Etude des effets de l'installation de l'irrigation par aspersion en conditions d'irrigation paysanne andine – Cangahua – Equateur

Dans les Andes équatoriennes l'agriculture est en majorité pratiquée par de petits producteurs paysans. Ces agriculteurs font souvent partie de populations ayant été actrices de fortes luttes pour la terre et pour l'eau depuis le XXè siècl e. Dans la région de Cangahua (proche de Quito) la population vit entre 2800 et 3600 m d'altitude et bénéficie de l'eau d'irrigation depuis la fin des années 80. Pourtant la dotation en eau pour les familles est très basse. A partir des années 2000, un système d'irrigation par aspersion a été installé dans la plupart des communautés de Cangahua. La présente étude a pour objectifs d'analyser les effets de l'arrivée de l'irrigation par aspersion à l'échelle des communautés et à l'échelle des exploitations agricoles. Des enquêtes ont été menées auprès de 62 producteurs, 7 dirigeants de communautés et des ingénieurs d'une ONG locale. Au niveau des communautés, l'effet le plus mentionné est la baisse des conflits liés à l'eau. L'arrivée de l'irrigation par aspersion a également modifié les règles d'organisation au sein des communautés, le rôle de l'aiguadier et l'organisation des mingas (travaux collectifs). Quatre types de producteurs ont été identifiés dans la zone de l'étude : les éleveurs bovins laitiers, les producteurs d'oignons, les producteurs diversifiés et enfin les producteurs pluriactifs. Les effets de l'irrigation par aspersion varient suivant ces typologies : les agriculteurs ont augmenté la superficie irriguée et l'efficience de l'irrigation dans les exploitations et ont introduit de nouvelles productions. La sécurité de l'irrigation leur a apporté une confiance dan s la production agricole et ils s'impliquent davantage dans leur exploitation. A l'inverse, la baisse de la quantité de travail d'irrigation permet de gagner du temps libre, parfois utilisé par les producteurs pour avoir un emploi secondaire dans les entreprises de fleurs de la vallée ou le secteur de la construction dans les villes. L'arrivée de l'aspersion, si elle n'a pas impulsé de nouveau x processus dans la zone de l'étude, a modifié les trajectoires suivies par les producteurs. Ces trajectoires sont diverses et antagonistes : on observe des agriculteurs qui se spécialisent tandis que d'autres diversifient leur production, certains s'im pliquent d'avantage dans l'exploitation agricole alors que d'autres ont des emplois secondaires, et enfin certains investissent dans l'amélioration de leurs vaches laitières et d'autres dans des élevages de petits animaux comme les cochons d'inde ou les porcs. L'adoption massive de l'irrigation par aspersion dans ces communautés montre que les objectifs d'augmentation de la production et des revenus des agriculteurs sont globalement atteints. Il est cependant à noter que l'organisation de la Junta de Aguas et l'accompagnement des institutions de développement dans la mise en place de l'aspersion ont largement contribué à son adoption. Enfin, les effets dépendent aussi de facteurs explicatifs liés à la disponibilité des ressources naturelles, la capacité d'investissement, le niveau d'organisation de la communauté, sa situation géographique et son histoire. La présence de ces facteurs influence l'adoption de l'aspersion et le déroulement des processus en cours dans les communautés. Pour finir, la mise en place d'un nouveau système d'irrigation doit prendre en compte les dimensions de production et de commercialisation pour que le développement des communautés soit complet (Résumé d'auteur

Multiresidue determination of 256 pesticides in lavandin essential oil by LC/ESI/sSRM: advantages and drawbacks of a sampling method involving evaporation under nitrogen

