Incorporating risk attitudes in an irrigation reservoir management model

Thesis develops a technique whereby the attitudes towards risks of decision makers could be incorporated into a stochastic dynamic programming model of a reservoir by identifying the optimal release policy for the reservoir.Development of optimal release policies for reservoirs with explicit recognition of the stochastic environment, e.g., uncertainty in future inflows, in which reservoirs must operate has been dominated by optimisation models which use summative measures of reservoir performance, e.g., expected benefits or costs. This study argues that these existing summative metrics do not adequately represent the desirability of a release strategy, and that they only constitute a nominally 'rational' decision making approach which may in fact be at odds with the true attitudes of the decision maker(s) towards the risk aspects of the decisions associated with that strategy. This situation is particularly relevant for reservoirs designed and operated to supply water to irrigation projects. In irrigation projects the possibility of individual farm bankruptcies arising from crop failure due to short-term water shortage must be balanced against maximising long-term benefits. A means for a more complete representation and evaluation of the possible consequences (likelihoods and magnitudes of a range of outcomes) associated with a release decision is therefore necessary. A model capable of replicating the manner in which risks associated with reservoir release decisions are perceived, interpreted and compared by a decision maker is proposed. The model is based upon Neural Network (NN) theory, and enables the more complete representation of the risk function of a particular decision to be considered in making decisions on reservoir releases. The neural network used to perform the decision making process is a feed-forward back-propagation network. The use of a more complete representation of the risks associated with the decisions in a release policy has been limited by existing optimisation frameworks. However this decision-making model is able to be used in a Stochastic Dynamic Programming (SDP) approach to give a Neural Network -Stochastic Dynamic Programming (NN -SDP) model. The resulting integrated model allows the attitudes towards risk of a decision maker to be considered explicitly in defining the optimal release policy. At each stage of the dynamic program, a risk curve is developed for each of the candidate release decisions. The neural network then selects the 'best' risk curve, and thereby the optimal release decision, through a pair-wise comparison process of these risk curves. Training of a neural network to perform this task is achieved using pairwise comparisons elicited from a decision maker a priori. The approach is demonstrated by application to the Fairbairn reservoir in Central Queensland, Australia. Release policies based on the risk preferences of three different decision makers were derived for this reservoir. Comparisons were then conducted against an optimal policy obtained using a SDP model with an objective function based on the more traditional expected squared deficit from target. The release policies reflecting the risk preferences of each of the three decision makers, and derived from the NN -SDP formulation, exhibited hedging and maintained the reservoir at levels higher than those associated with an operation policy defined solely by the expected squared deficit objective function. These results are consistent with previous studies on risk perceptions of decision makers which indicate that farmers tend to be risk averse. The NN -SDP model, and particularly its ability to consider a more comprehensive interpretation of risk in the development of water allocation and water release policies, is a significant step towards improving the ability of water resource managers to reflect and model risk more appropriately in the mathematical models used to identify optimal operating policies for reservoir systems

Impact des mutations OPG chez Erwinia chrysanthemi (recherche de suppresseurs et analyse protéomique des mutants)

Erwinia chrysanthemi est une entérobactérie phytopathogène pectinolytique faisant partie de la subdivision g des protéobactéries. Elle infecte un large spectre de plantes hôtes engendrant la pourriture molle. L'apparition de cette pourriture molle dépend de la synthèse et de la sécrétion d'une batterie d'exoenzymes (cellulases, protéases et pectate-Iyases) capable de dégrader les composants de la paroi des cellules végétales. Néamnoins, l'expression de nombreux autres gènes est nécessaire à la virulence de cette bactérie. En effet, les mutants déficients en glucanes périplasmiques osmorégulés (OPG) d'E. chrysanthemi sont totalement non virulents. Les OPG sont constitués de 5 à 12 résidus de glucose liés en b,1-2, branchés en b,1-6 et sont d'autant plus abondants que l'osmolarité du milieu est faible. Ces mutants présentent un phénotype pléïotrope: ils sont hypersensibles aux sels biliaires, la synthèse d'exopolysaccharides est augmentée, la synthèse et la sécrétion d"exo-enzymes ainsl que la motilité sont réduites. Un phénotype similaire, mais atténué, est observé chez les mutants du système ToI. Les OPG comme les protéines ToI apparaissent nécessaires au maintien de l'intégrité de l'enveloppe. Des mutations suppressives restaurant la motilité des mutants opg ont été isolées. Elles rétablissent l'essentiel du phénotype sauvage (virulence sur tubercules de pommes de terre, sécrétion des exo-enzymes, résistance aux sels biliaires, colonies redevenues non muqueuses et motilité, à l'exception de la virulence sur feuille d'endive). Une des mutations identifiées rcsC2 supprime également les phénotypes des mutants toI.Cette mutation rcsC2 affecte un système capteur-régulateur rcsBCD impliqué dans la régulation de gènes cibles en réponse à un ou des signaux de nature inconnue et nécessaire au pouvoir pathogène des bactéries chez les animaux et chez les plantes. Les fonctions des gènes cibles régulés par ce système, correspondent pour une grande part aux fonctions altérées par l'absence d'OPG chez E. chrysanthemi. Ces résultats nous laissent penser que les OPG pourraient être une des molécules captées par le système RscBCD. De plus, en parallèle à cette étude, une analyse protéomique comparative du mutant opgG par rapport à la souche sauvage d'E. chrysanthemi, nous a permis de mettre en évidence une altération importante des fonctions cellulaires allant des structures de l'enveloppe qui était notre seule hypothèse quant à l'impact de l'absence d' OPG, mais nous constatons également une altération d'expression des protéines du métabolisme énergétique, de certains systèmes de transport et de protémes impliquées dans la dégradation et la conformation des protéines souvent induites en réponse à divers stress. L'ensemble de ces résultats nous laisse penser que les OPG pourraient être des molécules captées par un jeu de systèmes à deux composants afin de permettre à la bactérie de répondre à une multitude de stress rencontrés dans l' environnement.LILLE1-BU (590092102) / SudocSudocFranceF

