From Substrate to Coating: Micro- and Surface Analysis Techniques for the Development of Steel Products

For the development of ultra high strength steel and hyperdrawable steel grades precipitates had to be tailored at the nanoscale. Microbeam techniques helped to reach a superior quality of metallic coatings and a superb adhesion to the steel substrate. In this paper the use of micro-analytical techniques in steel product development is illustrated.     

Anodic oxidation of chiral sulfinylamines: a new route to highly diastereoselective α-alkylation of piperidine

The anodic oxidation of some chiral non-racemic N-arylsulfinyl piperidines was investigated and for the first time α methoxylated sulfinyl piperidines were obtained. The so-formed compounds are equivalent of chiral N-sulfinyliminiums and used as new intermediates for the preparation of chiral α-substituted piperidine derivatives in good yield and diastereoselectivity.     

Influence of the structure of the mesogenic core on the thermotropic properties of ω-unsaturated fluorinated liquid crystals

Three series of calamitic liquid crystals have been prepared, consisting of a mesogenic core attached to which is a perfluorinated chain via a thioester linkage, and a hydrocarbon chain containing a terminal double bond. The rigid core is either a monophenyl, biphenyl or phenyl benzoate group. The mesomorphic properties were characterized by polarizing optical microscopy and differential scanning calorimetry. The influence of the structure of the mesogenic core and of the hydrocarbon chain length on mesomorphic behaviour was studied. Increasing the length of the alkyl chain strongly reduces the mesomorphic behaviour while increasing the number of aromatic rings in the core increases the transition temperatures, with the widest LC range observed for derivatives with the phenyl benzoate core. The introduction of a single ring as the mesogenic core is considered of great interest in the development of low cost liquid crystal materials.     

Contra-directional and other power flows in periodic iris-loaded circular waveguide (H-waves)

Physics of H-eigenwaves in a periodic iris-loaded circular waveguide is generally characterized using a number of the typical power flows. Both the reflectionless flows and the ones contra-directional over the guide's cross-section are included, as well as the curlsome ones and others.     

Some Improvements in the Method of the Weakly Conjugate Operator

We present some improvements in the method of the weakly conjugate operator, one variant of the Mourre theory. When applied to certain two-body Schrödinger operators, this leads to a limiting absorption principle that is uniform on the positive real axis.     

Adiabatic 1H decoupling scheme for very accurate intensity measurements in 13C NMR

Adiabatic proton decoupling has been optimized in order to obtain accurate quantitative measurements of intensities on 13C NMR spectra. For each offset, the minimum adiabaticity factor (Km) reached during the pulse was computed. This K(m) profile was used to optimize the peak value and the swept frequency range of the adiabatic pulses. With a cosinus amplitude modulation, offset-independent-adiabaticity, and the M4P5-M4P9-M4P5'-M4P9' phase cycle, an accuracy of 2 per thousand for the 13C NMR measurements was reached. An approach using bi-labeled 13C acetic acid and ethanol at 99% allowed a fine experimental determination of the uniformity of the decoupling profile. The comparison with WALTZ-16 highlights the improvements in the uniformity of the proton decoupling.     

Magnetic properties and magnetic structures of Cu3(OD)4XO4, X=Se or S: cycloidal versus collinear antiferromagnetic structure

We report a comparative study of the magnetic properties of synthetic Cu3(OH)4(SO4)x(SeO4)1-x and the magnetic structures of the parent compounds. All compounds are isostructural and belong to the orthorhombic class of parent compounds. They consist of 3-legged ribbons of edge-sharing copper octahedra connected by micro3-OH and XO4 (X=S or Se). XO4 acts both as one-atom and three-atom bridges to connect seven Cu atoms (six Cu(2) and one Cu(1)) belonging to three neighboring ribbons. The two end members behave as low-dimensional AF with a long-range antiferromagnetic state below 5 (X=S) and 8 K (X=Se); the former shows evidence of a canting. Analyses of the neutron powder diffraction data for X=S were shown to display an ordered magnetic state (k=0 0 0) where the moments of Cu(2) within the two outer legs are collinear and parallel within each leg but antiparallel from each other; the orientation of the moments of Cu(2) is the c axis. In contrast, for X=Se k=approximately 1/7 0 0 and the magnetic structure is cycloidal and transforms progressively from being incommensurate (T>3 K) to commensurate (T相似文献   

First Occurrence of Tetrazines in Aqueous Solution: Electrochemistry and Fluorescence

The photophysical and electrochemical properties of tetrazines substituted by linear 2,3‐naphtalimide antennas and/or adamantane groups specifically dedicated to host–guest interactions with cyclodextrins are studied both in organic and aqueous media. In acetonitrile solvent, the reduction potential of tetrazine leading to the anion radical is shifted, depending on the electron‐withdrawing power of the substituent of the tetrazines. Due to the hydrophobic character of these compounds, their solubilization in aqueous solution is achieved successively in presence of either β‐cyclodextrins or gold nanoparticules modified by β‐cyclodextrins. We demonstrate that the formation of the inclusion compound tetrazine–cyclodextrin allows the solubilization of the tetrazines in aqueous solution. The supramolecular assemblies obtained in water retain tetrazine's emission properties, yielding a yellow fluorescence.     

Stereochimie de la cycloaddition sur les ethers butadienyliques d'alcools chiraux. Derives en 4 et 6 de glucosides perbenzylés

Two partially protected derivatives of α-D-glucose with one free OH group function, benzyl 2,3,6-tri-O--α-D-glucopyranoside 2 and benzyl-2,3,4-tri-$\text{O}$-benzyl-α-D-glucopyranoside 4 were prepared. Base-catalysed addition of the diyne-diol 5 onto these sugars gave trans-cis mixtures of enynyl ethers, 6 and 8 from compound 2, and 7 and 9 from compound 4. Catalytic partial hydrogenation gave the corresponding butadienyl ethers 10 and 12 from 6 and 8, and 11 and 13 from 7 and 9. All trans-cis mixtures obtained could be readily separated by fractionnal crystallisation or column chromatography, thus making for the first time pure trans and cis enynyl ethers readily available in quantity. The cycloaddition of butyl glyoxylate onto the trans dienes led to mixtures of dia-stereoisomeric, dihydropyrannyl ethers, 14 (β-L) 18 (α-D) and 22 (β-D) from diene 10, and 16 (β-L), 20 (α-D) and 24 (β-D) from diene 11. Configurations were ascribed by the use of already described methods. This study brings to a number of five all examined reactions of cycloaddition onto butadienyl ethers of chiral alcohols. In each case a strong preference is observed for one of the faces of the prochiral butadienyl ether, but no great preference for the endo path of cycloaddition.