The structure and photoluminescence of a ZnO phosphor synthesized by the sol gel method under praseodymium doping.

This work outlines some interesting results regarding the effects of Pr3+ substitution on the structural and optical properties of (x = 0 and 0.02) samples. Our samples were synthesized using the Pechini sol-gel method. The structural study using Rietveld refinement of XRD patterns showed a hexagonal structure with the P63mc space group for all the samples and also the existence of a secondary phase attributed to the praseodymium oxide (Pr6O11) for 2% wt Pr-doped ZnO. The refinement results revealed that both the lattice parameter and the unit cell volume increase with the increase of Pr content. X-ray peak broadening analysis was used to evaluate the crystallite size and lattice strain by the Williamson-Hall (W-H) method and size-strain plot method (SSPM). The physical parameters such as strain, stress and energy density values were also calculated using the W-H method with different models, namely uniform deformation model (UDM), uniform stress deformation model (USDM) and uniform deformation energy model (UDEDM). The obtained results showed that the mean particle size of the ZnO and Pr0.01Zn0.97O estimated from W-H analysis and the SSPM method are highly intercorrelated. Shifting of the absorption edge to lower wavelength and blue shift of the band gap are observed in the UV-visible spectra of Pr-doped ZnO samples. Particular emphasis was put on the PL measurements of such composites. A noticeable decrease of the maximum intensity of PL response was found after adding Pr3+ to ZnO. This finding is discussed in terms of the photo excited limitation of electron-hole pairs in such nanocomposites.

Study of diffuse phase transition and relaxor ferroelectric behavior of Ba0.97Bi0.02Ti0.9Zr0.05Nb0.04O3 ceramic.

In the present work, structural and dielectrics properties of polycrystalline sample Ba0.97Bi0.02Ti0.9Zr0.05Nb0.04O3 (BBTZN) prepared by a molten-salt method were investigated. X-ray diffraction analyses revealed the formation of a single-phase pseudocubic structure with a Pm3̄m space group. Unlike the trend observed in classic ferroelectrics, the temperature dependence of the dielectric constants showed the presence of three sequences of structural phase transitions. In fact, the local disorder provides a frequency dependent relaxor like behaviours attributed to the dynamic of polar nanoregions (PNRs). The diffuse phase transition (DPT) analyzed using the modified Curie-Weiss law and Lorenz formula confirms the presence of short-range association between the nanopolar domains. The obtained values of the degree of diffuseness are found to be in the range of 1.58-1.78 due to the existence of different states of polarization and, hence, different relaxation times in different regions. The frequency dependence of temperature at dielectric maxima, which is governed by the production of PNRs at a high temperature, satisfies the Vogel-Fulcher (V-F) law. The temperature dependence of the electric modulus for various frequencies indicating a thermally activated relaxation ascribed to the Maxwell-Wagner (M-W) space charge relaxation phenomenon.

Critical phenomena and estimation of the spontaneous magnetization from a mean field analysis of the magnetic entropy change in La0.7Ca0.1Pb0.2Mn0.95Al0.025Sn0.025O3.

In the present work, we have studied the universal critical behavior in the perovskite-manganite compound La0.7Ca0.1Pb0.2Mn0.95Al0.025Sn0.025O3. Experimental results revealed that all samples exhibit a second-order magnetic phase transition. To study the critical behavior of the paramagnetic-ferromagnetic transition, various techniques such as modified Arrott plots, the Kouvel-Fisher method and critical isotherm analysis were used to determine the values of the Curie temperature T C, as well as the critical exponents ß (corresponding to the spontaneous magnetization), γ (corresponding to the initial susceptibility) and δ (corresponding to the critical magnetization isotherm). The critical exponent values for our sample are consistent with the prediction of the mean field model (ß = 0.46, γ = 1.0, and δ = 2.94 at an average T C = 302.12 K), indicating that the magnetic interactions are long-range. The reliability of the critical exponent values was confirmed by the Widom scaling relation (WSR) and the universal scaling hypothesis. Moreover, to estimate the spontaneous magnetization of La0.7Ca0.1Pb0.2Mn0.95Al0.025Sn0.025O3 perovskite, we used the magnetic entropy change (ΔS M), obtained from isothermal magnetization. The results obtained through this approach are compared to those obtained from classical analysis using Arrott curves. An excellent agreement is found between this approach and the one obtained from the extrapolation of the Arrott curves.

