Pyrolysis of 2-butyne/vinylacetylene mixtures between 350 and 450°C

Vinylacetylene and 2-butyne mixtures were pyrolyzed at 350–450°C in the absence and presence of O₂ and NO. The major product of the reaction is a polymer, but o-xylene is also produced and was studied as the species of interest. The C₈H₁₀ formation rate is first-order in C₄H₄ and C₄H₆. The rate coefficient is best fitted by though it is not inconsistent with where R is the ideal gas constant in kJ/mol-K. O-xylene formation occurs by two processes: a concerted molecular mechanism (?67%) and a singlet diradical mechanism (?33%).     

Medium loss optical fibres and cables

Many of the uses to which fibres will be put in the next few years will require at most 100 MHz bandwidth and relatively short fibre lengths. Research has therefore been concentrated on producing a high numerical aperture fibre using normal lead silicate glasses. Details are given for commercially available fibres having attenuation less than 100 dB km^-1 in the range 800–900 nm. These are available in both bundle and single fibres, the former sheathed in pvc and the latter in polypropylene.     

Autocrosslinkable methyl-2-phenylethylpolysiloxane stationary phase for capillary column gas chromatography

Methyl-2-phenylethylpolysiloxane polymers have been synthesized for comparison with methylphenylpolysiloxane stationary phases for gas chromatography. The 50% 2-phenylethyl polysiloxane was found to be autocrosslinkable at 260°C without addition of free redical initiator. Although the selectivity of this phase appears to be similar to the 50% phenyl polysiloxane, its thermal stability is not as high.     

Identification of dominant odor chemicals emanating from explosives for use in developing optimal training aid combinations and mimics for canine detection

Despite the recent surge in the publication of novel instrumental sensors for explosives detection, canines are still widely regarded as one of the most effective real-time field method of explosives detection. In the work presented, headspace analysis is performed by solid phase microextraction (SPME)/gas chromatography-mass spectrometry (GC-MS), and gas chromatography-electron capture detection (GC-ECD), and used to identify dominant explosive odor chemicals seen at room temperature. The activity of the odor chemicals detected was determined through field trials using certified law enforcement explosives detection canines. A chemical is considered an active explosive odor when a trained and certified explosives detection canine alerts to a sample containing that target chemical (with the required controls in place). A sample to which the canine does not alert may be considered an inactive odor, but it should be noted that an inactive odor might still have the potential to enhance an active odor's effect. The results presented indicate that TNT and cast explosives share a common odor signature, and the same may be said for plasticized explosives such as Composition 4 (C-4) and Detasheet. Conversely, smokeless powders may be demonstrated not to share common odors. The implications of these results on the optimal selection of canine training aids are discussed.     

Coordination chemistry of the water-soluble ligand TPPTP and formation of a [Mo(CO)5(m-TPPTP)] monolayer on an alumina surface

Phosphonate and phosphonic acid functionalized phosphine complexes of platinum(II) were prepared via direct reaction of the ligands with K2PtCl4 in water. Either cis or trans geometries were found depending on the nature of the ligand. The crystal structure of P(3-C6H4PO3H2)3.2H2O (6b) (triclinic, P1, a = 8.3501(6) A, b = 10.1907(6) A, c = 14.6529(14) A, alpha = 94.177(6) degrees, beta = 105.885(6) degrees, gamma = 108.784(5) degrees, Z = 2) shows a layered arrangement of the phosphonic acid. The phosphonodiamide complex cis-[PtCl2(P[4-C6H4PO[N(CH3]2]]3)2].3H2O (10) was synthesized in 89% yield and hydrolyzed to the phosphonic acid complex using dilute HCl. Aqueous phase and silica gel supported catalytic phosphonylation of phenyl triflate using palladium phosphine complexes was achieved. A molybdenum complex, Mo(CO)5[P3-C6H4PO3H2)3] (11), was synthesized in situ and grafted to an alumina surface. XPS, RBS, and AFM studies confirm the formation of a monolayer of 11 on the alumina surface.     

Functional one-dimensional lipid bilayers on carbon nanotube templates

Use of biological machines and environments in novel bioinorganic nanostructures is critical for development of new types of biosensors, bio-NEMS devices, and functional materials. Lipid bilayers that mimic a cell membrane have already played an important role in such applications. We present supported lipid bilayers that spontaneously assemble in a continuous nanoshell around a template of a carbon nanotube wrapped with hydrophilic polymer cushion layers. We demonstrate that such 1-D lipid membranes are fluid and can heal defects, even over repeated damage-recovery cycles. A simple diffusion model can describe mobility of lipid molecules in these 1-D nanoshells. These structures could lead to the development of new classes of biosensors and bioelectronic devices.     

A Monte Carlo treatment of the decay of80mBr,a novel Auger electron emitting isotope with potential for therapy

Monte Carlo calculations were done to simulate the decay of^80mBr in order to estimate the energies and distribution of Auger and Coster-Kronig electrons emitted in this de-excitation process. Results show that for an isolated atom, the average number of electrons emitted per decay is 6.926 and 8.016 for an atom in the condensed state. These values agree well with experimental results of Wexler and Anderson. The average calculated electron energies were 1122 eV and 991 eV with ranges of 8.02 A° and 6.71 A° in unit density matter for the isolated an condensed states, respectively. These results will be used to estimate localized energy deposition which will be correlated to the radiotoxic effects of^80mBr-bromo-deoxyuridine as measured in experiments currently underway in our laboratory using cell cultures. Our aim is to assess the radiotoxicity of low energy, short range electrons for its eventual use in cancer therapy.Deceased, to whose memory this paper is dedicated.     

The formation of NO+ from the reaction of N2(2+) with O2

We have studied the potentially ionospherically significant reaction between N(2)2+ with O2 using position-sensitive coincidence spectroscopy. We observe both nondissociative and dissociative electron transfer reactions as well as two channels involving the formation of NO+. The NO+ product is formed together with either N+ and O in one bond-forming channel or O+ and N in the other bond-forming channel. Using the scattering diagrams derived from the coincidence data, it seems clear that both bond-forming reactions proceed via a collision complex [N2O2]2+. This collision complex then decays by loss of a neutral atom to form a daughter dication (NO2(2+) or N2O2+), which then decays by charge separation to yield the observed products.     

Evaluation of laboratory performance in IMEP water interlaboratory comparisons

The aim of International Evaluation Programme (IMEP) is to present objectively the quality of chemical measurements. Participants in IMEP compare their reported measurement results with independent external certified reference values with demonstrated traceability and uncertainty, as evaluated according to international guidelines. Three major interlaboratory comparisons (ILCs), IMEP-6, IMEP-9 and IMEP-12, on trace elements in water were carried out from 1994 to 2000. Participants' results for Cd, Fe and Pb concentrations from these three different IMEP water ILCs were compared by means of suitable performance indicators. The performance evaluation criteria were set according to the requirements stated in the Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Two different performance indicators were selected for evaluation of the individual participants' results: the commonly used z-score and the not so well-known E _n number. The group performance indicator is based on the variation of z-scores. To assess the individual measurement performance, not only the deviation of the reported measurement values from the certified reference value, but also criteria for maximum and minimum acceptable uncertainties were taken into account. The participants' performance is also reviewed by means of using a simple graphical tool, called “Naji-plots”.