113 research outputs found
La banque de données d'humidité du dol des "WAB" de jachère et mil du supersite central : contribution de l'Institut des radio-isotopes à l'expérience Hapex-Sahel
Strain-induced Evolution of Electronic Band Structures in a Twisted Graphene Bilayer
Here we study the evolution of local electronic properties of a twisted
graphene bilayer induced by a strain and a high curvature. The strain and
curvature strongly affect the local band structures of the twisted graphene
bilayer; the energy difference of the two low-energy van Hove singularities
decreases with increasing the lattice deformations and the states condensed
into well-defined pseudo-Landau levels, which mimic the quantization of massive
Dirac fermions in a magnetic field of about 100 T, along a graphene wrinkle.
The joint effect of strain and out-of-plane distortion in the graphene wrinkle
also results in a valley polarization with a significant gap, i.e., the
eight-fold degenerate Landau level at the charge neutrality point is splitted
into two four-fold degenerate quartets polarized on each layer. These results
suggest that strained graphene bilayer could be an ideal platform to realize
the high-temperature zero-field quantum valley Hall effect.Comment: 4 figure
X-Ray Analysis of Oxygen-induced Perpendicular Magnetic Anisotropy in Pt/Co/AlOx trilayer
X-ray spectroscopy measurements have been performed on a series of Pt/Co/AlOx
trilayers to investigate the role of Co oxidation in the perpendicular magnetic
anisotropy of the Co/AlOx interface. It is observed that high temperature
annealing modifies the magnetic properties of the Co layer, inducing an
enhancement of the perpendicular magnetic anisotropy. The microscopic
structural properties are analyzed via X-ray Absorption Spectroscopy, X-ray
Magnetic Circular Dichroism and X-ray Photoelectron Spectroscopy measurements.
It is shown that annealing enhances the amount of interfacial oxide, which may
be at the origin of a strong perpendicular magnetic anisotropy
Fibulin-2 Is a Driver of Malignant Progression in Lung Adenocarcinoma
The extracellular matrix of epithelial tumors undergoes structural remodeling during periods of
uncontrolled growth, creating regional heterogeneity and torsional stress. How matrix integrity is
maintained in the face of dynamic biophysical forces is largely undefined. Here we investigated the
role of fibulin-2, a matrix glycoprotein that functions biomechanically as an inter-molecular clasp and
thereby facilitates supra-molecular assembly. Fibulin-2 was abundant in the extracellular matrix of
human lung adenocarcinomas and was highly expressed in tumor cell lines derived from mice that
develop metastatic lung adenocarcinoma from co-expression of mutant K-ras and p53. Loss-offunction
experiments in tumor cells revealed that fibulin-2 was required for tumor cells to grow and
metastasize in syngeneic mice, a surprising finding given that other intra-tumoral cell types are known
to secrete fibulin-2. However, tumor cells grew and metastasized equally well in Fbln2-null and -wildtype
littermates, implying that malignant progression was dependent specifically upon tumor cellderived
fibulin-2, which could not be offset by other cellular sources of fibulin-2. Fibulin-2 deficiency
impaired the ability of tumor cells to migrate and invade in Boyden chambers, to create a stiff
extracellular matrix in mice, to cross-link secreted collagen, and to adhere to collagen. We conclude
that fibulin-2 is a driver of malignant progression in lung adenocarcinoma and plays an unexpected
role in collagen cross-linking and tumor cell adherence to collagen
Soil measurements during HAPEX-Sahel intensive observation period
This article describes measurements made at each site and for each vegetation cover as part of the soils program for the HAPEX-Sahel regional scale experiment. The measurements were based on an initial sampling scheme and included profile soil water content, surface soil water content, soil water potential, infiltration rates, additional measurements on core samples, and grain size analysis. The measurements were used to categorize the state of the surface and profile soil water regimes during the experiment and to derive functional relationships for the soil water characteristic curve, unsaturated hydraulic conductivity function, and infiltration function. Sample results for different supersites and different vegetation covers are presented showing soil water profiles and total soil water storage on days corresponding to the experimental ‘Golden Days’. Sample results are also presented for spatial and temporal distribution of surface moisture content and infiltration tests. The results demonstrate that the major experimental objective of monitoring the supersites during the most rapid vegetative growth stage with the largest change of the surface energy balance following the rainy season was very nearly achieved. Separation of the effects of probable root activity and drainage of the soil profile is possible. The potential for localized advection between the bare soil and vegetation strips of the tiger bush sites is demonstrate
Systematic and Evolutionary Insights Derived from mtDNA COI Barcode Diversity in the Decapoda (Crustacea: Malacostraca)
Background: Decapods are the most recognizable of all crustaceans and comprise a dominant group of benthic invertebrates of the continental shelf and slope, including many species of economic importance. Of the 17635 morphologically described Decapoda species, only 5.4% are represented by COI barcode region sequences. It therefore remains a challenge to compile regional databases that identify and analyse the extent and patterns of decapod diversity throughout the world. Methodology/Principal Findings: We contributed 101 decapod species from the North East Atlantic, the Gulf of Cadiz and the Mediterranean Sea, of which 81 species represent novel COI records. Within the newly-generated dataset, 3.6% of the species barcodes conflicted with the assigned morphological taxonomic identification, highlighting both the apparent taxonomic ambiguity among certain groups, and the need for an accelerated and independent taxonomic approach. Using the combined COI barcode projects from the Barcode of Life Database, we provide the most comprehensive COI data set so far examined for the Order (1572 sequences of 528 species, 213 genera, and 67 families). Patterns within families show a general predicted molecular hierarchy, but the scale of divergence at each taxonomic level appears to vary extensively between families. The range values of mean K2P distance observed were: within species 0.285% to 1.375%, within genus 6.376% to 20.924% and within family 11.392% to 25.617%. Nucleotide composition varied greatly across decapods, ranging from 30.8 % to 49.4 % GC content. Conclusions/Significance: Decapod biological diversity was quantified by identifying putative cryptic species allowing a rapid assessment of taxon diversity in groups that have until now received limited morphological and systematic examination. We highlight taxonomic groups or species with unusual nucleotide composition or evolutionary rates. Such data are relevant to strategies for conservation of existing decapod biodiversity, as well as elucidating the mechanisms and constraints shaping the patterns observed.FCT - SFRH/BD/25568/ 2006EC FP6 - GOCE-CT-2005-511234 HERMESFCT - PTDC/MAR/69892/2006 LusomarBo
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