The determination of 256 multiclass pesticides in lavandin essential oil has been performed by liquid chromatography–electrospray ionization tandem mass spectrometry using the scheduled selected reaction monitoring mode available on a quadrupole-linear ion trap mass spectrometer. With the aim of improving the limits of quantification (LOQs) of the target molecules, a sampling step based on evaporation of the essential oil under a nitrogen flow assisted by controlled heating was tested. The LOQs determined in this case were compared with the values obtained with the classic dilution preparation method. With sampling by dilution, 247 pesticides were detected and quantified at low concentration, with 74 % of the pesticides having LOQs of 10 μg L-1 or less. With the evaporation method, a global improvement of the LOQs was observed, with lower LOQs for 92 active substances and LOQs of 10 μg L-1 or less for 82.8 % of the pesticides. Almost twice as many active substances had an LOQ of 1 μg L-1 or less when the evaporation method was used. Some pesticides exhibited poor recovery or high variance caused by volatilization or degradation during the evaporation step. This behavior was evidenced by the case of thiophanate-methyl, which is degraded to carbendazim. Figure Sampling method by dilution or evaporation in the multiresidue determination of pesticides in essential oils by LC/M

Multiresidue Analysis of Multiclass Pesticides in Lavandin Essential Oil by LC/MS/MS Using the Scheduled Selected Reaction Monitoring Mode

In this paper we describe the development of the first multiclass pesticide residue method applied to essential oils. A total of 70 pesticides covering a wide range of polarity and currently used on essential oil crops have been included in the method. The procedure consists of a 10-fold dilution of lavandin essential oil followed by a direct injection analysis by liquid chromatography/tandem mass spectrometry. The system used is an API 4000 QTrap equipped with an electrospray ionization interface and operating in scheduled selected reaction monitoring acquisition mode. Matrix effects were evaluated by comparing the slopes of matrix-matched and solvent-based calibration curves. Weak signal suppression or enhancement (<20%) was observed for most of the compounds. Method sensitivity was determined statistically by the injection of five matrix-matched calibration curves with the distribution’s normality and the variance’s homogeneity checked before establishment of a suitable regression model. Limits of detection (LODs) and quantification (LOQs) were then determined using the blank standard’s deviation and the slope of the mean curve. The analytical method has been validated for 67 of the 70 pesticides and meets the following LOQs: ≤1 μg/L for 9 pesticides, ≤5 μg/L for 44, ≤10 μg/L for 9, and ≤20 μg/L for

Transmembrane potential polarization, calcium influx, and receptor conformational state modulate the sensitivity of the imidacloprid-insensitive neuronal insect nicotinic acetylcholine receptor to neonicotinoid insecticides

Neonicotinoid insecticides act selectively on insect nicotinic acetylcholine receptors (nAChRs). Recent studies revealed that their efficiency was altered by the phosphorylation/dephosphorylation process and the intracellular signaling pathway involved in the regulation of nAChRs. Using whole-cell patch-clamp electrophysiology adapted for dissociated cockroach dorsal unpaired median (DUM) neurons, we demonstrated that intracellular factors involved in the regulation of nAChR function modulated neonicotinoid sensitivity. DUM neurons were known to express two alpha-bungarotoxin-insensitive nAChR subtypes: nAChR1 and nAChR2. Whereas nAChR1 was sensitive to imidacloprid, nAChR2 was insensitive to this insecticide. Here, we demonstrated that, like nicotine, acetamiprid and clothianidin, other types of neonicotinoid insecticides, acted as agonists on the nAChR2 subtype. Using acetamiprid, we revealed that both steady-state depolarization and hyperpolarization affected nAChR2 sensitivity. The measurement of the input membrane resistance indicated that change in the acetamiprid-induced agonist activity was related to the receptor conformational state. Using cadmium chloride, omega-conotoxin GVIA, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-acetamide (LOE 908), we found that inhibition of calcium influx through high voltage-activated calcium channels and transient receptor potential gamma (TRPgamma) activated by both depolarization and hyperpolarization increased nAChR2 sensitivity to acetamiprid. Finally, using N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7), forskolin, and cAMP, we demonstrated that adenylyl cyclase sensitive to the calcium/calmodulin complex regulated internal cAMP concentration, which in turn modulated TRPgamma function and nAChR2 sensitivity to acetamiprid. Similar TRPgamma-induced modulatory effects were also obtained when clothianidin was tested. These findings bring insights into the signaling pathway modulating neonicotinoid efficiency and open novel strategies for optimizing insect pest control

