Interaction of NO2 with hydrocarbon soot: focus on HONO yield, surface modification, and mechanism

Using a coated-wall flow tube connected to a mass spectrometer, the heterogeneous conversion of NO2 to HONO on dry hydrocarbon soot surfaces has been studied at room temperature and 243 K. Particular attention was given to the measurement of the HONO yield as a function of hydrocarbon fuel, NO2 partial pressure, extent of uptake, and surface oxidation state. In all cases, the yield is invariant of these parameters and close to unity, indicative of an irreversible oxidation mechanism by which the NO2 abstracts an H atom from the surface. XPS analysis shows that the surface N content does not measurably increase with NO2 exposure. There is minimal surface reactivity regeneration with time or via exposure to high relative humidity. A BET surface area measurement of the entire soot film exposed to NO2 was used to determine the amount of HONO that can be generated from the soot surface per unit surface area, prior to its deactivation. The reduction of NO2 to HONO on soot is unlikely to account for the observed nighttime buildup of HONO in polluted urban environments.     

Dihydrothienopsoralens: New furocoumarins as potential photoreacting agents

A series of new dihydrothienopsoralen derivatives were synthesized from 6-hydroxybenzo[b]furan in four steps in good yield. These compounds were prepared as potential photosensitizing and chemotherapeutic agents for psoriasis. The spectroscopy study in also reported and showed an absorbance at λ = 364 nm and fluorescence at λ = 440 nm with high molar absorptivity, wave length used to perform the photochemical and photobiological experiments.     

亚胺膦R_3PNH(R =CH_3,Cl)的极性及P-N键性质的理论研究

用从头算方法在B3LYP/ 6 31G 水平上对亚胺膦R3PNH(R =CH3,Cl)进行了理论计算研究。结果表明这两种亚胺膦的极性 ,P -N键性质及分子轨道存在明显差异 ,亚胺膦 (CH3) 3P =NH及其P -N键的极性很强 ,而Cl3P =NH的极性则较弱。与Cl3P =NH相比 (CH3) 3P =NH可能是较好的类Wittig反应试剂。     

Phase-amplitude characterization of a high-repetition-rate quantum dash passively mode-locked laser

We apply a novel phase-amplitude characterization method to a one-section quantum dash-based passively mode-locked laser at a 42.2 GHz repetition rate. The method relies on the measurement of the spectral phase of the longitudinal modes by the successive analysis of the correlation signal of a group of three adjacent modes. It provides both the temporal shape of the intensity and the phase of the emitted signal. A pulse of 1.5 ps of width is measured, and a pedestal is exhibited. Extinction ratio limitation is explained by investigating the origin of this pedestal. The accuracy of the method is estimated by comparing the measured autocorrelation signal and the calculated one from the phase analysis.     

Germanium based photonic components toward a full silicon/germanium photonic platform

Lately, germanium based materials attract a lot of interest as they can overcome some limits inherent to standard Silicon Photonics devices and can be used notably in Mid-Infra-Red sensing applications. The quality of epitaxially grown intrinsic and doped materials is critical to reach the targeted performances. One of the main challenges in the field remains the fabrication of efficient group-IV laser sources compatible with the microelectronics industry, seen as an alternative to the complexity of integration of III-V lasers on Si. The difficulties come from the fact that the group-IV semiconductor bandgap has to be transformed from indirect to direct, using high tensile strains or by alloying germanium with tin. Here, we review recent progresses on critical germanium-based photonic components such as waveguides, photodiodes and modulators and discuss the latest advances towards germanium-based lasers. We show that novel optical germanium-On-Insulator (GeOI) substrates fabricated by the Smart Cut? technology is a key feature for future Si - Complementary Metal Oxide Semiconductor (CMOS) - compatible laser demonstration. This review hints at a future photonics platform based on germanium and Silicon.     

Fundamental symmetries studies with cold trapped francium atoms at ISAC

Francium combines a heavy nucleus (Z = 87) with the simple atomic structure of alkalis and is a very promising candidate for precision tests of fundamental symmetries such as atomic parity non-conservation measurements. Fr has no stable isotopes, and the ISAC radioactive beam facility at TRIUMF, equipped with an actinide target, promises to provide record quantities of Fr atoms, up to 10¹⁰/s for some isotopes. We discuss our plans for a Fr on-line laser trapping facility at ISAC and experiments with samples of cold Fr atoms. We outline our plans for a measurement of the nuclear anapole moment – a parity non-conserving, time-reversal conserving moment that arises from weak interactions between nucleons – in a chain of Fr isotopes. Its measurement is a unique probe for neutral weak interactions inside the nucleus.