Fitting lactation curves of dairy cattle in different types of herds in Tunisia

peer reviewedThe incomplete gamma function was used to fit lactation curves of Holstein-Friesian cows in four types of herds in Tunisia. A total of 8640 records were used in the analysis. These included 1269, 637, 239, and 498 first lactation and 2986, 1441, 650, and 920 second and later lactation records in four herd groups namely investors, state, cooperative, and farmers' herds, respectively. The effects of environmental variables, production sector, herd, parity, first test-day date, calving year, and calving season on the main lactation curve traits were analysed. The factors associated with milk yield at the beginning of lactation and the decreasing phase of the curve, persistency, and peak yield varied significantly (P<0.01) with all variables. The ascending phase of the lactation curve was not affected by parity and calving year, while days in milk until peak depended only on the rank of lactation. The state herds had the lowest peak and total yields. The summer season was unfavourable for milk production. In contrast to first lactation cows, third lactation cows had the highest peak and total yields. Milk yield was highly correlated with peak yield (r = 0.79) and was not related to persistency measure. (C) 2003 Elsevier B.V. All rights reserved

EFFECTS OF FEEDING SYSTEM AND BREED ON LAMB PRODUCTIVE AND CARCASS CHARACTERISTICS IN THE SOUTH MEDITERRANEAN REGION

The objective of this study was to evaluate the effect of feeding regimes and breed type on growth, non-carcass components and carcass characteristics of light lambs. Twenty four light lambs from the rustic fat-tailed Barbarine (BB) breed and 21 from the thin-tailed Sicilo-Sarde (SS) breed were used. For each breed, animals were divided into 3 groups (8 BB and 7 SS breed, each) by live weight (LW). Two groups were conducted on rotational grazing of barley grass (GB) or perennial ryegrass (GR) and received daily 350 g of concentrate per lamb. The last group was conducted on feedlot system (FL) with 450 g of ryegrass hay and 650 g of the same concentrate per lamb per day. The whole grass yield was 5 t DM/ha for ryegrass prairie and 4.2 for barley one. The final LW was higher for GB and GR lambs (28.3 kg) than for FL ones (26.9 kg). Irrespective to breed, the average daily gain was higher for both grazing groups than FL system, 144, 137 and 121 g for GR, GB and FL regimes, respectively. Slaughter LW was higher for BB (29.0 kg) than SS breed (26.5 kg). Barbarine lambs had more fat (23 vs. 17%) and less muscle (53 vs. 57%) than SS ones. FL lambs carcasses were more adipose (26%) than those of both grass groups (18%), while grass lambs had more muscle (57 vs. 51%). Grazing grass based diets increased carcass muscle and decreased fat proportions, which could be a useful feeding strategy to naturally manipulate lamb meat nutritional characteristics

Elimination of Nitrates Contained in Leachate by Adsorption on Mixture Bentonite-Lime and Sodium Bentonite

In this work, we studied the elimination possibility of the nitrate content in leachate of a technical burying centre (Boumergued / Algeria) by  adsorption on sodium bentonite  of Maghnia and mixture bentonite-lime. The tests have been realized in synthetic solutions of distilled water. The adsorption results show rapid kinetics at the ends of a duration exceeding 2 hours to sodium bentonite, this time decreases to 20 minutes for the bentonite-lime mixture, with elimination rates equal to 45% and 96% respectively

