Kinetic modulation of pulsed chronopotentiometric polymeric membrane ion sensors by polyelectrolyte multilayers

Polymeric membrane ion-selective electrodes are normally interrogated by zero current potentiometry, and their selectivity is understood to be primarily dependent on an extraction/ion-exchange equilibrium between the aqueous sample and polymeric membrane. If concentration gradients in the contacting diffusion layers are insubstantial, the membrane response is thought to be rather independent of kinetic processes such as surface blocking effects. In this work, the surface of calcium-selective polymeric ion-selective electrodes is coated with polyelectrolyte multilayers as evidenced by zeta potential measurements, atomic force microscopy, and electrochemical impedance spectroscopy. Indeed, such multilayers have no effect on their potentiometric response if the membranes are formulated in a traditional manner, containing a lipophilic ion exchanger and a calcium-selective ionophore. However, drastic changes in the potential response are observed if the membranes are operated in a recently introduced kinetic mode using pulsed chronopotentiometry. The results suggest that the assembled nanostructured multilayers drastically alter the kinetics of ion transport to the sensing membrane, making use of the effect that polyelectrolyte multilayers have different permeabilities toward ions with different valences. The results have implications to the design of chemically selective ion sensors since surface-localized kinetic limitations can now be used as an additional dimension to tune the operational ion selectivity.     

Genomic structure,cloning and expression of two phospholipase D isoenzymes from white cabbage

Phospholipase D (PLD) from cabbage is interesting as biocatalyst in phospholipid transformation. To provide the basis for genetic engineering of the enzyme, gene cloning and sequencing were carried out. We have recently identified two isoenzymes, PLD1 and PLD2, on the basis of their cDNAs, here we describe their genomic structure consisting of 3404 and 3614 bp, respectively. Based on their sequence, PLD1 and PLD2 can be assigned to the α‐type of plant PLDs, they contain two HKD motifs and the C2 domain with a phosphatidylinositol 4,5‐bisphosphate (PIP₂) binding motif. Starting from pld1 cDNA, expression studies were carried out. Whereas expression using constructs with StrepTactin or Glutathion S‐transferase tags was not successful, soluble active enzyme was produced from constructs without tag. pld2 was expressed accordingly. Both enzymes were purified by Ca²⁺‐mediated hydrophobic interaction chromatography to high purity. N‐terminal sequencing of PLD1 and PLD2 revealed that the Met‐free N‐termini of both enzymes correspond to sequences derived from the coding region of the pld1 and pld2 genes, respectively. Both recombinant enzymes showed highest hydrolytic activities at pH 5.5 to 5.6, independent of Ca²⁺ concentration (10—100 mM). The optimum Ca²⁺ concentration was 45 mM for PLD1 and PLD2. Both enzymes showed comparable activities in hydrolysis and transphosphatidylation of phospholipids.     

Reproducible manufacturing of dye‐sensitized solar cells on a semi‐automated baseline

A fully operational baseline consisting of dedicated equipment to process nanocrystalline dye‐sensitized solar cell devices has been installed at ECN. This baseline focuses on the production of glass/glass devices with dimensions up to 10×10 cm². Present power conversion efficiencies of 6% obtained for cell areas of 2ċ5 cm² are successfully translated to 100 cm² devices with an active area of 68 cm² by application of identical cell components. The power conversion efficiency with respect to total area was 4%. Processing of a large number of devices in the baseline shows good results in terms of process reliability and yield. The overall yield for a series of 27 devices (10×10 cm²) was 96%, while 84% (22 of the remaining 26 devices) generated a cell efficiency within 7% deviation from the average value (4ċ3%). The reproducibility of the titanium dioxide (TiO₂) colloid synthesis has been investigated. The deviation from the average efficiency (4ċ9%) of three batches of colloid was at most 3ċ2%. These results prove that complete device manufacturing of nc‐DSC by a baseline process, starting with colloid synthesis is reproducible for surfaces up to 10×10 cm². Copyright © 2003 John Wiley & Sons, Ltd.     