Random laser action in self-organized para-sexiphenyl nanofibers grown by hot-wall epitaxy

We report on the observation of amplified spontaneous emission and random lasing in self-organized crystalline para-sexiphenyl nanofibers. Using subpicosecond excitation, a lasing threshold is observed on the 0-1 emission band near 425 nm at excitation fluences as low as 0.5 muJ/cm(2) (6x10(16) cm(-3) equivalent density), near the onset of density-dependent recombination processes. The dependence of the nonlinear emission spectrum on both the pump intensity and position of the excitation area are attributed to the interplay between random lasing and amplified spontaneous emission occurring along the nanofibers

Effect of thiamethoxam on cockroach locomotor activity is associated with its metabolite clothianidin

BACKGROUND: In the present study, the effect of thiamethoxam and clothianidin on the locomotor activity of American cockroach, Periplaneta americana (L.), was evaluated. Because it has been proposed that thiamethoxam is metabolised to clothianidin, high-performance liquid chromatography coupled with mass spectrometry was used to evaluate the amount of clothianidin on thiamethoxam-treated cockroaches. RESULTS: One hour after neonicotinoid treatment, the time spent in the open-field-like apparatus significantly increased, suggesting a decrease in locomotor activity. The percentage of cockroaches displaying locomotor activity was significantly reduced 1 h after haemolymph application of 1 nmol g(-1) neonicotinoid, while no significant effect was found after topical and oral administration. However, at 24 and 48 h, all neonicotinoids were able to reduce locomotor activity, depending on their concentrations and the way they were applied. Interestingly, it was found that thiamethoxam was converted to clothianidin 1 h after application, but the amount of clothianidin did not rise proportionately to thiamethoxam, especially after oral administration. CONCLUSION: The data suggest that the effect of thiamethoxam on cockroach locomotor activity is due in part to clothianidin action because (1) thiamethoxam levels remained persistent 48 h after application and (2) the amount of clothianidin in cockroach tissues was consistent with the toxicity of thiamethoxam

Intramolecular Cyclization of N-phenyl N'(2-chloroethyl)ureas leads to Active N-phenyl-4,5-dihydrooxazol-2-amines Alkylating β-Tubulin Glu198 and Prohibitin Asp40

International audienceThe cyclization of anticancer drugs into active intermediates has been reported mainly for DNA alkylating molecules including nitrosoureas. We previously defined the original cytotoxic mechanism of anticancerous phenyl '(2-chloroethyl)ureas (CEUs) that involves their reactivity towards cellular proteins and not against DNA; two CEUs subsets have been shown to alkylate β-tubulin and prohibitin leading to inhibition of cell proliferation by G/M or G/S cell cycle arrest. In this study, we demonstrated that cyclic derivatives of CEUs, -phenyl-4,5-dihydrooxazol-2-amines (Oxas) are two to threefold more active than CEUs and share the same cytotoxic properties in B16F0 melanoma cells. Moreover, the CEU original covalent binding by an ester linkage on β-tubulin Glu198 and prohibitin Asp40 was maintained with Oxas. Surprisingly, we observed that Oxas were spontaneously formed from CEUs in the cell culture medium and were also detected within the cells. Our results suggest that the intramolecular cyclization of CEUs leads to active Oxas that should then be considered as the key intermediates for protein alkylation. These results could be useful for the design of new prodrugs for cancer chemotherapy

Développement d'outils microbiologiques et chimiques permettant d'identifier l'origine des pollutions fécales dans les eaux de baignades