La chimiothérapie néoadjuvante associée à une radiothérapie stéréotaxique isotoxique à hautes doses (iHD-SBRT) augmente-t-elle les complications postopératoires après duodénopancréatectomie céphalique (DPC) pour cancer du pancréas ?

info:eu-repo/semantics/publishe

A Localized Phage-Based Antimicrobial System: Effect of Alginate on Phage Desorption from β-TCP Ceramic Bone Substitutes

Tricalcium phosphate (TCP) is a prosthetic material commonly used as a bone substitute to repair osteoarticular diseases and injuries. In this type of bone reconstruction surgery, antibiotics remain the common preventive and therapeutic treatment for bacterial infection. Nevertheless, the emergence of multi-resistant strains requires complimentary or alternative treatments. Today, one of the promising alternative approaches is phage therapy. Phages are bacterial viruses that have several advantages over chemotherapy, such as the specificity of bacterial strain, the absence of side effects, and a rapid response. In this work, we studied the impact of alginate hydrogels for overlaying λvir-phage-loaded β-TCP ceramic bone substitutes, delaying the phage desorption. The results show that the use of a 1% alginate–CaCl2 hydrogel overlapping the β-TCP ceramic pellets leads to higher initial phage concentration on the material and extends the released time of phages to two weeks when compared with control pellets. These alginate-coated biomaterials also generate faster bacterial lysis kinetics and could therefore be a good practical prosthetic device for bone and joint surgeries by allowing local treatment of bacterial infections with phage therapy for a longer period of time

No evidence for the presence and control of tumor growth by cytoplasmic stress granules in pancreatic cancer

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Level of contamination and impact of pesticides in cupped oyster, Crassostrea gigas , reared in a shellfish production area in Normandy (France)

International audienc

What Should Guide the Performance of Venous Resection During Pancreaticoduodenectomy for Pancreatic Ductal Adenocarcinoma with Venous Contact?

Complete surgical resection, most often associated with perioperative chemotherapy, is the only way to offer a chance of cure for patients with pancreatic cancer. One of the most important factors in determining survival outcome that can be influenced by the surgeon is the R0 resection. However, the proximity of mesenteric vessels in cephalic pancreatic tumors, especially the mesenterico-portal venous axis, results in an increased risk of vein involvement and/or the presence of malignant cells in the venous bed margin. A concomitant venous resection can be performed to decrease the risk of a positive margin. Given the additional technical difficulty that this implies, many surgeons seek a path between the tumor and the vein, hoping for the absence of tumor infiltration into the perivascular tissue on pathologic analysis, particularly in cases with administration of neoadjuvant therapy. The definition of optimal surgical margin remains a subject of debate, but at least 1 mm is an independent predictor of survival after pancreatic cancer surgical resection. Although preoperative radiologic assessment is essential for accurate planning of a pancreatic resection, intraoperative decision-making with regard to resection of the mesenterico-portal vein in tumors with a venous contact remains unclear and variable. Although venous histologic involvement and perivascular infiltration are not accurately predictable preoperatively, clinicians must examine the existing criteria and normograms to guide their surgical management according to the integration of new imaging techniques, preoperative chemotherapy use, tumor biology and molecular histopathology, and surgical techniques.info:eu-repo/semantics/publishe

La difficile appréciation de la « valeur égale » d'un travail : un arrêt peu compréhensible

International audienceSoc. 26 juin 2008, pourvoi n° 06-46.204, à paraître au Bulleti

Intensified neoadjuvant treatment sequence with chemotherapy followed by SBRT for a borderline resectable pancreatic cancer: a plea for prospective evaluation.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death and its 5-year overall survival is poor. Surgery remains the only curative treatment but less than 20% of the patients are resectable at diagnosis. New treatment options for the management of metastatic disease have recently emerged, and with them the question of their use in preoperative strategy. Neoadjuvant sequence may increase the achievement of R0 resection margins in borderline resectable tumours but also the proportion of patients who will receive chemotherapy. We report a case of borderline resectable PDAC treated with duodenopancreatectomy after neoadjuvant treatment consisting of chemotherapy and SBRT.info:eu-repo/semantics/publishe