Enquête séroépidémiologique de la rhinopneumonie des équidés en Tunisie

Une enquête séroépidémiologique, réalisée sur 789 équidés (400 élevés au Nord-Est de la Tunisie, 389 dans la région du Sahel et du Centre), a permis de détecter, par le test de fixation du complément, des anticorps spécifiques contre le virus de la rhinopneumonie équine. Les résultats ont montré que 15 équidés (1,9 %) étaient séropositifs, avec des taux variables d'anticorps fixant le complément. Ces résultats sont discutés en relation avec ceux obtenus par d'autres auteurs en Tunisie et dans les pays voisins

The Regulation of Ion Homeostasis, Growth, and Biomass Allocation in Date Palm Ex Vitro Plants Depends on the Level of Water Salinity

The date palm, a central plant in the fragile oasis ecosystem, is considered one of the fruit species most tolerant to salt stress. However, the tolerance mechanisms involved are yet to be addressed and their evaluation until now was mainly based on heterogenous plant material such as seedlings or limited to in vitro experiment conditions. For these reasons, we propose to deepen our knowledge of the morphological and physiological responses to salt stress using acclimated ex vitro plants resulting from the propagation of a single genotype. The plants were irrigated with 0, 150, 300, or 450 mM NaCl solutions for four months. Our results showed that the influence of water salinity on growth and ion-homeostasis regulation was very dependent on stress levels. The 150 mM NaCl concentration was found to improve dry biomass by about 35%, but at higher salt concentrations (300 and 450 mM) it decreased by 40–65%. The shoot:root dry mass ratio decreased significantly at the 150 mM NaCl water concentration and then increased with increasing water salt concentration. The leaf:root ratio for Na+ and Cl− decreased significantly with increasing water salinity up to a concentration of 300 mM NaCl, and then stabilized with similar values for 300 mM and 450 mM NaCl. In contrast to Na+ and Cl−, leaf K+ content was significantly higher in the leaf than in the root for all salt treatments. Unlike Na+ and K+, Cl− was expelled to the surface of leaves in response to increased water salinity. Overall, date palm plants appear to be more capable of excluding Cl− than Na+ and of changing biomass allocation according to salt-stress level, and their leaves and roots both appear to play an important role in this tolerance strategy.All authors are funded through the Small Research group project from the Deanship of Scientific Research at King Khalid University under research grant number (R.G.P.1/295/43).Peer reviewe

Differential effect of water salinity levels on gas exchange, chlorophyll fluorescence and antioxidant compounds in ex vitro date palm plants

In this study, the response to salt stress was evaluated in ex vitro acclimated date palm plants, regenerated from in vitro culture multiplication. The plants, eighteen-month-old, were irrigated with 0 (control), 150, 300 or 450 mM NaCl solutions (high to very high-water salinity). Photosynthesis parameters and antioxidant compounds were determined at the end of the experiment in leaves. At 150 mM NaCl, net CO2 assimilation rate and internal CO2 concentration were not impaired; while transpiration and stomatal conductance decreased by 60 and 70%, respectively. By increasing salt concentrations, all gas exchanges parameters were decreased. Measurement of chlorophyll fluorescence and P700 redox state showed that PSII and PSI machineries were significantly enhanced under 150 mM NaCl, conditions. With the 300 mM NaCl, the PSI parameters remained unchanged compared to control, while some of the PSII parameters, such as NPQ and Y (NPQ), were increased. At 450 mM NaCl, photosystems functionality was light intensity (PAR) dependent. Only at low PAR, a significant increase of some PSI and PSII parameters was observed. At the contrary, with high PAR, most of the energy conversion functions were significantly reduced, especially those related to PSI, indicating that PSI was more susceptible for damage by salinity than PSII. To overcome high salinity stress, ex vitro date palm plants mobilized a cascade of physio-biochemical pathways including the antioxidant activity and proline biosynthesis. Overall, the salinity of irrigation water, and up to 150 mM, improves the physiological performance of ex vitro date palm plants, which manage to tolerate very high levels of this stress.The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through the large research Groups projects (Project under grant number (RGP. 2/73/44)).Peer reviewe

Magnetocaloric properties in Ln(0.67)Ba(0.33)Mn(1-x)Fe(x)O(3) (Ln = La or Pr) manganites

International audienceWe have investigated the magnetocaloric properties of Ln(0.67)Ba(0.33)Mn(1-x)Fe(x)O(3) (Ln = La or Pr) manganites with x=0 and 0.05. All compounds present a maximum and large magnetocaloric effect near the Curie temperature (T-C). The associated maximum value of the magnetic entropy change, at 5 T applied change in the magnetic field, is 4.37 J.kg(-1).K-1 for Pr0.67Ba0.33MnO3 manganite with a T-C value of 205 K. The corresponding relative cooling power (RCP) reaches 230 J.kg(-1). All the samples present similar RCP values that are relatively high and are promising materials to be used in ecologically friendly magnetic refrigeration technology. Iron doping reduces both T-C and Delta S-M(max) and spreads the temperature working range with an almost constant RCP and can then be used to tune the working conditions of a refrigerator device. (C) 2011 Elsevier B.V. All rights reserved

Critical Behavior of La0.67Ba0.33Mn0.95Fe0.05O3 Manganite

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Magnetic Entropy Change by Mean-Field Theory for the Second-Order Phase Transition Manganite Nd0.6Sr0.3Ca0.1Mn0.975Fe0.025O3

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Above room temperature magnetocaloric effect in perovskite Pr0.6Sr0.4MnO3

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Effect of Fe doping on properties of Pr 0.67 Ba 0.33 Mn 1-x Fe x O 3 perovskites

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