Timing and detuning studies of a synchronously pumped mode-locked dye laser

The timing relationship between a synchronously pumped mode-locked dye laser and its pump laser is explored experimentally and theoretically. The experimental data is in quantitative agreement with numerical solutions of a semiclassical model that includes no free parameters. The data also agrees qualitatively with an approximate, analytic distillation of this model which is presented here for the first time. Our study has a direct bearing on the jitter and the long term stability of these important ultrashort pulse lasers.     

Synthesis, reactivity ratios and characterization of hydroquinone promoted CT co-polymerization of styrene and methyl methacrylate in a room temperature ionic liquid

For the first time, charge transfer (CT) co-polymerization of styrene and methyl methacrylate, promoted by hydroquinone (HQ) at various feed compositions, has been achieved in a hydrophobic ionic liquid. The co-polymers have been characterized for thermal and molecular weight properties. The molecular weights obtained for the co-polymers made in ionic liquid were found to be slightly lower than the corresponding polymers synthesized in conventional solvent. The reactivity ratios of the co-polymers have been computed and compared with conventional CT polymerization. The reactivity ratios of Sty-MMA indicate that the co-polymerization has a tendency to alternate and to produce a higher styrene content in the co-polymers. The numerical values of the inverse of r₁ and r₂ indicate that both monomer radicals have a distinct cross propagation tendency.     

Novel Lewis-base ionic liquids replacing typical anions

We have synthesized two kinds of new Lewis-base ionic liquids (ILs); one is based on the relatively strong Lewis basic acetate anion, and the other is a salt composed of a mono-alkylated diamine such that the Lewis base site is incorporated in the cation. 1-Octyl-4-aza-1-azonia-bicyclo[2.2.2]octane bis(trifluoromethanesulfonyl)amide, [C₈dabco]TFSA, and N-butyl-N-methylpyrrolidinium acetate, [p_1,4]OAc, melted into fluid liquids at 26 and 81 °C, respectively. The thermal decomposition of [p_1,4]OAc started at around 150 °C, whereas the thermal stability of [C₈dabco]TFSA was almost equal to that of typical TFSA-based ILs in spite of the Lewis base site. This suggests that if the Lewis base site is incorporated into the cation the IL can maintain higher thermal stability. In addition, as a further result of the presence of the basic nitrogen, [C₈dabco]TFSA can dissolve hydrated Cu(NO₃)₂ whereas the other TFSA-based ILs cannot.     

Temperature dependence of the magnetic penetration depth in YBa2Cu3O6.95

We report precision transverse fieldSR measurements of the internal field distribution in the vortex state of crystalline YBa₂Cu₃O_6.95. A novel low background apparatus was used to study a mosaic sample of three high quality single crystals (T_c=93.3K). The observed frequency spectra in magnetic fields of 5kG and 15 kG applied along the c-axis have the characteristic features expected for a regular vortex lattice with some additional broadening. From a preliminary analysis we find that [(0)/(T)]² has a linear temperature coefficient forT<30 K. Such a term is inconsistent with simple s-wave pairing in the superconducting state. These results support recent microwave measurements of(T) on similar crystals in zero applied field but differ significantly from previousSR reports on sintered powders and crystals with lower T_c.This research was supported by the Natural Sciences and Engineering Research Council of Canada.     

Analysis of novel imidazoles from isolated perfused rabbit heart by two high-performance liquid chromatographic methods.

The paper reports two analytical high-performance liquid chromatographic methods to detect and quantify cardiac-derived histidyl derivatives. Method A relies on relative hydrophobicities as a basis of separation. Method B is an ion-pairing method in which the compounds are eluted in an entirely different order. Fractions collected from method A have been co-eluted in admixture in method B with authentic reference compounds. Thus the existence of the following imidazole ring-containing compounds derived from heart have been confirmed: N-acetylhistidine, N-acetyl-1-methylhistidine, N-acetylcarnosine, N-acetylhomocarnosine, homocarnosine, anserine, carnosine, balenine. Compounds were found in both tissue samples and perfusates.