The basic bundle gerbe on unitary groups

We consider the construction of the basic bundle gerbe on SU(n)$SU\left(n\right)$ introduced by Meinrenken and show that it extends to a range of groups with unitary actions on a Hilbert space including U(n)$U\left(n\right)$ and _Up(H)$U_p\left(H\right)$, the Banach Lie group of unitaries differing from the identity by an element of a Schatten ideal. In all these cases we give an explicit connection and curving on the basic bundle gerbe and calculate the real Dixmier–Douady class. Extensive use is made of the holomorphic functional calculus for operators on a Hilbert space.     

Light beats the spread: “non‐diffracting” beams

“Non‐diffracting” beams do not spread as they propagate. This property is useful in many areas. Here, the theory, generation, properties, and applications of various “non‐diffracting” beams, including the Bessel beam, Mathieu beam, and Airy beam is reviewed. Applications include imaging, micromanipulation, nonlinear optics, and optical transfection.     

First experiments on the Australian Synchrotron Imaging and Medical beamline,including investigations of the effective source size in respect of X‐ray imaging

The Imaging and Medical beamline at the Australian Synchrotron achieved `first light' in December 2008. Here, the first experiments performed on the beamline are reported, which involved both X‐ray imaging and tomography studies for a range of samples. The use of a plastic‐edge phantom for quantitative measurements of contrast and resolution proved to be very instructive and helped to confirm certain parameter values such as the effective horizontal source size, detector resolution and average X‐ray energy for the polychromatic beam.     

Micellar effects on photoinduced redox reactions of Fe(bpy)2(CN)2

Excitation of solutions of Fe(bipy)₂(CN)₂ by a 266-nm laser pulse produces a hydrated electron and the oxidized complex, Fe(bipy)₂ (CN)₂⁺, in the primary photochemical step, in homogeneous aqueous solution as well as in aqueous solutions containing cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) micelles. In all cases nascent hydrated electrons react with ground state Fe(bipy)₂(CN)₂ to form Fe(bipy)₂(CN)₂⁻, and comparison of the decay constants in the three media (H₂O: k = 2.8 × 10¹⁰ M⁻¹ s⁻¹; CTAB: k = 2.9 × 10¹⁰ M⁻¹ s⁻¹; SDS: k = 5.5 × 10⁹ M⁻¹ s⁻¹), shows that the reaction is essentially unaffected by CTAB micelles but is much slower in SDS solution. Similar micellar effects were found for the back reaction between e_aq⁻ and Fe(bpy)₂(CN)₂⁺. Rate constants for the scavenging of the photogenerated hydrated electrons by methyl viologen (MV²⁺) cations and NO₃⁻ anions were measured in the three systems, and the results indicate that for scavenging by MV²⁺ the rate constants are decreased in the micelle systems (k in H₂O, 8.4 × 10¹⁰; CTAB, 3.5 × 10¹⁰ and SDS, 1.58 × 10¹⁰ M⁻¹ s⁻¹), whereas for NO₃⁻ the CTAB micelle decreases while the SDS micelle enhances the scavenging compared to water solution (k in H₂O, 8.3 × 10⁹; CTAB, 7 × 10⁸; and SDS, 2.05 × 10¹⁰ M⁻¹ s⁻¹). For the comproportionation reaction between Fe(bipy)₂(CN)₂⁺ and Fe(bipy)₂(CN)₂⁻ both micelles reduce the rate (k in H₂O, 3.3 × 10¹⁰; CTAB, 2.3 × 10¹⁰; and SDS, 1.05 × 10¹⁰ M⁻¹s⁻¹), but while the reaction of Fe(bipy)₂(CN)₂⁺ with MV⁺ is increased in CTAB compared to water, it is slowed in SDS (k in H₂O, 2.4 × 10¹⁰; CTAB, 8.9 × 10¹⁰; and SDS, 1.8 × 10¹⁰ M⁻¹s⁻¹). All effects observed in these microheterogeneous systems can be uniformly interpreted in terms of Coulombic interactions between the actual reactants and the charged surface of the micelles.     

