Zur Bestimmung des Strychnins

Ohne Zusammenfassung     

Ecotoxicity and analysis of nanomaterials in the aquatic environment

Nanotechnology is a major innovative scientific and economic growth area. However nanomaterial residues may have a detrimental effect on human health and the environment. To date there is a lack of quantitative ecotoxicity data, and recently there has been great scientific concern about the possible adverse effects that may be associated with manufactured nanomaterials. Nanomaterials are in the 1- to 100-nm size range and can be composed of many different base materials (carbon, silicon and metals, such as gold, cadmium and selenium) and they have different shapes. Particles in the nanometer size range do occur both in nature and as a result of existing industrial processes. Nevertheless, new engineered nanomaterials and nanostructures are different because they are being fabricated from the “bottom up”. Nanomaterial properties differ compared with those of the parent compounds because about 40–50% of the atoms in nanoparticles (NPs) are on the surface, resulting in greater reactivity than bulk materials. Therefore, it is expected that NPs will have different biological effects than parent compounds. In addition, release of manufactured NPs into the aquatic environment is largely an unknown. The surface properties and the very small size of NPs and nanotubes provide surfaces that may bind and transport toxic chemical pollutants, as well as possibly being toxic in their own right by generating reactive radicals. This review addresses hazards associated and ecotoxicological data on nanomaterials in the aquatic environment. Main weaknesses in ecotoxicological approaches, controversies and future needs are discussed. A brief discussion on the scarce number of analytical methods available to determinate nanomaterials in environmental samples is included.     

Synthesis of enantiopure C3- and C4-hydroxyretinals and their enzymatic reduction by ADH8 from Xenopus laevis

(R)-all-trans-3-hydroxyretinal 1, (S)-all-trans-4-hydroxyretinal and (R)-all-trans-4-hydroxyretinal have been synthesized stereoselectively by Horner-Wadsworth-Emmons and Stille cross-coupling as bond-forming reactions. The CBS method of ketone reduction was used in the enantioface-differentiation step to provide the precursors for the synthesis of the 4-hydroxyretinal enantiomers. The kinetic constants of Xenopus laevis ADH8 with these retinoids have been determined.     

An Extension to the Theory of Controlled Lagrangians Using the Helmholtz Conditions

Journal of Nonlinear Science - The Helmholtz conditions are necessary and sufficient conditions for a system of second-order differential equations to be variational, that is, equivalent to a...     

Luminescence and compositional studies for the identification of “fire-setting” features at prehistoric mine La Turquesa (Catalonia,Spain)

Journal of Radioanalytical and Nuclear Chemistry - Modern mining activities often leads to destruction of archaeological records, making difficult to date the contexts and tools. In this work, a...     

On the optimization of bipartite secret sharing schemes

Optimizing the ratio between the maximum length of the shares and the length of the secret value in secret sharing schemes for general access structures is an extremely difficult and long-standing open problem. In this paper, we study it for bipartite access structures, in which the set of participants is divided in two parts, and all participants in each part play an equivalent role. We focus on the search of lower bounds by using a special class of polymatroids that is introduced here, the tripartite ones. We present a method based on linear programming to compute, for every given bipartite access structure, the best lower bound that can be obtained by this combinatorial method. In addition, we obtain some general lower bounds that improve the previously known ones, and we construct optimal secret sharing schemes for a family of bipartite access structures.     

Efficient interdigitated back‐contacted silicon heterojunction solar cells

We present back‐contacted amorphous/crystalline silicon heterojunction solar cells (IBC‐SHJ) on n‐type substrates with fill factors exceeding 78% and high current densities, the latter enabled by a SiN_x /SiO₂ passivated phosphorus‐diffused front surface field. V_oc calculations based on carrier lifetime data of reference samples indicate that for the IBC architecture and the given amorphous silicon layer qualities an emitter buffer layer is crucial to reach a high V_oc, as known for both‐side contacted silicon heterojunction solar cells. A back surface field buffer layer has a minor influence. We observe a boost in solar cell V_oc of 40 mV and a simultaneous fill factor reduction introducing the buffer layer. The aperture‐area efficiency increases from 19.8 ± 0.4% to 20.2 ± 0.4%. Both, efficiencies and fill factors constitute a significant improvement over previously reported values. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Application of capillary electrophoresis in the quality control of osmotically treated water

Summary This paper discusses the use of capillary zone electrophoresis (CZE) with indirect UV detection for the separation and detection of ions. By use of a 70 cm×75 μm i.d. capillary at −15 kV and an electrophoretic buffer containing sodium chromate, 1-butanol, and cetyltrimethylammonium bromide as electroosmotic-flow modifier (pH 8) nine inorganic and organic anions were separated in less than 10 min. By use of the same type of capillary at 20 kV and an electrophoretic buffer containing imidazole and 18-crown-6 (pH 5) eight cations were separated in less than 5 min. The different variables that affect the separation were studied and optimized; the compounds were detected at low mg L⁻¹ levels after hydrodynamic injection under pressure. The method was tested with osmotically treated waters, and the results compared with those obtained by ion chromatography for anion analysis and by atomic absorption spectroscopy for cation analysis.     

An Effective Fluorescent Sensor for Choline-Containing Phospholipids

A set of weak CH⋅⋅⋅O interactions is responsible for the recognition of tetraalkylammonium ions (ball-and-stick structure) by the tripodal receptors depicted in the diagram, in which the binding pocket is lined with squaramide units. The association constants of the fluorescent receptors are remarkably high at about 10⁵ M ⁻¹ and can be used for signaling the presence of selected choline phospholipids. Z=RNH, where R=alkyl, arylamino; X⁻=BH₄⁻, Cl⁻, Br⁻, I⁻.     

Structural rocking filters in highly birefringent photonic crystal fiber

We report what we believe is the first example of efficient rocking filter formation in polarization-maintaining photonic crystal fiber. Very high coupling efficiencies (as much as -23.5-dB suppression of the input polarization) and loss of < 0.02 dB were achieved for fibers as short as 11 mm. The filters, which we prepared by periodic mechanical twisting and heating with a scanned CO2 laser beam, are highly compact, and they are expected to be temperature stable.