Robust and Selective Metathesis Catalysts for Oleochemical Applications

The screening of known ruthenium alkylidene complexes in the ethenolysis of methyl oleate shows that the Grubbs-type Ru-catalysts bearing two phosphine donor ligands exhibit high selectivity for the formation of terminal olefins. Second-generation ruthenium catalysts promote almost the exclusive formation of self-metathesis products. Complexes with chelating alkylidene moieties (Hoveyda-type) generally exhibit poor selectivity for both ethenolysis and self-metathesis products. Complexes 2b and 2d promote self-metathesis of methyl oleate with catalyst loading of 2?ppm without significant isomerization up to 110?°C (using 2d) and up to 150?°C (using 2b).     

Real-Time Analysis of Alarm Pheromone Emission by the Pea Aphid (<Emphasis Type="Italic">Acyrthosiphon Pisum</Emphasis>) Under Predation

Upon attack by predators or parasitoids, aphids emit volatile chemical alarm signals that warn other aphids of a potential risk of predation. Release rate of the major constituent of the alarm pheromone in pea aphids (Acyrthosiphon pisum), (E)-b-farnesene (EBF), was measured for all nymphal and the adult stage as aphids were attacked individually by lacewing (Chrysoperla carnae) larvae. Volatilization of EBF from aphids under attack was quantified continuously for 60 min at 2-min intervals with a rapid gas chromatography technique (zNose) to monitor headspace emissions. After an initial burst, EBF volatilization declined exponentially, and detectable amounts were still present after 30 min in most cases. Total emission of EBF averaged 16.33 +/- 1.54 ng and ranged from 1.18 to 48.85 ng. Emission was higher in nymphs as compared to adults. No differences between pea aphid life stages were detected for their speed of alarm signal emission in response to lacewing larvae attack. This is the first time that alarm pheromone emission from single aphids has been reported.     

Infiltration-Inhibiting Reaction of Gadolinium Zirconate Thermal Barrier Coatings with CMAS Melts

The thermochemical interaction between a Gd₂Zr₂O₇ thermal barrier coating synthesized by electron-beam physical vapor deposition and a model 33CaO–9MgO–13AlO_3/2–45SiO₂ (CMAS) melt with a melting point of ∼1240°C was investigated. A dense, fine-grained, ∼6-μm thick reaction layer formed after 4 h of isothermal exposure to 1300°C. It consisted primarily of an apatite phase based on Gd₈Ca₂(SiO₄)₆O₂ and fluorite ZrO₂ with Gd and Ca in a solid solution. Remarkably, melt infiltration into the intercolumnar gaps was largely suppressed, with penetration rarely exceeding ∼30 μm below the original surface. The microstructural evidence suggests a mechanism in which CMAS infiltration is arrested by rapid filling of the gaps with crystalline reaction products, followed by slow attack of the column tips.     

Optimized dispersion of nanoparticles for biological in vitro and in vivo studies

Background

The aim of this study was to establish and validate a practical method to disperse nanoparticles in physiological solutions for biological in vitro and in vivo studies.

Results

TiO₂ (rutile) dispersions were prepared in distilled water, PBS, or RPMI 1640 cell culture medium. Different ultrasound energies, various dispersion stabilizers (human, bovine, and mouse serum albumin, Tween 80, and mouse serum), various concentrations of stabilizers, and different sequences of preparation steps were applied. The size distribution of dispersed nanoparticles was analyzed by dynamic light scattering and zeta potential was measured using phase analysis light scattering. Nanoparticle size was also verified by transmission electron microscopy. A specific ultrasound energy of 4.2 × 10⁵ kJ/m³ was sufficient to disaggregate TiO₂ (rutile) nanoparticles, whereas higher energy input did not further improve size reduction. The optimal sequence was first to sonicate the nanoparticles in water, then to add dispersion stabilizers, and finally to add buffered salt solution to the dispersion. The formation of coarse TiO₂ (rutile) agglomerates in PBS or RPMI was prevented by addition of 1.5 mg/ml of human, bovine or mouse serum albumin, or mouse serum. The required concentration of albumin to stabilize the nanoparticle dispersion depended on the concentration of the nanoparticles in the dispersion. TiO₂ (rutile) particle dispersions at a concentration lower than 0.2 mg/ml could be stabilized by the addition of 1.5 mg/ml albumin. TiO₂ (rutile) particle dispersions prepared by this method were stable for up to at least 1 week. This method was suitable for preparing dispersions without coarse agglomerates (average diameter < 290 nm) from nanosized TiO₂ (rutile), ZnO, Ag, SiO_x, SWNT, MWNT, and diesel SRM2975 particulate matter.

Conclusion

The optimized dispersion method presented here appears to be effective and practicable for preparing dispersions of nanoparticles in physiological solutions without creating coarse agglomerates.     

High-resolution, very broadband force measurements by solid-state laser transducers

Novel high-performance force transducers are discussed. Force measurement is based on the photoelastic effect in solid-state lasers (diode-pumped Nd:YAG) and provides an electrical frequency output. Our experiments demonstrate that the dynamic range of a single monolithic laser transducer covers at least 9 decades in which the output frequency is strictly proportional to the input force magnitude. Within the measurement bandwidth from DC up to at least 100 kHz force modulation frequency, static sensitivity of the transducer equals its dynamic sensitivity. Furthermore, input signals with modulation frequencies up to the MHz range can also be detected. The total measurement range covered by the applied laser technology ranges from nano-newton to mega-newton depending on the size of the laser crystals.     

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.