Coherent view of crystal chemistry and ab initio analyses of Pb(II) and Bi(III) Lone Pair in square planar coordination

The stereochemistry of 6s2 (E) lone pair of divalent Pb and trivalent Bi (PbII and BiIII designated by M*) in structurally related PbO, PbFX (X= Cl, Br, I), BiOX (X= F, Cl, Br, I) and Bi2NbO5F is rationalized. The lone pair LP presence determined by its sphere of influence E, equal to those of oxygen or fluorine anions, was settled by its center then giving M*-E directions and distances. Detailed description of structural features of both elements in the title compounds characterized by [PbEO]n and [BiEO]n layers allowed to show the evolution of M*-E distance versus the changes with the square pyramidal SP coordination polyhedra. All are different, in red PbO one finds {PbEO4E4} square antiprism, a {[Bi.E]O4X4Xapical} monocapped square antiprism in PbFX and BiOX and {BiEO4F4}square antiprism in Bi2NbO5F. To analyze the crystal chemistry results, the electronic structures of these compounds were calculated within density functional theory DFT. Real space analyses of electron localization illustrate a full volume development of the lone pair on PbII within {PbEO4E4} in PbOE, {PbEF4X4} in PbFXE and Bi(III) within {BiEO4X4} square antiprisms, contrary to Bi(III) within {[Bi.E]O4F4Fapical} monocapped square antiprism. Larger hardness (larger bulk modules B0) and band gap characterize BiOF versus PbO due to the presence of F which brings antibonding Bi-F interactions oppositely to mainly bonding Bi-O. In PbFX and BiOX series there is a systematic decrease of B0 with the increasing volume following the nature and size of X which is decreasingly electronegative and increasingly large. The electronic densities of states mirror these effects through the relative energy position and relative electronegativities of F/X and O/X leading to decrease the band gap.Comment: 20 text pages/ 10 multifigures/large review article, J. Progress Solid State Chemistry, under production MAY 201

Hydrologic controls on seasonal and inter-annual variability of Congo River particulate organic matter source and reservoir age

We present dissolved organic carbon (DOC) concentrations, particulate organic matter (POM) composition (δ13C, δ15N, ∆14C, N/C), and particulate glycerol dialkyl glycerol tetraether (GDGT) distributions from a 34-month time-series near the mouth of the Congo River. An end-member mixing model using δ13C and N/C indicates that exported POM is consistently dominated by C3 rainforest soil sources, with increasing contribution from C3 vegetation and decreasing contribution from phytoplankton at high discharge. Large C4 inputs are never observed despite covering ≈ 13% of the catchment. Low and variable ∆14C values during 2011 [annual mean = (− 148 ± 82) ‰], when discharge from left-bank tributaries located in the southern hemisphere reached record lows, likely reflect a bias toward pre-aged POM derived from the Cuvette Congolaise swamp forest. In contrast, ∆14C values were stable near − 50‰ between January and June 2013, when left-bank discharge was highest. We suggest that headwater POM is replaced and/or diluted by C3 vegetation and pre-aged soils during transit through the Cuvette Congolaise, whereas left-bank tributaries export significantly less pre-aged material. GDGT distributions provide further evidence for seasonal and inter-annual variability in soil provenance. The cyclization of branched tetraethers and the GDGT-0 to crenarchaeol ratio are positively correlated with discharge (r ≥ 0.70; p-value ≤ 4.3 × 10− 5) due to the incorporation of swamp-forest soils when discharge from right-bank tributaries located in the northern hemisphere is high. Both metrics reach record lows during 2013, supporting our interpretation of increased left-bank contribution at this time. We conclude that hydrologic variability is a major control of POM provenance in the Congo River Basin and that tropical wetlands can be a significant POM source despite their small geographic coverage

Macroscopic ferroelectricity and piezoelectricity in nanostructured BiScO3–PbTiO3 ceramics

