Biosynthesis of conjugatable saccharidic moieties of GM2 and GM3 gangliosides by engineered E. coli

Oligosaccharidic moieties of GM(2) and GM(3) gangliosides bearing an allyl or a propargyl aglycon, are efficiently biosynthesized on the gram scale by growing metabolically engineered Escherichia coli cells in the presence of the corresponding lactoside acceptors and sialic acid.     

Oxygen and nitrogen Lewis base adducts of [UO2(OTf)2]. Crystal structures of polypyridine complexes with out-of-plane uranyl equatorial coordination

Dissolution of [UO2(OTf)2](1) in anhydrous thf, dme or py led to the formation of the complexes [UO2(OTf)2(thf)3](2), [UO2(OTf)2(dme)](3) and [UO2(OTf)2(py)3](4), respectively. Compounds 2 and 4 are neutral monomers in the solid state as well as the chloride [UO2Cl2(py)3](5) which was prepared in a similar way as for from the dimer [[UO2Cl2(thf)2]2]. Addition of 4 equivalents of triphenylphosphine oxide (tppo) to 1 afforded, in pyridine, the dicationic species [UO2(tppo)4][OTf]2 (6). The bi- or terdentate nitrogen molecules 2,2'-bipy, phen or terpy reacted with 1 in acetonitrile or pyridine to give [UO2(OTf)2(bipy)2](7), [UO2(phen)3][OTf]2(8), [UO2(OTf)2(terpy)](9) and [UO2(terpy)2][OTf]2(10), respectively. The hydroxide compound [[UO2(OH)(terpy)]2][OTf]2(11) was obtained by hydrolysis in air of 1 in a mixture of acetonitrile and ethanol in the presence of terpyridine. The X-ray crystal structures of , and reveal a novel coordination geometry for the uranyl ion, the uranium atom being in a rhombohedral environment; the six coordinating ligands atoms of the [UO2]2+ ion are separated into two parallel and staggered equilateral triangles and the UO2 axis is perpendicular to these triangles, passing through their centre. The structures of the mono(terpy) complexes 9 and 11 show the uranium atoms in a distorted pentagonal bipyramidal configuration with the nitrogen atom of the central pyridine ring of the terpy ligand significantly displaced from the equatorial plane.     

Reconstruction of physics objects at the Circular Electron Positron Collider with Arbor

After the Higgs discovery, precise measurements of the Higgs properties and the electroweak observables become vital for the experimental particle physics. A powerful Higgs/Z factory, the Circular Electron Positron Collider (CEPC) is proposed. The Particle Flow oriented detector design is proposed to the CEPC and a Particle Flow algorithm, Arbor is optimized accordingly. We summarize the physics object reconstruction performance of the Particle Flow oriented detector design with Arbor algorithm and conclude that this combination fulfills the physics requirement of CEPC.     

Thermotropic liquid crystalline properties of semiperfluoroalkyloxyphenyl and perfluoroalkylphenyl β-D-glucopyranosides

The synthesis of two series of semiperfluoroalkyloxyphenyl and perfluoroalkylphenyl β-D-glucopyranosides is described. Their mesomorphic properties are studied by DSC, polarized optical microscopy and X-ray diffraction. All mesophases are identified as smectic A with a bimolecular in-layer arrangement.     

M?ssbauer spectroscopy: analysis and predictions for Li-ion batteries

Due to their high storage capacity Sn-based materials are of considerable interest as negative electrode for Li-ion batteries. However the strong volume change occurring during the alloy formation strongly limits the electrochemical performances (cycle and time life). Analysis by M?ssbauer spectroscopy using model compounds (Sn, Sn-Li and transition metal-Sn alloys) shows that the volume expansion is related to the structural change from a Sn based network to a Li based network. Two types of materials are proposed here to overcome this problem: tin dispersion in an electrochemically inactive oxide matrix with buffer role to absorb volume changes or tin alloying with an inactive transition metal to minimize the volume expansion. The use of M?ssbauer spectroscopy (in situ operando mode) allows a dynamic approach which is essential to understand the fundamental causes of ageing on cycling and to define then the key issues to be solved for material’s application.     

