A novel system for reducing leaching from formulations of anionic herbicides: clay-liposomes

A new approach was developed for reducing leaching of herbicides and contamination of groundwater. Liposome-clay formulations of the anionic herbicides sulfometuron and sulfosulfuron were designed for slow release by incorporating the herbicide in positively charged vesicles of didodecyldimethylammonium (DDAB), which were adsorbed on the negatively charged clay, montmorillonite. Freeze fracture electron microscopy demonstrated the existence of DDAB vesicles and aggregated structures on external clay surfaces. X-ray diffraction results for DDAB with montmorillonite imply the existence of DDAB bilayers with an oblique orientation to the basal plane within the clay interlayer space at adsorbed amounts beyond the cation exchange capacity of the clay. Adding DDAB with sulfometuron or sulfosulfuron to montmorillonite yielded 95% or 83% adsorption of the herbicide at optimal ratios. Liposome-clay formulations exhibited slow release of the herbicides in water. Analytical measurements in soil columns demonstrated 2-10-fold reduction in leaching of the herbicides from liposome-clay formulations in comparison with commercial formulations. Percents of root growth inhibition of a test plant in the upper soil depths were severalfold higher for the liposome-clay formulations than for the commercial ones. Consequently, liposome-clay formulations of anionic herbicides can solve environmental and economical problems by reducing their leaching.     

All-Solid-State Power Modulator for Pulsed Corona Plasma Reactors

Atmospheric pressure pulsed corona plasma (PCP) reactors of wire-plate design offer novel solutions to environmental issues and to a number of industrial processes. Emerging applications include indoor air sterilization and odor removal in air conditioning systems, chemical synthesis in non-thermal plasmas, and plasma reforming of gaseous fuels. We previously reported on experimental investigations of a laboratory size, wire-plate plasma reactor for pulsed corona treatment of gas flows. Operation with gas flow, at pulse repetition frequencies of between 10 pps and 200 pps, has been achieved at pulse voltage amplitudes of between 10 and >30 kV, at pulse durations of around 0.3 mus (FWHM). High efficiencies of up to 70 g/kWh have been reported using an all-solid-state pulse generator. In this work, we report on the development of all-solid-state power modulators for use with nonlinear loads like pulse corona plasmas. The pulse generators are based on a fast thyristor switch discharging pulse capacitors, a pulse step-up transformer, and one or two stages of magnetic pulse compression. At pulse repetition rates of up to 200 pps, amplitudes of > 30 kV into a resistive-capacitive load (1 kOmega200 pF) have been achieved, at risetimes of about 80 ns and a pulse width of 0.3 mus. The pulse generator is insensitive to load variations, in particular to sparking in the reactor. An advanced generator version uses two magnetic pulse compression stages resulting in even shorter rise times. The modulator and its performance concerning experimental results will be described in detail when driving a pulsed corona reactor.     

Properties of a fluorescent bezafibrate derivative (DNS-X). A new tool to study peroxisome proliferation and fatty acid β-oxidation

The first peroxisome proliferator-activated receptor (PPAR) was cloned in 1990 by Issemann and Green. Many studies have reported the importance of this receptor in the control of gene expression of enzymes involved in lipid metabolic pathways including mitochondrial and peroxisomal fatty acid β-oxidation, lipoprotein structure [apolipoprotein (apo) A2, apo Clll], and fatty acid synthase. By using radiolabeled molecules, it was shown that peroxisome proliferators bind and activate PPAR. As an alternative method, we developed a fluorescent dansyl (1-dimethyl-aminonaphthalene-5-sulfonyl) derivative peroxisome proliferator from bezafibrate (DNS-X), a hypolipidemic agent that exhibits an in vitro peroxisome proliferative activity on rat Fao-hepatic derived cultured cells. However, until now, the effect of this new compound on the liver of animals and subcellular localization was unknown. In addition to in vivo rat studies, we present a more efficient large-scale technique of DNS-X purification. Treating rats (DNS-X in the diet at 0.3% w/w) for 6 d leads to a hepatomegaly and a marked increase in liver peroxisomal palmitoyl-CoA oxidase activity. We also developed a method to localize and quantify DNS-X in tissues or cell compartment organelles. The primarily cytosolic distribution of DNS-X was confirmed by direct visualization using fluorescence microscopy of cultured Fao cells. Finally, transfection assay demonstrated that DNS-X enhanced the PPARα activity as well as other peroxisome proliferators do.     