3 pages, 4 figures.-- PACS: 77.80.Bh; 73.61.Ng; 77.84.Dy; 77.80.Fm; 81.20.EvWe have studied the macroscopic electrical properties of highly dense, nanostructured ceramics of BiScO3–PbTiO3 with high Curie temperature and piezoelectric activity. Materials were processed by spark plasma sintering of nanocrystalline powder obtained by mechanosynthesis. Results indicate that the nanostructured material still presents the ferroelectric transition above 700 K. Ferroelectric switching is unambiguously demonstrated. Furthermore, ceramic disks were poled and their radial piezoelectric resonance was excited, which has not been achieved in nanostructured BaTiO3 ceramics.Funded by MEC (Spain) through the MAT2007-61884 and MAT2008-02003/NAN projects. H.A. and T.H. thank the financial support by MEC (JdC Programme) and MAEAECI, respectively. Collaboration between ICMM and CEMES is framed within the ESF COST Action 539 ELENA.Peer reviewe

The role of P 3s2 lone pair (E) in structure, properties and phase transitions of black phosphorus. Stereochemistry and ab initio topology analyses

An approach merging crystal chemistry and density functional theory (DFT) electron localization function (ELF) taking P 3s2 lone pair (E) into account induces a full renewal of stereochemistry of black phosphorus, its crystal network evolutions and phase transitions under increasing pressures from atmospheric up to 32 GPa. Orthorhombic (Cmce) black P at ambient pressure, shows a packing of puckered [P]n layers - orthogonal to [010] - separated by a large free interspace (3.071 Å), which actually is partially filled by lone pairs (E) (P-E ~ 0.8 Å). Each P exhibits its lone pair pointing outside the [P]n layer, sandwiching it between two [E]n layers into a new stacking sequence … [EP2E]n … denoted O-[PE]n. The free interspace between [EP2E]n layers is much smaller 1.858 Å but allows sliding along [001]. The pressure evolving up to 2.66 GPa, all structural details have been followed and reported, including the layer thickness reduction along [010] and the sliding along [001] of consecutive layers. A mechanism for the phase transition occurring around 5.5 GPa is proposed. Depicted in the trigonal system the new layered phase R-[PE]n involves a bond rearrangement through E-E layer in zigzag phosphorus layers and P-E rotation and alignment with the A axis. Now, the phosphorene layers have P-E patterns oriented towards each other in their interspace. A very particular phenomenon occurs around ~11 GPa the lone pair centroid Ec (P-Ec = 0.73 Å) splits into three partially occupied sites Ed around the A axis which explains observed variations in properties at this critical pressure. So, we claim that there are two trigonal phases, R1-[PE] up to 11 GPa followed by a second form R2-[PE] directly caused by lone pair displacement from Ec to Ed and its influence on layer stacking. A further layer sliding brings the phosphorus atomic layers close enough to each other to establish new P-P bonds and then to cause an ultimate transition to cubic system, with a new structure, isostructural to Po. The mechanisms of the transitions are detailed

EUSECTRA: European Nuclear Security Training Centre providing hands-on training and education in Nuclear Security and Safeguards

The European Nuclear Security Training Centre (EUSECTRA) inaugurated under this global name about 10 years ago and operated by the European Commission Joint Research Centre (JRC), located both on the Karlsruhe (Germany) and Ispra (Italy) sites, includes a large variety of capacity building and professional development activities which span from the hands-on training for nuclear security and safeguards actors (e.g. respectively border guards or customs and nuclear inspectors) to educational efforts in both nuclear security and safeguards. Whereas the first ones, which gave rise to the new name, focus mainly on detection, on-site assistance, crime-scene management, technical reach-back and nuclear forensics capabilities, the second includes all aspects of nuclear safeguards analytical measurements, containment and surveillance, verification technologies and methodologies etc. This paper provides an overview of the most salient developments in these areas of both technical and academic teaching engagement in the last decade and includes some hints to the potential for enhanced collaboration with the International Nuclear Security Educational Network (INSEN

Matériaux solide conducteur thermodurcissable (Application aux plaques bipolaires pour pile à combustible)

