A Chain‐Elongated Oligophenylenevinylene Electrolyte Increases Microbial Membrane Stability

A novel conjugated oligoelectrolyte (COE) material, named S6 , is designed to have a lipid‐bilayer stabilizing topology afforded by an extended oligophenylenevinylene backbone. S6 intercalates biological membranes acting as a hydrophobic support for glycerophospholipid acyl chains. Indeed, Escherichia coli treated with S6 exhibits a twofold improvement in butanol tolerance, a relevant feature to achieve within the general context of modifying microorganisms used in biofuel production. Filamentous growth, a morphological stress response to butanol toxicity in E. coli, is observed in untreated cells after incubation with 0.9% butanol (v/v), but is mitigated by S6 treatment. Real‐time fluorescence imaging using giant unilamellar vesicles reveals the extent to which S6 counters membrane instability. Moreover, S6 also reduces butanol‐induced lipopolysaccharide release from the outer membrane to further maintain cell integrity. These findings highlight a deliberate effort in the molecular design of a chain‐elongated COE to stabilize microbial membranes against environmental challenges.     

Packing mechanics of fiber reinforcements

Theories of fiber packing, of use in manufacturing composite materials, are developed. The maximum packing fraction of force free fibers is estimated based on a statistical analysis of the distribution of fiber-fiber contact points. The new expressions are more general than previous ones by allowing for a distribution in fiber length and orientation. The forced packing beyond this limit is governed by the bending of fiber segments between contact points. A micromechanical theory is developed for this, again based on the contact point statistics, and equations relating the force response per unit area of a fiber bed to the fiber volume fraction are derived for three basic types of assembly: a general 3D wad, a planar mat of dispersed fibers, and a bundle of almost parallel fibers. Other types of reinforcement structure, such as woven fabrics, and the effect of lubrication are also treated briefly.     

Are tradable green certificates a cost-efficient policy driving technical change or a rent-generating machine? Lessons from Sweden 2003–2008

In the European policy debate, tradable green certificates (TGC) have been suggested to be a superior regulatory framework for promoting the diffusion of renewable electricity technologies. The purpose of this paper is to assess the performance of the Swedish TGC system, contributing to the European debate on the suitability of different types of frameworks. The expectations of the TGC system were that it would: (a) be effective in terms of increasing the supply of “green” electricity; (b) do this in a cost effective manner (from both a social and a consumer perspective); (c) generate an equitable distribution of costs and benefits and (d) drive technical change. So far, it has performed adequately in terms of effectiveness and social cost effectiveness. However, consumer costs have been substantially higher than expected, very large rents are generated and, at best, it contributes marginally to technical change. Thus, a TGC framework should be selected if the overriding concern is to minimize short term social costs of reaching a certain goal with a high degree of predictability. However, it cannot be expected to also drive technical change, keep consumer costs down and be equitable. Such trade-offs need to be revealed and not obscured by analysts.     

Numerical derivation of dispersion coefficients for flow through three‐dimensional randomly packed beds of monodisperse spheres

The longitudinal (D_L) and transverse (D_T) dispersion coefficients for flow through randomly packed beds of discrete monosized spherical particles are studied. The three‐dimensional (3‐D) porous‐medium model consists of thousands of spherical particles that are divided into cells using Voronoi diagrams. The relationship between the variation of the dual stream function and the vorticity between neighboring particles is derived using Laurent series. The whole flow pattern at low particle Reynolds number is then obtained by minimization of the dissipation rate of energy with respect to the dual stream function. The D_L is obtained by fitting the resulting effluent curve to a 1‐D solution of a continuous model. The D_T is obtained by fitting the numerical concentration profile to an approximate 2‐D solution. The derived D_L and D_T values are in agreement with 3‐D experimental data from the literature enabling a study of the effects of pore structure and porosity on D_L and D_T. © 2013 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J 60: 749–761, 2014     

Simultaneous extraction and fractionation of polycyclic aromatic hydrocarbons and their oxygenated derivatives in soil using selective pressurized liquid extraction

In this study, a selective pressurized liquid extraction (PLE) method which can extract polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives (oxy-PAHs) from contaminated soil and simultaneously separate them into two fractions was developed. The method uses extraction cells packed with a chromatographic adsorbent and extraction solvents of increasing polarity. Several experiments were conducted on both spiked and authentic contaminated soil samples. Different types of adsorbents, combinations of extraction solvents, and extraction temperatures were tested in order to find a method that could fulfill the purpose of the study. The final method was based on extraction cells packed with 2% deactivated silica gel. The PAHs were extracted with cyclohexane/dichloromethane (9:1) at 120 degrees C, after which the oxy-PAHs where extracted with cyclohexane/dichloromethane (1:3) at 150 degrees C. The PAHs and oxy-PAHs were efficiently separated into two fractions, and only trace amounts of some compounds were found in the inappropriate fraction. The recoveries of the PAHs were mostly above 70% and of the oxy-PAHs, above 90%. The linearity of the method was good, and the calibration curves for most compounds had a regression coefficient better than 0.99 and an intercept close to the origin of coordinates. When the selective PLE method was applied to seven authentic soil samples, the results were found to be in good agreement with those of a reference method based on Soxhlet extraction and silica gel cleanup and also in good agreement with the certified reference values available for one of the soils. The selective PLE method is faster and consumes less solvent than a traditional method based on separate extraction and fractionation steps. The selective PLE method is, therefore, suitable for the concurrent analysis of PAHs and oxy-PAHs during large-scale soil contamination studies. This will provide more information about the soil contamination and the levels of toxicity than an ordinary PAH analysis.     

Context adaptable driver information – Or,what do whom need and want when?

This study deals with a first step towards context adaptive functionality of a Driver Information System.     

Flow design of guiding device for downstream fish migration

Downstream migrating smolt must be guided around hydropower plants to avoid fish mortality due to the turbines. In Piteå River, which is already regulated, open spillways serve this purpose but few fish find this route. Hence, action must be taken to enhance downstream fish migration. One way to attract the fish to the spillways is to direct the surface flow towards them by means of a guiding device. The hydrodynamic design of one such device is outlined using numerical calculations of the flow upstream the spillways and by the assumption that the fish moves near the surface of the water. A number of geometries are evaluated by starting from a straight impermeable barrier that extends 2 m down from the water surface and stretches over a part of the river. A major result is that it is possible to redirect the surface water towards the spillways at very low spilling rates which means high energy efficiency. Another finding was that the device should stretch over a large part of the river. For optimal functionality, the spilling should match the guiding device geometry. High spilling implies that the guiding has a low impact while for low spilling the geometry is crucial for successful downstream migration. Copyright © 2009 John Wiley & Sons, Ltd.     

Digital speckle photography: visualization of mesoflow through clustered fiber networks

Digital speckle photography (DSP) is used for velocity field measurements inside a fiber network. The width of the channels in which the flow is measured is typically less than 1 mm. Therefore a microscope is used to image the fiber network. When we sample 30 images/s and separate the moving parts of the images from the stationary parts, the velocity field can be deduced with DSP.