Automated Particle Analysis of Populations of Silver Halide Microcrystals by Electron Probe Microanalysis under Cryogenic Conditions

An automated particle analysis routine is implemented on an electron microprobe for analyzing the chemical composition and projective area of populations of individual silver halide microcrystals. An LN2 cryostage is used to prevent material degradation due to reaction with the impinging electron beam. The background in the EDX spectra is lowered by depositing the microcrystals on a carbon-coated copper grid, mounted in a transmission holder. The ILα/AgLα net X-ray intensity ratio, obtained from a spectrum-fitting algorithm, is used to determine the crystal composition by means of a standard-based calibration curve. The uncertainty on the concentration measurement of individual microcrystals is calculated using the uncertainties on the net X-ray counts and the uncertainties on the calibration curve. The area measurement is optimized by introducing a gray value histogram correction on each individual measurement. Overlapping microcrystals are scrapped from the analysis by defining a maximum shape factor, against which the shape factor of the microcrystal is tested. To minimize problems with drift of the cryostage, spectrum acquisition is carried out immediately after a single microcrystal has been located, based on the backscattered electron image. Several applications are discussed.     

Evaluation of concepts for hydrogen – chlorine fuel cells

Three different concepts for H₂–Cl₂ fuel cells have been evaluated. An ordinary PEM fuel cell based on a Nafion membrane, a fuel cell based on a combination of circulating hydrochloric acid and a Nafion membrane and a system based on a phosphoric acid doped Polybenzimidazole (PBI) membrane. None of the investigated systems were able to demonstrate stable operation under the conditions used in this study, due to electrocatalyst corrosion, membrane dehydration and/or electrode flooding. All systems studied achieved open circuit voltages close to the reversible thermodynamic value for production of aqueous hydrochloric acid, suggesting formation of dissolved HCl in the electrolyte and fast electrode kinetics.     

Synthesis, characterisation and decomposition of 1,3-benzene disulfonyl azide; a cross-linking agent for polyolefins

We have studied the thermal decomposition of 1,3-benzenedisulfonyl azide (1,3-BDSA), and verified that sulfonyl nitrenes formed are able to cross-link polyolefins, including PP. The decomposition was studied with DSC, TGA, and the GC–MS analysis of gaseous products. Both the decomposition of pure 1,3-BDSA and 1,3-BDSA dissolved in a polyolefin were studied. Decomposition occurs by loss of nitrogen giving sulfonyl nitrenes. In the polyolefin nitrenes cross-links the carbon chains by C–H insertion. Cross-linking of PP was verified with SEC. SEC showed no signs of decomposition of PP. Decomposition in the polyolefin was a first order reaction with a half-life of 25.7 s at 200 °C. Hence, 1,3-BDSA is suited for processing with polyolefins. Decomposition of pure 1,3-BDSA is more complicated with unwanted products such as SO₂ and benzene being formed, thereby emphasising the need for good blending when used in polyolefins.     

Health effects of residential wood smoke particles: the importance of combustion conditions and physicochemical particle properties

Background  

Residential wood combustion is now recognized as a major particle source in many developed countries, and the number of studies investigating the negative health effects associated with wood smoke exposure is currently increasing. The combustion appliances in use today provide highly variable combustion conditions resulting in large variations in the physicochemical characteristics of the emitted particles. These differences in physicochemical properties are likely to influence the biological effects induced by the wood smoke particles.     

Use of life cycle assessments to evaluate the environmental footprint of contaminated sediment remediation

Ecological and human risks often drive the selection of remedial alternatives for contaminated sediments. Traditional human and ecological risk assessment (HERA) includes assessing risk for benthic organisms and aquatic fauna associated with exposure to contaminated sediments before and after remediation as well as risk for human exposure but does not consider the environmental footprint associated with implementing remedial alternatives. Assessment of environmental effects over the whole life cycle (i.e., Life Cycle Assessment, LCA) could complement HERA and help in selecting the most appropriate sediment management alternative. Even though LCA has been developed and applied in multiple environmental management cases, applications to contaminated sediments and marine ecosystems are in general less frequent. This paper implements LCA methodology for the case of the polychlorinated dibenzo-p-dioxins and -furans (PCDD/F)-contaminated Grenland fjord in Norway. LCA was applied to investigate the environmental footprint of different active and passive thin-layer capping alternatives as compared to natural recovery. The results showed that capping was preferable to natural recovery when analysis is limited to effects related to the site contamination. Incorporation of impacts related to the use of resources and energy during the implementation of a thin layer cap increase the environmental footprint by over 1 order of magnitude, making capping inferior to the natural recovery alternative. Use of biomass-derived activated carbon, where carbon dioxide is sequestered during the production process, reduces the overall environmental impact to that of natural recovery. The results from this study show that LCA may be a valuable tool for assessing the environmental footprint of sediment remediation projects and for sustainable sediment management.     

Efficient domain decomposition methods for elliptic problems arising from flows in heterogeneous porous media

In this paper we study domain decomposition methods for solving some elliptic problem arising from flows in heterogeneous porous media. Due to the multiple scale nature of the elliptic coefficients arising from the heterogeneous formations, the construction of efficient domain decomposition methods for these problems requires a coarse solver which is adaptive to the fine scale features, [4]. We propose the use of a multiscale coarse solver based on a finite volume – finite element formulation. The resulting domain decomposition methods seem to induce a convergence rate nearly independent of the aspect ratio of the extreme permeability values within the substructures. A rigorous convergence analysis based on the Schwarz framework is carried out, and we demonstrate the efficiency and robustness of the preconditioner through numerical experiments which include problems with multiple scale coefficients, as well as problems with continuous scales. Communicated by: G. Wittum     

Elevated levels of polybrominated diphenyl ethers (PBDEs) in fish from Lake Mjøsa, Norway

Surprisingly high levels of PBDEs (polybrominated diphenyl ethers) in fish from Lake Mj?sa watercourse initialized a more detailed study of PBDE contamination in the Lake Mj?sa region as well as fish from other lakes in southeast Norway. With exception of the fish from Lake Mj?sa, the sum concentration of PBDEs in trout was, on a wet weight (ww) basis, in the range of 0.3-40 ng/g (21-1215 ng/g lipid weight (lw)) in fish fillet and 39-446 ng/g (125-915 ng/g lw) in burbot liver. The PBDE levels in fish from Lake Mj?sa, was found in the range of 72-1120 ng/g ww (2348-16,753 ng/g lw) in trout and 156-2265 ng/g ww (4201-45,144 ng/g lw) in burbot. It was later confirmed that the elevated levels in Lake Mj?sa were mainly caused by the release of PBDEs to the water from a textile manufacturer in the town of Lillehammer. In addition to PBDE levels in fish we also present information on the spatial distribution of PBDEs in air around the Mj?sa watercourse, based on the complementary use of passive air samples and analysis of moss, including data on measured air concentrations. The results confirm the presence of an active source of atmospheric PBDEs in the region of Lillehammer. Although this source appears to have a limited impact on atmospheric levels towards the southern reaches of the lake, it could still be a significant source of PBDEs to the lake as a whole. However, more research is needed to better understand and quantify the relative importance of various sources and pathways for which PBDEs enter Lake Mj?sa in order to support the development of future control strategies.