Theoretical studies of atmospheric molecules: SCF and correlated energy levels for the NO2, NO 2 + and NO 2 − systems

SCF and MC-SCF/CI calculations were carried out on the low-lying electronic states of NO₂, NO ₂ ⁺ and NO ₂ ^– , using a double-zeta quality basis set of contracted Gaussian functions. The calculations were performed primarily at the equilibrium geometry (R _NO = 2.25 a_o, _ONO=134 °) of theX ² A ₁ state of NO₂. SCF calculations on NO ₂ ⁺ in a linear conformation were also performed. Results are presented and compared with experiment and other calculations.Research supported in part by Air Force Delivery Orders F33615-72-M-5015 and MIPR889474-00117 and Air Force Office of Scientific Research and in part by the United States Energy Research and Development Administration.     

Determination of hexamethylene diisocyanate-based isocyanates in spray-painting operations. Part 2. Comparison of high performance liquid chromatography with capillary zone electrophoresis

A capillary zone electrophoresis (CZE) approach was developed for the determination of hexamethylene diisocyanate (HDI) monomer and HDI-based oligomers. A comparison of CZE with high performance liquid chromatography (HPLC) indicates that the CZE separation completely isolates isocyanates from excess solvent, derivatizing reagent and pigment while offering a fivefold increase in sensitivity. The CZE approach allows for the quantification of HDI monomer and oligomer within a 1 min time window under the run conditions selected. For the determination of HDI-based oligomer, provided that the relative response with respect to HDI monomer is calculated, there is no significant difference (p < 0.05, n = 10) in the isocyanate air concentration when using either HPLC or CZE. The results are significant because they indicate that CZE has advantages for the determination of both HDI-based oligomer and HDI monomer generated during spray-painting operations.     

Gold-catalyzed cycloisomerization of N-Propargylindole-2-carboxamides: application toward the synthesis of lavendamycin analogues

A series of N-propargylindole-2-carboxamides were found to undergo a AuCl 3-catalyzed cycloisomerization to give beta-carbolinones in high yield. The corresponding beta-chlorocarboline derivative was prepared and used for Pd(0)-catalyzed cross-coupling chemistry directed toward the synthesis of lavendamycin analogues.     

Determination by high-frequency and -field EPR of zero-field splitting in iron(IV) oxo complexes: implications for intermediates in nonheme iron enzymes

[Fe(IV)O](2+) species have been implicated as the active form of many nonheme iron enzymes. The electronic structures of iron(IV) oxo complexes are thus of great interest. High-frequency and -field electron paramagnetic resonance is employed to determine accurately the spin Hamiltonian parameters of two stable complexes that contain the FeO unit: [FeO(TMC)(CH 3CN)](CF 3SO 3) 2, where TMC = tetramethylcyclam and [FeO(N4py)](CF 3SO 3) 2, where N4Py = bis(2-pyridylmethyl)bis(2-pyridyl)methylamine. Both complexes exhibit zero-field splittings that are positive, almost perfectly axial, and of very large magnitude: D = +26.95(5) and +22.05(5) cm (-1), respectively. These definitive experimental values can serve as the basis for further computational studies to unravel the electronic structures of such complexes.     

High energy gain of trapped electrons in a tapered, diffraction-dominated inverse-free-electron laser

Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an inverse-free-electron-laser (IFEL) accelerator experiment. A 14.5 MeV electron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and field amplitude. The Rayleigh range of the laser, approximately 1.8 cm, is much shorter than the undulator length yielding a diffraction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV/m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator.     

The effects of distance and neighborhood union conditions on hamiltonian properties in graphs

We prove that a 2-connected graph G of order p is hamiltonian if for all distinct vertices u and v, dist(u,v) = 2 implies that |N(u) U N(v)| ? (2p - 1)/3. We also demonstrate hamiltonian-connected and traceability properties in graphs under similar conditions.     

Emission of α-particles in deep inelastic reactions induced by 148 MeV 14N

Energy and angular correlations between α-particles and heavy ejectiles have been measured for 148 MeV ¹⁴N incident on ¹²C, ²⁷Al and ⁵⁸Ni targets. The coincidence cross sections for ejectiles with Z < 6 may be parametrised as a product of singles cross sections for the detection of α-particles and heavy ions. For ²⁷Al and ⁵⁸Ni targets, this indicates that the α-particles are emitted at an early stage of the reaction prior to the formation of the deep inelastic fragments. For the ¹²C target, however, kinematic effects are found to dominate the observed correlations. For $\text{Z ≧ 6}$ ejectiles the observed correlations appear consistent with the emission of α-particles from the recoiling nucleus produed in the reaction.     

Crystallographic shear in the Nb2O5WO3 and Ta2O5WO3 systems

Crystallographic shear (CS) phases occurring in the Nb₂O₅WO₃ and Ta₂O₅WO₃ systems near to WO₃ were characterized by X-ray diffraction and high-resolution transmission electron microscopy. The Nb₂O₅WO₃ samples were heated at 1600K. They contained ordered {104} and {001} CS planes and wavy CS which were composed of intergrowths of {104} and {001} CS segments. The composition range over which the {104} CS series extended was from (Nb,W)O_2.954 i.e., (Nb,W)₆₅O₁₉₂, to (Nb,W)O_2.942, i.e., (Nb,W)₅₂O₁₅₃. The composition range over which the {001} CS series extended was from (Nb,W)O_2.9375, i.e., (Nb,W)₁₆O₄₇ to (Nb,W)O_2.875, i.e., (Nb,W)₈O₂₃. The Ta₂O₅WO₃ samples were prepared at 1593, 1623, and 1672K. At lower temperatures ordered {103} CS phases were found, with a composition range extending between (Ta,W)O_2.960, i.e., (Ta,W)₅₀O₁₄₈, to (Ta,W)O_2.944, i.e., (Ta,W)₃₆O₁₀₆. At 1673K ordered {103} CS phases occurred, as did wavy CS composed of intergrowths of {103} and {104} CS segments.     

Comparing Handheld Meters and Electronic Dosimeters for Measuring Ultraviolet Levels under Shade and in the Sun

This study aimed to compare the validity, reliability and practicality of alternative portable methods for measuring erythemal UVR levels in passive recreation areas in public parks. UVR levels were measured for point in time comparisons between Solarmeter 6.5 handheld meters and time‐stamped electronic dosimeters in a large central park in Melbourne, Australia. Observations were made at 20 locations in the park by two research assistants under two conditions: (1) matched shade (2) contrasting shade—no shade. Comparisons were also made with scientific instruments on the UVR monitoring station rooftop and by remotely selecting UV records and forecasts on cloud‐free dates of park observations. There was good agreement between the portable UVR instruments in the park setting as confirmed via Bland Altman plots, while the dosimeter appeared less sensitive to change in shade conditions. The rooftop measurements showed that the Solarmeter 6.5 UVR readings were comparable to those of the adjacent rooftop instruments. The practicalities of using the dosimeters and Solarmeters for behavioral studies are discussed. These findings provide a basis for use of the Solarmeter 6.5 to measure changes in UVR levels due to different environmental conditions with relative accuracy for intervention studies in outdoor settings.