Conception et optimisation robuste des réseaux de télécommunications

Les réseaux de communication devenant de plus en plus présents dans nos activités quotidiennes, l'interruption ou une une dégradation significative des services fournis par le réseau deviennent de moins en moins tolérables. Une conception robuste des réseaux de communication, anticipant les pannes éventuelles d'équipements ou les variations du trafic, devient donc de plus en plus nécessaire. Cette thèse traite de plusieurs problèmes de conception et de planification robustes. Nous étudions tout d'abord le problème de la conception et du dimensionnement d'une topologie de communication résiliente et proposons un modèle de conception intégrant les coûts et contraintes des équipements ainsi que de nombreuses contraintes opérationnelles (nœuds potentiels, capacités modulaires, délais de communication). Un algorithme exact et deux approximations sont proposés pour résoudre ce problème. Les résultats numériques montrent que des économies substantielles peuvent être effectuées en intégrant les coûts d'équipements dans la phase amont de la conception. Les variations sur les volumes de trafic sont devenus un des problèmes majeurs auxquels sont confrontés les opérateurs. Il devient ainsi nécessaire d'intégrer explicitement l'incertitude sur la demande en trafic dans les problèmes de planification. Nous étudions deux problèmes d'optimisation robuste du routage : (1) le problème de conception des VPN dans le cadre du modèle hose et (2) le problème d'optimisation des métriques de routage IGP avec incertitude sur la demande. Nous formulons des modèles mathématiques de chacun de ces problèmes et proposons des heuristiques basées sur des techniques de recherche locale pour les résoudre.With communication networks getting more and more present in our daily activities, network outages or even significant degradations of the quality of service become less and less tolerable. This calls for a robust design of communication networks anticipating possible failures or shifts in the expected traffic demands. This thesis addresses several robust design and planning problems arising in the telecommunication area. We first address the problem of designing and dimensioning a survivable network topology. We propose a novel network design model integrating all equipment costs and constraints and including several operational constraints (potential nodes, modular capacities, delay constraints). One exact and two heuristic algorithms are proposed to solve this problem. Numerical results show that significant cost-savings can be achieved when equipment costs are taken into account in the early stages of the design process. The variation in traffic volumes has become one of the most important problems faced by network operators. Designing a network using a single ``busy hour'' traffic matrix more and more strains credibility due to the high volatility of traffic patterns. Thus, there is a need to incorporate demand uncertainty into the network routing problems explicitly. We study two robust route optimization problems: (1) the problem of VPN design under the hose model of demand uncertainty and (2) the problem of link weight optimization under demand uncertainty. We establish mathematical models for both problems and propose efficient approximation algorithms based on local-search techniques to solve them

Mise au point d’un protocole de recellularisation d’une matrice bronchique équine décellularisée

Les interactions entre la matrice extracellulaire et le muscle lisse jouent un rôle important dans l’asthme, principalement dans le remodelage bronchique asthmatique. Leur étude in vitro semble donner des résultats souvent non extrapolables in vivo, les modèles monocouches n’étant pas fidèles aux interactions tridimensionnelles se produisant du vivant des patients. Cette étude est une mise au point d’un protocole de décellularisation et de recellularisation d’une bronche équine par des cellules musculaires lisses bronchiques. Elle a pour but l’investigation d’une manière plus fidèle à un environnement in vivo de l’impact d’une matrice extracellulaire bronchique asthmatique sur la variation du phénotype des cellules musculaires lisses bronchiques et réciproquement. Une bonne décellularisation nous permettrait d’obtenir une bronche équine exempte de cellules, mais qui maintiendrait une architecture et une composition matricielle inchangées. L’élimination du matériel cellulaire est nécessaire afin de ne pas confondre les cellules natives du tissu avec les cellules de culture et de ne pas affecter la qualité de la recellularisation. Suite à la décellularisation d’une bronche équine au moyen du protocole Triton / Sodium déoxycholate, nous avons obtenu une bronche acellulaire (échafaud) présentant une très faible quantité d’ADN double brin (moins de 100 pg/100 mg de poids sec) et l’ADN restant était d’un poids moléculaire inférieur à 100 paires de bases. Cet échafaud a maintenu une très bonne architecture et un contenu protéique presque inchangé en collagènes, en fibronectine et en élastine. La recellularisation de cette matrice avec des cellules musculaires lisses bronchiques primaires a donné des résultats exploitables entre 31 et 41 jours de culture. L’évaluation histologique des recellularisations a montré une colonisation spécifique des cellules musculaires lisses bronchiques de la matrice du muscle lisse bronchique. Cette étude montre qu’il est possible de décellulariser une bronche tout en maintenant un contenu protéique et une architecture favorables à sa recellularisation par des cellules musculaires lisses bronchiques. Ceci représente une base valable pour l’étude subséquente de l’effet de la matrice extracellulaire asthmatique sur le phénotype des cellules musculaires lisses bronchiques.The interactions between the bronchial extracellular matrix and the bronchial smooth muscle contribute to the asthmatic bronchial remodeling. Results from in vitro studies indicate that the in vitro monolayer models do not recapitulate the complex interactions occurring in vivo. Decellularized tissues are natural three-dimensional matrices permitting the investigation of these interactions as closely as possible to the in vivo models. The aim of this study was to develop a protocol for the decellularization and recellularization of an equine bronchus by bronchial smooth muscle cells. Its purpose is to investigate how the asthmatic bronchial extracellular matrix affects the bronchial smooth muscle cells phenotype. A good decellularization is characterized by a respiratory bronchus completely free of cells while the architecture and the matricial composition remain unchanged. The elimination of the cellular material is necessary to not confound the native cells of the tissue with the cells of culture and to not affect the quality of the recellularization. Following the decellularization of an equine respiratory bronchus using Triton / Sodium deoxycholate protocol, we obtained an acellular bronchus (scaffold) presenting very low double-stranded DNA concentrations (less than 100 pg/100 mg dry weight) and the molecular weight of the remnant DNA was less than 100 base pair. This scaffold maintained a very good architecture and the protein content remained almost unchanged. The recellularization of this matrix gave usable results between 31 and 41 days. The histological evaluation of the recellularizations showed a specific colonisation of the muscular extracellular matrix by bronchial smooth muscle cells. This study shows that it is possible to decellularize an equine bronchus while maintaining a protein composition and an architecture favorable to its recellularization by bronchial smooth muscle cells. This represents a valid basis for the subsequent study of the effect of the extracellular asthmatic matrix on the smooth muscle cells phenotype