Parmi les nouvelles technologies pour l énergie inscrites dans un contexte de développement durable, les piles à combustible à membrane échangeuse de protons (PEMFC) présentent des aspects séduisants. Toutefois, pour rendre cette technologie compatible avec une application à grande échelle, elle doit répondre à des exigences strictes en termes de coût, performance, et durabilité. Alors que les plaques bipolaires métalliques sont pénalisées par leur résistance à la corrosion et celles en graphite par leurs propriétés mécaniques et leur coût (dû aux phases d usinage des canaux), les plaques bipolaires composites apparaissent attrayantes en raison de leurs propriétés et performances et de leur coût. Cette thèse s inscrit dans ce cadre, en proposant un matériau composite à matrice organique de type époxy et charges conductrices de graphite. L objectif de notre étude consiste à mettre au point un matériau thermodurcissable à base d une formulation époxyde solide (permettant de contrôler sa chimie et plus particulièrement sa réactivité) fortement chargée en graphite. Deux formulations différentes sont étudiées. La première est à base de prépolymère époxy appelé DGEBA et de dicyandiamide (DDA) comme durcisseur. L autre formulation étudiée est constituée de DGEBA et de durcisseur : le 3,3 ,4,4 -benzophénone dianhydride tétracarboxylique (BTDA). Ces deux formulations ont la particularité d être très réactives à haute température (180-200C) caractérisées par des temps de gel très courts (plus petit que 1min) afin d avoir un temps de cycle de réticulation court pour une industrialisation de la fabrication. De plus, ces mêmes matrices ont montré une bonne stabilité chimique à température ambiante ainsi qu une bonne stabilité thermique du système réticulé compatible avec la température d utilisation des piles en fonctionnement. Concernant les réseaux composites résultant de la polymérisation DGEBA/BTDA et DGEBA/DDA, le module au plateau caoutchoutique est dominé par le taux de charge qui est très élevé (85%), celui-ci est ainsi très proche d un réseau à l autre et reste supérieur à 1 GPa. Nous constatons une viscosité relativement élevée pour les systèmes fortement chargés, point à prendre en compte lors du procédé de transformation. Enfin, la dernière partie des travaux réalisés concerne l étude de mélange constitué de la matrice thermodurcissable (DGEBA/DDA/urée) modifiée par un thermoplastique (PEI). L originalité et l intérêt de ce travail résident dans l incorporation de charges conductrices afin que celles-ci puissent se disperser dans la phase continue ou co-continue époxyde-amine lors de la séparation de phase pour limiter la proportion de charges et ainsi la viscosité des systèmes chargés. L autre intérêt est d améliorer les propriétés de résistance à la rupture du réseau époxyde TD final grâce à la présence de la phase thermoplastique séparée.Among the new technologies for energy for sustainable development, PEM fuel cells offer seducing aspects. However, in order to make this technology fit large scale application requirements, it has to comply with stringent cost, performance, and durability criteria. While metal bipolar plates are penalized by their corrosion resistance and those based on graphite by their mechanical properties and cost (due to machining phases of the channels), the composite bipolar plates appear attractive because of their properties, performance and their cost. In such a frame, the goal of this PhD was to propose a composite material based on an epoxy matrix and graphite conductive fillers.The aim of our study was to develop a thermosetting material based on a solid epoxy formulation (to control its chemistry and in particular its reactivity) highly filled with graphite. Two different formulations were studied. The first was based on the epoxy prepolymer DGEBA and dicyandiamine (DDA) as a hardener. The other formulation studied was composed of DGEBA and curing agent: 3,3 ,4,4 benzophenone tetracarboxylic dianhydride (BTDA). Both formulations have the particularity to be very reactive at high temperature (180-200 C) characterized by very short gel time (less than 1min) to have a short curing cycle for the industrialization of the production. In addition, these matrixes have shown good chemical stability at room temperature and good thermal stability of cross-linked system compatible with the operating temperature of the fuel cell. On composite network resulting from the polymerization DGEBA / BTDA and DGEBA / DDA, the rubbery modulus appears to be dominated by the loading rate, very high (85%), and is above 1 GPa. We see a high viscosity for highly filled systems, point to consider during the process of transformation. The final part of the work concerned the study of blend of the thermosetting matrix (DGEBA / DDA / urea) modified with a thermoplastic (PEI). The originality and interest of this work is the incorporation of conductive fillers so that they can be dispersed in the continuous or co-continuous structure during the phase separation to limit the proportion of charges and and the viscosity of filled systems. The other interest is to improve the properties of tensile strength of the thermosetting epoxy network with the presence of the thermoplastic phase.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

Table Ronde : L’Arche de Zoé, dérive unique ou produit d’un système ?

