Linking hopping conductivity to giant dielectric permittivity in oxides

With the promise of electronics breakthrough, giant dielectric permittivity materials are under deep investigations. In most of the oxides where such behavior was observed, charged defects at interfaces are quoted for such giant behavior to occur but the underlying conduction and localization mechanisms are not well known. Comparing macroscopic dielectric relaxation to microscopic dynamics of charged defects resulting from electron paramagnetic resonance investigations we identify the actual charged defects in the case of BaTiO3 ceramics and composites. This link between the thermal activation at these two complementary scales may be extended to the numerous oxides were giant dielectric behavior was found

Cerebellum: links between development, developmental disorders and motor learning

The study of the links and interactions between development and motor learning has noticeable implications for the understanding and management of neurodevelopmental disorders. This is particularly relevant for the cerebellum which is critical for sensorimotor learning. The olivocerebellar pathway is a key pathway contributing to learning of motor skills. Its developmental maturation and remodeling are being unraveled. Advances in genetics have led to major improvements in our appraisal of the genes involved in cerebellar development, especially studies in mutant mice. Cerebellar neurogenesis is compartmentalized in relationship with neurotransmitter fate. The Engrailed-2 gene is a major actor of the specification of cerebellar cell types and late embryogenic morphogenesis. Math1, expressed by the rhombic lip, is required for the genesis of glutamatergic neurons. Mutants deficient for the transcription factor Ptf1a display a lack of Purkinje cells and gabaergic interneurons. Rora gene contributes to the developmental signaling between granule cells and Purkinje neurons. The expression profile of sonic hedgehog in postnatal stages determines the final size/shape of the cerebellum. Genes affecting the development impact upon the physiological properties of the cerebellar circuits. For instance, receptors are developmentally regulated and their action interferes directly with developmental processes. Another field of research which is expanding relates to very preterm neonates. They are at risk for cerebellar lesions, which may themselves impair the developmental events. Very preterm neonates often show sensori-motor deficits, highlighting another major link between impaired developments and learning deficiencies. Pathways playing a critical role in cerebellar development are likely to become therapeutical targets for several neurodevelopmental disorders

Break-down of the density-of-states description of scanning tunneling spectroscopy in supported metal clusters

Low-temperature scanning tunneling spectroscopy allows to probe the electronic properties of clusters at surfaces with unprecedented accuracy. By means of quantum transport theory, using realistic tunneling tips, we obtain conductance curves which considerably deviate from the cluster's density of states. Our study explains the remarkably small number of peaks in the conductance spectra observed in recent experiments. We demonstrate that the unambiguous characterization of the states on the supported clusters can be achieved with energy-resolved images, obtained from a theoretical analysis which mimics the experimental imaging procedure.Comment: 5 pages, 3 figure

β-Glucan synthase induction in mushrooms grown on olive mill wastewaters

Beta-1-3-Glucan synthase activity and its induction by olive mill wastewaters (OMW) was studied in ten fungal strains (Auricularia auricula-judae, Lentinula edodes, Pleurotus eryngii, Stropharia aeruginosa, Agrocybe aegerita, P. pulmonarius, Armillaria mellea, P. ferulae, P. ostreatus, P. nebrodensis). A microtiter-based enzymatic assay on -1-3-glucan synthase activity was carried out on all mycelia growth both on the control medium and on OMW. Among the fungi assayed, L. edodes -1-3-glucan synthase was highly enhanced in OMW. The main components of OMW, i.e. phenols and lipids, were added separately to the control medium, to highlight the mechanism of L. edodes -1-3-glucan synthase induction. A Southern blot analysis and PCR with degenerated primers were carried out to detect the presence of fks1-like genes in these Basidiomycetes. The sequences obtained from the ten Basidiomycota were remarkably similar to fks1 from Filobasidiella neoformans. Spectrofluorimetric and RT-PCR analyses of -1-3-glucan synthase were performed on the mycelia of L. edodes. In this fungus, a strong stimulation of -1-3-glucan synthase mRNA and protein was recorded in the presence of OMW and phenol

Albert Geerts One of the "young boys"

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Stoichiometry and Grain Boundaries Control by Spark Plasma Sintering in Ba0.6Sr0.4TiO3:Mn/MgO Composites

LaNbO4/La3NbO7 and LaNbO4/LaNb3O9 cer-cer composites were prepared by impregnating Ca-doped LaNbO4 powder, synthesized by spray pyrolysis, with La- or Nb-precursor solutions. The sintering of the calcined powders was investigated by dilatometry, and dense composites were prepared by conventional sintering, hot pressing, and spark plasma sintering. The particle size of the starting powders was about 50 nm, and the average grain size of the dense materials ranged from 100 nm and upwards, depending on the sintering temperature, sintering procedure, and the phase composition. The unit cell parameters of LaNbO4 showed a finite size effect and approached the cell parameters of tetragonal LaNbO4 with decreasing crystallite size, both for the single-phase material and the composites. The minority phase (La3NbO7 or LaNb3O9) were observed as isolated grains and accumulated at triple points and not along the grain boundaries, pointing to a large dihedral angle between the phases. The calcium-solubility in the minority phases was larger than in LaNbO4, which corresponds well with previous reports. The electrical conductivity of the heterodoped materials was similar to, or lower than, that for Ca-doped LaNbO4

Separating the Weak Lensing and Kinetic SZ Effects from CMB Temperature Maps

A new generation of CMB experiments will soon make sensitive high resolution maps of the microwave sky. At angular scales less than $\sim$10 arcminutes, most CMB anisotropies are generated at z $< 1000$, rather than at the surface of last scattering. Therefore, these maps potentially contain an enormous amount of information about the evolution of structure. Whereas spectral information can distinguish the thermal Sunyaev-Zeldovich (tSZ) effect from other anisotropies, the spectral form of anisotropies generated by the gravitational lensing and the kinetic Sunyaev-Zeldovich (kSZ) effects are identical. While spectrally identical, the statistical properties of these effects are different. We introduce a new real-space statistic, $<\theta (\hat{n})^3 \theta (\hat{m})>_c$, and show that it is identically zero for weakly lensed primary anisotropies and, therefore, allows a direct measurement of the kSZ effect. Measuring this statistic can offer a new tool for studing the reionization epoch. Models with the same optical depth, but different reionization histories, can differ by more than a factor of 3 in the amplitude of the kSZ-generated non-Gaussian signal.Comment: 13 pages, 1 figur

Foreword

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Early lire imprints the hierarchy of T cell clone sizes

The adaptive immune system responds to pathogens by selecting clones of cells with specific receptors. While clonal selection in response to particular antigens has been studied in detail, it is unknown how a lifetime of exposures to many antigens collectively shape the immune repertoire. Here, using mathematical modeling and statistical analyses of T cell receptor sequencing data, we develop a quantitative theory of human T cell dynamics compatible with the statistical laws of repertoire organization. We find that clonal expansions during a perinatal time window leave a long-lasting imprint on the human T cell repertoire, which is only slowly reshaped by fluctuating clonal selection during adult life. Our work provides a mechanism for how early clonal dynamics imprint the hierarchy of T cell clone sizes with implications for pathogen defense and autoimmunity