The multiple-scale can assist in identifying the information required to cater for the needs of various decision-makers and land use planners. It also provides a key to develop technology packages for intensified and sustainable use. It can be used for the extrapolation of site-specific information to geographically different areas, with similar characteristics

Evaluation des pratiques de gestion des adventices en riziculture irriguee dans la localite de Daloa, centre-ouest de la Cote d’Ivoire

Le riz est l’aliment principal pour la quasi-totalité des populations vivant en Côte d’Ivoire. Cependant, les adventices sont considérées comme la contrainte biologique la plus importante faisant obstacle à la production rizicole. L’objectif de cette étude menée en 2015 était d’évaluer différentes techniques de gestion des adventices en riziculture irriguée, dans la localité de Daloa, au Centre-Ouest de la Côte d’Ivoire. Pour ce faire, une parcelle témoin et 3 parcelles tests ont été testées dans un dispositif en blocs aléatoires complets avec 4 répétitions. Un seul paramètre a fait l’objet d’évaluation au niveau des adventices, à savoir l’indice d’abondance-dominance à 15 ; 30 ; 45 et 60 JAR. Cinq paramètres ont été évalués sur le riz à la maturité physiologique. Ce sont : le nombre de talles et de panicules par poquet, la hauteur des plants, la longueur des panicules et le rendement paddy. Les résultats ont montré que les méthodes de gestion de l’enherbement ont un effet significatif sur l’indice d’abondance-dominance des adventices et les paramètres agronomiques du riz. En effet, l’application du pendiméthaline en pré-levée des adventices suivie d’un désherbage manuel à 30 JAR permet de mieux maîtriser l’enherbement et améliore les paramètres agronomiques du riz.Mots clés: mauvaises herbes, riz, pratiques de gestion, abondance-dominance, Côte d’IvoireEnglish Title: Assessment of management practices of weeds on irrigated rice in from Daloa, central-west of Cote d’IvoireEnglish AbstractRice is the main food for almost all populations living in Côte d’Ivoire. However, weeds are considered the most important biological constraint to rice production.The objective of this study, carried out in 2015, was to evaluate different management techniques of weeds on irrigated rice in from Daloa, Central-West of Côte d’Ivoire. To do a control plot and 3 parcels tests were tested in a randomized complete block with four replications. One parameter has been evaluated in weeds namely the abundance-dominance indexnotes 15; 30; 45 and 60 DAP. Five (05) parameters were evaluated in rice to physiological maturity. These are: number of tillers per hill, number of panicles per hill, plant height, length of panicle and paddy yield. The results showed that management practices of weeds have a significant effect on the abundance-dominance index of weeds and the agronomic parameters of rice.Indeed, the application of pendimethalin in pre-emergence of weeds followed by a manual weeding at 30 DAP allows better control of weeding and improves the agronomic parameters of the rice.Keywords: weeds, rice, management practices, abundance-dominance, côte d’ivoir

Adventices hôtes alternatifs de virus en culture de solanaceae en Côte D’Ivoire

Un inventaire de la flore adventice a été effectué dans des parcelles de piment, tomate et aubergine à Divo, Sinfra et Djebonoua durant l'année 2013. Au cours de ce recensement, 31 échantillons de feuilles de mauvaises herbes présentant des symptômes de viroses ont été prélevés. Les espèces dont les feuilles ont été prélevées sont : d'Ageratum  conyzoides, Boerhavia diffusa, Chromolaena odorata, Euphorbia heterophylla, Croton hirtus. Ces échantillons ont été soumis au test DAS-ELISA en vue de la la détection des virus. Ce travail a permis d'identifier le Cumcumber mosaic virus (CMV), le Peper veinal mosaic virus (PVMV) et le Potato virus Y (PVYN) chez Chromolaena odorata. Ces virus sont responsables de dégâts importants en culture de Solanaceae. Les mauvaises herbes : Chromolaena odorata, Ageratum conyzoides,  Boerhavia diffusa, Croton hirtus et Euphorbia heterophylla sont des réservoirs de ces virus. Les résultats de la présente étude mettent en évidence le rôle des adventices dans le maintien et la dissémination des virus en culture de Solanaceae.Mots-clés : Adventice, CMV, PVMV, PVYN, Solanaceae