Table ronde organisée le 19 décembre 2007 à l’initiative de Joseph Dato, professeur associé à l’Université de Grenoble, membre du Conseil d’administration de Médecins du Monde. La vidéo du débat est disponible sur www.medecinsdumonde.org Débat animé par Françoise Jeanson, médecin, ancienne présidente de Médecins du Monde. Avec Michel Galy, sociologue, revue Cultures et Conflits, Jean-Paul Ngoupande, ancien Premier ministre de la République centrafricaine, Pierre Micheletti, médecin, président de Médecins du Monde, Rony Brauman, médecin, ancien président de Médecins Sans Frontières, professeur associé à Sciences-Po Paris, Pierre Ganz, rédacteur en chef, Radio France Internationale, et la participation de trois « grands témoins » : Blandine Destremau, Bruno David et Frédéric Tissot

Lymphopenia combined with low TCR diversity (divpenia) predicts poor overall survival in metastatic breast cancer patients

Lymphopenia (< 1Giga/L) detected before initiation of chemotherapy is a predictive factor for death in metastatic solid tumors. Combinatorial T cell repertoire (TCR) diversity was investigated and tested either alone or in combination with lymphopenia as a prognostic factor at diagnosis for overall survival (OS) in metastatic breast cancer (MBC) patients. The combinatorial TCR diversity was measured by semi quantitative multi-N-plex PCR on blood samples before the initiation of the first line chemotherapy in a development (n = 66) and validation (n = 67) MBC patient cohorts. A prognostic score, combining lymphocyte count and TCR diversity was evaluated. Univariate and multivariate analyses of prognostic factors for OS were performed in both cohorts. Lymphopenia and severe restriction of TCR diversity called “divpenia” (diversity ≤ 33%) were independently associated with shorter OS. Lympho-divpenia combining lymphopenia and severe divpenia accurately identified patients with poor OS in both cohorts (7.6 and 10.6 vs 24.5 and 22.9 mo). In multivariate analysis including other prognostic clinical factors, lympho-divpenia was found to be an independent prognostic factor in the pooled cohort (p = 0.005) along with lack of HER2 and hormonal receptors expression (p = 0.011) and anemia (p = 0.009). Lympho-divpenia is a novel prognostic factor that will be used to improve quality of MBC patients’ medical care

Selection of CalB immobilization method to be used in continuous oil transesterification: Analysis of the economical impact

Enzymatic transesterification of triglycerides in a continuous way is always a great challenge with a large field of applications for biodiesel, bio-lubricant, bio-surfactant, etc. productions. The lipase B from Candida antarctica (CalB) is the most appreciated enzyme because of its high activity and its non-regio-selectivity toward positions of fatty acid residues on glycerol backbone of triglycerides. Nevertheless, in the field of heterogeneous catalysis, we demonstrated that the medium hydrophilic nature of the support used for its commercial form (Lewatit VPOC1600) is a limitation. Glycerol is adsorbed onto support inducing drastic decrease in enzyme activity. Glycerol would form a hydrophilic layer around the enzyme resulting in diffusional limitations during triglyceride transfer to the enzyme. Accurel MP, a very hydrophobic macroporous polymer of propylene, was found not to adsorb glycerol. Immobilization conditions using this support were optimized. The best support was Accurel MP1001 (particle size<1000μm) and a pre-treatment of the support with acetone instead of ethanol enables the adsorption rate and the immobilized enzyme quantity to be maximized. An economical approach (maximization of the process net present value) was expanded in order to explore the impact of immobilization on development of an industrial packed bed reactor. The crucial ratio between the quantity of lipase and the quantity of support, taking into account enzyme, support and equipped packed bed reactor costs was optimized in this sense. The biocatalyst cost was found as largely the main cost centre (2–10 times higher than the investments for the reactor vessel). In consequence, optimal conditions for immobilization were a compromise between this immobilization yield (90% of lipase immobilized), biocatalyst activity, reactor volume and total investments