Synthesis and structure of novel sugar-substituted bipyridine complexes of rhenium and 99m-technetium

Novel ligands have been obtained from the reaction of 4,4'-dibromomethyl-2,2'-bipyridine with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosylthiol, 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosylthiol or 2,3,4,6-tetra-O-acetyl-alpha-D-thioacetylmannopyranoside in which the sugar residues are thioglycosidically linked to the bipyridine in the 4,4'-position. Cleavage of the acetyl groups affords hydrophilic symmetric ligands with free hydroxyl groups. Reaction of the new glycoconjugated ligands (L) with [Re(CO)(5)Cl] yields fluorescent complexes of general formula [Re(L)(CO)(3)Cl], which were characterised by mass spectrometry, elemental analysis and (1)H and (13)C NMR, IR, UV/Vis and fluorescence spectroscopy. These complexes exhibit excellent solubility and stability in organic solvents or water, depending on the residues of the sugar. One complex, namely tricarbonyl-4,4'-bis[(2,3,4,6-tetra-O-acetyl-beta-D-glycopyranosyl)thiomethyl]-2,2'-bipyridinerheniumtricarbonylo chloride, has been characterised by X-ray crystallography. A non-symmetric structure of the complexes could be assigned. Radiolabelling of the unprotected ligands with [(99m)Tc(H(2)O)(3)(CO)(3)](+) affords the corresponding water-soluble technetium complexes (in quantitative yields), which were characterised by their HPLC radiation traces. The formed complexes are stable for several hours in the presence of histidine but show partial ligand-exchange after one day.     

Infrared electroluminescence from a Si MOS structure with Ge in the oxide

We report on room-temperature infrared electroluminescence (EL) from metal-oxide-semiconductor devices made from Si. We compare the luminescence from RF sputtered oxide films containing SiO₂ with and without Ge by using a composite target and luminescence from a SiO₂ layer made by rapid thermal oxidation. The sputtered films were annealed in the temperature range 600-900 °C. This densifies the films and is likely to reduce the concentration of defects. A luminescence peak located around 1150-1170 nm is observed at current densities as low as 0.1 A/cm². The corresponding photon energy is close to that of the Si band gap. In addition, we observe several broad luminescence bands in the range 1000-1750 nm. These bands get stronger with Ge in the SiO₂ film. Some of these bands have previously been suggested and are directly associated with Ge. Since we observe that the intensity is correlated with the presence of Ge while the mere presence of the bands is not, we discuss the EL bands being due to defects which concentration is influenced by Ge in the oxide.     

High pressure performance of thin Pd–23%Ag/stainless steel composite membranes in water gas shift gas mixtures; influence of dilution, mass transfer and surface effects on the hydrogen flux

The hydrogen permeation and stability of tubular palladium alloy (Pd–23%Ag) composite membranes have been investigated at elevated temperatures and pressures. In our analysis we differentiate between dilution of hydrogen by other gas components, hydrogen depletion along the membrane length, concentration polarization adjacent to the membrane surface, and effects due to surface adsorption, on the hydrogen flux. A maximum H₂ flux of 1223 mL cm⁻² min⁻¹ or 8.4 mol m⁻² s⁻¹ was obtained at 400 °C and 26 bar hydrogen feed pressure, corresponding to a permeance of 6.4 × 10⁻³ mol m⁻² s⁻¹ Pa^−0.5. A good linear relationship was found between hydrogen flux and pressure as predicted for rate controlling bulk diffusion. In a mixture of 50% H₂ + 50% N₂ a maximum H₂ flux of 230 mL cm⁻² min⁻¹ and separation factor of 1400 were achieved at 26 bar. The large reduction in hydrogen flux is mainly caused by the build-up of a hydrogen-depleted concentration polarization layer adjacent to the membrane due to insufficient mass transport in the gas phase. Substituting N₂ with CO₂ results in further reduction of flux, but not as large as for CO where adsorption prevail as the dominating flow controlling factor. In WGS conditions (57.5% H₂, 18.7% CO₂, 3.8% CO, 1.2% CH₄ and 18.7% steam), a H₂ permeance of 1.1 × 10⁻³ mol m⁻² s⁻¹ Pa^−0.5 was found at 400 °C and 26 bar feed pressure. Operating the membrane for 500 h under various conditions (WGS and H₂ + N₂ mixtures) at 26 bars indicated no membrane failure, but a small decrease in flux. A peculiar flux inhibiting effect of long term exposure to high concentration of N₂ was observed. The membrane surface was deformed and expanded after operation, mainly following the topography of the macroporous support.     

