Inverse angle dependence of the reflection colours of cholesteric polymeric liquid crystals mixed with pigments

Measurements on thin layers of cholesteric liquid crystals with a cyclic polysiloxane backbone show the usual angle dependence of the reflection wavelength, namely a shift to shorter wavelengths with increasing angle of observation. By mixing these liquid-crystalline side chain polymers with suitable pigments or dyes or by choice of a suitable coloured background, a red shift of the reflection colour with increasing angle can be obtained.     

Spatial mode cleaning by femtosecond filamentation in air

By studying the conical emission of a blue femtosecond laser filament in air, it is shown that self-improvement of the beams' spatial mode quality occurs for a self-guided laser pulse.     

Comparison of magnetic resonance imaging of inhaled SF6 with respiratory gas analysis

Magnetic resonance imaging of inhaled fluorinated inert gases ((19)F-MRI) such as sulfur hexafluoride (SF(6)) allows for analysis of ventilated air spaces. In this study, the possibility of using this technique to image lung function was assessed. For this, (19)F-MRI of inhaled SF(6) was compared with respiratory gas analysis, which is a global but reliable measure of alveolar gas fraction. Five anesthetized pigs underwent multiple-breath wash-in procedures with a gas mixture of 70% SF(6) and 30% oxygen. Two-dimensional (19)F-MRI and end-expiratory gas fraction analysis were performed after 4 to 24 inhaled breaths. Signal intensity of (19)F-MRI and end-expiratory SF(6) fraction were evaluated with respect to linear correlation and reproducibility. Time constants were estimated by both MRI and respiratory gas analysis data and compared for agreement. A good linear correlation between signal intensity and end-expiratory gas fraction was found (correlation coefficient 0.99+/-0.01). The data were reproducible (standard error of signal intensity 8% vs. that of gas fraction 5%) and the comparison of time constants yielded a sufficient agreement. According to the good linear correlation and the acceptable reproducibility, we suggest the (19)F-MRI to be a valuable tool for quantification of intrapulmonary SF(6) and hence lung function.     

Electrooxidation of pyrrole-terminated self-assembled lipoic acid derivatives

New pyrrole derivatives, pyrrolyl lipoic acid (Py-LA 3) and dipyrrolyl lipoic acid (Py₂-LA 2) have been used for surface attachment and immobilisation on gold surfaces, by self-assembly. The electrooxidation of the surface-confined pyrroles was analysed by cyclic voltammetry and the modified electrodes morphological and thickness changes addressed by scanning probe microscopy and ellipsometry. The data support the formation of oligomers as a result of the pendant-pyrrolyl units ease oxidation but provide no evidence of an effective subsequent polymerisation.     

A novel fullerene lipoic acid derivative: Synthesis and preparation of self-assembled monolayers on gold

Synthesis and preparation of self-assembled monolayers of a novel fullerene lipoic acid derivative on gold are reported. The presence of densely packed SAMs was confirmed by ellipsometry and cyclic voltammetry. The electrochemical response of the modified electrode in organic media exhibits the first two redox peaks characteristic of the extended π-electron system of fullerene. C₆₀ surface coverage (1.4 × 10⁻¹⁰ mol cm⁻²) has been electrochemically determined by the redox process of the adsorbed fullerene moiety and by reductive desorption of the SAM in strong alkaline solution. Electrochemical data indicate that all four sulphur atoms are involved in the self-assembly process, providing an increase of SAM stability in comparison to mono or di-thiolated appended molecules. Visualisation of discrete fullerene molecules by scanning tunnelling microscopy supplied further evidence for gold modification and molecular distribution on the surface. Mixed monolayers of hexanethiol and fullerene derivatives in a proportion of 1:2 have been also studied with the purpose of controlling the amount and distribution of fullerene units on the gold surface.     

Carbocyclic phenylhydrazines in the Fischer Indole Synthesis—I: Reactions with cycloalkanones

Reactions of 1-phenylpyrazolidine with a variety of cycloalkanones yield 5-(3-aminopropyl)-cycloalk[b]indoles2a, 2c, 2d, 2e, 2f, 2g; with N-benzoyl-4-piperidone the product is3; 2-methylcyclohexanone and 2-carbethoxycyclohexanone yield4a and4b resp. while 1,2-cyclohexanedione yields5.     

Tobacco Mosaic Virus as a Carrier for Small Molecules I. The preparation and characterization of a TMV/α-melanotropin conjugate

The use of tobacco mosaic virus (TMV) covalently loaded with hormones or other small molecules for various purposes including receptor detection and isolation is proposed. The basic principle is that of cooperative affinity interactions involving (large) numbers of artificially introduced sites (e.g. hormones) of the modified virus on the one hand and membrane-bound sites (e.g. receptors) of a cell or of a cellmembrane particle on the other. In order to test the feasibility of such TMV/hormone conjugates, TMV carrying about 500 molecules of a biologically active α-melanotropin analogue was synthesized, and characterized by its aspect under the electron microscope, by its infectivity, its melanophore-stimulating activity, and its reaction with antisera against α-melanotropin. The observed hormonal activity is in accordance with the idea of cooperative affinity interactions.     

Enantioselektive Verseifung der Diacetate von 2-Nitro-1,3-diolen mit Schweineleber-Esterase und Herstellung enantiomerenreiner Derivate von 2-Nitro-allylalkoholen (chirale Verknüpfungsreagenzien)

Enantioselective Saponification of Diacetates of 2-Nitro-1,3-propanediols by Pig-Liver Esterase and Preparation of Enantiomerically Pure Derivatives of 2-Nitro-allylic Alcohols (Chiral Multiple-Coupling Reagents) The reproducible enantioselective saponification of open-chain and cyclic diacetates of meso-2-nitro-1,3-propanediols (see 4b – 13b ) with pig-liver esterase (PLE) gives monoacetates (see 4c – l3c ) of > 95% enantiomeric excess. The Re enantiotopic acetate group appears to be saponified preferentially, as proved by the X-ray crystal structure analysis of three camphanoates 4d , 6d , and 7d . Elimination of H₂O or AcOH from the hydroxy acetates thus available gives derivatives of nitro-allylic alcohols (see 20 – 24 , 27 , and 29 ) which are subjected to diastereoselective Michael additions or S_N2′ substitutions.