The induction of microsomal cytochrome P4501A1 by polycyclic aromatic hydrocarbons represents an interesting response by which mammalian cells adapt to xenobiotic exposure. Enzyme induction reflects increased transcription of the corresponding CYP1A1 gene. Analyses of the induction mechanism using genetic, biochemical, and molecular biological approaches have revealed a novel transcriptional regulatory pathway that involves ligand-dependent heterodimerization between two basic helix-loop-helix proteins (the Ah receptor and Arnt), interaction of the heterodimer with a xenobiotic-responsive enhancer, transmission of the induction signal from the enhancer to the CYP1A1 promoter, and alterations in chromatin structure. Current techniques permit examination of the induction mechanism in intact cells and analyses of the CYP1A1 gene in its native chromosomal configuration. Such experiments generate new insights into the control of mammalian transcription that are of relatively broad interest.

A near-infrared diode laser sensor is presented that is capable of measuring time-varying gas temperature and water vapour concentration at temperatures up to 1050 K and pressures up to 25 atm with a bandwidth of 7.5 kHz. Measurements with noise-equivalent-absorbances of the order of 10−3 (10−5 Hz−1/2) are made possible in dynamic environments through the use of wavelength modulation spectroscopy (WMS) with second harmonic detection (2f) on two water vapour spectral features near 7203.9 and 7435.6 cm−1. Laser performance characteristics that become important at the large modulation depths needed at high pressures are accounted for in the WMS-2f signal analysis, and the utility of normalization by the 1f signal to correct for variations in laser intensity, transmission and detector gain is presented. Laboratory measurements with the sensor system in a static cell with known temperature and pressure agree to 3% RMS in temperature and 4% RMS in H2O mole fraction for 500 < T < 900 K and 1 < P < 25 atm. The sensor time response is demonstrated in a high-pressure shock tube where shock wave transients are successfully captured, the average measured post-shock temperature agrees within 1% of the expected value, and H2O mole fraction agrees within 8%.

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005

Magnetic nanoparticles are suitable for applications such as biosensing [1] and contrast agents for magnetic resonance imaging [2] etc. Iron nanoparticles have the advantage of high saturation magnetization for these applications. However, oxidation at ambient condition makes this advantage rarely available. Encapsulating iron nanoparticles by graphitic carbon is one of the solutions to this problem.In this work, Fe-C core-shell nanoparticles are successfully synthesized. The approach is similar to Kong's method for carbon nanotubes [3]. For the transmission electron microscopy (TEM) study, the nanoparticles are transferred to a holey carbon TEM grids by applying a drop of nanoparticle suspension to the grids which are then air-dried. A Philips CM300 TEM operated at 150KeV was used for the TEM study.