Early establishment response of different Pinus nigra ssp. salzmanii seed sources on contrasting environments: Implications for future reforestation programs and assisted population migration.

Forest restoration constitutes an important issue within adaptive environmental management for climate change at global scale. However, effective implementation of these programs can only be achieved by revising current seed transfer guidelines, as they lack inherent spatial and temporal dynamics associated with climate change. In this sense, provenance trials may provide key information on the relative performance of different populations and/or genotypes under changing ecological conditions. This study addresses a methodological approach to evaluate early plantation performance and the consequent phenotypic plasticity and the pattern of the adaptation of different seed sources in contrasting environments. To this end, six seed sources of Salzmann pine were tested at three contrasting trial sites testing a hypothetical assisted population migration. Adaptation at each site was assessed through Joint Regression and Additive Main effect and Multiplication Interaction (AMMI) models. Most of the observed variation was attributed to the environment (above 90% for all traits), even so genotype and genotype by environment interaction (GxE) were significant. Seedlings out-planted under better site conditions did not differ in survival but in height growth. However, on sites with higher constraints, survival differed among seed sources and diameter growth was high. The adaptation analyses (AMMI) indicated that the cold-continental seed source 'Soria' performed as a generalist seed source, whereas 'Cordilleras Béticas', the southernmost seed source, was more adapted to harsh environments (frost and drought) in terms of survival. The results supported partially the hypothesis that assisted migration of seed sources makes sense within limited transfer distances, and this was reinforced by the GxE results. The present study could be valuable to address adaptive transfer of seedings in ecological restoration and to determine the suitable seed sources for reforestation programs and assisted population migration under climatic changes. The reported results are based on 3 years' data and need to be considered in this context.

Protective effect of Enterococcus faecalis DAPTO 512 on the intestinal tract and gut mucosa: milk allergy application.

The allergenicity of ß-lactoglobulin (ß-Lg) was studied by using Ussing chamber in a murine model of ß-Lg allergy supplemented with hydrolysates obtained after fermentation of milk for 48 h at 37 (°)C with Enterococcus faecalis DAPTO 512, isolated from cow milk and identified by 16S rDNA sequence analysis. Balb/c mice were sensitised intraperitoneally with ß-Lg. Three groups of mice were formed: group 1, composed of naive mice used as control received only NaCl; group 2, positive control composed of mice sensitised intraperitoneally with ß-Lg; group 3, formed by mice which were given hydrolysates of 48 h then sensitised with ß-Lg. After 48 h of fermentation ß-casein and ß-Lg were degraded by E. faecalis DAPTO 512. ß-Lg immunisation was associated with strong IgG and IgE production in case of positive controls and a significant increase in short current circuit (Isc) and high conductance (G) responses were observed. The control and the hydrolysate groups showed a significant decrease in the production of IgG and IgE anti ß-Lg compared to the positive control. The allergenic potential of ß-Lg was markedly reduced in the group that received hydrolysates (Isc and G remained unchanged after intestine challenge with ß-Lg). The histological scrutiny showed villi atrophy, lymphocyte hyperplasia and a significant chorion detachment in the positive control group. In the group administered with hydrolysates of fermented milk, inflammatory signs were lower, the villi were long and thin and lymphocytes were less dense. The results showed that feeding of milk fermented with E. faecalis DAPTO 512 during 18 days prior to ß-Lg allergy induction exerts a protecting effect on the murine intestine and induces a significant decrease in the ß-Lg allergenicity.

[Experience with the regionalization of transfusion advice]. / Expérience de régionalisation du conseil transfusionnel.

We represent an organization of transfusionnel advice at a regional level and we develop arguments and stages having allowed us to lead to this choice. This target was reached in two stages, which took place over 3 years. The regional transfusionnel advice leans on three fundamental points: a planned permanent organization, skilled and formed actors as well as adapted tools. Tending to a homogeneous organization between every blood bank center seems to be coherent towards the current configuration of blood donation in France.