La qualité de gouvernance et le triangle croissance-inégalité-pauvreté

The main objective of the present study is to identify the mechanisms through which governance affects at the same time inequality, poverty and growth. The study covers the period 1996-2012 which corresponds to the adoption of the Millennium Development Goals (MDGs). The latter has, as a primary objective, reducing to a certain extent the proportion of people living in extreme poverty. To answer our research question, we use a structural model with simultaneous equations on Panel data. The results of the econometric estimates show that in the case of low-income countries, improving the quality of governance does not lead directly to the reduction of poverty. However, for middle-income countries with a certain level of economic development, poverty can be reduced through governance reforms. Indeed, at a certain level of development, the nature of the political regime, the political stability and the effectiveness of government can contribute to reducing poverty. In addition, our results show that governance variables have a dual effect. The first effect on economic growth is positive while the second effect on inequality is negative. These effects are found for the three groups under study

Modélisation et simulation de la structure de solidification dans les superalliages base-nickel : application AM1

AM1 is a nickel-based superalloy that Snecma relies on to elaborate single crystal turbine blades having complex geometry and high resistance to extreme conditions of temperature and pressure. However, controlling heat flux during solidification process is difficult because of many reasons such as the complex geometry, the way of clustering parts and the superalloy solidification kinetics. Consequently, stray grain nucleation can occur in the undercooling liquid. Therefore, it is important to precisely identify critical undercooled zones during solidification. To do this, a new coupling algorithm is integrated in Procast software through its CAFE module. This coupling considers liquid→solid transformation in solving thermal problem. Thus, predicted recalescence during stray grain nucleation can be observed. Enthalpy→temperature conversion is based on tabulated solidification paths depending on cooling rate computed at each Finite Element node. Solidification paths are calculated using a new microsegregation model based on total mass and solute mass conservation equations over a representative volume element. It includes both finite diffusion in phases and growth kinetics for multicomponent alloys. It is also coupled with a thermodynamic software for equilibrium computation. The microsegregation model fits experimental data provided by quenching tests on AM1 superalloy.L'alliage de première génération (AM1) est un superalliage base-nickel utilisé par la Snecma pour élaborer des aubes de turbine monocristallines de géométrie complexe capables de résister aux conditions extrêmes de température et de pression. Cependant, lors du procédé de solidification, le contrôle du flux de chaleur est difficile pour des raisons de complexité de la géométrie, de la mise en grappe des pièces ou de la cinétique de solidification de l'alliage. Par conséquent, le risque de germination parasite peut avoir lieu dans le liquide surfondu. Pour comprendre l'origine de la germination parasite, il est important d'identifier avec précision la variation des isothermes dans la pièce au cours de la solidification pour localiser les zones de surfusion critiques. Pour ce faire, nous avons prédit par simulation numérique la germination et la croissance des grains au cours de la solidification. Nous avons implémenté dans le module CAFE du code Procast un algorithme de couplage permettant de tenir compte de la transformation liquide→solide dans la résolution du problème thermique. Ce couplage a permis de prédire le phénomène de recalescence qui témoigne de la germination parasite. La conversion enthalpie→température dans ce couplage tient compte de plusieurs chemins de solidification qui dépendent du taux de refroidissement à chaque nœud du maillage éléments-finis. Ces chemins de solidification sont tabulés grâce à un nouveau modèle de microségrégation conçu pour les alliages multicomposés en solidification dendritique colonnaire et équiaxe. Ce modèle est basé sur les équations de conservation de la masse totale et de la masse des solutés moyennées sur un volume représentatif. Dans ce modèle, la diffusion des espèces chimiques est contrôlée dans toutes les phases. Le modèle est aussi couplé avec un logiciel de calcul thermodynamique et un modèle de cinétique de croissance dendritique conçu pour les alliages multicomposés. Les prédictions du modèle retrouvent d'expériences menées sur l'AM1