Spin Trapping Hydroxyl and Aryl Radicals of One-Electron Reduced Anticancer Benzotriazine 1,4-Dioxides

Hypoxia in tumors results in resistance to both chemotherapy and radiotherapy treatments but affords an environment in which hypoxia-activated prodrugs (HAP) are activated upon bioreduction to release targeted cytotoxins. The benzotriazine 1,4-di-N-oxide (BTO) HAP, tirapazamine (TPZ, 1), has undergone extensive clinical evaluation in combination with radiotherapy to assist in the killing of hypoxic tumor cells. Although compound 1 did not gain approval for clinical use, it has spurred on the development of other BTOs, such as the 3-alkyl analogue, SN30000, 2. There is general agreement that the cytotoxin(s) from BTOs arise from the one-electron reduced form of the compounds. Identifying the cytotoxic radicals, and whether they play a role in the selective killing of hypoxic tumor cells, is important for continued development of the BTO class of anticancer prodrugs. In this study, nitrone spin-traps, combined with electron spin resonance, give evidence for the formation of aryl radicals from compounds 1, 2 and 3-phenyl analogues, compounds 3 and 4, which form carbon C-centered radicals. In addition, high concentrations of DEPMPO (5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide) spin-trap the •OH radical. The combination of spin-traps with high concentrations of DMSO and methanol also give evidence for the involvement of strongly oxidizing radicals. The failure to spin-trap methyl radicals with PBN (N-tert-butylphenylnitrone) on the bioreduction of compound 2, in the presence of DMSO, implies that free •OH radicals are not released from the protonated radical anions of compound 2. The spin-trapping of •OH radicals by high concentrations of DEPMPO, and the radical species arising from DMSO and methanol give both direct and indirect evidence for the scavenging of •OH radicals that are involved in an intramolecular process. Hypoxia-selective cytotoxicity is not related to the formation of aryl radicals from the BTO compounds as they are associated with high aerobic cytotoxicity.     

Stability under γ irradiation aging of an EPOXY/AMINE resin embedding simulated nuclear waste: Critical assessment of the techniques investigating chemical structure (IR and SIM spectroscopies) and bulk properties (DMA,DSC)

In order to predict the long term behaviour of materials simulating embedded nuclear waste (concentrate of evaporated radioactive effluents, mixture of anionic and cationic exchange resin), several techniques have been used:

• — Infrared and HSF-SIMS spectroscopies to investigate chemical structure: no significant differences have been observed between irradiated epoxy resin matrix samples and non-irradiated ones. No structural modification in the materials have been evidenced but some ion exchange resin irradiated in water seem to trap chlorine while releasing their borate content.
• — Dynamic mechanical analysis (DMA) to follow the irradiation effect on relaxational mechanisms. A small increase of the temperature T_α associated with the glass transition temperature for a weak total dose whereas a decrease of T_α for greater doses have been detected (these variations are however close to measurement errors).
• — Differential scanning calorimetry (DSC) to follow the thermal behaviour of the γ irradiated simulated radioactive materials: DSC results agree with those obtained using DMA.

     

Isoscalar monopole strength in 100Mo: an indicator for static triaxial deformation in the ground state

We perform deformation constraint symmetry-unrestricted three-dimensional time-dependent density functional theory (TDDFT) calculations for the isoscalar monopole (ISM) mode in ¹⁰⁰Mo. Monopole moments are obtained as a function of time using time propagating states based on different deformations. A Fourier transform is then performed on the obtained response functions. The resulting ISM strength functions are compared with experimental data. For the static potential-energy-surface (PES) calculations, the results using the SkM* and UNEDF1 energy-density functionals (EDFs) show spherical ground states and considerable softness in the triaxial deformation. The PES obtained with the SLy4 EDF shows static triaxial deformation. The TDDFT results based on different deformations show that a quadrupole deformation (characterized by \begin{document}$ \beta_2 $\end{document}) value of 0.25–0.30 gives a two-peak structure of the strength functions. Increasing triaxial deformation (characterized by γ) from 0\begin{document}$ ^{\circ} $\end{document} to 30\begin{document}$ ^{\circ} $\end{document} results in the occurrence of an additional peak between the two, making the general shape of the strength functions closer to that of the data. Our microscopic TDDFT analyses suggest that ¹⁰⁰Mo is triaxially deformed in the ground state. The calculated isoscalar \begin{document}$ Q_{20} $\end{document} and \begin{document}$ Q_{22} $\end{document} strength functions show peaks at lower energies. The coupling of these two modes with the ISM mode is the reason for the three-peak/plateau structure in the strengths of ¹⁰⁰Mo.