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Two series of hydrogen-bonded liquid-crystalline ferrocenes have been prepared by reacting ferrocene derivatives carrying a carboxylic acid function and two flexible alkyl chains (containing n = 8, 10, or 12 carbon atoms) with stilbazoles bearing a flexible alkyl chain (containing m = 6 or 10 carbon atoms). The first family of materials (m = 6; n = 8, 10, 12) gave rise to smectic A/C and/or cubic (Ia3̄d space group) phases, and the second series of complexes (m = 10; n = 8, 10, 12) displayed cubic phases (Ia3̄d space group). A subtle balance between the volume occupied by the central core and the flexible chains, as well as the surface between both parts, are responsible for the formation of the mesophases. Hydrogen bonding is an elegant alternative to covalent bonding for the design of ferrocene-containing liquid crystals.

Physical methods make it possible to combine analytical imaging with isotopic labelling in biological studies. With radioactive isotopes, track- radioautography may be used (in parallel with conventional grain-density radioautography) for high lateral resolution, even with energetic β-rays; in macroradioautography, filmless methods (gaseous detectors, scintillation counters, and storage phosphor screen devices) have remarkable performances. Neutron capture radiography is used mainly for the detection and imaging of one stable isotope of a few elements which have no radioisotope of practical use. With nuclear microprobes, nuclear reaction analysis and scattering analysis may serve to discriminate between isotopes (including stable isotopes). Secondary ion mass spectrometry images any isotope of almost any element with very good detection limits and a resolution better (sometimes much better) than 1 μm. Preventing the diffusion of mobile substances during the preparation of the biological specimens is still...

The reaction of benzylpalladium complexes of type trans-[Pd(CH2C6H4Y)(X)(PR3)2] (2) with isocyanides yields imidoyl complexes that exist in solution as equilibrium mixtures of the corresponding imine ([Pd(C(NR‘)CH2C6H4Y)(X)(PR3)2], 3-im) and enamine ([Pd(C(NHR‘CHC6H4Y)(X)(PR3)2, 3-en) tautomers. While the equilibrium constant is markedly affected by the electronic effect exerted by the substituents at the phenyl ring (Y), the effect of the metal fragment is less pronounced and is dominated by steric factors. Both tautomeric forms can also be found in the solid state, and the X-ray structures of complexes of type 2, 3-im, and 3-en have been determined.

A convenient and large scale preparation of new mono- and bis-hydroxy substituted 4,4′-bis(dialkylaminostyryl)-2,2′-bipyridines is reported. Their coordination studies to [Ru(DEAS-bpy) 2 ] 2+ (DEAS-bpy = 4,4′-bis(diethylaminostyryl)-2,2′-bipyridine) are also described.

Oxygen deficient YBa 2 Cu 3 O x thin films, in-situ deposited by laser ablation on (100) SrTiO 3 substrates have been treated ex-situ under diluted NF 3 flow at 280°C. After a short time of treatment, a clear improvement of the superconducting behaviour, i.e. an increase of Tc and a decrease of the inductive transition width are observed. Comparisons are made between reactions under NF 3 and under O 2 or N 2 in the same conditions of reactions, leading to the conclusion that in all cases the NF 3 treatment is the best to improve the superconducting behaviour of these thin films. The kinetics of the NF 3 reaction with these films is compared to the one previously observed for oxygen deficient thin films deposited by laser ablation on (100) MgO.

Direct observation of charged particle induced nuclear reactions, proton induced gamma-ray emission and elastic scattering proved to be specific methods to determine the distribution of the isotopes of light elements in the near surface region of solids. In this paper, we have intended to emphasize the real capabilities of nuclear microanalysis to perform local isotope ratio measurements. After a presentation of the scientific requirements for isotope study and a brief description of the experimental methods, we are going to discuss concrete examples concerning H, Li, B, C, N, O, Mg, Si and S isotopic composition in various media.

We report on the hole transport characteristics, as measured by time of flight, of a family of symmetrically substituted dialkoxy poly($p$-phenylenevinylene) polymers with different side-chain length. As side-chain length is decreased, the magnitude of the hole mobility ${\ensuremath{\mu}}_{h}$ increases while the field dependence of ${\ensuremath{\mu}}_{h}$ becomes more positive and the temperature dependence of ${\ensuremath{\mu}}_{h}$ becomes stronger. For the shortest side-chain derivative studied, ${\ensuremath{\mu}}_{h}$ exceeds ${10}^{\ensuremath{-}4}\text{ }{\text{cm}}^{2}\text{ }{\text{V}}^{\ensuremath{-}1}\text{ }{\text{s}}^{\ensuremath{-}1}$ at electric fields greater than ${10}^{5}\text{ }\text{V}\text{ }{\text{cm}}^{\ensuremath{-}1}$. The trend in magnitude of ${\ensuremath{\mu}}_{h}$ with side-chain length is consistent with the expected increase in electronic wave-function overlap as interchain separation decreases, while the trends in electric-field and temperature dependences of ${\ensuremath{\mu}}_{h}$ are consistent with increasing site energy disorder. We show that the electrostatic contribution to the site energy difference for pairs of oligomers follows the observed trend as a function of interchain separation, although the pairwise contribution is too small to explain the data quantitatively. Nonresonant Raman spectroscopy is used to characterize the microstructure of our films. We construct spatial maps of the Raman ratio ${I}_{1280}/{I}_{1581}$ and confirm an expected decrease in average film density with side-chain extension. The structural heterogeneity in the maps is analyzed but no clear correlation is observed with transport properties, suggesting that the structural variations relevant for charge transport occur on a length scale finer than the resolution of $\ensuremath{\sim}1\text{ }\ensuremath{\mu}\text{m}$.