Previous studies have suggested that breath gases may be related to simultaneous blood glucose and blood ketone levels in adults with type 2 and type 1 diabetes. The aims of this study were to investigate these relationships in children and young people with type 1 diabetes in order to assess the efficacy of a simple breath test as a non-invasive means of diabetes management. Gases were collected in breath bags and measurements were compared with capillary blood glucose and ketone levels taken at the same time on a single visit to a routine hospital clinic in 113 subjects (59 male, age 7 years 11 months-18 years 3 months) with type 1 diabetes. The patients were well-controlled with relatively low concentrations of the blood ketone measured (β hydroxybutyrate, 0-0.4 mmol l(-1)). Breath acetone levels were found to increase with blood β hydroxybutyrate levels and a significant relationship was found between the two (Spearman's rank correlation ρ = 0.364, p < 10(-4)). A weak positive relationship was found between blood glucose and breath acetone (ρ = 0.16, p = 0.1), but led to the conclusion that single breath measurements of acetone do not provide a good measure of blood glucose levels in this cohort. This result suggests a potential to develop breath gas analysis to provide an alternative to blood testing for ketone measurement, for example to assist with the management of type 1 diabetes.

Methyl iodide photolysis at 193 nm has been studied through probing the I((2)P(1/2)-(2)P(3/2)) transition in the atomic iodine photofragment using diode laser spectroscopy. The I((2)P(1/2)) quantum yield has been determined through two different diode laser techniques and then compared. Frequency-modulated diode laser based absorption spectroscopy was used to extract nascent Doppler lineshapes from which an I((2)P(1/2)) quantum yield of unity is inferred. However when diode laser gain/absorption measurements were made, an I((2)P(1/2)) quantum yield of 0.68 ± 0.04 was found. The reason for this discrepancy is shown to lie in the diode laser gain/absorption method. Molecular iodine is found to be formed during the experiment via atomic iodine recombination and then in turn dissociates to produce both I((2)P(1/2)) and I((2)P(3/2)), thus distorting the returned quantum yield. This conclusion is supported both by the reduction of the I((2)P(1/2)) quantum yield with number of photolysis laser shots when measured using this technique and by the presence of fluoresence which is shown to have excited-state lifetimes and quenching rates that are consistent with those previously measured for the D and D' states of molecular iodine.

A photoelectron-photoelectron coincidence spectrometer, incorporating two independent toroidal analyzers, has been developed to study photodouble ionization of gas targets using synchrotron radiation. The energy-resolved and angle-dispersed electron images are recorded using two-dimensional position-sensitive detectors. The design and performance of the spectrometer is described, with particular emphasis on the electron optical properties of toroidal deflectors and their associated electrostatic lenses. The operation and calibration of the spectrometer are discussed and sample (␥,2e) results of helium are presented.

Absolute peak absorption cross sections and pressure broadening coefficients have been recorded with sub-Doppler limited instrumental resolution for selected rotational lines in the 2(0)(2)4(0)(1) vibronic band of the formaldehyde A(1)A2-X(1)A1 electronic transition. The measured absorption cross sections range between (0.18 +/- 0.01) and (10.1 +/- 0.08) x 10(-19) cm2 molecule(-1) and are considerably larger than values from the literature recorded using apparatus where instrumental broadening was significant. However, comparisons with spectral simulations with equivalent resolution from Smith et al. (J. Phys. Chem. A 2006, 110, 11645-11653) are in excellent agreement. Pressure broadening was studied for the collision partners CH2O, CO2, N2, O2, Ne, Kr, Ar, and He, and the resulting broadening coefficients were found to be reduced in comparison to equivalent values measured in infrared regions, consistent with the reduced dipole moment of the upper state probed in this work. Cavity-enhanced absorption spectroscopy (CEAS) measurements were undertaken using calibrated low concentration (2.9-4.6 ppmv) samples from a permeation source and demonstrate a noise equivalent absorption of 1.2 x 10(-6) cm(-1) Hz(-1/2). This implies a minimum detectable formaldehyde concentration with the current system in atmospheric air of 172 ppbv Hz(-1/2).

The collisional loss of vibrational energy from chemically activated CH3CH2F and CH2FCH2F formed with average energies of 91 and 92.5 kcal mol'1, respectively, has been studied at 300 K with four bath gases, SFe, C02, N2, and He. These chemically activated molecules were formed by combination of CH3 with CH2F and of CH2F with CH2F. The data cover an extensive range of pressure and permit the assignment of the mean energy transfer per collision and the form of the transition probability distribution. For He the (AEd) values were 1.0 kcal mol"1 with an exponential distribution for both C2H6F and C2H4F2. The ( ) values for C2H6F or C2H4F2 were virtually the same and ranged from 2.0 to 5.0 kcal mol"1 for N2, C02, and SFe; these transition probability distributions were of the Gaussian type (represented here by a stepladder model). The results for CH3CH2F and CH2FCH2F are compared to previous findings for CH3CF3 and CH2C1CH2C1 from this laboratory. The deactivation efficiency for SF6 is similar for all four molecules. However, the deactivation of CH3CF3 by N2 and C02 is less efficient than for for the other three molecules. The He deactivation efficiencies for the fluoroethanes are all similar, but substantially smaller than for C2H4C12.