Quantification of four major metabolites of embryotoxic N-methyl- and N-ethyl-2-pyrrolidone in human urine by cooled-injection gas chromatography and isotope dilution mass spectrometry

N-Methyl- and N-ethyl-2-pyrollidone (NMP and NEP) are frequently used industrial solvents and were shown to be embryotoxic in animal experiments. We developed a sensitive, specific, and robust analytical method based on cooled-injection (CIS) gas chromatography and isotope dilution mass spectrometry to analyze 5-hydroxy-N-ethyl-2-pyrrolidone (5-HNEP) and 2-hydroxy-N-ethylsuccinimide (2-HESI), two newly identified presumed metabolites of NEP, and their corresponding methyl counterparts (5-HNMP, 2-HMSI) in human urine. The urine was spiked with deuterium-labeled analogues of these metabolites. The analytes were separated from urinary matrix by solid-phase extraction and silylated prior to quantification. Validation of this method was carried out by using both, spiked pooled urine samples and urine samples from 56 individuals of the general population with no known occupational exposure to NMP and NEP. Interday and intraday imprecision was better than 8% for all metabolites, while the limits of detection were between 5 and 20 μg/L depending on the analyte. The high sensitivity of the method enables us to quantify NMP and NEP metabolites at current environmental exposures by human biomonitoring.     

Low-temperature atmospheric pressure argon plasma treatment and hybrid laser-plasma ablation of barite crown and heavy flint glass

We report on atmospheric pressure argon plasma-based surface treatment and hybrid laser-plasma ablation of barite crown glass N-BaK4 and heavy flint glass SF5. By pure plasma treatment, a significant surface smoothing, as well as an increase in both the surface energy and the strength of the investigated glass surfaces, was achieved. It was shown that for both glasses, hybrid laser plasma ablation allows an increase in the ablation depth by a factor of 2.1 with respect to pure laser ablation. The ablated volume was increased by an averaged factor of 1.5 for N-BaK4 and 3.7 for SF5.     

A plasmonic fano switch

Plasmonic clusters can support Fano resonances, where the line shape characteristics are controlled by cluster geometry. Here we show that clusters with a hemicircular central disk surrounded by a circular ring of closely spaced, coupled nanodisks yield Fano-like and non-Fano-like spectra for orthogonal incident polarization orientations. When this structure is incorporated into an uniquely broadband, liquid crystal device geometry, the entire Fano resonance spectrum can be switched on and off in a voltage-dependent manner. A reversible transition between the Fano-like and non-Fano-like spectra is induced by relatively low (～6 V) applied voltages, resulting in a complete on/off switching of the transparency window.     

Electrochemically stable gold nanoclusters in HOPG nanopits

Gold nanoparticles on highly oriented pyrolytic graphite (HOPG) electrodes are synthesized. They are stabilized in nanosized pits of well defined depth in the graphite surface. These pits are created by energetic cluster impact followed by etching under a well controlled oxygen atmosphere. We succeeded in the preparation of highly dispersed and stable Au electrodes with gold particles with a mean diameter smaller than 5 nm. The stability of the gold nanostructures for electrochemical applications has been tested by performing cyclic voltammetric measurements in 0.5 M H₂SO₄. While conventionally prepared sputter deposited electrodes show highly unstable structures in this size range, Au clusters stabilized in the nanosized containers are stable.     

Flow frictional characteristics of microencapsulated phase change material suspensions flowing through rectangular minichannels

1 Introduction MEPCM, i.e. microencapsulated phase change material, is formed as shown in Fig. 1 by packing phase change material (PCM) into a microcapsule with a solid but flexible shell; the size of the MEPCM particles ranges from 1 to 100 μm[1,2]. The shell separates the core PCM (solid or liquid) from outside substances and tolerates volume changes in the core due to phase change. Widespread applications of MEPCM include: enhancing performance of fluid convective heat transfer, te…     

Low-temperature growth of well-crystalline Co3O4 hexagonal nanodisks as anode material for lithium-ion batteries

Uniform hexagonal-shaped cobalt oxide (Co₃O₄) nanodisks were prepared in large scale via facile aqueous solution based hydrothermal process at 110 °C. The detailed structural characterizations confirmed that the synthesized products are hexagonal cobalt oxide nanodisks, possessing very well-crystalline cubic spinel structure. A coin cell of type −2032 was assembled using the synthesized Co₃O₄ nanodisks and its charge–discharge profile was analyzed between the voltages 0.01 and to 2.5 V vs. Li/Li⁺ reference electrode. The electrochemical cell composed of Li/Co₃O₄ delivered an initial lithium insertion capacity of 2039 mAh/g. Although the cell exhibited high irreversible capacity during the first four cycles, the columbic efficiency has been improved upon cycling.     

Estimation of reinforcement in compatibilized polypropylene nanocomposites by extensional rheology

Structural characterization in polymer nanocomposites is usually performed using X‐ray scattering and microscopic techniques, whereas the improvements in processing and mechanical properties are commonly investigated by rotational rheometry and tensile testing. However, all of these techniques are time consuming and require quite expensive scientific equipment. It has been shown that a fast and efficient way of estimating the level of reinforcement in polymer nanocomposites can be performed by melt extensional rheology, because it is possible to correlate the level of melt strength with mechanical properties, which reflect both the 3D network formed by the clay platelets/polymer chains as well as final molecular structure in the filled system. The physical network made of silicate filler and polymer matrix has been evaluated by X‐ray diffraction and transmission electron microscopy. Extensional rheometry and tensile testing have been used to measure efficiency of the compatibilizer amount in a polypropylene‐nanoclay system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The High Resolution NMR Structure of Parvulustat (Z‐2685) from Streptomyces parvulus FH‐1641: Comparison with Tendamistat from Streptomyces tendae 4158

The protein parvulustat (Z‐2685) from Streptomyces parvulus comprises 78 amino acids and functions as a highly efficient α‐amylase inhibitor. Parvulustat shares 29.6 % overall amino acid sequence identity to the well‐known α‐amylase inhibitor tendamistat. Among the conserved residues are the two disulfide bridges (C9–C25, C43–C70) and the active‐site motif (W16, R17, Y18). Here, we report the high‐resolution NMR structure of parvulustat based on NOEs, J couplings, chemical shifts and hydrogen‐exchange data. In addition, we studied the dynamical properties of parvulustat by heteronuclear relaxation measurements. We compare the structure of parvulustat with the structure of tendamistat in terms of secondary structure elements, charges and hydrophobicity. The overall structural composition is very similar, but there are distinct differences including the active‐site region. These structural and dynamical differences indicate that for parvulustat an induced‐fit mechanism for binding to α‐amylase might take place, since the structure of tendamistat does not change upon binding to α‐amylase.