Effect of zinc and iron on the (micro-)structure and copper charge excess of the YBaCuO superconductor

Samples of YBa₂(Cu_1–y Zn _y )₃O_7–y and YBa₂(Cu_1–y Fe _y )₃O_7+x , withy in the range 0.0–0.16 for zinc and 0.0–0.30 for iron were synthesized by solid-state reaction. The solubility limit has been found to be equal to 7% and 19 at % for zinc and iron, respectively. Zinc has little effect on the structure which remains orthorhombic throughout all the zinc concentration range, while iron induces an important structural modification (tweed structure formation). Both impurities induce grain-growth inhibition but densification appears to be independent of the impurity content with respect to the undoped material. However, iodometry shows that the oxygen stoichiometry decreases in zinc-doped samples while it increases in iron-doped samples. Charge balance resulting from the dopant charge and the evolution of the copper charge with doping have been invoked. In zinc-doped samples, the copper charge excess (copper charge fraction>2) decreases sharply for 0.0y<0.04, then it shows a plateau-like behaviour for 0.04y<0.06, while in iron-doped samples, it decreases almost monotonically. Confirming some of our previous results there is a correlatedT _c decrease in the case of zinc-doped samples (occurrence of aT _c plateau) and in the case of iron-doped samples (quasi monotonical decrease). This difference has been interpreted in terms of structural changes related to the different substitution behaviour of zinc and iron.     

Replication-Deficient Lymphocytic Choriomeningitis Virus-Vectored Vaccine Candidate for the Induction of T Cell Immunity against Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) represents a major burden to global health, and refined vaccines are needed. Replication-deficient lymphocytic choriomeningitis virus (rLCMV)-based vaccine vectors against cytomegalovirus have proven safe for human use and elicited robust T cell responses in a large proportion of vaccine recipients. Here, we developed an rLCMV vaccine expressing the Mtb antigens TB10.4 and Ag85B. In mice, rLCMV elicited high frequencies of polyfunctional Mtb-specific CD8 and CD4 T cell responses. CD8 but not CD4 T cells were efficiently boosted upon vector re-vaccination. High-frequency responses were also observed in neonatally vaccinated mice, and co-administration of rLCMV with Expanded Program of Immunization (EPI) vaccines did not result in substantial reciprocal interference. Importantly, rLCMV immunization significantly reduced the lung Mtb burden upon aerosol challenge, resulting in improved lung ventilation. Protection was associated with increased CD8 T cell recruitment but reduced CD4 T cell infiltration upon Mtb challenge. When combining rLCMV with BCG vaccination in a heterologous prime-boost regimen, responses to the rLCMV-encoded Mtb antigens were further augmented, but protection was not significantly different from rLCMV or BCG vaccination alone. This work suggests that rLCMV may show utility for neonatal and/or adult vaccination efforts against pulmonary tuberculosis.     

Antioxidative effect of compounds isolated from Globularia alypum L. structure-activity relationship

The antioxidant activity of the Globularia alypum phytochemicals were evaluated for their capacity to scavenge the 1,1-diphenyl-2-dipicrylhydrazyl (DPPH°) free radical and some structure-activity relationships were obtained. Assay guided fractionation led to the isolation of syringin, four phenylethanoids, four flavonoids and six iridoids as the main constituents of the extract and their antioxidant activity was determined. The obtained results showed that the activity towards the DPPH° free radical was mainly due to the flavonoid and phenyl ethanoid constituents which were most active free radical scavengers than iridoids. Among the tested flavonoids, 6-hydroxyluteolin glycosides showed the strongest activity, suggesting that the presence of the 6-hydroxyl group was a favourable structural feature of flavonoids with regard to DPPH° scavenging effect. The isolated phenylethanoid glycosides all showed potent antioxidant activity and their capacity to scavenge free DPPH° radical was greater than BHT. Their high antioxidant activity could be attributed to the caffeoyl moieties contained in them, while iridoids showed moderate free radical scavenging activity. The obtained results demonstrated that some of the isolated compounds play an important role for the antioxidant activity of G. alypum and give a scientific basis to the use of this plant in traditional medicine. The hydromethanolic extract of G. alypum could thus be considered as a source of potential antioxidants and will promote the reasonable usage of this plant in food technology and processing as well as for medical use.     