Short Intense Laser Pulse Collapse in Near-Critical Plasma

It is observed that the interaction of an intense ultra-short laser pulse with an overdense gas jet results in the pulse collapse and the deposition of a significant part of energy in a small and well localized volume in the rising part of the gas jet, where the electrons are efficiently accelerated and heated. A collisionless plasma expansion over 150 microns at a sub-relativistic velocity (~c/3) has been optically monitored in time and space, and attributed to the quasistatic field ionization of the gas associated to the hot electron current. Numerical simulations in good agreement with the observations suggest the acceleration in the collapse region of relativistic electrons, along with the excitation of a sizeable magnetic dipole that sustains the electron current over several picoseconds. Perspectives of ion beam generation at high repetition rate directly from gas jets are discussed

Estimating the net return of a remote calving alarm system in a dairy farm

The aim of the study was to evaluate the net return of the implementation of a remote calving monitoring system for obstetrical and neonatal assistance on the herd economy in a dairy farm model. A total of 680 parturitions over a 7-yr period were evaluated. Age at first calving was restricted from 23 to 27 mo for primiparous cows to be included. Among groups of cows that were ready to calve in a 15-d interval, primiparous and multiparous were randomly assigned to the experimental group and monitored through a calving alarm system, whereas the others accounted for controls. Final parturition groups were as follows: control primiparous (CPP, n = 218), control multiparous (CM, n = 345), monitored primiparous (MPP, n = 56), and monitored multiparous (MM, n = 61). Monitored groups received prompt calving assistance and first neonatal care, whereas the presence of farm personnel was discontinuous for controls. A biological model was built considering significant differences in calf loss, early culling, milk production, and days open between groups. Then, a partial budget model was used to estimate costs and net return on a simulated herd of 100 lactating cows. Incidence of calf death was greater in control groups (11.06% and 10.73% in CPP and CM, respectively) compared with monitored cows (0.00% and 1.69% in MPP and MM, respectively). Multiparous cows with calf loss had increased relative risk (relative risk = 3.487) for early culling compared with multiparous counterparts with no neonatal loss. Daily milk production in the first 2 mo was 3.79 kg greater in multiparous cows with no dead calf, compared with their counterparts. A significant difference in median days open was found in MPP and CPP (118 and 148 d, respectively). In the final economic model, different simulations were analyzed. They were created assuming different prices or hypothesizing calving monitoring only in primiparous animals. The model estimated different, but always positive, net return. In conclusion, implementing a calving alarm system led to a net return from \u20ac37 to 90 per cow per year (\u20ac1 = US$1.15 at the time of the study). However, the device alone is not sufficient: it must be supported by qualified calving monitoring and assistance. Optimized personnel presence in the calving area at the right time leads to prompt calving and neonatal calf assistance and colostrum feeding within the first hours of life, thus reducing calf death and days open, and increasing milk production

Investigation of rodent reservoirs of emerging pathogens in Côte d'Ivoire, West Africa

Background: One of the main health problems in West Africa remains upsurge of emerging pathogens. Ebola virus disease outbreak occurred in 2014 in Liberia, Guinea and Sierra Leone, Monkeypox virus in Nigeria in 2017 and most recently Lassa virus in Nigeria, Togo and Benin in 2018.  These pathogens have animal reservoirs as vectors for transmission. Proper investigation of the pathogens in their rodent vectors could help  reduce and manage their emergence and spread. Methodology: This study was conducted with an approval from the Côte d’Ivoire Bioethics Community. Small mammal trappings were carried out in  9 sites within three zones namely, peri-urban, peri-rural and protected areas. Liver, lung and kidney tissues from trapped small mammals were  sampled in accordance with the recommended conditions of biosafety and bioethics. The organs were transported in liquid nitrogen to the  laboratory. Molecular tests were used to detect pathogens. Orthopoxviruses and Monkeypox virus were detected in the organs by PCR using  consensus primers targeting the virus surface membrane haemagglutinin (HA) genes, while Leptospira species were detected by PCR using primers  targeting the rrs and lfb1 genes. Results: Out of 4930 night-traps, 256 (5.19%) small mammals were trapped including Crocidura, Rattus, Lophuromys, Praomys, Mus and Mastomys.  Leptospira species were detected in 6 genera from 7 study sites and the infected small mammals accounted for 13.3%. Leptospira sp was detected  mainly in the rodent vector genera Rattus (32.3%), Lophuromys (29.0%), and Praomys (16.1%). Three species of Leptospira were detected and  Leptospira interrogans was the most common frequent species (74.2%). Monkeypox virus was not detected from studied small mammals. Conclusion: The initial data from our investigation indicates the presence of Leptospira sp in rodent vectors, Rattus, Lophuromys and Praomys,  which are the potential small mammalian reservoirs of this pathogen in Cote d’Ivoire