Bifunctional electrodes for unitised regenerative fuel cells

The effects of different configurations and compositions of platinum and iridium oxide electrodes for the oxygen reaction of unitised regenerative fuel cells (URFC) are reported. Bifunctional oxygen electrodes are important for URFC development because favourable properties for the fuel cell and the electrolysis modes must be combined into a single electrode. The bifunctional electrodes were studied under different combinations of catalyst mixtures, multilayer arrangements and segmented configurations with single catalyst areas. Distinct electrochemical behaviour was observed for both modes and can be explained on the basis of impedance spectroscopy. The mixture of both catalysts performs best for the present stage of electrode development. Also, the multilayer electrodes yielded good results with the potential for optimisation. The influence of ionic and electronic resistances on the relative performance is demonstrated. However, penalties due to cross currents in the heterogeneous electrodes were identified and explained by comparing the performance curves with electrodes composed of a single catalyst. Potential improvements for the different compositions are discussed.     

Direct Evidence for Membrane Transport of Host-Plant-Derived Pyrrolizidine Alkaloid N-Oxides in Two Leaf Beetle Genera

The chrysomelid leaf beetles Longitarsus jacobaeae, Oreina cacaliae, and O. speciosissima sequester pyrrolizidine alkaloids from their asteracean host plants and store them as nontoxic N-oxides. Previous analyses showed that Longitarsus is able to N-oxidize protoxic tertiary PAs, but did not resolve in which form N-oxides are taken up. For Oreina, beetles seem able to directly transmit the polar PA N-oxides from the gut into the hemolymph and prevent any reduction of them in the gut yielding protoxic free bases. Here, we confirm the predicted direct uptake of PAs as N-oxides by Oreina, and elucidate the situation for Longitarsus by applying double-labeled [14C]senecionine [18O]N-oxide as tracer. The beetles were fed with the tracer and subsequently senecionine N-oxide was recovered from the defensive secretions (Oreina) and beetle extracts (Longitarsus), purified by HPLC, and submitted to ESI-MS, GC-MS, and analysis of the specific radioactivity. The 18O-label is retained without any loss in the labeled senecionine N-oxide recovered from the two Oreina species. Analysis of the Longitarsus experiment was complicated by a contamination of the HPLC-purified senecionine N-oxide with a second compound, identified as a dihydrosenecionine N-oxide by high-resolution CID analysis. The dihydrosenecionine N-oxide, probably the 15,20-dihydro derivative, constitutes a major idiosyncratic senecionine metabolite present in the beetle. The recovered senecionine N-oxide retained 74% 18O-label. The remaining 25% is mostly due to loss of 18O by reduction and subsequent re-N-oxidation. The experiments confirm for both beetle genera a direct uptake of the polar nontoxic PA N-oxides, which requires specific membrane carriers. Accumulation of detrimental free base PA is prevented by glucosylation (Oreina) or N-oxidation (Longitarsus).     

First Sex Pheromone of the Order Strepsiptera: (3R,5R,9R)-3,5,9-Trimethyldodecanal in Stylops melittae Kirby, 1802

The twisted-wing parasites (Strepsiptera) are an unusual and small order of insects with about 600 known species. As obligate endoparasitoids, they develop and spend most of their lives living in other insects. Adults show an extreme sexual dimorphism: The free-living males have large eyes, branched antennae, reduced forewings, and well developed hind wings, while the neotenic females of most species lack all external characters that normally define an insect, remain endoparasitic, and only extrude the cephalothorax from the host. Due to the males’ short life span of only a few hours, there must be an efficient means of mate finding. This is believed to be mediated by chemical cues released by virgin females. Here, we report the first identification and synthesis of a female-produced strepsipteran sex pheromone, (3R,5R,9R)-3,5,9-trimethyldodecanal, from Stylops melittae, a species parasitizing andrenid bees. We found this highly EAD-active compound to be present in cephalothoraxes of and released from unmated females, and synthetic samples proved to be extremely attractive when offered in the field during the swarming period of the males. The structural features of this new natural compound may further support the re-establishment of the Strepsiptera as the closest living relatives of the Coleoptera.     

Electrospun Silica—Polybenzimidazole Nanocomposite Fibers

A new route for the manufacturing of silica/poly(benzimidazole) (PBI) nanocomposites fibers is described. PBI was synthesized via melt polycondensation and polycondensation in poly(phosphoric acid). Solutions of PBI and silica nanoparticles in N,N‐dimethylacetamide (DMAc) were electrospun to fibers and non‐wovens. The resulting materials were analyzed by ATR‐IR spectroscopy, small‐angle X‐ray scattering (SAXS) and nitrogen sorption measurements. The non‐wovens could be processed towards dense, cross‐linked membranes by hot pressing and treatment with p‐xylylene dichloride.