Microscopic Origin of the PTC Effect in Niobium-Doped Barium Titanate

The influence of bulk conductivity on the PTC effect of Nb-doped barium titanate is investigated. Both macroscopic and microscopic resistance measurements are performed as a function of temperature. The macroscopic measurement refers to the whole sample while the microscopic one, obtained by photolithography techniques, concerns only several grains. The results show that the increase of resistivity occurs in two steps: first, an abrupt variation at the Curie temperature T_c which is ascribed to the phase transition in the bulk; second, a continuous increase above T_c which is usually explained from grain boundary potential barriers only. However, our results suggest that a nonnegligible contribution of the bulk is also involved in this increase above T_c .     

Dietary factors associated with obesity indicators and level of sports participation in Flemish adults: a cross-sectional study

Background  

Obesity develops when energy intake continuously exceeds energy expenditure, causing a fundamental chronic energy imbalance. Societal and behavioural changes over the last decades are held responsible for the considerable increase in sedentary lifestyles and inappropriate dietary patterns. The role of dietary fat and other dietary factors in the aetiology and maintenance of excess weight is controversial. The purposes of the present study were to investigate the dietary factors associated with body mass index (BMI) and waist circumference (WC), and to analyse whether dietary intake varies between subjects with different levels of sports participation.     

Influence of Iron Doping on the Microstructure of YBa2(Cu1−xFex)3O7−δ Ceramics

Porosity, grain growth, phase composition, and microstructural defects were studied in sintered YBa₂ (Cu_1−x)₃O_7−x ceramics for x values up to 0.3. The porosity of the samples, related to the sintering mechanism, was independent of iron concentration. A linear dependence of the grain size with the inverse of the iron concentration was found, strongly suggesting grain boundary segregation of iron. The solubility limit was estimated to be x = 0.18 at 950°C in O₂. Beyond this limit, a new microstructural component was found consisting of YBa₂(Cu_1−xFe_x)₃O_7−δ, YBaCuFeO₅ and Ba(Cu,Fe)O₂. The transition from an orthorhombic twin to an orthorhombic tweed phase and a tetragonal phase was detected by polarized light microscopy.     

Controlling stabilization of oil-in-water emulsions with lignins through fractionation,functionalization, and formulation

Lignins, heterogeneous assemblies of polyphenolic oligomers present in lignocellulosic plant biomass, are valorized mainly by combustion because of their low solubility in commonly used solvents. However, in addition to antioxidant, anti-UV and antimicrobial properties, and marked interfacial properties are part of lignins physicochemical properties, thus making them good candidates for sustainable colloids. It is hypothesized that lignins solubility and emulsifying performances could be modulated by fractionation, functionalization, and formulation strategies. The importance of the solvent, and of the pH on lignins solubilization in aqueous phase was investigated. Accordingly, simple O/W emulsions stabilized by different lignins were designed and characterized. The whole results demonstrated that lignins solubility in water can be optimized using appropriate co-solvent and pH readjustment resulting in a homogeneous dispersion with only 7.2 ± 1.8% wt/wt of insoluble lignins. Both fractionation and biocatalytic modification of lignins allowed increasing stabilization of the oil–water interface by limiting coalescence (23%–24% of relative increase of the D90) compared with non-fractionated lignins (32%), thus advocating their potential use as multifunctional emulsion stabilizers. As a result, a direct link between the molar mass profile of lignins and their ability to stabilize the oil–water interface as well as to reduce emulsion's sedimentation could be established.