Novel Nanosized Aluminium Carboxylates: Synthesis,Characterization and Use as Nanofillers for Protective Polymeric Coatings

A mixture of novel aluminium carboxylate nanoparticles and aluminium hydroxide ultrafine powder was prepared via precipitation reaction between Al(2‐PrO)₃ and maleic acid. In this mixture both free primary particles occur (mean geometrical size around 40 nm) together with a secondary agglomerated particle fraction of sizes in the low micrometer region. However, centrifugation processes allowed for the removal of the latter and resulted in the formation of size stable nanopowders. Up to 30 wt.‐% of these particles were incorporated into acrylate matrices resulting in low‐viscosity formulations with [η] < 1 000 mPa · s, which allowed for roller application and even spray coating of these nanocomposites at room temperature. Radiation curing of such coatings was accomplished via UV irradiation. In comparison to the corresponding SiO₂‐based nanocomposites and carboxylate alumoxane fillers, the cured coatings revealed significantly improved surface mechanical properties.

     

Aminolevulinic Acid-Mediated Photodynamic Therapy of Human Meningioma: An in Vitro Study on Primary Cell Lines

Objective: Five-aminolevulinic acid (5-ALA)-induced porphyrins in malignant gliomas are potent photosensitizers. Promising results of ALA-PDT (photodynamic therapy) in recurrent glioblastomas have been published. Recently, 5-ALA-induced fluorescence was studied in meningioma surgery. Here, we present an experimental study of ALA-PDT in an in vitro model of primary meningioma cell lines. Methods: We processed native tumor material obtained intra-operatively within 24 h for cell culture. Epithelial membrane antigen (EMA) immunohistochemistry was performed after the first passage to confirm that cells were meningioma cells. For 5-ALA-PDT treatment, about 5000 cells per well were seeded in 20 wells of a blank 96-well plate. Each block of 4 wells was inoculated with 150 µL of 0, 25, 50 and 100 µg/mL 5-ALA solutions; one block was used as negative control without 5-ALA and without PDT. Following incubation for 3 h PDT was performed using a laser (635 nm, 18.75 J/cm²). The therapeutic response was analyzed by the water soluble tetrazolium salt (WST-1) cell viability assay 90 min after PDT. Results: 5-ALA-PDT was performed in 14 primary meningioma cell lines. EMA expression was verified in 10 primary cell cultures. The remaining 4 were EMA negative and PDT was without any effect in these cultures. All 10 EMA-positive cell lines showed a significant and dose-dependent decrease in viability rate (p < 0.001). Cell survival at 5-ALA concentrations of 12.5, 25, 50 and 100 μg/mL was 96.5% ± 7.6%, 67.9% ± 29.9%, 24.0% ± 16.7% and 13.8% ± 7.5%, respectively. For the negative controls (no 5-ALA/PDT and ALA/no PDT), the viability rates were 101.72% ± 3.5% and 100.17% ± 3.6%, respectively. The LD₅₀ for 5-ALA was estimated between 25 and 50 µg/mL. Conclusion: This study reveals dose-dependent cytotoxic effects of 5-ALA-PDT on primary cell lines of meningiomas. Either 5-ALA or PDT alone did not affect cell survival. Further efforts are necessary to study the potential therapeutic effects of 5-ALA-PDT in vivo.     

Protonated Phosphazenes: Structures and Hydrogen‐Bonding Organocatalysts for Carbonyl Bond Activation

The synthesis and application of protonated phosphazeniums as hydrogen‐bond donor groups was demonstrated in the solid state and in solution. In particular, their catalytic activity was shown in the activation of the carbonyl group within cyclic esters, using a benchmark reaction, that is, in the ring‐opening polymerization of lactide and valerolactone, in the presence of a basic co‐catalyst. The reactions proceed differently depending on monomers and/or phosphazenium salts. The impact of catalysts and reactants steric hindrance upon the outcome of the reaction is then highlighted and discussed.

     

Imagewise Structuring of Diazosulfonate Polymer Films by UV Light and Laser Irradiation – A Comparison

Diazosulfonate polymers are applied as photo resins for printing plates and imaged via UV light and IR laser irradiation. Both methods lead to sufficient differentiation in the exposed areas to allow image formation upon printing. Changes in the exposed areas compared to the unexposed sites are studied via UV and IR spectroscopy and the surface properties are characterized using contact angle measurements, ellipsometry, and atomic force microscopy. Upon UV irradiation the polymer films retain their smooth surface but the changes in the solubility and wetting behavior are considerable. Laser imaging leads to a thermally induced foaming of the polymer film, and thus to a different ink accepting behavior.     

Microchemical engineering of catalytic reactions

The catalytic reduction of NO with H₂ or CO and the O₂+H₂ reaction have been investigated at low pressure (p < 10^-3 mbar) on microstructured bimetallic Pt(100)/Rh and Pt(100)/Ti surfaces prepared by lithographic techniques. Photoemission electron microscopy (PEEM) was the spatially resolving technique used. It is shown that diffusional coupling leads to dynamic effects which are size-dependent and thus can be controlled through the design of the surface microstructure. In connection with periodic parameter forcing these dynamic effects can potentially be exploited to improve the yield and selectivity of catalytic reactions. This revised version was published online in July 2006 with corrections to the Cover Date.