     

Network formation by aza‐Michael addition of primary amines to vinyl end groups of enzymatically synthesized poly(glycerol adipate)

A highly efficient approach for the synthesis of polyester‐based networks via aza‐Michael addition of primary amines to α,β‐unsaturated (vinyl) end groups of poly(glycerol adipate) (PGA) was achieved. By acylation of PGA with 6‐(Fmoc‐amino)hexanoic acid side chains via Steglich esterification, protected amine‐functionalized PGA was obtained. This was followed by the removal of fluorenylmethyloxycarbonyl (Fmoc) protecting groups and the synthesis of PGA‐based networks under catalyst‐free conditions. The successful conjugate addition of primary amines to vinyl end groups and network formation were confirmed using ¹³C magic angle spinning NMR and Fourier transform infrared spectroscopy. Network heterogeneity and defects were quantitatively investigated using ¹H double‐quantum NMR spectroscopy. Finally, a hydrogel was prepared with potential biomedical applications.     

High-level secretion of recombinant monomeric murine and human single-chain Fv antibodies from Drosophila S2 cells

Single-chain variable fragment (scFvs) antibodies are small polypeptides (～26 kD) containing the heavy (V(H)) and light (V(L)) immunoglobulin domains of a parent antibody connected by a flexible linker. In addition to being frequently used in diagnostics and therapy for an increasing number of human diseases, scFvs are important tools for structural biology as crystallization chaperones. Although scFvs can be expressed in many different organisms, the expression level of an scFv strongly depends on its particular amino acid sequence. We report here a system allowing for easy and efficient cloning of (i) scFvs selected by phage display and (ii) individual heavy and light chain sequences from hybridoma cDNA into expression plasmids engineered for secretion of the recombinant fragment produced in Drosophila S2 cells. We validated the method by producing five scFvs derived from human and murine parent antibodies directed against various antigens. The production yields varied between 5 and 12 mg monomeric scFv per liter of supernatant, indicating a relative independence on the individual sequences. The recombinant scFvs bound their cognate antigen with high affinity, comparable with the parent antibodies. The suitability of the produced recombinant fragments for structural studies was demonstrated by crystallization and structure determination of one of the produced scFvs, derived from a broadly neutralizing antibody against the major glycoprotein E2 of the hepatitis C virus. Structural comparison with the Protein Data Bank revealed the typical spatial organization of V(H) and V(L) domains, further validating the here-reported expression system.     

Workflow View Driven Cross-Organizational Interoperability in a Web Service Environment

Workflow technology has recently been employed not only within businesses but also as a framework for implementing e-services over the Internet. Such e-services typically require collaborative enactment of workflows across multiple organizations. In this paper, we propose the use of workflow views as a fundamental support mechanism for the interoperability of multiple workflows across business organizations. We present a meta-model of workflow views and their semantics using a cross-organization workflow example based on a supply-chain e-service. We also formulate an interoperation model of workflow views and its consistency criteria. Finally, this paper presents an implementation of the model based on XML and contemporary Web services technologies, with adaptation to our E-ADOME workflow engine.     

Accessory cells mediate hairy-cell proliferation by mechanism(s) involving both adhesion and TNF alpha secretion

The mechanisms responsible for hairy-cell (HC) growth both in vitro and in vivo are still unclear. In a recent study we showed that monocytes/macrophages induce HC proliferation in vitro. The purpose of the present paper is to examine the specificity of this accessory cell effect and to establish the mechanism(s) involved. We demonstrate that the effect is not confined to monocytes/macrophages but is also potentially seen with a range of other cell types. However, at low accessory cell:HC ratios (< 1:20) only human umbilical vein endothelial cells (HUVEC) and macrophages induce HC proliferation. We suggest that these observations are of pathophysiological significance in relation to the close association frequently observed between HCs and endothelial cells/macrophages in the liver and spleen of patients with hairy-cell leukaemia (HCL). Regarding the mechanisms of the accessory cell effect, we show that both soluble factors and cell contact are important. A blocking anti-TNF alpha antibody abrogated the HC proliferation induced by HUVEC supernatant, indicating the involvement of this cytokine. Interaction of HCs with HUVEC via CD11b and 11c leucocyte integrins was shown to be important in the contact effect. Our demonstration of the involvement of both cytokines and cell contact in HC proliferation is in accord with what is already known about the control of B-cell growth and differentiation. More specifically, our results suggest that TNF alpha and interaction with endothelial cells/macrophages via leucocyte integrins are involved in the proliferation of late B-cells of the maturational stage represented by HCs.     

Engineered versus standard evolutionary algorithms: A case study in batch scheduling with recourse

An engineered evolutionary algorithm for a realistic chemical batch scheduling problem with uncertain data is developed systematically. The problem is formulated as a two stage stochastic integer program with discrete scenarios. The model is solved by a stage decomposition-based hybrid algorithm using an evolutionary algorithm combined with mixed-integer programming. Earlier experiments with a standard evolutionary algorithm led to the hypothesis that the constrained search space is not covered well such that in some cases the population converges to a subset of the solution space which does not include the best known solution. An efficient engineered evolutionary algorithm is developed which is shown to cover the feasible set significantly better such that a high quality feasible schedule can be generated comparatively fast. As the hierarchical structure of the case study is typical for many batch scheduling problems, some general principles may be postulated from the experience gained here.