Grignard condensation routes to 1,3‐disilacyclobutane‐containing cyclolinear polycarbosilanes

Alkylene‐ and arylene‐bridged cyclolinear polycarbosilanes (CLPCS) with 1,3‐disilacyclobutane (DSCB) rings incorporated in the main chain of the polymer were prepared by polycondensation between corresponding di‐functional DSCB derivatives and di‐Grignard reagents. Well‐defined, low molecular weight (M_n = 3–5K; DP = 17–26), hexylene‐ and phenylene‐bridged CLPCS polymers were obtained without appreciable ring opening of the DSCB rings. Large exothermic peaks were observed in the DSC for these CLPCSs, which indicated, along with the IR spectra, that crosslinking occurred on heating to about 250 °C via the ring opening of the embedded, alternating, DSCB rings. Moreover, PB‐CLPCS undergoes photochemically induced crosslinking on UV irradiation to form crosslinked polycarbosilane network films. The spin‐cast, cured, films of these CLPCSs exhibit relatively low dielectric constants and promising thermal and mechanical properties for applications in electronics, for example, directly UV‐photoimprinted low‐k dielectrics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1547–1557     

Etude par RMN de la relaxation spin réseau d'un syst`eme AB de noyaux en interconversion lente

Nuclear Overhauser effects allow us to determine all transition probabilities in a two-spin AB system, using a triple resonance apparatus we have constructed. Theoretical and experimental studies of the relaxation in the special case where the nuclei belong to a molecule interconverting slowly between two different conformations have been made, and the exchange ratio has been deduced.     

Préparation et Étude Physico-chimique de Quelques Copolyamides Aromatiques Séquencés. I. Synthèse des Copolycondensats Séquencés

A two-stage low-temperature solution polycondensation process is described for the synthesis of two kinds of block copolyamides: poly(p-biphenylene terephtalamide-co-adipamide) and poly(2,5-dimethyl trans-piperazine terephthalamide-co-adipamide). The reactivity of oligomeric end groups in various solvents is examined. This study ascertains the influence of the nature of the solvent on the extent of polycondensation. End groups seem to be more reactive in a medium in which the polyamide is soluble; this property is used for the synthesis of block copolycondensates.     

Combining planar and central chirality in ferrocene thiophosphine-sulfoxides

Novel chiral ferrocenylthiophosphine–sulfoxide and phosphine–sulfoxide derivatives possessing planar chirality for the ferrocene moiety and central chirality at the sulfur atom have been synthesized. These ligands can be obtained as pure diastereoisomers in both racemic and enantiomerically pure forms. Complete characterization by XRD analysis has allowed the assignment of the absolute configuration in each case. Preliminary coordination studies of the phosphine–sulfoxide ligands on platinum are also reported. These show chelating complexation by the phosphorous and sulfur atoms.     

Calcium-based hydrated minerals: Promising halogen-free flame retardant and fire resistant additives for polyethylene and ethylene vinyl acetate copolymers

In this study, we evaluated the potential flame retardant effect of calcium-based hydrated minerals, such as hydrated lime, partially and completely hydrated dolomitic limes in polyethylene (MDPE) and ethylene vinyl acetate copolymers (EVA) and compared to that obtained with magnesium di-hydroxide (MDH). The most significant flame retardant effects, observed using the mass loss calorimeter test, indicated that Ca-based MDPE composites showed similar peak Heat Release Rate (pHRR) level to that obtained with MDH composite while the pHRR was lower for Ca-based fillers in EVA compositions. X-ray Diffraction (XRD) data, combined with thermal analysis results, indicated that the calcium di-hydroxide plays a role in the formation of an intumescent cohesive residue during the combustion. Indeed, Ca(OH)₂ reacts with CO₂ formed during the thermal degradation of the polymer to generate CaCO₃ (calcium carbonate) that contributes to the enhancement of the mechanical resistance of the residue.