X-ray diffraction study of a polybutadiene, side chain, mesomorphic polymer

A side chain, mesomorphic polymer has been synthesized, starting from a commercial polybutadiene main chain. A preliminary X-ray diffraction study shows the influence of the degree of substitution and the spacer length on the interdigited S_A layer thickness, particularly for strongly polar alkoxycyanobiphenyl mesogens. Some hypotheses are deduced about the particular odd-even effect observed with this backbone and on the conformation of the main and side chains.     

Detonability of simple and representative components of pyrolysis products of kerosene: pulsed detonation engine application

The use of liquid fuels such as kerosene is of interest for the Pulse Detonation Engine (PDE). In this context, a representative gaseous mixture of the lighter products resulting from the decomposition of a kerosene of type JP-10 was studied. The detonability limits of simple components (hydrogen, ethylene, propylene) and mixtures of these components were tested in a 50 mm diameter and 2.5 m long detonation tube. This dimension is compatible with the applications of the aircraft industry and more particularly the PDE. The influences of the nitrogen dilution, geometry of the DDT device (Schelkin spiral), ignition energy and initial pressure were investigated. This paper was based on work that was presented at the 19th International Colloquium on the Dynamics of Explosions and Reactive Systems, Hakone, Japan, July 27 - August 1, 2003. Communicated by J.E. Shepherd     

Short laser pulse generation: Part one

The status of short laser pulse generation is reviewed. Achievements, limitations and potential of techniques producing pulses shorter than 50 ns, from the ultra-violet to the infra-red, are examined.In this half of the paper the physical principles underlying the generation of ultra-short pulses are introduced and the methods of Q-switching, gain switching, cavity dumping and mode-locking are considered.     

Evaluation of the Efficiency of a Double Spark Plug to Improve the Performances of Combustion Engines: Pressure Measurement and Plasma Investigations

Plasma Chemistry and Plasma Processing - The ignition sparks provided by the conventional spark plug (CSP) do not always ensure a fast and complete combustion of the hydrocarbon–air mixture....     

Numerical study on transmission of multimode laser pulses by dye molecules

A theoretical model and a numerical study of the transmission of multimode laser pulses by malachite green dye are presented. Excited state absorption is taken into account. The transmitted pulses exhibit increased intensity fluctuations moderated by the excited state absorption. Reference is made to recent experimental results.     

Elimination of the concentration dependence in mass isotopomer abundance mass spectrometry of methyl palmitate using metastable atom bombardment

An important problem in mass isotopomer abundance mass spectrometry (MIAMS) is the dependence of measured mass isotopomer abundances on sample concentration. We have evaluated the role of ionization energy on mass isotopomer abundance ratios of methyl palmitate as a function of sample concentration. Ionization energy was varied using electron impact ionization (EI) and metastable atom bombardment (MAB). The latter generates a beam of metastable species capable of ionizing analyte molecules by Penning ionization. We observed that ionization of methyl palmitate by EI (70 eV) showed the greatest molecular ion fragmentation and also showed the greatest dependence of relative isotopomer abundance ratios on sample concentration. Ionization using the 3P2 and 3P0 states of metastable krypton (9.92 and 10.56 eV, respectively) resulted in almost no molecular ion fragmentation, and the isotopomer abundances quantified were essentially independent of sample concentration. Ionization using the 3P2 and 3P0 states of metastable argon (11.55 and 11.72 eV, respectively) showed molecular ion fragmentation intermediate between that of EI and MAB(Kr) and showed an isotopomer concentration dependence which was less severe than that observed with EI but more severe than that observed with MAB(Kr). The observed decrease in the dependence of isotopomer abundance on sample concentration with a decrease in molecular ion fragmentation is consistent with the hypothesis that proton transfer from a fragment cation to a neutral molecule is the gas phase reaction mechanism responsible for the concentration dependence. Alternative explanations, e.g., hydrogen abstraction from a neutral molecule to a molecular cation, is not supported by these results. Moreover, the MAB ionization technique shows potential for eliminating one source of error in MIAMS measurements of methyl palmitate, in particular, and of fatty acids methyl esters, in general.     

An electro-optical technique to vary continuously a laser pulse

The principle of a new technique to vary continuously the duration of a laser pulse using an electro-optical modulator is described. An experiment using a ruby laser demonstrates the validity of the idea.