Stability of X‐ray cellulose crystallite orientation parameters in native cotton with change of location and year of growth

In this article, data on cellulose crystallite orientation parameters measured in terms of the Hermans orientation factor, average angle of orientation (α_m), and 40, 50, and 75% X‐ray angles in respect to the same 13 cotton cultivars grown at different agroclimatic locations and in different crop years in India are presented and discussed. It was observed that whereas the average values of the X‐ray orientation parameters are different for different varieties they remain practically invariant within individual varieties with change of the location of growth. The orientation parameters, therefore, appear to be genetic in origin and independent of the agroclimatic conditions of growth. It is believed that these results can be suitably exploited by cotton breeders in evolving varieties with an increased strength of fibers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 269–276, 1999     

Is There Room for Families in the Inner City? Life-Stage Blenders Challenging Planning

This paper addresses the phenomenon of families returning to inner cities. With evidence from the first qualitative study done on families residing in inner-city Helsinki, it demonstrates that urban living reduces the sharp divide between life before having children and family life. Urban parents stay in the city much for the same reasons they first moved there: because they are attracted to population density, good amenities and good public transport. Living in the city enables a lifestyle where different life stages blend into each other. The paper, however, reveals that there is a lack of understanding among city planners and politicians about family needs in the inner city. By adopting a framework of the reviewed literature, the paper draws on the argument that modernist ideals on proper family living still prevail. The paper suggests that planning must acknowledge that exclusionary life stages are eroding and creating a need to facilitate multiple forms of lifestyles.     

Gemeinsame österreichisch-ungarische Sedimentforschung im Rahmen des EFRE-Projektes SEDDON

The multiple uses of the Danube River for navigation, hydropower production and as a drinking water supply influence its ecological quality. Flow restrictions due to regulation as well as impacts on the sediment regime such as retention in the catchment area and interruption of the sediment continuum result in changes of the hydromorphological structures and can produce major problems in the context of sediment management. In light of these facts, cross-border investigations of sediment transport at the Danube River are called for. As there are no uniform research approaches shared by Austria and Hungary, the EU-funded project SEDDON (Sediment Research and Management at the Danube River) aims to compare different monitoring and modeling techniques used to determine sediment transport, and to develop mutual solutions. Further, the laboratory equipment currently used for hydraulic model experiments is evaluated and a research channel with a free flowing discharge of up to 10 m³/s without pumping will be constructed, allowing large-scale joint laboratory tests concerning sediment to be performed.     

Games to Create Awareness and Design Policies for Transboundary Cooperation in River Basins: Lessons from the Shariva Game of the Mekong River Commission

International river basins cover a vast majority of the land surface, international cooperation is therefore important for the proper management, and to assure equitable and effective use in the basins. Key elements to improve international cooperation are common understanding of the issues in the basin, understanding upstream-downstream impacts and sharing a common vision for the future. This article focuses on the role of games in international basin cooperation to create awareness and to support policy development. The paper analysed the effects of the game in creating awareness and upgrading knowledge amongst water and related professionals and in designing procedures for cooperation in transboundary river basins. This was analysed during the implementation of the game with 28 participants from the four Lower Mekong countries. The impact on creating awareness and upgrading knowledge was evaluated through the use of questionnaires and pre- and post evaluation questions and for the design of policies, a SWOT analysis was used to evaluate the usefulness of the policies and frameworks as well as to identify possible improvements to the framework. The game implementation proved to be an appropriate tool to provide a practical way for stakeholders to become acquainted with the administrative and technical tools available in the Lower Mekong Basin. Pre- and post test shows that participants gained substantial knowledge on transboundary cooperation and use of tools. The game was part of a longer training programme addressing all the issues, however, the participants gained additional knowledge and insight by playing the game, well above what they had learned during the earlier training workshops. Playing the game proved an important aspect in training and education of such complex systems. The study also shows the role games can play in policy analysis, in particular the way the game provided insight in the design of the policy and the development of procedures, and their function to review and update policies and procedures. A number of recommendations have been made to strengthen the role in both training and education as well as in design of procedures.