The study of catalysis by novel gas chromatographic techniques

Summary Studies of catalytic reactions have been made using differential (sample-vacancy) and stopped-flow gas chromatography. Reactions are often very sensitive to trace materials and in particular it has been necessary to devise a technique for removing oxygen from carrier-gas streams down to very low levels. The techniques and the results are often relevant to the more normal analytical applications of gas chromatography.Presented at Table Ronde sur les mesures physicochimiques par chromatographie en phase gazeuse (Lyons, November 13–14th, 1973), organized by Dr.robin (INSA, Villeurbanne)     

Sensitivity to disorder of the metallic state in the ruthenates

We report the results of transport measurements on SrRuO3, Sr3Ru2O7, and CaRuO3. In SrRuO3 and Sr3Ru2O7, our findings are consistent with the predictions of Fermi liquid theory, in contrast to previous reports based on samples with much shorter mean free paths. In CaRuO3, however, a T1.5 power law is seen in the resistivity in the high purity samples studied here. Our work gives concrete evidence that even the metallic state of the ruthenates is highly sensitive to disorder.     

The Fire/Heat Concept and Its Journey from Prehistoric Time into the Third Millennium

The notion of fire/light/heat/energy is recognized as an integrating element in the pathway of ordering matter and society, and its historical aspects are thoroughly reviewed. Fire is argued to be a philosophical archetype and its role in the early concept of four elements is discussed. The Indian, Arabic and Greek historical bases are mentioned. Alchemy is briefly reviewed as a source of the wider adoption of fire. The era of renaissance and the new age are also included. The message of fire/heat is nowadays focused on the progress of civilization, with the assumption of engines as information transducers based on the conscious exploitation of fire. The role of chaos is emphasized. Overall, a condensed but consistent view is given of the various concepts that emerged during the historical progress of the understanding of heat (noting 61 references). This revised version was published online in July 2006 with corrections to the Cover Date.     

Generalized stress/strain rate relations for creep of thin shells; a comparison of “exact” and approximate relations

A set of approximate generalized stress/strain rate relations which has been used for the stationary creep analysis of thin shells is compared with the corresponding ‘exact’ relations. The comparison is made by computing the functions from which the relations are derived and plotting the corresponding surfaces. Results are included for a limiting condition in which the stress/strain rate relations become those for a rigid-plastic material obeying the von Mises yield condition and associated flow rule. Although the comparison is made only for conditions valid in a cylindrical shell under rotationally symmetric loading, it indicates the errors which are likely to occur when the approximate relations are used in stationary creep analysis.     

Following radical pair reactions in solution: a step change in sensitivity using cavity ring-down detection

The study of radical pair intermediates in biological systems has been hampered by the low sensitivity of the optical techniques usually employed to investigate these highly reactive species. Understanding the physical principles governing the spin-selective and magneto-sensitive yields and kinetics of their reactions is essential in identifying the mechanism governing bird migration, and might have significance in the discussion of potential health hazards of electromagnetic radiation. Here, we demonstrate the powerful capabilities of optical cavity-enhanced techniques, such as cavity ring-down spectroscopy (CRDS) in monitoring radical recombination reactions and associated magnetic field effects (MFEs). These include submicrosecond time-resolution, high sensitivity (baseline noise on the order of 10(-6) absorbance units) and small (μL) sample volumes. Combined, we show that these represent significant advantages over the single-pass flash-photolysis techniques conventionally applied. The studies described here focus on photoinduced radical pair reactions involving the protein lysozyme and one of two possible photosensitizers: anthraquinone-2,6-disulphonate and flavin mononucleotide. CRDS-measured MFEs are observed in pump-probe experiments and discussed in terms of the sensitivity gains and sample-volume minimization afforded by CRDS when compared with flash photolysis methods. Finally, CRDS is applied to an in vitro MFE study of intramolecular electron transfer in the DNA-repair enzyme, Escherichia coli photolyase, a protein closely related to cryptochrome which has been proposed to mediate animal magnetoreception.     

Combinatorial wetting in colour: an optofluidic nose

We present a colourimetric litmus test for simple differentiation of organic liquids based on wetting, which achieves chemical specificity without a significant sacrifice in portability or ease-of-use. Chemical specificity is derived from the combination of colourimetric wetting patterns produced by liquids in an array of inverse opal films, each having a graded wettability, but using different surface groups to define that gradient.     

The chemistry of trifluoramine oxide. VII. Photolytic Generation and electron spin resonance spectra of F2NO radicals

Photolysis of solid F₃NO at ?196° produces the F₂NO radical identified by its 9-line ESR spectrum consisting of a fluorine split 1:2:1 triplet (a_F = 143.0 G), each component of which is further split by ¹⁴N into 1:1:1 triplets (a_N = 94.5 G), with g = 2.0093. Trifluoramine oxide enriched with ¹⁵N provided the expected 6-line spectrum of F₂¹⁵NO comprised of the fluorine triplet (a_F = 142.6 G) each component of which is further split by ¹⁵N into doublets (a_N = 132.3 G), with g = 2.0094. The data are best interpreted in terms of a pyramidal structure for F₂NO.