Microstructural characterization of self-supported 1.6 μm Pd/Ag membranes

The microstructures of self-supported 1.6 μm thick Pd/23 wt% Ag membranes grown by magnetron sputtering and tested for hydrogen permeability under water–gas shift reaction conditions at different temperatures have been studied. The highest hydrogen permeation was observed through the membrane tested at the highest temperature. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and secondary ion mass spectroscopy were used to characterize the membranes. The grain structure is highly textured and the surface topology is roughened as a function of testing temperature. Hydrogen was trapped in the membranes, localized at and near the feed surface, and the level increased with temperature. The Ag composition at some positions on the feed side of the membrane tested at the highest temperature was reduced to around 5 wt%, probably due to the presence of impurities in the feed gas. This dealloying was associated with the presence of Fe impurity and is probably the cause of small satellite peaks in the X-ray diffractograms.     

Determination of primary aromatic amines in water food simulant using solid-phase analytical derivatization followed by gas chromatography coupled with mass spectrometry

Solid phase analytical derivatization with trifluoroacetic anhydride has been introduced as sample preparation for the determination of primary aromatic amines in water by gas chromatography coupled with mass spectrometry. Water was used as a food simulant for testing migration from laminated flexible food packaging materials. The method was evaluated for 8 primary aromatic amines in 200 ml water samples, which resulted in detection limits in the 0.1-0.4 microg/l range, relative standard deviations in the 4-17% range and acceptable linearity (R2 = 0.997-1.000). Detectable levels of 2,4-diaminotoluene, 2,6-diaminotoluene and 4,4'-methylenedianiline were found in water food simulant from some of the investigated food packaging materials.     

Hydrogen permeation of thin,free-standing Pd/Ag23% membranes before and after heat treatment in air

Free-standing Pd/Ag23 wt% membranes with five different thicknesses ranging from ∼1.3 to ∼5.0 μm were prepared by magnetron sputtering. The hydrogen permeation was determined before and after a thermal treatment in air at 300 °C. For all membranes studied, the thermal treatment resulted in enhanced permeation, and for some membranes, the hydrogen flux more than doubled. A permeance of 1.7 × 10⁻² mol/m² s Pa^0.5 was observed for ∼1.3 μm thick membranes, which is one of the highest reported. Bulk diffusion was found to be the main rate-limiting step after thermal treatment in air. The permeability was quite similar for all membranes studied after this treatment, with a mean value of 2.1 × 10⁻⁸ ± 5 × 10⁻¹⁰ mol m/m² s Pa^0.5. Topography studies by atomic force microscopy showed that the samples thermally treated in air had higher surface roughness, larger surface area and larger surface grains than samples not heat-treated in air.     

Wide-angle vision for road views

The field-of-view of a wide-angle image is greater than (say) 90 degrees, and so contains more information than available in a standard image. A wide field-of-view is more advantageous than standard input for understanding the geometry of 3D scenes, and for estimating the poses of panoramic sensors within such scenes. Thus, wide-angle imaging sensors and methodologies are commonly used in various road-safety, street surveillance, street virtual touring, or street 3D modelling applications. The paper reviews related wide-angle vision technologies by focusing on mathematical issues rather than on hardware.     

On the redistribution of6Li + ions implanted into polypropylene foils

⁶Li⁺ (150 keV) was implanted into thin polypropylene foils at fluences of 1 x 10¹³ to 1 x 1014 cm^–2. Subsequent neutron depth profiling measurements of the Li distributions revealed considerable deviations from the expected ballistic range profiles. This Li redistribution was simulated by a numerical computer calculation. The best fit between measurements and simulations was obtained by assuming that (i) Li redistributes immediately after its ballistic slowing-down, (ii) the Li mobility is enhanced in the radiation-damaged polymer region, the local diffusion enhancement being controlled by the target's electronic damage, (iii) mobile Li is readily trapped at radiation-induced defects, their density being proportional to the target's electronic damage, (iv) these traps are saturable ones, and (v) Li migration is not restricted to the ion track region, but proceeds also through the neighboring unirradiated bulk, though with slower speed.