In situ analysis of solvents on breath and blood: a selected ion flow tube mass spectrometric study

We report measurements of residual vapour levels of xylenes and trimethylbenzenes, present following a floor re-surfacing procedure, using the technique of selected ion flow tube mass spectrometry (SIFT-MS). A subject exposed to controlled amounts of xylene and mesitylene was monitored by direct breath exhalation over a 4-hour period after exposure to the volatile organic compounds (VOCs) had stopped. The headspace gases above 5 mL blood samples taken over this period were also monitored. The decays of the solvent levels with time were fitted to a two-compartment model with residence times for xylene and mesitylene of 0.37 h and 0.38 h, respectively (compartment one) and 2.5 h and 2.8 h, respectively (compartment two).     

Scales for rectangular horns

The scales presented are useful both for design of optimum horns for a given gain, and for finding the gains of rectangular horns from the dimensions. This article further illustrates the relationships among various parameters of rectangular horns. Although the design method started with a waveguide width-to-height ratio of 2:1, the method produces suitable designs for other waveguide ratios.     

Phase difference between linear components of ellipticallypolarized waves from amplitude only measurements

An amplitude-only measurement setup can measure the axial ratio and tilt angle of an elliptically polarized wave. During design, both the amplitude and phase of the linear components are needed. The equipment measures the amplitudes directly. A nomograph, using the well-known relationships between polarization components determines the phase of the vertical component relative to the horizontal. The value of the nomograph goes beyond the stated objective, because it shows the relationships between the variables. The nomograph gives both the requirements for good circularity, and the sensitivity of the various parameters     

Polybenzimidazochinazoline: Hochtemperaturbest?ndige Matrix-Stoffe

Ohne Zusammenfassung     

Satellite phenomena in the X-ray photoelectron spectra of lanthanide trihydroxides

Using the direct CI method perturbation corrections to the Koopmans ionization energies have been obtained up to order 10 for the molecules CN^? and H₂O. The results are compared with those from the fully converged CI and B_k-type calculations. The convergence of the perturbation series is found to be quite slow although substantial improvement is possible using a variation-perturbation method.     

Matrix isolation study of the vacuum-ultraviolet photolysis of HCCIF2 and of HCCl2F. Infrared spectra of the parent molecules and of the ClCF2 and FCCl2 free radicals

Studies of the vacuum-ultraviolet photolysis of HCClF₂ and of HCCl₂F isolated in argon and nitrogen matrices at 14°K have led to the infrared spectroscopic identification of the free radicals ClCF₂ and FCCl₂, respectively. Support for this identification has been obtained from studies of the vacuum-ultraviolet photolysis of DCClF₂, of DCCl₂F, and of H¹³CCl₂F, as well as from studies of halogen-atom abstraction from CClF₃ and from CCl₃F by sodium atoms in an argon matrix environment. The CCl bonds of FCCl₂, like those of CCl₃ and of HCCl₂, appear to be exceptionally strong. Gas-phase infrared spectral data are also reported for DCClF₂ and for DCCl₂F, not previously studied. Vibrational assignments are proposed for these two molecules, and data supporting the reassignment of one of the CF stretching fundamentals of HCClF₂ are presented.     

An investigation into the mechanisms of DNA strand breakage by direct ionization of variably hydrated plasmid DNA

The mechanisms by which ionizing radiation directly causes strand breaks in DNA were investigated by comparing the chemical yield of DNA-trapped free radicals to the chemical yield of DNA single strand break (ssb) and double strand break (dsb), as a function of hydration (Gamma). Solid-state films of plasmid pUC18, hydrated to 2.5 < Gamma < 22.5 mol, were X-irradiated at 4 K, warmed to room temperature, and dissolved in water. Free radical yields were determined by EPR at 4 K. With use of the same samples, Gel electrophoresis was used to measure the chemical yield of total strand breaks, which includes prompt plus heat labile ssb; G'total(ssb) decreased from 0.092 +/- 0.016 micromol/J at Gamma= 2.5 to 0.066 +/- 0.008 micromol/J at Gamma= 22.5. Most provocative is that at Gamma= 2.5 the yield of total ssb exceeds the yield of trapped deoxyribose radicals: G'total(ssb) - G'sugar(fr) = 0.06 +/- 0.02 micromol/J. Nearly 2/3 of the strand breaks are derived from precursors other than radicals trapped on the deoxyribose moiety. To account for these nonradical precursors, we hypothesize that strand breaks are produced by two one-electron oxidations at a single deoxyribose residue within an ionization cluster.