Sur la synthèse de commandes prédictives tolérantes aux défauts à base de modèles T-S flous

This thesis mainly focuses on Fuzzy Fault Tolerant Predictive Control for a class of nonlinear systems. The Takagi-Sugeno (T-S) fuzzy approach is introduced as a modelling technique in order to consider the active control methods adapted to linear models. To obtain the convex form, two approches are applied in this work, the proposed global non stationary linearization method and the sector nonlinearity approach. The contributions of this thesis and novelties with respect to other works are based on a combination between Parallel Distributed Compensation control law and Model Predictive Control where the T-S fuzzy aspect uses measured and unmeasured premise variables. The optimization problem is formulated as a quadratic programming problem. A nonlinear observer and A T-S fuzzy observer are designed for the proposed strategies, in order to estimate faults and system state variables. The controller and observer gains are obtained by solving Linear Matrix Inequalities (LMIs) derived from the Lyapunov theory. Convergences are performed by using Lyapunov asymptotic stability and L2 optimization. Actually, the use of the sector nonlinearity approach has reduced the conservatism related to the number of LMIs to solve. On top of that, the chosen form of the candidate function of Lyapunov and the T-S fuzzy structure have significantly decreased the pessimism of sufficient stability conditions derived from Lyapunov theories. The proposed Fuzzy model based predictive control is designed to achieve desired set points and control objectives in the the healthy operating and to accommodate and tolerate unexpected faults. Furthermore, the uncertain case and robustness with respect to constraints are investigated. The effectiveness and the validity of the proposed Fault Tolerant Control (FTC) strategies is illustrated through an application to an academic example and to a Diesel Engine Air Path (DEAP) system.Cette thèse porte sur la synthèse de lois de commande prédictive floue tolérante aux défauts pour les systèmes non linéaires modélisés selon l'approche dite T-S. Ma contribution est de proposer une FMPC (Fuzzy Model-based Predictive Control) visant à améliorer les performances d'un système non linéaire tout en respectant les contraintes sur la commande. L’optimisation de la commande nécessite la résolution d'un problème de programmation quadratique et une résolution d’inégalités matricielles linéaires (LMIs) dérivées des thèories de Lyapunov. La stratégie proposée a été appliquée en simulation à un système SISO non linéaire puis au système d'air d'un moteur Diesel en présence de défauts de type actionneur, capteur ou système, de perturbations et d'incertitudes de modélisatio

La qualité de gouvernance et le triangle croissance-inégalité-pauvreté

The main objective of the present study is to identify the mechanisms through which governance affects at the same time inequality, poverty and growth. The study covers the period 1996-2012 which corresponds to the adoption of the Millennium Development Goals (MDGs). The latter has, as a primary objective, reducing to a certain extent the proportion of people living in extreme poverty. To answer our research question, we use a structural model with simultaneous equations on Panel data. The results of the econometric estimates show that in the case of low-income countries, improving the quality of governance does not lead directly to the reduction of poverty. However, for middle-income countries with a certain level of economic development, poverty can be reduced through governance reforms. Indeed, at a certain level of development, the nature of the political regime, the political stability and the effectiveness of government can contribute to reducing poverty. In addition, our results show that governance variables have a dual effect. The first effect on economic growth is positive while the second effect on inequality is negative. These effects are found for the three groups under study