Severe inhibition of maize wall degradation by synthetic lignins formed with coniferaldehyde

Although the enzymatic or ruminal degradability of plants deficient in cinnamyl alcohol dehydrogenase (CAD) is often greater than their normal counterparts, factors responsible for these degradability differences have not been identified. Since lignins in CAD deficient plants often contain elevated concentrations of aldehydes, we used a cell-wall model system to evaluate what effect aldehyde-containing lignins have on the hydrolysis of cell walls by fungal enzymes. Varying ratios of coniferaldehyde and coniferyl alcohol were polymerised into non-lignified primary walls of maize (Zea mays L) by wall-bound peroxidase and exogenously supplied H₂O₂. Coniferaldehyde lignins formed fewer cross-linked structures with other wall components, but they were much more inhibitory to cell wall degradation than lignins formed with coniferyl alcohol. This suggests that the improved degradability of CAD deficient plants is not related to the incorporation of p-hydroxycinnamaldehyde units into lignin. Degradability differences were diminished if enzyme loadings were increased and if hydrophobic aldehyde groups in lignins were reduced to their corresponding alcohols by ethanolic sodium borohydride. © 1998 Society of Chemical Industry.     

Novel Potential Enantioselective Phase Transfer Catalysts Based on Lupinine

Ten N-alkylated lupininium derivatives 5–8 were prepared as potential enantioselective phase transfer catalysts. Compounds 5a–d , 6a–d contain four asymmetric centers (including one in the side chain) with known configuration resting on an X-ray structure. Preliminary PT catalytic experiments in several reactions gave high chemical yields but relatively disappointing enantioselectivities.     

The effects of spinning conditions on asymmetric 6FDA/6FDAM polyimide hollow fibers for air separation

We have found that the chemistries of inner and external coagulants, gelation bath temperature, and air gap distance have profound effects on 6FDA-polyimde hollow-fiber morphology and performance. This 6FDA-polyimide is made of 50 mol % 2,2′-bis(3,4′-dicarboxyphenyl) hexafluoro propane dianhydride (6FDA) and 50 mol % 2,2′-bis(3-aminophenyl) hexafluoro propane (4,4′ 6F-diamine) (6FDAM). An increase in air gap distance tends to induce three-dimensional open-cell pore formation. Raising bath temperature has a similar effect. Multilayer finger-void structure can be completely eliminated if one properly chooses a bore-fluid flow rate and a gelation bath temperature. Experimental data demonstrate that the location of the dense layer can be shifted from the inner skin to the outer skin based on the chemistry (solubility parameter) of coagulants. The location of finger voids is also dependent on the chemistry of coagulants, and the dense layer location may shift from the inner surface to the external surface or appear in both surfaces dependent on the differences in solubility and coagulation rate. A defect-free 6FDA/6FDAM polyimide fiber with a selectivity of 4.73 and a permeance of 38.1 GPU is produced. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1555–1569, 1997     

Aerobic Oxidation of Vicinal Diols Catalyzed by an Anderson‐Type Polyoxometalate, [IMo6O24]5–

An Anderson‐type polyoxometalate, [I^VIIMo₆O₂₄]^5–, has been used as a catalyst for the aerobic oxidation at 80 °C of vicinal diols (glycols). This is the first report on the use of such a polyoxometalate as an oxidation catalyst. Reactivity and selectivity were dependent on the substrate. Thus, aryl‐substituted diols yielded mostly the carbon‐carbon bond cleavage products, while 1,2‐cyclohexanediol yielded cyclohexanone‐2‐ol and 1,2‐cyclohexanedione. Aliphatic diols were less reactive but yielded carbon‐carbon bond cleavage products in the presence of additional acid. An abbreviated mechanistic study was carried out indicating that the polyoxometalate oxidizes the diol to the various products even under anaerobic conditions. The reduced polyoxometalates (heteropoly blues and heteropoly browns) formed in the oxidation of the diols are re‐oxidized by the molecular oxygen.     

Abriebschutzbeschichtung von Kunststoffen durch plasmaaktivierte Hochratebedampfung. Abrasion Resistant Coatings on Plastics by Plasma Activated High Rate Deposition

Transparent plastics, e.g. PMMA or Polycarbonate, have low weight, optical clarity and processing benefits of a thermoplastic. A great disadvantage of such plastics is the lack of abrasion resistance. Therefore the plastics have to be protected for practical application. SiO₂ layers perform very well as clear abrasion resistant layers. The typical layer thickness ranges from 1 μm to 6 μm depending on the required abrasion resistance. To get an abrasion resistance comparable to float glass a layer thickness of about 6 μm for SiO₂ layers is needed. The layers are deposited by the HAD‐process (hollow cathode activated deposition). There the coating material is evaporated by an electron beam and is deposited on the substrate by adding reactive gases (e.g. O₂, N₂O or organic monomers) at the presence of an intensive plasma. A special hollow cathode, adapted to this process, is used as plasma source. The typical deposition rates are 300 nm/s to 600 nm/s for the deposition of SiO₂.     

Prediction of the open-circuit voltage of solar cells from the steady-state photoconductance

The steady-state photoconductance is a relevant parameter for solar cells. Minority carrier lifetimes, surface recombination velocities, diffused region recombination and open-circuit voltages can be determined from an analysis of photoconductance data. Computer simulations of archetypical cases are used here to demonstrate the usefulness of such an analysis and, in particular, the possibility of predicting device voltages from contactless photoconductance measurements. Simple theoretical models are given to provide physical insight and guide the analysis. A systematic approach is described that permits diagnosis and identification of the dominant recombination mechanisms for a given device structure.© 1997 John Wiley & Sons, Ltd.     

Selective and self-validating breath-level detection of hydrogen sulfide in humid air by gold nanoparticle-functionalized nanotube arrays

We demonstrate the selective detection of hydrogen sulfide at breath concentration levels under humid airflow,using a self-validating 64-channel sensor array ba...     

Use of chicken egg-yolk antibodies against K88+ fimbrial antigen for quantitative analysis of enterotoxigenic Escherichia coli (ETEC) K88+ by a sandwich ELISA

An enzyme-linked immunosorbent sandwich assay (ELISA) has been developed to detect and quantify both the K88+ fimbrial antigen and the concentration of bacterial cells in fecal and other samples using anti-fimbrial chicken egg-yolk and anti-fimbrial rabbit serum antibodies. The assay has a sensitivity of 40 ng ml⁻¹ for K88+ fimbrial antigen and 10⁷ CFU ml⁻¹ for intact cells and cell homogenate. The inter- and intra-assay coefficients of variation (CV) for intact cells, homogenates, and fimbrial antigens were similar, suggesting that reproducible results can be obtained with any of the three preparations. In all cases the CV increased with decreasing concentration of the antigen, especially when very low concentrations of antigen were used. Fimbrial antigens had lower CV (values ranged from 2 to 37%, depending on its concentration) than standards prepared from either whole cells or homogenized cells (values ranged from 1 to 67%). The correlation between the actual number of cells as counted and the number as estimated from the ELISA using the amount of fimbrial antigen was r = 0.98, P < 0.001. The anti-K88+ polyclonal antibodies from chicken serum and egg yolk had little or no cross-reactivity with K99, 987P ETEC. The correlation (r) between the fecal score for diarrhea and the number of E coli in the fecal swab was high, r = 0.80 (n = 64, P < 0.0001). The assay is sensitive and specific and provides a good estimate of the amount of fimbrial protein or the number of K88+ ETEC in the sample. © 1999 Society of Chemical Industry