La pollution organique issue des effluents d'élevage et des stations d'épuration urbaines conduit à un problème essentiel de santé publique lié à la contamination des eaux de surface où s'exercent des activités sensibles telles que la baignade. S'il est possible de déterminer les pollutions localisées liées à un dysfonctionnement des systèmes de traitement, il est beaucoup plus difficile d'identifier les pollutions organiques diffuses qui participent pourtant majoritairement à la dégradation de la qualité des eaux de surface. La problématique des pollutions diffuses est d'autant plus importante que la nouvelle réglementation européenne concernant les eaux de baignade (Directive 2006/7/CE) demande de constituer des profils de baignade qui nécessitent une identification et une hiérarchisation des sources de pollutions fécales. Le dénombrement de Escherichia coli et des entérocoques intestinaux stipulé par les textes réglementaires européens, représente actuellement le seul outil analytique permettant la mise en évidence d'une contamination fécale du milieu aquatique, sans toutefois différencier l'origine humaine ou animale de cette contamination. Il est donc nécessaire de développer de nouvelles méthodes de détection de la pollution fécale qui puissent non seulement mettre en évidence une contamination mais aussi en indiquer l'origine. C'est d'ailleurs dans cet objectif que s'est développé depuis quelques années, le concept de "Microbial Source Tracking" ("Traceurs de Sources Microbiennes") qui consiste à identifier à l'aide de marqueurs microbiologiques ou chimiques les sources de pollutions fécales. Dans ce contexte, six laboratoires de recherche se sont associés pour développer des techniques de traçage des contaminations fécales afin de proposer un outil opérationnel utilisable pour différencier les sources de pollution, de leur point d'émission jusqu'au milieu récepteur final que constituent les eaux de surface. Les marqueurs qui ont fait l'objet de cette étude sont des molécules chimiques naturelles (stéroïdes, caféine), des molécules de synthèse retrouvées dans les effluents de stations d'épuration ou des rapports de fluorescence de la matière organique ainsi que des micro-organismes (bactériophages, bactéries). A la suite des développements méthodologiques, plusieurs marqueurs ont été sélectionnés : - bactéries appartenant aux groupes bactériens dominants du tractus intestinal humain (Bifidobacterium adolescentis) et porcin (Lactobacillus amylovorus) ; - Bacteroidales spécifiques des humains, porcins et bovins (HF183, Pig-2-Bac, Rum-2-Bac); - génogroupes humains des bactériophages F ARN spécifiques; - rapports de stéroïdes : coprostanol/(24ethylcoprostanol+coprostanol) (R1) et sitostanol/coprostanol (R2); - caféine, benzophénone et tri(2-chloroethyl)phosphate (TCEP)

A cultural kaleidoscope: managing the European company

This thesis provides a comparative study of managerial practices in Europe. Patterns of behaviour and preferred modes of organisation are identified in four countries, based on an in-depth case study of a chosen/specific European company. While the corporate culture and industry remain constant, national context manifests itself as the essential variable between the different operations. The thesis proposes/argues that this factor — national context — is a powerful variable which frames the activity of management. Europe is a continent of diversity; each nation has unique traditions, particular historical and cultural roots as well as its own institutional framework. This diversity means that managers learn to operate in a manner that suits their particular context. The thesis documents such national divergence in terms of managerial practices and behaviour. The processes of integration of European Union member States and of globalisation also contribute towards the shaping of management. The case study company, as a leading provider of Information Technology services, is among the avant-garde pioneers of a technological, borderless world. Common pressures affecting managers across the board — and thus regardless of national context — are also identified: these include the pressure to achieve profit and efficiency. In addition, a degree of convergence between human resource management policies and practices also makes itself visible. The thesis demonstrates, above all, the influence of national culture and national environment vis-à-vis management; an argument which may be reaffirmed given the context of globalisation. In brief, a European company is a cultural kaleidoscop

TSF experiment for comparison of high Reynolds number turbulence in both HeI and HeII: First results

International audienceTSF experiment for comparison of high Reynolds number turbulence in both HeI and HeII: First result